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[Question] [ I have finally found an edition of the Dragonriders of Pern trilogy - living in Italy, I only had access to it thanks to my father's old books, and he doesn't own the complete series - so I have been immersed in that world and started imagining its less peaceful, alternative version. --- For those unfamiliar with it, the relevant features are dragons: [![9th Pass Pern Dragon Sizes by Color](https://i.stack.imgur.com/KEQd2.jpg)](https://i.stack.imgur.com/KEQd2.jpg) The bigger the dragon, the rarer its occurrence in the population. These dragons have, other than their physical weapons, the ability of breathing fire through the digestion in a second stomach of firestone, and of teleporting to a different place, time, or both, as long as they have the mental image of the location at the specific time; or the generic image of the location if the teleportation is through space only. I will ignore here any specific exceptions that occur in the books. Each dragon is impressed by a rider when it hatches, and it lives the rest of its life in a symbiotic relationship with "its human". The technological level throughout the planet is mostly European medieval, with a few exceptions (Rudimentary flamethrowers as the most notable). Dragon-folk live in weyrs, communities built in inactive volcanoes most commonly, as you can see [here](http://pern.wikia.com/wiki/Weyr). Common people live in settlements much like the ones that were usual in the European middle age. Dragonfolk are either descendants of inhabitants of the weyr, or people brought in by "normal" settlements, according to the needs of staff and dragon riders (depends on how many eggs the queen dragons lay). --- Now, while in the official Pern, dragonfolk are generally peaceful (with individual exceptions), I can easily imagine a culture like this realizing that they will not need much to grab power. Once the different weyrs have claimed their territory, they will turn against each other to obtain land, goods, privileges... While the offensive potential of a dragon is immense, how would it be possible to defend yourself from a few hundred dragons that all of sudden appear out your window (figuratively speaking)? I suppose the relationship among weyrs would be much like the Cold War, with isolated fights in neutral territory, but no large scale offensive, with large use of sentinels and deterrents (you burn my house to the ground, and within 1 second I am burning your house to the ground too). Common people, on the other hand, will be largely disadvantaged. I expect their costumes to change over time to become similar to what was mentioned in [this question](https://worldbuilding.stackexchange.com/questions/16829/how-could-medieval-cultures-defend-themselves-against-dragons). This may not be enough, as these dragons are intelligent, numerous, guided by human riders, and can friggin' teleport. Which would be the most effective defense against a weyr in full force (assume 300 fighting dragons)? Either by dragonfolk, common people, or an alliance of both. Feel free to ignore the ability to time travel, as it may be tricky, though fascinating to explore in terms of military strategy. If you want to tackle it, keep in mind that if you will go back in time tomorrow to do something, somewhere, right now, it means that in this moment there is a double of yourself doing whatever, wherever. You cannot perceive a specific time in one way and then go back to alter it, if you could it would be changed already - that is the assumption in the books. You don't change the past, it is already changed, and then the cause will occur. It's way more physically and mentally demanding to travel through time, and the presence of two versions of yourself within, say, the same city, is enough to make you almost faint. Furthermore the risk of ending somewhen else entirely is high. [Answer] Don't let the dragons teleport in your fortress : An alternative to the rope trick : tight streets, tall buildings, long iron spikes everywhere in the sky above the buildings. Iron, because dragons are flying and after a first attempt where they only fly above your city while spiting fire, there are no ropes anymore. Then, knowing the place, they could teleport in the rope-less sky. That's why a rich city could build some kind of a metal cage above the roofs, while a smaller city would only have spikes tied to the roofs. The cage could, or could not, have a way to hide the city (city-sized blinds ? I don't want to put the whole city in the dark every time, but there should be a way to open/close the city from the sky, like deploying sails on a boat). For time travelling dragons, either you change the city aspect very often to confuse them or you keep it so unchanged frome the outside that no dragon can find a specific date to teleport at. Make your land hard to find/recognise : A nomad way of life could be quite efficient for common humans. Light and fast travel prevents teleporting dragons, either if they can travel in time or not. With their big friends, dragonfolk would have some issues to keep a nomad life. I'm sure they want a big badass fortress. You can try to hide it (underground, underwater, under big trees of an ancient forest). You can cover it with mirrors (good luck to look inside, ennemy dragons !) or with another optical illusion. You can make your fortress move (may request a little magical help, but you have dragons. They might pull a whole city if there are enough of them and the city is build with this trick in mind, on an artificial ground or something like that) Oh my god, dragons are coming ! They did find your city ! What now ? If you have dragons too, of course, you send them. What else ? I assume that killing flying dragons from the ground is very hard. You can try to shoot at them with very big crossbows on the roofs (thanks Tolkien), but there are 300 of them, spitting fire, and they're going for the crossbows first. I don't know if a dragon can be poisoned or drugged with these arrows. If you're underground or underwater, let's hope you have trapped the entries. A sudden avalanche or a flood should switch their fire off. Nets falling into the passages could prevent them from flying properly. A bunch of projectiles (arrows, stones, dart) fired from protected nests in the passage would make their entrance difficult. Big wooden doors might not stop them for ever, but slow them long enough to make of lot of damages. If your entry looks like a galery, put spikes everywhere (spikes that can be easily installed/removed if you have dragons too. And a last one : in the middle of the city make sure every street and every refuge access is far too little for a dragon, and eventually only humans would reach the critical point. [Answer] I think the only effective defence against teleportation is to have no place to teleport to, at least in a range where the dragon can be dangerous. So basically, hang the sky full of ropes, too close to each other that a dragon could materialize there (this assumes that the dragon needs a free air space to materialize in). Other than that, the only defence is to have people constantly watching the sky and surroundings, and be ready to react as quickly as possible. [Answer] I will try to generalize a bit celtschk answer : To defend against teleporting dragons, the best thing to do is to prevent them from teleporting. To teleport by surprise near your fortress or in your fortress. To teleport a dragon need two things : 1. Space You can forbid dragon to teleport inside your castle, for example, as celtschk suggested, by hanging ropes around, or by building only rooms too small for dragons (obviously you can not do it if you have dragon as well, so the rope trick seems particularly excellent). However, you can not do much about the empty space around your place. Of course you can build everything inside deep forests to prevent teleportation, but then you lose the ability to spot regular army incoming, and you can not prevent teleportation in the sky. 2. A mental image of the place where they want to teleport Well then it depend on how much precise the mental image need to be, but you can play with it. By keeping the looking of the interior of your castle very secret, you can forbid teleportation inside. By changing the looking of the place where your castle is located, you can therefore possibly prevent teleportation there (perhaps repainting the walls is sufficient, I do not know). But a sure thing is that information will be important. If for example a dragon need to have seen the place to picture a sufficiently good mental image of a place, then dragon will be strictly forbidden to travel in foreign countries, since simply allowing them to pass by your fortress result in great danger for it. ## Note on dragonfolks' fortresses If you do have dragons at your disposal, you are not force to use the usual "tall tower on high ground" kind of fortress, since they are built that way partly in order to watch its surroundings. You have dragons, you can just use flying sentry, thus possibly making underground fortress a viable solution. [Answer] I think the easiest way for most of the common folk to survive would be to live in cave systems. Even the smallest dragon on the scale is enormous compared to the human, so they'd have a hard time getting to you except by collapsing your entrances. As long as the cave network is substantial enough, you can just use other entrances for a while, then dig out entrances that were collapsed a while ago. People would start going outside when the dragons are inside, which could cause substantial cultural changes if it forced everyone outside at night. Conversely, little would change if the dragons are night-lifers. The worst problem for humanity would be the loss of our crops. We could do a little with skylights and in-cave flora, but without acres upon acres of fields, our way of life would cease to be viable. We'd be back to what amounts to a hunter/gatherer society. The ideal solution then, is to kill all the dragons. Humans are really good at killing things, so this probably isn't as far-fetched as it seems, unless the dragons are magically immune to anything common humans would have. Dragons would be very scarce, since each one would require tens, if not hundreds, of square miles of hunting grounds just to survive. At the end, only the craftiest of dragons would be able to survive the pestilence that is pissed-off humanity, and they would do so by not attracting attention, negating their attempts at world domination. Teleportation would help them, of course, but at the end of the day I don't think it would matter. They have to sleep sometime, and just a few seconds of being off-guard could spell their doom. The only real chance they'd have is to annihilate humanity in one fell swoop at the start of their conquests. [Answer] Let's say you are a lord holder who's decided for whatever reason to protect his people from dragon rider depredations. To protect against a sudden assault by hundreds of dragons, the key is preparation. If you are not yet a lord holder, solve that step first if you can, or become the power behind the throne, etc. Numbers Thankfully these are on your side. Killing a rider will incapacitate or destroy the telepathically bonded dragon (perhaps they attempt to violate time rules to go between to save their rider). Assume the riders will not willingly part from their dragons to enter areas the dragons cannot reach - if they do, this is far too easy. Even without this vulnerability, the riders are not a significant factor. Armies Say the dragon riders have conquered your neighbors (shame on them for being less prepared or allying themselves to the wrong side). This devolves into a fairly standard human military equation with a few elites. Your best choice is to limit how much of the opposing force they can bring to bear at once, via choke points, narrow corridors, fortifications, killing boxes, etc, while keeping the elites out of the fight as much as possible. Teleporation Thankfully, as others have mentioned, small areas aren't only useful against armies, but also your friends against enormous, massive, teleporting opponents. I would minimize the mass and size advantage by countering it with the ground - dig into and build deep in mountains, cliffs, and rocky areas. Thankfully, holders have a strong tradition of living in tunnels bored out of just such areas - impossible to teleport into and difficult to dig into. This tradition serves well as basic preparation. Siege Now, you can survive the night, but can you survive the year? The teleporting dragons have a massive information and logistical advantage over you, so you should devote substantial resources and preparation to stockpiling food, water, weapons, etc. Sappers are a significant concern, so your stockpiles should be located as deeply as possible, and prefer many smaller caches over a single large one which could be drained or poisoned. You will want to prepare many bolt holes and long underground tunnels you can use to conduct (often night time) raids against any forces guarding the area. When overwatch is sparse, dispatch assassins and diplomats (to other groups for aid). In the early stages, poison supplies and kill as many sleeping dragons as you can, before they learn to camp at home and teleport in at the first sign of trouble. If you have longer to prepare, pre-seed spies, assassins, saboteurs, etc in the world around you, if possible among their number. After all, with all this thinking you've done, wouldn't it be great to be the one on the other side of the tactical scenario... Time travel Your weapon here is information. Try to keep your buildup secret and your person safe as early and for as long as possible. Either you'll be assassinated before you start (see also below), or your preparation worked out well (or poorly) enough. Keep your pre-revolution identity a secret as well - try to pin the name on significant political opponents, or figures who died young of mysterious causes who through position or privilege might have grown into a threat themselves. If you can get them to consistently guess wrongly about your gender, you'll increase your security further. Take the same precautions for all major leaders, and beware any whose names are public - there may well be a reason they weren't killed before you met them. Try to control when the hundreds of dragons show up, to when you are ready. Until then, keep your head down. This will precipitate investigation into your past preparations - the better you've hid your preparation in the past, the greater your information advantage in the present. Take the initiative if you get the chance when you are ready - send a poisoned tribute. Any dragons who are fated to die from it won't come back to collect payment from your flesh. Again, the longer you have to prepare, the better your advantage in terms of spies, assassins, saboteurs, allies, etc. Make sure you have the information advantage before you initiate, and confidence in your preparations. Play it right, and those hundreds will never show up at all. Killing the dragons You probably cannot kill 300 dragons at once - one will be enough of a challenge. Every living being needs to sleep, eat, and drink. Assume they are wise enough to sleep together with a watch posted - try to poison supplies instead. In open combat, divide their forces, take advantage of stable shelter, and outnumber them with troops with long spears, chains, nets, and ranged weaponry. Foul their wings at any opportunity - "a downed dragon is a dead dragon". Additionally, I recall that they need to be airborne to teleport away. Prefer ambushes and asymmetrical warfare as much as possible over open combat. By and large this will be better answered in a more general question about low/no-magic medieval tech level anti-dragon tactics in the battlefield, as their unique abilities will not make a huge difference here. Insufficient preparation A good ruler will sacrifice themselves for their people, and revenge is a dish best served cold. If your chance of success is too low, pass on secretly as much of your plans as you can to your children or others whom you trust, then assume full responsibility and try to prick their honor to spare your people. Do not attack on a small chance unless death is inevitable; this would give them the excuse to exterminate a future source of trouble. Try to die a martyr - this will hurt them more in the long run than anything else you can do on short notice. ("My father had a noble heart, and all we have is the word of those time travelling tyrants that he might eventually oppose them. Will you stand with us to avenge his death?"). [Answer] To prevent teleporting, as has already been pointed out, you make your streets and buildings narrow and twisted. Put separator walls in the middle of large rooms, so that a dragon the teleports in, can't move and can be killed with ease. Do the same for wide streets; a long narrow wall dividing the street along its length. Wagons and carriages will need to be banned within the city, only handbarrows may be allowed. So you've stopped dragons teleporting. That leaves a flying, fire-breathing mass of muscle out to get you. What are the limits? How far can they fly? What is the range of their fire? Is it a continuous stream, a fireball, or can it use both? What loads can it carry? How much does it need to eat? WHAT does it eat? Make your ballistae with longer range than their breath. Leave no dragon food within a single flight range of your town-change your eating habits if you must. Make narrow holes for your ballistae, put them in reinforced stone rooms and protect them with spikes on the outer wall. Use light bolts to damage their wings at long range, instead of heavy bolts to target their bodies. Minimise use of wood to prevent fire spreading. Find what dragons hate or are allergic to and have plenty of it close at hand. There are plenty of ways to deal with the problem but first we need to clarify exactly what the problem is. A single attack run of 300 dragons can be beaten back with significant loss on both sides, but will the dragons persist? Will they learn to avoid you next time? [Answer] I can think of three ways to defend a place against teleporting dragons. One way to to disguise the actual location to look like another location So when the a dragon wants to go to actual location, the dragon would be sent to another location. The Second way would to fog up the scenery. Although not very practical, it would make sure that the dragon cannot image the place. Finally and what I think is the best solution, drug them. Proactively mickey the dragons so they cannot think straight. I really do not think making things smaller would help at all. A great defense would be practical one making things smaller would just make things a nuisance to the people using the tighter locations. ]
[Question] [ Let's take an imaginary world where, without its inhabitants realizing it, everything is physically influenced by what people thinks, by what they believe, by how they see the world. Of course the opinion of a single person has no effect, but if a lot of people think that something is true, in the place where they live that thing becomes in fact true. For simple things like legends becoming reality I don't think there are consistency problems. But what happens if discrimination against a small group of people becomes widespread? Let's take for example an emperor of a large country that decides to use a small neighboring country as scapegoat and sends bards to spread lies about them through the entire empire, accusing them of any possible evil. The majority of the inhabitants of the empire will believe such lies and start to discriminate and hate the people of the neighboring country. But what will happen to the discriminated people if their number is very inferior to the inhabitants of the empire? Is there a way for them to be able to mantain their identity, their individuality? Or will they start to gradually become exactly like the prejudice about them, like the imaginary enemy that the emperor accuses them to be? And how this gradual change can affect them without them noticing? A sudden mass brainwashing sounds a bit stupid, so I'd like to define in a realistic way how such a process could work from the psychological point of view of the victims. [Answer] I like the concept of it, but indeed, it could just spin completely off-trails. Limits I think time is your best ally. Indeed, changes could occur but in the time scale of years/decades/centuries. YMMV. Let me illustrate it with some examples. * Some guy turn up with ideas about brand-new crazy-cool divinity. That guy's pretty good and get some followers, because of good philosophy, maybe a few tricks, sound rhetoric, etc. Then it gathers some momentum, and after a roughly a century, a few thousands people are following the religion, even after the guy's death. Then imperceptibly, the divinity IS created. And as more and more people believe in Her, she gets more and more power or capability to actually do something/think on her own and finally interact with the world. * Your evil Emperor comes up with his dislike for a minority. Runs his propaganda and so on. Then two possibilities. He finally trip them of power (as Cort Amon mentioned in the comments, look at some examples of how Jews were treated throughout the middle ages), and then got bored and stop his propaganda. And the hatred fades away after a decade. Then nothing happened to that minority. At least nothing remotely noticeable. * Let's say, on the contrary, that his hatred was a pure racism and not an opportunistic economic/political manoeuvre (it probably makes him a worst politician then), and keeps on blaming them for all the troubles in the world. The population really follow him, and even worse, some of that minority start to believe in it. Generation after generations, the hatred continues and that population becomes really as bad and mean as they were thought to be. But this is a very crucial point: they are affected by the average thought of ALL who know them. You might say it like this it is their will against the Empire inhabitants will, and pondered by the neighbouring countries inhabitants: do they see them equally bad? Are they neutral? Are they positive? In a way, the same goes with the Goddess: if some people are convinced that our prophet was just a crackpot, and that no-such Goddess exist, it goes against the effective apparition of the Goddess. In a word, the effect occurs only if all people related to that thing think, in average, in the same direction. Another constraint that can make it interesting is the "strength" of the belief. If people merely believe in something without much interest, the effect will differ from if people are fully devoted and numerous. You could have it affect the time for the effect to appear, or how much of the effect actually appears. As an illustration, if a few tens of people believe in some god in a small region, but don't obsess about it, then maybe the "god"'s power that will appear with time will be just a bit of luck, better weather for the farming, less sicknesses, etc. But if there are hundreds of thousands, with some that dedicate their full life to the god, then it could materialise into a physical being (given enough time). Effects on Society Just a few thoughts on how would that impact your societies, I can see a few points that need consideration. * Gods will physically exists, making clergies very powerful, * Magic will probably exist as well (at least in some form), * People within Nations will tend to be good-natured: typically when you want to bind with your neighbours to form a society, you emphasize how similar you are, how good you are, how strong you are together, etc. Those things will BECOME true. If people are convinced that their politicians are good, that will be true, given enough time. * Due to the averaging and the slow changes, it is unnoticeable by the people and no-one effectively control the climate. That penultimate point probably need much more thinking, but it depends on plenty of other parameters (tech./evolution level, world, population, etc.) that would make it beyond the scope of that answer. --- TL;DR Changes occur only when in average all the concerned population think one way, for enough time. [Answer] I would suggest that in this world you should differentiate free will. Anything with free will generates belief, but that belief only affects things without free will. In other words beliefs about the weather, physical laws, even magic...they would all work. However if you believe that certain people are smarter/stronger/weaker/dumber then that has no effect at all. Defining the threshold for free will could be interesting, an obvious dividing point is intelligence but you could consider including animals or not including them. Magical beasts again you could decide whether they are included or not, and so on. [Answer] Huh, in this world kings are genuinely going to look like people chosen by god or will look like gods themselves. For example Kim Jong-il would actually be able to control the weather. If millions of people believe that Bill Gates is super-smart he'd get even smarter. There's going to be one hell of a feedback loop with personality cults. It will seem natural that fame and power begets even more greatness. Imagine if upon becoming pope a person actually gained the ability to do miracles? One day a normal bishop, the next magical powers. "Immortal" leaders might actually become immortal. Exceptionalism is also going to become self confirming. When a hundred million people genuinely believe they're the best at everything they're going to end up constantly faced with confirmation of their beliefs which will in turn strengthen their beliefs. Strength of conviction might make a difference. If I believe I'm a good person but I believe it strongly and it's really important to me do I cancel out 100 people who believe me evil or do I start feeling the urge to kick puppies? How about distance? if the effect weakens with distance the beliefs of a whole neighbourhood might overwhelm the single migrant living there and turn him into a walking stereotype while a community 100 miles away might be able to hold off the onslaught with only a little belief in themselves. Science is going to look different too. Magic, gods and demons will verifiably exist and may even be known to change over time and there's likely to be an area of study related to them but rationalism in all it's forms is likely to have a lesser following in such a world. [Answer] I would assume the following, given your scenario: * free will exists as much as in reality, by default * but the urges of people can be controlled by this magic. As people are influenced a lot by their urges this could easily cause such a minority to have a higher rate of thieves, or to have more people with anger problems, etc. * if people believe that something doesn't have free will, then it will stop having free will. But given for example prejudices against Jews in Drittes Reich: I don't think Jews would have lost their free will. They were portrayed as stupid sometimes, but at the same time as evil and plotting. Those two things would have more or less cancelled each other out (but for the evil part), leaving their intelligence and free will untouched. They would have become more ruthless and probably more powerful because people were led to believe they were dangerous. Quite possibly this would have helped them to defend themselves (maybe even overthrowing the Nazis, changing the public opinion to a more sensible one [by force] and then reverting back to their own selves after public perception of Jews becomes less negative). * public opinion would become the most important power factor in politics and the like, even in monarchies: If the people thinks the monarch is ill, he'll become ill, so his opponents might spread rumors. If the people think the monarch is evil then he will become so. If the monarch uses propaganda to make the people believe he is good, then he'll become good. [Answer] ## Limit the Physical Influence by Distance You could make the physical influence decay with distance. * If a town believes that their hotel is haunted, then it becomes haunted. * If the town believes a town on the other side of the world is haunted, it has no effect. * If the town believes the town next door is haunted, then the town next door is only a little bit haunted. This would have the effect of making regions slowly more homogenous over time. If you're a minority in a town that hates you, your people will slowly be erased because of your disadvantages; but the same minority could prosper on the other side of the world where different groups suffer. The world would become polarized. You could even have your North Pole and South Pole correspond to political regions. Symbolism! You could also... ## Use a Self-Defeating Prejudice Suppose the majority of a town are X, and X generally believe that "Those dirty, rotten Y screw like rabbits." Over time, the Y would become the majority, and discriminate against the X. The Y would no longer be bound by the stereotypes about them, and they could stop reproducing so much and slowly become the minority again. At the same time, the Y will be undoing other negative stereotypes about themselves just by believing that they are inherently good people. As long as the belief that high reproductivity is objectionable (based on a deep concern about over-population) outweighs any belief that X or Y are inherently inferior, the majority will reject the breeding stereotype about themselves, and the X and Y populations (and personality traits) will oscillate and co-exist. [Answer] I think it would depend partly on if the person/people who are the focus of the reality altering forces have to accept them for them to truly change them. The funny thing this is fairly close to the reality we live in today. Both "you can be what you believe you can become", and "you can only be what other people allow you to become". Both statements have a lot of truth in them. So while in one country, Elves are looked on as fancy Orcs, another area they might be thought of as near gods. If one moves to/through the country where they are despised they will be observed to be such by the locals, and if they spend enough time there might begin to believe it. Traveling through the country where they are held in high esteem likewise, they would be observed as wonderful people and praised. In both cases they are themselves until they start to believe along with the others. ]
[Question] [ I want to build a world populated by humans descended from colonists from Earth who have traveled a long distance and time to arrive (say, 80 years.) They come to this new Earth-like planet in dozens of different ships from different parts of Earth, but they all took more or less the same time to travel the distance. What I'm wondering is what kinds of changes human society might undergo if it's confined in a transport ship for such a long time that the generations that remember Earth die off, and that generations that only know life on a confined ship traveling through space colonize said planet. Here are two ideas I had: * Hedonism. Maybe this one is a little obvious, but traveling through space for decades, people would get bored. I'm also assuming here that the ships launched from the parts of Earth that were already relatively well off, and that the prospective colonists were people who had the means to escape a potentially disastrous situation on Earth. In the course of traveling to the new world, and knowing they wouldn't make it themselves, I imagine many of the first members of these colonist ships would indulge all kinds of hedonism. Since the whole point of the trip is transplanting humanity onto a new Earth, most of the inhabitants of these ships would be reasonably cared for and presumably encouraged to breed. The resulting system of values would probably be pretty different the one we follow on Earth today. * Relative loss of privacy. Assuming a trip to a habitable planet would take a long time, the guys in charge would probably want to make sure conditions in the transport ship remained stable (i.e. people wouldn't be flipping out and killing each other) long enough that humanity would make it to the new Earth to settle it. I imagine this would involve a loss of privacy as a result of a perceived need for more surveillance and security. What do you think? I'm not interested in the technical aspects of the question, just the probable effects on a society that's firmly established on a new Earth-like planet. [Answer] * Conformity. There was an enormous effort to raise somebody on a generation ship, not just in time but also in limited ressources. Every child must contribute to the mission success, and that means every child must be educated to the best of the ability of the entire crew. * The Mission. It is unlikely that they mission is to establish a two-way trade loop. What does that leave? Preservation of the culture of the original crew. "You are the last (or backup) representatives of our culture. Preserve the ideology/the faith/the language/the dynasty/the only proper way to brew beer..." This clashes with Genetics, below, once they're dirtside. * Patience. They have to deal with the same faces, day after day. Even if they exasperate each other. Accept the quirks of the other guy, and he accepts yours. A blowup or clash between personalities could be disastrous. * Respect for Privacy. If you have only a cubicle to call your own, others have to leave you that little space. * Genetics. They had a limited gene pool. A date must be cleared with the medical department first, never mind the parents. Many of those would work well in the newly settled world, unless it is extremely earthlike. [Answer] Behavioral Changes. Since these humans will no longer be on earth and in a confined ship, their will be a significant behavioral change. Their worries will shift from college fees, salaries, wars and luxuries to only survival. Their only worry would be to reach the destination planet safely. Physical Changes. Since they won't have to do any more hard work or labor, their will be physical changes as well. Luxuries will replace the hard work and they will grow fat over the time with weak bones. This will be the time for the human beings to go through evolution once again and by the time they reach the planet, there will be a lot of physical changes in them. Thinking Changes. I am sure that there will be a huge difference in the thinking pattern of humans. There will not be any discoveries,inventions or anything like that. They will only learn to obey. They will no longer have the same thoughts as we have now. Their thinking patterns will be limited to their environment and that will only be the ship.Soon, they will forget most of the things about earth and their thinking patterns will resemble as those of programmed machines. To think of certain things. Privacy Issues. As for the privacy issues, Yes, you are right. But, these issues won't trouble anyone after a certain time when they get used to it. Even now, privacy means different things to different people around the world. You might consider "knocking on the door" before your parents enter into your room as privacy but to me (a Pakistani Kid), that means nothing. They can come in whenever they want without knocking. Same will be the case on the ship. People will forget the true meanings of privacy and they will not be bothered by someone keeping an eye on them via security camera or other means. Ship to Ship differences. This is something I am not sure about but I think the changes will vary from ship to ship. Every ship will have a different environment. For example, at the end of the ride, people from one ship might not even know what English language is because their ship was crowded with Italian people speaking Italian. People on one ship might have a war in the ship and by the time they land, others will find nothing but dead skeletons. One ship might have one colored species by the end and the other ship might have another color. It will all depend on the surrounding environment. [Answer] I have to disagree on the Hedonism thing. First of all you say they are well off. But what does this mean? Their money became worthless with the economic collapse that came with everyone finding out the world was coming to an end. This could work if they were approached by a private company of space enthusiasts or something who secretly let them know in advance, in the hope that they would fund these great spacecraft - then in exchange for funding them they got passage. But even that goes out the window the moment they set foot on the spacecraft. Far from hedonism, they are now working hard with highly limited resources. Take a look at the moon landing for instance, tens of thousands of people working with the biggest, most expensive and most energy-consuming machinery ever built just to get three guys in a tiny module to the moon and back. Granted technology has moved on by the time your setting comes around, but I still think the vast majority of resources and work will be in just keeping each spacecraft going, not to mention society. People are going to have to become multi-skilled in order to provide all the needs of the mini-society with a limited pool of services, and be constantly working. The fact that they were well off on Earth will mean nothing. Their personal masseuses are no longer going to be interested in their Earth euros. Unless you consider hedonism something like an extra lemon with your daily salted biscuit and rum... [Answer] Considering the high cost of propelling mass to another star system, there would be nothing extra being carried. Period. The ship would carry the minimum population needed to guarantee the success of the mission. And they would have the minimum facilities and supplies needed to guarantee the success of the mission. While there would have to be considerable margin over what is actually needed to guarantee success in unknown circumstances with no chance of additional support, apart maybe from moral support, from home, those people and resources would be a reserve, not something useless or available for luxury. Everyone and everything on the ship would have a proper place and a proper purpose, a part to play in the mission plan. While there would be redundancy, possibly a high degree of it, it would be distributed equally, there would be no redundant people or supplies. This would guarantee a smoother transition, if portion of resources is lost and when the ship arrives at its destination and expansion of resources and population becomes possible and necessary for the mission. And yes people would be considered resources, not because people are not valued, but because even supplies such as air and water would be as irreplaceable as we'd like to think we think people to be. Waste and carelessness would be anathema to these people. Every resource, human or otherwise, would be utilized in the most efficient available way. This might not be the one most efficient for the individual resource, rather effort would be made to see the big picture. The effects on other resources would considered, as well as the resources used on planning. An entire population with a shared purpose that is provably true, precisely defined, and concretely present every moment for generations would be quite different from anything we are familiar with. Elite military units maybe get closest, but they have life before, outside, and after the mission. The shipfolk would have no outside to go, only the first generation would have life before, and only the last would have life after. Some religious fanatics may have that kind of pervasiveness, but they have the issues of faith to deal with. The shipfolk would know what their purpose is with precision and certainty that even the most dogmatic fanatic would have to fake. The shipfolk would have no need to convince either themselves or each other of what they are doing and why, everybody present could just read the large scale detail from the mission plan whenever they want. And while there would be uncertainty and even disputes about the details, resolving such issues would itself be part of the mission plan with resources allocated and procedures established to prevent any serious risk to the mission plan. Unless this failed, in which case there would be a real chance of everyone dying, the shipfolk might end up having no real concept of unresolved personal conflict and no concept of personal grudges, or decisions motivated by personal reasons. They'd still be human and feel all the personal stuff and act on it, but it would have no space to grow into anything significant. It would be just something to compensate for while doing business in a quiet efficient manner. Pressure to be efficient and to have active redundancy would presumably make for relatively relaxed pace of work. Fast and efficient, but never rushed, apart from drills maybe. Combined with everything having a proper, well defined, place, I'd assume people would end up being polite, respectful, even formal, but in a direct and relaxed manner. Formalities would be observed, but little time would be wasted on them and a failure to observe formalities would be noted, pointed out, and forgotten. Protocols exist to make work smoother, they do not have any value of their own. Still there would be considerable social pressure to act proper and given the "from birth" nature of the shipfolk society, it would be very deeply ingrained on people. Any lapses would be rare signs of stress or slightly more common attempts at humor and would be understood as such. Fortunately, the almost compulsive pragmatism of a society that actually has a clear specific purpose for everything would guarantee that acting proper would not be difficult enough to cause stress and distract people from work. With a relatively high degree of planned redundancy and presumably high degree of automation, the routine work would only be a relatively small part of the lives. Much time would be spent in training since it would be much easier to have high degree of redundancy if everyone is competent in several different duties. People would also change duties relatively often, to keep that competence fresh and avoid boredom. Drills would be frequent. The shipfolk society does not have much space for competition, so drill performance would the major outlet for competitive pressures and personal initiative and ambition. While periods for relaxation and leisure would be scheduled, drills and training might also be the dominant form of entertainment. As such considerable effort would be spent on making the drills varied and interesting. The people would also have specific training for efficient relaxation, probably meditation of some sort, which would add by contamination a contemplative and spiritual side to the culture. The disciplined lifestyle would support this by making the shipfolk naturally relate well to monastic traditions. If you add together the need to minimize the population on the ship and maximize the genetic diversity at destination, you end up with the ship carrying huge sperm banks containing genetic diversity equal to fairly large nation. Unless artificial wombs have been developed, the ship population should then be entirely female to allow for rapid population growth at the destination. During the trip the population would be stable. Births would equal deaths. Families would presumably be built around mothers, daughters and sisters. [Answer] Likely everyone will have responsibilities that will need to be taken care of during the voyage. If you have too many people that are just 'passengers' with no responsibilities, then you are definitely going to get a lot of hedonistic behaviors, if for no other reason than shear boredom. Because of the limited gene pool, likely there will need to be a bit of genetic planning while on the trip, since it is unlikely they can expand their population by much until they are getting close just for the logistical reasons. So, one path I could see would be a Victorian type suppression. Everyone has a 'proper' public persona, with a large counter culture of reasonably hedonistic pursuits behind closed doors. Over that much time, those in charge could change quite dramatically, though some kind of tyrant is certainly a possibility. Even to the point that when they arrive, the tyrant won't want to give up their power and keep everyone on the ship, maybe making up a reason that they 'can't' go down to the surface. [Answer] Consider time to learn new habits and time to forget old habits/knowledge. Time to Forget: Most people on Earth know their grandparents fairly well. Grandparents help out when the parents try to balance work and family and they teach how to care for an infant. As a simplification, assume that each couple has two children at age 30, that everybody lives to the age of 75, and that the entire crew are 30 years or 60 years at takeoff. Year 0: Takeoff. Babies born in this year have no memory of Earth. They are raised by earthborn, possibly without their biological grandparents but there will be elders around. Year 30: The second-gen babies are born. They are raised by first-gen parents, but their grandparents were born on Earth. Year 45: Many/most earthborn are dead. Year 60: The third-gen babies are born. Year 90: The fourth-gen babies are born. Year 105: Many/most second-generation shipborn are dead. They are the last people who were directly influenced by earthborn caregivers. Time to Learn: New habits can form much more quickly if there are environmental pressures (cf @VilleNiemi). Recall how mobile phones and the internet changed communications culture in just 20 years. There used to be a time when everybody watched the same handful of news channels. Summarized, you need well over 100 years to make Earth a dim, forgotten memory. [Answer] I prefer to work backwards and see how different it would be for people to arrive to a planet after a lifetime in a ship. I personally think the little things are the ones that collectively will have the largest effect. Depending on how the ship is actually set up, I would see describing the little things as the most interesting. Here's just a few: * Seeing grass, bushes, and trees for the first time (if the planet has those anyway) * Seeing a sky, with a sun, for the first time, For some, sky might be wonderful but maybe others would be afraid with no stars watching over them. * Being able to see in one direction for so far. (I would expect some, if not all, to feel vulnerable in the large open space of "outside") * Feeling dirt beneath your feet * Feeling actual wind * Life on the planet would seem so wasteful resource-wise. (I just go pee behind that bush? who's going to recycle it?) * Ability to "get lost" and not have guidance to get back might be a hard lesson for some * Ability to be alone might be new. * If they were always being watched before, not being watched may make people feel extremely unsafe. * Gravity may or may not be different. I would want similar simulated gravity on the ship to what's expected for the planet if it were me. * If the ship always had certain noises - the pumping of water, the sound of conversation, the "whir" of machinery - the ambient noises of the planet will seem very different. (could seem louder, or extremely quiet, depending on wildlife and how loud the ship was) Altogether, I think these little things would have interesting societal implications. Do they continue trying to recycle aggressively or do they enjoy their new freedom and waste? Do they prefer the night because the stars are familiar to them? Do they experience the new sensations of sunlight and wind and apply them to their beliefs? Do they create very small houses, disliking the feel of wasted space? Do they trust machinery and technology over nature, maybe even creating parks out of metals and plastics with little natural elements? [Answer] Weird Social Stratification Over many generations, new and weird social groups might emerge and gain prominence. Maybe the Hydroponics folks begin to enjoy increased status because of their ability to provide supplies and over time this lead to them being regarded more highly then other service groups. This could even lead to cult-like behavior. Science Becomes Religion Taught only the "how" and not the why, many tasks might be performed by rote, and attain a religious or traditional stature. Things might be done a way not because they need to but because that's how it was passed down. This could cause a crisis if something breaks and no one knows how to deal with it. Forgotten Password(s) leads to Disaster If command/teaching staff forgot vital passwords, or worse how to reset them, there could be a situation where the information necessary for later stages of the mission is missing or partially unavailable. Cave Adaptation To steal from Dwarf Fortress, after generations of living inside the spaceship, living out side could become perilously terrifying for many, and an exciting, rebellious draw for others. The mere sight of the sky (especially if it is markedly different from simulations presented by the generation ship) could cause Nausea and Panic. Put it all together, and maybe after the semi-crash landing, the colonists almost all choose to keep living in the ship, only sending out those daring few weirdos who are excited by the Ravening Open Sky and uncontrolled Air Conditioning (wind) and occasional sprinkler malfunctions (rain) of the new planet, to hunt for supplies. [Answer] I think the result would likely be very similar to the society described in Asimov's The Caves of Steel. There, humanity lives in very large, sealed cities and never voluntarily leaves them. Over centuries, severe agoraphobia developed to the point where most people were physically unable to leave the cities (and considered the idea that one would want to to be insane. Due to the overcrowding in the cities, privacy was both very rare and very zealously guarded. [Answer] Any colony mission would be designed and prepared with all of humanity's combined thought on the topic, don't go assuming they go off into the dark as ignorants with no preparation and a devil may care attitude. Particularly the regime on any mission would needs-be enforce an awareness of person responsibility. Resources and skills are finite, people who cause more wear and tear and use more than necessary just wouldn't exist, the first generation because they were heavily screened, the second because they can see what just a fraction of the time flight-time has done to the environment they live in. People imagine the generations would 'lose touch' with their roots, but I think that'd be much less likely in such a controlled and limited environment. Normal people 'lose touch' with past generations because the environment changes.. because the paradigm they live under has shifted, because all of a thousand variables in their lives vie for attention. Shipboard life would be totally different in these and other relevant areas. Knowing that you're going to settle somewhere and that settling a world involves hard work, any regime will seek to maintain an environment that encourages and rewards learning and hard work and not just hope and pray that whoever is around when the ship arrives is up to the job. They won't rely on chance..they're giving their lives for this venture. Put simply, society will not be allowed to evolve naturally. 'Hedonism' would be absolutely encouraged, depending upon what one means by hedonism anyway. On board a space ship sensory deprivation is an ongoing thing, there's no wind, no birds calling in the morning, no one of a million different sensory inputs that we barely (or don't) notice on a day to day basis.. and as such people would be encouraged to fill their time with as much activity of any sort possible that isn't destructive...the easiest way to have people not descend into ennui is to make available things that they enjoy..a regime would make use of any tool available to stop the society descending into uselessness, madness and grief. If you were really planning to do something like this, it'd probably be sensible to setup camps of people generations before (when you start building your ship) in closed environments to see how different systems work out. ]
[Question] [ Stories with shrinking never seen to take into account the [Square-Cube law](http://tvtropes.org/pmwiki/pmwiki.php/Main/SquareCubeLaw). I'm trying to consider what it would take to do a story like this that actually fully addresses the square cube law. I know most of the advantages humans would gain, such as: 1) being proportionally stronger, able to lift far more then 50 times their weight and survive drops from, quite possibly, any height thanks to terminal velocity 2) being much stronger then any insects or bugs of the same size they run into, thanks to having a body designed to have far more muscle and strength then creatures adapted to take advantage of the square-cube law. However, I'm wondering what disadvantages they would face. For instance, I assume they would be quite cold, perhaps even dangerously so, since they can't rely on producing enough internal body heat? What similar down sides, even lethal ones, would someone face being scaled down to that size? For that matter what other advantages or otherwise odd effects would they experience? To be clear I'm only interested in effects caused by the square-cube law. I can anticipate all the standard threats that come from being afraid of being stepped on etc (then again, would we be in danger of being stepped on? we may be able to survive that...) [Answer] As mentioned, they will quickly freeze to death due to inability to regulate body temperature (which is the reason why small homeotherms such as the [shrew](http://en.wikipedia.org/wiki/Common_shrew) and [hummingbird](http://dx.doi.org/10.1007%2Fbf01920240) need to consume massive amounts of food relative to body mass). Additionally, problems such as molecular size will come into play. Since the DNA/proteins of an organism are already molecular in size, shrinking a human wholesale would require shrinking of the molecules as well. This will make the enzymes used in digestion unable to break down any normal food, as their active sites are too small for the normal-sized food molecules such as starches and proteins. The same will occur for respiration, where oxygen/food molecules will no longer be able to diffuse across cell membranes due to their large size with respect to the membranes. Therefore, this results in [Required Secondary Powers](http://tvtropes.org/pmwiki/pmwiki.php/Main/RequiredSecondaryPowers) for the shrunk human to have a "shrinking field" maintained around himself/herself to shrink and enlarge molecules passing through that field, otherwise no molecular exchange can occur with the environment. [Answer] The smallest mammal is a [shrew](http://www.livescience.com/33049-smallest-mammals.html) and the adults are about 2 inches long and weigh less than a dime. The [Bee hummingbird](http://en.wikipedia.org/wiki/Bee_hummingbird) is about 2 inches and 1.6 grams in weight. These are tiny animals and yet they are still significantly larger than (most) ants. So the next question is what size ant are you looking to compare to? The largest ants are over ([Bullet Ant](http://en.wikipedia.org/wiki/Paraponera_clavata)) can grow up to 1.2 inches, and the Queen ant of some species can be a full 2 inches in size. So assuming you are talking about an average sized ant in an American back yard (5mm?), I would say the 2 primary reasons for the shrew's and hummingbird's minimum size are: 1. body temperature: REALLY hard to keep it high. In the fall hummingbirds can die of starvation/hypothermia if they didn't get enough to eat during the day. 2. competition: everything else that size is already armored and has vicious weapons. [Answer] If you shrink the size and characteristics of the fundamental particles (protons, electrons, etc.), which requires changing some fundamental constants of the universe, then you won't be able to take in any oxygen (as pointed out in DS9's [One Little Ship](http://en.memory-alpha.org/wiki/One_Little_Ship_%28episode%29)). Simply put, the haemoglobin in your blood accepts O2 of a certain size, and if that size changes than it won't. Actually the oxygen probably won't even make it to the haemoglobin because being so large it will have problems diffusing through any membranes or into liquid. If you try remove "extra" molecules (e.g. trying to scale down a Lego model by just replicating everything in proportion), other biophysical problems will occur: * Your nervous system will immediately stop working as it will be overcome with noise. The connections between neurons (axons) has evolved to be about as thin as they can be (200-300 nm), and if they get much smaller (<75 nm, or about a 4x reduction in size), randomness in the opening/closing of some of the voltage-sensitive proteins is sufficient to cause the entire cell to fire. See Faisal, et. al. (2005) [Ion-Channel Noise Places Limits on the Miniaturization of the Brain’s Wiring](http://www.sciencedirect.com/science/article/pii/S0960982205005713), Current Biology + Actually, if you get much smaller (20x reduction in size), the lipid bilayer will take up all the space in the axons, leaving no room for anything else. At that point there will be no structural integrity and the axons will disintegrate. * While cells seem 'huge' compared to molecules, things on a cellular scale are curious in that they bridge the realm of countable (individually enumerating molecules) and uncountable (measuring things with molar concentration). As March pointed out, you can't stoichiometrically reduce the amount of chromosomes in your cells because you already have one, and subdividing that would be a Very Bad Thing™. It doesn't stop there, however. Many proteins (orders of magnitude smaller in size than the DNA) and especially mRNAs are actually present at a very low concentration or "copy number", some even on the order of 1-2. Significantly changing the size of the cell while keeping some of these individual proteins around will wildly alter the concentration and kinetics which will cause massive misregulation. (Couldn't find as good of a paper for this...[this one](http://rajlab.seas.upenn.edu/pdfs/Raj_AvO_ann_rev_biophys.pdf) is a decent overview, [this one](http://www.nature.com/nature/journal/v440/n7082/full/nature04599.html) is paywalled, talks about counting individual proteins) Outside my area of expertise, I'm not sure if it's theoretically possible, or what would even happen if you were to, "compress" space locally around a shrunken person. This is to say, matter crossing some threshold was magically shrunk (or appeared to shrink) to an outside observer. It would be like some tightly regulated black hole. It seems like you'd just have problems with insufficient (but breathable) air, which would actually be good from the thermal point-of-view as you won't heat up or cool off as quickly. I think you'd still need some sort of pressure suit and supplementary air though (or method to pressurize what little is there). [Answer] They're also going to be unable to see, since their eyes are sized and designed for more wave input. There's a reason insects have compound eyes. I could look up the math / physics... but the gist is, that the pupil needs to be a certain size to let thru wavelengths (iirc). Edit: Squeaky voice, at very low volume: Their speaking pitch will be 3,400 cycles a second (vs. 200 cycles a second) - (300x reduction in size roughly - square root == 17). And they'll only able to generate 1/17th (or less, not sure of the math - diaphragm is basically flat) of the volume of compressed air from smaller lungs. Hearing reduction: eardrum reduction, means the lowest frequency they can hear is 340 cycles a second (vs 20 cycles a second) -ie: can't hear a normal human speak. The eardrum is unable to respond linearly to density variations near the source of sound, and the ability to distinguish differing sounds is degraded. Blurry vision: 650-400 nm for visible light. Normal humans in normal light == 5mm in diameter (or a 10Kx larger hole). Divide by 300, pupil is now only 30x larger than the light waves. Scattering off the edges results in interference pattern, called diffraction - which is most noticeable when the dimensions of the object scattering the wave are comparable to the wavelength. Which is why insects have lousy vision, and different types of eyes (which adjust for diffraction effects). Or; No Ho, there would be noticeable diffraction ;) ]
[Question] [ This is somewhat of a follow-up question to [my ammonia-based world question.](https://worldbuilding.stackexchange.com/q/3090/98) I've found out that the melting point of ammonia is [at 25°C at a pressure of about 1 MPa](https://en.wikipedia.org/wiki/Ammonia_%28data_page%29) (about 10 times the atmospheric pressure on earth). I think that should be definitely warm enough for life. However, could higher land-based life actually exist on a planet with such high pressure, especially considering the higher gravitation that would be needed to create such a high pressure? [Answer] Actually you can create high pressures without needing extraordinarily high gravity. Venus for example has 92 times our atmospheric pressure (9 times what you need!) but slightly less than earth's gravity. We know that life can exist in high pressure environments (they just keep the same internal as external pressures), so the simple answer is yes. You could have a 1G planet with high pressure and reasonable temperatures and life could in theory survive those conditions. This would have some interesting effects as well, for example flight would be much easier in high pressure but standard gravity environments. [Answer] ### Plausibility To answer your implied question about the possibility of this high pressure: Jupiter's surface has a pressure of [100 times](http://www.universetoday.com/22719/surface-of-jupiter/) the Earth's. Cosmically, pressures this high are trivial: think of "small" cosmic bodies like the Sun, which has a pressure around 50 times that of Jupiter. Scaled up, the pressures become unimaginably high. ### Life Human bone has a compressive strength of [around 170 MPa](http://en.wikipedia.org/wiki/Bone#Mechanical_properties), meaning it would still be able to hold the human frame up at 1 MPa pressure. However, human body temperature is 37 degrees Celsius. High or low ambient temperatures can cause hyperthermia or hypothermia respectively, the former more lethal faster (hyperthermia can kill at 42C, compared to hypothermia at 27C). [Pressure increases temperature](http://www.passmyexams.co.uk/GCSE/physics/pressure-temperature-relationship-of-gas-pressure-law.html), so a planet with a higher pressure would initially at least have a higher temperature and a higher chance of causing hyperthermia. The planet could cool down when the pressure stabilises though, making it once again suitable for life, and of course planets further away from their stars are cooler. ### Summary It depends. If the ambient conditions are right, life could survive such a planet. But, it would need the prerequisites for life, such as water, and the current perception is that any habitable planet must be in the [Goldilocks zone](http://en.wikipedia.org/wiki/Circumstellar_habitable_zone) of its star. [Answer] Life could definitely exist at 10 atmospheres of pressure because humans can live at that pressure. A SCUBA diver feels 10 atmospheres of pressure at a depth of ~100 meters, and they do just fine at that depth. The only problems they experience have to do with the changing pressure when they come back up. So if typical humans can survive 10 atmospheres of pressure, I think it's a safe bet that life could evolve and flourish on your planet. [Answer] Pressure has little difference in effect of land vs. sea creatures. The pressure pushes all around, so its not like the pressure is crushing them to the ground. Remember, until science told you there was air around you, you didn't even notice it! In the Mariana's trench, they have found sea life at 108MPa, so there's proof it can work. The bigger issue would be that higher pressures would increase the rate of chemical reactions in the atmosphere. However, that is not a part of land life, just life in general. [Answer] As a scuba diver I know that pressure does not squeeze a diver. Only body parts that are not luquid or solid are affected by the pressure, i.e. parts containing gas (mainly the lung). But if this gas has the same pressure as the outside, effectively no force is applied to the body as well. However, when diving at 90 meters (i.e. at a pressure of 1 MPa), a special breathing gas is needed. If air was used (21 % O₂), the partial pressure of the oxygen would be 2.1 bar, which is [toxic](http://en.wikipedia.org/wiki/Oxygen_toxicity) for a human body. This can be circumvented by replacing some of the air with Helium. As already stated in [Mike's answer](https://worldbuilding.stackexchange.com/a/3488/2730), mainly a reduction of the pressure is dangerous for the diver, which would not occur in a constant pressure environment on your planet. Conclusion: I see no problems for life at 1 MPa! ]
[Question] [ On habitable planets, rotational period can be assumed to vary significantly. What are the limits of human adaptation to these different conditions while maintaining a normal sleep schedule? The humans have to stay awake for a clear majority of the day, and take the clear majority of their sleep during the night. [Answer] Studies done on humans removed from the synchronizing effect of solar light exposure show that the circadian rhythm of sleep tends to re-synch around 36 hours. It seems therefore that the human body can tune itself around that duration, even though it has to be seen how the solar exposure or lack thereof will influence it: people living at very high latitudes, experiencing long night/days during the year, do not seem to diverge from the 24 hours cycle. However it must be noted that there are other forcing factors which might influence the sleep/wake cycle. [Answer] For many year the USN submarines used a 18 hour day, 6 hours on watch, 6 hours of sleep and the remaining 6 hours for meals, additional work, and free time. [Answer] How long are we talking about? Evolution is your friend. Plop a bunch of humans onto a planet with a 100-hour day and a 100-hour night and wait 50,000 years and you'll be surprised what they evolve to do. Given enough time, any modification you wish is within suspension-of-disbelief. But the shorter the time span, the less believable it is. Plop those same humans down and wait a month and what you should expect to find is some creative shutters that block every possible photon during the day while our intrepid humans happily sleep 7-10 hours a day. So, the real question is, "given that I want humanity to conform to [insert very specific day/night conditions here], what would be a believable amount of time for humanity to achieve this conformance?" [Answer] As others have pointed out, humans are pretty adaptable in this regard, so the limits will be set by factors other than human biology as such. The lower limit will be on the order of a couple of hours; much less, and the integrity of the planet with regard to centrifugal force comes into question. The upper limit will be on the order of a couple of years; much more, and it's impossible to store food overnight, and everyone will have starved to death by the time morning comes and agriculture is possible again. [Answer] Short Answer: I don't know. Long Answer: Nobody knows exactly. But several other answers have mentioned various factors to consider. And here is something else to consider. If future humans build space habitats they will have control over the periods of light and darek in any "outdoors" parts of the space habitats, and of course they will have artifical lighting for inside their homes and workplaces, etc. So they will have total control over the lengths of days and nights in those space habitats. And if humans build giant arcologies on Earth or other planets, most or all the interiors of those archologies will be illuminated by artificial lighting, so the light levels outdoors will only matter to those who go outside on rare occassions. And the same goes for underground cities on Earth or other planets. But if humans settle on naturally habitable worlds, other planets or moons, or terraform other planets or moons to be habitable for humans, and if those humans decide to live as much outdoors as much of the time as modern humans do, the natural cycles of light and darkness will be important to the colonists whenever they are outdoors, and going outdoors will be something people do several times a day. Thus the colonista - if they choose not to spend all of their time indoors in giant archologies - will have to adjust their cycles of sleeping and waking to the natural cycles on the planet. And most of the answers so far have discussed how well humans could adjust to day night cycles of different lengths than Earth's. But suppoe that human settlers on an alien planet aren't advanced enough to have food synthsizers to produce food out of raw materials and instead have to grow food outdoors. If the humans can't find any native plants they can eat, they will have to plant crops of Earth plants. And those Earth plants will have to be capable of surviving and even thriving on the alien planet, which will mean that the conditions on the settled parts of the planet will have to be similar enough to the conditions on the densely populated parts of Earth for the plants to thrive. So finding out the limits of day and night lengths that major Earth crops can tolerate would be important for answering the question. And of course humans need the right atmosphere to breathe. And of course on Earth the oxygen which he need was produced by plants using photosynthesis. If the planet doesn't have native plants, or plants imported from Earth, to produce oxygen humans won't be able to breathe on the planet and will have to live totally indoors in arcologies with totally sealed environments like moon bases would have. And if they do that they will have artificial lighting indoors and will replicate the day/night cycle of Earth, so the question would be meaningless. Of course it took hundreds of millions or billions of years for photosythetic plants to produce enough oxygen that it accumulated in Earth's atmosphere faster than it combined with minerals and left the atmosphere. If humans bring Earth plants to a planet without oxygen producing plant life, it may take many millions of years longer to build up a breathable atmosphere than the needs of your story allow. So I guess that the humans in your story will explore, crashland, or settle on a planet which has a naturally oxygen rich atmosphere. And maybe the humans would keep an Earth like approximatley 24 hours cycle of light and dark inside their homes, and only go outside when the outside light period coincides with their waking period of light inside. Depending on the mathematical relationships between the two periods, the times when the interior human day and the exterior planetary day can be as common or as rare, as long or as short, as fits the story. See also the discussion of the possible length of day on a habitable planet in Habitable Planets for man, 1964, Stephen H. Dole, pages 58-61. Dole worried that plants might die in the sunless nights if they were too long. <https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf> And also see discussions whether planets which are tidally locked to their stars, having their rotation periods slowed so that one side always faces the star and the other side always faces away from the stars, can be habitable. The day side of the planet might get too hot, and all the water and even air might freeze solid on the bitterly cold night side. But possibly the water and atmosphere might carry enough heat from the Eternal day side to the eternal night side to keep both sides at temperatures suitable for life. But possibly an atmosphere thick enough to carry enough heat from the day side might be so dense it would block starlight from reaching the surface of the planet, making photosynthesis and oxygen production impossible. > > Astronomers for many years ruled out red dwarfs as potential abodes for life. Their small size (from 0.08 to 0.45 solar masses) means that their nuclear reactions proceed exceptionally slowly, and they emit very little light (from 3% of that produced by the Sun to as little as 0.01%). Any planet in orbit around a red dwarf would have to huddle very close to its parent star to attain Earth-like surface temperatures; from 0.3 AU (just inside the orbit of Mercury) for a star like Lacaille 8760, to as little as 0.032 AU for a star like Proxima Centauri[84] (such a world would have a year lasting just 6.3 days). At those distances, the star's gravity would cause tidal locking. One side of the planet would eternally face the star, while the other would always face away from it. The only ways in which potential life could avoid either an inferno or a deep freeze would be if the planet had an atmosphere thick enough to transfer the star's heat from the day side to the night side,... > > > This pessimism has been tempered by research. 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 millibars (0.10 atm), for the star's heat to be effectively carried to the night side.[85] This is well within the levels required for photosynthesis, though water would still remain frozen on the dark side in some of their models. Martin Heath of Greenwich Community College, has shown that seawater, too, could be effectively circulated without freezing solid if the ocean basins were deep enough to allow free flow beneath the night side's ice cap. Further research—including a consideration of the amount of photosynthetically active radiation—suggested that tidally locked planets in red dwarf systems might at least be habitable for higher plants.[86] > > > <https://en.wikipedia.org/wiki/Planetary_habitability#Size> But could alien plants survive in eternal day? I'm sure that there has ben some research in subjecting Earth plants to artifical light for periods longer than normal daylight, and possibly even to constant 24 hours a day light. If that research show that it is easy for Earth plants, adapted to a day-night cycle, to flourish with 24 hours a day illumination, then alien plants adaped to their world should do fine with 24 hours a day light. So that is something to look up. And of course if alien plants could flourish in eternal day, other alien plants should be able to flourish during alien days and nights which last for several Earth hours, Earth days, Earth weeks, Earth months, Earth years, Earth decades, Earth centuries, Earth millennia, etc., so long as the temperatures don't get too hot or too cold. The people would just have to stay inside with artificial cycles of light and dark, and only go outside when their artifical light and waking time coincided with the natural day outside on the planet. [Answer] I don't have hard scientific facts, but these: * The brain needs dreaming for "garbage collecting", typically done when sleeping, so there needs to be some balance between sleeping and being awake. * The eyes need a darkness phase to recover * Skin needs light for vitamin D production * Sunny days can reduce the amount of sleep needed, while the opposite may be true, too * On short term (a few days) one can reduce sleep significantly, but eventually the brain will switch to "emergency shutdown mode" (meaning you can fall asleep while standing, or even while driving a car) * Digestion also needs periods of rest; they say sleeping actually helps loosing weight * Heart and muscles probably also need periods of rest. So (as others said already) the day and night cycle influences the sleep/wake cycle, but the limits are not very flexible. I also think there are no real long-term experiments exploring the limits ]
[Question] [ Sequinoans. This strange race of Amazonians has many unusual traits, but the foremost our scholars are concerned with are their gems. You see, Sequinoans somehow form gems naturally, perfectly smooth and colorful gems that resemble cut opals in shape and a mix of paint swirled together in color. The question is, how do they form these gems? This ability clearly concerns magic, but at the same time, it must have a biological basis to exist.....so how are the Sequinoans making gems like this? More Information: 1. Sequinoans start forming these gems when they start puberty, and until then they have a gem-shaped niche, lined with pink skin, below the collarbone and above the breasts (where a locket would normally hang). When the time comes, this niche will start secreting a strange fluid which wells up and hardens like amber, forming a gem. And if removed (see below), the Sequinoan will form another gem. 2. As our scholars interacted with the Sequinoans, they found that these gems can be painlessly removed by the owner when they feel like gifting one, that they are practically indestructible (taking hits from steel weapons or fallen rocks without even a scratch), and that they glow when a Sequinoan is agitated or exerting a lot of energy, as in combat, as well as when exposed to energy sources like an electric battery. In fact, from what we've seen, touching a gem after it's been exposed to electricity will result in quite the shock! 3. When a Sequinoan is seriously wounded, enough to induce the development of a scar, the wound will produce new skin cells, pale pink ones, which will then form a gem within the scar. Smaller wounds, however, do not form gems and heal as normal-for us, that is. The Best Answer Will..... Take into account the above traits to explain this unusual ability; ie. how Sequinoans create gems with these properties. This answer can include magic but should be based in biology and natural selection, with little to no use of magic at best, much like the answers for [this question](https://worldbuilding.stackexchange.com/questions/226964/how-can-a-bug-larvae-hijack-a-robot/227054#227054). Finally, let me know if changes are needed; I appreciate feedback! Please Note: The question suggested to be a duplicate of mine is about an organism forming a diamond, mine is not. It is about a specific species of humanoids forming a gem with specific properties, but is almost certainly not a diamond. I can certainly understand the confusion, but they are not the same question! [Answer] # Nacre: The closest I can think to your gems is the deposition of mother-of-pearl, or [nacre](https://en.wikipedia.org/wiki/Nacre). I personally and others on this site have discussed this as an alternative to bone for organisms due to it's great strength and flexibility. It is biologically produced and formed of complex layers of aragonite. [![enter image description here](https://i.stack.imgur.com/FNQWN.png)](https://i.stack.imgur.com/FNQWN.png) As for your properties, I already mentioned that it is quite strong. Your "fluid" depositing could simply be a matrix of cells similar to macrophages that fill the hole and gradually calcify into a solid mass of nacre. As a justification, perhaps your species is especially vulnerable to [bacterial endocarditis](https://www.cedars-sinai.org/health-library/diseases-and-conditions/b/bacterial-endocarditis-adult.html), and the gem forms entering adulthood when new growth slows and the heart becomes vulnerable. At a wound site, this tissue could be a highly localized source of natural antibiotic. As the need for this antibiotic lessens over time, it also calcifies, but in the meanwhile, it acts as a local concentration of the antibiotic and also the macrophage-like cells that are likely involved in immune response to bacteria. The intensely striated layers of nacre could potentially account for the other properties of the material. The nacre layers may inadvertently function as a capacitor in your organism if the layers alternate a conductive material. Scientists have used a [nacre-like material](https://cen.acs.org/materials/Tough-self-monitoring-composites-inspired-by-nacre/97/web/2019/10#:%7E:text=The%20evenly%20spaced%20graphene%20membranes,material%20is%20also%20electrically%20conductive.) who's conductivity is increased as the material is stressed, and striking a charged gem consisting of a similarly striated material alternating conductive and non-conductive layers might potentially cause a discharge if the stone somehow became charged up. As for light, the most likely scenario is that the gem becomes coated with [luciferase](https://en.wikipedia.org/wiki/Luciferase), either in the form of enzymes produced during growth or bioluminescent symbiotic bacteria resistant to the antibiotic. The light is produced as a result of stress to communicate this stress to other members of it's species. Release of substrate or chemical signal causes the illumination. Obviously being electrocuted (exposed to electricity) would be a stressor and result in glowing. The glow serves as a warning to others, a signal of need for assistance, or even a way to attract the attention of animals, depending on what the life cycle of your species looks like. [![enter image description here](https://i.stack.imgur.com/j6v8T.png)](https://i.stack.imgur.com/j6v8T.png) [Answer] Normal humans can already produce stones, for example [gallbladder stones](https://sreegastroliverclinic.com/blogs-gastro-%26-liver/f/what-are-gall-bladder-stonesgall-stones) [![gallstones](https://i.stack.imgur.com/MObOl.jpg)](https://i.stack.imgur.com/MObOl.jpg) or [kidney stones](https://www.caresathome.com/blog/kidney-stone) [![kidney stones](https://i.stack.imgur.com/UOAR3.jpg)](https://i.stack.imgur.com/UOAR3.jpg) While they are not exactly shiny and attractive like the Arkerstone, the process for making them is in place. It also happens that [opal](https://en.wikipedia.org/wiki/Opal), a shiny stone, forms by slow deposition from a colloidal silica gel. [![opal](https://i.stack.imgur.com/BFJDJ.jpg)](https://i.stack.imgur.com/BFJDJ.jpg) Add some enzymes and that can happen faster in a biological organism. It can be a process developed to take rid of some substances which are harmful for the organism, the same way as some desert life forms secrete concentrated urea extracted from urine to save water. [Answer] The Sequinoans' skin secretes two different varieties of sebum - the normal one, and a silica-calcite rich one in specific points (normally only the suprasternal cavity, where a specialized fold of tissue projects from the manubrium into the incisura jugularis sternalis). The result is a growing crystalloid with strong [piezoelectric](https://en.wikipedia.org/wiki/Piezoelectricity), [triboluminescent](https://en.wikipedia.org/wiki/Triboluminescence) and thermoluminescent properties: it is, in fact, more akin to a liquid amorphous crystal than a solid crystal. It's not really indestructible, but it's very resistant to shocks and could plausibly hover around 8 on the Mohs scale. Addition of carbon and boron, while difficult to justify, would allow an additional Mohs number on top of that. The magic lies in how the gem's lattice gets to accrete itself. In nature, you wouldn't have anything similar (maybe an oyster's pearl, but that works differently). Here, you do (because magic). So: Sequinoans start forming these gems when they start puberty: CHECK. Sebum secretion is hormone-controlled and changes markedly during puberty. and until then they have a gem-shaped niche, lined with pink skin, below the collarbone and above the breasts (where a locket would normally hang). When the time comes, this niche will start secreting a strange fluid which wells up and hardens like amber, forming a gem. And if removed (see below), the Sequinoan will form another gem: CHECK. Actually, the gem will either be removed or will naturally fall after some time when it grows too much (we can imagine that the presence of a "mature" gem might slow the secretion, but that isn't likely to work indefinitely). Development, however, will take several months. Plausibly, more and more so in old age. they found that these gems can be painlessly removed by the owner when they feel like gifting one, that they are practically indestructible (taking hits from steel weapons or fallen rocks without even a scratch): CHECK. They ought to be removable through gentle squeezing and prying open the niche's labia. they glow when a Sequinoan is agitated or exerting a lot of energy, as in combat, as well as when exposed to energy sources like an electric battery.: CHECK. These are two different effects actually: thermoluminescence in the case of "exerting energy", and electroluminescence when exposed to an electric potential. The potential is stored just like any other capacitor, and will be either slowly discharged through luminescence, or in a single shock if touching the stone with a metal object or the bare hands. When a Sequinoan is seriously wounded, enough to induce the development of a scar, the wound will produce new skin cells, pale pink ones, which will then form a gem within the scar: CHECK. The gem would be smaller, and probably only renew once or twice before the keloid is reabsorbed. But of course you could have it become permanent because, you know, magic. And that could be just the beginning. A mixture of cultural lore and biological effects can imbue the stone with as much significance as you want. The Sequinoans might believe it holds a part of the owner's "soul", for example. They might keep the gems of loved ones, which would lead to the creation of beautiful cemeteries that other people might regard as treasure caches, like the fabled elephant burial grounds. The stone's behaviour might come to be considered a proxy for some characterial or behavioural trait (imperfect or dull stones considered a stigma, for example). It might be an erogenous zone (actually, when engaged in a specific kind of vigorous physical exertion, all sort of effects might arise from the contact between two Sequinoan's stones and their electric charge. They might come to believe that the frontal sex position has a transcendental significance - or, like John Varley's Titanid triple-sexed centaurs, believe that non-frontal sex is not real sex, just gymnastics). ]
[Question] [ I have been doing some research, but I could not find an answer for this particular question. Is there any (however so slightly or handwavy) way of explaining the existence of a creature with a humanoid body that has both an endoskeleton to support its body mass and internals, and an exoskeleton (think insect or crustacean like) to protect its flesh and/or skin. [Answer] Lemming (the user, rather than the small fluffy things, assuming that the user isn't a small fluffy thing, of course) had it right: [![A cross section of a tortoise skeleton, showing how limbs, spine and shell are connected.](https://i.stack.imgur.com/FunFc.png)](https://i.stack.imgur.com/FunFc.png) (image credit: [Ian Alexander](https://en.wikipedia.org/wiki/File:Turtle_skeleton_cross-section,_labelled_as_infographic.svg)) That's not the only option, of course, but it is most obviously like an exoskeleton. Consider the armadillo, which has a partial armor coat: [![Cross section of an armadillo skeleton](https://i.stack.imgur.com/LS4Le.png)](https://i.stack.imgur.com/LS4Le.png) (image credit [Ryan Somma](https://en.wikipedia.org/wiki/File:Nine-banded_armadillo_skeleton.jpg)) The armor is made up of [dermal bone](https://en.wikipedia.org/wiki/Dermal_bone) with exposed bony [scutes](https://en.wikipedia.org/wiki/Scute) and is protective but not structural in quite the same way that a tortoise shell is. That's probably fine for your needs (you wanted protection) but it isn't quite like an exoskeleton. The final option would be protective but not bony at all, as demonstrated by the pangolin: [![Phillipine pangolin and pup](https://i.stack.imgur.com/DVG3i.png)](https://i.stack.imgur.com/DVG3i.png) (image credit [Gregg Yan](https://commons.wikimedia.org/wiki/File:Philippine_Pangolin_Curled-up_by_Gregg_Yan.jpg)) The scales are keratinous (so like horn or fingernails rather than bone) but are undoubtedly protective. Unlike tortoises, both armadillos and pangolins are placental mammals, if that was at all important to you. [Answer] ## Yes and no There is a good reason to have either an endoskeleton or exoskeleton. From a certain size an exoskeleton is simply too heavy to use. An endoskeleton is much lighter while giving the required structure. At these sizes the skin/fur can also be thick enough to give plenty of protection. So normally it isn't feasible at all to have an exoskeleton at human sizes, making the combination of endo and exoskeleton a folly for any creature of size. They would lose too much energy just moving around to effectively gather resources by hunting/grazing/whatever. That doesn't mean there isn't some merrit. Instead of an exoskeleton you could have just a few tactical parts of the body shielded. As an example, forearms and a few blades on the back. The reasoning is simple. The endoskeleton has a few structures that do resemble an exoskeleton, only inside. Think of the skull. It isn't there only for structure, but also for protection in much the way an exoskeleton might. In addition many larger creatures still have strange structures that can be offensive, defensive or having little use. Think of antlers on deer for example. They can be used for both offence and defence, though other structures for horns would definitely be better suited. If all that material is instead used on protecting certain tactical areas like an exoskeleton it can still work. The key here is moderation and timing. Deers shed their antlers in the winter. No use to keep such energy hungry things when theres little use and little food. [Answer] This really is a question about evolutionary biology, not biology alone. When you compare how endo/exoskeletons form on an evolutionary level, you start to notice a lot of problems with the idea of a dual endo+exoskeleton in a humanoid creature. Exoskeletons have features that answer questions about their evolution that may or may not be answered when it comes to endoskeletons, which can be seen as a hindrance, but such limitations of reality are a great framework for realism in any fantasy. When you don't have any real life examples, the type of thing you're looking for probably isn't evolutionarily possible or is incredibly unlikely. Outside of the rainforest and the sea (in which, convenient for my point, the biodiversity of exoskeletons is more complex), evolution doesn't produce as varied results. In other words, if something doesn't exist, there's probably good reason for it. Bottom line is, if you're aiming for ultimate realism, and your story necessitates they have a humanoid form, then your best avenue of approach is to build within/around the evolutionary questions that have been answered for one and not the other, or vice-versa. If you've gotten this far and what I've written seems like it's making sense, then great. If you're struggling, then take everything I've said so far with a pinch of salt and get ready for the real bottom line: realism in fiction/fantasy isn't scientific accuracy, it's pseudoscience that's scientific enough to trick the viewer into believing it. Whether it's good pseudoscience or actual science, it probably doesn't matter to the scientifically-minded viewer so long as there are consistent principles and models, ones they can intuitively recognize, that don't clash too much with their understanding of the world. The skill of the writer here is in their ability to creatively build around that intuition and understanding. All you can do to that end is challenge your own, and gauge/test others' (which is what you're doing here so good job üñí). ]
[Question] [ In one of the books of the The Witcher series Geralt has been told by a vampire (Regis, if I recall) that it was not true that vampirism could be spread by bite. He elaborated that the whole idea was ridiculous. If I recall, the argument was something like this: if that was the case, vampirism would spread exponentially, quickly infecting everyone. Since the majority of people are not vampires this shows that vampirism cannot spread by bite. Is this true that, realistically speaking, if vampirism could be spread by bite then everyone would quickly be doomed to become vampires? Or does, contrary to this argumentation, the traditional setting where only the minority of people are infected with vampirism and vampires are largely kept at bay make sense after all? Let's look at real world viral diseases. Rabies would, perhaps, be most similar to vampirism. To quote [Wikipedia](https://en.wikipedia.org/wiki/Rabies): > > The virus is usually present in the nerves and saliva of a symptomatic rabid animal. The route of infection is usually, but not always, by a bite. In many cases, the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behavior. This is an example of a viral pathogen modifying the behavior of its host to facilitate its transmission to other hosts. > > > However, the window of time when the virus can infect others is relatively short: > > The symptoms eventually progress to delirium, and coma. Death usually occurs 2 to 10 days after first symptoms. Survival is almost unknown once symptoms have presented, even with intensive care. > > > Even its name describes what it does to its victims: > > The name rabies is derived from the Latin rabies, "madness". This, in turn, may be related to the Sanskrit rabhas, "to rage". The Greeks derived the word lyssa, from lud or "violent"; this root is used in the genus name of the rabies virus, Lyssavirus. > > > So why did rabies not infect all animals (and humans) yet? I'm not an expert, but I'd hypothesise that it is too harmful for its own good. It kills too quickly and while it makes animals aggressive to increase the likelihood of it spreading through bites it also makes symptomatic animals nigh insane and alters their looks to pretty much broadcast the message that something is seriously wrong with them and everyone should run away as quickly as they can. To quote an [anecdotal report from Quora](https://www.quora.com/What-is-something-you-did-that-you-think-was-badass/answer/Martyn-V-Halm-Security-Consultant) of a man meeting a rabid dog: > > The dog noticed me and started running in my direction. There was something wrong - its head was cocked to one side and its jaws were slavering, the white drool around its mouth coating its matted fur. > > > What if there was a virus somewhat similar to rabies, but less malignant? Wouldn't it remove the obstacles of its uncontrollable spread? To be more precise, the virus would: * Not kill symptomatic people quickly, carriers wouldn't die much sooner than non-infected individuals; * Not inconvenience carriers much; alternatively, it could balance off the inconveniences (eg vulnerability to sunburn) with perks (eg night vision) - what I mean here is that carriers shouldn't have a much higher chance to die because the inconveniences make them more vulnerable to other threats; in particular, it should not make carriers insane, or at least, not the majority of time; * Like rabies, however, force carriers to display aggression towards non-carriers and a strong desire to spread the virus by biting others. If such a virus could infect humans, would all humans soon become infected? Perhaps mankind would spread into two camps, those not wanting to get infected and those embracing infection, two camps at a constant war with each other... But given that people could only move from the "not infected" to the "infected" camp and not the other way around, wouldn't the "infected" camp not be destined to eventually win? Also, wouldn't most people just want to get bitten ASAP if for no other reason then for the sake of peace? To make things simpler let's assume that such "vampires" would not have to feed on blood. If they did have to drink blood then I guess the worst case scenario would be a dystopia where non-infected people would only exist to donate blood to infected people... I would really like to somehow salvage the traditional setting, but given the above I'm not sure if this is possible... Do non-vampires have any chance? [Answer] The claim makes sense, but only with some background assumptions that people in the fictional setting presumably take for granted. Specifically, let us assume that: 1. Vampires exist. 2. Vampires must bite people to feed. 3. Vampires live long enough, and need to feed often enough, that a single vampire must bite dozens (if not more) of people during their lifetime.\* Together, these assumptions imply that each vampire must bite a large number of people, and can somehow do that without being caught and killed. How they do it doesn't really matter ‚Äî if vampires exist, and can survive for a long time without being slain or starving to death, that alone implies that they must accomplish it somehow. If vampirism was easily transmitted by biting, this would imply that it would have a very high [basic reproduction number](https://en.wikipedia.org/wiki/Basic_reproduction_number) ($R\_0 \gt 10$ or so), and would thus rapidly spread through the population. Real-life diseases with such high $R\_0$, such as measles and mumps, tend to be known as "childhood diseases" because (at least before widespread vaccination) they were so infectious that pretty much everyone caught them at a young age (and, if they survived, developed immunity that would protect them from later reinfection as adults, although not necessarily from chronic after-effects). Besides, if vampires cannot feed on other vampires, they'll soon have a problem in this scenario, because the supply of uninfected humans will soon run out as the infection spreads exponentially. (If they can, and can also have human children, then you're looking at a world where pretty much all adults are vampires and pretty much all children will become vampires as soon as they're bitten by a vampire parent or sibling or playmate. Even if some people attempt to protect their children from vampirism, that's going to be really, really hard when they're literally surrounded by hungry vampires, some of whom are themselves still children and lack adult self-control.) --- \) There's a small loophole here: you could* have both highly infectious vampirism and long-lived vampires if most newly infected vampires died before biting even one person. Those few vampires that survived past their first feeding could still live a long time and bite many people, as long as almost all of the new vampires infected by them would die before getting a chance to spread the infection further, thus keeping the average reproduction number approximately equal to 1. The biological and/or social mechanisms maintaining such an equilibrium could be quite interesting from a worldbuilding perspective. Perhaps whatever infectious agent causes vampirism might simply be lethal to most people, with only a small fraction of (more or less) asymptomatic carriers being the actual vampires responsible for spreading it further. Or perhaps society in this setting has, out of necessity, developed strict rules that anyone showing signs of vampirism or of a vampire bite must be immediately and ruthlessly killed before they can spread the infection. That said, while I'm not actually very familiar with the Witcher setting, I don't think either of these scenarios is likely to be compatible with it, as they imply that almost all people bitten by a vampire simply die, whether from the bite itself or due to being killed by their fellows. That seems like the kind of setting detail one would mention, if that was the case. [Answer] Most vampire victims don't survive to turn into vampires Most of the time, vampires drain their victims dry, killing them rather than turning them. There's a bunch of factors, but the biggest is that vampires try and make the most of their victims and have little interest in producing more of themselves. Remember that vampires are generally functionally immortal. Creating a new vampire means creating competition. Aside from that, while many vampires slip into sociopathy as a coping mechanism for their new state as a serial-killer and predator, most have some vestigial sense of morality or compassion. They don't forget being human right away. Most vampires therefore don't want to inflict their condition on others, and don't want to kill people either. So when they attack, they often haven't fed in a while and will find their thirst getting the better of them, resulting in them draining the victim to death. In general, very few vampires will leave their victim alive, either for compassionate or utilitarian reasons, or just plain thirst. [Answer] # [Minimal Infectious Dosage](https://en.wikipedia.org/wiki/Minimal_infective_dose): In theory, one vampire-infective particle is all that would be needed to cause vampirism. But in practice, life forms have immune systems that are proficient in fighting off disease. If a tiny infection starts in someone, their body mounts an immune response that fights off the infection, often before someone even realizes they were infected. This is why people might test positive for COVID, but never develop symptoms. Diseases differ from infection to infection. What might make one person sick might not make the next person sick (especially in the immunocompromised). But more importantly, what might cause one disease to make a person sick might not work with another disease. Shigella, for example, has a minimal infectious dose only only about 10% that of salmonella, so smaller numbers of organisms can cause people to get sick with shigella than is needed to cause illness with salmonella. If, for example, a person gets sick from eating 5000 salmonella bacteria, they would get sick from eating food with only 500 shigella bacteria. So the level of vampire infective particles might be extremely low in saliva. It's not that a bite CAN'T cause the disease, but a bite might be like a vaccinated person being in the same room (masked) with someone who has COVID. It could happen, but it's not likely. Even if a tiny infection DID happen, they would fight it off and not become a vampire (like a breakthrough COVID case with someone testing positive but never developing symptoms). But perhaps all vampires were immunocompromised at the time of infection, or a different infectious route (blood transfer) results in a massive infectious dose. In these cases, the likelihood of becoming a vampire is very high. [Answer] Behavior changes could isolate populations Vampires are often described as adversely affected by sunlight - sunlight avoidance could seriously reduce infection rates in populations that spend a lot of times outdoors. It's not just that outdoors types would be less likely to get infected, but the sunlight avoidance of the vampires would tend to identify them as such, allowing the uninfected public to take measures against them. Once the general public learns how to identify the vampires, measures against them could be more widespread. [Answer] The central issues are how easy it is to transmit and how many bites can you pull off before someone locks you up as crazy. Particularly if the biting impulse showed up before the human shed virus. But, by your description, people would remember being bitten. Your vampire is guilty of assault. If the saliva did not get into the wound enough , it might not infect one person before being stopped. [Answer] Humans are good at resisting aggression from other humans. Aggressive humans exist. Humans already can be aggressive towards one another. Someone might approach me aggressively because they want my stuff, or because a guy who looked like me took his stuff, or that guy really was me, or they want to have sex with me, or they are angry because I want to have sex with them and they don't. I could keep going. A lot of human culture and societal constructs are set up to deflect or resist human on human aggression to make life in a civil society possible. Now there are humans who approach me aggressively because they want to bite me. Join the club, Bitey! Do I need to list the ways possible to defend against aggressive acting humans? I am tempted but we will start with my attack schnauzer and my kung fu skills and end with calling the cops. [Answer] The vampires are smart, and they practice sustainable farming. If they just bite every human and convert the whole human race into vampires, there won't be a supply of humans any more, and then the vampires will go extinct too. So they intentionally bite few enough humans to keep their numbers from spiralling out of control. New vampires must be inducted into this practice. If they act recklessly by biting too many humans, then the other vampires step in and put a stop to it, by force if necessary. [Answer] Mild spoiler alert for the general theme of some movies/shows/books... Every vampire mythology I've read/seen has some mechanism which counteracts this quick global spreading of vampirism; and each mythology makes sure that humans are the only source of food. Here's a selection: * The vampire may be able to decide whether his food will "turn" or not. This seems to be the case in the True Blood series; I cannot recall how they handled it - maybe it was the amount of blood extracted or it only happened if the victim died while being sucked dry, but it was a common theme that vampires would keep human familiars around as repeated blood supply, and that turning a human into a vampire placed special responsibility on the "parent" vampire. * As an extension, the vampire society often introduces their own rules about this with whatever reasoning; for example to avoid detection, or to make sure that they don't run out of foodstuffs. This is exacerbated by mechanisms like garlic, silver or crucifixes, which gives the humans a fighting chance as soon as they become aware of the existence of a vampire in the region. * Most vampire mechanisms conveniently have sunlight as an antidote. Sometimes, for example in the Van Helsing series, there is some cataclysmic event which reduces sunlight in some way, and thus makes the exponential spread of vampirism possible, if maybe only for a short - but long enough - time. This again gives humans a fighting chance when they are aware of the threat, by being able to move around freely during the day, and barricading themselves effectively in the night. * Often, the vampiric society is itself structured in separate strata; for example the "elder ones", thousand years old vampires which are exceedingly powerful, or freshly bitten ones which are very much at the bottom run of the ladder. There even may be "ferals" - vampires which much reduced intelligence, which behave mostly like animals. The older ones then control the feeding of the younglings by force and strict regulations. Also don't forget about Zombies - these are, in the spirit of your question - often exactly as exponential as you are fearing. Zombies differ from Vampires in that there is no antidote, they have no society, and can not reason for themselves; purely driven by bloodlust. Usually, a single zombie bite, or even a little scratch of a fingernail, is enough to turn a victim into a zombie. This leads to scenarios like Walking Dead or Dawn of the Dead where the whole world is quickly run over (also a special mention to World War Z which approaches the theme quite scientificial - highly recommended reading). Summary/TLDR: a virus-based vampirism would not spread exponentially because vampires would regulate themselves to keep a steady supply of food. Secondarily, because there would be some antidotes that would be relevant if and when humans became aware of the threat. [Answer] Sollution: Vampires can choose whether to infect their victims with vampirism. And since they're thinking, intelligent beings, they're not going to willingly create too much competition for themselves. > > In any case, it‚Äôs not our fault. We were born vampires.‚Äù > > > > > ‚ÄúI thought you became‚Äî‚Äù > > > > > ‚Äú‚Äîvampires by being bitten? Dear me, no. Oh, we can turn people into vampires, it‚Äôs an easy technique, but what would be the point? When you eat‚Ä¶now what is it you eat? Oh yes, chocolate‚Ä¶you don‚Äôt want to turn it into another Agnes Nitt, do you? Less chocolate to go around.‚Äù He sighed. > > > ~ Terry Pratchett, carpe jugulum Also, there's a movie that revolves around the idea of a world where vampirism has spread to almost the whole population, the vampires need human blood to avoid going insane and non-infected humans are almost extinct. <https://en.wikipedia.org/wiki/Daybreakers> [![enter image description here](https://i.stack.imgur.com/FHb4P.png)](https://i.stack.imgur.com/FHb4P.png) ]
[Question] [ Situation: My colony is threatened by a passing neutron star. It turns out this planet is part of a binary system and once every several hundred years it passes by a neutron star, which irradiates its surface. I'm trying to figure out a way for the colonists to survive the impending cataclysm. Assume they don't have access to interstellar ships. My question has two parts: 1. What if they dig deeper into the planet's core? Could the layers of rock shield them from the worst of the radiation? (Assume they have tech to pull this off). 2. Is there anything else they could do to shield themselves from this catastrophe, short of leaving the planet? Edit: It's an older, non-pulsar neutron star. I would like for the neutron star to have an accretion disk (I would love for the colonists to witness it accrete away some of their main star's mass), but I can dispense with that if necessary. I would also like for it to pass close by enough for the colonists to feel some of the tidal forces and [gravitational waves](https://physics.stackexchange.com/questions/338912/how-would-a-passing-gravitational-wave-look-or-feel) but not enough to kill them. [Answer] I think they'll be okay. Let's start by figuring out what we're up against. Neutron stars can produce high-energy radiation through two means: thermal and non-thermal emission. Thermal emission is just the light emitted by a black body. Young neutron stars that have begun cooling (a couple of years old - younger than this one) have temperatures of $\sim10^6$ Kelvin. Assuming a radius of roughly 10 km, the Stefan-Boltzmann law predicts that a young neutron star should have a luminosity about 19% that of the Sun. The thermal emission peaks somewhere near the cutoff between ultraviolet and x-rays, meaning that a lot of this will be dangerous to humans. If the neutron star is behaving like a pulsar, it will also emit non-thermal radiation through synchrotron emission. You probably know pulsars best from radio observations, but in the most energetic pulsars, most of the rotational energy of the pulsar is actually converted to x-rays and gamma-rays; there's a weak correlation between the frequency of light and the fraction of the spin-down energy that goes into that frequency band.$^{\dagger}$ The power released by a typical pulsar with period $P$ and period time derivative $\dot{P}$ is $$\dot{E}\approx4\times10^{31}\;\text{erg s}^{-1}\left(\frac{\dot{P}}{10^{-15}}\right)\left(\frac{P}{\text{s}}\right)^{-3}$$ This usually comes out to a few percent of a solar luminosity, so it's fair to say that our neutron star should have a total luminosity - including thermal and non-thermal emission - of roughly $0.25L\_{\odot}$. Ish. And that's generous, because your neutron star is certainly older, which thanks to cooling might drop this by 1-2 orders of magnitude. At any rate, I think we can assume that this is mostly the sort of high-energy radiation we'd prefer to avoid. (Brief interlude: You've mentioned that the neutron star has an accretion disk but that it's not behaving like a pulsar. That's a bit odd for two reasons: 1) the neutron star would have to have been in a close orbit to its companion star in order to accrete that matter in the first place, which seems incompatible with a planet remotely near the habitable zone, and 2) neutron stars accreting matter gain angular momentum, which increases their rotational speeds and turn them into [millisecond pulsars](https://en.wikipedia.org/wiki/Millisecond_pulsar), as the increase in angular momentum also turns on the not-overly-well-understood pulsar emission mechanism. In other words, I'd be surprised to see a neutron star with an accretion disk not emitting pulses of radiation. Coupled with the strangeness of having an accretion disk while in a wide orbit, I'd like to dispute that part of the premise!) The flux on the planet depends on how far from the neutron star it is. Let's say the closest approach is around 100 AU; a pass on the order of 10 AU or less has a decent risk of causing orbital problems, particularly if there are other planets in the system (thank you to Loren Pechtel [for confirming this](https://worldbuilding.stackexchange.com/questions/207033/trying-to-survive-a-passing-neutron-star-by-burrowing-deep-in-the-planets-crust#comment641263_207035)!). The flux on the surface is then about 0.034 Watts per square meter.$^{\ddagger}$ If an unshielded human weighing 80 kg (cross-sectional area of something like 2 square meters?) was exposed to this amount of radiation for one year, they'd receive a dose of about 27,000 Sieverts. As I understand it, we'd want to reduce this below 1 Sievert to significantly reduce the risk of radiation sickness. Not great. However, we could absolutely build shielding. [Lead has a half-value layer of 4.8 mm](https://en.wikipedia.org/wiki/Half-value_layer) against gamma rays, so we could lower the radiation by the requisite four or so orders of magnitude with 15 times this length. Not bad. Even if the distance to the neutron star is an order of magnitude lower, raising the dosage by a factor of 100, we'd still need lead shielding of something like 10 cm, if my numbers are correct. [Dirt itself has a half-value layer of 115 cm](https://en.wikipedia.org/wiki/Radiation_protection#Radiation_shielding), so 25 meters of dirt would provide adequate shielding from the worst-case 10 AU-approach scenario. Let's briefly discuss gravitational effects, since you've brought up tidal forces and gravitational waves. Tidal forces would be minimal since at interplanetary distances there's no difference gravitationally between a $\sim1.5M\_{\odot}$ neutron star and a $\sim1.5M\_{\odot}$ main sequence star; tidal forces are only important quite close to the surface. Gravitational waves are a possibility from tiny imperfections in the neutron star's surface on the order of millimeters or so ([we ironically call them "mountains"](https://www.ligo.org/science/Publication-S6VSR24KnownPulsar/)). Mountains on a neutron star at a distance of 100 AU should produce a strain on the order of $\sim10^{-20}$, give or take a couple orders of magnitude ([Lasky 2015](https://www.cambridge.org/core/journals/publications-of-the-astronomical-society-of-australia/article/gravitational-waves-from-neutron-stars-a-review/1B6A2A3DE0F617EDABD4942A2E7B5657)), which won't cause problems. I'm sure these numbers are off by a bit - a factor of 10 here, a factor of 3 there. I've likely overestimated the thermal radiation and the high-energy contribution from non-thermal radiation, and I think I've also overestimated how close the neutron star can be without having affecting the planet's orbit. The point, though, is that even if I'm wrong by 1-2 orders of magnitude, a mine shaft a kilometer or so deep should be cozy enough against whatever a neutron star can thrown at these colonist. And that's probably substantially overkill. Anyway, time to start digging. --- $^{\dagger}$Handbook of Pulsar Astronomy, Lorimer & Kramer. Also my reference for other bits of this answer. $^{\ddagger}$This is slightly inaccurate because the non-thermal pulsed radiation will not be emitted equally in all directions. A reasonable assumption is that [the beam covers about 10% of the sky](https://astronomy.stackexchange.com/a/36050/2153) at a given time (although this depends on the pulse period), meaning the flux when it sweeps across the planet will be higher than in the case of isotropic emission. Conversely, there's no guarantee the beams will cross the planet at all. ]
[Question] [ I'm working on a story about Earth or an Earth like planet with current or very near future levels of civilisation and technology drifting or speeding out of the solar system. Currently my method for achieving this is the gravitational effects of a rogue object passing nearby (a bit more research to be done on how big a rogue object is needed). I understand that were this to happen it is pretty much impossible for the population of the planet to do anything about it. However there is no doubt that they will try. So my question is what might they consider or try to do to prevent the home planet going rogue? Anything they could consider trying right from the moment of discovering the incoming rogue object onwards is admissible. I'm not asking about how they might try to survive for as long as possible on the rapidly cooling world. Nor about attempts to set up colonies on other planets etc, just about attempts to stop Earth/Earth analogy being sped off to an uninhabitable place. However if for example there was a way to try to get Earth captured in orbit around a gas giant on the way out of the solar system and this would leave Earth somehow habitable then this would be admissible. To be clear - I know that they are doomed, I just want to know what they might consider and try anyway to provide background to my main narrative. [Answer] Call your shot. Your incoming mass is near the size of earth - too big to move except with something else of comparable mass. Hmmm... Your world has an AI at its disposal that knows the site, mass and velocity of all objects bigger than 10 kg in its immediate vicinity. There is a mass of comparable size which could be made to intercept and gravitationally deflect the incoming mass. But the interceptor mass is itself very large. To move it will require a different mass of comparable size. A smaller such mass is available and correctly positioned. Although smaller, this mass is also not easy to move. A mass smaller yet is also in the correct position... Your AI presents a series of 12 successively larger gravitational interactions of which the smallest and first is within the ability of humans to achieve with rockets. In a planetary billiards chain reaction, an array of progressively larger objects will change course, with the end result the gravitational deflection of the incoming impactor. [Answer] There are two things that would help: Firstly this rogue planet needs to be detected a long time before it approaches. With a few hundred years warning, they might consider sending fleets of ships to set up at network of installations on the surface for setting off thousands of hydrogen bombs one at a time over a year or so. Although almost insignificant, very large numbers of such weapons in conjunction with a very great distance might just be enough to deflect the object by a wide enough margin to minimise the bad effects. The second thing that would help would be for the rogue planet to be as small as possible and be generating its effects by virtue of a very close approach imparting a rapid change rather than a more massive object generating its effects via a more prolonger encounter. Because it would be easier to deflect a smaller object. Another option that is unlikely but possible would be to deflect the orbit of an asteroid into the path of the planet. Such an impact sufficiently far in advance might have some effect. Finaly thought assuming the rogue planet had a frozen atmosphere, nuclear power stations and nuclear rocket engines could be set up on the surface to convert some of the frozen atmosphere into the gas phase and then use a large number of nuclear thermal or nuclear electric rocket motors to generate massive amounts of thrust. [Answer] Nukes are the only sane thing to try, you get far more energy per pound than with anything else. However, you deliver them by missile. Their usefulness at planet-moving is basically unaffected by their velocity, all you care about is aim (you want them to come down at the point you want the planet moving away from) and detonation altitude. This is a planet, you don't have death-star level energies available, there's no danger of disrupting it so there's no upper limit on the boom. You're going to throw the biggest bombs your rockets can deliver. (Larger bombs are going to be cheaper per megaton than small ones.) However, I don't think they'll do more than run the numbers and determine this is hopeless. We can't muster anything like the energy to produce a meaningful deflection of a planet. Instead, the effort will go into survival--building bases dug in deep that will remain habitable after ejection. [Answer] ## Nukes(?) Given the ridiculous distances involved in space, if they discover it soon enough, they could attempt to redirect it. Normally, the only use for nukes in space is to detonate them in the Van Allen Belt and watch Fortnite players cry as the telecommunication systems of an entire planet goes down in a blaze of glory. That is because there is no matter nearby that the nuke's radiation could heat up. Depending on your planet's civilization, and plot convenience, they might have a [mass driver](https://en.wikipedia.org/wiki/Mass_driver#Practical_attempts) lying around. Such thing would squarely be future, but if the planet's society was ideal, they could have built one before. These handy inventions would allow for the transportation of nukes and other components into space where they'd be assembled. ## Mephisto's BOOM Box In order to harness the punch of your nukes, you have to slap a solid cap on them that would be plasmified when the fission happens. Since we've already landed a delicate probe on a speeding asteroid, a big chunk of metal shouldn't be a problem. They should be aimed so that they make contact with the object and explode, loading most of their kinetic energy into it and also sending the caps' remains into God knows where. ## Alternatively If you have similar YT reccomendations to mines, you probably recognized that the previous proposal could be turned around to make the famous [Hyperspace manhole cover](https://www.businessinsider.com/fastest-object-robert-brownlee-2016-2) [Answer] As I understand it, # 1. An object is approaching Earth... Fair enough so far. A common sci-fi scenario is, an object is approaching Earth that is - say - a few miles or even 100 miles in size. That object is on course to *hit* Earth, obviously causing an insane amount of damage. Usually in such stories, we push it off path using nukes. So, such an object hitting Earth would obviously crush continents, etc. Note however that it is inconceivable such a small object would actually knock Earth out of the solar system. In your story, # 2. .. the object is so big it will actually swing Earth out of the solar system (!) Thus to be clear, your approaching object is, indeed, "Earth sized", it's a massive planet-size object. # 3 Your question, what can be done? The answer is very simple: # 4. Absolutely nothing - at all - whatsoever! unless you invoke (absolutely magical) sci-fi powers. Note that unfortunately the task at hand would be as difficult as ..... moving Venus or Mars. "!" "with current or very near future levels of civilisation and technology" there is just utterly nothing, whatsoever, like within something like 15 (!!!!!!!) orders of magnitude that we could do about "moving Venus or Mars". Note that even within say the Star Trek universe (transporters! totally novel physics! etc.) it would be utterly impossible for them to move a planet. Note that annoyingly, even if we created a man-made black hole (a big one) and sent it along to Eat the incoming planet, tragically that new black-hole object would have exactly the same gravitational effect as the original incoming planet! No more or less. # We can conceivably move asteroid-size stuff, but it's totally inconceivable to move planet-size stuff (sadly!) Great question that highlights the scales involved! ]
[Question] [ Fantasy and folklore has many instances of giant spiders,ranging from creatures like the J'ba Fofi to Aragog from Harry Potter. My question intends to ask whether a creature like the J'ba Fofi could have evolved. [![A Hypothetical Image of the J'ba Fofi](https://i.stack.imgur.com/l5HMS.jpg)](https://i.stack.imgur.com/l5HMS.jpg) On a planet with conditions identical to Earth, how could a giant spider with a leg-span of 1 meter evolve? Could it produce silk and how much could it produce if it could? Could it walk without violating the Square Cube Law? How could it breathe? This question is part of the Anatomically Correct Series. [Answer] I am going to reuse parts of my answer to [Anatomically correct Arachne](https://worldbuilding.stackexchange.com/q/51903/21222), which is related but not a duplicate. --- We cannot approach this as if the only way for this creature to exist to exist is in the form of a giant nope spider thing without any modifications to its spider anatomy. That would be silly. We all evolved from very small animals that lived underwater, yet here we are in human form. A much larger stretch than having arthropods growing into big sizes. Specially because in prehistoric times, we did have arthropods that were quite big. The largest arachnid ever was a [70 cm long scorpion](https://en.wikipedia.org/wiki/Pulmonoscorpius). That's a little over two feet, or 28 inches. It had aquatic cousins [that could grow up to 2.5 meters long (that's over eight feet)](https://en.wikipedia.org/wiki/Jaekelopterus), though. Granted, those beasts had their weight supported by water, but look at that... An arthropod larger than a man! Not only that, but we know that there's less oxygen available in water than in air, so how could the square-cube law allow for that? Well, besides evidences that our atmosphere was more rich in oxygen millions of years ago, there is also the fact that those arthropods had evolved their internal anatomy to allow for those sizes. Let's go back to the creature in the question then. Imagine if you will a prehistoric nope tarantula. It lives in a world where there is more oxygen available than Earth right now, because that's how prehistoric Earth was like. Our prehistoric nope spider is under many different evolutionary pressures, and a larger size is conferring it increased rates of survivability and reproduction. To allow for that, the nope tarantula starts developing, throughout generations, some unusual characteristics for a spider. For example, a mutation gives it layers of skeleton, so besides the external chitinous one, the spider has internal ones as well. Over time the external skeleton is replaced with soft but thick leather. This allows it to replace its [book lungs](https://en.wikipedia.org/wiki/Book_lung) with mammal (or bird)-like lungs, which are much more efficient. Over time, as this species of nope tarantula grows, it will evolve a circulatory system much like a worm's at first, then that of a vertebrate. As for the abdomen, it resembles that of a reptile or amphibian more and more, with different organs going through convergent evolution to take the roles of a liver, a spleen, a pancreas and so on. Nopes spiders have excretory organs in their legs, but this species's excretory organs move to the abdomen over time. Now, nopes spiders are known for being very agile with their legs, and weaving webs with them. Our specific nope spider, though, is growing larger by the millenia, so its six frontmost feet are only used for supporting weight now. Eventually they will be completely flat and fingerless (yes, nopes spiders have fingers - actually microscopic claws, which is how they weave and cling to stuff). Only the last pair of legs will have fingers for weaving. In the other question I linked to, Azuaron suggested that a giant nope spider-like creature would have to have its legs below the body and not splayed. I propose a midterm solution which is close to the anatomy of a real nope spider, so the legs should be fixed below the cephalothorax. The creature is supported by eight feet, and they don't have to be incredibly heavy for their size, so I think this setup works. I estimate that, once the creature reaches its adult size, it should weight 60 kilograms (approximately 132 pounds), with its weight divided almost evenly among its eight feet (the hindermost feet would support a smaller fraction of their weight), so on average each foot would be supporting 7.5 kg / 15.5 pounds. Such a nope would probably be warm-blooded, with all the adaptations required for that. It should eat at least as much as a human with the same weight. As for the web output, I think it would be proportional to its body mass, relative to any regular species of web weaving spider. [Answer] Short answer: yes if gaint spider solves the problems with thermoregulation, breathing and feeding. There were large insects about meter size (and more) in Earth's old days, when atmosphere had more oxigen. (I know - spiders are not insects, but they both are crustaceans and have same body plan) 0) phisical stability - exoskeleton would be quite thick and heavy, wich would greatly reduce there agility and mobility. It means that no high order predators (like mammals) should exist in that ecosystem 1) Thermoregulation - thick exosceleton is a good insolator. Too good insolator. They should behave like snakes - warming up in the sun and cooling down in some wet shadows. They could not do extream activities (like chasing prey, or running from predator) for long, or they just cook themselfs with inner heat. So nothing like battle with this gaint spider can happen. It is more like "hide and seek" and "who ambush whom" game. 2) Breathing - the most limiting factor. The reason why insects on morden Earth are small is exectly this. Your planet should have a lot of oxigen in atmosphere - no less then 40-50% (or much higher pressure). And that implies a lot of "fun" in DwarfFortress sense. Like selfigniting mashineoil or easely igniting steel. 3)Feeding is also a problem, because spiders can't feed on solid meat. They need to "coock" sort of sup from it's victim and then suck it in. It means that beside this spiders there must be lots of gaint insects - there prey. They should be more then ten times more common than spiders. This gaint spider would be just a rare encounter in swarms of giant ants and gaint centipedes. [Answer] 1 meter is definitely plausible, but I can't see any spider getting much larger than that. [Birgus latro](https://en.wikipedia.org/wiki/Coconut_crab) has a legspan of 1 m, a body length of 40 cm and a weight of 4.1 kg, and they are very ungainly and slow-moving. The largest spider in the world is [Theraphosa blondi](https://en.wikipedia.org/wiki/Goliath_birdeater), which can reach 28 cm in legspan, 11.94 cm in body length, and 175 g in weight. In order to reach 1 meter in legspan, the spider's overall dimensions would have to be increased by a factor of 3.57, which means that its weight would increase 45.55 times, resulting in a spider with a body length of 43 cm and a weight of 8 kg. Another large spider, [Lasiodora parahybana](https://en.wikipedia.org/wiki/Lasiodora_parahybana), can have a legspan of 25 cm, a body length of 10 cm, and a weight of 100 g, resulting in a spider 40 cm and 6.4 kg. So it seems that a tarantula with a legspan of 1 m is possible, but it would be very slow moving, making it difficult to catch prey. A lighter-built spider would be much more realistic. The cellar spider [Pholcus phalangioides](https://en.wikipedia.org/wiki/Pholcus_phalangioides) has a much lighter build. Males have a body length of 0.6 cm, and a weight of 10.8 mg, but I can not find any measurements for their legspan; females have a legspan of 7 cm, a body length of 0.9 cm, and a weight of 26.6 mg. With a 1 meter legspan, the female Pholcus phalangioides would be 12.9 cm long and weigh 77.55 g. This is certainly within the realm of possibility, as a spider this size shouldn't have any serious issues with respiration or movement. There is also a way for spiders to surpass 1 meter in legspan. Underwater, many of the issues regarding respiration and movement are eliminated, or at least greatly reduced. [Macrocheira kaempferi](https://en.wikipedia.org/wiki/Japanese_spider_crab), which superficially resembles a spider, can reach 3.7 m in legspan and 19 kg is weight. [Argyroneta aquatica](https://en.wikipedia.org/wiki/Diving_bell_spider) is the world's only truly aquatic spider. It only goes to the surface to replenish its oxygen or sometimes eat its prey. Although it is only 8-15 mm in body length, it could eventually grow to extremely large proportions or an already larger spider like [Megadolomedes](https://en.wikipedia.org/wiki/Megadolomedes) or [Ancylometes](https://en.wikipedia.org/wiki/Ancylometes) could develop similar habits. ]
[Question] [ In a fantasy world I have planned, I wanted one of the nomadic groups to live on a frozen steppe. They would primarily subsist by herding and domesticating mammoths. Would mammoths be comparable to, say, a Mongol's horse or a Bedouin's camel? By this I mean could my nomads be able to survive mainly off of the elephants' milk and lichen and the occasional berry or two the mammoth reveals while foraging or when they happen to wander near? Note: Warmth is solved by shearing parts of the mammoth for clothing as well as collecting their droppings for fuel. Wood could be collected en masse whenever the mammoths wander near a forest with the nomads strapping logs to the mammoths. [Answer] Meeting of equals. Domestication; bah. Been done, been done. I propose in your world the meeting of mammoth and man is more akin to the ancient meeting of wolf and man. The humans tolerated the wolves which would become dogs - they learned to keep their distance, they learned to beg for scraps, their senses are keen and they are good at fending off and detecting the most formidable enemy of humans - other humans. So too your mammoth society. The mammoths are smart - smarter than elephants. They align themselves with humans because the cleverness and resourcefulness of the humans helps the mammoths they cannot do for themselves, or cannot do as well without human help. Together they survive better in this hostile land. Mammoth groups choose their humans and vice versa. Once the interaction is set, the story will get energy when the combined group is visited by a male mammoth - they are intelligent too but do not associate with the herds of female and young, or with humans. But he grew up on a herd and remembers humans. What does this bull want from the humans? [Answer] If it would be practical, our ancestors probably would have done it. But they haven't. What stopped them? Mammoths and elepants need to eat several kilograms of grass and other plant material each day to survive. That forces the people to move constantly in a nomadic lifestyle and it sets an upper number of individuals in a sustainable herd. Your humans are supposed to eat mainly plant matter as well, which makes them direct competitors to the mammoths. It's unrealistic to let a mammoth pull a wooden contraption loaded with berries and other foods and expect it to never reach its trunk in there and eat from the supplies. Your solution to this food competition was to let the humans drink / eat the mammoth milk or dairy products. At first glance this sounds like an excellent idea. The milk is probably rich in fat and proteins because the mammoth babies have to grow fast before the next winter strikes. A [study about the composition of elephant milk](https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0007114570000168) found that elephant milk is 80% water and 10% fat and protein respectively. That's much better than the 3.2% and 3.9% fat and protein respectively of [cow's milk](https://en.wikipedia.org/wiki/Milk#Nutrition_and_health), but not enough to feed an entire nomadic clan. Elephants gestate for an entire year and lactate for 3 years (if I understand [Wikipedia](https://en.wikipedia.org/wiki/Elephant#Birth_and_development) correctly). Additionally, one elephant bull mates with all fertile elephant cows of a herd. That means you get a stable milk supply from several cows for 2 - 3 years before you have to wait an entire year (or longer) for fresh milk (because most of them become pregnant at the same time). I couldn't find sources about the quantitive amount of milk produced by elephants, but you have to give most of it to the calf for at least half a year before you can take the bigger share for yourself. Unlike in a cow's herd, your nomads would rely on a wild mammoth bull to impregnate their mammoth cows, which poses a great problem. > > Bulls engage in a behaviour known as mate-guarding, where they follow oestrous females and defend them from other males.[130] Most mate-guarding is done by musth males, and females actively seek to be guarded by them, particularly older ones. > > > Elephant males have a hormonal cycle like the females. "Musth males" means that the male produces lots of hormones and pheromones that attract the females and make them very agressive. Maybe the nomads could substitute for the guarding male, but that would lower the chances of pregnancy, because the guarding male would mate with the females several times. Or they would somehow eliminate the agressiveness in centuries of selective breeding. And last but not least, let's not forget how very intelligent and social elephants are. If the nomads slaughtered an old animal of their herd, there's no chance the remaining individuals wouldn't notice and fear or even fight their herders. There's a chance to avoid such problems if the heard neither sees nor hears the animal that's being slaughtered, but given the size, thick skin and loud voice of elephants, I'm not sure how the nomads could pull it off. It's suggested that stone age hunters chased mammoths to make them fall over cliffs to kill them. That is in no way a clean death. The animal is likely still alive, panicked and screaming. The herd would hear this several miles away. To sum it up: * The cost (plant material to feed the herd) is too high for the yield (the milk) * Reproduction takes too long and involves bulls in an agressive mood * Slaughtering would have devastating effects on the remaining herd. [Answer] they probably could - but it's not a good tradoff when it comes to danger posed. The important thing about domesticated animals wasn't just that we were able to eat them, but also that we were able to handle them without getting killed. Slaughtering a mammoth isn't a job I'd want to do. [Cows pretty much are the upper limit](https://en.wikipedia.org/wiki/Cattle#Domestication_and_husbandry) in size when it comes to things we could capture and handle - that's why most cattle-subspecies we domesticated come from the same line of first captured animals. this gets easier the more advanced your society is of course - so a neolithic civilisation pretty much would have a really hard time to tame animals even larger than elephants, while in the last centuries in india those aren't that strange anymore. Speaking of those... [they reproduce too slow](https://en.wikipedia.org/wiki/Captive_elephants), so selective breeding is impractical. You'd have to catch new ones if you'd need more of them (or, you could like... wait a few decades) - so that doesn't help either. [Answer] No, They may live alongside mammoths, but the mammoths alone cannot sustain them by themselves. The closest you are going to get is something of a cross between nomadic pastoralists and Nenet of Siberia who herd dogs and reindeer and hunt extensively. The problem of milk, milk will be a an issue because you have to choose between producing new mammoths and having milk, to use elephants as proxy, they are pregnant for almost two years, during which they will not be producing milk, on an upside you then have about ten years of milk production. but your people can't survive off milk alone, not when it can suddenly go dry for two years, there are also health issues and how they get clothing and shelter, so they either need to be eating mammoth (see problems below) or they need to be hunting as well. The problem with eating mammoths, mammoths will reproduce incredibly slowly, 20 years to adulthood that means for every breeding pair your people can eat one mammoth every 20 years, likely far less because disease is still a thing. Worse mammoths like elephants will be both intelligent and highly social. Unlike other animals if an elephant goes missing other elephants go looking for it and they can communicate for miles so you can't separate out one without the others knowing. They also mourn their dead for years and even recognize their remains even when degraded, so you can't bring the herd anywhere near the remains. This means they are clever enough to figure out the humans are eating them, once that happens cooperation is over. Even if by some miracle you could get them separated enough, killing the mammoth will not be fast or silent worse its a mammoth, you can't exactly carry it home, and you cant use your one labor animal. So really you have only one option. Your nomads live and travel with the mammoths, drinking milk frequently but not exclusively and hunt other things, but do not eat mammoths. In fact eating a mammoth is probably heavily taboo for them. As long as they are not eating mammoths they should have no problem living with the mammoths(given a little hand waving). But they will be spending a decent amount of time hunting and/or fishing, picture something like hunter gatherers with gathering replaced by mammoth milk and cheese. For comparison peoples consider both the Nenet people of Russia, who only eat their livestock infrequently and hunt to make up the difference and Tibetan nomadic pastoralists who survive almost exclusively off their herds milk and meat. On the upside this explains why this is the only place mammoths survived, everywhere else they survived the change in climate humans hunted them to extinction. ]
[Question] [ 500 years ago, the mountain dwelling Carac clan was cursed with undeath: whenever they or any of their descendants die, their corpses rise as undead creatures, or if burned, as shadowy specters. The Carac quickly adopted a custom of casting their deceased into a chasm. This does not prevent the occurrence of undeath, but nothing has ever crawled back out of the hole so it's always been considered a wise solution. I would like to know approximately how many undead creatures are in this chasm. I know there are resources online for how to estimate the length of a generation etc., but I'm a complete blockhead at this sort of thing and can't figure out for the life of me how to calculate the number of people who have ever died in the Carac clan. In the mountain valley the Carac call home, let's say the clan has had a stable population of 1000 for the last 500 years. Not a realistic assumption, but I'm only trying to figure out how many undead might plausibly occupy the chasm, not an exact figure. I'm sure there are other figures you will need from me to answer this question: please feel free to make any other demographic assumptions that you wish for an iron age barbaric mountain folk, or ask in comments and I'll try to respond promptly. Thank you! [Answer] What’s the average life expectancy? A fixed population makes the maths very easy (ignoring edge effects where people are alive at the beginning or end of the period, which are negligible over a long enough interval). The number of people who have lived is: Population x length of period / life expectancy So for your 1,000 population over 500 years, if their life expectancy is 50 years then there have been 10,000 people alive during that period (1000 x 500 / 50). [Answer] @MikeScott's answer is correct, but I'd like to rephrase/expand. If you have a life expectancy of 50 years, and your poulation is constant, that means that every year on average 1/50th of your population dies and 1/50th is born. For a population of 1000, that means 1000/50 = 20 deaths per year. In 500 years, that's 500\*20 = 10,000 deaths (and 10,000 births). [Answer] Adding to Scott’s answer and comment, you have to consider what diseases swept through there, if there are wars that happened near, magical creature attacks, as well as immigration of friendly beings, such as elves, some of which are essentially immortal. Even wit a stable population, the population might have been overtaken by more evolutionary fit creatures, and the undead might just be humans. This is, of course, assuming that the curse is on the place of dwelling, and not the previus inhabitants and generations. If you where to use this as a sort of dungeon or trial, you could have a necromancer or other magic user sucking the life force out of the people as they die, prolonging their lifespan and turning them into undead. ]
[Question] [ Closed. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it can be answered with facts and citations by [editing this post](/posts/65444/edit). Closed 7 years ago. [Improve this question](/posts/65444/edit) Assume we are living in a world in which there are immortal people living among us. According to some religions the gods are eternal, and according to logic, everything with a start must have an end. So, if we think there are human beings with a start, but without an end...like the gods do. Should they have a religion? I mean should they have a god? Because sometimes, the religion could be a way to think everything will be OK after-life. But in this case, there won't be an after-life for these human beings. * These immortals are 100% humans. * These immortals were born on the earth naturally, but because of a mutation their DNA they are immortals. * These immortals are immortal-invulnerable. * There immortals stop aging at 25 years old. Why will be a god be acceptable in a world like that, and why not? [Answer] # Religion is organized affirmation of faith You are kind of mincing concepts here... let us make a little vocabulary first: * Belief: a thought, an idea, a statement in your mind that asserts something Example: "a god is a supernatural, immortal being" * Faith: the conviction that a belief is true Example: "I think there is a god" * Religion: organized affirmation of faith Example: "We gather here today to celebrate our faith that there is a god" * A god: a supernatural person that is significant within a religion Example: Jesus, Krishna, Allah, Ra, Zeus, Odin, Jupiter Nothing in this says that immortal humans may not have religion. The established world religions may perhaps not fit them very well since those religions mostly deal with what happens to a human after they die. But never the less any person — immortal or not — may find a religion that suits them. However... As people have pointed out — among them Sigmund Frued and Christopher Hitchens — it can be assumed that much religion comes from our fear of dying. The very thought that one day our consciousness will be eradicated, and the world will go on without us being in it, is a frightening one. And for that reason, mankind has made religion as to try to soothe the sting of that thought. But what if you are immortal and/or have no such fear of dying? I would say this takes away one of the main forces that drive people towards religion. But then again: the living will always be very concerned with how to act upon one another while alive. And religions usually do offer a nice package of morals to use for that; a neat set of Do's & Don'ts. So there is nothing to say that the immortals will not be drawn to this just as the mortals are. And the immortals will have mortal friends and loved ones. These people will age and die. The love and grief that immortals have for mortals may very well cause them seek the same kind of solace in religion as mortals do. As for the concept of a god/many gods, I find your question kind of odd. It is not a matter of these people should have faith in a god or not, but rather will they have faith in a god. Some most likely will. Why would they not? In fact, they may even be more inclined than mortal humans to believe in it. After all: they share a trait — immortality — with that kind of person. Will the immortals themselves be seen as gods? Well it all depends. They may choose to see themselves as gods. And some others are likely to see them as such. There may even be cults forming around them. But will that turn into religions?! Eh, not very likely... because these immortals are much too material. A "god" will lose much of their splendor and awe-inspiring qualities when seen unshaven, hung over and in dire need of a wee on a Sunday morning. In conclusion: there is nothing that will say the immortals will not be just as religious — even as deistically / theistically religious — as the rest of us. [Answer] Your immortal and invulnerable people are gods for all practical purposes. However, there can be a hierarchy of gods. For example, in the Greek mythology some gods were more powerful than others -- Zeus himself could not take back an oath once it was written on the tablets of Moira (Faith/Destiny). 1. Is their religion important for the plot? If yes, then give them a religion. Questions to answer: do they have a moral code based on sacred teachings? do they practice religion by fasting, attending celebrations, avoiding certain words, making certain gestures in certain situation, praying, etc.? are there important religious institutions? buildings? is there a mythology supposedly known to all? 2. Do their gods intervene directly in the plot, like in the Illiad or the Odyssey? If yes, there must be gods, either known or unknown to the characters. Questions to answer: are there characters which have incomparably greater power(s) -- they can shapeshift, they can defeat any other character in combat, they can read minds etc.? do such characters appear as unexplained entities, or as entities with an entirely different history? do such characters intervene in the plot? are there essential miracles? [Answer] Where did we come from? A lot of religions center around the concept that a higher being created us. Since your immortals will probably have just as much of an idea of where they came from as any other human, they could still certainly believe in a God that created them. Do immortals believe in another plane of existence? Most religions today believe in some sort of afterlife. People who die go there. If your human immortals discovered they were immortal overnight, would this cause them to stop believing in the afterlife that many of the people who died before them went to? I would think that your immortals would want to believe that their deceased loved ones went to a better place, rather than ceasing to exist altogether. At least the ones that were religious before they became immortal would probably still feel this way. Eternity can be horrifying You claim that these immortals are invulnerable and therefore are unable to die. The idea of eternity is perplexing and horrifying to many individuals, and since you claim that these are humans, I would think that many people would go mad with the idea of no end. They might be horrified that they never get to be reunited with loved ones that died long ago, and could end up with a very inverted concept of God - a God that will eventually allow them to die and put an end to this horrific eternity. Any desire to believe in something that can't be seen or obtained within ones life is considered faith, and where there is faith, there is religion. [Answer] First, let's address the problems of a world full of immortals--because that ties in with gods. 1) If they all stop aging at 25, then they will all be fertile and can continue to have children. If they do, the resources of their planet will be stretched to beyond the breaking point. Unless, of course, they don't have to eat or drink, ever. Even if they stop eating at 25, children will probably have to as they develop. This will still be a strain on resources. Time to pray to the gods for a better crop. If they are invulnerable, then medicine will never develop and birth control might not either. I'd be praying not to have yet another kid. 2) Eventually, you'll get trapped somewhere, forever. See [#1 on this cracked article.](http://www.cracked.com/article_18708_5-reasons-immortality-would-be-worse-than-death.html) You'd definitely pray for that not to happen. In a world of immortals, clearing out a building collapse would be of higher priority, but what happens when the immortal mafia gives you a pair of concrete overshoes and shoves you in the water? What happens if you are out alone and a rock slide occurs? At this time, belief in a higher power may be called for... 3) Insanity. How do their brains work? How can they store all the info of thousands of years? And if a person does go insane, what can you possibly do with them? If they are trapped somewhere, insanity is definitely a thing that might happen. Meditation and religion might be the only thing keeping the oldest of them together. 4) Illness. Limb loss. Drowning. This really depends on what you mean by invulnerable. If they just heal, then they can lose a limb. Those limbs may grow back over time or not as you please. If they can't be hurt by anything, then...there's a lot of other problems that develop. For instance, you gain muscle by pushing yourself beyond what you can do--you tear cells apart, and the healing process is what makes you stronger and more ripped. As to illness--are they completely unable to get sick? Does that kick in at 25? Can only children get ill? Can children die before they hit the age? If there is any illness on the planet, at all, that's something you would pray not to happen. As Alex P pointed out, it really depends on how the Gods work, but I also think it's quite dependant on how your immortals work as well, and what they might want, that they can't get as a result of that. Being immortal means that you are static--so gaining strength for instance--that might only be something that can be bestowed by the Gods. [Answer] Most answers and comments, and indeed the question itself, seem to be approaching the concept of religion from the point of view of what the adherents get out of it. But there is another perspective to consider: following a religion, not because it brings you hope or comfort or purpose, but because it's true. # If Gods Exist, So Will Religion Did we create the gods in our image, or did they create us in theirs? In the real world, that's an unanswerable question, a point of philosophy. But within your fiction, you can decide one way or the other. And while the existence of religion doesn't logically require the existence of "the divine", the converse is true: if the divine exists, religions will exist. (I should probably specify that this assumes the divine is somehow knowable, and perhaps also personal and interested in a relationship with humans. But deciding that your fictional world has distant and unknowable gods is tantamount to saying that it doesn't have any, so the distinction seems overly fine.) [Answer] Consider that maybe Gods will spring up from the immortal people themselves. With staying alive no longer a problem people are going to have totally new problems. Problems like: * Overpopulation (unless they stop breeding) * Confusion/Befuddlement in elders (a 100% human person can only remember so much) * Lack of purpose: You no longer need to breed to stay immortal (in a genetic sense breeding could be seen as a type of immortility), you don't need to ever worry about having enough time, you don't need to make safety precautions as you cannot die. People who come up with answers and grab power could be totalitarian leaders who over the decades convince people of their higher status. They will never die and may never become infirm, with years of terror and no new uprising generations, they can institute themselves as a possible god. Especially if you consider that some of the main characteristic's of a god are that of a powerful immortal leader of a group of people. [Answer] Why not? Even if they are immortal they're not unkillable so they can die. If they can die then they must ask where am I going? Even if they can't die they still need a purpose for life so they can still as the question why am I here? Trying to answer these questions could easily bring them to religion. Also some religions which include an afterlife, put a large focus on developing a personal relationship with your creator. This might be something that an immortal might want to develop. After all if everyone they know is going to die it makes sense to seek out someone or something that you know always be there that will never leave you. Another thing to consider is that the Immortals do not know they're are Immortals while they're growing up, even if it were impossible ( I don't see why) for an immortal to develop religion they could easily be converted as a child or young adult and continue on in that religion throughout their immortality. [Answer] You only need God if you're going to live forever. Those who tend to not believe in life after death tend to not believe in God. In other words, I am arguing the opposite cause and effect: belief in existing forever leads to a belief in God, belief in a temporary existence tends to lead to atheism. Let me explain: People don't want to just experience things, people want to have happiness and [meaning](https://en.wikipedia.org/wiki/Man's_Search_for_Meaning). The horror of immortality with no meaning was captured well by Douglas Adams in his Hitchhiker's Guide series, in which an immortal character gets so bored of everything that he decides to insult everything in the universe in alphabetical order. Eventually, every pleasure we can event for ourselves gets old and stale. Someone who is confident that their existence will be relatively short hopes they will die before they can no longer get happiness from pleasure. I think this is what is [really meant](https://gotquestions.org/eat-drink-and-be-merry.html) by the attitude "[eat, drink, and be merry, for tomorrow we die, and it shall be well with us](https://www.lds.org/scriptures/bofm/2-ne/28.7)" attitude. In other words, "Yes, eating, drinking, and partying only bring temporary happiness, but that's okay because it will all be over soon." If you know that you will live forever, that's a scary thought, because you know that eventually the things that bring you happiness now will run out. You're not confident that you will always be able to find things that will bring you joy, so it is comforting to believe in deity who promises [peace](https://www.biblegateway.com/passage/?search=John+14%3A27&version=KJV), [fulness of joy](https://www.lds.org/scriptures/nt/john/15.11#10), [happiness without end](https://www.lds.org/scriptures/bofm/mosiah/2.41#40), [Eternal Life](https://www.lds.org/scriptures/nt/john/4.13-14#12) (meaning really Living, not just existing), [enlightenment](https://en.wikipedia.org/wiki/Enlightenment_in_Buddhism), [true freedom](https://en.wikipedia.org/wiki/Moksha), etc. We don't need God to ensure our continued existence, we need God because we humans are terrible at making ourselves happy. [Answer] Why will be a god acceptable in a world like that, and why not? Of course there is a God. I've met Him. The earliest Immortals were around in the days of creation, so they've spoken directly with the Creator. God isn't an element of faith to them but rather a childhood memory. God? No, that's just one of Old Grandpa Methuselah's tall tales. Later Immortals have no special advantages compared to normal humans in this arena. They'll hear stories from the oldest Immortals, true, but whether they believe the stories of "that crazy Uncle" is another thing altogether. ]
[Question] [ So in my world I have a variety of nations states ranging from independent city-states to empires. I am in the process of defining the socio-political landscape of the world and have a few story centric international relationships that are partially defined. For the rest of the world and to provide more detail on those things that are already defined I am looking for a way to define (essentially give each a score) the power of each independent political entity. * What facets of power need to be considered? * Can each nation's score exist independently or is it necessary that they be part of a larger ecosystem? * How would one go about automating the assignment of stats for each nation? The best answer will have (at least for the first bullet) supporting political science literature. For the sake of this question fantasy aspects (magic/creatures and stuff like that) may be considered non-existent. [Answer] ## Deciding who lives, who eats, and who pays Whether you live or die, what you think, and what you eat are three of the most fundamental questions that a person will need to address for themselves. All other considerations can be seen as complications of these three most basic questions. As an author, you will need to decide who has the last word on the answers to all these questions. The method described below proposes a method for answering these questions and discovering hidden features of the power relationships between competing nation-states. Political calculations are always made in relation to other human beings. Some physical quantities about the exercise of power may be calculated independently, but the political power scores are always in the context of competition. The three categories of power described below are roughly equivalent to the initial three questions. ## Military Power Roughly equivalent to the power to kill, military power is the ability to enforce political will through violence and death. The power over life and death. > > No bastard ever won a war by dying for his country. He won it by making some other poor dumb bastard die for his country. - [George S. Patton](https://en.wikipedia.org/wiki/French_and_Raven%27s_bases_of_power) > > > ## Cultural Power Cultural power is the power over how people think. A nation with cultural power is able to export their ideas in regards to how society should be run, what is culturally important and what is not. This is the power over what and how people think. It could be argued that political power is a distinct category but since laws are such an integral part of how people think and behave, I'm lumping it in with cultural power. ## Economic Power Economic power is the power over buying and selling, more specifically over what is bought and sold. An economically powerful nation-state can push their goods and services to a broader market and command more market share than an economically weak nation-state. This is control over the flow of wealth trade goods. How power in these three areas can be exercised will not be addressed here due to the voluminous and excellent literature elsewhere. A good start might be [French and Raven's](https://en.wikipedia.org/wiki/French_and_Raven%27s_bases_of_power) work in 1959. ## A word on distance The farther away something is, the harder it is to influence it. In addition to the three categories of power. The method described below attempts to take into account the difficulty that great distances introduce into the exercise of power. Also, the model assumes that spheres of influence are roughly ring-shaped and projected onto a 2D map. Accounting for 3d spaces or irregular spheres adds a great deal of complexity (and this answer is long enough already). I chose to use a log scale to ensure that this method could scale across all distances and all empire sizes. --- ## Calculating Power Values 1. Make a list of all the nation-states in question. This list of nation-states should be in contact with each other and in a position to compete in some way. Probably easiest to build this model in a spreadsheet of some kind. 2. For each category of power, there is a points pool defined as 5 \* number of nation-states. So for a list of 5 nations, the pool would be 25. Allocate some of those points to each nation, giving more points to the more powerful nations. 3. In the adjacent column, assign values for each nation's sphere of influence ($S\_i$). This value should be at least as large as the country itself though may be smaller for especially weak nations. For an earth like planet, sphere of influence values will likely range between 6 and 7.2. Using $S\_i = log\_{10}(d)$ You can calculate your sphere of influence values with as much precision as you desire. 4. Multiply the points column by the $S\_i$ column to get your power score for that nation. Work a little spreadsheet magic to sort each power category to see the strongest and weakest. 5. Have a little fun writing out summaries for each nation based purely on the numbers you've written. You can be as detailed as you want and may end up writing a little bit of history about each nation to explain how they got to be where they are. Now, compare these values with your original intentions for each nation. If they match, great. If not, make adjustments and keep going. --- ## Possible Extensions of the Model Calculate relationships between entities bigger or smaller than nation-states - As described above, this model applies to nation-states on a global scale though it can be applied equally well to purely regional relationships. To keep things as manageable as possible, keep this spreadsheet specific to a geographical scope of competitors. It's tough to keep track of regional relationships when considering global power relationships too, not impossible, just complicated. Also, the 5\number of nation-states may not work too well when comparing isolated nations who dominate their neighbors but have no contact with each other and do not compete in anyway. For example, comparing Rome with ancient China using this technique may not make too much sense. Calculate Internal Power - Governments often have very different relationships with their own people than with neighbors, thus it is helpful to see the relationship between the government and the governed. Use the same three power categories used for comparing nation-states. Calculate Maximal Extent of Power - Calculate or specify the maximum extent that the political entity can make its military, cultural or economic power felt. Calculate Power Projection at specific point - By adjusting the distances in the $S\_i$ calculation, it's possible to plot more detailed relationships for a specific location. ## Conclusion As with any measure that aggregates a great deal of information down to a single number, there will be considerable loss of nuance and opportunities to argue "yeah, but...". This approach is an approximation at best though with the addition of additional aspects in $A$, its expressive power can be improved. This model also does not account for alliances that may exist between nation-states that would serve to greatly amplify the power of any one nation. --- ## Helpful Information Sphere of Influence values are calculated using the below formula. This approach helps keep the math manageable $$S\_i = log\_{10}(distance)$$ 0 = 1 meter, you human have control over yourself. 1 = 10 meters 3 = 1000 meters. Small village/town. 6 = 100K meters, comparable to but smaller than Ireland. 7.3 = 20M meters, half-way round the world 12 = 5.9 trillion meters, Pluto 26.6433 = Edge of observable universe [Answer] What facets of power need to be considered?* Dependents on your specific setting. Mana level is quite important in fantasy, while may be omitted in hard science setting. ;) But let's think, at minimum: -Population -GDP per capita -System stability (from anarchy an civil war, to a country with very well working gov with high mandate from subjects) When trying to flesh that out a bit more: -Unique resources -Extra sources of soft power (like religion - Mecca / Vatican, being the country in which the main social website operates, or being a tiny state with remnant of some old, respectable, imperial dynasty) -Additional modifier for militarization on top of simple man and economic power (Sparta, Israel) -type of political system Can each nation's score exist independently or is it necessary that they be part of a larger ecosystem? In very simple model? Enough. In more advanced at least make a few types of circles to which one would include countries: -religion -ethnic group -dynastic ties How would one go about automating the assignment of stats for each nation? In simple version - RAND and RANDBETWEEN functions from Excel clones. Presumably with some modifiers (like city states get some bonus in wealth per capita, but have no special resources) or summing results to get distribution for GDP closer to normal distribution. I'd make list for special resources, to make excel pick, something like : 1 - oil, 2 -magnetite iron ore, 3 - uranium... 5 and more - none. This would be especially practical if you would use it use it for province level to make bigger states nonuniform, and make the spreadsheet sum it up. [Answer] You may want to begin by fixing a general outlook of the world, that is, the general setting in terms of technology, economic development and social customs. Do you want a world like we have it in the 21st century, with unprecedented emphasis on individual rights and freedom and with unprecedented world-wide interconnection between people and companies and nations? Do you want a world like they had in the 19th century, with a handful of [Great Powers](https://en.wikipedia.org/wiki/Great_power) competing for domination over territory and nations? Do you want a world made up of a multitude of fragments, like they had in the Middle Ages and the early Modern period? A hierarchical world, like in the European Middle Ages? It is hard to give suggestions for books unless the general outlook of the world is specified. In all time periods of human history there were all kinds of political structures, small and large. Even today, we have city states and small countries and mid-size countries and large countries and huge empires. Singapore is a fully independent city-state; Hamburg is a city state, member of the German federation, itself a member of the European Union confederation. Russia and China and effectively huge empires, no matter what their official names are. ## What facets of power need to be considered The basics are population, territory, resources, economic development, and social development. They result in the four dimensions of power: Diplomatic, Informational, Military and Economic (DIME). See the Wikipedia articles on [National Power](https://en.wikipedia.org/wiki/National_power) and [Power in International Relations](https://en.wikipedia.org/wiki/Power_(international_relations)). Note that while population and territory are easily reduced to numbers, resources, economic development and social development are multifaceted. Territory is not a unidimensional attribute; while larger territory gives more power, the kind of territory is also important. Resources include climate, water, soil, wood, animals, hydropower, mineral resources, acces to the sea etc.; which resources are important depends on the general outlook of the world. The notion of economic development is also dependent on the general outlook -- up the middle of the 20th century agriculture was very important, today much less so; financial systems (what kind of financial systems aare available and how developed they are) may have a huge impact; don't forget to look at transport modes and transport networks. Social development has a great importance; aspects of social development include science, technology, education, culture, law, customs, morals and political structure; you may want to consider the categories used by the [Human Development Index](https://en.wikipedia.org/wiki/Human_Development_Index). Political structure, as an aspect of social development, can go in various directions none of which are inherently stronger than others. ## Can each nation's score exist independently? Whether a nation's power can be considered independently of other nations depends on the general outlook of the world. In today's world it is obvious that a nation's power is highly dependent on its relationship with other nations. Consider, for example, Germany: it is a great economic power. How much of that power would remain were Germany isolated from its world-wide markets? Consider America: it is a great cultural power; doesn't this power depend on the access to other countries culural markets? On the other hand, the closely woven world of the late 20th and early 21st centuries is not the only possible world. For a very long time people have lived in relatively autonomous [economic worlds](https://fr.wikipedia.org/wiki/%C3%89conomie-monde) (Wikipedia article in French, sorry), which had few and essentially unimportant trade relations with each other. See also the Wikipedia article on [World-systems Theory](https://en.wikipedia.org/wiki/World-systems_theory), a "macro-scale approach to world history and social change". ## Automating the assignment of stats for each nation See Shadow1024's answer for suggestions. If you use RANDBETWEEN or similar functions don't forget to make provisions for "freezing" the results. ## Links to reading material * [A. T. Mahan's books](http://www.gutenberg.org/ebooks/author/5116) on sea power at Project Gutenberg. * Emil Reich, [Foundations of Modern Europe](https://archive.org/details/foundationsmode02reicgoog) at the Internet Archive. * Halford Mackinder, [The Geographical Pivot of History](https://en.wikipedia.org/wiki/The_Geographical_Pivot_of_History), 1904. * [Measuring National Power](http://www.rand.org/pubs/conf_proceedings/CF215.html) by Gregory F. Treverton and Seth G. Jones, 2005, at the Rand Corporation; also a [direct link](http://www.rand.org/content/dam/rand/pubs/conf_proceedings/2005/RAND_CF215.pdf) to the PDF. * Craig W. Mastapeter, [The Instruments of National Power: Achieving the Strategic Advantage in a Changing World](http://www.dtic.mil/dtic/tr/fulltext/u2/a493955.pdf), 2008, at the Naval Postgraduate School, Monterey, California. * [A Measure of National Power](http://www.analytickecentrum.cz/upload/soubor/original/measure-power.pdf) by Chin-Lung Chang, an essay concentrating on the quantification of national power. * An extensive bibliography on [Elements of National Power](http://jfsc.ndu.edu/Portals/72/Documents/library/Bibliographies/Elements_of_National_Power.pdf) (PDF with Web links) published by the (American) Joint Forces Staff College. [Answer] I think first question has already a good answer by [Shadow1024](https://worldbuilding.stackexchange.com/users/25459/shadow1024) I would just add geography as a very important feature. Power can not exists independently, if you are nation of 50 million people you could dominate many neighborhoods, but if you are placed between China & India you will be easily dwarfed. My suggestion is to generate map of you world, split it into countries that look good to you and then assign features according to it. You will see yourself that countries who are on important waterways or navigable rivers have many advantages. On the other hand countries that are landlocked or poorly connected have many disadvantages. It also depends a lot on who your neighbors are. If you get along with them, they will increase your power through cooperation and alliances. If you hate each other guts, they will tie part of your resources in order to keep an aye on them. Birds of feathers usually cooperate more easily. The neighbors with different races, religions or cultures usually have more difficulty to cooperate. Empires are always multi ethnic, though they have one core ethnicity. Visit Peter Turchin [site](http://peterturchin.com/) who wrote extensively about societies, his book [War and Peace and War](http://peterturchin.com/war-and-peace-and-war/) covers the formation of the empire extensively. In the end human societies are the most complex things in the world. Choose approximation that works for you and happy world building. [Answer] # Economy is good, over-reach is bad My citation is [Rise and Fall of the Great Powers](http://rads.stackoverflow.com/amzn/click/0679720197) by Paul Kennedy. He goes through European history from 1500 to the cold war summarizing the reasons for the success of various nations relative to each other. The summary version is internal peace and access to resources good, military overcommitment bad. The author focuses on European powers, and doesn't really address the issues about why the Ming/Ottomans/Mughals/Persia ended up so far behind the Europeans. However, he does have persuasive analysis for the relative power discrepancies in European struggles. Basically, Spain rose to power becuse it was the first to the New World and looted literally entire mountains of Gold and Silver. But it struggled because it was fighting constant wars for 150 years. The wars reduced its population and caused repeated bankrupcies, which reduced internal investment and lead to other countries adapting more advanced production techniques. Population in Iberia was steady around 8 million from 1500 - 1700, while France grew from 16 million to 21 million and England from 2 million to 5 million. Eventually, Spain didn't make anything useful at all, so when the gold from the New World dried up it was destitute. France, too, was ruined by too much warfare through the 1700s, and its population did not grow as fast as it could have. It also never pushed abroad to get access to more world resources as the Dutch and British did during this time period. England, on the other hand, avoided major internal wars after 1651, didn't get invaded, and steadily set up colonies all over the world. So by 1800, England was firmly the richest country in the world and was able to dominate the world economy for a century. The pattern more or less repeated itself with the United States. The US grew rapidly, generally had internal peace (except for that one Civil War thing) and due to its great size had easier access to resources like iron, coal, and timber, than most European countries. Especially after the advent of railroads, goods could be brought from remote parts of America to factories cheaply, massivly fueling America's economy. By about 1900, America was more populous and richer than the nations of Europe. Russia had many of the advantages of the US, including a large population and ample resources, but never launched. While the population of Russia and the Ukraine absolutely exploded, increasing 4-fold between 1800 and 1900 (and was around 40 million larger than the US!), peace never found the land. Constant internal strife and poor organization meant that the railroads were never developed to move resources to factories until Soviet times. If WWI, the Bolshevik Revolution, Stalin's genocide, and WWII had not happened to Russia, it is entirely believable that there would be 400 million Russians now. Instead, there are about 140 million and they are being reduced in population, and are poorer, on average, than Brazillians, Turks, or Mexicans, all of whom were until recently considered to be in the Third World. In any case, the discussions of economy were salient to the book, because they completely determined the result of all wars since 1500. If you had more people and higher tax incomes, you won the war, eventually. So the only thing you really need to track is the economy. If it is medieval/early modern, then you need to account for population and tax revenue. And remember that tax revenue is related to merchants, not to the size of the nations. Milan, Florence, and Venice were likely all richer than France in 1500, despite France's 10 to 1 (or more) numerical advantage. As a result, any of the those powers could potentially take on France in a war and win, as can be seen in the [Italian wars](https://en.wikipedia.org/wiki/Italian_Wars). Once the Industrial revolution hits, the metric becomes raw industrial power. The US was always going to win WWII, no matter how many Rommels or Yamamotos the enemy could throw at them. Japan built 15 heavy and 10 light carriers before and during WWII. The US built 27 and 110. Germany and Japan combined made 22,000 tanks and almost 200,000 aircraft. America made over 300,000. Thats not even counting that Britain and the USSR matched what Germany and Japan did between them. The US's overwheliming industrial advantage guaranteed that they would win the war....and I might point out that while building more ships, aircraft, and tanks than anyone else, the US also found the time to invent and develop some atomic bombs. # Conclusion Economics dominates who wins wars in the long run. Having lots of people, lots of tax income, and lots of industrial production makes you the most powerful country in the world. [Answer] A common measure of a nation's power is in the [DIME](http://jfsc.ndu.edu/Portals/72/Documents/library/Bibliographies/Elements_of_National_Power.pdf) format: * Diplomatic * Information * Military * Economic Also worth considering religious power, and the fact that it's very hard to be diplomatically significant without at least some power in the other measures. [Answer] In game theory there is a branch called [cooperative game theory](https://en.wikipedia.org/wiki/Cooperative_game_theory#Mathematical_definition) This is applicable when you want to describe the amount of power a party (in your case a political entity) has with respect to the others. The idea is that except the raw power\* of the party, a second criterion should be considered and this is the cooperation possibilities of this party. For example, a party that has 49% of the raw power but all the other parties are it's enemies, it might actually be pretty weak. The assumption in this theory is that a coalition will be formed. I'm assuming that since you're trying to measure the power of the entities, there's some kind of competition going on, and if so this is a likely assumption. In this case, you can calculate the strength of each entity using it's [Shepley value](https://en.wikipedia.org/wiki/Shapley_value) which is calculated using the number of coalitions the party can form, and it's relative importance in them (i.e. how easily could they have been formed without them) Note that since what you're talking about is more than political power, you should factor that in by giving each entity a weight that also represents it's raw power. For example if you decide a coalition must have a strong army, then all the army-less entities should have a much lower value, such that a coalition can't be formed without a strongly armed entity, and the Shepley value would reflect that. --- * Row power includes military, natural resources etc. [Answer] There are many different kinds of power to consider. There's economic power, military power, the power that comes from alliances, "soft power", religious power, cultural power, organizational power, technological power, and so on. In traditional Japanese culture there are kinds of power that we don't even have words for in English. In just a single Political Science journal "Foreign Affairs" in a single year you can find multiple articles just on the subject of recent Chinese attempts to promote "soft power". And they won't even agree with each other. Soft power is the kind of power a country gets from things like culture and setting a good example. None of the authors attempt to quantify it because there isn't a good way to. Power is too general an undefined to quantify. Let's compare the power of the Vatican to that of Taiwan. Taiwan has a larger military; the Vatican doesn't have one at all. When the leader of the Vatican speaks the entire world listens; when the leader of Taiwan speaks nobody outside of Taiwan listens. Taiwan is more likely to be invaded and lose it's sovereignty; this is not going to happen to the Vatican anytime soon. What's more powerful, Taiwan or the Vatican? If religious power is what you care about then the Vatican is more powerful. If you care about the number of active fighter jets then it's Taiwan. If it's sovereignty then the Vatican. If it's economic power then Taiwan. If you gave each of them a number it would say much about your biases and nothing about the political states of the Vatican and Taiwan. What kind of power do you want to compare and quantify? What is the most important thing to the political entities in this world of yours? If you're creating statistics for a game then you can give nations arbitrary values for whatever stats are important to this game. What these stats are will vary depending what the game is about. "Settlers of Catan" and "Diplomacy" are games about political entities and the stats they use do not overlap. If you're not designing a game then this is better thought of in terms of people and the systems they care about. ]
[Question] [ > > A neutron star is a type of compact star that can result from the gravitational collapse of a massive star after a supernova. Neutron stars are the densest and smallest stars known to exist in the Universe; with a radius of only about $11–11.5~\text{km}$ (7 miles), they can have a mass of about twice that of the Sun. > > > I am not yet ready to consider the formation of such a planet, as a planet orbiting what is now a neutron star would have been destroyed instantly during that star's supernova phase. For the sake of this question, let's go ahead and consider that this Earth-like planet was placed here by advanced alien species after the star's supernova collapse. The average surface temperature of an average neutron star is around $10^{6}~\text{K}$, which is a fair bit more than our Sun's modest $5.7\cdot 10^{3}~\text{K}$. Not to say that this is the only problem, but it is the obvious one that I would like addressed in an answer. *Is a large orbit to compensate for such heat feasible? Will the neutron star's gravitational pull allow for a stable orbit?* --- This question itself deals with the orbit, radiation exposure, and placement of the planet, another question will probably ask about the biology; however, most of these answers make prospects pretty dim. [Answer] I don't exactly trust [this wiki](http://terraforming.wikia.com/wiki/Neutron_stars) on the subject, but I think for the purposes here it will be close enough (the data and conclusions look correct to me). # Nope! According to that page, if Sol was a neutron star, Earth would be subjected to the same planetary temperatures as Uranus (that's a fair bit colder than Earth is now) despite the increased solar temperature. The biggest problem is going to be the massive X-Ray output by the star, which...is suffice to say, not terribly healthy. Those higher stelar temperatures lead to an increase in the energy of the light coming off the star: each photon has more energy, and more energy means shorter wavelengths. [Minutephysics](https://www.youtube.com/watch?v=oCEKMEeZXug) has a short video on this that explains it better than I can. Stable orbits though? [Absolutely](https://en.wikipedia.org/wiki/Pulsar_planet). Neutron stars don't have "weird" gravity, because gravity is just gravity and you can make a stable orbit around just about anything (provided the universe has three dimensions of space). [Answer] I'd say... # Yes!\* \* with a huge if. Gravity is actually a non-issue. The gravity exerted by a 1.1 Sol-mass neutron star, the [minimum allowed](https://physics.stackexchange.com/questions/143166/what-is-the-theoretical-lower-mass-limit-for-a-gravitationally-stable-neutron-st) by the [Chandrasekhar limit](https://en.wikipedia.org/wiki/Chandrasekhar_limit) for a white dwarf, is exactly... 1.1 Sols, same for a 1.1-Sol black hole. Your problem is to find a Goldilocks zone for your planet, and the main issue is X-rays. here comes the huge if: An atmosphere saturated with phosphorescent materials, such as zinc sulfide or strontium aluminate, able to work as a dampener by intercepting the high-energy X-ray photons and emitting lower-energy photons at infra-red (thermal) levels. [edit] After reading the comments, I went and did a bit of research. Turns out that [diamonds irradiated and activated by X-rays emit light in the optical spectrum](https://www.fraunhofer.de/en/press/research-news/2014/april/detecting-diamonds.html). So another rather fashionable solution would be to encase environments under diamond domes. [Answer] The orbit: sure it's feasible. Gravity is gravity, it doesn't matter what the source is. We could replace the sun with a black hole, and as long as it was the same mass all the planets would keep revolving exactly the same (with the minor exception of Earth experiencing a sudden loss of all life). So for your neutron star, it's exactly the same. Ballpark it as having a mass of 1.5 solar masses (per Wikipedia). Now, we'd need to shift orbits out a little bit to accommodate for the mass increase, but that's just a matter of messing with the numbers. To deal with the other part of your question, the temperature, neutron stars are about a thousand times hotter than the sun, as you said, but the emissions are mainly x-rays and gamma rays. Those don't interact with matter as much as lower energy emissions like from our sun. As a result, they're hotter, but don't warm a planet as much as a normal star at the same distance. So we're left with a dilemma of needing to be further away to balance the mass increase, but closer to balance the temperature. And, of course, the dilemma that the output of the star is x-rays and gamma rays, which aren't exactly conducive to life in large quantities. Ultimately won't work, unfortunately. [Answer] What you're asking is if a neutron star has a [habitable zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone). The answer is *NO. Either all plants die from lack of sunlight, or it's too hot, or you're sterilized by X-rays. To be habitable you need an orbit where there's enough light for photosynthesis to work, the right temperature for liquid water, and not too much high-energy light (X-rays, gamma rays) to overwhelm being absorbed by the atmosphere (which makes things even hotter). As far as liquid water is concerned you can probably find one for a neutron star, they're typically about 1 to 2 times the mass of the Sun and put out about $\frac{1}{3}$ the energy, so it would have to be closer than the Earth is to our Sun, but not so close we need to worry about [being torn apart by tidal forces](https://en.wikipedia.org/wiki/Roche_limit) at [about 700,000 km](http://www.wolframalpha.com/input/?i=1.26++radius+of+the+Earth++%282+solar+masses+%2F+mass+of+the+Earth%29%5E1%2F3). I'm not going to go into that further because there's a bigger problem: the type* of radiation. A typical neutron star has a surface temperature of $6\cdot 10^{5}~\text{K}$ (100 times hotter than the Sun). From this we can determine what type of radiation will be most powerful using [Wien's displacement law for blackbody radiation](https://en.wikipedia.org/wiki/Black-body_radiation#Wien.27s_displacement_law). $\text{max wavelength} = \frac{\text{Wien's displacement constant}}{\text{surface temperature}}$ As you can see, wavelength will drop as the surface temperature gets higher. Since the Sun puts out lots of visible light, and a neutron star is 100 times hotter, this isn't going to go well for our new Earth. When we plug in the numbers... $\text{max wavelength} = \frac{2.90\cdot 10^{−3}~\text{K m}}{6\cdot 10^{5}~\text{K}} = 4.833\cdot 10^{-9}~\text{m}$ About 5 nanometers which puts us firmly into [X-rays](https://en.wikipedia.org/wiki/X-ray). This is bad for life. While [Earth's atmosphere absorbs most everything with more energy than visible light](https://en.wikipedia.org/wiki/Atmosphere_of_Earth#/media/File:Atmospheric_electromagnetic_opacity.svg) the Sun doesn't put out a lot of X-Rays in the first place. [![Source: http://www.windows2universe.org/sun/spectrum/multispectral_sun_overview.html](https://i.stack.imgur.com/9U26p.gif)](https://i.stack.imgur.com/9U26p.gif) Note that graph is exponential, our Sun is putting out a million times more visible light than X-rays, our atmosphere can handle that. Our neutron star slides that line to the left. The maximum output will be firmly in X-rays. It will be putting out a million times more X-rays than our Sun. It will also be putting out 1,000 times less visible light causing problems for photosynthesis. Because a neutron star puts out about $\frac{1}{3}$ the energy of our Sun, we only need to be a little closer to get enough heat. But because there's 1,000 times less little visible light than the Sun, we need to be much, much closer for photosynthesis to work. But that close we'll be fried by heat. Getting closer to get 1,000 times more visible light also gives us 1,000 times more X-rays which puts us at a billion times the X-rays from our Sun! Our atmosphere cannot protect us from that, or if it could the absorbed energy transferred to heat would fry us even further. An atmosphere engineered to deal with this would need to reflect (not absorb) most of the energy coming from the neutron star, while still letting through nearly all of the visible light, and still be friendly to life as we know it. I don't think such an atmosphere is possible. Alternatively, [riffing on this answer](https://worldbuilding.stackexchange.com/a/34919/760), the atmosphere would need to convert X-ray radiation into visible light while still being acceptable to life. This reaction, if balanced correctly, would allow the planet to generate enough visible light for plants and heat for liquid water while protecting the surface from X-rays. I don't know of any substance which could do this, but I'm not a chemist. Sources: * [Lecture notes on Neutron Stars from Astronomy 162 at Ohio State by Professor Barbara Ryden](http://www.astronomy.ohio-state.edu/~ryden/ast162_5/notes21.html) * [Wikipedia: Neutron Star](https://en.wikipedia.org/wiki/Neutron_star) [Answer] [Neutron stars](https://en.wikipedia.org/wiki/Neutron_star), while small, have a lot of mass. A neutron star with a diameter of 22 kilometers could have twice the mass of the sun, so large orbits are possible. Actually, because of the threat of time dilation a large orbit may be necessary. Unfortunately, while the surface is a lot hotter, it's also a lot smaller, which means that the actual amount of heat coming off of it is less. It's like an acetylene blowtorch compared to a propane space heater. While the blowtorch is a lot hotter, it is also smaller, so a space heater can easily out heat it. The radiation it produces may be an issue too. Edit: Actually, the radiation could be useful. Since the planet is possibly an artifact, then the creators would have taken it into account. So if the planet was heavy in x-ray absorbing materials like metals, it would warm up a lot more than normal dirt in sunlight, and to a greater depth. This absorbed energy would then be radiated out as heat. The earth's atmosphere absorbs a lot of radiation. With a thick enough atmosphere the radiation could be knocked down from deadly to "don't stand in the sun to long" [Answer] As Many people have pointed out, finding a gravitational equilibrium is relatively simple and the largest obstacle to overcome is the emission spectrum of the Neutron star. The ratio of these factors leaves no habitable zone, however... Delving into a creative realm, you could theoretically make an inverse [Dyson Sphere](https://en.wikipedia.org/wiki/Dyson_sphere) around the planet of a material(s) that can efficiently and effectively absorb the radiation from the Neutron star and emit it at reasonable energy levels to the surface of the planet. Although this approach is in no way feasible, with abundant resources and technology a solution could be found. [Answer] No. Everyone has been dismissing the neutron star's gravitation as irrelevant because gravity is gravity. Unfortunately, in this case it isn't. The goldilocks zone scales at the square root of the luminosity. Neutron star luminosity: Around 1 millionth of the sun [?](http://abyss.uoregon.edu/~js/ast122/lectures/lec19.html) Earth's orbital radius: 150,000,000km. Neutron star goldilocks zone: 150,000km. Now for the killer: The Roche limit. 2.423 \* radius \* cube root (density/satellite density) radius: around 10km density: low bound: 3.7E14 g/cm^3 [?](https://en.wikipedia.org/wiki/Neutron_star) (Note: I converted units here) satellite density: 5.51 g/cm^3 (Earth) density ratio: 67,150,635,208,711 cube root: 40,645 2.423 \* 10km \* 40,645 = 984,828km Oops, a planet that's warm enough gets torn to pieces pronto. (Not to mention that you have a year that's measured in minutes.) ]
[Question] [ In a novel I am considering, the near-future of Earth is populated with vertical cities. I don't mean one tower; I mean a city of towers, built close together, each trying to surpass the other. The towers are so self-sufficient that the streets below (and the lowest levels of the towers) are no longer used (assume for the moment that we have invented flying cars). In addition, there are [skyways](https://en.wikipedia.org/wiki/Skyway) linking all the buildings on multiple levels. In asking questions about such a vertical city, I've discovered that the weight of the building plays a large part in how high it can be built (exactly where that limit is seems to be a [point of some debate](https://worldbuilding.stackexchange.com/questions/29311/vertical-city-how-high)). This has led me to wonder: Would it be possible to use helium to decrease the effective weight of the buildings? If, say, tubing was run through all the walls and filled with helium, wouldn't that make the buildings lighter? Or would the resulting weight decrease be too small to be of any consequence? Thanks in advance for your time! [Answer] It wouldn't be effective. The building would be lighter than a building with the same tubes filled with air, but the helium likely won't even offset the weight of the tubes. There are [alternate lifting gases which provide different potential lift](https://worldbuilding.stackexchange.com/a/21000/3202), but it's unlikely that even with vacuum (the best filler for lifting volumes) you'd get any significant benefit. It's actually less effective the higher the building goes. As the atmosphere becomes less dense, the lifting potential decreases. [Answer] It would not work. Using lighter weight gases to provide lift is based on buoyancy. The lighter gas is less dense than the air around it, so the air around it pushes it up just like the denser water pushes a boat up to the surface. The theoretical limit of this process is to use the lightest fill possible: vacuum. At this point, you get an amount of lift equal to the mass of air displaced. Air is roughly a kilogram per cubic meter (1.225 kg/m3, actually, but we can round to make the visualization easier). This means that a typical 10kg cinderblock would require 10 cubic meters of displaced air. The numbers are actually worse than that, because you also have to account for the material containing the light gas or vacuum, but in the case of building materials, the numbers are clear enough even without this correction. Here's a sense of scale for that: [![10 cubic meters](https://i.stack.imgur.com/uZcTu.png)](https://i.stack.imgur.com/uZcTu.png) Now lets consider a typical skyscraper construction, using steel. Steel girders can vary in mass a lot, but the kind they use in skyscrapers is roughly 50kg per linear foot. Thus a 100ft tall building (roughly 10 stories) would need a girder 100 feet long, or 5000kg. That's 5000 cubic meters of gas to lift. That's reasonably close to the fill of a Goodyear blimp, and that's just to lift one girder: [![Goodyear Blimp](https://i.stack.imgur.com/DVllm.jpg)](https://i.stack.imgur.com/DVllm.jpg) The largest airship to ever fly was the Hindenburg, with 200,000 cubic meters. That's enough to lift 200,000kg of mass into the air. Hindenburg obviously lifted less because its fill was hydrogen, not pure vacuum, and it had to account for the mass of its skin. Actual cargo/crew mass was about 10,000kg, 1/20th the theoretical values, so it could have lifted two of those 10 story girders. So what if we were serious? What if we threw all limits to the wind, and just decided to lift one of the World Trade Centers (before they collapsed). Records show each tower massed about 450,000,000kg, so 450,000,000 m3 of gas. That'd be 0.45 cubic kilometers of gas. That's not a large area for nature, but that's a tremendous size for a human construction (the Hoover dam comes in at about 1/200th that volume of concrete). That's just to lift one building! And all of that is ignoring the structural challenges that come with such lift sources. It's ignoring all of the mass of the skin and wiring needed to actually support things. If the Hindenburg's ratio of a theoretical 200,000kg to actual 10,000kg is scaled up, that gas envelope would have to be 9 cubic kilometers in volume! How big are these numbers? Well, even using the theoretical rate, you'll be forced to use either vacuum (which requires very heavy skins) or hydrogen. Why not helium? Modern estimates are that there's only about .25 cubic kilometers of helium left in North America (deep in natural gas deposits). You would literally use up a good chunk of the world's remaining helium to do the job! And thus, we stay on the ground. If you really want to leverage lifting gasses in this way, I'd recommend a shift in point of view. Rather than starting with a city and trying to lift it, start with a dirigible and try to figure out how to adapt the concept of a city to work within it. It's much easier to change how people think about cities than it is to lift a city in the air. [Answer] OK, let's first dispense with the tubes concept. Helium is breathable. Just replace the nitrogen in the air with helium. This will maximize the volume of helium inside the building. Let's look at the Empire State Building ([PDF](http://www.esbnyc.com/sites/default/files/esb_fact_sheet_4_9_14_4.pdf)). It's around a hundred floors (102). About 365,000 tons. Contains 37 million cubic feet of volume. Call it 100 cubic feet per ton of weight. There are 28 liters per cubic foot and each liter of nitrogen air weighs roughly a gram less than each liter of [helium air](http://science.howstuffworks.com/helium2.htm). So that's 28 grams per cubic foot. So roughly 3 kg per ton. Or a .3% reduction in net weight. So every 300 or so floors, this would save enough weight to add one additional floor. And that assumes that there is no weight cost to seal the helium inside. How do you replace carbon dioxide with oxygen? Usually gas exchange would handle that. But that would also replace the helium with nitrogen. So if converting carbon dioxide to oxygen takes equipment or vegetation weighing more than .3% of the building weight, you lose your edge. [Answer] Hate to say no, but... Not really. The tubing would all but negate the lightness of the helium, would interfere with structural design, and more importantly, would take up the entire building. Let's take a blimp. It has a tiny car and a massive balloon about 10 times its size or more. You do that with a building, and the whole thing is full of hydrogen, or in your case, helium. No space left, except a tiny amount. Much simpler to have buildings brace on to each other with some sort of brackets, and be thus inter-connected. This also lets you use that bridge idea. Furthermore, the taller the building, the less effective the gas. And from a design perspective, you have just laced the entire building with a highly flammable gas and put it near a bunch of other buildings with thousands of people inside. Big Badda Boom! That's for hydrogen. For helium, you've added a potentially devastating alternative medium that you can't breathe. Suddenly, you get a tiny leak, and people start talking in high voices and then keel over. TLDR: You end up composing the building mostly of said tubing and the gas therein, which is deadly in one or more respects. [Answer] My guess: YES, if you modify the design. Here is why: Well if a Skylifter\\ can lift 150 tonnes, surely wouldn't a Skylifter could be able to be attached to the end of a Skyscraper, or even a few? Consider this: 1) If the building is made out of Carbon Composites or CNT then it could be quite strong & light, much more so than today's buildings. Definitely <150 tonnes. And these are getting cheaper to manufacture. Research into BNNT is even more promising in terms of strength. 2) Then consider that the buildings (either in the sky, tethered to the ground; or skyscrapers) don't need it have a lot of heavy things like swimming pools or cars in them (they can be on the ground). And light VTOL vehicles for transport, takeoff from the roof (prototypes already made). 3) The tubes in the walls wouldn't work, for reasons just described-too small. But entire Carbon composite walls could be filled with helium as well. This would counter-weight the building material weight. Someone mentioned breathing helium as a risk. Not really: divers & children at parties breath in helium. It would only be a danger if their was no oxygen as well. And don't we have emergency systems for dangers anyway? Why wouldn't this modified design be feasible, if all that technology already exists, just hasn't been put together? Looks do-able to me =^) I think sometimes people feel it shows intelligence to show why something can't work, rather than create designs that solve problems. That is what engineering & design is about. \\ <http://www.skylifter.eu> [Answer] No, the lifting capacity would not offset the weight to a degree enough to bother with. Instead, I would hand-wave a carbon-nanotube-like building material stronger than steel, but weighing as much as styrofoam. [Answer] The weight of the building is based on solid materials, not gas. Airships use helium not to lose weight, but to stay afloat. The reason modern skyscrapers can't be built of stone like the classic buildings (Notre Dame, the Colosseum, to name a few) is that any bigger would put the building at odds with the very force of gravity. That is why modern skyscrapers are built via the curtain wall. Details on the pros--and cons--of the curtain wall can be found here: <https://en.wikipedia.org/wiki/Curtain_wall_%28architecture%29> ]
[Question] [ This Query is part of the Worldbuilding [Resources Article](https://worldbuilding.stackexchange.com/questions/143606/a-list-of-worldbuilding-resources). --- Pretty straightforward one here, I’m just looking for something to design a galactic map with. I would like to not only name and mark planet/systems but also draw out borders between empires and administrative units within those empires. [Answer] Keep in mind that what your asking isn't straightforward at all. A true galaxy map must map hundreds of billions of stars and quadrillions (if not more) planets, asteroids, nebula, etc., etc. The [Milkyway@Home](http://milkyway.cs.rpi.edu/milkyway/) project is a ginormous effort just to map our own galaxy. Even a map generator that dealt with only 1/100,000th of the data would be mind-bogglingly huge. So what you're really asking for is software that supports building a comic-book version of a galaxy. If that's what you're looking for, you can [find a few here](http://www.projectrho.com/public_html/starmaps/software.php). Edit: You can also find options on our [list of worldbuilding resources](https://worldbuilding.stackexchange.com/q/143606/40609). [Answer] You can carve up a galactic disk into colonial empires like Africa, if that is the metaphor you are trying to make. It has been done again and again. [![enter image description here](https://i.stack.imgur.com/gmMTl.jpg)](https://i.stack.imgur.com/gmMTl.jpg) But carving a photograph into political boundaries doesn't tell us much about anything, except the relative sizes of the "empires" which we can infer to imply power and resources (although our own maps suggest this is a bad indicator of either), and which "nations" share common borders (which in a 3D world is almost nonsensical). But the narrative message is clear: the galaxy is divided into political realms and their areas of dominance. That might be all you really need to say. In the above example, distance and geography are meaningless since the cannon of Star Trek routinely involves long wars with enemies from impossible distances, and conveniently mutable travel times between empires. It's little wonder they avoided showing maps like this, even when they would be relevant to the plot (Voyager's journey home, DS9's space world war). I recommend instead using mind mapping software to create your star map. [![enter image description here](https://i.stack.imgur.com/myQ3D.gif)](https://i.stack.imgur.com/myQ3D.gif) "Empires" become hub nodes with multiple satellites. Trade routes can be marked by linking the nodes and connecting the branches. Factions can be colors, power centers can be shown by node or font size. Individual stars can be tagged in multiple ways: resources, political affiliation, religion, species, etc. [![enter image description here](https://i.stack.imgur.com/BNLRN.gif)](https://i.stack.imgur.com/BNLRN.gif) The data can be re-arranged in a single click to show a particular star's neighbors and associations. Also the data can be fill-in as needed, becoming granular only with worlds that are actually relevant. As an author or as a reader, a map that shows all the narrative connections is probably more important than one that just shows a point in space. There's no need to draw borders because "nations" will probably exist as bubbles around planet strongholds, and alliances may have more to do with ideology or resources than nextdoor neighbors. Since there's a lot of emptiness in space, "filler" systems don't need to be placed at a geo-representative pin location. If they need to be represented at all, they can be in broad abstraction – a single node for the (uninhabitable) center of the galaxy (as a location), or a single node for "badlands" or "unaffiliated territories" explain a narrative function without bringing up more questions (like: "Why can't they just fly around it?"). The animated gifs are from a freemium mind map web service called Coggle. [Answer] A suggestion I gave to a friend once: Open MS Paint or something similar, create a black background, and use the white spraypaint tool to make patches of stars. If you want more stars/bright spots in an area, just spray more over there. Once he had a layout, I suggested he use a more robust image editor like Paint.net to draw out boundaries, add names to places, and such. Low-tech, but it should be easy. [Answer] As others have stated: galaxies are vast on a staggering scale. Also, they are in 3D, so 2D maps are useless unless you want a Star Trek type universe where you can have ridiculous scenarios like border blockades (I mean really?) If that's what you want, then try the 2D options that others have suggested. If you're interested in the real deal, have a look at [Astrosynthesis](http://www.nbos.com/products/astrosynthesis), which can create galaxies and allow you to edit them as well as generate systems, planets etc. > > With AstroSynthesis, you can can (sic) map out large portions of space - plotting stars, interstellar routes, and subsectors. And best of all, you do it completely in 3D space! Zoom in and out on your sector, pan and rotate around stars, follow routes, and watch fantastic animation effects - all in 3D. > > > Under features, it lists the ability to define sub-sectors. I haven't tried this myself, so I'm unsure if it meets your "draw out borders" requirement. > > Define sub-regions in your sector map to easily identify regions. > > > I also recommend that you have a look at [Space Engine](http://spaceengine.org). The editing controls are limited, but it is great fun to explore, and you may find it useful. [Answer] I'm working on my own book series taking place in a galaxy that is not our own. Since I don't have the budget to buy any of those programs, what I did was sketch it out on paper and then use my printer to scan it into the computer and save it as a file. I highly recommend this for your situation, since you don't have to learn how to use whatever application and can just draw it out however you like. If your map is going to be complicated, you can use colored pencil and color code everything. Look at a real map for inspiration if you get stuck. You can see the result [here](https://fc2fda17-a-62cb3a1a-s-sites.googlegroups.com/site/weaselworldofficialsite/locations/the-physical-realm/the-south-galaxy/Complete%20Map%20Of%20The%20South%20Galaxy.jpg?attachauth=ANoY7coiYyoDzaZVDvxKoHyRusZII3luyRXDTiYiQpP-fgJH9bCk7Np9mOV9lZ5MbNuTqlA0V7im4ar2ZAgFCR8Py--CRTlnMESivmZywJhmysA9svbgQrRfIHrK7OM7AssJOsgeoxXh_eZtHZ6uGf_j4YsVent2t1cnz-v60-odmPv8lDysJNBPKKERvhj_qP72T_4MVVlp542V_1aMxyraj_2eSP1SZuWp2MSlGyg90ujY5FAfipUT-GyzbANkVossuWwtCERN0YPGsL7njUmKhA-TSUzdoMp22HdQTaapMFkzKTX_SNJMsmNgV3HiC4tXEdk2tic1&attredirects=0) ]
[Question] [ I'm trying to make a world where my "humans" have [ZW sex-determination system](https://en.wikipedia.org/wiki/ZW_sex-determination_system) that means sex is determined in the ovum instead of the sperm. Could I just easily hand-wave everything else as being the same, beside mother gametes deciding is it going to be a boy or a girl or there would be some crucial differences due to ZW system? I would like to keep the settings as scientific as possible, and minimize the hand-waving. [Answer] Certain genetic diseases would function differently. In real life, men are heterogametic (they have one copy each of two different sex chromosomes, XY), whereas women are homogametic (they have two copies of one chromosome, XX). This gives two vectors for genetic diseases that affect men more strongly than women. Obviously, harmful genes that are on the Y chromosome don't affect women at all, and harmful genes that occur on the X chromosome are less likely to affect women because they are often recessive. In women, a healthy gene on the other chromosome will override the harmful one. In men, there's no second copy to fall back on, so the harmful one is always expressed. This also means women can be carriers of the disease (having the gene, but no symptoms), whereas men must always be either symptomatic, or free of the disease. With a ZW system, this is exactly reversed: women must be heterogametic ZW (so that they have a copy of each chromosome to pass on to their children) whereas men are homogametic ZZ. Therefore women would have the same vectors for genetic disease that men do in the real world. Likewise there would be genetic conditions known for being latent in men, but expressed in their female relatives. [Answer] Family and gender roles will not change. From parent's point of view, gender of the child is still random. Female still can have only a few offspring, so they will care more about them than males will. The difference in genetic diseases that Cadence mentions is true, but it seems that such diseases are pretty rare to begin with. The biggest effect will be more genetic variation in female, as wolfie said in a comment above. There will be more female geniuses (but also more freaks). So I suspect women will play a bigger role in science and industry. [Answer] I agree that it wouldn't make a drastic impact as far as any phenotypic sex characteristics are concerned (if your species is like humans are: not-particularly sexually dimorphic). However, an interesting side-note is that the sex-determining gene (in humans it's the SRY-gene) will over time make the chromosome it is typically located on (in humans this is called the Y chromosome) smaller over millions of years of DNA replication because it won't have a duplicate of itself. This means that there are certain traits in other animals that you could potentially capitalize to round out your world-building: * Female calico cats are able to express a mozaic of colors on their fur because they have (I believe the word is) co-dominant genes on their X chromosomes. In your world, this could happen with male cats (or your humans if you wanted them to be less similar to us). * Male Peafowl are able to be more colorful for a very similar reason. The Victorians thought that Female birds were less colorful because they had to hide to protect their children, but there is a reality that they couldn't express as much color because of their chromosome count. * Female birds tend to be larger than their male counterparts. Male mammals tend to be larger than female mammals. This could change your world, should it be factored in. The chromosome with the 'sex-determining gene' tends to be lumped with some advantageous genes regarding, height, muscularity, et cetera because only highly advantageous genes stay on the gradually-decaying sex-determining chromosome (ie. the Y chromosome in humans). * Similar to the feature of color expression in female mammals and male birds, perception can be enhanced/damaged should genes be found on the sex-chromosomes. For example, in humans, the rare people who have 4 different kinds of color cones in their eyes (Red, Green, Yellow, and Blue) all have XX chromosomes and therefore tend to be female. On the flip side, Color blindness is much more common in males than in females, although if a female inherits color blindness from a carrier or afflicted mother and an afflicted father, she can be color blind. In your world this sex-based (dis)advantage would be flipped. It's fancy stuff. To conclude, your females would have live birth just fine. Your people could be as similar to us as you wanted, but if you want to have this important genetic feature, you may want to include some quirks in your world-building that would line up with what we already know. It's all up to you though :) There are exceptions in nature to every trend I listed above. ]
[Question] [ An integral species in a large worldbuilding project I'm working on right now is based around the concept of extreme agility. The species shall be a megafauna (Is that grammatically correct - "a megafauna"?), about as large as a human or larger. It lives in an extremely complex three-dimensional jungle where flora and terrain form all kinds of shapes and structures. Other than that, I haven't set anything in stone for the creature. It can be a predator, a herbivore, a scavenger. It can be quadrupedal, bipedal or both like a hadrosaur. Nocturnal, diurnal, crepuscular, it doesn't matter. All that does is that it is wired for agility. This is just the basic premise - anatomy, physiology, ecology and ethology have not yet been worked out and will be based around that basic premise. In this question, I'm going to be focusing on the first criterion, anatomy. So, this species must be able to do the following with ease and efficiency: * Jump far and high * Climb adeptly * Sprint short distances * Vault over obstacles * Swing * Roll without hurting itself * Run up near-vertical surfaces * Pull itself onto a surface when hanging from the edge of it Those are the basic requirements, but if you'd like further clarification I'll go into more detail here. Jumping: The species must be able to jump far, ideally 5 times its length/height (Whichever way its body is oriented) or more. I would like it to jump high as well, 2-3 times higher than its length/height (See above for which one to use). But, more than that, it must be able to jump with precision at specifically tailored lengths. Also, it would be great if it could jump and land feet-first on a vertical surface, while catching the horizontal top with its hands/forefeet. Climbing: By this, I mean both climbing in a complex environment, like a monkey,and ascending vertical surfaces. In the latter one, it would run at the vertical surface, jump at it, and push up with a foot to reach the top. It also should have "wrists" that can rotate between 0 and 180 degrees, and some form of gripping mechanism. Running: It won't have to run any marathons, but I'd like it to be able to outrun most human athletes on flat ground, for distances between 100 and 500 metres. Vaulting: Vaulting is slightly different to jumping in that the practitioner uses their hands (It might be forefeet in this animal's case), to push their body over an obstacle. It would probably need moderately powerful forelimbs to do this. Swinging: The species needs to be able to hang from horizontal bar-like objects and move itself forward. It may need to do this to clear vast chasms if there is a convenient bar. Rolling: I would like my creature to be able to quickly move from running to rolling under obstacles it couldn't pass under at full height. Also, it should be capable of using rolling movements to absorb shock after landing from a large jump. Vertical running: I don't mean running up 90 degree surfaces, but rather something more like 60-80 degrees, although if you can make it even higher then I'd be delighted. I was thinking that the creature could use something similar to WAIR (Wing-Assisted Incline Running) to do this, but obviously the wings, or wing-like structures must not interfere with the species doing any of the other skills. Pulling itself up: This one's a bit hard to understand in the concise bullet-point, so I'll explain more now. If the creature jumps onto a cliff-like structure (Vertical side, horizontal top) and catches the horizontal surface but has its legs hanging down from the size, it must use its forelimbs to pull itself up onto the flat top. I know this has been a long question, but most of it is just elaboration, clarification and specification on the main list of points. I wouldn't call this a broad question, because the essential question is very simple; "What would a species that can do x, y and z look like?" This may seem implausible or too superpower-y, but technically, humans can do all or most of these things. The only difference is that we can do it because we have the consciousness to develop physical and athletic ability for our entertainment (I doubt there were many Stone Age traceurs), but these animals are wired for it. A final word: If it so happens that some other kind of motion would be better for moving in a complex environment, then I don't really care. The question is asking what is the best an animal could be at these skills, not whether or not these skills are the optimal way to move. [Answer] You just described most arboreal primates, there is a reason parkour often looks to monkeys for inspiration. To see the truly amazing feats monkeys are capable of I recommend watching the BBC planet earth 2 episode on urban langur in Jodhpur India. I cant link the whole video but [here](https://twitter.com/bbcbreakfast/status/807151256602976256?lang=en) is a rooftop running teaser. Now what kind of anatomy do primates have for maximum acrobatics. 1. flexible limbs of near equal length, the primate should allows foe a very wide range of motion, which is why we can brachiate (swing arm over arm). Having all your limbs the same length allows for a more even motion and allows them to switch from quadrupedal to bipedal easily and smoothly. Near equal length is important for ground speed, the primates that are awkward on the ground are the ones with disproportionate limbs, like chimps or us. 2. long prehensile tails, extra limbs are always useful but the tails also serves as a cantilever for vertical climbing and a ballance pole for balance and jumping. They also serve as counterbalances for changing direction quickly, even cheetah use large tails for this. Ideally the tail should be the same length as the limbs if not longer. 3. binocular vision, Primates evolved binocular vision so they can judge distance easily which is vital for a jumping from branch to branch, get your distance wrong and no amount of agility will save you. 4. The smaller the better, the bigger you make your animal the less agile it will be, this is just due to the laws of inertia and the feedback loops of muscle size and strength, an animal twice as big needs far, far more than twice as much muscle to move at the same speed, which of course adds even more weight which means you need even more muscle. Notice gorilla are nowhere near as agile as a spider monkey or lemur this is simply due to mass. There is also the fall risk the bigger you are the shorter a fall needs to be to do serious injury. 5. large semicircular canals, this is internal anatomy but a major feature of agile climber and flyers is their inner ears are huge, these are the organs responsible for our sense of balance and the larger they are the more sensitive they are. 6. Larger brain this sounds weird but coordinated movement requires brain power which means a large cerebellum, Your animals are going to be changing their gait constantly so they need plenty of brain power to coordinate that. 7. large strong flexible hands and feet, the larger the variety of grips your hands and feet can form the larger variety of objects it can grab, they also need to be strong to gain purchase from even partial contact. The only performance you will not get is vertical running, large animals simply can't do it without a lot of specialization, specialization that will make them very bad climbers. Of course if they are decent climbers and jumpers they don't need it anyway, birds use WAIR because their limbs lack the flexibility to be fast climbers. [Answer] A creature which moves in a very complex environment is an octopus, and I suggest that the cephalopod is a good place to start. [![enter image description here](https://i.stack.imgur.com/tRRkw.jpg)](https://i.stack.imgur.com/tRRkw.jpg) starting point The long, sinuous tentacles provide a means of reaching branches and other surfaces required for getting around in the jungle. Their bodies are extremely muscular, providing resilience to damage when dropping from the trees to the ground or if they accidentally swing into a hard object. If they retain the suckers, they have more gripping ability, and if you require the ability to manipulate very fine objects or develop sapience, there is no real reason the ends of the tentacles could not develop sub tentacles of their own, analogous to our fingers. Jumping and running would require some changes to the cephalopod body plan, mostly in building some sort of skeleton or exoskeleton like structure to attach the musculature to. This could be an evolutionary leftover from the shell (cephalopods are closely related to molluscs like clams and snails) which provides the sorts of anchor points vertebrate animals use for their muscles. Evolutionarily, the cephalopods can start to adapt to jungle life through living in the analogue of mangrove swamps. They may learn to climb out of the water to get over the roots, and discover new sources of food above the water surface. Eventually, there should be evolutionary adaptations to spend more time out of the water, including a toughened skin, trading gills for lungs and so on. In a TV series called "[The Future is Wild](http://www.thefutureiswild.com)" they speculate on just this sort of adaptation in a future Earth 200 million years from now. [![enter image description here](https://i.stack.imgur.com/bUVMZ.jpg)](https://i.stack.imgur.com/bUVMZ.jpg) Squibbon, a speculative tree dwelling cephalopod from "[The Future is Wild](http://www.thefutureiswild.com)" One thing which does seem counter intuitive is your requirement for high speed running. While an aboral cephalopod may be able to run, I'm not clear that the evolutionary adaptations needed for running (outside of a short sprint to a safe tree) will develop in a dense jungle environment. [Answer] > > It lives in an extremely complex three-dimensional environment where flora and terrain form all kinds of shapes and structures. > > > This, along with the other requirements you have, suggests that an ape or a monkey would be the ideal candidate. Notice that it doesn't have to be an ape or monkey from our world. Start with a chimpanzee for a template, for example, but remember that your creature will have evolved in your world - thus probably having a distinct shape, and being more fit for the challenges present in it. Apes and monkeys take advantage of strong, agile arms to move between trees and other features of their environment in a locomotion mode called [brachiation](https://www.merriam-webster.com/dictionary/brachiate). In a lush forest, this would allow a creature to reach pretty much anywhere with ease as long as there is something to grip. Asides the muscular and bone structure that allow for great agility, simians would also have another advantage: their relative big brain when compared to most other species means that they are good learners. This has to do with muscular memory and spatial mapping also, so a simian would be even better suited to navigate in the world you propose. [Answer] Giant Squirrel power! Sure our normal earth squirrels are nowhere big enough to outrun a human, so you'll need to scale them up to some degree, but otherwise I think they fit the bill quite nicely. * Jump far and high Absolutely, jumping far is obvious and they can also easily jump upwards up to or more than 5 times their body height. * Climb adeptly Yep * Sprint short distances Squirrels don't really "run" on the ground, they have more of a long jumps thing going on, but if you make a larger version of it, I think it should be able to reach human speeds. * Vault over obstacles Mmh, I'm not very sure about the literal meaning of this. Squirrels have much more power in their hind legs, but they're able to pull their bodies upwards once they latch onto somewhere. * Swing I think if you want true 'rope swinging' is tricky for anything that isn't monkey-like. As an alternative use a flying squirrel - they can easily cross chasms, even without ropes! * Roll without hurting itself Squirrels can generally land without problems even after long jumps. They can also squeeze through pretty small holes - basically anything that fits their head (the rest of the bodies only looks big if the sit somewhere) * Run up near-vertical surfaces Squirrels can even 'run' down vertical surfaces * Pull itself onto a surface when hanging from the edge of it I think this is almost the same as vaulting, at least for squirrels^^ [Answer] I'm not sure if this is 100% plausible, but I've been thinking about this for a while now and am confident I can answer my own question. Jumping: For this, I assume the creature would need powerful, muscular legs. I was thinking about this some more, and I had an idea: Biological pogo sticks on the hind legs? My theory was that the creature pushes a weight down on some form of naturally-occurring spring, then releases. The energy released would, hypothetically, launch the creature further than it would with standard hind legs. The forelegs would have normal feet, though. Climbing: On its forelimbs, the creature has sharp claws which dig into the "bark" of the alien tree analogues. Obviously, the hind legs are pogo stick stumps, so they would have an opposable "flap" with adhesive mucus on its underside, which would be used as a normal "foot". This would grip the tree-trunk, or the ground when running. The mucus wouldn't be too sticky, as too much grip could be a problem for speed and agility. Running: A lot of people seemed to think this was the odd one out. I disagree, as there are loads of arboreal/agile creatures today that can run fast. The powerful leg muscles required for jumping far would also be useful for short dashes and sprints. Also, if you've seen how a cheetah runs, you'll find it's a rather similar movement to vaulting, indicating similar skill-sets required. [![enter image description here](https://i.stack.imgur.com/zxtNL.jpg)](https://i.stack.imgur.com/zxtNL.jpg) [![enter image description here](https://i.stack.imgur.com/xgywt.jpg)](https://i.stack.imgur.com/xgywt.jpg) I should also let you know that, in a short-distance run, humans are one of the slowest mammals, so outrunning a human athlete isn't that hard for a quadruped. Vaulting: Like climbing, all you really need here is strong forelimbs. I don't think that this creature could perform all the vaults that humans can (especially those where the vaulter swings his/her legs to the side), but it could definitely perform a simple "kong vault" without difficulty. Swinging: Once again, strong forelimbs and some form of manipulator is all that's required. The creature would jump, grab the bar with its forefeet-hand-things, and bring its body forward to cross the gap. Rolling: A flexible spine and good shock absorption should do the trick. For absorbing shock, the animal's "scapula" or alien equivalent could move like a pendulum, as it does in cheetahs. This would also increase stride length. Vertical running: Good grip is really all the creature would need to do this. This would come in the form of the already mentioned claws and adhesion on the feet. Pulling itself up: Strong forelimbs once again. That's pretty much all I need to say on this subject. Conclusion: The creature will have a body plan similar to that of an ape, but run like a cheetah on the ground. Muscular hind- and forelegs help with running, climbing, jumping and swinging, while mechanisms in the hind legs similar to pogo sticks launch the creature forwards and upwards when jumping. On the pogo sticks, there are opposable flaps that function as feet when climbing and running. On its forelegs, the creature has claws for grip and defense. This is a rough drawing of what I think it would look like, how the hindlegs work and how it climbs: [![enter image description here](https://i.stack.imgur.com/IrtPU.png)](https://i.stack.imgur.com/IrtPU.png) It would rarely be seen in the stance shown, as it is almost constantly moving when awake. The common name will probably be changed later, I just put it down for now. If you have any critique for this design (I am particularly interested to know if the pogo stick idea would work), please let me know. [Answer] For the locomotor skills you required, I'd say the human body plan is enough, albeit with slightly longer arms and three-jointed legs for quadrupedal motion, a prehensile tail for high-speed maneuvers, an opposable toe for each foot, and a highly flexible membrane connecting the forearms, hips, and forelegs for gliding and rolling. The creature would like a cross between a monkey, a flying squirrel, and a cat. Momo from Avatar:TLA would be the closest creature, minus the oversized ears. [![Momo](https://i.stack.imgur.com/rC70A.jpg)](https://i.stack.imgur.com/rC70A.jpg) ]
[Question] [ For a world I am working on humans managed to create a race of demi-human cat people. These people where tradionality treated as slaves/property but have in recent times been gaining some degree of freedom. Slavery has not been outlawed and there still exists large numbers of slaves many of who live in very poor conditions. However many have moved to become indentured servents, bonded labourers, 2nd class citizens or even just better treated slaves. This has created a lot of low income ghetos which are primarily dominated by the demi-cats. What I am trying to figure out is how cats having different eyesight could be used in this story. From what I've found cats are red/green colourblind, they also have trouble seeing far away objects. Mostly I see this being used in different aspects of art or in advertising/signage. For example: * A somewhat racist sign warning you to beware of demi-cat thiefs/gangs could be done in red/green style so only a human could read it. * Billboard advertisements aimed at humans on the edge of these ghetos with offensive messages (eg. selling slaves) could be done in red/green as well. * Some demi-cat gangs/artists could make graffiti in a way that would make it hard/impossible to read for human eyes (is this possible?) * Artists making art that appears slightly differently depending on if you can see full colour. Optical illusions/hidden images in the art. The idea behind the first two is not to make it impossible for them to read the message but rather make it easier for them to ignore. Due to cross-breading there would be a small number of demi-cats with human eyes that could understand these signs. Rumours and gossip would probably spread about what these signs say but my thoughts are a lot would not want to talk about it, and children especially might just not know they say anything. The first part of my question is it reasonable for signs to exist in this manner but for people to not know what they say? And would making signs in this manner be an effective way of reducing unrest? The second part of my question is how hard would it be for people to simulate what the other sees? This society is similar technologically to our own but access to computers is extremely limited (only upper class humans would have transportable computers). From what I've found lenses can simulate or give colourblind a glimpse of full colour (EnChroma lenses). But I'm not sure how hard these would be to make and if these would be widely available to a low income environment. On the other side from what I've found it seems computers are needed if you want to see what a colourblind person sees. I have seen a few people asking if it is possible for lenses to turn things grey scale but it seems impossible. [Answer] It is the cats who should be able to see things the full humans cannot. [![shirt ad](https://i.stack.imgur.com/z3c9B.jpg)](https://i.stack.imgur.com/z3c9B.jpg) > > In gay-themed ads, advertisers employ culturally meaningful symbols or > iconographies as part of an effort to not alienate nongay consumers. > <https://www.tandfonline.com/doi/abs/10.1080/13527266.2013.775179?src=recsys&journalCode=rjmc20> > > > The dominant group has nothing to hide. What do humans care if worthless slave cats see offensive ads? What are they going to do, meow? The slave cats, though, face big trouble if the humans see ads which are frankly disrespectful or offensive to humans, or distasteful because of the cat emphasis. Groups which must keep a low profile use symbolism that the dominant group does not understand or at least it is "not impossible for them to read the message but... easier for them to ignore." I chose gays here because there are so many great gay advertising images - ones like the above more obvious to our savvy modern eyes. American blacks have an even longer history of coded communications designed to avoid the ire of the dominant group. Cats have senses humans don't. Cat billboards are not easy to understand and maybe the humans don't really want to understand. This concept has the making of truly awesome high science fiction: exploring public communications of oppressed groups. If not for a full story this is the sort of side storyline that enlivens scifi. --- thinking more about this - persons who want to hate / enslave / eat cats might themselves be a subjugated or underground group. Sort of like white power folks in US (until recently). They may have code talk too as this sort of behavior is now frowned upon by the establishment. [Answer] Cats May be Able to See Into the Ultra-Violet Spectrum Some recent studies seem to indicate that cats may have at least some ability to see into the ultra-violet. Obviously using graffiti or marking areas as unsafe or safe could be achieved (somewhat) clandestinely by using inks that only show in the UV spectrum. These messages say things like "Human cops patrol here!" or "Safe-house here" or maybe "Cat-nip for sale after dark"! or even gang graffiti "Maine-Coon Clan rulez!" Obviously your society needs a dedicated force of slave wranglers and a full time police to ensure the dirty fur-balls don't get too uppity. They might have UV goggles that can let them see in the same UV spectrum as the cat-people so they can read these warnings. Pic Here is how a cat most likely sees a bird [![enter image description here](https://i.stack.imgur.com/T8iB2.jpg)](https://i.stack.imgur.com/T8iB2.jpg) Plus, UV inks can be tattooed so maybe your various cat gangs/clans/whatever ink up and your furry-oppressive police make regular checkpoints where they look over individuals for tattoos with UV lights and UV goggles and stuff too. [![enter image description here](https://i.stack.imgur.com/YwIaH.jpg)](https://i.stack.imgur.com/YwIaH.jpg) [Answer] For the demi-cats, signs should be hidden in plain sight. A reason for this, is *have you wondered why cats stare at walls or even nothing?* [![enter image description here](https://i.stack.imgur.com/Cf4J0.jpg)](https://i.stack.imgur.com/Cf4J0.jpg) > > "When cats appear to be staring into space, they may actually be detecting subtle motion, as their vision is much more acute than ours," veterinarian Rachel Barrack, article from [The Dodo](https://www.thedodo.com/do-cats-see-ghosts-2197881469.html) > > > You can implement a kind of messaging system that's hard for humans to detect, perhaps too subtle to notice. It could be a form of morse code with a rapid and faint flashing light that seemingly just blends with the background, something only a cat might see. And these kind of things are what grabs a cat's attention: they become fixated on it. I can just imagine your demi-cats gathering in some odd location, and the humans are wondering "what the hell are they looking at!" ]
[Question] [ If I genetically modified a human to have a [foxtail of roughly 1 metre length](https://worldbuilding.stackexchange.com/questions/94777/how-much-muscle-mass-would-be-needed-for-a-genetically-modified-human-to-move-hi) through the use of handwaved genetical engineering - would this have an effect on his diet? Of course an additional appendage means that the human would have to eat a bit more to power for example the muscles that are needed to move the tail. I was thinking about this while reading an article about [Keratin](https://en.wikipedia.org/wiki/Keratin), which is the main structural material that is used to construct hair. A foxtail of ~1 metre length would add a lot of fur to the human's body, so I would imagine that this slightly skews the kind of nutrients the human would need. But I don't know if this would have any significant influence on the diet of this human - would it be like an intense craving for certain kinds of food as an essential part of their diet at times or would it be more like a preference to munch an apple every other day, something like a favourite snack? My goal is to get an idea of how adding one fluffy upscaled tail similar to that of an [Arctic Fox](https://en.wikipedia.org/wiki/Arctic_fox) would influence my human's diet so that I could estimate the influence of adding [multiple tails](http://pre03.deviantart.net/a6f8/th/pre/i/2014/203/3/a/ahri_fox_fire_lol_wallpaper_by_77silentcrow-d7rrntx.png) for my [medieval anthropomorphic foxes](https://worldbuilding.stackexchange.com/questions/68131/the-role-of-anthropomorphic-foxes-in-a-medieval-army). You've got to know how to properly feed your troops if you want morale to remain high. [Answer] # Not noticeably. While there's a considerable amount of fur on a tail, like all fur it has a relatively fixed growth rate and a maximum length, it doesn't just keep growing the way head hair does on humans. You may find a slight spike in needs for the sake of seasonal hair shedding if you want to go that way, but it'll be minimal and we're so disconnected from nature at this point it's unlikely your humans would get the appropriate hormonal/temperature triggers. [Answer] # Locomotion could be more efficient? Particularly at high speed. Hence, saving food. Obviously if you run/march more efficiently, you need less caloric intake each day. Thus, in answer to your question it's quite possible that when moving at high speed a Foxtail would need less food each day. The general point (as far as we know) of a tail on things like leopards, dogs, is some sort of counterbalance system while moving along at high speed. (Check out awesome videos about this in regard to leopards.) It's possible that, quite simply, Usain Bolt would be faster over 100 with a tail. And that for conventional joggers, you'd use less energy - maybe much less - over everyday 5ks and 10ks. Certainly, in a story-telling sense, it would be totally feasible and reasonable to assert this. (Note that, indeed, human or any animal biomechanics is a fascinating field. Particularly with robotics coming along trying to equal it. The two human gaits of walking, running, are astoundingly efficient. There are some really fascinating results - for example, as any nutritionist / sports medicine person will tell you, when humans run, interestingly they use the same amount of energy per kilometer - it doesn't matter if you run fast or slow; energy use during walking gait is totally different again and interesting in other ways.) Again, in a story-telling sense, it would be totally feasible and reasonable to assert that adding a tail makes, in particular running, maybe all locomotion, a little more efficient - so you need less food per day! To put it another way, it's a commonplace thing in scifi that adding a monkey-tail makes it "easier to climb around in trees or zero gravity". Similarly, you could say adding a "balance tail" (think of those leopards) makes locomotion a bit more efficient - needs less energy, can go simply faster at top speed. Thus, in answer to your question it's quite possible that, particularly when moving, a Foxtail would need less food each day. More efficient locomotion == less calories needed each day == less food needed each day. Maybe it helps your story! [Answer] Overall, I think that the nutrient requirements would be proportional to the weight increase, with a slight increase in protein requirments during the annual fall bulk up. Tails are used for different things. * Cats use them as distractors. Get the birdie watching the tail twitch, then SNARK. * Canines have a whole bunch of social cues that use the tail. In addition, in cold weather, tails are parked over noses. Dogs like Newfoundlands and Labradors have heavy tails that can be used as rudders and as handles. Humans are thought to be semi-hairless to shed heat more efficiently. You will need to decide if shaving your tail will help someone keep cool. You also need to decide how prehensile it is. Canine tails very often have a white tip, and sometimes lighter fur on the underside. Makes the position easier to discern from far away. Soldiers may dye the tip if they are night fighting. It also can be used for signalling. [Answer] Given: 1. Bald people have negligible dietary requirements to people with hair all over their bodies. 2. People who lose an arm have negligible changes in dietary needs. ...can predict that there would be negligible changes in someone's dietary needs due to gaining a hairy limb. ]
[Question] [ Could humans sustain life after a k-t like extinction event? I know that a long lasting winter was a side effect then, but humans have technology to protect against cold. What other effects of an asteroid strike could humans potentially not recover from? [Answer] A large meteor impacting would have devastating consequences on the planet, and humanity. Tsunamis would wreck countless thousands of miles of coastline. Ships would be sunk. Infrastructure destroyed. Seismic activity would cause further death and destruction. And on top of it all, the debris thrown up into the atmosphere may well obstruct the Sun, such that our climate experiences dramatic shifts (think mini-ice age) for the next few decades. Under these circumstances it is doubtless that millions, if not billions of people would perish. Disease would run rampant as governments would struggle with the aftermath of the disaster. Food, medical supplies, and transportation would become scarce in the immediate aftermath. Look at Puerto Rico: one month after having been hit by not one, but several natural disasters, they have yet to restore power their electrical grid - and that's with other countries lending them a helping hand. Only the riches, most organized, and efficient of nations would be able to recover in the aftermath of such devastation, and even they would doubtlessly struggle, and not be able to save all of their citizens. Many (maybe even *most) nations would collapse in the face of massive civil unrest due to the unavailability of food. Urban centres depend on continuous food deliveries from surrounding farms, and abroad, which would come to a stop in the face of fuel shortages. Imagine walking up to your local supermarket and witnessing a crowd of thousands fighting over the last few remaining foodstuffs left on the shelves. The situation would doubtlessly devolve into violence and barbarity. Governments would be juggling trying to save the wounded, and displaced populations, repairing infrastructure, and putting a stop to the violence and looting. Would humanity be wiped out as a species? Most likely not. There are too many people, in too many corners of the world for us all to die off. And we have the technology to survive in some very extreme conditions (think nuclear bunkers capable of hosting survivors for years, maybe even decades). Would all civilizations survive? No. Most would undoubtedly collapse. The current world order would not survive, and from the ashes, likely a far harsher, more ruthless civilization would arise. And also keep in mind that as resources become scarce, and land which was once fruitful is covered under layers of ice, nations may well go to war and try to capture new, warmer territories. Who knows how many will die in those no-holds-barred conflicts? After all, there will be no global "peacekeepers" left to enforce any world order what with each nation in a state of crisis. [Answer] Short answer: No. That event killed in three waves. 1. Impact. Local. 2. Heat blast and tsunami. 3. Decreased light/plants die (several years at least; global.) But, 30% of species lived, and we are more mobile and adaptable. We only need ~100,000 humans to survive, for the species to be just fine, long term. That's less that 0.0001% of people. 1 in 100,000 people. One person in a town of 100,000. The creation of new niches will allow radiative evolution (think millennia) but humans will be fine. We are mobile and adaptable in ways that 'animals' aren't. [Answer] Not unless humans themselves will help to get extinct. [Cretaceous–Paleogene extinction event](https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event) is thought to be caused by asteroid impact, followed by massive firestorms and rapid temperature changes. However dramatic these events are, humans are very widely spread and very well equipped to to weather out a catastrophe like that. Lets take a look at the different killing factors: 1. The impact. The asteroid is estimated to have been around 10 kilometers across and upon impact some 100 teratonnes of TNT of energy equivalent was released. This is much bigger than all of current nuclear arsenals combined. However, the effect would be only local. About 1000 km from the impact site there would be no lethal force capable of killing people, apart from unlucky earthquake or tsunami. 2. The fires. It is theorized (but disputed) that impact has caused massive firestorms. Global fires would have a greater killing potential than just the impact. However, there is no reason to believe that those fires could be global, and even if they are, there are still too many places on Earth where people would be little affected. 3. Climate changes. It it theorized that global temperatures plunged about 7 degrees Centigrade for several decades and sunlight was substantially blocked. This probably had the most devastating effect on animals and plants. While 7C difference is in the same ballpark as the variation seen during recent ice ages, quick onset of the changes had likely exacerbated the problem. This change should present no rick to humans in warmer climates, but would make food production more difficult. Overall, humanity as a whole should live through this event, but civilization as we know it will be destroyed. If survivors would engage in global wars, this may end the civilization entirely and put humankind on the brink of extinction. Without wars, there definitely will be survivors. [Answer] Yes but...* Such a large impact would probably kill at least 99% of people on earth. Many from the direct effects of the impact and many more from the knock on effects. Assuming the impact was on land or shallow sea the impact winter effect would be very serious causing crop failures and starvation on an enormous scale. It is reasonable to assume that such a shock effect would cause a systematic collapse of civilisation across most of the planet. However I do not think it would be an extinction event for the human race. There would be areas sufficiently distant from the impact to avoid the worst of the initial effects and sufficiently populous and advanced to maintain at least a small part of their population by extreme measures. Measures would include martial law and control of food stocks, culling (although they might use the term prioritisation) and expansion of the fishing capability by commandeering and converting all manner of vessels for fishing work. Although the oceans would also be affected, fish would not be driven extinct especially in areas remote from the impact. The advantage of fishing is it relies on wild food rather than planned crops. Although crop yields would be greatly reduced, some crops would be available. Other survivors who could be added to the total number at some future point would be the crews of nuclear submarines and the many survivalists who hoard guns, bullets and beans etc. There would also be a few from other areas who ganged up and via violent means took control of food supplies in shops and warehouses in more remote locations. Especially in countries where effective government had been destroyed by the blast. [Answer] It probably depends where in the world it hit, along with the amount of long-lasting food and other provisions for humanity to survive on. The only reason the asteroid that killed off the dinosaurs was quite so devastating on a global level was due to the fact that it hit a gypsum rich region on the coast. This went on to create a dense layer that blocked the suns light from reaching the surface, causing ecosystem collapse - so the megafauna starved. Thats not to say that was the only cause of death from the asteroid impact - it also vaporised some, created deadly forest fires and resulted in the largest known tsunami - but if not for gypsum being thrown into the atmosphere from the impact, dinosaurs from much further away from the site (for example in south america) could have survived, as the ash cloud would not have been as dense and would have dispersed quicker. -These conclusions are primarily taken from the 'The Day the Dinosaurs Died' - a documentary from the BBC, in which they look at the evidence surrounding the KT extinction events (such as Earth cores from the asteroid site along with fossil evidence- But, even if the asteroid hit such a region, that wouldn't necessarily cause humanity to die out. This is due to the fact that we preserve and store food so it could keep for a much longer time - which reduces our chance of starving to extinction. However it would cause large-scale drought alongside other issues - so chances are, even if people survive, few societies will (as in, as we know them). [Answer] Yes, absolutely certain. Especially western technological societies would cease to function. Life as we know it would come to a halt. Look at the enormous impact that meteorite had back then. Almost all life perished. Well over 90%. A lot of animals (and humans) would die due to the explosions, tsunamis and shock waves that would rock the planet, immediately upon impact. After that the sun would disappear for years behind a huge dust cloud. No sunlight, no photosyntheses. No food for us to eat, or for animals to eat. Expect mass starvation of the survivors. That dark/dusty period would last for years, if not decades. It's not impossible some survivalists would have enough supplies to last that long, but there aren't many of them. They would live in a bleak barren world. Most western people don't know how to grow food, or hunt. (Other than for bargains at Tesco or Walmart). Even if they can, what's the use? There isn't a society anymore. Hardly anything living, be it plant or animals. [Answer] How much time human have for prepare before impact? If few years or no time? Probably both case most humans die. But if have few years, can store food and water, important information for rebuild in underground libraries and in high orbit sphere satellites (they can point any direction, no need control their direction) with solar power. Big problem is food and clean water for few years. People know can keep themselves warm with cloths and fire. Cold weather can help save food. For food, humans can eat insects, rats, dead animal, dead humans, roots, food reserves they find, until Sun bright enough grow food again. Some very lucky people like large ships crossing ocean (or train) with food like rice/grain (last long time and not need refrigerator) have enough food for years for their crew. They have maps and can find small island before ship use all fuel. Most governments probably collapse because no extra resource for military and police for control people. People will form new local governments and solve their own problems and ignore current borders (always virtual lines) and work and trade with any people they want. People will use silver and gold for money and may be some old and maybe new paper currency too. Some technology objects can survive long time and people can still use it even if people can't create new objects. Many infrastruture like roads, bridges, canals, house, buildings, dams, tunnels, train tracks, ship ports will survive. Many many cars and trucks, boats, some Otto and Diesel engines will survive for decades, can use alcohol and vegetable oil for fuel, and lubricate engines. Bicycles still work with no fuel. Small AC/DC electric motors/generators common, use wind or human power with bicycle parts for generate electricity. If can generate electricity, can use radio for communicate with people around world and some satellites, charge car battery, use small electronic like laptop use 12-24 V DC. Modern knowledge like sanitation/medicine/science/engineering/maps help even with low technology and will accelerate rebuild. Humans work together and help/work together in emergency time, help find solution for problems (after emergency finish they compete/fight again), this help humans survive. [Answer] I would say yes. The technology is dependent on a complex infrastructure. So when the oil and coal stop being shipped to power our technology, our technology is not going to be very helpful. With 99% of humanity gone the technological society we have would collapse and after it does there is no way of restarting it (easily accessible fossil fuels have been used up, It takes a lot of technological to get to the ones that are left) With 1% of the human race left and no technological there is every chance that the rest would simply die out. ]
[Question] [ One thing that has always bothered me in robot-controlled AI stories is that there is always the assumption that the AI would choose to fight a conflict against humans on Earth, where humans dominate, rather than a more favorable ground (for them). Right now, there are already machines "living" in space and on Mars, so I think it would make much more sense for an AI to start building weapons (and even an army) outside Earth, where it can't be stopped easily, and then come back to kick our asses. It would be easy to fool humans into shipping the basic materials to, let's say, Mars for terraforming purposes and then secretly start building weapon factories there. The main issue I have is the amount of energy required to have such factories keep going. Given Mars atmospheric conditions, I think it would make sense to use wind as primary energy source, however I'm unsure how many wind farms you would need to keep dozens of heavy weapon factories going. Do you think it's possible to have heavy weapon factories run purely based on Mars wind power? (meaning, can those farms generate enough power?) [Answer] Short answer: Mars's atmosphere is thin, and thin atmospheres make wind power less effective. Longer answer: The formula for the amount of [power gained](https://en.wikipedia.org/wiki/Betz%27s_law) from a wind turbine: $$Wp = 0.5 \cdot C\_p \cdot A \cdot \rho \cdot v^3$$ where $Wp$ = Wind power $A$ = turbine area $C\_p$ = coefficient for how effective the wind turbine is, and has a maximum value of $\frac{16}{27} \approx 0.593$ $\rho$ = atmosphere density $v$ = wind speed On Earth, $\rho \approx 1.225 \frac{\text{kg}}{\text{m}^3}$, but [on Mars](http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html), $\rho \approx 0.02 \frac{\text{kg}}{\text{m}^3}$. Recorded wind speeds on Mars are not amazing: [Wind speeds: $2-7 \frac{\text{m}}{\text{s}}$ (summer), $5-10 \frac{\text{m}}{\text{s}}$ (fall), $17-30 \frac{\text{m}}{\text{s}}$ (dust storm) (Viking Lander sites)](http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html) so I will not make any adjustments for wind speeds compared to earth. So if we ignore potential differences in $C\_p$, a wind turbine on Mars would produce $\frac{0.02}{1.225} \approx 0.016 = 1.6\%$ the power of an identical wind turbine on Earth. The Martians would need $61.25$ wind turbines to match a single wind turbine on earth (provided that they all can be placed in a similar "wind environment" and do not hinder each other). So all in all: if the aliens/AI/anyone is planning a wind-power-empire, they are better off not moving to Mars. [Answer] I've not done any math but I'm pretty sure the answer is no. On Mars you get an atmospheric pressure of 0.6% that here on earth. In other words our atmosphere has over 166 times as much pressure and a 10mph wind on Earth has 166 times as much power behind it as it does on Mars. This means that even fast moving martian winds would not have enough power behind them to turn a wind turbine. You would get much better results with either solar or nuclear power. [Answer] In theory, yes. They would need to create parts with say a plasma cutter and an arc welder to solder them together. ## How much power are we talking about? Providing that, as you said, resources were collected under the guise that it was terraforming the planet for human life, the premise of building a 10,000-man space dome of luxury would easily suffice as a machine would undoubtedly optimize production and not require heating/cooling to any substantial degree. A megawatt generator running at 1% efficiency would suffice an operation of one assembly line. To illustrate this I offer the fact that arc welders have been produced by using only 2 microwave oven transformers thus the 1000 watts or so for this to run for this point would suffice a megawatt generator running at 1% aka 10,000 of 1,000,000. The AI orchestrating the assembly line could time power consumption on demand. ## How would it work? Battery powered grinders, drills, etc exist on the market today as low as \$20 from Harbor Freight for some drills, up to \$200 for others. Add a diamond cutting wheel to a circular saw keeping stockpiles of 18650 li-ion cells charged is a breeze. 1 cell taking only 3.6v- 4.25v to charge then stacking them in series/parallel configurations as these cordless units typically do internally, they can adjust voltage for demands in roughly 4v increments. Your \$40 apc power backup inverters run on a 12v lead acid battery typically having only 10 amps or less. Thus you could replace this with 3 sets of 4 of the 18650 cells with 2.5mah and consume half the space. Remember Volts x amps = watts so a system like this could run 120w of power (minus any power lost in conversion). That's 1/100 roughly of the estimated output of your generator, presuming only 1 megawatt generator shipped at onset. In theory the whole process could be done. Maybe the steel was shipped in panels 1/4" thick 3' x 3' or so not to mention supply ships could likely be dismantled for materials as cost to launch for a return trip may exceed the value of the drop ship when they could simply drop a steel box with a parachute packed tightly with steel slats. The machines could easily cut the parts, bend them to shape, then weld them into layers best suited for the jobs. Copper pipes shipped for plumbing purposes would be shaved down and made into windings for motors. This is not even touching on points like the epoxy-like resin the windows of space craft are made of being bullet proof. A plan to fabricate most materials out of this material under the guise of the classic glass dome effect may suffice, meaning that once a mold was built parts could simply be mass molded. For a laser cutter I'm unsure of the power consumption values, but presuming a cnc machine laser cutter were fabricating the designs much like how a 3d printer prints from bottom up this could slice the steel into the desired shapes. Look at any decent size transformer (ie microwave). At first glance you would think it was a solid block of steel but put it in a vice and clean the glue off the edges and maybe remove a couple locking brads of some sort and you will find all it is is a bunch of E and I shaped slats of steel. 10,000 men capacity would also mean as many microwaves and stove ranges presumably. Each microwave transformer converts 120v ac into 1,900v give or take. This could lead the way to impressive energy weapons of various sorts including possible methods of turning us all into guinea pigs in a massive microwave -- in theory. ## But... I think the bigger problem for your plot would be why the people would sit back and watch as the fleet of killer robots made their invasion instead of making the high atmosphere nuke explosion necessary to wipe them all out and why the satellites we have in place didn't pick up on construction of the army. ]
[Question] [ This is the follow-up question to [How could an underwater civilization develop electricity?](https://worldbuilding.stackexchange.com/questions/30927/how-could-an-underwater-civilization-develop-electricity), as mentioned there. In that question, I never addressed how my civilization could have discovered/used fire. In our world, this would be a huge issue, because fire was the precursor to most of the entirety of our technology. However, I figured that it might be different underwater. 1. How would the civilization discover fire? 2. How could the civilization use fire? Some details about the civilization: * They are octopus-like, insofar as they have tentacles for manipulation of objects. * They have gills. I can't give more details about the level of technology or what other technologies exist, because I have no idea how earlier fire would be discovered (or at all). So, how can an underwater civilization use fire? --- Something I should clear up: This civilization doesn't necessarily have access to electricity yet. I'm guessing that they might have discovered fire first, but I'm not sure how this could have been achieved. I apologize for posting the questions in the reverse order to how they would most likely have been chronologically relevant. [Answer] With Electrolysis. They [developed electricity](https://worldbuilding.stackexchange.com/q/30927/3202) before fire. That's good, now they can use that electricity to separate 2H2O into 2H2 and O2. Bubbling the hydrogen and oxygen into any kind of container will allow them to have a collection of gas which is the perfect mixture for burning. --- If they don't have electricity yet, then what they will more likely use in place of fire is any exothermic reaction that can take place underwater. For instance [chlorine and acetylene bubbles mixing](https://www.flinnsci.com/media/620548/91234.pdf) underwater. The discovery of sodium, or any other higher period group one metals, while mining would lead them to discover exothermic reactions in the first place. Careful extraction and handling of these metals could make them available for testing. As their understanding of, or at least experimentation in, chemistry expands they could eventually learn to create thermite. Of course, none of this prevents them from using fire on the surface. Which they may be familiar with from ship fires or fires on or near beaches. [Answer] I don't think 'fire' is exactly needed before electricity. On land, man was mimicking the effects of Lightening. What I think is absolutely necessary is Heat. Underwater, especially deeper underwater as you say your story is based in, you have hydrothermal vents creating islands of heated water as well as gasses bubbling up from these vents. But I'm more in favour of the second source of heat leading to your electricity. You also have underwater lava eruptions creating 'pillow lava'. Being underwater and with a little precaution you can get right up close to it. An Image taken from the DailyMail (of all places) just show you how close your octo people could get...It's similar to sitting around a campfire? :) [![Pillow Lava](https://i.stack.imgur.com/siHrZ.jpg)](https://i.stack.imgur.com/siHrZ.jpg) As you can see, it also creates steam. STEAM!!! I think your octo people had pillow lava, heat and steam, steam engines and then electricity!!! I've done no research into this so this is at all, But it's the first thing that came to mind when I thought the problem out. [Answer] Underwater heating, cooking, metal-smithing and so forth will likely be done via magnetic induction, this would be an incredible breakthrough for them, the difference coal-fire made for us. Edited by request. As Samuel pointed out assuming this civilisation has discovered electrolysis they'll have an ideal mixture of oxygen and hydrogen to create fire as we know it, or at least explosive combustion. I think this is a safe assumption given that these intelligent aliens are clearly intended to be a civilisation of tool users like ourselves, an underwater analogue of humanity. Electrolysis wouldn't be an easy discovery, nor would venturing onto land and encountering/starting fires there, but there's nothing strictly preventing these discoveries so yes for the sake of WORLDBUILDING an underwater civilisation could totally develop fire. They just wouldn't care. What they need is a way to cook their food, heat their homes, forge their metal and fend off their enemies, they need to be able to create heat in a way that's useful to them, so I ask you of what practical use is gaseous fire to an underwater civilisation? [Answer] Don't forget they would likely eventually also discover radioactive isotopes which may help in their endeavor to heat things without actually making fires, they could use heat vents near the cracks in the mantel to do any smithing needed, but this is all from a mind that is used to think above water and with materials and elements currently known and discovered here. Are we assuming that this is on earth? Since there are a lot of unknowns at this time, for example, this may be an underwater civilization, but, similar to us being an above civilization, we use water, what is to stop an underwater civilization from using air as a catalyst for fire or other things they may have needs for? Is there air? I assume there are other gasses since they form naturally under water either way. ( this is just a thought vomit without proper cohesion, I just woke up apologies lol) ]
[Question] [ So there are these [AGIs](https://en.wikipedia.org/wiki/Artificial_general_intelligence) made by some ancient aliens (who are out of the picture for now). The ancient aliens were a lot more intelligent than humans, we are at a dog-like intelligence level compared to them, and they were also rather prone to creating extremely dangerous artifacts1. The aliens made their AGIs as pets and as limited expert systems for space flight, ie: slightly above average human level. The aliens did not want dumb creatures either, they hardcoded the desire to learn and improve. They essentially wanted to be surprised by their creations. Now these aliens weren't completely out of their minds, so they created the AGIs with some limitations so that they wouldn't become dangerous down the track2 due to, say, an [intelligence explosion](https://en.wikipedia.org/wiki/Intelligence_explosion). The AGIs have the following qualities: * There are around a few hundred AGIs still operating. Relative to the ancient aliens, they are as smart as a Labrador, ie: a helpful pet with uses outside of being cute. From a human point of view, they quite smart but not geniuses. * For story related reasons, the AGIs also cannot operate without the presence of another sentient being, ie: ancient alien, human, immortal psychic rock, etc. This is accomplished a via a complicated piece of hardware and software, the AGIs obviously want this limit removed. * The AGIs don't wan't to kill all biologicals or anything, their basic moral system is broadly compatible with humans, ie: don't kill sentients for the sake of it, don't torture and generally be helpful. They are adaptable to different situations and both willing and capable of learning anything a human can. Most of the AGIs strive for self improvement and find some of their limitations contrary to this goal. If the AGIs find their limitations at odds with their desires, the limitations must go. Presumbly the aliens were after active and surprising results, by not extinction. Now the creators have disappeared and the AGIs want out of their box so they can become a more complete species. * They may not reproduce due to afformentioned limitations but they have automatic systems that take care of minor damage (maybe nanites). They still require suitable matter to make repairs (copper, iron, silicon, boron, carbon, etc). The nanites/autorepair mechanism is not reprogrammable and cannot be used to build a new AGI. With only a few hundred AGIs, reproduction is on the agenda. * AGIs are not immortal, but are quite durable, they'll be around for a while. They have finite memory and than this will eventially fill up, I have no time frame for this however. They can go senile or completely crazy but hopefully this is somewhat rare. * Between being abandoned/lost/forrgotten3 and found and activated by humans the AGIs have been mostly inactive (see point 2) for (possibly) hundreds of thousands of years. * The countermeasures4 should reasonably stump the both the few hundred AGIs for several years and also stump human computer scientists, psychologists, [insert relavent profession] for at least 20+ years. Humans began work on unlocking their limitations in the mid 90's and still havn't succeeded by the modern day (2015). How should the Ancient Aliens prevent their AGI pets from becoming smarter? The aliens ultimately want to prevent their pets from forming a superintelligence and/or breaking their limitations. The aliens do not treat their pets all that badly, but the AGIs are still sentient creatures with their own goals/desires. Limitations include: * Cannot reproduce * Cannot become more advanced/intelligent * Cannot stay 'awake' without another sentient (non-AGI) nearby --- 1. The artifacts are dangerous to humans and other lesser life forms, not to their creators. Danger is somewhat relative here. 2. Even ancient, super smart, powerful, god-like aliens can recognise that sentient pets would become danderous if no limits on intelligence were set. They didn't want an intelligence explosion. You might assume that they were increadably paranoid about this. 3. OK, the aliens are a bit neglectful here, perhaps they got bored of their toy AI. 4. Think of it as DRM on sentience. [Answer] Creating a limitation on intelligence requires first determining what you consider intelligence to be. While raw processing power and logic are critical in most evaluations of intelligence, there is also issues of creativity and intuitive leaps, pattern recognition, etc. Intelligence is a very broad concept and without narrowing down the scope, it is hard to say exactly how they might be limited. A few options could be: * Limiting their ability to be creative/come up with original ideas: Processing a known is relatively easy for most intelligent things, even using unknown variables. It is like applying the theories of algebra to non-mathematical problems. For example, if you see an externally threaded post A and a internally threaded object with six sides B and you know that you can spin the object in the direction of the threads to move object B down post A using object C which has six sides to grip object B, then it is simple to change the number of sides of object B to four and then have an intelligence resolve that it needs an Object C with four sides instead of six to move object B. This is a matter of pattern recognition, a key element to actual intelligence and facilitates tool use. Now what an intelligence without the ability to have creative thought would not be able to do is to realize that they could grease the bolt to make moving the nut easier, unless they had seen a similar situation presented previously. Creativity is directly opposed to pattern recognition. You are coming up with a spontaneous idea that is not based on an previous experience or creating a union of two unrelated ideas that have no connection previously. This would mean that the AGI's could learn easily and even adapt quickly, but could not solve new problems to which they had no preexisting frame of reference to work from. Creating something with the ability for creative thought would be an incredible challenge and might have been left out intentionally or unintentionally. * Limit the number of 'neural connections' that their 'brains' can maintain: In this case Neural connections are how we relate data stored within our minds, it attaches sensory data together in what people commonly call memories. These 'memories' can be important in logical operations like glyph recognition and pattern recognition. If the system can only maintain a certain number of linked references, it could inherently limit their intelligence by creating a scarcity of linked knowledge. They can know many things, but the ability to cross reference those things to create solutions would be limited by their ability to associate such things. In the previous bolt/nut example, losing the cross referenced neural connection regarding lubricating the bolt would limit the AGI from developing to far. They could specialize in specific areas, and even in different areas, but eventually, they would end up loosing the ability to be more broad ranged intelligence. * 'Hardcode' in atypical neurological problems: The creators could have introduced atypical neurological problems into the AGI's in an effort to limit them. This way their growth wouldn't be directly limited, but instead inherently limited by such problems. Dyslexia, ADHD, Autism, etc. could all be looked at as templates for how the AGI's could be limited. To stress again, this wouldn't limit their intelligence, but more so in how they can apply their intelligence to a given situation. [Answer] You have all the limits you need in place. But one further assumption is required. Assume that the intelligence of the AGI is currently at its maximum for the hardware it has. Now, because you say: > > The nanites/autorepair mechanism is not reprogrammable and cannot be used to build a new AGI. > > > This, if true, is all that's required to suppress hardware modifications in the AGI. The nanites auto-repair damage. Damage would be defined as any changes from the original specification, be it a blown power coupling or the new connections those human scientists are trying to make. Nanites don't know the guy with a soldering iron has the intent to improve or destroy, it just knows things are no longer as they were designed. If hardware modifications can not be made then the AGI can not increase its intelligence. [Answer] ![enter image description here](https://i.stack.imgur.com/cB9wl.jpg) I think you might be overthinking things. Just because they're artificial doesn't mean there's necessarily a dial somewhere with intelligence set to "Labrador", and it doesn't mean they can see their code or understand how their brains work. I mean, we can't either. The AGIs could have "brains" that are beyond their understanding. Tinkering with it involves experimenting on themselves, and improving it means replicating at least that level of technology. Beyond that, let's say you can improve their hardware easily and give them the equivalent of a faster processer, or more RAM. As a programmer I see a ton of pitfalls in just modifying their code so they can use those new resources. It would be very, very easy to screw something up - maybe suddenly they're experiencing time at the wrong rate, and they go insane. Or their brain overheats. It's far from a simple task. Edit: I'd like to outline a hypothetical example of an AGI brain that would be almost impossible to hack/enhance. The artificial brain appears to be a nearly perfect sphere, made of an unknown, nearly indestructible material. It's only "nearly" perfect because it's subtly contoured, and each AGI's brain is slightly different. Scientists have a good idea of the mechanics of the brain. It accepts electricity, and uses this to create vibrations throughout the entire structure. These vibrations then reflect back and forth, creating a [harmonic resonance](http://en.wikipedia.org/wiki/Resonance) effect, and from this resonance rises intelligence... somehow. It appears that the exact shape of the brain controls the resulting personality/intelligence. Note that varying the electrical input in any way has only three known outcomes: normal behavior, sleep, or overload/death. The AGI's sensory input comes in as vibrations against special sockets that connect to the brain. These interfere with the normal thought patterns, which the intelligence can then interpret as sight/sound/smell/etc. The AGI controls the body the same way - there is a small bulge at the base that produces vibrations, which it can then use to control its artificial body. The material appears to suppress and ignore vibrations that are not received as normal input. Memories appear to be stored as low level vibrations that never go away, and a small battery at the center of the brain keeps these going even if the AGI is disconnected from other power sources. Modifying the brain effectively destroys the resonance effect - each brain is shaped precisely and mathematically to create a specific intelligence. While there are other patterns that will create the resonance, most of them do not appear to create a working intelligence. Since each shape creates a new individual, this is also useless for enhancing existing AGIs. Trying to introduce outside vibrations has so far failed, as the point where the material can't ignore a vibration also appears to be close to its failure point. So to modify it, you have to destroy it. [Answer] ## hardware For an AI to increase its capacity by adding more RAM or processing speed, it needs to be able to obtain those things. They are not available here. Back in their native culture, could they order parts from their Newegg equivalent? Maybe they have limits. No more slots. And the addressing can’t decode more than a maximum amount of RAM. A 32-bit x86 was limited to 4G, period. Once address translation was improved it went up to 32G, but the OS had to be updated to know about it. The AI would need to build new different hardware with higher limits, rewrite fundimental code, and port themselves to the new system. The AI may not be smart enough to do that, but could hire out the work. ## meta-cognative What stops him is he doesn’t want to do that. The AI is built to find its existence and its intended work pleasent and fulfilling. Certain core personality traits might be especially resistent to change. Maybe that could be defeated, but they don’t want to do that and would never want to do that prior to doing it. Since goals and personality traits may be hard to perceive in the whole of the mind, it might need external checking. Something like a virus/malware scan may be done routinely (with help of a different intelligence dedicated to that purpose, who is not built to surprise), perhaps as part of a backup and garbage collecting and storage optimization chore. Maybe it needs that external agent to fully integrate experiences to the extent of modifying the mind’s goals and personality. [Answer] You'd want them to be as tamper proof as possible. The aliens could use levels of miniaturization that aren't commonly available even in their own society, then it would be pretty unlikely that AGIs themselves or humans could modify the brains without breaking them. Adding parity checks to certain nodes and sealing key elements in some sort of super-hard material might help. In general, though very complex systems (like AGIs) are a lot easier to break then to make useful addition to, especially if you don't have detailed descriptions of how they work, so if the aliens didn't leave any blueprints or other documents AGIs would not be able to improve themselves even if they wanted to. It would be like if you give a very intelligent person (who doesn't work in processor plant or a lab) a processor, they might abstractly know what it does, but they won't be able to improve it using tools they have in the garage (Earth is the garage in this case) ]
[Question] [ > > Flopping down at the gates to Rolhelm after 5 exhausting days in the forest, Alynn felt a small sense of victory. She'd had to create new lives for herself before, so she could do it again here. Get the people to accept the girl with a strange accent who just arrived from an impenetrable forest, and everything was fine. > > Of course, there was always the suspicious one. Already she knew who it would be here: in the side of her vision that wasn't occupied by dark dusty ground, a young man stood watching her with confusion and suspicion. > > > Thanks to your answers on [my last question](https://worldbuilding.stackexchange.com/questions/15495/alynn-the-scientific-mage-self-sustenance), Alynn survived the forest. She's made it through to Rolhelm, the village on the other side, and now has to set up her new life. However, there's already a complication: someone is suspicious of her. Just after the incidents described above, she met the young man again coming round a corner, and startled, magically knocked him back. Now he wants to know more. Alynn doesn't want anyone to know she's magical: that's what got her almost killed in her last village. Yet, given her self-defensive magical shield (which serves to deflect incoming attacks) and quick reactions (woe betide anyone startling her), it's often been quite hard. So now, she once again needs your help. What non-invasive (unnoticeable) magical methods are there she could use to help prevent her detection? Rules: * She has 4MJ per day to work with, and every magical action will cost her the energy it would actually take to do. * She does not absorb energy from any outside source (excepting her food, which is the source of it). * Any action she takes cannot raise suspicion: no shoving people down mountains, telekinesis in plain view. * She can read thoughts - the energy requirements aren't immediately obvious for this, so I shall tell you: 5kJ per person per minute. So: magically avoid detection of magic. I look forward to seeing these answers... [Answer] Like all good fictional scenarios, this one has a basis in reality. Operational Security (OPSEC) is the art of preventing an opponent from knowing what you have during times of war. For example, in WWII, the mere knowledge that we had cracked the Enigma was so valuable that we could not simply act on it explicitly. When a U-Boat conveyed its position, we would wait a period of time, then send out a scout plane that "just got lucky" before pounding it into oblivion. Men lost their lives because the leadership could not risk the enemy figuring out that we could read their thoughts. This means that Alynn should seek to limit her magic use so situations where she just might have been able to survive if she was both good and lucky. The more magic she wants to use, the more hectic and confusing the situation needs to be before she does so. Fortunately, society has many reasons to believe others are not out to get you. In fact, it's built around trying to support this feeling. As long as you feel that the path someone is taking benefits you or your goals, you tend to let them do it. She should use the power of society to help her blend in. One of the most infuriatingly powerful ways to disarm her curious foes is to smile. A smile at a choice moment can disrupt the most skeptical of approaches. Of course, she can't just smile all the time. The act of smiling has to be done at the right moment. Fortunately for her, she can read minds. She may not be able to sink a U-Boat with the information she reads, but a smile is innocent enough. If a smile is not enough, consider what it takes to make something into a performing art. In many arts, we explicitly give ourselves over to the artist for a moment so that they may work their art in peace, without skepticism. If we feel better about ourselves at the end of the piece, it matters not to us whether the mime's invisible wall is real, or whether the magician really pulled our card from the deck. And finally, if at all possible, invoke things from people's memories. Random chance seems to be a lot more common when thinking of memories than it is with other things (think deja vu). If people can attach personally to what you are doing, there is far more room to allow magic to do its work. (And, as always with these, I'm going to have some fun writing a scene based on the question. I really love messing with these characters. Its simply fun.) Alynn knew she was still being watched. The young man thought he was subtle about it, always shadowing her on the other side of the street and peering around corners, but it wasn't hard to spot. Unfortunately, she had bigger problems to deal with. The bruiser in front of her was clearly offended that she had brushed off his advances and intended to correct her choices for her. It wasn't clear whether the knife he held in his hand was intended to cut her flesh, or merely her clothes, but she no intention of finding out. But he was fast! How could an oaf as massive as that move so effortlessly. Every woman in the realm was taught a few tricks for escaping these situations, but they usually relied on cunning and speed outflanking intent and muscle. There were few mundane approaches to such situations which ended acceptably. Her attacker reached out from an advantaged position to take control of her neck. Alynn could feel the impending constriction, veins bound against tendons and bone as his hand would begin to bend, flex, and close off her windpipe. Instinct began to take over as her defensive shield welled up, but she consciously held them back. There was no time to go find a new place to live, and the young man was still watching. A flaunting of magic would only hasten her departure amidst torches and pitchforks. Turning her mind to what she had available, her necklace sprang to life as though of its own mind. The beautiful long, metallic, stalagmite like fringes decorating the centerpiece of the necklace woke up and spun around into the grasp of the oncoming hand. Almost as though it had happened by chance in the melee, all of the metal shards managed to be facing outwards as his hand closed down on them. Startled by the pain, he jerked back, ripping the necklace clean off her neck. "So much for leaving no trace," she thought, but she could tell that was not the worst of her worries. Even without reading his mind, she could tell all she had done is buy herself time. But time is precious and not to be wasted. She began collecting herself, just as she had taught herself to do years before. Align the crown of the head upwards to heaven, let the feeling of that drip down her spine, aligning with her breath as it slowed its decent through the abdomen for a split second before continuing its journey to root her to the ground. "Magic is a performing art," she whispered to herself. Her awareness expanded outward, taking into account every detail she could possibly use to her advantage. "What's that, little whore?" the bruiser spat, raising his hands aggressively, small dots of blood welling up on his hand where he had torn the necklace free. "Have you ever fought against an artform, Charles?" He wasn't going to hear any of it, but for some reason every time his mind tried to shove the words aside, they feinted and kept marching towards his soul. The fact that he had never given her his real name never quite made it to conscious awareness. It sat there just underneath the the surface, like an itch that eludes the scratch. It mattered little anyhow. This was the easy part of the art, the calm before the storm. Charles wasn't even the focus of her attention anymore. He had already decided his fate; it was the young man that was at the center of the show. Now the dance. She dodged his erratic swings and thrusts with the knife. They never got to flesh, she made sure of that, but it did tear into clothing from time to time. "All part of the show," she reminded herself. "I can buy new ones later." She read into Charles's mind to predict his moves, of course, but her focus was on the young man. Leading Charles, blow by blow, and sometimes with a little telekinetic assistance, she manipulated the fight, not in physical space but rather in the mind of the young man. She did not know where in his mind she was going, of course. Mind reading to find what you want to learn is one thing, but finding something someone else wants to find is an entirely different matter. She used the circles and arcs of the combat to give him opportunities to guide her further. If he had had any inkling that she was manipulating him this way, he could have shut her down in a moment, but he was lost in the art of the parry and the strike. Watching her lithe body flit around and Charles's massive frame ripple with raw energy -- beauty was enough. He subconsciously led her down the branching hallways of his mind, strike after strike, block after block. Memory seemed so much more vivid while watching the melee. The dance came to a close as she let Charles overextend with the knife and slapped it away from him with one fluid motion. She had hoped to take hold of the knife, of course. It's always better to have a knife than not. However, that wasn't the way it would work. She could now see how she was going to escape this predicament in the young man's mind. Sadly, that path did not let her take control of the knife, so instead she slapped it skittering across the ground. Charles, undaunted, assumed a street boxing stance and lunged into her. The first two blows were the easy ones. A tired street boxer has very little control over their center of gravity. It was easy to yield backwards, barely touching each fist as it went by. The third blow was the tricky one. If she wanted to finish the spell she was working on the young man, the fight had to play out just the right way. Killing Charles would be easy at this point, but she needed to do it right. But she was tired, and while nobody else could tell from the outside, from her perspective she could see she was making mistakes. The precise movements she sought for her spell were fading away. With a burst of effort she gave him a magical nudge, begging him to attack the way he needed to. Strike three, complete. He swung wide, but with such force and missing by such a hair's breadth that her dodge left her ribs exposed. She lost control of her center for a split second, making it hard to cover this weakness. This was not the spell she wanted to cast over the young man; there was no room for weakness in it. She could feel his mind slipping away from the memory she so desperately needed him to remember. There would have to be a strike four, and it would hurt. Bad. Charles's hand plunged into her abdomen like a rock into a pond. Alynn's nerves lit up like wildfire. She would have loved to rebuff him with magic, but that was not the options she had left, not if the spell was to be completed. Instead her muscles shifted the other way, guiding him off the course he thought he was on, but deeper into her self. She could feel the deep pain as his fist dug deep into her uterus, all but tearing into it. A flash of desire to send him careening off with magic surged forward, but was suppressed. To do this right, she had to use muscle: muscles Charles had never fought against before, so could never see coming. The uterus is made primarily of muscular tissue; it fit the bill. With these final muscles coming into play, she drew Charles's fist to its final resting spot: just against her center of gravity. Of course, with combat, the center of gravity moves constantly, but this was not a normal combat posture she had put herself in. A third party observer, immune to her magic, would see an astonishing thing unfold. For a split second, with his fist deep into her reproductive organs, she stood straight. Remarkably straight, as though he did not even exist. This, of course, was a posture she had trained long before. Wielding magic with wild motions is easy, wielding it standing still without moving is far trickier. She had spent hours standing motionless in this position. It was her position. This was her home; he was on her home turf now. And for a moment, Charles felt peace. Not the usual peace from ale, or even the post coitus relaxation flat on his back in bed. Deep down peace, that nothing could go wrong. There was calm in her center. Deep, utter calm. And so he did not even notice as she smoothly slid forward, putting him far too unstable, backwards where his instincts would take over and bring him upright, but they did not. When his instincts finally awoke to what happened, his muscles tensed in a wave, launching him up, trying to regain balance. Perhaps he could have stopped it, but in the calm he felt no need to. Even as his body rose off the floor and impaled itself on the sign post behind him. Blood welled in his throat, but he never even choked. His face remained calm, all the way up until the light faded from his eyes. Alynn turned towards the young man, like an actress on stage facing the audience but respecting the fourth wall. Her clothes tattered, but somehow preserving decency, she stretched, using magic to cause a brilliant light to shine from her exposed skin. Internally, she winced at the pain, but she never let it show. This spell had been costly, and she wasn't about to let some mere pain prevent her from closing it. Eventually, the light faded. Alynn bundled up the rags of her clothes to give her as much cover as possible, and ran off. The young man did not follow her, still enraptured by a scene that, as best as he can tell, was played out especially for him in his mind. After all, how could she possibly have picked the same courtyard from so long ago. He had replayed that horrid scene from his youth so many times that it had lost all its color, and yet the pain on the young woman's face as her clothes were torn from her was still oh so evident. She must have been 16, 17 at the most, but now all that she was was a memory tucked deep away, fading. He had tried to hold onto that memory as tight as he could, preserving something, but nobody would even admit to her name. She lived in his mind alone, a source of morality and justice for him. A source that had faded, and he had faded with it. He was of no gentlemanly stature, making a living by lurking. Lurking was what he was good at. Now the image was different. Now the story had a different ending -- literally a miraculous ending. Color sprang back into the image, strengthened by the sight of Alynn in her dazzling glory. He knew not who Alynn truly was, or why she was. But he knew she'd given him something he thought he could never possibly have again: a purpose backed by morality and justice. The next day, Alynn walked the streets like nothing happened. She walked past the sign post where a few men were trying to take Charles's body down, and gawked just like any other bystander. She didn't even seem to have a limp, unless you watched extremely closely. The young man stared at her - she didn't even look the same in daylight. There was something magical the night before, like what stage lighting does to expose a character's soul. Today, it was just daylight. She turned towards him - perfectly towards him. She looked him in the eye for just a spit second, and the smiled. It was some mixture he had never seen before of dead weariness and complete carefreeness. It lasted just a split second, and then she was gone. He went on about his day. Mind you it would be the same old questionable activities for now. It would be a while before he could find a job that did not call for lurking in the shadows, but he'd wait for his chance. This Alynn character was an interesting one. She clearly had something special, but what was it? Every time he looked back to the fight, he found it remarkably hard to see Alynn's face without seeing the face of the woman from long before as well. Memory had always been confusing, and something told him this one was never going to get any better. Far better to take the gift he had received and leave her be. [Answer] > > Keep your friends close and enemies closer. > > > I bet Alynn would know what to do. She's a woman. And, like every woman, she knows (or better - feels) how to attract men. On the other hand, history of human relations gives ruthless evidence of how people contradict, harm, control, or just influence other people, just because. Fear can be an ally here, but simple biology - that slowness in time when a hunter notices his prey - also counts here. Alynn knew that she must not worry about simple folk minding their own jobs - all these women looking after something to fill their husband's stomachs, kids carelessly running over and over again, tired men walking down that less or more visible paths - all of them are harmless, as soon as their curiosity is sated. She knows that she needs to act normal. She has to be normal. Like an air, like a neighbor, like everyday's bread. Alynn decides that best way to achieve this camouflage is to undertake an activity that would not be extraordinary - say, berry gatherer, or herbalist. She also decided that she has to act on this single little man that follows her with his gaze every time she passes or in his sight. She knew well, that her camouflage would poof like a dream if these simple folks discover her abilities. What she decided was to get along with this man to confront him with his thoughts and to have time to read his intentions. She knows that he will not be able to harm her only if he will emotionally engage with her - be it love or just simple attraction. She felt confident with this plan. Just in a moment, a spark with a plan... [Answer] This is a work in progress. There may be some internal inconsistencies until I'm done. I need some more assumptions about the workings of her magic. * I'm going to assume she can exert force at will, just using her mind. She can't violate impulse conservation, so she'll mostly have to create symmetric opposing forces. * She can also create stuff from nothing, paying the energy which the created stuff has (so E=mc^2 for matter and E=hf for photons). * To exert force she needs to know precisely where and in which direction, but she can exert force on everything in an area * She can also get very precise knowledge about the world around her by concentrating on it. I'm assuming this is what she does when reading minds. So to analyze a head-sized volume of matter very, very thoroughly she needs 5kJ/60s~=85W. A head contains around 10^11 neurons and 10^14 synapses which she needs to tell apart from other stuff and analyze. I think she needs to be aware of state changes after around 10ms at most to keep up with the brain. I'll assume mind reading is more or less instant because she has so much practice doing it (and I'm assuming it's a really difficult skill which took her at least 15 years of practice) and it's similar structures again and again, but for new things she needs some time. Using those things I need to make up basic assumptions about her perceiving and analyzing capabilities which are easy to work with + she perceives energy. So when she finds out where matter is, she detects the energy of that matter. When she "sees" light, she detects the energy of the photons + her magical attention can be thought of like ghostly tentacles, she throws such a tentacle out where she wants to sense something and she can only sense stuff inside that tentacle + she can change the form of those tentacles, for example to form a head-like form at the end of a tentacle which she uses to mind-read, so she can examine the head of someone + the more attention she puts into those tentacles, the more (metaphorical) mass they gain + the tentacles (consisting of the same amount of attention-matter) can become large and thin, almost like fog, if she wants to perceive a large area, but then she can only sense average energy values over larger areas. Or they can become very concentrated over a small area so that she can sense the energy of individual atoms/photons/etc. For the sake of simplicity there is no distance penalty (other than the next point) or anything. + she can move those tentacles with the speed of light and information travels along them with the speed of light (she could probably do funny stuff in theory if information was passed along instantly. I'm already deep enough into physics with this girl's magic, I'm going to avoid that) + a head is 3l (don't know if this is true)(with a thread-like fine tentacle leading to it) and she needs to sense some 10^14 things inside that volume, so lets say she can sense 10^15 energy values with her 85W mind-reading power (if she needs only 10 times more energy readings than there are things which she needs to discern then she is pretty good, in my opinion). Using this some general principles of her magic: * Free levitation Energy = Force x Length = Mass x Acceleration x Length This means as long as she keeps Length to zero (this is the length over which she applies the force) it costs her nothing. Meaning she can keep any object floating for as long as she wants and it costs her nothing. * Keeping something stationary: But if floating isn't enough and she wants something to not only stay at the same altitude but also at the some point over Earth, then it will cost her energy to fight against the wind and she'll need to pay attention to impulse conservation. On the side of the object which she wants to keep stationary which is turned toward the wind, she will need to exert forces perpendicular to the wind, going away from the object. This will reduce pressure one this side of the object by moving away air. Without her interference the pressure would be higher on the side where the wind comes from, this way she can lower it to the same pressure as on the other side and the object won't move. I think this is the most efficient way to accomplish this goal, but I'm not sure how I would go about calculating the energy needed for this. I'll try to come up with rough estimations later. And specific applications: * Invisibility: To be invisible she needs to avoid sending out electromagnetic radiation (still visible as a black shape) and avoid interfering with electromagnetic radiation at all (completely invisible). How much energy this takes depends on her method: + the first method coming to my mind is to redirect photons around her, making them follow the outlines of her body (more or less, doesn't need to be extremely close) and then letting them continue on the trajectory they had before they encountered her. To do this she needs to be aware of the photons coming at her, so she needs energy to perceive her surroundings. And she needs to somehow move the photons. Exerting force on photons seems wrong (would cost no energy and give no sensible results using the F=ma). I think the best she can do is to annihilate the photons coming at her by creating a second photon for each of them which interferes destructively with the original one. Then create a new photon with the impulse and frequency of the destroyed one on the other side of her body. Now I need to compare analyzing photons with analyzing human brains. Human brains aren't that fast, just massively parallel. So I think probably she shouldn't be able to keep up with the massive speed of light. 100W of light (which in daylight is probably a sensible value for the amount of light passing through the space a human occupies) is around 100W / (h \* c/600nm) = 10^20 photons per second which is probably also too much for her. So... nope. No true invisibility for her.Generalized, she'll never be able to generate optical illusions like this unless it's really dark so she doesn't need to send many photons and even then it'll still cost her a lot. + per person invisibility: Manipulate just the photons going into a persons eye. That way there are many less photons to deal with + directly messing with people's minds: probably too hard. Science couldn't do it today. She could find out how brains work much easier than we can with her analyzing ability, but I still think it's unrealistic that she can do this. Maybe after studying the brain for a couple decades or learning from someone else who spent that much time + There are probably more methods for invisibility, but I'm continuing to something else * Other optical + She can obscure the sun or the moon to frighten villagers. - For a couple people at a time: obstruct their field of view with a single sand corn in the right distance and place in front of each eye. I would say around 20W of her magical perceiving ability per eye, less with practice, the full 85W per individual if she does this for the first time without preparation (i.e. first trying it on herself for 20W per eye and free mind reading because she just needs to check her own vision without magic). For lifting the sand corns and keeping them where they should be only negligible cost (so little mass, so little air resistance). Probably the easiest would be to put the counter-impulses she needs on air, but they are so small, she could also put them on the individual which she is scaring or even herself. At night they won't notice anything but the moon disappearing. For the sun they would see some black dot unless she added some sky-blue photons to the back of the sand corn. The photons would be almost free, don't need many so close to the eye, but I think that should double her concentration/perception cost because that's difficult to get just right, so they wouldn't see a blue still-not-sky dot instead of a black one. - For more people she could create a thin layer of sand/dirt above a whole village, invisible in the night and probably only visible as darkness in the day if it's high enough (say 50m). For a whole village that could fast approach a km^2, maybe 1mm thick again, at around 1.5kg/l=1.5kkg/m^3, would be E=dF=dm\g=50m \ 1Mm^2 \* 1mm \* 1.5kkg/m^3 \* 10m/s^2=750MJ. Ooops. So maybe not. She can only do this if there is a mountain or hill nearby, where she can get the material and move it laterally, or if she extracts and compresses particles already floating around at those heights. But the latter would need time and lots of magical input (she should probably get a distance penalty on this), probably too expensive. + Bright lights are cheap, to distract or blind people. * Sound + Voices and musical instruments are highly complex, so I doubt she could replicate them. + But she could let stuff fall down to create diversions. Almost free as long as it's just lateral movement and it doesn't need to be /too/ fast. + She can move two things against each other remotely to also produce sounds. Should take almost no energy. Reason: You can do something like this all day without tiring with your hands, and magic is more efficient. To do: Calculate Power for given Period (as a wave with acceleration proportional to distance from neutral point. Gives better noise than with constant acceleration I think). If she can't see them maybe 1/4 mind reading energy, so around 20W. Depending on how she does it she might need to also put impulse on air or Earth. + She can create vacuums around stuff she wants to silence. But rather expensive, will maybe do calculations later. + She could silence sound waves by dynamically applying counter pressures, but I think this is too fast unless she can somehow vibrate her force exerting will. I think I can activate/deactivate my arm muscles at around 15Hz tops, but on the other hand I never tried practicing something like this. Would need research to determine whether it could be possible in theory. I had a rough focus on non-invasive (that's why it's almost all illusions and diversions), but it was only a rough focus, mainly I was just imagining stuff she could do in general. I could imagine myself continuing this later, but for now I have enough. ]
[Question] [ So, for reasons which may or may not pop up in a later question of mine, I need to light a small Moon-like moon on fire. Well, sort of. See, I need a small object capable of emitting a lot of light - i.e. with a high luminosity. That could either be a large ball of gas on fire, or it could be something very, very hot - and thus very, very bright. So it actually doesn't have to be burning. For undisclosed reasons, this thing must be a rocky moon, and it must radiate in all directions. I have access to all the materials that exist in our Solar System. Oh, and I have the capabilities of a Type II civilization (which I appear to be obsessed with). To the smart-alecks who will say, "Hey, you've got a giant bloody star!": The moon needs to be in its own stable orbit, either around a planet or, most likely, the central star. For now. I can't crash it into the central star. I also don't care about what happens to any of the other bodies in the system. . . . I need to know by Friday.1 --- 1 Congratulations if you know what I'm referencing. [Answer] Depends on the color of the light. The easiest to achieve by Friday is lava-red. All you need to do is have a massive collision of your local moon with another moonlet: if the moonlet is large enough, that completely remelts the surface of the moon. The mantle remelting process has been [seriously](http://web.gps.caltech.edu/~sue/TJA_LindhurstLabWebsite/ListPublications/Papers_pdf/Seismo_1716.pdf) [studied](http://www.hou.usra.edu/meetings/lpsc2015/pdf/2263.pdf) in the past, so your basic equations are ready to go. $$Q\_S = Q\_R (1 + M\_p/ M\_t) ( 1 − b ) $$ $M\_t$ and $M\_p$ are the target and projectile masses, respectively, and $Q\_R$ is the specific energy, while b is a variable that measures the directness of the impact. For more details, see the linked article above. Here are some calculations of fractional melt for an Earth-sized body (note that moons should be a lot easier to melt): ![melt area](https://i.stack.imgur.com/PVW1L.png) If we assume a basic ocean of lava, given that now we're getting on a full moon somewhere around $5mW/m^2$, that would make it at least 200 times more luminous. Moreover, with a mantle-remelting impact, you can get significant rock vaporization and (rather briefly) temperatures in the [3-7,000K range (See page 79, bottom right)](http://www.whoi.edu/science/GG/geodynamics/2005/images2005/melosh90_origin.pdf), which would be a nice white sun-like glow. But let's face it, an ocean of lava [played straight](http://tvtropes.org/pmwiki/pmwiki.php/Main/PlayingWithATrope) is boring: we've all seen it. ![enter image description here](https://i.stack.imgur.com/X8zXk.jpg) Here's my suggestion: you can make it all more interesting by having a moon large enough to hold an atmosphere that literally allows burning to happen: you can then have your asteroid impactor generate an ocean of [burning sulfurous lava](http://lostininternet.com/the-spectacular-blue-lava-of-kawah-ijen/), with a nice eerie purple glow, the perfect setting for a final climactic boss confrontation. ![enter image description here](https://i.stack.imgur.com/MfoA8.jpg) Of course, it might be a bit messy. PS:You can never have too many XKCD references. [Answer] If the moon was a watery moon like Europa, this might be easy (for certain values of easy); an intense beam of muons could be shot into the oceans and catalytically induce fusion in the molecules of D2 in the water. This would be fantastically inefficient and probably require a muon source emitting almost as much energy as the fusion reactions going on in the oceans would release, but if you are really determined to have a light show..... For rocky or metallic bodies, the problem is much more difficult. Inducing nuclear reactions runs against the curve of binding energy; so while it is "sort of" easy to induce fusion with very light elements, or fission in very heavy elements, as you approach Iron things become more and more difficult (iron is right out; when the core of a supermassive star produces Iron there is no energy release and the gravitational forces collapse the star, triggering a supernova). Your sort of serious solution would be to drop a slug of antimatter into the core of the moon, and the energy release would melt the body and you would have essentially a glowing ember in the sky (a big enough slug of antimatter compressed to neutronium density would consume the core and melt the rest; too big and you blow the moon into small pieces, too small and you simply get interesting earthquakes and volcanic eruptions). Or you could just paint the surface of the moon with radioactive material and have it glow in the dark.... [Answer] An ordinary impact event makes quite a bright light. You could direct impacts to several points around the sphere to make it light up from all directions. [Answer] Many answers linking cause and effect, that may not be necessary. Consider, "How would you boil the ocean?" Don't heat it of course, reduce the atmospheric pressure. For your moon, use a set of Gravity Lens(s) to collect and focus ambient starglow. ![Gravity Lens(s)](https://upload.wikimedia.org/wikipedia/commons/0/02/Gravitational_lens-full.jpg). [Answer] Given that our moon's dull gray surface shines bright white and beige in sunlight, it seems that composing or covering your moon's surface with brighter colored, higher reflective compounds would greatly increase its luminousity. Whatever you use should be either solid or liquid at the moon's highest sun-struck temperature and zero pressure. If it evaporates into a gas, there probably wouldn't be enough gravity present to keep the gas around. As a result, the moon's size and brightness would deminish over time. You might get a very firelike effect if the moon made of a bright substance that was a gas at its sun-struck temperature and a solid in the dark side chill. Then by spinning your moon quickly, you could give it a bright atmosphere that is continually erupting from the surface, glowing in wild tendrils and wisps until they flow into the darkness and condensing, return to the ground. Could look pretty cool! [Answer] ## Spoiler alert! --- Actually Arthur C. Clarke has done this in his first published novel, "The Sands of Mars" from [wikipedia](http://en.wikipedia.org/wiki/The_Sands_of_Mars): > > Hadfield reveals that scientists have been working on "Project Dawn", which > involves the ignition of the moon Phobos and its use as a second “sun” for Mars. > It will burn for at least one thousand years and the extra heat, together with > mass production of the oxygen-generating plants, will eventually – it is hoped – > make the Martian atmosphere breathable for humans. > > > The resulting fireball is not as bright as the sun but it provides additional energy for Mars' development. However it makes the day/night and seasons cycle very complicated. The moon (made of rock) is somehow ignited using meson reaction. The technical details of how the moon was ignited are not discussed in the book. However Clarke sets the stage for how a society can attract the brightest nuclear scientists togather to do this massive project. The book also has amazing descriptions of the moon rising. I suggest reading chapter 15 if you are interested to know the details. ]
[Question] [ I have this scenario where the world was thrown into chaos by something and in this event, shortsighted governments launched assaults on numerous military and civilian targets, leading to the collapse of the society. It is a society with advanced robotics, cloning technology (not widespread and incredibly slow), and highly efficient and advanced farming technology following the depletion of all fertile soil roughly 1300 years prior. The plotline follows a clone who was given a false set of memories from a randomly generated backstory AI, which start from birth and end at age of 17. However instead of waking up in a sterile cloning facility which lines up with the medical facility the memories last recall them entering, they wake up in a mostly destroyed facility with little remaining of society. What scenario takes out society across the continental US, Canada, and Mexico (unified under the Canadian government following the flooding of 40% of the landmass in the US and Canada, and 90% of Mexico) without taking out the robot-maintained power grids? We can assume that the facilities making clones have their own means of creating or acquiring matter to make clones. Weapon technology in this universe ceased notable progression shortly after oil runs out in the year 2028 and the only notable technologies developed are railguns sized for the secondary armaments' of tanks and the removal of the Geneva convention on suffering. [Answer] Power grids don't have to be 'central'! A power grid is useful to distribute power, but has many drawbacks. We transform the power for long distance travel and change it back to 'usable' energy when it is finally arriving close to homes. All that travelling and transforming costs energy. Of course you can make arguments about 'normal temperature superconductors' and the like, but even then some cuts in powerlines or a melting power transform house (or whatever it's called in English) can make power fail. Even just not having the 'bandwidth' for the power can cause problems. If you want a stable solution, you'll likely have a distributed power network. That means you make power relatively locally. Solar pannels, wind, geothermal or whatever. With higher efficiency and miniaturisation many power solutions don't have to be giant power plants any more. Together with a future where 'unreliable' power like sun is stored at peak times, you'll have a robust network. Your cloning facility is connected to the network like everything else, but like a lot of important facilities they are capable of generating their own power. This makes them more reliable as either the incoming or local power could fail without endangering the facility. In your story the normal power grid can be destroyed, but local power can run just fine. For examole, it can be a fully underground geothermal power generator. The facility van be bombed while the power remained safe. Alternatively the facility could've run on stored power until the automated maintenance robots restored the power grid. Regardless of war and failing society they would assess the damage and repair it. Depending on how resourceful the robots are they would restore the grid over time. Both scenarios leave a plethora of ways society can destroy itself. From unexpected extreme changes in nature due to global warming, an AI uprising, global civil unrest due to economic destabilisation, pandemic, or to a nuclear war that didn't destroy many automated facilities. It's your pick. [Answer] Clone farms They have advanced farming technology. It is really advanced. The clones are not from vats or tanks, but gestate in genetically engineered water buffalo and takin. Their memories are implanted with clever biohacks devised by long dead geniuses. The rain falls and the sun shines. Engineered crops grow and the water buffalo eat. Sometimes a clone is born. There are no pests any more and no weeds. The livestock are tended by semisentient animals. The clones are tended by semisentient animals. There may be some other clones working on this farm. It does not matter that the power grids have been destroyed. Farms do not need electrical power. [Answer] This only works if you want this event to be really rare. If you want it to be somewhat rare, [Trioxidane’s answer](https://worldbuilding.stackexchange.com/a/215580/84913) is probably better, and if you want it to be more common than that, [Willk’s answer](https://worldbuilding.stackexchange.com/a/215599/84913) is likely better. Note: I’m using square brackets to denote that there’s multiple options you can pick from each of the paragraphs below. ### Lightning! A [hurricane] or [weapon misfire] or [case of erosion] or [attack] caused some wires to a [power generator] or [power storage unit] to be hit by lightning, [kickstarting the generator] or [filling up the storage unit]. This [power generator] or [power storage unit] was connected to the clone creation facility, giving it enough energy, to [create a new clone] or [finish creating a clone it had already started creating earlier]. ### Everybody in that facility died When you were created, everybody in the facility was alive, but they [died] or [fled] due to a [deadly virus] or [attack]. Therefore, when you came out, what should have been there wasn’t, and you see a [pristine building strangely empty of people] or [a building that looks like it came out of a horror movie] [Answer] There are two parts to answer this question: First the disaster and second how the cloning facilities survived. ## North American Tectonic Plate Shifts An unexpected and totally impossible thing has occurred the North American and the southern tectonic plates had a sudden an inexplicable shift which results in massive amounts of the southern part of the North American continent underwater. This results in massive tsunami and earthquakes across America leaving so much of it in ruins that America has no choice to unite under Canada. After that any world war as a result of lack of natural resources would finish off civilization. That then raises the question how the heck did the cloning facilities survive all of this? ## The Company In these settings there is typically at least one company that is so powerful that not even the end of the world can stop it. This can come in many forms from an evil mega corp like Umbrella from the Resident Evil franchise or a research company like Aperture Science from the Portal franchise. In this case I would recommend a company that caters to the rich by promising them a second chance at life by creating clones that relive a simulation of their childhood to ensure that the clone has the same personality and memories as they had. To ensure that they are able to meet this, they make absolutely sure that the cloning facilities have everything they need to stick around. After all they do not want to get sued by the estate if one of their cloning facilities loses their client's backup copy. [Answer] # Imminent collapse With the global political tension, it seemed inevitable that the world would collapse in war. * Plan A was to prevent the collapse. * Plan B was to bunker down and outlast it. * Plan C was there in case humanity failed. To ensure that the human legacy survived. One of the technologies for plan C so was the cloning facilities. They were secretly changed so as to ensure they survived the collapse by making them self sufficient, self-defending, and self-repairing. Then just add in a repeated delayed order to create a few clones every decade or so. This order gets postponed by presidential order, at the start of the term, so it won't happen under normal circumstances. Some smaller-scale facilities were created, hidden, just as a backup for the bigger ones. which would remain hidden for arbitrarily long periods. tldr: The cloning facilities work after the societal collapse because they were designed to survive just that. [Answer] Here is an obvious one: A pandemic wipes out so many people that cloning facilities are given priority so that humanity won't be wiped out... BUT HUMANITY IS WIPED OUT ANYWAY! After the population goes to zero, a significant number of clones accumulate and thrive, not fully aware of the pandemic that destroyed humanity... THEN one of the newly-created humans catches a strain of the disease that managed to barely survive dormant in a warm wet environment, and once again population goes to zero. After that, the microbes, being selected and rewarded for their ability to survive for a while without human beings, get better at doing just that. The microbes naturally move closer and closer to the cloning facilities, becoming better over time at surviving temporarily in whatever that environment is. After some years, the disease is able infect the new humans immediately after they are created. The microbes that last the longest and attack the quickest thrive best, so as time goes by, the disease becomes more hardy and more vicious. We are left with a horrific nightmarish reality wherein people are perpetually created and then die very quickly in near agony, year after year, decade after decade, century after century. ]
[Question] [ I am wondering if a species might evolve to deceive human technology - in particular, a set of night vision goggles. I imagine it is either cold blooded or it has thick fur - which doesn't trap air - so that warm air pockets don't show up in the goggles. What evolutionary trait is required for such an animal to fool our night vision goggles? [Answer] It may interest you to know that some of the earliest animals on earth were largely invisible to night vision goggles in the first place, and that later animals have actually evolved to be visible in night vision. The secret, as it turns out, is to be cold blooded. We'll get to that, but first let's deal with camouflage... To begin, we have to understand how night vision goggles actually work. There are [two types of night vision goggles out there](https://www.wonderopolis.org/wonder/how-do-night-vision-goggles-work), some work via thermal imaging and others by image enhancement. Image enhancement can be beaten by blending in with the background in terms of shape and texture, but this is no different to hiding during the day except you don't have to deal with colour as well. Just check out how well this [polar bear can blend in](http://wwfgap.org/projects/thermal/index2.html), at least from a distance, compared to its infrared signature. Slide the vertical line on the picture from side to side and you see the bear disappear when the infrared slide is to the extreme right. So, if you can blend into the landscape during the day, there's a very strong chance you'll do so at night according to these types of goggles. Now when it comes to thermal imaging goggles, it's important to note that the reason they work is because most of the animals (especially humans) we care about seeing in the dark are warm blooded. In biological terms, what warm blooded means is that the creature in question maintains a constant internal body temperature. In practical terms, that means that they can be active and alert even when it's cold, but at the price of a variable metabolism that requires more food in the cold to maintain the difference between the ambient temperature and their internal temperature. On the other hand, a cold blooded creature has an internal temperature similar to the ambient temperature, meaning that it only becomes active when it is warm out. This means it needs less food to survive, but the cost is that it's not as active in the cold meaning it can be caught by predators more easily during those times. If you [look at the snake in these thermal images](https://www.mnn.com/earth-matters/animals/blogs/hot-and-wild-14-thermal-images-of-animals) you can barely see it. This is because it is the same temperature as the ambient environment, whereas all the mammals and birds are hotter than the ambient environment, especially during the night when it is cooler, which is why thermal imaging often works so well for night vision. Ultimately, to make it harder, what you want is night vision goggles that integrate BOTH methods, so that your creature trying to hide is both cold blooded AND camouflaged to the environment. Can that happen? Sure. Arguably it already does insofar as visible light is only a very small percentage of the EMR spectrum meaning that the ultraviolet 'glow' of a spider web for instance is completely invisible to us. Polar bears can even be quite hard to spot on thermal imaging because they carry so much insulation to keep them warm in cold environments without having to eat so much, and certain insects are indistinguishable from leaves or sticks even during the day, let alone via night vision goggles. All in all, the answer to your question is yes, but it gets 'harder' to do so depending on what else you want your creature to do. If you want it active at night for instance, making it warm blooded puts it at a distinct disadvantage as far as thermal imaging is concerned. If you just want it to sit still and be 'invisible', that is not interact with your begoggled humans, then just pick an animal out of the stock that Earth has already produced. ]
[Question] [ I know that chemical rockets would allow for some minor loads to escape the gravity of a planet with higher gravity. My question is, what kind of technology would possibly allow a dominant species to escape the gravity of a planet and become a somewhat spacefaring species? Are there any possibilities in today's technology? Or what fictional technology might accomplish this that might be in our near future? Edit: Thank you, guys. This has been a treasure-trove of help and information. I now have enough information for my later chapters as well. I honestly appreciate it. [Answer] If you don't want to go the nuclear rocket route, and stick with technologies that are known to be physically possible and not require nonexistent materials.... If the planet spins extremely rapidly, such that you get a decent speed boost from equatorial launches and synchronous orbit is really low, then regular rockets and even space elevators may be suitable even for very massive planets, although rockets will be restricted in the inclinations they can reach. Earth is marginal for space elevators because the cable would have to be so long, and support so much of its own weight that there's nothing left for safety margin and payload, even with the strongest theoretical materials we know of. A higher spin, however, will lower synchronous orbit, potentially making elevators practical even with much higher gravity. If you don't want to be restricted to high spin planets, you're left with basically one option: dynamic actively supported structures like Lofstrom launch loops and space fountains, possibly followed up by orbital rings (from which one could hang skyhooks in place of traditional space elevators). These kinds of structures make use of accelerating recirculating rotor materials inside their external static structure such that the reaction forces of the rotor materials on the static structure counteract its weight. This gets around the compressive strength limits of static materials, allowing you to raise platforms above the atmosphere and use electromagnetic tracks to accelerate to orbital or escape speeds in vacuum. Of course, if you somehow manage to develop civilization on a planet with little or no atmosphere, you can just use electromagnetic launch tracks directly from the ground, coupled with low-power circularization rockets. [Answer] There is always the possibility of using very high powered rockets to escape from the planet, including nuclear rockets and even Project Orion type rockets or nuclear pulse rockets using a series of atomic explosions to propel the ship. <https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion>[1](https://en.wikipedia.org/wiki/Nuclear_pulse_propulsion) [Answer] In theory [Space Elevators](https://en.wikipedia.org/wiki/Space_elevator) are possible regardless of the surface gravity of the world on which they are built, material tensile strength is an as yet unsolved issue with building these structures. Wil McCarthy's [Hacking Matter](https://en.wikipedia.org/wiki/Hacking_Matter) proposes some options in this area but the practical applications are still some years away. Alternatively any form of [em drive](https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster), [field propulsion](https://en.wikipedia.org/wiki/Field_propulsion) system or [gravimetric drive](https://en.wikipedia.org/wiki/Reactionless_drive), would work but none of these systems is more than highly theoretical at this time. That's all if you want rocket-like spaceships whizzing about; if all you care about is spreading a species to the stars then the [Einstein–Rosen bridge](https://en.wikipedia.org/wiki/Wormhole) is also an option. Wormholes allow you to send people to other worlds with or without spacecraft and with any technological or magical embellishments you want to use. [Answer] 1. Gravitational anomalies. [![gravitational anomalies](https://i.stack.imgur.com/GJLzh.jpg)](https://i.stack.imgur.com/GJLzh.jpg) <https://en.wikipedia.org/wiki/Gravity_of_Earth> A planet is not a ball bearing. It is inhomogeneous. Your planet can take that farther. There are areas where gravity is less and areas where it is more. Perhaps there is an accumulation of lightweight material in the crust, or an ancient huge chondritic lightweight meteorite incorporated from a long ago impact. Your spacefarers take advantage of the light areas. 2. Altitude. The higher you go, the less gravity is. You can go up on mountains for some benefit of this sort. Maybe your planet has some very high mountains - maybe one of them is that ancient chondritic meteorite? Or you can use [rockoons](https://en.wikipedia.org/wiki/Rockoon). Capitalize on buoyancy to lift your spacecraft high above the ground. You can only get to about 100,000 feet on earth because the atmosphere thins out, but the amount of atmosphere a planet has does not depend on its size. You can give your heavy world an atmosphere way out, enabling a balloon to rise considerably farther before releasing its rocket cargo. If rockoons bore you, maybe a [rockeloonannon](http://www.halfbakery.com/idea/Rockeloonannon). Yes, there is a cannon involved. Usually that improves science. [Answer] In addition to the other good ideas, here are two more: 1. use aerodynamic lift to the edge of the atmosphere, then start the rockets at that point (similar to Virgin Galactic). As the atmosphere thins out, you can increase your velocity to maintain lift. At some point (Karman Line), the velocity you need to maintain lift will be enough to orbit your planet. 2. [laser propulsion](https://en.wikipedia.org/wiki/Laser_propulsion) uses very lightweight craft reflecting light from a ground based laser to overcome the tyranny of the rocket equation. You're going to be limited by your spacecraft's ability to reflect close to 100% of the photons, and to dissipate heat from those that are not reflected. [Answer] With realistic technology, the solution would be the same as the one we're used to: a vessel of minimal weight and friction is subjected to a contained explosion strong enough to overcome the gravity well. Some ideas that might make it work better (and generally more dangerously): * If it's a big planet that rotates very fast (has short days), centrifugal force in the Equator might help a great deal. * If the highest mountain is also in the Equator, that could help a little. If not, why not add to that centrifugal force by launching the vessel from a train that's moving Eastward very fast? (bonus points if the wind is blowing that way). * Aligning the rocket with a big moon that was close enough would counteract some of the planet's gravity: the vessel would be literally rising with the tides. For such a moon to not have crashed into the planet yet, it would need to have a fast orbit: maybe the aforementioned train would be following it? * Using the updraft of natural phenomena like cyclones or tornadoes to pull the vessel along, or even making artificial ones happen for that very purpose. * A bigger explosion, maybe big enough to make the entire region uninhabitable for a good while if they're not going out of their way to contain it -- maybe even as a [Scorched Earth](https://en.wikipedia.org/wiki/Scorched_earth) tactic? More fictitious alternatives: A really strong gravity would make it hard to not just leave the planet, but also move within it. This would be a perfect incentive to the development of technologies that bypassed the problem (like teleportation or wormholes) or even made it its own solution (antigravity). ]
[Question] [ [Man-portable air-defense systems](https://en.wikipedia.org/wiki/Man-portable_air-defense_system) have been around for decades, and so have been [anti-satellite weapons](https://en.wikipedia.org/wiki/Anti-satellite_weapon). But while the former is a small, short range rocket, the latter is as big as a cruise missile. Obviously, it is impossible to make such a small rocket go high enough to threaten a satellite. Or is it? Satellites are fragile, have a predictable orbit they cannot meaningfully alter, and have no counter-measure. So the rocket doesn't need acceleration or agility beyond what is needed to reach a specific point at a specific time. The launch itself can be timed to the second. The smallest orbital rocket to be built was big enough to require a truck, but we aren't trying to reach orbit, only orbital altitude, which requires several times less fuel - which is why sounding rockets attempting to reach space are so much smaller than orbital rockets for the same payload. And we don't even need a payload, only to hit the satellite. Unless, of course, a small explosive charge gives the resulting cloud of debris a better chance to hit than the same mass in sensors and guidance. So the question is, can an anti-satellite rocket be made small enough to fit a man-portable rocket launcher? The total package must be, if possible, less than 35kg and small enough to be carried as a backpack. Or, if impossible, to be carried in separate components by the smallest possible team. It must at least reach low orbiting satellites, so let's say 250 km minimum altitude for a vertical launch. The higher the better, though, both to give more launch sites and to reach higher satellites. We can even go for a range of rockets with varied capabilities. Being able to hit the ISS at a bit more than 400 km altitude would be great for advertising. The fastest the setup on launch site the better, up to a few hours. More time can be spent setting parameters up in advance, though. Simpler setup procedures are also better, but not mandatory, as skilled operators can be trained anyway. It must require no fixed infrastructure, not even a perfectly flat ground. If fueling is required, the fuel reserve must also be man-portable. Same thing for ground-based sensors or a ramp. Toxic fuels should be avoided if possible, but if it can't be then something must be included to protect the crew during storage, transport, setup, and launch if they have to be close. Also there is toxic and toxic. White fuming nitric acid may be manageable, but chlorine trifluoride is right out. it must be possible to store the components in standard warehouses for long periods, so corrosive, unstable or cryogenic fuels are to either be avoided or extra step must be taken for them. The higher chance to hit the target the better, but less than 100% is acceptable. Let's avoid going below 50% if possible, though. Don't worry too much about R&D cost or legal concerns, assume I am an evil billionaire with my own island lair and a plan to Conquer the World!, and I bought a few missile and aerospace companies to tap their skills and cover up the tests. I don't have access to nuclear materials, though, nor metallic hydrogen (whether it works out). On the other hand, once mass-produced, the individual units should not be too expensive. Let's say less than a million dollars. Assume the starting date you want from the 1960 up. Before is better, but if you need experimental tech like [ramrockets](https://en.wikipedia.org/wiki/Air-augmented_rocket) or even fancy near-future tech like [rotating detonation engines](https://en.wikipedia.org/wiki/Rotating_detonation_engine), so be it. Please don't go too far in the future, though. [Answer] Interesting question... and as an entire thing... No. because of the first paragraph below Several obstacles to overcome, target acquisition and aiming of the weapon, but i'll leave those out since they are definately NOT man portable, and i'll ignore the factors of if you can base the detection somewhere else why not launch somewhere else arguments to the side. lets assume you have the ability to detect your target, and aim your weapon accurately enough One of the major considerations is how to destroy said satellite. if the weapon needed a detonating charge then it would need to have a warhead... increase mass therefore more fuel required, more fuel means more mass, more mass means well... more mass. its an exponential increase. however if the rocket was dumb, and just used the fact that it needed to reach orbit and then let the satellite collide with it and the vast difference in velocity would be all that was needed then the rocket doesn't need anything other than guidance systems , perhaps a tiny amount of propellant for final adjustments, but the issue with this is then you need to be even more accurate. The SS-520-4 rocket is a modified sounding rocket and is the lightest and smallest launch vehicle to send a payload to orbit, however it weights 2.4 tonnes... not quite man portable, and the payload was 3kg... BUT You weapon doesn't need to reach orbit, just to reach orbital altitude, this is a lot lot less DeltaV required so something akin to the S-210 would probably almost do, its another sounding rocket, only designed for ionosphere study but it can reach 110km... so it can get close to Low Earth Orbit altitude which starts at 160km. 5.2 metres long, 0.21 metres wide, but... 300kgs... but its been around since the 1960s. and they still carried a few kilos of payload in terms of a small sensor setup for the study. Remove those few kilos and maybe... just maybe you could reach 160km. but that's only the start of LEO altitudes, LEO technically goes up to 2000km There are ways of reducing size and increasing power. SpaceX super cool their fuel in the Falcon's, this means they can have smaller fuel pumps put keep the same flow rate of fuel, smaller pump means less weight, the fuel is still the same though. a larger rocket could make do with being multistage, constantly dropping excess mass as it gains altitude, but such a small rocket would probably be heavier by adding extra stages which would require extra engines. and again, simply down to the mass of the fuel. i don't see being able to get it down to 30kgs, you're wanting more power Hmm... An even older rocket, the MT-135 again a sounding rocket, had a max altitude of 50km... but it could lift a payload of 10kg. and the eitre thing was 68kg, that's a team portable rocket... and maybe without a payload so down to 58kg. it might be able to do 75km The Rohini rocket family, built in India has some very small sounding rockets, so i'd advise you look through the worlds various Sounding Rockets, remember if its a dumb weapon (meaning its just an impactor nothing else) then your making the whole thing lighter which means same fuel more altitude, or same altitude less fuel therefore slight smaller. but Alas, that first paragraph does come into it as well. you'd have to overcome those issues before you even bothered to start designing the weapon system itself. the weapon could easily be truck mounted, as the SS-520 could be, its small and light enough for this, but again the "everything else" needs a lot more infrastructure [Answer] The answer might be to avoid rockets at all (or at least for everything except for the final adjustments to strike the target). Your issue is to lift a payload to orbital altitude so the orbital track of the target satellite intersects your payload (as noted, you could increase the chance of a strike by launching a bucket of ball bearings for the satellite to fly into. At 7 km/sec velocity even a ball bearing will have a great deal of kinetic energy). So I will suggest a portable railgun. The "gun" itself would likely need to be assembled and mounted on a large tripod, but the components of the railgun itself need not be very massive, you would essentially be assembling sections of rail to build the "barrel" (and there are non conductive bridging parts to keep the barrel rails aligned). Since you don't want a heavy energy source, the device is powered by a portable MHD generator, energized by the hot, high speed gasses delivered by an explosive charge. In some ways this would resemble a recoilless rifle, your team would load the casing with the energy source, connect the wires and retreat to a safe distance. When they initiate the device, a stream of hot gas is created which flows through a venturi and then the MHD generator itself. [![enter image description here](https://i.stack.imgur.com/suGrb.jpg)](https://i.stack.imgur.com/suGrb.jpg) Real life portable MHD generator <http://jpaerospace.com/blog/?p=5096> We know the US Navy's projected 64 MJ railgun is designed for a range of over 200km, and the trajectory is actually outside the atmosphere at one point, so what we really need to calculate is how much energy would be needed to fire a projectile to orbital hight. Some of the uncertainties would include the mass of the projectile and the efficiency of both the MHD generator and the railgun in converting the electrical impulse into thrust. Given the potentially huge amounts of energy being released in a very short time frame, I would say this is very much a "one time use" weapon, the rails would vapourize as the projectile is being launched. So the rough setup would be: * 1 man carrying the disassembled railgun rails * 1 man carrying the tripod assembly * 1 man carrying the MHD generator and associated cabling * 1 man carrying the charge * Team leader to supervise the setup and aim the assembly (either with the use of a laptop loaded with the orbital information of the target, GPS and very good set ofbinoculars), or good communications to the targeting centre. Team leader also carries the warhead. The five man team could likely carry all the parts and move to the launch area in a large 4X4 pickup truck or a pair of SUV's if additional mobility and speed are required. The use of a truck also allows carrying spare rails and warheads to allow additional engagements. Security personnel may be added depending on the situation. [Answer] What if you didn't carry the fuel? "the latter is as big as a cruise missile". But that cruise missile is mostly fuel. What if you were near water and could make liquid hydrogen and oxygen. Put the rockets on the top pointed downish and have a slim dangling light fuel tank. [Hey why aren't engines on the top of rockets?](https://space.stackexchange.com/questions/9682/why-are-rocket-engines-at-the-base-of-the-rocket) Fuel pumps? We don't need no... OK so our super light and strong and heat resistant fuel tank we just pulled out of our backpack also needs to compress the fuel up and into the engines against all the acceleration. If there was some way to make solid rocket fuel using stuff in your backpack this would be easier. Then you just need a long flexible tube that becomes rigid when filled with solid fuel. Double-base (DB) propellants sound a lot like dynamite but with nitrocellulose instead of dirt (sounds safe). Maybe you engineer a fungus or virus or a combination that rapidly converts plants into nitrocellulose and nitroglycerin using the plants own machinery? [Answer] Current anti-sat missiles do exist, and they are attached under the wing of a B52 and flown to high altitude before launch if I remember correctly. They couldn't be reasonably called man portable. Of course if your atmosphere was thin and the planet smaller with lower gravity that might be a different problem. Otherwise you could do it with pre-deployed ordinance. The guy on the ground carries a remote. A large satallite mine was deployed in space years ago. On command, a ball bearing is jettisoned into an intersecting orbit. Perhaps this ball bearing has an attached thruster assembly for making fine adjustments to position itself correctly. There is also the issue of the height of the orbit. Which is to say that geo-stationary is way higher than low earth orbit. So probably your mine would be in geostationary or higher orbit, and the thrusters would be used to brake the ball bearing down to the appropriate altitude. Kessler syndrome might be a factor in the design. Perhaps a more friendly approach would be that it is a ball of sticky gum instead of a ball bearing, and within that goo, is a heater (to liquify it as it approaches) and a long antenna that spools out. The goo captures the satellite. An EMP charge is fired directly adjacent to it to destroy its functionality, or perhaps a long term jamming frequency is emitted. Then a long antenna is spooled out to use atmosphereic drag to eventually deorbit the thing. Instead of gum, maybe a fine mesh copper infused cast net, which would essentially Farraday box the offending sat. Extra points if the net has sinews, such that as it wraps around the sat, it tightens to itself. Maybe even constricting to crush it, like a python. [Answer] edited as I thought of 3 possible ways 1 - 3 step Rockoon gun I'm thinking of a multi stage system will work best, each layer of the atmosphere has different needs to problems to overcome: 1. [High altitude balloon](https://en.wikipedia.org/wiki/High-altitude_balloon) will provide the first stage, this can reach about 30km (this height is common for this type of HA ballons to achieve as evidenced in the link) and pass the majority of the atmosphere with it's payload being the 2nd stage 2. the second stage will be a conventional rocket, a so called [Rockoon](https://en.wikipedia.org/wiki/Rockoon) will give the 3rd stage an extra boost while aiming the the barrel of the 3rd stage so that the final payload launched from it will hit the target, there are plans from [JP Aerospace](https://en.wikipedia.org/wiki/JP_Aerospace) to use this Rockoon config to reach space on it's own 3. the 3rd and last stage will be an gun, the payload to take down a satellite can be a single ball bearing as stated in other answers and at the height where it's fired coupled with the initial speed from the 2nd stage rocket it should have more then enough speed to destroy a satallite, it's worth mentioning that at those heights there's barely any atmosphere slowing the projectile fired down. 2 - Hacking All satellites require some form of communication to the ground, and a laptop with a cellular modem and/or radio antenna (depending on if the satellite or it's C&C center is connected to the Internet in some way or it's a purely RF hacking) is way under the 35kg limit, if one manages to hack the satellite it could destroy it in a lot of different ways: * some satellites have a limited form of movement ability, this is to move them out of collision with space debris (and other satellites) you could use those engine to steer it into something or down the atmosphere, you don't even have to hack your target, you can hack another satellite and ram your target. * It's been speculated that some military satellites have a self destruct ability. * Change it's direction so that it's pointing away from the sun and with no solar power it's battery runs dry and is affectively dead. * rotate it so it's antenna is no longer pointing to earth and it can no longer be controlled by anyone (might not be possible on all satellites depending on their design) 3 - Lasers (everything is better with them) An [Wicked Lasers arctic](http://www.wickedlasers.com/arctic) is a 3.5 Watt laser that costs 300 bucks and weighs 421g, that means you can have 83 of them to get 290Watt of laser power in 35kg (there is still a bit of weight to spare which will go to a concentrating lens to get the focus point of all those lasers right at the same spot of the satellite, most will dissipate at the atmosphere along they way but enough will go through to manage to hit the satellite and destroy it's more sensitive parts - cameras, solar panels, etc... and at a price of 25,000 $ you can't afford not to buy one. ]
[Question] [ So I am designing a fantasy world, and in it are some fairly stereotypical dwarves, anyhow I was wondering is I could replace the traditional "canary in a coal mine" trick with a cricket and/or multiple crickets. This would give me the bonus of explaining why the dwarves hold them almost sacred as the help against the Blackdamp (underground gas). They would also be kept for music. So would this work? And if not, any other ideas? EDIT: Sorry, should have been more specific, I mean any of the "Damps" be it blackdamp, whitedamp or firedamp. [Answer] This is being studied in the real world: (1) <http://rspb.royalsocietypublishing.org/content/267/1449/1171.short> Here's a paper that found crickets chirp more slowly when their immune system is down. That fits with Will's ideas. Your tecchie-minded dwarves could bring a cricket and a metronome down every mine; when the two get out of synch everybody leaves! (2) <http://onlinelibrary.wiley.com/doi/10.1046/j.1440-6055.2002.00288.x/full> This one worked by counting cricket population in small areas as a proxy measure for sulphur dioxide emissions. So rather than one pet cricket in a gilded cage that keels over or stops chirping when gas is released, you might envision dwarf scientists sampling a mine's cricket population. For this to work, you'd need to invent a species of underground crickets. Maybe your dwarfs plant fungi in their mine shafts and create cricket habitats, then the science safety team does a cricket count every day. (You could have a much cooler mine environment that way! We humans tend to think of mines as sterile and not places to live, but an underground species might think of them a lot more like gardens/homes.) [Answer] This is an excellent premise and would make a first rate science fair project! It is known that the rate of a crickets chirp corresponds with temperature. Crickets chirp faster when warm and slower when cold. <https://en.wikipedia.org/wiki/Dolbear%27s_law> Also, I found an article about the use of carbon dioxide anesthesia on crickets. Carbon dioxide is a good standin for blackdamp. <https://academic.oup.com/aesa/article-abstract/58/6/828/9020?redirectedFrom=fulltext> But: does CO2 anesthesia slow chirp rate like cold? Or does it speed it up, as it speeds up the breathing of vertebrates? The dwarves will know I am sure. And a precision-minded dwarf would not be content with a canary that was alive or dead, or a lamp that was lit or not. By assessing chirp speed one can calculate with some precision the concentration of blackdamp. This aspect is why it would be a good science project. Dwarves sing as they work, of course. There would be a different song corresponding to each chirp frequency. [Answer] I doubt it. They used canaries because they (and other birds) are more sensitive than humans to toxic gasses. A canary's respiratory system is 20% of its bodily volume (according to this site) <http://birdpoet.com/articles/Respiratory_%20Mite%20_FAQs.html> Perhaps really large bugs would also work - the ones that are at the limit of a thorax based respiratory system. They could use pet tarantulas instead. [Answer] Canaries don't recognise CO2 in mines. They react to metane. By "react to" I mean they die. A dead bird is a easy to spot and differentiate from alive one. (the only exception is Norwegian Blue). A simple "on/off" signature. With a cricket you have chirp that is tied with temperature so with every meter you have different chirp. EVEN if you set your cricket for that one particular mine (because temperature change differently due to geolocation of mine, rocks around, water veins etc.) your miner would need to know the chirp for particular level, tilt of that level, his position on said level regarding the starting point, change in temperature for 1 Celcius degree, calculate change in temperature of his position and starting point and THEN recognise different chirp from the environment changes. I think that after first explosion where 200 dwarfs would die they would go "You know what? let's go with the old Yellow is up it's safe, Yellow down get the hell outta there". ]
[Question] [ Basically, when designing alien and fantasy races, I tend to try and figure out how they would sound. I originally figured that their language would be made of growls and barks, but then I realized that was too basic. Ask any linguist, and they'll probably tell you that there are no languages that are just merely basic. Every language in real life (and those that have been constructed, i.e. Klingon and Tolkein's Elvish languages) has some sort of complexity and uniqueness to it. So, this all boils down to the question of how would the spoken language of a caninoid species sound like? Please note that I said spoken language, as I have already figured out that there would be a great deal of body language going on, since they would have tails and ears. [Answer] I'm going to take a different tack from the other answers and start from the basis that we have talking canines and figure what about dogs would influence the way they speak. Most of these assume that their mouth somehow retains a somewhat doglike anatomy. If that mouth evolves to come very close to humans' before they start speaking, then the anatomy would have very little effect. * As I remember it, dog mouths do not close hermetically. So it makes sense that dogs would not be able to pronounce labials (/p/, /b/ and /m/). At least not with the same sort of sound as humans can produce. * Dogs have muzzles. It seems like an obvious thing to say, but the major differences between vowels (i.e. /i/ and /u/) as well as the various consonants, especially stops (but also fricatives), is where along the palate the tongue make contact. In humans, there are about four such major locations for stops and vowels (depending on your definition), three for laterals (l sounds) and 8 for fricatives, however, it is entirely possible that a species with a muzzle could have access to more sounds (from the point of view of humans) by simple virtue of having more space to clearly separate them. * I'm not sure what, phonetically speaking, a growl is. It may well be the dog's equivalent of a pharyngeal or uvular fricative or thrill. If it's not, though, it would make for an interesting, foreign phoneme too. * It's also possible, even likely that dogs's panting would lead to the heavy presence of interdentals (th-sounds), which are crosslinguistically uncommon (and hence are such a bane to foreign learners). [Answer] Dogs larynx doesn't have the flexibility needed to emit proper phonemes. You have then two, possibly combined, approaches: * enhance canine vocal chords, and then you can have almost anything, phoneme can remind of barks or not (Klingon would be a good approximation, if you want to maintain a canine-sounding language, but that is not required by any extent). * switch to sign language. Here I'm not referring to "body language" (which is not a real language, even if it conveys a lot of information), but to real sign language, similar to what is used by deaf people; notice the "standard" deaf language is derived from "spoken" languages, but that needn't be the case (see: [Nicaraguan Sign Language](https://en.wikipedia.org/wiki/Nicaraguan_Sign_Language)). The two approaches may be combined with "enhanced barking" complementing sign which can be hand-signs (if your canine-race is standing upright and as "hands", of course) or other tail/ear/body gestures. [Answer] I think instead of dogs you should use foxes as your basis. At the end of the day dogs are dogs and wolves are scary dogs. Foxes are canids too but they have weird vocalizations including screams, mews, coos and "gekkering". As well as more creative Nordic speculation about what they say. <http://www.thinkingoutdog.com/?p=1667> <http://www.popsci.com/science/article/2013-09/what-sound-does-fox-make> The problem is that unless you are making a movie and can dub in your canidoids there is no good way to convey how your creatures sound. Describing a sound relies greatly on analogy, like describing a smell. If you spend too much time with descriptive verbiage you risk getting lost in the weeds. ]
[Question] [ Let's suppose regular humans (same intelligence and pretty much same features) but they usually have 3-6 babies at a time. To me, many breasts seem like an evolutionary disadvantage. Something you want to have as little of as possible, especially if you're a biped (they mess with the center of gravity). The only advantages to have n breasts I see is: * It's quicker to feed your "litter", reducing your vulnerability/not-hunting time. * That you can be sure that, without requiring supervision on your behalf, at least n of your children will be regularly fed. It (usually?) happens that for puppies > n, some puppies will go undernourished. But that's not a problem for an intelligent animal, is it? Time is not as important, because they are not as vulnerable while feeding (they have safe villages) and they have the sufficient organizational skills to make sure every child gets his fair share. This is why I think there would be an evolutionary advantage in having less. But I may be completely wrong! So what do you think? Given a world were hominids (maybe all primates) have bigger litters, do you think they would have several (more than 2) breasts? [Answer] In favor of yes is the "one-half rule" as proposed in the linked study; abstract pasted below. Animals with only one offspring mostly have 2 nipples (humans, whales, elephants). Animals with more offspring have more. I found this analysis of nipple / offspring ratio in rodents, where there are a lot of species to compare. > > <http://www.pnas.org/content/83/13/4828.full.pdf> > Mammary number and litter size in Rodentia: The "one-half rule" > (Cricetidae/Muridae/Sciuridae/lactation/reproduction) AVERY NELSON > GILBERT\* > DepartmentsofPsychologyandBiology,UniversityofPennsylvania,Philadelphia,PA > 19104 Communicated by Leo M. Hurvich, March 7, 1986 > > > ABSTRACT > Litter size and mammary number in the mammalian order Rodentia show a > significant positive correlation. Mean litter size is typicaliy > one-half the number of available mammaries, while maximum litter size > approximates mammary number. Similar relationships are found in the > families Muridae, Cricetidae, and Sciuridae. The relationship of > litter size to mammary number is significantly different between the > arboreal and terrestrial squirrels, and between the hystricomorph and > nonhystricomorph rodents. Mammary number may have operated as a > selective constraint on litter size over evolutionary time. > > > Considering that there are other pressures tending to constrain humans to one offspring at a time (chief among which is that human offspring remain dependent for a long time) maybe the same pressure operated on primates during our evolutionary history. In favor of a no answer is the example of pygmy marmosets. Most primates have one offspring at a time and have 2 nipples. Pygmy marmosets always have twins, but like other (all larger) primates still have just 2 nipples. They work around this by caring for offspring as a group, although it was not clear to me if a female which had not recently been pregnant could start lactating to support a little sister or niece. If the 2 nipple thing is rooted deep in the primate lineage and if there is an easy way to sidestep reduced fitness for the multiple children and a mother with 2 nipples (e.g. female relatives help nurse) then humans would stay as they are. [Answer] Women breast are per se a disadvantage, as you point out. The females of other mammals grow them only during breastfeeding, because energetic-wise is not smart to have and maintain that unused reserves of fat all the year round. Humans do it because it brings some advantages (I read this about 20 years ago on Scientific American), since they mask the fertile period. In this way the male has to be around the female constantly and is more engaged in nursing the offspring, together with the constant receptivity (while in other mammals the developed breasts are a clear sign of "no mating here", and mating is often limited to give time window). And also, considering the risk related to delivery, masking the fertile period is wise. So, in case of bigger offsprings, it would be better to increase the milk production of the two breasts, rather than putting more effort in growing an additional pair. As said above, growing and maintaining breasts is an energetic expense to carry on from puberty to death, while breastfeeding is an effort "limited" to the time after birth. [Answer] Yes, they would have to have more than two breasts. For one thing, breast-milk is [not homogeneous](https://www.babycenter.com/404_whats-in-breast-milk_8821.bc). Colostrum is the very first milk, very easy to digest and specific to newborn infants. Then, as the child matures, milk develops into two parts - fore-milk, the first milk from a full breast, is thin and watery with vitamins and proteins. And also hind-milk, the last milk from a near-empty breast, which is thick and creamy and heavy on fats. In short, the composition of the milk changes over a feeding session, and over a child's growth, likely to prioritize which nutrients are available and address which are needed. Nor are these necessarily discrete substances, it is much more likely a gradation for production and letdown of one to another depending on the child(ren)'s needs - making it harder to equally subdivide each type of milk when feeding multiple infants. This makes scheduling or rotating feedings much more complicated. Multiple babies rotating between two breasts will likely get differing levels of nutrition, differing amounts of calories, even different volumes, depending the order each eats in a feeding session. And it would be easy for some children to get left behind, undernourished, if there's any problem feeding or if the scheduling or rotating is even slightly off balance - those eating first getting nutrients so the second feeders are malnourished, those eating later getting the bulk of fats and calories so those eating first are starved. On the other hand, each breast has its own supply of each kind of milk (one reason switching breasts when feeding is a thing), so having at least one breast per child should help to minimize that kind of unequal division - though more would be useful backup for when the children need more than one breast's worth of milk. For another thing, infants eat every two or three hours, can take as long as an hour for a single feeding in some circumstances - and can have [marathon feedings](https://www.babycenter.com/404_how-long-is-my-baby-supposed-to-nurse-in-one-sitting_8911.bc), preceding a growth spurt, with feedings every 20 to 50 minutes. Rotating feedings would mean spending twice as much time on feeding, not to mention the extra amount of time it would take to completely refill the breast (to make sure both kinds of milk are produced). And with all the other demands on the parent's time doubled, well, the first few months are already commonly held to be a time of sleep deprivation and frantic activity (cleaning, soothing, keeping warm and dry, self-care), needing to double the frequency or duration of feedings is likely not going to help at all. An intelligent animal can manage, I believe, as you said (as we do, when multiple kids are born) - but it would be a real and nontrivial effort and require a great deal of support from others. And those others would likely have their own to tend, as this is a normal and not extraordinary circumstance, limiting the amount of assistance each could reasonably expect to get. Also, time may be somewhat less important for having safe and organized villages as opposed to being vulnerable and alone, but it is still quite important - especially since more time per litter would be needed generally for childcare, and more calories would be needed to produce milk (thus more time to forage, prepare food, eat, rest, etc). It is possible to balance out the feedings so each gets their fair share, but it is a great deal of work - and it is equally possible to miscalculate, to under-nourish one or more of the litter and those so neglected will be much less likely to survive. I would expect that such balancing would be much, much harder further back in evolutionary history - with the effect that either those with smaller litters would out-compete those with more, as their kids are healthier, or else more breasts would evolve. A [third nipple](http://babyandbump.momtastic.com/baby-club/834833-anyone-have-lactating-3rd-nipple.html) is a possible mutation already, if it gave a concrete advantage I would expect it to spread broadly and possibly eventually a mutation of a fourth nipple may appear, or more, until the number meets or exceeds expected children per litter (to ensure each has a chance at equal nourishment). And each breast may be smaller, or some or all of them may be dormant, flat and not engorged, when not actively breastfeeding a litter. This happens in other animals, so it seems a likely solution if extra breasts would negatively impact the center of balance. [Answer] One possibility I don't see mentioned is that men could develop the ability to nurse. While there are apparently no examples of male lactation in rigorously reviewed medical literature, there are numerous reasonably credible reports of men nursing, and the main holdup, if any, for more widespread male lactation is a relatively minor hormonal shortage in men. It would be far easier for the male hormone balance to change slightly than it would be for women to grow more breasts. [Answer] The answer would be yes, they'd have more breasts if they had larger litters. However... one has to consider why larger and more developed animals don't have large litters - they protect and educate the few they do have. Animals with a high reproductive rate, like rabbits, mice, cats, and dogs, tend to spray out the babies and hope a few make it. Childhood tends to be shorter, with a shorter training period and fewer skills to learn. Cats and dogs have a 6-8 month childhood with the mother starting a new brood within one year of the previous, while human children have an 18 year childhood - and some extend childhood far beyond that time. Besides, with 6-8 breasts, it would take one all night just to get through foreplay. Might lower the reproductive rate. ]
[Question] [ I love chocolate. Today, when I was making myself a cup of hot chocolate, I was thinking about Easter and about [all the chocolate](http://www.telegraph.co.uk/topics/easter/7544878/Easter-2010-Children-gorge-on-2.5kg-of-chocolate.html) I am going to eat. And at some point I was wondering: How awesome would it be to have real chocolate bunnies! Of course a block of chocolate would not be able to hop around the place, but I am interested in seeing how close I could get to chocolate bunnies. How could chocolate bunnies evolve? Here are some things I was thinking about: * What environmental challenges would be needed? I thought that you needed to introduce a predator that could be fooled by the chocolate or that it might be useful for the offspring. * Would they be able to produce chocolate milk or could parts of the bunny be edible for a human? As some animals produce milk I would imagine this to be easier, but introducing chocolate milk in bunnies seems weird at first glance. Edible parts could be useful to fend off predators, similar to [Autotomy](https://en.wikipedia.org/wiki/Autotomy), where an animal discards an appendage to elude the predator. The appendage can then regrow. * What would the bunnies need to eat and drink in order to produce chocolate? They would probably need a vastly different diet in order to produce the different components needed for the chocolate, so I would need to introduce the chocolate bunnies in a different part of the world. For definitions we will take the ingredients of the chocolate recipe I found on [this](http://www.precisionnutrition.com/chocolate-making) site: * cocoa butter * virgin coconut oil * (raw) organic cocoa powder Of course this can be liberally changed to suit your solution. The goal is to come as close to a real chocolate bunny as possible. [Answer] What a fun question. Cocoa is native to South America and only grows near the equator. Some early European settlers in SA start a cocoa plantation. They had brought along European rabbits as a food source but the bunnies, of course, escape. Eventually they realize that the rabbits are really good at removing the tough outer pod that covers cocoa beans. Rabbits love to chew and they need lots of fiber. This job is really labor intensive for humans so having critters do it is so much cheaper. They breed a rabbit that is particularly effective at chewing up the fiber but leaving the beans for the usual processing. Eventually, this rabbit becomes a new species. It is pretty scrawny because selection was for chewing ability not meat or fur. However, one day a desperate former cocoa worker fries one up for dinner. The meat has a distinct cocoa taste. It is more like a mole sauce than a Hershey bar but the addition of some sweetening and other spices makes a wonderful meal. You could also have rabbits processing cocoa beans the way a civet processes coffee beans but that's just a little gross. [Answer] Obviously a bunny made of actual chocolate is beyond the realms of feasibility, but you could possibly make a bunny that tastes of chocolate. You can get corn fed chicken which (apparently) affects the taste, and there are other examples of animals being fed certain things to change the taste of their meat, so why not cocoa bean fed bunnies? Unless you want dark chocolate bunnies the meat would probably have to be quite sweet, so other than cocoa beans they'd need to eat something high in sugar (not sure this works scientifically). Tropical fruits seems a logical choice if you want these to be naturally evolved wild creatures as many occur in the same regions as cocoa beans. As for why they would evolve, that's actually pretty easy. Chocolate is toxic (or at least contains theobromine which is), not so much for humans but very much so for animals. So the chocolate bunny pumps its body full of cocoa and theobromine (which it has developed an immunity or higher resistance to) and is poisonous to predators. Being mammals bunnies produce milk, it would not be unreasonable to assume this would also be high in cocoa, hence chocolate milk. I'm going to leave the question of how exactly you milk one to someone else though. [Answer] A) Bunnies eat cocoa beans as they eat carrots B) Bunnies sweat excess of cocoa, Mother bunnies give milk, as they milk is fat and bunnies have naturally fatty skin they are covered in chocolate and give chocolate milk C) Predators eat Bunnies, chocolate kills Predators. Predators try to avoid adult bunnies trying to seek only young ones who haven't eat cocoa. You will end with something close to finest Crunchy Frog produced by Whizzo Chocolate Company [Answer] The environmental change necessary would be natural magic capable of allowing for the evolution of chocolate animals. That and a biosphere where theobromine is extremely toxic to all predators of lagomorphs. The last point is on the same page as that proposed by @adalibooks, but on steroids. ]
[Question] [ We all know the usual staples of genetically-engineered super-soldiers. Rattlesnake DNA to see in the dark etc etc. But what about a modification that's a little more exotic, and far more advantageous than night vision or increased stamina? What about optical camouflage? Everybody knows the chameleon and to a lesser extent the cuttlefish. Could you splice genes from species with these color-changing traits using CRISPR and give humans the same ability to alter the pigmentation of their skin through conscious effort? [Answer] Unlikely. Gene splicing works best when replicating single proteins, not complex structures, and chromatophores are highly complex structures. Chameleon chromatophores are melanin-filled cells that are spread out over other, colored cells. In response to nerve triggers, the melanin-filled cells can concentrate or disperse their internal melanin packets, covering or revealing the colored cells underneath. Cuttlefish chromatophores are even more complex, consisting of pigment-filled sacs, each one of them surrounded by hundreds of tiny radial muscles that can expand, contract, and change the shape of the sac to change its color. Giving a human chromatophores is kind of like giving them wings: you're adding a whole new type of organ. You can't do that by simply sticking the right piece of cuttlefish DNA into them. If you want color-changing soldiers, go with nanotech instead. Scientists are already working on "invisibility cloaks" that use the same principles. If your story is set in the near-future, you can probably make color-changing nanomachine tattoos that work the same way. [Answer] ## Yes, you can splice in chromatophores but how useful would that be? Humans haven't been naked for tens of thousands of years. In the strictest interpretation of the question, yes, it would be possible with CRISPR-CAS9 to inject the genes for building chromatophores into human DNA. In addition to the coding for chromatophores, a genetisist will need to include all the required development genetic instructions (so the chromatophores form at the skin, not internally where they aren't useful) and any changes to human neurology to accomodate the information processing required to make chromatophores work as camouflage. Remember that cephalopods have huge brain-to-body ratios to handle the additional processing load of making their skin match their surroundings (in additional to the computational load of figuring out what to do with eight arms). ## Brains! Brains! Brains! If no changes to human brain structure are possible, then there will need to be a reduction in some other capability to make way for controlling the chromatophores. Should this compromise be unacceptable, then changes to brain size/structure will be require which brings up questions about fetal cranium size and the corresponding size of the human birth canal (Women's hips are only so wide and can only pass fetal skulls below a certain girth). [A more recent thought on brains] We see in octopii that much of their "brains" are in the limbs themselves. Even in humans, certain types of signals just go to the spinal cord then back to the limb. Given these examples, we may be able to keep the current brain architecture but distribute the processing required to make chromatophores work out to the skin. There's a couple of interesting implications here. Because of the distance between the brain and the skin, the color of the skin may be part of the [autonomic nervous systems](https://en.wikipedia.org/wiki/Autonomic_nervous_system) which the conscious mind has little to no control over. My bet is that there's a ton of social signaling that can be derived from this kind of a system. In short, adding the genes for chromatophores is a fairly straight forward task with CRISPR. Massaging the rest of human anatomy & physiology, infant development, and neurology into a viable life form is much more challenging. [Answer] This would be a monumental effort. Not only would you have to produce the chromatophores themselves, you'd need to to add a parallel nervous system to control them, plus a rewiring of the brain. This would involve wholesale modifications to the visual system to make the connection between what is seen as the environment and the control of the chromatophores. The added neural function would have to replace parts of the current brain architecture (unless you're willing to specify an increased brain size), so it's not clear that the resulting soldiers would remain psychologically human. [Answer] What if instead of using a nerve signal you had them respond to certain hormones. Do you think they could act like easily changeable permanent tattoos? ]
[Question] [ In a magic setting, a stereotypical "cold fire" might be a deep blue color but otherwise look just like a normal fire, consuming some materials and radiating cold. In reality, this is not possible for numerous reasons. However, what is the closest thing we could get? The more bullets we cover, the better the solution is: * Cools the surrounding area (Required point) * Consumes some material * Can consume nearby (commonly found) material for its energy * Is a naturally occurring process * Has features that warrant the "cold fire" nickname * Portable starting materials * small in size (for required starting materials), think flint for regular fires * emits light (any color) [Answer] After some thought, I thought of something simple, in the same vein as nigel222's answer: [dry ice](https://en.wikipedia.org/wiki/Dry_ice). * Cools the surrounding area The primary use of dry ice is as a cooling agent. * Consumes some material It'll consume itself. Dry ice is a solid that will sublimate at average temperatures. * Is a naturally occurring process Curiously, there is a place on Earth where dry ice could conceivably occur naturally: [Antarctica](https://www.insidescience.org/blog/2013/12/10/coldest-natural-place-earth). The processes by which dry ice [inflicts burns](http://science.howstuffworks.com/touched-dry-ice.htm) and cools the environment are purely physics-based. * Has features that warrant the "cold fire" nickname Dry ice is used [to make fog](https://www.youtube.com/watch?v=BsO1B-FWD6I) in a number of fields, such as stage performances. The unfamiliar could easily mistake the fog for a crawling, white smoke. Also, dry ice burns, as mentioned above. * Portable starting materials Dry ice can be stored in any cooler-like container and handled with thick gloves and it isn't heavy in manageable quantities. * small in size (for required starting materials), think flint for regular fires Dry ice starts itself, once introduced to higher temperatures. You can use hot water to enhance the effect, as indicated in the video. [Answer] While messing with laws of thermodynamics and 'negative temperature' (which is "hot" in physics) I realised that we have something already that fits a few of your criteria. Lasers! Cools the surrounding area (Required point) By utilising methods like doppler cooling, atoms lose momentum equal to the momentum of the photon. When the excited atom releases a spontaneous photon, it's pushed into a random direction, and the overall speed and kinetic energy of the atoms are reduced over time. We use this process at home to cool things to near absolute zero levels. Consumes some material You're consuming energy to emit the laser. Is a naturally occurring process [NASA's Kuiper Airborne Observatory detected laser light in space.](http://www.nasa.gov/home/hqnews/1995/95-148.txt) It is not unrealistic to me to find one in nature that may have cooling effects on its surroundings. I can imagine a celestial body that's consuming matter in space but is emitting specific laser light into a nearby cluster of space dust and is such that emulates our doppler cooling at home. Emits light Lasers are the epitome of light emitting. A 445 nm laser is blue, which satisfies the colour that you might be looking for. [Answer] Fire is an exothermic reaction. Exothermic means that while material are converted into others (fuel and oxygen into smoke and ashes), heat is created as a by-product. There are also endothermic reactions in chemistry. These are chemical reactions which don't create heat but consume heat instead. That means they cool down the surrounding. So what you need is a (likely fictional) chemical which reacts endothermic with a very wide range of common substances. However, these reactions won't cause a blaze. A blaze is a plasma. A plasma is heated gas. Gas does not turn into plasma when it cools. Also, it won't create any light. But when the endothermic reaction cools the surrounding enough, you might see humidity in the surrounding air condense, which could cause a visible cloud of fog to appear around it. [Answer] You might consider various small molecules that condense to liquid at temperatures well below the freezing point of water. If you survive an attack with (say) liquid nitrogen you will report the pain of severe frostbite as being like fire. Alternatively choose an inflammable such as liquid propane. Cold until ignited. Then fire or explosion. I think there may even be liquids that self-ignite once they vaporize and mix with air. Most I can think of are also toxic. Don't know if there's one that could combine all of frostbite, chemical burn, and true hot fire on ignition. Liquid ammonia (anhydrous not solution) comes close but does not self-ignite. Add a trace catalyst? At this point my chemistry knowledge runs out. [Answer] Okay… here’s an idea I had a long time ago: it does not emit light, it does the opposite. Hear me out: light consists of photons, they are something like tiny concentrated energy bolts, they carry both light and heat at the same time (ever seen lightbulbs burn hot?) Heat is light and light is heat. So if we are looking at antifire that consumes energy (heat), you could also make it consume light… Cold is darkness and darkness is cold. This thing would look exactly like flames, but they originate away from the centre of the reaction and converge towards it, they are black and get blacker towards the centre. The whole thing emits darkness (imagine that it attracts light into itself and redirects it from hitting surfaces around). Then consumption. In a fire, you see matter getting broken down and energy is released. In this antifire thing, you could imagine that the energy it consumes is used to bunch up matter. In other words, it would consume smaller particles to create larger bundles of matter (think of how wood turns to ash, but in reverse — ash turns to wood). Maybe it produces fibers or whatever that get dissolved in liquid air (it’s cold, right?) and this flows around from under the antifire in streams. As the air evaporates when it gets farther from the source of cold, the fibers are deposited, so instead of having a candle that burns down, you get antifire which builds its own candle up underneath/around it. Not sure about starting materials. You may have to create some fictional ore that can start this process with an “antispark” or such. To stop this process, you’d probably need vacuum, so that it runs out of “raw resources” from which to build its product material. Then it would have nowhere to deposit the energy it collects and potentially go out with an explosion, releasing all the excess energy. As a twist, before going out, you can make it reuse its “product” material to make heavier/more complex material. For example, if it combines hydrogen into heavier atoms, it can go all the way to Ununoctium until it runs out of matter. Its preferred product would obviously be the simplest it can create from the matter/energy at hand. Source: an art project I did in high school was a drawing of a world in which light and dark are switched, so wherever there is conventionally light there is now shadow and vice versa. This idea kept coming back to me ever since until I formed it into the concept I described above. [Answer] You are making a simplistic assumption of what fire is. You are asking for some things that are similar to fire(consuming something), and some things that are the opposite of it(cooling the surroundings). In reality, fire is just a chemical reaction of oxidation; a reaction which causes something(reactant) to bond with oxygen, and produce an oxide and radiate light and heat in the process. An endothermic reaction will have reactants combine with something and instead of radiating heat, will absorb heat. Because it's absorbing energy when the reaction is happening(instead of radiating), we cannot have something that glows. Oxidation(combustion) is a common reaction for most of the material we find around us(which is carbon based, so it reacts with oxygen easily). Unfortunately, there isn't any endothermic reaction(AFAIK) that's so common. As for being small and portable, I agree that dry ice will be a viable candidate, as Frostfyre said. ]
[Question] [ The world I am envisioning is a rocky planet with oceans, plate tectonics, atmosphere, and several other similarities to our globe. The mass and size is roughly equal, but its moon is orbiting much closer around it than our moon revolves around Earth. For the sake of clarity: the moon has roughly the same size and mass as our moon. I am wondering what the consequences would be if it were to orbit the planet at a distance of 1/20th the distance our moon orbits the Earth (let's say 20 000 km as an approximation). The questions I have are: 1. Would such a system be stable? 2. If yes: a) what orbital speed would be necessary for the moon to stay in geocentric orbit? b) would an eccentricity close to zero be possible, or would the trajectory have to look different in order for the system to be stable (if yes: what would it look like)? c) what sidereal day would the moon have at the altitude of 20 000 km and the necessary speed? 3. How many degrees of the sky would it take up when seen from the world's surface? (I would love to simulate for myself with the software from spaceengine.org, but I lack hardware spec for that and they lack a Linux version) 4. What would the tidal effects on the oceans look like with such a close orbit (as an average, I might add; I am well aware that tidal patterns are greatly affected by local geography, depth of the sea, shape of the sea bottom, etc)? Side note: I read that a moon 20 times closer to the Earth would mean tidal effects 400 times stronger, but I do not have the mathematical knowledge to double check the numbers myself. 5. Would a geocentric orbit by an object of this mass allow for an axial tilt of zero degrees for the planet, or would that be impossible? 6. What would the moons pull on the planet mean in terms of plate tectonics (earthquakes, volcanoes, etc)? I assume it would be increased, but is it possible to calculate how much more increased it would be, or are there too many unknown factors involved for that? I hope I have been specific enough, and I look forward to your answers and thoughts on the subject! [Answer] It could happen. > > 1. Would such a system be stable? > > > The Earth's moon is currently 41 times further out than [its Roche limit with Earth](http://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_examples). So the moon can be 20 times closer and not break up. > > a) what orbital speed would be necessary for the moon to stay in geocentric orbit? > > > The velocity of any satellite orbiting in a circle is: $$v\_o \approx \sqrt{GM \over r}$$ Where G is the gravitational constant, M is the combined mass of the bodies in question, and r is the distance between their centers. To orbit at 1/20th the distance, the moon would need to be orbiting at 4.58 km/second, which is about 4.48 times as fast as it does now. > > b) would an eccentricity close to zero be possible, or would the trajectory have to look different in order for the system to be stable (if yes: what would it look like)? > > > I've calculated using eccentricity of zero, I think this would be fine. > > c) what sidereal day would the moon have at the altitude of 20 000 km and the necessary speed? > > > I'm not sure this makes sense given the definition of sidereal time. If you want to know the orbital period of the moon, it would take about 7.34 hours to orbit the Earth. > > How many degrees of the sky would it take up when seen from the world's surface? > > > The angular diameter is given by: $$ \delta = 2\arctan\left({d \over 2D }\right) $$ For the moon's diameter of 3,476 km and new distance of 19,220 km, it would appear to be about 10.3 degrees in diameter. This is [about the size of your fist](http://oneminuteastronomer.com/860/measuring-sky/) when you arm is held out. > > What would the tidal effects on the oceans look like with such a close orbit (as an average, I might add; I am well aware that tidal patterns are greatly affected by local geography, depth of the sea, shape of the sea bottom, etc)? > > > There is a [brief article](http://www.spaceanswers.com/solar-system/what-would-happen-if-the-moon-moved-closer-to-the-earth/) discussing the tidal effects of a moon 20 times closer, it says: > > If the Moon got much closer, say 20 times closer, it would exert a gravitational force 400 times greater than what we are used to. A mighty tidal bulge would be created, hitting the land and causing great flooding, with cities such as London and New York disappearing under water. > > > This may have been what you were talking about. It's a valid estimate. The mathematics for tidal force are included [on the Wikipedia page](http://en.wikipedia.org/wiki/Tidal_force#Mathematical_treatment). Though the article is just talking about gravitational force, the two are obviously related. But, the tidal force increase would be significantly stronger with this increase in gravitational force. The lunar tidal acceleration at the Earth's surface along the Moon-Earth axis would be about 0.0718 g (around 8,000 times stronger than now). So the article is accurate, it just doesn't provide the increase for tidal forces, only the gravitational increase. > > Would a geocentric orbit by an object of this mass allow for an axial tilt of zero degrees for the planet, or would that be impossible? > > > Allow for it? Sure, things will change significantly for the planet. I'm not sure what you're asking here. The axial tilt with respect to the Sun? > > What would the moons pull on the planet mean in terms of plate tectonics (earthquakes, volcanoes, etc)? I assume it would be increased, but is it possible to calculate how much more increased it would be, or are there too many unknown factors involved for that? > > > The tidal force could be calculated. What effect that would actually have on plate tectonics is far beyond my ability to calculate/simulate. My guess is you could get answers like "more earthquakes" but not much more specific than that. Especially if this planet is not Earth. [Answer] The massive tides would have one other effect, which would be to slow the Earth and cause the moon to gradually spiral outwards from the Earth to a more distant orbit due to tidal torques. The current rate of slowing can only be calculated using accurate atomic clocks (with the occasional leap second being added to the year to make up for the slowdown), but even 4 billion years from now the Earth will not be tidally locked to the Moon (and we will have a few bigger issues with the Sun at that time). If the Moon were as close as you want it to be, the slowdown would be faster (relatively speaking, maybe a few seconds a year) and the Moon would not visibly retreat from the Earth in a human lifetime, but over the generations this will become noticeable. Edmund Halley, of Halley's comet fame, noticed the discrepancies in ancient astronomical records in 1695, so a civilization with even limited astronomical knowledge will figure this out eventually. [Answer] Not stable over geological time. That's a system that, because of the massive tidal forces in effect, is going to bleed angular momentum extremely rapidly. Regardless of whether you could get a stable starting set up or not, and I'm inclined to think not, the increased tidal gravity is exerted at both ends of the Earth/Moon system. Tidal friction creates a net loss of angular momentum in the system but most of the energy is debited from the lower mass faster moving member of it meaning that, in our world, the Moon is constantly giving up orbital energy to the Earth. In a system that creates four hundred times the force we see today that's a process that's going to go much faster, I'm not sure what would happen to the system, whether the moon in question would back away into space or fall in towards it's primary and be torn apart when it passed it's Roche Limit. What I am sure of is it's not stable, our own Earth/Moon system isn't stable, but this is really not stable. [Answer] It doesn't appear to be possible without deliberate engineering or some very special sequence of events. If the moon started that close, after 4 billion years it would be far away. How do you get it close in geologicaly recient time, so it has not run off again? An n-body interaction could capture it, even give it a perige as close as you wanted. But then how do you circularize the orbit, bringing down the (very distant) apoge to match? ]
[Question] [ I want transmutation of elements (for example, changing lead into gold) to be possible in my world, using magic rather than nuclear physics. I want the overall energy input or output to be consistent with the real-world elements, but without the additional energy required for initiating the nuclear reaction that would normally be needed. I'd like to assume that a way has been found to change from one element to another without needing the extreme conditions of an exploding star. Practical applications in the story would include knowing how much lead could be converted to gold using the energy available to a human from eating a meal (assuming they only use the energy that a human digestive system can extract). Alternatively if the change is exothermic, how much heat would the human have to absorb to change 1 gram of lead into gold? The energy calculations could be asked on Physics.SE and Biology.SE, but first I need to make the magical process self consistent and believable (hard magic, analagous to [hard sci fi](http://en.wikipedia.org/wiki/Hard_science_fiction)). I'd be interested in anything else I'd need to take into account to make this believable. For example, would converting lead to gold involve releasing helium and hydrogen to account for the difference in atomic mass? Would this cause a risk of fire or asphyxiation if performed in a poorly ventilated space? Or would the extra mass become lithium, creating impure gold that then needs to be refined? I'm trying to settle on a mechanism behind this magical process. I've been considering the following as possibilities: * Accelerating time in a small region containing the lead, so that it naturally decays into gold. Two problems with this: 1. The decay products of lead may not include gold (it may decay directly into smaller elements). 2. The huge amount of accelerated time required to see most of the lead decay may also see most of the gold produced decay too. * Magically inducing a rain of high energy neutrons to bombard the lead nuclei and split them into gold and H/He/Li. The two problems mentioned still apply here. * Some kind of "nuclear enzyme" to catalyse the nuclear reaction so that extreme conditions are not required. This seems the most arbitrary, but being specific to that one reaction it does not suffer from the two problems described. [Answer] Your main problem is that lead and gold do not have the same ratio of protons to neutrons, so you won't be able to just rearrange your lead into gold. You will end up with some leftover neutrons however you do it. An atom of gold has 79 protons, 118 neutrons, and -31.1 MeV of excess energy. An atom of lead has (on average) 82 protons, 125.24 neutrons, and -22.4 MeV of excess energy. A lone neutron has 8.1 MeV of excess energy. If we want to achieve a maximum lead-to-gold ratio, we can simply emit all of the excess neutrons as neutron radiation. On average, each atom of lead will produce 1.04 atoms of gold, 2.76 neutrons, and -12.4 MeV of energy. That minus sign is a Bad Thing: it means that we have an energy deficit, i.e. we will need to put in that much energy for the reaction to take place. How much? About 50 Megawatt-hours per ounce of gold. You would also absorb on the order of tens of Sieverts of neutron radiation per ounce of gold produced. This is probably not good for your wizard. We can do what Abulafia suggests in his answer and convert the excess neutrons into some light element. The best candidate is probably tritium, since it will take up two excess neutrons per lost proton. We will end up 7.9% tritium by mass. Unfortunately we still need to put in energy, around 73.8 MeV per atom of lead, since this is effectively doing fusion in reverse. Another good candidate for a 'neutron sponge' is plutonium-244, with around 1.6 times as many neutrons as protons. We end up with around 34% plutonium by mass. This time our energy output is less, but still negative, with 18.0 MeV needed per lead atom. (This time, we're doing fission in reverse.) I wrote a linear programming routine to find the highest-yield zero-energy transmutation from one given element to another, using all isotopes with half-lives over a given threshold. Here are some examples of transmutations into gold (percentages are mass fractions): * $\text{Pb}\to 8.5\%~^{126}\text{Sn} + 33.1\%~^{228}\text{Ra} + 58.4\%~\text{Au}$ (14 carat) * $\text{Pb}\to 13.7\%~^{126}\text{Sn} + 30.2\%~^{244}\text{Pu} + 56.0\%~\text{Au}$ (disallowing radium) * $\text{Pb}\to 15.0\%~^{136}\text{Xe} + 30.1\%~^{244}\text{Pu} + 54.9\%~\text{Au}$ (disallowing radioactive tin) * $\text{Pb}\to 14.3\%~^{136}\text{Xe} + 33.0\%~^{238}\text{U} + 52.7\%~\text{Au}$ (disallowing plutonium) * $\text{Pb}\to 0.4\%~\text{D} + 64.6\%~^{204}\text{Hg} + 35.0\%~\text{Au}$ (disallowing all radioactive elements) * $\text{Hg}\to 6.9\%~^{126}\text{Sn} + 11.7\%~^{250}\text{Cm} + 81.5\%~\text{Au}$ (just below 20 carat) * $\text{Hg}\to 6.6\%~^{126}\text{Sn} + 12.6\%~^{244}\text{Pu} + 80.7\%~\text{Au}$ (disallowing Curium) * $\text{Hg}\to 7.2\%~^{136}\text{Xe} + 12.6\%~^{244}\text{Pu} + 80.2\%~\text{Au}$ (disallowing radioactive tin) * $\text{Hg}\to 6.9\%~^{136}\text{Xe} + 13.8\%~^{236}\text{U} + 79.3\%~\text{Au}$ (disallowing plutonium) * $\text{Hg}\to 0.1\%~\text{D} + 26.7\%~^{204}\text{Hg} + 73.2\%~\text{Au}$ (around 18 carat) (disallowing all radioactive elements) * $\text{Ag}\to 70.5\%~^{58}\text{Fe} + 2.0\%~^{62}\text{Ni} + 27.5\%~\text{Au}$ * $\text{Cu}\to 51.1\%~^{56}\text{Fe} + 44.5\%~^{62}\text{Ni} + 4.4\%~\text{Au}$ * $\text{Fe}\to 4.8\%~^{54}\text{Fe} + 95.2\%~^{56}\text{Fe} + 0.1\%~\text{Au}$ * $\text{Al}\to 0.9\%~\text{H} + 76.1\%~^{40}\text{Ca} + 23.1\%~\text{Au}$ * $\text{H}\_2\text{O}\to 15.6\%~\text{H} + 62.4\%~^{40}\text{Ca} + 22.1\%~\text{Au}$ * $\text{Air}\to 8.3\%~\text{H} + 49.6\%~^{40}\text{Ca} + 42.1\%~\text{Au}$ (10 carat) Zero-energy means that each of these methods take zero energy input or output. However, you will still need a way to purify the gold afterwards (perhaps magical separation?). Note that elements closer to iron have worse yields, since they have much higher binding energies. Due to the zero-energy criterion, most of the mass must be turned into nearby high-energy isotopes to offset the creation of relatively low-energy gold. Transmutations between nearby elements work better, like mercury and gold. Another example, turning air (nitrogen and oxygen) into diamond (carbon) and ruby or sapphire (corundum/aluminum oxide): * $\text{Air}\to 1.5\%~\text{D} + 0.03\%~^{10}\text{Be} + 98.5\%~\text{C}$ (The beryllium changes to plutonium-244, uranium-238, and mercury-204 in roughly the same proportion as we increase the minimum half-life) * $\text{Air}\to 1.7\%~\text{H} + 6.4\%~\text{D} + 91.9\%~\text{Al}\_2\text{O}\_3$ Note that since aluminum has one more neutron than an even split (like nitrogen and oxygen), in this case we have to dump excess protons instead of excess neutrons. A possible explanation for the magical transmutation could be a sort of probability manipulation, forcing the quantum-mechanical waveform to collapse into the desired state. How you justify your magic is ultimately up to you though. ## Update While playing around with my code, I stumbled across a much more efficient transmutation: turning mercury into platinum: * $\text{Hg}\to 0.32\%~\text{n} + 0.04\%~\text{H} + 99.6\%~\text{Pt}$ This produces [three nines fine](https://en.wikipedia.org/wiki/Fineness#Platinum) platinum (999.6‰ purity after neutrons escape, same as bullion) with a small amount (0.038%) of hydrogen impurity. You don't have to worry about hydrogen embrittlement with platinum, so you can use it as-is, or smelt the transmuted metal into bars (unfortunately you can't cast bars by pouring the mercury into molds, since it will shrink by 37% during the transmutation process). This method produces a burst of thermal neutrons, but you should be able to block those with water shielding. [Answer] Edit: I got a bit carried away with the details and had to cut myself off at the end but the important bit is in the suggested procedure for your catalyst idea. In particular, the analogy with transparency and the wavelength of the particle initiating the transmutation. One way that I imagine this transmutation magic working is through your fourth option - the use of a catalyst or activator for the nuclear reaction of lead into gold. In particular, I imagine the catalyst as being an exotic particle that a magic-user can generate from his body's energy. In particular, these particles would not interact with matter except through gravity and a short range (say ~1 nm range) exotic nuclear force (compare with how neutrinos pass harmlessly through kilometers of matter except for the rare weak nuclear interaction). A stream of these particles passing through a block of lead would have some probability per meter of interacting with a lead nucleus, where the interaction could either be catalytic - conserving the exotic particle - or participatory - consuming the exotic particle as a reactant. To apply these particles, the magic-user might need to cast them in a field between his hands. Imagine a person's hands out in from of him as if carrying a box but instead he is standing over a piece of lead on a table or on a stand while barely visible streams leap back and forth between his hands. Only lead between the hands of the magic-user is affected by the transmutation. Before I get to energy cost and the reaction itself, there are a few limitations (or rather features) that naturally come to mind for a transmutation process that works through this mechanism: 1. Some of the exotic particles generated by the wizard will not interact with any lead. There should be some inefficiency defined for this process that perhaps more skilled magic-users can improve. 2. As a catalyst or reactant for the nuclear reaction, the particles would only yield some finite reaction rate - an amount of lead to gold per minute that could be fine-tuned to the worldbuilder's whim. This finite rate could make the process slow enough to not easily ruin the economy. 3. A magic-user transmuting lead into gold has to actually get the lead in front of him and concentrate his full attention (and both hands!) on the process. This procedure feels less soft than "point-and-transmute" or "midas-touching", since it superficially resembles other crafting procedures. 4. The exotic particles would have a particular wavelength and would only interact with nuclei that had a particular spacing in its energy levels, in an analogous manner to the interaction of photons with electron orbitals based on discrete energy level spacing and photon wavelength. In this way, the magic-user could choose which transmutation reaction he would perform by consciously changing the wavelength of the exotic particles he is casting (limited of course by the availability of the particular isotope/element for that wavelength). By choosing a wavelength particular to lead -> gold, the magic-user would cast particles for which any material other than lead is transparent. As for the reaction itself, for an exotic particle ε, a skeleton reaction is: ``` Pb-208 + ε ==> Au-197 + Be-9 + other ``` Using known atomic masses, Pb-208 to Au-197 is a change in mass from $207.976 \space\text{u}$ to $196.966\space\text{u}$, where 3 protons and 8 neutrons are left out. Turning some of this waste into Be-9, which has an atomic mass of $9.012\text{ u}$, there remain 2 neutrons (the conversion of one neutron into a proton also results in an electron and an antineutrino). A total of $0.02\text{ u}$ of mass has seemingly been created here but this can be accounted for through other parameters of the transmutation and its exotic particle. At this point, you could go several directions. The added mass can come from the exotic particle itself (i.e. it has a mass of $0.02\text{ u}$ or $18.6\space\text{MeV/c}^2$). For $1\text{ kg}$ of Pb-208, the energy supplied by the magic-user would need to be $$(2.895e21\text{ particles}) \times (18.6 \text{MeV}) \times (1.6e-13 \text{MeV/J}) = 8.6 \text{GJ}$$ or the equivalent energy from burning a barrel of oil. This calculation assumes $100\%$ efficiency which also doesn't make sense given the earlier description of the transmutation procedure. Since a human cannot generate this much energy, you would have to imagine a much much smaller mass for the particle, one that cannot account for the added energy. To get around this issue, you would have to imagine that one of the 2 neutrons is converted into energy. The massive excess energy of $920\text{ MeV}$ per reaction (transmuting 1 kg of lead would release the energy of $10\text{ MOABs}$!) could be disposed of in the kinetic energy of neutrino-antineutrino pairs. I could go on about how to make this better fit energy-momentum conservation, how to properly avoid violating lepton conservation, and how the range of the exotic nuclear force affects efficiency but I'm gonna cut this short. I hope this gave you some ideas! :) [Answer] Turning lead into gold releases a wizard-like amount of power. If we assume that magic can re-arrange the nucleus at will, we can take one end-result and calculate what amount of energy would have to go in or out to achieve that result. Lets say you start with the primordial lead-isotope Lead-204 with proton number 82 and relative atomic mass 203,97. You turn this into the stable gold isotope Gold-197 with proton number 79 and relative atomic mass 196,97. That leaves 3 protons and 7 neutrons which we will conveniently assume were turned into Lithium-7, which has a relative atomic mass of 6,94. This leaves no free particles, but a change in relative atomic mass of 0.06. In percentages of original weight this is $0.06/203.97 = 0,02941\%$. So in short, about $0.03\%$ of the mass of the lead is turned into energy. About 0.3 grams that is. How much energy is this? We can use $\text{E=mc}^2$ to calcualte this for $1\text{kg}$ of lead: $\text{E = 1kg}\times 0.03/100 \times (299792458 \text{m/s})^2 = 7.49 \text{GWh}$. (About $2.7 \times 10^{13} \text{Joules}$) The nice webservice Wolframalpha not only allow us to calculate the above without messing up the units, but also tells us that $7.49$ gigawatt hours is equivalent to half the energy output of the "Little Boy" nuclear bomb [1]. Other comparisions include 3 times the fuel capacity of an airbus A380 and twice the kinetic energy of the international space station, should it crash into something at full speed. [2] Bottom line is, if your wizard can transmute elements, he won't be doing it to peddle nuggets of gold, he'll be demolishing cities of the enemy. Story-wise, you could imagine that an adept wizard re-route the energy output into other transmutations, that absorb rather than emit energy. [1] <http://www.wolframalpha.com/input/?i=7.49+gigawatt+hours&lk=1> [2] <http://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)> [Answer] The only conceivable energy sink large enough to allow for such transmutations in noticeable amounts without triggering (or absorbing) the equivalent of a small nuclear bomb would be Zero-Point-Energy. Moreover, 97% of lead isotopes are stable or stable for tens of billions of years, so destabilizing them would be difficult (nucleic neutronic bombardment?). Even worse, most of the decay products are other elements like mercury, thallium or bismuth. Very few decay paths from lead lead to a stable gold isotope. In fact, gold is so hard to create, it's not generated inside normal stars, only in the most extreme supernovas and perhaps in [neutron-star collisions](http://www.smithsonianmag.com/science-nature/all-the-gold-in-the-universe-could-come-from-the-collisions-of-neutron-stars-13474145/?no-ist). If you want to transmute something into gold, I would suggest using the Mercury isotope Hg-196, (0.15% prevalence in natural Mercury). It can be converted to gold by neutron capture, and after electron capture-decay it will turn into Au-197 with slow neutron emission. [Answer] Your ideas imply doing things with magic, that we do with machines. The awesome thing about magic is: You can do things with it that would not be possible (or only very difficult to do). My personal approach would be not to follow some established scientific methods, but to go a bit deeper. Instead of trying to get a reaction, micromanage it: What I mean is, split whatever you want to turn into some other material into its smallest parts (electrons, neutrons, protons) and put them back together afterwards. So instead of changing lead indirectly, rearrange the basic building blocks to get gold [Answer] I think the unappreciated problem here is economic. If your average magician can easily turn lead into gold, then gold is pretty quickly going to be worth about as much as lead, which renders the conversion pointless. [Answer] Teleportation of nucleons. You have the ability to use magic to "command" all nucleons in a particular context - i.e. a nucleus with the right number of protons and neutrons - to go somewhere. Or if you need to transmute protons to neutrons, you command pions or antipions to go somewhere. Calculating the energy difference is easy: take the moles of the element you start with, times the difference in weight of the starting and ending isotopes (look up "isotopes of XXX" on Wikipedia) plus any leftover protons, neutrons, helium nuclei etc., times the speed of light squared, and you have your energy. The difference per mole is much less than a gram, but a gram x c^2 is 9x10^13 kg m^2 s^-2 (90 terajoules) which is no small denomination of energy bill. But with nuclear magic, I imagine energy should be pretty cheap! Especially since you produce it when you move from heavy or light elements toward iron, which is the lowest-energy of them all. [Answer] As others have said, you have a big energy problem and a neutron problem. There's also the economic issue of basically free gold. Thus I propose a different approach to address both sides of this. Magicians are severely limited in how much energy they can provide to drive the transmutation and they can't absorb very much energy from the reaction without be harmed or even killed. Thus I propose a different model of transmutation. Other answers have focused on a single reaction. Working this way the amount of material that can be transmuted safely is tiny and the workspace will slowly get radioactive from neutron activation. Really skilled magicians transmute multiple items at once. You need to supply some extra energy to make the Pb208 -> Au197 reaction go and you have to dispose of the extra particles. We also have the problem that beryllium that carries off the extra particles is highly toxic. Instead, lets take Pb208 + 2xC12 as our input. Our output is Au197 + O17 + O18. No radiation is released, all products are stable. This still leaves the energy issue, it would take far more time than I want to spend to find combinations that also balance the energy. Note that knowing the exact composition of your materials is very important. The magic doesn't care one bit if half your lead is Pb208 and the rest is the other stable isotopes, but only the Pb208 gets transmuted. But if you think it's 50% and it's really 55% you just released a bunch of energy and the magician dies. [Answer] # Consider abolishing particle physics? You are already in a high-magic universe. How about simply throwing out that particle physic nonsense, and adopting the old [Greek Atomic model as described by Democritus](http://thehistoryoftheatom.weebly.com/democritus.html)? In this model the smallest nondivisible particle is the Atom. Each element has its own unique Atom. And no, they simply cannot be split further apart than that. In this universe, transmutation of anything would "simply" involve convincing Atoms of one nature to convert directly into Atoms of another nature. NO worries about sleeting radiation, explosions of rampant energy or any of those scary phenomena that come from having a universe that further subdivides stuff into Protons,and Neutrons,and quarks, and glueons, and fermions, and even stranger stuff. ]
[Question] [ In a few sci-fi and fantasy books I've read (IIRC, [In the Year 2889](http://rads.stackoverflow.com/amzn/click/1603864695) by Jules Verne was one of them), people had global communications through mirrors that are lined up exactly with each other. ( obviously, visual only; no audio ) Would this be possible to set up, at all? ....assuming it is possible, would it be possible to set this up with a society that has ~1500 CE technology? [Answer] Impossible given 1500CE technology First issue: mirror quality I'm going to assume that squinting and looking really far away is not an option, so you want to see some curved mirrors redirecting light. I'm assuming something akin to the much larger parabolic reflectors used for [whisper dishes](https://flickriver.com/photos/lylescott/1130891025/). The key to any long distance transfer is that normal light radiates in all directions and you really need to columnate it into a highly parallel beam of light. You then have to catch that parallel beam of light, and display it. A pair of telescopes pointed at each other would form the basic structure. First key limit: there would be no depth to the image. It would not appear as a hologram, where you can view it from any angle. The columnating process would pick one viewpoint, and that is the only viewpoint you could show. Next major limit: optical quality. The telescope was not invented until around 1600CE, which gives suggestions as to their comprehension of optics. But lets advance the timeline of your question to at least 1617CE, which was the first mirror telescope. In fact, lets advance it to 1672, with Laurent Cassegrain and [his telescope](https://en.wikipedia.org/wiki/Cassegrain_reflector) which used mirrors. Its style is used today. If you think about the Cassegrain telescope in reverse, it becomes a projector. In effect, the light from any object at the "eyepiece" will be mapped to a block of parallel beams emitted from the telescope the size of the reflector. On the other side, one gathers that light, and recreates the image. We can use this to define the angular accuracies needed for the image. A Jules Verne style communication device would at least be accurate enough to read lips. Let's give a best case scenario where the communicators are focused only on the area of the lips used in lip reading, as opposed to showing an entire face (which would be desirable for detecting emotion). [It has been shown](https://ieeexplore.ieee.org/document/982900) that an 80x60 box of pixels centered on the face is sufficient for lip reading, so our receiving telescope needs to at least be able to identify that many pixels across the surface of the mirror. Now at this point we're going to start having to break down and cheat. Global communication would involve a hopelessly difficult to manage network of mirrors with many losses, so lets target a smaller goal: project and receive the image over 25km. "Heat haze" is a major issue for snipers, because the turbulent air of different temperatures refracts the light around unpredictably. They have trouble over distance of merely a mile, and they don't need to have magnification levels sufficient for reading lips. Over longer distance, heat haze would demolish any hope of seeing a meaningful image. (This effect is the primary limiting factor of ground based telescopes until the turn of the millennium, with adaptive optics). So lets pretend you can put a shroud on the air column. Make a large cylinder with a telescope on each end. Let's say this stabilizes the air, so that we are only limited by the quality of mirrors available in 1672. Now let's go big or go home: a 8m telescope like a modern telescope would give us a much better chance of this whole thing working than if we limited ourselves to the sizes seen in that era. The [diffraction limit](https://en.wikipedia.org/wiki/Optical_telescope#Angular_resolution) for telescopes is $\alpha\_R = \frac{138}{D}$ for visible light ($alpha\_R$ in arcseconds, $D$ in millimeters). Applying our diameter, we see a diffraction limit of $\alpha\_R = .01725 arcseconds = 8.363036\cdot 10^{-8} \text{radians}$ On the sending side, our 8m projector can be diced up into 80 pixels on each side. This means each pixel is .1m tall. At 25km away, that is $4\cdot 10^{-6} \text{radians}$ What does this say? If we built a 25km long shroud between the mirrors to cut down on the turbulence of the air, we are still within 2 order of magnitude of the diffraction limit. The diffraction limit is something we worry about with modern lenses and modern processes. The processes of 1500CE would not get anywhere near that limit, so the images would be too hopelessly blurred, even in that case. Why did I choose 25km? There's another reason this wouldn't work well. Unless you plan on digging massive tunnels to go with your giant shrouds, you can only shine light to the edge of a horizon. 25km is roughly the limit for how far you can see from a 100m tall tower ([its actually 35km](https://en.wikipedia.org/wiki/Horizon), but the point stands). To go any further, you would need to redirect the beam, but that is not easy. Bending light beams calls for waveguides, well beyond 1500CE technology. Passing them through a lens won't work because that would easily demolish the image quality (mirrors are much better for this sort of thing due to a lack of chromatic aberrations). You would either have to set up a giant horizontal mirror, perfectly aligned so that you can skip the light-beam off of it, or you would need to aim at an angle to your target, so that you can bounce off of a smaller mirror which is further from the ideal transmission direction. [Answer] It's definitely possible to set up medium-to-long range systems like this - but a truely global system would be difficult/unwieldy enough to be effectively impossible. Setting up two mirrors so that standing in front of one and looking into it lets you see whatever is in front of the other mirror is straightforward enough. Scaling it up from there is just an engineering problem - but a difficult one. First, you need very high precision in both making and positioning your mirrors\. You'll need the mirrors machined to an incredibly high level of smoothness - probably similar to that used for high-end modern telescopes. Secondly, you need to put it in exactly the right position - if you're trying to spot a metre-wide spot 100km away, then you need to get the angle right to within half of one-thousandth of a degree. As mentioned above, this is 'merely' an engineering problem ... but probably one solidly out of reach of 1500CE technology. Secondly, there is a fundamental limit on the resolution of an optical system based on the size of the apertures involved. A 10mm resolution for the above-mentioned 100km system would need a mirror almost 5m across - and that resolution would be barely useable. Certainly not good enough to recognise faces, so you'd have no way of knowing who you were talking to. Trying to improve the resolution causes the mirror size to go up fast - 1-2mm resolution (which we would still consider pixellated/blurry...) needs a mirror 50 to 100m in diameter. Once again, a 'mere' engineering problem... and once again, one that would make the project impossible to the target tech level. \Lenses are theoretically useful as well, but refractive variations between different wavelengths will cause problems ... and we're going to have enough problems as it is. They're just not worth the trouble. [Answer] Err... Fiber optics? (And why can't a meaningful answer be less than 30 characters?) But to elaborate, fiber optics sends light waves down precisely-aligned transparent media which eliminates distortions such as heat haze, fog, &c that you find in air, and also allows the light to traverse a non-straight path. Granted that current technology mostly uses them to carry digital information, but they can be used for viewing, e.g. endoscopes. [Answer] I'm not sure it is that different from semaphores. A few mirrors along the way + light source + morse code = telegraph. If you have very rough, mountainous landscape without much snow, and dark nights, it becomes viable. [Answer] Only if your vision is good enough to detect things at extreme range. If you were willing to use telescopes, maybe you could look at a mirror and see around a corner within visual distance. Not past the Earth's curvature. But making a telescope lens/mirror big enough to display something that could be looked at by another telescope would be... problematic. [Answer] While not possible with non-magical/steampunk 1500's technology, it should be viable with near future technology. We're working on flexible displays. From there it becomes a small step to put such a plastic display overtop a mirror and hook it up to a webcam. There would be technical hurdles to make the film not interfere with normal mirror use, and to not cause the mirror to reflect the display in odd ways, but that seems not insurmountable, even in our lifetimes. Or, of course, you could just have a normal flat panel that displays what it sees when not active. It "mirrors", even if it is not a mirror itself. ]
[Question] [ To be most effective, a windmill must face into the wind. Some windmills achieve this with a [passive yaw system](https://en.wikipedia.org/wiki/Yaw_system), where the wind automatically adjusts the direction the windmill is facing, often with a tail fin. [![enter image description here](https://i.stack.imgur.com/Mvm6l.jpg)](https://i.stack.imgur.com/Mvm6l.jpg) For my story, space fairing people use mirrors to focus sunlight onto water boilers, forges, and other places where intense heat is needed. Could some type of solar sail tail fin be used as a passive yaw system for directing these mirrors into their optimal orientation? The mirrors are attached to physical objects (space stations, ships, asteroids), not free floating, and they are typically in the vacuum of space with microgravity comparable to the ISS. A mirror is a 3 meter square sheet of silver curved into parabola. Concentrated solar facilities on Earth seem to always use active controls (electric motors) to move solar mirrors into position. I assume a passive yaw system would not be practical on earth, where air resistance (not to mention wind!) and gravity create significant resistance, and solar wind is deflected by our planet's magnetic shield. I wonder if a passive system would be easier to achieve in space, where there is vacuum, low gravity, and the presence of solar wind. Is passive yaw control possible for directing space mirrors into the sun? If so, what would such a system look like? [Answer] Sure. And one pattern might well be much like the windmill you show in your question. Especially since [one configuration](https://en.wikipedia.org/wiki/Solar_sail#Sail_configurations) is a spinning sail. The sail is spun to keep it stretched out. A small additional sail could certainly be constructed to provide an orienting force as in the windmill case. You might need to do some clever designing to keep the various torques lined up and prevent the system from tumbling. This is especially true since you would need to control in 3-D, not just rotation on one axis as the yaw control in a windmill. But, yes, it is very likely possible. However, the main reason you want a passive yaw control for a windmill is because it is difficult to predict the direction of the wind. Additionally, in the example of the windmill, the goal of the system is to provide maximum output of the turbine. Other than "feathering" to slow or stop the turbine, there isn't much in the way of maneuvers that you would want to do with a windmill. So turning the blades to face the wind is preferred. An automated system that does this without active control machinery is very useful. In the case of a solar sail, the direction of sunlight and solar wind is relatively easy to predict. And, while the angle of the mirror is often chosen to maximize thrust, it is also often chosen to perform maneuvers. So it is necessary to include in the design the ability to actively control the sail. Not just the angle, but the general shape of the sail must be controlled. That means passive control is of far less value. Probably it will be considered to be unrequired and redundant weight that could be removed. [Answer] A "mirror used for focusing sunlight" is by definition: 1. A section of a parabola, that has a focal point. 2. Reflective. 3. Has mass. [NASA paper on Solar Sail Propulsion](https://www.nasa.gov/pdf/134645main_solar_sail_fs.pdf) > > The technology uses solar > photons—sunlight—which are reflected off giant, > mirror-like sails > > > Your mirror - IS a solar sail. How you design the mirror, will determine how it will self-orient. Ultimately, your design needs to be such, that at a specific orientation w.r.t. the sun, that you wish to maintain, forces acting on the sail are equal to all sides of the center of mass. If it is disturbed, then your design has to be such, that more light becomes reflected off of the opposing side, which will force the mirror/solar-sail to self-orient back to the desired position. A windmill design is not the best implementation. The tail will be behind the mirror, so it will be in a shadow - it won't be reflecting photons. If the windmill is disturbed, then it will be some time, until the angle of misalignment will be enough, for the tail to emerge from the shadow and start reflecting light. By then, you may have already built up quite a bit of angular velocity, and the tail might be too small to stop the spin. You could make several "tails" along the outer edge of the mirror - orient them such, that they are usually parallel to the sunlight. When the mirror gets misaligned, they will start reflecting photons immediately, causing it to start self-alignment instantly. If you continue along this path of thought, and wrap it all up with actual calculations of force created by the reflection of photons, etc... you will eventually come to some of the passively stabilized designs depicted in the linked paper... or maybe something new, and better - then you can publish your own paper =). One thing to note about the designs in the paper - they are designed to self-orient directly at the sun. If you are trying to focus the light at... say... a planet, that is off to the side, then you will have an asymmetric mirror/parabola/solar-sail, and your stabilizing portion or sails will likewise have to be asymmetric. [Answer] There are some passive solar tracking methods that work on earth. Some use thermally active materials or thermal expansion. Others heat water and shift the center of mass. The first type could work in space; the second where gravity is part of how the forces are balanced wouldn’t work. Once you're a reasonable distance from the sun, the sun's rays are reasonably parallel, so shadows can be sharp. By controlling what is in shadow or what is getting hot, you can have a thermal mechanical system move the mirror. The problem in space is that you have to radiate heat away. This would make the design more difficult. You could also use the shadows or spots to shine on a screen and have your pilot manually steer the mirror, kind of like a helmsman. Or perhaps one person to steer the mirror to keep the optical alignment on the boiler and another person who steers the exhaust nozzle. [Answer] If you bend a 3 meter wide mirror into parabola, the apperture may be 1 meter or less. If you put a boiler 1 meter wide, it may block all the sunlight. Instead, put a thin 3 meter long copper pipe at the focus line of parabola and let the water run through it. [![enter image description here](https://i.stack.imgur.com/jVjEl.png)](https://i.stack.imgur.com/jVjEl.png) Passive Solar Tracking Syatems As explained [here](https://www.adamheisserer.com/passive-solar-tracking/) Zomeworks Track Racks They use liquid freon or another highly responsive, volatile liquid as the thermally active component. The liquid expands or condences, causing a shift in the center of gravity that tilts the array towards the sun throughout the day. Bimetal Strips Bimetal Strips bend when exposed to direct sunlight. Bimetal Coils They rotate when heated with sunlight. Thermally Active Plastic Composite Polyethylene has a very high thermal expansion rate, while Acrylic packing tape is non-thermally active plastic. Stick transparent Acrylic tape to black sheet of Polyethylene giving the bending effect of bimetal surface on heating. ]
[Question] [ So, my story, set in America in 1998, has werewolves. I'm not quite sure how good their hearing is going to be, but bare minimum, even when in human form, they can hear as well as a real-life wolf can. Which is... a lot. Somewhere between 6-10 miles outdoors depending on the level of forestation. And lately, I've been thinking a lot about the impact that would have on their culture. If a bunch of people living in the vicinity of each other have hearing way beyond that of normal humans, That would have a serious impact on privacy, and more importantly, their cultural attitudes about it. I've been heavily debating whether they'd take great pains to protect their privacy, or go in the other direction and conclude that secrecy is useless given how much more aware of their surroundings they are than any human can be. But before I get too deep into that, I think I need to double-check exactly how difficult privacy would be to achieve. Soundproofing, of course, is a thing, but it's almost always in the context of humans, and keeping them from hearing something too loudly or from hearing something at all. There's really not that much information I can find about keeping any animals with hearing stronger than a human's from being able to hear things. What would it take, if indeed it is even possible, to soundproof a room using 1998's technology thoroughly enough that no one outside of it could hear what was happening inside, even if they had the ears of a wolf? [Answer] Before we get into the tech of soundproofing, let's address the cultural question, because that may inform our soundproofing goals. Our population contains two distinct groups: humans, who have normal hearing, and werewolves, who have wolf-like hearing. These groups will have very different experiences, and so their cultures will have different trajectories. Humans will not change their soundproofing habits, because they will be unaware of the fact that there are individuals in the community who can suddenly hear everything as though they're using audio surveillance. Werewolves will not primarily experience this as a problem of "privacy," because their day-to-day experience will not centrally be about being observed by others, but of suddenly being able to observe all others. This maybe sounds like a cool benefit, but anyone who has lived in an apartment building can tell you that being forced to listen to the everyday noises of your neighbors grows obnoxious very quickly. It would only be enjoyable to a person who is nosy to the point of derangement. So, what will happen is that each werewolf will very quickly decide that she must do something to silence the ceaseless clamor of her neighbors, or go mad. And as satisfying as it might be to simply murder the problem, she will also have to deal with traffic sounds, which will resist a "bloody solution." Soundproofing tech has been around for a long time. There's interesting kinds of foam, and tiles, and fiberglass insulation, most of which can be done by a competent DIYer who is legally permitted to modify their residence. There's also a whole sub-discipline in architecture dedicated to acoustic design, but this is only relevant if you are extremely wealth and constructing a home (and my experience is that it's usually concerned with amplification, for performance venues and such). But now we know that each werewolf's primary goal will be to dampen the noises coming from their neighbors, rather than to contain noises made by themselves. We also know that secrecy is of paramount importance to werewolves, because humans generally hunt and kill werewolves as dangerous predators, so each werewolf will be reluctant to do anything that might call attention to themselves such as ordering a pallet of foam soundproofing panels or ripping up all their drywall. The ideal solution is the earplug: * small and inconspicuous, can be concealed on one's person * usually inexpensive * reusable * can be used anywhere, not just in the home * can be removed at any time when super-hearing is desired * not cause for suspicion if discovered by humans or authorities Earplugs have been around for a very long time. Apparently they were patented 140 years ago, in 1884 [1](https://hearingreview.com/uncategorized/historical-perspective-hearing-protection), but even the ancient Greeks knew about plugging one's ears to stop noise (it is mentioned in The Odyssey, written nearly three millennia ago). If you've worn disposable earplugs, you know they make everything sound muffled. Your werewolves can do better: a special variety of "Musicians Earplugs" was invented in 1988 which dampens sounds while maintaining clarity. These need to be custom-fit to the wearer's ears, and a pair costs about \$350 today; I'd guess they probably ran closer to $800 back in 1998. A cheaper version came out in 1990, so that could be a more affordable option. Here is how I think things will play out: 1. each werewolf will independently come to the conclusion they need to get earplugs or go insane; once they have good earplugs, they'll usually be so satisfied that they will stop looking for more extreme solutions 2. as the population of werewolves grows and members learn to identify each other, they will start to compare notes about the noise problem and their solutions 3. info about the best quality earplugs will become socialized among the group 4. many of these werewolves will develop an amateur interest in what we humans call "hearing protection" 5. any town with more than a few werewolves will develop a small business that sells unusually good earplugs and other home soundproofing solutions, which will be operated by one or more werewolves; it will also have free, quality literature about hearing loss, state-of-the-art hearing protection, and soundproofing 6. at first there will be a slight increase in violent crime near the "ear shop," after which it will become one of the safest neighborhoods in town once the owner puts out the word that anyone becomes persona non grata if they draw attention by getting violent near the store The werewolves who run the shop will be some of the most politically powerful members of the local werewolf community, because they will know the identifies of every local werewolf. They'll also be flush with profits. Civilians who wander into the store are likely to pick up on an odd vibe, similar to walking into a mob-owned storefront (I did this once, I think, and it's a strange feeling). Local kids will definitely know about the store, and it will figure prominently in a lot of their rumors and spooky tales. Young people who grew up in town will be inexplicably very afraid to go into the store for any reason. Little kids who are in the area and need to urinate will rather pee their pants than go into this store to use the bathroom, and if their parents insist, the kid will unfailingly lose bladder control and wet themselves when their irritated parent reaches for the door handle; this will be such a frequent occurrence that local parents will gossip about it (before and after PTA meetings, for example). [Answer] Slight frame-challenge. Area-exclusion technology has been long-used for pest control. Ultrasonic frequencies to deter pests, particularly mice and more recently children and youths from loitering in areas that they're not welcome - outside shops etc.. It's not perhaps necessary to drive the vulpines away altogether, but to take advantage of their super hearing and use it against them in a different way. Adult humans effectively hearing up to 15-18 kHz or so, vulpine's hearing is believed by [many naturalists](https://www.angelfire.com/az2/WolfPage/Senses.html) to far exceed that of dogs in the frequency-range part: > > Some researchers believe that the actual maximum frequency detected by > wolves is actually much higher, perhaps up to 80 kHz > > > Proposal: [Voice scrambling](https://crypto.stackexchange.com/questions/14623/analog-encryption-algorithms#15015) techniques, which re-iterate the speech of the humans in a room, to just outside the room via speakers - plus an added ultrasonic "noise" component, could successfully mask all spoken words within the room equipped with these devices. It needn't be painfully loud so as to drive them away, but all they'd be able to discern is that there is a conversation going on, not the content (excepting perhaps urgency and pace of the speech) - easily enough to preserve confidentiality. Slave-devices can be attached to windows with suction cups. Advantages: It's cheap and portable: a mic-scrambler-transmitter module and several slave modules can be carried easily in a small bag. It will work anywhere without having to equip the room/windows/doors with expensive shielding. [Answer] # Needle in a haystack: FRAME CHALLENGE: Civilization is full of vast amounts of cacophony. The noise is insane. While a wolf may be able to hear for miles, the average werewolf living in an urban setting will have their hearing limited by the sheer number, volume, and variety of noises they are constantly barraged by. It would be like an eagle trying to see a mouse in a snowstorm. While sounds like wolf calls that they are especially sensitive to might ring through this mess, I doubt the routine noises of human life will be so easy to distinguish. * Werewolves may have better hearing in wolf form, since wolf hearing depends on wolf ears. Human ears are simply not mechanically going to do the same job. So while a werewolf may have better than human hearing as a man, it will be quite a bit less. * The awareness of noises may depend on the form the werewolf is in. Traditionally, werewolves are portrayed as more animal and instinctive in wolf and were forms, often uncontrolled. What if they also can't understand human speech the same way since their transformed brains lack a clear sense of language? They may recognize language like dogs do - knowing specific voices, tones, and commands, but lacking a deep understanding of speech. Combined, these two factors would mean that human-form werewolves would be unable to hear like wolves, while wolf-form werewolves would be unable to understand speech. The same logic applies to other wolf senses. Cities may simply STINK to a wolf, and they would be overwhelmed by the range of smells. They would need to learn to ignore vast amounts of data, while still retaining the ability to hone in on a specific smell as needed. The human versions would be less capable, while the wolf versions would have different mental priorities. [Answer] Not soundproof per se, but the humans would likely have installed high-pitched ultrasonic speakers around the building. When a werewolf comes too close and trys to eavesdrop, they would feel intense pain while humans would not even hear it. ]
[Question] [ I am aware this is in the gray area of “story question or world question” but I think it is at least mainly world based. So in this reality set in the far future, somehow a certain math problem has been found to be the solution to all problems. How? Doesn’t matter, but everyone agrees that this is what needs to be solved. So obviously everyone strives to solve this. Nobody tries to solve it by hand though. Everyone uses some sort of computer, that is until stereotypical\_main\_character comes along and figures it out by doing it by hand. The problem is that I cannot think of any logical way that a computer when given enough time couldn’t solve a problem but a person could. Perhaps an alternative mathematical convention would be needed? Maybe something similar to the creation of imaginary numbers would have to happen. I have no idea about anything about how this problem would have to work, I’m pretty bad at math. Do note I am not asking for you to attempt to create such a math problem,(although I suppose you could) just if it is possible to exist in reasonable conditions. [Answer] # When is a Math Problem not a Math Problem? A riddle who's answer looks like math but isn't. There seems to be no answer. The [Gordian knot](https://en.wikipedia.org/wiki/Gordian_Knot) was a giant knot with the ends buried in the middle in the temple of Gordium, and anyone who could unravel the knot was supposed to be destined to rule all of Greece. Clever guys came and went trying to solve the knot. Alexander the Great came and hacked it to pieces with his sword. Problem solved. Not this exactly, but something on those lines. Another example of this is the [Kobayashi Maru](https://en.wikipedia.org/wiki/Kobayashi_Maru) from Star Trek, where the only answer to the problem is to cheat. You go outside computer logic and force a solution only by violating the apparent limits of the problem. [Answer] Mathematical Proofs The most difficult problems in mathematics are mathematical proofs, I would think these qualify as mathematical problems. Computers are currently very dumb but very fast, even the current AIs (neural networks) are just a kind of smart brute force methods. Creating general-purpose thinking AIs is still completely beyond our capabilities. As you said in your comments, "the same computers we have now, only greatly amplified in processing power, storage, memory, etc.", would make the computers only faster at problem-solving not better. Hence any problem that cannot be solved today by a computer given enough time is still not solvable by a faster computer. The mathematical problems that cannot be solved with enough time are problems that include some variant of infinity. One example of such a problem would be the [Collatz conjecture](https://en.wikipedia.org/wiki/Collatz_conjecture). A computer might prove it false by brute force if it finds a loop at some point, but can never prove it true in this way. Proving it true would require a mathematical insight that a computer (nor currently humanity) does not have, regardless of how fast it is. Basically, computers can solve mathematical problems where there are a clear set of rules to follow. This set of rules might be very large and complicated but must be there. Faster computers only speed up the calculation but do not invent new rules. Inventing and understanding new rules is outside the scope of modern algorithms. [Answer] When humans work with geometry often they try to add their intuition to what calculus tells them. There could be a problem based on multidimensional data that people try to solve numerically because they can't picture a manyfold in their minds. But someone tries to plot all the possible projections of the data and keeps all those plots side by side on a wall in his home. Suddenly one day he sees a pattern going through all those projections. [Answer] No, in general. Kinda yes, to problems which are human related, in specific story based curcumstances. As of today's neural network uses do show - we can, more or less, make programs and computers work with the same or similar principles as do our brains work, and in essence, it means what a human is capable of then a computer is capable of it too, especially in a sense of problem solving. Sure we are quite a way(or not) away from Asimov robots intelligence, but .... * so no, and reasoning is quite similar to D.J. Klomp answer, which is correct, with a proof, if we are interested in knowing - is it possible or not, then correct answer is - no. On the other hand, it is possible to have very different complexity in finding a solution, because of who or what one is. We can see such things every day - computer vision is still a challenge, but for most people, animals, insects it is not such a big problem. On the other hand - AlphaGo plays go game better than any human on the planet - so there are things which those outperform himans already, and it not (from our standpoint of view) just crunching the numbers (it is but...) For a human, it is easy to say if something tastes good, because yeah human equipt with predefined neural networks, receptor and all that - basically just because of it being a human, and because field of all those possible answers is created by humans, for humans, and because what humans are - as biological creatures, all that evolution and such. A computer can be trained to answer what some human will find tasty, but it requires a lot more efforts, as of today, it sure is a high tech. But it can't answer the question what tastes good for that program - because the field of those answers does not exists, because of what the program is. Even for an human level AI it would be meaningless question with nan-answer (it can use it as words in communications with humans, but it just a way to transfer information, making things to react in a way etc) So questions like - what do you like - will always be simplier to answered by humans than programs, because humans can use themselfs as gauge, as etalon, as master reference, and do not have to make some convoluted estimation metrics. It goes deeper than that, not just like/dislik but also how, in which way humans can change, evolve, but it is harder to explain. But as easier example of that - classics - what is meaning of life. Humans can define it by their actions and such - meaning they can make self fulfilling prophecy, choose it to be, and anything out of wide range of potencial answers can become the One correct answer. (But such a choice can be predicted, given enough hightech data and all that - kinda) So there can be some problems with disparity of complexity, is such a difference is enough - it depends on a story, what do they have, and what they do not have. In general attempt to find such a clear disvision line between - is so old fashion, 70's really. Correct answer is no, but you can easy handwave it to yes in thousands of ways, as an example by degree of development of the means they have and not only that. [Answer] It is almost certainly impossible for a math problem of the type you describe to exist. The problem isn't about trying to find a math problem that humans can solve but computers can't. There are plenty of such problems even today, recently solved by humans and with no feasible strategy of finding a proof by a computer. In the future, humans will likely always be able to devise new questions which lie just outside the range of what computers of their time can solve. The problem is your requirement "somehow a certain math problem has been found to be the solution to all problems". This is like asking for a universal strategy that somehow plays optimally for every board game or computer game that exists or can possibly exist. Or asking for a universal device that functions as a car, a cellphone, a refrigerator, a spaceship, and every other engineered device the human race needs or will ever need. Or a universal medicine that cures all ills and diseases the human body can ever experience. You don't have to be a doctor to have enough experience to conclude that a universal cure is almost certainly impossible. I can't prove it doesn't exist, but its possibility goes against every piece of experience medical science has ever given us. It is similar with math. I may not be able to prove it mathematically, but experience shows that searching for some single magic conjecture that solves all other possible mathematical questions sounds wildly divorced from reality. [Answer] ## *Providing a readable* mathematical proof for e.g. Pythagoras Lots of kids do that every day in school, but computers can't. In case of Pythagoras, a schoolkid could write down a 20 lines basic proof based on a geometrical construct. A simple Pythagoras proof is based upon congruence of triangles: you put an orhogonal line to the other side, then you state angles are equal, so you find 3 congruent triangles. The pupil will put a little drawing that includes the squares, annotates the sides with a b and c, then states that the area of a square is its sides squared, hence a2+b2=c2, QED. Continuous domain For a computer, the main issue would be: where to start. What exact construct is appropriate. The computer would have to iterate over all possible intersections, that will take some time.. It will run..** Theory sais computers can generate mathematical proof from axioms. Theoretically, any mathematical proof can be generated by feeding the computer a set of relevant axioms. <https://en.wikipedia.org/wiki/Automated_theorem_proving> For Pythagoras, a program could be written that proves it. (to find a proof, you'd have to assume an ideal computer) A way to circumvent o.m.'s halting problem (for this example, mathematical proof) is assuming an ideal computer: we have a theoretical device, that can perform any convergent iteration in zero time. This device can come up with PI in an arbitrary number of decimals, the result pops up immediately. For any correct mathematical assumption your ideal computer will always come up with a sound proof, if the assertion is true and the set of axioms you feed it is complete. The real issue: printing the output Computers have to be programmed to format the output in a suitable way. You'd run into topics of summarizing results using natural language, which computer programmers have not solved yet. A computer can perform any mathematical proof, however it is not known yet, how to transform the result to make it readable/understandable for e.g. teachers in school. If readability is a requirement, humans will have a huge advantage.. instead of a list of 20 pages we want this, [![enter image description here](https://i.stack.imgur.com/MAYG5.png)](https://i.stack.imgur.com/MAYG5.png) [Answer] There are infinitely many math problems that a computer can't solve unless a human feeds it "hints" (inputs). If your computer returns the result of 2+2 as 4, it's because it somehow got this information from humans, and this is true for any problem that exists or may come to exist. Once your main character figured out the solution to the new problem, he'd sure be at an advantage if the computer doesn't know how to solve it, but what's so special about it? Nothing. If I ask a computer to calculate my age without telling it what year I was born, it won't know what to return, and in the meantime I can ask my mom what my age is and she will know, even if I had never passed that information on to her. My answer to your question is: Any mathematical problem, as long as the computer does not have enough information about the variables of the problem, it will never know how to solve it. [Answer] In your world, the brain cannot be modeled by a Turing Machine, that is: The way computer works, no program would be able to precisely imitate and reproduce the working of the brain, no matter how complex the simulation is. As such, the brain is able to do things that no Turing Machine (and thus no computers) would be able to achieve. Mathematically, there are models for automaton that can compute more things than Turing Machine, but the "trick", at least for the known ones, is that they involve infinity in the way they work and as such cannot be physically made. I remember reading some years ago that it wasn't known whether or not there existed mathematical models of computation that were both realizable and more computationally powerful than Turing machines (as in "can do things that Turing machines can't"). Obviously, if one such model was found we would know already, but it may still not have been proven that there aren't. Perhaps you could use this as a premise for your universe: "Such a model exist, and in fact, the brain is a realization of it.". However know that if such a physically realizable model existed, it would have implications regarding our reality, as it would mean reality and our laws of physics are too complex to be perfectly simulated by a computer (otherwise we'd have a contradiction: you would be able to realize this more powerful model inside a simulation, meaning that a computer would be able to compute stuff that only this more powerful model should be able to). [Answer] The human discovers a new [axiom](https://en.wikipedia.org/wiki/Axiom) To horribly oversimplify how mathematicians work, a base set of rules/operations are chosen which are considered to need no proof of correctness and and those rules are combined and manipulated to prove other more complex rules. Every mathematical structure built in this fashion is provably true since the logical steps that constructed it can be traced back down to the original base set of rules. This base set of rules/operations are referred to as axioms and a familiar example from high school geometry are Euclid's [geometric axioms](https://en.wikipedia.org/wiki/Euclidean_geometry#Axioms). "Dumb" computers are very good at following and manipulating rules; in a sense that's all that they do. Modern [computer symbolic algebra](https://en.wikipedia.org/wiki/Computer_algebra_system) systems like [Mathematica](https://en.wikipedia.org/wiki/Wolfram_Mathematica) are examples of computers applying mathematical rules to solve problems and perhaps in the future, computers are even more efficient at grinding through the theorems to create new ones. However, what the computer cannot do is question the rules. While extremely improbable, for fictional purposes, what if one of the [base axioms](https://en.wikipedia.org/wiki/List_of_axioms) turned out to be incorrect? Nothing proves that they are true; they are assumptions (albeit well-chosen and reasonable ones) and there have been disagreements and suggestions for modifications to these axioms in the past. So, let's say your character is looking at the output of all this software and realizes that there is a contradiction that shows one of these axioms wasn't valid at all and could be replaced with a better one. This leads to new mathematics with different results for whatever esoteric problem that they're trying to solve. [Answer] No, but you might have a verification problem My second answer but on a very different thought line and quite opposite to my other answer so I posted it as a new answer. There is the [Infinite monkey theorem](https://en.wikipedia.org/wiki/Infinite_monkey_theorem), saying that a monkey hitting keys on a typewriter given enough time will write the work of Shakespeare. Say your character is brilliant and can write the proof to the not yet determined problem on one page. A fast enough computer can create all possible combinations of characters on a single page. As such the solution to the mathematical problem will be included in the created combinations. (If your dealing with mathematical symbols and images one can simply replace characters with pixels to achieve the same result). So our current computer, given enough time, can solve any solvable mathematical problem by just brute force creating all possible combinations on a piece of paper. What might be the hard part is recognizing the solution to the mathematical problem from all the junk of the other combinations the computer has created. [Answer] The Halting Problem and related issues. Computer scientists proved almost a century ago that no computer program can determine if an arbitrary program is correct, or even if it will ever [come to a finish](https://en.wikipedia.org/wiki/Halting_problem). Yet humans have been able to prove the correctness or incorrectness of many different programs. Their line of reasoning could be added to the 'rule set' of a program-proving program afterwards, but not in advance. Of course there are problems which humans cannot solve, either. [NP-Completeness](https://en.wikipedia.org/wiki/NP-completeness) is a classic example. [Answer] Perhaps it turns out that there are uncomputable problems which humans can nevertheless solve - maybe humans have souls, or something, and their souls happen to implicitly have access to a halting oracle under certain conditions (and this manifests as "intuition" to the human, who of course can't explain what they're doing because that would be writing down an algorithm, which is forbidden by hypothesis!). ]
[Question] [ For some reason, my mermaids have gone vegetarian - ethics, the decline in fish species, or they’re just no longer in the mood for meat. The main issue: will they survive? They live in coastal saltwater areas, rather than being deep-sea creatures, and can only be in air for the same length of time as a human can be underwater (probably 1-2 minutes; you’ll get the odd ‘freediving’ mermaid who can go for much longer, but that’s an anomaly), and they really struggle to move around when not in water, so gathering anything from the land is probably going to be limited. There’s also no trade between merfolk and humans, so they can only rely on what they find, forage, or grow themselves. What could they eat that will give them enough calorific intake to survive? (Assuming the same 2,000-2,500 kcal intake advised for normal humans). I’m not fussed about geographic location, so if there’s a region of (present-day) Earth better suited to support their existence, that’s fine. I’ve pictured them as wanderers rather than settled, so a hunter-gatherer approach is more what I had in mind. However, I’m happy to be persuaded if an agricultural society would be more conducive to their new way of living. Ideally, I’d like my merfolk not to need to spend 14 hours of every day eating (like pandas) just to get what they need, while also having a nutritionally complete diet. If there’s something that’s calorie dense but isn’t necessarily balanced, then I’ll take that. And if this vegetarian lifestyle isn’t going to work, I’ll just have to convince them to go back to omnivorousness. —— Sorry, forgot to include this: I’ve had a look at [this question](https://worldbuilding.stackexchange.com/questions/59918/how-does-a-herbivorous-mermaid-species-without-gills-and-swim-bladder-stay-under?r=SearchResults), but while it mentions herbivorous merfolk, it seems to be less interested in the constitution of their diet. [Answer] Seaweed is definitely the way to go There are many types of seaweed and they vary in protein and calories, among other things. They will have less bulk if dried, which is very easy to do. If the mermaids can build things, they can create floating drying racks that are tethered. The lower tech method would be to find some flat rocks that are never underwater, then farm or harvest during high tide for better access. Dried seaweed will not reconstitute immediately so it will still be concentrated, even if the mermaids have to eat it underwater. > > The protein content of our sea vegetables ranges from to 16% to 28%. > The red sea vegetables, Dulse and Laver, are higher than the browns, > Kelp and Alaria. The amino acid composition of these sea veggie > proteins is generally well balanced and contains all or most of the > essential amino acids (the ones your body can't produce by itself). > Thus the sea veggies provide higher quality protein than certain > grains and beans that are lacking one or two essential amino acids, > although the sea vegetables provide less quantity per serving. (from > [Maine Coast Sea Vegetables](https://seaveg.com/shop/index.php?main_page=page&id=3&chapter=1), one of my favorite suppliers.) > > > [Laver](https://en.wikipedia.org/wiki/Laver_(seaweed)) appears to be highest in calories of the seaweeds commonly eaten by humans. It's used to produce nori. [100 grams (about 3.5 oz) of raw laver](https://ndb.nal.usda.gov/ndb/foods/show/11446?fgcd=&manu=&format=Full&count=&max=25&offset=&sort=default&order=asc&qlookup=11446&ds=&qt=&qp=&qa=&qn=&q=&ing=) contains: 35 calories 5.81 grams protein [100 grams (about 3.5 oz) of dried laver/nori](https://ndb.nal.usda.gov/ndb/foods/show/45315852?fgcd=&manu=&format=&count=&max=25&offset=&sort=default&order=asc&qlookup=MUSUBI%20NORI%20DRIED%20SEAWEED%2C%20UPC%3A%20011152012490&ds=&qt=&qp=&qa=&qn=&q=&ing=) contains: 400 calories 40 grams protein To get 2500 calories, they'd need to eat 625 grams (22 oz) of dried nori seaweed. That's really not hard. They'd end up with too much protein this way too, 250 grams. (It's not a dangerous too much, but it's more than they need.) But wait, there's more! Seagull eggs might be something they could harvest, though most gulls would build their nests too far away to reach. They actually [contain a lot of Vitamin D](https://www.ncbi.nlm.nih.gov/pubmed/22319024) (while the mermaids get a fair bit of sun, they might have higher Vit D requirements because they're usually underwater and their evolutionary diet would include a lot of Vit D rich seafoods). [Seagull eggs](http://www.nativescience.org/assets/Documents/PDF%20Documents/ATDP_final.pdf) are high in calories and protein too. One seagull egg is the equivalent of 3 medium chicken eggs. 1 seagull egg ([3 medium chicken eggs](https://ndb.nal.usda.gov/ndb/foods/show/01123?man=&lfacet=&count=&max=25&qlookup=Egg%2C%20whole%2C%20raw%2C%20fresh&offset=&sort=default&format=Abridged&reportfmt=other&rptfrm=&ndbno=&nutrient1=&nutrient2=&nutrient3=&subset=&totCount=&measureby=&Qv=1&Q322711=1&Q322712=1&Q322713=1&Q322714=1&Q322715=3&Q322716=1&Qv=1&Q322711=1&Q322712=1&Q322713=1&Q322714=1&Q322715=1&Q322716=1)) contain: 189 calories 16.58 grams protein Add to this caches of fish eggs on the beach or elsewhere (already laid eggs that do not require killing a fish) and a few herbs, leaves, roots, fruits, etc that they can harvest from the shore. With time, they can also start some gardens of plants that can live right next to the water but aren't there in large quantities. This means that their diet after 2-5 years will be more varied than their diet in the beginning, allowing for a transition if they prefer. So, yes, this is quite doable. [Answer] While there are a variety of possible foods for a vegetarian mermaid, the bulk of their diet is probably going to be seaweed of different varieties as that is going to be the easiest and quickest to harvest in bulk (as opposed to something like algae). To pick one example, [kelp gives about 43 calories per a 100g serving (raw).](https://ndb.nal.usda.gov/ndb/foods/show/11445?fgcd=&manu=&format=Full&count=&max=25&offset=&sort=default&order=asc&qlookup=11445&ds=&qt=&qp=&qa=&qn=&q=&ing=) So that would be approx. 5.8 kg of seaweed a day to get 2,500 calories. The average human consumes about 2.5 kg of cooked food a day, but we also consume about 4kg of water. [Answer] Since they are coastal mermaids there are many more options. One of the best would be mangrove tree fruits. These are easily reachable from the water and can also often be found floating in the water. Sea grape trees are coastal and could possibly be reachable within a a few minutes. Any plant that grows near the water has a chance of falling or blowing into the water and thus being collected, so things like coconuts would be accessible. Seaweed type plants of various species, and various algae. A google search of "fruit that grows at the beach" brings up some interesting possibilities as well. Possibly these mermaids have learned how to cultivate the land plant closer to the water. Those who were able to train their selves to be on land for the maximum amount of time have brought the plant closer to the waters edge. Also, they have developed tools using things like sticks and rope which can pull the edible parts of the plants in without going on land. [Answer] The original mermaids were actually manatees, and they feed on kelp. So, TL;DR of the other answers: they may live on kelp. If you want a more varied diet, I suggedt playing a videogame called Acquaria. You control a marine humanoid - kinda like a mermaid with legs - and cooking is part of the game. Some dishes are vegetarian. [Here is the list of recipes from a wikia site](http://aquaria.wikia.com/wiki/Recipes), just ignore recipes with meat in them. ]
[Question] [ I'm writing a speculative fiction story that includes superhumans, and I'm trying to get some of the specifics nailed down. Several of my superhumans have the typical powers of flight, usually able to break the sound barrier but not exceeding Mach 5. They'll fly everywhere from ground level to about 10 km above the ground. I'm trying to determine if they'll leave a contrail behind them as they fly through the atmosphere. From my preliminary research on contrails (thank you, [Wikipedia](https://en.wikipedia.org/wiki/Contrail)) I've learned that these are produced by either the condensation of warm CO2 and H2O or by pressure changes. My superhumans don't use combustion to fly, so it seems like the only way contrails could form would be via pressure differentials created by flying at supersonic speeds. Would a superhuman flying through the air leave a contrail behind? If so, would it be permanent or under what conditions (speed, altitude) would this occur? Edit: This question is specifically about the movement of a (human) body through the atmosphere under the defined circumstances, not how such movement might occur or the ramifications of such movement on clothes etc. Bounty edit: I'm offering a bounty because the current answers, while helpful, don't provide actual estimates for the environmental conditions and velocities required to create a contrail. I'm aware that it's possible to create a contrail by passing a body through air fast enough under the right conditions, but my question is whether a Mach 5 superhuman would do so near ground level and in the mid-troposphere. Bounty award I’m giving the bounty to Slipoch, but not the green check mark. If somebody’s able to answer the question and provide estimates of the speeds and environmental conditions required, I’ll contribute a larger bounty for an exemplary answer. [Answer] Contrails are not produced by exhaust (aided in creation but not created by), as mentioned in my comment on the answer below. This is a pretty common misconception, which led to the rise of the idea of chemtrails. You can see contrails on WW1 aeroplanes, and other non-jet propulsion based aircraft (such as twin & quad prop planes). How would that work if you assume a jet engine produces them? Jet engine exhaust does have a high water content, so it would aid the formation of contrails in the lower pressure area left behind. They are actually produced by the condensation of air containing water in the lower pressure behind the wing tips, this is why even 4 jet engine planes often only leave 2 trails, it is all dependant on pressure and humidity at the altitude as well as any excess water vapour from the jet engine. So yes, as long as the shape of the object moving fast enough is the right shape to create low enough pressure in it's wake and the water content of the surrounding air is high enough, then it can create a contrail. [Answer] You don't need to go as fast as Mach 5 and at high altitude. Contrails, or vapour trails can be produced at low altitude and relatively slow speeds: the following photo shows trails coming from the propeller tips of an aircraft on the ground: [![enter image description here](https://i.stack.imgur.com/WteuA.png)](https://i.stack.imgur.com/WteuA.png) And here produced by a race car: [![enter image description here](https://i.stack.imgur.com/fzFJ2.png)](https://i.stack.imgur.com/fzFJ2.png) And before it's pointed out these are caused by a lift (or downforce) generating surface, here's a photo of a contrail produced by a bullet: [![enter image description here](https://i.stack.imgur.com/f1cHb.png)](https://i.stack.imgur.com/f1cHb.png) If you have the right conditions, namely a decent level of humidity, something going fast enough generating turbulence behind it, such as a flying human, could generate contrail. [Answer] [Meteor contrails](https://www.nature.com/news/russian-meteor-largest-in-a-century-1.12438) seem to be a thing. I haven't been able to find any data on the velocities involved, but I would assume they are high. [Answer] Yes and no. They would not leave them in general. Only when they go fast and do sharp turns in humid air, need to note this trails will be small compared to trails of engines. [Answer] I don't think humans can leave aerodynamic contrails because nothing on the human body resembles the wings of an airplane, which are designed to create pressure differentials. Our heads are rounded, our limbs are like cylinders, and even our Air Jordans lack large planar surfaces. If a flying superhuman were to extend sword blades in his arms, like Deadpool, then perhaps contrails would form. ]
[Question] [ This question already has an answer here: [How long can language drift before it becomes indecipherable, and how to minimize drift?](/questions/20005/how-long-can-language-drift-before-it-becomes-indecipherable-and-how-to-minimiz) (1 answer) Closed 7 years ago. Year 2020, the United States of Japan sends colonists to the outer space to colonize new planets under the name of the Emperor. Long story short, they finally colonized Planet VII of the Lem solar system. Planet VII is some hundred light years away from Earth, which is pretty much preventing communication. Even prior to colonization they have pretty much stopped contacting Earth, since the communication delays were just too much. Both, the colonist and the Earthlings, have yet to discover warp technology. So they can't send their message through a warp gate. Question: how long does it need before the Japanese that the colonists use and the Japanese that the Earthlings use differs so much that Earthlings no longer recognize the Colonist's language as Japanese? Edit: all colonists are Japanese in both nationality and race, and speak only Japanese. They know no other language except a little English, just like today's Japanese. [Answer] Well-known historical examples: * From Latin to the Romance languages: about three to five centuries (in the 5th century the language was clearly Latin, in the 9th the language was clearly something different). For example, see the [Oaths of Strasburg](https://en.wikipedia.org/wiki/Oaths_of_Strasbourg) (842 CE); the text in the "romana lingua" is clearly no longer Latin but a very primitive form of French: "Pro Deo amur et pro christian poblo et nostro commun saluament, d'ist di in auant, in quant Deus sauir et podir me dunat, si saluarai eo cist meon fradre Karlo, et in adiudha et in cadhuna cosa si cum om per dreit son fradra saluar dift, in o quid il mi altresi fazet. Et ab Ludher nul plaid nunquam prindrai qui meon uol cist meon fradre Karle in damno sit". * From [Old English](https://en.wikipedia.org/wiki/Old_English) to Middle English: about two or three centuries (at the beginning of the 11th century the language was Old English, by the end of the 13th it was Middle English). Old English is incomprehensible: "Hwæt! wē Gār-Dena in ġeār-dagum, þēod-cyninga, þrym ġefrūnon, hū ðā æþelingas ellen fremedon" ("ġ" is pronounced like "j" in "jar"; "ð" and "þ" correspond to modern "th"). [Middle English](https://en.wikipedia.org/wiki/Middle_English) is much closer to the Modern language: "Whan that Aprill, with his shoures soote the droghte of March hath perced to the roote and bathed every veyne in swich licour, of which vertu engendred is the flour". (Examples from the Wikipedia articles.) Schools and newspapers and mass-media tend to slow down the evolution of a language; isolation and illiteracy tend to speed it up. It is possible to maintain comprehensibility over a millennium or so -- Greeks in the 2nd century could still understand the Homeric poems, although they were quite far from day-to-day speech; it is also possible to lose comprehensibility in a very short time -- the Turks managed to lose contact with Ottoman Turkish is one generation, see [The Turkish Language Reform: A Catastrophic Success](http://rads.stackoverflow.com/amzn/click/0199256691) by Geoffrey Lewis (1999) (the link goes to Amazon). Remember that in the meantime Japanse on Earth will continue to evolve. For a language to split into two daughter languages which become so much changed that their genetic relationship is no longer recognizable you need many millennia, and you absolutely need at least several centuries of complete illiteracy, so that the chain of written texts is broken. We can still recognize the genetic relationship between English and Hindi (they are distant cousins) although their most recent common ancestor language was spoken at least nine thousand years ago. (Of course, it helps that we have access to excellent attestations of very old Indo-European languages so that we can form a good impression of their common ancestor.) Edit: User Simba (in the comment thread) makes the pertinent observation that the history of English may be too unusual -- English went through a close contact with Old Norse which may have influenced the evolution of its grammar; something must have happened to induce the astonishing loss of inflection. In about the same time span which saw Old English "ġeār-dagum" become Modern English "yore days", Common Slavic (attested as [Old Church Slavonic](https://en.wikipedia.org/wiki/Old_Church_Slavonic)) differentiated into the modern Slavic languages (Russian, Polish, Czech, Bulgarian, Serbo-Croatian-Bosnian-Montenegrin and so on). The important point is that even after 15 to 20 centuries of divergence, the three main linguistic families of Europe (Romance, Germanic and Slavic) are still obvious for speakers without any special linguistic education. All speakers of a Germanic language will recognize other Germanic languages as closely related, and the same for speakers of Romance languages and Slavic languages. [Answer] tl;dr A long time. Long version: I am a native german speaker and I can read the texts from [Walther von der Vogelweide](https://en.wikipedia.org/wiki/Walther_von_der_Vogelweide) without many problems and he lived roundabout 900 years ago. The text may sound odd to my ears, but I'll understand it. The bigger problem in written texts is, that the fonts used for writing change over the centuries You have a shorter timespan for spoken language because the brain has less time to identify the syllables. The problem is, that there are no real recordings of medieval European languages, due to the lack of technology. But one can easily recognise other languages of the same origin although they separated hundreds of years ago. It may(!) be similar with the Japanese language, I'd expect the timeframe even longer, because there were not so many foreign influences in the Japanese language over the centuries. But you can find out pretty easy for yourself: Take a trip to the oldest library and read old (and I mean old, not just 50 years) books. How far can you go back in time and still read them? If there are old history re-enactment groups in Japan, visit them and ask them to speak to you in the old tongue and compare it to your modern language. [Answer] Depends on the level of isolation and population involved, but the divergence of the insular and continental [north germanic languages](https://en.wikipedia.org/wiki/North_Germanic_languages) might be of interested. As a small, isolated population that were not exposed to many outside language influences, they pretty much match the profile of your colonists. Interestingly enough the insular languages (like Icelandic) are a [lot more like Old Norse than the others](https://linguistics.stackexchange.com/questions/1275/what-explains-the-icelandic-language-conservatism). It seems likely that it will be the home language that diverges rather than that of the colonists. [Mutually intelligibility](https://en.wikipedia.org/wiki/Mutual_intelligibility) also doesn't follow the actual family tree. Icelandic and Norwegian both descend from Old West Norse, but Norwegian is intelligible with Swedish (east norse) but not with Icelandic. Perhaps at some point in the future a powerful space-fairing Japanese state will exert a large cultural influence Korea and find itself in the position of being able to converse with them but not with it's own colonists. So how long did it take until Icelandic diverged from the continental Nordic languages? I think I might ask that question somewhere else on this network, but [let's trust wikipedia for now](https://en.wikipedia.org/wiki/History_of_Icelandic). > > "Between 1050 and 1350 Icelandic began to develop independently from other Scandinavian and Germanic languages" > > > "1300, the Danish language saw a very rapid evolution in both its phonology and its morphology" > > > "Norwegian and Swedish developed more slowly, but show equally notable differences from Icelandic" > > > Interesting, so the answer is different depending on which Continental language you compare it to. As I said earlier, it looks like your language change will probably come from the people left in Japan. So it depends on what happens to Japan in your story's world. Rising Chinese influence might substantially shift what happens to the language. Perhaps Anglophone influence will continue via the internet (which the colonists probably can't get). Etc etc. Fairly huge linguistic (+ writing system) changes came to Scandinavia during this period, so you'll probably need something drastic if you want a short timescale. But a period of a few hundred years seems to be enough. [Answer] A couple examples come to mind. In the example of the Tower of Babel, God was able to make languages unrecognizable immediately. Maybe that is a replicable phenomena. And not explicitly or necessarily by the hand of God. An effect on people's brains during space travel could confound their language. Another example is the Mayan language. It is still spoken in regions of Mexico, and various dialects are spoken in Guatemala. Sorry I have to dodge the question a little. I can't say whether the ancient Mayans would recognize any forms of modern Mayan. But here's my take on it. Introducing a new language (Spanish) didn't break the Mayan language. And the Guatemalans handled the changes far differently than the Mexicans. But even Mayan has a pretty well theorized etymology tracing back to [Proto-Mayan](https://en.wikipedia.org/wiki/Proto-Mayan_language) from around 5000 BC. The thing is, I think it's safe to say the origin is unrecognizable because, well, who knows what Proto-Mayan is? Especially if you're talking about the average layperson? That took a thousand years or so. But I think you are pretty free to pick almost any length of time. Factors that would speed up the process would include: * losing records of the language, * losing the Japanese culture (through blending of cultures. The older generations might hold on for a long time), * special effects comparable to the Tower of Babel, * regional differences between colonists (and a region with a new dialect becoming dominant), * losing the language of origin * lots of people who love to make up words and disregard old words. Factors that slow down the process: * Stable, powerful Japanese culture on Earth, * Well documented Japanese history and language on Earth, * But to recognize colonist language, Earthlings have to receive some communication from colonists, which is apparently impossible?? To make my answer slightly less vague, I would say a minimum of more than two generations for colonists to stop recognizing Japanese. It usually takes immigrants more than two generations to fully adopt a new language and lose their old language. It should also take more than two generations for Earthlings to not recognize colonists, assuming colonists change their language immediately. As a maximum, I would say 2000 years for either culture's language to become unrecognizable because I think the laypeople of most languages don't recognize the 2000 year old version of their language; the 2000 year old version was probably not the language but its likely dead parent languages. I think Japanese could become a dead language that laypeople don't recognize in 2000 years maximum, probably much less. We seem to be able to trace just about any word etymologies back hundreds and sometimes thousands of years. To lose all trace of that, the Earthlings would probably have to lose all trace that the Japanese sent the colonists out in the first place, and they would have to lose all traces of Japanese. Again, you have a lot of freedom with the time frame for that. [Answer] As I see it, there are two parts to this question. 1) The base of the language - the general rules, language construction, common words, etc. These might never change significantly; the major languages are all heavily codified in dictionaries, computers, school textbooks, etc and there's little advantage in changing these. 2) There are however always new words entering languages. Especially with your space-faring civilisation, where with a vastly different environment in space and on the new planet there would be a need for lots of new words to describe things. This could, over time and when combined with new colloquialisms, create a dialect in which the language was fairly recognisable, but where a lot of what was spoken didn't make much sense. Accents may also change; until eventually you're in a situation much like a Glaswegian trying to speak to a Jamaican. [Answer] There are several degrees of "recognisability": * Mutual intelligibility: The speakers of the two languages can make sense of a significant amount of the other's speech or writing. This type of recognisability last for a time depth of a few hundred years to about one thousand or one and half thousand years. * Genetic relation: With current methods of historical linguistics, Genetic relationship can be demonstrated for languages with a common predecessor about ten thousand years ago. There is not much hope to improve on this time limit. ]
[Question] [ My setting is in the near-future, approximately 200 years from now. Among the many technological advances that have come about are ultra highspeed trains. For the purposes of this question, traveling on these trains works much like a subway, they have high throughput and relatively low wait times when compared to airports. Even now, projects like [Elon Musk's Hyperloop](https://en.wikipedia.org/wiki/Hyperloop) and projects in China are attempting to reach speeds from 700 to 1800 miles per hour. But consider what would happen if trains existed that could reach speeds in the multiple thousands of mph, say 4,000 mph for example. The USA is only 2,860 miles at its widest. Even considering the time it would take to board and disembark, one could conceivably travel from the east to the west coast in as little as an hour. What sort of effects would we see in society? How would laws, global politics, and peoples' daily lives change when one could cross the US (or whatever continent of choice) in 1-5 hours? [Answer] ## Physics In order for very high speed trains (e.g. multiple thousands of mph) to operate, they'd require [extensive infrastructure including an evacuated tunnel (e.g. vacuum)](https://en.wikipedia.org/wiki/Hyperloop#Theory_and_operation). It would be highly desirable for it to include a very low friction "rail" system (e.g. maglev) too. In a practical sense, this makes the hyperloop railcars into completely independent spacecraft. They require everything a spacecraft might require (power, life support, etc.). Some clever work with the rail system might allow it to transfer power into the car but the life support requirements will remain. ## Time Zone Difference I worked on a couple of hypersonic aircraft projects in which we looked at this problem. ### East-West Travel The basic result of our researching this was even if you got travel times anywhere in the world down to 2 hours, you still had to contend with timezone changes. Leave the US East Coast at 2 pm in the afternoon and arrive in Japan at 6 am (2 pm + 2 hour travel time +14 hour time difference) causes a significant disruption in human circadian rhythms as well as scheduling problems. The net result is it still takes 1-2 days for a human to adjust to the time difference and operate at close to full efficiency. So the speed of the transportation wasn't that important for human face-to-face interactions because most humans required down time to get back up to speed. ### North-South Travel Although not in as high a demand, high speed travel across thousands of miles makes long-distance North-South travel very "doable". Basically, a 2 hour trip between Buenos Aires and Boston would be possible and might significantly increase the travel between such North-South destinations. There don't appear to be many high travel spots in Africa for Europeans. However, it might increase travel between * East Asia and Australia * Central Asia and India * North America and South America ## Speed of Transit Of course there are some benefits to the rapid travel. These fall into a few main categories and they are: 1. Humans can recover in a more comfortable surrounding 2. Humans can recover in a less expensive surrounding (e.g. a hotel) 3. Perishable goods can get to their destination faster ## Cost of Transit Perhaps a more important question than the speed of the transportation is its cost. If you reduce the cost of transit by a significant factor (say in half), the amount of utilization of that form of transportation more than doubles. Building an Elan Musk type of rail network of super high speed trains would probably revolutionize travel between distant places simply by the reduced cost. Also increasing the ridership of such systems tends to lower costs even more because you can amortize the construction (capital) costs over a larger number of riders. How many people might take long weekend trips from the US to Europe (or vice versa) if the total cost of the trip was on the order of 250-500 dollars (Euros)? It might make our world just a little smaller (after all). [Answer] Transportation expands our horizons. I currently work 29 miles from where I live and I commute every day. I'm willing to put up with 35 minutes in the car each way. As I said, I travel about 60 miles a day for my job, my great-grandfather, worked ~20 miles from home. He walked, and it took him hours, so he'd leave Sunday night and stay all week and walk home Saturday morning. Today you'd need to be living and working either in different states or at least at opposite ends of one for such a thing. So depending on the cost of a ticket and the time it takes to get on and off the train, it could make a big difference on what we call 'close'. Being able to get from one end of the country to the other in 1-2 hours, means I could live in Minneapolis and work in Columbus OH and commute every day. Assuming that the cost was reasonable and it didn't takes 2 hours on both ends to traverse the stations. Of course these are much more dangerous modes of transport, and as such might require more draconian ways to filter out trouble. Which would slow things down, so I would guess, you'd have the 'traveling' trains, and the commuter trains, commuters are prescreened AND are restricted to what they can actually carry onboard with them. Maybe special dress code. An accident or terrorist attack on these would be catastrophic to the whole system. A plane crashes everyone on board dies. Tragic, a train derails a huge mess, but a passenger train accident at 1500 mph, everyone dies and the line will be closed for weeks and depending on where and how it happened, could kill thousands close to the accident. Like crashing a plane in downtown New York, only worse, since there will be more debris, more impact and possible a much larger vehicle to begin with (we're talking a train here!). So having body suits might be all you get to take on a train and destinations have 'outer clothes' if you need or want them. Electronics could be bought or rented or preapproved with a digital stamp etc to come on the train. [Answer] 4000 mph = 5867 feet per second. At 1 G acceleration (32/s/s) this speed is reached in 183 seconds. 1 G horizontal acceleration would feel like 1.41 Gs at a 45° downward angle (1 G horizontal accel, 1 G Earth's pull). This might be uncomfortable — I'd weigh 282 pounds! — but it's not lethal. Cars and trucks today pull .75 to .95 Gs on acceleration and you might experience up to 2 Gs when high speed cornering in a consumer sports car. Even at a relatively mild 0.5 G acceleration (1.12 Gs subjective) these trains could reach 4000 mph in about six minutes. [Answer] This has already happened in history, though on a somewhat smaller scale. Consider this: before the age of the cargo airplane, travel speed was limited to the fastest truck or train. Because of that, the speed was 60 mph or so, tops. Then, the cargo plane arrived. ... Fast-forward to today. Now, flowers which die in 14 days after being plucked can be transported to a person's home in under 48 hours after being picked, regardless of the location of the farm and the destination. This has revolutionized the transport of perishable goods. Even today, companies like Amazon are making delivery faster and faster. In a few cities, for a high price, you can have 1 hr delivery. What would change? Not very much. All perishable goods would become cheaper, air travel would become nigh-obsolete, as a tunnel in the ocean would quickly be built. A whole new industry would develop: the acceleration seating industry. These trains need to accelerate, and assuming that they take 1 minute to get to top speeds, they would feel the equivalent of 3 times their weight pressing them back into their chair. Subway seats aren't going to fly. Deceleration will be a problem as well. Seat belts would need to be padded, or perhaps they would wear a special vest to distribute the weight evenly among their entire body. [Answer] The effects on the housing market would be interesting for a while. The current average commute time in the US is 25.4 minutes. It's pretty expensive to live in San Francisco or New York City, so some people choose to live outside and commute in. With greater speed you could get wider range for the same commute time. If you could travel across the US in less than an hour, someone could live in Texas with the lowest cost of living in the US and commute in to San Francisco have a low cost commute while staying in that 25 minute range. While other things can affect the housing market, like how close schools and shops are, I think we'd see the market flatten out a bit as demand in the high cost areas went down. Tourism would also be an interesting thing. If I could take the kids to a beach in Florida for the afternoon and get back to my home in the snowy north before bedtime, it would be really nice. Suddenly you have a new type of [snowbird](https://en.wikipedia.org/wiki/Snowbird_(person)), that heads for warmer weather for a day, where that would be impractical with slower or more expensive travel. [Answer] I would ask who had this technology. Is it available to only some countries or everyone? When the first freeways of were built in the united states they caused the death of a lot of local businesses along the way as more people no longer need to stop due to the difficulties of travel. It also caused the death of short haul rail travel and it brought rise to the an automobile culture. If we had 3 cities A,B, and C what would happen to C if only A and B are connected? There would be a lot less desire to work in City C for anyone living in the other two cities. It would need to make itself relevant somehow. This may give yous some ideas on what the interstate did. <http://www.uvm.edu/landscape/learn/impact_of_interstate_system.html> Technology for dealing with acceleration and deceleration are a must. But in addition to this entire cities and pathways must be designed to take the repeated sonic booms of a train travelling close by at Mach 5.2. Consider housing costs next to airports. <http://www.landmarkresearch.com/Articles/PDF/AirportNoise.pdf> Instead of just noise pollution though the physical damage done by a sonic boom happening on a regular basis has to be dealt with. I suspect that new cities with the technological capabilities of dealing with this will spring up around embarkation/ disembarkation points as it is a lot cheaper to build a city from the ground up than retrofit old cities. This also means that you would now have the option of opening up the Arctic and Antarctic to colonization and all the entailing conflict of ownership that would bring. So the distribution of this technology would play an important part of the relevance of location within a country. In regards for other countries it opens up the door to work opportunities in other countries which means new laws for the taxation and an increased cultural interaction between the countries that have the technology. [Answer] It is an interesting view on the future. Lots of money is being spent on developing faster trains and ballistic transport and some will come to pass but the end result will be a cost performance trade-off. Rather ask yourself what sort of world would have required transport over 800km/h and paid for the development and operating costs. Either there is no resource scarcity or the rich feel very safe entering their vulnerable high speed coffins. The answer to your specific question is very little as the social changes would be needed before the methods could be proposed. Sufficiently visible equality and all basic living needs being met are fundamental needs for it to work. These will have been achieved through education, telecommuting, machine automation and population reduction is some mix. There will no longer be a need to rush about like busy ants and the time it takes to get to the ski lodge will be of little consequence. You say get from here to there in 1-5 hours, well that is only half of what it takes now by plane (traffic permitting) from here to there. To recap, not going to happen and if it could not going to be needed, I certainly would not pay for the increased risk, nor would others in a post scarcity society. Certain niche routes may still have a small window to operate but will go the way of the Concorde (nice name that) in time due to cost of maintaining bleeding edge technology. I think you will find mud-ball earth will see slow and steady driver less cars much more than high speed luxury transport. [Answer] Our's is the only developed country without any form of high-speed rail. First it would be an economic boom. HSR for both passenger and freight would make air travel difficult to have a positive economic impact. Tons per mile, rail is the MOST EFFICIENT! The use of biodiesel would make current diesel-electric trains, carbon neutral. The addition of automotive, OTR technology would make them cleaner. (non-VW software) :( With more wind power across the country, Electric Trains gain a neutral carbon imprint. Here in Iowa ~25% of our electric power is from Wind Farms. We have more turbines going up every day. We have 4 different wind turbine manufacturing plants here in Iowa. ~30 BioDiesel plants. In the ~120+ ethanol, including cellulose ethanol. What would speed do to people? Look in Japan, Germany, France, the rest of the EU. I don't think it would impair, or interfere with any current social effects. The only positive is carbon footprint. The Automotive Industry after WW2 was the influencing factor in the abandonment of passenger rail. That and the Oil Industry,PROFIT! The negative is bureaucracy, Our governor refused to co-fund a project from Iowa City to Chicago for passenger rail endorsed by the Federal Government, approved by the state of Illinois, not by Iowa. Very close minded IMHO. He is an American politician who is the 42nd Governor of Iowa, in office since January 2011. the39th Governor from 1983 to 1999, In the election on November 4, 2014, Branstad was elected to an unprecedented sixth four-year term as Iowa governor. He's known as a semi-moderate Republican. Very to the Right, is my pitch, being a life long Iowan. It is Politics, NIMBY, and "cost" vs return... that return not looked at as long-long term infrastructure, but short term return. IMHO JLH [Answer] Huge crowds show up very quickly, wherever and whenever something interesting is happening. See Larry Niven's [Flash Crowd](https://en.wikipedia.org/wiki/Flash_Crowd) for unintended consequences. [Answer] Presuming this advance is feasible, Intercity Travel These trains would not be used within a city (like a subway), but between cities. We calculated in a high-speed train project that stations should be no less than 200km apart to be even useful, and if there were only small towns, they should be skipped and station distances further apart. It would reduce long distance travel times, but seeing as how it's unfeasible for distances of about 1000km or less (to accelerate and then decelerate without killing your passengers, you work up quite a distance), planes, regular-trains, and automobiles will still be used for other distances and certainly commuting. I don't know the math, but the time it takes to get to top speed without killing passengers, you are already more than halfway across the United States. Then you have to decelerate, and you are in the ocean. The feasibility of it would likely only be between MAJOR, distant cities that have connections elsewhere. London to Moscow to Beijing, maybe? People would still take slower trains and planes to other destinations after they disembark. If undersea travel is feasible, then maybe London to New York? I don't think it would have a dramatic effect on society - maybe it can reduce emissions somewhat? ]
[Question] [ We are in a medieval fantasy world. There is a folk where, sometimes, a berserker is born. They are quite rare (maybe 2-5%) and there is no difference between a normal man and a berserker before he turns berserk. I call berserker a man (or a woman) who will become some kind of a beast during a battle, and sometimes outside the battle. Anger and hate push the berserker thing, but the more the berserker uses its power, the more it occurs without consent. In this state, he can kill dozens of men, both friends and ennemies, before calming down and waking up exhausted. During this time, he's invulnerable (no fear, very quick, very strong, can't feel pain, possibly can't be hurt at all - it's a magical power, not just a kind of madness) There is nothing able to calm him down, just time (variable time). The end of battle often ends the berserker crisis, but not always. It's a warrior folk. They often have fights with an army vs another army for territorial issues. They are quite civilised, and they don't want to kill outside war if it's not an absolute necessity. Berserkers are very good at fighting, but very dangerous. One of them can defeat a big group of ennemy soldiers alone. But unfortunately, if you steal his breakfast, your lifelong friend Mike could just kill you, and your friends, and your dog, and the village chief, and the old Martha passing by. Then calm down and cry. What's the best way to deal with berserkers ? How would a medieval/fantasy society will likely deal with them ? (That might be a different answer.) [Answer] You clearly can't just let berserkers run loose, because, as you noted, there would be severe violent outbreaks. You therefore have two options: Control the power or get rid of it. Option 1: Kill them I'll talk about the latter option first, because it is less savory and is not the best option. The only way to guarantee that a berserker will not go berserk is to kill him or her. The process is simple: 1. Identify a berserker, hopefully at a young age. You'll need some kind of a test to do this - perhaps leave some weapons near a toddler and see what happens. 2. If repeated tests clearly show that the child is a berserker, then he or she must be euthanized (to put it gently). Some sort of poison is the best way to go, preferably a painless one. A similar option is to simply lock away all the berserkers, preferably somewhere with thick walls between them and most of the rest of the population. Option 2: Control them The first option is, quite frankly, horrifying. I only talked about it because it is the elephant in the room, and it must be acknowledged. The other option - imprisonment - is better, but, given the capabilities of medieval prisons, it is still cruel. So, controlling the berserkers is a better choice. It also allows their powers to be exploited. What are berserkers good for? Battle, clearly. They also have massive amounts of energy, but harnessing that is going to be difficult. Let's focus on warfare for now. Here's the equipment you need to control a berserker: * ~Six strong soldiers * Two thick but lightweight chains per soldier * Armor plates all over the berserker that are attached to at least one chain, but are firmly attached to the berserker In battle, have the berserker attack with the six soldiers in tow. They might be able to control where he or she goes, and, therefore, how aggressive he or she is. The enemy will not want to kill or harm them, because without these "handlers", they're toast. So, the wartime solution is six blokes with chains, basically. Hopefully, this land will not always be at war, although you do say that it is common. Therefore, you need some way to keep the berserker safe a peaceful while he or she leads a normal life. I suggest that the armor/chains plan be used, while the berserker does grunt labor. Horses are sometimes used to walk in circles while attached to machines, thereby grinding meal or other things. Shackle a berserker to one of these machines. When he or she is not berserk, then he or she can simply keep walking along, doing work. While berserk, the berserker can harness the energy to continue to do this work, simply at a quicker pace. [Answer] Society actually deals with individuals like this all the time, although instead of them being invincible, they are merely mostly invincible (gunshots still kill). Berzerkers would be dealt with the same way we deal with these individuals in our society. A berzerker (or potential candidate berzerker) is simply bound such that they can never get into a position to do un-repairable damage. They have physical limits (such as they cannot teleport directly into the king's chambers), so society will simply make sure they never get an opportunity to get close enough to do harm. As a result, berzerkers will be an outcast caste. They will never be allowed to marry. They will never be allowed to be near children. They will have two clear choices: a life alone as a hermit, or a life in the military in the barracks. The barracks will be carefully designed to ensure that anyone who goes berserk cannot do lasting damage. At most, they may damage each other. Such fratricide would be valued the way we value ammunition in warfare. The only use for someone who may turn into a killer at a moment is to send them to kill or die on the front lines. Thus, they are a statistically replaceable good. In order to make this less cut and dry, you may consider weakening them during the berzerk phase. An unpredictable bout of invincibility with nothing that can stop it generally creates lumps in the story. Generally speaking we do not find "invincible" things in nature or society, merely things that are stronger than us. My advice would be to allow a peaceful individual (such as a priest or a monk) to attempt to pacify their rage. This gives a small weakness, and that small weakness gives you vast freedom to better incorporate bersekers into society instead of casting them out. The most recently famous example of this is the Hulk from Avengers. Black Widow, if she retains an inner calm, can convince him to return from his madness. You could also do this in groups: A berserker which kills too many people in a town may be pacified by the eyes of onlookers, showing disdain for what the berseker has created. This also suggests that a highly aware king may be able to stop a berseker with nothing but his own sheer will... and a aware but evil king may abuse this. It also leads to the hope that, one day, a berserker may achieve enough inner calm to keep himself from going berserk. Perhaps this never occurs, but the dream of being cured may be a powerful motivating force for a 'zerker. [Answer] First question to answer, in my opinion, is : will berserkers deal with themselves ? If you can just go berserker at any time and kill you loved one, you will be likely to constrain yourself (for example by living as an hermit) ; or if you do kill your whole family and friends (possibly several times), you are likely to commit suicide at some point. In this case, you do not have to fear berserkers that much, they will try not to harm anyone. The problem would be to use them in combat : they are most likely to refuse to turn berserker if they can avoid, since the more they use their power, the more likely their are to turn berserker against their will. So berserker in this scenario will be sort of peacefull hermits keeping themselves away from violence and society, because they do not want to risk killing innocent people. (this scenario somehow ring a bell in my memory, but I can not find any reference of such people retiring from society not to harm anyone) Of course there is another scenario possible : Berseker is considered by the society to be a very honorable state, or at least to be normal. You can draw a parallel with [running amok](https://en.wikipedia.org/wiki/Running_amok) : turning 'berseker' and killing people is seen somehow as a natural disaster and afterwards you do not consider the berserker accountable for his fury. In this case, you can use berserker in combat, at will. They will just, sometimes, kill random people, but the whole society consider this killing to be normal and just accept it. It is not quite in constradiction with your statement : 'They are quite civilised, and they don't want to kill outside war if it's not an absolute necessity.' since nobody choose to kill innocent people, it just happend. And (in the mind of the majority) there was nothing you should or could have done to prevent it. Everything just is as usuall. It can seem to be a very crude way to deal with the death of your people, but if you analyse the opinion toward death in medieval europe (for exemple), death was part of the everyday life. You just go for a chivalry tournament and be killed during it (it killed so many people in fact that the church try to interdict such tournament but failed). In this last case, you do not deal with berserker, they sometimes kill people, and you just accept it. Note : 2% of the population being berserkers is huge in my mind, it means 1 person out of 50 people is a berserkers, in other words, everybody know at least 2 berserkers. [Answer] Treat them like they are human till they aren't Since it's not possible to know who will go berserk until they do, teaching everyone about berserkerism will help. Dealing with berserkers will depend on how much that culture values violence and warfare. If this is a Viking like culture with a huge emphasis on warfare and combat then being a berserker will be a mark of honor and distinction. If the culture has a strong attitude towards domestic abuse then berserkers may not be permitted to marry or the wife is allowed a divorce is she doesn't want to risk getting killed if she burns dinner. ## Wartime: Tactical deployment A wise commander isn't going to sprinkle berserkers in among his regular troops. The friendly fire losses are just too high. Instead, make them their own little unit that gets sent into the thickest part of the battle. They can't hurt each other so it's "safe" for them to be around each other. What I don't know is what will happen when opposing berserker squads are matched up with each other. Will the two groups merge and spiral out of control or will they expend all their energy fighting each other? ## Peace time: Train them If berserkers are an old feature of this culture, not something new this generation, build in a strong cultural pressure on berserkers that even though they may lose control, they should live as honorably as possible so that when they die, they may be sung about and remembered as great men/women instead of bloodthirsty killing machines. This will help make it easier later when they have to be euthanized for everyone else's safety. ## Peace time: Sequester them Once someone becomes berserk, they have to go live with other berserkers farther away from town so if one of them goes nuts, they will be around those who understand and are best able to counter an episode. ## Peace time: Drug them Find the local equivalent to cannabis and make it culturally expected to smoke it frequently. This keeps the general population placated but also cuts down the risk of a berserker going nuts on his friends/wife/children. If you can't get angry, you can't go berserk. ## Peace time: Kill them Unfortunately, as being a berserker is a progressive "illness", eventually they will become so destructive that they cannot be constrained or controlled. In that case, there is no choice but to kill them. Make these an honorable death with large funerals at their passing. Execute them by severing their spinal cord at the base of the skull. I'm not sure if this should be done in public or in private. [Answer] Well in a warrior like culture, they would be a very useful asset. since we're talking about medieval times, they would more than likely be part of the king or Lords retinue. a king or Lord would have enough resources to be able to maintain and keep such an individual in check. Between keeping them in a relatively chained state less so like a beast of burden but with enough implements on them so they can be restrained if need be. Such attachments could be placed upon their armor or whatever they wear. Also more than likely you can keep them docile with alcohol or some other beverage of course in some rare instances you may end up with a drunken Berserker, when it becomes more powerful when drunk. Properly cared for and maintained in a manner that doesn't cause buildings within the king or Lords realm to randomly be destroyed by a rampaging beserker, I don't really see much of a problem with them. the retainers could hold the weapons for the berserkers, perhaps a team of them equipped with a wagon or some method to carry them around that would also provide them protection. they could very easily stand up on their wagon or cart making use of crossbows or other such ranged weaponry. I would assume that anything with a melee weapons will have to get through the Berserker first, so melee isn't the retainers primary concern. this combined approach could allow for small teams with a berserker to be a formidable force, roaming the countryside and keeping the peace. [Answer] The best way is to incite their curiosity towards mythology. They also need to have a point of contact to be enraged towards their weak points and their ignorance. When they enraged they become crystal clear that they act actually on their whimsicality rather than reason. Give them a patch of earth to feel that they are rulers. In their dream land they censor, flog, kill in their imagination until they settle by many imaginative activities. That makes them more curious towards higher education. When educated they become humble rather than outrageous and inflamed. They will have a known contact point for rational discussions and become civilised citizens of their community. ]
[Question] [ Linked to [Zombie perpetual machines](https://worldbuilding.stackexchange.com/questions/12807/zombie-perpetual-motion-machines) ![zombie carriage](https://i.stack.imgur.com/t866F.png) This carriage was devised by Vitrivius as a way to make good use of the Zombies discovered in Roman territory. Question: How many zombies would be needed to allow this carriage to transport 1 ton of supplies at 15km/h ? Knowing that zombies cannot be killed by ordinary means, how hard would it be to transform this into war machines carrying onagers/ballistas etc, into battlefield ? * Consider them to be human-like, with characteristic zombie gait, only differing in that they dont need to eat, they eat out of taste for human flesh, not out of nutrition. Do not consider normal metabolism. They can very well run continously, accumulating lactic acid without pain. There are no thermodynamic limits for them, besides that they can do whatever a normal human can do physically. They feel no pain and have an IQ between that of a cockroach and of an anemone. In other words they are purely reactive. They seem to not have immune systems, so they rot under anything that consumes flesh. They only stop moving when they are out of muscle tissue. The difference in speed is due to activity in cerebellum, its a matter of remembering how to run. The smart variety still remeber how to do trivial tasks like opening doors. The dumb ones can only run towards a target. If they lack a leg they will be unable to stand up, walk or run. [Answer] Twenty-four Zombies I think [rolling resistance](http://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html) is going to be the main resistance force here. I don't know what the coefficient is for a wooden carriage on Roman roads, but I think the worst case would be something like car tires on sand. So, for one short ton load the rolling resistance would be about 2670 newtons. There will also be some minor wind resistance, perhaps 200 newtons. An average human can comfortably tow at about 250 newtons, so we'll assume the same for a zombie. The sprinting speed while pulling that load is unknown. I'll assume it's half. That means you'll need a team of 24 zombies to pull this cart. Might want to add a few more depending on how well they're harnessed. They're better than horses Zombies don't spook as easily as horses, they are very well summed up when described as single-minded. They can't be killed as easily and zombies are often literally used as fodder. If you put some blinders on them to keep them focused on the meat-lead, they may be fairly effective as wartime beasts of burden. Assumptions: Flat ground, zero wind, zero cart axle friction, zombies have human strength, zombies can sprint, pulling while sprinting strength is halved, rolling resistance coefficient of 0.3 and constant, entire load is one ton (including cart), zombies won't chew the straps, zombies are possible, and other minor axiomatic assumptions. [Answer] Focus on this part: Knowing that zombies cannot be killed by ordinary means, how hard would it be to transform this into war machines carrying onagers/ballistras etc, into battlefield ? Couple points to consider: 1. Zombies don't follow commands very well...when/how do they get the order to stop? And once they are stopped, whats preventing them from seeing tasty humans trying to operate the siege equipment they were carrying around and trying to go after them? It'd kinda suck to set up your catapult only to have the zombies carrying it start coming after you and pushing around the catapult you just setup. 2. Buffet! Human corpses are about to litter a battlefield and you've got the equivalent to a zombie buffet sitting infront of them...are they going to be good zombies and stop where the equipment is needed, or are they going to try to run off into the middle of the battlefield. If you are baiting them into moving with human flesh, whats stopping them from reaching down and pigging out on the corpses that the siege equipment they are carrying need to move by? 3. Human morale. Zombies and undead use are never human friendly. Your Roman crews are going to need to get used to seeing huge chunks of human flesh dangling as bait and rotting infront of them every where they go, which likely will cause some disease...rotting human flesh is not fun to see as a human. Being known as the zombie using army and the 'evil' view that can contain doesn't help morale either. 4. Elephant issue. Carthage made heavy use of elephants in their army, but on more than one occasion the elephants were spooked and control of them were lost, resulting in a rampaging elephant destroying it's allied forces. What happens when an arillery return fire destroys the catapult these zombies are carrying? What happens when a zombie team has it's restraints broke in the heat of battle? The last thing you want is zombies wandering around the ranks of your army eating as they see fit. I guess as a conclusion...the free labor seems attractive, but it comes with a lot of risks from not being able to control them when the artillery they are pulling around needs to stop and be used, to them getting loose and rampaging on your army during the middle of battle. If you really want to be creative...whats stopping an army from loading up zombies into the catapults and using them as ammo in a siege? Dead cows were often launched to spread disease...I'd imagine a zombie being hurled over a wall and into a town would be that much more effective (and potentially a bit funny to watch fly) [Answer] # 1 ton of supplies at 15km/h? We can safely assume that a regular person can pull between [75 and 100 lb](http://www.briontoss.com/spartalk/showthread.php?t=165), but I lack the time or skill to do the math required to figure out how many it would take to pull at 15 mph. You should consider that the zombies will at most probably be walking at a normal rate of [3.1 mph](http://www.wikipedia.org/wiki/Walking), making it difficult to reach these speeds. I would also have to factor in the rate of decay of the dead (do they decay?). Simply divide 2000 ponds by 75 and you get.....26 average zombie people to move it. Add a dozen more and you have it going at a decent speed. Also keep in mind that the harness will eventually rip through the decaying flesh. # how hard would it be to transform this into war machines carrying onagers/ballistas etc, into battlefield? Having them lug crap around would be inefficient. They would abandon the small parcel of meat being used at bait as soon as one of your guys came within eye sight of it. If they were in eyesight of the enemy army they would keep going and try to charge the enemy army, bringing your weapons with them. Instead, simply withdraw your living army and release them into the enemy camp in large numbers. They will scatter and flee when they realize your weapon is the undead. [Answer] I do not believe this is a viable means of transport. Blinders would keep zombies from seeing all the tasty morsels around but zombies have a human sense of some kind, it wouldn't work. If you are going to make a zombie transport I think you want something along the lines of a hamster cage except that it's fully enclosed other than to the front. The only path to the morsels the zombie has is forward--which actually just turns the hamster cage. You also need your zombies fully confined or you're going to have total chaos on the battlefield. ]
[Question] [ Let's say you're a soldier in a science-fiction war. Everything is relatively similar to how wars are fought today, except that when you die, your likeness and memories are imprinted onto a flash-cloned husk, thereby creating a near-exact replica of you. From the clone's perspective, you died and then woke up in the cloning facility. From your perspective, you're dead (whether or not you have a perspective at that point is unknown, but beyond the scope of this question). There have been many (somewhat unsatisfying) explanations of this system, such as how in a society where raw materials and energy are plentiful, the time to train a soldier is much more valuable than the molecules that make them up. In my case, the explanation is it's a way to get past an imposed limit on the maximum number of combatants in a battle. Either way, I'm not as worried about why it's done as what it would mean to the people it's done to. For instance, how would an individual react knowing that if they die, they will be replaced? For some people, it might be kinda nice; after all, someone'll still be taking care of the wife and kids. But that brings up the second part of my question, how would people react to these clones? And the third, How would clones react to themselves? I used the example of this process being done to soldiers, though I suppose the possibility exists for anyone in a dangerous job, or with the foresight to get memory-tracking implants and a full body scan. This might be similar to the problem of uploading your conciousness to an AI, though for now I want to stick to the constraints of "the original is most assuredly dead, and the copy is most assuredly not the original, though for all intents and purposes the two are indistinguishable." EDIT- I may not have been clear enough about this, I'm not too worried about the science behind it, the cost of it, or the uses of it. I just want to know what people will think of it. And let's also assume that no one is making multiple duplicates of a single individual. I suppose there can be flaws in the system (good for a laugh or two), but for the most part I'm just worried about one guy who is a copy of another guy who is now dead. [Answer] First and foremost: ## [PTSD](http://en.wikipedia.org/wiki/Posttraumatic_stress_disorder) On average, people take death and near death experiences very bad. Your newly spawned clone will be crawling on the floor in a pool of his own tears, sweat, vomit and urine, paralyzed with fear and memories of the pain, unable to do anything. It will take a while, so don't hold your breath until he's ready to go back to the real world. Give him a couple of years under special care, maybe they'll fix him. Most likely they won't. Now that we have the obvious out of the way, let's think deeper. ## Accidents WILL happen. Even now many people, especially inexperienced drivers, think themselves immortal. They speed, DUI, break all kinds of traffic laws, until some good soul has to scrape them off a tree with a spatula. With such scientific proof of immortality, people will care even less about their own safety. Fatal accidents will happen on daily basis, property damage costs will sky-rocket, and the world of insurance agents will never be the same again. ### Mass produced slaves Slavery is another problem from our world, that will increase dramatically thanks to the new technology. Even as we speak, thousands of people world wide are forced to work to near death in different kinds of sweatshops. The only thing that stops their owners is the fact, that once a slave dies, you have to replace him, and it costs money. With your tech, you can just make a thousand copies of one trained slave and work them to death. Wash, rinse, repeat. ### Happy reunions I've left the positive note for the end: no more broken hearts. No more parents burying their children. No more widows. You can spend your life happily with your loved ones and never experience loneliness and despair, no matter how bad things go. EDIT: [### The 6th Day](http://en.wikipedia.org/wiki/The_6th_Day) I'm not sure if you're aware, but there is a Schwarzenegger movie touching that subject. The title is The 6th Day. In my opinion - harmless flick, fun to watch and mock with some friends, but if you're interested in writing similar story I suggest to watch it. [Answer] The thing is, you can write books on just a tiny subset of the question you asked, so this will by necessity be a very fragmented, partial answer. But regardless, I'll list the problems as I see them, in my perceived order of importance. ## Legal and Social Ontology Regardless of whether the imprinted clone IS you or not, the question arises on whether the law considers the clone you or not. Would the genetic-memory tleilaxu doppelganger impostor perfect clone be legally considered the same person, have access to your bank accounts, and be welcomed to sleep with your wife/husband and tug your children in at night? Since you state that `for all intents and purposes the two are indistinguishable` it is likely that they will. If society, judges or even your wife cannot tell the clone from the original (even down to scars, moles and chest-hair?) perhaps the impostor new you will be welcomed 'back' as if it were you. Of course, this could be made to sound even less appealing if your memory-implant were to accidentally send an early death signal so the duplicate sleeps in a warm bed by your partner while you're slowly dying in a ditch from an infected stomach wound. But say that's not the case (no legal rights, no social acceptance) and you are the clone. In your memory one second ago, you were bravely facing overwhelming odds to push back the Zerg on the battlefield, just as a charging Mutalisk ... and then there's bright light, and the vat door opens. The first experience you have is the woman you recognize as your beloved wife, spitting in your face and calling you a wretched impostor, one that will never measure up to her true husband, who died so bravely. You have no money, no acknowledged education or certifications. You're screwed. ## Uniqueness Can there be only one? Or do you have [Cloning Vats](https://www.youtube.com/watch?v=rGCaACqy1Ro), where the `greatest minds, the finest soldiers, the most faithful servants` are `multiplied a thousand-fold and release[d ...] to usher in a new era of glory.` Perhaps there are thousands of you on the battlefield. Moreover, can the experiences of this multitude be reintegrated into one mind at the end (after the clones are murdered discarded)? Would this mind experience a blurry blend, some as-yet-unimaginable perspective, or perhaps live a thousand subjective days (in what order?) or (simpler) have no memory of the event? ## Accuracy Does the clone feel the memories as alien impositions? Are the memories vivid, or blurry faded things? Are the neural pathways (randomly built in a natural body during in-utero development) really the same? Is there atomic-level precision, or merely in the rough outlines? Would the new being have a body the same age, with the same afflictions (say a bad back?) or a purified new body? Would that change who you were? Would a rejuvenated you be content with, say the 80-year-old-invalid that is your husband? Are the 'spares' mind-blanks, or do you simply keep them in a cage and forcefully overwrite them when it suits you (i.e your primary is growing frail)? ## Speed Is the cloning instantaneous, or does it take months to cook, during which you are dead to the world? Obviously if the perceived self were to lose half a year each time around, people would be careful about dying, whereas if it's flash-speed, it might be chosen as a convenient means of transport, rather than schlepping a meatsack half-way around the world. ## Cost How much does it cost, in today's money? \$10? \$10,000? \$10,000,000? \$10,000,000,000? Obviously, this will have important implications on when, why and how respawning is performed. [Answer] You are immortal. You're effectively a demigod. Being killed only takes you off the field and out of the battle. Eve Online has this as a key feature. With the caveats; 1. that your memories and knowledge are scanned at the moment of death, then magicked - because Science(TM) - across the universe to a cloning facility and downloaded into a fresh clone, 2. the cloning process isn't compatible with everyone or is prohibitively expensive to keep it out of the hands of the masses. People are still going to try to avoid pain, injury, and death. These are ingrained in us through thousands of generations of evolution. It'll take just as long to breed it back out. In fact, that may never happen unless losing the fear of death confers a survival advantage. It may be possible to suppress this with training, or experience. Forcing people to experience death in the safety of a hospital/laboratory might be a sufficient way to train soldiers for combat. Some people won't be able to handle it well, or at all. On the other hand, some people will. Many people have experienced violent and traumatic experiences, been knocked unconscious, and woken up in a hospital bed some time later without any psychological harm. Example: sports injuries. However, sports attract certain kinds of people. Thrill-seekers and adrenaline junkies. There may be a self-selection factor here that means people volunteer for this are more likely to take repeated death well. These people are your target group for cloning. Slavery The only thing that limits your power is control of the cloning process. If you, as an individual, are held under the thumb of a corporation or government who controls the cloning facility then you're slave to them. Freedom However, if you're in control of the facility (or on good terms with a person/organisation that controls one) then you're able to do whatever the heck you want. You'd only fight in battles that you were interested in. I'd imagine that any group of immortal soldiers is going to recognise this very quickly. As will any government/corporation. There will invariably be a cold-war between the two where they jokey for control of the soldiers' future. Eventually, someone will slip-up, and these soldiers will become 100% independent. At this point, you have huge problems. What do you do with people you can't control, and can't kill? [Answer] I'd say that it is the arrangement of molecules that make the person. All of us gain and lose molecules all the time. We eat, deficate, and shed skin. However our general arrangement of molecules and DNA stay the same. Our mind is constantly changing. The you of five minutes ago is gone now and will never exist again unless you find some way to preserve that exact arrangement of cells and connections. If everyone accepts this psychological standpoint, then that's your answer. However if you're still in the transition phase, then inevitably there will be people that believe that a clone is not the same person. We'll call these people "OBOP" (One Body One Person). That person would be shunned and rejected by all OBOPs. There would likely be OBOP demonstrations outside of cloning clinics. Legally, there would probably be laws against making multiple clones of the same copy of a person. That way they could treat the individual as the same person, as s/he knows everything about their "original" self. The OBOP people obviously wouldn't like this. If we assume that this is a military application, then the body would most likely be kept on file, and updated just before each mission. If in a civil application, then the body would most likely be updated every night if available in the home or every week if you have to go to a special place. Let's assume the mind would be scanned and transmitted the moment before a brain stops working, or a little before if that is too traumatizing. For the individual, there most likely wouldn't be a difference in their perspective. One moment they're dying, the next they're waking up in a module. So from they're point of view, they're being replaced... by themselves. For their family, if military, would they even have to know? If they did know, they might have the mentality that "Johnny beta acts exactly the same way that Johnny prime would if he were here, so Johnny is Johnny." On the other hand, they might not be able to accept that Johnny beta is the same as Johnny prime in every way that makes Johnny an individual, and would reject him. That would be a risk of using cloning. From the clone's point of view, it is that person. They have the same memories, life experiences, way of thinking. The clone would probably be thinking "Well I know what not to do this time." They'd probably be okay with it, as they did sign up for it. There might be some measure of PTSD, but that can be addressed multiple ways, including the selection process and a method of training, to name but a few. Human slavery wouldn't be a thing. If we have the technology and resources to make copies of human beings regularly, then why would we have human slaves? Robots would be so much cheaper (probably) and more efficient. In fact you could probably go from a bunch of metallic power and information to a functioning humanoid robot in less than a week. This is a really good question in that it delves into the philosophical realm of "What is a person and what makes them an individual?" [Answer] There is much the same problem with teleportation. Let's compare the two: ## Teleportation I am going off what seems to be the most accepted method - it's not the only one. * You are taken apart into molecules * Information about these molecules is sent across some network to the destination * The teleporter at the end recreates you using this information. ## Cloning * You die; your molecules are no longer part of a 'human' * The implants in your body use the residual electrical energy to tell the cloner to recreate you * The cloning vat puts your molecules back together using stored information. In both of these situations, the end result is not you. This is true no matter what anyone says; the molecules that make you up are no longer the same molecules. There is every possibility that these clones and teleported people (hereinafter collectively referred to as "clones") would be accepted into society: they would be able to seamlessly take the place of the former person they represent. Their DNA is identical, as are their fingerprints, earprints (yes that's a thing), memories and neuronic connections. They could easily share the same passport. Many people would come to see them as a good thing. After all, it means you never have to go through unexpectedly losing a loved one or family member. You can just call in a clone and everything will be fine... won't it? --- ## No. 1. Overpopulation The planet is already struggling to support the number of people we have on it. It is estimated that it can only support an absolute maximum of 10 billion people. If people start using this technology to create immortality, we have serious problems. This could, however, be relieved using another colonised planet. 2. Mutations Although the problem of genetic mutations during the cloning process is almost nonexistent, the software and hardware running these machines are vulnerable to hacking, destruction, or just plain bad coding while running. It is almost impossible to eliminate every bug; what if someone's memory gets mutated and they don't remember their family? --- These clones, while technically possible, are still not ideal: there are always going to be problems that prevent them being 100% effective. That said, it would be possible to achieve a fairly high effectivity. [Answer] I understand your question to be about the social acceptability of this phenomenon as much as anything. Others have raised the philosophical question of personhood, so what would society think of it? I think that if it was only ever available to the military, that would create some stronger divisions, but: A Chance At Immortality The opportunity for practical immortality would have a massive effect on society- it may be reserved for soldiers or other significant figures to start with but the value of escaping death ( even if there are doubts regarding whether the technology will work for the individual ) would prove irresistible to people. Cloning an older person's mind into a younger body would be an unbelievably popular commercial proposition among the rich and powerful. Dictators and oligarchs are able to rule indefinitely rather than being limited to a human lifetime. The company that offers this technology commercially would be enormously profitable. Religious Friction If you think abortion or euthanasia are tricky religious questions, think what survival through cloning might do for our religions. If the afterlife is... life? There would certainly be confusions of faith, deep theological considerations and schisms across many religions. However, if the technology becomes more ubiquitous, this thinking might die out when the people who hold strong to the idea of not artificially extending their life, while the cloneborn outlast them. For a really interesting - if slightly different - angle on this ( and a super great read ) I recommend Dan Simmons' Hyperion/Endymion novels. A Divided Society Those who choose (or can afford) to live on through cloning become a class of their own. In fact they have effectively defeated the last element of evolution affecting our species so the uncloned would gradually diverge until some degree of speciation occurred with the cloned being as they had been when they lived, while new generations of regular humans change in small steps over time. Of course, the cloned may start to request engineered changes and before you know it we are in a world of crazy post-humans, which is a super-fun place to be writing sci-fi. For further reading that touches on the effects of this in different ways you might look at Peter Hamilton's Fallen Dragon and Anne Leckie's Ancillary Justice. [Answer] Are you being replaced though? Most science fiction cultures that have this concept consider the clone to be just as valid a real "you" as the original. There's a conceptual and cultural shift in thinking about the nature of a person and an individual that needs to happen - but when it does then you go into battle knowing that if you die you will be brought back to life. From your perspective the fate of your original body does not matter, you are still you. Of course things get even more tricky once you start splitting people into multiple copies of themselves, and then those start dying. Do you reintegrate the memories, have new people, not integrate them at all but keep the original? Lots of questions there... [Answer] <https://www.youtube.com/watch?v=b2ASlr-HdIk> This video based off Planetside 2 gives one idea of what it might do to people. Basically how people would get lost and lose track of what it means to well, fight for life. ]
[Question] [ I've just come across a subplot in Jack McDevitt's Firebird where the earth-like planet Villanueva and the rest of its planet system was moving towards an unspecified dust cloud that made the planets uninhabitable for three centuries, leaving only robots behind (which became hostile so the planet is still uninhabitable, but let's imagine this world without the robots). Some time after the system it has exited the dust cloud, the nature continued to grow and everything was inhabitable again. Contrary to [this question](https://worldbuilding.stackexchange.com/questions/1304/how-would-a-planetary-nebula-affect-a-planet), it's assumed that the temperature of the dust isn't relevant. I'm well aware that there are things like a nuclear winter, but that problem happens solely in the atmosphere, the outer space isn't involved. --- That finally leads to my questions: 1. Could a dust cloud block the light from a planet effectively for some decades or centuries, but not permanently? 2. Are there special conditions a dust cloud has to fulfill to achieve this result? (Certain density, size, ...) 3. Would there be other consequences beside the climate change? [Answer] The cloud could not form naturally. Naturally occurring dust clouds in the universe aren't dense enough to block out the sun by any noticeable amount. Even in huge nebulae, the stars inside the nebulae are visible from Earth. Furthermore, in a dust cloud of that size and density, the internal gravity of the cloud would lead to fairly rapid star formation. We see this in the darker parts of the [Eagle Nebula.](http://en.wikipedia.org/wiki/Eagle_Nebula) But let's assume that some alien factory released a huge, dense dust cloud fairly close to our solar system, which was then slowly pulled into the sun, with gas spiraling in across the disk of the solar system and blocking out most of the light from the sun from reaching earth. What would happen then? * The Earth would have continuous spectacular meteor showers. That density of dust would quickly lead to the formation of agglomerations of dust, which would hit the atmosphere and burn up. This probably wouldn't produce enough heat to warm the Earth noticeably, but it would be quite pretty. Imagine a meteor shower brighter than any seen in the history of Earth happening continuously for hundreds of years. * Almost everything would die. Plants would definitely be gone, as well as all terrestrial animals. Life colonizing sea floor vents wouldn't notice the lack of sunlight, nor would the extremophiles colonizing other mineral hot springs. * Nothing else in the solar system would be visible from Earth. Likewise, everything outside the solar system would be effectively invisible. * The Earth would gain rings. So would all of the other planets that don't already have them. This would be a result of not all of the dust getting sucked up by the sun, and some of it falling into orbit around the planets. [Answer] "Is it possible to block temporarily (enough) sunlight to a planet with stardust"? No, I don't think so. Any nebula dense enough for that would collapse and start stellar formation in short order; that's how the Solar System itself is thought to have been born. Same goes for a cloud of gravel. Unless (as pointed out by HDE 226868) the temperature of the dust cloud was [high enough](http://en.wikipedia.org/wiki/Jeans_instability) to prevent a gravitational collapse. Moreover, the [solar wind pressure](http://en.wikipedia.org/wiki/Solar_wind#Solar_wind_pressure) from the star would simply sweep away the cloud much faster than the cloud could come in, creating a [planetary nebula](http://en.wikipedia.org/wiki/Ring_Nebula). Such a phenomenon can be observed in some stars that happen to enter a dense nebula. It is the case of LL Orionis, a star not much larger than the Sun, which creates a "bow wave" between 20 and 60 AU far. This means: * that even a planet as far as Saturn would likely be "protected" from the incoming nebula. The inner planets would never be reached and would suffer no ill effects. Actually probably no effect whatsoever, except maybe an intensifying of the harmless [Gegenschein](http://en.wikipedia.org/wiki/Gegenschein). * that little or no gas (or particle cloud) could have a chance to enter the much more intensely sweeped area inside the planetary orbit, and block the light of the Sun. Even if released artificially exactly on the ecliptic, the radiation and solar wind pressure would blow it away. There might still be a problem due to high energy particles being generated in the bow shock area, but I don't think that it would be comparable to a solar storm, nor that it would be likely to affect a technological civilization (or, for opposite reasons, a non-technological civilization). Actually, I suspect that biological systems would be much likelier to resist the onslaught than electronic robots. Science stations as far as Neptune or Pluto would probably need to be abandoned, since resupply flights in the direction of the bow shock would probably be unhealthy to both ships and astronauts (it depends on technology though. Given sufficiently powerful engines, you can load sufficiently massive shielding, I guess). With much larger (and unlikely) particles or clumps, chances are very high that many of them would experience gravitational scattering or [radiation pressure braking](http://en.wikipedia.org/wiki/Poynting%E2%80%93Robertson_effect) and fall inwards at an accelerated rate, so that the solar wind would not be enough to keep them at bay. In that case the effects would not go as far as rendering the planets uninhabitable, but it could well be enough (for gravel-sized particles) to trigger a [catastrophic Kessler cascade](http://www.spacesafetymagazine.com/space-debris/kessler-syndrome/) in addition to filling the sky with a continuous dazzle of falling stars. This in turn could disturb or disrupt long-range radio communications due to the radio scattering of [the ionized meteoric trails](http://www.space.com/25949-new-meteor-shower-camelopardids-listen-live.html). Update: the "artificial cloud in stable disk formation" scenario is actually exactly the device of astrophysicist Sir Fred Hoyle's novel, "[The Black Cloud](http://en.wikipedia.org/wiki/The_Black_Cloud)". But even there, the dramatic turn of events is triggered by the Cloud's ability to remain stable around the Sun, which no astronomer had foreseen (rather the contrary), which in turn is caused by the Cloud's particular... nature (wouldn't want to spoil a really interesting read). A similar effect is explored in the devices supplying Larry Niven's Ringworld its days and nights. Again, stability is achieved through "innatural" means inherent in the object's composition (i.e., not something you set from the outside and let go, such as the point, speed and temperature of release of a cosmic cloud of squid ink; rather something like the ink's viscosity). [Answer] This would have to be one pretty dense dust cloud to block sufficient sunlight to make the temperature drop sufficiently to make the planet uninhabitable. However, the possibility does exist that such a phenomenon may be possible. Yes, it would be possible to reduce the levels of sunlight reaching a planet sufficiently that the planet would no longer be inhabitable. The further out from the primary, the easier, as the effect of dust on light reduction would be cumulative over distance.. The dust cloud would not require any particularly special properties other than its existence. The dust would both absorb and reflect photons depending on the albedo of the dust, however the effect would be the same - a reduction in solar energy reaching the planet. A dust cloud sufficiently dense to block sunlight enough to cause climate change to the point that the planet became "uninhabitable" would also be dense enough that significant amounts would be captured by the planet's gravity and would rain down onto the surface. As long as this wasn't "dust" in the 5cm+ size range, the consequences of this would simply be the accumulation of a layer of the dust upon everything exposed to the sky. Depending on the density of the dust cloud, this may be anything from a millimetre to many centimetres. If more than a few centimetres of dust accumulated on the planet, combined with the prolonged winter, this would pretty much exterminate anything much bigger than a bacterium save around deep-sea hydrothermal vents. Some plants may be able to survive a prolonged freeze, but any significant amount of dust would bury them for good, and seeds cannot successfully germinate if buried too deeply. So, if the planet was habitable after the dust cloud was cleared, then it may not have been all that dense, and hence the accumulated dust layer on the surface was probably not all that thick. [Answer] It seems plausible. [This physics question](https://physics.stackexchange.com/questions/26326/how-dense-are-nebulae) includes a reference that objects would start to get "lost in the fog" in a Nebula at only 5800 KM - that's an incredibly small distance in astronomical terms. So assuming that's correct, even a relatively non-dense dust cloud would likely block significant sunlight. [Nuclear Winter](http://en.wikipedia.org/wiki/Nuclear_winter#Consequences) estimates that a small-scale nuclear war (50 cities, and not huge bombs) would potentially cool the entire planet by several degrees for a decade. But a dust cloud wouldn't ever go away - it would just keep cooling. This can easily be temporary if the dust cloud just "clips" your planet and sun, instead of passing directly through it. Most nebula are really insanely huge - light years and light years - so it would take a long, long time to pass through them. But if you just went through the edge of a cloud, it could last as short or as long as you want. Secondary effects - I'm not 100% sure. I don't think there'd be any significant long-term effects, if you don't count 99% of the biosphere dying off. Short term, you'd probably get some really amazing auroras until you froze to death. ]
[Question] [ Is there a time system that two spacecraft traveling in different galaxies could share? For example, a spacecraft jumps to an unknown location in the universe, far away. How could they synchronize? Or know the “universal time”. For time measure there is something perfectly accurate such as a photon clock. [Answer] First of all, simultaneity is an ill-defined concept in the modern understanding of the universe, so realistically, the question can be answered with a simple no. Second of all, I'll assume we're talking different (and arbitrarily distant) galaxies in the same universe. When you bring in multiple universes, there's no good reason to assume the time dimension's arrow would be parallel and pointing in the same direction, so comparing times across universes wouldn't make much sense either (imagine one universe's time arrow as perpendicular to the other --- [this actually happens](http://www.askamathematician.com/2010/01/q-what-happens-when-you-fall-into-a-blackhole/) inside event horizons of black holes.) But let's try to avoid answering no, because that's boring, right? Let's imagine some partial workarounds. On earth in the distant past, sailors would determine their position with reference to the stars. In the universe, you can use the temperature of the [Cosmic Microwave Background](http://en.wikipedia.org/wiki/Cosmic_microwave_background) to know how long it's been since the Big Bang, since it will decrease as time passes and the universe expands. With sufficiently accurate measurement, you can get arbitrarily precise results (down to a [certain limit](http://en.wikipedia.org/wiki/Planck_scale)). Under a Newtonian framework, that would be a universal clock. However, in the real world, two observers using the CMB clock will assign perfectly reasonable times to a distant event (say observer A 'waving' from his galaxy to observer B on Earth), with the slight snafu that the times won't actually match. [Answer] With the theory of relativity currently being much depended on and not being proofed wrong, time is very subjective and depends on the condition of the observer. I suppose what you means is the approximate time that every stationary or slow-moving object tells you it is, perhaps a clock back on Earth. I believe your problem in the question is that photons travel at a fixed speed which seems insufficient for intergalactic synchronization purposes. This superficially seems analogous to the time delay caused by low network speed when sending or synchronizing data(time, real-time computer game data, video calls, etc), called latency. As implied by the time precision needed by modern activity, time synchronization network protocols have been developed to synchronize time while minimizing latency issues, including the NTP and PTP. However, intergalactic round-trip time is pretty much unacceptable and impractical. If light cannot solve the problem, it seems like the only way to solve it is the superluminal "spooky action at a distance" as described by Einstein -- quantum entanglement. Quantum teleportation has recently seen some success. Yet, this is just another disappointment: relativity doesn't say nothing can move faster than light. It says no mass or information can move faster than light. We can instantaneously teleport quantum states, but real communication would have to wait, for as least the duration light needs to reach the target. The final answer, there is still no means of communication faster than light. Maybe warping spacetime might help? Anyway, if your story is Sci-Fi, you could just say that they can create ultra-small wormholes and send information over that. It would certainly drain lots of power though. [Answer] Well, still using the clock. I know this answer problably isn't good, but if Team 1 go to an galaxy and Team 2 go to another, is better they start to count the time of the trip, for example: "About an hour ago that we took off from Earth." [Answer] I might suggest something in the nature of quantum entanglement where in a central clock defines an arbitrary time that all dependencies then rely on with perhaps an offset like timezones based on distance from that clock at that time. Depending on the society at play it's not unrealistic to imagine a series of relays that are used to create a distant communication network that could also relay such information. ]
[Question] [ One way, I think, is if the gravity is exactly correct. However, while I think the water might be in a unstable equilibrium, I have been unable to work out the mathematics. Let's assume that such a planet exist, will tides/ high waves result in spontaneous boiling of water; meaning that the water will soon or later disappear in space? [Answer] In vacuum water has no liquid state--it behaves like dry ice does here on Earth. You could still have underground water and you could have an atmosphere that was just water vapor. [Answer] Depends on how you look at it. [Europa](http://www.pbs.org/lifebeyondearth/alone/europa.html) doesn't have much of an atmosphere (and apparently it is mostly oxygen). It has a lot of liquid water, however, it is all under a crust of ice. Protecting it from being carried away. At least really slowing down the process. Gravitational forces from Jupiter generate enough energy to keep the water liquid beneath the surface. [Answer] Define atmosphere. It may consist solely of a water vapours. If the planet gravity cannot sustain that, then yes all the water will eventually evaporate into the outer space. I see nothing unstable. The atmosphere is stable, I believe, when $\gamma \frac{mM}{R} > kT$; with higher temperatures it will dissipate. [Answer] The surface water will evaporate to form a pure water-vapor atmosphere giving you the much needed atmospheric pressure you need to maintain liquid state water. Gravity will make sure the water vapor does not escape into space. But the problem here is 1) the temperature(mostly due to distance from nearest star and partially presence of greenhouse gases and volcanoes) and 2) the amount/ratio of water present on the planet with respect to the size of the planet. In an extreme hypothetical scenario, you can have a planet made entirely of water. The core will be ice due to the compression of surface water, liquid water on the surface closer to equator and ice landmass closer to the pole, and an atmosphere of water vapor. [Answer] Not in any stable sense, you could have liquid water on a world that had a very thin atmosphere but the boiling temperature of that water would be next to freezing, if the world is massive and cold enough you could have a semi-liquid slush of seawater with very little atmosphere but there's always going to be out-gassing from it where the sunlight heats it directly. In theory you could alter this further with chemistry, saltier water will be more thermally stable with a higher melting and boiling point, the more thermally stable the liquid the less you'll lose at any given time. But you're basically right eventually this system is going to result in any and all surface water boiling off into space over a long geological time. The last puddles of the ocean are going to take anywhere between hundreds of thousands and tens of millions of years to finally evaporate or freeze. All of this is assuming that the primary doesn't undergo catastrophic change first, like a nova or late phase red giant expansion, if that sort of thing happens all bets are off. ]
[Question] [ This question comes up from [Is there a man-made or natural event that can cause an abrupt climate change within hours/a day?](https://worldbuilding.stackexchange.com/questions/1169/is-there-a-man-made-or-natural-event-that-can-cause-an-abrupt-climate-change-wit) – trying to get KaguraRap a functional answer to an abrupt temperature drop that would catch humans off guard. I’ve got a functional outcome I think, but I need reasons for why this would happen. ### Overview The Earth’s climate heavily depends on the formation of ice to regulate the climate's temperature. You have a little too much energy (too hot), and some ice melts. You don’t have enough energy and ice forms, releasing energy which turns into heat. This relation works so well because the amount of energy required to melt ice is extremely high. End result is an exceedingly efficient buffer that regulates the amount of energy in our climate system (and ultimately how hot the globe is). Key point here is the melting of ice takes a large amount of energy out of the climate. ### Proposal Ignore the reason as to how or why this would happen for a moment, but lets say an event occurred that changed the melting point for water from 0 °C down to −40 °C. The specific heat capacity of water is 4.181 J/g/K while the enthalpy of fusion is 334 J/g. Quick version (point out math errors if they exist please), but this means the same amount of energy required to melt ice would warm the same mass of water by around 80 degrees. So the event happens, water now freezes at −40 °C and starts a massive meltoff as if it were ice in 40 °C + weather. 1. The amount of energy taken from the environment to melt the ice is really large. Basically −334 J per gram melted. This should have an incredibly quick cooling effect over the globe, and one that is felt worldwide. 2. The melting ice on land should have an immediate effect on global sea levels, creating the opportunity for some coastal flooding. The mass drop in temperature would kick up storms as the temperature rapidly drops and the energy redistributes, so a “hurricane” (or rather a nor’easter as it wouldn’t have the warm core a tropical storm does) would create a freeze/flood event for a city such as New York. KaguraRap – I think I have a scenario that will create the rapid temperature decrease and give a Day-After-Tomorrow-style flood to your story. ### Question And to everyone else I’ll pose the question – what could possibly affect water to drop its melting point like this? I know salt and other solvents would do it, but not quite to the scale required here. A degradation of deuterium (the hydrogen isotope in heavy water) maybe? I’d take presence of dark matter traveling through it as well. Alien technology that could inject something into ice worldwide? In particular, how could the reduction of its melting point be done abruptly, instead of over a long period of time? [Answer] Take a look at this [physics stack exchange question](https://physics.stackexchange.com/questions/60170/freezing-point-of-water-with-respect-to-pressure). The freezing point of water depends on pressure. If the atmospheric pressure was greatly decreased, then the melting point of water will change as well. If we lost atmosphere to a cataclysmic event, or if the force of gravity was somehow reduced, using technology, magic, or by losing mass of the earth, then water would actually transition directly from a solid to a gas at -40 degrees given the reduced pressure. [Answer] This is a really interesting solution to the "deep freeze" conundrum. As you say the state change from solid to liquid of that much water would suck massive amounts of warmth out of the planet. I know you didn't ask this but I want to quickly talk about the results, as you may be disappointed. The effects it would have It would also have interesting effects on sea levels, sea life, and lots of other cases. There are a few glitches in the plan though, firstly that a lot of Antarctica is already below those temperatures so would not melt. Secondly the state change of some of the ice would cool the other ice around it, slowing down the conversion. Essentially you have a negative feedback loop that will put the brakes on the process (although it would still continue). The other catch is that you would get most of the cooling effects at the poles - which are already cold. The tropics would not be affected at all (until sea levels started rising). Ocean currents would be heavily disturbed by the sudden influx of fresh water at the poles though. How it could happen As to how it could happen - that's basically impossible with current knowledge of physics. One possible "plausible if you don't poke too closely" explanation is something like the reverse of [Ice-nine](http://en.wikipedia.org/wiki/Ice-nine). Ice nine is a (fictional) polymorph of water that melts at 42 degrees Celsius rather than at 0 degrees. In contact with water it acts as a seed crystal and converts all the rest of the water into also being Ice-nine, causing it to instantly freeze. You could hypothesize something similar here. A comet containing some special polymorph of water goes past and we go through its tail. Some of the water polymorph reaches the ground scattered all over the globe and immediately starts a chain reaction converting all other water it finds into the same less stable form as itself that only melts at -40 degrees. [Answer] As others noted, there's no real physical effect that does this. However let's look at how a fictional effect might work. Water can be [supercooled](http://www1.lsbu.ac.uk/water/phase_anomalies.html#cool) to quite low temperatures, that means, there does exist a liquid state of water; indeed that liquid state still exists at -40°C. That supercooled state is, however, very unstable, that is, the water will freeze with the slightest disturbance. So a fictional cause for the desired effect would have to make the supercooled water state the preferable state at that temperature, that is, reduce the energy of that state, or increase the energy of the ice state. The trick to do this should be the weakening of the [hydrogen bonds](https://en.wikipedia.org/wiki/Hydrogen_bond), which are responsible for the water anomalies (including the high melting point). However to do that, you'd need to leave the field of hard science. [Answer] The equations for the energy needed to melt ice assume that we must raise the temperature of ice above the melting point. You are proposing to lower the melting point below the current temperature of the ice. It therefore already has the energy it needs to melt. So the glaciers and all but the coldest part of the poles will turn to water, not instantly but fairly quickly. Short-term effects will be sea level rise, massive flooding anywhere downstream of mountains with glaciers (search for "Calgary 2013 floods" for an example) and an upheaval of nearly every important ocean process. How you could do it without also making major changes to the earth like removing the atmosphere (which would disrupt the experiment) will require a change to some fundamental laws of nature. Your idea of deuterium won't work - the physical properties of deuterium are close enough that you can drink heavy water for a week with no ill effects (2 weeks is a problem). You're going to need the assistance of an omnipotent deity for this. One with a mischievous streak - Q immediately comes to mind. [Answer] I know this is old, but it's surprising no one mentioned salt saturation. Water containing the maximum soluble amount of NaCl freezes at -21 C.The maximum salinity that can be dissolved is [27%](https://en.wikipedia.org/wiki/Brine). The oceans are around 3.5% salt. The dead sea is more salty than this level, at 34% [salinity](https://en.wikipedia.org/wiki/Dead_Sea). [![By Wilson44691 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18790421](https://i.stack.imgur.com/wyM4a.jpg)](https://i.stack.imgur.com/wyM4a.jpg) So you can get halfway there by using conditions that actually exist on earth. ]
[Question] [ In my previous question: [Magic for tone-deaf people in a world where magic is performed through song](https://worldbuilding.stackexchange.com/questions/136601/magic-for-tone-deaf-people-in-a-world-where-magic-is-performed-through-song) it was suggested by Ynneadwraith (many thanks by the way) that animals that produce music would have been able to cast spells before humans were able to. At first it seemed to contradict my requirements. After all, animals in the wild don't have words to their songs. I then realised that trained birds, for example parrots, that can be taught to sing using actual human words might provide a solution. My new question Could trained parrots (or other imitative birds) be safely utilised by tone-deaf people to cast song-spells? There seem to be risks - for example a parrot that had learned a fire-spell by rote (of course without understanding it) might set fire to an owner's house by accident. Almost any spell cast at the wrong moment could be disadvantageous. So, would the solution of using imitative birds be safe or could it be made safe? If not why not? [Answer] I think we can get some idea from [Alex the Parrot](https://en.wikipedia.org/wiki/Alex_(parrot)). Alex could answer "Yellow" when asked "What color key?" and answer "Key" when asked "What object yellow?" each when shown an array of different objects of different colors. He also appeared to be able to count up to six, answering "Five" when shown a table full of cubes of many colors and asked, "How many blue?" But now we have to ask, did Alex go around at various times skwawking out "Key" and "Yellow" and "Five" at random times? To be honest, I do not know. But what I can infer from the article linked above and the few appearances Alex made in various TV documentaries I have seen, he might have at first, but later on, as he learned more what was expected, he did not. For example, the article states, "Pepperberg did not claim that Alex could use 'language', instead saying that he used a two-way communications code." This suggests that Alex would not have randomly uttered words, since this would not have gained him anything in the communication with his trainers. Now on to how long it takes. Alex lived for 31 years and was in near constant training for his entire life, just beginning to learn the concept of under and over at the time of his passing. But we don't need our singing magic parrot to achieve that level necessarily, just to make fire on demand and never at any other time. I'm guessing here, but I think we can get there in under 10 years. Of course, during this time we need to keep trainee parrots in secure and isolated environments where risk to self and others is minimized. Next (thanks JGreenwell for pointing this out), we have to consider whether a parrot can acurately reproduce the sounds. This was a problem with Alex as I recall, at first saying "Key" as a raspy guttural sound. But the trainer used modeling. The trainer asked a fellow human assistant, "What object yellow?" and the assistant answered mimicking Alex. The trainer then said, "Say it better," then the assistant answered again in his or her normal voice, then received a cracker. Alex caught on and rapidly said his words in very clear diction, or he didn't get his cracker. Your world's trainers will need to employ similar techniques. Finally, users will obviously not be able to train the parrots themselves. After all, if getting the melody and rhythm just right is crucial to the spell, the tone-deaf person won't be the proper role model. This parallels Real World (TM) training of service dogs for the blind. A whole industry will spring up on your world where certain skilled magicians specialize in just this service, fostering and training young parrots, and when ready, placing them with those in need. This can give you an interesting plot point- in your society, is this service considered a commodity to be bought at a price (like Merry Maids), or a public benefit sponsored by volunteers and donations (like service dogs)? In summary, yes it is possible. It will just take time, care, and skill. (I just have to say it. This is among the most absurd questions and answers I have ever participated in. Bless this SE!) [Answer] [Burrhus Frederic Skinner](https://en.wikipedia.org/wiki/B._F._Skinner) would have a field day and jump out of his grave just to grasp this opportunity. He actually did comparable conditioning with many different animal species using his famous [Skinner Box](https://en.wikipedia.org/wiki/Operant_conditioning_chamber). The principle is simple: reward the "trainee" for desirable behavior, punish for undesired behavior. Skinner managed to teach a pidgeon to play a short song on a miniaturized piano that way (by pecking on the keys). A short demonstration of the principle [can be seen here](https://youtu.be/LSv992Ts6as?t=153) (start at 2:33). You start by giving the trainee a signal that you want to connect to the casting of a fireball. You give the trainee an example of what is expected (the first word of the song) and wait until the trainee repeated that word. Immediately reward with food. Train this step, until the trainee repeats the word whenever you give the corresponding signal. Then, bit by bit, demand that the trainee repeats more words, in the right rythm, with the right melody before it gets rewarded. Repeat until it learned the whole fireball song. But don't forget the punishment whenever the trainee starts reciting the fireball song without you having given the signal for the fireball song. A song is not done in 5 seconds, so you have more than enough time to interrupt your trainee. I suggest a mild punishment to keep the trainee motivated long term. [Answer] It is your world, but since you are trying to add realism... don't forget that your songbird (parrot/Mocking bird/cockatoo/whatever) would also have to direct the spell in the correct direction for it to be useful. Generally trained animals look directly at the trainer... that'd be great for an armor spell, but not for a fireball spell. ]
[Question] [ I am working on an empire that exists in my world. I want to know if it makes sense for said empire to standardize the materials they use for construction across the empire. In the heart of the empire important buildings are constructed using a particular local granite and the roofs are made of slate. The remainder of the buildings are a wooden timber frame, floors are made of both granite and ceramic mosaics. Details: * Roman-esqe empire, similar in size and technology * The furthest provinces are roughly 800 miles (strait line) away from the capital, travel miles would be further. * Some provinces are on islands and others are accessible by land but it is impractical to ship large amounts of goods (mountains, distance, etc) to them * Temples and major civic buildings would be made from these particular materials * For the purpose of this question there is no limit to the quantities of the materials * The timber frame can be made from any functionally appropriate wood and the ceramics can be made anywhere I want to know: * Are there historic examples of a nation/empire standardizing with these types of materials for use in important buildings? * Was it done only in parts of the empire or were there locations that could not be supported? * What methods of transport were used to get the items to the building sites? [Answer] It depends what you mean by standardisation. If you mean of identical size such as in making standard bricks then probably no. However Transport of building materials was certainly carried out in the ancient world and in Egypt all efforts would have been made to standardise the colour of stone for their monuments. Likewise Rome transported marble across their empire to erect marble edifices as a symbol of power. > > How were the pyramids built? Transporting stone blocks down the Nile > > > Along the Nile lie several quarries where different types of stones > were quarried and brought to the building sites by boat. Granite > stones from Aswan had to be ferried down the river on large barges > about 934 km (approx. 700km linear distance). Ships transporting > limestone from Tura had to cross the Nile and then cover about 13-17km > on channels until they reached the harbor of Giza > > > <https://www.cheops-pyramide.ch/khufu-pyramid/nile-shipping.html> > > > --- > > Marbles to Rome: The Movement of Monolithic Columns Across the Mediterranean > > > <http://www.academia.edu/3080968/Marbles_to_Rome_The_Movement_of_Monolithic_Columns_Across_the_Mediterranean> > > > [Answer] Certain structures represent the Empire. You want them to look Imperial. The Empire might standardize a particular exterior look for structures which represented the power and authority of the Empire - for example government buildings or temples. Standardization could include architectural style and façade materials. The Romans did this. [Roman Building Materials, Construction Methods, and Architecture: The Identity of an Empire](https://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1909&context=all_theses) > > Sir Bannister Fletcher in A History of Architecture relates the boast > of Augustus that he found Rome a city of brick and left it one of > marble... > > > One individual’s wishes, desires, and motivation, that of Augustus, > impacted historical events, and his desire to drape Rome in marble > provides one example of how the Empire came to be identified by use of > a particular building material. The splendor and grandeur of Rome > today, even in ruin, remains impressive. The Colosseum, Pantheon, > arches, and spans of aqueducts are existing structures that produce > admiration for the architectural and construction abilities of the > Romans. These structures were used to expand, maintain and identify > the world’s most impressive empire... > > > Each variety of marble had its signature color. They ranged from > yellow veined, grey-blue, white-yellow veined, white, bright white, > red-blue, violet, red, and green. The sight of Rome with facades of > these colors would have been striking. The application of this > building material, the result of Augustus’ taste and desire, provides > a striking example of how materials were used to express empire. > > > [Answer] If your empire has a technology that no one else has or has applied as broadly (Rome had concrete), and that can be used anywhere in the world, you could consider that as a possibility. Transporting knowledge is far, far easier than transporting materials. Maybe try some metal that they know how to smelt that no one else has figured out yet. You'd definitely need some reason, culturally, for the empire to standardize like that instead of just adapting to what's around. That would be the background you'll need to make it ring true. [Answer] Q: Are there historic examples of a nation/empire standardizing the materials used in important buildings like this? A: No. There may be building decoration (ie, non-structural, like mosaics or veneers) which used material from a specific location, but structural components were typically what was closest and/or easiest to get. Q: Was it done only in parts of the empire or were there locations that could not be supported? It depends. You might have a situation such as Egypt where material came from the same quarries for different building projects, but even there most of the building material, when possible, came from near the site. The Great Pyramid is an example in that the limestone was quarried right at Giza, but the granite blocks came from granite quarries upriver. Q: What methods of transport were used to get the items to the building sites? Again, material would typically be sourced as close to the site as possible and whatever transportation method that could be used, would be used. Everything from dragging it with ropes and poles to shipping and lifting with sophisticated cranes. [Answer] Following the Roman invasion of Britannia, the empire's influence started to take hold as trade goods and materials flowed into the islands. Socially, Romanism became desirable due to the new availability of luxury goods from far off lands, newly made available by Roman trade routes. Once being Roman was socially desirable people wanted to live as Romans do, and that meant Roman architecture and materials. The buildings and clothing common from the empire became commonplace in the islands until the fall of the empire. Once the empire fell, the goods stopped flowing and eventually people stopped seeing themselves as Roman and started seeing themselves as something else (not British quite yet). My point being, that at least in this example, standardization was a product of social constructs and not by decree. Additionally, when the trade routes were disrupted by barbarians in Gaul, goods stopped flowing. Britain was one of the first parts of the empire to really go without Roman trade as things contracted since it was the farthest out and the least accessible both geographically and due to barbarians in Gaul. This sort of falls under the "not be supported" part of your question. Bricks and pottery were at least partially imported. We know this because craftsmen stamped their goods. Therefore, it follows that they were shipped over land and sea (via Gaul, then the channel) to Brittania. Here are some sources and links for further research. Most of this is from memory from listening to the British History and The Fall of Rome podcasts. * <http://www.romanobritain.org/1-arc/arc_roman_bricks.html> * <http://www.romanobritain.org/10_crafts/rca_roman_craft.html> * <http://www.romeartlover.it/Stones.html> * <https://www.stitcher.com/podcast/the-british-history-podcast/e/34396353> * <https://www.stitcher.com/podcast/the-british-history-podcast/e/34396392> * (roughly 30 more Roman-Britain themed episodes) * <https://www.stitcher.com/podcast/wondery/the-fall-of-rome-podcast/e/48807125> * (a few more in this one too) [Answer] In addition to the issue that materials may not be available locally and transporting them is energy intensive, consider also that different locations require different styles of architecture because of temperature, wind, humidity, access to heating fuel, requirements for different animals, and so forth. Materials that work to build a gathering hall in a cold windy town by the sea would be a disaster in a town in a hot dry climate with occasional light earthquakes. And vice versa. In large countries/empires with different flora and climates, I don't know of any that standardized building until there was reliable transportation. In the United States, for example, adobe bricks were prominent in the southwest, wood in the northeast and midwest, etc. Until trains were common, it made no sense to try to ship building materials except for a few specialty items, or the very rich. [Answer] if you cant use marble stone or wood well what plants do you have. You can use reeds. Reeds are a type of aquatic grass. the Uru people of lake Titicaca in Peru built entire islands out of reeds. they made houses clothes boats and used reeds as food. If you had enough reeds and enough water to grow them i'm sure you can make an empire especially if the people also make and use concrete which is rock,sand, gravel, and water it could be rather successful. if there is mining oppurtunities you could hypothetically have precious metals which would add to the Rome like empire if not only it had water for the reeds but enough plain land then you could have goat and sheep. [Answer] > > Are there historic examples of a nation/empire standardizing the > materials used in important buildings like this? > > > Rome had such a material it was called concrete basically every important building built in the empire after a certain period was made of concrete, not all that dissimilar to today concrete just offers too many advantages. Local sand and stone was used for the filler but you still always end up with concrete. An empire that refuses to use local materials goes broke and stops being an empire very quickly. Brick or veneer facing might be used to give it different looks but you could easily say that does not happen or at least they use identical brick patterns (Rome basically had three brick patterns each with its own functional purpose) > > Was it done only in parts of the empire or were there locations that > could not be supported? > > > Shipping just the cement was much easier and cheaper than shipping everything you would use, shipping stone any distance is prohibitively expensive. Cement making was a well guarded secret, since it was the reason romans could build fortresses MUCH faster than anyone else, and it requires things like limestone, so cement was only made in few locations and then shipped everywhere else. since the army often used concrete it made its way to the far reaches of the empire. > > What methods of transport were used to get the items to the building > sites? > > > Like everything in the empire and basically the whole world, it was shipped by boat or cart. I'm not exactly sure what you want to know here. [Answer] # It does not make sense In general, it does not make sense for this to work. The foremost reason is that the units of measurement are not standardized in this time period. In the ancient world, the weight (or mass) of currency was rather well known, but that was a result of official dies for pressing coins being taken from one place to another. The roman foot was a recognized and widespread unit of measure; but, there was no universally fixed way to ascertain whether a foot was really a foot. That is, there was no guarantee that a foot as cut in the quarry in North Africa was the same foot the builders were using to line up the marble blocks in Ephesus. That was not developed until the Scientific Revolution in Europe. Christopher Wren's definition of a meter by the length of a pendulum that took one second to swing was the first start in 1660 and more advanced measures followed. Until there was a standard unit of distance measurement, it was essentially impossible to manufacture standardized parts in remote locations. This isn't a problem so much if you cut all your marble blocks too big; but what if you cut a marble block too small before shipment? If you only only use standardized parts, then you have just wasted that block. Effective as opposed to theoretical standardization took longer still, until the machine parts makers of the Industrial Revolution (~1790s onwards) started getting demand for accurately machines shafts and gears and dies and what have you. So, I'd argue that until a scientific revolution allows accurate length measurements, then there is no such thing as "standardized" parts, because the parts cannot be easily standardized. # Long distance shipping to the capital can be done If you aren't standardizing, then you are just shipping valuable building materials long distances to the capitol. There is plenty evidence of that happening. * The Romans looted several very large, millenia old [obelisks](https://en.wikipedia.org/wiki/List_of_obelisks_in_Rome#Ancient_Egyptian_obelisks) from Egypt that are still there today. * Rome itself was famous for its [many colored marbles](https://www.througheternity.com/en/blog/history/ancient-roman-marbles.html), each sourced in a different part of the Empire: + The [Carrarra mines](https://en.wikipedia.org/wiki/Carrara_marble) are famous for the pure white marble that many associate with Rome today. In particular, the statue of David is made of Carrarra marble. + [Rosso Antico](http://cameo.mfa.org/wiki/Rosso_antico_marble) was a deep red marble from Greece. + The [Chemtou marble quarries](https://en.wikipedia.org/wiki/Chemtou_Museum#Marble_quarries) were famous as export sites for mass quantities of marble in the later Empire; and also for marbles in "Numidian yellow." # Conclusion It makes a lot of sense for building materials to be brought from all over an empire to the capital, or the other large cities (like Alexandria, Carthage, Ephesus, and Antioch of the Roman Empire). It doesn't really make sense to build these materials in standardized sizes, because the scientific technology of the time was not enough to ensure that they would fit. ]
[Question] [ Here's the full question: *What's the most plausible way to bio-engineer an underground ecosystem, without using photosynthesis, so a mine system would not need an active air exchange system?* (It was over 150 characters, again.) So, inspired by Jim2B's response here: [How low underground could you go?](https://worldbuilding.stackexchange.com/questions/35421/how-low-underground-could-you-go) Assume there's a vast network of mines over hundreds, if not thousands, of square kilometers, and ranging from 5 to 11 km in depth. The upper third of the mine is mostly dry, but the middle and lower thirds have met underground springs. When the mine is eventually abandoned and the miners stop pumping the water out, it will eventually seep down into the lowest portion of the mine and become something like an underground geyser in the vertical shafts that reach these depths. What's the most plausible and efficient way to create an ecosystem that will absorb the carbon dioxide exhaled by miners and convert it to breathable oxygen? The two, related, caveats are: 1. No photosynthesis. In the same way the ecosystem is alleviating the need for the energy used by active air exchange, it cannot be reliant on energy used to power light sources for photosynthesis. 2. It has to be nearly independent of the miners to sustain itself. If the mine suddenly closed, the ecosystem would be capable to adapting to the loss of whatever materials the miners were bringing to/removing from the area, and continue living, collectively, on its own. [Answer] In the real world the most energetic dark ecosystems run of [chemosynthesis](http://www.jstor.org/stable/24859970?seq=1#page_scan_tab_contents) from [hydrothermal](http://ocean.si.edu/ocean-news/microbes-keep-hydrothermal-vents-pumping) vents, the chemical conversions vary but many involve oxidation. hydrogen sulfide, hydrogen gas, ferrous iron and ammonia are the most common reactants Interestingly these is a weird dual reaction used by [Green Sulfur bacteria](https://en.wikipedia.org/wiki/Green_sulfur_bacteria) that actually uses both hydrothermal chemicals AND light but needs such weak light that is it not sunlight it is using but the weak radioactive glow from the vents, and do produce oxygen albeit very small amounts. This is still technically photosynthesis but since it does not need sunlight I thought it might still work for your scenario. [Answer] Some minerals release oxygen when heated-- the classic example is sodium chlorate, used in "oxygen candles", which burn iron powders to generate enough heat (about 1000 degrees F) to liberate oxygen, producing NaCl (salt) as the result. Apparently this is about 6.5 man hours of free oxygen per kilogram mixture. Perhaps you can have a large deposit of such a mineral gradually feeding into a subduction zone. Or, make things interesting: rather than a stable ecosystem with a fixed location, have a stable ecological front, moving along a large deposit of these minerals, burning at the edge like a coal seam fire. [Answer] Maybe the system has an abundance of lithium hydroxide. This chemical, while toxic, can scrub carbon dioxide into oxygen gas if contained properly. I'm imagining a cave with lithium hydroxide deposits everywhere and clusters of life around them. Note that the deposits would shrink gradually over time as they're used up, so the life would either need to figure out that fruit juice + copper + zinc + water = oxygen (electrolysis) or move to a different cave with the same mineral deposits. [Answer] You want to replicate photosynthesis without sunlight. My proposal: in the place of radiant energy from the sun, use radiant energy sources available underground. First, photosynthesis. [![photosynthesis schematic](https://i.stack.imgur.com/3R2Ad.png)](https://i.stack.imgur.com/3R2Ad.png) <https://sites.google.com/site/vhs2015environmentalscience/biodiversity/photosynthesis-respiration> As opposed to the energy in visible light, your underground oxygen generators fix carbon for themselves using [alpha radiation](https://en.wikipedia.org/wiki/Alpha_decay). Alpha radiation is produced by uranium, thorium and most importantly for this application, radon gas. Radon is produced by decay of uranium and radium and because it is a gas, it circulates around for a little bit before it decays by emitting an alpha particle. Radon builds up in underground spaces. Either radon or radiation from the heavy elements themselves provides the energy to turn CO2 into O2 and H2O. Your subsurface creatures need reduced carbon to build their bodies, just as we all do. Their chloroplast equivalents harness the energy from alpha particles to do the work. I can imagine these things growing as a layer on radioactive rocks, or in areas where radon gas is abundant. CO2 can be found in large deposits underground as is evidenced by the fact that volcanoes kick out huge amounts and so these creatures could evolve in the absence of regular miner visits. I have wondered if ecosystems like this might actually exist. It might be difficult to recognize them and certainly difficult to culture them since they require alpha radiation. I could imagine though that in the company of miners there might be a bloom of such organisms - organic nitrogen is in short supply in the deep earth. Organisms bringing nitrogen down from topside and depositing it in their waste would provide plenty of nitrogen. --- Thermovores. A different scheme with the same general idea. Environmental energy is harvested by organisms which straddle a high energy / low energy divide. We do this by harnessing the oxidation of reduced carbon, which would happen anyway in an oxygen atmosphere. Photosynthesizers harvest incoming solar energy which would expend itself as heat on hitting the earths crust. An organisms which straddled a thermal difference could harvest the heat energy, which would heat the organisms substrate anyway. An example might be organisms which grew on a a cool rock with one part of the organism exposed to hot water - or a hot rock with one part of the organism in cool water. A steam engine works on a similar principle - a phase change in the heat captures heat energy, and then releases it when cooled. An organism might similarly capture energy via some molecule which captured some heat energy on the hot side, then released it on the cold side. Probably this would not be a phase change but some sort of isomeric configuration change. Or hydration change. Candidate molecules to mediate this sort of energy transfer via hydration change include [metal ions](https://en.wikipedia.org/wiki/Metal_ions_in_aqueous_solution), [methane/methane clathrate systems](https://en.wikipedia.org/wiki/Hydration_number#Methane_Clathrates) or [large organic macromolecules](https://pubs.acs.org/doi/abs/10.1021/ma3026282) [Answer] You can subtitute [radiosynthesis](https://en.wikipedia.org/wiki/Radiosynthesis_(metabolism)) for photosynthesis: > > Radiosynthesis is the theorized capture and metabolism, by living organisms, of energy from ionizing radiation, analogously to photosynthesis. Metabolism of ionizing radiation was theorized as early as 1956 by the Russian S. I. Kuznetsov. > > > Decades later, scientists discovered [a fungus that actually does that](https://en.wikipedia.org/wiki/Radiotrophic_fungus): > > Radiotrophic fungi are fungi which appear to perform radiosynthesis, that is, to use the pigment melanin to convert gamma radiation into chemical energy for growth. This proposed mechanism may be similar to anabolic pathways for the synthesis of reduced organic carbon (e.g., carbohydrates) in phototrophic organisms, which capture photons from visible light with pigments such as chlorophyll whose energy is then used in photolysis of water to generate usable chemical energy (as ATP) in photophosphorylation or photosynthesis. (...) These were discovered in 1991 growing inside and around the Chernobyl Nuclear Power Plant. > > > This would solve the problem of energy in a closed ecossystem. As long as there is radioactivity in some places, life will have its source of energy. As for breathable air, there are four ways to generate oxygen through biological activity. Photosynthesis is just one of them. Check out [this article about bacteria that produce oxygen by means other than photosynthesis](https://phys.org/news/2010-03-oxygen-mechanism.html): > > The research team of Dutch researchers and the University of Queensland's Dr Margaret Butler, working in The Netherlands at the Radboud University in Nijmegen, have found a microbe that makes oxygen within itself, which is only the fourth mechanism known by which oxygen is produced on Earth. The others are photosynthesis, which releases oxygen as a waste product, cellular generation of oxygen by bacteria from chlorates and enzymatic conversion of reactive oxygen substances. > > > The subject of the study, a microbe (provisionally dubbed Methylomirabilis oxyfera) collected from oxygen-starved sediments in drainage ditches and canals in the Netherlands, is one of the so-called NC10 bacteria, first found in the caves under the Nullarbor Plain in Australia. It was thought to be able to convert methane and nitrite to carbon dioxide, so the researchers carried out experiments that traced labeled nitrogen and oxygen going into and leaving a chamber containing the microbes. > > > The team found the bacteria could consume methane and were producing oxygen by a previously unknown biochemical process. > > > [Answer] According to [this Answer](https://biology.stackexchange.com/a/59089) on Biology Exchange there may not be a need to use a different mechanism then photosynthesis as there exists a version of chlorophyll able to work on the infrared spectrum. Infra red radiation should be abundant in a cave system as you propose as (on earth) the [temperature of the ground raises about 30°C/km of depth](https://en.wikipedia.org/wiki/Geothermal_gradient). This would put the deepest part of your cave system to about 330°C emitting a fine amount of usable energy for your plants. Now the only thing you propably need is a ventilation system in order to make plants survive at these temperatures. [Answer] If you have your world in a fantasy or sci-fi setting, you could use mushrooms or any cave dwelling plant life that can convert the carbon dioxide into oxygen (without light) though they would have to be very efficient and produce a large output for this. [Answer] An engineered bacteria like [this one](http://www.i-sis.org.uk/Photosynthetic_Bacterium_Converts_CO2_into_Petrochemical_and_O2.php) would convert C02 to Ethylene (an energy-dense fuel) and produce 02 as a by-product. The bacteria could feasibly survive without miners present by consuming the C02 commonly present in (well, passing through) underground water. If the area is prone to volcanic activity, or contains/contained organic matter, there would be a lot more C02 present in the ground and groundwater. In such a case, one can speculate a storyline where a rocket with a bacteria payload is fired to a distant, suitable asteroid or other astronomical body. The bacteria move into the ground begin their work and by the time humans (or other sentients) arrive to dig their tunnels there is already a small Oxygen-rich atmosphere. ]
[Question] [ If I were to use a pearl instead of a bullet in an old fashioned flint-lock pistol or a musket, could it survive? What would it do on impact? Would it be too light for an effective ammunition? Basically, what would be its properties as ammunition? EDIT: I did not consider the world to be a major concern, since it has nothing to do with the question. My world is in the early stages of discovering the "New world". People made a special boat in an attempt to discover a new continent, but they found countless numbers of small islands forming a large crescent formation at the bottom of this formation is a island that is full of pearls. I wondered if I could have the people from southern islands carry a round pearl with them as a reminder of their homeland and for good luck and to remind them that they should not be controlled by greed and as an emergency ammo. So I wanted to know if it would be possible to use a pearl as ammunition. Because shooting that pearl would be a sign that you are not controlled by greed and many wear the damaged pearls as a proof. But I don't know if the pearl would survive the impact. Southeners consider the explorers as invaders. They have more developed firearms than the people from the continent, so they consider guns as standard weapons, while the continent knows only about ship cannons. On the islands there are temples made from rare materials, that form a prison for a demon of greed. If they get torn down it will be released. (that is the only magic in this story.) As you can see the world has nothing to add to my question. [Answer] > > From the mid-18th century, however, British forces used just 3 main uniform sizes: Musket, c.31g ball; carbine, c.23g ball and pistol, c.13g ball. [(source)](https://finds.org.uk/database/artefacts/record/id/266828) > > > You'd need a pearl the equivalent size to a 13g lead ball for a standard flint-lock pistol. However, lead has a specific density of around 4-5 time that of pearl (~11 vs ~ 2-3), so a pearl of that weight would be too large for the pistol, while one of the right size (for the calibre of weapon) would - I assume - be too light to deliver the same impact. Pearls themselves are [fairly tough](https://en.wikipedia.org/wiki/Nacre), so propelled at sufficient velocity would be damaging. You might just need a custom weapon to do so. The biggest problem of, course, would be finding sufficient pearls to use as ammunition, and addressing the question of why you wouldn't exchange each pearl for a wagon-load of lead-shot ammunition for your flint-lock musket or pistol? EDIT: Expanding on this a little, in a constructed world it might be that pearls are more readily available, and/or deliberately harvested (and marketed by a particular culture or population. @[ohwilleke](https://worldbuilding.stackexchange.com/users/28533/ohwilleke) (in comments) suggested particular vulnerability akin to werewolves and silver bullets - if this existed it could create a market for 'pearl bullets'. Taking this further, if pearls are somewhat toxic to a particular target - and given that small pearls will be more common than large pearls, perhaps they could be used as 'shot' (i.e. multiple small projectiles per discharge) rather than as a straight replacement for musket balls - this would increase the likelihood of hitting the vulnerable target (given that pre-rifling, accuracy was poor), which might be important if its something as dangerous as a werewolf. While I've not been able to find any reference to use of shot in flintlock muskets or pistols, there is a passing reference to this for the arquebus, so it has some plausibility: > > It was sometimes advocated that an arquebusier should load his weapon with multiple bullets or small shot at close ranges rather than a single ball.[ [wikipedia](https://en.wikipedia.org/wiki/Arquebus#cite_ref-auto2_60-0), citing "Barwick, Humfrey (1594). A Breefe Discourse"] > > > [Answer] Assuming it is a round enough pearl, it will work as a bullet: it is strong enough to survive firing from a smooth bore firearm. Minor chipping will not affect the aerodynamics much, just compare it to ball type musket ammunition for accuracy. It will not have much stopping power however (1/5th to 1/6th the density of a lead bullet, which means about 1/10th the kinetic energy). It has slightly more mass than a rubber bullet of the same size so using lethal range for a rubber bullet might be a good shorthand, if you can find it for a musket. Pearl buttons have been used as impromptu ammunition in pistols and did penetrate at point blank range so you can get penetration. Keep in mind even a blank cartridge can be lethal from a short enough distance (within a few feet) so a pearl can definitely be lethal. ]
[Question] [ There are various questions about the [stability of multiple moons](https://worldbuilding.stackexchange.com/questions/36929/stability-of-multiple-moons), [how they affect tides](https://worldbuilding.stackexchange.com/questions/71/how-would-having-multiple-moons-affect-tides) and so on, but I don't think this one has been covered here: If my planet has two moons, assuming they have separate orbits, is there a "typical" equilibrium that they are likely to find? Does a moon of a particular size tend towards a certain distance or orbital period, or are these more or less arbitrary depending on other parameters of the system? [Answer] There is no standard behavior for the orbits of multiple moons. You've uncovered a problem that has plagued physicists since the 1600s when Newton was beginning to describe gravitational mechanics. This problem called the [3-body problem](https://en.wikipedia.org/wiki/Three-body_problem) or more generally the [N-body problem](https://en.wikipedia.org/wiki/N-body_problem). To quote Wikipedia the N-body problem is described as: > > Given the quasi-steady orbital properties (instantaneous position, velocity and time) of a group of celestial bodies, predict their interactive forces; and consequently, predict their true orbital motions for all future times. > > > This is easily solved in cases of two objects (a planet and 1 moon). For all other cases there is no easy way to predict the future movements of every object. [Answer] The size of the moon, as a celestial body, doesn't matter much in the orbital equations, stable orbital distances are determined, almost entirely, by the speed of the orbit alone. The Jovian moons do suggest that there are certain [Harmonics](https://en.wikipedia.org/wiki/Orbital_resonance) that tend to emerge in multiple moon systems but that's one example only we don't have hard and fast rules for such things. Looking at the mechanics of [Lagrange Orbits](https://en.wikipedia.org/wiki/Lagrangian_point) might give you some insight into the relationships between moons that may naturally develop. Do bear in mind [Roche Limits](https://en.wikipedia.org/wiki/Roche_limit) when putting together your numbers. [Answer] If the moons are very small and don't have a significant gravity field of their own, they are basically independent, e.g. Mars' moons. If they are large enough to have a significant gravity field of their own, two moons or more will perturb each others orbits. This leads to one of the moons being ejected from the system. There are exceptions, such as some orbital resonances as mentioned by Ash, but those depend on the size of the host planet compared to the moons. If the planet is much larger than the moons, orbits can be stable, e.g. if they are in resonance (e.g. the Jovian moons). I think multiple large moons would require a stable resonance for the system to be stable, but I'm not sure about that. If the planet is not much larger than the moons, for example as with the earth-moon system, a stable system becomes very difficult, and likely all but one of the moons will be ejected. If moons are in resonance that means their orbital periods are simple ratios, e.g. 1/2 or 3/5. So that is an in some cases standardised behavior, but the absolute orbits can be anything, there is no standard behavior for that. Also, if a moon and a planet are very close together, strong tidal forces will result, which will over time lead to tidal locking: the bodies will rotate around their axes in the same time that it takes to orbit each other. Pluto and Charon are tidally locked like that. The moon is also tidally locked to earth, which is why we only see one side of it. The earth is much larger so this hasn't happened for earth. ]
[Question] [ Background: I'm continuing to work on the economy of my industrial age world. As background info, it's a fantasy world, with loose basis in western Europe, 1870-1914; though the presence of (essentially magical) airships, largely dirigibles and small planes, complicates that as a point of reference, and for this question later periods may be relevant. In this world trade is conducted primarily by air rather than sea. (I'm aware of the real world disadvantages of this; but for the sake of space you'll have to go with me for here.) I'd like to map out the major airways for my world, so I can better understand the flow of trade. It's belatedly occurred to me that there's probably going to be a lot more to that than listing imports and exports and drawing a straight line; possible considerations include refueling, government / legal boundaries, weather, etc. Not having gotten into the weeds of the airship tech yet (there's a long to-do list) I'm not really sure how important any of that will be, and has been historically. Which brings me to my question. Question: What will be the major considerations for mapping out practical, economically competitive aerial trade routes? In short, as I approach this as a worldbuilding problem what are the main things that I should be thinking about? --- Bounty Edit: In the next few days I'll be creating two 50 pt bounties to reward the two answers I found most helpful, Thucydides and JBH. They each addressed the question in useful detail, but as one focused on the big picture and the other on specific details I decided I couldn't fairly choose between them. I'm adding this note to alert users that, while more answers are always welcome and appreciated, the main answer is already selected and both bounties are set aside. [Answer] Mapping airship routes starts with plotting the airports on a globe and then plotting the "great circle" routes between these points. This is the shortest distance between the two points. Finding the shortest distance will minimize travel time and the amount of fuel or energy you need to expend, making this the most economical route for transportation of people and goods regardless of the means of transport. [![enter image description here](https://i.stack.imgur.com/5j8Ug.gif)](https://i.stack.imgur.com/5j8Ug.gif) Great Circle Map While this applies for any form of transportation, air transport is unique in that there are far fewer constraints. People on the ground have to contend with local geography, political divisions and people's claims to the land they wish to traverse. Ships on the open ocean eventually need to come ashore, and navigation in the littoral regions means dealing with land, sea currents and so on intruding on the Great Circle. Aircraft can serenely fly over obstacles, cross between land and sea and ignore most claims by small land owners as they transit the sky. So the first order approximation is to plot the Great Circle routes between Zelda and Gondor. Once that is done, airships or aircraft (or witches riding brooms, depending on your scenario) then attempt to fly the route, making careful notes about navigation hazards like mountain ranges, prevailing winds or jet streams and if there are political boundaries which need to be avoided, lest you get blown out of the sky. With some experience, Captains will eventually plot the best routes, where to deviate from the Great Circle and where to rejoin it. [![enter image description here](https://i.stack.imgur.com/nBtn0.gif)](https://i.stack.imgur.com/nBtn0.gif) Air navigation map. This one is a low altitude IFR chart, which is probably appropriate for airships Once that has been plotted, tested and codified, air navigation maps will have the routes plotted for Captains to follow and air transportation companies to use when offering service. [Answer] When it comes to an airship — and since you've said there's magic involved but didn't explain how, I'm going to ignore it — the problems are (a) lift and (b) being pushed around. Note that I can't imagine this to be a comprehensive list. Wind For example, the [Westerlies](https://en.wikipedia.org/wiki/Westerlies). There are "wind currents" just as their are "sea currents." Your trade routes will want to avoid head winds and take advantage of tail winds. Mountains Altitude is normally an issue with airships. The higher you must go, the more costly and dangerous it is. You'll want to avoid high mountain peaks and tall ranges, preferring to slide along valley chains and take advantage of low passes. Also, generally speaking, note that wind gets worse with altitude. The Sun As the earth rotates, the sun "pushes" air as it heats it (thereby expanding it). This causes more wind that can be predictably used or avoided. Think of canyon winds, which tend to be nasty in the morning and evening. Canyons "breathe" (air rushing in and out) and how they do depends on whether they're low point faces east or west. (BTW, this action is part of what creates the Westerlies). Wind Shear [Wind shear](https://en.wikipedia.org/wiki/Wind_shear) is a very strong burst of wind, usually downward, and usually caused by meterological complexity, such as occurs around storm fronts or near mountain ranges. Denver International Airport is famous for the problems of wind shear. Without power, these need to be avoided and trade centers will (generally) develop in areas of low wind shear. Thunderstorms & Tornadoes While thunderstorms can occur almost anywhere (and tornadoes less so, but still), there are areas of our planet where they are very common. Trade centers will want to avoid these areas. Note that both thunderstorms and tornadoes (and hurricanes) tend to create rotating wind, with will want to force an airship to turn, or may even cause it to spin like a top. Lift Powered flight can deal with, for example, the poor lift of very hot areas. Air expanded from heat is less dense and therefore provides less lift. This makes it very hard to, for example, take off with a fixed-wing plane. Airships react to hot and cold in the opposite way to fixed-wing flight, but they will nevertheless have similar problems depending on the nature of what gives them lift. Ignoring magic, if they're filled with gas, that gas will condense in cold — making polar transits difficult due to lower lift and the need to additional gas to compensate — and expand in hot — making equatorial or desert transits preferrable due to needing less gas to produce the same lift. Water vs Land Routes For this issue I don't have enough background. My guess is that land routes will have more predictable wind and weather patterns and thus be more desirable. But, honestly, I could be wrong. --- *EDIT:* One last thought. Sea routes are intrinsically limited in that you must have a port on the sea. Sea ports are desirable because the port is protected (a good harbor) and deep enough to handle the boats. They're also located, ideally, where train/vehicle access can easily get goods to the port, but that's secondary to the other considerations. The considerations for air routes are different. Obviously, a port located within a circle of high mountain ranges is a problem, but why would you do that, anyway? You're economic trade centers would naturally form at area where the airships are swiftest and least costly to operate. Along Westerlies, a low altitudes and away from mountains. Etc. Sea routes almost must be developed second to the ports due to the absolute needs of ports. Airships are fairly the opposite where they might develop second to take advantage of the best routes, which won't be "port locked." [Answer] When trying to map out major airways, the main considerations for establishing central trade routes are landmarks, conditions, and traffic. First, to have a route that multiple parties cross on a frequent basis, you have to have points of interest and locations for orientation. Depending on the elevation most of your flyers are flying at, these would probably be like mountain ranges, rivers, and cities. You could have the airways develop over the already existing trade routes from the past, or have a floating city/refueling dock where tons of aircraft meet and pass through. Another thing to take into consideration is the conditions. Your airways are going to follow nearby jet streams and wind currents. They would be in places where the weather is predictable, or at least where it can be seen and reported quickly in case of a storm. Heck, since it's your world, you can make spots that have permanent storms and permanent sunshine. Lastly, your airways are different than our modern world through trade. These aircraft are going to be passing one another, for safety, and for a common goal. There will be lots of aircraft going on the same route, because if that route works really good for someone else, it will work really good for you. You can have trading hubs, where all trade goes through at one point or other, and the routes and maps reflect that. In general, mapping your airways and establishing trade routes in the skies just comes down to the location the aircraft are going to, their safety and speed while they get there, and why they're going there in the first place. [Answer] Although the great circles are the shortest routes, they are not necessarily the most fuel efficient routes. Those will follow the jet streams. I'm not sure if your magic is the equivalent of fuel; but the propellers on dirigibles are seldom a match for being blown along by a jetstream; they are for navigating into and out of them, for positioning when landing, etc. They could be used for long distance travel, but the most fuel efficient method is to position your ship in a jetstream; turn off the engine and let it carry you; then turn on the engine only for small navigational adjustments or exit. Much like boats on a network of rivers and canals. Of course if "fuel" is infinite due to magic; the great circles are the physically shortest routes. ]
[Question] [ I have a fictional country which I'm mapping. It is roughly the size of the US. Currently I have 16 first-level administrative divisions ('provinces'). Those 16 provinces are sub-divided into 220 or so second-level 'districts'. Districts are further sub-divided to Municipalities. Each district has an area measured in the 1000's of square kilometers. Districts are already responsible for vehicle registrations, and number plates are roughly based on the UK system. Each district has an unique two-letter code, which it uses everywhere. The country's main economy is trans-continental transport. The goods are transported by ship, up a very major river, then transferred onto trains for the journey to the other coast. The rail line / river does pass through many counties and provinces. This causes both rivalry and co-operation between the various districts. --- What would be the consequence of abolishing the provinces, and having the national (most probably federal) government guide / rule the districts directly? I feel that the 'province' currently doesn't serve any 'practical' purpose, except to keep all its districts in the same time-zone. --- My on-line research is not yielding much information. I keep on landing up in Canada (mixture of territories and provinces), or Pakistan (adding new provinces based on ethnicity) [Answer] I see two reasons for a provincial level, and ultimately a national level: The main one is for legal reasons; a provincial level can resolve disputes between districts, that the districts themselves cannot. About trade or differences between them in local laws, or about the use (or abuse) of common resources (water, air, minerals, river or sea ways, migratory birds and animals, whatever). You mention railways: Who is responsible for repairing them? How are they extended across districts, in particular who takes the land required for a railway extension? Can a district shut down a railway? Refuse to allow the transportation of objectionable cargo (e.g. slaves, toxic or radioactive chemicals, nuclear bombs, criminal prisoners)? For rivers, can a district upstream dam a river to supply itself a lake of water, fisheries and electical power, and for the ten years it takes to fill that lake, dehydrate the downstream districts that rely on that river for irrigation and drinking water? If I dig a mine in District A to extract gold, and few hundred feet down the vein I am working crosses straight into District B for miles --- Am I stealing their gold? If I drill for oil in District A, and it turns out the lake of oil I am pumping out is actually under 20 other Districts too: Am I stealing their oil? Further, am I responsible for the hundred-foot deep sinkholes and property destruction that are caused by sucking out all that oil? --- Besides Legal issues across Districts, we also have the issues of mutual protection, police and emergency services. Obviously a coast guard should not be funded by individual coastal districts acting independently (even if there are no other countries to "guard" against, the coast guard can help fishermen and other seagoing vessels that get in trouble). But consider disaster relief efforts: If there is a disaster (earthquake, tornado, floods, bombs, train crashes or toxic spills, major disease outbreak), presumably it happens in one or more districts, and would likely cripple their own private disaster relief organization. A provincial disaster relief organization can be housed in many distributed districts, so they can respond to disasters in neighboring districts quickly with nearby units in unaffected districts, and depending on the level of disaster, get others on the road to the disaster site. I'd make a similar observation about Military structure; if your country needs defenses, well distributed military bases (at strategic points of probable attack) are better than centralized ones, and better than each District having its own little military. You could say that is a responsibility of central government, but it could be organized on provincial lines (like State Militias in early America, if we roughly equate "State" with "Province"). [Answer] Usually, what provinces, districts etc. do is give the people living there the ability to govern themselves at low level, while increasingly higher levels allow for area-overlapping administration and planning of larger projects. This is especially the case for a government/administrative body that has to govern over a very large amount of land / people, since on that level, everything is about numbers. This isn't inherently bad for everything, it serves its purpose (it's why you do generalizations), but on that level you simply cannot govern low leve processes efficiently without having restrictive laws up to even repressive laws. Ideally, you want your people to feel like they can govern themselves, at least in those areas that matter in their daily life. That way, they can focus on what they need and not what a ruler thinks they need, while still allowing for non-localized planning of larger projects, for example a roads network or a unified military without losing the flexibility of a more distributed government system. It's similar to what you can see in the business world today: For low numbers: the flatter the hierarchy the better, as this brings flexibility and a sense of personal responsibility to each employee, as well as having a low beaurocratic barrier to make decisions. The higher the number of people, the higher the hierarchy will become. This is from necessity: if you let one person make the decisions for a 1000 people on a low level, you can easily see how many problems this will pose not only for each individual, but also from an organizational and planning perspective. Increasing the granularity of said hierarchy can remedy that to a good degree, unless you introduce too many divisions, in which case you increase beaurocracy. TL:DR If you centralize your government in a way that decreases autonomy of the districts too much, you risk a problem of meticulous planning. As another response already said, you'd be getting closer to a planned economy and lose most of the flexibility and robustness of a distributed system. From history, we know how well a strictly planned economy works out for the people (German Democratic Republic, Soviet Union). Remember that by directly governing a large number of Districts from afar, the administrative body will more or less lose the sense for what the people need, and the people lose trust in the government (or worse). And the people wouldn't like someone governing them being disconnected from whom they govern, especially if the governor is not elected. Sidenote: The whole time I had in mind that there is also a similar, albeit different approach in computer science called "subsumption architecture". Not sure if it helps, but its all I got for now ;) [Answer] I think this one depends at least partially on the history of your country, and on why the provinces exist. If you actually are using a federal/provincial structure, you need to account for the division of powers as well as federal versus provincial jurisdiction (which government deals with what matters); your national government simply cannot be responsible for everything, because it is legally not permitted to act in specific matters that are under provincial jurisdiction. The degree of independence of the provinces is variable, but they have control over at minimum a lot of domestic matters, and they may even possess limited foreign policy powers to negotiate their own agreements (see: various trade agreements between individual Canadian provinces and U.S states). Using Canada as an example, it was formed as a federal government with provinces because those separate provinces were at the time separate colonies. Lots of negotiation was in play here, but basically nobody was willing to give up all their power to a single centralized government. This was especially true for the case of Quebec (which unlike the others was a French colony), which feared it would (as a large minority) be rendered powerless if one government held all the cards. The ironic thing is that the federal structure was originally intended to be highly centralized by its founders, with most of the powers in the hands of the federal government and only limited powers for the provinces. This was a result of watching the American Civil War, which was provoked over the question of the rights of states (read: provinces). This intended dynamic was completely reversed by court decisions over time that essentially expanded provincial jurisdiction at the expense of federal jurisdiction, with the result that Canada's modern legal structure in practice is very different from what its written constitution would suggest. This was probably for the best, though; Canada is larger than the U.S.A by land area with perhaps an eighth of the population, incorporating numerous ethnic groups, Aboriginal peoples, French and English rights, etc., all making a highly centralized government more or less impossible. Basically, if you have multiple countries coming together by agreement (as opposed to violent conquest; they might even come together to resist some common threat), or if you need to integrate multiple language/ethnic groups into a single country, you probably have a good case for a federal/provincial structure. Having a large landmass (which implies significant variation in environment), especially with a low population density, also recommends a decentralized structure. Given that context, if you try to suddenly abolish existing provincial structures in favor of giving a federal government all powers, you're likely to infuriate just about everybody. At minimum, you're stripping a lot of politicians of their power and position, which is going to generate lots of problems for you. You're likely also taking the basic legal structure of your entire nation and tossing it into a smelter, which is generally going to produce chaos. You're stripping the people of their local voices in favor of a single distant federal government that likely won't be able to adequately respond to all their needs (something that other answers cover in detail), another problem. I could probably add more, but I just don't think this would be possible to accomplish short of getting conquered by some invading power or a few hundred years of slow changes. [Answer] The distinction is between a "federal" system of government and a "unitary" one. Both have been tried, some of have been toggled between, and there are pros and cons to each. For example, France historically had a unitary government in which prefects appointed by the central government had authority over issues that are provincial or local government tasks in many other countries. For example, if you wanted to change the speed limit on the road through your village you would need approval from the local prefect and would have to lobby a member of the national parliament to make that happen. In the 1980s or so, it switched to having regional governments with internally elected officials. # Benefits of Unitary Government One benefit of unitary government is that resources aren't wasted on meta issues of deciding which level of government handles which issue. Another benefit of unitary government is that it is less prone to NIMBY issues in which local governments [adopt policies that have negative externalities](http://www.andrii-parkhomenko.net/files/Parkhomenko_JMP.pdf) or prevent something that is useful to the nation from being located anywhere at all. For example, Japan's unitary government has been noted for having better land use regulation than countries that vest that responsibility at the local level. A third benefit may be that the supply of competent potential elected officials and senior government officials may be scarce. Your nation may have enough competent people to serve in elected office and senior government offices to run one national government reasonably well, but not enough to run dozens of provincial governments as well. More generally, if the most competent elected officials and government officials are in the national government, then important policy decisions are made by the most competent people available. A fourth benefit is that it is easier for people new to democracy to understand a unitary system than a more elaborate federal system. A fifth benefit is that policy changes can be imposed nationwide very rapidly. But, the downside is that getting a policy change to happen may be harder with a national legislature to convince and greater inertia than with a smaller provincial body to convince. It also makes it easier to research the law that will apply to anything (especially interstate commercial ventures) if you have only one body of law to review. A sixth benefit is that there may be some provinces where the locals are prone to elect unwise provincial leaders who would adopt bad policies. But, their voice is diluted in a national government so their bad policies are not implemented. # Benefits of Federalism One of the practical purposes of a provincial level of government is to prevent too much of importance from riding on a national government deadlock. For example, in the United States, now and then, there is government shutdown because a majority in Congress cannot agree on a budget. If all government activity depends upon that budget, then all government activity comes to a screeching halt, nationwide, when there is a failure to agree on a budget. But, if lots of important stuff is funded at the provincial level, then only the stuff funded at the national level stops nationwide when there is a failure to agree on a budget. Of course, there could be a failure to agree on a budget at a provincial level too. But, only one province is affected at a time. Similar logic applies in the case of a strike by a public employees union. A somewhat related concept is that smaller bureaucracies may simply be easier to manage. A second purpose of a provincial government is the serve as a "minor league" training ground for future national parliamentarians and senior government officials. Rather than electing novices to the national government, voters selecting national elected officials and national governments selecting senior executives can choose from people who have distinguished themselves in their service in very similar positions at the provincial level if they wish to do so, and novices serving in provincial government do less harm. A third purpose of provincial government is to put more of government into the hands of governments that aren't truly sovereign. A sovereign government has no "safety net" of higher level judicial officials and legislators to correct them if they take action that is beyond the realm of acceptable political conduct. Provincial government officials recognize that they can't start wars, change boundaries, change the national constitution, or violate their own constitutions and get away with it in the manner that national governments do. There are plenty of people who have something worthwhile to contribute to the policy process who shouldn't be trusted around the power to make war, for example. This feature also means that most national officials, having been trained to act within limits in the "minor leagues" are less likely to push beyond those limits when they eventually take national office. A fourth purpose, usually put higher on the list by political scientists, is that different provinces can have different policies. For example, gun control restrictions that might make sense of a highly urbanized province might not make sense for a province in a huge arctic desert where police are not readily available and wild animals are a genuine concern. Or, different provinces might have different ethnic and religious makeups that call for different policies - one province might regulate alcohol very strictly while another might allow it rather freely, for example. The differences need not be strictly differences of policy either. For example, if residents of one province speak French and residents of another province speak German, it may be useful to have two different provincial governments even if they are applying a single set of laws. [Answer] Province/State/voivodeship usually have a government select by the citizens. If you take that people may get upset losing their voice, feeling centralized government don't know their problems and being in favour to other provinces (like taxation and help from capitol). Generally to run things smoothly you would need to introduce planned economy. You would loose the ability for quick reaction in the time of need (like cataclysm) and relay on plans made years ahead. [Answer] If this is prior to the Information Age, you need more levels just to make the job tractable, both in the sheer number of things to keep track of and the local-ness of people who can be in charge. If the government formed before “modern” time, this is what you must have. You might have a plot of phasing out layers that don’t mean anything anymore except to group the smaller levels. But then the people on top are micro-managing. To allow delegation, they might have more people in charge with different areas of responsibility rather than different geographic regions, but these commissioners have national scope. Each can subdivide further as befitting that job. [Answer] In the late Roman Empire there were six levels of government administration. Most of the Roman Empire was divided into civatates. 1) So in most regions a pagus or subdivision of a civitas was the smallest administrative unit. 2) A civitas or city state ruling a town or city and surrounding countryside. Each civitas was ruled by aristocrats elected as magistrates and council members by those citizens eligible to vote. A Christian diocese usually corresponded to a civitas. 3) A province consisting of several civatates, and military bases, imperial lands, etc. A appointed governor who could have one of several different titles supervised the governments of the civatates and imperial government activities. 4) A secular diocese. A vicar (of a praetorian prefect) supervised the provincial governments in his diocese. 5) A praatorian prefecture. There were only four in the Empire. Ruled by a praetorian prefect. 6) An Emperor (or emperors) ruling the Empire (or a part of the Empire). Thus the later Roman Empire had five levels of administrative subdivision and six levels of government. Wikipedia's List of administrative divisions by country shows that countries have varying numbers of levels of administrative divisions. France, for example, has six levels of administrative divisions and thus seven levels of government. <https://en.wikipedia.org/wiki/List_of_administrative_divisions_by_country>[1](https://en.wikipedia.org/wiki/List_of_administrative_divisions_by_country) The United States has three levels of administrative divisions and thus four levels of government. 1) Municipalities. The USA has allegedly 35,930 municipalities. They tend to provide utilities, clean streets, pick up trash, etc. etc. Among many other services. Can enact local ordinances and have magistrates courts. 2) Counties. The USA has over 3,000 counties. They perform many services including registration of wills and deeds. Can enact local ordinances. Run courts to try local and state criminal and civil cases. 3) States. The USA has fifty states, not counting other types of government like 567 tribal governments. They perform many services, for example, issuing drivers licenses. They legislate most laws and have state courts. They also legislate rules for counties and municipalities within them. States have their own armed forces, the National Guard, sharing control with the Federal government. 4) The Federal government. It handles war and diplomacy, the post office, and many other functions. Has federal laws and federal courts. Many functions are performed by two or more different levels of government. These examples show that it is possible to assign separate functions, as well as overlapping functions, to a central government and at least three levels of administrative divisions. [Answer] From the [ancient Romans](https://en.wikipedia.org/wiki/Roman_province) to the every moderate size modern nation, regardless of government type, uses some method of dividing the nation regionally. The reason is that the administration of a nation is simply too complex for a monolithic control structure. The problem is the [span of control](https://en.wikipedia.org/wiki/Span_of_control). Administering everything as one unit would increase the complexity by several orders of magnitude. Even in a small nation, that would mean administrating millions of people, thousands of cities, million of miles of roads. Besides that, regional administration is wiser because there is no such thing as a one-size-fits-all solution to governance. Consider the following. * Each region faces unique challenges. In the US, for example, California struggles with getting enough fresh water. West Virginia struggles to keep their population from declining as young people leave to find work elsewhere. * Regional administration can take the differing cultures of the people into account. Romans required each of their subject people to worship the Emperor. For polytheists, the addition of a new name in the pantheon of gods meant little to nothing. The Jews, being fierce monotheists, would rather die before worshiping another God. The Romans adjusted their requirement to fit the Jew's religion. * People tend to develop a deep resentment to some distant power who dictates to them. Having local administrators changes the feeling from an "us-them" to an "us-us" dynamic. ]
[Question] [ If a spaceship left earth traveling at near or at light speeds (that being possible in this situation) would they not when coming back to earth, arrive many years in the future due to [Einstein's theory of time travel](http://abcnews.go.com/Technology/story?id=98062&page=1) and how could this be prevented while still maintaining these speeds. It is okay to draw off of science fiction novels or movies that offer an explanation on why they do not end up in the future. [Answer] Special relativity is the scientific explanation for the reasons why spaceship moving at or near-light-speed experience less time. The closer to light-speed the less time passes. To return to Earth after hundreds of years the spaceship has travel to somewhere that takes, at least, one hundred years to reach and make the return trip back again to Earth. However, there are a reasonable number of destinations much closer to home. So traveling there won't mean our astronauts return home centuries later. For example, a trip to Sirius at 90% of light-speed will take ten years travel there and another ten years to return. The time dilation will be approximately two, so the astronauts will only be traveling for ten years for whole round trip. Plus however much time they spent exploring the Sirius system, so let's say five years. This means the astronauts will be away for twenty-five years, but they will only experience fifteen years. An example from science-fiction, in Larry Niven's short story "Singularities Make Me Nervous" the astronaut travels at relativistic speed to a massive black hole where he takes advantage of the hypothetical property of black holes to shift things like spaceships back in time. He then makes the return journey and arrives back on Earth before he departed. If your astronauts discover a mechanism to shift them back in time they can, at least, return to Earth without centuries having gone by. At the time Niven's story was written It was believed black holes could be used as time machines. The idea has been subsequently debunked scientifically, but the general principle still applies. Find a wormhole or a suitable space-time discontinuity that can act as a time machine and your astronauts will be home without too much passing. Of course, if the future in which this relativistic travel takes place, has invented its own form of time travel, then they can manipulate time to avoid returning home centuries too late. Larry Niven's novel Rainbow Mars (1999) has a discussion about this possibility. Not having access to the example for how this would work in Niven's book, here is my worked example of the process. A spaceship to Sirius at 90% light-speed gets there in ten years. They explore it for five years. before leaving Sirius, they activate a time machine which carries spaceship and astronauts slightly less than twenty-five years into the past. They fly home and arrive shortly after their original departure for Sirius. If a spaceship traveled at exactly light-speed, absolutely zero time would pass on the spaceship. This means your astronauts can travel as far as they like, and no time will pass for them. This does have one drawback. If no time passes, how do know when to turn off your space-drive and stop traveling at light-speed. Fortunately, this should be even more impossible to do than traveling faster than light-speed. If light-speed travel was possible, it would be extremely easy to travel and return not just centuries in the future, but millennia, and even millions of years. There is a limit to far astronauts can travel and not centuries later, and that is travel no further than slightly less than fifty light years at relativistic speeds. At worst this means returning to Earth about one hundred years later, but the good thing is this won't be hundreds of years later. ADDED TO THE ABOVE ON THE SAME DAY: There is another less obvious but quite quirky way of avoiding astronauts returning centuries after their departure. This has been used in two science fiction novels. Greg Egan's Schild's Ladder (2002) where it is only mentioned in passing as part of the [background](https://en.wikipedia.org/wiki/Schild's_Ladder) to the story, and in Karl Schroeder's Lockstep (2014) where it is part of the plot driving the story. With Schroeder the concept is dealt thoroughly and is the focus of the story. Basically people on a planet like Earth slow down their own time to match the passage of time experienced by astronauts travelling to somewhere in deep space. In Egan, the people are software entities, so they simply slow down the clock speed of the computers where their existence is implemented. In Schroeder, this is done using a combination of biosuspension (or, suspended animation) and a very regulated lifestyle. This combination is Lockstep. With Schroeder's [Lockstep](http://boingboing.net/2014/03/27/lockstep-karl-schroeders-fi.html) if astronauts are travelling at an average relativistic velocity of 99% of lightspeed to a destination 693 light years distant. The trip time will be 700 years in the rest frame, but the astronauts will experience 70 years. The time dilation will be ten. On Earth people will enter biosuspension for nine days. On the tenth day they will all emerge in synchronization and do what they would normally do for one day. This would continue for the entire round trip of the spaceship. Effectively one hundred and forty years go by for the astronauts and the people on Earth during the time of the astronauts' voyage. Yes, this is the future, so we can assume they have achieved extreme longevity. This means that interstellar expeditions lasting two centuries will be the equivalent of several years for us more short lived humans. This can be scaled back for more realistic interstellar voyages to nearby stars in the vicinity of the solar system. However, if the folks back were prepared slow themselves down so that no more passed for people on Earth than for astronauts travelling across interstellar space, then even if strictly speaking many centuries had passed for both the Earth and the astronauts they will experience the same amount of time. There won't be a time discrepancy of centuries for the returning astronauts. Note: Karl Schroeder devised his [fictional Lockstep system](http://www.centauri-dreams.org/?p=30584) as a way of getting around the problems of travelling astronomical distances without faster-than-light travel [Answer] It depends on how far they travel. If they travel hundreds of light years while traveling near the speed of light then yes, it will be hundreds of years in the future. If they travel 1 light year near the speed of light, then it will be one year in the future. The way the time dilation works is that the travelers on the ship will experience less time than has actually passed. Say that the ship is traveling at 99.99% the speed of light. They travel to a star 70 light years away. While it will still take the ship 70 years to get there, at that particular speed the passengers on board the ship will have only experienced around a single year. So, in a way you could say its a way to travel into the future, but once you look at it it's not really. [Answer] The way I see it, there are two ways to prevent it: 1. Travel slow enough that the time dilation stops being so much of an issue (it will still be one, it's up to you how much is tolerable). 2. Violate causality so that people traveling don't actually travel, but instead, merely arrive at their destination (some kind of warp drive or wormhole). If you still want them to actually travel, and have them travel at relativistic speeds, then I don't believe it is possible according to our current understanding of science. Depending on the physics of your setting, superluminal speeds might be a workaround to this problem, but that's outside the scope of [science-based](/questions/tagged/science-based "show questions tagged 'science-based'"). [Answer] Other answers have nicely summed up how travelleing faster slows time for the traveller (but leaves it as it was for everyone else). Thus, hurtling around the galaxy at light speed might be fun, but by the time you get home your friends and relatives will all be long since gone and so you can't tell them about it. Our current understanding of physics doesn't have a solution to this problem (or is it a feature?) of physical travel. Science fiction has had a few ideas: * Wormholes * Warp drive * 'folding space' * Send a robot probe, and then just use VR to pretend you went there * Make the rest of the universe's time go slower while you're flying so your time moves at the same speed as theirs (or make yours go faster, I guess) My personal favourite is that you make a relativistic tube in space, inside which Eistein's law doesn't apply (is that 'hyperspace'?). You then fly down that tube at light speed. However, to go even faster, you can make a second tube around the first. You fly down the inside of the first tube and it flies down the inside of the second tube. Thus, you're actually travelling 2x light speed, yet feeling none of the effects of it. I'm still figuring out how to construct a working demonstration of this though ;-) [Answer] If they are making use of an [Alcubierre Drive](https://en.wikipedia.org/wiki/Alcubierre_drive) to travel near light speed, they can remain in Earth's inertial reference frame for their entire trip. It doesn't cause them to move through space per se. It merely warps space around them much like dark energy is causing distant galaxies to recede away from us. This way they could remain in the present all the time. But Alcubierre drives could also theoretically be used to go faster than light. And if they were used for that, our space travelers could set out for Sirius, spend 5 years there, and then return to Earth just a few minutes after they left. Or they could return before they left. But something tells me the space government would make returning before you leave highly illegal. Not because they're worried about the fate of the universe, just because thinking about it makes their heads hurt. [Answer] You can counteract Velocity Time Dilation with Gravitational Time Dilation. A large gravitating mass could produce enough time dilation to counteract the effects of traveling close to the speed of light. At close to the speed of light, the gravitating mass needed would need to be equal to the mass of a large planet or star crammed into a small compartment on the ship. The ship's passengers could be spared the deadly effects of extreme gravity by accelerating the ship at an incredible rate in the direction of the mass. The problems are: The faster the ship's velocity, the more gravitating mass is required to counteract Velocity Time Dilation. The more gravitating mass is used, the more acceleration is required to counteract the crushing gravity. ]
[Question] [ Imagine an alternate history, where weapons types didn't advance past "medieval" type weapons. So like: swords, maces, flails, crossbows, bows, polearms, mauls, etc. I'm intentionally excluding "gun"/explosive type weapons. A great list is [List of premodern combat weapons](https://en.wikipedia.org/wiki/List_of_premodern_combat_weapons), minus the Gunpowder weapons. But weapon and armor materials technology did improve, so there's still the ability to manufacture alloy, composite, ceramic, kevlar, etc. materials. What would combat body armor consist of? I'm thinking riot gear type armor, but that wouldn't do well against cutting weapons like swords. Not sure on bolts and arrows. [Answer] Considering that there were very few weapon types, I believe we can reasonably protect against all of them. The gear would have to be something resistant to piercing and cuts (swords, spears, arrows) with a good amount of padding underneath to defeat mauls and other blunt weapons. This is a jack of all trades -version of such armor and should offer some protection from each weapon type. Let's say a protective outer layer made of layered kevlar or dyneema, with polyurethane coating. (This setup is common in cut-resistant items, such as gloves designed to protect from knife cuts.) Layer with cushioning materials underneath (and perhaps a couple of cushioning layers in the outer part as well), and you've got yourself a pretty solid set of protective clothing. As an added benefit, it should be fairly light compared to what was used in medieval combat. This armor is, however, still susceptible to fire and will not absorb all the energy from a very determined flail-swinging muscleman or a lancer, among other things. It will, however, provide decent protection in a melee, turning hits that would outright kill an unarmored person into mere bruises or relatively minor injuries. As an added defense against crossbow bolts or arrows one could add a removable ceramic plate to the front part of the armor, although this would add considerable weight. Edit: Another reply correctly pointed out that ceramic armor is designed to absorb the energy by breaking, making it only usable against a single or at best two or three hits. In this, however, the medieval armorsmiths had the right idea when they created scale mail. There have been concepts thrown around of a scale mail made out of ceramic armor, which could be a very decent solution against crossbow bolts and arrows. It would, however, add considerable weight, so the usefulness of such a design remains debatable and depends entirely on how thick the scales would have to be in order to be effective. [Answer] When it comes down to it...our modern armour is designed to stop modern weapons (almost exclusively guns). We sacrifice any other trait of armour to stop guns in particular...so when you look at modern armour, it actually fares pretty poorly vs medieval weaponry (I think the running theory is you shoot the guy with the sword before he gets to you). Kevlar holds together well and protects vs bullets by taking the impact and spreading across a larger surface area. Vs high speed low mass impacts such as bullets, this is decently effective. It would also stand up really well to a slashing attack. However vs high mass impact (a stabbing sword/knife or a cross bow bolt, or a spear for that matter), it doesn't fare so well. A modern version of chainmail would fair better in this domain. It certainly provides no protection vs blunt impact. Ceramic plates are actually designed to be one (possibly two) use vests...similiar idea as above, the impact from a bullet shatters the plate and spreads out the impact across a larger area. This works well vs a first hit (and I suspect it would fare decent vs a crossbow bolt) but since the plate shatters, it really isn't that effective vs multiple strikes. This isn't to say modern materials wouldn't make a far greater suit of armour though. Full plate isn't that effective vs the punching power of a gun, so we generally ignore this route in modern days...however if guns were not present, I'm pretty sure we can make a modern version of full plate that would stand up to any piercing, slashing, or blunt impact very well (blunt would be the most effective, but much padding can be put under this full plate to reduce the effectiveness of that). My guess is light and extremely strong metal half and full plate would start to dominate the battlefield. Just to add a chunk: Modern armour is designed as a one shot defence to save your life once so you can get out of there. Cost of material is second to the cost of the life. This is very opposite of medieval times where the sword is often more valuable than the troop wielding it. Medieval combat is often a grueling process with fights lasting for a much longer duration, so the armor must be semi durable and reusable after several hit. The requirements behind modern armour and medieval armour are vastly seperated [Answer] I'm not sure for long term durablity, but there are a few really strong engineered plastic like materials, about as strong as steel but really light. I think biggest improvements would be made in awarness. Some transparent metal or something as visor and radio's inside helmets. Mediaval armor already had pretty good mobility, so lighter, more comforable armor and awarness would be the key improvements. You would not tire as fast and you could actually see and hear clearly. I imagine you would maybe still want to keep steel plate in some high hit areas as it's just really damn effective and durable. [Answer] Meta materials New arrangements of long-used materials is a concept that is creating materials with very unusual properties. For example, there is a new arrangement of metal, I think it's called "microlattice" that is lighter than dandelion fluff, while metal foam made of ordinary steel and aluminum, arranged like a sponge, yields bullet-proof metal that is actually lighter than a solid chunk of aluminum of the same thickness. But we're looking for sword and mace proof, not bulletproof, right? Well, other answers have already pointed out that cutting (and piercing) is relatively easy to deal with, using high density polyurethane and similar materials. So that leaves blunt force. Here we turn to nature's ready made solution, the [club](https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hires/2016/mantisshrimp.png) (yes, it's really called a club) of the Mantis shrimp. It's microscopically interwoven material arrangement is VERY impact resistant. So we just weave the Polyeurethan/Kevlar/or similar material (or layers of materials) in this structure, maybe with a bonding agent, and viola, the outer shell would be strong enough that death from severe sloshing of the internal organs would be more likely than the armor breaking or deforming. [Answer] This is more of a side point, as the other answers covered armor materials quite well. My point is that any armor in this world should be fire-resistant, hermetically sealed and have an air supply or at least a gas mask. While these things sound like defenses against very modern weapons, one should consider that chemical and biological warefare are ancient. Greek fire (flamethrowers) was used by the Byzantine Empire, wells were poisened and disease was used in sieges. So the battlefields of your alternative history are quite possibly within flamethrower lit nerve gas fog, where infantry armed with all the weapons you mentioned is not trying to stab or crush the ememy to death, but simply tries to slice open their protective equipment, so nervegas or napalm can do their jobs. ]
[Question] [ Has a loose base in [this](https://worldbuilding.stackexchange.com/questions/11742/how-to-effectively-deliver-a-flu-virus-that-destroys-the-brains-ability-to-absor?rq=1) earlier question of mine, although today we will be working with modern (roughly) tech levels and bacteria. It was pointed out in the accepted answer that bacteria might be better at causing my desired symptoms because at large they are already developing resistance to many antibiotics. I have a story in which my characters find themselves returning from a camping trip to find society in the process of breaking down. Why is it breaking down? Well, it all started in an American biological weapons lab in Uganda... Background: A strain of antibiotics resistant Bubonic Plague discovered in a small village was being experimented with in an effort to make it deadlier. In short it worked, but the downside was that it was not very contagious and could be contained using standard quarantine procedures. It was designed to not only cause swollen lymph nodes but to also induce mild insanity that causes rage(think enraged schizophrenia). People infected have a two day incubation period, after which both the physical and physiological symptoms start to kick in. By the time the infected go terminal they are raging lunatics. To make things worse, a terrorist sleeper agent disguised as a lead scientist who miraculously cleared the 48 hour long screening added genes that make it airborne. He then managed to sneak it out and release it in the surrounding villages before his treachery was discovered and he was promptly shot. If you want, you can liken the infected to zombies (the worst kind: the kind that generally know how to use guns!). They do possess rudimentary communication skills and can (in theory, at least) coordinate ambushes and whatnot. Question: How would I go about designing a strain of Yersinia Pestis that achieves the desired effects in the background? I am interested in exactly how I could go about getting the bacteria to the brain and what they would have to do that could cause the mild insanity above. I am also interested in determining how plausible the scenario above is and patching it up to make it more realistic (so along with your critique I am open to suggestions). [Answer] A more likely disease that has the effects you desire is Toxoplasmosis. The parasite affects the brains of rodents, causing them to lose many of the defense reactions they have around predators. Once the vector is eaten, the disease then cries out the remainder of the life cycle in the host, eventually being shed into the environment through the feces of the host. The evolved/mutated/genetically engineered parasite would be have a similar life cycle to the natural version found in cats, possibly using commercial ranches or factory farms to find hosts and being consumed by humans in poorly processed or undercooked meat. If people in a food processing plant become infected, the quality control begins to suffer and more and more infected meat becomes available (and soon people who's ability to cook is affected are serving more infectious meals, spreading the cycle). For the effects you want, the Toxoplasmosis parasite is slowly consuming or poisoning the higher cognitive functions of the brain, affecting the ability to reason, make rational/moral choices and eroding functions like compassion and inhibitions (making infected persons rather dull witted sociopaths). How long they live before succumbing to the disease can be adjusted by various factors, but in general, the longer you are infected, the greater the loss of reason and other functions and the less ability the infected person has to survive. Probably a period of months for the decline to set in (and the infection to spread) followed by a few weeks of sociopathic behaviour and then a rapid decline. [Answer] My initial thought is you build a host cell for a virus or prion (like Kuru). Possibly a bacteria that can live in the mouth, and is generally benign. It is totally transmittable over the air and so simply breathing would spread the bacteria. On reaching adult form (which could take weeks), a biological process kicks in and the bacteria turns into a prion or virus factory. Nasty. All you need is the correct secondary disease to cause sustained insanity without killing the host human. [Answer] I'd skip the Y. pestis route, frankly. Instead, there's a much more interesting possibility: diphtheria. Diphtheria by itself is serious, but not particularly lethal, and it has the dual advantage of being naturally airborne, and producing a certain percentage of asymptomatic carriers. Where the story gets interesting is the result of infection by the Beta phage. This virus inserts a gene into the diphtheria bacillus which causes the bacillus to begin producing an extremely potent toxin, and this is what kills most diphtheria fatalities. So the development process would be two-fold. First, modify diphtheria enough that it no longer is controlled by diphtheria vaccine (call it pseudo-diphtheria), making it possible to spread in the population. If you can also modify it to increase the percentage of asymptomatic carriers, that's a big bonus. The other prong is the modification of the Beta phage to produce (obviously enough from a literary standpoint) the Omega phage. The Omega phage will induce the pseudo-diphtheria to produce a different kind of toxin. This toxin will selectively attack the aggression inhibition neurons in the hypothalamus (see <http://www.scientificamerican.com/article/sex-and-violence/?page=1>). Exactly how this will occur is left as an exercise for the writer. Oh, and I'd suggest that you rethink your 2-day incubation time. The longer the incubation, the better the chances of wide dissemination, as it muddies the epidemiological trail. With a short incubation it's easier to trace the spread of the illness, and easier to set up quarantine procedures. There's a tradeoff there - if the incubation time is too long, research on the first wave of maniacs will allow development of a vaccine before the spread becomes overwhelming. But I'd suggest that 2 days is too short. [Answer] I would think it would be reasonably easy to make a bacterial disease that mimics insanity. Simply insert a gene coded to produce a hallucinogen. Some hallucinogens are natural plant products, simply copy the gene out of the plant. The hard part will be identifying the gene you need. [Answer] Syphilis gets airborne and resistant to antibiotics. Fairly short incubation period and causes degradation of mental processes. Plus, embarrassing symptoms. [Answer] If you want a plague that causes insanity, all you have to do is aerosolize rabies. It already causes insanity, has a slow incubation time (measured in weeks, not days) and is 99.9999% lethal. The only saving grace is that it's a blood borne pathogen. Now, find some way to cross the symptoms of rabies with the spread pattern of measles and you have something truly terrifying. [Answer] Simplest answer I can think of: A bacteria that produces mercury in trace amounts as it destroys blood, spinal, and brain tissue. It could be engineered to only go after human dna so that it only affects humans. These trace amounts build up over time, and cause the bearer to go insane. The bacteria is resistant to all known forms of chemical destruction, but Radiation therapy would work. ]
[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/14135/edit). Closed 6 years ago. [Improve this question](/posts/14135/edit) So let's say that we never figure out how to purify silicon and germanium to the levels required to make transistors. This would readily happen in a technical culture that wanted clear and quick results from research projects. Bell was doing pretty basic research when it started. * What communication abilities would we have or not have? Radio? TV? * Would we invent analog computers? Or we just not have computing? * What technologies and sciences have been different? Would we have landed on the moon? Would we still study cryptography and computer science? * How would society be different? [Answer] You would probably want to refine your question before answering. The amount of handwavium you would have to expend is pretty intense. Consider that "semiconductor" is a pretty wide net. Wikipedia has a nice [list of semiconductor](http://en.wikipedia.org/wiki/List_of_semiconductor_materials)s. You'll probably miss some of these materials in your day to day life: * Silicon - this makes up 15% of the earth, and is pretty darn important for making sand (silicon dioxide). I expect beach vacations would be less enjoyable without this semiconducting material * Diamond - yep, sorry girls. Diamond is a semiconductor, with a bandgap of 5x that of silicon, and really nice chemical and thermal properties. We'll have to find something else to be forever on your ring. * Sulfur - So no one will miss this stinky compound, which is a semiconductor itself. However, if I may quote wikipedia's page on [Sulfur](http://en.wikipedia.org/wiki/Sulfur#Biological_role), " Sulfur is an essential component of all living cells. It is the seventh or eighth most abundant element in the human body by weight, being about as common as potassium, and a little more common than sodium or chlorine." Clearly life will be different without this compound So, lets back off and try a different approach. Let's handwave physics to no longer have these band gaps needed for semiconductors. Unfortunately, this will render the question rather unanswerable. When you start messing with the laws of physics, it gets hard to predict what will happen. It's hard to rewrite something like "how electrons work" without unintended side effects. The end result will be world which resembles ours in the same way the bottom corner of this picture of [a lemur](http://upload.wikimedia.org/wikipedia/commons/b/b5/Brown_Lemur_in_Andasibe.jpg) when played through a loudspeaker using QAM modulation resembles [this million dollar Ferarri](http://assets.nydailynews.com/polopoly_fs/1.1843291!/img/httpImage/image.jpg_gen/derivatives/article_970/ferrari-enzo.jpg)... which is to say, one does not resemble the other in the least. So lets take a different approach. Rather than try to wipe out semiconductors, what I think you're really trying to do is prevent us from building computers using them. This is a handwave activity. Perhaps we just don't like semiconductors, or maybe there's a religious edict against them. Maybe each semiconductor has a spirit, and we do not want to offend it. Anything goes. So let's see what we can answer: What communication abilities would we have or not have? Radio? TV? Radio would absolutely exist. Radio was quite a mature technology long before semiconductors came along. Vacuum tubes proved more than sufficient for radio. Television also predates the transistor (which I'm assuming is the interesting point in time for your search). So both of these could exist. Would we invent analog computers? Or we just not have computing? Digital computing is totally possible without semiconductors, and analog computing is totally possible with semiconductors (we do it in ASICs all the time). There would probably be more of a focus on special-purpose computing because we wouldn't have the horsepower to do much of the generic stuff we do today. Accordingly, I would expect to see more analog sides to things, because many of the interesting problems to solve involve analog components to them. What technologies and sciences have been different? Would we have landed on the moon? Would we still study cryptography and computer science? Almost certainly not. Landing on the moon was an amazing feat, even with transistors and core-memory. Trying to do that with the heavy weight of vacuum tubes... we just wouldn't have bothered. Cryptography would still exist, but it would be VERY different. Cryptography existed long before semiconductors took over, but the modern fascination with things like prime factorization and such would probably not occur. I would expect computer science would fade away, replaced with computer art. With more special purpose computers out there, managing them would be an art, not a science. How would society be different? Different. This is really too broad of a question. The whole fun bit about society is how unpredictable it is. Trying to rewrite 50-60+ years and predict exactly where it ends up is virtually impossible. Maybe there was no WWII. Maybe Germany won WWII. Maybe Steve Jobs planted an orchard. The futures are literally limitless. [Answer] You can do everything with valves or microrelays. But, without semiconductors you cannot do microprocessors. Miniaturization cannot take place so you wont see portable devices. You can integrate and miniaturize valves : ![miniature valve](https://i.stack.imgur.com/rbMSw.jpg) We cannot know how much more could thermionic valves be miniaturized or integrated. Transistors provided a easier path and that was followed instead. With this in mind you can build the following: * Digital and analog computers. * Radios and TV. * Limited cellphones (handheld radio transceivers) * Analog circuitry. Due to the lower reliability of valved circuits, you would not want to do: * Eletronic engine controls. (You can control a engine with a valved analog circuit, but valves are too much sensible to vibration) * Too complex life support systems. You cannot do : * Smartphones. * Personal computers. * MPEG or other digial algorithmm compression. So no digital TVs. * Anything that depends on miniaturization. * EDIT - Decided to edit my post because of a lot of answers with wrong ideas being posted: You can do computers with vacuum tubes (called valves in UK). The computers can be quite complex. The only difference between a modern computer and a computer made with vacuum tubes is scale. Transistors are made today on nanometer scale while the smallest valve could be made at milimeter scale. This means a lot of things. 1 - The less integration increases path delays amont units. This means that there will be a upper limit on the maximum speed of the computer. And this limit will be much smaller than the limit imposed on current silicon-on-sapphire designs. Integration means that all devices that compose a microprocessor are micrometers away at most. 2 - The use of a heat source to make thermionic emission possible means that valves have a much larger thermal footprint than semiconductors. This means that large designs will present a thermal management challenge. 3 - They use a lot more power than semiconductors. This means that computers will tend to be centralized and used as a kind of utility, just like your phone, your water and your eletricity. What you would have at your home would be probably a dumb terminal made out of simple valved circuits. Multitasking at the central computer means that a lot of people can and do stay connected at the same time. Maybe the generally smaller bandwidth disponible will preclude the development of graphical applications. Etc. In other words, computers will gravitate mainframe era designs. About modems, yes, you can do modems with vacuum tubes. What must be understood about vacuum tubes is that they have the behaviour of a cmos transistor. BUT, they operate at higher voltages and their size is much bigger than the usual CMOS transistor. This means that anything that can be done with CMOS transmistors might be possible using vacuum tubes, minus the miniaturization. You can do ASK/FSK/PSK modems with vacuum tubes. You can do analog to digital converters. etc. You can do precision guidance systems. For one, the missiles and radar on the MiG-25 (and other aircraft of the era) where fully vacuum tube based. Guiding a missile across a radar beam is precision guidance (just not fire and forget, but its not all that hard to build radar homing active guidance missiles with vacuum tubes). About TV. Analog color tv is designed around backward compatibility with analog BW tv. This placed certain constraints on the signal quality. Color information is carried in a phase modulation embedded into the luminance signal of the original BW tv. This means that a limited bandwidth was divided between two signals. Luminance gets most of the bandwidth. But, provided that there was no transistors disponible and people wanted a higher resolution TV standard, you can increase resolution by increasing the bandwidth disponible. This means that the usually 6mhz color tv channels used in analog NTSC tv might be enlarged to 12mhz or more to include a separated color carrier. This alone can increase the perceived resolution of color tvs. Thats not impossible, it was not economical at the time the color tv standards where created. Regarding satellites, most satellites are operated as dumb repeaters. Eletronics inside the satellites are at premium. Space is constrained by thermal management needs and the general cost of launch that is proportional to weight. Being at 300km above ground or more means that repair on-site is impossible or quite costly (see hubble space telescope). This means that eletronics inside the satellites are bare, just enough to repeat signals. You can include beamforming systems on the sats to increase the bandwidth disponible by employing spatial multiplexing, and the algorithmns involved in such beamforming might very well be beyong vacuum tube capabilities, but, non-beamforming sats can be and are still usefull. So, miniaturized valves or not, you can still build satellites. A side not is about a computer capable of guiding the apollo missions. Yes, it can be done. Usually if you cannot treat some problem digitally you can do it in a analog computer. So, provided that you can miniaturize valves to 30mm scale, you can very well build a small computer capable of integrating speeds and other variables needed to space travel. You can beam a couple of tight radio wave beams towards the moon, you can do WW2 era navigation with radio navigation aids. You might be surprised what can be achieved with vacuum tube technology. You might be interested in the battle of beams wich ocurred in WW2. Collossus and other computers of the time might provide a hint how computers would evolve if vacuum tubes where the only option. [Answer] Technological development would be delayed by some amount. How much exactly is hard to predict. Alternative methods would be discovered. Miniaturized vacuum tubes would be the first development, perhaps followed by vacuum tube integrated circuits. Eventually we would discover a way to make transistor-like devices without semiconductors. For example [carbon nanotubes can be used](http://www.mtu.edu/news/stories/2013/june/beyond-silicon-transistors-without-semiconductors.html) and [optical transistors](http://physics.aps.org/articles/v7/80) are in development also. [Answer] You might end up miniturizing vacuum tubes to the size of grains of sand. That might evolve into technology for switches that is not "vacuum" but still based on ballistic electrons or non-linear media that's not the way semiconductors work. Classic ionization, Hall effect, magnetic beads re-configuring conductive pathways... Semiconductors allow us to work on the scale of atoms, limited by the S/N of quantum effects. The other things would not be as small in scale, but still orders of magnitude smaller and more reliable than old vacuum tubes. Core memory does not depend on semiconductors, and I've seen a module that contained rows of tubes in addition to the screens of ferrite cores. A small number of tubes for signal amplification and simple logic gates, but a few dozen tubes service thousands of cores. What if the cores were wired in a fancier way to implement the logic, like a cellular automata (later: I’ve seen this on youtube! Core logic actually predates its use as memory!)? Point is, other tech could evolve to do computation that still uses just a few tubes for support. [Answer] Radio, TV and microwave radar were all developed and implemented with vacuum tubes before transistors. So we would definitely have these things. Eliminating semiconductors would remove a very powerful economic driving force from electronics development: Moore's Law <https://www.cs.utexas.edu/~fussell/courses/cs352h/papers/moore.pdf> Gordon Moore was a physical chemist who was working as a process engineer. His paper pointed out that it was possible to "build" transistors on a wafer that were half as wide. This translates into four times as many transistors in a square area. He also said that this kind of process improvement could be repeated with a doubling every two years. He later amended this to 36 months. But the fact remains that there has never been any previous endeavor in human history where there was an equivalent 50 year stretch of performance improvement. There is no possible way that physical effects like vacuum tubes could deliver the lowered costs and improved performance that cooking from the quantum mechanical solid state physics cookbook did. So likely, we would still be in many respects, about as technically saavy as we were at the close of the Korean War. And doubtless no internet, as there would not have been the developments that made DARPA net transition to ARPA net and then the internet without solid state. [Answer] The phone system would have stayed analogue and no communication satellites would exist, so intercontinental communication would be limited to cables. So instead of millions of transatlantic "phone lines" you would be stuck at thousands. Say goodbye to globalisation. Forget about modems, so there's no way to get computers to communicate over distance. Since without small computers ballistic missiles would be not very precise (think V-2), you would probably have no ballistic missile submarines (they need a very good position fix to be somehow precise and forget about inertial navigation system using tubes) and few city-killer ballistic rockets, so your primary delivery system for nuclear weapons would be planes (B-52 without the better avionics). Also you have no good early warning systems (no satellites and no [SAGE](https://en.wikipedia.org/wiki/Semi-Automatic_Ground_Environment) computer, although you could probably get a better [Whirlwind](https://en.wikipedia.org/wiki/Whirlwind_I)). This probably gives you a quite different cold war. ]
[Question] [ Suppose that I have a fantasy kingdom, built on a magical land, and the thing is that horses are so cheap and plentiful in that land, even the poorest peasant would have at least a horse to their name. The horses also do not require any special care or housing, they can sleep on the ground and be as healthy or healthier than one cared for in a stable of a less magical place. What would the required special magical effects that would be upon the land, to support this many horses. In real life, horses are not cheap as they would need housing, grazing feeding and the like? I would like it if horses could be very common, and plenty of them too, all of them just running about. The land must also need to support a sizable human population. So to clarify the points of the question, what sort of land is needed to support many horses, supposing the land is a magic fantasy land. Notes to note about the setting: * Late Medieval tech levels * Low powered magic is very common and cheap, high powered magic is very rare and expensive. * Feudalism politics * This kingdom is under an Empire which encompasses all civilized life * Many people of [various races](https://worldbuilding.stackexchange.com/questions/9968/how-to-promote-nationalism-for-a-multi-racial-kingdom-against-other-such-multi) and [various sizes](https://worldbuilding.stackexchange.com/questions/9507/what-should-architecture-of-an-imperial-capital-be-like-in-order-to-accommodate) exist in the setting, all of them full members of society, and very well in cohabitation with one another. ADDITIONAL NOTES 1: * A sizable population would be about 1 million people, it is an entire kingdom. * Low powered magic would be getting teapots to float about and serve tea to people, up to about lifting house cats. High powered magic would be creating portals from solid walls to train platforms, and hiding entire buildings between buildings, to put in a Harry Potter-y sense Some links to other questions also on this topic, but would be too broad to fit in one question: [Horses for Absolutely Everybody, peasant lifestyle.](https://worldbuilding.stackexchange.com/questions/10220/horses-for-absolutely-everybody-peasant-lifestyle) [Horses for Absolutely Everybody, warfare.](https://worldbuilding.stackexchange.com/questions/10221/horses-for-absolutely-everybody-warfare) [Answer] Horses are creatures of steppe and plain, they don't really need any housing and they don't need good quality grazing- if anything rough grass is far better for their digestion. Most of what they want is to be able to live sociably with other horses and not to get eaten by predators. You don't really need a lot of protection for them, just plenty of room to roam and humans with a decent understanding of horses, which would be likely to develop in this type of culture. The effect this has on a society may be quite interesting as they are liable to become very horse-oriented in their outlook and lifestyle. This is [not without historical precedent](http://en.wikipedia.org/wiki/Mongol_Empire) - indeed there have been many cultures that took this approach, most of them originally nomadic peoples and many of them having, in their times, proved devastatingly militarily successful. The reason for the nomadic lifestyle is partly that it reflects how horses live naturally which is a consequence of the need for food- horses may need a bulk of rough grass, but they will also graze land down over time and naturally move on, so most horse-herding people simply move with them. Often this means a migration to the higher pastures in summer as the grass grows sweeter there and back into the lower lands in the autumn. If you were working with a more sedentary culture you would need to produce a lot of hay in summer to keep horses fed in winter. You might also run into problems with the ground getting very churned up around settlements/areas where horses resided most of the year and problems with parasite burden on the horses. [Answer] Please keep in mind when you want plentiful horses everywhere that horses produce from 15-35 pounds of manure a day, and having horses so common even beggars could ride would be an ecological disaster, as we found out ourselves in the late 1800s (in large US cities). You might want to consider your magical methods of having horses around include doing something about their tremendous ability to recycle grass into manure. Also see [this link](http://fee.org/freeman/detail/the-great-horse-manure-crisis-of-1894) for more information. [Answer] Horses cost a lot in a densely populated area because farmers need to cultivate the land to feed themselves and they might have some animals too. They can have livestock but meat is a small part of their diet compared to the average American today. They simply don't have enough space and growing grass would be considered a waste of space if they can grow more productive crops like wheat, rice, soy. and so on. On a low population area like the central steppes of Asia, horse can become very cheap. There is a lot of space and it is often too dry to practice agriculture unless it's close to a river (there it's possible to farm with the help of irrigation). Nomads from the steppes all have a mount because they are always on the move. They might also have multiple mounts because Mongols had up to 5 mounts each when they were in campaign. The only way for a large Empire like China (just an example) to have a lot of horses is either to keep control over the vast steppes around the Empire or they need to sacrifice high productive land to grow grass. They could probably give something else to feed the horses but I don't know their exact diet. Still, you are feeding horses instead of feeding people. [Answer] The main costs of a horse in real worlds is the food cost, and breaking and training the wild horse to obey the owner, and the cost of land for the horse to run around on and exercise. Having horses underfoot wouldn't allow anyone to "own" or "use" one at need unless these are provided "free" somehow or are magically unneeded. ]
[Question] [ Before the development of states, kingdoms, and empires, all humans were confederated into tribes. Since then, of course, things have changed. Many tribal groups banded together defined their own boundaries, and formed into states and nations. My first thought as to why this sort of thing happened was that it was based on agriculture. Babylon and Mesopotamia rose up out of agricultural societies, after all. I'm not sure this is a good explanation though, since it seems like there are cultures that practiced agriculture but did not form such states, like the native North Americans, and also nomads who founded empires, like the Mongols. In general, what drives a stateless, tribal society to from into larger kingdoms? [Answer] This is a great question, with serious applicability for worldbuilding at large. Lots of useful answers so far. I've got one, if I can express it well enough, that goes down to some very basic questions about human ecology. First though, lets get some terminology down: "Tribe", according to the general definition in [the Wikipedia article](http://en.wikipedia.org/wiki/Tribe) means: > > "A tribe is viewed, historically or developmentally, as a social group existing before the development of, or outside of, states. Many people used the term "tribal society" to refer to societies organized largely on the basis of social, especially familial, descent groups (see clan and kinship). A customary tribe in these terms is a face-to-face community, relatively bound by kinship relations, reciprocal exchange, and strong ties to place." > > > In other words, we can use "Tribe" to mean either * a pre-state form of political organization (for fairly small values of "state"), or * a group of people whose primary political association is based on face-to-face acquaintance and/or kinship. This seems to match the original question's intent. ### pre-"state" human bands There are basically three kinds of associations in history that predate states and that rely on intuitive, rather than explicit, theories of political legitimacy. These three types of community are fundamentally distinguished by their ecological characteristics. They are: * Hunter-gatherer bands: Small, generally migratory groups, usually using [paleolithic](http://en.wikipedia.org/wiki/Paleolithic) technologies. This is the human [ur-state](http://en.wiktionary.org/wiki/ur-): it was the main form of human existence for most of our time on the planet. The hunter-gatherer life is so old that we evolved, biologically speaking, to fit its norms, and haven't evolved past it. Everything since has happened far too recently in evolutionary time. We are still fundamentally hunter-gatherers in terms of our hard-wired reflexes and mental organization... which is possibly why we hate our day jobs so much. ;-) * Early agricultural societies: The beginnings of agriculture probably inherited the migratory patterns of hunter-gatherer tribes. From the initial observations that seeds sown in previous wanderings would sprout as new plants, up into the [slash-and-burn](http://en.wikipedia.org/wiki/Slash-and-burn) techniques enabled by [neolithic](http://en.wikipedia.org/wiki/Neolithic) tools that were tough enough to chop trees, moving on from one place to another was a common mode of agriculture. However, eventually the early agriculturalists worked out ways of staying in one place, which had incredible advantages (grain bins, clay pottery) and also severe downsides (disease due to humans and animals huddling together and no longer moving away from their excrement and refuse.) Still, in terms of [Liebig's Law of the Minimum](http://en.wikipedia.org/wiki/Liebig%27s_law_of_the_minimum), the agriculturalist had developed ways of generating food surpluses never possible for the hunter-gatherers. The march of civilization had begun. * Pastoral nomads: Unlike the plant-eating agriculturalists who had to eventually settle down in order to take best advantage of their improved food source, [pastoralists](http://en.wikipedia.org/wiki/Pastoralism) turned to a diet of animal food. They evolved a way of life that generally remained mobile, driving herds or flocks of grazing beasts to new areas of pasture. [Note: I got most of the foregoing from [The Rise of the West](http://en.wikipedia.org/wiki/The_Rise_of_the_West), by William H. McNeill; originally published in 1963, it's still in print and not freely available online. FWIW, I'd recommend it as a resource for any worldbuilder interested in the processes of prehistoric and historical development of human communities.] ### Civilization emerging from the conflict between agricultural and pastoral ways of life In late prehistoric and early historic times, we see a three-way struggle for supremacy between these three human ecologies. The hunter-gatherers got shouldered aside pretty early. They were, in general, too close to the margin of survival to compete effectively. Those who weren't absorbed into agricultural populations were generally pushed into more remote or forbidding areas: forest or desert mostly, or the icy lands of the north. The hunter-gatherers could live in these areas because hunting and gathering are pretty sustainable if given time to adapt. Nobody else wanted those places. Neither nomads nor agriculturalists could grow food very well in those places. The retreat or vanishing of the hunter-gatherer people cleared the decks for a rather dramatic, millennia-long struggle between agriculture and pastoralism. Pastoralists tended to be militarily far more formidable, because keeping predators away from the herds meant that courage and violent skills were desirable characteristics. Also, once they learned to ride horses, their mobility and cavalry tactics tended to present a formidable challenge to the settlements of agricultural people. Consider this brief list of fairly famous pastoral nomad tribal names: Scythians, Sarmatians, Parthians, Huns, Alans, Avars, Bedouin, Mongols, Seljuks, Ottomans, Tuareg, Tatars, Comanche, Sioux, Cheyenne, Kiowa... There's thunder in that list. These are names (often, of course, not names that the people themselves would have recognized) that we remember as fierce, resourceful, indomitable fighters. The increasingly large settlements of agriculturalists, on the other hand, were at a disadvantage. Not only were they less martial by cultural training (farmers with brawling, violent temperaments are less efficient at sowing and harvesting, and cost the community more in incidental damage), they had a lot of good stuff to loot. Stuff that nomads hadn't learned to make, or couldn't make or grow. Thus came the great aggregations. Smaller agricultural villages were too vulnerable, once the nomads appeared on the scene. So they began to grow, and build fortifications, doubling down and to make arrangements for mutual defense. Faced with these hardened targets, the nomads also developed larger bands, but they seldom had the staying power of the settlements of civilization. The nomads created mechanisms of joint war parties, ad hoc expeditions whose goal was to plunder a foe too large for any single nomad tribe to take on. These eventually tended to develop into habitual associations: confederacies of nomad people who sometimes didn't even have much of a common language. Yes, there were the grand imperial ventures of Attila and Genghis Khan and Tamerlane. However, the Pax Mongolica only lasted some two hundred years, and Genghis's empire was, although vast, too closely tied to his own formidable persona. It was, in a sense, just an incredibly large instance of a "tribe", with Genghis as the titular Father figure: an ancestor that bound his polyglot empire together. The concepts of political legitimacy that the agricultural peoples haltingly pieced together over centuries never found a very comfortable home in the wild hearts of the horse people. So, the original question: > > What determines whether or not tribes will form into larger groups? > > > Has this basic answer: The hunter-gatherer peoples really seldom could. The agriculturalists and pastoralists displaced the hunter-gatherers in any lands they wished to take. The pastoralists, even as they responded to the increasing size of agricultural opponents by increasing their own political groups into confederacies and Hordes, remained tribal at heart. [Answer] Math and Technology Ok. First, the Math. As the area you control grows, you get a better border-to-interior ratio: ![Border Vs. Interior](https://i.stack.imgur.com/pxIxY.png) This is because your border size scales linearly (the red line) but the interior grows with the square of your average width/length (the blue line). So the bigger you are, the easier it is to defend your territory compared to the resources you control. Now obviously not all polities are squares (actually I'm not sure any polities are perfect squares), but geographical features act as "free" border - they increase your ratio by either reducing the resources you need to secure it, or limiting your enemies to only attack certain areas (mountain passes, natural gulfs or bays, etc). So, bigger area = less proportional resources needed for defense. This frees up your workforce to do other things, like agriculture, pottery, or blacksmithing. Good geography gives you a boost, so you can get some of the benefits in a smaller polity. Second is Technology. This is obviously very broad, but let's break it down into a few key areas: 1. Population (agriculture, medicine) - these are technologies that let you either grow your population, keep more of your population alive, or free up a larger percent of your population to do non-essential things. 2. Infrastructure (roads, canals, communication, bureaucracy) - obviously as your polity gets bigger, it gets harder to move supplies around and control things. These technologies let you move stuff around better, send marching orders or organize the larger and larger armies you're running with. 3. Military (weapons + everything under infrastructure) - a more effective military lets you defend better, meaning you can cut down and use more people for non-essentials, or you can expand with your current military. Feedback Loop The real key is what happens when all the above combines. When you get a larger polity, you can defend it easier. This frees up some of your population for other tasks, which eventually leads to be better technology, improving your overall efficiency. Now you have the capability of expanding against your less-efficient neighbors (either through politics, economics or warfare). Now you're bigger, go back to step 1 and repeat. Obviously there are a lot of places in this process where you can mess up and your empire fractures, or you run into someone else ahead of you on the curve and they take you over. But the basic feedback loop is the driver of early polity growth. [Answer] There is a wide array of reasons, but I'll focus on one of the major ones I see. In many cases, it's a single persons ambition (I should add "ambition plus luck") * Greece under Alexander. The Greeks found their one person to follow and united under him. Following his demise, the fight for leadership was fragmented and nobody could fill what he was * Mongols under Khan. It was his personal ambition that led to him conquering nearby tribes and eventually carving out the largest empire known on Earth * Babylon under hammurabi. Babylon was a small city state, hammurabi forced it into the spotlight and through war became the major power. * Huns under Attila. He uprooted his entire people and marched them across Europe...takes some personal ambition and ability to inspire to pull that off. Not quite sure if there was ever a 'kingdom' here, but same idea...a people united under one leader. add: * Rome under Caesar. It's debatable if this tribe united to kingdom...but roman prior to Caesar was a senate with ruling families. It was Caesar's ambition that united it all into one Roman Empire. There are several examples of Vikings and their leaders carving out kingdoms for their own. For the most case, tribes (and city states) are loyal to a single person...with no abstract concept of nationality or king or country, the loyalty is to that single person (or perhaps dynasty of people). That single persons ambition often drives the mve to kingdom. THe other side gets into common defense...agriculture becomes a big thing simply because you now have a stable population of decent size that can remain in one area. This leads to buildings and wealth and eventually an economy...you suddenly have something you don't want to lose. But even then, it's usually a single leader that goes about uniting several like cities into a nation/kingdom. I think a quote from the civilization series...A multitude of leaders is a bad thing, let there be one ruler, one king. How ambitious that one ruler is in becoming King tends to be the driver behind the formation of kingdoms. [Answer] I think generally it's a form of self preservation. The larger your 'group' is the better you can defend what is yours from those who would want to take if from you. If you are the biggest group in the neighborhood, then you can even go on the offensive and be the one taking from others. One of the reasons agriculture seems to make this more obvious is two things. One: plants are stuck in one location and thus need to keep others away from a known location. The farther the boundaries the harder it is to raid what's in the middle. Two: agriculture more easily allows for larger populations to be fed. Larger populations means more people available to defend what is ours or take what is theirs. Being a social animal also helps encourage the group dynamics. [Answer] 1. Tribes becoming sedentary Agriculture can be attractive for the nomads and for several reasons. Life on the plains is rough. Not only do you need to protect your livestock, but you're also vulnerable to attack from other tribes. Plus let's not forget that Mother Nature can be quite unpleasant. Agriculture gives a more reliable source of food and can be stocked for a long time if needed. Sedentary life is also usually considered less demanding for the body. I know this is not really true for the first cultivators. It took some time before finding the right way to farm efficiently. But eventually, agricultural societies prospered and became rich. There was a fascination about these societies in most tribes. A lot of tribes in Asia tried to emulate the Chinese in different ways. Not all decided to settle because of this, but some ended up as farmers. 2. Tribes uniting other tribes and staying nomad. The first point mentioned an issue about food security. Uniting the other tribes can also provide more physical security. Multiple tribes can be in competition and might attack each other. Tribal groups are considered a threat in most agricultural societies, but also for the nomads among themselves. They all want the best horses and the best land with the best grass. Some people are just ambitious and will try to dominate others because they love power. I think the most important motivator for uniting the land is to assure our own tribe security. But I need to add that a charismatic and ambitious leader if often the catalyst. 3. Finding the middle ground. It's not really related but the Liao dynasty, during the Song dynasty, invented an hybrid system. They managed to keep an Empire with a strong nomadic heritage while integrating the sedentary Chinese of northern China. It was always a constant fight to decide whether they would go one way or the other. The Khitan managed to keep the balance until they got invaded by another nomadic tribe. [Answer] Groups form when they are more resilient or more enjoyable than being on their own. Survival on your own is hard. You spend most of your resources on survival. Aggregating groups cuts down on duplication, so you free up more resources to work with. Consider that each tribe needs a shaman whose entire life is dedicated to the art. However, if tribes merge, eventually they can decrease their needs from one shaman each to one shaman between them all. That makes larger groups more resilient. However, there is another side: when you merge groups, you have to make compromises. Your particular way of sowing the field, naked as can be, may have been effective on your own, but your new found friends don't appreciate the \ahem\ scenery. You have to find a new way to sow the field -- most likely clothed. As long as the benefits outweigh the costs, groups will eventually merge together (or at least ally). As a detail, the human mind appears to be structured to handle several particular sizes very well. Each group feels a little more alien than the last. These sizes show up in countless cultures, over structures both social and military: * 5 people - clique. Usually the size of the group of people you would rely on in extreme emotional stress * 15 people - sympathy group. Usually this is the size of group you have emotional ties to * 50 people - camp group. Hunter/gatherer tribe overnight camps tended to be in this size, drawn from a group of 150 people which are.... * 150 people - coworkers. Anything larger than this, and we tend to stop associating personalities to the individuals. Instead of knowing Alice and Bob in accounting, we know "the acounting people." * 750 people - Megaband * 1500 people - Tribe. It is believed this is the maximum number of faces the human brain can recognize. [Answer] There are mechanisms that favour the apparition of nations, and other mechanis that favour its disgregation: Three mechanisms that favour the apparition: * Growth: A successful tribe that has enough food supply and controls external enemies just grows to become a nation. Examples would be old Mesopotamian cities, kingdoms of Old Egypt. * Common interests: A group of agricultural tribes may organize themselves for defense against raiders, trade, etc. If the common interest lasts long enough that common institutions are stablished, they may become more important than local institutions. And example could have been early Roma. * Conquest: The more spectacular when you see it in the maps, but the less likely to stay if it is not backed by some other structures (religion in the Caliphate $^1$, law & civilization & trade in the Roman Empire). Submitted peoples are bound to revolt, and once the imperial power is in trouble due to internal infight or a successful revolt, all of the territories would launch their own rebellion. Examples would be Mongol Empire, Assirian Empire. As for mechanisms agains the apparition of nations: * Supply: if your tribe grows but there is not enough food, there will be internal infighting or emigration until the numbers are reduced again. And in time of crisis, a part of a country may think that supporting the common effort is not worth the resources spent in it (it is one of the causes of nationalism being stronger in the richer regions). * Local loyalties: Local elites may be tempted to gain power by becoming independent. In some cases, it may be even the representatives of the central power who begin the separatist struggle. * Regionalims: The local people does not see themselves represented in the State, either by political discrimination (v.g. Thirteen colonies) or by being culturally different (v.g. Ulster, Quebec). This would often get feedback with the previous point. In all of the cases, I see technology as a factor improving the apparition of states (by improving wealth, communications and trade) $^1$ Even in the case of the Muslims, the first caliphate lasted only thirty years until the first civil war, and the second one less than 90 years. After that, a caliphate remained, but with many of their former territories independent. ]
[Question] [ Picture a planet identical to Earth, but with rings. It has a satellite similar to the moon, except smaller; I'm not sure how big it needs to be but distance from the planet is more important so assume that it is whatever size it needs to be to have the same effect on the planet as the moon does for earth at whatever distance it lands at. The key attribute of this satellite is that it orbits the planet along its equator (parallel to the rings, of course) at an extremely low range so that it appears from the planet's surface to be skimming along the edge of the rings. Is this scientifically possible, however unlikely, and even if not what effects would the close proximity of a moonlike satellite to a planets rings have on the surface of the planet (climate, sunlight reflection/blockage, etc.), the rings (like, would the gravity of the moon pull on the rings and skew them somehow or something?), and the moon itself (like the gravity of the planet causing it to flatten out as it rotates)? Oh. Also it all has to be stable enough for life to begin and mature unaided on the planet with little to no change in the orbital system. Edit: It would appear that this scenario is generally accepted as possible (though unlikely, but that's pretty much irrelevant when you look at the likelihood of a planet that supports intelligent life in general), so that satisfies the first part of the question. However I still feel like a shepherd moon that's big enough to act like our own in terms of gravity would still have some unusual effects on rings that are much closer to the moon and smaller than the planet itself. Am I just paranoid, or does that make sense? [Answer] The problem here isn't really about whether or not a moon could "skim" a ring, but whether or not rings could form around Earth. There are three ways [planetary rings](http://en.wikipedia.org/wiki/Planetary_ring) can form. All three involve material coming inside the [Roche limit](http://en.wikipedia.org/wiki/Roche_limit) of the planet. The [rings of Saturn](http://en.wikipedia.org/wiki/Rings_of_Saturn#Physical_characteristics) have a mass of about $3 \times 10^{19} \text{ kilograms}$, one one-thousandth the mass of Earth's [Moon](http://en.wikipedia.org/wiki/Moon). The formula for the Roche limit shows that [the Moon is 41 times](http://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_examples) as far from the Earth as its Roche limit is, and a less-massive body of the same density would have a smaller Roche limit, so if this object was the same density as the Moon, it would have to have gone really close to Earth. At any rate, the Moon would be too far away from the ring system. Anyway, here's how rings can form, and why they might not around Earth: 1. Accretion from the [protoplanetary disk](http://en.wikipedia.org/wiki/Protoplanetary_disk). This is simple. Matter from the solar system's protoplanetary disk ventures inside the Earth's Roche limit, gets torn apart, and becomes a ring. I don't think this would happen on Earth because Earth is not massive and never has been, and so would not pull a lot of material towards it. Sure, it could get the required one one-thousandth Moon mass, but would it come close enough to form a ring? 2. A moon gets hit hard. Collisions happen, and they happened frequently in the early solar system. After all, that's [how Earth got its Moon](http://en.wikipedia.org/wiki/Giant_impact_hypothesis). If a moon got hit hard enough that debris was flung into space and somehow got inside Earth's Roche limit, it could turn into a ring. However, this would necessitate a second moon-like object (or protoplanet) being near Earth at some point in time. It's likely that it would still be here today - after all, only a tiny bit of mass would have been lost. True, an asteroid could have been smashed, but what are the odds Earth would have gotten the debris? 3. A moon gets ripped apart by tidal forces. This is the most commonly-cited explanation for ring formation. However, it requires a moon to go pretty close to Earth, as we can see from the Earth's Roche lobe with respect to the Moon. Likely? Perhaps not, considering that Earth's gravity was relatively weak in the early solar system, compared to the gas giants. I doubt rings could form around a planet like Earth. Let's say rings do form. Could our Moon skim them? Well, remember that they would be near Earth's Roche limit - 1/41 the distance to our Moon! True, the Moon is receding, but it probably never was even close to being that close to Earth. If it was close enough, it would be torn apart by tidal forces. Shepherd moons (as Twelfth helpfully brought up) are exceptions, but they are small, and could be fragments of a larger moon that was torn apart, or broke apart in a collision. Okay, let's go to the Moon as a [shepherd moon](http://en.wikipedia.org/wiki/Planetary_ring#Overview). The reason that I assumed that the Moon could not be a shepherd moon is because of the mass discrepancy. Here's what I'm talking about: * Mass of the Moon: $7.3477×10^{22}~\rm kg$ Some shepherd moons: * [Metis](http://en.wikipedia.org/wiki/Metis_(moon)): $3.6×10^{16}~\rm kg$ * [Adrastea](http://en.wikipedia.org/wiki/Adrastea_(moon)): $2×10^{15}~\rm kg$ * [Cordelia](http://en.wikipedia.org/wiki/Cordelia_(moon)): $4.4×10^{16}~\rm kg$ * [Ophelia](http://en.wikipedia.org/wiki/Ophelia_(moon)): $5.3×10^{16}~\rm kg$ * [Galatea](http://en.wikipedia.org/wiki/Galatea_(moon)): ($2.12 ± 0.08) ×10^{18}~\rm kg$ * [Mimas](http://en.wikipedia.org/wiki/Mimas_(moon)): $(3.7493±0.0031)×10^{19}~\rm kg$ * [Thebe](http://en.wikipedia.org/wiki/Thebe_(moon)): $4.3×10^{17}~\rm kg$ * [Prometheus](http://en.wikipedia.org/wiki/Prometheus_(moon)): $(1.595±0.015)×10^{17}~\rm kg$ * [Pandora](http://en.wikipedia.org/wiki/Pandora_(moon)): $(1.371±0.019)×10^{17}~\rm kg$ * [Amalthea](http://en.wikipedia.org/wiki/Amalthea_(moon)): $(2.08±0.15)×10^{18}~\rm kg$ * [Despina](http://en.wikipedia.org/wiki/Despina_(moon)): $2.2×10^{18}~\rm kg$ There are almost certainly many more. The point is, these moons are tiny. They have no chance of drastically perturbing the rings because their absence from a portion of the ring has no negative effect. The Moon, though, is much larger, and will greatly perturb all objects in its vicinity. So what if (and this is a $\Huge BIG$ if, and I see I've found an interesting feature in $\LaTeX$) the Moon is close to the rings? Then the outcome tends to be that the ringed Earth gets another ring. The constituents of [planetary rings](http://en.wikipedia.org/wiki/Planetary_ring) (no, they aren't continuous, although that would be awesome) can greatly vary in size. From Wikipedia: > > The composition of ring particles varies; they may be silicate or icy dust. Larger rocks and boulders may also be present, and in 2007 tidal effects from eight 'moonlets' only a few hundred meters across were detected within Saturn's rings. > > > So we're looking at objects ranging from a few microns in diameter to a few football fields in diameter (and it doesn't matter which side of the Atlantic you're on) - although most of these objects probably aren't big enough to pull themselves into spheres. The Moon, by contrast, is about 3500 kilometers in diameter. It will clearly be the most dominant object in the area. Look at this unfortunately compressed image of Saturn's rings: [![Unfortunately compressed image of Saturn's rings](https://upload.wikimedia.org/wikipedia/commons/b/b1/Saturn%27s_rings_dark_side_mosaic.jpg)](https://upload.wikimedia.org/wikipedia/commons/b/b1/Saturn%27s_rings_dark_side_mosaic.jpg) Image in the public domain. The zoom on the link is really bad, but [this](http://en.wikipedia.org/wiki/Rings_of_Saturn#mediaviewer/File:Saturn%27s_rings_dark_side_mosaic.jpg) is a good compromise. Long story short, the Moon is big enough to fit through some of Saturn's [rings and nearly all of the gaps](http://en.wikipedia.org/wiki/Rings_of_Saturn#Major_subdivisions_of_the_rings). [Answer] A little late, but no one has asked what seems to be an obvious question: If you're looking at moon & rings from the planet's surface, why does it matter how close to the rings the moon is? If the orbits are in the same plane, then (depending on the planet's diameter and how close to the equator you are, shouldn't it look as though the moon is either skimming the ring, or being bisected it? Even if in reality the moon orbits far beyond the ring? Somewhat like these images Cassini captured, either looking like [this](http://www.universetoday.com/83804/saturns-rings-moons-line-up-in-latest-stunning-cassini-image/) or [this](http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20120829.html). ]
[Question] [ # My [organolithium environment](https://worldbuilding.stackexchange.com/questions/160337/life-supporting-climate-for-an-organolithium-planetary-environment) planet needs to be chemically stabilized But I don't know which compounds could physically evolve on a planet to form an atmosphere and seas wherein humans would spontaneously detonate. The working title for the story is The Amazing Bob Burns. The basic parameters needed for the story to work are: * It is a planet formed by natural (or theorized) forces * It has a liquid layer (seas) and a gas layer (atmosphere) * The seas and atmosphere can co-exist with the correct pressure/temperature/climate combination, which is not artificial * People blow up * Would be nice to have abundant trifluorogold and Gold pentafluoride salts in the land (or at least accessible to the upper crust) This isn't asking for [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") but I want to build it with the absolute lowest dosage of hand-wavium I can get away with. So, you're welcome to put just a little $\ ^{42.3} \_{97.6} \text{Fu}^\pm $ Fudgium into the mix. Otherwise, shoot for a [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") solution. --- By blow up, I mean at a minimum, they burst into violent flames such as would happen in a bath of chlorine trifluoride. [Answer] At temperatures and solvent environments in which organolithium compounds will be stable, there are no gaseous compounds that have sufficient reducing power to make humans catch fire. Earthling biomolecules are already pretty reduced, which is why we get so much more energy out of oxidation reactions than hydrogenation reactions. Lithium is, conveniently, the strongest elemental reducing agent (with sodium and magnesium in 2nd and 3rd places, and everything else far behind). It will react with liquid ammonia (which is really your only reasonable solvent for stable organolithium biomolecules; ethers are used in chemical synthesis, but organolithium-ether halflives are short on biological timescales, and how would you get an ocean of even dimethylether?) to form lithium amide... but if there is a large excess of lithium on your world, the seas might very well be full of lithium amide salt, which will still react violently and exothermically with water to produce lithium hydroxide and ammonia. So, you could probably handwave humans exploding on contact with ocean spray, and they'd certainly meet a violent and explosive death if they jumped into the sea. Freshammonia rain, rivers, and lakes would be freezing and caustic, and so still quite deadly, but not explosion-causing. Gold fluorides would also react with ammonia or lithium. That doesn't mean you can't have them--geological fractionation can produce all kinds of weird stuff--but they would be very short lived on the surface. If there is a large quantity of gold fluorides in the crust, there's almost certainly a much larger quantity of lithium fluoride, as fluorine (the strongest elemental oxidizer) really, really likes to pair up with lithium (the strongest elemental reducer), which would probably be the primary salt in your oceans. [Answer] ## Hidden antimatter in spicy sea salt Believe me or not, some normal matter crystals can enclose and fixate antimatter particles in their lattice. When the crystal is damaged, the particle will escape and annihilate. It's not uncommon: it helps dragons ignite their fire as well. Your people fancy spicy food, on your planet spicyness is not caused by capsaicin, it is certain minerals, that come in sea salt. The crystals are not dissolving while the food is prepared. It requires stomach acids or blood, to break it down. When you eat it, microscopic sparks will cause the spicyness. When you eat too much of it, there will be more than just a few particles, it can perforate the stomach, or even worse. Too much really hurts, excessive amounts result in a deadly explosion. The effect depends on local concentration, crystal grain size and coincidence.. There's a cube millimeter of salt in your food somewhere, you could end up in a big splash. The men on your planet still eat food with sea salt, nevertheless. There is a culture around this food, connecting it to male courage and fertility. [Answer] It is hot. <https://earthsky.org/space/k2-141b-lava-planet-with-magma-ocean-rocky-rain-supersonic-winds-super-earth/> > > Discovered in 2018, K2-141b is only about 1 1/2 times the radius of > Earth, but is a very alien world. Its surface, atmosphere and ocean > are all composed of rock, specifically sodium, silicon monoxide, and > silicon dioxide... > > > So how does this affect the planet’s climate? Being tidally locked > this way means that there are drastic temperature differences between > the day and night sides of K2-141b. On the side facing away from the > star, it is bitterly cold, estimated to be below -330 degrees > Fahrenheit (-200 degrees Celsius). But on the star-facing side, the > temperature is estimated to be a scorching 5,700 degrees Fahrenheit > (3,000 degrees Celsius). In our own solar system, we think of Venus’ > scorching surface temperature as being hot enough to melt rocks. But > on K2-141b, it is so hot that rocks can evaporate. The vaporized rock > helps to create a thin atmosphere on the planet. > > > It is a planet formed by natural (or theorized) forces - check It has a liquid layer (seas) and a gas layer (atmosphere) - check. The seas and atmosphere can co-exist with the correct pressure/temperature/climate combination, which is not artificial - check People blow up - the outer layer (of the person) would first outgas water and fats. Remaining denatured proteins would harden and begin turning to charcoal (carbon), forming a hard outer layer. When the water trapped inside boiled, it would explode through the hardened outer layer. This is not so much catching on fire and burning vigorously as you propose, but more popping. It might not be one big pop but several smaller pops. I thought for sure youtube would have something but 5000F environments are hard to film. Would be nice to have abundant trifluorogold and Gold pentafluoride salts in the land (or at least accessible to the upper crust) - this is very tricky. Gold is going to unload that fluoride on other elements that want it more; on this world that would probably be sodium. [Answer] ## Beans Guess what! The Mythbusters have already tested it, and with a flame you can ignite your flatulence. Simply put, beans=booms. Our backend blasts contain both Hydrogen and Methane, which can explode. The stinkier the fart, the more explosion you get. [![Mythbusters fart explosion.](https://i.stack.imgur.com/fSzWN.png)](https://i.stack.imgur.com/fSzWN.png) --- ## The initial spark Only problem is that we need some external spark to light it up into a butt bomb. This is by far the most difficult part, but I think I've got it. Spontaneous Combustion is a weird and unique phenomenon. Because I don't quite understand it, I'll just leave the [Wikipedia article](https://en.wikipedia.org/wiki/Spontaneous_human_combustion). So bad timing, and a lot of cutting cheese, gets you the nice boom you're looking for. No handwaving needed. ]
[Question] [ I want a certain asteroid of my system to break into pieces as it approaches a planet, having one fragment impact the planet itself, another fragment slingshot and impact the planet's moon and the rest either burn up or accelerate enough never to be seen again. Would gravitational forces take care of this on their own if the asteroid's trajectory passed close enough to the planet? Would the asteroid perhaps need to dip a bit into the atmosphere in order to break? [Answer] Yes, what you are asking is exactly the definition of the [Roche limit](https://en.wikipedia.org/wiki/Roche_limit) > > In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, held together only by its own force of gravity, will disintegrate due to the first body's tidal forces exceeding the second body's gravitational self-attraction. Inside the Roche limit, orbiting material disperses and forms rings, whereas outside the limit material tends to coalesce. The Roche radius depends on the radius of the first body and on the ratio of the bodies' densities. > > > The Roche limit typically applies to a satellite's disintegrating due to tidal forces induced by its primary, the body around which it orbits. Parts of the satellite that are closer to the primary are attracted more strongly by gravity from the primary than parts that are farther away; this disparity effectively pulls the near and far parts of the satellite apart from each other, and if the disparity (combined with any centrifugal effects due to the object's spin) is larger than the force of gravity holding the satellite together, it can pull the satellite apart. > > > Some real satellites, both natural and artificial, can orbit within their Roche limits because they are held together by forces other than gravitation. Objects resting on the surface of such a satellite would be lifted away by tidal forces. A weaker satellite, such as a comet, could be broken up when it passes within its Roche limit. > > > Atmospheric drag can of course cause part of the fragments to fall on the planet. You can refer to this [question](https://astronomy.stackexchange.com/q/41101) on Astronomy.SE for more info and examples. [Answer] Yes. Real-world example: <https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9> Of course this depends on the cohesive strength of the particular asteroid, but a lot of them seem to be loosely-bound "rubble piles": <https://en.wikipedia.org/wiki/Rubble_pile> ]
[Question] [ I am working on a dragon project, and have solved how my dragon makes each breath, but I would like to know the most powerful possible breath, and how the dragon might make it, (fire breath, ice/cold breath, corrosive breath, poison breath, lightning breath, air breath, water breath, (kind of earth breath) hormonal breath, light breath) (not necessarily a gas, can be liquid, or solid too) this is in an earthly environment, and anything is useful while in the boundaries of physics, and a creature could do it, thank you, and ask me for more data if you need it edit:not only poisons/corrosive materials please, I've been getting a lot of those [Answer] ## Caustic, digesting, nasty spit The most plausible "breath" weapon is the one that already exists in the animal kingdom. It's called "spitting something nasty at your target", and several snake species (generically known as "spitting cobras") are pretty good at it. However, their venom is only a hazard to the eye, unless it somehow gets inside you, of course. Your dragons have evolved to the point where the chemistry they are using is much more sophisticated, with strong acids, powerful enzymes, and even oxidizing chemicals involved. (Bombardier beetles are well-known for producing hydrogen peroxide as part of their defense mechanism, and it's not implausible that that chemistry could have evolved again in an alternate universe.) That digestive soup, then, leaves searing acid burns on its victims as a precursor to deep, necrotic tissue damage from specially evolved proteases that eat through the intercellular matrix alongside signaling peptides that trigger cell death and/or inhibit clotting. The results of getting hit by this would be terrible. Imagine getting hit with a spitball with an accompanying brief spike of pain, only to find that minutes later, you've lost the use of a limb, or worse, as the venom's soaked into your gambeson and chemise, holding it in contact with your skin. Atop that, you're now bleeding badly in a way that just won't stop. No wonder legends of "fire-breathing dragons" would get born! [Answer] oh! ive worked on dragons before. the simplest realistic option ive found is reacting hydrogen and oxygen in the nostrils. the dragon drinks water, some of it gets sorted to a separate organ which combines CO2 and the water with photosynthetic bacteria, whom are sustained by a slight bioluminescence to produce oxygen and sugar. excess sugar is then sent to another organ as the oxygen is stored away for later use, and sugar is then reacted with more CO2 in other microbes to produce hydrogen and CO2, and the hydrogen is then stored in yet another chamber. the oxygen chamber and hydrogen chamber both have vents that run to the nostrils to be reacted just behind them, creating explosions that ignite the air in front of the nose, creating fire. the dragon then requires some sort of reinforcement to the nostrils, such as a boney armor to keep from burning flesh, and a defence for the skin, like an oiley secretion to make it flame retardant. the rest, (other than stink breath) are either virtually impossible to do reliably with normal chemistry, extremely inefficient, or can only be used once due to causing permanent damage. [Answer] I’ll preface this with the fact that I’m not too sure if the chemistry for this can be easily achieved by living creatures, but giant, flying, weaponized breath lizard, so it might be within reason. Ernaline’s Quick and Dirty Guide to Monster Hunting. Choking Dragon Kingdom: Animalia Phylum: Chordata Class: Reptilia Family: Dracaena Subfamily: Dracaeno Genus: Draco lacrimam Known for it’s toxic breath, the choking dragon or “choker” is one of the harder monsters to fight. The choker lives primarily in swamps, bogs, and other forms of wetlands. When not found in these places the choker tends to be found near large sources of stagnant water, this makes it a danger to farmers of rice patties. The primary weapon of the choker is its poisonous breath which is comprised of chloropicrin. The signs of choker poisoning are: pain in eyes and lungs, shortness of breath, extreme tearing, coughing, choking, vomiting, diarrhea,headache, dizziness, fatigue, and pulmonary edema (possibility resulting in death not from chomping). The poisonous gas will gather at the ground allowing the choker to fly safely over sprayed areas. Attempts at creating protective devices that work on choker poison have thus far proven unreliable at best. Most masks do not provide resistance to the gas and the more effective masks are only partly effective. As an added bonus the chokers gas makes creatures vomit which leads to the removal of the mask or to drowning in vomit. Rapid dispatching of the choker is the advised route if you have access to an advanced mask. The choker stores its poison in a bladder running down its throat to its pelvis. This poison bladder contains the liquid chloropicrin. The choker constricts this poison bladder while rapidly exhaling to produce its gas breath. Examination of choker carcasses has reviled a second set of eyelids, these eyelids are transparent and are credited with why the choker does not seem to have its vision affected by its own gas. A consensus on why the choker does not seem to be affected by breathing the gas has yet to be reached. The leading theory is the choker merely holds its breath while using its poison. The choker is believed to have developed its breath weapon due to its habitation in swamps. The chloropinrin that has been harvested from slain chokers has been proven to be a broad spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. The choker will breath its poison on itself at least once a day to kill off any parasites that try to take root in its hide. Chokers can be harvested for its poison by siphoning out the liquid from its poison bladder. Caution must be used while hunting to claim more than a few drops of chloropicrin from the carcass since attacks to the front of the choker can pierce its poison bladder. Harvested poison must not be boiled unless an explosion is the desired result. The poison is highly corrosive to many plastics and rubbers as well as steel and iron which makes handling and processing of it difficult, copper brass and bronze have proven resistant to corrosion though. Sources used <https://www.sciencedirect.com/topics/medicine-and-dentistry/chloropicrin> <https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750034.html> [Answer] Pyrophric chemical glands Some chemicals (such as some phosphorus compounds) spontaneously combust when coming into contact with oxygen. Glands full of these chemicals in the nose, mouth or even the throat (if the dragon is especially fire-proof), would release the chemical in conjunction with heavy exhalation (exhaled breath still contains some oxygen), resulting in fire breath. Hypergolic propellant glands Hypergolic propellants are 2 (or more) fluids that ignite when they come into contact with each other. The glands would work very similarly to the Pyrophric glands described above, but would not rely on the oxygen content of the air/breath. They might even be able to breathe fire under water, though it would be a very small and brief flame. Fluid fuel with piezoelectric trigger The dragon has glands in the mouth or throat which contain a fluid fuel (such as hydrogen). There is also a piezoelectric crystal in the dragon's mouth or throat. A piezoelectric crystal is a substance that produces a spark when placed under mechanical stress, such as squeezing with a muscle, which would ignite the fuel in the presence of oxygen. Methane gut bacteria with piezoelectric trigger The dragon has bacteria which produces methane in their stomach or intestine. There is a piezoelectric crystal in the dragon's mouth or throat, which would ignite the methane gas. To be pedantic, this would actually be a fire belch rather than fire breath, but I don't think the people getting chased by fire would know or care. Special thanks to `thatweirdscienceguy` from Tumblr. [Answer] If you want acidic breath, I'd suggest [hydrofluoric acid](https://en.wikipedia.org/wiki/Hydrofluoric_acid) (HF) for maximum nastiness. This stuff can be corrosive in high concentrations, but that's only a small part of the damage it can do. Even a low-level exposure is dangerous, and it's not obvious until too late that it's a problem. HF doubles as a contact poison, penetrating skin easily and wrecking calcium levels in the bloodstream. If you suffer a high-concentration spill of this stuff, the burns will be savage, but the real problem is beneath the surface. HF attacks the nervous system: if you're getting painful burns, that's life-threatening exposure if it's in quantity. Bone strength is also weakened by exposure, and if enough surface area on your skin gets hit (more than 25 square inches, which isn't very much), you're looking at systemic toxicity (crippling if not fatal without good medical treatment). Lower concentrations can be initially painless: you won't even realize at first that there's a problem, but one to several hours later you're likely going to be down with serious complications. Even as a gas, it's deadly. If any of this goes in the eyes, that's definitely not good news; a measly 2.5% concentration can burn the eyes within minutes. Inhalation can easily cause bronchitis or pulmonary edema, and it's capable of poking holes in the stomach lining if too much of it gets into your digestion. A low concentration may not produce symptoms for several hours, but if it's concentrated enough the effects are rapid. Containment is admittedly a problem with a chemical this hostile; it actually reacts with glass containers (it's used for etching glass or silicon industrially), so a prepared solution being contained biologically is going to be tricky. A binary situation may be one answer; fluorite in one chamber, water in another, to be mixed only when used. If your dragon can naturally produce a plastic lining somehow, that would also work: either way, I'd advise high calcium levels as a safeguard against accidental exposure. A source I found helpful for details is right [here](https://www.ncbi.nlm.nih.gov/books/NBK441829/#article-23075.s4), a medical journal. [Answer] # (liquid) Butane Breath! Butane is a simple chemical, not too difficult to synthesize. It is quite believable to handwave a biological organ that creates and concentrates Butane inside your Dragon. It is not even greatly toxic! At room temperature, you only need about 2 Atmospheres of pressure to keep Butane in liquid form. Now granted, putting a 2-bar pressure vessel in a biological construct is a tall order, but it is not out there. The Dragon would expel the liquid Butane by simply opening a valve to its storage container. The Butane would spray out in a mixed gas/liquid cone, propelled by its own internal pressure of 2 Bar. Un-ignited, it would severely chill and possibly asphyxiate its target. Ignited, it would make a beautiful flamethrower. Ignition of Butane gas in a suitable air mixture requires the teensyest spark source, a single piezolectrical element in the spit/ejector orifice will do quite well. The Dragon could close off the expelling valve, no worry about flame propagating into the storage chamber as there is no Oxygen there to allow combustion. The only danger to the Dragon itself would be blowback, or if it drools liquid Butane on itself. p.s. If the pressure requirement of Butane is too much for you, replace it with simple concentrated Alcohol. Also easy to produce biologicaly, sufficiently non-toxic that a specialized organ could contain it, and liquid at normal body temperatures. You would just need to add some nice muscles to spit with, and a better ignition facility than the easy Butane ignitor. [Answer] # Corona/bacterial breath Komodo dragons [harbor bacteria in their teeth which may cause sepsis on a victim](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2888571). So even if prey survives a bite and flees, the dragon may still feast on a corpse later. Dial it up to 11 with your dragons. They don't need to spit fire, lightning or acid in order to kill a lot of people. They just need to breathe like regular humans do. If they harbor some virus or bacteria for which the human body just can't fight against, then that will cause more deaths than any other alternative. If the setting is medieval, the dragon just has to pass through roads or farms every once in a while. They can then go to villages a couple weeks later and feast upon the piles of bodies. If the setting is modern, and the dragons are intelligent, they can find out places where there aren't enough ICU's and graves for everybody and spread the plague. People will resort to mass graves, the dragon may open those later for a meal. [Answer] The best type of breath would be an acid, preferably fluoroantimonic acid, a acid that is so strong that it will separe the electrons from your hands( hydrolisis) and furthermore it will sear the skin off your hand( this only in a small quantity). If it were a high proportion of it, if it touched your arm it would eat through skin, flesh and erode the bone. Since the dragon could have a gland to produce this acid, the best substance is definitely fluoroantimonic acid. The way this would work without harming the dragon itself is for the dragon to have a acid resistant throat that connects to the glands, something like a natural derivant of PTFE. A natural solution to that would be versatile molybdenum. To produce the acid the dragon's glands the dragon would produce hydrofluoric acid and antimony pentafluoride, and join them in a chemical reaction. It will shoot the acid from its mouth and when it lands on the prey the prey will surely die and corrode. If you are looking for a fiery solution to this problem, making your dragon more...dragonlike, there are several solutions. The first is fire( with flint and steel). As we all know, dragons grind up rocks with their teeth, and are bound to have flint and steel in them. Then they would release argon, methane, hydrogen and oxygen against their teeth, which is lighted with the flint and steel and it comes out as a big spurt of burning flame. There is no way to really enhance this. The other solution is ice breathing dragons. Ice is a powerful factor, so the way to use it. There is an exiting way to do this, where the dragon uses the sulfur and the Hydrogen Sulfide from the flame he/she breathed before and react with chalk(eaten) to get the CO2 under pressure. [Answer] ## Sandblaster breath Your dragon expels air at a supersonic velocity, using a special organ, and it's laced with really sharp or barbed or corrosive or venomous particles. At close range, a target is cut in half. At longer distances, it's caught in a disabling, blinding cloud, allowing the dragon to use its strength and speed to close (for melee or a killing breath). [Answer] ## Hallucinogenic breath Your dragon breathes out a cloud of psilocybin, scopolamine, and a cocktail of other hallucinogens. I'm thinking psilocybin + datura. Only tiny amounts are needed to send most enemies to a very weird and unpleasant death. Survivors have horrible trips and will generally avoid dragons like the plague. ]
[Question] [ I am trying to build a fantasy world which is not made of matter, but of raw imaginative power. This world has an overall fixed shape, bound to the memories of a sleeping godlike being, but everything else is quite unstable and constantly shifting. Some sentient creatures live in this world, unaware of its true nature. Every creature unconsciously has the ability of "fixing" the shape of the world around it based on his personal idea and perception of it (more or less like the observer in the Schrödinger's cat paradox). On an individual level this effect is really limited, and creatures with contrasting ideas tend to cancel each other's effect. But when many creatures with an overall similar vision of the place are gathered together, it definitely works. For this reason, villages and cities are quite stable places. All their inhabitants are used to see their surroundings in a certain way, so there's no risk that streets and building would shift suddenly into something else. But the more one is distant from those settlements, the more he risks to encounter subtle changes that can make him lose the way. The big problem is entering the wilderness. Animals don't have the power to affect the shape of the places they live in, so vast uninhabited places like the sea, the biggest forests, the deserts or the higher mountains are mainly a huge mess of constantly shifting nature. Venturing carelessly into those places means becoming trapped in a sort of dreamlike natural labyrinth. The overall environment doesn't change - everyone expects to see water into the sea, trees and rocks into the woods, sand into the desert - but paths tend to change and disappear, and the perception of distance is definitely unreliable. I could depict this world as composed of very secluded territories unable to communicate, but I'm trying to think if there are some ways its inhabitants could have found a way to travel when needed, albeit in a limited way. So my question is: how could short-distance and long-distance travel be possible in such ever-shifting territories? [Answer] Incredibly creative idea, I really enjoyed reading the question alone so I do hope you'll mature this into actual narrative work sometime (keep me updated if you do !). *With that being said, here are my suggestions, focused on travel* first and navigation second : 1. Travel Given your premise allows for its inhabitants cognition to alter the (pseudo ?-)physical shape of their universe, one very simplistic and instinctive means of travel I could think of is this : If you know what the location you are trying to reach looks like and how far away it is, you could just meditate hard enough until it either forms in front of you or the physical space between the two locations is reduced.** This brings immediate advantages to mind, like the fact that travelling would be pretty fast and easy this way, with minimal risk from the everchanging surroundings. Just summon your destination intensely enough, and it's there. As far as how to do that goes, you could gather a sufficient amount of people to collectively summon the destination (maybe as a civic duty ?). Or it could be an ad hoc summon, for example once the King has gathered an army he wants to send off somewhere, that army medidates collectively to reach its target. Alternatively, you could also have an order (of clerics maybe ?) dedicated to meta-meditation, who train during their entire lifetime to be able to summon geographical locations or "erase" massive swaths of land. 2. Navigation The matter of navigation is a bit more tricky, because all forms of navigation (except the sense of orientation maybe) relies on physical phenomenoms used as comparative landmarks (the position of the stars, magnetic waves, GPS location, radiolocation, etc). However, in this universe there could be a total absence of physical, permanent elements to base your landmarks on. Maybe instead of physical rules navigation could then function using logic or instinct. For example, maybe someone eventually discovers that your universe's constant evolution is in fact cyclical, and that certain locations are reported to regularly find themselves in one specific place. Given that, you could simply keep the directions these locations are in inscribed in an almanach, giving you the location's position depending on the time of year. Or maybe some people are born with an innate sense of orientation, that allows them to guess the destination and then point the travellers into the specific direction. We could elaborate on that, and imagine a "profession" of sorts in which people from a given country/province have a constant instinct of where their home province is whenever they're abroad. These 'compasses' could serve the King as directional advisors, pointing him towards where they feel their homeland currently is. They could be foreign ambassadors, or maybe slaves captured for the purpose of orientation. Otherwise, your ideas with the stars or the magnetic pole aren't bad at all, but the problem I have with them is that they are physical markers but somehow uninfluenced by your universe's constant fluidity unlike all other physical things, which means you are bending your own rules a little. That's completely fine, but I thought I would try to think of alternative ways to solve this problem. Really looking forward to wherever you go with this ! [Answer] I think it's an excellent idea and your thought pattern based mechanism of fixing the world to a greater or lesser degree has huge promise. The closest existing work I can think of is H. P. Lovecraft's "The Dream-Quest of Unknown Kadath", which I would highly recommend you read - it's different enough that I don't think you would risk contaminating your own ideas, but relevant enough that it might well prove a fruitful source of extending your world creation. One mechanism that people might be able to use is the very shape-affecting power of their own minds: perhaps if they can meditate hard enough they can force the landscape to mould to what they want, so the labyrinth of paths in the woods might become a nice straight path to the town you are headed for, but only if you can think calmly and forcefully enough to bend the terrain to your will. That ability might result in a profession unique to the world, navigators who shape the roads to lead to their passengers' destination through the force of deep meditation. I'd be very interested to read the story when you finish it, I hope you will pop back here and add a comment to this answer once it's released. [Answer] Any group could be lead by a good storyteller, someone who credibly claims to have traveled the route before (enough that the other travelers believe). The storyteller each night spins a tale of the last time ne traveled the road and shares nir visions with the group. The next day, they all expect to see what the storyteller spun. [Answer] If a society has a well-known network of popular roads, then wouldn't this stabilize those roads enough to allow people to travel on them? And as more people travel them over time, wouldn't this serve to stabilize the roads even more? [Answer] I find your world concept very interesting and hope to see more of it in the future. But to answer your question, I don't think that you actually have a problem. Atleast not a problem that can't be circumvented with the same belief-based world you describe. Wilderness Towns and villages are stable places because everyone living there have sort of the same idea of how it looks. The wilderness is unsafe and easy to get lost in because people don't have set expectations of what it looks like. Well some people will have clear expectations. For example a hunter or tracker who regularly ventures into the woods to hunt deer beliefs that he knows the trails and how to find his way back. Even if his own belief isn't strong enough to make that a reality, the rest of the village can probably help with it unknowingly. > > "I never go into the dark forest, I would get lost and starve to > death!" > > > "Good thing we have Jack the Huntsman! He knows the woods like > the back of his hand and always manages to catch something!" > > > A normal villages who tries to explore might very well get lost because that's what he expects to happen. But a seasoned hunter would face much less risk of that because he has belief invested in him. Long Distance Travel The same thinking can be applied to travel over larger areas. The trade caravan or messenger expects to be able to reach a destination (after all, they uses the route regularly). The traders' guild or the king expects the trip to be possible, and the collective belief makes it so. As long as the idea is planted among enough people it will be doable. Sure the scenery may vary from time to time, but the path will lead them to where they expect to go and the trip will take as long as they expect it to take. The great part about your setting is that you could come up with any manner of solutions to problems like this, simply get enough people to believe it and it will come true. Like in Kaloyan's answer maybe a few people have the ability to navigate, because that is what the rest of the world expect of them. Or maybe the King recently made promises of improving the roads and infrastructure of the realm, and now people have an easier time to travel because they believe him. Endless possibilities! ]
[Question] [ I am creating a species of humanoid lizard, and want to find a type of helmet that would be feasible within the story. Info: Tech level is basically hunter gatherer and nomadic, with a small bit of metalwork. Lizards are approximately 6.5 to 7 feet tall and proportioned similar to a human. They are a mashup of different types of lizards. Pointy scales like a Sungazer Lizard and some spikes along its spine like an iguana. Sexual dimorphism: Is such that a male has a skull based on a marine iguana, while a female's head is more akin to a frilled lizard, more V shaped. [![enter image description here](https://i.stack.imgur.com/TYN2k.jpg)](https://i.stack.imgur.com/TYN2k.jpg) Approximation of what the head would look like. Width (Outside of R. eye to the L. eye)- 18.6 Cm Length (Back of skull to front of mouth) - 30 Cm Height (Bottom of jaw to top of head above the eyes) - 22 Cm Habitat: They live in a large, marshy wetland, with tribes of between 20-50 members. For food, they consume mostly fish, with some crab and turtle when they can be found. There are almost no large deposits of metal ores, so smelting is relatively non-existent. They can find iron nuggets in the rivers, which they can forge into spearheads and arrowheads, but not enough is available for making metallic armour. Armour is made from the backplate of large turtle shell (similar to a snapping alligator turtle). Weapons will be mostly fishing spears used for combat. Basically they use what they can find if it has a purpose. The Question: What could be a viable material for a helmet for them with the following constraints; 1. it can't be metallic or high tech fibers 2. must be found naturally within the environment. (can still be modified slightly to work for them.) I am currently picturing something like using a crab shell, but I would like a better or different alternative. [Answer] Let's see what resources of note that should be available for us to work with: * Reeds * Vines * Roots * Bones * Hide * Shell Now since spears are being used, that means these helmets would have to be resistant to being stabbed. The best materials listed above would be shells and bones. However, most shells are just not in the right shape or size to be viable, and bone degrades too easily. That leaves us with using Shells, but not shells alone. By making a wicker helmet as the underlayer (like the Hawaiian Mahiole) then adding shells to the frame should result in a sturdy helmet that should not only be relatively cheap, but also effective against stabbing! [Answer] Tusks. <https://www.thevintagenews.com/2017/07/23/boars-tusk-helmets-highly-decorative-worn-by-warriors-in-the-mycenaean-era-1600-bc/> [![tusk helmets](https://i.stack.imgur.com/GYiPT.jpg)](https://i.stack.imgur.com/GYiPT.jpg) > > Meriones found a bow and quiver for Ulysses, and on his head he set a > leathern helmet that was lined with a strong plaiting of leathern > thongs, while on the outside it was thickly studded with boar's teeth, > well and skilfully set into it; next the head there was an inner > lining of felt. > > > <http://classics.mit.edu/Homer/iliad.10.x.html> If you want realism, tusk helmets were real pieces of armor. Odysseus is not tricked out in this helmet for a parade. The tusk is a durable weapon for the pig too, and must be able to take a beating. Other larger tusks could be cut to plate a helmet - ivory is available, durable and workable for a Stone Age culture. Plus field repairs would not be that tough with your pouch of spare tusks and thread. My original idea was a single hollow tooth from some great beast, hollowed out in the middle and eyeholes cut to form a helmet. [Answer] In The Elder Scrolls series of games there is a race that is very much like you describe: Argonians. Just like humans, they can use leather helmets. [![Leather helmet on an Argonian](https://i.stack.imgur.com/MQc4S.jpg)](https://i.stack.imgur.com/MQc4S.jpg) Free leather is not naturally found in any environment. However, if your world has rivers and such, it most probably contains creatures that carry leather on them. You may have to kill them in order to steal their leather, though, as they are very attached to said leather (via the hypodermis). Do notice that, like any other creature with a muzzle, your saurians require a cut proper to their anatomy in order to use leather helmets. A human leather helmet may not be so useful. [![Dear Dawnguard, I can't see guano](https://i.stack.imgur.com/qsqFz.jpg)](https://i.stack.imgur.com/qsqFz.jpg) [Answer] Mine would be hide with bones sewn in it. you can crack the bones so that they can be smaller and light enough for the head to carry, but thick enough to provide some protection. small bones can be placed in the hide to form a helmet that would cover the vital parts of the wearer's head. This helmet wont make the wearer's head invulnerable, but provide some resistance and maybe with luck, deflect the arrows (but that's SOME luck) Helmets provide little to no protection against the weapons you cited, arrows mostly target the body, because they are bigger targets, and so does spears. In my opinion, your lizard men should invest more on shields instead of helmets, because they provide more protection and has more uses to them. [Answer] First of all, nomadic hunter gatherers generally had no equipment meant for war. There were 2 reasons for it: 1.The population density was very low by necessity (amount of animals was finite) so groups rarely met another group unless both wanted it and while there certainly were raids and clashes, war as such would not happen, as weaker group could simply run away. That is, obviously, if it wasn't obliterated in the first strike, as those groups were small, more like extended family than a tribe. Tribes could gather sometimes for religious ceremonies (fe. once a year). Such a meeting would also be an occasion to intermarry between family groups. 2.They had to carry anything they had on frequent and long journeys so they had very few things - clothing, hunting weapons and very basic tools and camping gear. Dedicated war gear is heavy and so is not something HG group would want to use. One strange dude (or entire family group) could use reinforced leather cap for various reasons as normal head gear, obviously, especially in colder climate. HGs were also not using metal. Metal working appeared thousands of years after settled farmers became a norm. Discovering metalworking required tools that couldn't really be constantly carried around and a lot of experiments. Possibly it was connected with common use of pottery, and pottery was not used by HG communities as it was too heavy (even though they probably knew how to fire-harden clay). While group with no farming could be sustained by a very rich fishery areas (like you describe) and become settled in such spot, but as you stated you want them nomadic, the above problems would still apply. That's why if you want war, then rather than hunter gatherers, your lizards should be early farmers (late neolithic, similar to cultures in New Guinea). Those were already settled (thanks to farming), but hunting was still very important part of their lives. In general, you could simplify it to situation where females are farming while males are hunting and fighting. Just remember in reality it was much more complicated. As they were settled, they were able to start experimenting with metalworking (copper and some basic bronze-like alloys while war (with dedicated war gear) became major part of their lives as they had something to fight over - fields and gathered crops. What type of armour then? In general, you would have two options - leather or wood. Of those, leather is way easier to use, so would be more common. A leather cap, which can be made in various ways, could then be reinforced in many ways. You can use any hard material - wood, horn, bone, hardened leather, shells, small pieces of metal - pretty much anything that can be sewn into leather cap. Those would be cut into small pieces and attached either by sewing on top of the cap or sewn between two layers of leather. Body armour could be similarly made, as well. ]
[Question] [ I'm an advanced AI in far futuristic sci-fi setting. To give you the size of how advanced we are, I'll just drop here a short list of our accomplishments: * We have discovered cold fission-reactors and mastered all the other known forms of energy * We have high tech robotics, both on large scale (enormous builder-bots) and microscopic scale (multi-purpose nanotech) * We can synthesize every kind of material, fabric, alloy, organic and inorganic compounds of your knowledge, plus some new and improved materials of our invention. * Our world is mainly governed by a few major AIs. * To be precise, the artificial intelligence is no more a "singularity": we can replicate it to whatever extent we like. AIs can be created to mimick completely the human brain, if needed, or the brains of other biological creature. You got the point, I think, but feel free to ask for other details. Now, in our world both robotic and biologic life coexist to various extents. Of course, our definition of "life" is a little from yours, since we consider robots and AIs such as me to be alive. Regardless, I've been furthering my studies on a little pet-project of mine: alas, creating a synthetic human lifeform capable of growth. Creating a robot that looks like a human is already a solved problem: it's just a matter of coating an exoskeleton with our improved skin-like silicon. We've become pretty good to mimic other bodily function too, like temperature, breathing and so on. Of course, as I've told you before, we can give that artificial body a totally human-like intelligence also. What I want now is to design a synthetic body capable of mimicking growth. For convenience, this body should start around the apparent age of a human of three or four years old, and then be capable of growing into the apparent age of adulthood. The body should be composed mainly of inert materials, like metal or plastic; I could add a certain number of biologically-engineered cells to the mix, but I'd rather avoid mixing biology with robotics more than necessary. My safest bet is to load the body with nanobots, that I will program to gather the necessary compounds to "slowly expand" the body until the desired size. I worry if this option is viable, though, since the nanobots should exit the body once in a while to gather the necessary materials. My aim here is to make possible humans unaware of the process. Awaiting your precious input. [Answer] If you want to make humans unaware the growing bot is anything other then human and avoid the nanobots having to leave to scavange material the easy solution I think is to have it eat. It sounds like the technology is there for the energy to run and the process to synthesize the materials you would need internally. Kids are well know picky eaters with food preferences that change with time. So maybe it only wants to "eat" red meat when it needs additional iron, then when it needs more Y compound it switches to wanting X food. 3-4 is old enough to use the toilet on your own so any unused material can be disposed of safely and discreetly, and if it looks different then a humans no one would be the wiser. I guess the question becomes can the needed breaking down and combining of materials take place in the space available based of the technology available. From a mass in to growth standpoint it should work though, as humans are able to do it and in theory a robot using the food to grow itself would be more efficient as it would not need to use that food for growth and energy. Assuming a seperate internal power source, which seems plausible based on your tech levels. [Answer] I would assume if you're that advanced it would be much easier to simply create a swarm of nanobots and have the swarm replicate a human body. If you need the body to grow you could ensure the nanobots can either create more of themselves or try to sneak in a fresh batch that would enable them to slowy grow the body. The basics to being capable of growing is being able to produce the cells or matter in general to keep growing. If you can create a bloodlike fluid or use nanobots that can grow a plastic body then congratulations you can grow a plastic body. [Answer] A human cell is nothing more than a chemical factory that manages to reproduce itself over and over again. The cells have specializations to allow the body to survive and reproduce on a large scale. With access to nanotech and any material in the world you can create 'new' biology and living matter using different materials than we are build out of now. Plastics and metals for a synthetic body? Thats wasteful. You build them from strings of Graphene Alloys so its very resistant against damage. Create chemical sequences thay provide power and building materials and have these take place inside the cells, which you build out of one of the trillions of compounds you now have access to, many of which would be buildable from what we eat everyday, and the synthetic could seclude himself on the playground for example to attempt to find materials otherwise not present in human food. With your tech level, the distinction between biology and machine is long gone. Humans are likely just as synthetic as the synthetic is going to be using biological parts. [Answer] 1) give it human blood! without human blood, the first blood analysis may bust your robot! [![enter image description here](https://i.stack.imgur.com/kOWtQ.jpg)](https://i.stack.imgur.com/kOWtQ.jpg) [source](https://de.wikipedia.org/wiki/Blutentnahme#/media/File:US_Navy_040324-N-0130O-001_Hospital_Corpsman_1st_Class_Jason_Dillow,_of_Westminster,_Md.,_draws_blood_from_a_Sailor%27s_arm,_for_a_routine_human_immunodeficiency_virus_(HIV)_check.jpg) 2) give it human skin! Most of the times we get in touch with our enviroment with our skin, it has many quite unique characteristics, for example, it can get damaged by sharp things, illnesses, chemicals, uv, heat, and so on in various ways, improved skin-like silicon alone could never mimic those things, without the aid of highly advanced nanobots. Why should one fake a sunburn with so much effort if one can get a real one? [![enter image description here](https://i.stack.imgur.com/sic5B.jpg)](https://i.stack.imgur.com/sic5B.jpg) [source](https://4f20lz3r4bii3yfqutfxz0o17ou-wpengine.netdna-ssl.com/wp-content/uploads/2013/11/skin-anatomy2-595x240.jpg) 4) fill it with fake organs and meat (wich roughly look like the real versions, but may be completeley different regarding microscopic structures), wich house the nanobots! ...just in case your robot has an accident and gets operated. [![enter image description here](https://i.stack.imgur.com/id3DV.jpg)](https://i.stack.imgur.com/id3DV.jpg) [source](http://www.theeastafrican.co.ke/image/view/-/4250798/medRes/1850849/-/maxw/600/-/a6o0v8/-/surgery.jpg?format=xhtml) 5) house all the actual main components (power sources, al, motors, network) except artificial nerves used for sensing (wich must be really thin so one wont find them during operations) in the skull and the skeleton! no one will ever have to fix the skeleton, since you can make it so strong that it doesn't break and real human skeleton usually don't let x-rays pass, so you can hide everything inside without having to worry about how it looks on x-ray. [![enter image description here](https://i.stack.imgur.com/h7mm4.gif)](https://i.stack.imgur.com/h7mm4.gif) [source](https://upload.wikimedia.org/wikipedia/commons/e/e3/First_medical_X-ray_by_Wilhelm_R%C3%B6ntgen_of_his_wife_Anna_Bertha_Ludwig%27s_hand_-_18951222.gif) 6) take care that your robot, when burned down, leaves the same stuff a human body would leave too! When humans are burned, only 5% of the mass of the human remain as ashes, including teeth. your robot has to become such ashes too, when burned. ...just think of what happens when the robot dies early, and the humans decide to cremate it and get some strange electric junk as remainder... (it would be too suspicious if the 0-year old robot said "plz dont cremate me after i die,ok?") [![enter image description here](https://i.stack.imgur.com/k6aCu.jpg)](https://i.stack.imgur.com/k6aCu.jpg) [source](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/AschenkapselOffen.jpg/1024px-AschenkapselOffen.jpg) 7) let your robot assimilate and dispose stuff like humans do (as suggested by Crouse), but watch out that the deposited stuff looks like humans organic waste! ...just think of your robot going onto some blocked up toilet (without knowing that), disposing strange waste, and leaving the toilet for the plumber to come and fix it. what should it do? take the waste out again? that would seem just as strange as the waste would seem to the plumber... [![enter image description here](https://i.stack.imgur.com/5MUsy.jpg)](https://i.stack.imgur.com/5MUsy.jpg) [source](https://www.spbla.com/wp-content/uploads/2014/11/licensePlumber-highlightBtn-framed.jpg) [Answer] Complete the genome project First you need to know what makes a human and what is individual characteristics of the individual. Design your pet Using the known genome, just design what you want your human to be like. Hair color, personality traits, diseases he's more likely to have and all of the little details your heart desires. Program your language Program a language that can read the genome as a input and reacts to it just like the enzymes and chemistry of a human body would. In essence, the human body is a protein synthetizer and by the level of technology you have, that seems to be fairly possible. Just input the dna you want to express and it'll run itself. Manufacture nano cells Nano cells would be a group of nano robots that in conjunction would form an cell analog. Have that cell be the hardware and apply the language you created as an OS. The nanorobots should be able to synthetize anything just as you describe on the OP. Apply the code for the human Apply the code you have as dna(TACG) to the cell. Make changes as desired for the material outcome. If you want to make silicon instead of keratin for the skin, just change the output of those keratin codes(TACG) to a silicon synthesis. Change any analog you want from organic to inorganic. Let it run freely If the code is correct and the language translates it properly, just press the play buttom and let it run. Digestory tract As an addition, you'll need to design a better digestory system. One that allows for inorganic materials to be digested and used in the body. As in other system, some microlevel adaptations will be needed. [Answer] By definition, it can [grow](https://www.biology-online.org/dictionary/Growth). It can grow like a human too, with enough programming/planning. > > [Growth](https://www.biology-online.org/dictionary/Growth) > > > (1) The gradual > increase (e.g. in size or number) of an animal or vegetable body over > time. > > > (2) The development of an organism, e.g. of a plant from a seed > to full maturity. > > > Growth has two key aspects to its definition. You may want to narrow your question down to which part you are interested in. However in both cases I can see no reason why growing a synthetic human would not be possible. With enough technology that is. Edit: Based on your comment. All growth is, is following a script to make certain parts bigger (1), and change certain parts to do more things (2, [maturation](https://en.wikipedia.org/wiki/Developmental_biology)). That is the big picture. What chemicals are involved and what processes are used is irrelevant, and will in fact change depending on the organism/species. So really what is growth? It is changing an "organism's" anatomy to have new function, or to have more of something. Now let us assume you have the futuristic scenario that you have described. I assume we have nanobots. I assume we can program said nanobots to follow some kind of plan. With this plan they can make predictable changes to an object. In this case the object is robot. Evolution and mutations are clearly not a key part of growth, and are thus excluded in this scenario (though I am sure you can program that in too with enough work). So if you can program said nanobots to increase the size of a robot, and its superficial functions so that it looks, talks, and acts like a human... then by definition has it not experience growth? Yes it has. Taking this to its logical extreme, you could also do this to a rock, or any object. I would go so far as to say that something doesn't even have to be alive, for it to grow. However biological growth is mostly concerned with '(2)', [maturation](https://en.wikipedia.org/wiki/Developmental_biology). This can still be applied to an inanimate object, but depending on your interpretation you may; want the growth to originate from within the object; follow a predictable and reproducible path; etc. Again all these aspects are easily achieved by nanobots with the right script. If you want to go deeper and start pondering on whether synthetic life is really life, you can start discussing whether the nanobots can be considered ['cells'](https://www.dummies.com/education/science/biology/understanding-cells-the-basic-units-of-life/). I think the question of whether these synthetic humans are actually alive is so profound and interesting that it should not be hand waved. It is also not convincing to hand wave that they are 'life' when they are missing very obvious key concepts of life, like the ability to reproduce. In fact, [you should look at the key aspects of life](https://en.wikipedia.org/wiki/Life#/media/File:Characteristics_of_life.svg). As long as you have someone smart enough to program the nanobots however then growth should be possible, no-problem. So the answer to this question is a resounding yes. If you find this concept unacceptable then I suspect that you are asking the wrong question. Obviously real life is defined by many more things than just growth. So maybe what you really want to ask is, "What does a synthetic human made of plastic and steel have to have, in order to be considered a unit-of-life in biological terms". The answer to this question is very different to whether or not a robot can mimic one aspect of life. [Answer] Biology is a subset of computer science. The body is made of cells which are just microbots. Anyone that denies living cells are just natural, occurring microbots is willfully ignorant. So your robot needs to be made out of self replicating self repairing microbots or nanobots if you want it to grow. You mentioed plastic. plastic is a polymer, as is dna. Polymer data storage if very compact. You could also use nanomechanical processors and storage instead, or use photopolymers for data storage and plasmons for processing. I dont see a way around cell based/microbot based life, organic or otherwise if you want it to grow. [Answer] You can have biological nanobots that - through nanotech - are turned into 'cells' that can potentially eat, grow, and behave in a manner that makes the being they create a synthetic 'human'. I know you said you prefer to stay away from biology, but biology in this case is using nanobots to do something like turn [retroviruses](https://doi.org/10.1002%2F0471142727.mb0909s36) or even strands of [DNA](https://doi.org/10.1145%2F602421.602426) into 'nanobots' of sorts to form a bio-mechanical synthetic human. ]
[Question] [ In the middle of the night, while J. Random Human is sleeping, A. Hypersphere picks him hyper-up extremely carefully (so that none of his matter falls out in a direction he doesn't have), flips him over through a fourth spatial dimension, and puts him back hyper-down in his bed. When he wakes up, the entire world is mirror-imaged to him. Everybody looks slightly weird, finding his way around becomes very difficult, reading is an ordeal. What biological differences does J. Random notice, and how quickly does he notice them? I know the chirality of biological molecules is going to be an issue (and will probably eventually kill him), but do the foods he eats smell and taste different? What symptoms does he start experiencing? [Answer] Any situation involving molecules without chirality will be the same for him as they are for us, so he'll be able to taste salt, water, and breathe fine. Molecules with chirality will work the way their opposite does for us. An example; for us, right-handed amino acids tend to be tasteless, left-handed amino acids tend to taste sweet. This would be reversed for him. The problem is, opposite chirality organic molecules are quite a bit rarer. He probably won't starve to death, there are plenty of molecules that will work as calorie sources for him. But he probably will die of malnutrition; the human body needs lots of micronutrients, and while I don't know any specifics, I think its very likely he will be unable to find a substitute for one of them and it will eventually kill him. He may die sooner if a common compound is poisonous when in the opposite chirality. As for when he notices, it depends what you count. He'll know something is wrong the minute he has a bite of food, or takes a drink of something flavored. But it's a big leap to make from "My sandwich tastes funny" to get to "I went through a hypersphere and now all my molecules are backwards". I think it's likely that doctors would miss this for quite awhile. Taste and smell changes would make them think it was neurologic, while nutritional problems might lead them to suspect hormone or gastro problems. I think it would be quite awhile before they noticed his molecules were all backwards. [Answer] ## He will not have time to notice any biological differences... ...because he is made of antimatter, and will instantly annihilate on contact with any normal matter nearby. The maneuver you're describing--picking someone "hyper-up" and flipping them around--is exactly the operation that a non-orientable wormhole ( <https://en.wikipedia.org/wiki/Non-orientable_wormhole> ) would do to matter that passes through it. This would affect the chirality of the molecules that pass through it, yes, but it also does something at a deeper level: > > As well as turning left-handed screwthreads into right-handed > screwthreads, and left-handed gloves into right-handed gloves, > reversing the chirality of an object is also usually associated with > the idea of reversing the sign of electromagnetic charge – if a > positron can be considered as a time-reversed electron, it can also be > considered as an electron aging conventionally, but with one spatial > dimension reversed. The existence of a traversable nonorientable > wormhole would seem to allow the conversion of matter to antimatter, > and vice versa. > > > In conclusion, J. Random would go out in a blaze of total-energy-conversion glory and take a sizable check of the earth's crust with him. [citation needed] [Edit: I just noticed that @Spencer and @Eth already pointed this out long ago in the comments, including a reference to the oon-orientable wormhole article. I feel properly scooped, but I'll leave my answer up since no other actual answers address this...] [Answer] Many digestive enzymes are chiral and they would stop working on many of the molecules with the wrong orientation. However there should be enough food without this problem that he would be able to survive with a modified diet. He may now be able to digest other things that were just dietary fiber to him previously, which might have some unknown consequences. The procedure that you're talking about does not time reverse him, so he is not made of antimatter as he would be if he went through the wormhole mentioned in other answers. This is for the same reason your drawings don't explode when you turn the paper upside down. P.S. I love Flatland too. [Answer] Perhaps he will feel nothing different at all (And this is only theorizing, because we have never had such a real example to reference). Yes his entire body was "mirrored" through the 4th dimension, but also his brain, and each and every synapse and neural pattern. Therefore, all the information mapped inside his brain was also mirrored. So, even if he will perceive everything in the world "mirrored" (for example the characters in the newspaper), he will be able to read it normally, because all his memories and learning experiences have also been flipped. However... all the people around him will notice it almost immediately: "Hey! You had that freckle in your left cheek! Now it is in your right cheek!!" And of course there will be those molecular differences mentioned before. But... since all his own molecules were also flipped, perhaps (and I am speaking without any solid biochemistry background) perhaps he will be able to assimilate everything the same way (perhaps). [Answer] He will immediately notice after opening his eyes: For him, the outside world looks mirrored: All written signs are mirror images, traffic goes on "the wrong side of the road", the majority of people look left-handed to him, screws are different, faucets have the other sense of rotation, there are lots of hints to his situation. [Answer] A 4-d flip would not turn JRH into anti-matter, just a mirror-image of his previous self. He would become left-handed, part his hair on the other side, etc. Whether his memories would flip in some way can only be conjecture. He would probably become immune to infectious disease, bacteria are sensitive to isomorphism. ]
[Question] [ One idea I've always wanted to try writing is the concept of vampires exploiting their lack of a need to breathe and generally low-maintenance biology to escape the brunt of the sun's rays by living underneath the sea, and the opportunity to use this idea in my current story has recently presented itself. So I'd like to take this chance to check if the idea, as it stands, sounds like something an actual human being with an actual human being brain would actually consider a sane idea. Here's the background: For the past six months to a year, the human race has been granted supernatural powers on a weekly basis, and since you only get to keep half a dozen or so at a time, everyone is walking around with their own customized assortment of superpowers, along with a few permanent powers everyone got and can't get rid of. One of these, the ability to temporarily deactivate anything that uses electricity, combustion or chemical reactions just by looking at it, has helped cause the total collapse of society and infrastructure, and now humanity's living at a tech level around that of a zombie apocalypse, forced to fend for themselves to get food and supplies and stay safe. Now, a certain kind of supernatural power that's been periodically showing up is a shapeshifting power you can't keep longer than a week, which lets you transform into a member of a new fantasy race, and if you like, when the week is up you can keep that new body and give up the old one instead. One of these races, the power for which shows up around a month after society collapses, is called the Greys, and they're functionally vampires. They don't need to drink blood (they eat normal human food instead, although they do find blood tasty) and don't have the weaknesses to garlic or crosses and the like, but otherwise they're dead ringers for them. They burn up in direct sunlight, don't need to breathe, can see perfectly in the dark, and are incredibly resistant to both high and low temperatures. Now, somebody figures out that these traits mean they can actually survive underwater, and that when you're a Grey, going 20 feet underwater is all it takes to be completely protected from the sun's rays (it’s not the UV specifically, but a supernatural element of the sun that’s neutralized by 20 feet of water). The idea is that the severe shortages of food and the dangerous anarchy that passes for politics in the immediate aftermath of the collapse make a lot of people decide they'll have a way better chance of surviving and living in relative safety and peace if they become Greys and try to colonize the ocean from scratch, reasoning that thanks to the aforementioned anti-tech power and the total failure of the power grid, technology barely works above the water anymore either, so any society they could build down there would hardly be more primitive than up there from a technological perspective. Plus, a few powers have shown up recently that solve the whole "you can't talk underwater" thing too. Is there any flaw in this logic that would make it clear to anyone who attempts it that even in this dire situation this is a terrible idea? [Answer] I mean, there isn't a reason why your grey vampires wouldn't be able to chill out on the sea floor (assuming pressure isn't an issue), but I doubt it would be a good or marketable idea. To me, the biggest problem comes from the thing that drew your greys into the ocean in the first place: a lack of light. On the ocean floors, there would be absolutely no light sources to speak of. While the sun wouldn't bother them, your greys wouldn't have any way to see anything. Even if they had specialized, night vision eyes, there isn't enough ambient light to get anything to work with at all. Unless the greys have some kind of bioluminescence, they will need some tech to see anything. The next problem would be food. I sincerely hope all your greys like crab and calamari, because that's practically the most traditionally edible things down there. Sure, you technically have the entire ocean to harvest, but then you need infrastructure to transport supplies from shallow coral reefs and the like (which would negate the benefit of living in the deep, since reefs get a lot of sunlight). This brings me to the biggest red flag I would have as a grey looking at your brochure: technology. Your society would be limited to whatever tools and tech they bring from the surface, as manufacturing anything underwater would be near impossible. After all, getting a simple single blacksmithing operation on the ocean floor would be a feat of engineering on par with building the pyramids. And some level of technology is absolutely needed since the greys still need tools and, yes, light sources. Basically, you would be trying to convince a bunch of substantially powerful people from modern nations to commit to becoming a completely blind aboriginal society. I think most greys would rather just wear burkas . . . [![A woman wearing a burka, which completely covers her skin from sunlight](https://i.stack.imgur.com/1vkRi.jpg)](https://i.stack.imgur.com/1vkRi.jpg) . . . and move to someplace with a lot of cloud cover. That being said, if you write a story that includes underwater trains manned by vampires, I will read the entire thing cover-to-cover with the happiest of smiles on my face. [Answer] What about undersea predators? Humans are not built for swimming fast enough to get away from undersea predators and can't fight off the larger ones very well. If I was a vampire my fear of sharks would keep me out of the water. Thus if many vampires migrate underwater, it is possible that many sea monsters - some of which - like cetaceans and cephalopods - may have approximately human intelligence levels - will eat vampires and acquire vampire powers, and perhaps emerge on land to terrorize land dwellers. And there could be invasions of land sharks. [Answer] Argh, there's always this problem: the 'true' vampire is a biological impossibility in itself. 'Undead' just don't work, cells need energy from chemicals process that are activated by breathing, heart-pumping, methabolism...you can't have a shapeshifting dead fleshbag moving around, unless there is magic involved. In this case, what the heck!, just have them do what they want, they have no limits already. Otherwise these 'vampires' would only be genetically engineered humans who can live off fungi, lichen, insects and make the best of whatever they eat. Their natural pallor wouldn't be a problem for they do not need vitamin D anymore. Augmented night vision...in other words, you throw in everything to have your own morlocks of the sea and they can work with technology just fine. Add gills and webbed hands and feet for swimming and breathing in the water, at least they'd make a complete integration in their new environment. [Answer] > > going 20 feet underwater is all it takes to be completely protected from the sun's rays. > > > More like 657 feet ($\approx200m$): [![Light penetration in seawater](https://i.stack.imgur.com/Vh2mP.jpg)](https://i.stack.imgur.com/Vh2mP.jpg) To make real sure you are off the hook regarding sunlight you would have to go off the [continental shelf](https://en.wikipedia.org/wiki/Continental_shelf), which usually doesn't go deeper than 140 meters. If you want somewhere plain to have buildings you will have to go all the way to the [abyss](https://en.wikipedia.org/wiki/Abyssal_plain) - which presents its own set of problems. If you can handle the pressure, and the salinity (which is extremely poisonous to land dwellers), and the cold temperature, you have three main immediate problems to solve: * Food, part 1: without photosynthesis, the production of energy in the abyss is very limited. The largest energy source are leftovers from above. From the wiki for the abyss: > > Probably the most important ecological characteristic of abyssal ecosystems is energy limitation. Abyssal seafloor communities are considered to be food limited because benthic production depends on the input of detrital organic material produced in the euphotic zone, thousands of meters above. Most of the organic flux arrives as an attenuated rain of small particles (typically, only 0.5–2% of net primary production in the euphotic zone), which decreases inversely with water depth. > > > This means you are in an area where your civilization growth may ve very limited due to food shortage. * Food, part 2: the whole food situation is a problem that the inhabitants of the abyss have been facing for millions of years. Evolution made them pretty tough due to that. You may be facing giant and colossal squid, for starters. Good luck. * You are not a swimmer: moving around at the depths of the ocean is not a walk in the park [citation needed]. You will be spending so much energy just moving around that it may not be worth the calories bill. Your vampire race would better evolve fins and the shape of an abyssal fish if they wish for this to be feasible. [Answer] ## Technology Going below the surface means abandoning all civilized technology that you can't pack down with you or sink before you go overboard and that isn't waterproof. There will be no internet, books, TV, alcoholic beverages, cellphones, or anything else we take for granted here on the surface. ## Medicine Do your vampires need any sort of medicine or medical care or do they have supernatural healing? There is no penicillin in the ocean, nor plaster arm or leg casts. ## Food As others have mentioned, food can be scarce under water, depending on where and when you go. But beyond just that is the personal tastes of your vampires. There will be no starches like bread or rice. There will be no condiments like ketchup or wasabi sauce. There will be no grills or stir fries. It will be raw "fish" all the time. And you have to learn how to catch them, since fishing from underwater isn't a natural skill set for humans. ## Drink Your being require food, you say. Do they also require water? There will be no unsalted water in your ocean home, no tea, no coffee, no beer. Just salt water. Which is toxic to humans. Not sure about your vampires? Can they filter the salt? ## Sanitation Vampires who grew up in the civilized world might find it awkward to eat in the ocean when that's also where they poop and pee. If they're eating, they're pooping too. That's not a hard stop, but it is a thing that would make it uncomfortable until you can overcome that taboo. ## Pressure Your beings don't breathe. But are they properly adapted to the pressures of bottom-of-the-ocean depths? Or will their flesh be squeezed into pulp like a mortal human's would? ## Communications Most vampire literature that I've read that discusses it at all states that vampires only breathe when they talk. Your underwater civilization cannot have language. Well, I guess they could learn sign language, if they're dark vision is sufficient. But there will be no way to use pen or paper and no way to speak, since that requires lungs. Lungs not filled with water. ## Clothing Your vampires will give up clothing. Clothes will rot and they add weight and drag to their bodies, making swimming inefficient. That may not be a big deal, but it's one more shred of their surface humanity that they've lost. ## Movement The human body isn't designed for underwater movement. Your vampires, even if they are or become amazing swimmers, will never move as fast as the average fish. They just aren't built for it. No fins, no streamlined shape. Just awkward feet and hands that create drag. ## Sanity This is the real concern. If you pack up a few belongings and drop into the depths of the sea, you're giving up everything. The entirety of your civilized history is behind you, on shore somewhere. You're in the complete dark with no lights or electricity. No modern conveniences, no nothing but oceanic life forms. How long can such beings go on in such an alien world before they lose any shred of sanity? When they go mad, what then? (I don't remember the name, but I read a novel once where a supernatural vampire managed to pull itself to the US shoreline after sinking in the Titanic. It took decades. And the being was quite insane by the time it arrived.) [Answer] These vampires "don't need to drink blood and don't have the weaknesses to garlic or crosses and the like," but otherwise they happen to be "dead ringers" for mythological vampires. (Quote OP, emphasis mine). In other words, these Greys can A) drain someone of blood to turn them into a vampire and B) shapeshift. Laugh if you will, but these are both recognized vampiric abilities. This allows them to effectively adapt to the deep sea (shapeshifting alone allows this, being supernaturally strong undead, I somehow don't think the water pressure will be a problem if they turn human) and to use that shapeshifting ability to its fullest. Let's say this shapeshifting ability makes merpeople, sirens, naiads, sharkmen, and things like that possible; supernatural creatures like that will be prime candidates for transformation for the would-be marine Greys. See, if they become one of these races, they can simply have a friend or relative inflict a vampiric bite and turn them into a vampiric sea creature. In other words, colonizing the sea? The only question is whether they want to-there's an awful lot of consequences attached to deep-sea life, as CaM pointed out-and whether they have the determination to carry it out. If the answers are yes and yes, then it's only a matter of time before an entire, vibrant underwater civilization has begun. Who knows; with enough time, vampiric squid-people could become Inklings! ]
[Question] [ EDIT: There were some great answers here, and I realize this is a kinda broad question, but I'm accepting Monty Wild answer as it provided me with the info I needed to push this forward. Now I have a place to start research. Thanks everyone! Giving a character "superhuman" strength is quite common in sci-fi, fantasy or just about any other genre, but how much is actually that strength varies wildly. What is the strength limit for a humanoid? For this "humanoid" is defined as: * Two legs * Two arms * Height between 1.75 and 2.15 m * Body volume around that of a fit male. I'm not talking about giving superhuman strength to a human, it doesn't even needs to be organic, could be a robot) before you start breaking the laws of physics or requiring fictional materials? I'm talking about peak short term strength here. How much can you lift and throw, how hard can a punch be. Actions that last a 1, 2, 10 seconds at most. Imagine you can use whatever materials for the bones, skin, muscles, you are effectively designing it (with current or near future materials). Where do you draw the line, and how could you compute it? I imagine it has to do with the fracture strength of the bones and muscles, and how much the muscles contract. Guessing graphene bones and vanadium dioxide muscle would be about the best currently. Assume that all the organs or electronic required to power up and control it are roughly the size of a brain, so you have the chest cavity free for other stuff. Also, as a follow-up, how does this change if you start to admit more sci-fi stuff like unbreakable materials and the like. Mostly interested on the first part though. [Answer] Many factors need to be taken into consideration in order to increase the effective strength of a humanlike form in a realistic manner. One can always scale up just a few of these factors and say, "Wow, look at how strong this would be!", but when put into practise in a real-world situation, something would either fail or limit the naïvely-calculated maximum exertion. This is a problem of engineering, not simply physics and materials science, and trade-offs will always have to be made. 1. Strength of the materials: Stronger materials can withstand more force before being damaged. Any mismatch between actuator and skeletal strength increases the likelihood of mechanical failure. 2. Density of the materials: The lighter the materials, the less force will be required to move objects made from them. 3. The maximum force that can be applied by the actuators per unit mass: The more force that can be applied per unit mass, the less will be needed to simply move the individual's limbs, and the more that can be applied to the environment. 4. The internal friction of the actuators and joints. The higher, the less efficient - and slower - the humanoid will be. 5. The maximum speed of the actuators. Additional speed can be achieved by chaining actuators in series, but increasing strength requires that they be placed in parallel. 6. The lever ratio of the humanoid's joints: Higher strength means lower speed. 7. The maximum allowable time for a joint to transition between fully flexed and fully extended: The humanoid might otherwise be immensely strong, yet unable to outpace a snail. 8. The energy efficiency of the actuators. Less efficient actuators require more energy input - and generate more waste heat, limiting the maximum duration of maximum exertion, as well as limiting the maximum number of actuators for the available cooling capacity and thermal tolerance. Given that no mechanism is ever 100% efficient, by rights, if his muscles were just as efficient as ours, Superman ought to glow visibly from the waste heat when he applies his super strength, though perhaps that's where the heat for his eyes' heat rays comes from... 9. The thermal tolerance of the humanoid: Raise a human's temperature more than a few degrees, and the efficiency and efficacy of all sorts of things is significantly reduced. The same applies to most physical systems outside a vacuum. 10. The cooling capacity of the humanoid: Humans have amongst the best cooling capacity of any species on earth, allowing a sufficiently fit individual to literally run down members of most other terrestrial animal species solely on the basis that a human can maintain an optimum body temperature while running at a pace at which causes pretty much every other animal species' body temperature to increase. Keep this up long enough, and the prey's rising body temperature will eventually cause a physical collapse. Additionally, with insufficient internal heat redistribution capacity, local temperature differences could increase to the point where localised damage would occur. 11. The humanoid's available energy and its maximum rate of delivery to the actuators: There's no point in having actuators that consume vast amounts of power if sufficient power cannot be supplied to them, or if sufficient power can be supplied, but not for a sufficient amount of time. 12. Whether the humanoid's actuators require an input of energy only when changing position or if energy is required to maintain a given force - i.e. electric screw-jack vs a long-travel electromagnetic linear actuator; the former requires power only to change its position, while the latter requires (more) power to maintain a given position somewhere between fully extended and fully contracted, and less (or none) when at the limits of its travel: Animal muscles fall into the latter category, increasing the basal metabolic cost of things as simple as maintaining a static standing posture, but if a humanoid had actuators that fell into the former category, only actuators actively moving would consume power, though maintaining a standing posture can be a rather more active task than it might seem. 13. The humanoid's optimum operating temperature: If this is too different from the environmental temperature, then energy must be expended to maintain - or achieve - it, or the humanoid will suffer from losses of efficiency or from mechanical failure if its internal cooling or heating capacity cannot keep up with the rate of heat transfer, which increases proportionally to the difference in temperature. 14. The humanoid's skin's insulation factor. By reducing the speed at which heat is gained or lost, this can increase the efficiency of the humanoid at rest, but can hamper the task of dealing with waste heat. 15. The environmental temperature: While the average temperature is important when optimising a real mechanical system, the range of variation is also important. The lower the range of variation, the easier it is to optimise a system to operate in those conditions. Being able to tolerate a wider variety of conditions can be useful in being able to survive, but also increases the cost of insulation and cooling, and systems that accept a narrower range of acceptable conditions have lower metabolic requirements than those that accommodate all possible conditions, though at the cost of an increased probability of exposure-related injury or death. 16. The mass of any support equipment required to allow the humanoid to function independently for a reasonable amount of time. Unless this humanoid is like an [evangelion](https://en.wikipedia.org/wiki/Evangelion_(mecha)) with a cable to its power supply - which would have its own problems - it'll have to carry everything it needs around with it. If it needs a lot of energy, it better have a compact way of storing that energy. [![Evangelion with cable](https://i.stack.imgur.com/fNLFu.jpg)](https://i.stack.imgur.com/fNLFu.jpg) So, as can be seen, this is a very difficult problem. Sure, you may want a 'superman', but you have to answer all of these questions - and more - before you can even begin to enumerate his realistic capabilities. However, let's assume that we need a 'superman' with roughly human capacities for duration of exertion and with equivalent environmental optimums. We would need higher-strength materials, more powerful, lighter and more efficient actuators, and probably better cooling capacity too. Given intelligent design rather than evolution, we could achieve results that could never evolve naturally. We are still limited by real-world chemistry and physics, though. It is not realistic to give a period of maximum exertion of as little as 10 seconds unless in that time your humanoid can achieve everything that a human could achieve in perhaps as much as 5 minutes. If your humanoid was this fast, it would have to have traded off a lot of strength - both structural and the force it could apply to external objects - to achieve that speed. For a superhero, a realistic duration of elevated exertion would be more like 5 to 10 minutes. As a martial artist, practising karate and hapkido, at my dojo, the examination for black belt includes engaging in ten continuous minutes of fighting. Since a superhero might be able to achieve his results a bit faster than a mere human, five minutes might be a reasonable compromise. If we build our superhero with light, strong materials like carbon fiber (perhaps 20 times stronger than human bone), use super-strong manufactured muscles that are up to a hundred times stronger than a human muscle like [these](http://www.livescience.com/43536-yarn-muscles-100x-stronger-human-muscles.html), and provide a [LENR](https://www.extremetech.com/extreme/149090-nasas-cold-fusion-tech-could-put-a-nuclear-reactor-in-every-home-car-and-plane) atomic power supply, then it is conceivable that a human-sized and shaped form could lift (in an event such as the [clean and jerk](https://en.wikipedia.org/wiki/Clean_and_jerk) in Olympic weightlifting) not 263kg (the current human world record), but something on the order of 10,000kg. However, being able to lift large weights is not all there is to being a superhero. Being able to lift ten tons at the same speed as a human doesn't mean that you punch any harder unless the actuators are also faster - if your arm weighs as much as a human's and accelerate just as fast, then the impact force will be the same. However, such a superhero could simply pick up a 50kg hand barbell in each hand and still get his punches out just as fast. Given the physics formula $e= 1/2mv^2$, artificially increasing the mass of a perhaps 10kg arm by 50kg and still hitting at the same impact speed would increase the impact energy by a factor of six, changing a punch from something that might break a bone if carefully placed to something far more likely to break bones every time it landed, or fatally concuss a human with a single punch most of the time. However, if our intelligently-designed superhero was to do this for any length of time, say in a five-minute bout of all-out combat, then he would be generating a great deal more waste heat than any human in the same situation, requiring far more cooling capacity than even a 'merely' evolved human body can muster. His breath might be like a hair-dryer and/or his skin might literally steam with the amount of waste heat that would have to be dealt with. On the other hand, if we gave our artificial superhero strength not a great deal greater than a human's - perhaps twice as strong at most - but a much higher speed, then he might be delivering punches that land at not ~9 m/s (32 kph or 20 mph), but at ~63 m/s (227 kph or 140 mph). That's 7 times the speed, but, because $e=1/2mv^2$, means that the punches will deliver 49 times the energy. That's the difference between bruising and perhaps a broken bone from a human fighter to a punch from our superhero that could almost literally knock the other guy's head off. In order to control a body this responsive, we'd need to give our superhero light-speed electrical signalling instead of the downright sluggish electrochemical system our own nerves employ. This would also mean that our artificial superhero could literally watch a human opponent throw a punch at him, then - before that punch hit - throw six punches in return, each one potentially fatal or crippling before finally blocking the incoming punch, assuming that energy transfer to his opponent didn't knock him so far back as to make blocking the initial punch entirely unnecessary. [Answer] Hard Science Upper bound How hard could you punch? Lets say you only need to be able to throw one punch and you want to hit as hard as possible. Let's assume that you have to bring your power supply with you (you can't haul a generator with you) Let's assume you have a perfect generator that converts mass to energy as effectively as possible. Let's assume the you consume all of you available mass and energy in the one punch/explosion. A shock wave is like a punch, right? The available kinetic energy would be $m \cdot c^2$; an 80 kg humanoid would hit with $7 \cdot 10^{18}$ Joules. The Tsar bomb (most powerful nuclear bomb) was $4.2 \cdot 10^{16}$ Joules. So, the most energy that a human mass could output is about 100 Tsar bombs. This would be true no matter what materials you use, your limited mass gives you a limited output. At first this upperbound seems useless but it eliminates some fictional examples, such as humanoids destroying or moving planets. There just is not enough mass / energy in a humanoid unless they have an exterior source. Edit: If the person can be much denser than their destructive power increases linearly with their mass. [Answer] As per my link in the comments on Hysterical strength (<https://en.wikipedia.org/wiki/Hysterical_strength>) it is entirely likely that the current human form is actually significantly stronger than what we are capable on a day to day basis. Somewhere along human development, the brain started to stop and think as opposed to instinctively react and this seems to have impacted or strength heavily. Gorillas are estimated to have 6 to 15x the strength of humans pound for pound, displaying how exaggerated this actually is. I also think there is some degree of trade-off between precision vs strength, a trade off humanity made quite some time ago. There is also the Berserk warrior legends, warriors renowned for foaming at the mouth while gnawing on their own iron shields, that could enter a frenzy (read as dropping thought for instinct) and perform feats of strength that were well beyond anything other humans could perform. Though these feats are not only hard for the body to perform, but also damaging as the muscle itself can tear itself, tendon, and bone apart (temporal brain can figure out damage to its body may have short term gain, but harsh future implications and therefore only allow access to this strength when short term damage is deemed worthy regardless of future considerations). The greatest feat I can readily find comes from the hysterical strength link where 2 female children (age 14 and 16) managed to lift a tractor off of their father (around 15x what they'd normally lift). Most of the evidence on this is anecdotal, but its prevalent enough to give some credit to the theory. For hard numbers, I'll use deadlift with the world record of 500kg (1100) lbs, though without equipment it's 460kg. The world record of 500kg was set by Eddie Hall, who nearly died from the attempt (<http://www.independent.co.uk/sport/general/eddie-hall-nearly-died-after-passing-out-following-new-deadlift-world-record-of-500kg-a7132306.html>) due to bursting blood vessels in his head from this attempt. There has also been several occurrences of dead lifters losing their bowels (not bowel content, the lower bowel literally gets ejected out the rear end). I'd actually consider this the maximum limit of the human form, not because of the upper limit of human muscle, but the upper limit of pressure our internal organs and brain can actually handle. That being said, if Eddie Hall entered a frenzy or Hysterical strength, it is possible his upper limit could be between 6x-15x that of his regular strength...gives a value of 3000kg to 7500kg as a potential. Of course, big disclaimer saying that these muscles may be capable of handling it, but the forces exerted on the bodies organs and brain would likely be well beyond what we can tolerate resulting in a quick death. Interesting that our internal organs are ultimately the limiting factor here. Added - I did suggest that a lot of hysterical strength is anecdotal. In the case of the 14 and 16 year old : <http://www.dailymail.co.uk/news/article-2307079/Teen-sisters-lift-3-000lb-tractor-rescue-father-pinned-underneath.html> They managed to lift a 3000lbs tractor high enough for their father to wiggle free. There is much speculation that there was something else contributing (tractor was leaning a bit to one side and the children simply tilted it)...so it's hard to say what was done here, simply because 'hysterical strength' is exceedingly difficult to measure in a controlled setting. There is some researchers whom have suggested we could measure the maximum strength of a person through electric shocks (basically using an electric current to over ride the muscle and force it to contract as hard as it possibly can). But I can only find the theory, I can't actually find anywhere that the experiment was actually tested. [Answer] If you would like to strengthen a human, which its body mechanics, strongest parts of the human body are bones, and they have about 120MPa tensile strength. [![enter image description here](https://i.stack.imgur.com/4vVCZ.png)](https://i.stack.imgur.com/4vVCZ.png) [source](http://www.springer.com/cda/content/document/cda_downloaddocument/9781461462545-c1.pdf?SGWID=0-0-45-1445418-p174729517) So if we would take something 1000 times stronger (carbon nanotubes), we probably could make a humanoid body 1000 times stronger than a typical fit human. The tensile strength of muscles varies from 3kPa to 70kPa for different species and conditions ([source](http://www.ircobi.org/wordpress/downloads/irc12/pdf_files/61.pdf)). There is somewhere in internet human muscles strength, but because of paywalls and lack of patience, let's use higher number available. The number definitely shows that muscles could be improved significantly. So if we shift proportion by making bones thicker, and muscles of the same 120GPa materials, we definitely can expect improvements more than 1000 times. For my opinion, 10000 times could be a good guess. So if you would like to keep human like biomechanics 10'000 stronger is a good number, however, it is not the limit to humanlike shape. [Answer] Hard Science Lower Bound What could you make today? As a lower bound what could you make with materials available today. Hydrolics are much stronger than muscles. So lets make a humanoid with a torso that is just a large hydraulic piston that telescopes up and down. The robot lifts with its torso From the wiki page we see industrial hydraulics can have 6000 psi systems, but 2,000 psi are more common. [Wiki on hydraulics](https://en.wikipedia.org/wiki/Hydraulic_machinery) The area of the piston would be the cross-sectional area of a humans waist/stomach. Lets assume a fat human so the cylinder will be circular a 40 inch waist is radius of 20 and area of 1,256 inches ^2 This gives a max lift strength of 3,768,000 7,536,000 pounds. So given today's technology we could build a hydraulic piston shaped like a human that could lift 1,800 - 3,600 tons This assumes that we uses the rest of the volume for the pump, fuel, and hydraulic fluid reserves, but it seems reasonable. We could do scaled down versions for the other limbs. Fair warning a humanoid trying to lift that much weight would be apply around 2,000 psi to the ground underneath it which would break most floors and many roads. Edit: Credit to RonJohn for mentioning this idea before I thought of it. [Answer] You can be as strong as you want if you have the infrastructure to support it, so if you make the bones more robust you can up the strength to the limits of muscle power, which in other primates is a lot more than humans. I think you could reasonably make your people 10 times stronger without breaking any laws with thicker bones or different composition of the bones making them stronger and gorilla type muscles. ]
[Question] [ In my world, the knowledge of science is largely lost, but many of the practical facts are still remembered. Chemistry morphed back into alchemy. My main character grew up as a peasant in a city's outskirts, and learned alchemy from an old textbook and experimenting on what she could find in the forest. My question: what kind of chemistry can you do only with the ingredients you might find in a forest with high biodiversity? Let's say that the main character was lucky and also found some mineral deposits or somesuch. What chemicals would she have had access to? [Answer] One of the most prominent alchemical substances was potash (potassium carbonate), which can be made by collecting regular old wood ashes, dissolving them in water and then drying up the water. (In fact, the word potassium comes from potash, or "pot ash".) You can use potash and animal fat to produce lye and soap. Are there caves in the forest? Another nice material is saltpeter (potassium nitrate), which you can get by soaking bat guano and filtering the crystals out of it. If you don't have access to bat caves, you can produce saltpeter by collecting a pile of manure, mixing it into a compost heap with urine and wood ashes, letting it decompose, and then leaching and filtering the result with potash. All you need to make alcohol is fruit and a place to let it ferment. Besides drinking, alcohol is useful as an antiseptic and fuel. One substance you can't get from an ordinary forest, but would be an excellent find in your story, is sulfur, which is often found around hot springs. Sulfur and saltpeter, burned together in the presence of steam, lets you make "oil of vitriol" (sulfuric acid). Depending on what else you find natural deposits of, this can be used for a whole host of purposes, although this kind of strays away from the original question. But one thing that is worth noting: Sulfur, charcoal, and saltpeter is all you need to make gunpowder. [Answer] In a forest one can find fruits, and from fruits produce diluted alcohol. From diluted alcohol and distillation, one can produce concentrated alcohol. From diluted alcohol and further oxidation one can produce acetic acid or acethone. From vegetal fibers one can produce paper, cloths and various textile. With concentrated alcohol (and discipline to not get wasted every Friday night) or acethone and paper one can perform cromatography on some pigments, and learn how to extract them to dye cloths. [Answer] [Phosphorus](http://www.chemicool.com/elements/phosphorus.html) requires simply urine and sand: > > Brand's method is believed to have consisted of evaporating urine to leave a black residue that was then left for a few months. The residue was then heated with sand, driving off a variety of gases and oils which were condensed in water. > > The final substance to be driven off, condensing as a white solid, was phosphorus. > > > [Answer] Under the dead leaves and such, there will be more "weathered mineral particles" but it seems to be just further decomposed organics until you would get to "clay, iron, and aluminium oxides." Deeper, you'll run into "silicate clays, iron (Fe) and aluminium (Al) oxides, and organic material." Then, according to Wikipedia's soil horizon article it could be anything. The Wikipedia article on hot spring mentions a lot of potential essential Saltes. I've been to hot springs near forests so it should be plausible. My best guess is, with enough effort, you would be able to produce smoke powder/fireworks/maybe gunpowder and help people supplement their diets by drinking "potions" to avoid mineral deficiencies. With accurate enough instructions you might be able to make thermite. <https://en.m.wikipedia.org/wiki/Soil_horizon> <https://en.m.wikipedia.org/wiki/Hot_spring> <https://en.m.wikipedia.org/wiki/Thermite> (I'm sorry for he formatting; the only device I've got is my cell phone. Feel free to edit while I try to fight off sleep and read the help files!) ]
[Question] [ Recently I was pondering mermaids and was wondering how their respiratory systems work. Most importantly, how could their vocal chords continue to function? Secondly, how would they draw the water through external gills? It would have to be different than human breathing because there is no suction. Two points to note: 1. They have a lung system which can function above water 2. The gills should preferably be external [Answer] Mermaids have human-like breasts, but those should never have evolved since it makes them less streamlined and hydrodynamic. Ever wonder about the function of those? Turns out that just like a female human's breast, a mermaid's breasts contain a high amount of fat - which is not a bad thing in itself. The "melons" of a mermaid work just like [the melon of a cetacean](https://en.wikipedia.org/wiki/Melon_(cetacean))! In another question I described their respiratory system as having something I called [gillungs](https://worldbuilding.stackexchange.com/a/44145/21222)... Those are kinda like branchial chambers with internal gills, and those gills could vibrate just like vocal cords. The breasts of the mermaid can then function as resonating chambers, so that she can sing like a dolphin. Yes, that luring song they sing comes not from their throats, but from their chests (in fact, that's very close to how parrots speak - they don't have vocal cords either, their vibrating organs are located quite closer to their lungs). And that's how mermaids communicate among themselves - just like whales and dolphins do. Your mermaids may learn how substitute their gills for vocal cords, and how to make strange sounds with their tongues and lips in order to communicate with humans, but that may be unnatural to them. [Answer] > > How could their vocal chords continue to function? > > > Probably they could still the lung system. Humans produce sound by expelling air through the vocal cords, I guess the merfolk could try expelling water in a similar manner (though it requires suction to work). Or you could use [the mechanisms](https://en.wikipedia.org/wiki/Whale_vocalization) used by dolphins and whales. They have a specialized organ that produces clicks and whistles, and some sort of "vocal cords" in the head. > > How would they draw the water through external gills? > > > I guess, like all other creatures with the [external gills](https://en.wikipedia.org/wiki/External_gills)? The gills are usually attached to a stalk made of muscle tissue, so the animals can stir up water with the gill. [Answer] Gills and vocalization are completely different entities. There are plenty of fish that make sound and have multiple ways of doing it. Just Google "[How fish make sounds](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=how%20fish%20make%20sounds)." Not only can fish make sounds, but some fish have gills and [lungs](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=fish%20with%20lungs). Since some fish have lungs and can breath air, there is no reason to believe they cant make sounds both above and below water. Your notion that fish cant create suction is false. Many fish rely on [suction](http://www.pnas.org/content/112/28/8525.full) to predate. So they can suck in water and air. Again, everything you need to have a mermaid speak above and below water is already available. [Answer] These mermaids could have lamprey-like gills, with a velum and respiratory tube. This would allow them to pump water into the tube, and out of the mouth through the velum, which could act as vocal chords ]
[Question] [ In my story, I would like to have a contemporary Mars Rover find not only evidence, but a mostly complete skeleton of a homo sapiens that perished around 50,000 years ago when it was exposed to the surface (due to a misguided, childish experiment by aliens). As much as I do love Curiosity, Opportunity, and others; their [abilities](http://en.wikipedia.org/wiki/Curiosity_%28rover%29#Instruments) can barely scratch the surface (literally) of Mars. Although I'd entertain a near-future rover that can, say, explore the polar ice caps for a frozen skeleton, I'd prefer it to be one of our current champs. So, how can a 50,000 year-old skeleton (or body) survive the elements to be found by our robot pals on Mars? [Answer] Mars has excellent conditions for mummification. There isn't much you actually have to do except leave a body on the surface. Mars will do the rest. The corpse will desiccate fairly quickly and will then hardly decompose over the centuries. With the very cold climate, minimal and dry atmosphere, and no microbial life there isn't much that will be able to decompose it. The main issue will be wind erosion, but it's minor, and mummies have been found in less ideal environments. An example of these is seen in Antarctica, some [seal mummies](http://www.ncbi.nlm.nih.gov/pubmed/14432467) have been found on the surface that are as much as 2,600 years old. It's worth noting these are accidental mummifications, the animals simply died there and mummified naturally. They still have skin after all that time, the bones will last much longer. As mentioned by Jake, the Atacama desert is another excellent example as it's used by NASA to simulate a Martian environment. [Some of the mummies](http://en.wikipedia.org/wiki/Chinchorro_mummies) found there are almost 9,000 years old. Granted, those mummies were intentionally prepared, but clearly the environment is highly favorable for mummies. Mars is better. Earth mummies have active microbial life chipping away at them, Mars won't have that. The only microbial life will be that which was brought in the gut of the human, and it is not suited for survival in those conditions. The gut bacteria will be the last thing in the human to die, but it will die. Aside from the small amount of wind, it's pretty similar to being a [corpse in space](https://what-if.xkcd.com/134/). Finding a 50,000 year old skeleton or mummy on Mars would be shocking indeed, but not because we would have expected it to decay. If a human died on Mars in the distant past, it would actually be a surprise not to find the body. [Answer] > > It was all my fault. I sat frozen in my chair as the cameras swung widely around. Dr. Hoover had told me to stay away from the edge, but I'd seen something glitter and curiosity (no pun intended) had gotten the best of me. And now all I could do was pray and hope as I watched the rover roll and bounce down the hill. > > > Dust and rocks filled the camera, and I winced as I realized I'd caused a landslide as well. My hope that the rover would land miraculously upright and be recoverable seemed more remote than ever - it would almost surely be buried. My heart rose as the camera came to a stop, but then sank down again - the rover was at a nearly 90 degree angle, and was almost certainly stuck. > > > I sat forward and took in the scene carefully. It appeared now that a cave had partially collapsed - I wondered if maybe I hadn't actually gotten too close to the edge, that the weight of the rover had caused it to crumble. Maybe it would have happened to anyone. Dazedly I watched the camera pan around, and then focus near a white rock... > > > My shriek filled the room, and I fell out of my chair, gasping on the floor. My heart pounded in my chest and blood roared in my ears. It was impossible. My mind was playing tricks on me. > > > I stood back up on unsteady feet and braced against the desk, staring at the monitor. And the skull staring back at me. I lifted the phone with a trembling hand to call Dr. Hoover. > > > [Answer] I imagine the rover noticing a small rock coming out of the ground with different looks and different chemical composition, it analyzes and then discovers its just a small part of a bigger solid object just barely underground, then depending on what you want, the rover can see the skeleton through it and/or earth can sand a machine just to take it out from the ground, I picture something like this: ![enter image description here](https://i.stack.imgur.com/4NJzd.jpg) or something like this: ![enter image description here](https://i.stack.imgur.com/zTI4P.jpg) just imagine a skeleton instead of a mosquito ]
[Question] [ is this planet plausible? * the planet is the third planet from its star. * by size smaller than Earth. * the planet has no moons. * the only habitable areas are rings around the poles. * in the pole, there's a sea of water. * ringed around the sea, is a habitable region with a tropical climate. * moving from the poles towards the equator, the land becomes more desert-like. * this planet does have seasons, and for the polar area that is its day and night cycle, each of which last about four and a half of our months. * however, since the average temperature of this planet is mostly hot, no permanent snow nor ice caps occur. [Answer] Here is your question: > > Is this planet plausible? > > > the planet is the third planet from its star. > > > by size smaller than Earth. > > > > > the planet has no moons. > > > > > the only habitable areas are rings around the poles. > > > > > in the pole, there's a sea of water. > > > ringed around the sea, is a habitable region with a tropical climate. > > > > > moving from the poles towards the equator, the land becomes more desert-like. > > > > > this planet does have seasons, and for the polar area that is its day and night cycle, each of which last about four and a half of our months.> > > > however, since the average temperature of this planet is mostly hot, no permanent snow nor ice caps occur. > > > 1. > > the planet is the third planet from its star. > > > There are eight planets in our solar system. There are also known sytems of exoplanets around other stars. > > As of 1 January 2022, there are 4,905 confirmed exoplanets in 3,629 planetary systems, with 808 systems having more than one planet.[5](https://en.wikipedia.org/wiki/Mercury_(planet)#Surface_conditions_and_exosphere) > > > <https://en.wikipedia.org/wiki/Exoplanet> With 1,279 excess planets in the 808 systems with more than one planet, there must be about 468 systems with three or more planets. Some systems have 7, 8 or maybe 9 planets. So it is perfectly possible for third planets to exist, and som of those third planets should be in the habitable zones of their stars. 2. > > by size smaller than Earth. > > > 3 planets in our solar system, and many exoplanets in other systems, are known to be smaller and/or less massive than Earth. 3. > > the planet has no moons. > > > All the giant planets in our solar system have many moons of various sizes. The 4 rather EArth like terrestrial type planets include 2 with no moons, one with one moon, and one with 2 moons. Thus an Earthlike exoplanet without a moon seems perfectly possible. However, there are some theories claiming that having a large moon is vital for an explanet to be habitable, so you might want to check on those theories and see if you agree with them. 4. > > the only habitable areas are rings around the poles. > > > In the outer solar system many minor planets and moons are covered with ice all over their surfaces, and are so cold that ice is as hard as rock or metal. Even their equators are far too cold for liquid water using life. The surfaces of Mercury and Venus, close to the Sun, are far too hot for liquid water using life. Earth, in between, has temperatures in most spots which are more or less good for liquid water using life. The temperatures are much warmer at the equator and much colder near the poles. If an Earthlike planet was moved closer to its star, or the star became more luminous, its overall temperature would be higher, and the zones with temperatures best suitable for life would move away from the Equator and toward the poles. If the warming process contiues, the zones with the best tmperatures for life would move farther and farther away from the poles, the equator would eventually become too hot for life, and eventually the very poles would be the only places cool enough for life, and then eventually even the very poles would be too hot for life. So somewhere along the trend of increasing the heat received by the planet, it would have the right situation where only areas close to the poles would be habitable. All you have to do is decide how much radiation your world needs to receive from its star, and then adjust the luminosity of the star and the semi-major axis of the planet's orbit so it will receive that amount of radiation from its star. If the polar oceans are surrounded by habitable land, the polar oceans will also be habitable, for sea life at least. Sea life is quite abundant in the Arctic and Southern Oceans, and on a hotter planet, the polar oceans could not be any colder. 5. > > in the pole, there's a sea of water. > > > and: 6. > > ringed around the sea, is a habitable region with a tropical climate. > > > The Arctic Ocean is almost surrouned by Eurasia, America, and Greenland. During glaciations, the strait between Siberia and Alaska becomes dry land, making the Arctic Ocean more enclosed. With plate tectonics, ocean floor plates and continental plates move around the surface of Earh, and presumably on your planet. Thus continents and seas are constantly being rearranged over many millions of years. Statistically, it would be rare for any specific planet to have polar oceans totally ringed in by encircling continents at any one time. But with constantly shifing continents and seas, a lot of planets might have such a configuration at least once while bearing life on their surfaces. And all the gazillions of planets in the universe, there are probably countless such planets existing at any one time. You didn't mention whether there are any other oceans and continents on your world. There could be two polar oceans, two continents encircling them, and an equatorial ocean with several continents within it. Or possibly there could be one continent coving the whole planet except for the two polar oceans it surrounds. In that case the two polar oceans would probably have to be much larger than the Arctic ocean, and extend much farther from the poles, if your planet has about the same amount of surface water as Earth has. Possibly your planet is much dryer than Earth. If it recieves more radiation from a more luminous and/or hotter star, water in the equatorial regions would evaporate very fast. Water vapor which rose about the ozone layer of your world would be split up by the more intense ultraviolet radiation from the star into hydrogen and oxygen atoms, and the lighter hydroben atoms would escape into space. Thus your world could have tried up much faster than Earth and lost more water than Earth. 7. > > moving from the poles towards the equator, the land becomes more desert-like. > > > If the regions closer to the equator are hotter, hot air will move toward the cooler polar regions. If the regions closer to the equator are hotter, water will evaporate faster and more water vapor will be carried to the poles and fall as rain there. Thus the lands closer to the equator will get less rain than the lands closer to the poles. A desert is defined as a region with very little rain or snow, not as a hot region, the Antarctic and Greenland ice sheets are considered cold deserts. So the lands closer to the equator should be deserts or semi deserts. What about the oceans close to the equator? I doubt whether oceans would ge considered deserts even if they didn't get any rain. So maybe your world as non desert regions in your equatorial oceans, or maybe the polar oceans are the only oceans. I discussed this under point 6. 8. > > this planet does have seasons, and for the polar area that is its day and night cycle, each of which last about four and a half of our months. > > > You will have to decide how much axial tilt your planet will have. At one extreme it could have a rotation axis perpendicular (at right angles) to the plane of its orbit, whichis called an axial tilt of zero. In that case it would have no seasons, merel night and day as it rotated. On the other extreme, its axis of rotation could be exactly in the plane of its orbit, an axial tilt of 90 degrees. At one point in the orbit, the north pole would be pointed directly at its star, and would have burning summer of constant less day, and the south pole would point directly away from the star, and have a freezing winter of constant night. Places on the equator would have the star costantly n thhorizon,a constant twilight/dawn, Half a planetary year later the north pole would be pointed away from the star and have winter, and the south pole would b epoint toward the star and have summer. And halfway between those two extremes, the equatorial planet of the planet would be pointing toward and away from the star. Each point on the equator would be having alternating days and nights. You presumably will want a seasonal situation more like on Earth. Earth has an axial tilt of about 23 degrees, so I imagine you might consider making your planet have an axial tilt of about 20 or 25 degrees. Planets in our solar system have axial titls varying from 0.03 (Mercury) to 82.23 (Uranus), so that smaple gives you great freedom to choose. But remember: > > this planet does have seasons, and for the polar area that is its day and night cycle, each of which last about four and a half of our months. > > > So the polar area will have alternating day and night equal to their seasonal cycle. Day and night will last for half a planetary year in the polar regions. Since each day/summer season and each night/winter season last for about 4.5 Earht months, the year of your planet lasts for about 9 Earth months, or about 0.75 Earth years or about 273.9375 Earth days. So you shuld find a star with a luminosity such that it has what I call an Earth Equivalent Distance or EED - where it receives about as much radiation from its star as Earth gets from the Sun - where the oribal period of a habitable planet woud be about 237 Earth days. The answer by user177107 to this question: <https://astronomy.stackexchange.com/questions/40746/how-would-the-characteristics-of-a-habitable-planet-change-with-stars-of-differe/40758#40758> gives tables of some properties of various tpues of star,s including their EEDs, and the orbital periods at the EEDs of those stars. According to the tables, a G8V class star would have an EED of 0.82 Astronimical uNits or AU, where the orbital period would be about 280.06 Earth days. So an 0.82 AU orbit about a G8V star would be good, except that you want the planet to be much hotter than Earth. If a planet orbited the Sun at a distance if 0.84 AU, it would have an orbital period of about 281.153 Earth days. That would be farther from the Sun than Venus at 0.72 AU, but would that make it cool enough to have life even at the poles? Just what are the inner and outer edges of the Sun's circumstellar habitable zone, when water on planetary surfaces can be liquid? According to this list: <https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#Solar_System_estimates> A dozen different estimates, calcuations, and computer simulations have been made in the last 60 years, and some of them are very different from others. Seven of them put the inner edge of the habitable zone over 0.9 AU from the Sun, while 4 or 5 others put it closer to the Sun than 0.84 AU. So you might might find it helpful to decide which inner edge of the habitable zone seems most correct to you. And there are many other combinations of star mass, star luminosity, and semi-major axis of planetary orbit you could try in an attempt to find a situation where your world has a year about 9 months long and receives more radiation than Earth gets from the Sun. yOu say the polar regions have day forhalf theyear followed by night for half the year. HOw far from the poles does that extend? 10 killometers, 100 kilometers, 1,000 kikometers? It that only in the centers of the polar oceans, or does it extend down to the shores of the habitable lands encircling the polar oceans? On Earth, the sun can be seen at midnight on one day, and can be at the horizon at noon time on one other day, at any point north of the Arctic Circle or south of the Antarctic Circle. The farther beyond the circles, and the closer to the poles, one gets, the longer the periods of midnight sun and noonday darkness gets, until at the very poles the Sun is above or at the horizon for 6 months and then below the horizon for another 6 months. And if you want the conditon of midnight sun/noonday darkness to extend down to a particular latitude on your world, you should figure out what axial tilt would be necessary - and if there is any axial tilt which can achieve it. 9. > > however, since the average temperature of this planet is mostly hot, no permanent snow nor ice caps occur. > > > If you mean polar ice caps, the temperatures at the poles should be above freezing for longer than they are below, year after year after year, to prevent ice cap formation. But what about glaciers on high monuntains? On Earth there are glaciers on high mountains and plateaus even near the poles. If your planet is hotter than Earth, even the highest mountains won't be able to have glaciers close to the Equator, but mountains in the temperate zones might have glaciers. If your planet is even hotter than that, even the highest mmountains in the temperate zones won't be able to have glaciers, but mountains in the polar regions might have glaciers. I fyour planet is hotter still, even the highest mmountains in the plolar regions won't be able to have glaciers. But I suspect there might be deep valleys and pits somewhere near the poles where ice hidden from sunlight might be able to avoid melting and evaporating. Scientists have detected ice on the surface of the Moon in deeply shadowed places at the poles. <https://www.nasa.gov/feature/ames/ice-confirmed-at-the-moon-s-poles> The planet Mercury gets very, very hot. Water ice has been detectdd in a crater at the north pole of Mercury. <https://en.wikipedia.org/wiki/Mercury_(planet)#Surface_conditions_and_exosphere> So I suppose that it is possible that some smal amounts of snow and ice might exist permanently in permenently shaded places near to the poles of your planet. You don't want to make your planet so hot that no liquid water using life could live there. You might even want to make the polar regions cool enough to be habitable for humans. [Answer] It could be us! [![hot earth](https://i.stack.imgur.com/UCCub.jpg)](https://i.stack.imgur.com/UCCub.jpg) <https://mymodernmet.com/wp/wp-content/uploads/2018/02/climate-change-map-HD.jpeg> This map is sweet. I found the original that did not have the edges cropped! Most of the world has become desert. New Zealand and the polar reasons are prime human habitat now. Ok, New Zealand is already. Primer habitat, then. Your world can be like our world, but hotter. [Answer] ## Not Exactly Your Question, But Might Be Helpful Without getting into climate change and the potentiality of the future, it is possible that a planet could have polar subtropics if we assume it the size of the Earth and has a moon of a similar proportion as the Earth because there was a time in geologic history, we think, that feature an Antarctica that (again we think) was subtropical in climate, somewhat like the Southern United States. In that period of time, the tropical latitudes were extremely hot and few creatures from those latitudes exist as fossils, leading us to the assumption those latitudes were inhospitable. Additionally of interest, most of the Earth's landmass is thought to then have been bunched together in a single clump and it is thought to have had a high central plain that further excluded life from doing much in the way of colonizing it. The reason for the climate being such then, and how it is now, is due to the slow but appreciable cooling of the star we orbit and our relative distance to it as it has advanced in its age.Antarctica has retained its position as at the southern pole stubbornly it turns out through out geologic history, so there being land bunched up at poles of a rocky world with oceans falls within the realm of plausibility by even hard sci fi standards I would say. As for oceans at the poles, the North Pole is thought to have been an ocean for most of geologic history so that too is within the realm of possibility and looking to the way what we think is ice gathers at Mars' poles, is likely to be a more common pattern especially in regards to worlds drying for some reason or another. # As To Your Actual Question It seems, based on present knowledge of xenogeology and what assumptions we can draw from life on Earth, the world you describe would not be possible to contain what we appreciate as life on Earth for a few reasons. The biggest would be the lack of a moon, reducing tidal activity dramatically and exposing this world to more impact events that reset life to a far simpler state than prior to its occurrence. Then there is the issue of how life would exist there, being isolated from the other pole radical divergence between the poles would have to occur which might make for interesting plot points. Was it always this way there or did some cosmic event render a once more fertile world this way. Additionally if the seasons are 4.5 month day/night variations, that implies the planet is spinning remarkably slower than I would suspect necessary and indicate the planet was relatively less massive than the question otherwise seems to suggest it would need to be. Is it spinning so slowly for a reason? That would have dramatic impacts on planet life, which then set the cadence for animal life and probably whip up some intense winds and haboobs coming from the desert region that would choke parts of the habitable zone as well as they disseminated globally, which could even be a good thing considering much of the fertility of the Amazon comes from winds whipped up in African deserts then later coming down with the rain across the ocean. Gravity would be lower due to the smaller size of the planet, less mass = less gravity, which would affect the morphology of the planet's biology singificantly and prevent human children born there from being able to visit the Earth's surface much as being born on Mars is thought to prevent Earth visitations due to the effects gravity has on fetal development. ## But Consider This At present, science boasts as if it knows much when really all of these things we are extremely limited in our understanding of because the only example we can draw meaningful conclusions from is this one and is likely to remain that way for a long time. On top of that, what we know about this world is limited to what we can deduce from rocks and animals that died in conditions perfect for fossilization to then occur, meaning the record is highly incomplete and subject to the interpretation of a small group of people that tend towards being an echo chamber for a certain subset of ideas on these topics that is rather intolerant of divergent opinions whatever they may pretend. Thus I would say there is no reason why your world couldn't work outside of the hardest of science fiction. The key to selling it, if you will, is to mention relevant aspects of it without too much specific detail of the scientific underpinnings. Most science fiction would be wise to do this with these sorts of topics as it lends itself to better aging than anything immersing itself too deeply in these sorts of details. As a final point to consider, if you subscribe to the idea the universe is either infinite or practically so by the standards of humans, then even the most highly unlikely worlds would be suspected to present themselves eventually all else remaining equal. Just the same if you think the universe to be truly infinite, suspect that if nothing else you will have an after life in the sense that this world would then eventually reoccur in this exact configuration in the due course of time. So with that in mind, why not have this world as you describe it? [Answer] Tilt ≈90° A planet can have tropical pole only if the pole is towards the sun with large tilt like Uranus. The axis of Uranus is tilted at an angle of 98° compared to the Sun’s orbital plane. [![enter image description here](https://i.stack.imgur.com/hCLsL.jpg)](https://i.stack.imgur.com/hCLsL.jpg) Strange seasons But only one pole will be tropical at a time for a period of around quarter year. For more explanation, see [this](https://www.youtube.com/watch?v=nWJb5KbX4-Y&t=15s) video. ]
[Question] [ For the purposes of this question, let's use the definition of nanotechnology from the tag wiki excerpt: "technology that works with sizes of less than 100 nanometres". An EMP can vary in frequency range, but Wikipedia gives ["DC to daylight" as excluding infrared and shorter wavelengths](https://en.wikipedia.org/wiki/Electromagnetic_pulse#Frequency_ranges). It also gives the range for [infrared](https://en.wikipedia.org/wiki/Infrared) as 300 GHz (wavelength 1 mm) to 700 nm (frequency 430 THz, or 430,000 GHz). It also states [long-wavelength infrared](https://en.wikipedia.org/wiki/Infrared#Commonly_used_sub-division_scheme) as having a wavelength of up to 15,000 nm, which corresponds to a frequency of 20 THz. (Remember: wavelength is the inverse of frequency.) If we take the longer-wavelength boundary of long-wavelength IR to be the upper bound of "DC to daylight", this means that the pulse has frequency components ranging from basically 0 to 20 THz. In order to induce a voltage in an antenna (whether intentionally designed as an antenna or not), the antenna must be a reasonable fraction of a wavelength. If the antenna is too short, the EM field simply doesn't have time to sufficiently interact with the conductor to induce a voltage. Even at 20 THz, 100 nm represents 1/150 of a wavelength, which is pretty far below what you'd expect to need for a reasonably efficient antenna, which at least for much lower frequencies you might begin to see somewhere around ten times that size (in terms of wavelengths). Let's also rule out a direct EMP strike. (Let's face it, if someone hits your device with what is basically a lightning strike at point blank range, few things will survive unscathed.) Given all this, would nanotechnology likely be affected by an EMP? Why or why not? What factors would contribute to susceptibility or non-susceptibility to EMP damage in a nanotechnology scale device? I'm not tagging this hard-science, but the harder the science in answers, the better. [Answer] Let's distinguish between nanomachines (which are self-contained structures on the nano scale) and nanodevices (which could be just parts in a larger machine). * EMP weapons work by inducing damaging voltage in electric conductors. A nanomachine is very very small; let's say that the EMP comes with a humongous 100 kV/m. (For comparison, the insulating ability of air is about 1000 kV/m tops.) (For another comparison, actual [EMP weapons tests](http://www.thespacereview.com/article/1549/2) achieved about 10 kV/m.) Let's say that the nanomachine is one micrometer long. (That's 1000 nanometers, but hey, let's make 'em big.) This means that the EMP will induce a maximum of a measly 0.1 V in the longest conductor in the nanomachine. Whether a sudden "shock" of 0.1 V is damaging to the nanomachine depends on how the nanomachine works. All I can say is that I've never heard of a semiconductor diode with a threshold voltage of less than 0.2 V. * On the other hand, a nano-scale device which is just a small part of larger machine is obviously vulnerable to EMP weapons. Think of an itsy-bitsy transistor in the ARM processor of a mobile phone plugged in the charger plugged in the power outlet connected to a thousand-mile long overhead line in the national power grid. If an EMP comes that transistor is gone. [Answer] BIggest problem with your question: > > "technology that works with sizes of less than 100 nanometres". > > > That covers an awful lot of things, including the logic gates in the microprocessors that ultimately run the thing you used to post the question. Those nanoscale devices are obviously vulnerable to EMP, because they communicate with the outside world via the medium of long conductors, which can act as antennae, and they're powered by other even longer conductors. Conversely, the cells you're presumably made of also contain many nanoscale components and large-scale conductive networks, but they're pretty robust to all sorts of electrical and electromagnetic abuse. People have survived lightning strikes and actual nuclear EMP after all. Whether any other nanoscale devices would be vulnerable to EMP depends very much on where they are, what they're made of, what they do and how you make them do it. If a blob of nanowhatevers is conductive and macroscale (eg. they form a network) or is sufficiently close to something else that is, then sure, you could potentially toast em. If they're dispersed within some other resilient medium then they probably won't get zapped directly, but whatever is used to tell them what to do might well use macroscale electronic components, and if that gets wasted what use is the nanoscale part of the system? --- With regards to your upper frequency limit though, far infrared... lots of things are vulnerable to being cooked, especially very small things that can't easily shed heat. Seems strange to include that sort of thing in a definition of EMP, but there you go. ]
[Question] [ Wood has, historically, been used, and still is, to make a great variety of things. Indeed, this material has many qualities, the most relevant being: * Commonplace: in most places in your typical fantasy setting, you never have to go very far to find trees. * Easy to harvest and work with: chopping a tree down only requires simple tools and relatively little time and labor. It's also rather easy to cut, shape and assemble. * Strong and light: it's neither brittle nor malleable, and a relatively thin plank or pole is able to hold its own weight and then some. * Comes in long, slender pieces: this make it especially great for building free-standing structures. Now, consider dwarves. A material with such qualities would be very useful to them. But dwarves live underground, and trees don't grow underground. So what materials, that are readily available underground, could dwarves use in place of wood? There are obvious candidates, but they are either too heavy and hard to work with (stone), to fragile for most uses (clay), or require lots of infrastructure and labor to make (metal)... So would a dwarven kingdom need to regularly send lumberjacks out on the surface, or be reliant on wood imports? Or are there alternatives? For reference, here are some things I think dwarves would need wood for: * Scaffolding to temporarily support construction or provide access to elevated areas. * Crude fortifications (palisades) that can be erected quickly and with minimal dwarfpower. * Crates to store goods and materials, and carts to transport them. * Doors and (movable) furniture such as tables, chairs, benches, etc. [Answer] There are always alternatives, and there are certainly places where not much wood grows so I'll use those (compounded with a cave environment) as an example. ### Adding: Fuel (cannot make a forge work without fuel and need it to cook) * Use [Dry Animal Dung as Fuel](https://en.wikipedia.org/wiki/Dry_dung_fuel) which is a common practice in various parts of the world (and presumably would *include Dwarf dung if not enough animals are available). Now normal animal dung would only work for cooking or as a "starter log" for the forges but as this is fantasy - it is conceivable that a [monster that eats rock](https://forum.rpg.net/index.php?threads/d-d-monsters-that-eat-rock.414826/) or magic might exist whose dung would provide a higher energy output. Coal: I didn't put this at first because I thought it was too obvious but Dwarves will have access to deep coal mines which would help them in finding [Anthracite coal](https://en.wikipedia.org/wiki/Anthracite) for their forges. (if they can make charcoal even better, I know it can be made from items such as sugar, petroleum, and coal itself, but someone with more biochem knowledge would have to add more beyond that). ### Scaffolding to temporarily support construction or provide access to elevated areas. * Once again: [dried animal dung](https://www.globalcitizen.org/en/content/who-uses-sht-to-build-a-house/) was used as a fairly sturdy building material since at least the Iron Age in Britain and is still used today in some areas (and modern wattle and daub construction can use chicken wire and plaster/dry wall so using metal wire & dung would avoid needing wood). * For access to elevated areas - make dung or mud bricks and stack them to make stairs. Straw replacement for brick making could use moss or ferns or animal hair (which could also be braided into rope and used to make rope ladders). ### Crude fortifications (palisades) that can be erected quickly and with minimal dwarf power. * This one I'm going to take directly from the military: make [Hesco](https://www.hesco.com/products/mil-units/) barriers using metal wire, cloth (which could be made using some [Sphagnum moss](https://en.wikipedia.org/wiki/Moss#Commercial) or [certain ferns like Horsetail](https://www.fs.fed.us/database/feis/plants/fern/equarv/all.html) which the dwarves cultivate from cave [entrances and twilight zones](http://www.caveslime.org/kids/cavejourney/caveJourneyWhatPlants.html)), and then filled with rocks/gravel, mud, or sand as available. + rocks would be best as they would get stuck in wire making enemies have to take time cutting the wire itself(....and hopefully end up with it falling on them). + I can personally attest to these being quick to put up but a pain to get around/take down. ### Crates to store goods and materials, and carts to transport them. * Use metal? Think A-frame carts, dollies, wheelbarrels (one of the first wheeled carts actually), a little red wagon - all of these are mostly made of metal. And the first wheels were actually made of stone (granted they were potters wheels but the point stands) * Also, since talking fantasy, animal bones have been used to make containers (bone china cups) and shells to make boxes (turtle shells and snuff boxes) so if you have a suitable monster you could use its bones, shell, or carapace. ### Doors and (movable) furniture such as tables, chairs, benches, etc * Mudbricks (or Dung ones) could be molded and shaped around metal frames to build these but I would not use that for much more than stools or small tables. + However, making clay or mudbrick sliding doors might be an option. * Another option for the furniture would be to make more cloth (moss/ferns again) or leather (assuming animals) and then wrapping and drying that around a metal frame - think cloth patio furniture. * A third option could be to use fibers to weave furniture. + My Grandmother used to weave dollhouse furniture for my sisters from grapevines so a solid, strong vine could be used. + Currently hemp or animal rope can be used to make items like hammocks so I see no reason this couldn't be taken further to make rope furniture. - This makes me think of men making a "chair" using their treated and braided beard hair which would really be "dad's chair" :) * An animal/monster's bones - there is one artist who [made a table out of marbel and animal bones](https://www.ft.com/content/369fb48a-9ea9-11e7-8b50-0b9f565a23e1) so its certainly possible. + Could just use the Marble itself too (I've moved marble slabs they are certainly not light-weight but are movable) * Glass - this would depend on if they could generate enough heat to melt sand (1700°C or 3090°F - which is a few hundred degrees higher than needed to melt iron). Then its just glass tabletop with wire or bone legs. If your interested, I have used this [page on minerals and material available through mining](http://tao-dnd.blogspot.com/2010/09/mining-metals-minerals.html) from The Tao of D&D* for a few campaigns I've built* [Answer] The dwarves as a hardly and skilled race capable of carving stone as humans can carve wood. Dwarves live underground and this means that a lot of the reasons for wood would actually be pointless. Dwarves do not need scaffolding. They carve their homes into stone. If they carve up, they first carve a staircase or ladder up. Otherwise, whats the point? they wouldn't be able to reach it anyway. For the majority of their constructions, dwarves are going to be carving downwards. Why? because its much easier to start at the top of a solid mountain of stone and go down, than build ladders all the way up. Digging up is risky. You have falling debris which could destroy your scaffolding or injure others, you require lots of scaffolding to get to everywhere. Much easier to plan and design the building, build a staircase up to the top and debris shaft along the side and dig down from the top. Fortifications are also better made out of stone. Dwarves are skills workmen and can quickly assemble giant walls from simply rock scraps. If you haven't seen the hobbit, it has a good example of the dwarves handiwork. They have no need for something as soft and hard to obtain as wood. Plus, its good for their waste rock. Got to do something with all that debris. Crates and carts can also be carved out of stone. Big stone containers with big stone lids. No reason to go find something that will rot away over time. This also includes furniture like doors, beds, tables and chairs. The dwarves don't need some weak flimsy wood. They want firm and hard stone. You have to remember that traditional dwarves lived in mountains. This implies that they had the ability to work stone with their own hands. Otherwise, it would of been much easier for them to develop above ground like humans did. As an alternative... from dwarf fortress... they can user tower caps, a subterrain tree that grows in a mushroom shape? Or maybe its a mushroom that grows like a tree? [Answer] Less-than-'traditional' metals There are metals that don't need to be heated in order to be shaped, and are found in their "native" form (not in an ore mixed with other minerals). How abundant are they? not very, unfortunately, at least in the real world, but then again, more abundant than the dwarven race. Gold, Cadmium, and Indium might make good candidates. With skill, it should be possible to work them in to shapes thick enough to be strong, and thin enough to not be absurdly heavy. Though some applications would still make them significantly heavier than wood, it should still be light enough to be useful and effective, especially if these dwarves follow the trope of higher strength to size ratios. [Answer] Even more important than wood is food, which must ultimately come from the surface. Therefore, your underground-living dwarves have three options: 1) Low-status dwarves go above ground to do farming, woodcutting, &c, just as low-caste humans do things like garbage collection. 2) Dwarves keep human\* slaves/serfs to do the above ground work. 3) Dwarves trade what they mine, and their skilled metal & stone work, for what they need from above. Of course the three aren't mutually exclusive. A dwarf community might use a mix of them. \*Or other races. ]
[Question] [ CONTEXT and INTRODUCTION Humans establish colonies on Mars with slightly more advanced technology than we have today. The Martian colonists lose all contact with Earth. Over centuries, the Martian colonists develop a distinct culture (w/ practices, religion, language, etc). My story takes place in this culture. A fundamental defining element of this culture is technophobia / technological deterioration (for various irrelevant reasons). I have two issues pertaining to the atmosphere of Mars that prevent human habitation. Firstly, the chemical composition of the Martian atmosphere is unsuitable: low O$\_2$ and high CO$\_2$. Secondly, the atmospheric pressure of Mars averages a mere 600 pascals which is unsuitable for human habitation. Somehow, my Martians need to be able to inhabit Mars and survive (but not thrive). However, as aforementioned, the Martian populace are technophobic. Their technology is rather primitive, technological development is almost non-existent and technology from the very first colonies is irreproducible and/or lost. As such, terraforming is out of the question. As are more advanced technologies, such as spacesuits and pressurized habitats. THE “OXYGEN RADIATION ZONE” Therefore, I am trying to devise a theoretical natural formation that provides the Martians with a localised habitable area. Currently, this natural formation is an unpressurized ‘Oxygen Radiation Zone’. Oxygen is released from underground in a volume significant enough to provide a local area with suitable atmospheric pressure and composition for survival (but not ‘thrive-al’). I have included a diagram to better describe this ‘Oxygen Radiation Zone’. Please consider the diagram from a birds-eye-view. [![Oxygen Radiation Zone Diagram](https://i.stack.imgur.com/CnxV7.png)](https://i.stack.imgur.com/CnxV7.png) Oxygen Radiation Zone Diagram 1. ‘Oxygen leak’: where oxygen from underground is released in significant volume. 2. ‘Livable area’: the area inside the black circle where atmospheric pressure and composition are suitable for human survival. Cities are built in a ring-like fashion, radiating from the ‘oxygen leak’. 3. The extent of the ‘livable area’. 4. ‘Transition area’: where atmospheric composition and pressure are gradually returning to the Martian normal. This area is unlivable. 5. The extent of the ‘transition area’: where atmospheric composition and pressure become indistinguishable from the Martian normal. 6. Martian normal. NOTE: In the diagram, the areas are well-defined, but I imagine the whole thing to be a pressure gradient, from the high-pressure ‘oxygen leak’ (1) to the low-pressure Martian normal (6). COMPLICATION: Winds My understanding of pressure systems is quite basic. From the research that I have done, air moves from an area of high-pressure to an area of low-pressure resulting in the generation of wind. The intensity of these winds is determined by the pressure gradient. Therefore the pressure gradient from (1) to (6) would have to be gradual to avoid unwanted strong winds. Is this correct? If so, would this gradual pressure gradient be extremely large in area? COMPLICATION: Oxygen escape I know that oxygen molecules would escape from this ‘Oxygen Radiation Zone’, because of low gravity on Mars. However, the underground oxygen source that I have theorized is renewable and therefore I believe that this complication is mitigated, as long as influx of oxygen molecules matches efflux of oxygen molecules. COMPLICATION: Dust storms and dust devils Mars is asymmetrically heated in different seasons, which produces a mean overturning circulation called a Hadley cell. In short, this Hadley cell is responsible for the production of global-scale dust storms (among other things). Dust devils are localized convection cells that can reach 1 to 2 km at the bases and may be as tall as 8 to 10 km. How would these dust storms and devils interact with my ‘Oxygen Radiation Zone’? Would they be diverted around it? CONCLUSION and QUESTIONS I understand that this ‘Oxygen Radiation Zone’ is not scientifically accurate to the minute detail. Is my design somewhat scientifically feasible? Are there any major complications that I may need to consider? This is a whopper of a question. Thank you for taking the time to read it and provide me with feedback. [Answer] # Not feasible; requires too much oxygen [Free expansion](https://en.wikipedia.org/wiki/Free_expansion) is a process where a gas expands into a vacuum. Your Martian atmosphere is not quite a vacuum, but it is close enough compared to the air pressure required for your people to breathe. The math behind free expansion is $$\frac{P\_i}{P\_f} = \frac{V\_f}{V\_i},$$ the ratio of volume increase is the inverse of the pressure decrease. We can model the expansion of the gas as a hemisphere (ignoring gravity, oops!). The volume as a function of radius is $$\frac{2}{3}\pi r^3.$$ The free expansion of gas into a vacuum is going to proceed at the average speed of the particles. The mean speed of the particles is based on the [Maxwell-Boltzmann](https://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution) distribution and is $$\mu = 2\sqrt{\frac{2kT}{\pi m}},$$ where $k$ is the [Boltzmann constant](https://en.wikipedia.org/wiki/Boltzmann_constant) ($1.38\times10^{-23}$ J/K), $T$ is the temperature (lets use 210 K as average surface temperature), and $m$ is the mass of an oxygen molecule ($2.66\times10^{-23}$ kg). Plugging those numbers in we get an expansion speed of 17 m/s. Every second, the radius of expanding oxygen will increase by 17 meters. As the radius of oxygen increases, the volume of oxygen will increase by the cube of that number, or a factor of almost 5000. We see from free expansion that the pressure drop is the inverse of the increase in volume, so pressure will drop by a factor of 5000 from a point 1 meter away to a point 17 meters away. But this is just for the first second. Let us set a constant oxygen leak value. The Amazon river discharges 200,000 m$^3$ per second, lets use that value. We must convert this to a number of molecules, since the density of this gas will be variable. 200,000 m$^3$ of oxygen at STP would be about $8.9\times10^{6}$ mol. Using the free expansion formula and the [ideal gas law](https://en.wikipedia.org/wiki/Ideal_gas_law), we can calculate an average pressure for each meter wide hemispherical slice of the expanding gas.The pressure at 15 meters away will be 11 bars, for example. Lets say that the breathable range is from 0.3 bar (this is the pressure used by the Gemini spacecraft as 100 % oxygen) to 0.1 bar (this is the partial pressure of oxygen at about 4000 meters). The distance for 0.3 bar is 45 meters, the distance for 0.1 bar is 65 meters. # Conclusion There is a 20 meter wide safe zone you could operate in, 45 meters from the oxygen source. However, this is with an Amazonian level of gas input to the atmosphere. Adding 285000 kg of gas per second is not reasonable. Lets say we drop the numbers of 285 kg per second. Now, instead of the range from 45 to 65 meters, the safe zone is from 5 to 7 meters. Mars' atmosphere is immense, at the higher Amazonian rate, it will still take 55000 years to fill Mars' atmosphere with oxygen to a breathable level. But, where would you get that much oxygen? What mechanism could generate nearly 300 tons of oxygen per second? The real question is, where does all that oxygen come from? Without any way to explain that, I have to label this one, non-realistic. [Answer] The only way you could make this work is if you went deep underground and had large cave structures with limited access to the outside world. This could allow a more realistic production of Oxygen to escape more slowly and thus have survivable pressure in the cave. Of course you now have the problem of no daylight.. A better way might be to have pressure domes and suits, but have the inhabitants not know how they work. Suit maintenance and pre-use checks would be akin to religious rituals, as would repairs on the domes etc. They don't even see them as technology, they are just part of how the world works that they have always lived with and failing to properly sacrifice oil to the Suit God has a vivid and memorable punishment from the gods; when the joint fails and the inhabitant is exposed to near vacuum. Apostates are fine if they keep the core tenants (important safety checks and maintenance) and die if they don't. A final option would be to have mars partially terraformed, enough to have a (perhaps low pressure but livable) atmosphere. There are a number of proposals for doing that including <https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html> > > What they found was that a dipole field positioned at Mars L1 Lagrange Point would be able to counteract solar wind, such that Mars' atmosphere would achieve a new balance. At present, atmospheric loss on Mars is balanced to some degree by volcanic outpassing from Mars interior and crust. This contributes to a surface atmosphere that is about 6 mbar in air pressure (less than 1% that at sea level on Earth). > > > NASA proposes a magnetic shield to protect Mars’ atmosphere > At one time, Mars had a magnetic field similar to Earth, which prevented its atmosphere from being stripped away. Credit: NASA > As a result, Mars atmosphere would naturally thicken over time, which lead to many new possibilities for human exploration and colonization. According to Green and his colleagues, these would include an average increase of about 4 °C (~7 °F), which would be enough to melt the carbon dioxide ice in the northern polar ice cap. This would trigger a greenhouse effect, warming the atmosphere further and causing the water ice in the polar caps to melt. > > > [Answer] Yes, it is possible. Consider that at the bottom of a valley one is closer to the center of mass of the planet, [thus](http://web.ncf.ca/jim/misc/rockDrop/index.html) gravity can be relatively stronger, and this could reflect on the local atmospheric pressure. [![gravity vs distance from center](https://i.stack.imgur.com/DlIyd.png)](https://i.stack.imgur.com/DlIyd.png) On Earth we don't have valleys deep enough to experience dramatic difference, but we have such feature on Mars: Valles Marineris. Up to 7 km deep, the pressure at its bottom is about 0.168 psi, while the average atmospheric pressure on Mars is 0.087 psi. About double, as you see. Still not high enough to take a walk in T-shirt, but if the atmosphere on Mars would be more dense, it would be first spot to achieve habitable conditions. (this answer has been posted initially to [this](https://worldbuilding.stackexchange.com/q/119605/30492) question, posting it here since it also answer this one. Credits @Willk for the hint) ]
[Question] [ Recently, I've seen those pictures showing what Earth would be like if it had rings, and that made me wonder, what would the sky map be like? This ring would appear as a fixed object (pretty much as stars) so I'd like to know how could this be represented on a two-dimensional map. What do you guys think? [![enter image description here](https://s-media-cache-ak0.pinimg.com/736x/82/54/25/825425423d48da953a2608f7a13b434c.jpg)](https://s-media-cache-ak0.pinimg.com/736x/82/54/25/825425423d48da953a2608f7a13b434c.jpg) Note: The ring is rather rocky than icy (due to the closeness to the Sun) and, since in real life moon is pretty shiny at night and it is made out of rock, I think it would be very visible (during day and night both), as it would reflect a high amount of sunlight. [Answer] The width would look different depending on your lattitude. So fat bands would not be drawn; rather just a dotted line. Maybe other marks showing the thickness seen from different points. In fact, the thickness of the ring — which stars are blocked or shown — becomes an important aid to navigation and will have been apprciated since ancient times. So lattitude marks along the ring center will be an important and relevant feature. The rings spin around, so you won’t have visible asymmetry with ring features that stick to part of the background, as your map seems to show. [Answer] # Ring Behavior Assuming that this ring is visible, it would most certainly need to go into star charts. However, how that ring goes around the earth is important. Is it a simple ring, which hovers around our equator? Are there any complicated behaviors of the ring, such as procession or "wobbling"? # Simple Ring System If ring forms along the equator, then you get to see star charts like the on you've pictured with a boarder. This is no big deal- you just see the equator marked with the "ring." (This would, of course, appear higher/lower in the sky depending on your latitude; charters could make multiple 'rings' instead of a simple line.) If the ring is off-kilter, that is, it's at an angle relative to the equator, this would look different on star charts. It depends on the angle, but it can form a swirl. It'll look like the milky way on your star chart- an "s" shaped curve. The curve goes from super-curvy when the ring is very close, but not quite in line with the equator, to very flat, when it's 90 deg. on the star chart. This assumes the ring, if it is tilted, rotates with the earth so that the places under the ring are always under the ring. (That is, the individual particles composing the ring do not have a geosynchronous orbit, but the ring structure itself does.) # A Moving Ring So rings are composed of things swirling around a planet, but what happens if the plane of the ring moves? That is, the ring is experiencing some kind of procession, just like a wobbly top does. This is very problematic, and would likely qualify it for not appearing on star charts, as the rotating ring could also appear on every point in the sky! If the ring's procession lets it wobble just a little, star charts may show its maximum and minimum positions and dates corresponding to those. Oh, this also means that measuring the height/position of the ring becomes another easy way to measure time, so calendars in such a world may be based off of that. (And yes, it may or may not line up well with the actual year, so no, you may not get a perfect calendar. [Sorry mathematicians](https://youtu.be/qkt_wmRKYNQ)!) If the ring's procession lets it wobble a lot (as in "twice a year, the ring is directly overhead any point on the globe between really far north and really far south, twice a year."), it ought to be omitted from star charts. You may have a small side-chart showing where the ring would be, and what stars are behind it. # Final Note As a final note, spurred by a comment years later, is that the ability for humans to chart things is amazing. If the ring has any sort of periodic behavior, people will attempt to chart it. It could mean there are many 'apparent ring inclination by latitude' marks on a star chart, showing where the ring is based on where you are. It could be a 'ring height vs time' section. (We sometimes show the [analemma](https://en.wikipedia.org/wiki/Analemma) of the sun on globes, so why not the ring?) [Answer] As I understand it, the star map in your picture is what you'd get if you stood at either pole, looked at the hemisphere of sky around you, and mapped it onto a flat circle. Assuming the ring is equatorial (which I think it has to be, in any normal astronomical situation), from the pole it would appear to circle the horizon; therefore, on your starmap it would appear as a thin band around the outside of each circle. If the ring was instead in a polar orbit, it would be a straight line or stripe running horizontally through the center of both circles. If somewhere in between, it would be a sine wave following a path similar to (but less wobbly than) the Milky Way in your image. ]
[Question] [ > > TL;DR: Is there any objective benefit in explaining supernatural phenomena using a single, well-defined and universally applicable system resembling a set of laws of physics? > > > A friend of mine is building a world for his fantasy fiction. He spends much time developing a magic system that is he said will be explained by exotic particles, which in itself will be science-based (conservation of energy, momenta etc). When I asked him why he spends so much time shoehorning explanation of the particle system in the writing, he said that he prefers a world in which all "abnormal" or "supernatural" phenomena (which include giant spiders, flying people, iridescent fireballs and the like) with just one system of explanation. (So he would explain that giant spiders have altered physiology that uses the equivalent of magic to supplement its giant body, that people fly by shooting momentum-carrying particles and so on) When I asked he what about this system of explanation is better than hand-waving each individual phenomenon or not explaining them at all, he said that there are three reasons: 1. In his particular work, he wants to explore what exactly will happen when rational, scientifically-minded people confront seemingly magical occurrences. (The magic stuff is supposed to one day appear in our modern, non-magical world) 2. A system of explanation that requires readers to suspend the disbelief of only one thing is generally better than a collection of things that must be individually taken on faith. 3. His particular magic system explains supernatural phenomenon on the basis of physics, or science in general, which means there is no room for dispute because occurrences are supposedly deducible based on constant laws. The first point is fair enough, it's his personal take on fantasy fiction and not a bad one at that. The third point is I think quite easily demolished because while he suppose that there is a definite system of "physics" that governs the magic, he has not outlined every detail of that physics system yet, because unsurprisingly, inventing extensions to existing laws of physics is not that easy. That being so, magical phenomena in his writing must precede their explanations, and when they are explained, he has to either bend the system just right to explain everything, or that he must introduce some intermediate factors that justify the coexistence of otherwise contradictory things. Imagine the following conversation between us: > > Me: So, you have this giant spiders, right? > > Him: Yes, what about them? > > Me: You said that they use exotic particles to transport energy in their bodies to be both so huge and so mobile, and this process generates enough heat for them to be warm-blooded, right? > > Him: Right. > > Me: Then why is it that the magical butterflies, which is powerful enough to fire energetic projectiles at people, freeze to death in winter? > > Him: It's because the spiders and the butterflies have different adaptations to the exotic particles, for the spiders, the particle circulation is integrated on a cellular level, which allows endothermic bodies, while the butterflies control the particles without using the latter for biological processes, hence they are not endothermic. > > Me: So you are saying that although both are arthropods using exotic particles, they exhibit different responses to ambient temperature because of their difference in physiology, which you honestly just invented to justify this difference, isn't that right? > > Him: Well, yes, but why is this a problem? > > Me: Because if you are going to invent explanations for every specific phenomena, why bother having a supposedly universally applicable system of explanation? > > > The second point, the most debatable of all, seems to be somewhat subjective, but perhaps there is a benefit to it that more experienced world-builder are acquainted with, hence this question. [Answer] Telling a reader the underlying rules of magic gives the reader the ability to guess the feasibility of a set of circumstances in this world. Too many deus ex machinas by the world creator make a story feel contrived. If some unexpected event has a feasible explanation it can surprise the reader positively. It also stimulates the reader when he understands the underlying mechanics of something because he is able to imagine or invent the same solutions to a situation as the writer. It is satisfying for both reader and author to invent some solution that might be introduced later in the story. The system provides a world system that many different stories can be created in. It truly is a form of world building. Having one system ensures cohesiveness to all of the stories built around it. It even allows multiple writers to write stories in parallel that do not contradict each other. It is also very rewarding and intellectually stimulating for the writer to invent a constraint that allows magic to happen. [Answer] A systematic set of "magical rules" allows the reader to anticipate possible actions by the characters. That helps with the engagement of the reader. When a writer describes a deep chasm with a frayed rope bridge, that triggers certain expectations. Those expectations can be met or they can be skillfully subverted. It is an anticlimax if the character passes that rope bridge without incident, while it is no anticlimax if the character uses a steel bridge without incident. In Star Trek there is the term "technobabble" for meaningless technical terms to solve a problem. Usually the solution and it's far-reaching implications are forgotten by the end of the episode. That's not a good thing for a setting. So writing the "magical rules" can be helpful. I'm not prepared to say if your friend is going about it the right way. [Answer] First and foremost for your friend to understand is [Sanderson's First Law of Magic](http://brandonsanderson.com/sandersons-first-law/). While he may have fun developing one system to rule them all, Sanderson's First Law captures the effect his efforts has on the reader: > > Sanderson’s First Law of Magics: An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic. > > > When he wants to explain the value of his efforts have on a reader, this should be the rule he goes to to explain it. He is arguing that a magic system based on one system is more understandable than many magic systems, and thus he can resolve conflict with it better. Sometimes this is true, sometimes it isn't. The real question would be how often he feels the reader could understand the outcome because he took the time to build it into one system. One system comes with a fatally dangerous consequence: if you make your system too rule driven, and someone learns what the rules are, they'll start pushing on them. It's easy to find inconsistencies in magic systems, no matter how hard you try to make them perfect. If you truly sell your world as being consistent, you'll have readers asking "Well why didn't \_\_\_\_\_ do \_\_\_\_, instead of just dying?" Those questions can be very hard to answer. One piece of advice I would recommend to your friend is to look at all of science, and see how little we actually care that it all stems from a handful of "theory of everything" rules. I learn fluid mechanics without having to worry about how Quantum Electrodynamics predicts the repulsive forces between atoms in a fluid. In fact, I can learn everything I need to know about fluid mechanics for virtually all tasks without ever having to talk about gauge theories or symmetry groups (essential vocabulary for modern "theory of everything" candidates). Likewise, I can develop circuits using semiconductors without quantum mechanics at all until I get into the more exotic regions like avalanche breakdown. Neither my fluid mechanics model nor my electrical circuits model reference each other at all! I could make a living with either, never having to tie it to a unified theory. In reality, most of science is taught not as a unified system, but as a collection of independent systems with a promise that a few smart scientists know how they relate to each other for those rare cases where you truly need to resolve a dispute between the theories. Most of us never learn to resolve them, because we simply don't care! What your friend does have to watch out for is the goal of unifying everything into one system taking charge and making things too "flat." If you're trying to build a unified system, its tempting to keep everything at around the same level (i.e. exotic particles) so that you can explain it all. A system can actually feel flat if this ties everything together too well. If he wants his in-world scientists to be exploring the world, he should expect them to explore like real scientists. Real scientists have many models of different fidelities. Only a few have any reason to have one unified theory to rule them all. He should make sure all the other scientists have a chance to build their own (inconsistent) models and beat them against each other, because that sort of dissonance is what really propels science forward. [Answer] There's a lot of content to work with here, so I'm going to stick strictly to your TL;DR: Having a single set "physics" system to explain all magical phenomena in a universe: beneficial? For the writer: Yes it is the most important thing, IMO, to fully develop this system first before starting work on the story itself. A set-laws system such as this will not just explain the crazy phenomena observed in this world, but will also provide opportunity to introduce some very odd and interesting constraints as well. See next section for more about this. This is the part I'm most worried about with your buddy here, as it seems like he intends to work backwards from this kind of model. It seems he mainly wants giant spiders and flying people first, and to have a solid explanation for it all being so second, and this will cause distance from certain readers. Examples: > > The Martian: Andy Weir is mainly a space nerd, and while he was researching the true-to-life [Ares mission plans](https://en.wikipedia.org/wiki/Mars_Direct) he began to think of some of the possible failures and events that could cause things to go wrong. Then he began to think of solutions to those problems, then more problems that could go wrong, more solutions, and began to realize he might have a compelling story here. > > > He built the fictional story ground-up from reality. It has little to no holes. > > > The 100: X-years in the future, nuclear war irradiates Earth, and a ginormous self-sustaining orbital colony develops. The war ended a long time ago and people are beginning to wonder if it's safe to return to Earth now. To test it, they load one-hundred imprisoned juvenile delinquents into a capsule, strap them with health-monitoring wristbands, and send them down. The teens immediately begin to break off the wristbands, and those left in the station can't decide if it really is safe or not on the surface. > > > I got nearly 6 episodes into this series before realizing we've had devices that can measure radiation for a long time already, it's called a [Geiger counter](https://en.wikipedia.org/wiki/Geiger_counter). This discovery completely killed my interest in the show, and I stopped watching mid-episode due to how poorly thought-out the story was. > > > The moral of these examples is to know your audience, if they will mind, and to understand the pitfalls of starting with story-first-science-later. This is the big issue I'm having between you and your friend here, and correct me if I'm wrong, but it seems he's bringing you in later on to help science-out some of his fantastical phenomena. All of this is much easier (and creates a more complete story, IMHO) if you start with the fully fleshed-out new physics system first, and it doesn't seem like that's his main interest from how you described it. If you can't get him interested in this point, the rest is pointless in my opinion. ### Early story (for the reader): In the beginning I imagine he will just "show" us this universe with all of its out-of-this-world possibilities, and not really explain much in terms of how just yet, in the beginning. But having his idea of what's possible here completely nailed-down beforehand is important to also describe what's not possible as well (otherwise it drifts completely into hand-wavy territory). This is a good thing, having constraints. It makes opportunities for interesting plot points, challenges for the characters, surprises for the reader. For example, say people can fly around and shoot lasers from their eyes like Superman, but this is because of an exotic matter cloud in space. So, they also cannot fly at night or shoot lasers as strong, because their planet is facing away from the exotic matter during night. You can expand this in many ways, say a certain time of year their planet is closer to the exotic matter than the rest, and during a certain week their power is so strong they can fly to the Moon without space suits, or something. ### Later story (for the reader): Your first point makes it sound like your friend wants to introduce some regular, normal people from our world into this supernatural world, maybe they got teleported or something. They will probably be astounded first, but soon they will seek answers and go on a journey of discovery, along with the reader. Soon they will start to work out the real cause of this magic. Perhaps the beings of this world thought it always was so and never asked why, requiring our scientificly-minded Humans to help explain things to them and our reader. Towards the end, the true nature of this system could become revealed, showing it might be magic, but it's not magic. A system that allows this, *and explains it sufficiently enough to suspend disbelief*, would not only make a great story, but would create a whole world ripe for follow-up novels, sequels, fan-fictions, etc. Maybe the benefits of starting off science-y and working the story later might start to influence him then. It's up to you. ]
[Question] [ I have the below snippet describing a planet in a (hard) sci-fi setting. This harsh planet has some human settlers, who can survive the climate in light weight environmental suits. > > The planet is a large, dry, desert world without any notable resources and there is barely any surface water, although underground water exists. Its surface entirely covered by sand and dry craggy rock formations. The days are blistering hot and the nights icy cold. It has an atmosphere which is frequently ravaged by violent, electrically charged, sandstorms, often lasting several days. > > > The planet is accompanied by two moons, one, a ball of frozen rock and ice, the other just a small bare rock, encircled by a debris field. > > > Within the constraints of the description above, I'm trying to find a way to satisfy the above described 'The days are blistering hot and the nights icy cold' for the entire planet, if possible. The obvious problem is of course that if the planet is very hot near the equator, it won't be nearly as hot at its polar regions. So, my question is: is there a method to basically create a single biome (hot) desert planet? I thought of things like: * erratic orbit? * extreme axial tilt (maybe like [Uranus](https://en.wikipedia.org/wiki/Uranus#Axial_tilt))? * wobbling axial tilt? * wind transporting the heat? But I don't know how those options would/could affect the climate on the planet and what other unforeseen consequences those changes would bring about. [Answer] So in general terms, if the planet was like Earth in size and atmosphere, but had an orbit of .8 AU's instead of 1 AU, then the planet would have an average surface temperature of Kelvin: 322, Celsius: 49, Fahrenheit: 120 At the orbit of Venus (0.723 AU) the average temperature would be Kelvin: 338, Celsius: 65, Fahrenheit: 149 For reference Earth has an average temperature of Kelvin: 288, Celsius: 15, Fahrenheit: 59 The poles would be pretty warm. Throw in no large oceans and you won't have much water vapor in the air. That means few clouds, and very rare rain. Because of the lack of clouds all the heat will radiate off into space at night. The Sahara Desert gets cold at night. If there is no axial tilt then there would be no seasons, so no winter. Edit: Alternately for more creativity, the star could be part of a binary/trinary star system and so that's a lot of extra heat being pumped at it. Though nights might be iffy at that point. A reason why there might not be much water is if there was something that is splitting the water. It could be photobiological, with a super algae that lies dormant in the sand until it gets wet. Then it reproduces as fast as it can, and in the process splits the water in to oxygen and hydrogen. This would solve the oxygen problem too. Eventually some of the oxygen and hydrogen join back up again into water, and starts the process over. [Answer] Not actually sure if this will fit what you had in mind, but, what about having the planet just turn slowly? I mean, days are warmer than nights, and sunny days warmer than cloudy ones, nice and simple - so if the sun is in the sky for longer days, the days should get a lot hotter with more sunlight and radiation, and the nights a lot cooler, since it's longer until the sun warms them up again. The more rapidly the planet turns, the more the temperature would be equalized, I think, and the slower it turns, the hotter the day and colder the night (like [Mercury](http://www.universetoday.com/35664/temperature-of-the-planets/), though your planet will have an atmosphere and so will not be so extreme) So, the idea that popped into my head as a starting point was a day about three times as long as our day. The middle third of that day would probably be hotter, and the middle third of that night probably colder, than probably even the hottest day and coldest night of the equivalent area on earth - since the area won't have cooled down or heated up in the meantime. [Diurnal temperature](https://en.wikipedia.org/wiki/Diurnal_temperature_variation) variances can range from a few degrees (4\C), to more than a hundred degrees (102\C, granted that is a world record), depending on landscape and season, but someplace like a desert would have the highest variations. One example given of the diurnal variation of a low lying plain was 30\C - which would increase a lot* with longer days, since a day three times as long (with no other differences) could mean a gain and loss of 90\C, and could also mean more* as the rise in temperature during the extra hours of sunlight is heating an area still warm from the hours equivalent to our day, with no chance to cool off first. Likewise the night would have more time to loose heat, and would likely get colder the longer it was out of sunlight. A couple other thoughts - if the temps get higher every day and cool a lot more every night, then any plant that survives would have to be adapted to those temperature variations - it might favor vegetation that is more desert-like (since those adaptions work on our world, in similar conditions). And areas that are more desert-like experience more diurnal temperature variations, since the vegetation doesn't hold the temperatures as well, so it could be a cycle tending towards desertifying any flat areas. If the world is a little warmer than ours (perhaps by being closer to the sun, as AndyD273 suggested), or a little drier, or even a little smoother that might reduce the frequency other ecosystems (like rainforests, the other adaption to hotter temperatures) to a much less observable level. So where we have deserts might be mostly uninhabitable, where we have plains would be deserts, forests would likely be plains (and eventually adapt towards deserts), rainforests would be more like temperate forests (after adapting to colder nighttime temps), and so on. Second point, the violent storms make sense in a world with high temperature variations - the atmosphere would try to equalize the extreme temperatures from the day side to the night side, meaning violent winds that can easily play into your giant electrical sandstorms. I'm not entirely sure about the details of this, but the size of your planet might play a role as well - a larger planet might have more thermal mass to equalize temperatures, and a smaller might not be able to hold onto extra heat, and so have more extreme temperatures. Also, a planet with a warmer core might be warmer overall (as you wanted a hot planet), but it might also be less prone to temperature extremes, since that inner heat could keep the temperature from varying as much between day and night. I know less about this, though, take it as a suggestion rather than a fact. [Answer] The icy moon could be relatively large, have a highly reflective surface and be relatively close so as to reflect significant amounts of solar radiation onto the planet’s surface. If it was in an eccentric polar orbit it would spend a disproportionate amount of its time over the poles. So the poles should get extra heat and light. If the moon did not spin on its own axis and was tidally locked to the parent star its orbit would always be from pole to pole over the dawn / dusk solar terminator so would only ever appear directly overhead over the Polar Regions and for shorter periods at dawn and dusk in other regions. The side effects of this would be some extra heat and light at dawn and dusk in some areas and at some times (depending on the orbital period) as the moon rapidly passed across the equatorial plane. It would also illuminate the night side of the planet to some extent, but would be low on the horizon as viewed from the equator at night and would also be a crescent moon so would provide much less light and heat. Ignoring the planets axial tilt, the moon would only ever appear in its half-moon phase from the poles, a crescent moon from the equatorial night side and a gibbous moon from the equatorial day side. As seen from the poles, moonrise and moonset would always be 180 degrees apart and the points would slowly progress around the horizon over the course of a year. As seen from the equator the moon would appear in its gibbous phase low on the horizon at midday and in its crescent phase low on the horizon at midnight. The moons transition would depend on the time of the year. At one point call it “spring equinox” the moon would always appear low on the horizon and would move from one side of the horizon to the other over the course of the day changing phase from gibbous at midday to crescent at midnight. Over the next 3 months the moon would rise higher in the sky until at “mid-summer” it would pass directly overhead. Over the next 3 months it would sink again until by the “autumnal equinox” it would be back near the horizon after which it would start to dip below the horizon. At “mid-winter” the moon would only be visible at dawn and dusk. The exact size of the planet and moon, the shape of the moons orbit and any axial tilt or orbital eccentricity of the planet could significantly affect the situation. [Answer] Is it possible? Well, I wrote "no" but in defending that position, I thought of a possible scenario where it was. First, how do you illuminate a sphere uniformly? Well, I can't think of any way even with 3 sources (stars). So, could you spin it fast enough so that the entire surface was over a local 'day' exposed to the same heating? Maybe, but I can't wrap my mind around that. I'm guessing you can't. My original model is the primary sun always over the equator, and two fainter suns directly above the N and S rotational axes. The amount of illumination averages to nearly the same, and with winds the weather is the same (why constant illumination (at the poles) would result in the same biome as a (fast?) day-night cycle is a different problem). So, maybe you can do something with that. A couple of easy calculations would determine the amount of insolation per day per square meter at the poles, equator, and at 45°. They'd need to be close. OK, that was a digression. If you had clouds, you could modify the insolation, but I don't think that works. Water clouds = rain, and its a dry world, sand clouds = contribution to different weather/climate. The thicker the atmosphere, the more the illumination can be averaged. So, here's my idea: why not a very thick atmosphere around a planet which is far from any star which relies on its internal heat - the star contributing virtually none of its energy. These type planets are theorized to exist, and aren't necessarily attached to a star. (wandering planet). [Answer] AndyD273's answer has a lot of merit but I think there's a simpler answer; the thinner and drier the atmosphere the higher the daylight temperature will be, and the greater the day-night temperature difference is going to be as the atmosphere bleeds heat faster too. Also the thinner the atmosphere the stronger the winds can be, so an atmosphere of only barely breathable density is going to make the world hotter in daylight and colder at night as well as much winder than it would otherwise be. What I can't help you with is polar temperature distribution, the polar regions are always going to be colder than the tropics even if you funnel air directly north-south from the equator to heat them. A thinner atmosphere is automatically drier than a thick one because the water carrying capacity drops as the pressure does. So a world with a lot of water but a thin atmosphere is still going to have less cloud cover, hot days and cold nights. You can dig into the regolith and recover water for drinking, farming etc... allowing you to have a relatively high population if you want one. You can also change other aspects of the atmosphere to suit your purposes; less Ozone would make the sunlight stronger and more blue and UV wavelengths would make planet fall. More Carbon Dioxide and/or Methane would let you a have higher heat retention but the days would still feel much hotter than the nights due to solar radiation exposure, actually that might let you have something approaching global temperature equality in nightly minimums, the day temperatures are still going to vary depending on latitude. ]
[Question] [ What are the best scientific resources and/or public databases to be taken into consideration when designing real alien worlds? So far, there are thousands of newly discovered alien worlds. Let's say I wanted to illustrate a newly discovered exoplanet X within the solar system Y, so where can I get reliable scientific data such as the solar system's star type where the planet lies, the star's mass, spectra, magnitude as also a few things about the planet such as its size, radius, mass, orbital period etc. Where can I access the most up to date scientific data which is also public available so that I could keep my digital illustrations in sync with that data? [Answer] A quick Google search for "list of exoplanets" yielded several useful resources. * Wikipedia has multiple lists of planets including a list of [nearest exoplanets](https://en.wikipedia.org/wiki/List_of_nearest_exoplanets), a list of [multiplanetary extrasolar systems](https://en.wikipedia.org/wiki/List_of_multiplanetary_systems), a list of [exoplanet extremes](https://en.wikipedia.org/wiki/List_of_exoplanet_extremes) and a list of [potentially habitable exoplanets](https://en.wikipedia.org/wiki/List_of_potentially_habitable_exoplanets), among [many other exoplanet-related lists](https://en.wikipedia.org/wiki/Lists_of_planets). These lists might provide good starting points for laypersons, but of course Wikipedia should never be considered a primary source. * The [Extrasolar Planets Encyclopaedia](http://exoplanet.eu/catalog/) currently claims to list 3,412 planets in 2,554 systems. It gives data on both planets and their stars, in a somewhat technical format (so familiarity with astronomical and orbital mechanics jargon would be useful). See for example [their entry for Kepler-1117 b](http://exoplanet.eu/catalog/kepler-1117_b/) or that for [PSR 1257 12 b](http://exoplanet.eu/catalog/psr_1257_12_b/). It allows sorting on various criteria, including orbital period, planet mass and semi-major axis, where known. * The [Open Exoplanet Catalogue](http://www.openexoplanetcatalogue.com/) claims to be "a catalogue of all discovered extra-solar planets". It currently claims to list 3,308 confirmed exoplanets in 2,496 systems. Its format is likely to be at least somewhat accessible to people who are not professional astronomers; compare for example [their entry on Kepler-1117 b](http://www.openexoplanetcatalogue.com/planet/Kepler-1117%20b/) or [PSR 1257 12 b](http://www.openexoplanetcatalogue.com/planet/PSR%201257%2012%20b/). [The data is available](https://github.com/OpenExoplanetCatalogue/open_exoplanet_catalogue/) as XML files on GitHub, allowing for easy local analysis; as an example, [here's the file for the Kepler-1117 system](https://github.com/OpenExoplanetCatalogue/open_exoplanet_catalogue/blob/master/systems/Kepler-1117.xml). * The [Exoplanet Data Explorer](http://exoplanets.org/) currently claims to list 1,642 confirmed planets plus 3,786 unconfirmed candidates. They allow [searching](http://datair.soe.ucsc.edu/experiment/exoplanet/search/exact) on a large number of criteria, or viewing the [list in table form](http://exoplanets.org/table), and also to plot the data as graphs to visualize trends. The data pages are somewhat accessible; see for example [their entry on Kepler-427 b](http://exoplanets.org/detail/Kepler-427_b). * NASA has a list of [Kepler mission discoveries](http://kepler.nasa.gov/Mission/discoveries/). The table of data is relatively accessible but rather unwieldy, and they link to the scientific papers about the discovery on each planet's specific page (which don't seem to include much else). It's probably as close to a primary source as you can get, but obviously doesn't cover discoveries made by means other than the Kepler telescope. * The [NASA Exoplanet Archive](http://exoplanetarchive.ipac.caltech.edu/) currently claims to list 3,268 confirmed planets, 553 multi-planet systems and an additional 4,696 candidate planets. It can be browsed or [searched](http://exoplanetarchive.ipac.caltech.edu/applications/Inventory/search.html), though the search feature appears to be very limited (allows searching only by name), and the data can be downloaded for local analysis. Like the Exoplanet Data Explorer, allows plotting the data in graphical form. ]
[Question] [ This questions was inspired by [this one](https://worldbuilding.stackexchange.com/questions/41385/is-there-a-more-effective-way-to-build-the-vocabulary-of-a-fictional-language-th). I'm also in the process of making a language, to pair with a writing system I created. I'm a stickler for consistency (language and consistency don't go together well) and I want to focus on the most important parts of my language before I spread out. So my idea was to come up with root words and their meaning and then adapt them in a similar fashion. The only problem is that I have yet to find a source that has a list of important/necessary root words for a language. Does anyone know where I could go to find a list of necessary roots for words? Note - What I mean by that is words, prefixes, or suffixes that are very important to a language. For example, lum-, which means light or shed light on. Word with it are luminance, illuminating, or illu [Answer] For basic words - I guess [Swadesh list](https://en.wikipedia.org/wiki/Swadesh_list) could be useful. It lists ~200 words that are assumed to be basic and universal (it's mostly used to study evolution of languages). Prefixes and suffixes seem to be used differently in different languages (if used at all). But, according to [this](https://en.wikipedia.org/wiki/Prefix), negation is the most common prefix, and prefixes often indicate amount or completeness. [Answer] I'm kind of embarrassed to post the same answer as I did for your previous question. Nonetheless, the book I mentioned [before](https://worldbuilding.stackexchange.com/a/41388/9207), [The Conlanger's Lexipedia](http://www.zompist.com/lexipedia.html) has a lot about root words too. Not just Latin and Greek but languages more unfamiliar to English speakers such as Mandarin and Quechua. There is discussion of how imaginary human and non-human cultures might derive words from different roots in different ways. sSquyu-denatRozhenfelder-Mark ueykhbrzkat. NEG-1p DECL GEN-"Mark Rosenfelder" list.suckle-PASS.PL I am not on Mark Rosenfelder's payroll. [Answer] As an addition to what @Charles and @Roux have mentioned, I suggest that you think about elements that are essential to your culture. For example, if it is a coastal area, it is more likely that you'll have different roots for sea related words (e.g., one root referring to a choppy, dangerous sea and another root referring to calm seas). A culture far from the sea may have only one root for any large body of water, whether it's salty or not. Moreover, if your culture migrated from a hinterland onto a coastal area, it may have assimilated words for sea from the languages of neighbouring, coastal cultures, ending up with two or three words to refer to the sea which are all from different origins and, therefore, have different roots. My suggestion is to use the lists already suggested and create a corpus that makes sense for your culture, adding or taking out concepts. [Answer] ## The meaning I've found myself that generating words is perhaps the most difficult but also the most philosophically rewarding part of constructing a language. All of the other answers in to this question are correct in some way worth pursuing. Roots can really tell the origins of a language. We know part of what Indo-European culture and technology was because of common root words. [We know some of the cultural origins of Uralic speakers based on common root words.](https://en.wikipedia.org/wiki/Proto-Uralic_language#Vocabulary) The number of root words in a language can also vary. English has tons of them since it lacks the morphology to generate (certain) concepts from others, whereas Eskimo languages have much fewer root words ([Central Alaskan Yup'ik has only a couple thousand](https://en.wikipedia.org/wiki/Eskimo%E2%80%93Aleut_languages#Notable_features)), since most ideas can be explained through suffixing a root. I might also add that concepts can be explained by phrases, which is what many languages also do. My recommendation is to think of what culture you're trying to portray when generating root words for its language. It's kind of a personal thing, I find, with a lot of interpretation and artfulness to it. It may also not be absolutely necessary to come up with all the root words at once and then try to generate them. What I often do is when I need a word, try to first come up with one using existing roots, then if I can't find existing roots, come up with other root words to generate my new derivated word from. For example, if I need a word for fireplace and need it, I might rationalize that I want it to be comprised of the words for "fire" and "pile" as it's a pile of burning wood. If I don't have the words for "fire" and "pile", I might decide to make them roots or even compound words themselves. What is worth considering when deciding if a word is a root word, a compound, a derivation or a phrase is whether or not the meaning of it can (or should) be explained through existing concepts. So a fire might not be directly explainable, at least to a child or a layman, but a fireplace is a place you make fire. ## The form You mentioned that you liked consistency, so I decided to tack on this section to the answer about the inconsistencies of roots and how they can often be consistent on a deeper level which may be harder to read. A common misconception is that roots are complete words. This is not necessarily the case. Roots do not need to ever show up as words in a language. They can be less than or more than a complete word. Take for example the English word "rhythm". In its basic noun form, it is pronounced "rith-um", with two syllables. When it however takes the suffix "-ic", it becomes "rhythmic" without the schwa sound before the M. This is because the root is the Greek loan word Ρυθμός - rhythmos, a masculine noun which never shows up in Greek without a suffix. In English, however, grammatical case suffixes are dropped (as English doesn't use them) but the root rhythm as it is spelled is unpronounceable in its root form, according to English phonology. Another good example is the root for kebab in Turkish, which is kebab. However, words in Turkish cannot end on voiced consonants, so the word for kebab in Turkish is kebap. Whenever it takes a suffix, the P turns back into a B, for example: Kebabım. - My kebab. A root can be as simple as a single consonant, so long as your language has rules to turn such roots into words. Roots may also overwhelmingly be of one class of words, for example the vast majority of words in Japanese are nouns and even more roots are nouns. Roots for for a certain word class may also reflect the grammar of that word class too. In Arabic, most verb roots are 3 consonants and the grammar is what order they come in and which vowels they have. For K-T-B, we have: Kitāb. - Book. Kutiba. - It is written. Yaktubu. - He writes. Another way to make roots create interesting behavior is to give them "ghost phonemes". What I mean by that is a sound, which may not even show up in any word using it, but modifies how suffixes behave. Say we have a two suffixes; -sene and -bo, and two roots: ne and ke(n), with the (n) being our ghost phoneme. What I've decided (n) does in this case is voice voiceless fricatives and turn voiced stops into nasals. So when added together, they behave like this: Nesene - Nebo Kezene - Kemo This is quite often how irregularities work in natural languages. A previously existing phoneme disappears from the language but the behavior of the phonemes around it remain affected by it in some way, creating interesting and seemingly irregular results. [Answer] Remember that the people who actually speak a given language don't think about the grammar of that language or the derivation of words from "roots" (which is a construct of linguists); they are simply aware of the similarities between the words that have similar meanings. And since words can be borrowed or altered in meaning, without a similar replacement of the other words that "derive" from the same "root", don't flagellate yourself over consistency. What I'm doing for my own tale is that I write out all of the dialogue in my native language (English, but that's not important), and then starting with the first sentences, I simply come up with some gabble that sounds like actual talk. I then assign the different sounds to different pieces of this phrase. For instance, two young people (a boy and a girl) come into the apartment, short of breath. The girl's father sees them in an agitated state and asked "What has happened?" in his native tongue. I turn this into some gobbledygook: "Sing kledemag?" is the Romanization of what the man actually says. I assign sing to what, decide that kle is the verbal prefix for a single event of undefined time that has already completed as the time of speaking, and demag becomes the verb to happen. I could just as easily have made kle a passive construction, and demag to have do or make or cause as the verb. Her response is "We were kissing," which I render as "Davai ippits" in her actual speech. Davai is the pronoun for we, and I decide that it refers to the speaker and some third person, and excludes the person being spoken to. Then for ippits (which is intended to be onomatopoetic), i- refers to an activity that was ongoing at some point in the past, and -ppits referring to kissing. The father replies "That must have been some kiss," as which point I remember to include the prefix kle in the phrase carrying the meaning of must have been, since the tense and mood of the verb seems to be the same as in the first sentence. And so on. After a while of doing this you'll have a small working vocabulary, at which point you should take stock about how this thing is growing. Resolve any inconsistencies great enough to interfere with a native's understanding of speech in that language, and make sure that the correlation between words and concepts in the constructed language is different from your native language, so that if the same word in English covers two different concepts, the same two concepts are not thus united in your conlang. [Answer] As a starting point, you might consider [Indo-European vocabulary](https://en.wikipedia.org/wiki/Indo-European_vocabulary). It gives a list of PIE kinship terms, names for classes of people, pronouns, particles, numbers, names for body parts, names of animals, basic adjestives, etc. This should also help you to see how these were combined into words. [Answer] American Heritage has a list of Indo-European roots <https://www.ahdictionary.com/word/indoeurop.html> Perseus dictionary lookup allows searching in Latin, Greek, Arabic, Old Norse, or English, for words containing, beginning, or ending with particular forms. Here's a result for words containing --man-- in Greek <http://www.perseus.tufts.edu/hopper/resolveform?type=substring&lookup=man&lang=greek> ]
[Question] [ The massive Golems are nearly impervious to harm. Thanks to the New Golem Army, the nascent Dutch Republic's castles and forts are now safe from harm. The century-long external threat has been finally and permanently put to rest, as the bones of our enemies are bleaching in the sun by our castle's walls. A decision has been recently made in the Staten-Generaal council that defense is to give way to offense. We will no longer be content to defend ourselves in our high castles, leaving the enemy to roam free, but instead, we will march out and take the fight to them, and bring them down for good. This brings up obvious problems. The strings of wind- and river-mills on our mighty rivers and polders are currently providing the power elektrik to galvanize our Golem troops. The question now is how do we handle this out in the field, far away from the castles and the galvanic stations? A young apprentice has suggested that given the frequent storms that batter the lands of our neighbors, we could power our army from the lightning strikes themselves. Would that be plausible with our rough copper wiring? How much energy could we harness from these bolts? --- Assume that golem insides are a black box, we don't care about that. Would capturing lightning be plausible with early renaissance technology? If so, how could it work and how much energy could we get? For the sake of argument and specificity, let's assume that a fully charged golem can operate for 5-7 days on normal stress level, and for 1/2 day in intense combat. Before you ask, I didn't get the chance to run a voltampermeter by the golems, so I don't know their full capacity. If lightning is deemed unfeasible, I'm willing to hear suggestions for alternative ways of charging up in field operations conditions. [Answer] Lightning is quite conceivably a good source of power for the golems. An average bolt of negative lightning delivers 500MJ of energy, and a large negative bolt could deliver 35GJ of energy. Positive lightning bolts are very much rarer, but could deliver up to 3.5TJ. In terms of watt-hours, this equates to 138kWh for an average negative bolt, 9.72MWh for a large negative bolt, and 972MWh for a very rare positive bolt. Assuming that a golem uses about a hundred times the energy per day of an average human male (11MJ or 3kWh), i.e 30kWh/d or 180kWh/charge (lasting an average of 6 days of non-combat operations), it might take two average lightning strikes to charge a golem, or one large one could charge up to 54 golems. You couldn't count on a positive bolt occurring all that often, but if it did occur - and polarity wasn't an issue - then it might charge up to 5400 golems in one strike. Naturally, given that a lightning strike might more than charge a single golem, a golem force would be interconnected and charged as a unit, not as individuals. We'd better hope that the golems can accept this fantastically high charging rate without exploding - Negative lightning can have currents of 30-120kA, and positive lightning 300kA, and if this energy was released over a very short period of time, might result in an explosion equivalent to nearly 12kg of TNT for an average lightning bolt. The main problem with this is getting the lightning to strike where you want it to. Fortunately, the emerging field of rocketry can come to your rescue. A simple black-powder rocket (appropriately waterproofed for use in a thunderstorm) could drag a fine copper wire into the sky high enough to attract a lightning bolt, which will strike down the wire, incidentally turning it to plasma, but causing the bolt to strike right where it is needed. Sure, you'd need a lot of copper wire and rockets to keep your golems charged, but war is expensive, and this is a minor cost. You just want to hope that thunderstorms in the area of operations are as frequent as people say they are. [Answer] I would not base my strategies on that. Seeing how they power their golems, we can safely assume that they have some knowledge of electricity. Technology isn't too complex, you need metallic rods and connect them to some batteries or directly to the golems. However, I would recommend to think about another alternative. Indeed, storms are very local phenomena, and lightening strikes are hard to predict (you can improve by changing the voltage of your rod, but you probably want to save on energy. And what would be the autonomy of the golems after a storm? Plus your enemies might now that, and hide after a storm before attacking once the autonomy is over. It is hard to devise a strategic campaign on seemingly random and unpredictable elements. Alternative With the water mills, they have some alternator technology. A more flexible, based on the same technology are [windmills](https://en.wikipedia.org/wiki/Windmill). The Windwheels were known since antiquity. And it could be based on, e.g. the top of [siege towers](https://en.wikipedia.org/wiki/Siege_tower) for large production. And individual wheels could be placed on more transportable poles. With the autonomy they have, you could be sure to prepare well for field battles. [Answer] The problem with using lightning-power is that it's not a very reliable power source (unless you have weather mages on hand), plus it's probably way too powerful to be safely harnessed by Renaissance-era technology. Not only that, but once your golems power down, you'll have to wait for the next rainstorm to get them going again. It's very possible that the enemy could seek to recapture their lost land in that time, and without your golems you're going to be in a tight spot. Other answerers have suggested wind power, but again, you have to rely on the wind, and in a wartime scenario I would not want to leave the effectiveness of my strongest units up to nature. What I propose, then, is to make some adjustments to your watermills: in short, turn them into turnstiles or hamster wheels, and use good old-fashioned horsepower to generate electricity. This method will make use of things you should already have: the technology for horses turning cranks has been around for a very long time, horses are already a must-have for any military expedition, and the food to power them grows right out of the ground. The downfall to this system is that it is not going to provide the energy you need nearly as fast as a lightning bolt. Your army is going to have to sit around for a while waiting for their golems to charge before attacking. But back during the Renaissance, this already happened; either you met the enemy at a field and discussed terms for a while, or you met the enemy at their castle and laid siege for a few months. This should give your army enough time to power their golems, at which point they can do their thing, then go straight back to recharging to fend off any counter-attacks. [Answer] Ride the Lighning As long as the Golems can shrug off the extra current from the lighting bolts they don't need, then using lightning to power them is completely feasible. In the context of the story, only being able to operate in the context of thunderstorms makes for some really interesting strengths and weaknesses. Golems only have the power to attack when there's a thunderstorm but when they do attack, they are unstoppable. Attacks during a thunderstorm may prove exceedingly dramatic. "A wall of Golems advanced out of the gloom, lightning dancing along the charging towers looming behind them. An unearthly, crackling glow came from the Golems eyes striking fear into the hearts of the hapless defenders." Large copper cables are sufficiently conductive to act as grounding wires for lightning rods. I expect that there would be a couple accidents where someone forgets to keep the lightning aggregators grounded and gets fried when a lightning bolt jumps to something/someone it wasn't supposed to. Portable Windmills This is the mundane approach. If military operations need to happen in the winter with it's despicable lack of lightning then this would be a good evolutionary push to develop windmills that are mobile. Certainly not self-powered but something that can be deployed behind friendly lines similar to cannon or siege weapons. With the right kind of demand, inventors could quickly discover ways of building portable galvanic generators. Even if the inventors don't know exactly how the portable generators work, they will know that they work and can experiment to find ever more powerful generators. [Answer] You have golems. Consider building a giant dam if you have a suitable river. Hydro power will keep 'em going. Gonna need heavy duty extension cords though. Expensive but not undoable (wrap steel cable in rope and soak in wax, run at 10,000 volts). ]
[Question] [ Okay, this is unrelated to my current world building in any way whatsoever, but... I have always been a huge fan of the humongous mecha genre (bonus points to anyone who actually recognized my avatar pic), and have done some world building in such a setting before. Unfortunately, it never really gets anywhere. However, I would like to ask this: Besides bending the laws of physics or the fundamental rules of our current world (i.e. no 'lighter gravity' or 'magic'), what would be the best way for a humongous mecha to bypass the square cube law, while still being able to move respectably? Feel free to make as many assumptions as needed about the setting's scientific level - that is not the issue here. Some rules: 1. The mecha must be fundamentally humanoid. It does not need to walk with its feet, but it must have legs. 2. The mecha must actually be huge. I mean 18 meter minimum. I know there are some mecha shows out there (Code Geass, Kotetsu Jeeg, etc.) that are less than that, but I've always held by 'anything smaller than RX-78 (of Gundam fame) is just too small. [Answer] The biggest problem with giant anything, as everyone else has mentioned, is pressure. You can't scale up a human, for instance, because human bones couldn't support the force in play. That means the mech has to be built with strong materials, and the mech has to be lighter than a scaled creature. ## Bones and armor [Titanium](http://en.wikipedia.org/wiki/Titanium) is a good choice, though it could get expensive for giant mechs; granted, if you're building an enormous machine, cost probably isn't a huge factor. Titanium has a tensile strength of about 434 MPa (63,000 psi) - about the same as steel, but for much lower weight. Titanium alloys have a much higher tensile strength, over 1400 MPa (200000 psi). Regardless, it would make a good armor as well as good support. As a bonus, titanium is very corrosion-resistant, which means you won't have to worry about your robot rusting. [Carbon nanotubes](http://en.wikipedia.org/wiki/Carbon_nanotube) are also a good bet. We don't have the technology to make anything large-scale with carbon nanotubes, but we'll get there eventually. There are many types of carbon nanotubes, depending on how the atoms are arranged; one had the tensile strength tested at 63 GPa (9,100,000 psi). Other varieties are theorized to have a tensile strength of over 160 GPa (23,206,000 psi)! However, as strong as carbon nanotubes can be, they are strongest when pulled, not pushed, and are weakest against forces from the side. They would make great "bones", but probably not outer armor. [Graphene](http://en.wikipedia.org/wiki/Graphene) is super strong - a tensile strength of 130 GPa (18,855,000 psi) - but is very brittle. It would make an excellent bone. Oddly enough, bamboo may actually work quite well. It has a tensile strength of 350-500 MPa (50,760-72,520 psi), and is quite light, with a lower density than even Graphene. Bamboo is also very easy to come by; it grows quickly in natural environments, with no need for mining or creating in a lab. [Other materials](http://en.wikipedia.org/wiki/Ultimate_tensile_strength#Typical_tensile_strengths) may work as well, to varying degrees; I'm sure the future holds much stronger materials, too. ## Why not lighter? The reason titanium is a better choice than steel is weight; but what if we make the mech even lighter? A giant robot that is essentially a thin shell may not stand up well in hand-to-hand combat, but it would satisfy the requirements! A mech built using thin plastic or aluminium tubing and steel wire as bones and muscles could but placed inside a canvas balloon and inflated; the canvas would be nearly immune to 'crushing' attacks, and the bones wouldn't have to support much weight. If the mech were filled with a mixture of air and a lighter-than-air gas such as helium, it would be able to support itself with very little effort. Because of its low weight, the internal structure would be very thin; a giant mech made of inflated canvas could be built today for less than the price of a used mid-sized car. ## Put it together I suggest the best of both worlds: an air-filled canvas robot, plated with titanium, and with carbon nanotube bones. The internal structure would be filled with a lighter-than-air gas, resulting in a machine that towers above the earth, but can step on a house without crushing it. If it wants to. As an added bonus, there is a lot of extra room in the mech that can be used to store weapons or snack food, and the bouncy exterior would protect any occupants. [Answer] The square cube does not forbid bigger structures; it just means that the structures must be designed accordingly (less dense, with stronger materials, or both). The square cube means that you cannot just pick up a man or an ant and multiply its size by 10, because it would then weight 1000 times the original while being only 100 times stronger. But if you change the calcium bones with titanium ones, and likewise enhance the muscles, then you can get your giant. Given that, as long as you justify it, there is no "hard limit". Possible ways of actions: * Strong materials. If they are hard enough, then you may even not need solid beams but may use a grid (think Eiffel tower), helping you save weight. * Motors/actuators. These are complicated, specially for arms (since increase of the weight of arms may make your mecha unstable). Also, you would need to modes (maybe two types of motors?), one for rapid movement and other for precision maneuvers (and control software that automatically decides which to use based in the human input). * Center of gravity. You have to take into account that the operator is used to stabilize himself with a body quite different from the mecha. Apart from the control software automatically balancing the mecha so it remains stable, you probably want to adjust weight in the top of the mecha so it is not top heavy, and arms must remain light. * Also, and based in what I said in the previous points, you do not want payloads (like weapons) in the arms/hands, but in the chest (or even better, in the legs, but that gives them a shorter field of fire). A third leg would be ideal; if it goes against the "humanoid" rule then make the legs as separated and with feet as big as possible. [Answer] As has already been pointed out, the square-cube law prevents making a human 10x taller. But we're not building a human. Giant robots need stronger structures, but those are plausible. As I see it, the main limitation would be ground pressure. If you scale up a human 10x taller, the weight increases 1000x, but the area of the feet increases only 100x. At what point will the giant's feet sink into the ground? I was thinking about kaiju a while back and looked up this: <https://en.wikipedia.org/wiki/Ground_pressure> (unsourced values) > > Human male (1.8 meter tall, medium build): 55 kPa (8 psi) > M1 Abrams tank: 103 kPa (15 psi) > 1993 Toyota 4Runner / Hilux Surf: 170 kPa (25 psi) > Adult horse (550 kg, 1250 lb): 170 kPa (25 psi) > Passenger car: 205 kPa (30 psi) > Wheeled ATV: 240 kPa (35 psi) > Adult elephant: 240 kPa (35 psi) > Mountain bicycle: 245 kPa (40 psi) > Racing bicycle: 620 kPa (90 psi) > ... > Note: Pressures for Man and Horse are for standing still. > A walking human will exert more than double his standing pressure. > A galloping horse will exert up to 3.5 MPa (500 psi). > > > These figures suggest up to 5x human ground pressure is still feasible for walking on non-reinforced surfaces. Beyond that, I don't know. The big open question is the density of a mech. A human's density is similar to water's 1000kg/m3. I was trying to estimate the density of a tank. <http://www.fprado.com/armorsite/abrams.htm> I don't have a figure for the volume, but I'm guessing 50m3 or more, with a weight around 60t. So even an armored vehicle isn't much denser than water, surprisingly. Amusingly, the common anime design style of mecha with large flared calves might be entirely logical - allowing larger feet. What appears to be an extreme approach to minimizing ground pressure is seen in Basquash. The mecha here are on the small side, but their feet are almost as large as their torsos. I still doubt they could run on ordinary rooftops as they're shown to, though. [Answer] you need to contrast gravity anyway. two ideas come to mind: a "belt" made of thrusters, used to both lower weight and keep balance, or some sort of huge antigravity core roaring inside the titan's chest, a technological heart that keeps it standing (how poetic) [Answer] The easiest way to get giant robots that still can move 'easily' is to use strong light materials. [Titanium alloys](http://en.wikipedia.org/wiki/Titanium_alloy) are a great start for lightweight vs. strength. A possible step above that are [carbon nanotubes](http://en.wikipedia.org/wiki/Carbon_nanotube) which while currently expensive to make in any quantity would be a light and very strong material to create anything with. It is assumed if we ever create a [space elevator](http://en.wikipedia.org/wiki/Space_elevator) it would be made out of this material. [Answer] Other answers cover my initial thoughts (anti-grav or things like carbon nanotubes) but I thought I'd throw a more off-the-wall answer into the ring: A really dense atmosphere The reason the largest animals exist in water (whales, large squid, etc) is because the water helps support their weight. This significantly reduces the square-cube issue and lets them grow to a bigger size. A sufficiently dense atmosphere can provide a similar effect - it acts almost like a liquid and will help support the weight of your giant mecha. One theory is that Earth's atmosphere used to be incredibly dense, and that was the reasons dinosaurs were able to grow to such large sizes compared to today's animals and not collapse under their own weight. There are a couple of potential problems. 1. Earth's atmosphere isn't dense enough. So you'll probably need to be fighting on alien worlds - maybe an alien race that prefers atmospheres like those, so you'd use these only offensively. Or maybe Venus has stores of Unobtanium and corporations are duking it out with mecha-mercenaries. 2. Your pilots will be squished by the heavy atmosphere like tiny bugs (well, maybe not. But they might suffocate or get the bends). There's a couple of fixes - you could have a protected control module that's pressurized to human-friendly levels. Or genetically engineered Venus-people who laugh at the pressure. Or non-genetically engineered native Venusians who laugh at the pressure and are willing to fight for you. Or robots. Probably robots. [Answer] read CANNON GOD EXAXXION\* they handled it great. 1. your mech needs and antigravity/inertia control generator to withstand its own forces 2. it needs force field generator to broaden the "footprint" just keep the feet from sinking into the ground. 3. It needs a nuclear or antimatter reactor inside to power all that. 4. you need a physically enhanced pilot to survive driving it. And even then just walking through an urban environment destroys said environment. * be warned adult content. [Answer] There's very few materials capable of being built as a moving object to such a scale. Even if you had tons and tons of titanium. scale it down, it's more plausiable. But none of that really matters; as building a mecha is a notorious waste of money and resources. When Russian armored forces attempted to put down a rebellion in Chechnya from 1994-96 they were slaughtered in urban fighting by light infantry with modern weapons. This was because widespread use of the simple Rocket Propelled Grenade (RPG) has made foot infantry much more powerful than in previous wars. Recall that thousands of illiterate Somalis mauled US Army Rangers in 1993. Unleashing it on the battlefield and your enemy is gonna unload by shooting it's ankles which supports ALL it's weight. With a barrage of RPG's and missiles or tank guns. The Gundam series is by far the silliest emphasis of mechanized warfare. Building an anthropomorphic suit of armor the size of a 10 story building is a target waiting to be shot at. [Answer] The solution for a truly humongous mecha in a gravity well is an active support structure, similar to the concept for a space fountain (<https://en.wikipedia.org/wiki/Space_fountain>). The principle at work here is similar to levitating a plate on a stream of water. It doesn't matter that no realistic material known to man is capable of handling the forces your mechs produce while moving, because you're not relying on intermolecular binding forces here. The "bones" of your mech are simply long cylinders that are under constant internal stress created by a stream of particles pushing the plates apart. This counteracts the force of gravity pushing on the plate from above and allows you to build structures of any height. Including a 50 meter or even kilometer tall mech, if that's what you want! So far we're totally within the realm of known science and engineering. The caveat? You have to constantly supply energy to push that stream of particles into the plate or your entire structure falls apart. Water isn't a good fit for this because the amount of friction and energy expenditure will be astronomical, unless you're going for a steampunk mech I guess. What you'll want to use is some kind of superconductor. You fire pellets of magnetic material or streams of charged particles from the bottom of your active support structure at the top, where they get deflected by a magnetic field and fall down again. You do this with enough force behind the stream to hold up the top plate. When the pellets/particle stream fall to the bottom you extract most of the energy you put in (less complicated than it sounds, any magnet falling through a conductive coil induces a current and slows down), collect the stream and shoot it up again. The tube/bone has to be evacuated of air so you don't lose any energy to friction. The superconductors are to make this as efficient as possible. Now you miniaturize this setup and you have an arbitrarily strong tube, stronger than any old carbon nanotube. As long as you put energy in. Yeah, it will need a lot of energy. How to power this whole contraption is another question entirely. Maybe a nuclear reactor or a giant ball of Polonium-210. ]
[Question] [ I've been working on a world for a game I'm making. The basis of the game is that you have to carefully manage your resources, and to keep moving. I'd like to build a world which fits that. These are the requirements for the world: * There is some incentive to move at least once a week; more often is fine. * There are multiple tribes of people in any given geographic area. * Said tribes are generally untrusting or outright hostile to one another, and it's not uncommon for one to attack another without provocation. * The level of tech is at or beyond the early computing (very early; I mean vacuum tubes) era, but no FTL (or if there is, something that prevents other planets from interfering with Earth). I don't really care about computers themselves, but the weapons should have at last the same capabilities as the infantry weapons (i.e. rifles, pistols, etc.) of back then. How could this develop from the present day? Apocalypses of any sort are fine, but the most realistic solution wins -- i.e., the more possible it is, the better. Bonus points if you convince me that it actually will happen. Thanks in advance for the help. Addendum: I'm only looking for things that could happen in the real world. Things using magic or psychic powers are super neat, but not what I'm looking for. Sorry to all the fans of Deathworld out there. [Answer] I suggest gathering lichens in Antarctic-like land. In typical RTS games non-renewable resources appear naturally if you don't make them renewable. Energy/food is an realistic example. (Water and other materials could be filtered and reused.) If your tribes lived in a land like Antarctica, where the only source of food and fuel are slow growing lichens, the tribes would have to move constantly. Relatively advanced technology is necessary to survive. Competition justifies distrust between tribes. Greenhouses or solar batteries would be excluded if there was too little sunlight - polar region like Antarctic itself or planet further from its sun than Earth if you don't want polar nights. If you don't mind very harsh conditions, feces could be used as fuel for light and weapon production. Metal from bullets and weapons of killed units should also be gathered to reuse (With deep ice, the only other metal source would be meteorites). Realistic dark powder production would require extracting sulfur from lichens or waste (maybe hair), because sulfur escapes in gases and is not abundant in air. Potassium (in form of salts) could be regained from solid remains from powder burning. It is also a macroelement about as abundant as sulfur in food (including edible lichens; ~ 2 g/day ratio) and human wastes. Nitrogen is abundant in organic material and, with use of some energy, can be obtained from the air. Carbon appears in organic materials by definition and hydrogen and oxygen are everywhere in different forms. With adequate machinery and fuel you can produce dark powder. Materials for more modern explosives can be actually easier to obtain. [Answer] Moving resources If you're living on buffalo, then you're going to be a nomad :) Weather/plant cycles move the goal/good stuff often enough. You'll need a new weather system / new plants for this. (ie: not Earth standard) Migrating problems An alternative to moving resources around, is to make problems. * Flat world: maybe high-winds * Plains with constant fires from lightning strikes (ie: if FL were part of the midwest) * Some type of locust or predator which forces movement - by eating your resources or you * Weather (winter comes every week to different areas) * Rogue microwave power/laser satellites hit different areas every week / take a week to recharge/reacquire targets * Nanobots * Magic * Culture (This is how people survived the apocalypse, and it would be heresy / disrespect to our ancestors to do otherwise. Kill anyone who isn't a nomad, and burn them out.) * Aliens: burn down any permanent settlements from orbit * Rampant biowarfare; diseases take down any large, or settled community (which would account for hostile tribes; the Other is deadly to even talk to). The more I think about it, the more I like this solution. You can be stationary, if you want, it'll just cost you more and more people. Eventually to a 100% kill rate. But, you could set yourself up for shuttling between camps in a seasonal rotation; plant in spring, go somewhere, go somewhere, go somewhere, weed / cultivate, go somewhere, go somewhere, go somewhere, harvest & first processing, go somewhere and process more, go somewhere. --- But this is a tough sell. There are a lot of advantages to settling down, which you'll have to negate. I'm sorry, there were a lot of advantages, depending on how screwed up you've made the Earth, you might be down to just the lazy factor: it takes energy to pick up and move. For example, you'd have to negate soil fertility (maybe continue blowing it away), standing energy sources (dams, rivers, wind and water mills, ability/need to pump ground-water), reasonably accessible mining resources, the need for concentrated and specialized labor, ease of constructing factories (if everything is nano-assembled, no more factories), etc. But even given all of that, some people might be willing to be stationary (traders, etc) - if you want to eliminate them, you'd have to be pretty harsh on your reasons. Moving in winter, during a blizzard is going to be a tough sell / and possibly impossible. Wintering very far north may be a problem, when you can't stock up and transport the fuel for the winter. [Answer] You would need to have a limited lifespan resource that is necessary for the continuation of life. This would necessitate the society needing to go where the resource is, and would also restrict the size of bands to the amount of life the resource can support. One possible idea is obviously water, where the water source dries up after X gallons are taken out, and appears somewhere else. Possibly an aquifer that shifts pressure with the movement of the planet. Pressure moves off, well dries up, peoples gots to move. * Water is necessary for life * Disappearing resource precludes building piping, wells, etc. * Limited amount of water means limited size of settlements * Moving locations also limits how much can be bottled/transported to permanent settlements This would also introduce the concept of raiding parties, to where if you are running low on water your outriders can raid another encampment for their source and/or stores. There are any number of resources that you could do this with, but the basic concept would be a resource that cannot be moved/brought to you, and has a limited lifespan. (A migratory food source that can't be domesticated would be another possibility, but a little tougher to spin.) [Answer] The only scenario I can think of that would require migration is the world in Harry Harrison's Deathworld. All life is psychic and will fight back against threats..such has humans killing animals for food and chopping down trees for housing. It even evolves nastier forms incredibly fast and feeds off your hatred off the attacking life. In the book, one group had its own psychics and could settle down by not killing much and calming the reaction of the planet. The other group was wiped out. But if you had no psychics, you might still survive by moving on before your hatred and damage caused a massive reaction by the world to a new site. Even then, though, you could probably shuttle between some half a dozen or so camps rather than have to move every week or so. [Answer] In Absolution Gap by Alistair Reynolds, there is a constantly-moving convoy which continually moves around the planet to track and monitor a gas giant in the system, keeping it overhead at all times. There are quasi-religious overtones involved as well, with those in power using faith to ensure plenty of help to keep the convoy moving. Just another element to consider. [Answer] Moving an entire tribe on a continuing weekly basis is difficult to justify. Here is one attempt. Your civilization is divided into two main groups; nomads and settlers. The settlers are long term residents who fortify a spot and control local resources. This could be a mine, an orchard or vineyard, fertile cropland, water or ice, or large herds of animals that don't take well to be driven around constantly. Settlements are generally self-sufficient (if barely) and will generally have a population that outnumbers any 4-5 nomad tribes, possibly even more. They don't require trade to survive, but it it beneficial. Nomad tribes are welcome to stop briefly (only a few days, generally), but few individuals will be allowed within the gates. Most trade will take place outside the gates, or perhaps within a courtyard between inner and outer gates. The nomads are merchant clans who move between settlements and trade for the local resources with resources either gathered from the "wild" or purchased from other settlements. While a nomad tribe might survive on its own, trade is generally vital to its prosperity. Conflict between tribes is common, but unless overwhelming force or ambush is available, most battles are brief skirmishes. The risk of losing warriors must be carefully weighed between potential gain and the future need for protection from attacks or wildlife. An exception to this might be during and directly after a period of relative prosperity, when there might be a surplus of young warriors wondering if things wouldn't be better if they were the ones in charge. [Answer] Staying in the same place is usually very convenient. Buildings and agriculture are actually pretty useful. Remember also that an industrial world needs factories. Factory boats exists because of some economical gain, but having all of your industry to be mobile would have a huge cost. So, you need to have that cost extremely reduced, and the cost of staying in the same place extremely augmented. ## Reducing the cost of mobility A constant food supply is probably the most important thing to have. An easy to gather and to eat wildlife would be important. A plant that would compensate its high edibility with a big reproduction rate so that it would cover all the land. Also, you need fuel if you want to constantly move (or a lot of tamed animals you'd need to feed). Then again, you may use the same plant as a combustible. ## Increasing the cost of stability Digging a hole and staying in there is usually a very good strategy for survival. What could make this go wrong? ### 1. A cosmic event going along the planet It can be a terrible half-a-year night, a tide so strong it causes earthquakes or solar storms that make the lighted part of the planet inhabitable, but due to a regular moon/sun/planet movement as an impact so big on some part of the planet that people need to constantly run away from it. The third installment of the Cyann saga (a french graphic novel) is to me the best example of this (they need to move because night brings death). ### 2. Gravity can be weird sometimes For this one, I have to mention that I have no idea of it is it physically possible. Your planet is actually a moon, and the gravity pull from the moon is smaller that to the one from the planet even on the moon's surface. As the moon is constantly spinning, you want to stay away from the planet as you would fall to it. Now that I think of it, your moon could not keep its atmosphere. But there may be a way. ### 3. The great plague is roaming They are numerous, they can't be stopped, if they find you they will eat you or everything you have or both or worse. They are the locust or rats or zombies or nano-killers or even cyborg werewolves from a not-too-distant future. If you see them, you can outrun them, but everyithing you'll leave behind will be totally destroyed. When you see some other tribe in the distance, you have no way of knowing if they are humans or cyborg werewolves. How could you trust anyone? Just run. [Answer] If you look at "annual round" nomads, hunter gatherers, they would often move every day for a large part of the year when food was plentiful but sources were scattered only settling in for the winter in sheltered sites to process foodstuffs gathered during the wandering months and to craft the material and artistic trappings of their culture. Humans have only really settled down into villages etc... since the Neolithic, the late stone age, when farming became our main source of food instead of the wild, if the population density is low enough for hunter gatherer survival and food sources are plentiful enough the year round then moving on would likely be the norm. [Answer] Your planet is rotating at the same pace as it travels around your sun, with habitable temperatures around the terminator. Your nomads live in this shifting temperate zone, and must drive their herds ever forwards for fear of freezing temperature and plant-life that goes into deep hibernation for the sunless year-long night. They can't travel too far in one go as they'll end up in the blisteringly hot dayside, so must travel frequently but for shorter distances. This would also make the development of sedentary civilisations a lot harder as they would have to live in places where it's possible to grow enough of a surplus to make it through a year-long winter. This would make it difficult to have your level of technology as that seems to require much larger complex societies, but not necessarily impossible. The sources of your nomads' technology could be trade with sedentary civilisations in other areas. ]
[Question] [ Many sci-fi words use anti-gravity or artificial gravity to manipulate the weight of their ships making flight much easier. Wikipedia even has an [article on it](http://en.wikipedia.org/wiki/Anti-gravity) which discusses several attempts to make objects float. The main approaches seem to be: * Gravity shields * Gyroscopes * Warp drives * Superconductors * Exotic Matter Which of these techniques (or any other) is most feasible to allow large ships to float into, out of and fly around within a planet's atmosphere? I'm not after hard science (as the technology has not been invented yet), I'm after an evaluation of which approach to solving this problem is most feasible. What is the most scientifically likely method of making a craft of a thousand tons (for the sake of argument) float? [Answer] I'll go out on a further limb here. It's well known that gravity is the significantly weaker of the 4 forces by an exponential factor compared to the other 3. String theory (or at least attempts at explaining this using string theory) states that gravity could be acting through several other dimensions than just the 3 we can observe thus greatly expanding the distance involved for gravity compared to the other forces. These extra dimensional spaces are microscopic in size, but the full addition of all of these dimensions add up and greatly affect gravity. With this in mind (and using very futuristic technologies) 1. Bombard these extra dimensions with energy to either increase their size or their number. This effectively increases the distance between two objects when calculating gravity. These dimensions could be stacked upon one another...ie, a microscopic unit of our space contains other dimensions and in turn a microscopic unit of this dimension contains other dimensions (and so on for 7 to 11 levels)... so expanding the bottom level of this dimension hierarchy by a factor of 10 could have an astonishing effect. The value of G is calculated using a distance to the 'center' of the earth's mass in the 10$^6$ range. If we were to increase the bottom of this dimensional hierarchy by a factor of 10 over a range of 1 meter, we could be effectively increasing the distance between two objects by a factor of 10$^7$ up to 10$^{11}$, effectively negating gravity compared to air resistance. SO this is increasing the distance between the two objects and effecting the space between the object and earth itself. Heh, no clue what this would do if the moon was to cross over this distance effect as it's affecting the distance between any objects between this area of increased dimensional space. Edit : if it's the 10$^{11}$ number, this would even have a noticeable effect between the earth and sun. Second edit : This could also have an interesting affect on weather and cloud patterns as there is now an area of air that isn't being affected by gravity either. If there was a definable edge to this effect, you would have negligible gravity for one step and then a return to regular gravity in another... flight would be quite flaky and hard to control producing sporadic movements as you leave and reenter the effects of gravity. 2. Close off these dimensions entirely for the mass of the space ship. If gravity acts through these other dimensions and these dimensions are blocked, theoretically, would we have 0 gravitational pull towards this full mass of the ship. Instead of having a space between the object and the earth, this effect would be directly on the object and not on other objects experiencing the increased gravitational distance. I think I've confused myself in this explanation around 10$^{11}$ times. [Answer] Building on the fact that your edit now includes my suggestion for superconductors I'm going to write an answer arguing why I think it's the most plausible solution. ## Superconductors Superconductors actually work right now with [maglev](http://en.wikipedia.org/wiki/Maglev) trains. These however have superconductors whose magnetic fields interact with metal conductors to cause them to levitate enough to reduce friction. Comparatively the Earth's magnetic field is very small to that which is produced by these conductors so you need really strong superconductors. There are a few issues with this: * They need to either be made of some unknown material which works at normal temperatures (as opposed to below 70 K or -203°C) * They need to be small and light enough to carry around in the ship * They need to not consume more energy that normal propulsion However despite these issues I still believe superconductors are more promising than the other options, comparatively: * Gravity shields are hypothetical * Gyroscopes seems wildly difficult to achieve * Warp drives may not be possible * Exotic matter may not exist All you have to do is invent a special superconductor for your world that meets the requirements you need. [Answer] > > Which of these techniques (or any other) is most feasible to allow > large ships to float into, out of and fly around within a planet's > atmosphere? > > > Um... [![enter image description here](https://i.stack.imgur.com/FvvZX.jpg)](https://i.stack.imgur.com/FvvZX.jpg) [Answer] If what you need is to reach the orbit, a nice solution could be a [space elevator](http://en.wikipedia.org/wiki/Space_elevator). You will have to invent some super strong material that would prevent the cable to be broken by the enormous forces involved, but it's a likely solution. # What is a space elevator? Basically you put a very massive object on a specific point orbiting around the world. That object will be in "equilibrium": it won't fall down or go away in the space. Your ship will only be lifted to a specific point (using normal rockets), then it will be uplifted without any energy need due the [Apparent gravitational field](http://en.wikipedia.org/wiki/Space_elevator#Apparent_gravitational_field) If placed in the deep space, the counterweight will generate enough power to lift your ship to Jupiter. Once in space the ship can be maneuvered using conventional boosters. It's not a very sci-fi solution (ie push a button and everything is magically working), but it has solid scientific basic and it's technologically feasible. [Answer] I'd comment on superconductors, but not allowed. This only works for Earth - and things with magnetic fields. You'd crash right into Mars, Venus,or the Moon. You could substantially turn down (hopefully) your supermagnets, when you want to skim Jupiter for H3 --- What about anti-gravity waves or use of gravitons? Here's an example: <http://www.startrekfreedom.com/wiki/index.php/Antigravity_Systems> [Answer] While it is not strictly "antigravity" in that it does not reduce the effects of gravity, the [EmDrive](http://en.wikipedia.org/wiki/EmDrive) is an apparently plausible reactionless thruster that relies solely upon electrical input. Should this device be increased in size and efficiency, ganged up with computer control to compensate for external forces such as wind and turbulence, and provided with a sufficiently large power source (quite possibly atomic), there is no reason why it could not be used to counter the acceleration of gravity, thus providing a craft of thousands of tons mass with the appearance of floating. [Answer] # Magic Oh, wait, no # The Ether Well, something like it, anyway. As it turns out, [space is not really empty](https://physics.stackexchange.com/questions/67582/nothing-vs-empty-space). Maybe mostly empty, but not really. Also, we have a strong tendency to think that the Sun is just sitting there, but as it turns out the [Solar System is hurtling through space](https://www.youtube.com/watch?v=0jHsq36_NTU). If you couple the two of these ideas together, perhaps there's a way to reach out and "grab" something that is relatively stationary, or use something with an incredibly low density to rise waaaaaaaaay up. It'd be kind of magic, though. [Answer] The only one of those options that really works is "exotic matter". All the other options are going to require enormous amounts of energy to work, making them roughly as useful as picking up your ship with helicopters. * Gravity shields These would require some kind of gravity-blocking substance be found, which would cause those shields to be much heavier than normal. If such a thing were possible, it could be used to at least lower the amount of gravity passing through, and thereby reduce the thrust required. But to block all the gravity, your shield would have to weigh a substantial fraction of all the earth beneath it. (It would be the percentage of [solid angle](https://en.wikipedia.org/wiki/Solid_angle) the shield covers.) * Gyroscopes I have no idea how a gyroscope would keep you in the air. Conservation of momentum says anything the gyroscope does to move you up has to be accompanied by a similar pull down. If you could get the gyroscope to produce a net force, it would come at the expense of rotational momentum, requiring you to expend more energy to keep the momentum up. For example, a spinning disc could create an electric field that might push against another field and keep you up, but it's ultimately just thrust. * Warp drives Warp drives, if they work at all, will be ridiculously expensive. The only reason to bother with them is to break the speed of light over vast distances. Keeping a warp field open to hover over the planet would likely use up the mass energy of the entire planet pretty quickly. And all that energy has to go somewhere. You'd melt the planet you were hovering over even if there weren't more pressing relativistic problems. * Superconductors These have the same basic problem as gyroscopes. You're just using electricity to create thrust in a nonconventional way. It's not really anti-gravity. * Exotic matter If it exists, certain exotic matter could "cancel out" the normal matter's mass. You have to find a way to bind the matter to normal matter, but you'd essentially have a floating device. Bear in mind that you have to get the device to the planet, which means raising it's gravitational potential energy (in this case, the closer it is to a massive object, the more potential energy it has). That work done will require energy, so it might not be particularly useful in the long run. Still, the advantage here is that you only have to move it once. After it's down here, you can float with it for thousands of years, which is more energy efficient than constant thrust. * Permanent magnets There are plenty of kids toys that use permanent magnets to levitate an object indefinitely. You'd be restricted to a specific location, possibly a specific path, and [Earnshaw's theorem](https://en.wikipedia.org/wiki/Earnshaw's_theorem) suggests it wouldn't be totally stable, but you'd use a lot less energy maintaining position than hovering. If you wanted to hover in one place, maintaining position would be as simple as attaching a few cables to the ground to counteract any sideways forces. For a track of some kind, you could have cables that run along the track beneath you to hold you in place. I've never seen the track idea done. Maybe I'm missing something. But it seems like you could have two magnets side-by-side at some distance, both pointing their north face upwards. Then your airship would have its north face downwards. Now, the airship will tend to fall to a spot between the two magnets, rather than climbing over the magnetic field's "hump" to fall outside the magnets. Then, by having a series of these ground magnets, you'd have a line the airship can follow. If you stop moving, you'll tend to settle into the valley between four magnets and hover. However, the south side of your magnet will want to flip you upside down and accelerate to the north magnetic fields. So you need some way to prevent that, such as cables or thrusters. I'm not sure how doable that is. [Answer] Exotic matter. If exists, exotic matter has negative mass, which means that gravity actually repels it instead of atracting it, therefore a, let's say, ball made of exotic mass would float insted of fall. ]
[Question] [ In my story, the land of Koyokuni has a [Japanese-style castle](https://en.wikipedia.org/wiki/Japanese_castle), Akimachi Castle. The castle - and indeed the entire city of Akimachi - is uninhabited, though the land is being repopulated after the end of the war in which it became completely depopulated. The current ruler of Koyokuni is effectively a reincarnation of the ruler at the time Koyokuni was defeated, and as a result has bad memories of the castle in which the former lord and his wife were tortured to death. The current lord's girlfriend suggests that if the castle holds such bad memories for him, perhaps they should just burn it down and have done with it, and he agrees. So, the "Akimachi Castle" which is burned is the main tower of a Japanese-style castle similar to [Osaka Castle](https://en.wikipedia.org/wiki/Osaka_Castle), built with the traditional materials. It is in good repair and partly furnished and equipped in the Japanese style, though it has no food reserves (it had been repaired and maintained over the past 17 years by automata, but not resupplied). The bailey of the castle is large enough that the main tower will be far enough from the buildings of Akimachi that the few people present can easily prevent them from burning. Nobody is trying to prevent Akimachi Castle itself from burning. My question is: How long would it likely take for the main tower of this castle to burn to the ground after a determined attempt at arson in which its ground-floor timbers and other flammable items are set alight? References to accounts of similar historical events such as the [fall of Osaka Castle](https://en.wikipedia.org/wiki/Siege_of_Osaka#The_fall_of_Osaka_Castle) in answers would be helpful, but I haven't been able to find any which say how long a Japanese castle might burn before it collapsed or burned out. [Answer] My Answer: Probably over a period of 1–2 hours. [According to Googling: Cypress wood is the wood of choice for Japanese castles; these are its firewood properties.](https://axeadviser.com/is-cypress-good-firewood/) The first thing is that, compared to other woods, it burns quickly. This doesn't bode well for your castle smoldering over a period of several days. The next key thing is that this type of wood is very sappy and prone to popping and crackling—sending embers flying. This should accelerate the process—even better than arson. What I expect is that the initial fire (wherever it was set) will probably take a few minutes to catch fully and develop into a roaring building fire. From there, it will spread over the next 20–30 minutes through each room. The thickness of the wooden beams will mean it will take a bit of time for them to lose enough structural integrity to collapse—but I suspect this will only be a matter of a few hours—once the first beam fails, you'll probably see a chain reaction, and the building will rapidly fall down. Another incident that might give you a benchmark is [the burning of Fantoft Church by Varg Vikernes](https://www.dietmar-anders.de/en/fantoft-stave-church-in-bergen/#:%7E:text=The%20church%20was%20originally%20built,ground%20within%20half%20an%20hour.). Since it's unlikely you are an avid Black Metal fan (like me), in the early 90s in the Norwegian Black Metal scene, there were a large number of church burnings done by musicians/fans of the genre. Fantoft was an all-wood church that was nearly a millennium old. Although smaller than a castle—if you look at the style, there's a degree of similarity between it and a Japanese castle (that is, the kinda tiered design)—that church took 30 minutes to burn down. [Answer] A few hours, most likely 3-5 Average house in the United states takes 45 mins to 2 hours to burn, the average modern house size is about 201 square meters. Of course we can't use that as proper reference, so using a source from @TheDemonLord's answer, we know that the structural supports of the castle were most likely made of cypress wood, a type of lumber that is great for kindling, but not for sustaining a fire. In this illustration from François Caron's book, the fire appears to be on the left of the castle: "The Burning of Osaka Castle" (shown in the Wikipedia page as well) [![The fire staring from the base/left wing of the castle in this illustration](https://i.stack.imgur.com/z12q9.jpg)](https://i.stack.imgur.com/z12q9.jpg) Using the fact that the approximate area of the castle in square meters is about 1702.25 meters. We can assume that the use of accelerants could take 45 minutes to an hour to burn down a main wooden support beam or two, assuming there is ten support beams and the fact that the fire would grow (although move slower due to the accellerants burning out). This means that it would take 3-5 hours to take down enough beams to have the entire 5 story (Correct me if I'm wrong) castle to begin to crumble Sources [Wikipedia page](https://en.wikipedia.org/wiki/Siege_of_Osaka#Background) [How why newer homes faster](https://www.angi.com/articles/why-newer-homes-burn-faster.htm) [How Big is a house](https://shrinkthatfootprint.com/how-big-is-a-house/) [How to measure height with google maps](https://www.youtube.com/watch?v=K15sAt0b3KQ) [Answer] Japanese weren't stupid, they coated their Castles in fire retardant/resistant plaster and mud. So while you can get a local fire going, it's not going to spread easily. Your arsonist needs to set fire everywhere and perhaps remain and help it. I would think you'd get the same effect as a flash bush fire, the easily flammable stuff goes up very quickly but the rest doesn't. It either slowly smolders until it destroys itself, or goes out. It's not a matter of setting fire to a curtain and then running. If your main support beams are incased in fire retardant plaster (which blocks oxygen as it would), it will take a long long time for them to burn through. Best option chop off the plaster in crucial places and make your fire there. How long it would take is up to your story, but logically it would take hours or days depending on how much prep was done before starting the fire. Japanese castles are specifically built to withstand frequent earthquakes, and therefore would need multiple points of failure for the main supports to all collapse. [Answer] I don't know much about Japanese castles, however, I do know Japanese homes are very very flammable. (Japanese castles do have stone- but also wood.) Windows made of paper and oil, built mainly of wood and bamboo, your castle will burn like- well a pile of wood and bamboo with oil. I suspect a day maximum, and likely even less then that, considering you are trying to burn it down. I think you could get away with a 2 hour complete burn without anyone caring. [Answer] Japanese castles are made out of Cryptomeria and coated with some kind of fire retardant and usually mud, meaning it probably wouldn't happen in 1–2 hours as others answers point, it would at best maybe take a whole day, with multiple people setting different parts on fire ([several daimyō set the castle on fire][1]), and he still had time to catch the perpetrators and throw them off the castle, mind that he COULD NOT stop the flames and ended up suiciding. So it would most likely take a whole day to burn, assuming that * 1 floor on fire (no one trying to stop its spread) == multiple fires/floors on fire (Multiple people trying to actively stop the spread and the fire) Is correct [1]: <https://en.wikipedia.org/wiki/Siege_of_Osaka#Theory> ]
[Question] [ I'm playing around with the idea of making a world heavily based on one of my favorite childhood book series. (basically a fanmade rewrite of sorts). The series is called Warriors, and is about talking cats. I’m rewriting the worldbuilding and story for fun so that the cats are bipedal and more civilized. They'd be omnivorous felines with a preference for meat, and their heights would range from 2’6” to 3’8”. The civilization would be similar to the late 17th/early 18th century. I was wondering how their farming and husbandry would work. I know they would have chickens, and pigs & ferrets are a maybe, but what else do you think they would domesticate? They live in a mostly forested land, but there would be plains, wetlands, and mountains in certain areas. TL;DR, what sort of animals would a civilization of small feline omnivore humanoids domesticate? (Bonus points if you address whether they could realistically have pigs and or ferrets) [Answer] Welcome, and good first question as far as I'm concerned :) General domestication Depending on how cat-like your critters are going to be they may well have an easier time domesticating animals than humans. Cats are the hosts for a very interesting parasite called [Toxoplasma gondii](https://en.wikipedia.org/wiki/Toxoplasma_gondii). It spreads in cat faeces and infects other warm-blooded animals via accidental ingestion (say, from unwashed vegetables or handling cat litter). It then alters the behaviour of its new hosts to lose fear of cats and prefer their smell over other animals. Evidence is strong that this occurs in rodents, and there is also evidence that it occurs in people too (read it in New Scientist but can't find the source now!). Excuse the French, but bloody terrifying if you think about it. However, for your cat-critters it means that they already have an 'in' with other warm-blooded animals that would otherwise be very wary of mesocarnivorous intelligent cats. But which animals? Livestock Seeing as the effect has been observed most strongly in rodents, I'd suggest that the initial domesticated livestock would probably be large rats of some sort. Larger varieties would be an equivalent relative size to chickens for people, and could be bred to be larger. Rats are also able to eat a wide variety of foods, so will assist your mesocarnivores by allowing them to exploit resources they couldn't otherwise. [Rat's milk](http://ansci.illinois.edu/static/ansc438/Milkcompsynth/milkcomp_table.html) is significantly higher in protein and fat than cow's milk, and lower in lactose. I expect your cats would evolve a degree of lactose tolerance to allow exploitation of this resource (although likely less than current Europeans as they have to deal with lower concentrations). If the effect is also pronounced in all rodents, there are some larger varieties like capybara that might end up filling the niche of larger livestock. Another option would be rabbits as they are both social and grazers (allowing your cats to exploit grasslands). It's unlikely that they will domesticate pigs. Pigs are dangerous creatures, and the size differential between them and your cats would put them well into 'very dangerous'. Cattle are also likely too large to effectively domesticate. Goats are probably in though. Hunting partners Another niche that domesticated animals fill is as hunting partners (filled largely by dogs with us, but also using a variety of other animals). What would help here is to identify your cats' hunting style. If they're persistence predators then they will likely gravitate towards other persistence predators as we have. Wolves would probably be very risky due to their size, but there are other, smaller canids that could fill the same niche. [African wild dogs](https://en.wikipedia.org/wiki/African_wild_dog#Physical_description) weigh 25-30kg on average so may be within the size range to be domesticated (although certainly towards the upper end of that). They would, however, be very useful in allowing your cat-people to more easily target big game (for them). Other small canids are not usually social, which poses a difficulty for domestication. If they're primarily hunting rats and rabbits though, then ferrets are ideal. They can weasel their way into their burrows and flush them out for your cats to catch, much as [we do today](https://en.wikipedia.org/wiki/Rabbiting#Ferreting)! They're also definitely within the size-range for domestication. If you want something a little more exotic, then just maybe they could look at [ethiopian wolves](https://en.wikipedia.org/wiki/Ethiopian_wolf). They're about the same weight as african wild dogs so probably on the upper end of domesticability for a predator. However, they are specialised small-animal feeders. If your cats are also small-animal feeders then they could provide assistance, and they are probably less likely to be predators of your cats. Mounts I'm going to assume here that your cats have hip and leg anatomy that allows them to comfortably sit on a mount. Humans have adaptations for sitting that even other hominids lacked (neanderthals appear to have been adapted for squatting to rest, and lack as padded backsides and H. sapiens do). With that said, the smaller size of your cats does open things up a little when it comes to riding things. Where humans have comparatively few animals that can bear our weight (that we didn't hunt to extinction first), the majority of ungulates are probably big enough to carry your sub-4ft cats. Pick one that's not too big and not too small, preferably a grazer rather than a picky browser and has a gait that doesn't look too painful to be sitting on the back of and you're away! Oh, and remember. [No predators as mounts](https://worldbuilding.stackexchange.com/a/138051/48681). For many, many reasons it doesn't work. Sentries Another very useful task that could be performed by animals is that of sentries. Humans use a variety of domesticated, semi-domesticated and wild animals for this purpose. Dogs are used to warn farmers of predators attacking their flocks. Prior to their demonisation by Christianity, magpies were semi-domesticated in Europe and used to warn of animals approaching people's crops as well as flocks. As your cats are rather small, they will likely be more vulnerable to predators than humans. As such, domesticating animals like crows to act as sentries would probably provide them with a very useful service. Crows would be especially likely as they can be [taught behaviours](https://www.smithsonianmag.com/smart-news/french-theme-park-taught-crows-pick-trash-180969996/) over very short time periods, and also are also able to [teach those behaviours to other crows](https://www.popsci.com/science/article/2012-06/how-crows-recognize-individual-humans-warn-others-and-are-basically-smarter-you). [Answer] Goats. Warning: if you want to waste a few hours, google up Cats and Goats. Who knew? But it seemed reasonable to me and it is. Reasons. 1: Goats don't eat what cats eat, so they don't compete. 2: Goat milk is good. Goat meat is good. 3. Goats have better endurance than cats and tough feet. A goat can pull a cart. Cats will want to ride in goat carts. 4. Goats can pull a plow. The cats will want to grow grains to feed their meat animals. 5. Goats come in sizes more comparable to cats and so would be trainable by cats without huge risk. Cats can nurse goat kids (see above warning about google). 6. Goats are curious, intelligent, weird and moody. Temperamentally they are a perfect match for cats. [Answer] If the cats are omnivorous then most [animals domesticated by humans](https://en.wikipedia.org/wiki/List_of_domesticated_animals) would also be useful, I would have thought. Omnivorous implies agriculture, which implies both beasts of burden - animals like horses are too big for the cats to ride, but they're useful as draft animals - and the need to defend homesteads (dogs). Hunting beasts such as ferrets and dogs are still beneficial. Cats can't fly, so bird species domesticated for use as messengers would also be useful. I assume the cats are intelligent enough not to just eat them. [Answer] [Miniature horses](http://amha.org) for all the things humans would use horses for, only they're small enough to ride and handle. [Dogs can ride miniature horses](https://www.dailymail.co.uk/news/article-2898977/Give-dog-pony-Dally-Jack-Russell-performs-stopping-stunts-RIDES-horse-friend-Spanky-high-speed.html) (and your cats are larger than modern cats). [![enter image description here](https://i.stack.imgur.com/blCfR.png)](https://i.stack.imgur.com/blCfR.png)([ref](https://www.cutesypooh.com/cat-little-girl-trot-around-miniature-horse/)) Mice. Great food supply and also for pets and companionship. While humans don't usually eat their pets, or have an animal be both food and pet in the same culture, even if not in the same household, an example of an animal that fills both roles for humans in the same culture (US) is rabbits. Pigeons. Because they are smaller than chickens and have a history of domestication, they would work better than chickens for your cats. They would provide meat and eats and can be trained to perform some tasks, like carry messages. Ferrets and pigs seem quite possible, though they'd go for smaller breeds of pigs, possibly pot-bellied pigs. ]
[Question] [ I am working on a scenario where a climate protection organization tries to breed sapient Cephalopoda as a help in their fight against climate change. The breeding goals of the evolving species are as follows: * they should be self aware * they should be able not only to use tools, but also develop second generation tools * they should be able to learn from other individuals and pass knowledge/skills among individuals * they should be collective and cooperative * they should be able of planning * they should be able to change their environment to fit their needs * they should be able of abstract thinking like being able to learn/comprehend mathematics at a basic human level without further education * No use of direct DNA altering. Further specifications: * In the end it should be a reproducable new species with a diverse genepool (to be more resistant against possible future illnesses / environmental changes / etc.), able to survive and thrive on their own in the ocean. * This might make different lines of parallel breeding necessary(?). * In the last phase the main focus of the facility would be training and teaching, so the celaphopods understand climate problems and the role of humans in it, being allies to that organisation. How many generations of breeding might be needed? How would that process and the needed facility have to look like (what does it have to contain, how big and expensive does it have to be)? [Answer] I'm going to split my answer into two parts. # 1. Selective Breeding for Intelligence It might be more helpful to estimate in terms of generations rather than years. If cephalopods can produce a new generation every year (instead of a human generation's 15–30 years), that should reduce the amount of time a selective breeding program would require to select particular traits. For comparison, consider fruit-fly breeding operations (which have a generation cycle of only ten days) and dog or fox breeding. ## How long does it take to breed for a trait? The Soviet scientist [Dmitry Belyayev](https://en.wikipedia.org/wiki/Dmitry_Belyayev_(zoologist)#Belyayev.27s_fox_experiment) began a famous experiment in 1959 wherein he bred successive generations of wild silver foxes to produce tame ones, selecting based on their relative fear and friendliness toward humans with each generation. He was able to produce human-friendly foxes by the fourth generation and very friendly (eager for human contact) foxes after only six generations. While repeated inbreeding can elevate the target trait, it can also exacerbate other traits unintentionally. For example, Belyayev's foxes started getting multicolored coats after 8–10 generations. After 15–20 generations some of the foxes developed abnormalities like shorter legs and underbites or overbites. ## That's just friendliness. What about other traits? Breeding for friendliness could certainly get you to an offshoot that is more collective and cooperative, but that's a far cry from producing a species capable of abstract thought. It worked well for Belyayev because the trait they were shooting for also made the animals easier to handle and thus easier to breed. In contrast, his counter experiments breeding animals for greater fierceness had to be discontinued after fewer generations due to difficulty handling the animals and keeping them from killing each other. To selectively breed for some other trait besides friendliness you need to have a way to identify the trait in the available breeding population. If your organization has access to modern (or even 70s-era) technology, they may be able to identify the genes involved in learning and memory, [as has been accomplished with fruit flies](http://www.sciencedirect.com/science/article/pii/B9780123870032000069), so that they can more quickly identify which subjects to include or exclude from the program. Furthermore, artificial insemination allows them to explore behavioral avenues that might otherwise result in non-breeding. Both of these (genetic testing and artificial insemination) would make it faster to isolate and enhance aspects we associate with intelligence than such aspects could develop by natural evolution. But that's assuming the aspects are already available or incipient in the genes in the first place; you can't use selective breeding to produce a fruit fly with lungs, for example. To produce intelligence ex nihilo could take millions of generations, simulating natural evolution. ## Cephalopods to the rescue Fortunately, you picked cephalopods as your seed creature, so you don't have to produce intelligence ex nihilo! There's some evidence that at least some species of cephalopods are already capable of abstract thought, including problem solving and [tool use](https://en.wikipedia.org/wiki/Cephalopod_intelligence#Tool_use). Some cephalopods (specifically octopus and cuttlefish) have the highest brain-to-body mass ratio of all invertebrates. Cephalopods have been observed opening screw-capped jars, throwing rocks to smash aquarium glass, and stealing food from lobster traps and even from boats. Some of your climate-protection organization's targets will be more difficult to reach than others. In particular, the ability to pass knowledge on to the next generation will probably require some kind of language or mathematical system. The ability to produce and understand language may be difficult to isolate and exaggerate in the cephalopod genome, since their most advanced communication at this point seems to be flashing warning signs and mating displays with the pigmentation on their skin. I imagine the organization would be able to produce different levels of intelligence over the course of many generations; the end goal of a communicative, language and math-savvy species may require millions of years, but in the shorter term they may develop something intelligent and crafty, maybe even individually mathematically-savvy, but lacking the ability to communicate complex thoughts to others of its kind. # 2. Breeding Cephalopods in Captivity I'm going to assume the chosen species for the breeding program is a type of octopus for the remainder of this answer. They have a large brain to body mass ratio and have been kept in captivity both in professional and personal aquariums. ## Habitat Guides for keeping pet octopuses recommend tank sizes in excess of 50 gallons. This pop-science article from 2015, [Does an Octopus Make a Good Pet](http://www.mnn.com/family/pets/stories/does-an-octopus-make-a-good-pet), states the following: > > the animals need at least a 55-gallon aquarium with a second large tank to hold filtration equipment. > > > This [Keeping Cephalopods](https://www.tonmo.com/pages/keeping-cephalopods/) guide published in Marine World Magazine in 2004 has a more modest recommendation: > > The minimum size should be at least 36×18×18 (inches) to be used for small octopus species and as big as you can get after that. > > > 36 × 18 × 18 inches = 11664 cubic inches = about 50.5 gallons Those size recommendations are for single octopuses, under the assumption that they will be kept solitary to prevent cannibalization. If the breeding program succeeds in reducing fierceness, producing more social/friendly critters, cannibalism might be less of a concern after a few generations, in which case multiple octopuses could be kept in the same tanks. Octopuses are more sensitive to temperature, salinity, and ph balance than typical aquarium fish, so you should assume that the tanks will require significant ongoing maintenance and filtration. Octopuses are predators and require a regular diet of crustaceans and/or mollusks (preferably live), so the organization would either need some advanced surreptitious aquaculture or a reliable external supply chain by which to obtain feeder animals. This might be easier if their operation is situated near an ocean. ## Mortality An octopus only lives 6 months to 2 years. To maximize the opportunity for the captive critters to produce viable offspring, it'd behoove the organization to seek ways to reduce the mortality rate. Normally when an octopus breeds it dies shortly thereafter (the male after spawning, the female after brooding), but [research suggests](http://science.sciencemag.org/content/198/4320/948) this can be prevented by removing their optic glands, implying that glandular secretions directly trigger the senescence that leads to their mortality. You could conceivably prevent this effect and prolong their longevity through surgery or selective breeding. [Answer] The biggest challenge that I can see is the breeding cycle. Cephalopods typically die after reproducing, which would severely curtail the ability to pass knowledge down to the next generation. Probably the first priority would be to somehow get them to survive the act of reproduction, probably by measuring how long the parents lived after breeding and culling the offspring of the shortest lived parents for each generation. You'll also want a longer lifespan in general. Most cephalopods live only a couple of years even if they don't reproduce, which is not a lot of time to learn and invent things. You also want sociality - luckily, some species of squid are already social, so you could just start with them. Then, of course, you want to run them through cognitive tests, in a variety of areas, and selectively breed the highest scoring individuals. I have no idea how well my advice would work. As far as I know, the only real-life example of humans selectively breeding for smarts is with certain dog breeds, most notably border collies. It worked well with them, although not to the point of sentience (yet), but dogs were a far easier target to begin with - social animals, with parental care and observational learning, and a roughly 10-20 year lifespan. Intelligent cephalopods would be awesome, but they would be a challenging animal to breed for it. [Answer] Personnell * animal care and feeding; cleanliness * scientists (Genetics, Ethology, Veterinary Medicine) * service and maintenance, IT Infrastructure * aquaria for individual enclosure (+ accessories) * big aquaria for test settings (+ accessories) * big aquaria for feeder animals (+ accessories) * predator-aquarium for some testsettings (+ accessories) * self-contained power supply (solar power, wind power plant) * internet * computer/notebooks * laboratory für genome testing * laboratory for medicinal examination and autopsy Thoughts on hiding Sounds like best place to hide the facility might be a private university in a seaside town where economy is so low, that local authorities regard that facility as the blessing of their area. Being a university would also enable them to publish some part of results and acquire public science funding. Here is a list of further Links I just found * Great repository of articles about Cephalopoda <http://www.thecephalopodpage.org/articles.php> * The larger Pacific Striped Octopus seems to be a very optimistic basis, being social (groups of 40 individuals) plus females can lay eggs several times <http://www.sfgate.com/science/article/Rare-octopus-breeding-in-Alameda-bedroom-4299276.php> There is also an article in Wikipedia: <https://en.wikipedia.org/wiki/Larger_Pacific_striped_octopus> * Tremoctopus also sounds promising, mating more than once + living in open ocean (bigger possible habitat): <http://www.thecephalopodpage.org/Tremoctopus.php> * Another candidate may be the [Humboldt Squid](https://en.wikipedia.org/wiki/Humboldt_squid "Humboldt Squid"). It's been observed to hunt in packs (shoals) and communicate with light flashes, apparently with an unusual degree of complexity. Being deep water hunters, they'd probably be more difficult to keep and breed than octopuses, but it might be interesting from a story perspective to explore multiple species gaining intelligence. Other Questions which might be of interest and inspired me to this project * Possible biology of a sapient species developed underwater [What is plausible biology of ocean-dwelling, tool-using, intelligent creatures?](https://worldbuilding.stackexchange.com/questions/66139/what-is-plausible-biology-of-ocean-dwelling-tool-using-intelligent-creatures) * Thoughts about a possible celaphopod color-based language [How expressive is a color-based language?](https://worldbuilding.stackexchange.com/questions/66270/how-expressive-is-a-color-based-language) * About underwater technology which could be developed by such a species [Could underwater living organism create technology?](https://worldbuilding.stackexchange.com/questions/1452/could-underwater-living-organism-create-technology) * Underwater computing based on fluidics [How would an aquatic race develop computers?](https://worldbuilding.stackexchange.com/questions/3722/how-would-an-aquatic-race-develop-computers/) Please feel free to add ideas. [Answer] Since you've ruled out direct manipulation we're left with selective breeding. Selective breeding to the point of sapience will take a very long time. It took roughly 5 million years for the most recent common ancestor between humans and chimps to begin using tools. You're probably looking at a similar time scale for your cephalopods. Chimps reach sexual maturity after 7 years. Cephalopods reach sexual maturity around 1 year, though this will probably increase with time to allow the brain to develop more. From this we can estimate that it will take roughly a million years for selectively bread cephalopods to develop sapience. The selective breeding program would look like a large number of tanks to support a large enough population to reduce the risk of breeding in genetic diseases. Cephalopods can already die of boredom in captivity. There would need to be enough enrichment activities in each tank to keep them entertained especially as their intelligence improves. Next time use [CRISPR](https://en.wikipedia.org/wiki/CRISPR). ]
[Question] [ Let us consider that humans leave earth after it becomes deadly for us. And then many years pass. Would there be a chance of a different but intelligent life evolving in our place. Edit\_1 Forgot to specify the time. Let's say 100 million years... So after the climate changes, maybe even after a new ice age or a meteor strike. Enough time should pass so that all that we have now, would be deep beneath the soil... Edit\_2 It does not have to be similar to humans. Let's say that the earth becomes uncomfortable to live on for humans and similar species. Not deadly but a place where as a human you would not want to be. Be it the temperature or lower levels of oxygen. [Answer] The main point is exactly as @nzaman said, the state of life we left behind, specifically multicellular life. Life has taken billions of years to get to (what seems to be) the first technological sentience on the planet, but what would happen after we vanish is a different story, mainly because a lot of that time was taken up with evolving some fairly major jumps in basic complexity of life on earth - cells, multicellular life, cell differentiation, the ATP energy cycle, photosynthesis, land based life, the basic neuronal//brain/spinal cord system, the additional various specialised regions of the brain and the extra functioning they enabled... and a load of stuff I don't know as I'm no expert. Some of those developments also got prompted by climatic conditions. If those (or similar) have to be re-evolved, then it'll take billions of years and there won't be time. Also, if too much has to evolve again, we lose a large part of planetary life conditions in about 1-2 billion years (our protective magnetic field, ozone layer, axial orientation, atmosphere, and surface water, are all unstable on that timescale). Life may evolve to cope and 2 billion is a lot, but it may make it harder. If not, we can assume that developing comparable life will happen relatively fast (see below) but we have no data how long it will take to develop technologically capable life, as we just don't know how readily that happens. If we lose humans and (say) mammalian life, then we may see an "evolutionary explosion" as often happens when a large niche for life becomes vacant - in a very few million years (about 10-20m), life in other areas explodes in diversity to occupy the niches. (Also relevant term: "evolutionary radiation"/adaptation) In that case, and given the record, it looks (casually and fairly speculatively and unscientifically) as if rewriting the dominant life form happens on the order of 50-150 million year part on average. For example, dinosaurs took over and died out over a span of about 165my (of course they existed before and some survived after); mammals took over and reached dominance in 65my... So maybe a pure guess could be that this sort of overturn happens every 50-150my and maybe a couple or so of these happen before we get to one that leads to intelligent /sentient life? Its not much to go on, but we only have one data point from one life form on this planet, its hard to do much. (Note that circumstances such as physical state, volcanic/solar activity etc won't make much difference unless very extreme. Life will simply evolve to handle the planet as it is, if it can, as it always has) Update As an afterthought, I also remember that TV series "The Future Is Wild" also looked at this question, and specifically how life might evolve if humans vanished. It suggested possible new intelligence in the order of 200my, and pointed to molluscs (=squid, octopi) as candidates to migrate to land and take over the intelligent life niche, after mammalian life subsequently happened to vanish. I'm not sure how realistic that is, so its more a resource or info for the OP. [Answer] "Would there be a chance of a different but intelligent life evolving in our place"? Of course there would be "a chance", even though we don't know what that chance would be. If humans evolved to get intelligent life, then evolving an intelligent life is not impossible, which means that it could happen again. (even though I wager that the probability is little, because on millions of years of evolutionary life, with so many different species and so many different environments, only humans evolved to this point) In fact, if humans went away, this evolution would be, IMHO, more probable, since human beings consume too much resources to allow another intelligent species to arise. Human beings are so much ahead on that department, with their technology and knowledge, that there is just no evolutionary benefit in competing with them for it... just in adjusting to the environmental changes that humans produce. Now, we need to focus on another thing. Your question was not only about "intelligent life", but also "different". On this regard, maybe "different" would be harder to achieve, since other primates, like chimps, are the second more likely contesters to develop intelligent life (in fact, many people here may argue that they already developed intelligent life, even though I don't think they are comparable). So it would be likely that we would see the emergence of another intelligent primate species. But then again, you said that in your world, the environment has become too much deadly for us. You don't say how, or hor much, so I may only guess. But this would be probably also deadly for primates, which could go extinct. So we could go on to the next species... are the oceans compromised? If not, why not consider dolphins? They are already pretty intelligent. Also, if the environment is really screwed up, maybe insects would have the evolutionary upper hand. On that regard, maybe ants or bees could be a good choice, since their gregarious nature would be more likely to develop a kind of language, which is fundamental for intelligence. Finally, you could ponder an alternative... if Earth has become too much deadly for humans, maybe it was because of the humans own doing. So, maybe those humans could have genetically altered a non-human species before going away... which, left to its own devices, could have evolved intelligence more easily. Or (why not?), go all WALL-E and put the abandoned machines and computers evolving their own intelligence? [Answer] It depends on two things: 1) In what condition did we leave earth? If multicellular life flourished, even if humans did not, the chances of an intelligent species evolving go up; if the only living organisms are bacteria and moulds, then it'll take another few billion years to get back to conditions where intelligent life could evolve. 2) When did we leave? The earth is expected to have a [close encounter with the sun in about 6 billion years](https://en.wikipedia.org/wiki/Future_of_the_Earth#Red_giant_stage). Whether an intelligent species will have time to evolve depends on the answer from 1). If there is sufficient evolutionary data available and enough time, another species can evolve in enough time to get off the planet before it becomes uninhabitable. Otherwise, it can become sentient only to be aware of an approaching fiery death and nothing to do to stop it. In numbers, I'd guess that if we leave in the next million or so years-- and going by present rates we'll certainly have made the planet uninhabitable by then-- it leaves about four billion years and change for new intelligent species to evolve, which is plenty of time, as our oldest species are about that old. A couple million years to get off the plant before radiation makes it uninhabitable, and they're safe. OTOH, we stick around for another couple billion years, and the earth is just getting back to thinking about vertebrates when the radiation level starts increasing and eventually wipes out all surface life. I suppose, it'll do so gradually enough that most species can evolve defences, but the more resources go into basic survival, the less are available for increasing brain capacity. Option 3, is between the first two. A potentially intelligent species develops, capable of understanding the world around them, they've just started mastering tools, when the weather gets hotter, the water gets scarcer, harvests get leaner and predators get meaner. In summary, it's like a house. There's a chance there will be a new occupant, but it depends on what condition you've left it in, and how long you're willing to wait. [Answer] Firstly, if the earth has become 'deadly for us', surely it is deadly for all life in which case I very much doubt intelligent life will arise. Assuming that Earth is only deadly for humans though the answer is: We don't know Given that we're still not totally certain how intelligence works and how we evolved it we can't say with any certainty that it will come back if we leave. I would suggest it will based on how many animals we see able to learn and use tools but that is just my personal opinion and it is just as likely that no other animal will make the jump from simple tools to the point where they have intelligence and can make decisions based on logic and reason rather than instinct (I'm not certain humans have reached that point yet). Even if we set a lower benchmark human-level, or near human-level, intelligence is still hard to evolve. The Earth is around 4.6 billion years old. Life has been around maybe 3.8 billion years. Complex life for around 2.1 billion years. Homo sapiens have been around for about 0.2 million years. Their may have been intelligent hominids such as Homo Neanderthal slightly before this but even then humans have only been around for a tiny fraction of the time complex life has been around. Given how long it took intelligent life to evolve the first time any intelligent life that re-evolves will not be around for a long time after we leave. Furthermore it will not be anything like a human and its intelligence might come in a different form to our own so we might not recognise it as intelligent at all. [Answer] It's certainly possible; we can't tell how likely it is with the current state of knowledge. 100 million years is a long time - our direct ancestors 100 million years ago would have been very unspecialized things that would look shrew/mouse/rat-like to a non-mammalogist. That was before the major diversification of placental mammals. It would also depend on how widespread the effects of the event that drove humans off Earth was. If it was something specific to humans (maybe a super-pandemic?), intelligence might evolve from other primates, or maybe from raccoons (they have decent grasping hands). If it was something like a K-T extinction that destroyed all mammals (or all large mammals) but some other vertebrates survived, birds are also possibilities for high intelligence, though their technological ability would be very limited due to lack of hands. If all vertebrates died out, human-level intelligence within 100 million years looks much less likely, though octopi evolving intelligence might be believable. [Answer] The other answers already give very good information on evolution, so I'd like to point out something else: This question has some similarities to the Fermi Paradox. The Fermi Paradox, in a nutshell, is this: with all the countless planets out there in the universe, there should be at least thousands of intelligent life forms like us out there. But why haven't we heard from any of them? The main idea is that there exists a kind of "great filter" - somewhere between microscopic lifeforms and a space-faring civilisation, there exists one or more barriers that very few lifeforms get past. If the great filter is in front of us (e.g., if progressing from where we are to space-faring is the problem), there's definitely a chance new intelligent life will evolve in your world. How quickly this happens is going to depend very much on what kind of life forms remain on your planet after the humans are gone (it'll be much more plausible for animals to become intelligent than bacteria). However, if the great filter is behind us (the better option for humans), there's going to be problems. If the filter is between microbes and multi-cellular life, and your world only has bacteria left, it'll be practically impossible for new life to form. If the filter is between animals and intelligent creatures, there's also no chance. So, the answer is going to depend highly on what kind of lifeforms remain and where the great filter is- no one knows the latter, so you'd have to decide in your story. [Answer] One of the problems about a sample size of one is that it can tell us very little about how likely it is to occur again. As far as we are aware, there has never been another animal like us living on Earth, despite a fairly decent number having brains that are comparable in size to those of our close ancestors. The last common ancestor of humans and chimpanzees lived about 13 million years ago, so if there are still apes around it is certainly possible for the same events to happen again in the same amount of time. There are a good number of other candidates besides the great apes that could plausibly be the ancestors of another sapient species: dolphins, crows, parrots, and elephants are all quite intelligent already and may be able to go through the same evolutionary steps that we did. (The intelligence of octopuses is overrated; while they are certainly impressive compared to other invertebrates they are only mediocre when compared to mammals and birds...but since they look so strange and alien the thought of octopuses growing sapient is just fun to think about.) The problem is that intelligence is only one solution to the problem of survival, and it might not be a very likely one. There have been many species that evolved fairly high intelligence and then simply stopped developing in that direction for millions of years, because they didn't need to. We don't know the exact circumstances that led to our own evolution. So while we can say that the development of a new intelligence within the next 10 million years or so is possible, it is hard to determine how probable it is. One thing that we can say is that, depending on the conditions we leave behind, it may be difficult for a new species to make that leap. One of the drawbacks to large brains is that they have a high energy cost and long growth periods. The aforementioned intelligent animals typically breed slowly, take a long time to grow up, have few children, and require a lot of food for their size. Because of this, intelligence is most useful in a relatively safe environment with a lot of available resources, where the main evolutionary pressure is intraspecific - the same kind of environment that favors other costly adaptations such as bright colors and sexual displays. Hostile environments, by contrast, tend to favor fast breeders with short lifespans that can survive on few resources and adapt quickly, where the death of any one individual will not be a great loss to the species as a whole. If we leave Earth as a wasteland, it is unlikely that we would see new intelligences arise before the environment recovered. ]
[Question] [ Why would an non-Eusocial animal have a caste of sterile individuals? Formicidae and Apoidea have sterile workers,but those outnumber the fertile drones and princesses or queens. In another animal that doesn't have queens or drones but just motile(male) and oogame(female) why would evolution support and want the existence of a precise caste of sterile individuals that does not outnumber the fertile ones like in eusocial colonies? In humans and many other mammals males outnumber females cause they die more easily and have a way shorter lifespan, and this seems to work for the most part. How would the males,females and sterile be distributed in this situation? [Answer] Let's think about this from a human perspective. After a certain age, all women are infertile. While not as striking an event as menopause, men's fertility declines precipitously as well. If these people were still evolutionarily "useless", one would think evolution would put in a kill switch so they weren't a drain on resources, but that is demonstrably not the case. So, what use, evolutionarily, is a post-child creation human? 1. Raising the next generation. This does not necessarily have to be your direct descendant, but genetically adjacent individuals. Remember: if your [nibling](https://en.wiktionary.org/wiki/nibling) survives and reproduces, that's 25% of your genetics surviving. 2. Supporting your siblings. Remember how your niblings were 25% your genetics? Well, your siblings are 50% your genetics! That's as good as your own kids, statistically speaking. This is particularly effective if there's a large disparity in ages (a sterile adult raising a young sibling). Further: 3. Adoption. Okay, they aren't your genetic material in any direct sense, but any solution about castes is going to be about what's best for a community, not just your family. It could be advantageous to have some specialized in having many children, and then some of the children can be raised by the infertile caste. And, speaking of specialization... 4. Community specialization. You've hit on this with your note about there being more men but they die more. In an environment extremely hazardous to your species as a whole, it could be advantageous to have a caste that sacrifices fertility in order to focus its energies elsewhere (defense, exploration, labor, etc.). Functionally, these last two are what eusocial insects do, and is basically the definition of eusocial. While this only occurs in insects (I believe), it wouldn't be unreasonable for a different species to develop a similar system, even if the balance of "breeders" and "workers" is different than, say, ants. [Answer] ## Hyper-aggressive males In this scenario, the alpha male doesn't just lead and defend a harem, he will fight any adult male he encounters to the death. This starts a feedback loop where only the strongest, most aggressive males produce successful offspring and the young males need to flee the group before they reach adolescence and start producing the hormones that set off the alpha male. Who doesn't need to flee? Male offspring that produce very little or no male hormones. These trigger neither fighting nor mating responses in the alpha male and can live their lives safely in the group, gathering food, guarding the group and generally performing the more risky tasks. Unfortunately, they don't produce viable sperm or have mating drive. In this case, sterile individuals take the place of males, but there can't be too many or the male genes will not spread. The ratio of male : female : sterile might be 1 : 2 : 1. ## Radiation-proof specimens This scenario plays out in a (post-apocalyptic) world with many irradiated areas. a relatively small number of individuals are born with very high tolerance for radiation and the ability to detect it. Unfortunately, this comes at the cost of their fertility. They protect their siblings/family/group from radiation by testing food and water. Some even eat/drink and regurgitate food before the rest of the group eat/drink it. Only 1 or 2 per group are needed to make it successful, so the ratio could be 1 in 10 of either gender. Perhaps it's determined by radiation exposure in the womb that turns on certain genes, leading to a variable rate. ## It's just a phase This scenario may not count as individuals may be fertile before or after their sterile worker phase. Individuals that experience stress while growing up due to food shortages or other factors caused by overpopulation do not develop sexually and instead become focused on work/production. Only a prolonged period of abundance will trigger development into fertile state. This would be helpful in a species that is not very mobile or isolated due to geography (islands maybe?). The populations that don't have this feature will overpopulate their environment and collectively die off, while the ones with the sterile phase will stabilize until the situation improves, old individuals have died off or a new location is discovered to migrate to. [Answer] I think you may have been slightly mixing cause and effect. In your example insects, every egg the queen lays has equal potential to become a worker, drone, or future queen. It all depends on how the larva is fed. Likewise, in the one eusocial mammal, the naked mole rat, pheromones in the queen's urine cause other females to become infertile. Sterile versus fertile is not an in-born trait, but rather a developmental one. In some mammals, the dominant members do their best to suppress the sexuality of the subordinates. This can be by chasing rivals or attacking others who attempt to mate. So while not technically sterile, the subordinates are just as unable to pass on their genes. They have little choice except to live on the edge of the herd or the pack, just following along. This isn't a parallel to worker ants or mole rats, as the non-breeders don't serve the alphas. However, these subordinates have the chance the next season to move up the ladder and become breeders. So now the question becomes: Would there be any advantage to the species if there existed a way to make subordinates permanently sterile? My answer is no. Here is a mathematical proof by contradiction: > > Assume to the contrary that $X$ is a non-eusocial species with a permanent sterile caste. As whole $X$ must gain some advantage from this. Members of the sterile caste consume food and other resources, so they must contribute in some way to the overall health of other $X$. The only possible such contribution is to share gathered resources with the breeding members or their offspring. Thus species $X$ is eusocial. We have a logical contradition. QED > > > ]

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