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[Question] [ The world of Baros (b'a:rəs) has low gravity (around 0.5g), thick, moist atmosphere (2-3 bar), and lots of volcanoes. Humans mostly inhabit sunny elevated areas, separated by relatively dark and CO2-rich lowlands. The humanity is at roughly medieval tech level. Now one of the features I want there is a plant that grows on bare cliffs, using symbiotic bacteria and its own roots to cut its way through micro cracks. This plant is domesticated and selected for rapid growth and deeper rooting. Bacteria are producing oxalic acid which is [already used by lichens to crush basalt](http://www.geo.mtu.edu/~raman/papers2/ChenetalCatena.pdf). UPD: The wild variation relies on birds for nutrients and seed distribution, and grows berries to attract them. Domestic one is dependent on humans' aid. The rock in question is similar to Earth's [alkali basalts](https://en.wikipedia.org/wiki/Basalt) (Mg/Ca/Na/K silicates with Fe, Ti and Al oxides) and should be able to withstand temperature changes, water, knocking, and scratching for ages. Say I want the roots to penetrate 5-10cm of rock in 2-3 months. Afterwards other means (driving in wedges and making them swallow? Or maybe just a sledgehammer?) would be used to dismantle weakened rock into convenient small blocks of stone. [Nice terraces](https://www.google.com/search?q=terrace+agriculture&tbm=isch) are left behind. Is it possible at all? Should it be a shrub? A grass? (Trees seem to be ruled out, for one cannot plant trees in tight rows - or...?) Maybe such plants already exist on Earth? Last but not least, is such technique feasible at all for a medieval society? [Answer] The main benefit of being able to grow on rock (of any kind) is that other plants can't, which gives the species that can an edge in getting living space and sunlight. The downside is that shortage of nutrients requires either some other form of getting them or very slow growth. You presumably want the process to be as fast as possible, so the question essentially comes down to alternate ways of getting nutrients. I will suggest two as an example, but I am sure you will be able to think up more. The plant can grow underwater with the water carrying the nutrients. You can find such plants on many coastal areas, so real world examples to base the plant on are available. I think real world plants prefer adhesives though. Deep roots gives no advantage over shallow roots and a good adhesive. This would require that people build temporary pools of water for the plant to grow on. The plant could get extra nutrients by catching insects. Such plants could presumably be simply fed with cultivated insects. Plants like this also generally have shallow roots. If you do not get nutrients from your roots, there is no benefit in making them deeper than needed to anchor the plant. And solid rock makes for superior anchoring point. So I think the optimal plant to use would be fast growing and spreading plant with shallow roots and very low and small visible part. Something along the lines of moss. I also think underwater solution would work better than feeding insects to plants few millimeters in size. You would only be able to crush a very shallow layer of rock per cycle, but the cycles would potentially be very fast. And since a plant with roots penetrating deep into rock seems unlikely due to lack of compelling benefit, shallow roots version is probably the choice of necessity. And of course the shallow roots fast cycles version would also be much more precise. You would be able to create ornamentation and inscriptions with precise outlines and delicate features. Also smaller the plant is less water you will need to provide. Small enough plant could be painted as a gel to surface in the morning and rubbed out of the surface along with some softened rock in the evening. [Answer] High CO2 concentrations is good for agriculture and also anaerobic bacteria. Maybe it's most feasible to make bacterias use that CO2 to produce carbonic acid (if you find a large source of hydrogen, like water) to attack the rock. Plants will need water anyway. Maybe you can provide carbonic acid resistant bioengineered crops using that bacteria in symbiosis to bricks/soften that rock. Also remember some plants grow better in excess of sunlight others not. Maybe the thick atmosphere clouds visible light but can let UV pass. In that case you plants can also be engineered to get more of this wavelength. If genetics is that advanced on your world you even can mess with chlorophyll making a variant. It can have a interesting effect on leaf colors making it range from dark blue/purple to white. Edit OP make a good point with oxalic acid. In that case to rapid deteriorate rock a plant/bacteria symbiosis to acid attack the rock and soften it sounds good for me. If sunlight is not a problem it can even help with some cultures like potatoes, is left to OP to decide how rock-eating potato crisps will taste. More Edit Light atmospheric scattering and absorption is complicated because depends on the many atmosphere layers, each one interacting in a different way. Without the ozone layer UV can be a problem. Also you star can have a very different [light spectrum](https://en.wikipedia.org/wiki/Stellar_classification). Also if your planet got lots of deep valleys with gaps where there are lacks of oxygen it can get [cyanobacterias](https://en.wikipedia.org/wiki/Cyanobacteria) for example. If you want to goo deep (no pun intended) you can read [this](http://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/) article about photosynthesis & solar radiation ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. The Halo video game's extended universe book [Halo: Evolutions](http://www.halopedia.org/Halo:_Evolutions_-_Essential_Tales_of_the_Halo_Universe) describes the [Battle of Psi Serpentis](http://www.halopedia.org/Battle_of_Psi_Serpentis), in which a superjovian planet is converted into a brown dwarf via massive nuclear bombardment of its core, destroying the vastly more powerful pursuing Covenant alien fleet. > > The Covenant fleet regrouped and pursued Cole's fleet until a group of Insurrectionist vessels emerged from slipspace. Led by the heavily modified Bellicose, they opened fire on the Covenant, losing a quarter of their number. Once they attacked they smashed through the Covenant formation and withdrew from the system. Cole himself moved Everest deeper into Viperidae's gravity well while the UNSC fleet proceeded to disengage. The Admiral then issued a broadcast to the pursuing Covenant ships, boasting of his own achievements while scoffing at their claim to righteousness. Sensing and accepting the challenge, the Covenant moved to attack Everest, but their plasma was deflected by the magnetosphere of the planet. > > > Cole moved Everest past the point of no return from Viperidae's gravity well, and launched a barrage of missiles at the lead ship in the Covenant formation. Nuclear fire destroyed the ship but there was little damage done to the rest of the fleet. > > > While the Covenant fleet was distracted by the barrage, Cole had launched one hundred Shiva nuclear warheads into Viperidae's unstable core. The resulting ignition caused the planet to go nova, undergoing stellar fusion and briefly becoming a brown dwarf. The resulting shockwave obliterated all of the Covenant ships, reduced Viperidae to a smoldering rock, and presumably destroyed Everest. > > > Is such a battle tactic actually valid, in the sense that would launching a large number of nuclear weapons at the core of a superjovian planet be sufficient to cause it to ignite into a brown dwarf? If so, how much energy is required to make this happen? [Answer] # $2.55\times10^{45}\text{ Joules}$. But it probably won't work. There are a few things we need to get straight here, namely, the differences between brown dwarfs and giant planets. Here are two of the most important:[[1]](https://en.wikipedia.org/wiki/Brown_dwarf) * Mass. Brown dwarfs are, at the lower mass end, greater than ~13 Jupiter masses, and there's a murky transition zone between low-mass brown dwarfs and high-mass gas giants (see [Burgasser](http://astro.berkeley.edu/%7Egmarcy/astro160/papers/brown_dwarfs_failed_stars.pdf)). Other categories of object, like sub-brown dwarfs, only serve to muddle the waters. But most brown dwarfs are in the dozens of Jupiter masses, extending to about 80 Jupiter masses. So to make a super-Jupiter (actually a technical term) a brown dwarf, you'd have to increase its mass. As Samuel calculated, this change in mass comes out to ~2.55$\times$1045 Joules. * Structure. Structure is very important when analyzing substellar objects. [Brown dwarfs don't really have layers](http://news.discovery.com/space/astronomy/violent-storms-rage-on-nearby-brown-dwarf-110913.htm), while gas giants typically do. So you'd need to somehow figure out a way to get rid of all the layers of matter in a gas giant to make it more like a brown dwarf. Composition is a related factor, although many of the same compounds (even besides hydrogen and helium) are present in brown dwarfs. [This answer on Physics Stack Exchange](https://physics.stackexchange.com/a/34624/56299) (which is fantastic) states that you would need a deuterium layer for fusion to happen as is the case in a brown dwarf, which makes sense. You'd need to change both of these things in order to turn a gas giant into even a low-mass brown dwarf. There's also one more issue: Setting off a nuclear explosion wouldn't do much (surprising, right?). Why? Well, you could set off a whole bunch of nuclear weapons, thereby raising the temperature and pressure in a certain volume. But you would have a tough time sustaining the necessary conditions for hydrogen fusion ([at least ~107 Kelvin, for the p-p chain](http://www2.astro.psu.edu/users/alex/astro497_6.pdf)). Obviously, [nuclear weapons reach this temperature](http://fas.org/nuke/intro/nuke/thermal.htm), but they quickly cool. The temperature would quickly drop, as would pressure. You might get a little bit of fusion going, but I doubt it would be enough to sustain hydrogen fusion - unless you increased the mass. [This document](http://www.fas.org/sgp/othergov/doe/lanl/docs1/00329010.pdf) found that no runaway fusion would be possible in an Earth-like atmosphere, and I suspect that similar mechanisms of energy loss would exist here, making it impossible for fusion to happen as you intend. It would be much easier to reach conditions necessary for deuterium fusion - and I would assume that that requires a lower starting temperature - but a sustained reaction would be just as hard. For fun, here's how fast thermal radiation emission drops (again, from [here](http://fas.org/nuke/intro/nuke/thermal.htm)): [![](https://i.stack.imgur.com/9WSLk.png)](https://i.stack.imgur.com/9WSLk.png) Note that this would, of course, be increased if you increased the number of weapons detonated (would 100 really be enough?). That said, I'd be worried about how you propose to bring the weapons so deep into the brown dwarf. I would think that before reaching the core, where the conditions for fusion would be best, temperatures and pressures could cause premature detonation, leading to a much less effective use of the weapons. --- Some other random criticisms of the scenario: * Viperidae most likely did not have any heavier elements inside it, so it would not turn to "rock" afterwards. I don't know what the result would be, but a substantial portion might remain as gas. * A gas giant should not have an "unstable core". * There isn't a "point of no return" from the "gravity well", as Viperidae is not a black hole, although perhaps this referred to low fuel levels. * The shockwave might not be too powerful unless material was ejected to carry it. Space is not a vacuum, but it still doesn't (in general) conduct shockwaves too well unless the medium is dense enough. I take it, however, that you don't really care about these points that much. [Answer] In short, no, this isn't a valid battle tactic. A nuclear weapon would have little to no effect on even a small gas giant. The key isn't energy, it's mass. A nuclear bombardment from orbit might have a total detonated yield in the gigatons or even teratons of TNT. That sounds like a lot, and it is, if you are considering what it would do to conditions on our own planet. However, that's not even a drop in the bucket of the forces and energies at work inside a gas giant, never mind a superjovian. The key, as I said, is mass. It takes about 25-40 Jupiter masses before you start seeing sustained deuterium burning (depending on the exact makeup of the giant, the amount of solar gain from its star and what, exactly, you consider enough sub-fusion activity to draw a line in the sand between gas giant and brown dwarf). If the planet's currently around 20 MJ, you'd have to feed 5 additional Jupiters' worth of mass into the gas giant to even have a chance of seeing a net energy output from deuterium burning. We have nothing anywhere near the technology needed to move this kind of mass in anything approaching a war timescale. If we did, the tactic of igniting a superjovian to make it a weapon would be superfluous; you could simply carve a large chunk out of a nearby moon and throw it at your pursuers in a high-speed shotgun blast of Europe-sized asteroids. ]
[Question] [ Expanding upon [this answer](https://worldbuilding.stackexchange.com/questions/28681/making-a-longer-lasting-person/28687#28687). ## Background Assume some forward looking and rich person realizes that some day humanity will go to the stars. However, with human life expectancy so low, generation ships possess too many potential sociological pit-falls. This forward looking individual begins a completely voluntary and secret selective breeding program to increase human life expectancy. I imagine it would look like the one in [Methuselah's Children](https://en.wikipedia.org/wiki/Methuselah%27s_Children). The essence is, a well-endowed foundation researches living people's blood lines. They look for people with extremely high percentage of very long-lived ancestors and that those ancestors remained "vital" for all or most of their lives. When they find candidates, the candidate receives a letter indicating they've been selected and it provides details on how to pursue the matter if they are interested. Male and female candidates receive money for reproducing with another candidate identified by the foundation. If the couple elects to remain together for forming a family and having more than one child, then the financial rewards are much higher than the compensation for simply producing one baby. Children of such couplings are automatically considered for future pairings and support by the foundation. You can couple the ideas from Methuselah's Children with those of Richard Dawkins to get your program going faster (basically couples must have their kids after a specified age). ## The Situation The foundation has successfully produced humans whose life expediencies range from 500-1000 years. Human space travel technology has advanced enough to contemplate sending a ship to another star. ## The Question How does this wealthy, secret, extremely long-lived society of people get invited to fly in the first ships to the stars? [Answer] As the comments pointed out, there are a few flaws in this setting. Nevertheless we might attempt to provide a reasonable path. ### Flaws * Evolution is not so fast. The plan to select individuals to with particular family history to reproduce, and gradually increase the lifetime expectancy of the new born is slightly unclear ground. But I'm not a biologist. Even if we assume that it works, I'm pretty sure that a life expectancy increase of 5 years per generation is more than optimist. As in the linked post, a generation would consist of 30-35 years. On that basis, to go from a life expectancy of 100 years to 500 years, that would be 80 generations, so with 35 years in average (probably earlier for the first ones and later for the later ones) you need 2800 years of careful selection. And this is very optimistic. * You need a rather large group. Life expectancy depends on a lot of factors, but even people with the rights genes for longer life aren't free of other risks. In particular a genetic diversity prevents you from getting everyone wiped out with the first virus. It would be a pity to go on for 1000 years, spending a lot of careful attention and secretive actions to get your 5 families wiped out by the latest flu streak, because they were genetically unprotected. And you need to consider the other risks of a very limited pool (I won't come back to that, some others did it much better than I would on other posts around). * Hard to keep secret. A few thousands individuals living a few hundreds years, with on the whole several hundreds of thousands of people involved. Good luck keeping it secret. You can hardly get 50 people involved in something without having one of the babbling about it. The amount involved is just beyond what is plausible. The one way to do it would be to separate the whole subjects from the rest of the society. But again, careful to the evolution strike when you get out of your protective hide-out. * This point is linked to the previous two. Old Age isn't the only cause of death. Just living longer does not exempt you from dying in another form. Accidents, injuries, illnesses, etc. you name it. Even if you get them isolated, they might fight against each other. And you might end-up in exactly the same problem as generation ship. Worse still, even their families are programmed. And it's lasting much longer! You essentially have similar problems than generation-ships, but for longer time. And considering that the long isolation, you might have people that could make the trip, but I'm not sure they would be considered humans anymore. I think you'd be on much better ground investing on cryo deep-sleeps and AI to fly the ships. ### How to get on-board Now for the following, will hand-waved away the previous objections. Let us assume that somehow, you manage to get a few hundreds of people living up to 500 years. You want them to be kept secret and living in the middle of the population. Due to their extraordinary longevity, you need them to move on regular basis, to avoid raising suspicion. This implies some logistics, and money, but you mentioned money wasn't an issue. However, the organisation has to be closed to the political powers on their countries. You don't get to change the identities of a few thousands people without attracting some interests by the government. And the best way to keep it silent, is to make sure that the people who's job it is to check that are looking away. Another reason to keep close to power is that while you concentrate on building a crew for the ships, you need to be involved in any space exploration program, to be ready at the right time, prepare your crews for the specifics, and at the same time orient those projects in the right way. These points indicates that you need some hidden, strong and continuous lobbying in the political, economical and scientific leading circles. It is preferable not to bring your new humans on the post. Those groups are usually too exposed to the public opinion to actually hide. You need to form some illuminaty-like group which coordinate the lobbying and implications. And you need to carefully avoid being identified as a united group. If you want to be in the USA, you'd probably do well to have some politicians on both side. And many people involved in your cause without knowing about it. When the time comes, many leaders are working for you, and most probably you were the one creating the final project anyway. [Answer] > > How does this wealthy, secret, extremely long-lived society of people get invited to fly in the first ships to the stars? > > > That is pretty easy. They will be rich and powerful enough using their long lives to actually pay for the ship and control who is going to be on it. Many of them might even have several needed specialties for the trip. Others can spend decades preparing for one. Since the breeding program is started solely for this purpose (and he has a lot of money) I can't imagine that they won't keep their fingers in all the pies controlling the first actual colony ship to leave Earth [Answer] The long lived group will have the most interest in exploration and colonization of the stars, both because they will have the resources (due to compound interest) and the incentive to leave (since most people will either want to steal the secret of immortality or just their accumulated wealth). The problem, which most people have identified, is that the long lived people will have to work in secret and carefully make their plans without being discovered. The most difficult stage will be to actually create the starship project; it will be very difficult to hide this (for the most part the project will not be concealable, since using known physics and technology, a gigantic Orion pulse drive or solar sail ship will be needed to survive the trip), and especially the crew selection process will be under a great deal of scrutiny and comment. A bunch of people can't just appear out of nowhere to become the crew of a starship; the people who apply will be under intense media scrutiny and interest (and of course there will be legions of fanboys and stalkers who will also be very interested in the process and astronauts). I suspect there will have to be a sort of "two stage" process, where the long lived are gradually and over a long period of time moved into space as technicians or colonists, and then after a change of their identities to work on the starship project. ]
[Question] [ Lets say you have a small group of space colonists. They were screened for sickness, viral and bacterial, as thoroughly as we knew how before being sent off to the colony and all were found healthy. They traveled for years in a fully sanitized ship before reaching their new colony, which is isolated from all other humanity, or other earth-animals. Effectively there is no one to catch a cold from on this new planet. How long would it take for sickness and disease (viral and bacterial, not counting things like cancers) in this population? What length of time would it take for the equivalent of your common cold to pop up? How long would it take for more dangerous potentially life-threatening illnesses to crop up? [Answer] First of all, the colonists might become reactionary to some component of the equipment in their environment. Everything ages. Metals oxidize and flake, or react with other chemicals in the environment. Synthetics also break down due to heat, light, and mechanical stress. Second, any healthy human is going to carry their own viral, bacterial and fungal load. Mutation is a fact of life for these critters. I think the chances of one person developing a variant germ that affects the others are pretty high. The human genome can also experience epigenetic changes due to the factors I mentioned. I'd have to take a wild guess and say that symptoms would be noted in the first 5 years. For instance, a "cold" could be anything from a histaminic reaction to infection by someone else's mutated germ. Of course, your colonists would likely carry along some very sophisticated equipment and medical expertise. [Answer] Every healthy human being consists of a huge number of microbes living inside him/her. More than a dozen of these microbes are those which cause diseases. As long as the immune system of the person stays strong, these microbes act as "good citizens" and stay in their limits. Once the immune system is compromised (malnutrition, blood loss, or any other weakness), these microbes start showing their dark side and get nasty. So ... your space colonists have all the necessary ingredients for an epidemic within them. Once any of them gets weak, the microbes will get him/her sick and if it is a transmittable disease, soon an epidemic would break out. If you are looking to learn about the speed of microbe evolution, here is a link that would help you. It is about an experiment designed just at what you are looking for: the speed of evolution in microbes. [E. Coli Long Term Evolution Experiment](https://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment) [Answer] The length of time that the colony can go without getting sick will depend on the mutation rate of the bacteria/viruses/prions that the colonists brought with them. At mission start, the bacteria will be in homeostasis with the colonist's immune systems. (For simplicity, I'm going to refer to all infectious agents as bacteria.) As bacteria breed, they mutate, picking up and dropping traits that increase or decrease their survival. If a mutation results in a strain of bacteria that a colonist's immune system can't handle without symptoms then the colonist will get sick. From there, the nature of the mutation will dictate how well the bacteria spreads and the exact symptoms of the illness. Also, individual colonists may experience weaker immune systems as a result of stress, malnutrition or age which will make their bodies better breeding grounds for bacteria. Since there's a proportional relationship between the number of bacteria generations and the number of mutations, the longer a bacteria population survives, the more likely it is to have a mutation that will enable it to get a colonist sick. ]
[Question] [ Let's suppose we live in different star system with two similar-sized planets (with a mass of three and a half Earths.) We live in Planet A, which is habitable. For some reason, Planet 2, our neighbor, enters in collision orbit with our Planet 1. But us, Planet-1ers are not happy with this, so we somehow catch Planet 2 and keep it close together. Both planets end up as a double planet. Now, what would it take to catch Planet 2 and keep it orbiting along with ours? I'm aware that with current technology it is not possible, but let's suppose for a moment we have an advanced level of technology, but still not going off the laws of nature. [![Double Planet](https://i.stack.imgur.com/yNSKh.png)](https://i.stack.imgur.com/yNSKh.png) [Answer] It would be far easier to just move one of the planets a little so they don't collide if there's a large velocity difference. If the planets are just barely going to collide, it seems like it might make sense to try to catch one. The problem is once you've caught it, the two planets will destroy each other from gravity. Unless your magical tech device can magically prevent gravity from working, you'll get something like this: [![Planets melting onto each other from gravity.](https://i.stack.imgur.com/9vt9N.png)](https://i.stack.imgur.com/9vt9N.png) The only way you're going to avoid this is if the planets are far enough apart that they don't tear each other apart. At this point, the best bet is just to get the new planet into orbit around the old planet. I thought there was a question about how to move planets around, but I'm not finding it right now. [Answer] There are 2 separate tasks: avoiding collision and forming double planet. 1. To avoid collision you need to give incoming planet lateral push. If collision is far ahead then this push can be relatively small - for 1 year and 30K km miss you need only 1 m/s. Though, of course it is hard to change planets speed even by 1 m/s since we are talking about trillions of trillions kgs. But you can put engines on asteroid, and make it "hang" to the side of the planet so that gravitational pull from asteroid would change planets trajectory. 2. To form double planet on other hand is much harder. Two passing bodies don't just start rotating around each other on it's own. They need to lose speed to do that. Otherwise, as they come closer, they would speed up just enough to reach escape velocity(because there is conservation of energy - binary planet has less potential energy than 2 separate planets). And we are talking about losing some km/s. So this task is 3 orders of magnitude harder than the first one. So, if civilization thinks about creating double planet, then collision is not a threat, if it can barely escape a collision, then creation of double planet is out of question. [Answer] You'd probably need an artificial black hole as a stopgap measure to do the capturing but in theory you could get your two worlds orbiting a mutual centre of gravity like Pluto and Charon. I'm pretty sure that having done this the two worlds will be tidally locked to each other as they orbit that centre though so you're going to lose a lot of habitat on both worlds. If you actually have the technology to capture a world in this fashion you can probably produce a better outcome. ]
[Question] [ Suppose you have a 2+1 dimensional universe where the physics of that universe (we'll assume that the physics causes something similar to chemistry and that there is no gravity, but there is special relativity) allows life in the form of single cells to form. This universe will also be finite in space. Not that it has an edge, but more that it curves in on itself to form a sphere in three dimensions. The scale of this sphere would be pretty big relative to the sizes of the "atoms" of that universe so the large-scale positive curvature of space won't be significant at the scales we are talking about. My questions can basically be summed up by "what are the consequences?" Here are my questions: * Is it possible for a self-replicating cell (that means it has a membrane or some form of protection, it has "string-like instruction molecules" and it has molecules to carry out these instructions at the minimum) to be able to exist and function properly? * If it can (I think it would be able to), would this cell be able to evolve? * If this cell can evolve, is multicellular life a possibility? (e.g. 2-eyed creatures moving around with flippers and eating bits of edible material with mandibles or something like that) I understand this question may be a bit broad, but I don't have many ways of narrowing it down due to it being highly theoretical. However, the sorts of answers I am looking for are things like: * Fundamental problems/challenges that specifically 2 dimensional life would have to overcome * Consequences of the properties of the universe that could heavily impact supposed two-dimensional life * Side-effects affecting life * How realistic life's existence in this universe would be [Answer] Is it possible for a self-replicating cell (that means it has a membrane or some form of protection, it has "string-like instruction molecules" and it has molecules to carry out these instructions at the minimum) to be able to exist and function properly? Yes! Apart from the radically-different-physics cellular automaton examples referenced in other answers, DNA is already pretty much one-dimensional, and its copying process need not require more than 2 dimensions. A 2D linear genetic molecule can replicate, or permit itself to be read, essentially identically to a 3D linear genetic molecule--by unzipping down the middle, and accumulating complementary monomers on the exposed edges of each half. If it can (I think it would be able to), would this cell be able to evolve? Evolution only requires replication with variation. The self-replicating cellular automata described in other answers do not permit variation during replication (being completely deterministic, they make no mistakes--and if they did make mistakes, they would almost certainly be "fatal"). A 2D DNA-analog, however, would be just as susceptible to mutation as 3D DNA, and there is equally no barrier to 2D sex at the cellular level. If this cell can evolve, is multicellular life a possibility? (e.g. 2-eyed creatures moving around with flippers and eating bits of edible material with mandibles or something like that) Yes. The canonical example of such life is the Ardeans from The Planiverse. Their biology is heavily based on zipper-mechanisms to permit the passage of materials between the exterior and interior (i.e., eating and expelling waste) and between different sections of their bodies (pushing food along the alimentary canal, pumping blood). As a result, most Ardean creatures are actually two separate halves "glued" together most of the time (there are two exceptions in the book, the intelligent Nsana and their closest relatives, which eject waste through their mouths). Zipper-lock mechanisms are found all the way down to the cellular level, as part of a multi-layered cell membrane. Personally, however, I find that construction to be implausible at the cellular level; vesicle-based transport, combined with a lot more multi-nucleated "supercells" sharing a common cytoplasm than we are used to in our 3D biology, seem like much better solutions to the problem of transporting metabolic materials at the cellular level. Vesicle engulfment and expulsion may also be a decent transport strategy for macro-scale multicellular organisms, but velcro/zipper arrangements do make more sense at that scale. The other major issue that would need to be solved by complex animal life is signal crossing. Nerve networks just can't be made fully planar. Fortunately, however, there is a clever arrangement of 3 XOR gates that allows signal cross-over in only two dimensions, which should not be hard for biology to discover and implement in neurons. There is, however, another avenue to solving the crossover/transport problems, which may be exploited in parallel with those already mentioned, or possibly instead of: mutually-non-excluding matter. Solid materials in our universe cannot pass through each other fundamentally because of the Pauli exclusion principle; electron clouds bounce off each other not because they repel each other electrically (atoms are neutral, after all), but because multiple fermions of the same type can't occupy the same space at the same time. Change the type of particle, however, and exclusion no longer applies! (This is part of why, for example, muon-catalyzed fusion works--not only is muonium smaller than regular hydrogen, but a muon cloud can pass right through an electron cloud with no resistance.) So, consider (for example) a 2D universe with protons, neutrons, electrons... and magnetic monopole parallels for all of those. Each type of matter would still be able interact and form (weak) bonds with the other, such that you could form hybrid organisms composed of a mix of each type of matter (thus it is useful to eat both types of matter), but each type of matter would also be fully capable of passing right through the other, so it can be injested through special mono-material ports made of the complementary matter type. And of course, there are innumerable other ways you could modify the matter of your 2D world to make life easier--electromagnetic symmetry is just one off-the-cuff example. EDIT: On further contemplation, you probably don't want to use magmatter in 2D--magnetic fields are not mutually attractive in 2D, unlike 3D, so magmatter and electromatter can't actually form bound states. So, definitely just use that as an example of the kind of thing that might be possible; you'll have to come up with a different particle set to make the idea actually work in 2D. [Answer] There are some simple known cases of self-replicating patterns in 2D from "[Conway's Game of Life](https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life)," a set of rules for calculating successive game states of an infinite grid of square cells, each of which can take one of two states at any given moment. It is a cellular automaton, just like the environment for the Von Neumann universal constructors mentioned in Cort Ammon's answer. Wikipedia says the following on the subject: > > On May 18, 2010, Andrew J. Wade announced a self-constructing pattern > dubbed Gemini which creates a copy of itself while destroying its > parent. This pattern replicates in 34 million generations, and > uses an instruction tape made of gliders which oscillate between two > stable configurations made of Chapman-Greene construction arms. These, > in turn, create new copies of the pattern, and destroy the previous > copy. Gemini is also a spaceship, and is in fact the first spaceship > constructed in the Game of Life which is neither orthogonal nor purely > diagonal (these are called knightships). > > > On November 23, 2013, Dave Greene built the first replicator in > Conway's Game of Life that creates a complete copy of itself, > including the instruction tape. > > > --- One challenge for life like ours, with membranes and a liquid basis, is that no "tunnels" through membranes can exist without compromising the structural integrity. However, there are alternate ways of getting things across a membrane: gates or "zippers" that can close and open, or vesicle formation followed by dissolution of the vesicle membrane. Regarding evolution, I don't even know how life evolved from non-life in the 3D world! There's so much unclear about the early events of abiogenesis that I don't think you'd need to explain it in your world, either. After life is established, it seems natural to think that it would evolve over time. [Answer] [Von Neuman Universal Constructors](https://en.wikipedia.org/wiki/Von_Neumann_universal_constructor) are an example of how this might work out. They use a 29 state simulated automata to create a machine that can replicate itself. It's not physical, like you want, but its existence mathematically suggests that it is entirely possible to actually occur. The side effects depend less on the 2 dimensional nature and more on the particular rules of physics you employ, so it's hard to say things for sure. However, there are some interesting cases that show up. For one thing, the square/cubed law limiting the size of creatures changes dramatically, because there's only 2 dimensions. Also worth noting is that chaotic systems from differentiable systems don't show up until 3 dimensions. If you want any chaotic behavior, it either needs to be discrete (like celular automata) or another approach which does not depend on differential equations. If you subscribe to Dogulas Hofstadter's theories from [I Am a Strange Loop](https://en.wikipedia.org/wiki/I_Am_a_Strange_Loop), this poses significant limitations on the ability for "I" to arise from continuous processes -- it would have to occur as a side effect of discrete processes. [Answer] It is possible to have multicellular life in such a planet. However since it is two dimensional, it would he ghastly different from life on earth. Here I am assuming the two dimensions are length and height. * The creature would have to eject waste leftover of digested food through the same channel that it ate. That is, you cannot have a digestive canal running from one end of the animal to the other. It will divide the creature into two parts. * If two such creatures come in front of each other, they would never be able to cross each other. One would have to jump over the other. Good luck if two rows of creatures come in front of each other ... * If the creature has more than one eye, they would have to be arranged up-down, because a sideways dimension isn't even present. * The creatures would only need two legs for balancing themselves, instead of 3 or 4. ]
[Question] [ Set in the 15th century CE. Using the resources and technology available during that period of time, would a medieval age manned sub guarantees victory in a sea battle? How would such a sub be able to obliterate(sink) the likes of Ship of the line? Accidents and sucidal missions do not qualify as winning. [Answer] No, it's been tried several times before their successful deployment in the 20th century and they didn't work. The primary examples are the [Turtle](https://en.wikipedia.org/wiki/Turtle_%28submersible%29) (1776) and the [Hunley](https://en.wikipedia.org/wiki/H._L._Hunley) (1864). It wasn't until WWI that the proper set of technologies became available for U-Boats to be a major factor in warfare. Even with the primitive ASW defenses of the time the Germans [lost over 60% of their fleet](https://en.wikipedia.org/wiki/U-boat_Campaign_%28World_War_I%29#Aftermath). --- A submarine's sole advantage is to hide underwater. Thus a successful submarine must be able to do the following... * Stay submerged. * See submerged. * Move (rapidly) submerged. * Attack submerged. Staying submerged is a matter of keeping the air breathable. Medieval technology would have no way to do this: no [CO2 scrubbers](https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber), no compressed air storage, no [oxygen candles](https://en.wikipedia.org/wiki/Chemical_oxygen_generator). They could only submerge for a very short period of time before the crew would pass out. Alternatively, they could do as the [Turtle](https://en.wikipedia.org/wiki/Turtle_%28submersible%29) did and not fully submerge. Either way this greatly limits their ability to approach a vessel undetected. Next, how do you see without being seen? Telescopes and microscopes did not exist in the 15th century, nor did quality lenses. Even if they did, the scope housing would have to be sealed somehow. Early submarines used viewing blocks mounted in a shallow cupola which would peek just above the surface. This has the obvious disadvantage of being visible to the enemy. Prior to the electric motor, moving submerged was performed by manpower. The US Civil War era [H. L. Hunley](https://en.wikipedia.org/wiki/H._L._Hunley_%28submarine%29) of the [Confederate States](https://en.wikipedia.org/wiki/Confederate_States_of_America) Navy was the epitome of this. [Hand cranked by seven men](https://en.wikipedia.org/wiki/H._L._Hunley_%28submarine%29#/media/File:Hunley-1.jpg), it could manage only 4 knots, much slower than most sailing or steam ships, and barely enough to go against a strong current. All those men doing all that work would reduce the time it could spend underwater. Such a speed would make it only effective against anchored vessels, as was the Hunley's only success against the [USS Housatonic](https://en.wikipedia.org/wiki/Sinking_of_USS_Housatonic) (the Hunley did not survive the attack). It would also have a pitifully short range and only able to operate near the coast or be towed by a surface vessel. And finally, how do you attack? The [motor torpedo](https://en.wikipedia.org/wiki/Torpedo#Invention_of_the_modern_torpedo) wasn't invented until 1866 using compressed air to turn a propeller and a gyroscope to keep it on course. Early submarines attacked by attacking mines to the hulls of ships. The Turtle featured a drill and was thwarted by copper sheeting. The Hunley used a [spar torpedo](https://en.wikipedia.org/wiki/Spar_torpedo) which it would have to ram into the hull of a ship and release. Neither of these were particularly effective. --- In short, prior to WWI the submarine was only marginally effective at attacking anchored vessels in calm water close to a shoreline and at night. Even in WWI and WWII submarines were not a factor in fleet battles. They were simply too slow to keep up with the battle fleet. Instead, [they would be set up in long lines along the anticipated course the enemy fleet would take. The could then act as scouts and possibly take a few shots at the enemy](https://en.wikipedia.org/wiki/U-boat_Campaign_%28World_War_I%29#In_support_of_the_High_Seas_Fleet). This rarely worked; it failed in the [Battle Of Jutland](https://en.wikipedia.org/wiki/Battle_of_Jutland) and it failed in the [Battle of Midway](https://en.wikipedia.org/wiki/Battle_of_Midway). The US had some success with this tactic in the Pacific, but it wasn't until the advent of the nuclear submarine, which could go fast enough to keep up with a battle fleet, and good radios for communication that submarines could work effectively with a surface fleet. --- How would 15th century ships defend against these vessels? The same way early WWI vessels did... * Stay on the move. * Take a zig-zag course. * [Travel in convoys](https://en.wikipedia.org/wiki/Convoys_in_World_War_I). * Post look outs. * Lay mines. * Use [anti-submarine nets](https://en.wikipedia.org/wiki/Anti-submarine_net). * Ram them. This may seem ludicrous to you, but this is how the majority of submarines were destroyed in WWI. [ASDIC/SONAR](https://en.wikipedia.org/wiki/Sonar#ASDIC) was only a prototype, and depth charges weren't available until 1916. You had to spot a submarine with your eyes and ram it, or catch it on the surface and shoot it. 19 U-boats were destroyed by ramming, 20 by gunfire, and 58 by mines. It's surprisingly easy to spot a submarine underwater, especially one creeping along at 4 knots and just 10 feet below the surface. Once spotted, they were helpless. [Answer] See [this answer](https://worldbuilding.stackexchange.com/questions/19384/how-could-a-simple-submarine-be-built-using-100-bc-technology/19407#19407) of mine. A plausible medeval sub would be very different from what you have in mine. In particular, pressure vessels never worked until industrial times. Saying yours did is not plausible. My idea, detailed in the other post, is a mobile cason with divers in individual breathing gear. Casons were developed early for underwater harbor and tunneling work, and I explain how this work might lead tomthe discovery the your cement makes the air last longer, to then find the active ingredient and optimize it. So it could be built. So what? This question asks what good that might do for war. Without explosives, what could a sub do? They probably can't just drill holes in the ship: the occupents would notice and fill them. It's not enough damage fast enough. So what? ## defense against ships in a harbor A company of heavily armed men can sneak up on a ship, and swam over the sides in a surprise boarding operation. Or, sneak on board ninja-style. The invader's weapons and treasure can be tossed over. Cannons over the side to sink! And the locals can pick them up for their own use. Boarding is what Leonardo had in mind, it appears. He was a renounced weapons designer, so you might look into his notes. ## offense against a harbor A ship "safely" some distance from shore, or disguised as regular commercial traffic, could drop a work crew and equipment they use back home for maintaining and improving their own harbors, to... Mess up this foriegn harbor! Instread of clearing silt and removing hazards to new huge deep-draw vessels, stack up rocks and plant submerged spikes where they think the channel is clear! Undermine docks and tunnel into warehouse facilities. That's the kind of work the technology was developed for. ## fodder for stories So can it turn the tine of war? A story could be crafted where that is the case. The enemy's flagship is found in the morning to be empty of life with no alarm during the night. An invasion force finds its provisions are poisoned. things keep happening. [Answer] Yes a medieval sub could theoretically turn the tides of war. Can it guarantee it? Well, that depends on its effectiveness and how much the war relied on a naval fleet. Although the first submarine was built in [1620](https://en.wikipedia.org/wiki/History_of_submarines), there is no reason one couldnt have been built earlier. But how would it destroy large ships? With torpedoes, or at least an explosive device. [Gunpowder](http://www.bbc.co.uk/history/worldwars/war_tech_gallery_04.shtml) was first developed by the Chinese before 1000 BC. It was used to propel rockets and may have reached Europe via the Mongol invasions of the mid-13th century. So the ability to create weaponized explosives had matured long before your submarine. There are numerous ways someone could create in order to deliver the explosive to the enemy ship. That just takes some imagination. FYI - The first combat sub was the [H. L. Hunley](https://en.wikipedia.org/wiki/H._L._Hunley_(submarine)) was used during the American Civil War. It was human powered and used torpedoes is armaments. [Answer] You can build a submarine during medieval times with medieval technology, that would obliterate the enemy navy, but for it, you would need modern knowledge. So it's sort of a paradoxical situation. You would have all the required craftsmanship that would enable a submarine to stay submerged and be effective, but in those times nobody *knew* how to utilize that technology and come up with some ingenius underwater beast. What it means is, if somebody well versed in mechanics and hydraulics travels back in time to those days (15th century CE), they could incorporate their knowledge to build an extremely primitive, but nevertheless devastating sub (according to the standards of those times). But nobody born in that time knew how exactly to do that. I hope my point is clear. This how you are going to build such a submarine: # Building The Submarine You are going to build something that can carry 3-5 people and some good amounts of naphtha (crude petroleum. ~30 liters should be enough). The sub needs to be rocket shaped. As in, the general shape should be like a tower and the front side needs be pointed. The material needs to be heavy and strong, stainless steel, most preferably. Of course people of those times didn't know how to make stainless steel but you do. You would need to keep two holes in the sub. One in the front section (~3 ft diameter) and the other in the rear (~1 ft diameter). Both holes should be in the roof of the sub. From these holes, you would attach two metallic tubes. Rear tube is 10 feet long while the forward tube is 12 ft long. Both tubes need to be fixed (melt and merge). The forward tube has 4 mini-tubes in it. They all start together inside the main tube, but at the end, each turns at 90° angle away from the other. Since the tube is vertical to the sub, the mini-tubes would turn at 4 angels (front, right, left, back). Now you would need to fix thick mirrors at all the joints of these 4 tubes. When you are done, you would have an effective periscope that would enable you to look in all directions simultaneously. There's a very long (~200 meters), strong but relatively thin rope attached to the inner side of the front end of the sub (interleaved silk strings). # Testing Put the sub in the water with 5 men and 50 liters of refines naphtha (which should be practically equal to a mixture of gasoline, kerosine oil and diesel oil). Add/remove weight to/from the sub until it stabilizes at a depth of 8 ft + the height of the sub. That is, the sub should stabilize at a depth where both tubes are 2 feet above water. You are good to go now. # Usage There is no steering mechanism in the sub. You are going to move it using a very primitive way. One of the sub-operators is a diver. He would have to dive underwater and reach an enemy ship. Once there, he would attach the rope end (remember it is ~200 meters!) to the ship. Now he would tug the rope a couple of times to signal his comrades. Within the sub, the operators would simply pull on the rope to move the sub towards the enemy ship. Once there. A couple of men would disembark with the naphtha canister and pour ~5-10 liters of it on the side. Then get back in the sub. The diver would detach the rope from this enemy ship and dive in to attach it to another. Now once naphtha has been applied to the ship's side, your archers would only need to shoot a couple flaming arrows there and that side would burst aflame. It would take ~10-15 minutes for the fire to spread and take the whole ship ablaze. # Pros * No need to risk the lives and try the extremely risky boarding method. * Sub operates underwater and very silently. Nobody can see it moving. Even if it is detected, it cannot be destroyed by arrows as it is made of metal. * The men slap soaked clothes to the ship's side to coat it with naphtha. Takes only half a minute to deliver ~10 liters of naphtha. # Cons * Extremely slow, clumsy and primitive design. * The diver's job is highly dangerous. If detected, it would only take an arrow to kill him, rendering all the sub ineffective (unless you have more divers inside and have a larger sub). * If a flaming torch is thrown at the operatives while they are coating the ship's side with naphtha ... ]
[Question] [ A common question seems to be how to survive tsunamis / floodings and the like. However I'm interested in what a building would look like after a year under the water. Depending on the depth and the increasing pressure, as each part of the building is able to withstand differing amounts of pressure / erosion / animal life encroachment... Do windows survive for long? Will wood warp and crack, will doors be able to stay adhered to their frames or would they inevitably float to the surface? A direct analogy I can draw is with sunk boats, but they're usually designed for more aquatic purposes than buildings, so perhaps not a wholly usable comparison. What would a building under water truly be like after a year? [Answer] It all depends, mostly on the materials used, salinity, pH levels, oxygen concentration, temperature, availability of calcium carbonate and water currents/waves. These effects are non-linear, for example, corrosion rates generally increase with temperature, but if you raise the temperature further in can slow corrosion by removing oxygen (among other things). Calcium carbonates (e.g. limestone) in the water can deposit scale that protects the underlying materials. You often see these scales on water pipes. These scales can protect the materials for a long time. There are many examples of buildings and towns that have been submerged for long periods of time. Many are intentional and result from building reservoirs, but almost all of these are fresh water. Since we build ships, we have also studied the issues associated with submerged materials used in ships. Building materials. Sheetrock is rapidly ruined. Wood treated with creosote survives for a long time, 50 or 100 years is usually not ruined. Creosote is not much used anymore for marine applications due to environmental concerns. The other treatments are not as effective, but I don't have actual survival times. Plywood may delaminate within a few years depending upon the glue. Steel -- Steel used in construction is rarely stainless, so corrosion begins immediately as even fresh water always conducts current. Depending upon the other materials this may be accelerated greatly because of galvanic effects. In fresh water, the rate of corrosion depends upon very minor environmental differences, including the consistency of the steel the result is often pitting where the slightly more corrosive gets used up in preference to the other areas. Experimental data is not even particularly accurate because the results are so variable. Salt water is just a worse problem as electrical conductivity is high. Some coatings will protect steel for quite a while (even decades), but they all eventually fail due to imperfect coating and leaching of the material. Zinc-dipped steel is best known and for good reason. It is very effective as coverage is nearly perfect and the Zinc will be sacrificed first during corrosion. It will still fail eventually (cracks in the coating, etc.) but I don't expect this to be common in construction. It certainly is not used for the steel fasteners that many constructions depend upon. I.e., once the nails go, the building collapses. For a nice online guide that gives a hint of the difficulty see [Fundamentals of Metallic Corrosion in Fresh Water](http://www.roscoemoss.com/wp-content/uploads/publications/fmcf.pdf) Windows may tend to survive better than you might expect because they are frequently designed to resist moisture problems, so the wood is treated and the glues are moisture resistant. Still, just observe the deterioration of a leaky window and you will know that they really don't survive that well. So what does last? Stone and kiln dried ceramics. You might get thousands of years from some of these. However, the mortar is first common point of failure. Some mortars can fail within a decade, others might last for a hundred years or even somewhat longer. If you have mortarless stone construction and you don't have problems due to earthquakes or excessive currents or wave you could live there when the waters recede a few centuries later. The end result of all this variability is that we don't simply design construction to last for 50 years in underwater environments. We design the best we can and begin a program of inspection and maintenance. We have to inspect because we don't know when failure will occur and the maintenance is needed because failure will occur if we don't prevent it. --- So what about 1 year of submersion. Any structure would require cleaning, refinishing, etc. before it would be usable. Note that most flooding also means sewer overflows are included in the floodwaters. Definite intensive cleanup is required and well as repainting, etc. In general terms. Wood -- unless specially treated for water, the wood will be damaged beyond what you would wish to use. This includes most windows as construction materials are often selected based on price rather than quality in residential usage. Plywood is even less likely to be usable as water can interpenetrate common plywood more easily than bulk wood. Steel -- unless specially treated for water, significant corrosion will be present making the cost of cleanup very high. If steel fasteners are used in construction, it will be unsound (or at least not provably sound) Brick, concrete, stone -- Most mortars should survive and be safe to use after a year underwater provided they have had sufficient time to cure completely prior to flooding -- still a nasty cleanup job will be needed and the organic materials, etc. will get into every nook and cranny. [Answer] ### The building structure may do OK, but the devil is in the details Gary Walker gave a good comprehensive description of what will happen to the structural materials - wood, brick, steel, etc. But there is a lot more to a modern building: * Electrical Everything electrical - wiring, HVAC equipment, thermostats, lighting - will fall apart pretty quickly. Circuit breakers (which are much more complex than the fuses of yesteryear), light bulbs (incandescent will (literally) crack under the pressure; CFLs and LEDs will die a quick death as the electronics rot), telephone equipment, alarm systems - even an ordinary "in & out" flood will ruin much of that and extended submersion will ruin it all. * Plumbing Even though plumbing is designed to transport water, many of the parts are not designed to have water on the outside and will corrode. * HVAC In addition to the electrical components (compressors, air handlers, thermostats, control circuits) all becoming junk very quickly, the duct work will rust and/or be covered with mold, algae and other wonderful stuff. * Floor Coverings Carpeting won't last more than a few days. Wood won't last much longer as it starts to warp. Ceramic tile may be the only flooring that lasts the year. * Walls While walls themselves may do OK - particularly brick and stone - paint, wallpaper and other wall treatments would be ruined very quickly. Drywall won't fare well - it doesn't last if it isn't "dry". * Miscellaneous Doors will likely be ruined - steel will rust, wood will warp. Railings, hinges, poles and other hardware will rust or rot. Insulation (fiberglass, foam, etc.) will get really nasty. Plus plenty of other things I haven't thought of yet. In short, even if a building is structurally sound (doubtful), if you were to somehow get it out of the water after a year it would likely be cheaper to tear it down and start from scratch than to replace every bit of electrical wiring & equipment, HVAC systems and floor covering; clean/dry & repaint all walls; replace doors & windows, plumbing fixtures, etc. ]
[Question] [ A cave-bound society with radios. Consider that: * This is a three level network of caverns. * The radio is internal and doesn't need to connect to the outside. * The level of technology is sort of what you'd get from a not very historically consistent steampunk(ish) novel. In an isolated, underground society, would having a radio with radio stations work? (I know the cave's going to be horrible for radio waves) But is there a way to make it work? If not with radio waves, what could be used to make a radio like system? [Answer] Depends on the size of the caverns and the distances between inhabited places. There might just not be enough need for radio broadcasting to develop - just [put the cable](https://en.wikipedia.org/wiki/Cable_radio) through the caves (cable radio has been especially popular in Soviet Union). If there is an electrical network, you can broadcast the radio channels through it, the cabling is already there. Alternatively, if the caverns are big and you want portable sets, low power ubiquitous transmitters (one per cave, fed from the cable) is what you want. In any case, you are looking for long waves (if you want diffraction to neighbour caves) and reflection resistant system, which means [FM](https://en.wikipedia.org/wiki/Frequency_modulation), if not even more sophisticated norm (or outright digital, which needs rather high level of technology). These are unfortunately somewhat contradictory conditions, with long waves (~ hundred kHz) you won't get enough bandwidth for FM. [Answer] While a low-frequency radio could be used in a "through-the-earth" configuration, such communications are extremely narrowband -- real systems that do this are limited to one-way text paging or perhaps an "emergency alarm button" for a return channel. (These systems are limited to sub-3kHz ELF frequencies in order to get adequate ground penetration.) More realistic communications (NBFM voice, two-way short messaging, narrowband data) require the use of "leaky feeder" or "radiating cable" technology, using higher frequencies run over a special coaxial cable that's fabricated with slots in the shield so it acts as a continuous antenna. This would require repeaters in the cable every-so-often, but depending on the frequencies at hand, this is not difficult to solve -- they can be powered by superimposing DC on the feeder cable, and operation at VHF frequencies was feasible with WWII-era vacuum tube technology (if not slightly before then, even). [Answer] Assuming no other changes to radio technology, then the best way to move radio waves between caverns would be to use wave guides. Waveguides are simply metal pipes or ducts that confine the waves within and allow them to propagate over long distances without attenuation (the spherical waves emitted from a typical dipole antenna fall off due to the inverse square law, besides being absorbed by the cavern materials). In practical terms, a transmitter would have one or more wave guides fanning out towards the various connecting passageways to the other caverns it is meant to service. the ends of the waveguides can be left open at the entryway to the other cavern, to allow the waves to propagate into the cavern and let people pick up signals. This would be fairly efficient for one way broadcast radio (much like real radio even today), but you would not realistically be able to transmit two way traffic like WiFi or VHF voice radio in this manner, unless the transmitters and receivers are placed at each end of the waveguide. At that point you may as well use wire as the transmission medium rather than radio waves. The other issue is the waveguide will have to extend into each cavern you want to transmit to, so if you have a string of caverns, then the Cave Broadcasting Corporation "World News Service" would need a maze of waveguides leading into each cave. This would be rather inefficient, and eventually there would be signal loss at the end of the longer waveguides. Depending on the frequency being used, the radio waveguides might also be rather large, which could be a problem if the passageways are small or have very sharp corners, and also if multiple radio stations are trying to broadcast (imagine a service corridor with lots of pipes and ducts to get the idea). ]
[Question] [ I am a scriptwriter working on a science fiction story. As best as I can I like to reconcile my imaginary places to within the constraints of reality. Here is my problem: Kettrah [![enter image description here](https://i.stack.imgur.com/1ghPi.jpg)](https://i.stack.imgur.com/1ghPi.jpg) Kettrah is by most means a tidally locked planet which mean that it rotates on one axis in the same time it takes to complete its orbit. However this planet is different in that it also rotates while it is tidally locked. Thus the north pole is locked to the star and the planet spins around that axis while the locked pole moves on its own axis to always face the star. If you're having trouble picturing this: Imagine Uranus, but with one pole always facing the Sun. [![enter image description here](https://i.stack.imgur.com/ojKx4.jpg)](https://i.stack.imgur.com/ojKx4.jpg) [Source](http://astronomy.nju.edu.cn/~lixd/GA/AT4/AT413/HTML/AT41303.htm) My questions are: Can a planet have two rotational axes? If so is there a way to lock one pole to a star? [Answer] Yes, this is possible; the rotation that keeps the pole pointed toward the star would be considered to be [precession](https://en.wikipedia.org/wiki/Precession). If this planet was in a close orbit around a red dwarf star, it would be close enough that it would be tidally locked, and gravity would provide the necessary torque, while remaining in the star's habitable zone. [Answer] No An object rotating without any outside forces on it will have one stationary angular momentum vector. In order to have a precession of this angular momentum vector, torque must be applied. This torque added (integrated) over time will add to the current angular momentum vector to give the new angular momentum vector. In order for the angular momentum vector to always point towards (or away from) the sun the torque applied would have to be strong enough in magnitude that it could stop the planet rotation in quarter year. That might not be so bad except the direction the torque would be rather difficult to achieve. If you consider the axis of motion of the planet around the sun as up, then the torque would have to be pushing the bottom of the planet and pulling on the top. Unfortunately, since the planet is rotating, those halves are switching twice a day, so any gravitational pull would net do nothing, unless your day was really long (like if a day was equal to a year and thus the planet was tidally locked) But there is another type of precession, a [torque free precession](https://en.wikipedia.org/wiki/Precession#Torque-free) where the axis of instantaneous rotation changes while the axis of angular momentum remains stationary. However, this could also not produce the desired movement as the two axis cannot point in opposite directions (or even be perpendicular) but in your described movement the axis of rotation points in completely the opposite direction every half year. [Answer] I don't think it is possible to achieve this for a planet orbiting a star. But you could in effect achieve this with a moon that's tidally locked to a planet, which it orbits in a [sun-synchronous orbit](https://en.wikipedia.org/wiki/Sun-synchronous_orbit). This requires a fast-rotating planet (so it has a strong equatorial bulge). For Earth it's not possible (all sun-synchronous orbits lie within the Roche limit), but for a Jupiter-like planet it might in principle work. The mass of a gas giant would easily allow for an Earth-sized moon. Mind, a moon in such a specific, nearly polar orbit is pretty unlikely... also, the planet [would probably have massive volcanic activity](https://en.wikipedia.org/wiki/Io_(moon)) because of the planet's tidal influence. ]
[Question] [ I have a story set in a world similar to x-men where some people develop powers like x-men. However, it's not a superhero story, it takes place on a college campus and mainly focused on everyday life, discussion of powered vs no powered relations, and the mentoring relationship of protagonist and another young child. The protagonist is going to be the type that likes to find useful ways to exploit normal powers, and both of the main characters powers are not things that you would want to use in the obvious overt ways in every-day life. Thus I'm trying to figure out what other tricks the protagonist may come up with to use these abilities. The protagonists ability is to block the powers of others around him from working, or more accurately to absorb the energy that fuels active powers before they can manifest. However, intentionally blocking the abilities of someone else is rude, at the very least, if not arguably criminal. Besides which some people go through such severe transformations that they can only survive due to passive powers helping them to, for instance, breath despite having developed gills, so blocking everyone's powers around him could potentially kill someone; he very quickly learns to not project his blocking field for this reason. Some of the interesting effect he manages is to sense the power he is blocking and where it came from, making him able to sense active powers used around him, and thus who has powers (he always absorbs a little of the power, even when not actively blocking), and eventually he develops enough of a 'feel' for powers to get a rough idea of the kind of power someone has by what he is absorbing; nothing specific. He also has a young child he is playing mentor for who has the ability to read and effect minds, but uit only works on a subconscious level (both his and the targets subconscious). The kid can't read your social security number or what your think about Firefly, but he can get a general 'feel' for someone's subconscious thoughts; which acts as part ability to emotion by sensing the 'feeling' of the subconscious, and part an ability to judge character by sensing rather their subconscious thoughts are positive ones, sneaky etc. The kid does not fully consciously understand or control what he is sensing, getting his own subconscious impression of the other person, and it's left ambiguous what all he can gleam. The kid can also slightly effect someone's subconscious thoughts, inclining them to be more accepting of an idea, to feel a certain way, or to start thinking about a certain topic; though it is not an overt control and he can't force anyone into something they are truly oppose to; and it's not clear how much he is aware of or controls this ability either, thankfully he doesn't do this too often at first. The protagonist is afraid that a child that can subtle manipulate others to get what he wants will grow up horrible spoiled and bad if he gets in the habit of exploiting his power. When the kid acts curious about his newly developed powers the protagonist would thus want to distract the kid away from realizing the true power by teaching him other nifty, but harmless, tricks. This is the part I really need help with, what other tricks could he come up with to entertain the kid and help the kid learn about his powers while distracting him away from the obvious uses. As of now the only trick I have is to be able to learn to sense who is behind him by learning the 'feel' of someone else's subconscious mind. In fact he creates a whole game off of that idea that he gets other kids involved in (making the kid 'guess' which kid is sneaking up on him effectively). What other tricks could either of these two use, particularly the kid, to do interesting things with their powers. They don't even have to be useful, just a novel game for the child to distract would be good. [Answer] You should [Dexter](https://en.wikipedia.org/wiki/Dexter_(TV_series)) him. For reference, Dexter is a sociopath who's taught by his adopted police officer father to channel his homicidal nature in constructive ways - in other words, against those who deserve it. The main tool he uses is to teach Dexter a restrictive code of ethics and behavior that ensures (to a reasonable extent) that he only murders the guilty. In your case, you should teach the child to either 1) help the unhappy become happy or 2) get guilty people arrested. Your game structure should basically be: 1. Give the child a target name. 2. Have them get a subconscious read on the target. 3. Teach them how to use the information they gleaned to look for other info, research the target and eventually figure out how to help them. This should channel the kid's power more toward the "sensing" end of the spectrum, while also teaching them alternative tools and not solely to rely on their power. As an aside: > > When the kid acts curious about his newly developed powers the protagonist would thus want to distract the kid away from realizing the true power by teaching him other nifty, but harmless, tricks > > > If you do this, the kid will eventually realize what you're doing, at which point you will lose the trust of the extraordinarily dangerous individual you've been teaching. This may mean that he'll start to ignore all of your teachings. He'll also start to use his new ability unsupervised, possibly on you. Instead of hiding it, tell him about it but point out why it's dangerous. Educate him about the kind of psychological pitfalls he could fall into if he's manipulating everyone around him. And when he inevitably messes up, make sure he's aware of what he did: > > "But what went wrong? I don't understand!" > > > Father stopped and cleaned his glasses, thinking. I waited impatiently, sick to my stomach. Images of Angie's mother flashed through my mind, piles of new clothes around her, hands bleeding through the bandages as she mindlessly sewed on and on. > > > "Your friend Angie is poor. Her mother didn't work. So you made her think that work was important, so she'd have money." > > > I swallowed hard past the lump in my throat. "Right." > > > He looked at me patiently. "More important than her health?" > > > I protested. "Of course not. I mean..." I trailed off as the realization hit me. I felt sick to my stomach at what I'd done. > > > His large hand patted my shoulder. "We'll come up with a plan, then go back and fix things. But I want you to remember this, son. Humans aren't simple or easy. Far better to fix things with words." He gave me a squeeze, then continued walking. > > > I trailed after in a daze, bloody fingers flashing through my mind. > > > [Answer] Does this power have a maximum range? If so, kidnap the kid, take him to an island somewhere, stock the pantry with canned goods, and wait it out. Children in general are monsters, and this kid in particular is a potential antichrist. This isn't one of those parenting scenarios you want to handle by skimming through some Dr. Spock or maybe trying out a few hints from Dear Abby. Lock it down now, lock it down tight, and keep it locked down until you can train the kid to be a 70th-level Buddhist or something. [Answer] Honestly, the only reason I can think of to have someone with power nullification guard a kid like that is to use the nullification powers on him. Seriously, this kid's power is literally undetectable mind control. The only games I could think to use would be some kind of radar game, like flashlight tag minus the flashlight, or training him for survival, like playing ninja by sensing where people are. [Answer] I think the example of a game that you have given is a good starting point for other practices. Other game-type exercises the child could be exposed to are simple lie-detector type games (whether or not another player is being truthful) or more complex games based on similar concepts such as poker. With the example of poker the child may be able to tell when his opponent has missed his draw (e.g. a failed straight or flush draw) due to feelings of disappointment, when they are holding a strong hand (feelings of excitement or greed) or when they are hesitant to call a raise (feelings of fear or worry). The difficulty level could be raised by introducing players who are aware of the child's ability (such as the protagonist) who might be capable of emotionally bluffing the child (e.g. by focusing on the potential win of a hand they incur excitement and cause the child to overestimate the strength of their hand) But I also think that teaching the child to use their abilities through games is not a particularly good practice because it will teach the child how to use their abilities without passing on any of the responsibilities of doing so. Eventually, the child will grow up and realize the full extent of their powers [Answer] The protagonist can sense that the kid has powers to read minds. This goes to reason that there are other people with similar powers. If such a power exists, it can be assumed that the government also has access to these people, as this would be extremely useful for solving power-related crimes. I think your best bet here is to simply teach the child to never use his powers at all, as once one of the alphabet intelligence agencies realize what he is capable off, they would stop at nothing at getting a hold of a foolproof lie detector / intelligence gathering agent. ]
[Question] [ Part of this story I'm writing involves a human subspecies who are adapted to extremely high altitudes -- as high or higher than our real world's Tibetan population, let's say. I've done research that indicates that the Tibetan adaptation to high altitudes in part involves either a decreased red blood cell count or a dramatically reduced amount of hemoglobin. I'm not sure if those terms are synonymous (I'm guessing they are), but sources agree on it being related to the EPAS1 gene. Anyways, I'm thinking about using the same mechanism for this population, although since they live higher up, and they've had a longer time to adapt, I assume they would have a proportionately more intense version of the Tibetan adaptations. What I want to know is whether a significantly reduced red blood cell count, across this population, would be visibly discernible in their blood to the unaided eye, and thus what color their blood would be relative to lowlander red blood. Would it be less vibrantly red? More so? I initially wanted blood as vibrant as red paint, but I'm trying to be realistic. An absence of sources detailing Tibetans having differently colored blood, to me, points to them not having differently colored blood. And I suspect blood color would vary more with degree of oxygenation than it would with cell count. [Answer] You won't notice a difference. What the research is showing is that Tibetans don't have the elevated red blood cell count or hemoglobin levels expected when others (lowlanders like me) go to high elevations. Essentially, they have blood that more closely matches what lowlanders have at low elevations, but still do quite alright. As stated in [this paper](http://www.case.edu/affil/tibet/booksAndPapers/Hemoglobin%20Conc-Tibetans.pdf): > > The Tibetan hemoglobin distribution closely resembled that from a > comparable, sea-level sample from the United States, whereas the Aymara > distribution was shifted toward 3–4 gm/dl higher values. > > > The Aymara don't have this gene ([EGLN1](http://www.nature.com/ng/journal/v46/n9/full/ng.3067.html)) which keeps the hemoglobin levels low, but they also live at fairly high altitudes. When lowlanders go to higher elevations our red blood cell count increases and hemoglobin concentration increases. This helps us get enough oxygen, but it also causes altitude sickness, so is detrimental over long periods of time. So, you may notice a difference at altitude, but it's the lowlanders who will have slightly different color of blood. But the difference is small. ![enter image description here](https://i.stack.imgur.com/u9ZQn.jpg) Tibetan males and sea level American males are in the ~14µg/dL range (the second to rightmost block). A lowlander going to high altitude will have a blood color darker than the rightmost block, at >19µg/dL. I actually can't find a suitable image for how deep/dark the color gets, but the trend seems to indicate it will get quite dark. ]
[Question] [ I'm coming up with a science fiction world for an assignment. Would it be possible for a planet like Earth to be eaten by a giant alien creature that moves through space at a relatively slow speed and still remain somewhat intact after impact with the back of creatures stomach (assuming the creatures insides is almost like a tunnel). Most research proves that any large impact with Earth would be cataclysmic, I'm just curious that if the speed of which the impact occurs, could it potentially be survivable if the people on this planet had time to build bunkers and technologies that could help them withstand a certain amount of the impact or other destructive results of the incident? Also would a creature of the size required to eat a planet be able to exist? It's very far fetched and unbelievable, but I'm just looking for some way of backing it up logically so it's not completely ridiculous. If that's possible. [Answer] could it potentially be survivable if the people on this planet had time to build bunkers and technologies that could help them withstand a certain amount of the impact or other destructive results of the incident? I foresee a few problems. 1. It'll block out sunlight, so the entire food-chain is going to die. People with it. 2. A giant space alien is going to have lots of mass. Things with mass have gravity. Surrounding a planet is going to have an apparent drop in gravity as suddenly you're going to be pulled 'upwards' towards the alien. 3. A spinning Earth has a *lot* of rotational inertia. There's been questions on changing the Earth's spin answered in [detail](https://worldbuilding.stackexchange.com/questions/8408/could-we-still-live-if-earths-spin-speed-slowed-down-by-90) [before](https://worldbuilding.stackexchange.com/questions/8425/if-earth-spin-decreased-how-can-i-get-it-spinning-faster), and the prognosis is that the Earth is going to [continue doing what it wants come hell or high-water](https://what-if.xkcd.com/26/). An alien eating us will scour the surface of the Earth flat. No more buildings. No more mountains. Also would a creature of the size required to eat a planet be able to exist? Consider the size of such a massive creature and the effect its own gravity would have on itself. The creature needs to be bigger than Earth, so it's going to be very massive. While it doesn't need to be more massive than Earth, it does need to be hollow. Massive and hollow don't play well together. This sort of alien needs to be very carefully balanced and incredibly strong otherwise it'll collapse in on itself. The impact of a planet to the inner-surface is more than likely going to upset that balance. [Answer] An early "modern" [science fiction story was written by a famous astromomer Fred Hoyle](http://www.wikipedia.org/wiki/The_Black_Cloud). I recall a series of novels about space vampires bred to combat a threat that was a fine wisp that gathered itself over the planet and ate it. David Gerrold, perhaps? And don't forget [one of our planets is missing](http://www.wikipedia.org/wiki/One_of_Our_Planets_Is_Missing) from Star Trek TAS. So, there is plenty of precedent for the idea. You ought to read some of those at the very least. You can probably take latitude with what it means to be eaten. So don't think of a giant star-sized animal, which would be fantasy and not hard SF by today's standards. Get creative. Maybe nanobots are disassembling all the planets, perhaps to create a [Matrioshka Brain](https://en.wikipedia.org/wiki/Matrioshka_brain). Perhaps it is moving in from a different dimension of space where scale is different, and Earth seems small. It might be a grey goo apocalypse of our own making. For an actual huge creature, an extended cloud or gossamer gause sounds like a good idea, so you avoid the huge mass but it can be very large and what mass you do have can spread out and balance out the gravity. Contradicting user6511, the source doesn't need to be larger than Earth. It could be a small seed or swarm that converts the planet into more of the same like a virus "eating" a cell, and disperses many many small copies over time. A survivable scenario at least for individuals in a bunker would be the idea of a wisp gathering around the planet and eating just the thin skin of biosphere. The bulk of the rock would be unaffected, but people often think of the biosphere as "the earth" e.g. how human action is "destroying the planet". [Answer] The are many objects in space that are large enough to swallow the earth. Many in our own solar system. Neptune is 3.9 times the earths size but could fit the volume of 57 earths within it. A living planet could definitely consume the earth. <http://www.universetoday.com/22058/neptune-compared-to-earth/> The breakdown of the earth as the surface rotation changed to meet that of the consumer could be part of a digestive system mechanic similar to teeth/chewing(this would also take a long time as the RPMs at the earths surface are so low{.00069 RPM}[or would this depend more upon linear motion? Should it change depending upon how the two objects met?]). Now what if one of the supper earths hidden within the outer edges of our solar system was an egg for such a creature and it just recently hatched and started moving closer to the more edible sized planets closer to the warmth of the sun Mars, Earth, and Venus? Perhaps it wonders about the Kipper belt first, consuming smaller objects. We might have thousands of years to ready a response. It might even eat our moon first. <http://time.com/3673527/super-earths-possibly-discovered/> Humans could launch themselves into space creating orbital habitats. These could be short term habitats and humans will soon land on the back of the beast. Or long term meant to survive once the beast leaves. Tunnels could also be built to the center of the earth (science fiction tech level right now).The seismic activities of the first contact would be the largest issue I think. If human built structures survived this then life could continue. Since the current RPM's of the earth would take eons to wear through the crust. Humanity would need an alternative power source to grow food. If nuclear is not good enough, then we can use geothermal as we approach the core. ]
[Question] [ I asked a similar [question](https://space.stackexchange.com/questions/9133/what-sensations-would-i-feel-on-a-space-elevator) (in a SpaceEx manner) on Space Exploration, but here I've made it a bit more ... worldbuilding. We have a nice Space Elevator, and I'm in charge of the luxury guest accommodation for the six-day round trip. Setting aside the design considerations, I am interested in what the experience would be physically. Standard conceptual 50,000km space elevator attached to a counterweight; accelerating at low altitudes, then a constant velocity, and then a deceleration. What effects will my guests feel (1) accelerating upwards at low altitudes, (2) constant velocity at very high altitudes, (3) deceleration, but 'looking up' at the Earth, and (4) stationary on the counterweight. No numbers needed, just "then they fall to the ceiling..." You see, I have to design the suite right, with seatbelts, beds, showers, etc. for the most discerning guest! [Answer] The [apparent gravity](http://en.wikipedia.org/wiki/Space_elevator#Apparent_gravitational_field) felt from the Earth as one travels up a space elevator is given by: $g\_{apparent} = -G {{M}\over{r^2}}+\omega^2r$ Where $G$ is the gravitational constant, $M$ is the mass of the Earth, $r$ is the distance from that point to Earth's center, and $\omega$ is Earth's rotation speed. I plotted this as a function of distance from Earth's surface. Down at the surface gravity is normal, shown here as -9.8 $m/s^2$. ![enter image description here](https://i.stack.imgur.com/kyEoX.png) At around 35,000 km, the zero gravity point is hit and begins to reverse (this would be geosynchronous orbit if they weren't attached to the Earth). So, as others have noted, there will be a small amount of apparent gravity at 50,000 km, but it's in the opposite direction of Earth's. It seems then, that one good design for a hotel room is one which can flip its orientation. As the elevator begins it departure from Earth it can begin slowly and then continue to increase its acceleration to make up for lost gravity, or at least taper the effect to ease guests into zero gravity. Flipping the orientation of the hotel room at around 10 km above the ground while beginning to decelerate will provide a zero gravity coast through the natural zero gravity point. Additionally this will help reduce the vertigo felt by people at lower altitudes. Finally settling at around 2% Earth gravity with a fantastic view out of the skylights of the Earth below. [Answer] I did the math for extra credit. 1. is easy: just like in an elevator at its lowest point, your distinguished guests will feel heavier. How much heavier depends on how fast it is accelerating upwards. Specifically, they will feel 1+(a/9.8) times as heavy, where a is acceleration in m/s^2. 2. is also easy: if they aren't accelerating, it is just like standing still. As they get farther away from Earth, they will slowly start feeling lighter. Specifically, they will feel 6000000^2/(6000000+e)^2 times as heavy, where e is the elevation above the surface of the Earth in m. 3. is the complicated part: it depends on how fast they are decelerating. If they are decelerating slowly (less than 1G), they will feel lighter, but still right-side up, like when an elevator is at its highest point. With such high altitudes this will barely be noticeable. At 1G, they will be perfectly weightless. Above 1G, they will feel flipped upside down and be pulled slightly towards the ceiling of the elevator. Specifically, they will feel an acceleration of a-9.8\*g(e), where a is the acceleration and g(e) is the weight from step 2. You need to be careful to limit the accelerations to about 5G in the first step and about 2G in the third. You don't want your esteemed passengers dying on you (too much paperwork). 4. is again simple: we plug in the elevation to the equation from step 2 to find that gravity at 50000000m is about 1.1% of surface gravity, which is not quite negligible. If they are very careful, they should be able to stand on the earthward wall of the station. The slightest push will send them careening out into the same weightless environment they have on space stations. ]
[Question] [ This question already has answers here: [On a planet without seasons, how would people track years?](/questions/2672/on-a-planet-without-seasons-how-would-people-track-years) (7 answers) Closed 8 years ago. Suppose a civilisation on a moonless planet that is in an orbit with so little inclination and so circular that there are no noticeable seasons anywhere on the planet. An alemna would be just a single point. Would this civilisation develop the notion of a year? If not, how would long-term timekeeping work? "750,000 days CE"? [Answer] Yes. There are many cultures on earth that don't really experience a change of seasons, like most of the south pacific islands which only really experience a 5 degree temperature change between their hot and cool seasons ("summer" and "winter"). A world that experienced no change in seasons at all would still find something to measure time by. We base our years off of one complete orbit of the earth around the sun, but cultures like the Maya (who only experienced two seasons: the dry and wet seasons) had several different calendars, including a 260-day calendar, with 20 periods of 13 days used to determine the time of religious and ceremonial events. Each day was numbered from one to thirteen, and then repeated. Every culture measured time differently, but in most cultures the calendar was based off of watching the sky. Most people in the western world have never seen the night sky due to light or air pollution, but back in the day everyone stared at the heavens in wonder and amazement, many mapped the stars and their movements, navigated by them, and looked up into them for understanding. Even a planet with an exceptionally plain orbit would still have a great view of the cosmos and passing asteroids. They perhaps could measure years by the annual appearance of an observable planet or comet that passes near their orbit every few hundred days or so. As long as there were days, and their planet moved through space, there would still be some meathod of tracking time. [Answer] They would know about years, but it likely would not be the most common tracking method.. They'd be able to determine the length of a year fairly early on using astronomical observations of other planets. This could happen fairly early, but would be more of a scientific curiosity than something that would impact daily life. If there are no other planets (unlikely, but possible) then they'd need pretty advanced telescopes and scientific knowledge to figure it out. For common use there would probably be some sort of artificial time construct, measured in days, that was used for bureaucracy and bookkeeping. For example they might track somewhere in the 30-1,000 day range, and use that in place of our "year". [Answer] With no moon, no inclination, and no seasonality, there's no reason to distinguish planetary rotation about the sun (although an elliptical orbit would still produce seasons, albeit almost unnoticeable...) They might make "weeks" based off of digits-either five for one hand, ten for both hands, or twenty for fingers and toes. Finger/toe counting of days is always accessible, and might form their "month," but there are more useful measures. In all likelihood, they would measure time by crop plantings (I was born thirty harvests ago) or some regular weather event. That would easily happen once they reach some agricultural milestones. From there, they begin to abstract: I will pay you in two harvest's time, this house costs two bushels every harvest cycle, etc. So "months" become some predictable harvest cycle, perhaps for grain "Years" might be a longer growing plant's harvest cycle, such as nuts, which is expressed as a multiple of months: "There are ten wheat harvests for each nut harvest." Or it would be the time it takes for a tree to viably produce its first harvest. This would make it an important economic marker: "I will pay you back when I have my orchard grown" is expressed as "I'll pay in one tree." So someone would say: "I am thirty nuts/trees and five wheat old." ]
[Question] [ # Background We all know that our species evolve during and after the last ice age, (or is it sufficient to say that they evolve at the end of ice age?). ## A. Initial Condition Suppose I had another planet with similar ancestor of human-and-apes species, but they evolve on the beginning of ice age (in reverse of human evolution). ## B. Desired End Result The goal is the civilization starts with environments similar to ours (they starts at environment similar to our origins, but slightly warmer and with open fields of grass, similar to our starting environment), but at the moment they reached technological advancement similar to our current technology, instead of experiencing global warming, they'll experience global cooling. ## C. Assumptions The time-frame is around 250.000 years, from the warm era to glacial era, and that's the time the species have to evolve through, and assume that the end result of the species would be human-like. Is the setting plausible? (the setting could allow evolution of human-like species) or should I consider different settings to evolve human-like species that their civilization at our current tech level is in the middle of ice age? --- Note: Due to debate on comments, I would like to rephrase the question. --- # The Question: Assume C, then, 1. Is setting on A plausible to make end result similar to B? 2. Or should I consider different initial condition to reach B? [Answer] As noted, anatomically modern humans evolved before the last ice age. The evolution of behavioral modernity took place about 50,000 years ago, and is still not fully understood. Perhaps the stress of living in an ice age environment promoted the traits that led to behaviourally modern humans. The other possibility is that the ice age would lead to physical evolution, as small bands of proto humans are isolated by ranges of glaciers and live in different environmental ranges. Humans trapped in Europe might eventually evolve in ways similar to the Neanderthal people, who were physically changed in ways that favoured living in a cold climate (large noses to pre warm the air they breathed, shorter bodies and limbs to reduce surface area, etc.). Modern Inuit people have similar adaptations, and if they had been isolated more completely and for longer periods of time, they would probably have developed further adaptations to the cold. Other groups of protohumans might have become adapted to foraging across the great steppes and savannahs of Asia and Africa, since the cold dry global climate would have limited the growth of forests. These humans would be much taller and long limbed, to allow them to cover long distances and run down prey. Once again, we see hints in some groups like the Maassai, who are generally much taller than similar populations. How extreme these adaptations become wold depend a lot on factors like how hard and deep the ice age is, and more important, how long the various populations are isolated from each other. If we wait long enough, then these peoples will become separate species (although this might take tens of thousands of years). One other factor to take into account is you suggest this takes place as the protohumans become technologically proficient. Even with Paleolithic technology, humans were able to adapt and overcome pretty extreme environments, including the arctic, and literally walked around the world, crossing oceans and seas along the way. This sort of adaptability helped humans survive and become the dominant species they are today, but also makes having isolated populations able to evolve in peace very unlikely. Homo floresiensis seems to have evolved into their final form after being isolated in their island archipelago anywhere from 100,000 to 1,000,000 years ago (there is a great deal of uncertainty about when they arrived and indeed what their actual evolutionary background is), but were apparently never in contact with our own Ancestors between their arrival and extinction 12,000 years ago. Other human species like the Neanderthals and Denisovans were indeed in contact with our Ancestors, and most peoples in the modern human family were in limited contact with each other through trade and exploration even in ancient times, so there was enough interbreeding and movement between populations to prevent humanity from evolving into different species. [Answer] # Is Your Setting Viable? Yes. Actually, it looks like (modern) humans evolved before the last glacial period. The wiki article on humans say the first "modern" humans appeared around [200 000 years ago](http://en.wikipedia.org/wiki/Human#Evidence_from_the_fossil_record). The [last glacial period](http://en.wikipedia.org/wiki/Last_glacial_period) was from 110 000 to 12 000 years ago. It looks like humans did evolve before the Ice Age! # Side Note Evolution of the Human species is still happening. It happens when people mate, when people are born, and when people die. It happens when people value certain attributes over others. Evolution has happened and is happening as you read this very paragraph. The time scale, however, is very long. I wouldn't expect a new species of human to pop up tomorrow, or in the next 1000 years. In fact, the most recent estimate of the last human-chimp common ancestor was [5 to 6 million years ago](http://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_common_ancestor). That being said, we can see some differences in humans down the line from us. For instance, the ability to consume milk as an adult seems to be a recent evolutionary thing. In fact, it looks like [the people who can do so are the mutants](https://www.youtube.com/watch?v=ecZbhf96W9k)! ]
[Question] [ Aliens are building a "space highway" through our solar system. They love our Jupiter, so they decided to put gas pump with bar on its orbit. After realizing that we cannot do anything about it and if asked, [they can fake our agreement](https://worldbuilding.stackexchange.com/a/15127/2071), they decided to put such gas pump there without even trying to contact us. The question is: Who on Earth, and how fast, will realise that something alien is happening around Jupiter? Background for space highway: It is set of precalculated dimensional jumps which will always throw you out near something with gravitational pull. Then you, as driver of vehicle, can decide if you are going to use gravity of such object for next jump or if you will make a stop here and refuel. (Or take kids for a snack to McJupiters) Aliens use mixture of FTL communication and normal radio waves. Neither the ships nor gas station try to hide themselves, because they assume "everything is legal" Such gas pump opened for business half an hour ago. Who can realise something is going on? And especially, can average space fan with customer level equipment see something there? Assume size of such pump as big as [Phobos](http://en.wikipedia.org/wiki/Phobos_%28moon%29) This is "local highway" - assume 10 000 vehicles going throught the jump during an Earth day. The gas pump can hold up to 15 space vehicles at a time. Common alien ship is about as big as ISS is. Pump itself has artificial gravity. The pump has "standard" beam, which you approve in your ship computer and all navigation is done for you. Which means, that most sub-FTL communication is done directionally [Answer] Given your parameters, Earth will discover this almost immediately (with a small lag due to the speed of light). The various signals emitted from the space bar, spacecraft, traffic regulation systems and so on will be picked up by sensitive astronomical radio telescopes, the Deep Space Network (which sends message traffic to and from various space probes, including the New Horizons probe nearing Pluto and the Voyager spacecraft exiting the solar system) and some of the military systems as well. In terms of nations who have access to these systems, this is effectively the United States and allied nations, Russia, China, the EU and India, roughly in that order. If alien spacecraft follow regular Newtonian physics in space, then they will probably be using rockets, which can also be visible from great distances, especially in infrared wavelengths. Space telescopes will have little difficulty picking them out once focused on the region. Oddly, any current Earthly spacecraft in the Jupiter system will have less ability to track and record these events, since the ground controllers will need fairly precise information to reprogram the orbits of these craft and point the cameras and other instruments at the Space Bar. Much of the problem is these space probes do not have powerful engines, and would need months of reprogramming and minor orbital adjustments to get into a series of orbital "slingshots" around the various moons to get in position (and even then is most likely to just be able to do a flypast). Now while your question points out that we don't have any ability to do something about this now, I'm pretty sure once the situation becomes clear there will be a great deal of effort put into becoming able to do something; ranging from sending nasty cease and desist orders via radio to training battalions of Space Marines and building rockets that really are capable of delivering them to Jupiter (we have lots of theoretical and early prototype systems, mostly using nuclear fission energy, which can do the job, we just need to start bending metal and doing the advanced R&D to make them more affordable and efficient). The most fearsome weapons in our arsenals: legions of Space Lawyers, will likely arrive once the Marines have secured a landing zone. The Galactic Empire will tremble once they realize just what has been unleashed from Sol III! [Answer] Jupiter is big enough and bright enough to be easily viewable with the naked eye from Earth. Perhaps as a result of this, it is a favorite target for amateur astronomers to [train their backyard telescopes on](https://i.imgur.com/jWxGvRh.gif). In this time lapse, you can see Jupiter's moon Io transiting the planet; in the first few frames is when it is most visible as a bright circle of light against the black behind the planet. Io is approximately 3,600 km in diameter, which makes it a bit more than 100 times larger than your Phobos-sized gas station. Keeping in mind that the image linked above is actually reduced by ~30% (at least according to the specs [quoted by the original backyard astronomer](http://www.reddit.com/r/gifs/comments/31zynw/jupiter_rotation_timelapse_taken_with_my_backyard/cq6it45) who provided this image) and suffers some image quality degradation due to weather and the post-processing methods used, and that it would almost certainly have lights of its own and not just reflect that of the sun, I feel like the answer would be that yes, your gas station would be visible to (some, at least) backyard amateur astronomers (as a tiny point of light orbiting the planet), which means it would certainly be visible to the pros with their "big boy toys". How long would it take to be spotted? Unless it's being towed into orbit fully-constructed, or construction is quick enough that it takes place entirely on the "dark side" of the planet, we'd see it dozens of times over before construction is even completed. That's not even considering the thermal blasts of rocket engines and heat signatures of hot spacecraft buzzing around the thing, or the radio signals in use. ]
[Question] [ We are in an alternate universe where everything is almost exactly the same. The difference is that each person is born with a single plant. Plants cannot be grown or recreated in any way. The only plants in the universe are the ones each person is born with, detached from their body. This plant provides enough oxygen for one person to be distributed among all people within 100 feet. So if there is only one plant and two people, they will slowly run out of oxygen and die. If there is one plant and 10 people, they will quickly run out of oxygen and die. If there are 100 plants in the same spot, and a single human 101 feet away, they will quickly suffocate. The plants are average in that they require medium water, medium sunlight, medium soil, etc. The plants can die before their human counterpart if not taken care of. But if their human dies, the plant will die. Aside from this, there is no link between a specific human and their plant (aside from DNA testing). If a person steals a plant, that stolen plant will provide them oxygen as long as they are within 100 feet of it, but if the theft leads to the suffocation and death of the plants owner, the plant will die. Animals, including humans, have no need for food. But insects will eat plants. What sort of organized crime would this create? How would the government control things differently? [Answer] Organized crime jobs would be plant assassination and plantnapping. Herbicides would be banned by international treaty. I'm wondering if instead of saying oxygen, it's some other kind of field. Like a radiation or something. People need it, but other creatures don't. The people also let off a kind of radiation that has a much greater range, and is unique to each person. The plants need that radiation to function, but only the specific signature of their persons radiation will work. The plants can focus their field, and will focus it on anyone within range, which it determines based on their radiation. So they can see other peoples fields, but it won't sustain them. By focusing their field on more than one person, they have less power per person. Communities would be formed of large, dense populations to get as much field overlap as possible. In these communities the closer to the physical core of the community you are, the more prestige you have. People on the outskirts would have to be careful since the field would be much thinner. People who'd plants were lost/stolen would live as close to the core as possible, though this would be a constant source of community tension, as "those freeloaders aren't pulling their weight". Any plantless person would want to become as valuable as possible socially, since being pushed out to the fringes would be a slow death. Or if they were particularly useless a quick death by excommunication from the community. Major research centers would focus on plant field creation, as well as people field mimicking, but these studies would be slowed since they would mostly be done on the terminally ill. No healthy person would risk experimenting on their own plant. A major crime would be fake plant creation. A person would buy a fake plant if their own died as a way to avoid looking like one of the freeloaders. Several political scandals occurred when it was discovered that candidates had artificially increased the size of their plants to look better. [Answer] I think that plantnapping would be huge, but plant assassination (herbicide), not so much. Power comes from the threat of killing off someone's plant, and if you actually kill it, you've pretty much killed the person, which only brings you power by setting an example. In which case, just killing the person does the job just as well, unless they die in some particularly horrible way via herbicide, but they die the same way as anyone who over-waters theirs. Protection racket would be huge too. "That's a nice bromeliad you've got there, squire. Be a real shame if something happened to it." After a few plants started to disappear, people would pay anything to keep theirs safe. Control the air-conditioning and plumbing in an area to create overnight frost or drought conditions that could affect a large population. Now you can sell your bottled water for whatever price you want. And maybe there's a second level of real protection. The mob owns an industrial plant that's been able to extract oxygen from some other source and they sell pressurized containers to their very best customers. ]
[Question] [ Since earthquakes, typhoons, tsunami and many natural disasters were measured or calculated to release more energy than many H-bombs can produce every seconds, can we one day harness this powerful force of nature and perhaps even control it? [Answer] I am going to expand [this great answer](https://worldbuilding.stackexchange.com/a/13256/2071) a bit: Natural disasters are really strong See [this video](https://www.youtube.com/watch?v=Egdtlnv6Gio) where wind turbine encounters a tornado. Around 2 minutes you can see the tornado tearing up wind turbine. So either you have to design your power plants to be extremly durable which is impractical (better to lose one "cheap" wind turbine than spend money on one expensive) Or, you have to build power plant designed purely for this purpose. Your investment return then would be more than 50 years. Good luck in getting investor. Power has to be consumed immediatelly: We have very limited means of storing electrical power. And harnessing natural disaster would produce a lot of electric surplus, which you have to get rid of and you have to do it now Being from Europe and being involved a bit in energy business, I will give you two little bit specific examples: In Nothern Sea, just above Germany, there is big farm of wind power plants. And even in "normal" days, it can happen, that wind blows too much, that you have to get rid of it at any cost. Thats why energy trading systems offer negative price, meaning that you are willing to pay someone for helping you getting rid of your surplus energy. How much do you have to balance in electric grid? My company (provider of trading system for energy in Germany) was announced by power companies, that power companies expected 10 Gigawatts of imbalance in grid during last solar eclipse, observed above Germany. To give you reference, one standard nulear power plant provides about 1000 MW = 1 Gigawatt of power to the grid. It was expected, that due lower light during the eclipse, the grid will lose imput of 10 nuclear power plants (less solar input during that day). So, expecitng only five times more from any natural disaster will give you 50 gigawatts of surplus - as if you turned on 50 nuclear power plants in single point of time. Good luck in earning money on that. Wrap up: While it could be done, there is no business scenario where you could profit on it [Answer] We do already. For example, I live in Tropical Far North Queensland. We occasionally get significant storms, including cyclones. These storms contain huge volumes of energy and can be very destructive. These storms also bring a huge volume of a very precious resource - water! By damming local rivers we can not only maintain a year long water supply, we can generate hydro-electric energy to power the city. This also applies to areas that often see flooding. In addition to dams I'd look into Geothermal energy - which may have strong links to seismic activity. Furthermore while not 'energy' per se volcanoes and some flooding (e.g. Nile) have been known to generate vast quantities of fertilizer - something that would be very expensive to generate manually. I note that there's an inherent contradiction of terms between 'disaster' and 'control'/'harness' - a 'disaster' by it's very nature cannot be controlled - but a strong, infrequent and energetic environmental system sometimes can. [Answer] In theory, yes. There are systems to generate power from [wind](http://en.wikipedia.org/wiki/Wind_power) or [tidal action](http://en.wikipedia.org/wiki/Tidal_power). You could place rugged versions of these systems into the path of a hurricane or a tsunami. In practice, no. A generator which can capture energy from a tsunami would be ill suited to get power from normal tides. The power plants would stand idle for most of the time, perhaps forever. It would help a little bit if there were better ways to predict the disasters, but would you really want to go in and set up power plants while everybody else is busy to board up houses and evacuate? And would the energy from that disaster be more than the energy to move the power plants into position? ]
[Question] [ Through extreme pollution and large-scale warfare with atomic, biological and chemical weapons Earth has become completely unable to sustain life. The atmosphere is toxic, the water undrinkable and all higher plant- and animal life has died. How would this affect the way it looks from orbit? More specifically, how would this picture look after such a catastrophe: ![enter image description here](https://i.stack.imgur.com/QNREr.jpg) Background: I am currently toying with an idea for a video game which takes place in Earth orbit after Earth became unhabitable. [Answer] Take a look at [the Sahara](https://www.google.com/maps/place/Sahara+Desert/@27.7751573,18.7468461,4030265m/data=!3m1!1e3!4m2!3m1!1s0x13883b64fb267151:0xd6406bdc582d7390) from Google Earth. That's about how things would look if all plant life was destroyed, just it would look like that everywhere. I don't think the atmosphere being toxic would change the look of the atmosphere much. It might make it greyer? That depends a lot on how the atmosphere is toxic. While on that subject, depending on what made the water "undrinkable" will dictate how the water looks. If it's pollution (and a loooooooooot of it) then it could end up looking more like a lake than anything, or if it was more of a subtle thing then the oceans would look similar to how the do now, but I don't think you necessarily need to consider that since ocean water is basically undrinkable already. All of this to say, I think you could color over most of the land masses as they are and have a successfully post-apocalyptic Earth. [Answer] It'll be shiny. ![Snowball](https://i.stack.imgur.com/EMA2d.gif) Let's say (unrealistically) that this was caused by extreme amounts of dust kicked up into the atmosphere by the mother of all nuclear winters. The pic is not fully accurate, in that to cover the landmass of earth with ice you'd have to first have the oceans retreat several hundreds of meters before freezing solid. It is possible that the earth DID freeze over nearly completely in the past, once in the Huronian glaciation during the Paleoproterozoic Era for about 300 Million years, and once in the aptly named Cryogenian period of the Neoproterozoic Era, on and off for about 100 million years. Since we're still here, both must've been a bit of hack job. So here it is this time, done properly. Note that the high albedo will reflect heat, and so perpetuate the iceball status long into the future. [Answer] In your situation, you've only rendered Earth incapable of hosting life. The obvious impact is that all of the green you see in your photo would no longer be there. The vast majority of what you see in the photo, though, is geographical. A planet's geography is generally unaffected by the causes that you listed (war, pollution, etc). This means that you won't see any drastic changes. Continents will still be continents, and mountain ranges will still be mountain ranges. You will be able to see land contours that are normally obscured by plant growth, but I'm not sure any of these would be substantial enough to be seen from space. Given your doomsday constraints, there's only one thing that springs to mind as something that would be visible from that great of a distance. The natural ocean currents flow in a roughly circular pattern, and it's common for things to get caught in the current and collect in a single place (e.g., the [Great Pacific Garbage Patch](https://en.wikipedia.org/wiki/Great_Pacific_garbage_patch)). In a world plagued by pollution, enough debris could collect and coalesce into a loosely-packed artificial island that could be visible from space. It might not have a sharp outline like a natural island, but it would be enough to cause obvious discoloration. [Answer] In the short term there's going to be a lot of grey clouds around. All those nukes (provided at least some of them are ground-burst) are going to kick up a lot of dust. Perhaps there is going to be some deliberate seeding of the atmosphere as well for economic warfare purposes. That will settle down over the next few years or so. Longer term its going to look much the same, save perhaps a few coastline changes (lots of groundburst nukes near the sea will let water into the craters) and the green on land will go away. The hue of the oceans would presumably change when all the photosynthetic life there dies off too. That said, it seems unlikley that a human war using the weapons you describe could actually wipe out all life. Nukes are destructive, and ionizing radiation makes things more difficult for organisms, but it seems unlikley that anyone is nuking the sea bed. Biological weapons necessarily imply life and good luck finding any chemical agent that is A: lethally toxic to every organism B: can be produced in such quantities to kill every organism and C: distributing it everywhere life lives, for example deep sea thermal vents and deep underground. I guess you might be able to kill of all photosynthetic life, and that which depends on it, so for a good few million years Earth would look dead. [Answer] I would say almost the same except the green is gone and replaced with yellow/brown. After that feel free to add your own things. [Answer] Oceans - Higher ocean level & smaller ; the extreme pollution contributed to a runaway greenhouse effect, which through warming, melted your poles. Colors - Brown where there is green. Rivers, etc. would remain the same, as trees - while they do contribute some, to local weather - do not have as large of an effect on major climate systems as land masses do. Clouds - Due to the destabilization and heating of the atmosphere, many more large accumulations of clouds near the equator (including more extreme storms) will be noticeable. Night - Well... it will be very dark during the night, instead of the twinkling of developed city lights. Other than that, I can't imagine it looks much different. Replace the green areas below with brown, and add violent stormcloud accumulations (I don't have photoshop on my laptop, sorry): ![enter image description here](https://i.stack.imgur.com/GkMSs.jpg) ]
[Question] [ Due to my [previous question](https://worldbuilding.stackexchange.com/questions/9862/tame-and-sovereign-dragons) being too broad, I have split the question up, however, most of the notes will be back at the previous question, so feel free to look up the notes there. The question is, what would the other human kingdoms think of the dragon-human kingdom? [Answer] I'm going to go for this one before editing my answer on the previous one, because I was giving this some serious thought today while driving. Feaurie Vladskovitz's answer hits a lot of the basic ideas that I'll be working off of: the dragon-knights are air superiority in a setting where air war is just getting off the ground, so they're going to represent a major threat that any other human kingdom in the setting will have to deal with if they plan to expand (or even just not be conquered). Before I look at how the other kingdoms (both enemy AND ally) might deal with this, I want to digress a moment into how the people of those neighboring kingdoms might feel about dragons as a weapon of war. This informs what their leaders might decide to do about dealing with the threat of dragons being used against them. ## How do people feel about the Dragon Kingdom? Let's look at some of the components going into this. 1. Fire is a really horrible way to die. And your dragons are fire-breathers, who can't be touched by conventional troops, and they can fly, which means they can appear anywhere above the battlefield to rain down hot, fiery death whenever they feel like it. While fire has been used as a weapon of war from time immemorial, its primary uses during the time period we're looking at (a medieval-ish setting) were during siege warfare, in area denial campaigns, and in demonstrations of dominance over conquered territory. This isn't to say burning arrows and the like didn't make an appearance on the battlefield too, but use of fire was much less when there was a risk of burning your own guys to death. (Check out Wikipedia's page on [early thermal weapons](http://en.wikipedia.org/wiki/Early_thermal_weapons) weapons for more on the use of fire in warfare.) So until the advent of dragons in warfare, your average soldier in the military of one of these various kingdoms had a relatively small risk of death by horrific burning, unless he was involved in a siege. And, the risks he took there were known risks that could be mitigated with the proper precautions (the page above has more on that). That all changed when the Dragon Kingdom brought flying flamethrowers into play, and now entire companies are being torched left and right by a single guy on the back of a flying lizard. Can you imagine how horrifying that would be? Even leaving aside the fact dragons themselves are terrifying to look upon, seeing one over the battlefield means you now have an astronomically higher chance of being burned to death, along with all your buddies, and there is nothing you can do about it. This is not to mention the potential use of dragons against farms, towns, or cities. Firebombing was rightly seen as an awful means of war during World War 2, and the dragon-knights would have the potential to implement it in your setting. Do they? Even if they don't, there's a lot of reason to be afraid of the threat of dragons just on the grounds of the use of fire. 2. Flying is cheating. While it's said "everything is fair in love and war," which is largely true for most of human history, war has been tamed by the conventions of warfare. Some kinds of behavior are considered off-limits for a civilized army, and soldiers were expected to more-or-less not engage in these behaviors in order to limit the horrors of war. You may want to consider whether your setting has a moral entity--like an established church, or widely followed religion, or something else entirely--that deals with ideas like just warfare and the proper usages of war. Regardless of how you choose to establish the [law of war](http://en.wikipedia.org/wiki/Law_of_war) in your setting, the introduction of dragons to warfare will seem like cheating at a gut level, because nothing and no one has a really good chance of standing toe-to-toe with a dragon. Consequently, every kingdom but their own might regard the dragon knights as cowards, because how much courage does it take to ride in on an indestructible war-machine and torch a bunch of guys who can't even reach you? Anyone--a brilliant mage, an incredibly lucky archer, a gutsy band of conventionals with a really clever idea--who could take them down would also be seen as a Big Damn Hero by their own people, because in the early stages of the use of dragons in warfare, the damn things seem pretty much invincible! 3. Those aren't even humans! Nor are they domesticated animals, like horses or elephants or anything else mankind have tamed and ridden into war. They're fully sapient members of the Dragon Kingdom's community, and let's face it, that's a little bit weird. Or a lot weird. Especially if the sovereign dragons are largely regarded by most humans as a special sort of talking animal, so the inclusion of the tame dragons into human society looks kind of like letting Mr. Ed vote in local elections. This will undoubtedly lead to nasty rumors about the dragon knights and their kingdom in the surrounding communities, too. Just how nasty those rumors are, and what their content are, well--I'll leave that up to you. One rumor that absolutely will show up, though, is that the Dragon Kingdom is not being ruled by its human ruler(s). Given the power difference between humans and dragons, and the fact "tame" dragons are demonstrably not tame the same way a domesticated animal is, the simplest and most obvious conclusion as to why such a kingdom works is that the dragons are running it, not the humans. Allied kingdoms might know better, in that they'd have more insight into the workings of the Dragon Kingdom--but they'd never be able to shake the niggling idea that the dragons are the ones in charge. Enemy kingdoms would incorporate this idea into their propaganda. If they're especially clever, they might even try to portray the average human citizen of the Dragon Kingdom as laboring under the yoke of the oppressive dragon knights (or might even believe that). --- PHEW. Sorry. That was a lot, and I can think of several more things to cover. I will leave those for now unless you want all the gory detail! ## So what should be done about the Dragon Kingdom? Or, how do we get rid of those damn dragons and bring war back to an equal footing? While these are mostly written with the enemies of the kingdom in mind, its allies will also be keeping these ideas in mind...and maybe working on them on the side, too. Even if the Dragon Kingdom has treated its allies with flawless courtesy in the past, it has an incredible weapon now, and there's no telling when it might decide to take over the rest of the empire for funsies. 1. Air support of our own. Feaurie touched on this one already, so I won't go into too much detail, except to add another possible option: Other kingdoms might try stealing sovereign dragon eggs or young to try and replicate what the Dragon Kingdom has. Or, they might just go to the tame dragons (or even the dragon-knight pairs) directly and try to get them to defect. The Dragon Kingdom might want to keep an eye on dragon immigration, if they even allow it, because that could be the seed of a new dragon air force going to the hands of their enemies. 2. Get rid of the damn things. Dragons might be difficult to take down on the field of battle, but that's not the only way to get rid of them. Poisoning their food supplies, introducing a plague that targets dragons, or simply trying to make the political situation in the Dragon Kingdom suddenly inhospitable are all potential options. Another option would be to target the Dragon Kingdom economically, and make it much harder for them to support dragons. (This is where it will be good to know what and how much dragons eat. Since they're warm-blooded, flying megafauna, I'm assuming "a lot and mostly meat". If the Dragon King doesn't itself have the required infrastructure to produce all that food, they're probably importing some of it, which is an economic weak point to be exploited.) If dragons won't fly in battle without their knights, then target the knights as well. Send assassins after them, disrupt their command structure, and make it impossible for the dragon teams to get onto the field. 3. Develop better anti-air capabilities. If somebody figures out a way to take out a dragon knight with magic (or massed archery, or anything else), you can bet knowledge of that will propagate like wildfire through that kingdom's military. Those kingdoms that do work out anti-air tactics might even share them, since it benefits everyone if dragons are used less in combat. 4. Make friends. Either ally with the Dragon Kingdom, or against them. If all that's keeping them from going wildly expansionistic is the presence of too many potential enemies, it's a good idea for you to make friends with all those potential enemies so you can reinforce each other if you're attacked. And, if the sovereign dragons aren't on a really good standing with the Dragon Kingdom, it might make sense to offer some kind of mutual protection pact that wouldn't hurt their draconic pride. They don't need to suffer themselves to be ridden into battle like beasts of burden--instead, for a regular cattle-tithe and the guarantee they won't get shot at by Xyzland's military, they can focus on taking out the dragon knights whenever they show up to fight... [Answer] Well, I think you basically have the answer from the previous question as well, that the other kingdoms would be wary, but I'll expand on this idea a bit. Basically, think of it as air superiority. This is even crazier than IRL, because a late medieval kingdom/army has no SAMs or AA batteries to deal with such airborne threats. Their only hope would really be in their mages, or their own dragon/griffin/eagle-terror-monster-hawk riders. I doubt even a legion of archers would realistically stand much of chance at stopping a dragonrider - it'd be like an army of guys trying to shoot down a luftwaffe fighter plane with M1 garands. Any neighboring kingdom would be faced with quite a predicament - pay fealty and play by their rules, or find a good anti-air weapon, probably in the form of their own flying attackers. Maybe a kingdom who was allied with the sparrows from your other question? Those sparrows wouldn't pose much of a threat against the dragons, but they might knock the riders off their steeds via hilarious amounts of annoyance. Edit: whoops I forgot to answer about the sovereign dragons. Okay, well, the answer doesn't really change, though people would be more willing to take action, due to it being less an 'act of war', and more a 'hunt'. Remember, back not even 100 years ago, people were more or less at peace with treating even others who looked just like us but with a different skin tone as though they were subhuman - it wouldn't be much of stretch at all for them to just hunt these 'wild' dragons down because they were 'starting to become a bother'. ]
[Question] [ What physical attributes of atmosphere and flora could cause clouds to form on a regular basis below the canopy of a forest between one-fourth and one-half the height of the forest, without impacting the global norm of high-altitude clouds (at thousands of feet)? Assume a non-Earth environment for answers to this question; specifically, an atmosphere as described in [this](https://worldbuilding.stackexchange.com/questions/9755/impact-on-the-sciences-with-helium-instead-of-nitrogen) question. If the ground composition is a factor, I have in mind a dense weave of roots a few dozen feet thick floating atop a deep ocean. The foundational plants in this composition are moss- or algae-like and extend out from a continent as a biological extension to the land area. The roots collect particles and corpses which allows for the growth of the forest. [Answer] There's no good way to get an in-forest cloud like you describe. Clouds form when saturated air cools to the point that it becomes supersaturated and water starts condensing out. Forests provide an insulating blanket and disrupt winds, so the air within them is fairly uniform in temperature and humidity. Your best bet is a [ground fog](https://en.wikipedia.org/wiki/Fog#Types) caused by the underlying ocean: a flow of cold water causes the forest floor to cool, creating a fog that rises from the ground upwards. It won't normally float above the ground, though. ]
[Question] [ Starting condition: I know how small cities form. It is mostly a trade center that requires an access to water and food. But some cities have more than 100 000+ people. Angkor, Cambodia had apparently more than 1 million people. How is it possible for cities to grow so big? Is it just because they have access to more food? * Climate: It is located under a subtropical or tropical climate according to this [classification](http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification). Mostly: Af, Am, Aw/As, Cfa, Cwa and Cwb. * Technology level: European middle age (late middle age to be more precise) * Magic does not play an important role. Result: A big city with several thousand people: 50 000-100 000 + Process: How can I achieve a high population? Since hot and humid climates receive more rain and can produce more food, is it a good assumption to say that large cities are more likely to form here than elsewhere ? [Answer] You'll need an impetus for forming a city rather than a scattered group of farming villages. Trade routes are good for this, particularly in places where there is a natural disruption of the route (ports, portages, etc.). Once you've got the initial incentive, the city will take on a life of its own: people will show up to provide services to the traders, then to the people serving the traders, manufacturing will be drawn by easy access to trade routes and a built-in market, which will in turn draw more trade routes, and so on -- growth will be driven by the presence of the city rather than by the original purpose of the city. You'll need a water supply to keep the city's growth from being constrained at a small size: it's easy to supply a farm off rainwater, but a city needs a reliable, concentrated source such as a river. If your society has strong civil engineering skills and plenty of production surplus, you can import water via aqueduct/canal, but that's a very resource-intensive process. You'll need a food supply, but it doesn't need to be nearby. Ancient Rome, for example, got much of its food from Egyptian farms. You'll need peace, or at least superior military strength. Your city isn't self-sufficient, so you need to keep any combat far away from the city's supply lines. Nothing destroys a city like a famine. [Answer] There are several things that can, and historically have, contribute[d] to the growth of a city. Just off the top of my head: * Defensibility against an enemy * Along a trade route (oasis, river, port) * Religion (sacred location that attracts pilgrims) * Salt (really, any important natural resource, but salt, in particular, was an important item in early civilized trade) ]
[Question] [ This question is about the same postapocalyptic future setting as this one, so you might want to refer to it, if you have any questions… about my question: [What species, if any, would survive this kind of apocalypse, and what would global environment be like?](https://worldbuilding.stackexchange.com/questions/3138/what-species-if-any-would-survive-this-kind-of-apocalypse-and-what-would-glob) Okay so this question is an outgrowth from *Dronz's answers to my initial question. I am assuming they were correct, as they sound correct. On a postapocalyptic future Earth, there has been an extremely destructive war between uber-shielded arcology megacities on the Earth's surface and rebelling space colonies that has left the Earth in a state somewhat (though not exactly) similar to the planet Venus today: partially molten crust, very dark, very hot, very wet and high-pressure atmosphere, choked with ash, dust, radioactivity, water vapor from partially boiled-away oceans, very little sunlight getting through, lots of lightning and high winds. This war was not just a simple nuclear war but also involved lots of other types of super-weapons including antimatter, plasma, nanotech, neutron, microwave, directed-energy, psionic, and spacetime-destroying weapons, to name a few. I am still not sure if any microbes could survive, I know in past mass extinctions some have, and there are types that can survive radiation, or heat, or whatever, but I'm not sure, will any survive this? I'm assuming no, but I'm still open to the possibility of maybe. So anyway, my question is, how long will the Earth stay in this kind of dark, hot, sunless radioactive soup? Is it possible that a lot of the atmosphere would escape into space after all this damage, like occurred on Mars in the distant past? Because my goal is to ultimately have the postapocalyptic world become a planet of lava plains and wasteland deserts, like the planet Arrakis from Dune, or Tatooine from Star Wars, or Athas from Dark Sun, or Southern California from Fallout,* or the Sahara Desert from real life. So, how, in the most realistic and scientifically accurate way possible, do I explain it going from the initial post-war state of radioactive, dark, hot, and wet, to the later mega-desert of still radioactive, but now sun-baked, (still) hot, and (now) dry? [Answer] Josh - burn the world and let out some sulphur and you'll have your effect here. Venus is a good example of run away warming...for the most case the 'global warming' term here is a direct relation towards our CO2 emissions, but sulphur and other gasses are extremely more effective at causing run away warming effects. And yes, it can last for extremely long periods...but some concerns to address * Due to the amount of water on earth, it is quite difficult to get extreme heat changes going. For every gram of water that is increased by 1 degree, you could raise the temperature of the same mass of air by 15 degrees or more. Removing waer (and ice) from the globe as part of your war would be quite useful in getting your intended result here. * Microbes can resist almost anything (atleast you will be able to fiund a few strains that have resistances to anything you can think of). Self DNA repairing Microbes exist that can readily resist radiation for example. * Earth plate tectonics do not readily make for a good setup with 'lava plains'...however a simple background of a large energy device could cause the Yellowstone super volcano to create a north american sized lava plain. To get the desert (and warm) effect, go for 2 large events. 1. release every bit of carbon on the surface into the air as CO2. Burn every forest, cause underground oil reserves to burn, and bring the CO2 levels of this planet back up to where it was early in the earths formation. 2. Add sulphur to the equation. 'Sour' gas is gas with a high sulphur content, having gas and oil reserves burn is one way of doing this. (an unintended effect here is the air pressure on the planet should increase with all this weight of new airborne matter...makes the planet that much more inhospitable. and sulphur stinks, your wasteland would suck to breathe).` The effects of above should be - without plant life, erosion will run away. soil will 'flatten' as it rapidly erodes and shift towards dust and sand. The Sahara is expanding already, this should aplify the expansion. - Between sulphur and high amounts of carbon, you should have the necessary ingredients to initiate extreme warming without the unintended nuclear winter effect. Still struggling to do something with all the earths water for you...without resorting to some form of weapon that removed it all, I'm not quite sure. - An explosion large enough to evaporate and eject water into space - An underground event that causes the majority of earths water to drain into the underground. This would be interesting as the water would still have a heat insulating effect, but not as much at the surface. Adding: Lets give this blowing the water off Earth scenario a go. The process I'm relying on here is Thermolysis...basically the degradation of molecules due to heat. At around 2000 degrees Celcius, water begins separating into it's base components at about a ratio of 3:100. At around 3000 degrees, this becomes closer to 50/50. Ok, the energy I'm talking here to achieve these temperatures is kinda silly, but plutonium and iridium work as catalysts in this reaction, bringing down the 3% line to around 1300 degrees...Pretty theoriectical and estimated, but 2000 degrees with a iridium and platinum catalyst should reduce 50% of water to hydrogen and oxygen to be released out into space (at that temps, I'd assume there is enough momentum to break free of earths gravity?). Ya, that seems a bit far fetched, and the temperatures involved would likely ignite close to anything nearby, maybe even the atmosphere. Let me see what else I can come up with. Heh, is a blackhole generated at the bottom of the ocean that collpases the water into it center doable? [Answer] Microbes could survive inside the shielded areas and underground and then re-colonize the outside even if none survived on the surface. It will take longer for larger lifeforms to emerge but some could well have survived, and again if not they will re-seed from the shielded areas. Radiation and heat will naturally return to normal over time. Wait a few centuries and everything will be fine on that measure. The reason for the humidity is that you evaporated all the oceans, so where did all that water go? You need to somehow get rid of all that water from the environment. The options really are: * Having the oceans reform * Locking the water away underground * Blowing the water into space * Converting the water into something else Most of these are hard to explain though. Possibly the simplest two options would be to say either that the weapon that evaporated the oceans also threw most of the water into space or that oceans did reform afterwards but the continents had reformed with a different layout. A single large continent would have vast desert areas. [Answer] I'm adding this as a second answer, because it's significantly different in scope. While my first answer was targeted towards some possible climatic impacts that would result, this answer will be directed towards the desired effect. The desired effect is [Desertification](http://en.wikipedia.org/wiki/Desertification), i.e. the process by which land is made inhospitable (esp. to plant life, or to agriculture). This does not necessarily require a low rainfall rate to accomplish. Wikipedia identifies the primary cause of desertification to be the removal of plant life, which can be caused by many factors. For example, aside from arid climates, it could be caused by overgrazing, or deforestation. In your case, I believe the cause would be devastating weapons damage, radiation fallout, lack of sunlight due to aerosol particles, etc... The loss of vegetation makes the soil incredibly vulnerable to erosion (especially in light of the potential Hypercanes I mentioned in my previous answer) which causes the "good" (nutrient-rich) soil to be lost, exposing poor soil, or even barren rock. This can even cause a spiral effect, in that it then leads to fewer plants, more erosion, poorer conditions, and thus even fewer plants. The region may still receive a fair amount of rainfall, but without a good soil and vegetation to trap it, it would just run off without really providing any benefit. [Answer] With regards to the existence of life on your new earth I agree with the consensus that no conventional microbes would be capable of surviving. However I think it is possible that new lifeforms could arise. Specifically you describe the use of nanobot weapons during the apocalypse. If any of these bots are capable of surviving the environment, and if they are capable of self-replication, then they could begin an entirely new branch of life. The harsh radiation could cause mutations in the programs of the bots and enable them to evolve in your new wasteland. Potentially you could see a thriving ecosystem of nanobot organisms feeding off the various forms of radiation, chemical energy, or each other. [Answer] With such a warm ocean, and humid atmosphere, extreme weather patterns known as [Hypercanes](http://en.wikipedia.org/wiki/Hypercane) are likely to form. Between the intense amounts of precipitation and winds, there will be a large amount of erosion. Despite the planet's overall warmth, the dust in the atmosphere blocking the sunlight might eventually lead to a cooling effect known as a [Nuclear Winter](http://en.wikipedia.org/wiki/Nuclear_winter). It's debated whether this type of effect would last for days, months, or years. It's actually possible that the combination of warm oceans and humid atmosphere (and thus high precipitation rates), coupled with cooling global temperatures from the dust clouds could lead to a build up of ice in the polar regions, and trigger an Ice Age. ]
[Question] [ I thought of the question "What would human civilization be like if our population was and always had been only thousands or tens of thousands and limited to a small area?" Then I realized this question had to be asked first. There are many non-human species on Earth with a small population in a small area. But is it likely or possible that an intelligent species would remain in this state? Hunter-gatherer societies are usually nomadic. This means they tend to scatter population. For a species to stay put, I guess they need sufficient food supply that even without agriculture, they don't need to move on. (Which raises the question: [will this species ever develop agriculture?](https://worldbuilding.stackexchange.com/questions/2895/could-a-technological-society-develop-without-agriculture)) I guess the core of the question is: Is an intelligent species without a drive to increase its population likely or feasible? [Answer] I find it hard to imagine a species without a drive to increase population. However, If you put said species on (say) an island on an ocean planet, they would find very good reasons not to increase their population. Looking at small south Pacific Island communities, however, I doubt they would reach our level of technology. After all, the Industrial Revolution was accompanied by a significant increase in population. Technological development doesn't really happen without cause, so your mini-civ would need a reason to advance. As you have implied that their population isn't really expanding, perhaps their "island" (i.e. habitable area) is becoming smaller? [Answer] Anything is possible --- * Immortality: If the group of creatures never dies, they will likely not have a drive to increase their population. More population means turbulent young creatures, that are annoying. + Cloning: This is a subset of the above option, but say the creatures have the ability to clone. If the creatures only have a limited ability to store cloning information, then maybe older creatures would not want more young creatures. New creatures would take up cloning space, possibly pushing out older creatures and ending their lives. * Danger: Say this species isn't the only species on the planet. The other species could place a ban on population growth, to prevent this species from becoming powerful. Or maybe your civilization is surrounded by hostile creatures which the group can't fight. * Control: The government could be trying to control the species. More people means more possibility of revolt. * Environment: if the creatures are in a mountainous or island environment, they will have limited space. The species could be intelligent enough to know that growing too numerous would cause problems. So they limit population growth in an effort to keep things peaceful. + A valid point with this approach is that such a speices wouldn't be very technologically advanced. But it's very possible that the speicies is actually a colony, cut off from the mother country. Then the colony would want to sit tight and stop from expanding, so that they don't over populate their space. If the society has specific jobs for each member, it is possible that none of the members of the island know how to make ships or transport vehicles. [Answer] Cheap and effective birth control methods available much earlier in the technological advancement process. Maybe they discover a special fruit, for example. Then, individual decisions add up to a decreased birth rate. (In many countries today on Earth, organic growth of non-immigrants is negative) Without a population pressure, the expansion pressure does not build up enough to create settlers. The limits of the easiest and safest arable lands fine-tunes the incentives for children into exatcly zero average growth, and they remain the civilization's borders for ages. [Answer] It is possible for humans to strive for population non-growth. You'd first have to modify us genetically so that we're not biologically programmed to do so. [Answer] It wouldn't be likely, but we can probably make it happen if we're willing to get a little creative and bend the requirements. My first thought was the [Shakers](http://www.npr.org/sections/thetwo-way/2017/01/03/508100617/one-of-the-last-shakers-dies). These are an almost extinct sect of Quakers who lived in self sufficient communes in the US. The main problem they had, or perk... depending on how you look at it, was that they were all celibate. Which explains why they have almost become extinct. So perhaps an early religion put an emphasis on celibacy, and so many people don't choose to have children, and instead contribute to scientific works. However, this may not work very well because in pre-industrial societies a large number of children are needed simply to offset deaths in childhood. Additionally in a pre-industrial society, given the inefficiency of agriculture, you need a lot of people working to provide for a few specialist workers. Though they will certainly need to devise some sort of agriculture in order to live in a small area with a higher population density, instead of a large area will low population density; which is typical of hunter gatherer nomads. The bigger issue I fear is simply that in order to achieve technological progress at all you do need a large population spread over a large area. This enables them to have the numbers to support a variety of specialisations and experiences necessary for development. If your people aren't lucky to live near strategic resources, then I can't imagine they will get far technologically. In this small area... do they have all the metals and fossil fuels they need? Probably not. Instead perhaps humanity spreads, achieves technological development, and then falls back to a safe place with limited resources after a catastrophic event; meaning they need to limit their numbers. The catastrophe could be anything. Meteor, super volcano, ice age, rising sea levels, nuclear war, global warming, a combination of the aforementioned? Consider the fate of [Easter Island](http://www.npr.org/sections/krulwich/2013/12/09/249728994/what-happened-on-easter-island-a-new-even-scarier-scenario); which was colonised, and then the population got too big, depleted the resources, and shrunk in size. But if resources were limited, how could they advance technologically? If the resources were plentiful, why would they not expand? Perhaps because the rest of the world is some sort of frozen or arid (maybe both?!) hellscape, and their little plot is the only safe oasis left. Perhaps this event happened so long ago that they start to believe that they only ever lived in this small place, tinkering away with physics equations and machines ever after. They would probably still need access to the outside world, if briefly, to extract resources necessary for survival and technology. But if the rest of the world is a grim place they probably would have automated outposts from which they can collect resources, perhaps remotely, to limit exposure. ]
[Question] [ Take any well-known aggressive/dominant/predatory animal - wolves, big cats, bears, dragons, etc. Now say this animal were to have two heads, each equal in all capacities. What would realistically change from it's single-headed brethren? I can imagine two possibilities: 1) Two heads would share (and split) the impulses of one body, reducing/sharing the aggression and impulses between them. For example, if a single-headed lion needs to eat a whole gazelle to feel satisfied, each head of a two-headed lion may think it only needs to eat half a gazelle. Two lion heads, each perceiving a fraction of the body's hunger, may be less driven to hunt. 2) Each head would get the full-blown drive of the body - in essence, a two-headed lion wants to hunt and eat two gazelles. This would surely make the multi-headed variety grow larger and become more dangerous, as it consumes and hunts twice as much with (arguably) twice as much drive. Do either of these options seem more realistic over the other? Are there additional factors I'm not considering? [Answer] In many ways the animal would function the same as it does with a single head, it would eat until full. It would hunt when hungry, sometimes the heads would fight each other but mostly they would get along. The "I'm full" hormones the stomach sends would reach both heads just fine for example. The main problem though is that the animal is just less well adapted as a predator than a single-headed version of itself. It's less well balanced, it's not as aerodynamic, it finds it harder to pass through small spaces or dodge obstacles. Reflexes are slowed by the two heads having to co-ordinate their actions. In fact about the only advantage it does have is that one head can keep watch while the other eats or sleeps. For apex predators though that is rarely a requirement and unless for some obscure way it evolved that way animals don't have the intelligence to co-ordinate that sort of activity. Not to mention the fact that the body would still want to all sleep at once even though the heads disagreed. [Answer] I think your first option would be closer to the truth. Both heads would receive the same 'hunger' impulses from the stomach. So it would go hunt, but with two heads eating it's prey, it would fill up it's stomach twice as fast. Both heads would also get the same 'I'm full' impulse from the stomach about the same time. The biggest difference would be in how fast it could consume the same amount of prey. ]
[Question] [ If humans selectively breed Azhdarchidaes, would humans be able to make them absolutely massive? Could humans breed them to be able to carry a pilot and fly them? [![enter image description here](https://i.stack.imgur.com/ST5gw.jpg)](https://i.stack.imgur.com/ST5gw.jpg) [Answer] No Quetzalcoatlus is already close to several theoretical limits for flying animals. <https://link.springer.com/article/10.1007/s13752-013-0118-y> <https://www.palass.org/careers/phd-opportunity/phd-pterosaur-flight-biomechanics-how-did-largest-airborne-animals-get-ground> <https://www.researchgate.net/publication/246692156_Limitations_on_animal_flight_performance> ]
[Question] [ I would like for my world to have two moons. I think it would look simply stunning at night. Also, I came up with a pretty cool idea for a "God Eye" cult. When the smaller moon would have crossed the orbit of the larger one, a lunar eclipse would occur, which would look like an eye. (A smaller black dot against a white moon. ) According to one theory, our planet once had 2 moons. One was around 1/4 of the size of our current moon. They existed together for a few million years before colliding, and our moon was created from the debris. My planet is supposed to be pretty Earthlike, with different landmasses but similar size and axial tilt. Could I pull this off? I'm not really a physics guy and English is not my first language, so I will really appreciate, in-depth answers. [Answer] If the orbits are well separated and/or resonant, there's no reason a second, smaller moon couldn't orbit Earth stably. This is aided by the fact that our Moon is much further from Earth than is the case with other "real" moons in the Solar System -- like those of Jupiter and Saturn and the ice giants, the ones that are big enough not to be captured asteroids or comets are in much closer orbits, despite their primaries being much larger and more massive than Earth. The complicating factor here might be Luna's chaotic orbit, which is due in part to the fact it's almost as much a co-orbital planet as it is a moon, along with the Earth's axial tilt and the Sun's gravity effects fighting over whether the Moon should orbit over the equator or in the ecliptic plane (with the result that it's neither). If your world has low/no axial tilt, then the orbits of the moons would tend to stay equatorial and a 4:1 resonance (for instance) would tend to keep them in place, as it does for Jupiter's Galilean moons. Your small moon would then eclipse the larger, more distant one (assuming it's in the same orbit as Luna) roughly every 8 days -- and if it's visually smaller, you'd see one moon surrounded by the other. ]
[Question] [ DISCLAIMER: I am an (intensely interested) layman, not a scientist. Please take my summation of the following concepts accordingly. I'm currently trying to worldbuild a plausible alien species down to the level of basic biochemistry, and at the moment I'm looking for alternative systems to RNA/DNA that can pass on genetic information. I'm not talking about stuff that essentially just uses the central principle and structure of DNA with some of the specifics changed, like [XNAs](https://en.wikipedia.org/wiki/Xeno_nucleic_acid) which just use a different sugar backbone, or [Hachimoji DNA](https://en.wikipedia.org/wiki/Hachimoji_DNA) which just adds on extra base pairs, I'm talking about plausible hypothesised systems that are radically different to what we use now. One of the more out-there proposals I've come across is Graham Cairns-Smith's [clay hypothesis](https://www.chemeurope.com/en/encyclopedia/Graham_Cairns-Smith.html), which posits that clay crystals were the first genetic material. The idea here is that crystal growth is a form of self-replication that "reproduces" its arrangement, and can even transmit defects. The pattern is then "passed along" when the crystal breaks (scission) and continues to grow independently from the original crystal. Eventually, a "genetic takeover" of sorts happens, where clay crystals that trap certain forms of molecules to their surface improve their replication and catalyse the formation of increasingly complex proto-organic molecules that eventually take over the original genetic substrate as the new genetic material. Schulman, Yurke and Winfree in their paper ["Robust self-replication of combinatorial information via crystal growth and scission"](https://www.pnas.org/doi/10.1073/pnas.1117813109) use the same principles to create a set of DNA "tiles" that replicate its sequence of tiles through crystal growth. Each tile has "sticky ends" that hybridise with each other, and under appropriate growth conditions, complementary sticky ends hybridise, while non-complementary sticky ends are unlikely to interact. The interaction of these sticky ends allows for accurate sequence replication during growth, and once crystal growth has propagated the sequence, these additional layers are then "cleaved" off through mechanical scission. Another early Earth candidate for genetic material, advanced by C. P. J. Maury, is amyloid structures - a ["β-sheet peptide-based prion-like amyloid system"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5897472/). It's posited that under the harsh prebiotic conditions of early Earth, beta-sheets would have been a plausible candidate for genetic material, since it is resistant to both UV and ionising radiation, and to high temperatures. Amyloids, in similar fashion to prions, can transfer conformational information, the changed three-dimensional architecture, to daughter molecules. (Would this essentially make early evolution Lamarckian?) In a [paper](https://www.proquest.com/openview/2406e3cc95bf4a1ee9a9467af4d587ce/1?pq-origsite=gscholar&cbl=136199), Maury, Liljeström and Zhao demonstrate the plausibility of the amyloid world hypothesis by creating a peptide called "EGGSVVAAD" that spontaneously forms amyloid fibrils. However, there are only a handful of novel ideas surrounding this I am aware of, and I'm not entirely sure if and how any of these systems of replication could achieve a significant level of biological complexity (save for something like a "genetic takeover" that effectively replaces the original system), because for complexity the information needs to not only self-replicate but also be interpreted as instructions for building things. I'm not aware of any paper for now that confidently advances a novel system explaining how an alternative replicator mechanism can be translated in this manner. The way DNA/RNA is translated is a fairly convoluted multi-step process and building such a system for any hypothetical replicator is probably very difficult. Most of the papers I come across are at the very basic level of "how can a sequence of information robustly self-reproduce and transmit its characteristics in a way that selection can operate on it", that additional layer of complexity surrounding translation is unfortunately not touched on (either because it's not part of their intention to create a general purpose replicator, or because they can't propose one). [Answer] “I'm currently trying to worldbuild a plausible alien species down to the level of basic biochemistry” The scope for novel molecules in chemistry is vast beyond imagination as there are more possible chemical compounds than there are atoms in the universe. From this perspective humanity knows virtually nothing of the possibilities of what might be achieved chemically. Even restricting the search to “just” existing terrestrial biochemistry doesn’t help much. Have a look at this link and scroll around using the arrow keys on the bottom right <http://biochemical-pathways.com/#/map/1> This is just a fraction of the real chemistry of life on Earth. The task that you have set yourself is daunting. Are there any alternative systems that would allow for the development of emergent complexity? As far as I am aware nobody knows for sure, but given the above I strongly suspect that there are many that could arise given a different arrangement of starting materials and conditions. You might find this book by Nick Lane to be of interest: <https://en.wikipedia.org/wiki/The_Vital_Question> Alkaline thermal vents produce exactly the conditions required for the origin of life. A high flux of carbon and energy directed over inorganic catalysts. The vent fluids also contain methane, ammonia hydrogen and sulphide and these vents don’t have a central vent they are more like sponges that can concentrate organic materials via thermophoresis. (Note the alkaline vents are distinct from the so called “black smokers”). He also has an interesting take on the emergence of eukaryotic cells suggesting that their emergence was a highly unlikely fluke event. If true we might expect any other life to be limited to single celled organisms on energy grounds. ]
[Question] [ This question already has answers here: [Does Earth Have What It Takes to Have Rings?](/questions/27887/does-earth-have-what-it-takes-to-have-rings) (4 answers) Closed 11 months ago. So, quite simply, is it possible for a planet in the habitable zone of its sun to possess rings like a gas giant? Naturally they would not be made of ice, but if this planet had a small moon which broke up, could the debris form a long-lasting ring around the equator? [Answer] Rings are not exactly long lasting, not in terms of cosmological scales, at least. According to the [most accredited theory](https://en.wikipedia.org/wiki/Theia_(planet)), the Moon was formed when a giant impact between the proto Earth and Theia projected a large amount of debris around the Earth itself, which then collapsed into what is today the Moon. Those debris, while they were not yet collapsed, formed a ring. True, the impact didsn't exactly made the Earth a habitable planet in the immediate aftermath. However, if the ring should have formed by an ice body fracturing under tidal forces during a close passage, there would be no obstacle to the presence of a ring and the presence of life on the surface. [Answer] It is theoretically possible for a planet in the habitable zone of its star to have rings, although it is unlikely. Gas giants like Saturn and Jupiter, which are much larger than terrestrial planets, have rings due to the presence of numerous small moons and the abundance of material in their atmospheres. Terrestrial planets, on the other hand, are generally much smaller and less massive, so it would be much more difficult for them to retain rings. In theory, if a planet in the habitable zone had a small moon that broke up, the debris could form a ring around the planet's equator. However, the ring would likely not be long-lasting, as the debris would eventually either re-coalesce into a moon or fall into the planet's atmosphere and burn up. The likelihood of a ring being formed and persistently existing for a significant period of time would depend on various factors, such as the size and mass of the moon, the size and mass of the planet, and the speed and trajectory of the debris after the moon broke up. ]
[Question] [ Background: Like many others here, I'm building a world for a story I'm writing. I'd like it to be taken for granted that a moon roughly the size of Earth that is habitable for humans could exist in a stable orbit around a gas giant, somewhat like Pandora from the Avatar franchise. From what I've read, this is a little improbable but plausible. I've also done a "simulation" using Universe Sandbox, and the orbits and temperatures seem to be reasonable for small time scales at least. Preferably, the moon would not be tidally locked, but more research makes me think that may not be possible over long time scales. Most of what I've researched also suggests extreme temperature variation and volcanic activity on the moon, but I think my civilization would be able to cope with those factors. However, I've read that the magnetosphere of Jupiter is around 20,000 times stronger Earth's, and that it reaches out far into space beyond the orbit of its moons. I read that this could cause some beneficial effects for my moon such as protecting it from solar wind, but could also present problems with radiation belts. I believe the radiation problem could be solved by the moon having a thick atmosphere (or by giving the moon itself a magnetic field!), but I don't know much about how the actual magnetic field would work, or the extent to which it would affect the moon. The humans would not be as technologically advanced as a typical sci-fi setting. They would range from 15th to 19th century levels of technology, and have well-organized societies and culture. They would not have evolved on the moon, but would have lived there for thousands of years at least. Also, this is my first post on this site! Please let me know if I should change anything. [This](https://worldbuilding.stackexchange.com/questions/210084/how-can-a-gas-giants-magnetosphere-affect-a-supposedly-habitable-tidally-locked) post is similar to what I am asking, but doesn't go into specific effects on humans and technology so I don't think it's redundant. Question: What effects (beneficial or harmful) could such a strong magnetosphere have on the moon and the humans living on it? Would it affect things like weather, magnetic devices like compasses, electricity, or even new types of tools the humans could create? For example, my first thought was that hanging a string with a magnetic stone on it would act like a compass and somehow be noticeably affected by the gas giant's astronomical position relative to the surface of the moon. But as mentioned before, I don't know the first thing about magnets so I could be completely wrong. The last part about tools is a little open-ended so any ideas are appreciated! However, I would like all answers to be science-based please. It doesn't need to be perfect hard science since I'm hand-waving some of the more difficult things about my world away personally, but what I'm really looking for is a good explanation of what effects the magnetosphere causes. Edit for clarity: I'm asking specifically about the magnetic fields and how they could affect things on the surface, not the consequential radiation. [Answer] The possible habitability of exomoons orbiting exoplanets in other star systems is a topic in astrobiology, the theoretical study of the possibility of life on other worlds. If exomoons can be habitable, that would make a significant increase in the number of habitable worlds in the galaxy, and extend the mass range of stars capable of having habitable worlds. Most stars in the galaxy are so dim that a planet orbiting in their habitable zone will be tidally locked to the star. One side will always face the star in eternal light and another side will always face away from the star in eternal darkness. Would such a planet be lifeless because of the heat on the sunward side and the cold on the dark side, where the atmosphere might freeze solid? Or would he air and water needed for a planet to be habitable transfer heat from the day side to the dark side, keeping the temperatures livable? That is a question. But if a planet has a large enough companion world, the tidal interactions with the companion world should tidally lock the planet to the companion world, preventing the planet from becoming tidally locked to the star, and thus the planet would have alternating day and night. In Habitable Planets for Man, 1964, Stephen H. Dole discussed the requirements for a planet to be habitable for humans, and thus for the natives of your world. <https://www.rand.org/content/dam/rand/pubs/reports/2005/R414.pdf> On pages 67 to 72 Dole discussed the necessary properties and mass range for stars capable of having human habitable planets. And on pages 72 to 75 Dole discussed how a planet in the habitable zone of a low mass star could become tidally locked to a massive companion world, preventing it from becoming tidally locked to its star and enabling it to have a succession of day and night. And in the last couple of decades there has been a lot of discussion of the possible habitability of giant exomoons orbiting giant planet in the habitable zones of their stars. So you should read a few scientific articles discussing the possibility of life on hypothetical giant exomoons of exoplanets. For example, "Exomoon habitability constrained by illumination and Tidal heating" Rene Heller and Roy Barnes, Astrobiology, 2013. The introduction explains the reasons for considering the habitability of exomoons, for example. Heller and Barnes introduced the concept of the habitable edge around a giant planet in that article. If a moon orbits its planet closer than the habitable edge, tidal heating of the moon will be excessive and the moon will lose its water from a runaway greenhouse effect. You asked about the magnetosphere of your giant planet and its effects on the habitability of your giant moon. Many planetary mass objects, or planemos, generate weaker or stronger magnetic fields by processes not yet completely understood, I think. And if a planemo has a magnetic field, and orbits close to a star, the magnetic field will interact with the charged particles in the solar wind to create a planetary magnetosphere. > > Earth's magnetic field, predominantly dipolar at its surface, is distorted further out by the solar wind. This is a stream of charged particles leaving the Sun's corona and accelerating to a speed of 200 to 1000 kilometres per second. They carry with them a magnetic field, the interplanetary magnetic field (IMF).[25] > > > > > The solar wind exerts a pressure, and if it could reach Earth's atmosphere it would erode it. However, it is kept away by the pressure of the Earth's magnetic field. The magnetopause, the area where the pressures balance, is the boundary of the magnetosphere. Despite its name, the magnetosphere is asymmetric, with the sunward side being about 10 Earth radii out but the other side stretching out in a magnetotail that extends beyond 200 Earth radii.[26] Sunward of the magnetopause is the bow shock, the area where the solar wind slows abruptly.[25] > > > Inside the magnetosphere is the plasmasphere, a donut-shaped region containing low-energy charged particles, or plasma. This region begins at a height of 60 km, extends up to 3 or 4 Earth radii, and includes the ionosphere. This region rotates with the Earth.[26] There are also two concentric tire-shaped regions, called the Van Allen radiation belts, with high-energy ions (energies from 0.1 to 10 MeV). The inner belt is 1–2 Earth radii out while the outer belt is at 4–7 Earth radii. The plasmasphere and Van Allen belts have partial overlap, with the extent of overlap varying greatly with solar activity.[27] > > > <https://en.wikipedia.org/wiki/Earth%27s_magnetic_field#Magnetosphere> Thus the Earth's magnetosphere is many larger than the radiation belts which contain dangerous radiation. So a manned space station orbiting Earth, for example, can orbit relatively safely in most parts of the magnetosphere, as long as it orbits outside of the radiation belts. And the magnetosphere of a giant planet like Jupiter should be similar in many ways to that of Earth. > > The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973. > > > The action of the magnetosphere traps and accelerates particles, producing intense belts of radiation similar to Earth's Van Allen belts, but thousands of times stronger. The interaction of energetic particles with the surfaces of Jupiter's largest moons markedly affects their chemical and physical properties. Those same particles also affect and are affected by the motions of the particles within Jupiter's tenuous planetary ring system. Radiation belts present a significant hazard for spacecraft and potentially to human space travelers > > > <https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter> The four Galilean moons of Jupiter orbit with semi-major axes of 421,800 kilometers (Io), 671,100 kilometers (Europa), 1,070,400 kilometers (Ganymede), and 1,882,700 kilometers (Callisto). Io and Europa are within a radiation belt, and a human on the surface of Europa would receive a lethal dose of radiation in a a few hours. > > The radiation level at the surface of Ganymede is considerably lower than at Europa, being 50–80 mSv (5–8 rem) per day, an amount that would cause severe illness or death in human beings exposed for two months.[94] > > > <https://en.wikipedia.org/wiki/Ganymede_(moon)#Physical_characteristics> > > Callisto is a lot lower. It's out of the radiation belts, but still inside Jupiter's colossal magnetosphere, protected from galactic cosmic rays (another radiation source). A human on the surface of Callisto would receive even less radiation then in deep space and even less than on our Moon. > > > <https://www.reddit.com/r/askscience/comments/316qay/how_dangerous_is_jupiters_radiation_at_different/> > > Its distance from Jupiter also means that the charged-particle flux from Jupiter's magnetosphere at its surface is relatively low—about 300 times lower than, for example, that at Europa. Hence, unlike the other Galilean moons, charged-particle irradiation has had a relatively minor effect on Callisto's surface.[11] The radiation level at Callisto's surface is equivalent to a dose of about 0.01 rem (0.1 mSv) per day, which is over ten times higher than Earth's average background radiation.[46][47] > > > <https://en.wikipedia.org/wiki/Callisto_(moon)> So it is good for your moon to be within the magnetosphere of your planet, but bad to be within the radiation belts which are within the magnetosphere of your planet. I don't know how to calculate what the best orbit would be for a moon orbiting a planet of a specific mass at a specific distance, the planet itself orbiting a specific star with a specific mass (and thus specific solar wind strength) at a specific distance. Unless you can find a way to calculate that, you will just have to guess at a size and mass of your planet and its moon and the orbit of the moon that puts the moon inside the magnetosphere and outside the radiation belts. Rene Heller and Jorge I. Zuluaga in "Magnetic Shielding of Exomoons beyond the circumplanetary habitable Edge" (2019) discusss the shielding of hypothetical Mars sized exomoons by the magnetospheres of their giant planets. <https://arxiv.org/pdf/1309.0811.pdf> They claim that Mars sized exomoons would probably not have their own magnetospheres to protect them from stellar wind and cosmic radiation, and so would be dependent on the magnetosphere's of their planets for protection. So they discuss the formation and evolution of the magnetospheres of giant planets, and at what distances they might extend to cover orbiting moons before the stellar wind eliminates the atmospheres of the moons. Of course a Mars size exomoon might be large enough to be habitable for some types of liquid water using life, but it would probably be too small to be habitable for humans anyway. There are many lifeforms on Earth which flourish where unprotected humans would swiftly die, so obviously moons or planets can be habitable for some liquid water using lifeforms without being habitable for humans. so you would want to use a more rare Earth mass exomoon as the setting, as described in the question. Such a large moon could probably generate its own magnetic field and its own magnetosphere and thus could orbit outside of the magnetic field of the planet. But since science has not yet fully explained the strength or weakness of the magnetic fields of all he moons and planets in our solar system, we can't be certain, so you might want to put the planet inside the magnetosphere of the giant planet anyway. A planet can only hold moons in stable orbits if they orbit at or less than about 0.333 to 0.50 of the radius of the planet's Hill sphere. The radius of a planet's Hill sphere is calculated from the mass of the planet, the mass of the star, the semi-major axis of the planet's orbit, and the eccentricity of the planet's orbit. <https://en.wikipedia.org/wiki/Hill_sphere> It is possible that some giant planets will have magnetospheres extending as far as 0.333 to 0.5 of their Hill radius and so all permanent moons would have to orbit within the magnetosphere anyway. Since you moon will probably be tidally locked to its planet, it will have one day night cycle during one orbit of the planet. Thus the closer the moon orbits the planet, the shorter its diurnal cycle will be, and the father it orbits from the planet, the longer the diurnal cycle will be, possibly becoming too hot for life in the day and too cold for life during the night. Anyway, these are my thoughts on the subject. [Answer] Your people need protection! That Jupiter radiation is charged particles. They are tough on things. If they go through your eyeball you see flashing lights. Your people need protection. You could do that Earth style with a magnetic field. A benefit of this is that the particulate radiation slamming into the field would cause some sweet auroras! [![aurora](https://i.stack.imgur.com/zDLiP.png)](https://i.stack.imgur.com/zDLiP.png)\ <https://en.wikipedia.org/wiki/Aurora> > > Auroras are the result of disturbances in the magnetosphere caused by > the solar wind. Major disturbances result from enhancements in the > speed of the solar wind from coronal holes and coronal mass ejections. > These disturbances alter the trajectories of charged particles in the > magnetospheric plasma. > > > Another way you could protect them is give the giant a ring. That works for Saturn. <https://en.wikipedia.org/wiki/Magnetosphere_of_Saturn> > > Saturn's radiation belts Saturn has relatively weak radiation belts, > because energetic particles are absorbed by the moons and particulate > material orbiting the planet.[.. > > > The innermost region of the magnetosphere near the rings is generally > devoid of energetic ions and electrons because they are absorbed by > ring particles > > > Maybe less auroras but the ring could look pretty cool in the sky. -- I think if you have a moon, you will not get tidally locked to your star / parent planet. Maybe a moon could block some radiation by virtue of its own magnetic field. Could a ring around your inhabited world prevent tidal locking like a moon? Could it soak up the charged particles like Saturns rings? ]
[Question] [ ## Blurb What would a ship with a 100 thousand tonne budged that needs to carry cryo-frozen cargo through 20 lightyears of interstellar space at 0.35C coasting velocity, using laser sails at both ends of the voyage, and putting the safety of the cargo above all else. (See "The Problem... Mk-2?" and "Edits") ## The Setting Side-note, I absolutely love this format. Let's say we use that big tractor ship I ought to make another post to check the math on, which can reach 0.7C. Let's call her the *ISV Not So* Venture Star. It's like it, but bigger. A lot bigger. And it carries a small team of colonists and the required materials for colonizing a star system. The 3D printers at their disposal cant make advanced microprocessors, sensors and other advanced machines, but they can print out the bulk of drones, vehicles and such, bringing the important bits from earth. They will stay in cryostasis for most of the voyage, a form of hibernation that slows metabolism to almost stopping, letting them sleep for decades. With the equipment they have, they build a dyson swarm- Well no. That isnt the right word. Dyson swarm evokes the idea of an advanced civilisation. This isnt even close. It's just a bunch of orbital solar panels and mirrors in a nice, even ring around the sun-like star. But theres a problem, they have a machine powered by suspension of disbelief, called a phase-gate. It works by some magical phenomena we have yet to discover and creates a region of spacetime that are linked. Go into one kilometer-wide door, come out of the other. For some reason, it runs on a flow of virtual particles which are directed by mass-energy, which in turn is held in suspension by some kind of magnet-like system, never discussed in the book. The point is that it needs a lot of cooling, and energy. Like a lot of energy. And it's extremely advanced, thus needing to be imported. But it's huge. ## The Problem How do we move this honking huge machine from earth, while being strangled to a wall by the tyranny of the rocket equation? We alleviated this with massive petawatt-power lasers to accelerate our ship, but we need to decelerate on our own when we arrive, which is a hairs-width from impossible, even when we use the most absurdly, stupidly dangerous fuel we possibly can. Anti-matter. ## The Solution Simple! We don't move them at the same time! Who said we need to ship the colonists and all the frozen cryo-samples of earth-life on the same ship? We can ship it on a bigger, much slower cargo ship, lets say at half-speed. Sure, it will be hammered by radiation and we can't ship people because they couldn't survive cryostasis and cosmic rays for that long, but a bunch of frozen seeds and eggs definitely won't care as much. But then we'ed still need engines to slow down... right? WRONG! If we got the ship up to moving at 0.35C with a massive laser-sail array powered by solar collectors around the sun, then we can do the same thing around the colony star, which we can call Ilus. The new flight plan would be as follows. Launch the slow ship, Aurea, using the laser batteries. Then collect antimatter for the next 2 decades. Then launch the fast ship, Theia, on route to Ilus. After 3 decades transit, the Theia arrives at Ilus and starts a (not really) dyson swarm. After a decade, the Aurea opens its sail and prepares to end its 6 decade journey. The small crew awaken in Trenton city and launch center, just to discover that they have 2 weeks left to fix a cascade of failures that have gotten progressively worse over their 9 years in cryosleep, waiting for the autonomous systems to finish building the dyson swarm, and with the one controller that was supposed to stand guard for their 6 month shift having vanished without a trace. And they have to repair and engage the laser, lest the Aurea and their ticket back to earth dash past at over 100,000 kilometers per second. Fantastic drama setting, like The Martian but theres an entire crew and a planet to work with, and at stake. ## The Problem... Mk-2? This is fantastic and all, but what would the Aurea even look like? Since it would be moving slower, it would need a much less extreme shield, possibly a hybrid ablative-whipple type, directly mounted to the bow of the ship. It would need cryogenic systems, which would make heat, and thus need large radiators. It would also need fusion reactors to power it, and thus fuel for it. It would need a small main hall-effect engine to keep at cruise speed, and some maneuvering engines and an onboard AI, and thus computers. The phase-gate ring would be disassembled into 6 sections and folded into the core of the ship, with a rigid truss from the shield to the reactor at the rear, fuel tanks behind the reactor and cargo modules ahead of the phase-gate. Along the entire length would be radiator panels which could double as Whipple shields around the phase-gate. I imagine something a little like the [Aion](https://www.artstation.com/artwork/GLl3B) or the [Kronos](https://www.deviantart.com/macrebisz/art/Kronos-1-in-Low-Earth-Orbit-582647310). What would be the best configuration for such a ship? (and is there any other considerations I need to make?) ## Credits This isn't strictly part of the question, but I want to say it. Thank you Sphennings, and you're getting me to drop the need for a scientific explanation, which would wreck any illusion of suspension-of-disbelief. To Starfish and Nosajimiki for their over-the-top math, and to BMF and many, many others for working out the technical details. Thank you everyone! Im writing and working on my book every day, and this is special because I am only just starting the book, and I know what the book is about, but I'm not locked in yet, so I can change and add the things that you guys worked out. >(^-^)< ## Edits and Tech Specs For future reference, the distance it will cross is around 20 light-years, give or take a few. The phase-gate unit is a 0.7km-wide ring, split into 6 even sections and totaling in at 3k tonnes. It also has a power ballast that slowly accumulates energy and releases it quickly, weighing around 2k tonnes in shipping containers of machinery. The weight budget of the starship is around 70k to 100k tonnes. The safety of the gate is the most important part of the mission, and the cryo-cargo is just a side-note. The ship needs to have some mechanism to expose a reflector shield at the front and rear of the ship during the laser-sail driven phases, and hide them away to to minimize risk of being damaged. The ship should be resilient as possible and carry as much and the most efficient shielding it can. The phase-gate will need a few months to upwards of a year be set up and the power system will also need time to charge and fire, after which more materials can be shipped in from earth, in the case that the cryo-cargo is damaged or lost. A loss nonetheless but not a big one, compared to loosing the phase-gate. The ship should be designed to be as safe and redundant as possible*. Thus, maneuvering engines and a backup main engine would be best, as the ship might need to do slingshots around planets and the star to loose speed. There is almost 7 decades of work and preparation all hinging on this one ship, so it should be built like it. [Answer] TL;DR: a couple of flat plate-like shields cut to match the ship's cross-sectional silhouette at the front (a thin shiny one foremost, a thicker grey or black one some distance behind it), engines behind that, and then the cargo, fuel, power plants, reaction mass, control systems etc. a looooong way behind that strung out on a bunch of cables. Not rigid. Doesn't do a flipover. --- Starship design is going to be driven by two main things: minimizing mass * not getting wasted by debris and radiation en route * not getting incinerated by your own propulsion system Your spacecraft has no significant engines (because boost and brake are done by lightsail) so you don't need to worry about huge tanks of fuel and reaction mass and nuclear rocket shielding and heat sinks and so on, so that's a good start. Lets consider your laundry list of stuff though: > > It would need cryogenic systems, which would make heat, and thus need large radiators. > > > Cryogenic systems for what? You don't have any meatbags to keep cool, and you don't have huge tanks of hydrogen (or worse, antihydrogen) to keep frosty. > > It would also need fusion reactors to power it, and thus fuel for it. > > > It is obviously fairly hard to work out how much power you need, and hence how much fuel you need for your reactors, but as you're not running life support, artificial gravity, enormous rockets or mag brakes it suggests you don't actually need very much. > > It would need a small main hall-effect engine to keep at cruise speed, and some maneuvering engines > > > The drag will be negligible in interstellar space. You don't need to maintain cruising speed because there's nothing to reduce it, though you almost certainly want to be able to do a bit of mid-source correction. You've got decades to line yourself up though, so the engines can be teeny tiny. You do still need to run engines during the flight though, because: > > a rigid truss from the shield to the reactor at the rear, fuel tanks behind the reactor and cargo modules ahead of the phase-gate. > > > I don't think the truss needs to be rigid. A flexible spacecraft has much less strict engineering constraints regarding stiffness and compressive loading (of which there will be none, unless something went very wrong), and probably weighs less into the bargain. The [Project Valkyrie](https://en.wikipedia.org/wiki/Project_Valkyrie) design was like this, and Charles Pellegrino (one of the people who worked on that design) was also a technical advisor to Avatar and contributed some of the ideas behind the Venture Star. Some very small engines at the front of the vessel can run at very low thrusts (even a tenth of a milligee might be excessive) during the flight to maintain tension on the rigging whilst the laser sail is not in action. Nuclear electric is fine for these... Hall effect, etc. Their exhaust is benign enough that you don't need lots of shielding, so long as the engines are angled outwards a teeny bit so as not to hose down the payload. > > Along the entire length would be radiator panels which could double as Whipple shields around the phase-gate. > > > It isn't clear that you need that much heat rejection, because your spacecraft isn't really doing a whole lot... running some small ion drives of some kind, and twiddling its virtual thumbs. --- So much for nit-picking. Lets move on to my next two constraints. At .35c, little things like hydrogen and helium nuclei are hitting you with a kinetic energy of 19.2MeV per nucleon, and big things like specs of dust are hitting you with the equivalent of 1.45 kilotonnes of TNT per gram. The [local interstellar medium](https://en.wikipedia.org/wiki/Local_Interstellar_Cloud) has a density of ~0.3 atoms per cubic centimeter, so if your whole 20ly journey is at a similar density and all the atoms are neutral hydrogen (they mostly will be), you'll sweep about 0.1g of matter per meter squared of the cross-sectional area of your spacecraft, which adds up to ~58 MJ of absorbed energy per meter squared (~14kg TNT equivalent) The radiation hazard from individual small nucleons, at least, isn't so bad. The particle energies are high, but [solar particle events](https://en.wikipedia.org/wiki/Solar_particle_event) can produce even higher energies and if you can build a laser array around the sun then you've obviously developed some ability to protect yourself from that sort of thing. At .35c, the [Lorentz factor](https://en.wikipedia.org/wiki/Lorentz_factor) is only ~1.06 so [relativistic aberration](https://en.wikipedia.org/wiki/Relativistic_aberration) is minimal (~20 degrees maximum for things perpendicular to you). This means that you still need to care about radiation hitting you from the sides, eg. [galactic cosmic rays](https://en.wikipedia.org/wiki/Cosmic_ray). You can't easily shield against those but again: you're talking about a mature spacefaring society, so they'll have good radiation hardened electronics and magnetic shielding. The dust hazard is obviously greater. [Dust Grain Damage to Interstellar Vehicles and Lightsails](https://ui.adsabs.harvard.edu/abs/2015JBIS...68..205E/abstract) (no free online source that I'm aware of, legitimate or otherwise) suggests that the first line of defense is actually a very thin foil shield, perhaps less than a micrometer thick, made of something like gold or beryllium. Like the outer layer of a Whipple shield its job isn't to stop incoming crud, but it liberates enough energy to at least partially ionize whatever hits it. Some distance behind the foil (and the further the better... at least 10m) you have a layer of something tough and refractory. Graphite is a simple option (and has some real-discussion and papers), but woven carbon nanotubes in a diamond matrix might be ideal. This probably needs to be a layer a few centimeters thick. It needs to be refractory so it doesn't melt too easily (splashes and vaporisation will wear down the shield over time) and it needs to be tough so impact shocks and gas buildup under the surface doesn't crack it. At just .35c, you might not need additional layers of armor. A paper that is readily available and free is [The interaction of relativistic spacecrafts with the interstellar medium](http://arxiv.org/abs/1608.05284) which might be worth a read. The authors suggest it is exceedingly unlikely for dust grains to be bigger than 3μm, and the authors of [Evaluation of the Hazard of Dust Impacts on Interstellar Spacecraft](https://www.osti.gov/pages/biblio/1525731) make similar assumptions, so the threat of the big bad kilotonne-nuke-dust-grain is probably minimal. You can scale the shielding depending on your paranoia and aesthetic requirements. The [Kronos](https://www.deviantart.com/macrebisz/art/Kronos-1-in-Low-Earth-Orbit-582647310) ship design you linked has this big curved shields much wider than the ship out in front which look very nice (if you like the sort of jellyfish aesthetic), but the outsize shield is wasted mass and the curvature is not necessary for a starship (and maybe not even for the Kronos). The [Aion](https://www.artstation.com/artwork/GLl3B) (or Ourea) has a big round shield, but at least it is there to protect the spinning habitat, although it would make more sense to save mass and shield the habitat modules instead. In any case, you don't have habitats or spun gravity. Your shields might not even be round (see the diamond/squished hexagon shape of the Venture Star shields, for example), but cut precisely to protect the silhouette of the ship behind them with no superfluous mass at all. The shields probably do have some rigid spars holding them in place and in shape. Behind them will be the propulsion bus, which holds your course correction and tensioning engines. Everything else dangles off that on a tensile spine... probably a bunch (at least 3, but probably more for redundancy) of woven nanotube cables if you can make them, spaced out a bit rather than as a single fat cord which can suffer from undesirable twisting and bending. At either end of the ship you'll have mount points to which can be fastened the lightsail or a laser shield. Everyone talks about spin-flips where your ship rotates 180 before entering the brake phase of its flight, but that's a) tricky with a flexible ship and b) exposes you to a horrendous amout of risk in the form of high-energy particles (which will wreck your electronics, even if radiation hardened... read [Radiation Hazard of Relativistic Interstellar Flight](https://arxiv.org/ftp/physics/papers/0610/0610030.pdf) for more information) and dust which will threaten potentially serious damage if you're unlucky. Flipping is fine for little interplanetary craft, but not big starships. After boost, you fold up your lightsail (mounted at the bow) and your protective shield (probably made of the same stuff, mounted at the stern) and tuck them all away neatly behind the shielding. For your brake phase, you remount the sail at the stern, and the laser shield at the bow. The shield will probably get battered by the ISM, but it is less important now and the regular shielding should be able to soak up stray laser illumination without serious damage. --- Now that I've answered your question, more or less, lets consider this bit of your mission design: > > But then we'd still need engines to slow down... right? WRONG! If we got the ship up to moving at 0.35C with a massive laser-sail array powered by solar collectors around the sun, then we can do the same thing around the colony star > > > I suspect the best way to park a relativistic starship is using magnetic brakes, which is using a large magnetic sail to initially brake against the interstellar medium (the sort of drag that killed the dream of the [Bussard ramjet](https://en.wikipedia.org/wiki/Bussard_ramjet) put to good use here) and then against the solar wind of your destination star. From [The Magnetic Sail Final Report to the NASA Institute of Advanced Concepts](http://www.niac.usra.edu/files/studies/final_report/320Zubrin.pdf), > > [a magnetic sail] could decelerate a starship traveling at 95 % lightspeed to about 4 % lightspeed in ~320 days, 1% in ~ 620 days, and 0.56% in 800 days Deceleration would start at 5.47 g’s but would later fall to 0.0058 gees. > > > This is perhaps a little optimistic, but it'd be an excellent way to slow down and even manoever in the destination system without the need for any infrastructure there, or the need to carry fuel and reaction mass for rockets (avoiding the issues of all that pesky antimatter). Obviously this spoils the drama of your setup somewhat, but no-one said that the mag brake of the Aurea had to work as planned... ]
[Question] [ I'm working on a story which is sci-fi so soft you could spread it on a cracker, but I'd like something semi plausible. I'm very likely overthinking things to an extreme, but I'd like someone with more of a science mind than I, to tell me if what I have is plausible on a surface level, or if there are certain blindingly obvious things I'm not taking into consideration that would trash this entirely. I've included as much relevant information as possible, but to try and keep the question as narrow as possible, I'd like to focus on adaptations for the light emitted by the star and the wavelengths they're capable of seeing and how that might affect their appearance. I've already looked [at this question](https://worldbuilding.stackexchange.com/questions/131889/extreme-adaptation-evolutionary-narrative-for-vantablack-like-skin-pigment), which is similar in scope (human-like origins and general Earth-like plausibility), but that's taking a pigment and working backwards, whereas I'm looking for what might naturally arise given the conditions available. # The Setting The basis of it is a tidally-locked, Earth-like planet around a red dwarf star, and for all intents and purposes, assume it's habitable to humans atmospherically and pressure-wise. Assume through heavy doses of handwavium they are able to control for factors like solar flares that might be a civilization-destroying problem. The light the planet receives is clearly dimmer and in a different wavelength than our sun. It obviously receives heavy doses of infrared and red light. It is an "eyeball planet", but a decently thick atmosphere (that may be artificially supported) and oceans manage to ease some of the more extreme temperature changes. Assume that, as with any eyeball planet, there are strong winds from night to day side. (This may cause a gradual pressure to live partly or completely underground, both as a radiation shield and protection from winds.) I'm thinking if there are plants (or anything that uses photosynthesis), they're likely black or very dark. # The Species One of the intelligent species of this planet are "humans" (pseudo-humans) initially created by another intelligent species (who has colonized the planet and evolved to adapt to it, but not originally from there). Think "Avatar, but the aliens create pseudo-humans to interact with other humanoid species because their weird alien bodies don't communicate very good" and you've got the gist of it. Think of the aliens as...intelligent like mycelium is intelligent: something with a sort of collective mind and senses. In their long ago past, they had a focus on communicating through light and shifting colour, remnants of which are still around, but they're less mobile now in favour of rooting to the earth. They are one aspect of an overarching collective mind that uses created bodies to communicate with other species. (See above about heavy doses of handwavium. I bring this up only because the focus on light and colour has some relevance.) Pseudo-humans start off artificially created, and then eventually reproduce on their own and become a self-sustaining population the aliens can 'pick' from. The aliens and pseudo-humans have a symbiotic relationship that ensures there's no competition for the same resources and enough benefits that they'd be cool with them occasionally controlling your body like a meat puppet for a bit. It's a weird trip for sure, but usually they come out of it no worse for wear. They are visually identical, but a recurring theme is that they are not human and such are capable of things that humans aren't (they can see into wavelengths that humans can't, I'm thinking UV but IR might be more plausible). Why? Well, the aliens might've slipped a little bit of their own genetics into it because it was available and easier, shhh. They have a range of skin/hair/eye tones as we do, although the underlying pigment doesn't have to be melanin, just so long as it looks like it to a human (that is, shades of brown/red in varying proportions). The aliens and pseudo-humans cull any mutations that are too wild (they want their human-sonas to be accurate after all). Like humans, pseudo-humans adapt to their environment and adapt their environment - dwellings can, at various points, be a mixture of above-ground dwellings, possibly shielded with regolith or dirt, or possibly even mycelium-like tendrils from the aliens, or below-ground dwellings to shield from excessive radiation. # The Premise The alien civilization collapses entirely, leaving the pseudo-humans to evolve and adapt on their own. The loss of their symbiotic relationship would be a huge societal blow, but assume the pseudo-humans manage to make it through the dark age/population collapse and don't go extinct. The story is set about a million years after this collapse, as I believe that might be enough time to see significant changes. I'm focused on the light emitted by the star and their ability to see into different wavelengths and adaptations for simplicity's sake. I'm doubtful there would be significant (visible) anatomical changes after a certain point, and I want there to be some sort of visual continuity (that is, you can see the human influence in them, this is not a Man After Man or All Tomorrows situation.) # The Question Given the elements outlined above, how would a species that is visually similar to modern humans, but have increased visual capabilities, adapt to the dimmer stellar light and differing wavelengths of light emitted by a red dwarf star over a million years? I'm thinking of: * A change in the eye shape or size to handle the different wavelengths of light they can see compared to a human (proportionally bigger in the skull/more visual processing sections in the brain, or different colours or pupil shapes) * Would the pigments in the skin/hair/eyes adapt to better protect against IR and/or red light, which a red dwarf will put out more than UV? If so, which colours would be most likely given the current constraints of human-like pigmentation? Or would there be no change overall? (I'm interested in both changes visible to pseudo-humans and changes visible to the normal human spectrum, or if a normal human can't see anything different but a pseudo-human could) * Or, would there be a skin tone that is more likely to crop up over time? Would the dimmer light of a red dwarf create evolutionary pressure for lighter skin, particularly if there was a push to remain underground? * Given that a red dwarf emits red light, would there be a significant visual change in colours overall? (I read somewhere that under a red sun, blue eyes wouldn't look blue, but I can't figure out what colour they would look like). I fully admit this question is broad, so I appreciate if it gets closed for that. I'm just wracking my brain here trying to figure out if any of this does play a role, and what that role looks like, or if "they look like humans even a million years later" is good enough. [Answer] all of the above. Also? they evolve into ants. If these beings are not already adapted to a red dwarf’s intense radiation, then they had bloody well better adapt toot sweet. Red dwarfs are nasty as stars go, and any life that evolves on planet’s orbiting them had better be well-adapted or they will go extinct. Radiation tolerant skin? That’s a must. UV or IR vision? Yes please! Big eyes? Well, a red dwarf emits less than a thousandth of the sun’s intense light, so yes, you want eyes that would slay the whole of Hollywood. Why evolve into ants? You describe these pseudo-humans already having a hive-mind and living in semi-underground dwellings; societal collapse means loss of agriculture and safety, and so they retreat even further below ground and allow only one female to breed at a time to minimise their food needs. As time goes on, this becomes the norm for the species, and once they are fully adapted for life on this world, they can find food more easily, but rather than return to everyone having babies, the matriarch just evolves to produce more. Immature females and males become workers, with most remaining immature until the queen dies, whereupon they all become sexually mature and leave to mingle with other colonies and start new ones. I give you homo termes; the termite man. [Answer] 1. They (mostly) dwell on the dark side. The hard radiation on the light side is bad for life. It is good for adding energy to organic molecules, though. These blow over to the dark side and are the base of the food pyramid, feeding fungus type organisms. It is not pitch black over there - the solar wind produces constant bright auroras which light the sky. You could give your people larger pupils like nocturnal animals have. You could give them epicanthic folds to do whatever those do. You could give your people [nicitating membranes](https://en.wikipedia.org/wiki/Nictitating_membrane) for wind protection. 2. They are many. In the days of the mycelium civilization there was not a need for a lot of humanoids. Their populations were controlled and kept at a low level. Now that has stopped. The population of humanoids has expanded to the carrying capacity of their world. 3. Genetic drift. [![black and white squirrels](https://i.stack.imgur.com/dotHO.jpg)](https://i.stack.imgur.com/dotHO.jpg) <https://www.roadsideamerica.com/story/29130> /The aliens and pseudo-humans cull any mutations that are too wild (they want their human-sonas to be accurate after all)./ In these post-mycelium days, there are no longer culls. The mycelia had standards but the humans are not so particular about how they appear. On this alien world there is really not much selective pressure on these humanoids. With the expansion of their population there has been genetic drift. Just as absent selective pressures against them, local urban populations of black or white squirrels occur in the sea of gray squirrels, your population of humanoids have local populations who differ considerably from the larger whole. There are selective pressures elsewhere that have altered populations. This includes the brightside dwellers, who have become quite different. The aquatic people are more different yet and might almost be a different species. These groups can appear in seasons 2 and 3. 4. Ability to meat puppet has become a rare trait. There was selective pressure in this direction. In the waning days of the mycelium civilization, there were some persons who could not be possessed by their alien masters and compelled to cull their babies. The trait thus conferred better genetic fitness. In these latter days there are still some people who can host mycelial minds but the relict mycelia are less interested in doing that. Most of them are less interested. The god of the Brightsiders is an iconoclast and remains very involved. [Answer] ## Too many possibilities I'm not a biologist, but I have toyed a lot with artificial life and such, and there are some essentials that probably apply universally. Evolution as a process is only limited by factors such as time, "luck", resources and the genetic code. In the end, it does not matter what kind of environment it is happening in, as long as there is a chance that anything benevolent can happen and repeat itself. Red dwarf as a sun should not be anything exceptional. Red dwarf may offer more time, though, but it also offers less high-energy radiation that provides a higher chance of random changes happening that are one half of what evolution is driven by. The other is selection, so evolution might on average be running slower but it has a chance to run longer when compared to Earth. Maybe it affects diversity, different species being more alike, or maybe not... there is no guarantee at all. Genetic code can be brittle, which means that small changes impact survivability so much that most mutations cause problems, in which case they rarely accumulate into bigger changes. Or, it can be robust so that organisms can accumulate smaller changes into bigger ones that eventually add up to a completely new functionality. But, this has hardly anything to do with environment apart from the fact that in environments where random mutations occur more frequently, genetic code might protect itself better, resulting in stubbornness against evolution (see eg [Deinococcus radiodurans](https://en.m.wikipedia.org/wiki/Deinococcus_radiodurans)). So, maybe genetic code on a planet orbiting a red dwarf is less protected, but there are so many other factors that sun alone is not enough to tell whether this is the case. So, in the end, maybe luck matters so much that anything goes. ]
[Question] [ I have a world where its mostly in ruins. But its run practically by corporations and smaller factions. A large part of the world is recovering from ecological collapse, massive pollution that travels by air and sea, warfare, lingering effects of bio and chemical warfare etc and intense radiation in certain areas. Essentially the environment is decaying. Basically, the world of Armored Core 4/4A if anyone's familiar with it. The story takes place later, where there is some reclamation of land pollution cleaning attempts. While large swaths of land are uninhabitable or non-arable, there's just enough safe zones to form larger factions that somewhat resemble early nation states. One of the issues I had was with food production. I want to make crop yields limited, essentially a food scarcity of sorts or the threat of a bad harvesting season causes major problems across the world. My research and some conversations have led me to the fact that a modern society with decent technology can make some pretty resilient crops. That and seeds/plants by themselves are pretty resilient. Chernobyl for example has fauna and even edible plants growing around the exclusion zone. Israel has done significant work in growing crops and making some very tough plants and seeds as well. Why would an otherwise near future/modern world with advanced technology in a somewhat post-apocalyptic/ environmentally challenged world struggle to grow crops/produce seeds on a consistent basis for the foreseeable future? Even if said world is on the slowest of slow paths to recovery when it comes to arable land Population for factions can range from city states to small countries or confederations. [Answer] ## Topsoil loss After you ruin the ground, topsoil does not just come back. topsoil can take hundreds or thousands or millions of years to recover naturally. Meters of topsoil loss can happen in a few years if you destroy the vegetation, which everything you listed can do. will it every place, no but it will effect a lot of places. [![enter image description here](https://i.stack.imgur.com/N3zBy.png)](https://i.stack.imgur.com/N3zBy.png) this is the type of soil loss deforestation creates. This is caused by bad farming practices mixed with climate change. [![enter image description here](https://i.stack.imgur.com/3SdUz.jpg)](https://i.stack.imgur.com/3SdUz.jpg) both of these took only a few years and everything you listed can and will result in massive soil losses. Using technology to rebuilding soil is incredibly difficult, incredibly expensive, and incredibly slow, even with advanced technology hundreds or thousands of years would be a generous timeline. to quote an old saying, Man — despite his artistic pretensions, his sophistication, and his many accomplishments — owes his existence to a six inch layer of topsoil and the fact that it rains. [Answer] Short answer: A man-made volcanic winter seems most plausible to me. Thanks to biological and chemical warfare, I see two main possibilities: Heavy metals could cause severe problems for food production. Maybe the plants themselves are fine, but they could contain heavy metals in concentrations that are poisonous to humans. Only in a few regions that were less affected, concentrations could be low enough so the plants are edible. Organic poisons might work as well, but they can be degraded more easily. This would probably mean, that some factions with less contaminated land might produce much more food than other. In theory it might be possible to engineer plants that would not take up the metals. This is why I like to following idea better: Simple thermodynamics cannot be engineered away. Even if your society is able to engineer plants as they like, the energy the plants use must come from somewhere. If incoming solar radiation is reduced, your plants will grow much worse, no matter what anyone does with them. This is quite plausible, it happens with volcanoes from time to time and it caused huge problems for societies before (<https://en.wikipedia.org/wiki/Volcanic_winter>). Given the scale of the pollution and the weapons used, I could imagine that some of them would be able to cause this. Especially if a big nuclear bomb is directed at an unstable volcano or as side effect from large-scale chemical weapons. Unlike to first scenario, this would be more of a global problem but would still benefit some warmer regions. [Answer] ## Desertification A biologically ruined planet is going to be lacking in vegetation, of course. This leads to some issues similar to what the central USA experienced during the Dust Bowl, and that African countries surrounding the Sahara already experience: desertification. Even if these population centers manage to grab hold and reclaim some land from the rampant pollution and clean it up, no amount of technology can instantly restore the top layers of soil in an area that has been blown to sand and dust. ## Wind Even if your groups can reclaim and restore enough vegetation in one area to establish consistent footholds for crop growing, they will need to deal with the wind. Farmers in the central United States will tend to plant rows of trees to act as wind breaks, because high-velocity straight-line winds can and will destroy crops by simply blowing them over. Even short crops can be damaged as their leaves and stems are ripped away by the winds. Your ruined location will not have trees, and it will take years of hard work and careful maintenance to grow wind-break trees, or to build and maintain wind-break walls of sufficient size. ## Growing Cycles I don’t know what kind of climate the ecological destruction of the planet has caused, but that is a big issue. If your planet has inconsistent growing cycles, even the heartiest will fail or come out poor in terms of yield. Even in our modern era we have issues with intermittent hot and cold cycles messing with plants, causing them to sprout early in unseasonably warm weather, which leads to lower yields, and then be destroyed when the cold returns suddenly and wipes out the vulnerable, sprouted crops. This phenomena also affects the next category of issue. ## Pollinators Virtually no plant yields without pollination, and also seeds would be difficult if not impossible to grow. Given the relatively ruined biosphere of your planet, those insects and creatures that perform the powerful job of pollination are going to few and far between. That means that, as the ecosystem slowly recovers, pollination will be a manual process for the humans maintaining the crops. This would be a very time-consuming and resource-intensive process regardless of the tech level of the groups. ## Conclusion There are a number of factors that would make maintaining plants and crops difficult for a high-tech society on a dying planet. Take your pick, mix and match, and have fun making life difficult for some fictional folks. [Answer] No workers. [![no workers](https://i.stack.imgur.com/6SczD.png)](https://i.stack.imgur.com/6SczD.png) <https://www.euronews.com/2022/06/10/it-s-just-not-happening-crops-go-to-waste-as-uk-farmers-struggle-to-find-workers> There are limited crops in your world because people don't want to work in fields. Crops rot in the ground because they are planted by hopeful farmers who then cannot find people willing to do the work of harvesting them. It is not that there are no people capable of doing this work. It is that these people choose to do other things, or nothing. Same as our world. [Answer] Germ Warfare [![enter image description here](https://i.stack.imgur.com/EG24l.png)](https://i.stack.imgur.com/EG24l.png) In the late stages of the war, both sides used airborne pathogens to attack each others' crops. As you say in a comment, "What happened during the war is in the air". The germ warfare was especially devastating since modern GMO crops have negligible biodiversity. So it was easy to devise a virus to infect all the corn in America or all the wheat in Europe. Both wilted and turned black in the fields. Based on the principle that it takes much longer to make a bake than to eat a cake, the effects of the pathogens linger half a century later. Even using further bioengineering to make the crops resist the pathogens, it is still difficult to grow crops. The solution was to return to heirloom crops. These produce far less food but, since they are all different, it is unlikely the entire harvest will succumb to this season's new virus. Oh did I mention the virus mutates every year? It mutates every year. [Answer] ## Indoor Farms Other answers have focused on how to make a food shortage, but the OP seems more interested in how to make the food supply unstable with some years/areas producing good yields while others suffer from major failures. The soil and atmosphere was completely ruined in the collapse; so, agriculture was forced to turn completely to indoor hydroponics/aeroponics farms because food had to be grown in doors in clean air. While the world's ecology is beginning to recover, these high-tech farms now hold a monopoly on food production, making them as hard to inch out of the food market as the oil industry is to push out of the energy market today. So even if alternative, more reliable food supplies become possible, lobbying and capitol advantages will keep the indoor farms in power long after their problems become apparent. So what makes these indoor farms so much more vulnerable than outdoor farms? With thier sophisticated climate control systems, you'd think they'd be super resilient, but that resilience breeds a very dangerous sort of trust. Farmers today are encouraged to produce over projected needs to account when low yields happen, but when your indoor farming complex always produces exactly 5 million tons of food every year, you learn to produce everything on tighter margins to improve profits... only these farms can not ALWAYS produce this much. Using artificial grow lights means a power grid failure could kill off an entire region's food supply in days. The need for specialized bulbs and synthetic fertilizers meaning your supply chains could be very easy to cut off during times of unrest also leading to massive crop failures. Also, your food production is much less spread out; so, a natural disaster like a fire or flood big enough to destroy a few acres of open farmland could now wipe out the one farming complex that feeds your entire city. And because everyone is maximizing profits, there is not much reserve available to be purchased from other places to cover your needs. ]
[Question] [ I have returned to this forum from Astronomy with this question because it immediately got down-voted. Maybe these hypothetical questions are more appropriate here? I am happy to take advice from Worldbuilding forum veterans. I am in the process of building a hypothetical solar system very similar to ours with only a few changes. I would like to test the viability of my modifications mathematically. Procedural answers are most welcome. As I have been advised in the comments by Angry Muppet and JBH, I am adding additional information for clarity below: My objective for moving planets is two-fold: (1) that I can create calendars and astrology specific to my "Earth," and (2) that Venus and Mars will orbit on the furthest edges of the habitable zone and therefore be able to have liquid water in some quantity somewhere on their surfaces. My concern is that by moving my hypothetical Venus, Earth, and Mars so close together they will affect each other so significantly during conjunctions that my solar system build is no longer viable, i.e., the hypothetical planetary orbits will not be stable over billions of years as ours have been. As advised by L.Dutch, I have edited the title question to specify the hypothetical semi-major axes. As advised by planetmaker from Astronomy, I am adding this additional information: planetmaker asked "How big a disturbance (in planetary orbit) is too big?" and "What time scales are we talking about?" An orbital disturbance is too big if the hypothetical Venus, Earth, and Mars cannot plausibly have retained their proposed semi-major axes long enough for habitable worlds to evolve. "Habitable" should be taken to mean a world with a liquid water ocean, temperate climate, and breathable air in at least some regions, which indicates the evolution of complex, oxygen-producing lifeforms. (I am aware that Mars' size is considered responsible in part for the loss of its oceans. I may increase the size of my Martian planet if necessary, but right now it is not relevant.) This leads me to suggest that a timescale of 4.5 billion years should be considered as baseline. Thank you for your help! [Answer] Final answer: the system remains stable. Let me explain exactly what I did. I ran an N-body simulation including the following planets: * Venus at 0.85 AU (other orbital parameters unchanged) * Earth at 1.1 AU (same) * Mars at 1.4 AU (same) * Jupiter and Saturn on their current orbits I didn't include Mercury (which would shorten the timestep needed for the simulation) or the ice giants (their influence should be minimal). I ran the simulation for 80 million years with a 10-day timestep. (I know I said 100 million years but I needed the machine for a separate simulation, and in general systems that go unstable do so relatively quickly). The planets' orbits remained nice and stable for the full duration of the simulation. Their orbital eccentricities and inclinations stayed in roughly the same range as they do on their current orbits (Earth's eccentricity goes between about zero and 0.05, same for Venus, a little higher for Mars -- see blog post [here](https://planetplanet.net/2022/08/22/billion-year-evolution-of-the-solar-system-climate-forcing-and-orbital-chaos/)). I fully expect the planets' orbits to remain stable indefinitely, so it's plausible to have a story as you describe. FYI the inner edge of the habitable zone is at about 0.95ish AU (not 0.85), at least for an atmosphere like Earth's. I suppose that if you're using Venus as an analog for a tidally-locked planet, then the inner edge is a bit closer, so maybe 0.85 is OK. ]
[Question] [ The setting I am working on is near future in a sense and involves veterans dealing with the aftereffects and trauma of war. However, in this setting war is extremely deadly even if not always fatal. More so than our current battlefields. For example, the use of loitering munitions is so prevalent that most infantry units operate from armored APCs with heavy active protection systems and dismount only if the situation calls for it. There is some light shielding so tanks, APCs etc. can take a few hits. Short of nuclear weapons (non-factor in the setting), the soldiers from all sides practically threw everything at each other over a protracted conflict that spanned years. Death is either very fast and unexpected via the use of PGMs or large explosives/artillery. Or slow and painful i.e., when armor piercing shots damage vehicles and maim the crew but don't outright kill them immediately because of shielding. The result of this is that there are a lot of injured and physically disabled veterans. By the end of the war, which ended in a stalemate with all sides hanging on by a thread, the majority of active-duty soldiers are heavily injured and or have major war related trauma. While not a majority, a decent percentage of each countries' population was recruited or conscripted during the war. The casualties were horrific regardless. Essentially to the point that the militaries of countries have to wipe away the majority of their armed forces and recruit or conscript from scratch due to the prevalence of severely injured soldiers (think Volksstrum levels of bad, but instead of the old and extremely young its mainly the heavily injured.). With all these returning veterans coming back home there is obviously a major reintegration problem. Especially with how violent the war was. One of the issues is that the fighting didn't really affect civilian areas. Civilians no doubt had their own stressors and issues, but the fighting largely took place off planet. As a result, civilians including the academic/medical community back home have a different and less popular view of the war and the soldiers (think Vietnam). Given the extra level of violence one could expect from close to far future conflicts between peer forces what would therapy/treatment look like on a systemic level. With the sudden influx of mass casualties returning from an entirely different planet at the end of the war, what medical and psychological advancements could one expect to be used to treat such a large group of returning veterans. Edit: Focused question based on feedback to focus on future treatments instead of "upper limit" on treatments. [Answer] # Near Future Medicine: *For purposes of this site, I am interpreting this as a request to know what cognitive and injury therapy and recovery will look like in the near future. At the upper limits, you can reprogram brains and memories, regrow entire bodies, or clone bodies and download new copies of the dead into new bodies, so there really is no "upper limit" except whatever tech level you allow.* Things don't look as bleak as you make them out. If your civilian areas are virtually undamaged, then research facilities, hospitals, and rehabilitative equipment is at your new, artificial fingertips. Look to current tech, and extrapolate. We are currently dealing with a lot of PTSD, and still botching it enough to be a bit embarrassing. But with drugs and possibly small implants, we are likely going to be able to selectively dull people's memories of trauma so they forget things they don't want to remember. Trauma memories are vivid, but memories are plastic. We are already doing this by having people relive trauma and giving them therapy and drugs to inhibit memory formation so the memories become dull. In this case, wide adoption of more advanced versions of this tech is likely. * Story-wise, this is a great opportunity to dream up odd side effects for this therapy, like it interfering with people remembering their past. There ARE going to be significant numbers of people operating with various cognitive deficits. There are interesting programs today working with apps that inform police about people's mental illnesses so the police can know more about people they encounter and how to deal with them safely. Your vets may all be required to carry some kind of device that notifies those around them about their deficiencies, authorizes the use of handicap facilities, and the like. * This could be extended to include implants that either directly stimulate the brain or remotely administer drugs to calm or sedate vets with violent outbursts, So a police officer might have a phone-like device that brings up a description of the person, their behaviors, and allows to calm or disable the vet remotely. * This could result in discrimination, legal challenges over freedoms, or people misusing this tech to fake disabilities or fake health to avoid embarrassment or discrimination. For paralysis, they are working on neural stimulation equipment that lets limbs respond to brain signals even if there isn't feedback. So people with damaged spinal cords can walk with minor assistance. This will get better, so a lot of people may experience a lot of numbness and lack of sensation, but still be able to (somewhat clumsily, and with like the need of some kind of feedback system) use legs and crippled arms. Scientists can already 3D print bone, and if they can lay down extracellular matrix with the appropriate markers (which they are already doing in animals) they may be able to regrow approximated limbs. Near-perfect, cell-matched ones can also be obtained by dissolving out all the cells from an existing donor limb and allowing the recipient's cells to colonize the resulting matrix. I've seen this done with mouse organs, and it's super-cool (okay, yeah, I'm a biology geek). Prosthetics will likely get better, lighter, and cheaper. While not likely mounted in the flesh like a cyborg, they will have directly signaled systems reading the user's brainwaves and providing some basic feedback for things like touch and temperature. Given the sheer number of people in your world with experience using such systems, other equipment (think cars, military vehicles, forklifts) may have feedback systems, so people are likely to be thought-controlling in increasing number of things in your society. [Answer] Your setting seems to be a reasonable extrapolation of warfare trends. There is a lot of medical literature about the differences between Vietnam and Iraq/Afghanistan in terms of survivability and conflict. With better training of the use of combat tourniquets, better medical evacuation times (at least in Iraq) and better body armor survivability went way up, but that meant a lot more Traumatic Brain Injury and loss of limbs. So a lot more people with severe injuries made it home. There has been some amazing progress made with prosthetics, research in interpreting nerve impulses and integrating them with prosthetics. Rehabilitation therapy has gotten much better. The variety of prosthetics for different purposes has also greatly increased and it is a reasonable extrapolation that some prosthetics might be more complicated machines that are controlled with the brain, or manipulated via the prosthetic interface. There is a lot of current concern about the next peer to peer conflict. Being able to handle mass casualties day in the 10's of thousands is very very different than something like an Iraq/Afghanistan where forward deploying a few surgeons, or training up medics to a very high level can make a big difference. Instead there is a big logistics problem, concerning how you extend someones life on the battlefield long enough such that they can be transported to an appropriate level of care. Some of that can be helped a lot with technology, stopping hemorrhaging in creative ways and preventing infection can go a long way. Artificial blood that can be stored at room temperature, or dehydrated blood you can store and have available for transfusions. Pain management, smart bandages for burn and wound care could help a lot. But as you mention there will be a lot of casualties where there may not be a lot that can be done, but and there will likely be a lot of very damaged people. All the physical stuff ties into the mental health aspects. With mental health it is a lot more complicated.... there is PTSD, but then there is a lot of stuff that doesn't rise to the level of PTSD and in my opinion that is a big gray area. There are a lot of people who make it day to day, contribute to society but struggle. Is it is due to their military experience, or other life circumstances? In just the normal civilian population there are a lot of traumatic experiences, PTSD and people who struggle as well. A huge portion of the PTSD and related mental health tied to how society views people who struggle and how those people feel integrated into society or not. Your story could go from any extreme between veterans being despised to them being viewed as very important to society. On the technology side though it seems that we now better understand that the brain is very plastic and can be trained to overcome some pretty severe deficits. There is some discussion about if some PTSD could be reduced if the brain was reset using psychotropic drugs. We also seem to know that things stress and trauma can impact things like impulse control, executive functioning. Like mentioned in the other answer, on the research side, there is interest if different parts of the brain be selectively stimulated, is that through an implanted device, or by applying strong magnetic field, or though light being shone though the skull and activating a drug in a certain region. A lot of this type of research has been funded or stimulated by military interests, but there should hopefully be much wider benefits to society. Things like cosmetic surgery are also important. It really helps in reintegrating, but it also hides the injury. If someone looks normal... how do you know that they were injured or are struggling. If you look at crime statistics, I think veterans as a group are less likely to commit crimes than the general population. However, veterans are clearly identified as a group and violence and domestic abuse are perceived as a problem and generally get blamed on military service. I think the professionals that look into these kinds of things have a more nuanced view and seem to think other factors beyond military service are also at fault. They also point out that only a very small number of veterans get diagnosed as having PTSD. The issue of violence and PTSD is particularly complicated. Self medication - in particular alcohol abuse seems to be a aggravating factor, but I think most people also understand that the overall social system is important. The conclusion of one study > > Co-occurring PTSD and alcohol misuse was associated with a marked increase in violence and aggression in veterans. Compared with veterans with neither PTSD nor alcohol misuse, veterans with PTSD and no alcohol misuse were not significantly more likely to be severely violent and were only marginally more likely to engage in other physical aggression. Attention to cumulative effects of multiple risk factors beyond diagnosis - including demographics, violence history, combat exposure, and veterans’ having money to cover basic needs like food, shelter, transportation, and medical care - is crucial for optimising violence risk management. > > > I think from a world building perspective - there is a lot that you can do projecting from future trends in technology, but the heart of your story probably ends up being about the human condition and how individuals interact with the society that they are in. [Answer] This is a [Frame Challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609) Our modern understanding of the effects of war on the individual soldier has, in my opinion, led us to erroneously believe that war today is somehow worse than it was in yesteryear. And that has led you to believe that it can be made ever so much worse, leading to asking just how much psychological damage can be fixed. You've included a description of weaponry that's designed to, theoretically, maximize psychological stress and you have created a condition (not hitting population centers) to maximize the separation between soldier and civilian. It's an entirely false premise. War is individually more brutal the further back you go in history Modern warfare is certainly more instantaneously destructive than wars in the past. But destructiveness alone doesn't create deeper scars on the individual soldier. The U.S. Civil War meets all of your criteria and yet I'd bet you think it's "less violent" than wars today or in your near future. Some states had to devote a third (a third!) of their annual budget to prosthetic limbs. Some towns lost all of their military-age men. Photographs of the battles are sickening and depict, in my opinion, as much or more violence as you're trying to consider. And it gets worse the further back you go. People a thousand years ago waded through blood, too often had to kill face-to-face, and had the pleasure of seeing bodies trampled by horses and chariots. Theirs was a day when all too often it took a long time to die. I believe it's false to believe that war today is more onerous than it was in the past. I believe it was, for the individual soldier, much more onerous in the past. Humanity simply didn't have the psychology skills to understand the problem. If you have any technology at all in your near future, that technology will be used to strike from a distance and remove the expensive-to-train and expensive-to-fix soldier from the field. Not surprisingly, "statistically" it appears that there was less cancer 200 years ago than today. That premise is false, too. People 200 years ago simply didn't understand cancer as well as we do today and so its consequences were recorded as something else, skewing the historical data. I believe you're affected by the same problem with the psychology of war. No modern war would ignore population centers Humanity has long since left behind the idea that civilians are not part of the military machine—that they should be left alone or protected because they're not a threat. They are, in fact, the greatest threat. Civilians make the bullets and the bandages. Civilians make policy. Civilians make war. Humanity learned a long time ago that if you want to win a war, you need to beat the capacity for war out of the civilian population. To make a point, nuclear weapons don't exist to fight armies. They exist to destroy population centers. Oh, we may try to be more surgical than in years past with so-called smart weapons that target and destroy specific factories, power generation plants and dams, government centers... but you're still attacking civilians. I'm not going to ask, but it wouldn't surprise me that you (like I) are a U.S. citizen. It's been 150 years since we experienced a war on our own soil—excluding the BLM riots, Capitol incursion, gangs, school bombings, and serial killers. I'm not being facetious, those are terrible things, but they're not a real war because they can't bring the "big guns" to bear. We Americans have a bit of a skewed idea about the tragedy of war because it's been a very, very long time since we experienced it first-hand. Unlike a great many other nations on our fair planet that have experienced it first hand and whose citizens likely have a very specific opinion about our average citizen's ability to know what real war is. Psychology is part of all wars, but it's not the driving purpose of any war No war would be fought for the purpose of hurting the surviving soldiers in a way that makes their continued presence in society a problem. Some wars are fought to humiliate the enemy. Some wars are fought to capture a resource. Some wars are fought to promote religion. Some wars are fought to "finalize a divorce." No war is fought to intentionally keep the enemy alive but in mental pain. I once had a discussion with a friend in the Finnish military. He made an interesting point. As part of his training, he was taught that, when possible, shoot to wound-and-disable, not to kill. The goal was two-fold: (a) to stop the other guy from shooting at you and (b) to force one or two other people to be engaged getting the wounded soldier off the field. The goal wasn't to cause the target soldier mental trauma. To quote U.S. Civil War general Tecumseh Sherman, "all war is hell." The goal was to cause as many people to stop shooting bullets as possible. But that's also a reflection of modern efforts to "civilize" warfare. During WWI we used gas and machine guns. During the US/USSR Cold War it was nuclear weapons. Today we worry about the use of biological weapons (to the point of a great many people thinking COVID-19 was a biological weapon run amok). Despite efforts to "civilize" war, I suspect that when you're in the proverbial trenches, the goal is reflected in a statement by U.S. general George Patton, “No dumb bastard ever won a war by going out and dying for his country. He won it by making some other dumb bastard die for his country.” But the central problem is that your question is the proverbial blind being led by the blind But here's the biggest problem: you don't know what you're doing. Unlike authors like Arthur C. Clark and Larry Niven who had advanced degrees before they wrote their works, you don't have an advanced degree in psychology (or you wouldn't be asking this question here). And you're asking people who don't have advanced degrees in psychology what the upper limit is—if there's any factual reduction in PTSD and other psychological trauma at all. The veterans I've spoken to all explain that the therapy/medicine helps them cope. It doesn't solve anything, because the memories remain and the cultural conditioning that makes those memories unacceptable/traumatic also remains. Unless you think that removing said conditioning or removing memories is a legitimate answer to your question. Oh, the consequences that technology would have on society! It's also been explored by SciFi before. Frankly, the only user I can think of who could possibly answer this question with authority is @Otkin, who hasn't posted a question or answer on the Stack since last March. ]
[Question] [ ## The legend The [Kim Quy](https://en.wikipedia.org/wiki/Kim_Quy) is a Vietnamese giant turtle god, whose specific trait is -you guessed it from the title- golden, supposedly living in and around waters, like the [Ho√†n Ki·∫øm Lake](https://en.wikipedia.org/wiki/Ho%C3%A0n_Ki%E1%BA%BFm_Lake) where part of its myth takes place. [![Depiction of Kim Quy in a temple](https://i.stack.imgur.com/lJy26.png)](https://i.stack.imgur.com/lJy26.png) Depiction of Kim Quy and the Heaven's Will sword at the Ho√†n Ki·∫øm temple. From [Wikimedia commons](https://commons.wikimedia.org/wiki/File:Kim_Qui_and_the_Restored_Sword_(Hoan_Kiem)_in_ceramics.jpg). It is known to appear in two of the Vietnamese legends. The first one is about an emperor receiving a mythical sword from Kim Quy, the second one another ruler who had troubles building his castle, whose Kim Quy also gave one of his claws to make a crossbow trigger. This crossbow was supposedly capable of firing many shots at a time and kill three hundreds soldiers with one press of the trigger. I'd like to reproduce this turtle for my own world (without going into too much details, it would be an adventure guild's symbol with a quite similar legend). Now, since its golden appearance is perhaps the most difficult to reproduce biologically and its very identifying trait, this question will focuses on his unusual, golden appearance that I'd like to explain. ## Therefore, how can a giant turtle appear golden? The goal is very simple : Make a very big river turtle look as golden as possible so that its title "Golden Turtle" is well-deserved. The more you can make it look golden, the better. If you can make it of actual gold, I guess it's even better! I do picture it is next-to-impossible to make a living being out of pure gold, so focus on what can be seen, then the insides after if you can. In the end, nobody in the legends would have dared to dissect the turtle, so who knows what its organs look like ü¶ã... To further help, here's what I know about this turtle (and the minimal constraints you should follow) : * Its exact size is not really told, but it is more often than not considered as being bigger than its normal counterparts like the ["Hoan Kiem" turtle](https://en.wikipedia.org/wiki/Hoan_Kiem_turtle). + From my sources, it can at the very least carry a sword on its back, but in the tale I heard they went as far as telling it was the size of a small boat1. If you can make it closer to the latter, it's nice as it would look more godly and mythical, but it's only a secondary, bonus objective. Focus on gold first. * It has claws big and hard enough to make a functional crossbow trigger. * It is able of swimming and diving underwater, so it shouldn't sink to the bottom :). The amount of time it can hold breath is unknown, but consider it should be long enough for a Kim Quy to approach and surface near an unaware Emperor on the shoreline. In order to give or reclaim a sword, for instance üê¢. * Its diet is not really known. We just know it has become deep friend with a human, so it mustn't be too aggressive towards them. * And of course, it's golden, especially the claws which is a key element of one of the legend. Answers which doesn't make the claw look golden won't fit the bill. So how can we explain this turtle looks so much like gold? --- --- 1 : [Source (in French)](https://www.stitcher.com/show/contes-des-soirs-perdus/episode/ep35-legende-vietnamienne-la-tortue-dor-85284279) [Answer] ### Borrow from the jewel beetle. To make it appear golden, I would take [jewel beetles](https://en.wikipedia.org/wiki/Buprestidae) as example. Their coloration depends on [structural coloration](https://en.wikipedia.org/wiki/Structural_coloration). Some look more metallic then others, some of them are yellow/golden. So If a turtle has shell/claws outer layer composed of the same/similar structures as jewel beetles it could give the appearance of being metallic gold. However wouldn't affect the bulk properties of the shell, claw. There is issue that it could be removed/damaged with physical wear/damage. But it is an example of giving the appearance of being metallic gold. ]
[Question] [ I am currently creating a country located in a place which experiences only subarctic/arctic climates in the real world. I would like to know how the region's climate could be artificially changed without causing change to the rest of the world. For example, I am thinking about a giant geyser powered by the Earth's core which generates massive heat. If that is not physically possible, what could be the other solutions? [Answer] All sorts of things cause local climates to vary (sometimes quite sharply) from their immediate surroundings. If you're wanting to make subarctic/arctic into tropical? That's going to be extremely difficult without some way to isolate airflow. If you're not warming it beyond cold-temperate, then a body of water located centrally and deep enough to be warmed by near-surface volcanic activity is a good start. Physically speaking, any energy (heat) present in the area will eventually move into the surroundings, causing changes in the global environment. If the area in question is kept smaller, that effect will be lost in the background noise of the rest of the climate. But if the region gets quite large, then you're going to have noticeable impacts on regional and possibly global scales. Artificial methods to accomplish this would involve mountain sculpting to impact rainfall/prevailing winds so that airflow exchange is reduced, the ability to change color scheme on a day/night cycle so that you get good absorption during the day but reduce radiative losses at night. Maintaining a high moisture content in the area will help retain heat once it's been warmed up in the first place. And, of course, any form of heating system can keep an area warm. There will be losses, but it's doable with enough energy - air-source heat pumps are a good mechanism because the energy you're loosing into the air surrounding the region is heat you took away from it in the first place. All of this will require levels of understanding of climate dynamics beyond what I'm aware of us having, but at a theory level it's possible. A MUCH simpler solution, however, would be an enclosure. A good enclosure isolates the airflow and powerfully reduces energy losses and energy demands. [Answer] Bring the ocean You will make your land coastal, by excavating and moving away lands that lie between your country and the ocean coast. The presence of large bodies of water in proximity to the land moderates the climate - this can be seen with Britain which is warmer than inland places at comparable latitide as well as San Diego which is cooler than sites only a little ways inland. ]
[Question] [ Being hit in the head with a blunt object, or accelerating too fast (in a rocket) can cause serious brain injuries for people. There are animals who seem to fare better, like woodpeckers. Apparently, they have some soft tissue and neck muscles adapted to cushion the impacts. Also rams seem to have a bone structure adapted to minimize the brain damage from impact. But, these animals also have smaller brains than people. I think their adaptation won't be good enough to guarantee brain safety against most impacts and sudden accelerations if their brains were our size. What would be a good set of adaptations for people to be more resistant to concussions and sudden accelerations, that wouldn't make them look too different from us? [Answer] ## Non-newtonian cerebrospinal fluid Protection from impact forces (blunt object etc) vs sudden acceleration/deceleration may not use the same mechanisms; in fact, if we had a more elastic skull, we'd probably suffer less from some deceleration injuries, but more from impact [1]. One of the reasons is that the brain is able to slosh around the skull a bit more than desirable - or more specifically, it has no good way to dissipate its acceleration through heat, except quite violently against the inner wall of the skull. This is because the cerebrospinal fluid is, well, a fluid, and does little to protect against non-compressive forces. Let's change this. When experiencing "normal" forces, as those generated by movement, the CS fluid remains a fluid; this allows it to carry out its normal functions of waste clearance, homeostasis, lubrication, protection from normal wear, etc. When struck with sudden force, however, the CS fluid behaves in a [non-Newtonian](https://en.wikipedia.org/wiki/Non-Newtonian_fluid) manner and becomes suddenly very viscous, effectively turning into a thick "glue" that a) limits the sloshing (so that the brain moves less relative to the skull, albeit experiencing more shear stress internally) and b) is able to dissipate much more energy in the form of heat, because of its higher viscosity. --- [1] We probably rarely needed deceleration protection before the widespread adoption of cars, and our evolution may have optimised for protection against rocks to the head instead. [Answer] Pneumatization of calvarium. <https://www.semanticscholar.org/paper/Hyperpneumatization-of-the-temporal%2C-occipital-and-Rebol-Munda/5ce992b733d447b0d7b9eedb63332a17ddf43044> > > Hyperpneumatization of the temporal, occipital and parietal bones J. > Rebol, A. Munda, M. Tos Published 1 September 2004 Medicine European > Archives of Oto-Rhino-Laryngology and Head & Neck > > > Hyperpneumatization of the temporal bone with extension into the > occipital bone and even the parietal bones is a rare condition. > According to a review of the literature, it mostly appears > unilaterally in men and on the right side. Often it is discovered when > complications like pneumatocele or pneumocephalus appear. The authors > review and analyze all reported cases of hyperpneumatization, its > symptoms, complications and treatment. We present a patient with > extensive pneumatization found in the mastoid process, temporal bone, > occipital bone and both parietal bones, who was discovered > accidentally.... > > > [![pneumatizaton of skull bones](https://i.stack.imgur.com/Gs19s.png)](https://i.stack.imgur.com/Gs19s.png) Pneumatization of skull bones can happen as an anatomic variant. Bones contain air instead of marrow. Your concussion resistant persons have pneumatization of the bones of the skull. They serve as crumple zones like the shock absorbing bumpers of a car. The exterior table of bone crumples into the interior gas space, absorbing the force rather than transmitting it to the brain through what is normally a series of liquid containing interior spaces (and causing a concussion), or accelerating the head (and causing deceleration injury to the brain). This would not protect the brain from rapid acceleration of the entirety of the body in a rocket, without impact to the skull. For that you need slower accelerating rockets. --- [Answer] The brain is fairly well insulated against shocks. The arachnoid space\* helps put a distance between the skull and the brains, reducing the damage a shock ripple could do. The problem is when the brain inside that space needs to accelerate/decellerate too fast. It will impact the skull across the arachnoid space and bruise the brain tissue. So your best bet is to increase the distance where the brain tissue can slow down, which means a larger head or a smaller brain. Thats about it I guess. The evolved creatures specifically have systems in place to cushion the head against shock and/or have smaller brains with larger space to move in to begin with. Maybe a cushioning reflex could be added to accelerate/decellerate the head along the same direction the impact will send the brain in order to reduce the speed difference and/or increase the distance over which you can accelerate/decellerate the brain. * not sure about the translation. This space is filled with spinal fluid to cushion the brain further. ]
[Question] [ I’ve gone and designed an entire earth-like planet where life had never evolved. Oil can be reached if needed—the purpose of this question is to find how far they can go and avoid it. (Oil is generated [the same way it is on earth](https://www.intechopen.com/chapters/41889)— formed over 30km deep in the asthenosphere and pushed up through fissures in the plates, creating deposits within 200M of the surface in some areas). Settlement: A human civilization has grown to just over 3 million population in 5 major enclosed cities. No life, so no oxygen. The outside air is toxic and the land is sterile (but has same basic elements we have so it’s easy for microbes to fertilize) Agriculture and foresting land is about 15 persons per acre, and this is their main oxygen supply besides geothermal powered chemical reactors. They use a trivial amount of combustion due to the scarcity of oxygen. No combustion engines or jets, or even open flames generally. # The problem My story needs to be set before petrochemicals and oil production, I don’t know when oil will become necessary (or if I’ve passed it already). Research: * Before petroleum we relied on animal fat, pectin, leather, rubber, etc., which is fine until you are taking your food supply to make plastics and lubricants. It’s unsustainable after a point, you need your plants and animals for food and oxygen and fertilizing. * Because oil has been successfully created in a lab, this problem accepts current abiogenic oil generation theory. Some have opinions, but biogenic oil isn’t a consideration in this problem. So the question is, how far can I go and avoid drilling for oil? When will the population density consume hydrocarbon products faster than the artificial biome can supply? [Answer] In the situation you describe, it looks like oil will hardly ever be a viable alternative. They have easy access to geothermal energy, while oil is 30 km underground (on Earth we barely managed to reach 12 km, and just for peeking, not for mining). It sounds like it will be way easier to find another geothermal spot and use it than to drill that deep. And if they need more raw materials, they can just build more locations where they can grow plants, and use them as starters for organic chemistry instead of oil. Unless there is scarce carbon in general on the surface, but I am hardly capable of figuring out how they made to their present moment with that situation. [Answer] ### Ensure colonists don't need hydrocarbons for energy. Since they got there from some where else. They use nuclear(fusion and fission) energy almost exclusively for energy. The colony planers knew ensured the new colony would have sufficient energy for their first 100 years. This would be to maximize probability of success. This would mean that demand for hydrocarbons as fuel would be near minimum. The colonists would extract hydrocarbons as chemistry feedstock as soon as it was economically feasible to do so, which will take some decades depending on deposit depth/size. If the deposits are deep enough they may never be economically viable. [Answer] # They will never need oil. Any hydrocarbons can be synthesized entirely artificially, or in bioreactors. You have water, and you have carbon, because you can grow plants. They may use plants to generate oxygen because it's convenient, and they get food as a byproduct, but they don't have to--if you just wanted oxygen, it would be more energy-efficient to produce oxygen directly by electrolysis, so as not to waste energy on all the other stuff that plants do to keep themselves alive. Similarly, you can get carbon and hydrogen as byproducts of water or CO2 electrolysis. Most likely, however, you don't even need to go that far. If life never evolved, so there's no atmospheric oxygen, there is almost certainly atmospheric methane. That can be extracted from the air and dehydrogenated. If there somehow isn't atmospheric methane, you can just use agricultural waste; dump manure into and inedible plant waste into a bacterial digester with bacteria artificially selected to maximize methane and oil production, and you'll be set. You don't need and can't use petroleum for energy (since there's no atmospheric oxygen to burn it with), so all you need to replace is chemical feedstocks, and that takes a far lower volume of material, which your colony should have no trouble synthesizing indefinitely if they don't start out dependent on large quantities of oil and thus don't need to transition away from it. ]
[Question] [ I’m glad I could find some other people on the internet that have these kind of ideas as well. I am also in no way qualified within the field of civil engineering just interested in this specific topic, so please feel free to correct me. My first thoughts upon this idea was to have “units” as such. Because of the hexagons unique properties to tile so well, and its tendency to make effectively “upscale” (see examples below to see what I mean) I thought it was perfect. The idea of having modules, or districts as my friend calls, them seemed also very appealing [![Example 1](https://i.stack.imgur.com/fOeEk.png)](https://i.stack.imgur.com/fOeEk.png) Here is the proposed model for a base unit. For future reference here is a key of what colours will represent: Red - Housing Yellow - Local community. Everything a person would need within walking distance (food stores, transport centres, gymnasiums etc.) This same design can be scaled up to accommodate more needs that only need to be within a small journey( more of that explained later down the post) [![Example 2](https://i.stack.imgur.com/oJEFr.png)](https://i.stack.imgur.com/oJEFr.png) Orange - Transport hub Blue - Medical/ general practitioners Green - School Pink - Shops and other services The same applies to more scaled up versions [![Example 3](https://i.stack.imgur.com/cB9pv.jpg)](https://i.stack.imgur.com/cB9pv.jpg) I would love some input into what needs to be included here As mentioned before this design is ideally supposed to be a car free area. Trains lines would run from yellow centres to orange centres and orange centres into the centre of the larger upscale (incomplete), and into other orange centres, making for a more time and energy efficient journey. This would allow for every single person to be within a maximum distance from a service, and the distance to be reasonable (e.g a 5-10 minute to commute to school) I am still aware that this design is highly impractical for real life use and there lie flaws within it, but I would appreciate any feedback people would be able to help me further develop this concept [Answer] Lots of Urban Planning and Geography students get enamored of hexagonal neighborhoods when they learn about [Central Place Theory](https://en.wikipedia.org/wiki/Central_place_theory). However, keep in mind that it's an abstraction for understanding or describing some basic concepts; the hexagonal structure is not intended to be prescriptive. The hexagonal shape is intended to convey that areas are more likely to be circular than rectangular or linear when movement friction is assumed to be similar in all directions. It's cleaner than drawing a lot of overlapping circles and then stopping to explain the overlap. Stuff to add to your model: * Cities grow for a reason -- the city's exports are more valuable than their imports. Your city needs a reason to exist. Maybe it's a port or trade crossroads. Maybe it's an administrative capital. Maybe it's home to a large institution (like a University). Maybe its an industrial center, located between resources. But that key reason(s) for existence is historically located near the center of the city (the city grew around that activity). * Land use evolves over time. Factories and hospitals and schools grow (or shrink) as demand and technologies and standards change, and if you want to keep them in the neighborhood your land use (and citizens) must be flexible. Residential housing stock ages and gets renewed, family sizes change, and family needs change -- a pedestrian city doesn't need many garages, but what happens when a fad comes along and a generation of residents very much want garages? Maybe a certain hexagon is residential for this generation. That doesn't mean it always will be the same use forever. You might consider designating which hexagons are appropriately located and ripe for recycling to another use, or for renewal. * Market area sizes don't match cleanly. If you have, say, 10,000 residents in a neighborhood, That won't match 2.0 day care centers and 1.0 dentists and 3.0 gymnasiums. Instead, you will get 2.5 day care centers, and they won't want to be located together. So each will be on a different side of the neighborhood, seemingly hiding in a "residential" hexagon instead of cleanly in the center "neighborhood commercial" hexagon. The day care center isn't doing anything wrong -- the model is wrong. The model is using the wrong hexagon size. There is no single hexagon size that cleanly covers every industry, every market. (The use of hexagons, you recall, is descriptive, not prescriptive). ]
[Question] [ From my understanding nuclear fission takes place in two different scenarios and correlates with the speed of a neutron. In terms of material, we have fissionable material which undergo nuclear fission after attaining a fast neutron or a relatively slow/low energy neutron. We also have fissile material which will only undergo fission when capturing a slow/low energy neutron. Nuclear fission in general happens when we start chucking neutrons at a heavy nucleus to cause it to become unstable and split into two. Massive amounts of energy and free neutrons are a byproduct of this reaction. Suppose I was to create a field that messed around with the required ranges to induce nuclear fission in both fissile and fissionable material such that the speeds never line up appropriately for the heavy nucleus we are throwing free neutrons at (i.e. neutrons are either too fast, or way to slow in a range based on the nucleus material type). Maybe I start violating the Pauli Exclusion Principle to mess with the critical energy required to start a fission reaction, or maybe I just use pure handwavium to get the field up and running. Either way, I am messing with neutrons such that when in the field they cannot induce a nuclear fission reaction based on their speed. What would the unforeseen consequences of this be? Would reality cease to be, or would we have a region with no nuclear fission possible with everything else fine and dandy. For example by messing with the speed and energy of free neutrons, would ionizing radiation from neutrons be possible, would radioactive decay even be possible, would it be possible to create isotopes etc. [Answer] Nuclear fission is mediated by the elctromagnetic force, which is trying to split a nucleus due to the repulsion between protons, and the strong force which holds the nucleons together. You probably shouldn't mess with the strength of the electromagnetic force, because you will probably break everything, from chemistry to the speed of light. If you were somehow able to increase the strength of the strong force, though, then you might be able to leave non-nuclear processes unaffected. A formerly [fissionable](https://en.wikipedia.org/wiki/Fissile_material#Fissile_vs_fissionable) nucleus like 235U would then always absorb a neutron turn into a heavier isotope like [236U](https://en.wikipedia.org/wiki/Uranium-236) and never undergo fission. [Spontaneous fission](https://en.wikipedia.org/wiki/Spontaneous_fission) will become much harder as will [alpha decay](https://en.wikipedia.org/wiki/Alpha_decay) and as such a lot of isotopes which are currently radioactive and unstable could become less unstable or even completely stable over any long timescales (so long as your stronger-force generator remains operational). Other kinds of radioactive decay such as [beta emission](https://en.wikipedia.org/wiki/Beta_decay) could still occur, and gamma radiation emission following neutron activation or beta decay will also be entirely possible because those processes aren't mediated by the strong force. Assuming your powers of strong-force-strengthening are limited, it will still be possible to induce fission in a sufficiently neutron-rich nucleus, so you've made the problem much harder (and maybe made it impractical to do make fission powerplants or weapons) but not eliminated it entirely. If you look at the [nuclear drip lines](https://en.wikipedia.org/wiki/Nuclear_drip_line) (where unstable nuclei can decay by proton or neutron emission) you'll probably find beta decay happening instead. It may also make it easier to induce fusion in light elements, though I'm not sure by how much. > > What would the unforeseen consequences of this be? > > > Assuming the size of the effect is small, you probably don't have to worry very much. If the effect were planetary scale, you risk things like cooling down the planet due to removing some or more of the [radioactive heating](https://www.berkeley.edu/news/media/releases/2003/12/10_heat.shtml) that keeps the core toasty. That risks stopping the geodynamo in a few tens of millenia, with all the problems that a lack of a planetary magnetic field can entail. Even larger scale effects that encompass stars will have more dramatic results. Increasing the strength of the strong force means that the [diproton](https://en.wikipedia.org/wiki/Isotopes_of_helium#Helium-2_(diproton)) could become stable. I'm not entirely sure what this would do, but it will almost certainly be Very Bad... relatively rapid conversion of hydrogen to helium would dramatically shorten the life of affected stars (to maybe millions of years) and their power output would substantially increase, toasting any planetary systems they might have. [Answer] Semi-Science, Inc. (A division of ACME, supplier of high tech equipment used by coyotes to deal with high speed avians throughout the Galaxy) has just what you need. Our Neutron Dampening Device slows down the speed of the neutrons enough to suppress nuclear chain reactions. A reactor subjected to a neutron dampening field (easily detectable by the strong breeze associated with high powered handwavium) might still operate, but the heat (and thus electric power generated) would be greatly reduced. A nuclear weapon (or nuclear primed fusion weapon) would either be cause an explosion reduced by 4 to 5 orders of magnitude or else the weapon will just end up as quick flash leaving behind a pile of half melted radiactive fragments. This shouldn't cause any major hiccups in reality. Just to be safe, we recommend not applying neutron damping technology to the core of a planet or to an entire star until further experiments have been conducted in uninhabited systems. Current models have a maximum radius of 200 km, which is more than enough to provide a high degree of protection against nuclear attack to ships, orbital facilities, and most cities. Remember, your own nuclear reactors will be producing little or no power. Consult our brochure regarding the possible effects on different models of fusion reactors. ]
[Question] [ Sponges are sessile animals with a unique way of getting nutrients: Instead of a mouth, they have many pores through which water can flow. This water then leaves through a single canal, with suspended materials being extracted and consumed Filter-feeding is found amongst motile animals of all scales, and comb jellies are capable of swimming, to some degree, with just cilia On the other hand, sponges lack nerves, which seem like it would severely limit their ability to swim, and to use that ability The specific sponge I'd like to know about would be around 20-30cm long and 5-8cm wide, with a leucon anatomy Would this sponge realistically be able to swim by its water flow system? [Answer] Sure. But not fast. As you note, a sponge can generate a current. Water comes in thru pores via the work of little flagellated cells and then exits through a common exit path. [Current-induced flow through living sponges in nature](https://www.pnas.org/content/pnas/74/5/2069.full.pdf) > > When ambient flow is minimal, a steady current through the osculum > presumably reflects the pumping activity of the sponge. For the > present animals, such active pumping rates ranged from 7.5 to 22 cm > sec1. No particular correlation was noticed between this pumping rate > and either species, size, or habitat. And these flow speeds are > similar to those, between 7.9 and 17.3 cm sec1, obtained by Reiswig > (8) on three very much larger species. I estimate that the rate of > water volume transport per unit volume of sponge per unit time > resulting from active pumping is within a factor of two of 0.20 sec1 > for the present animals. > > > It was interesting that big animals and small animals produced similar flow rates. Not what you would expect. But for the OP: if you can generate flow within your body you can in theory propel yourself with that flow. The question is how fast. If you are neutrally buoyant you don't need to fight gravity. As far as lateral motion more massive things will be slower. Less hydrodynamic things will be slower. But clearly slowth is compatible with life. You don't need to be a swordfish. There are lots of swimming animals that are slow. I looked for a while because I was sure there was a micro-organism with a hollow body that used flagella along the internal path of its hollow body. I could not turn one up! If anyone can find that thing, link please. [Answer] As they are now, probably not. I've found this paper [The Role of Current Induced Flow in the Design of the Sponge Body Plan](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3236749/) which suggests that actively pumping water through their bodies already uses up a significant portion of the energy they can generate. That's not to say that there isn't some room for handwaving in sponge-like things. From the wikipedia article on [sponges](https://en.wikipedia.org/wiki/Sponge#Movement): > > A few species can contract their whole bodies, and many can close their oscula and ostia. > > > That sounds like the beginnings of a jet-based propulsion system that might end up resembling something like a [salp](https://en.wikipedia.org/wiki/Salp) (though note salps are chordates and so have a nervous system). Cnidarians (the phylum which contains jellyfish) have nerves but [no centralized nervous system](https://en.wikipedia.org/wiki/Cnidaria#Nervous_system_and_senses) but some of them can swim well enough. Development of whatever mechanism contractile sponges already use could lead to something that can squirt its way about. > > Would this sponge realistically be able to swim by its water flow system? > > > With a contraction-driven jet, I'd say there's a solid maybe! With regular sponge-style continuous flow I'm not so sure. It would be energetically unfavorable, I suspect. ]
[Question] [ The world's fertility rate has fallen to about 2.4, and in the next few years may reach replacement levels (2.1) outside of Sub-Saharan Africa (where it's still 4-5, though falling quickly). Even some of the most conservative of wealthy societies, like American Mormons or Gulf-monarchy Arabs or the traditional (but not Orthodox) section of Israeli Jews, are approaching or have already reached replacement levels. Many countries, whether high-income or medium-income, now have fertility rates close to 1. And apart from Israel, where the fertility rate is 3 (mainly due to Arab-Israeli and especially Orthodox Jewish populations), no high-income country has a fertility rate above about 2. My question is, if we imagine there is a country - or a whole world of countries - that is far wealthier than any country that currently exists, in which adults have huge amounts of free time, money, large homes, incredible access to childcare, advanced medical science related to fertility, and the expectation of a long and mostly healthy lifespan, what might become the fertility rate of such a place? And what would the implications of this be - Malthusian? [Answer] The overwhelming evidence we have from around our world is that when women get access to better education, careers and health care, their fertility rates drop dramatically. In the US, for instance, the fertility rate is 4.1 for first-generation immigrants but 1.8 for the rest of the population. Simply put, when women grow up with other choices, the vast majority choose not to have many (or any) kids. So, in your world, unless you have some significant factor to counteract this (e.g. a misogynist religion) or a high level of immigration (from where?), expect your advanced society to quickly collapse and be replaced with a more primitive one having a much higher fertility rate. [Answer] So far as history has shown increasing income leads to decreasing birth rates. So far population have continue to decrease but it is possible that once incoming reach a certain level they population will even out. Or not it hard to see. Also consider your population tec level and life expectancy. If the technology is high enough it is they can make there own population. [Answer] The more money a woman makes, the more likely it is that she is gonna be picky about the partner she chooses to mate and have children with. 300 years ago it was normal for women to marry literally the first guy that they had a chance with, and have children as soon as possible to have a sustainance. as the culture of Madames and women's rights developed and women entered the business side of the world, birth rates have plumbed to an all time record low. if you want feritility levels to raise, make men richer than women, if you want fertility to go down then make women richer or as rich as men. Also another factor to take into consideration is competition, 75% of suicide victims are men, because the competition in the romance market as well as the business and education market is too high, it is noramal for mammals to be naturally lazy and choose death instead of wasting energy competiting in a game with low success rates. suicide rates are very important to the overall mood of the country and the fertility rate. In japan they have hikikomoris, in america they have basement dwellers and in china they have low layers. Those are men who gave up on reproduction and will never have children, in those countries, percentage of male virginity is raising every year, as well as male infedility cause all the women will have a smaller pool of men to choose from and will have to share or fight for the same men. like Other common things in dying societies are: -Women hating men and priding in not needing one and the fact that men are useless and holding the belief that women are opressed by society -Men hating women and priding in not needing one and the fact that women are useless and holding the belief that men are opressed by society -Prostitution at an all times high [Answer] An exponential series grows in the limit at the speed of its fastest growing component. What does that have to do with birthrates? Well, imagine a world where there is a wide distribution of birth rates, from 0 to say 10 per woman. After the first generation, those who have 0 children vanish, while those who have 10 children have expanded their % of the population 10-fold. Now, assuming there is some degree of inheritance (cultural/religious or biological) of the propensity towards large families (and there surely is), a fraction of the 10 children will also have large, perhaps 10 children families of their own. Assuming (absurdly) that everything else is stable, the 10-child families will come to dominate, within a number of generations dictated by their prevalence within the initial population. Even if some of their children have lower fertility, the overwhelming majority of humans born in the n-th generation will come from 10-child families. Note that the number 10 is picked just for illustration purposes. 5 children/woman would do the same, just take longer to do so. The only real physical limitations assuming a post-scarcity utopia are the gestational period and the health effects of spacing pregnancies too closely, and the availability of childcare. And you can easily see that the number could be a lot higher if we allow for artificial wombs, and could be orders of magnitude higher if progress in artificial general intelligence allows us to have artificial childcare. [Answer] Not that sanity is my specialty, but the only sane and non-destructive reasons I can think of for this is to either recover from a massive population loss (the Gerbil Apocalypse of 2134 wipes out anywhere between 21% to 93% of Earth's humans in 98% of all sampled parallel timelines) or to colonize a new world. Currently in this timeline, the nation of Niger has a fertility rate just under 7. This is the current record and is about where the USA was in 1800. Let's use that as our base point and see where we can push it. For a simple start, I'm mostly focusing on plain vanilla traditional reproductive methods for plain vanilla couples, but other options will also be considered. The original question was for people with plenty of money, but as many have pointed out, wealth alone is a very effective fertility suppressant. Instead, our optimal population explosion society needs to be post scarcity. Good tasting healthy food leads to better pregnancy outcomes. Having to work for food is a distraction. Good shelter also needs to be readily and easily available to keep parents and children safe and warm. So, we're going to need automated food production as well as either automated housing construction or super easy DIY house and expansion room kits. This alone won't make the average happy couple have 7 children. We need to add servants. Since we're in a post scarcity attempt at utopia, robotic servants are the logical choice. Forms may vary, but certain functions are critical. We need doc bots to make sure all goes as well as possible with pregnancies. We need nanny bots to take care of the upcoming tidal wave of children. We need house cleaning bots to pick up after all these kids. We'll need teacher bots to tame, I mean educate all these children. We'll need psychiatrist bots (probably doubling as bartender bots) to help the parents to not completely lose it too. All of the above makes having a lot of children less of a burden, but we still need more motivation. Our parents must be educated (brainwashed) to understand that increasing the population is an important duty for all members of this society. Their children need to also be taught this attitude. The success of this psychological conditioning is critical. Even a post scarcity society has social status and other rewards. Those who produce more children are rewarded. Those who fail (at least by choice) will be stigmatized. I think this would be enough to get fertility to 7. To go higher: Aim for multiple births. Fertility drugs is one choice. Implanting 3 or 4 embryos for every IVF attempt should get increase the odds too. With some surgery a hormone therapy, it may be possible to emplant embryos in males. Large scale studies would be needed to look for possible side effects in children gestated this way. Possible effects on a male body from one or many pregnancies are currently unknown. Nursing babies may be a wonderful thing, but does temporarily reduce the mothers chances of conceiving another child. If nursing is permitted, limit it to 3 months at most. Healthy women in developed countries remain fertile longer than those in the past or in less developed countries. Anything that can be done to add a few more fertile years adds more potential for racking up the baby count. Human choice would still be involved to some degree, but I belive under these conditions, average fertility could easily exceed 10 babies per couple. If this population boom is a planned event and all other priorities are rescinded, shift the male/female ratio (can be pushed a little by sperm separation techniques, can be pushed as far as you want via selecting which embryos to implant for IVF). If we only have an average of 4 babies per woman, we can jump from 10 adults producing 35 total babies (7 per couple) to 63 total babies by replacing 4 of the 5 males with females. If we can completely dump males, the total would be 70 babies. But there is one more option tha ends all limits. With a reasonable starting number of embryos (or eggs and sperm), some sort of safe and effective artificial wombs would free women in a situation like this from the unenviable role of baby factories. In this scenario, the potential limiting factors would be the number of artificial wombs, the production of factories for food, housing, and servant robots, and just how many dozen (hundred? thousand?!?) children running around per adult human would be acceptable. ]
[Question] [ On a planet like the earth with its same gravity and ecosystem what is the biggest a boney sea creature could get both in terms of size and weight. I don't mean biologically but literally, since this creature would be fed by humans not going out to hunt by itself. [Answer] I will honestly say that the limiting factor here is not a skeletal frame, but the size of the sea that they live in, that sea's ability to handle a huge output of feces, and the availability of food. Many or most creatures in the sea have figured out neutral buoyancy. Once that is established, if you creature doesn't have to move, then it can be merely a blob of flesh with a vestigial skeleton doing no other function than protecting a brain, or operating a jaw. The creature doesn't have to hunt, so it doesn't require mobility at all. What you will have is an enormous jellyfish with a few bones. There can be an argument that respiration can be a limiting factor if there is a central gill/lung organ center, but your creature did not put this limitation. Oxygen must be able to reach every cell in the body, even if it is miles away. That won't be practical without multiple sources of air/water (whichever it breathes). A central heart should be able to pump the whole system eventually no matter how many miles of veins they have to go through, but the blood must have oxygen when it gets to the cells far away from the heart. Multiple hearts are also an option. So, as I said, the circulation system has to be able to replenish oxygen many times along its path through the circulation system. This same limitation applies to sustinance, so your organism will need many "mouths" and stomachs to keep the blood nutrient-rich. There is an animal which already fits this description: a sponge. It breathes and eats through thousands of pores, all supported on an amorphous skeleton. It doesn't have or need muscles or mobility either, the sea brings food to it. It doesn't have or need a nervous system, but there's it should be possible for your creature to support one. So, your question really is; how large can a sponge physically get? I don't know that there is a limit as long as the sea can feed it, provide oxygen, and remove waste. Lymph, antibody, and other hormonal systems will also need to be duplicated in order for natural biological functions to operate very far from the organism's center. Heat dissipation would limit most terrestrial animals however if the creature had a natural endothermic process within its body metabolic heat can be reduced to a waste chemical and carried away in feces, where likely some other symbiotic organism consumes it and returns it to food. Based on a comment below, this deserves an example. As suggested by IndigoFenix, there will need to be a fractal-like division of conduits for resources beginning with larger cavers, then propagating down to smaller pores. Here is why: Assume your animal carries away heat by the common water + ammonium nitrate reaction we all know from medical cold packs. The animal will naturally produce ammonia, and through respiration it will oxidize this ammonia into nitric acid HNO$\ \_3$, which will then be neutralized again with more ammonia: $$\ NH\_3 (g) + HNO\_3 (aq) \to NH\_4 HNO\_3 (s) + 145.1 kJ \text{ energy.}$$ This heat energy must be near a place where it can be carried away, close to the dermis. So the larger pores—or caves—will be heated, and must be in an environment which favors heat removal by winds or ocean currents, or their human host. Possibly the human society uses this natural heat source in some symbiotic way, to run engines? But as you see this creates ammonium nitrate, which can now be carried through the system into the animal's core body, or wherever heat removal needs to happen. Ammonium nitrate is combined with water to remove internal heat through the reaction $$\ NH\_{4}NO\_{3}(s) \stackrel{H\_{2}O(l)}\longrightarrow NH\_{4}^{+} + NO\_{3}^{-} $$ This reaction is endothermic and absorbs heat in the production of a solution of ammonium and nitric acid in water, called the energy of solution.: $$ \Delta\textbf{H}\_{\text{sol}}=\sum\_{}^{}\text{(products)}-\sum\text{(reactants)}$$ The heat it absorbs however is less than the heat generated by forming the products, because we look to a table and find the Enthalpy of Formation of our reactants and products, then do the math: $$\ \begin{array}{\|c\|c\|} \hline \textbf{Compound} & {\Delta\textbf{H°}\_{\text{f}}} \\ \hline \text{NH}\_4^+ & -132.8 \text{ kJ/mol} \\ \hline \text{NH}\_4\text{NO}\_3 & -365.1 \text{ kJ/mol} \\ \hline \text{NO}\_3^- & -206.6 \text{ kJ/mol} \\ \hline \end{array} $$ So $\text{-132.8 + (-206.6) - (-365.1) = 25.7 kJ/mol} $. Life metabolic processes ultimately produce a net positive heat, but it is very possible to generate the heat near the body surface, carry the products to another area, and remove heat somewhere else. This accomplishes the thermal regulation brought up in another post. As to weight, the creature would need to be near neutral buoyancy so its mass will equal the mass of the water it displaces. Structural support by the skeleton is almost irrelevant. Whatever the weight of that mass of water is, is the weight of your creature. Consider this: your creature could have its heat-producing reactions primarily happening near the arctic and antarctic sea, then carry the ammonium nitrate thousands of miles away to the tropics, where the endothermic reaction takes place. A single organism could be manipulating global climate this way. There is no logical reason it could not. Almost all life has some sort of symbiotic relationship, and this creature will likely need many. For example, a cow can not digest its main food source, grass. It is a rumnant, and it would die without the bacteria and other organisms living inside its rumen. The reason cows and other ruminants are constantly "chewing their cud" is because they are actually processing their grass back-and-forth between their mouth and stomach. It's an amazing and complex process that requires the animal to be specially designed so it can help the bacteria which break down the green plants for it. All the amazing details on rumination can be studied in simple terms [at the US FDA here](https://www.fda.gov/animal-veterinary/animal-health-literacy/how-cows-eat-grass#:%7E:text=Cows%20are%20known%20as%20%E2%80%9Cruminants,stomach%20is%20called%20the%20rumen.&text=This%20process%20of%20swallowing%2C%20%E2%80%9Cun,more%20completely%2C%20which%20improves%20digestion.). It is very easy to see a human population having a symbiotic relationship with this living sea as well, because it has an explosive and fertilizer in its thermal regulation system. Controlled harvesting of this would greatly benefit any agricultural society. ]
[Question] [ On Earth (or another planet with an identical atmosphere), how high above sea level would a mountain have to rise so that its summit would no longer have any snow on it, not even temporary? The highest "typical" clouds on Earth are the cirrus clouds around 40,000 ft altitude, but the tops of Cumulonimbus clouds can get higher than 55,000 ft above the equator. But even above 60,000 ft there still occur clouds called [polar stratospheric clouds](https://en.wikipedia.org/wiki/Polar_stratospheric_cloud) and then there are [noctilucent clouds](https://en.wikipedia.org/wiki/Noctilucent_cloud) which can be as high as 53 miles - in outer space! Since these are made of ice crystals, could even those deposit on a mountain that is say 60,000 ft in elevation? So actually I don't ask on snow only, but on frost and ice as well. How high would a mountain have to be so that its summit would be bare rock (regardless of whether such mountain is physically possible to persist in the first place)? [Answer] The amount of ice in noctilucent clouds, or even cumulonimbus heads or typical cirrus, would take many centuries to deposit any depth on a peak above 50,000 feet -- and what you'd get wouldn't be "snow" so much as hoarfrost. Beyond that, direct sunlight would lead to rapid sublimation of deposited ice where it can reach, so you'd get significant deposits only in "cold trap" formations -- cracks in the rock that are (almost) permanently sheltered from direct sunlight. For amusement, look up the annual snowfall in central Antarctica, near the pole -- and then realize this is land only a thousand meters or so above sea level. Now imagine how much less precipitation you'd get when the temperature is 15-20 °C cooler, never varies by more than a couple degrees, and the humidity is effectively zero 99% of the time. If you specify "never" having even temporary snow, you'd need conditions in which any kind of deposit is impossible -- and mountains can't get that high on a planet the size of Earth (our gravity is high enough to prevent an Olympus Mons). Mountains can, in theory, reach 60,000 feet, which is high enough to be beyond any known phenomenon that can deposit ice on Earth (same would not be true with the kind of "atmosphere" the Moon has, BTW). Hawaii, measured from the deep ocean floor, is more than 33,000 feet to the peak of Mauna Kea (almost 14,000 above sea level), and there's no physical reason it couldn't be a bit higher -- but mountains that high form as "shield volcanoes", many times as wide as they are tall, not as towers taller than their width. This is partly due to the mechanics of vulcanism, and partly due to the compressive strength and weight of basaltic magmas. ]
[Question] [ From what I’ve researched, Saturn’s moon Titan is believed to have a methane cycle throughout its seasons. Particularly, during the winter season, methane rain falls, filling Titan’s lakes and rivers. However, between low wind speeds and gravity, the storms generally seem relatively tame, assuming one is already equipped against Titan’s cold and darkness. Could these rainstorms be powerful or unexpected enough to directly threaten a base of astronauts living on Titan? Could Titan’s lakes rise fast enough to catch someone off guard or swamp a campsite? I know there’s still very much we don’t know about Titan, but I was thinking of a monsoon/flash flooding scenario and do not know if that is vaguely realistic. If it helps, assume the resident humans are somehow hopelessly ignorant of Titan’s weather. [Answer] > > Could these rainstorms be powerful or unexpected enough to directly threaten a base of astronauts living on Titan? > > > Sure. On Earth we are used to expect certain weather because today we have a large network of observatories monitoring it and in the past we had a large collective memory of empirical observations helping us forecasting the local weather. Of course both of these will be missing on Titan upon arrival and will take time to build up. Apart from "common sense" advice, like not setting a camp in the bottom of what looks like a flow valley, colonist on Titan will be blissfully ignorant and at the mercy of the elements, and almost by definition the weather will be unexpected. To further increase the danger, we are not talking about liquid water, in which more or less we can manage or fight to float, but liquid methane, which is a tad colder and therefore more dangerous. [Answer] 1. Base is built in a [wadi](https://en.wikipedia.org/wiki/Wadi). [![wadi](https://i.stack.imgur.com/jWa3zm.jpg)](https://i.stack.imgur.com/jWa3zm.jpg) [source](https://inandaroundjerusalem.com/the_judean_desert_the_dead_sea_and_the_jordan_valley_-_introduction_summary_of_hikes_and_attractions/nahal_og) It is a great place for a base because the natural walls can help take some of the pressure for the pressurized interior of the base. 2. Wadi floods! It is scary! The methane rolls down the wadi. It covers the base. It could have been predicted but the builders were planetary scientists and did not recognize what the wadi was. 3. Base freezes under the methane. Built things act as a dam. The methane pools up in the wadi and freezes. The base is underneath. But it is no big thing to tunnel up to the surface. 4. Base frozen under the methane turns out to be better than it was. The methane is not very heavy. The base was already overbuilt and can easily withstand the weight. Having the base "underground" turns out to have advantages later in the story when new unexpected challenges turn up. Engineers who did not recognize they were building in a wadi and were castigated earlier in the story now strut around, taking credit. [Answer] If they are foolish enough to establish their base on danger zones. Now, water or any other liquid will flow to the line of the lowest resistance and signs of previous floods should exist. Even if they are not, common sense should tell them the main habitat should be on the upper ground. Be it only they'll appreciate a good comms reception, which is always better with direct line of sight. (no, I don't believe they'll carry solar panels to Titan, too much weight for too little reward, so sunlight exposure is not an issue). This being said (by [L.Dutch too](https://worldbuilding.stackexchange.com/a/217530/26061)), there are some circumstances that put the risk of danger from Titan's methane flooding at a lower one than Earth's water. * the density of liquid methane is 2/3s of that of water (0.657 kg/m³ more precisely) * the Titan's 0.138 g This two mean that the energy of a methanefall will have just 9% of the energy (per volume) of a waterfall from the same height on Earth. --- When you are out in the open, if you're skilled enough on hop-running (kangaroo style), you may get out of the way of a flash flooding (or even race in front of it in the same direction without getting caught. I don't know for sure, I should check what height is required for the methane to flood from to get to the speed a human can attain in low-g). Even more, jumping or climbing on higher ground should be less of a problem for the capabilities of an average human (assuming they didn't stay on couch-potato position long enough for the muscular atrophy to set in). --- Now, concerning silt, mud or rocks that a flash flood tends to dislocate on Earth and try to pile on you. One of the [NASA pages](https://solarsystem.nasa.gov/moons/saturn-moons/titan/in-depth/) informs that the liquid water is lava, the dunes are made of solid hydrocarbon (with a coffee ground like size), and the tectonic plates are likely made of water ice. All of those hydrocarbons are less dense than water, so if you survive under a 3m snow set on top of you by an avalanche on Earth, you should be able to survive uncrushed under... say hydrocarbons with 0.8 density of water at 0.138g... with about 27 meters of typical Titanian solids on top of you and you will be in a risky-but-maybe-survivable situation (assuming you have enough air to breath and the thick coat your using to fend off the -180C worth its money) --- Falling into a liquid methane pool? Maybe we got you covered (that is, if you don't take a plunge covered with just your swimsuit) Most of the hydrocarbons (liquid methane included) are non-polar and hydrophobic. Which means that a 100% cotton towel you always carry a towel is space, don't you? will likely not get liquid-methane-wet (awww, no fooling around with wet T-shirt contests or the like in college). Now, don't take the thing with the cotton towel literally, but... I'm pretty sure one can micro/nano structure the surface of the suit for outside activities in such a way that, with minimal heating across (BTW, the latent heat of evaporation for liquid methane is 8.17kJ/kM which is only 20% of water's) will create a layer of gaseous methane trapped into a the nanostructure and keeping the liquid methane away from your suit - such nanostructures [can stay dry](https://youtu.be/GcdB5bFwio4?t=226) underwater [for days](https://news.northwestern.edu/stories/2015/08/staying-dry-underwater/) on Earth, I'm pretty sure the same trick can be pulled for liquid methane too. That should take care of your survival would you be to fall into a liquid methane pool or have it dumped on you by a flash flooding. [Answer] I suspect that it's not that likely but is possible. For a story it should be easily possible to suspend disbelief. To increase the believability I would have a large more distant lake over top with methane. Assuming the methane can erode some of the sediment it should be possible to imagine a catastrophic failure moving a lot of methane like this: <https://www.youtube.com/watch?v=BNFQ1EJX4h0> Not going to be as rapid or as dramatic but could still be deadly. ]
[Question] [ So I've ran into a bit of an issue. Not knowing much about geology, I thought that I could get away with making a planet with 150% Earth radius with it still having a geology identical to that of Earth and 9.8 m/s gravity. I was wrong, to say the least. After having done a bit of research, I came across [this question](https://worldbuilding.stackexchange.com/questions/213516/consequences-of-a-super-light-super-earth) which made me realize how much more alien a simple increase in radius can make my terrestrial planet. Diamond sand? Cool. Possibility of no tectonic plates and no ores in the crust? Not so cool. As a compromise I tried doing a bit more math and got the following figures : Planet : 150% Earth radius, 280% Earth mass, 11.54 m/s gravity, 14.868 km/s escape velocity, 4.315 g/cm3 density, 2.25 AU orbit, atmosphere same as Earth Star : 506% Sun luminosity, 134% Sun diameter Taking this into account, what would I need to change about my planet in order for it to: * Have tectonic plates * Have a magnetic field capable of protecting the atmosphere * Not have a gravity higher than 13 m/s * Not have a radius lower than 140% that of Earth And in the end would... 1. The landscape be flatter, the same as on Earth, or with taller mountains? 2. The oceans be shallow and flat or like on Earth? 3. Would tectonic plates act different in any meaningful way? This is a part that confused me a bit as the two answers to the question I linked were a bit contradictory in that regard. EDIT: Clarified my question a bit. [Answer] Ok, make the core of the plant a little hotter, say by 500K, to make sure : * the outer core thick-ish and mobile and generating a strong enough magnetic field and the inner core still small * the mantle is fluid enough to allow some dynamics * the crust stays around 20-25km on the continental side 1.5R means 2.25 larger surface to radiate inner heat, so lets make sure we have enough of it to start with Last two bullets should ensure you still have tectonics without running-amok vulcanism. --- For a good measure, place an order for asteroids with everything Earth has in terms of the concentration of surface available elements and primary substances after the crust was formed - me thinks you'll need a wee more than twice the amount that Earth used. Water is important enough for the fluidity of the mantle and to encourage the subduction by providing some lubrication, so make sure you order enough of it to have some oceans as a reserve for... ummm... rainy days Also, ask for a surplus of oxygen. Not much, perhaps 5-10% will suffice, you'll see a bit later why. At 10-15% extra gravity: * if you planned well the volatiles, you'll have your atmosphere a bit thinner than Earth's at maybe an slightly increased pressure at sea level, but not enough to mess the radiative absorption/rejection/cooling-at-night-time or to increase the eolian erosion. * the maximum height of the mountains will be lower than the same on Earth, because at equal compressive strength of the rocks, a higher gravity means the rocks will crumble at lower max height. But even Earth doesn't have mountains to the max of allowed by the compressive strength of the rocks, so you can still have a Himalayan range. * besides, with a continental crust about the same as Earth, those mountains (and glaciers) will push the crust about the same depth into the mantle; after all, is a matter of buoyancy, thus independent of gravitational intensity, so pretty much the same [isostasy](https://rwu.pressbooks.pub/webboceanography/chapter/3-2-structure-of-earth/) that you see on Earth --- Ok. now we get to the need of enough magnetic field, even when diluted in a larger volume and the need of a bit extra oxygen. You see, that: > > Star : 506% Sun luminosity, 134% Sun diameter > > > buggered me. While you took the pain to get the same radiance per unit of surface on the planet (at 2.25AU), you needed to pump up the star's radiation power but could not afford to increase its size. As such, the power increased by a factor of 5, but the "reaction" volume increased only by 1.343 = 2.4 and the radiative surface by 1.342 = 1.8. [Stefan-Bolzmann law](https://www.omnicalculator.com/physics/stefan-boltzmann-law) says that the temperature of your star is about 7500k and [Wien's law](https://www.omnicalculator.com/physics/wiens-law) says peak emission happens at 390nm - which is near-UV. Your star is a [F-type main sequence](https://en.wikipedia.org/wiki/F-type_main-sequence_star#Habitability) and the habitability in Terran terms requires UV shielding. One on top of the other, you will need to: * use some oxygen to make ozone and keep it well inside the Van Allen belts * make sure you have enough magnetic field to sustain those belts against the stellar wind * never ever let the sapiens species there use (H)CFC for their refrigeration needs --- With all that, you should have a planet as good as Earth, just a bit larger. ]
[Question] [ The amount of energy required to change the rotational velocity of Venus in any meaningful way is immense. Requiring far more energy than humanity can muster at the present date. But I wonder if we can use the most powerful thing in our solar system, the sun, to affect the Venutian rotation? Can we turn Venus into a radiometer? Would the rotational velocity of Venus change if we shaded half of the planet? Shade the half rotating toward the sun and only allow sunlight to strike the half rotating away from the sun? Would the radiation pressure of the sun on the lighted half help to increase the rotational velocity of the planet? And if so, how long would it take for the rotation to match that of Earth? [Answer] This would be difficult to do, but it's easy to make an order-of-magnitude estimate of how difficult it is. We can estimate the angular acceleration this would produce on Venus by [calculating the radiation pressure](https://en.wikipedia.org/wiki/Radiation_pressure#Pressures_of_absorption_and_reflection) at its orbit, in an ideal scenario: $$P\_{\text{rad}}=\frac{2G\_{\text{SC}}}{c}\left(\frac{r}{\text{AU}}\right)^2\approx1.74\times10^{-5}\text{ Pascals}$$ with $G\_{\text{SC}}$ the solar constant and $r$ the orbital radius of Venus. The force is then $P\_{\text{rad}}$ multiplied by half of the cross-sectional area of Venus: $$F=P\_{\text{rad}}\cdot\frac{\pi}{2}R^2\approx10^9\text{ Newtons}$$ We can estimate the torque applied to Venus by $\tau\approx F\cdot(R/2)$ and calculate the angular acceleration by dividing this by the moment of inertia, giving $$\alpha\approx\frac{\frac{1}{2}FR}{\frac{2}{5}MR^2}\approx4.24\times10^{-23}\text{ radians s}^{-2}$$ Venus currently has a rotation speed of $\omega=3\times10^{-7}\text{ radians s}^{-1}$, so you'd need timescales of $$\Delta t=\frac{\omega}{\alpha}\approx300\text{ million years}$$ to make any significant change. ]
[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/207038/edit). Closed 2 years ago. [Improve this question](/posts/207038/edit) I realise now that this is not the right place to ask this question, but for anyone else who happens to stop by and is looking for a good reference to use to price their animals, I've found a resource that may help you: Dwarf Fortress' animals each have a value called pet value <http://dwarffortresswiki.org/index.php/40d:Pet#Value> which can be used as a good reference for pricing animals To see a specific animal's pet value look for the tamed attributes on the page of the animal in question. You can view all the animals here: <http://dwarffortresswiki.org/index.php/Category:DF2014:Animals> Additionally John left a good link to use for medieval prices: <http://web.archive.org/web/20110628231215/http://www.fordham.edu/halsall/source/medievalprices.html> [Answer] Think like a farmer or hunter. Get started by thinking of the cost of production. How much land do you need to rent for forage? Or how much does the food cost, for how long? (Sometimes you get a choice - you can lock the cow in a pen and feed it, or leave it "free range", with a modest difference in cost) If the animal is wild caught, think of how long it will take to hunt one - which depends on how many people are hunting them. Lobster was once considered a food for the poor, a scavenger that was easily caught. Then demand increased and so did the work needed to catch one. Last but not least, don't forget to price in market distortions. The farmer may not get nearly as much money as the consumer has to pay, depending on how tightly the market and transportation of food is controlled. Farmers as a whole may be chronically in debt, so much of the cash that reaches them may be going to the bank. Chancy distribution could mean that animals are lost or meat spoiled. Additionally, the price could be elevated by monopoly tactics or if the demand for the animal is increasing faster than it can reproduce. If you compare [raising ducks](http://www.suburbanhomesteading.com/raising-ducks-for-meat/barn) to [raising chickens](https://oldclayfarm.com/top-5-broiler-chicken-breeds-for-meat-production/), it becomes clear that in the real world there are many different considerations. You'd need a real farmer to give you reliable specifics, but just look through some of this! The chickens may actually need longer than the ducks to mature, but they can be kept in a smaller space and can be raised for egg production with their meat being only a nice extra. (But why aren't duck eggs comparable...?) The "conversion ratio" may be 2 pounds of feed for a chicken per pound, versus 3 for a duck. All these specifics affect the price. It may be easiest for you to get real world prices for each meat, then alter them according to what is different in your fantasy scenario. ]
[Question] [ Imagine a room where time flows infinitely faster inside of it than outside. If you are in the room, time outside the room is stopped, relative to you. But this room is not airtight. Air molecules inside a room are constantly in motion at velocities in the hundreds of meters per second. From my -- rudimentary -- understanding of particle physics, a problem emerges. When air molecules inside the room exit it, even for a fraction of a second, they slow to a halt due to the time distortion. Pressure can't force them back into the room, because time has stopped outside of the room. That means that air molecules can flow out, but they can't flow back in. I believe that over time, this would cause the room to depressurize to a near vacuum. Is this an accurate assumption? How quickly would this happen, from the point of view of someone inside the room? [Answer] > > That means that air molecules can flow out, but they can't flow back in. I believe that over time, this would cause the room to depressurize to a near vacuum. > > > > > Is this an accurate assumption? > > > I don't think so, not for your average room, but depends on the interface characteristics. This is my take on your scenario... As soon as a molecule exits the "time discontinuity" volume, its speed from the point of view of insiders drops to zero. The molecule is frozen in space, with a virtual temperature of absolute zero (no thermal agitation), and remains locked at its point of entry. Now, this would mean that the whole room is virtually exposed to hard vacuum. And so it is - at the beginning. But at the same time, let's imagine that in the room there is a compressed air tank that keeps pressure constant. Can the air continue flowing outwards? Forever? Obviously not, because it would quickly fill a very thin volume of time-frozen air on the room boundary, and this volume can't contain an infinite quantity of air. Time-freezing also blocks repulsive forces, so the air would be reduced to its covolume. Since liquid air has a density of 0.87, I think we can go with a time-frozen density of about that of water. Once the interface is saturated with time-frozen air, further molecules of air cannot penetrate the interface and bounce back inside the room. Now the crucial element is the thickness of the interface - how far can a molecule travel before being frozen. It cannot be thinner than the width of one molecule, of course, or it would act like an impenetrable wall (no air loss) from the start. If it is, say, one thousandth of a millimeter thick, then each square meter of interface (one million square millimeters) will eventually absorb one liter of air (one million by one thousandth cubic millimeters), and become a sheet of impenetrable time-frozen air. After that, the room will contain one liter of air less than before. A 5 x 4 x 3 = 60 m^3 room will lose (5x4 + (5+4)\3)\2 = 94 liters of air through roof, floor and walls, which is negligible. The air would travel at high speed, supersonic but not much faster, 464 m/s; the effect would be that of a loud "thwock!", and no more. Of course, if the interface is one millimeter deep, then it can absorb one thousand times more air before saturating, which means 94 cubic meters - and the room only holds 60. You would get an explosive decompression (the air loss should be a logarithmic curve, but it would be so steep as to make little difference). ]
[Question] [ My planet has a star that peaks in the violet part of the spectrum. Its atmosphere has a purple-ish hue due to this. My planet has a 40.6° axial tilt, giving it frigid winters and hot summers. Now, the fleshy parts of plants, like leaves, are yellow, since the optimal pigment for absorbing violet light is Xanthophyll, which reflects yellow light. I want the trees on my planet to have blue bark with yellow leaves. What would be the optimal tree bark color on my planet, and is there anyway I could have blue trees? [Answer] If the cellulose (or generically any substance used by the tree for making the bark) happens to be arranged in a periodic way, it might behave like a photonic crystal and therefore selectively reflect certain frequencies of the spectrum. This is why certain feathers or bugs seem to have metallic reflexes. The same can happen for bark, in principle. [Answer] ### So blue wood is really hard to do: * Copper Sulphate is a nice strong blue colour that dyes almost everything - it's also the active ingredient in those "root buster" products you put in your drains to kill tree roots getting into sewers. A literal tree poison * The blue / green wood you can buy at the hardware store is made by mixing Copper Chrome and Arsenic into the wood. These chemicals don't support growth - by design, it's a mould and termite protection. [![enter image description here](https://i.stack.imgur.com/ExNdF.jpg)](https://i.stack.imgur.com/ExNdF.jpg) (The blue is poison) So I see two ideas: 1. The tree is absorbing these chemicals from the ground and is able to do so as a natural form of protection against growth / insects / etc. I think this is a bit of a stretch - these chemicals kill trees as we know them, but these alien trees are not as we know them... 2. Coat the bark with a a creeper / vine like plant that's predominantly blue. Eg some variant of Wisteria blue vine [![enter image description here](https://i.stack.imgur.com/EJ4Ls.png)](https://i.stack.imgur.com/EJ4Ls.png) Or Climbing Hydrangeas: [![enter image description here](https://i.stack.imgur.com/lDk64.jpg)](https://i.stack.imgur.com/lDk64.jpg) ]
[Question] [ I will begin this with a disclaimer that I barely understand the p-adic analysis beyond very general ideas of what the p-adic numbers are and how they are constructed. But this is a question I've been pondering for a while now; is there something special about the real and complex numbers that make them a natural first attempt at creating algebraic closures of integers? Might an alternate chain of human development stumble upon a p-adic field prior to the reals? If this is possible how significant would this be for scientific development? Are the p-adic numbers in anyway better for approaching question in specific disciplines? [Answer] The difference between real and $p$-adic numbers is in how they measure size In the reals, a number becomes big when you add it to itself many times. For instance, $$1 + 1 + 1 + \cdots (\text{many times}) \cdots + 1 = \text{big number}$$ For $p$-adics, a number never grows beyond a fixed size no matter how many times you add it to itself. More importantly, it becomes small if $p$ divides it a lot. For instance (taking $p = 2$), let's call: an even number something like $10$, a "very even number" something like $24$ (i.e. divisible by $8$ rather than just $2$) an "extremely even number" something like $1024$ (divisible by $2^{10}$), and so on. The more even a number is, the smaller it is. So $1024$ is very small. But $1025 = 1024 + 1$ is not that small at all; it has the same size at $1$. So what? Why might a $p$-adic number system be invented? Well, it pinpoints numbers that are highly divisible by $p$. So if you had some alien culture with, say, a religious obsession with a particular prime $p = 7$, then they might have a strong motivation to devise a way to systematically keep track of which integers are divisible by lots and lots of $7$s. This is what the $p$-adic integers do. [Answer] It is quite possible - after all, we (for certain definition of "we") are using other fields. It happens $\mathbb{R}$ seems most intuitive, simple and "natural" to a layman (though it isn't, in fact), so that it is the first stop (as something that has a direct interpretation in geometry). The second stop is $\mathbb{C}$, less intuitive, but still somewhat explainable without heavy math, and very useful in physics. (Then there are vectors and matrices, but usually we do not call them "numbers"). What is however very feasible and somewhat surprising it did not happen on Earth is a widespread adoption of [hyperreals](https://en.wikipedia.org/wiki/Hyperreal_number). They also form a closed field, have almost all the properties of reals, tackle infinitesimals and infinities in a somewhat intuitive way, and make grasping calculus much easier. [Answer] Taking a different approach to the problem, lets posit the question as 'What would our math system be without fractions?' If we had never 'invented' the fraction, the only numbers we would have would be 'counting numbers'. There would be no 'real number system', methinks, because all of the issues with real numbers begins and ends with fractions (decimals are just an extension of fractions). Consider if the entire evolved math system and the concept of 'unity' had been totally different? Would we even have a need for anything past 'counting numbers' and 'integers'? Take for instance the process of taking a 'whole' pizza and divided it up into 8 pieces. Our 'math' creates a concept of a fraction of a whole - each piece is one-eighth of the whole, or 0.125 of the whole. But suppose this concept had never been created or even entertained by humans? Suppose, instead, we stopped at 'there are now eight 'wholes'? Without the concept of fractions, there would be no one-third fractions to become 0.333333333.... and thus no 'real' numbers. Consider the digitization of our accounting system. We have the concept of the 'dollar', and of 'pennies'. One hundred pennies make a dollar. So we use the 'fraction' (decimal) annotation of $3.20 to represent three dollars and twenty pennies. The British, with pounds and shillings and pence, could not ascribe to such notation. Every transaction was done with 'whole numbers' of counting individual pounds, shillings, and pence, not 'fractions of a pound' and 'decimals of a dollar'. Imagine if the concept had ended there? When the computer was invented, and thanks to a road trip to some quaint country-side pub, we use binary instead of decimal as the numerical representation in computer accounting, and the problem with digital notation of money soon became evident. In our accounting systems (spreadsheets and such) decimals - cents - were converted, in the computer circuitry, to bicemals. The problem is, amounts such as 13 cents, or 0.13, created an infinite bicemal when converted to binary. The digital computer could not handle it properly. Rounding occurred. Over thousands of transactions per day, the small differences added up. It is rumored that one bank almost went under, when their 'daily interest' calculations on the computer did not match with daily interest calculations computed manually. The books done manually did not balance with he computer numbers. The balance sheet was out by thousands of dollars. Fraud was suspected. It was a very common problem with early spreadsheets. The solution was to enter $8.13 as 813 pennies, not dollars, and revert back to using only counting numbers, not fractions and decimals. So, imagine a society that had never gotten their heads around fractions (like so many students in the early grades) and used only whole numbers (or, eventually, integers). This society would never have fractions, and thus decimals, and thus real numbers. Consider our concept of time. Sixty seconds form a minute. Each second is a unitary concept, and then we create a new unitary concept 'minute' out of the sum of the parts. But somewhere along the line, humans went in reverse. They thought only of the minute as being the primary unitary concept (instead of a 'bunch' of unitary concepts 'seconds') and created the system of 'A second is 1/60th of a minute'. Given the absolute chaotic confusion this presents when primary school teachers attempt to get it across to their students, it is definitely not a 'natural' concept, but a very 'contrived' concept. Suppose a society had never even conceived of fractions? Suppose they had developed a system of mathematical notation where the 'second' was always considered a 'unitary concept', not a 'fraction of the whole'? And 'one minute 30 seconds' was always referred to as 'one minute thirty seconds', not as 'one and a half minutes'? For division, 7 divided by 3 is 2 with one remainder, and it stops there. No 'one-third remainder'. That last remaining animal is not cut up into 'thirds', it remains a 'whole'. That is, this society wold END at integers, not develop any alternative system of representing fractions. No p-adic necessary. Elementary students would love it. It certainly makes their life easier. But that is the issue. We would not HAVE science as we now know it. Instead of dollars and cents, we might still be using the British system of pounds shillings, and pence. What would our science and math look like? Perhaps this answer could come from children who have never experienced the horror of 'fractions'. Methinks it would be far more based on biology and the environment, rather than physics and engineering. Whatever it looked like, it would be very different from our world. A true 'world-building' exercise. But one thing for sure, pies would always be round, and cake are square. [Answer] Mathematics is the science1 of developing formal models and applying them to get insights into the real world. Some of those models are more useful than others. Consider [euclidean](https://en.wikipedia.org/wiki/Euclidean_geometry) and [non-euclidean](https://en.wikipedia.org/wiki/Non-Euclidean_geometry) geometry. Euclidean geometry is taught in most schools because it is applicable to the real world at human-sized scales. Non-euclidean geometry is taught later, mostly because thinking about in comparison with euclidean geometry teaches thinking about models. When it comes to real numbers, studying them gives insight in some real-world physical processes and also teaches thinking about models. The former is a reason why sufficiently advanced aliens would probably know real numbers. To the core of your question, decades ago I went through the traditional human progression of mathematical education, and it seems natural to progress from integers to real numbers. That could be the bias I picked up from my teachers. --- 1 It isn't exactly like other hard sciences, but close enough for me to apply that label. ]
[Question] [ I'm designing a solar system with three planets in its hot zone, two in its cold zone and three in its habitable zone. All of the planets are rocky worlds of various sizes, except for the middle world of the habitable zone which I'd like to be a gas giant. Our system giant's gravitational forces have a lot of influence over the behaviour of everything orbiting the Sun, keeping everything more or less balanced and reshaping things every once in a while. Would having a single gas giant in such place as the middle of the habitable zone cause too much of an orbital havoc for there to be stability on the system? [Answer] ## It would be fine if you arrange the orbits properly. This system wouldn't necessarily be problematic if you can maintain stability via particular [orbital resonances](https://en.wikipedia.org/wiki/Orbital_resonance). We've discovered numerous compact systems whose stability is believed to be maintained on long timescales in this manner. [Kepler-90](https://en.wikipedia.org/wiki/Kepler-90) is a great example of a compact system kept in place by resonances; it's a roughly 2 billion-year-old Sun-like star that harbors eight planets within $\lesssim1$ AU. The outermost (and most massive) is roughly 2/3 the mass of Jupiter, orbiting right around 1 AU. The system you're proposing is quite similar - presumably just with a gas giant in the middle, not in the edge, and with an increased spacing of planets. You might be concerned by this rearrangement, but note that the gas giant is only $\sim0.3$ AU away from the next planet over. Some models predict that the Sun's habitable zone is $\sim0.5$ AU across, making it quite feasible to have a similar spacing here (though of course spacings much less than $0.3$ AU are still rather stable). L.Dutch cites the asteroid belt as a reason for worrying about stability; I'm not as concerned. The asteroid belt was formed in part due to unstable resonances relative to Jupiter's orbit, rather than stable resonances. The [Kirkwood gaps](https://en.wikipedia.org/wiki/Kirkwood_gap) are one set of notable results. But bear in mind that the presence of an additional gas giant can also lead to stable resonances, as I noted above, and may actually make it easier for compact, stable systems of terrestrial planets to form (see [Hands & Alexander 2016](https://ui.adsabs.harvard.edu/abs/2016MNRAS.456.4121H/abstract)). [Answer] > > Would having a single gas giant in such place as the middle of the habitable zone cause too much of an orbital havoc for there to be stability on the system? > > > Pretty much yes, unless the habitable zone is really extended to that the perturbations induced by the gas giant can be negligible. This is what happened in our solar system in the [asteroid belt](https://en.wikipedia.org/wiki/Asteroid_belt) [![enter image description here](https://i.stack.imgur.com/gVh0d.png)](https://i.stack.imgur.com/gVh0d.png) > > The asteroid belt formed from the primordial solar nebula as a group of planetesimals. Planetesimals are the smaller precursors of the protoplanets. Between Mars and Jupiter, however, gravitational perturbations from Jupiter imbued the protoplanets with too much orbital energy for them to accrete into a planet. Collisions became too violent, and instead of fusing together, the planetesimals and most of the protoplanets shattered. As a result, 99.9% of the asteroid belt's original mass was lost in the first 100 million years of the Solar System's history. Some fragments eventually found their way into the inner Solar System, leading to meteorite impacts with the inner planets. Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter. At these orbital distances, a Kirkwood gap occurs as they are swept into other orbits. > > > Just look at how big is the gap between the orbits of Mars and Jupiter when compared to the gap between the orbits of the inner planets, and compare it with the width of the habitable zone, roughly comprised between Venus and Mars orbits. ]
[Question] [ Okay, let's say that we have a starting population of 7.7 billion, and a brutal, month-long war wipes out 1.3 billion people. 1% of Earth is rendered uninhabitable by the war. This would put carrying capacity at 9.9 billion, and there is an population explosion afterwards. The last time the human population was at 6.4 billion was in 2004, where the growth rate was 1.25%. Let's assume that due to environmental damage, it is in fact closer to 1.2%, which is larger than what it is now (thanks, COVID). With that, I can estimate how long until the population reaches 7.7 billion people again, assuming a fixed rate. 7.7=6.4\1.012^t 1.20=1.012^t log[1.012]1.20=t t=15.5 yrs The real question is, is my 15.5-year estimate for how long it takes for a population-reducing event like the one I described realistic? Why or why not? [Answer] > > is my 13.9-year estimate for how long it takes for a population-reducing event like the one I described realistic? Why or why not? > > > First, it all depends on this statement of yours: `1% of Earth is rendered uninhabitable by the war.`. [71% of earth is water](https://en.wikipedia.org/wiki/Earth), and 29% is surface. [Roughly 57% of surface](http://www.zo.utexas.edu/courses/Thoc/land.html#:%7E:text=The%20total%20land%20surface%20area,billion%20acres%20of%20habitable%20land.) area is uninhabitable, which means you are left with 29%\43% = 12.47% of area as habitable. Even within this area, you will find clusters of populations centered around major cities and major cities around major rivers. Assuming you meant 1% of earth's area, sure, there is already a lot of area that is not habitable, so your rate is achievable. But the moment you meant to subtract 1% out of the 12.47% above, you will find effective habitable area available has decreased by ~8%. If this decrease happened in areas where major cities are located, or major centers of forests are located, you have seriously hurt the economy and the environment respectively, which will make a recovery seem more distant. Second, you are assuming people still want to breed like rabbits after that brutal war. But why should things normalise so soon? Statistically, roughly 1 in 7 persons died. Assuming an [average person knows 150 people](https://en.wikipedia.org/wiki/Dunbar%27s_number), an average person will know 21 people who died during the war. You haven't noted that only males die off in majority so the average sex ratio has been impacted, or any other such hypothesis (which happened during the world wars). So, the psychological effects of such a drastic war will be manifold, and a chunk of people may actually become disinterested from starting families, reinforcing a trend that is already seen in current era. [Answer] Since we are dealing with humans, the likelihood of the survivors losing interest in having sex is very low. On the other hand, after a devastating global war, production capacities and infrastructure necessary to supply contraceptives will be severely impacted. Reproduction generally correlates negatively with economic prosperity, which took a severe hit as well. On the gripping hand, i would expect far larger reproduction rates at least in the first few years after the war, unless ABC weapons impacted fertility, so your number is probably even too high. ]
[Question] [ Inspired by [this answer](https://worldbuilding.stackexchange.com/a/196170/82267) to [this question](https://worldbuilding.stackexchange.com/q/196164/82267). In my setting, there exist magical immortal mutants descended from humans who randomly became "magically active" and transformed into the first member of their own species, growing in number first by mating with humans and then with their own kind once said "own kind" reached critical mass. Several of these races are sea-dwelling, and in the process of working out their history, an interesting question came up. Given that a lot of sea life ideally wants to exist in water shallow enough for plant life to exist on the ocean floor, it makes sense to me that over time, the massively-underwater continent of [Zealandia](https://en.wikipedia.org/wiki/Zealandia) would become highly populated by merfolk and other such creatures. Here's the problem: in the 1800s, when photography started really picking up speed, immortals resolved that they had to let human knowledge of them fade into myth and legend. This was all well and good for the immortal species who could pass for human and could blend into human society. But with the merfolk and other aquatic immortals, owing to the fact that, crucially, humans do not live under the sea, this mandate eventually made it basically impossible for the seafolk to live anywhere that humans would regularly be around, because obviously if humans ever found conclusive proof that anything sentient lived under the ocean, that'd be a huge secrecy breach. Wherever they lived, they'd have to be able to use the assorted magical abilities at their combined disposal to keep humans away from it. So at some point in the past, the Zealandian seafolk destroyed their own underwater civilization and fled for other parts of the world. Some lived around remote seamounts. Some could pretend to be humans as long as they lived near water. Others fled into the unexplored and hostile abysses of the deepest ocean floors. But their ancestral home in Zealandia was no longer inhabitable due to human technology getting too powerful for them to be able to exist without being detected so close to human civilization. What would be the breaking point for this civilization? What would be the earliest technological advancement that would make it impossible, or at least extremely dangerous, for aquatic sentient creatures to live in the waters of Zealandia without themselves or their crude structures being discovered by humans? [Answer] Technologically, it would probably be sonar. Sonar is when humanity really started to look around underwater, rather than just dredge the bottom opportunistically or using sounding ropes to measure depth. Sonar really took off during World War Ii, and the ocean-going technology developed during World War Ii eventually led to things like the Alvin and the discovery of the mid-ocean ridges. Indeed there is a real-life parallel. When people started using sonar they found that the ocean had a "false bottom" that moved based on time of day. It turns our to be sonar scattering from massive densities of mesopelagic fish that no one knew existed. SCUBA, invented about the same time, would also be a huge threat. The first modern SCUBA system, the Aqua-Lung, was developed in 1942-1943. The 1930s was really the period where we stopped looking at the surface of the ocean and started really looking at what was underneath. A lot of the earlier bathyspheres, submarines, and breathing apparatuses were crude and easily avoidable. More broadly though? The Kanaks and the Maori would have noticed they were there, from tools washing onshore if nothing else, I don't know how much either fished in the open seas. The broader world wouldn't have known this given New Zealand and New Caledonia are relatively isolated and don't have extensive contacts with the rest of the world, but once Europeans made contact they would find out pretty shortly. James Cook's expeditions to New Zealand in 1769 and New Caledonia in 1775 would have been the writing on the wall. [Answer] ## Your main problem is that 'Zealandia' disappeared long before humans evolved on Earth Geological records indicate that the 'lost' continent of Zealandia submerged entirely about 23 plus million years ago. Long before there were any primates let alone humans on Earth. The islands of New Zealand then slowly began to emerge shortly after 20 million years ago. But they were still small, isolated, volcanic and vastly separated in distance from where humanity evolved in Africa where no true humans appeared about 200 thousand years ago! And humans didn't reach the vicinity of Zelandia (Australia) until about 40-50 thousand years ago and New Zeland itself 600 years or so ago! By which time 'Zealandia' was about 3000 to 1500 meters underwater! That is not 'shallow'. And even allowing for the fact that mer-people somehow managed to swim there and found a civilization in those shallow??? waters there would simply be nothing for them to build a 'civilization' with except sediment/mud and the occasion loose rock! I mean what are they going to do? Rub two sticks together to make fire? IMO you somehow have to fast forward the evolution of these creatures to a time period and location where humans were present and 'civilized'. ]
[Question] [ ## Setting The full society collapse is starting, and a group of people know it. It may or may not lead to a total extinction event. They can't protect a whole city but a couple of hectares is doable. The group is less than a hundred people. There is no real intent to protect/restore humanity as a whole, at least not until the apocalypse will end. It's a very near future, where reasonable tech advances of today are not experiments anymore, but commercial solutions instead. Fusion is still 20 years in the future, though. ## Premise They capture a fast breeder nuclear power plant which is operating and already manned by the qualified personnel. This type of the power plant is a common one in their timeframe, and watercooled "traditional" ones are slowly being obsoleted. The nation power grid is still functional, refueling happened yesterday and the nearby city is not razed to the ground yet. The nation is a powerful nuclear one, there's plenty of resources to plunder in future. ## Problem * What would be the immediate problems to solve? * What would be the short-term problems to solve? * What would be the long-term problems to solve? * What minimal set of issues should I handwave? Handwave food, aging and dangers to the power plant itself. Assume absolute protection of the facilities. Don't handwave water. Clean drinking water is still important. ## Notes 1. This is different from the [Can Average Joe reboot the nuclear power plant](https://worldbuilding.stackexchange.com/questions/28836/can-average-joe-reboot-the-nuclear-power-plant) and [Running a nuclear power plant in the post-apocalypse: is it possible?](https://worldbuilding.stackexchange.com/questions/185343/running-a-nuclear-power-plant-in-the-post-apocalypse-is-it-possible) because the power plant is already fully functional and manned by the qualified personnel. 2. Judging from the [How useful would a hydroelectric plant be in a post-apocalypse-world](https://worldbuilding.stackexchange.com/questions/149761/how-useful-would-a-hydroelectric-power-plant-be-in-the-post-apocalypse-world) it's doable with the dams. But for several reasons it is not desirable to replace a nuclear plant with a hydro one in the story. 3. Fast breeder reactor in general was chosen to reduce the need in the fuel. I understand that there's a lot of other problems aside from the fuel to think about. :D 4. Thank you. [Answer] Building a breeder reactor is easy, but not a fast breeder Building and operating a breeder reactor on post apocalyptic technology is the easy part. It is almost trivial to build a graphite breeder reactor that uses a thermal neutron spectrum with natural uranium. If you want a fast breeder, however, you need enriched uranium, something that will almost certainly be beyond your post-apocalyptic tech. This reactor would breed fissile plutonium, which could then be reburned in your reactor. Reprocessing the fuel rods into new fuel is the hard part The reprocessing of spent fuel requires enormous industrial infrastructure. The first problem is that you're going to need an industrial-sized hotbox for working with the spent fuel rods. This hotbox needs remote controlled robotics, video cameras, etc., and other technologies that will be difficult to come by in a post apocalyptic world. The even bigger problem is that you will need industrial scale chemical engineering to properly separate out the fuel from the wastes and neutron poisons. Add to this that you can't reprocess the fuel immediately. The irradiated fuel in a breeder reactor fuel cycle often needs to cool for at least 10 years in a spent fuel pool before it can be safely handled and worked with. Even then, it would be immediately lethal to anyone within 10 meters of an uncovered fuel rod, hence the requirement for a strong hotbox. But why though? Ultimately, the breeder reactor concept fell out of favor for one main reason: Uranium is plentiful. It's far cheaper and easier to dig up new uranium and burn that than to try and deal with all the mess of a breeder reactor. The infrastructure required to make new natural uranium fuel is far less complex than what you'd need to process the fuel rods from a breeder reactor. Even reprocessing spent fuel from a non-breeder reactor is more economically feasible. Other options There are a number of exotic reactor designs on the table right now that, at least in theory, are safer and easier to operate than the PWR and BWR designs currently used in the American nuclear reactor fleet. The Liquid-fluoride Thorium Reactor (LFTR) is probably the best design. It's a breeder reactor, is impossible to melt down because its fuel is already molten, can't explode because it doesn't use materials that can produce hydrogen, and works with thorium, which is far more common than uranium. It also can't be driven into a dangerous prompt critical state because it is self-limiting. Such a reactor would be far more likely to be operable by the average apocalypse survivor, but unfortunately it would be far less likely to be maintainable. Much like a breeder reactor, a LFTR reactor requires significant chemical infrastructure to properly filter out fuel from the molten salt. So even though the reactor is so safe and easy to use that someone with barely a high school education could operate it, they wouldn't be able to run it for very long since they'd need a literal chemical processing plant to keep it refueled. ]
[Question] [ This is set in a traditional [Isekai world](https://en.wikipedia.org/wiki/Isekai) with magic, medieval technology, and a feudal system. The protagonist wants to reshape a country to match his values, basically making the nation "good". He wants to improve the lives of slaves until eventually ending slavery, improve workers' wages, decrease corruption, etc. His primary resource is a veritable infinite amount of gold with little else at the outset. What are ways he could gain influence over the country in order to change the culture and laws? 1. Monopolize an industry, then leverage it to influence politicians and those in power. Economically taking over the food supply and threatening famine could be a drastic and powerful measure. 2. Financially support politicians and get them to rely on the main character for that money. Finding ways to decrease their other income and/or buy up their debt could speed this up. What are other creative methods? Would flooding the economy with gold be a way to cause hyperinflation? Could that be leveraged? Could debt schemes work? Could one invest in industries the king directly relies on giving leverage over the crown? [Answer] The protagonist has unlimited gold but needs to parlay it into financial capital, social capital, and political capital in order to effect change at the national level. It might be useful to think of tactics as being split into the carrot and the stick. The carrot (a.k.a. <https://en.wikipedia.org/wiki/Soft_power>) involves encouraging others to have the same goals as the protagonist and is more likely to win allies. This can include: * Indirect (e.g. doing things that make their domains more wealthy or powerful without their knowledge) support to nobles and local leaders who are sympathetic to the protagonist's cause. Unless there's a crisis or other urgent need by the recipient, direct support (e.g. gifts) will correctly be seen as attempting to buy influence and may backfire. * Find other nobles who are neutral to the protagonist and his cause but are enemies of his opponents and provide indirect support to make the neutral powerful enough to take down the opponent. (But bear in mind that nobles support each other; if the neutral later turns against the protagonist, they may find that they solved one problem by creating a bigger one down the road.) * Direct charitable donations or indirect support to religious leaders or religious orders whose ideals are close the protagonist's. Remember that religion is a profound influence in medieval times. Ideally, the religious organizations would openly declare slavery / corruption / etc. to be immoral. Again, beware of the appearance of giving out bribes. * Create deals or ties to the great merchant or banking dynasties and use that influence to carry out their goals. Having infinite gold means that business risk is eliminated, which is an unparalleled advantage. * Supporting organizations or individuals within them (e.g. guilds, chivalric orders, learned societies) who support the protagonist's ideals. If the protagonist can find the right person, they can even create new such organizations who have policies that are pro worker/anti-corruption as part of their charter. * Leading by example. The protagonist can navigate their way into de jure or de facto control over a region and demonstrate to the nobility that their policies lead to increased wealth / productivity from the population. The nobility might not care about morality or ethics but they do care very much about income. * Win influence by doing good works, e.g. creating orphanages, helping the poor, etc. A very common trope in isekai novels. * Providing technological boosts. Already discussed in other comments. * Become the supplier or manufacturer of something that can be provided to the domains of friendly nobles that gives them a military or economic advantage over their rivals. The stick (a.k.a. <https://en.wikipedia.org/wiki/Hard_power>) involves coercion. Direct confrontation is likely to be disastrous as discussed elsewhere but covert options are plentiful such as buying up scarce resources their opponents need, financing sabotage against the domains of hostile nobles or hiring away talented people from them, financing espionage to expose corruption, financing covert attacks on slave trading organizations (no slave traders left alive = no more new slaves), financing propaganda or rumor campaigns to stir up public sentiment against corruption, organizing and financing slave escapes / revolts, etc. Covert means covert; discovery of coercive tactics by the protagonist's allies may turn them against the protagonist. Whichever tactics the protagonist uses, they should not expect this to be cutely bloodless, as it is in isekai novels. Even if they're profiting on corruption, slavery, oppression, etc., a noble house is an extended family and will counterattack swiftly and viciously as a whole if their livelihood or prestige is threatened. All of the tactics above can be equally be used against the protagonists and their allies and they have the advantage of being long-established natives. Some prerequisites also should be borne in mind: * The protagonist must give considerable thought into inserting themselves as a respectable member of society in a way that disguises/protects their source of gold, unless they want to spend the rest of their lives in a dungeon being a goose laying golden eggs for someone else's benefit. They might, for example, be denounced as an agent of a foreign power or even an agent of an evil deity. They cannot count on anonymity; medieval communities are small, the merchant/banking community is smaller, the nobility is even smaller still, and anyone spreading money around in large quantities is going to be remembered. One way they might launder their magically gotten gold is to pretend to be a merchant from a far distant land who negotiates or buys their way into an impoverished merchant house in their target kingdom. * Second, the protagonist needs intel, both through personal observation and a network of people providing reliable information on the state of the world. A traveling merchant may be a way to visit various cities to find out what the culture is like, who's in power, what factions exist, what their views are, what their strengths and weaknesses are, etc. as well as the views of the common folk on their lot in life and the reforms. (Your protagonist may be unpleasantly surprised to find that the commoners don't actually care much about reform on moral grounds unless they themselves have been victims.) As part of the travels, the protagonist will probably want to meet and make friends with other merchants and townsfolk of influence, both to build their intelligence network and future power base. * The protagonist and their allies need protection against direct attack. In isekai novels, this is usually fulfilled by the attacker being ridiculously powerful themselves or being protected by their, ahem, bosom buddies so to speak. Lacking either of these, hiring security / troops is an option for your protagonist but it's worth remembering that they work for a paycheck and therefore have no personal loyalty to the protagonist and won't fight to the death for them or can be bribed away. * In order to have allies to support, the protagonist needs to gain allies in the first place. This will require them to have absurd levels of political acumen and interpersonal skills to both proselytize their cause and determine who will support them and who just wants their gold. tl;dr The protagonist is taking on a rather crummy task that requires them to be ridiculously overpowered, albeit in different ways than usual, and will probably take a lifetime or more to achieve. [Answer] If you monopolize any crucial industry in a medieval era, the king will send his nobles and army, and they will catch you and chop your head off. Particularly food. (And indeed, food is impractical because it's not cost-effective to ship it; the beasts of burden for anywhere not reachable by water eat more than they can carry very quickly. Locally grown food is HARD to monopolize.) But it's still best to work in an industry because what you really need is to improve technology. It is impossible to greatly increase workers' real wages without increasing the goods they can buy with them. There is some leeway -- the Black Death increased wages by removing much of the labor supply -- but the post-Black-Death living standard is probably not high enough for your taste, and also it was wiped out by population increase. Look for basic ways to replace hand labor with mechanical labor. Possibly you have magic automatons? Put them to work grinding grain, running spinning jennies, etc. Or use steam engines. Investigate the early Industrial Revolution and see what you can do. This will also substitute for unskilled labor, making slavery less economically useful To suborn the nobility and royalty, it is best to offer this as improvements THEY can use, though there is the danger that they will want to monopolize it; it was not unknown for people spreading "trade secrets" to be threatened with death. ]
[Question] [ Alright so I have a planet where the locals are about seventeenth century level of technology, meaning sailing ships and single shot black powder weapons are the standard and there is plenty of ocean to sail across. Also, this planet has a very visible ring. Now it is my understanding that navigation on a ringed planet would be slightly easier since it serves as a massive billboard saying “here is the equator” and you can adjust everything accordingly. But I am more curious to learn about the exact mechanics beyond, “here is my compass, that way is north, the ring is behind me so I need a minor coarse correction.” How would something like a sextant be used on a world like this? So, how do you use Age of Sail tools to navigate on the open ocean on a ringed planet? Edit: a lot of people keep suggesting a similar question but this is different, I am interested in the how I already know it’s possible I am interested in the how, please stop suggesting [How to navigate a ringed planet at night?](https://worldbuilding.stackexchange.com/questions/129633/how-to-navigate-a-ringed-planet-at-night) it doesn’t answer the question. [Answer] The ring would assist in navigation at least as much as the stars do. Not only do you have a metaphorical "north/south star" (which would be the apex of the ring), but both the altitude angle and the apparent thickness of the rings would tell you your latitude. The ring would probably be visible both day and night, and even when you can't actually see the ring apex due to cloud cover or the planet's umbra, you could probably estimate the location of the apex just by filling in the gap in the arc. In the case where you happen to have a visible feature in the ring (like maybe a shepherd moon), you could also use a calendar and clock to determine your longitude. In the rare case where that feature happens to be at the exact altitude of geo-stationary orbit, you wouldn't even need to know the date/time. Using a sextant to measure the ring altitude angle or geo-stationary moon would give you a much more accurate measurement of your position, so using a sextant for navigation would be invaluable. [Answer] ## Almost exactly the same as on Earth. All the ring really gives you is the location of the equator (it could conceivably be some other spot; the point is that it's a fixed point). Using a sextant, they can get their latitude from this. While it will be faster (and possibly more accurate) than latitude readings on earth, the technique will be substantially the same. Also, unless the ring happens to have some very visible "landmarks", it won't be useful for calculating longitude; they'll still need quadrants, sextants, and [some very good clocks.](https://en.wikipedia.org/wiki/Longitude_by_chronometer) ]
[Question] [ Would it be at all possible for a creature to generate or store water and expel it with enough force to repel enemies or hunt? I know there are already fish that do it (archer-fish) but I'm looking for a possibility of a creature that lives on land and can shoot water that it stores/generates hard enough to repel a large creature such as a bear or lion or uses it accurately to hunt large prey like deer or similar. [Answer] The bombardier beetle may be a good place to start for concepts. Wikipedia article [Here](https://en.wikipedia.org/wiki/Bombardier_beetle) The beetle generates two liquids that when combined reach a high temperature and is mainly used for defense. Scale it up, and it would be a formidable creature. [Answer] # Unlikely Injury (in combat, whether for defense or hunting) is a matter of delivering energy. A stream of water is not a particularly efficient mechanism for doing this. Air resistance to a stream of water is extreme (as the outer layers of the stream ablate off), and scales non-linearly with the velocity of the water. Moreover, whatever tissue is used to focus the stream must be capable of withstanding the pressure and erosion involved with expelling the water. Generally, parts of animals used to expel water (mouths, urinary tracts) have mucous membranes to protect against damage, but the greater the force required, the greater the damage to the creature expelling it. Water is also heavy. Carrying or propelling water uses an enormous amount of energy, and is generally only beneficial when the water is meant for the survival of the carrying creature, not if it is intended to be used. The archerfish's use of water as a weapon is simplified by the fact that it doesn't have to bring it along to wherever it intends to use it. So, with `reality-check` as a tag, I would say that it's hard to envision any scenario where such a defense/hunting mechanism would be an evolutionary advantage that outweighs its obvious and immediate drawbacks. Without `reality-check`, hunting still seems wildly unlikely (you'd be expending a lot of a valuable resource without any assurance of gaining it back) but there are a number of creatures that use similar approaches as defense mechanisms: * As mentioned above, the bombardier beetle uses a two-chemical exothermic defense * The [horned lizard](http://www.bbc.com/earth/story/20151105-if-it-has-to-a-horned-lizard-can-shoot-blood-from-its-eyes) shoots bad-tasting blood from its eyes into its predators' mouths (though specifically canids). * Skunks, famously. * [Lots of creatures pee as a defense](https://www.burkemuseum.org/collections-and-research/biology/herpetology/all-about-amphibians/frog-myths). This can startle a predator, and often smells bad, which can cause enough hesitation for the prey to escape. This generally isn't pure water, and depends on chemicals added by the creature's biology to make it an effective defense, but the groundwork is there. ]
[Question] [ I am creating a Space opera which involves highly advanced civilizations spreading throughout the universe to build the largest empires that they can. Dense supercluster nodes are areas which the most advanced flock to as these are the richest areas for matter and energy, and as these areas draw in surrounding galaxies less energy will be need to be spent to travel to and build empires and technology like Dyson swarms and other megastructures to manipulate the available energy. My story is fairly Hard-science and has no FTL but the advanced civilizations have gained immortality through various technological methods, so taking a very long trip to distant areas of space is not an issue. I have studied maps of supercluster arrangements extensively as well as trying to look for a pattern, due to our galaxy being the centre of most of these maps it seems like all matter forms in planes that meet in the centre which is our location but this just on the local scale. I stumbled across some maps which placed all the superclusters onto the nodes and edges of an octahedral pattern, with the voids being the volume of the octahedrons. This theory is known as the "Egg-carton" or Octahedral universe theory and I when compared to every large scale map of the universe it seems quite correct. [![enter image description here](https://i.stack.imgur.com/30cZI.gif)](https://i.stack.imgur.com/30cZI.gif) [![enter image description here](https://i.stack.imgur.com/HRcW0.jpg)](https://i.stack.imgur.com/HRcW0.jpg) [![enter image description here](https://i.stack.imgur.com/pv3IB.gif)](https://i.stack.imgur.com/pv3IB.gif) I dont wish to question this theory but I will accept it for my story and maps in my story but now my civilization has that information what can they do with it? I am asking for only hints and tips, maybe ideas present in other science fiction stories or lesser known and currently unaccepted theories. Knowing these diagonal paths of matter run through the observable universe could be used as paths for ships equipped with an ion scoop like a Bussard ramjet, flying down the filaments with an endless supply fuel but there are more efficient methods of travel in a no FTL universe which could reach higher speeds, so this idea is not really that useful I am not after a major part of my story to be written for me but any hints or tips, or even completely wild ideas are welcome to help me think of a way to use this Octahedral structure of the universe as a benefit to the advanced species in my story. Thank you. Bounty edits: As I have put this up as a bounty with authoritative reference I would prefer theories that can be backed up with maths on ways to manipulate or find a purpose for this structure but I will keep the rest of my question un edited for any answers that cannot be backed with maths. [Answer] ### Hub-spoke model for transit / trade / data The vertices of the touching octahedra are natural [transport hubs](https://en.wikipedia.org/wiki/Spoke%E2%80%93hub_distribution_paradigm), these allow for the more efficient distribution of resources around the universe. This assumes that there are things manufactured on one side of the universe that can't be made on the other. If this is false, then these hubs are for travellers, or for data. (Or travellers digitised and sent as data.) If the same molecules are available universe-wide and everything is made locally than cross-universe trade will be mostly IP, and the trade of IP will need communication hubs. As will banking and government functions. ### The octahedral structure stops the universe expanding. This is a bit out of left field, but if those galaxies are exhibiting forces (eg gravity) on each other, along the faces of a space filling tessellation of octahedra, that will be a 3D space filling of surfaces of equilateral triangles - the strongest polygon. With a slight modification of your diagram the universe can be filled with 60 degree angle triangles. There is a [tessellation of octahedra and tetrahedra](https://en.wikipedia.org/wiki/Octahedron#Tetrahedral_Truss) known for its strength and is "commonly regarded as the strongest structure for resisting cantilever stresses.". Why does the universe need a rigid, strong, structure? To stop it from stretching and ripping itself to pieces. [Answer] ## The Octahedral Universe lets Your Immortals Predict the Future If you are avoiding FTL travel, travel between galaxies takes serious time - even at significant fractions of the speed of light, you might spend 100s of millions of years getting to nearby galaxies. Civilizations - entire ecosystems - will rise and fall in that time. Visit the same solar system twice, with a trip to a different galaxy in between, and you may discover that the previously habitable planets are barren wastelands, and perhaps, if you are lucky, previously barren planets might support life. I'd argue that an Empire on this scale is utterly impossible, even for immortals. Central government hinges on the ability to enforce laws, and if you have 500 million years to avoid the consequences of rebellion, then rebellion is inevitable. Instead, your immortals travel through other beings' petty fiefdoms. They arrive with the force and knowledge that they have gained during their incredibly long lifetimes, and bargain for - or demand - the resources they need before moving on. Their fleets are feared and respected, for while they may lay waste to a system, they may also trade incredible technology for the material that they need. To the lesser species, they are like capricious gods, unknown and unknowable. ## Why Prediction Matters As the immortals travel through the vastness of space, they need to find the civilizations they want to interact with. With an endless procession of years ahead of them, your immortals will value the artistic, seeking new experiences and new treasures to admire. They will want to find new peoples. Knowing that the superclusters are the densest collections of matter and energy in space, they will know that they are most likely to discover new species and new civilizations if they travel to these locations. They can listen for radio signals from their intended destinations, and try to predict where on the development curve a given civilization is, and if the species will still exist when they arrive. Basically, the value of understanding the Octahedral Universe is it tells you where to look. Search here for new civilizations. Make your predictions based on travel time, and what you can scry across the vast, blackness of space. EDIT In response to some of the comments: The Immortals will never attempt to visit humanity, for example, from a different galaxy. By the time knowledge of humanity travels to a different galaxy at sub-light speeds, chances are the human race will no longer exist. Rather, the Immortals will look at the galaxies closest to the one they are in, and do a statistical analysis. They will know the state of stellar evolution, and have a rough idea of the resources available. They might know roughly how many space faring species existed in the galaxy several hundred million years ago, if one of their kin had reported back recently. They will try to predict how many intelligent species might exist in the galaxy by the time they arrive, based on all this past history. If the galaxy is a member of a supercluster will be an important factor, because it means there is an increased density of matter, energy, and (presumably) intelligent beings. This will be a very valuable piece of data in their analysis. Since all hard data about the destination is hundreds of millions of years out of date, educated guesses are all the Immortals. Models of civilization evolution will have to account for the presence of a supercluster. [Answer] I will focus on the travel part; I have more ideas on this :). It should be enough generic to work even if suddenly FTL travel is made possible, up to a certain speed/acceleration for some points though. ## Makes traveling between far away stars easier Having this kind of star structure will make travels much easier; Indeed, if you have linked stars in a straight line, then you need a lot less to pinpoint the exact angle to reach your destination. This difference is a bit like comparing polar coordinate systems to cartesian ones, and in fact you may even be able to pinpoint a general X, Y and Z to each octahedron vertice. Travel to these 3 coordinates, then focus again on the star you wish to reach as you get near enough to calculate the trajectory and slightly deviate towards it. It also simplifies signalisation, you have less point-to-point destinations, so you will mainly detect close-ranged colonies, or destinations to up to 8 vertices. This reduces efforts in maintaining a map of the galaxy, and helps in understanding it, too :). ## It creates star highways Moreover, star ship roads will be more focused than a pseudo-random or spheric configurations. Indeed, space stations and colonies will be along the lines, and since trade flows form between them, they will naturally shape fewer, big lines. If you notice you will lack crackers to supplement your moon cheese for your trip, you will know that there will be a starway K-class station to refuel and restock on them along the road. The main differences to car highways are that it's not exactly on the side of the road and you need to decelerate a long time to reach the relay without crashing into it... Unless! Unless it is moving along the same line you are traveling, just slightly slower so you can reach it. And that could be done, since you can reach many stars and clients on a single line traveling back and forth, so there is a clear benefit in doing so. ## It makes choosing a destination easier Because it is simpler to move along the lines and you have reasons to stay on them (a.k.a stars/planets), then populations will group around them, and especially the vertices at the crossing of several lines. Now, if your database about colonies in this sector is outdated, you will have an easier time to guess which zone is the most populated and which isn't. As an individual, you can choose to live secluded away from people (though it's rarely difficult to be alone in space), or stick to the biggest cities in the vertices. [Answer] While yes, it will make intergalactic travel easier, but controlling the expansion of the universe could have disastrous results. If there's too much gravity, then such a megastructure would threaten to cause the Big Crunch. And the species being immortal would bring up another issue: As they have potentially-indefinite lifespans, they will reproduce far slower than humans, so if there is something capable of severely reducing their population, it'll take a very long time for the population to regrow. So, they'd be more vulnerable to extinction than a mortal species, as by the time the next big calamity occurs, they don't have as much numbers. ]
[Question] [ Would there any scientifical explanation to a permanent rain (at least 2 years) everywhere on Earth ? Climate-change ? My best explanation at this point is accelerated ice cap melting. There must be about 25 millions km3 of water, which would be enough for a 3 mm/h rain for two years. But I don’t know what could cause that. [Answer] A asteroid the size of Greenland, made entirely of loosely packed chunks of ice, in a decaying elliptical orbit. Every few weeks or so, it brushes past the upper atmosphere and thousands of ~1m fragments break off. Those fragments burn up entirely in the atmosphere, increasing global humidity. This would also accelerate global warming - water vapour is a greenhouse gas, as well as white clouds becoming dark rain-heavy clouds will decrease planetary albedo. The extra water vapour will accumulate in the atmosphere, be distributed by high altitude winds, slowly descend, form clouds, and be eventually discharged as rain. Every few weeks the water is topped up by another pass of the asteroid, and whats left of the asteroid looses a little bit of speed. After about 20-30 passes, the asteroid will entirely enter the atmosphere, but it'll be at a shallow angle, loosely packed, and almost entirely burn up before impact. That should give the Earth a few solid years of rain. ### Why do we need to bring the water in from space? Using only water on Earth; This is really tricky, over water, you'll need to evaporate water while raining, water going back up and down again at the same time at the same place, carefully calibrated so that it doesn't push up too far (and build hail), or push up not enough (you'll just get a foggy mist, or it'll stop raining). You'd need to maintain this balance of wind and temperature overnight and through winter. You're not going to be able to get it to rain in Antarctica easily either. By bringing the water in from space in the form of evaporated ice, we can make it rain regardless of surface conditions. [Answer] Permanent fog How about a different approach? Reduce the pressure of the atmosphere. In lower atmosphere, water boils at much lower temperatures. This will also increase the evaporation at temperatures lower than the boiling point. This causes the oceans to have a near permanent layer of fog, interspersed with rain if I'm not mistaken. Still, there would be a lot less rain. Lots falling rain would already evaporate before hitting the ground and would require more to start falling. That being said, the air would contain much more moisture. This would also increase the temperature on the planet, making it more plausible that a lot of water evaporates and stays in the air. [Answer] If you could create ideal conditions, then it would be theoretically possible. The water doesn't come from the area where it is raining. So if you can have winds constantly bringing in clouds from the sea, and geological features and climate which causes the rain to condense from the clouds in the given area, then you would have permanent rain. The rain would then go into rivers, and into the ocean, constantly replenish the source. I doubt, though, that you will find such a place anywhere on Earth. Making sure that the rain never stops, no matter the local conditions or seasons would be really hard. ]
[Question] [ This might be a bit story based, but here goes- I have an idea for an arena for one of my civilizations which involves about 20 rings a yard wide and rotating each other at different speeds. the outer rings rotate slower so you don't get thrown to the wall as easily, and the wall itself rotates along with the outermost ring as well. each rings rotates at a random speed(not too fast or slow so that the centrifugal force throws you out, just enough to make you unsteady when changing rings). the only stationary ground is the center circle a yard wide. Each ring is a different base height than the ones next to it by at least four inches, enough to make you stumble. Apart from the base height, it gradually goes up about a foot(the amount of times it does this depends on which ring it is. closer rings do it less), which adds to the tripping hazards. when the arena starts, the fighters are start along the edge of the rings, which begin stopped, and quickly speed up over the course of thirty seconds. elimination is decided depending on the mode, which can include death, hitting the ground, or being tagged. so my question is this- what fighting techniques would someone use on this rotating arena for each game mode? the only weapons that start on the field are(if allowed) swords, shields, spears, and rarely bow and arrow. most times it is unarmed combat. [Answer] Go to the Centre. Boring answer. But the easiest place to fight from is the centre since it doesn't move. Here are some complications that prevent the whole game being a race to the centre: Complication (1) There are weapons scattered across the arena. When the match begins each player must quickly decide which weapon they want, compare to the distance from the centre, and make a decision. It is a trade-off mind-game between weapon choice and positioning. Complication (2) Some fighters prefer to not have the centre. Standing on the innermost ring means they can orbit the fighter on the centre. They train to take advantage of how the other fighter must constantly rotate. This is an extra advantage if you rotate towards your opponent's weapon side rather than shield side. Complication (3) Sometimes the rotation directions swap and the advantage flips around. Complication (4) Being on a lower level than your opponent gives you an advantage. See diagram. [![enter image description here](https://i.stack.imgur.com/kjMII.png)](https://i.stack.imgur.com/kjMII.png) If you are low down enough you can hit your opponents feet but they cannot hit you at all. Complication (5) Long weapons: A longer weapon allows you to threaten more adjacent rings. In normal circumstances when fighting a spear you want to close with them as quickly as possible. But in the arena this means you need to cross several rings quickly which is dangerous. Complication (2+5) If you favour the centre you invariably need to use a long weapon. If you don't your opponent can take as much time as they want to find a long weapon and then simply outrange you. Considering all of the above, the exact layout of long weapons will have a huge impact in the game. I would imagine the audience will make bets based on (a) history of the fighters preferring the centre or outside and (b) the starting weapon layout before the fighters enter. Bonus: In order to prevent camping and inertia one option is to have a time limit, or to add extra weapons near the edge of the arena as time goes on. Adding ranged weapons in particular would make the game much more dynamic. Note: When I wrote this I assumed there would only be two fighters. Things are probably different if there are six or seven, at leastt in a free-for-all. The centre is still the easiest place to fight from, but not if there are six others trying to knock you off. [Answer] Fighting will be rather the same unless on high level I imagine. If you jump from one platform to another, you're taking an awful risk. You use time to jump and balance out, making you an easy target. If you fall, you can automatically lose in one of the games, or be dragged to your opponent on a different ring, or at best just lay down on the same ring and quickly get to your feet. Fighting will likely take place on the same rings. It gives an equal footing (pun lucky coincidence), the speeds are known and of the least concern. The starting outside ring also has the most room to comfortably move. If one is left handed and the other right handed they might be on adjacent rings, but clashing once in a while makes any advantage you might get with a swing vanish after. So you need to win a swing, or go to the same ring with all tbe risks involved. Besides, being lower that your target might prove a disadvantage, unless you're ducking and only go for feet. Staffs and spears would be the weapon of choice. Besides it already being a great weapon, often winning of swords and such, you can use the momentum as well to unbalance or harm your opponent. First strike can mean a lot, but it would be a form of jousting in the end. Tag is the one that makes most sense. Here jumping from ring to ring can make a great difference, getting closer with the right ring, or further away with another. Problem is, whatever you do, you'll be in an advantage as the tagger. The other needs to take risk, or just run away on the same ring. If the tagger goes to a middle ring, they can always force getting closer by going on an alternate ring or stay close on one spinning the same way. ]
[Question] [ I recently created a concept of a realistic zombie virus after reading about DFTD, or Tasmanian Devil Facial Tumor disease, spread by bites. It creates tumors on the face and inside the mouth of the Tasmanian Devil, eventually resulting in death. I was hoping to take this concept and apply it to humans, where the tumors should grow within a month to the point where they press against the frontal lobe and cause inflammation of the brain and increased aggression as a byproduct, where infected humans will then begin to attempt to attack and bite others, spreading the disease. I was also hoping the brain inflammation and/or damage caused by these tumors could also affect locomotion, causing the classic zombie shamble. These humans, similarly to Tasmanian Devils, die within 6 - 8 months of infection. By the final months of infection tissue necrosis begins to set in after permanent brain damage. At this point they're almost complete vegetables. Is this possible? What are the limitations if so? [Answer] I think that to get zombie-like behaviour (aggression, esp. biting), you need to combine two different factors. 1. You need to get rid of normal human inhibitions. Those are quite deep down given by both our genetics and culture. An extreme, unbearable pain could be a good one (also could help you with limited joint movement to get the stiff zombie walk). When in extreme pain, people won't care about manners, comforts, hygiene, etc. For an added bit, the increased blood pressure in head when lying down, or trying to stand up, makes the pain so bad that your zombies prefer to rest (maybe with virtually no sleep for weeks to add some severe sleep deprivation) while standing, just leaning against a wall or something. There are zombies lying down in some films but most often they don't. Similar effect can be given by severe starvation, when a body is deprived of nutrients, the brain starts shutting down higher cognitive functions. This leads greatly into the other point: 2. You need to be hungry, very very very hungry, so that once your inhibitions are inhibited, you won't only be willing (and craving!) to eat any food around, including human flesh, but that even the sight of a piece of human skin would make you go and attack (and bite). An expert on starvation might correct me, but from what I heard, I understood that while starving from not eating anything at all is relatively less painful, it's much worse (although delaying the death) to eat very little but not nothing. I like the fungus idea by ProjectApex in the comment, that it could be a fungus. Well, imagine the fungus "stealing" glucose (and possibly ketones or anything else!) from your blood, leaving just enough for a very slow, debilitating and painful death, while leaving you able to walk, bite, and to some extent fight. This would need to couple with it speeding up your digestion, otherwise you'd be starving with a full stomach! (That got a bit dark, but hey, zombies ARE a very dark topic indeed!) Finally, the fungus could easily explain why the zombies don't try to eat each other! [Answer] I'm not a big fan of "zombie viruses". 28 Days Later may be the best of these, it's a rabanoid virus by the looks, the zombies eventually die of starvation, and the method of transmission means it might be possible to affect the victims as quickly as depicted. But generally it's a bad plot device. You've got a few problems with the mechanism of hostility/aggression. But nothing that can't be fixed with a little hand-wavium. Instead of it infecting the sites of the bites, this will metastasize. Tasmanian Devil disease is a transmissible cancer... the cancer cells originated on an individual many decades ago, but his cell line lives on in others. Just before it kills them. The Tasmanian devils aren't biting because of the disease, they're just nasty little shits always fighting each other. Maladaptive behaviors, eh? We do need your variant to affect the brain. And massively. You want extremely intense aggression, you want physical debilitation, lack of reason (or even personality). That affects all parts of the brain, so a purely mechanical etiology is out. This cancer will preferentially attack the human brain. All lobes, or almost all of them. But we can also throw in some skin lesions and general necrosis to give you the zombie look. The cancer's aggressive growth means that even if oncological treatments worked, they're biting their doctors long before they can get a course of chemo. And the brain damage is so extensive that the condition will be irreversible too, if that matters to you. This won't be a "3 hours later, full zombie" thing. The tumors themselves that cause this will be small (but many of them, thousands) which is enough to cause the change sin behavior and the icky looking sores and blooshot eyes and so forth. Probably looking at least 24 hours before infection spurs full conversion, but if the story allows and you want it to be more realistic, longer would be better. 72 hours, or even a full week would be enough for pea-sized tumors to occur. Realistically, these things will burn out really quickly too. They get a few days of shambling around at most. Some percentage of them would go really quickly, when the tumors infiltrate vital organs other than the brain. If it gets the heart or the lungs or kidneys, they'd probably drop before the other zombies. A few others will just stroke out when the tumors in the brain pinch off blood flow. Conversion rate won't go above 60% or 70%, the rest will just be made dead quick, possibly even before they could attack others. A smaller number might display truly bizarre (not necessarily zombie) behavior, as the infection randomly ruins parts of their brains. OCD behaviors, walking in circles, whatever. Classic zombie mob scenes might not work. There's no plausible mechanism for them to refrain from attacking each other. Not sure that's necessary though. ]
[Question] [ In many fantasy worlds, giants are as intelligent as human beings and others races that they either avoid stepping on or step on regularly. However, due to the square cube law, giants have a limited size where they can exist; but due to again the square cube law, the larger you are, the harder it is to keep a powerful brain up and running. Thus, my question in: How big can a giant get before getting to big to support a complex brain? The giants them selves will be confined to the laws of physics, and thus no magic is allowed. Also, these giants will be confined to the land and be adapted to such an environment (Large feet, stocky build, etc.) So no water buoyancy to help them. Edit. Due to the need for clarification as to why giants would loose human intelligence as thy get bigger, I will put a brief explanation on the issue of large, bipedal intelligence. The issue, per usual, is the Square Cube Law. I.e, the bigger something gets, its surface area goes up by square but the volume goes up by cube. This leads, to large bipedal any way, a need for increased muscle mass and bone structure. However, that new mass needs support to. This results in a viscous cycle where the organism would eventually get crushed under its own weight. Thus, weight savings need to be made, and for giants, the most likely weight saving measure that s first to go is intelligence. Here is a link for a video that explains it with more detail [here](https://www.youtube.com/watch?v=dbOSHoa7h3E) [Answer] Actually, the larger the animals, the easier it is for it to have a brain with human level intelligence. There is a minimum size of brain necessary for human level intelligence. Nobody knows what that minimum size is. There are approximately 6,500 known species of mammals at the present. <https://www.sciencedaily.com/releases/2018/02/180206090658.htm>[1](https://www.sciencedaily.com/releases/2018/02/180206090658.htm) The vast majority of them have tiny bodies with less mass than a human brain. The mass of an average human brain is about > > The adult human brain weighs on average about 1.5 kg (3.3 lb). > > > <https://en.wikipedia.org/wiki/Brain_size>[2](https://en.wikipedia.org/wiki/Brain_size) And many species of mammals have brains much smaller than that since their entire bodies are not that massive. But there are hundreds of large mammal species ranging in size from small humans to larger than humans. Mammals species with such large bodies can possibly support large brains. and some mammal species with such large bodies actually do support large brains. And there are about ninety or a hundred species of mammals, primates, proboscideans, and cetaceans, with brains roughly in the range of human size, and in some cases far larger. So it is possible than between one and about a hundred species of mammals on this planet are approximately as intelligent as humans and thus count as persons. Some person claim that the absolute size of the brain doesn't matter as much as the ratio of brain to body size. If an animal has a larger body it may need a larger brain to senses sensations from its larger body and to control its larger body. Thus it is possible that even the largest brained nonhuman mammal does not have a brain sufficiently large for human level intelligence. Some people might think that the size of brain necessary to control the body would scale with the dimensions of the animal. An animal twice as large would need twice as large a brain to control its body, in addition to the parts of the brain that give intelligence. Some people might think that the size of brain necessary to control the body would scale with the square of the dimensions of the animal, and thus with the surface area of the body. An animal twice as large would need four times as large a brain to control its body, in addition to the parts of the brain that give intelligence. Some people might think that the size of brain necessary to control the body would scale with the cube of the dimensions of the animal, and thus with the volume and mass of the body. An animal twice as large would need eight as large a brain to control its body, in addition to the parts of the brain that give intelligence. Note that having the brain scale linearly requires much less brain than having it scale as the square of dimensions, and having the brain scale with the square of the dimensions requires much less brain than having the brain scale with the cube of the dimensions. I also note that some body plans are much more complex than others and might need much larger brains to control than others. > > Brain-to-body mass ratio, also known as the brain-to-body weight ratio, is the ratio of brain mass to body mass, which is hypothesized to be a rough estimate of the intelligence of an animal, although fairly inaccurate in many cases. A more complex measurement, encephalization quotient, takes into account allometric effects of widely divergent body sizes across several taxa.[1](https://en.wikipedia.org/wiki/Brain_size) The raw brain-to-body mass ratio is however simpler to come by, and is still a useful tool for comparing encephalization within species or between fairly closely related species. > > > <https://en.wikipedia.org/wiki/Brain-to-body_mass_ratio>[3](https://en.wikipedia.org/wiki/Brain-to-body_mass_ratio) > > Encephalization quotient (EQ), encephalization level (EL) or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regression on a range of reference species.[12][13] It has been used as a proxy for intelligence and thus as a possible way of comparing the intelligences of different species. For this purpose it is a more refined measurement than the raw brain-to-body mass ratio, as it takes into account allometric effects. Expressed as a formula, the relationship has been developed for mammals and may not yield relevant results when applied outside this group.[14] > > > <https://en.wikipedia.org/wiki/Encephalization_quotient>[4](https://en.wikipedia.org/wiki/Encephalization_quotient) > > Encephalization quotient was developed in an attempt to provide a way of correlating an animal's physical characteristics with perceived intelligence. It improved on the previous attempt, brain-to-body mass ratio, so it has persisted. Subsequent work, notably Roth,[1](https://www.sciencedaily.com/releases/2018/02/180206090658.htm) found EQ to be flawed and suggested brain size was a better predictor, but that has problems as well.[unbalanced opinion?] > > > Currently the best predictor for intelligence across all animals is forebrain neuron count.[citation needed] This was not seen earlier because neuron counts were previously inaccurate for most animals. For example, human brain neuron count was given as 100 billion for decades before Herculano-Houzel[15][16] found a more reliable method of counting brain cells. > > > It could have been anticipated that EQ might be superseded because of both the number of exceptions and the growing complexity of the formulae it used. (See the rest of this article.)[unbalanced opinion?] The simplicity of counting neurons has replaced it.[citation needed] The concept in EQ of comparing the brain capacity exceeding that required for body sense and motor activity may yet live on to provide an even better prediction of intelligence, but that work has not been done yet.[citation needed][unbalanced opinion?] > > > <https://en.wikipedia.org/wiki/Encephalization_quotient#Perspective_on_intelligence_measures>[5](https://en.wikipedia.org/wiki/Encephalization_quotient#Perspective_on_intelligence_measures) Clearly there is still a lot of research to be done to predict how much brain is needed to control a body of specified size, and how much more brain is needed for intelligence. It seems to me that if a humanoid giant has a body that is ten times as massive as a human body, it might possibly need a brain tens times as massive as a human brain to control its body, and if has a body 100 times as massive as a human body it might possibly need a brain 100 times as massive as a human brain to control its body. But if the extra part of the brain needed for intelligence didn't have to be any larger than the extra part of the brain needed for intelligence in a human sized body, the giants could have total brain mass and energy consumption that was proportionally less than that of a human. And it is possible that the brain mass needed to control a body actually increases a bit less than with the cube of the body's dimensions, which would mean that your giant's brain size could be a bit smaller compared to its body mass and it could still be intelligent. So unless some expert in brain size relative to intelligence says that the best current estimates and calculations show a specific upper body size for an intelligent being, I would assume that a giant humanoid could be just as intelligent as a human with a somewhat smaller relative brain size. [Answer] Towards an Answer... The question of gigantic humanoids has come up in Worldbuilding a couple times in the past, and we do have some data on relative maximums in size for Homo sapiens. Historically, the [tallest human](https://en.wikipedia.org/wiki/Robert_Wadlow) ever was just under nine feet tall; and the [heaviest human](https://en.wikipedia.org/wiki/Jon_Brower_Minnoch) ever was 1,400 pounds (100 stone). Both men were at least of average intelligence: Brower was married, so must have been intelligent enough to apply for a license & answer during the ceremony; Wadlow graduated high school and entered college with the intention to study law (he would have made one imposing prosecutor!) Within Worldbuilding, the question of [greatest height](https://worldbuilding.stackexchange.com/questions/51686/what-would-be-the-tallest-possible-height-for-humanlike-creatures-in-earthlike-c) and [maximum possible dimensions](https://worldbuilding.stackexchange.com/questions/148861/mega-human-what-are-the-largest-possible-dimensions-of-a-human) for a human have arisen over the years, and I think may be helpful to you. The first query goes into some good detail of scaling and some of the pitfalls a human-like giant would face. The second query gives a rather larger maximum overall size, but also hints that various physiological factors will have to be sorted (heart size, heat transfer, blood pressure, etc). The raw range seems to be somewhere between 8 and 24 feet. The maximum height for a human-like giant that doesn't suffer from too many physiological issues and health problems seems to be in the nine to ten foot range. Given Halfthewed's comment about brain size to body mass & intelligence, I think it would be fair to offer the following answer: A human-like fantasy giant of 9 to 12 feet in height should possess perfectly normal human-like intelligence. And also: a human-like fantasy giant of 12 to 24 feet in height may very well possess perfectly normal human-like intelligence. [Answer] Like many organs, the vertebrate brain actually evolved because of our large size--the larger you are, the more you need a dedicated system to communicate quickly between cells. I don't see any reason being large would make anyone less intelligent. Elephants and whales are both pretty smart animals! However, because it takes longer for messages to travel the body, the larger you are, the slower your reflexes get, as well as your ability to think, period. If you've ever watched a fly move, you'll notice that its legs move faster than you can see. That's why! [Answer] Mammals have grown quite large without intelligence decreasing. When one compares whales to their smaller relatives: porpoise, orca; one doesn't find a marked decrease in intelligence. Whales have a fairly sophisticated vocabulary that is indicative of higher intellectual processes, more complex than most land mammals. And it is in the aquatic mammals that we find the greatest size variance. Intellectual capability does not necessarily decrease with larger size, at least when comparing large mammals to their smaller close relatives, which provides an intelligence comparison with the least number of extraneous variables. However, what you may also want to consider is: how large can a hominid get before the body layout cannot support the large size? This is assuming you don't want to alter physics as we know it. Upright creatures in the 30 foot tall range have existed as dinosaurs: T-Rex and Spinosauras. However, the very large bipedal dinosaurs all had a massive tail to counterbalance the body. As near as we can tell, they didn't walk upright, but in a position we might describe as hunched over. And that large size appears to be so they can take down larger prey - something humans do with intellect rather than size. In the real world, humans have evolved to their current size, because that's the size that has proven to be optimal for the conditions. It would be interesting (and realistic) to come up with a very large mammalian creature of the intellect and capability of a human, with a body optimized for the larger size. And the conditions under which such a size increase would be beneficial. ]
[Question] [ Back home, five million years ago, the warm, wet climate of the Miocene sloped downwards into the cooler, drier Pliocene before descending even further into the more so Pleistocene. The slope was so gradual that to my knowledge, no extinction events happened. But not in this alternate Earth. Five million years ago, the Miocene skipped the Pliocene and took a sharp drop to the Pleistocene. This drop in temperature happened so dramatically and so quickly that half of all plant and animal species became extinct, and the once-widespread rainforests had been cut down to their equatorial margins. (Like the refugia of back home.) But considering that rainforest species have always been resilient against ice ages, one must ask, in this ice age mass extinction, which latitude would actually be hit harder--the lower tropics or the middle temperate? [Answer] Tropical species would be more affected There were actually massive extinctions due to the Miocene cooling. A lot of animal groups were wiped out in the late Miocene-Pliocene due to climatic changes, including the chalicotheres, bone-crusher dogs, three-toed horses, oreodonts, sparassodonts, megatooth sharks, protoceratids, pseudotooth birds, small baleen whales, a lot of rhino groups, and more. The oceans were hit particularly hard and still haven't recovered by the present day (<https://www.nature.com/articles/s41559-017-0223-6>). It's just the rate of extinction wasn't high enough to qualify as a mass extinction. In real life, it was the tropical species that got screwed over the hardest. Most species adapted by moving further south, and for many species they got pushed so far south that there wasn't a lot of habitat left for them anymore (or even moving further south where conditions were nicer wasn't an option like in North America before the Panamanian landbridge formed), and they died. [Answer] That would depend on region... and what you mean by hard. Rain forests such as those found in India, Northern Australia, Soath East Asia would likely be very heavily hit. The rapid cooling will likely be playing havok with their monsoons which are critical for replenishing the water they loose. Rain forests that can sustain their own rainfall, such as the Amazon Rain Forest, and rainforest built over great untapped aquifiers, such as those around the K2 impact crater could sustain themselves in the face of interrupted rainfall for some time. All of them will be disrupted by the rapidly changing temperature. Expect the die off of tightly coupled species particularly if those species have some sort of mechanic around temperature, such as migration, seeding, nesting, etc... Temperate regions rely less on rainfall for maintaining the forest. Their chief issue will be how cold adapted the trees are. * Regions heavily populated by conifers will probably handle well. Conifers have been through many periods of extended cold. * Broadleaf evergreens will be hit hard as their leaves are destroyed by frost. * Broadleaf deciduous will survive, though only growing during the "summer" presuming summer months warm sufficiently. --- However this is if you take the view that a forest is the expected biome. What will likely happen is that many forests will transition in grasslands/tundra. Producing a resurgence in C4 plants. This will naturally provide a field day for every C4 herbivorous animal, and the resulting food chain that they bring with them. Naturally this isn't a terribly nice world for Nut/Fruit eaters... [Answer] I don't think this would really be a matter of latitude per se. Since the equaliser between all the rainforests of the world is a general resiliency against ice ages, I'd argue that the answer will then be: the rainforests of the latitude that has the fewest finicky species will be the less hard hit in your scenario. We tend to think of equatorial rainforests as being home to all kinds of species that rely on specific diets and environments. Those would probably be the first species to go extinct during a worldwide rapid cooling event, and thus it would make sense that the tropical latitudes would be harder hit. ]
[Question] [ Our traveler appears in a medieval world that with knowledge of the modern world. Maybe he has a copy of wikipedia in his head. He decides to take over the world but he does not take the normal path of gunpowder. Instead he invents long range communications with some sort of wireless telegraph. Could he do this in the 1500s or so. [Answer] Oh, yes, easily. Creating wire by various different methods has been around for [at least 4000 years](https://en.wikipedia.org/wiki/Wire#History) (for jewelery and decorative purposes). * A sheet of metal was cut into a strip and drawn through progressivley smaller holes in beads to smooth and elongate it. (A a big sheet and a helical strip could produce great lengths without the need for joining). Soft and conductive metals like gold and silver are particularly suited to this, or in-a-pinch tin would serve. * Two sets of orthogonal hammers were used on bars of metal to form square wire. * Insulation was then simply wrapping in cloth and coating in any of the available natural resins and thermoplatics (wax, rosin, shellac, tar etc.). The generation of radio frequency waves could then be achieved by creating a disk on a spindal, which would either have fixed magnets (naturally occuring haematite) around the circumference, or slots - the alternating of slots and metal when spun in a steady magnetic field would act as dipoles, with a coil nearby to pick up the alternating field. This would be spun at high speed until the desired frequency was achieved (as in the [Alexanderson Alternator](https://en.wikipedia.org/wiki/Alexanderson_alternator)). This could be geared (available since circa [400 BC](https://en.wikipedia.org/wiki/Gear#History)) such that a slave would power it - perhaps working to the rythym of hummed melody to keep the output speed the same. To modulate the transmission for voice, a [magnetic amplifier](https://en.wikipedia.org/wiki/Magnetic_amplifier) would then be used (essential in the early days of radio pre-valves). The aerial would not need to be miles long, just wound around a ceramic in the propper way to form a tuned [loaded coil](https://en.wikipedia.org/wiki/Loading_coil). [The microphone](https://en.wikipedia.org/wiki/Carbon_microphone) would be a simple carbon-granule affair behind a basic diphragm - like those used in telephones before the 1980s. (charcoal won't do, it does need graphite). The reciever The principles of using naturally occuring semiconductors in coal to create the heart of a [crystal radio](https://en.wikipedia.org/wiki/Crystal_radio) are well known. An adjustable [air capacitor](http://www.capacitorguide.com/air-capacitor/) would then be used to tune reception. The speaker would be a thin sheat of cleaved quartz (or other [piezoelectric material](https://en.wikipedia.org/wiki/Piezoelectricity#Materials)) with gold leaf to apply the electrical signal across it making a [crystal speaker](https://en.wikipedia.org/wiki/Crystal_radio). You are now free to conquer the know world and re-draw the maps as you see fit. [Answer] Short answer: no, I don't believe so. Science and technology are two different things. Letting aside uniform width conductors for coil wires, magnetic materials for coil cores, etc, you do need at least vacuum tubes. Which do require technological advancement in glass making (to match the dillation of glass and electrodes) and refractory metals for the electrodes (tungsten) and precision mechanical works. Sometimes I think Edison's bulb was revolutionary not because it brought the electric light, but because it showed how to build a fillament that doesn't burn when it gets to high temperatures. ]
[Question] [ One of many things that differs the pregnancy of my Keplerians and that of humans is that in Keplerians, there is a symptom that is equivalent to a positive pregnancy test. To explain this, first, I need to explain what goes on during a normal menstrual cycle in Keplerians. During a normal menstrual cycle in Keplerians, there is no bleeding directly from the vagina, all the bleeding is from the uterus. In their vagina, there is a layer of tissue similar to the endometrium of the uterus, but it responds to different hormones. These hormones that the vaginal endometrium responds to are pregnancy hormones. Now, let's say a Keplerian gets pregnant. The zygote is going to start dividing. This triggers pregnancy hormone production. As the pregnancy hormone increases, the vaginal endometrium thickens, up to a point. Then once it reaches the threshold of pregnancy hormone, the vaginal endometrium sloughs off until it is back to its normal thickness. This causes a painless vaginal bleed to happen several days after ovulation and this bleed is equivalent to a positive pregnancy test. The bleed happens to correspond with when the embryo implants into the uterus. This vaginal bleed in response to pregnancy hormones lasts for several days and so it is often called a "Vaginal Period". This not only confirms that the Keplerian is indeed pregnant, but it comes before the whole slew of pregnancy symptoms from nausea to abdominal rash. I know that there are real situations in humans where a change in hormone levels causes it to change from a positive feedback loop to a negative feedback loop involving the same hormones, with the menstrual cycle being one of those situations. So it isn't totally out of the question that the bodily equivalent of a positive pregnancy test in my Keplerians could be caused by a positive feedback loop changing into a negative feedback loop that leads to a leveling off of pregnancy hormone levels. However, is the painless vaginal bleed for several days a plausible symptom to be the bodily equivalent of a positive pregnancy test? [Answer] Ah, the old subvert the menstruation trope, if I had a dollar for every time that's come up, I'd have something around a whole dollar. A doctor once told me, after a test came back with potentially serious results, that "this is like you are walking down the street, tossing away dollar bills." It's not a normal occurrence, and it can happen for no reason but it can mean there is something very seriously wrong. We'll repeat the test, and if it's negative, then there is nothing to worry about." Fortunately, the test came back negative the second time. For a body to bleed without injury, and without purpose, is like that. Blood is important. And when a female is pregnant, their body needs every resource to ensure they and their progeny survive. So, arbitrarily bleed solely to signal conception seems inefficient. Maybe it only looks like bleeding. Maybe, pregnancy in your Keplerian triggers a shift in bodily functions. Human livers filter out dead blood cells from our circulatory system. Maybe pregnancy in your species taxes the liver and as an evolutionary adaption, the mechanism you are describing is actually filtering out soon to be dead blood cells so the liver has more filtration potential to keep mother and child alive and healthy. [Answer] There's as much logic or more to aliens having a bleed response from pregnancy as humans having one every month. It helps if you have some internal logic to explain it. For example, it could be a signal to males to leave a female alone (no point bothering this one...) or a sign someone is messing with a male's harem. Depending on social roles, it might even invoke a violent response to induce spontaneous abortion so the female would be available again for a different male to impregnate (biology is cruel). [Answer] Actually in humans bleeding can be a symptom of pregnancy. Specifically nose bleeds. This is because of hormonal changes and because the pregnant body has more blood running through it, resulting in higher blood pressure. <https://www.nhs.uk/pregnancy/related-conditions/common-symptoms/nosebleeds/> Maybe your aliens have some similar tissue which already bleeds easily and more so in pregnancy. ]
[Question] [ Societies have hierarchies: today they are loosely divided into an upperclass, middle-class, lower-class. Our world used to be more focused on a caste system with royals at the top, religious leaders second (sometimes vice versa), warriors, workers, farmers etc. What kind of class system could a future society have that is not divided by material matters, but by other matters. Let's imagine that we take our world 100 years into the future with technology expanding at the current rate. I'm thinking along the lines of administrators, but I am also open to other suggestions. Edit: in a computer-driven world, the castes might be administrators, programmers, users. But where would the hardware repair guys be, the tech guys, the producers, where would information officers be, where in this hierarchy could you find a police structure observing, even defenders. Because with administrators at the top, you basically override all the other hierarchies. This is basically at the core of any company and it creates quite a messy hierarchy. [Answer] Groups seem to create caste groupings based on what is valued. If you were ever in High School in the US, you might see athletic ability as the caste determination. The top caste when I went was the Football and Soccer teams, followed closely by Basketball, wrestling, tennis, etc. Cheerleaders and Drill Team (a cross between cheerleaders and highly choreographed dance troop) were included. That top caste was commonly called 'the jocks'. Then you had Preppies, those who may not have played in organized sports, but had a matching mentality to the Jocks, and usually had wealthy parents. A little lower you had Marching Band Geeks. The Normals were just people. Not so much picked on as ignored so long as they knew their place. Nerds and Geeks tended to be at the bottom. You can see the structure. Athletic ability was more prized than Money, which in turn was more prized than musical ability. The 'unclean' were any of those who were too smart but socially awkward. You have already identified what was valued in times past, Which was one's bloodline. IN modern times, it's money that matters more. For your future society, you have to decide what is valuable. Technological ability could be one aspect that a caste system evolves around. Those that write the code rule the universe. Or perhaps it could be Corporate ability, which is not too far removed from today. In something more dystopian you could look at Soviet Russia, where a caste system grew up around Party membership and the politicking one has to do within party ranks. You just have to decide what your society values and you should see the caste system fairly easily [Answer] It's really hard to predict 100 years, especially on general, grand terms. Predicting the future is the business of worldbuilding for thousands of sci-fi authors, who have all crafted their own visions. So instead of trying to predict that, I'm going to approach your question by outlining a possible way of, given a chosen set of predictions about the future, how could you take those and develop a caste system? A few basic ideas about castes: * Being in a higher caste has perks. The classes on top tend to do more desirable work and less undesirable work, or has access to more resources. This is a necessary feature or else people would not desire to be in the higher castes. * It is not trivial to move between castes. Otherwise anyone would do it and create inbalance. * The reasoning behind the castes has to be accepted by the majority of the population - otherwise there would be a revolt. So with that in mind, two good questions are: * Q1: What are the core values of this society? You get at these from philosophy, religion, and ethics. All of these determine the government and economics and culture which will dictate the castes. * Q2: What are the core problems in this society? The caste structure will change over time to solve those problems. Example: in modern America some of the core values we can see throughout our history are entrepeneurism, independence/freedom, and diversity. So, referencing Q1, core values of entrepeneurism and freedom lead us to the economic system of capitalism, and this leads us to the castes that we have based on income. And then we get to Q2, what are the problems with this system? Income inequality and overall selfishness, so we see those problems lead the government and culture to change and become more economically socialist...or maybe in the future a totally new economic system will emerge. I hope this example will be useful to you in building out a feasible world. [Answer] AlexP has made it clearer for me, at the highest level is the administrator, followed by a group of programmers, their main aim is to uphold the code, under which everything else has to be subsumed. The user being at the very bottom, while techies are way above them. Any political or police structure would be highly influenced by the ones upholding the code. ]
[Question] [ In [another question](https://worldbuilding.stackexchange.com/questions/160428), I talked about a form of magic that converts metabolic energy (i.e. the energy produced by biological processes in "animals", which for this purpose includes e.g. yeast) into kinetic energy, with essentially unbounded¹ ability to precisely direct that kinetic energy. In one answer / comment, Yakk [implied](https://worldbuilding.stackexchange.com/a/160476/43697) that this would give someone wielding this ability nearly unlimited power: > > There is enough energy in a 1 kg rock to throw everything on the island of Manhattan 100 km into the sky. > > > On the one hand, I can see where someone might wonder if this could incarnate [Maxwell's demon](https://en.wikipedia.org/wiki/Maxwell%27s_demon). On the other hand, looking at the thought experiment literally, it would seem that opening and closing the door would itself require work, never mind all the problems that conductive heat transfer raises. Is this — not the literal thought experiment, but the general idea — plausible? If so, what would be an example of an actual process by which one could extract "unlimited" energy using this "kinetic magic", and what limits could be applied to the wielding of magic that would prevent it, without preventing less, ah, "excessive" uses of magic? (The linked question notes some of the things I want to be able to do.) I will assume: * Initiation energy is limited to, at best, 2KWHr, and can be delivered at, at best, 5KW. Any process which would require exceeding those limits to start isn't feasible. * Magic can't simply convert matter directly to energy. The critical piece of the puzzle here is that magic can reduce entropy. For instance, it can turn a jumbled pile of blocks into a neat stack, or turn a bag of black and white marbles into piles separated by colors. Perhaps more importantly, it can² do these sorts of things on a molecular level, for example, fill a 1L container with pure argon taken from the surrounding atmosphere. A related question could be, how do you measure the energy value of information of this nature? Knowing that, it may be that the "obvious" limitation is that this energy cost must also be paid. Affirmative ("yes, this is world-breaking") answers should give a detailed explanation why this is the case, not just an assertion that it is. (¹ Not really, but for the purpose of this question, we'll go with that.) (² Actually, this is, at best, pushing the limits of what I'm going to allow, but again, for the sake of this question, we'll go with it.) [Answer] Since you are talking magic, you can impose limits however you wish. I'll tell you what I would do though. First limitation is to consider Magic to be energy. Seems like you are doing this already. It gives you a limit based in understood physics. You can neither create or destroy energy just like you can neither create or destroy Matter. You can rearrange things down to a molecular level, but you still do business with the laws of physics. Conservation of Mass and Conservation of Energy are key concepts here. Your Second limitation would be limited to the energy your Magic user can glean from metabolic processes. This takes away the ability to use the 1kg rock to toss Manhattan around. A metabolic process is loosely defined by layman like myself is the process of taking something you take in, break it down to useful compounds, then combine it to release energy. In an animal, this is breaking down food, converting it to glucose, and combining it with oxygen to release energy (laymans description) The upshot is that your magic user cannot use any more energy than they can take in and process as food. What they move, whether it's with their body or mind, takes the same amount of calories. If it takes 20 Calories to pick up boxes on your left and move it to your right using your hands, then it will take the same amount of calories to do it with your brain. If you want to travel a certain distance with brain power, it will burn the same amount of calories as you walking or running the same distance. This puts a solid limit to magic and keeps magic users from getting ridiculously OP. You did bring up Magic being able to combat entropy. Humans do this with their hands all the time. To stack a pile of bricks will simply cost the same amount of calories as walking over and using your hands. Separating colored marbles is the same. The thing about Entropy is that it takes over when you stop paying attention. Now comes some of the cool stuff. Humans are prevented from ultra fine manipulation of stuff like molecules without tools because fingers prevent that kind of control. Magic is different. It is the Magic, which has no form, that does the work and can therefore grab that argon molecule, and only the argon molecule, and transfer it to the glass. The ability to manipulate the physical shifts from the skill of the hand to the skill of the brain. You are still limited by how much energy you can derive from food. You're Magic User still won't be able to lift a 20 ton block without tools and help. However, your Magic User will be able to pull the rope attached to a pulley system that can lift the 20 ton block. In addition, imagination becomes your limiting factor. Your Magic User could do whatever they imagine, like maybe assassinating an enemy by pinching the carotid artery from 30 feet away. Or spooking a general's horse from a distance. Dice manipulation, moving the barrel of a gun before it's fired, and so on. That's how I would put limits on magic use. It's all about counting calories ]
[Question] [ There might be a way to build traversable wormholes without needing negative mass. Take a gander: <https://phys.org/news/2019-04-wormholes.html> Now, these wormholes have a big limitation, they can't be used for shortcuts, as they're longer than going straight to the destination. Still they sound neat, however, I lack the knowledge (and time) to look into how the poor worldbuilder could use these wormholes. I'm wondering if there are any features of these wormholes that could be exploited on the macro scale, and if yes, what? [Answer] I wanted to follow up on @John O's comment, there are a couple of obvious uses Extra storage The extra space can be used to store things you didn't have enough room for without wormholes. Infiltration A base inside one of these wormholes will have fewer entry points than one out in open space. A bank inside this wormhole has fewer directions to be attacked from. A prison would be virtually inescapable. Privacy/surveillance Because of the previous point, observing what's happening inside this wormhole, from the outside, is easier to prevent. You just cover up the entry points with heavy shielding and no one can see the experimental weaponry you're building on the inside. Safe passage Because of the limited number of entry points, you have an easier time controlling what is inside the passage. This can mean a reduced amount of debris endangering fast moving vessels, but it can also ensure the safety of very important cargo passing through. Sure, the traveled distance is longer, but that can be worth it if you can ensure the safe travel of, for example, the president between the capitol and their home planet. [Answer] If the ends of the wormhole can be moved, then maybe terraforming Let's imagine your explorers have travelled to a new solar system. It's got a type G sun, pretty much identical to our Sun. There may or may not be aliens living on an Earth-like planet in the habitable zone, in fact you aren't sure if there is such a planet there. Out in the distance, at a radius we might call "trans Neptunian"... you've got: * ice giants * A Pluto-like planet * A mostly rocky/metallic planet that's actually very like Earth, but doesn't get enough heat from the Sun at that distance to be habitable. So... * You open a large wormhole very near the sun, with it's other end about eight light-minutes away from that rocky planet. Sure, it'll take the light a bit longer to get through the wormhole to Planet Rock than it would if it were going directly, but that's only a short initial delay of less than a day. After that, the planet is getting as much sunlight (& so heat, UV etc.) from the sun as if it were at an Earth-like distance to it. Continuously. (You've just beaten the inverse-square law! Well done.) But there are still problems. 1. The gravitational effect of the Sun is also coming through that wormhole. Or at least, I think it is - people with more knowledge of physics, please comment! It'll change the planet's movements, and you don't want to destabilise the orbits of the other planets in the system. So you maybe open another wormhole first, with something very dense but emitting very little radiation, at the other end. By moving that wormhole, you use the mass of that larger body to tow the transneptunian rocky planet to a safer distance. Then you open the wormhole to the Sun. You'll still probably need to make occasional course corrections, nudging the existing planets a bit to keep them in orbit. I think. My knowledge of physics doesn't go far enough. Remember, if there are aliens living in a habitable zone planet, you don't want them to find their planet hurtling out of orbit. Possibly these small adjustments are viable with your future technology, but the wormhole towing trick is the only way you can move a planet over large distances. 2. You need to get oceans established. How long a timescale do you have? You could open another such wormhole, with an opening very close to the ice giant. The Sun's heat then evaporates the gas and begins to melt the icy core. Then you open another wormhole, through which the now liquid water pours - and comes out the other end on Planet Rock. If you're in a hurry, and you have a Pluto-like planet, you might be able to melt away the nitrogen ice crust and get at a useful liquid water mantle faster. 3. You don't want a planet that's effectively tidally locked. No problem! You just get that end of the wormhole moving so that it orbits the rocky planet. You probably make it take 24 hours to complete its orbit. Critique and discussion welcome, especially because I am using this idea in my story. [Answer] Make beacons. Yes, new wormholes make the trip longer, but stretched in the right way and kept open make a permanent highway from beacon to beacon (as long as they are powered). To create a new beacon it needs to be carried and installed there in normal space, and takes some time to stretch, but once set, it can be used for FTL travel. [Answer] Long distance communication on planet surface While your source does not state (or at least I didn't find it) how much longer this travel takes, it would presumably be shorter than a round-trip on the surface or bouncing off of satellites. Or at least require less infrastructure (depending on the energy required). A large-scale connection could, say, half the lags and greatly increase the bandwidth between continents (especially east Asia or Australia and the rest of the world). While doing back-of-envelope calculations, remember that signal propagation in copper is (AFAIK) roughly 2/3 of the speed of light. Or at least that's the approximation we use when designing electronics. ]
[Question] [ So, a lot of conflict in my story comes from misunderstanding and false information, here's a small sample: * Myth: Dragons represent the sin of greed + Fact: Being partly modeled after lace monitors and magpies, dragons are curious creatures by nature and they are just as intrigued by a mundane prism as they are by a diamond, what matters is how colorful and/or shiny an object is. * Myth: Gilgamesh was a chad and totally flipped the bird in nature's face by cutting some sacred trees down and got away with it + Fact: You see, there was this guy from the previous episode, Humbaba. Well he didn't exactly appreciate Gilgamesh's disposition so after a heated argument, that involved Gilg being flung around by one leg like a ragdoll, Gilgamesh agreed to plant some saplings to replenish the cut-down trees. * Myth: Humbaba had seven layers of armor + Fact: 1. Humbaba never existed as a separate person, it was just another fake identity of an unknown god. 2. Humbaba bought into the lies of the Jedi and arms manufacturers, who advertised his powered armor as being made of six layers, though it was actually "just" Chobham armor, where individual layers relied on each other to provide protection, misleading those who didn't know the Way of Warmongering. Now, the thing is, I have no point of reference when it comes to how, for what reasons and to which extent did humans exaggerate things. This is a problem, as my story heavily relies on "fake news". But I don't know how to manufacture realistic exaggerations. Is there any resource that analyzes or highlights patterns of that part of mythology? [Answer] There are some resources available online, but they are scarce and only tangentially relevant. You can check out [hyperbole in mythological comparisons](https://www.jstor.org/stable/289997?seq=1) or [hyperbole in literature](https://www.britannica.com/art/hyperbole) to get examples, but I suspect you won't find a meta-analysis. That's for good reason. Exaggeration happens for one of two reasons: [to embellish](https://www.huffpost.com/entry/why-exaggerating-your-sto_b_5504282) or [to teach](https://tvtropes.org/pmwiki/pmwiki.php/Main/BlackAndWhiteMorality). ## Exaggeration as embellishment It is a natural human tendency to make stories as interesting as possible. The more exaggerated a story is, the more exciting, and thus the more it spreads. In your example: > > Humbaba had seven layers of armor > > > The fact that it's armor doesn't matter. For all intents and purposes, Humbaba could have had a magical sword that spouted fire on command. What's important is that any element that can be expanded upon and embellished will make a myth successful. ## Exaggeration as a didactic tactic Exaggeration can also distort reality in ways that provide clear morals. In your example: > > Dragons represent the sin of greed > > > Something neutral becomes something evil in order to convey a moral lesson. Gray morality becomes black and white because it's more accessible to kids - and thus smarter-than-average lizards turn into ferocious beasts. There is some pattern in that dragons may represent the unknown, so they make easy antagonists. Still, what's more important is that the exaggeration serves to teach. TL;DR The "what" you are exaggerating means less than the "why." You can exaggerate any part of any myth and it will be believable; myths aren't supposed to be realistic, and there is no such thing as a "realistic exaggeration" because that defeats the purpose. You won't find a framework or meta-analysis of what gets exaggerated because it doesn't matter what - it matters why. [Answer] Please have a look to [Not the Onion](https://www.reddit.com/r/nottheonion/) It is filled with news that could not exist in any sane world. Yet they do. Apply the concept of Fog of War, that means, imperfect decisions made with the imperfect knowledge available at the time. When the dust settles, you can point fingers and say that great leaders made stupid mistakes, yet at the time, it was choosing the lesser evil. Example. Winston Churchill had to sacrifice a town in order to make sure D day would go smoothly. Because if they protected the town, the enemy would know their communications were compromised. Try to explain that to a kid with a smartphone today. That they had THE ADVANTAGE of decoding a fancy typewriter. The kid would scowl and scoff. "Why didn't they use wassap that is encrypted?" Bear in mind your myths predate current history by millennia. Even when they compare apples to apples, the value for a given item changes drastically over time. A single piece of gold was more than the income of a farmer for a year. And the dragon stole it. So it really stole a LOT of your money. Find the dragon's hoard and your farmer is set for life. Because among the hoard you find a handful of silver and gold coins. And that represents the earnings of a lifetime. But the hoard is tiny, a fistful of coins. So both are true. ]
[Question] [ Humans have invented a technology that allows for teleportation of matter across any distance. These devices can, in theory, be scaled up to any size, so long as the necessary construction materials are available. The drawback is that, while any matter can be transferred, there is no way to reassemble it on the other side. Anything that goes in will come out as a cloud of loose particles. In some cases this can mitigated, like re-condensing water vapor, or melting down metallic dust and forming it back into it's original shape. Of course, matter that is already in a particulate form goes through completely intact. Because of this, one of the primary uses of this technology is weather control. Need more rain for crops? Just transfer some from an urban area where it is not wanted. Now, scientists are preparing to construct an array of these devices and placing one side of each on Venus and the other side on Mars. Transferring part of Venus's atmosphere to Mars is the first step in a long term plan to terraform both. Future plans include transferring vast amounts of ice particles from elsewhere in the solar system to establish bodies of water and transferring organic soil "dust mulch" in which to kick start plant growth. Now for my actual questions: 1) Would the difference in atmospheric pressure cause too violent of a transfer? How might this be mitigated? 2) Would the thick, heavy atmosphere on Venus eventually equalize with the thin atmosphere on Mars? 3) If so, would the resultant pressure and chemical makeup of both atmospheres be even close to survivable for humans? Close enough that additional measures could reasonably be taken to make it survivable? Or deadly enough that this whole operation was pointless? 4) Assuming viability, could this process be completed within a reasonable amount of time? 5) To what extent could these devices be used to continually equalize temperature between the planets after atmospheric equalization has been established? [Answer] > > 1) Would the difference in atmospheric pressure cause too violent of a transfer? How might this be mitigated? > > > This is a tanker having the air sucked off of it. It starts at 1 atm and gradually lowers, until the metal can no longer withstand a pressure difference of less than 1 atm (since the tanker never reaches 0 atm inside): [![Moob! The opposite of boom, get it?](https://i.stack.imgur.com/rmsq8.gif)](https://i.stack.imgur.com/rmsq8.gif) Mean altitude atmospheric pressure is about 0.006 atm for Mars and 90 atm for Venus, so... Each mouth of your devices would be facing a shock about 90 more violent than that. If they are not made of handwavium, expect some really cinematographic destruction. > > 2) Would the thick, heavy atmosphere on Venus eventually equalize with the thin atmosphere on Mars? > > > As long as the devices don't break, yes. Depending on the flow you have, it might take quite long though. Think in terms of mass being transfered per time. > > 3) If so, would the resultant pressure and chemical makeup of both atmospheres be even close to survivable for humans? Close enough that additional measures could reasonably be taken to make it survivable? Or deadly enough that this whole operation was pointless? > > > At mean altitude in Venus you have rains of sulphuric acid. Venus's atmosphere will never be anywhere close to survivable to humans without modifying it considerably. > > 4) Assuming viability, could this process be completed within a reasonable amount of time? > > > What is reasonable for you? > > 5) To what extent could these devices be used to continually equalize temperature between the planets after atmospheric equalization has been established? > > > This is too broad, because it depends on how you spread those, the flow you can get, seasonal variations of sunlight on both planets... I suggest opening a new question just for this. ]
[Question] [ The pillars are spread out about a mile apart each, and they all come straight from the ground, slowly gets just a smidge smaller in the middle, and then get bigger near the top, reaching a height of two miles tall. And also would an extremely thick liquid (that isn't lava) underneath hell help? essentially the world is a massive pillar in general, with a layer of floating heaven being held up by pure white magic that goes up near infinitely, which underneath heaven is a flat earth about 200 miles in diameter, and about 1 mile deep. under that is hell, that seems to go on for thousands of miles, so the space of hell definitely accounts for all of earth. then under hell is an extremely thick black liquid going down near infinitely [Answer] TL;DR: For the pillars: nephritic jade. Sounds good, looks good, is super tough. Better hope you don't have earthquakes though. The ceiling is where you're gonna have real problems. A plain flat ceiling will collapse unless you use a roofing material with a really high tensile strength. You probably want to vault it, too. --- Lets look at a single pillar first. Though you've defined pillar spacing, you haven't mentioned pillar layout so it isn't entirely clear quite what proportion of the surface world each pillar supports. Lets imagine that it is a cylinder a mile across, and a mile high. I'm going to move to using metric units now, because imperial ones are weird. With a volume of about 3.27 billion cubic metres, and assuming it has the same density of continental crust, it'll have a weight of about 9.26 billion tonnes. Assuming the pillars are perfectly cylindrical (you said they weren't, but didn't give a minimum diameter) their cross-sectional area will be 2.03 million square metres and therefore the pressure they'll be under will be about 178.65MPa (for reference, the compressive strength of concrete can be as high as 25.57MPa, so your pillars need to have stronger than that). There's a frequently cited, but never actually referenced figure that suggests that the rock with the strongest compressive strength is [nephritic jade](https://en.wikipedia.org/wiki/Nephrite) at 400MPa. I'll take that figure as true, though it could be a load of cobblers for all I know (a figure cited [here](https://sci.geo.mineralogy.narkive.com/9i7dcli7/physical-properties-of-jade) suggests more like 370MPa, but it is still just about high enough for our needs). It has a density around 3.15g/cm3. The weight of the pillar and the earth above it combined give a pressure at the foot of the column of 278MPa. Using nephritic jade would give you a safety margin of about 1.43. Note that this is a static safety margin... if your hollow world experiences earthquakes, you might have more serious problems, but that's a question for another day. What I'm less sure about is the bulging of your pillars as they're squished from the top. I think they might be OK, but I'm quite far from certain on that. Maybe some nice metal reinforcing bands might help? --- The next problem is the unsupported span of earth between two pillars... there's at least a half-mile gap between the edge of one pillar and the start of the next (I say at least, because depending on how your pillars are laid out the gaps might be larger... in a square grid, the diagonal spacing is more like .91 miles) and that's a big span for rock to cover. Even nephrite with its impressive compressive strength isn't nearly as strong in tension and has a tendency to fracture instead of yielding. I threw some figures into the simple bending equation, and they didn't come out well. I'm not a structural engineer, so I won't repeat my amateur scribblings here because they're so far from an accurate assessment of the situation but: that roof ain't gonna hold, even if it were pure jade. The unsupported span is just too great. It'll crack in the middle, and everything will crash down into hell, crushing everything. Sure, the surface world will be ruined but hey! no hell anymore! You might be able to fix this with a carefully [vaulted ceiling](https://en.wikipedia.org/wiki/Vault_(architecture)), but I wouldn't want to say for sure. Really, you need to be making that ceiling out of some kind of reinforced composite if you don't want it to be crashing down on you. [Answer] Let's proceed with some approximation. Per your statement, the columns are equally spaced, 1 mile apart. If they are arranged in a square lattice, it means each column hold a cube of 1 cubic mile. The weight of a cubic mile of Earth, assuming it is basalt, will be given by its volumes times its density. Basalt density ranges around 2700 and 3100 $kg/m^3$, let's make it 3000, and 1 mile is 1609 m, which gives for our cube a mass of $M=1609^3 \cdot 3000 = 12.5 \cdot 10^{12} kg$, or $12.5 \cdot 10^{13} N$. Let's also simplify the shape of the column to be a cylinder 1 mile in diameter, its cross section will be $2 \cdot 10^6 m^2$, therefore the load will be $P=$$12.5 \cdot 10^{13} \over 2 \cdot 10^6$$=62.5 MPa$. That is $62.5 \cdot 10^3 kN/m^2$, out of my mind that's about thousand times what concrete can withstand. I think no real material can withstand that compressive load. ]
[Question] [ In theory organisms derived from birds through genetic engineering could resemble theropod dinosaurs. So my question is what animals would serve as the basis for the other two groups of dinosaurs (sauropodomorpha and ornithischia)? (I'm not trying to re-create dinosaurs, merely create look-a-likes). [Answer] Still birds. Therapoda, sauropodomorpha, and ornithischia all have a common ancestor (and, in fact, that common ancestor is the taxonomic definition of "dinosaur"). So, if you've got the genetic modification mojo sufficient to dial a bird back to something resembling therapoda, you can do the same for its sister classes. Probably using bird eggs, replacing the nuclear DNA, and fertilizing/hatching the result. Ornithischia would be particularly easy, since the build/gait of that family is explicitly birdlike. Now, as [Shadowzee](https://worldbuilding.stackexchange.com/a/158469/36850) suggests, you could potentially cheat with sauropodomorpha with some modern animals and extensive modification, but a combination of genetic modification and breeding would probably more closely approximate "dinosaurs". This all said, to quote Dr. Henry Wu: > > Nothing ... is natural, we have always filled gaps in the genome with the DNA of other animals. And if the genetic code was pure, many of them would look quite different. But you didn't ask for reality, you asked for more teeth. > > > [Answer] Crocodilians and birds, that gives you all the relevant genetic material you can possibly get. Then you just have a metric buttload of engineering and breeding to go through. you will have to go through several generations just to get something that can produce big enough eggs. [Answer] I would imagine from just pure physical similarities, you could probably use elephants, rhinoceroses or giraffes to fit your purpose. They have the size and body shape already, but would require adjustments to how quickly they grow and the addition of bone growths on their body to better resemble the dinosaurs you seek. While birds and reptiles might be more closely related on a genetic scale, there are far too many physical changes that would need to be applied to use them as the basis for your genetic modification. You also do not have the same environmental factors in play, so a more traditional dinosaur might not even survive in today's environment. ]
[Question] [ I recently watched Wifi Ralph. There is a scene where > > Disney princesses teach Vanellope a mechanism that allows her to unlock the wonderful, magical power of diegetic music. > > > Didn't want to read the spoiler? No problem, here goes an explanation. [Diegetic music](https://en.wikipedia.org/wiki/Diegetic_music) is a part of the soundtrack for audiovisual work that is generated within the world and thus is heard by the characters. Usually, in Disney works, the power of diegetic singing seems to be ubiquitously present in populations (think of Belle and Moana's introduction songs, in which whole villages harmonize into it). Yet not all characters are able to sing properly (i.e.: Donald Duck, whose bad, tone deaf singing can even be weaponized), suggesting that this ability is a genetic trait rather than a physics paradigm of such worlds. --- Characters that can break into song at will and in any place usually have orchestral backing to their singing. This means they have an internal, organic jukebox which can mimic most (if not all) musical instruments, and which is loud enough to be perceived as such. How would this fit into their anatomy? What would the caloric costs involved be? --- For the purpose of this question, I am ignoring the fantastical powers of bending light and controlling the elements which usually accompany diegetic songs (no walking through the air because you know the colors of the wind, for example). For the purpose of this question, I am also assuming that all characters capable of diegetic singing are gifted with [absolute pitch](https://en.wikipedia.org/wiki/Absolute_pitch). --- Part of the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798). [Answer] You could use the Lyrebird, arguably the best sound mimicking animal, as a base for an 'organic jukebox'. Birds have a syrinx that can mimic a wide array of sounds. The syrinx, which is pretty much a chamber supported by cartilage slightly (very slightly!) similar to a larynx, is located just under the bird's voicebox, enabling it to make nearly any sound, plus different ones at the same time. So diegetic singers could have multiple or one syrinx in their throats. That's the most anatomically correct jukebox I can think of at the moment, and it shouldn't have many if any adverse affects on the singer, though, like any song, it does take energy. Likely not much more than normal singing, though. Here's a study on respritory and metabolic affects on birds singing louder, if you like. <https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023198> Out of curiosity, why do you assume diegetic singers have absolute pitch? Maybe I'm wrong, but I've never seen people shout "Sing in Am! Now F#!" to the singer. ]
[Question] [ I've plans for somewhat 'realistic' (and that's already quite a stretch of the word) superhuman characters whose muscles have the strength, density, and tensile strength that can stop most low-powered firearms (probably a 9mm pistol at the most). I figured that strength and density doesn't play a huge role with stopping bullets, but do offer some defense against stabs and slashes (and the super strength thing). An object's tensile strength is usually what stops bullets, but a muscle's tensile strength is usually quite low (no matter how much you weightlift), so I was wondering if having bullet-stopping tensile strength on one's muscles would drastically change a character's physical characteristics? Specifically, would it change what they look like? Would they still even look human? [Answer] My friend, grab graphene and roll it. Voilá! nano tubes. These are posed as real world wonders that can make almost anything (except leaving the lab so far.... ) [Artificial muscles made from nanotubes.](https://phys.org/news/2011-10-carbon-nanotube-muscles-giant-motors.html) The mechanical upper limits are dictated by the weakest part of the chain. In this case, since the material that makes the muscle can take TONNES per strand of hair, your ligaments will snap. Say your ligaments are anchored to the bone using nano tech too.....Your bones snap. So you add a graphene matrix in your bones. Now you can take a hit. Lets distribute that energy even further. Add non newtonian layers that hardens on violent impact like suspended silica or calcium on some liquid. [Liquid armor on the wiki](https://en.wikipedia.org/wiki/Liquid_Armor) The end result? Get shot, your skin outer layer gets damaged but as soon as it hits the subdermal muscle tissue, it inflicts pressure. The pressure makes the suspended particles push the strata out and harden. Since this is contained on a material taht can hold tonnnnnes of kilograms in tension, won't burst. Possible cons would be how to get a surgeon to operate you in the event you have a medical issue. Run of the mill tools won't cut it. Also you take all the energy since even a 50 cal won't pass! A full auto machinegun will push you, since it will transfer almost all the energy to you. A 50 cal could hurt your brain due to clashing inside your skull. Most common injury on traffic is when your organs hit your ribcage or brain hits the inner skull. Instantly accelerating as effect to .50 MBG to the triceps will mess your internal organs something fierce. 9Mil parabellum will be a risk on your head since your eyes lack protection. Also your fingers lack any real muscle group to shield them. All in all, a real dangerous individual who can take thousand of Nato 7.62 and lower bullets to the gut/arms/legs. And stands a fair chance to take a 50 cal and tell the tale. Not to shabby, eh? [Answer] There are 3 general ways to make something more bulletproof: ## 1. You can make it harder so that it can disintegrate the bullet on impact Your muscles' ability to give and flex is vital to motility. Making them hard enough to disintegrate a slug would make them useless as muscles; so, I highly recommend avoiding this approach. ## 2. You can make it thicker so that the bullet needs to ablate more material to penetrate it Thicker muscles would make you slightly more bullet resistant. A low calibre round that has to go through thicker pectoral muscles is less likely to make it past your rib cage to hit a vital organ, but muscles would have to be obsenely thick to actually stop anything bigger than a .22. Again, you run into the issue of mobility vs protection. As many bodybuilders can tell you, by the time your muscles get that thick, you lose most of your flexibility. ## 3. You can make it better at impact distribution. This leaves impact distribution. Your muscles are already great shock absorbers. It is why a person with good muscle tone can take a punch to the gut so much better than someone who is out of shape, but muscles have a weakness when it comes to being penetrated by bullets. They are [striated](https://en.wikipedia.org/wiki/Striated_muscle_tissue). This means they are made out of parallel fibers optimizing their ability to pull along their needed vector. Along that angle you can punish them all you want with relatively little risk of injury. However, bullets generally hit muscles along the sides which allow them to force themselves between the muscle fibers with relatively little force. If muscles were woven more like kevlar, they would be immensely harder to penetrate. Unlike thicker or harder muscles, woven muscles would not significantly reduce flexibility, but you might suffer a bit of a reduction in pulling strength since you are no longer pulling straight. Perhaps a better option for natural armor without seeming less human would be reinforcing your person's entire body with [dura mater](https://en.wikipedia.org/wiki/Dura_mater). Dura mater is the outermost protective membrane that covers your brain and spine. It is exceptionally strong, flexible, and made out of irregular cross-woven fibers. A [report from the New Jersey Public Health System](https://www.state.nj.us/health/spinalcord/documents/reports_pubs/2004/04-2903.01.pdf) shows that the dura mater of rats can withstand 1.3 million Pascals of stress, which is a lot especially given their size. By layering dura mater between your skin and striated muscles, your person would look, feel, and move very much like a normal person, but when shot by a low caliber round, the fibers of the dura mater would distribute the impact across a large cross section of muscles instead of letting it just pierce between them. With the impact distributed, your muscles could do what they do well and compress. By distributing the impact across a larger surface, you'd probably have torn skin, plenty of bruising, and some some serious muscle inflammation after getting shot, but the bullet be a lot less likely to be able to impact in major organs. ]
[Question] [ I'm working on an idea for a story. It takes place in the somewhat distant future, say 200-300 years. Some time between now and then, an event occurs which causes all computers to simultaneously fail. This event is NOT the result of terrorism or malice, it is more or less, an accident. (specifically it is caused by a well-intentioned AI that is less powerful than expected and cannot withstand the strain of all the tasks it is given) For the purposes of the story, I want this event to greatly reduce the population of Earth, and also effectively put an end to most or all major cities. I don't want it to threaten extinction, just reduce the number of humans by some large percentage (a lot of leeway here). My problem is, I'm not sure what we could rely on so heavily that would cause this much destruction. I imagine that the following thing would happen all nearly simultaneously: * Complete failure of power grid * Meltdown of all nuclear power plants * High-tech farming equipment no longer functions or malfunctions * Traffic lights, streetlights, trains, subways all either fail or malfunction How much actual damage would these failures do? Would these things alone be enough? What other consequences could there be? EDIT for clarity: I am not looking for something that would cause technology to fail, I am looking for the effects of loss of all technology and how it would reduce the human population. [Answer] The answer to this is actually much more mundane than you might think: ## Food Supply Keeping cities fed, watered, and clean is a masterpiece of logistics. Agriculture, food processing, and delivery is all carefully coordinated to bring thousands of tonnes of food into major cities daily. You don't need high-tech tractors to fail to induce widespread starvation, just having the delivery databases go away would be sufficient to kill millions. Then, of course, as food rots where it's delivered in excess or lies undelivered, you have food riots, as starving people break into places rumoured to have food. This destroys more infrastructure, breaks up society, and encourages pestilence in its wake. It's a very real "for want of a nail" situation that could happen at any point. In the wake of the food supply failing, other logistics/manufacturing would fail as well. Depending on the urban population density, the death toll could be in the billions, worldwide. As a side note... Of the points you mention, "Nuclear meltdown" is the least likely. As has been explained on this site many times, abrupt failures of various systems in nuclear power plants leads to the plant either shutting down or permanently safeing itself unless something catastrophic (earth quake, bombing, tsunami) happens to the structure of the plant. Most nuclear plants, even lacking their computers, would just quietly shut down forever, rather than melt down. [Answer] I'm not sure if this helps, but in case you have not read it yet, there is a book called The World Without Us, by Alan Weisman. There we learn how long the nuclear plants and buildings will last if there are no humans left (they disappeared from one day to the next) to maintain them. Since your story is about the sudden loss of technology, some of the consequences should be similar or the same as the scenario of the sudden disappearance of humans (and there are probably a list of beneficial sources he used to write it). But if this takes place a couple of hundred years from now, I'm assuming the technology have evolved, which would affect society in a way it doesn't today. [Answer] Well one easy thing would be artificial wombs. If people are mostly grown in tanks and therefore probably all sterilized the loss of tech would mean that the next generation is going to be very small and the population crash happens non violently. Even short of this the failure of medical infrastructure is going to have an impact. No more robot doctors or pill factories is gonna kill a lot of people. Also the possibility of the failure of containment systems could mean something like smallpox is released again and kills huge numbers. ]
[Question] [ I'd like to know if a climate with snowy and gloomy winters and rainy and cloudy summers is possible. Because the climate of Russia in summer is sunny enough and the Icelandic ones isn't so snowy. So a climate snowy in winter and rainy in summer but with forests and the possibility to sustain life, what characteristics are required? I want an almost always overcast sky. Thanks for the answers. I forgot to mention that this type of climate, is for a Europe-like continent in a planet that orbits a star less bright than the sun. [Answer] 1. Put your place between the ocean and a mountain range. Wet air coming in from the ocean tends to dump its water on the ocean side of the mountains. You get a climate like Portland or Seattle. 2. Put your place far enough north that it gets cold. Then the wet air dumping water will come down as snow. Possibly a lot of snow. The ocean will prevent it from getting bitterly cold. The northern latitude will prevent it from getting too hot. You wind up with someplace like Anchorage Alaska or Buffalo NY -nice temperatures all year round, and near constant rain and snow. [Answer] Ursula K. LeGuin does a good job with this kind of environment in "The Left Hand of Darkness". Direct sunlight isn't needed, so long as there is enough radiant energy to grow some kind of crops, or to support a sufficient amount of wildlife for a hunter/gatherer society to live off of. A sunny region can produce 600 calories per square centimeter of arable land; an environment like you're describing might produce less than 100 per square centimeter, which puts corresponding restrictions on population size. It would probably demand a fishing industry, which could shift solar energy conversion to off-shore sources (like algae and other aquatic plants) and bring in essential fats and protiens from fish or aquatic mammals. Technically speaking, you could create an environment with no solar energy at all, so long as you found an alternate source of energy to convert into organic sugars. Think about hydrothermal vents in the deep ocean, and their associated colonies of worms and shrimp and exotic bacteria, except on a massive scale... Not a place I'd want to live, thought. ]
[Question] [ Gray skin and red eyes is a common look for Dark Elves, and I have a similar race in my own world. But what would physically cause such an appearance? Hard Requirements: 1. Must not be the result of severe life-altering disease or require extreme deviation from normal human biology. 2. Must be true gray, not purple or dark brown or something. soft requirements: 1. Should be permanent and inheritable, not just a temporary state or tattoos. 2. Should not cause bizarre texture or scaly/rocky look. The gray people should be potentially pretty, because otherwise they'd be called goblins, not elves. I've had a thought that my gray people are gray because, like an elephant or dolphin, their skin is thicker and so fewer blood vessels show through. EDIT: I've now been informed that elephants and rhinos have gray pigmentation. I wasn't aware such things existed. Would that cause them to look excessively wrinkly or chubby or sandy though? Another possible explanation is that they ingest something that makes their skin grey, much like argyria. However, that particular condition actually makes the skin more shiny purple than gray. I'm not aware of a condition that makes you gray like Dark Elves, that doesn't also kill you. So these guys don't really look like the glamorous but grim dark elves that we want in fantasy, but it's halfway there. I know how to satisfy the hard requirements, but not the soft ones. I was originally going to also ask about red-to-yellow eyes, but they're covering that over in [How would red eyes occur in a human (without underlying medical conditions)?](https://worldbuilding.stackexchange.com/questions/28060/how-would-red-eyes-occur-in-a-human-without-underlying-medical-conditions) [Answer] I can think of two explanations for your grey-skinned people. The first is the obvious explanation. They have a pigmentation that is grey. Just because we don't see this manifestation in our population doesn't mean that there isn't an organic compound that can produce the effect. The other explanation is that they have two forms of pigmentation -- one black and one white -- that populate their skin in a uniform distribution at a specific ratio. In short, their skin is pixelated with tiny black and white dots. When viewed from a distance, the human (or elven) eye will see this as grey. The ratio of black and white dots determines the darkness of the grey since not all individuals may have the same shading. [![enter image description here](https://i.stack.imgur.com/1cObl.png)](https://i.stack.imgur.com/1cObl.png) The hairless guinea pig sporting its 'grey' skin ]
[Question] [ I recently saw [this](https://worldbuilding.stackexchange.com/a/154453/58321) answers where it was suggested that the galactic core could illuminate a planet suffiently to make sure it is always summer on one side of the planet. This got me curious and after some research I came across [this](https://earthsky.org/space/what-does-the-center-of-the-galaxy-look-like). > > Astronomers have estimated that the total luminosity of the central dozen or so light-years of our galaxy is equal to about 10 million suns. That sounds big and bright – until you recall that the center of our galaxy is 25,000 light-years away. At that distance, if interstellar dust weren’t in the way, our unaided eyes would see the central part of our Milky Way galaxy as a central glow no bigger than the planet Venus, and no brighter than one of the stars of the Big Dipper. Interesting … but not blazingly bright. But wait. There’s more. The fact is that interstellar dust obscures more than just this central region. It also dims the light of billions of foreground stars, as well as stars surrounding the core itself. If there were no dust between us and the galactic center, the light of all the stars located toward the galaxy’s core would easily exceed that of a full moon. If you looked in that direction, you wouldn’t see much else but the combined glow of billions of stars. > > > While the first part of the article gives a value of luminosity, the second part points out why one should ignore it. *So given the fact that the galactic center is quite bright, yet itself a terrible place for planets due to gravitational interaction between stars, is there a habitable zone around the galactic centre* in which a planet on an orbit inclined enough that it won't be shadowed by the discs dust clouds could be habitable?** I know that when the planet will invariably cross the galactic disc it will receive much less light and have an ice-age, but this is beyond the scope of the question. I would actually prefer if formulas were given in the answers instead of a simple yes or no. [Answer] Well, let's do some back-of-the-envelope calculations and see where our intuition gets us. The sun gives off about 3.846 x 10^26 watts of power. At our distance from the sun, we get about 1360 watts per square meter of solar energy intensity. Let's be generous and round the sun's intensity up, and the needed solar energy for a habitable planet down, so we get 4 x 10^26 watts for the sun and 1000 watts per square meter of intensity. Multiply the figure for power by 10 million and we get the total power output of that central dozen-or-so light years of the galactic core, which comes out to about 4 x 10^33 watts. That's a lot of energy. The question is: Can a planet be outside that radius and receive enough energy to survive? Answering that is pretty simple. Just find the surface area of a sphere 12 light years across, which turns out to be 4.05 x 10^34 square meters. Divide 4 x 10^33 watts by 4.05 x 10^34 square meters, and we end up with... 0.988 watts per square meter; less than a thousandth of what we want to support life. And this is just at the perimeter of that brightest point in the galaxy. I'm not sure how I'd go about calculating the total power output of the entire galactic core, but my intuition tells me that if the brightest point in the galaxy can't muster the necessary intensity to light up a planet that's practically inside of it, I don't see how the much-less-dense galactic core will be able to do better to a planet that is outside the galactic core altogether. Although, going back to orbiting the 12-light-year area at the center of the galaxy, I suspect that you COULD make a habitat that could survive off of the radiance of the galactic core. It would need some truly gargantuan solar collectors, but considering that those can be mirrors made effectively out of aluminum foil, it is within the realm of possibility. Perhaps the planet itself could have an gigantic array of mirrors orbiting it, gathering the energy from an area a thousand times larger than the cross-sectional area of the planet itself, and bouncing it down to the surface. Again, though, this would require the planet to be within the bounds of the galactic core, a mere six light years from the center of the galaxy. EDIT: Actually, I take it back, sort of. The total power output of a region of space might be approximated by the total number of stars in that region of space. The total number of stars could be approximated by the volume of that region of space. The volume of an sphere increases with the cube of the radius of that area, while the surface area increases with square of the radius. With this in mind, if the central 12 light years of the galaxy was expanded out to 12,000 light years, with the same density of stars, then the power output would be a billion times greater while the surface area of the region would only be a million times greater, giving us close to the intensity we were looking for... except that a volume of this size can only be approximated as a point if you're pretty far away. If you're right up next to it, you aren't going to get anywhere near that much power, so it's still a bust. ]
[Question] [ ### A Question on the Balance of Ecosystems on the Microbial Scale Say that we had some living quarters on an Earth-like planet, within a moderately-sized base. The inhabitants of this base can freely roam the planet without environmental protection, and thus can bring back some less-than-pleasant microorganisms that like to group together then feed upon big sleeping things. As a result, before this base gets too large to keep proper tabs on all of its residents, the Powers that Be are investigating a sort of automated room-wide decontamination field. This field would trigger at regular intervals, and absolutely kill everything in the room, with no regard to size or composition. Safety is paramount, but not the focus here -- what the Powers are investigating at the moment is how this might affect the microecology of these areas. Simply put, how would completely wiping a room of all microbial life once a day affect the bodies of those living in said room? The Powers are aware that there are many beneficial microorganisms which we humans live in harmony with, such as [those that help us digest](https://www.ck12.org/biology/digestive-system-bacteria/lesson/Bacteria-in-the-Digestive-System-MS-LS/). Would a regular wipe harm these, or other symbiotic microbes the Powers may be unaware of? To be clear, the residents would be nowhere near these rooms when the sweep occurs, so there would be no direct cleansing of a person's internals -- though it is suspected that sleeping in a clean room may upset some delicate balance, or throw off one's immune system. Bonus points for explaining scalability. Perhaps a room means nothing in the grand scheme of things, since these humans will be out-and-about most of the time anyhow. But what if we did this to entire buildings -- might office workers start to suffer, spending all their time in massive clean zones? [Answer] Nothing, really. Here's what you aren't doing - getting rid of bacteria which is harmful to humans. Any bacteria that you bring in which is harmful to humans can live inside humans, and since humans are exempt from this treatment, all it takes is a human inside your sterile room for a few minutes, have him cough a few times, and presto! the room is now non-sterile and back to it's harmful to human state. The stuff you will kill is stuff non-harmful to humans, like fungi or really small mites. That said, there's a few different kinds of fungi that need to grow to produce spores which are harmful to humans, so you won't have to worry about wall mold. The fact remains that diffusion is a really strong force. If you irradiate one room at a time, randomly, you won't clean the base of airborne bacteria, because it'll just keep circulating, and reproduces fast when given a non-competitive environment (i.e. a human). Ditto to a building, it'll just take a few days to go back to normal. Now, would there be problems for humans if we just up and killed every single microorganism on the face of the planet that wasn't already in a human? No. The only microorganism humans have a symbiotic relationship with is mitochondria. So long as we can get nutrition, (which isn't dependant on bacteria either) humans will be fine. ]
[Question] [ Part of my story will be set on a planet where a culture similar to that of the Old West has arisen - cowboys, frontier towns, homesteaders, etc. In order to make this development more plausible, I want the entire surface of the planet, or large swathes of it, to be fairly similar in terms of climate and general nature to the Great Plains of America. The most important aspects here are the plain landscape, the infertile, dry soil, the extremely hot summers and freezing winters, the violent storms. Is there any specific scenario - a given orbit, a given star type, a given planet type, some set of planetary or solar characteristics - that would make this plausible? [Answer] In lieu of any other answers being written, the answer to your planetary configuration is primarily a matter of water. Some basics. The reason why living on the coast is so temperate (warmer nights, cooler days) to living in deserts and inland environments is that it is close to a massive body of water called the Ocean. Water is an ideal thermal mass; that is to say, water absorbs heat from the environment when it's hotter than the water, and then releases it when the environment cools. Deserts have the reputation of being really hot, but at nights they are also really cold because there is nothing slowly releasing the heat through the night like water does on the coast. The thing is, if you have a desert planet, you don't have enough water to support life. So, what you need is a planet on which the water does not evaporate as quickly. This means you either need a planet like Earth in terms of climate but with little water (say around 20% of the surface covered in a large central ocean) or a planet a little further out from the sun so it's colder, but carries more water to trap what heat comes in but without massive evaporation / condensation cycles that we have here on Earth. As has been mentioned in comments, you would want less water than Earth still, but you could get away with significantly more ocean as a percentage the further out you are from the sun, so long as your planet is still in the goldilocks zone. A final thought is that if your planet has a high concentration of greenhouse gases in its atmosphere, especially CO2, you're probably able to go out even a little further still, but the history of the earth tends to indicate that you shouldn't rely on such a mixture as a permanent feature of your atmosphere as it can change significantly over geological epochs. Better to be closer in where atmospheric gas ratio fluctuations can't cause global extinction events by freezing a planet over completely. In short though, the rule of thumb is that the less water (thermal mass) you have in your environment, the bigger the difference you'll see between summer and winter, day and night. ]
[Question] [ Ok so I was thinking about a way to hypothetically have undiscovered elements with bizarre properties (for unobtainium purposes). And an idea hit me: replace nucleons with heavier but stable counterparts to replace the strong nuclear force with gravity. Let’s consider the makeup of an atom of what I’m gonna call Heavy Matter: Heavy Protons, which have the same charge and properties of ordinary matter, but are about ten orders of magnitude heavier (the needed mass to make gravity as powerful as the strong nuclear force). Heavy neutrons, ditto. Heavy electrons - not muons for reasons that will become clear in a moment. What this would mean is the strong nuclear force would be matched and equaled by gravity in overpowering the Coulombic repulsion between the nuclei. This would have a strange effect; in the inverse to ordinary matter, heavier nuclei are more stable. For a light nucleus (like the elements we encounter in everyday life), the strong nuclear force is more than enough to overcome Coulombic repulsion - so all that ‘excess’ gravity would just crush the nuclei together, turning it into a miniature black hole that would vanish into Hawking radiation so quickly that it would barely have even existed. For a heavy nucleus (like the elements that are extremely unstable or non existent in real life) the remaining slack of the Coulombic repulsion that the range-limited strong nuclear force can’t meet is matched and equalled by gravity. This means you could have a stable element with an atomic number of say, 500. Everything I’ve written so far is kinda in the realm of plausibility, I think (that’s why I’m verifying it here). And now the ubontanium part comes in. The heavy particles also have the ability to nullify or weaken gravity, but only under very specific circumstances. This ability is related to charge; charge is directly proportional to nullification ability. What this means is the heavy electrons strengthen gravity and the heavy protons weaken it, so in a normal atom they just cancel out. However, ionise it and interesting stuff happens. Negative ions of material greatly increase gravity in a given area, although you can’t have that effect be too strong because the nucleus collapses in on itself and becomes a black hole, which makes that kind less useful. Positive ions of material reduce gravity in a given area. Since gravity is the attractive force in these nuclei, reducing it puts more bulk on the strong nuclear force and means you can’t really do that with the bigger Heavy elements because they just radioactively decay very rapidly. The lighter ones, however, can reduce, remove, and even reverse gravity. And that means you effectively have negative mass if you pick just the right Heavy element and heat it to an incredibly high temperature to ionise it. Which is the condition for the Alcubierre Drive, i.e one of the main feasible forms of FTL travel. How feasible is all this, ignoring the gravity alteration, which is what TvTropes would call my One Big Lie? Are there any affects of the heavier atomic particles, gravity stabilised nuclei, and ionisation = gravity alteration phenomenon that I haven’t anticipated? [Answer] Skeptical about antigravity. I already bought muons and heavy counterparts of nucleons. I am ok with other ones. I buy the heavy matter. I like the stable superheavys because everyone likes that. The unstable light ones is a cool ramification; OK with that. As Dutch points out you need some other route than supernovas to get this stuff. Possibly it is from another dimension or created artificially? But I am not with you on the jump to antigravity and that is your question. How do more massive particles counter gravity? Mass and space team up to make gravity. Gravity does not care about electrical charge as far as I know. [Answer] > > For a light nucleus [...] the strong nuclear force is more than enough to overcome Coulombic repulsion - so all that ‘excess’ gravity would just crush the nuclei together, turning it into a miniature black hole that would vanish into Hawking radiation so quickly that it would barely have even existed. For a heavy nucleus [...] the remaining slack of the Coulombic repulsion that the range-limited strong nuclear force can’t meet is matched and equalled by gravity. > > > In our universe light nuclei are formed or immediately after the big bang, or within the stars (up until Fe). Nuclei heavier than Fe are formed with supernova explosions. In your world light nuclei do not exist for long time, thus star do not exists, thus heavy nuclei cannot form: any nucleon will be turned into Hawking radiation way before it can form an heavy nucleus. ]
[Question] [ The gods have given up on the habital planet scheme and have decided to design this universe differently. They have filled it with a space structure called a banks orbital. These habitats are purpose-built space habitat forming a ring many miles in diameter. The rotation of the ring simulates both gravity and a day-night cycle comparable to a planetary body orbiting a star. These rings are massive, having the planet surface of 25 earths. Its inhabitants live on the inside of the ring, where continent-sized "plates" have been shaped to provide all sorts biomes. Many exist, such as deserts, jungles, etc. The natural environment and climate are similar to Earth, only covering a larger area. I want a way to determine how many people can live on these massive rings in total without it becoming overcrowded enough to cause an issue. Our world has about 7 billion people, so I determined that I should multiply that by 25. However, this sounds stupid. What can I do to find this answer? [Answer] How many people can a planet sustain depends on what is the standard of living that those people consider comfortable and what the planet can produce. If you think you cannot live without drinking sparkling ice cold water all year round it's not the same as if you settle for sipping water from down the river. For us earthling a somehow reasonable indicator is the ecological footprint, which, based on a set of habits, calculates how much surface of the planet is needed. That surface per person, given the planet surface, allows to calculate how many people can the planet sustain following those habits. $Max \ Sustainable \ People =$$Planet \ Surface \over Person \ Ecological \ Footprint$ Since you state that the ring world is Earth like, you can use a ecological footprint calculator available on line and do the math. Hint: according to this parameter, we are already using more than 1 Earth to sustain those 7 billion people. I just checked, and with my standard of living humanity would need 4.5 Earths to sustain itself. [Answer] If you want to find out the maximum possible you should choose the most densely populated places on Earth which have your desired standard of living and produce more food than needed. If you want to go to extremes, you might also check how much they waste with meat production, unused land, land used below the best used land (houses vs. skyscrapers, greenhouses vs. traditional farms and so on). The Netherlands has a high standard of living, a high population density and exports more food than it needs. It has 400 people/km2, and with above mentioned improvements could probably handle twice that with today's technology and standard of living. Earth has 500 million km2, of which around 400 million km2 can be made habitable (including swimming islands, as we are now seeing increasingly in the form of floating fish, mussle, and other farms). That makes a total of 25x200 billion people (as your ringworlds don't have poles), or 5 trillion people. ]
[Question] [ Okay so, this is kind of a disgusting question... sorry about that in advance, guys. Say you are super strong, super fast, and super durable. There is a not so strong, fast, or durable normal human standing within punching range, and you are a murderous sort and want to punch them. But not just punch them, your goal is to punch through them and connect your fist with their spine (aka put your fist nearly all the way through their body. Gross.) Let's say this normal human is a male of around average height, weight, and build. You are about 6 ft tall with what appears a healthy human physique (aka you may look muscular, but not appear extraordinarily fat). In actuality, though, you are denser and may weigh up to twice as much as an average human of your height and build (I suppose I am saying you may possess up to twice the mass?) If I understand this correctly, how hard a punch hits is determined by your fist's momentum, or the combination between mass and velocity. So my question is: What acceleration would you need to achieve during your attack in order to impart enough force to punch your fist into a human body? What happens to you if you do this? (By this I don't mean injury, as I've stated you are extremely durable. I am asking if punching with this much force would throw you off your feet/balance, etc.) If it's necessary, you can be wearing heavy armor on your arm and/or body to increase your overall weight; you are strong enough it won't slow you down. [Answer] You can get really complicated about this, but if we're really keeping in the spirit of the question you're asking, the answer is that "you can't punch someone hard enough to put a hole in them." Not unless the Puncher and the Punchee are made out of Different Stuff. The problem is that a fist and a chest (for example) have roughly the same density and the same structural integrity, more or less, so something that's made out of the same kind of materials as a human body is a: isn't physically CAPABLE of moving a fist that fast; b: if they could, the fist and the arm would take almost as much damage as the person getting punched would; and c: the punchee would be getting pushed backward by the blow, dissipating the force more rapidly than you can open up a hole through to their spine. Now, if your Punching hand is significantly harder and/or denser than a normal human body, then it doesn't have to move very fast at all in order to be able to go through someone. this is really the answer to your question tbh. If you want to punch a hole in someone with some science behind it, your puncher has to be punching with something a lot harder and stronger than what a human is made out of. [Answer] Im not sure if it would be possible but, in order to give this punch the best possible chance of punching through someone, here are some things to consider. Firstly, you will want your ‘target’ to be braced against something hard. The reason being is that, as you punched them, they would move and absorb a lot of the force. However, if they are braced against the floor or a tree trunk or a concrete wall, they arent going to move backwards as much, reducing the forces they can absorb. I will assume they are against the floor so that way, gravity is working with you, not against you. Next, we have to pick where about we are going to hit. This is pretty simple as we are trying to punch through to the spine so we know it is the front of the torso. Your best bet is likely through the lower half of the torso, if you aimed for the upper half, you’d need to also break through the rib cage. Now, you’d need to overcome the shearing strength of human skin and muscle (though i can’t find any source that tells you what this could be) but, assuming you could apply enough PSI to an area the size of a human fist (roughly 0.45 meters squared in this case) you might be able to do it. For the best effect, i would suggest your humanoid jumps and lands on the target’s soft tissue fist first, applying all of their bodyweight behind the target which is backed against a solid concrete floor. Alternatively, if you’re just trying to punch someone in their spine by punching through them, that would require a lot less force than punching a hole clean through them. [Answer] A quick ballpark I found one source that states the average shear strength for flesh is about 0.4 MPa or 60 psi. Seems somewhat reasonable based on the known danger of compressed air. Looking at my fist, I guess the area at about 8 sq inches. The means your punch would have to be about 480 lbs force - sustained through the punching depth from front to spine of about 8 inches. In reality, punching a person this hard would not be enough because the shear strength will be offset by compression of the targets flesh and momentum transfer. At a guess, I figure 1000 or even 2000 pounds of force is more realistic - but quite possibly not very accurate. I'll assume 1500 pounds. Force says nothing about speed, and in reality shear strength varies with speed (slow speeds gives more time for material to tear). These question then becomes how do expect to have 1500 pounds of force at the end of your punch. If you can supply 1500 pounds force continuously during a punch, you won't have to slow down during penetration, otherwise you need to be fast enough that that kinetic energy carries you through the punch as you can't supply enough force to maintain penetration based on continuous muscle force. This answer assumes the super strong person has material properties much stronger than the target, otherwise you have to compensate for the compression, etc. of the arm delivering the blow. [Answer] ### Their fist would be going as fast as a bullet. Your question is about how you'd go about hitting someone's fast enough that the thing you're hitting them with is able to punch a hole clean through their body. Fortunately, we have these in real life: they're called "bullets". A bullet is simply a small, dense mass that moves at a high enough velocity that it will punch a hole clean through the body of a human it strikes. There are a number of images on the Internet of the damage that a bullet can cause, using ballistic gel as a proxy for human flesh. So, in order for your murderous superhuman to punch a hole through a human body, their fist will need to go approximately as fast as a bullet. ]
[Question] [ In the world I am creating, a chunk of the USA, specifically in Northern Oregon, is teleported to another world. The teleported section has all infrastructure intact, including power generation in the form of hydroelectric dams and wind turbines, as well as water and sewage systems intact. The phone and radio towers within the region are undamaged. Specifically, I am wondering if the electricity would still work, as it is normally connected to a larger grid system, and if cellphones would still work, as while they have the towers, there is presumably no data center to actually manage them. My knowledge on the cell phone part is incredibly rough, so an overview as to why they would or wouldn't work would be appreciated. I would presume that a large portion of the internet wouldn't work, as while computers and phones would still be able to access it, they can't actually connect to any servers outside the teleported area. Is this assumption correct? [Answer] Electric power This might present some issues depending on the layout of the grid. Although there might be sufficient power to supply the state in total the power lines might not be capable of delivering that power to where it is needed. For instance there might be cases where power generated in neighbouring states fed cities in state and power stations in state fed cities out of state. Should these links be severed the remaining in state power lines might not be able to cope with distribution of power from in state power stations to in state cities. This issue would be unlikely to remove all power but could easily create local blackouts, brown outs and require some areas to be rationed to prevent overload. Other than distribution capacity there should be no other problem with running a separate piece of the National grid on its own. In fact that was how the power grid originally evolved. The internet The internet is designed to route around broken links so should be able to adapt to a reasonable extent, however there are some key infrastructure items that would be needed such as internet service providers, routers and DNS servers. I would be very surprised if there was none of this infrastructure in Northern Oregon. However as with power the location of these services and servers might not be optimal in the new world. Out of state links and satellite links would not work which would cause problems in rural areas. I suggest that the internet would be unavailable in some areas and would be available in other areas but at a very reduced rate. These problems would be exacerbated by the power issues, a location that did have sufficient internet connection and infrastructure might not have any power or might suffer from frequent outages that disrupted the service. Obviously there would be no connection between the teleported area and the rest of planet Earth so all internet data searches in the teleported area would be limited to the content of local servers in the teleported area. Mobile phones Similar situation to the internet as most traffic these days is effectively routed via the internet. Overall I would imagine there would be wide spread disruption although not total failure. Given time some of these issues could be overcome however lack of some basic facilities (steel, aluminium, transformer, power cable and other specialist equipment production) would greatly hamper efforts at restoration and initially cannibalisation of some facilities and infrastructure might be necessary in order to get other areas working. It would probably take decades to return to normality. [Answer] I think electricity will be a problem, and it will be the major one. Electricty: A synchronized power grid requires a certain balance between supply and demand. It is unclear what the demand in the affected area would be, but I doubt, that the supply could keep up. First, there is the hydroelectric power plants. The sources that feed their reservoirs would need to be teleported, too, otherwise the plants would become useless as soon as their reservoirs are depleted. Second, wind energy is not reliable enough to serve as the sole producer to supply the base demand of the grid. Both types of power stations cannot be used to satisfy peak demand, unless some of the hydroelectric plants are pumped storage plants, which in turn would make them unusable to cover base demand. Nuclear power plants, if there are any, might work for quite some time. However, they rely on the availability of an external power feed in order to be operated safely, e.g. for emergency measures. Plus, with an unreliably peaking demand due to an unstable power grid and a lack of means to moderate these peaks, you're probably better off keeping nuclear reactors off the grid. Then there is the issue with distribution. I assume that most, if not all, of the significant power stations of the area feed their output into a high-voltage transmission grid. According to [this map](https://upload.wikimedia.org/wikipedia/commons/d/d4/UnitedStatesPowerGrid.jpg), there seem to be some major nodes of the western transmission grid located in the area of northern Oregon. Still, it is quite likely that this grid will be disrupted and inoperational. Even if the teleported area still has enough power stations to meet the demand, their output will have no means of reaching the consumers. There might still be areas with decentralized, small power grids, but their power stations would probably rely on rather unpredictable renewables, like wind and solar power or on fossil fuels, that might not be available indefinitely in the new environment. Biomass plants could be a long term solution, but they require some sort of functioning agriculture/forestry and they are not feasible for large demands, e.g. the city of Portland. Water/Sewers: Without power, these services won't work either. Water pumps, sewer pumps, water treatment facilities; all will shut down in wide areas eventually, even if they can be kept running for a limited amount of time using generators. They could be hooked up to wind/solar power plants, if regionally available, but these are not suitable to run core infrastructure reliably, so there will likely be disruptions in service. That bears the potential of a sanitary crisis, especially in bigger cities. Communications: Radio communications, in the form of radio transceivers like walkie talkies, would probably suffer the least, as long as the devices still can be powered. There's not much physical infrastructure needed. A few aerials at most. Internet and mobile phone services will most certainly be unavailable or nigh unusable. They might technically be brought back online, albeit in a very reduced state, i.e. with an "internet" providing next to none of the well known services and a mobile network not capable of routing calls to any number outside the teleportation zone and with most of the apps and mobile services being broken, because they'd try to communicate with service endpoints and resources that are no longer reachable. Bringing those minimal forms of modern communication online would require resources and electrical power. Both of which will be in high demand to keep running what is left of the critical infrastructure. With supply lines for spare parts and raw materials severed, not to mention a potential lack of suitable production facilities in the teleported area, I highly doubt that internet and mobile phone services will be publicly available even in the long term. In my opinion, Instagram and Twitter will be the least of a concern in such a scenario. Other things: Given the large scale power outage I expect to take place in such a scenario, there's also impact on food supply, medical services and law and order to be expected. I think a decentralized society like ours would rather quickly deteriorate under such circumstances, and make room for small, centralized and self-sustained communities. ]
[Question] [ A Traveler from a very advanced civilization has visited the Solar system. He found the humans likable, and decided to leave them a boon. For some reason, he couldn't do anything directly to the Earth or humans, but what he conducted was a compete atmospheric terraforming of Venus and Mars. On day X, Venus and Mars' atmospheric composition and surface pressure has turned to be an exact match of the Earth's. Moreover, they got enough water vapor to form seas and even oceans. However, for the same unstated reasons, or completely other ones, the Traveler didn't do anything to the planets' interiors or even the minerals at the surface. The question: for how long would Venus and Mars stay habitable after terraforming? P.S. My definition of habitability is that some of the Earth animals and plants would be able to proliferate and humans can walk around without spacesuits (but some protective clothing is Ok). [Answer] Neither are habitable, but there are more reasons than just radiation that was the main focus of Tim's answer. Another key factor would be temperature. Even assuming (unstated in the question) that the traveler ALSO adjusted the atmospheric temperatures to match Earth temperatures at the same time he dumped ocean sized buckets of sea water on the planets and did the atmosphere swaps, it would be a very short time (probably just hours or days, almost certainly shorter than a week) before the distances between the planets and the Sun caused HUGE temperature issues. Temperatures here on Earth drop significantly just in the (relatively) tiny shade of a lunar eclipse. Venus would be especially similar to Earth, initially, due to similar size. But with Venus' slow rotation, the night side would freeze solid quite quickly while the day side oceans boiled. Mars, being so far away, would just freeze over entirely, day or night side. In both cases, the temperature of the atmosphere, even if breathable by composition, is no longer breathable by temperature. Cooked or frozen lungs are the result, without an environmental suite, which seems to be beyond the spirit of "humans can walk around without spacesuits" requirement of "habitability" [Answer] It would take millions of years for solar stripping to cause problems, and the atmosphere would be entirely sufficient as radiation shielding. This is especially so on Mars, which receives about half the solar radiation on Earth to begin with, and which will require over 2.6 times as much atmospheric mass per unit of ground area to achieve a full atmosphere of pressure due to its weaker gravitational field. Such an atmosphere would probably be more effective radiation shielding than Earth's atmosphere and magnetosphere combined. The "atmospheric composition and surface pressure has turned to be an exact match of the Earth's" part is actually where you run into trouble. Mars would get very cold...not as much as you might expect due to the very deep atmosphere, but probably inconveniently so. You'd want an atmosphere with an enhanced greenhouse effect. Venus has it worse: its lower gravity means it'd still have a deeper atmosphere than Earth's, better at trapping solar heat, while it gets twice as much heat in the first place. But that's not even the big problem: unless this mysterious visitor also adjusted the rotation rate of Venus, the solar day will be 117 times as long as Earth's. The daytime temperatures will quickly rise to something unreasonable even if not quite as extreme as they are today, and it might get colder than an Antarctic winter during the night. The poles would end up being the least extreme environments on the planet, but "habitable" might be a stretch. You'd want atmospheric adjustments to deal with the increased solar input, but that wouldn't be enough without also dealing with the rotation. [Answer] Neither are habitable from day one. Neither Mars or Venus have a magnetosphere. If your traveler did nothing to the internals of the planet, they didn't create one either. That means two things; 1) Your terraformed planets will slowly but regularly lose atmosphere thanks to the solar wind - you've brought Venus' atmospheric pressure down to a little over 1% of it's current levels, and you've increased Mars' by 100x, but both are currently losing atmosphere at a steady rate to solar winds and this won't change; all you've really done is changed when the atmospheres are depleted. 2) You've left the big X-Ray machine called the Sun full access to anything on the surface. That means, your humans on Earth simply can't live there unprotected by some form of shielding or dome, no matter how temperate or oxygenated the environment may be. Edit; \It should be noted that if there is an ionosphere on these new planets (and there would be) then at least some* of the radiation would be deflected and I don't have exact numbers on me as to what percentage of the solar wind would be deflected in the process of stripping away the atmosphere and what would still reach the surface of the planets. The Aurorae would be spectacular and life as we know it would be impossible because of EM interference, but it's possible that the surfaces would be habitable to at least some degree, although I suspect still dangerous over the long term.\* It should also be noted that life doesn't just magically appear in complex form because the environment is right. It took over a billion years for life on earth to reach any reasonable level of complexity, and your planets haven't started yet. Also, there's no oceans (no net change to minerality) so with the lack of a magnetosphere especially you don't have an ideal environment on which it could form on either planet. Add to that the fact that you can't just plant trees on Mars and they'll grow; trees are just one part of a complex biome including soil bacteria and other life forms breaking down humus that if those things are not present, then your tree dies in short order. The web of life on Earth is a amazingly complex and fragile and we often don't appreciate what we have in that regard. Just changing atmospheric pressures and temperatures does not a biome make and the worlds your traveler has made are no exception to that. It might be a lot easier to colonise either planet, but that doesn't make either habitable. [Answer] Terraforming Mars is a wash, there's not a lot of stuff on the planet. It's mass, gravity and lack of a magnetic field renders it useless even if it were habited; not without artificial schemes to thwart radiation. Venus is potentially terrform-able. But challenges include - Lowering it's average temperature from 864 degrees fahrenheit to 60. - Eliminating or sequestering it's co2 and sulfer dioxide rich atmosphere. - Finding a major source of Nitrogen to support plantlife and biological activity. - Introduction of water ]
[Question] [ "Tree" is (apparently) not a very well defined term as far as scientific classifications are concerned, so I'll put my own restrictions on it for this question: 1. Typical healthy adult specimens must reach 15 feet or 5 meters (yeah, I know it's not an exact conversion, and I don't really care because it's "close enough" for me) 2. Typical healthy adult specimens should have (or appear to have) a single trunk for each individual tree. (the occasional odd individual tree with 2 or 3 trunks emerging from the ground at or near the same spot is ok, as long as it's the except and not the rule for that species. Also, clonal colonies, such as quaking aspen, which could theoretically be composed of a single genetic individual taking up the entire forest population of trees also qualifies, as it "appears" to have individual specimens with individual trunks for each one, even though it's not) 3. The species must make use of [Secondary Growth](https://en.wikipedia.org/wiki/Secondary_growth), not just primary growth. 4. The species must be made of actual [Wood](https://en.wikipedia.org/wiki/Xylem), though the wood need not be useful as lumber. "Density" in terms of a forest, can also have some interesting variations in its definition, so for this question the key factors will be: 1. The average space in between the surfaces of the neighboring tree trunks, as opposed to the distance between their center-points, as measured from a height of 6 feet or 2 meters off the ground or below. Branches are not taken in to consideration for this density measurement. (so if two species both grow an average of 30 feet apart at the center-points of their trunks, the species with the thicker trunk will have the shorter distance between surfaces, and would edge out the other for that reason) 2. Only [Old Growth](https://en.wikipedia.org/wiki/Old-growth_forest) areas of forest should be considered, and only the Adult individual trees (those individuals that have reached the minimum height of 5 meters or 15 feet) are included in the density, while shorter/younger trees don't count toward the density. 3. Dead individual trees are included, even if they have partially tipped over, as long as they are still more vertical than not (pointing more than 45 degrees up from horizontal). Individuals that have fallen over (less than 45 degrees from horizontal) are not counted. I also understand that environmental factors will play a role, so feel free to adjust those environmental factors to whatever extreme is needed, as long as the species could still realistically grow, to meet the rest of the requirements, in the described environment, and so long as the environment does not require active influence from humans in order for the environment to exist on Earth. Also, descriptions of the related environments are not required, unless they are significantly different from the "real" environment of the species described. I also understand that it may not be realistic for a forest to be comprised entirely of a single species. For the sake of simplicity, feel free to assume that the forest is composed of only that species, unless a specific mixture of specific species, which can all grow in the same environment, would make a more dense forest for a specific reason. Finally, undergrowth is not considered relevant to the question. Only the proximity of the trees, themselves, to each other is relevant. TLDR, Recap: What species of tree yields the most dense forests? [Answer] Looking up some of the densest forest regions in the world, and then looking up some information on their biomes, it would appear that when we look at places like the Amazon Basin and the Australian Temperate Forest, we're looking at trees like cedars, pines and other trees that are mostly conifers, or tree junipers. So, I'd argue that in old growth forests, you don't want trees that create flowers or fruits to achieve density - you want trees that drop their seeds in pods like pinecones. These are less likely to be carried great distances by animals, less likely to have their seeds dispersed via consumption of fruit and subsequent defecation, and as such are more likely to (over time) achieve density through new trees growing up between the old ones until the area is quite dense. As for specific species, I cannot say off the top of my head but looking at information on the Amazon, it would appear that there is a wide variety of conifers in that forest. In the Australian Temperate Forest, the dominant species seems to be Cedar, which isn't a conifer but a juniper instead. Still, as far as a genus goes, the gymnosperms are definitely over represented in the density stakes across the world. ]
[Question] [ My story has a race exactly like humans, except they grow to be on average 9 feet tall. One of characters belongs to this race, but she is considered a dwarf to her people. This causes her to live with humans without much issue. She doesn’t stand out; if anything they think she is a human. Now my question is, would this be possible? [Answer] In my other answer, I described how dwafism would not be viable, Here is something that possibly COULD work. Rather than dwarfism, there is another route to go: Stunted growth creating a midget, instead of a dwarf. Your giants begin strongly resembling humans through their youth. Only after they get over two meters do their bones start to thicken, their hands and feet grow and their growth outward begins to match their growth upward. This would make a kind of sense, as your race of giants evolved to have their children appear to be human, and thus not hunted down and killed, as it would be a form of camouflage Your hero due to some disease (or curse) is trapped in what is a child's body for her race. Since she is in that child's body, she blends in with the resto of the humans. You may want to make it a bit more interesting by giving her some trait that would make her recognizable to her people, be it markings on her skin, the shape of her ears, or something else that is subtle, but her people would know to look for. [Answer] No, 9 foot tall giants are incompatible with our physiques which is why extremely tall people have multiple health problems. To have people that tall would mean multiple changes to our structure resulting in humanoids that look distinctly different. She may be able to live amongst humans, but not unnoticed. At best she would be considered extremely unfortunate in regards to her looks, or deformed. [Answer] A gigantic race would have to have thicker, and wider bones, be much stockier with larger lung capacity, and significantly wider. A dwarf of that race would look like Andre the Giant compressed down to 2 meters, with hands the size of a gorilla, shoes somewhere around size 26-27, and bones like tree trunks, and a massive head. She would look more like a beast than a normal human. [Answer] Unfortunately, the answer is probably no, unless you "hand-wave" the actual cause like you hand-wave the existence of the giants themselves. Hypopituitarism is "almost certainly" the only type of dwarfism that would get you close to what you're describing. There may be some other, extraordinarily rare, types that come closer, but it's certainly the most common type that comes anywhere close. All other (relatively common) types of dwarfism would cause other side effects that would make her distinctly not a 'normal' adult human, such as impaired mental capacity and delayed physical maturity (in other words, she'd look and act like an absurdly tall child, not passable as adult, even if the height, alone, were not an issue). In humans, an average female is about 5 foot 3 inches (it varies from place to place, and with accuracy of measurement, etc., but this number should be close enough to accurate to make my point). The average human female with Hypopituitarism is 4 foot 3 inches. If you scale up that difference, and an average giant is 9 feet, then a giant with Hypopituitarism would average about 7 foot 2 inches. While I'm sure there are normal human females in that height range, they are the exceptions, not the rule, and your giant would definitely "stand out" in any crowd, just like those exceptionally tall human females do. If you do the math in the other direction, and assume that this "dwarf giant" is average human female height of 5 foot 3 inches, and then scale up to normal height for your giant, the average giant female would be only about 6 foot 6 inches tall. In those ranges, any giant on the shorter end of normal could pass for a normal human on the taller end of normal, so a dwarf giant being able to mix in with humans wouldn't be anything really exceptional, she'd just be able to do it better than most other giants So: 1. Either this condition she has is absurdly rare, 2. or it doesn't correlate to any known human condition at all and is a specific issue among the giants themselves, 3. or it just plain won't work at all Handwave the cause, and don't base it on humans, if you're going to do it. If giants exist, their own unique form of dwarfism could also exist. [Answer] We're going to need some more information to properly answer this, but, as a general statement goes, pretty tall- the tallest human, Robert Wadlow, was 8'11.1". I would keep in mind that most humans that grow incredibly tall often suffer from heart problems, and die at a fairly young age. Wadlow died at age 22, for instance. Thus, this race would likely need a larger, more powerful heart and reinforced bones. Overall, I would hazard a maximum height of 13'-16' before major circulatory problems arise. Keep in mind that this is a ballpark guess, and with a little hand waving and evolutionary explanation, this could be extended to a much greater height. [Answer] It is possible for her to live as a Human, however she will likely be outcast a little as well due to her enormous size. She is roughly 2.7m which is way to high for normal houses. Her clothes and shoes will also be too large for normal sizes and will require them to be custom made. Any conventional vehicle she gets into will be far too small to sit or stand in. It is also possible for her to use this difference to rise to fame, but it will really depend on you the Creator of this scenario. For a quick comparison, the tallest man on earth 8'11. The current tallest man is roughly 8'3. Hagrid from harry potter is 8'6 and those blue Avatar people were 10'. [Answer] Human dwarfs are anyone 4'10" and under regardless of the sex. The average US height is 5'6". That is 88% of the average height, which is 7'11" for your fictional race. The shortest human ever was 1'9.5", the giant equivalent of this would be 2'11", so dwarfs of your species should range from 2'11" to 7'11". ]
[Question] [ I think an opportunity was missed when [this question](https://worldbuilding.stackexchange.com/questions/26620/mediterranean-sailing-times-distances) was asked, but closed. It is relevant to worldbuilding in the same way that [this question](https://worldbuilding.stackexchange.com/questions/124606/how-far-can-you-travel-on-horseback-while-pushing-the-horse-to-the-brink) and [this question](https://worldbuilding.stackexchange.com/questions/67455/travel-time-in-medieval-times) are, to determine how far apart specific locations such as land masses, islands, etc. should be placed from each other, or how large a particular large body of water should be to provide a particular level of separation between two places involved in the story. Or for deciding on a technology level for ship-building in a fictional society when using a predetermined geography, it is useful to know travel times and distances for different ship types and technologies from different time periods. How far could ancient, medieval, and otherwise pre-modern, ships travel in a month? Best answers will include information about both rowed (when applicable to the time-period) and sailing ships from a respectable variety of civilizations/groups/time-periods (e.g. viking era, ancient greek, ancient rome, middle-ages, etc.). To avoid over-complication, limit ship types to the largest 'standard' ships that would have been in common use for any time-period time for cargo, passenger travel, or war. And approximate distance ranges should be used, to account for variations among individual ship specimens, as opposed to specific distances of a single type in use in a particular time. [Answer] EXECUTIVE SUMMARY: Ancient ships: less than 1,000 km per month, potentially, assuming good weather, shoreline hugging, known waters, and a pressing need to do so. More likely is 250 km per week, especially assuming some serious R&R at the end of that week, to include time for planning and time to let weather blow over, etc. --- SOME DETAIL: Here are some notes I made some years ago when trying to figure out ancient ship speeds. The ships I was interested in were all pretty much galleys -- ships that were typically rowed, but had a primitive square sail that could be used when the wind was going your way. The other major factor was that a galley was designed more or less for day-travel only: it typically hugged the shoreline, and carried a day's worth of water, thus you had maybe 6 to 8 hours of travel time before having to knock off for the day and sleep on the shore. With all those caveats, I drew numbers from a book on ancient ships that for the life of me I cannot remember the name of. It seems that longships, triakonters, liburna, biremes and triremes had roughly similar speeds. The pentekonter may have been a bit faster. To wit: 7kph rowing average, and perhaps 8 to 9 kph for pentekonters, maybe. Double that if the wind was favorable, and for very short rowing bursts. Double THAT if the wind was ideal, which I assume is rare to nonexistent. Assume, then, that that's 50 km per day. In a week, a galley could therefore cover as much as 350 km. Although I bet actual weekly distances would be a standard deviation shorter (250 km). Therefore, in a month, I'd say no more than 1,000 km -- and probably less, since I doubt the ships and rowers were built to operate 30 days straight with no downtime. But your ship, if keeping to shorelines with known characteristics, could cruise around for several hundred km in a month if pressed to it. --- EVEN MORE NOTES: For a rule of thumb, realistic speed is roughly the same as marching speed. 2-5 knots. Occasionally faster under full steam with the wind at your back, even up to 15 knots, but not consistently. Ship ratio appears to be a good metric for predicting speed as well as carrying capacity, by the way: Larger ratio = faster ship, Smaller ratio = more payload. Ship size also apparently affects speed. And of course, skill also affects speed. Galley Era: 3000 BC to AD 1500, approximate * Galleys: "Vessels larger than boats, propelled primarily by oar power and only occasionally by sail." * Coast huggers. * Light. Operates in shallow waters, rivers, small bays. * Can be dragged on short overland routes. * Navigation by the sun, prevailing wind, and stars. * Stored in "ship sheds" on the shore. * Ships are transports. Wooden platforms for melee combat. * One (or more) rowers per oar. Design Considerations * Length implies => number of oars per side (1 per 1.5m?) * Up to 3 levels of oars per side; more levels = more upkeep, lower endurance (3 levels = typically just a day's worth of fresh water) * Can have multiple rowers per hull * Catamaran hull doubles the hull size, increases carrying capacity more. * Maximum rowing speed is 2x average rowing speed? * Speed under sail is 4x average rowing speed? * Some ships have a ram... Ships Light, fast, Scout/Raiding/Pirate vessels: Longships in general * 6 to 34 benches (on a side?) Longship & Triakonter * 24m x 5m * 16 oars per side, 32 rowers total. * Crew of 40, maximum capacity 70. * 28 kph under sail max * 14 kph rowing max Pentekonter * 38m x 4.5m * 25 oars per side, 50 rowers total. * ?? kph under sail max * 18 kph rowing max? Bireme or Liburna * 33m (or more) x 5m * 18 oars (or more) per side, 2 levels of rowers, 1 rower per oar. * 28 kph under sail max * 14 kph rowing max. * 7 kph rowing avg. Trireme * 3 levels of oars, 85 oars per side, 1 man per oar. * 14 kph rowing max. 7 kph avg. * Good offensive strength. Ram. * Only carries one day's worth of supplies (i.e. fresh water). * Lots of upkeep. * Tactically inferior to Liburna. * 24m to 37m or more. 3m to 5m wide. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. For my hard sci-fi story, I would like to have a planet similar to Titan (very cold, nitrogen atmosphere, methane seas) but with a surface gravity in the region of 1g. Could this occur, or would the greater gravity result in a significantly different atmosphere? [Answer] Based on this [chart](https://en.wikipedia.org/wiki/Atmosphere) [![escape velocity vs temperature chart](https://i.stack.imgur.com/tieIu.png)](https://i.stack.imgur.com/tieIu.png) with Earth escape velocity and Titan temperature your planet should be able to keep nitrogen and methane, like you ask, but also water, ammonia, oxygen, helium, carbon dioxide and xenon. Hydrogen might be borderline. If you don't have photosynthetic life forms it is likely that all the oxygen will be chemically bound to other atoms, due to its reactivity, and you will have no free oxygen. [Answer] ## That depends on if the planet is sole or a satellite of a giant planet. The presence of different chemical stuffs in the atmosphere or on the surface are defined: For simple stuffs: by second cosmic velocity from one side and temperature and molecule weight from the other. For complex stuffs: by second cosmic velocity from one side and temperature, atomic weight of the lightest component of the molecule and the radiation level in the exosphere from the other. For both variants the speed of input of the stuff into the atmosphere is utterly important, too. The processes are: for simple stuffs: The speeds of molecules is distributed statistically. (<https://www.khanacademy.org/science/physics/thermodynamics/temp-kinetic-theory-ideal-gas-law/a/what-is-the-maxwell-boltzmann-distribution>) There are always some fraction that have velocities above the second cosmic. And that fraction, in higher heights will be dissipated into space. That defines the speed of output of the stuff. The speed of input and output are balanced. For complex stuffs: The radiation makes molecules fell apart. And if they can, they are joining back. That can be prevented by the loss of a component. For example, water is divided into hydrogen and oxygen. The first is lighter and has much higher speeds of molecules. And speed of losing water is defined by the fraction of hydrogen in water vapor (defined by radiation) and fraction of hydrogen molecules, free atoms or ions, having second cosmic speed (defined by temperature). The speed of oxygen is 256 times smaller (gases have same temperature/energy and H2 is 16 times lighter than O2, so lesser mass should be compensated by 16^2 times higher speed), so its losses are negligible in comparison and it is always enough oxygen to restore the water molecule back. Again, the speed of coming and losing the stuff are balanced. So: 1. It is not acceleration that is important for gas keeping in the atmosphere, but the second cosmic speed. For example Saturn has same acceleration as the Earth, but much higher second cosmic (35m/s2), and does not lose even hydrogen. The question is undefined in this part. Let us say, you need a planet that is more Earth-like and the second cosmic is the same as ours (11m/s2). 2. Titan on its place does not lose nitrogen. Neither would the Earth there. The water is frozen and lies as rock. The same would be on the Earth. Titan has some methane as liquid. Not much, for it escapes by radiation dissipation and hydrogen losing. The Earth would lose less hydrogen, so, much more methane will be left. Seas will be larger. 3. At its place, the Earth significantly loses only hydrogen and helium. The question is, what will be with them if the Earth will have the Titan temperature. For much H in atmosphere will cause reaction with N and ammonia will snow onto the surface, leaving no N in gas state. [![enter image description here](https://i.stack.imgur.com/TY0lo.png)](https://i.stack.imgur.com/TY0lo.png) (<https://geosci.uchicago.edu/~kite/doc/Catling2009.pdf>) - look for explanation below the chart on the 4th page. According to the chart, if the planet will have the radiation and temperature as on Titan and second cosmic speed as on the Earth, the planet will NOT lose its hydrogen and as a result, it will have ammonia/hydrogen/helium atmosphere instead of the nitrogen one. Ammonia fells as snow and only H/He atmosphere remains. It will be so, if the planet will be separate one. But if it will be the satellite of a giant, the giant and Earth magnetospheres will react, thus greatly heating up the exosphere layers (look at the Earth and giant planets temperatures on the chart). And it WILL lose its hydrogen and helium and mainly nitrogen remains. ]
[Question] [ I have created a species that is basically a sort of land coral covered in a thick carapace made of rock. They live on an Earth-like planet (Class M as they say in Star Trek) and behave like coral does on Earth, except for not living underwater. They feed on tiny particulate of matter in suspension in the air, mostly pollens from plants (don't come there if you're allergic) and some sort of flying plankton. Their carapace isn't one thick sheet of rock, but made of many small sections that fit together. From the outside, it would look like a very rugged rock. On the inside, the coral lives around a core of crystal which grows as the coral grows. It sends tendrils into the ground to get minerals, much like the roots of a tree. They're mostly active at night, opening the carapace to send some sort of tendrils out to catch the food in suspension in the air; there's much more food at night because the local flowers send their pollens out at night en masse, and spend the day hidden under their shell, keeping the biological parts protected from the UVs coming from the local star and soaking up it's energy. The flowers grow year round thanks to a quasi absence of axial tilt. My question is how could it transmit solar energy through it's shell to feed the coral and store it in the crystals, and what kind of crystals would be most efficient to store the energy? I'm looking for biological processes here, or ways to adapt technological means into biological if it's believable. I was thinking of storing the energy in chemical form inside the crystals, to be released when needed by some chemical process. I'd like a science-based answer, though not hard-science and some handwavium is allowed since this will be used in a sci-fi setting. Thus not everything has to be exactly as it is here on our Earth. [Answer] ## Use calcite for the covering Corals are pretty cool already. They're symbiotic relationships between an animal (not a plant) very similar to a sea anemone and tiny dinoflagellate zooxanthellae that use photosynthesis to produce organic carbon from thin air. Now, I'm assuming that your land corals are constructed similarly. The external covering is likely calcite, just like oceanic corals, and is secreted by the organism to provide shelter. However, the outer covering of corals does more than provide shelter - it actually helps [refract the light in a meaningful way to improve the photosynthetic efficiency](https://www.frontiersin.org/articles/10.3389/fmicb.2014.00422/full) of the dinoflagellates: [![Refraction of light by the calcite skeleton of corals, from Roth 2014](https://i.stack.imgur.com/XwrWO.png)](https://i.stack.imgur.com/XwrWO.png) So, we can be assured that light will pass through the external covering of calcite and may actually help out the coral. This transparency also means that you'll lose a little bit of the "looking like a rock" aspect, but if you've ever seen "massive" corals they look almost exactly like rocks anyway: [![Coral bommie in Flower Garden Banks](https://i.stack.imgur.com/GvYnb.jpg)](https://i.stack.imgur.com/GvYnb.jpg) ## Use sugar for the internal crystals: [![Sugar crystals](https://i.stack.imgur.com/xGo4t.jpg)](https://i.stack.imgur.com/xGo4t.jpg) Now, this is a bit of a cop-out answer. Sugar isn't normally considered a "crystal", but it's almost perfect for what you're going for. Sugars are produced naturally by the photosynthetic processes, sometimes in excess with respect to the nutrients available. However, a sugar crystal does indeed store energy in a useful form, can be synthesized by the organisms, and can grow and shrink along with the health of the plant as a whole. I personally love this idea because it sets up a fascinating mythos, in which crystals of nearly-pure sugar can be collected from these coral creatures. Candyland, anyone? [Answer] To chemically store energy in this way you’ll need a physically stable and durable crystal that can be easily precipitated and then broken down in a chemical reaction with as little loss of embodied energy as possible, high energy density is also preferable. You'd ideally want an endothermic reaction because having absorbed the UV it will be converted into heat in the core of your land anemone but crystallisation is always exothermic, so it becomes a matter of getting maximum efficiency. I'm leaning towards something like [Aluminium Carbide](https://en.wikipedia.org/wiki/Aluminium_carbide), highly stable at reasonable temperatures but highly reactive in water. It also has high energy density and a high ratio of [Gibbs Free Energy](https://en.wikipedia.org/wiki/Gibbs_free_energy), which is the energy you get back when you dissolve the crystal, to [Enthalpy of Formation](https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation), the energy needed to form the crystal. Pure Carbon could possibly be even better but you run into issues about exact crystalline structures etc... and non biological precipitation methods, but you could have diamond cored critters if you want to go that way, they'd be more like Earthlife though. [Answer] You should consider gems that are not completely (or not at all) opaque. <https://en.m.wikipedia.org/wiki/Gemstone> The creature can absorb minerals from the soil and build its outer shell from those minerals. They are translucent and though may offer protection from UV, still allow letting in enough light for photosynthesis. I have never heard of a way to store energy in crystals, though. If you want the coral to harness wind power instead, it can use piezoelectric crystals to convert movements from wind force into a weak electric source. <https://sciencing.com/crystal-can-hold-electricity-energy-6886479.html> ]
[Question] [ [![The Great Carina Nebula](https://i.stack.imgur.com/Q3dZR.jpg)](https://i.stack.imgur.com/Q3dZR.jpg) How close should a planet be to the Great Carina Nebula for it's inhabitants to look up and see this in the night sky? I'm aware much of the sharpness of the view would be lost due to the atmosphere, but let's say you were on this hypothetical planet (and I'm assuming you can see the falcon shape in the image) and if you put up your hand and it measured exactly the length of your index finger from falcon-head to falcon-tail? How close is your planet to the nebula? [Answer] According to [Wikipedia](https://en.wikipedia.org/wiki/Carina_Nebula),the Great Carina Nebula is approximately 230 light years in radius. The formula for angular distance (how much of the night sky would be taken up) is : $ angle = atan( distance\_{opposite} / distance\_{adjacent} ) $. That gives you an answer in radians, which you must multiply by ($180 \over 3.141..$) to get the value in degrees. For an example: if the planet was 270 light years away, the nebula would take up 45 degrees (or about a quarter of) the night sky. The apparent magnitude of the Great Carina Nebula, again according to [Wikipedia](https://en.wikipedia.org/wiki/Carina_Nebula) is +1 which is within the range where it would be visible to the human eye according to the [same source](https://en.wikipedia.org/wiki/Apparent_magnitude). It would be roughly 40% of the brightness of Vega. ]
[Question] [ I'm building a colony that is an unintended eclectic museum of simultaneous, anachronistic stages of industry: Industrial, Machine Age, and Atomic+ (onward into more esoteric, advanced technologies that are strictly regulated for the sake of social experimentation). Prior to the construction of a pipeline, road, or rail networks and other transportation, I intend for zeppelins to be used to travel between coastal desalination plants and back to the main city. In addition to delivering drinking water, they would dump some of their water while passing over designated farmland to irrigate the crops, and if needed, also transport and dispense necessary fertilizers, insecticide, etc. I guess some would also stop at isolated plantations/farms to gather produce and deliver packages or necessary supplies for farmers and agricultural laborers. This is only intended as a temporary solution until proper transportation and irrigation infrastructure is built...so I can explain the existence of a retrofit fleet of zeppelins being weaponized later... Edit: Alright, probably unmodified, antiquated zeppelin designs are a miserable idea. Perhaps just magnetoships that use bags of lighter-than-air gasses to stabilize them, and appear aesthetically like antiquated zeppelins? Ach...But then what are all the problems with magnetoships that I don't know about? Or rather: What's a good freight vehicle that can float in the sky like a zeppelin? And now I'm intending a scenario or circumstance in which there is an obstacle that prevents the simultaneous development of infrastructure alongside the construction of the coastal desalination plants: "We need water. We need more of it than what's falling out of the sky. It's over there. There's something nasty/loathsome between here and there. So we went over it." It can maybe be a lake/river and its respective filtration/purification plant, since people keep yelling at me that desalination is a dumb idea. Untamed wilderness...Voracious indigenous organisms...Obstinate xeno-druid roadblocks...What would stop a bunch of salty blue-collar humans in high-vis vests and hard hats? A lot of things I'm sure, but enough that it just makes sense to fly over it in the meantime...instead of say, call in someone to fight it (due to anticipated, constant harassment or guerrilla tactics). Ugh, but now I've forgotten about the farms I wanted to irrigate with fly-by's... Edit: Consensus is that fly-by irrigation is impractical, but could I perhaps just have water stored as freight and offloaded at designated stops (plantations/farms) via a simple tower of pipes sticking up in the air, probably connected to a water tower or something? A stable docking procedure is probably required. Requested Details: * Planet is artificially constructed and terraformed (by a much more advanced faction distinct and separate from the colonists that the narrative is concerned with) * The conditions were intended to be very close to Earth-like but there are locations where it is obvious that the landscape is artificially sculpted on a massive scale...again, perhaps for the purpose of messing with/experimenting upon developing societies * in this universe/reality, magic (of many different kinds) is known about, it exists, it is an oddity and impractical because of its known inconsistency over the scope of different celestial bodies ("My fireball spell summons dancing meat-cubes on this planet .\_."). People try not to use it and stay away from it as much as possible...and it is considered distinct from occult and psychic shenanigans that are actually, and ironically, better understood and regulated... * In my intended context, an overarching "social/technological experiment" imposed on the colony is that antiquated technologies are known about, but not understood in-depth. Possibly, they require reverse-engineering from memory or nothing at all? The intention was to motivate the development of alternative technologies: "Building things differently," Or hopefully, better than they functioned as we knew them. * This is important for the anachronistic stratification of technology levels I mentioned first: Basically, there was a colony drop, the core of the ship is space-age tech, but only so much, and the people in charge of it shoo'd off the colonists, encouraging them to build around it with provided tools and materials from late Industrial Age tech and onward...because it was arbitrarily decided that that's when the curve of technological growth starts to get "interesting" ...I would word that more elegantly later in the terms of aforementioned sociological and technological experimentation of course... [Answer] # Not feasible Your planet might not have the same atmospheric conditions as Earth, or you may have some magical elements available to fill a zeppelin's lift envelope; you don't specify. But assuming Earth-like conditions and Earth-like zeppelins, irrigation by zeppelin is very impractical. The famous (for burning) [Hindenburg](https://en.wikipedia.org/wiki/LZ_129_Hindenburg#Specifications) had the largest envelope volume of any airship. It [generated](http://www.airships.net/helium-hydrogen-airships/) about 216,000 kg of lift (I know, the units are wacky) and had a mass of ~206,000 kg. So, it could only carry about 5 tons of payload, including passengers and what have you. By comparison, a [Boeing 777](https://en.wikipedia.org/wiki/Boeing_777#Specifications) can lift over 50 tons, depending on the model. Fertilizer is heavy; water is even heavier. A [corn field in Illinois](http://extension.cropsciences.illinois.edu/handbook/pdfs/chapter09.pdf) might use 150 lb of nitrogen fertilizer per acre for a season. A farmer's bulletin recommends a similar amount of potassium (137 lb) and phosphorous (134) addition. These [fields](https://waterdata.usgs.gov/il/nwis/water_use?format=html_table&rdb_compression=file&wu_area=State%20Total&wu_year=2015&wu_category=IC&wu_category_nms=Irrigation%252C%2BCrop) also average 191 million gallons per day for 601,000 acres of irrigated crops. That is just over a ton of water per acre, per day. One zeppelin trip fully loaded can carry enough fertilizer for about 22 acres, per season. It can carry enough water for 2 acres for a day. You're going to need a lot of zeppelins, at modern farming fertilizer and irrigation usage rates. [Answer] The only way I see a Zeppelin working is if it's extremely hard to get to the colony on foot and you have enough resources to warrant the building of the colony and open up new paths. For example, let's say you have two Cities on opposite sides of a huge mountain range. There are paths between each city, but they have to go around the mountain range (and assuming the straight line distance through the mountain range will still take more than a day via your main form of transportation). The paths are so long that zeppelins are viable in transporting cargo over the mountains (They transport less, but get there quicker and more reliably(?)). Now both cities could invest in building a path between the two of them through the mountain range. Assuming there was an almost ideal settlement area in the mountains, then your scenario might work. The cities start mining from each of there sides. They use the zeppelins to move supplies, materials and manpower into the mountain range to start construction work before the main crew gets there. Assuming a suitable location about half a days away, they start the construction of a city, using zeppelins to supply materials and manpower while proper transportation lines are being constructed. Something like this? maybe [![Example map](https://i.stack.imgur.com/1MmnO.png)](https://i.stack.imgur.com/1MmnO.png) [Answer] In addition to the issues of lift and payload capacity, Zeppelins and other LTA craft are essentially giant sails, and have great difficulty in flying in high winds or heavy weather conditions. This led to the crashes of many airships. From a practical point of view, the act of using an airship as an irrigation system would involve some pretty difficult flying, since you want to place the water "on target". The airship is moving slowly over the field, but the pilot needs to account for shifting winds, changing weight (the airship will become lighter as the water is delivered, and want to rise, while the pilot will want to remain relatively low to the ground). Utilization will also be horrible. Turning about at the end of the field will take a long time, then trying to line up and fly the next section of the field will also take a very long time. You will spend an inordinate amount of time trying to water just one field. Even watering the field with a cropduster would make more sense in terms of time allocated. Air delivery of water can take place, but using fixed wing aircraft like "water bombers", or helicopters to deliver water via bucket lift. If there were no other real alternative, the would be a very expensive way to irrigate a field. [Answer] Practically, Zeppelins are a pain. Even the ones filled with helium have all crashed in bad (and by "bad", I mean "high winds") weather. Just build the roads and ditches at the same time you're building the desalination plants (which themselves need a lot of energy, so you'll have to have that infrastructure built before the desalination plants come online, and you'll need roads to build power stations). ]
[Question] [ I have some large, megafauna level amphibians inhabiting a temperate rainforest with naturally high levels of humidity. Would my large amphibians have any problems maintaining a classic amphibian type of skin (smooth & slimy) or would they need skin for akin to reptilian scales? Thanks! (Ignore circulatory, Skeletal, and Respiratory problems that come with large amphibians) [Answer] In a rainforest with high relative humidity "normal" amphibian adaptations can work. If their environment ever dries out properly they'll need to get into pools or the like in a hurry though. Temperate Rainforests tend to have a dry-ish season unlike their tropical counterparts which are wet all year around. During those times you'll need refuge habitat in the form of wetlands or open water where they can wait out the dry months. [Answer] So long as the humidity is high enough, nope, they shouldn't have any problems with skin. In fact, larger amphibians ought to have an easier time, since they'll have a larger volume per unit surface area in which to store water, so they will lose it through their skin proportionately more slowly than a smaller creature. ]
[Question] [ First off, I apologize for this lengthy post. But in order to give you a clear understanding of everything, I think this is necessary. So I've been creating a world which has suffered through an apocalypse roughly 200 years ago, seen from the point where the story is supposed to start. However, I am worried the progression of events as I have created it may not make sense. Before, the civilization on that planet was technologically very advanced. In fact, roughly 70% of them had some sort of body-augmentation, basically making them cyborgs. These augmentations could range from an arm or leg, to almost their entire body. Most people lived in skyscrapers in big cities. Economy and production depended on machinery, most of which was entirely automated. All record-keeping had been moved to digital media as well, making paper unnecessary. Then came the apocalypse, which is basically the thing introducing a fantasy aspect into the story. It didn't happen entirely without warning. Over the course of a year, people started to notice that the animals all throughout the world started to become more aggressive over time. This change happened a lot slower in domestic animals than in wild animals though. Also, some of the wild animals, whose breeding wasn't watched over by the people, started to change over the course of several generations. It was not rapid, yet faster than normal evolution should be. Scientists researched the matter, but while it was unsettling, their level of technology and advanced weaponry allowed the people to continue living in safety and comfort. Therefore, most of the common populace didn't pay much mind to it. Until the big event happened. One day, all technology stops functioning. Not only that which relies on electricity, but it seems all man-made technology above medieval level stops working for reasons unknown. This obviously also includes the crumbling of the whole economy, money system and all records of knowledge. Also, body-augmentations cease working as well. A lot of people die immediately, due to vital parts of their bodies stopping to function. The rest are left in a world where all economy, all chance of remote conversations, and all knowledge they were able to access is gone. Also, they lost that which kept them safe from the animals, which have grown more aggressive. During the time which passes after that, people don't have problems regarding food for quite a while, as there are still many warehouses stocked and a lot less people to feed than there were before. However, most of them know nothing of basic craftsmanship, agriculture, or other basic concepts of everyday life. Most don't even know how to cook properly. Adding to that is the new danger from the outside. Over the next 100 years, people learned to adapt. New generations were born, which knew only this world. Knowledge and culture was slowly thriving, as it had taken them a lot of time to relearn what their early predecessors, who didn't have technology, once knew. In the meantime, their surroundings changed as well. The animals were not the only things changing rapidly. Their change had not ended with that event, they continued to change shape and get other traits with each generation that passed. However, the other thing changing were the plants. Mostly the forests. Area was reclaimed by plantlife a lot faster than should be possible. Also, it seemed that the adaptations of the animals were mostly for them to adapt to the newly growing forests. Going forward until 200 years after said apocalypse. People have reestablished life in small towns, some of them built in old ruins, but most of them built entirely anew. Mostly, their technology-level is at that of medieval times, since any progress beyond that is still hindered by whatever makes everything else cease functioning. Around the towns are areas where there are fields, surrounded by plains of either cut-down or burnt trees. Around these areas, dense forests cover most of the planet, aside from the oceans obviously. Most people never leave the town and the safe areas around it. Only those who go out to forage and hunt venture into the woods. And of course, those who search the old ruins. Because rarely, parts of old technology are still working, for reasons unknown. Most towns are further apart from one another, causing each to have it's own culture and in some, even religion. Travel or deliveries between towns are lengthy and dangerous. That's basically the progression of events. To clarify a few things: * The race living on the planet and the planet itself are similar enough to humans and earth that we can assume them to be humans on earth, for the simplicity of this question. * The apocalyptic event and the changes in the surroundings are the fantasy aspect of the story. Therefore whether those make sense doesn't need to be discussed here. * The state of the world where the story is supposed to take place (200 years after the apocalypse) is set and I would like to do as few changes to it as possible. The events leading up to that and the state of the world before the apocalypse can be changed though. And now to my actual question: * Does the progression of events make sense? As in, would this race develop as it did or would they reach another state at the end of these 200 years? * If they would reach another state at the end of these 200 years, how would I need to adjust the timeframe or the events to get things to fit? Edit to clarify: * The changes made by that apocalypse are still in effect. No technology (electric and non-electric) above medieval level functions, even if built correctly. Also the animals continue changing and becoming more agressive over the time after the apocalypse. * Even though for the simplicity of this question I asked we see this as humans on earth as base principle. It's not today's humans on today's earth. * As stated, before the apocalyps almost all knowledge was changed to digital media, with libraries being only kept here and there as remnants of the past. [Answer] Estimating a progress calendar to recovery is plain impossible, due to the multitude of factors involved, from environment to resources, to location, and so on. EXAMPLE 1: All villages and cities with harbors and ships and boats available will sustain less of a shock thanks to the food the sea can offer. Being able to navigate, as repeatedly proven in history, will transform the sea cities in their own republics (like it happened with Venice, Pisa, Amalfi, Genova) with a vast power. Given the widespread existence of equipped cities, the maritime nations will gain soon the greatest advantages, and the new wars will once again be fought on sea trade routes. EXAMPLE 2: All farming communities that relied on electronics to harvest their field will rapidly turn back to horsepower (literally!), cows, oxen...And having large amounts of cultivable lands intended for the once mass markets, they will be able to become important markets themselves. EXAMPLE 3: Cities are lost. No electronics means no water, no services, no maintenance at any level. They will be used as shelters along the way and progressively be scrapped but by bit until clusters of small ruins will be left. The surviving animals in the zoos, alas, will be killed for food and furs. Dogs and cats will revert to feral state. Dog breeds will be lost to wolves and coyotes. NO MORE GERMAN SHEPHERDS, SADFACE!!! EXAMPLE 4: Effects of apocalypse negligible in island communities, amazonian villages, aboriginals and African tribes, any nomadic communities. In fact, soon they will become THE experts to look out to guidance in a world without GPS and google maps. Luckily enough, there will be left enough libraries with their precious books untouched. Any government, now guided by the military elite to manage what's left of the country, will ransack all libraries to store up precious knowledge, while specialists of all disciplines will become the new highest-ranking hierarchy. Specialists will teach nw generations in a better schooling system than in our dark ages; no matter how new cults will try to suffocate knowledge, it just cannot be rebottled as if it never existd. We will recover faster onto a better lifestle. As per edit in the question: Ok, so all deposited knowledge is lost (btw, allow me, what kind of advanced civilization would be so utterly idiotic as to renounce to print at all goes beyond suspension of disbelief). Fortunately, there are still the specialists, the teachers, all the current's generation living repositories. AND the survived libraries will be the even more important treasure caches, to be defended with tooth and nail by the new governments. So, first step toward knowledge reconstruction is: back to paper. Apocalypse didn't destroy the materials with which paper can be realized without electronics, and Gutenberg taught us that serial printing doesn't require any electronics. So, diffusion of knowledge and schooling will take longer, but being the roots there, and being able to print, religion won't have the time to exert the same grip that it had during dark ages (when not only books were rare, but people was ignorant at all levels). And while societies around the world adapt to the new lifestyle based on non-electronic technology, schooling will take once again its own place. Scientists will have a better time, since they can actually prove the veridicity of their knowledge, they won't be treated as 'sorcerers'. Pasteur, for example, proved that it takes a common microscope to detect bacteria, thus negating the 'spontaneous generation' theory. Steam engines will be back with a vengeance, it will be more a steampunk world, but fully working. [Answer] The Biggest problem I see is that you can't just have all technology before medieval times just stop working. Where are technologies like generators or engines that don't require electricity to work, and saying that it stops is a huge blanket statement that will undermine the laws of physics as we know them. It might be better to say magic interfered with all non biological electrical systems and broke them by burning out all the circuits or something along those lines. The biggest problem you have after that is a lack of printed media. You really need to have printed media to be able to survive an apocalypse like this. Why can't all the smart people just write down what they know? Because a smart person can't remember everything they need to know. Because a smart person will still rely on technologies to perform complex computations, simulations and design verification. Because a smart person is also the most likely person to have an augmentation and is now dead. Basically people know the general technology path they need to develop and the end target to work towards which will speed things up, but it will always be a long road to recovery. I'd like to point out that books will likely still be present in society, it will just be used in areas like education and entertainment. They are still an industry and any industry will try and survive regardless of the technological competition like e-book and pdf copies. In addition, books being non electrical can't be hacked or easily falsified. So there will still be books around and people will still use them, but less people will do so. The next bit is food. If most people don't know how to cook food, they certainly don't know how to grow food. They keep going to super markets and warehouses to restock on food, but that will run out eventually. Most of your good preserved food is probably unusable since they would probably require a microwave, stove, oven and so on to cook. People have to resort to gas and fire to cook food now and that is most likely lost knowledge (also I assume gas won't work because your suppliers system is down). You will have some people who here cooks and what not who know what to do, but take away that 70% with augmentations and you have very few left. Your farmers who survive will also be in trouble. The problem with any advance society is that it requires more and more resources to feed and maintain. Farms nowadays have huge numbers of machines and tractors to help do everything from plough the field, kill weeds, fertilize and pick crops. Thats all gone. Back to manual farming with animals and hands. This is also going to be a problem with GMO foods which is probably what all your farmers use to grow crops. A lot of GMO foods seeds can't be used for a second or third generation. Seeds have to be constantly purchased because they are designed to not grow further generations. This means that a large number of your possible food production will just disappear because there is no way to access it anymore or grow new food from old seed stock. Once your food stock rots away, you can't produce anymore and people will start to starve. I say your food stock will rot away because you said most people can't cook anymore. This suggests that food is pre-prepared and packaged. Food like that probably won't last very long without refrigeration which is also gone and hence will probably rot away before most of it can be consumed. You probably won't have much canned food, because being technologically advanced, who the hell wants to eat food out of a can, when you can throw something into a microwave and get an instant and delicious feast. Skipping forward several years. People can't just rely on hunting to remain fed. People need to farm or gather food and with more people you need to farm and gather more. This means that people need to go out into the wild regularly to survive and they need a means to defend themselves. Your futuristic people would have forgotten old technologies like mining and blacksmithing as well as identifying edible plants. They would rely on weapons from before like guns and a huge supply of bullets which will probably be used up over the decades leaving them mostly defenseless. What you end up doing is throwing an advance civilization back to before the stone age. I say before the stone age because the knowledge required for stone, copper and iron would be lost. Only a very small amount of people would have access to that knowledge and apply it on a daily basis and with many of them dead only a few small groups would have access to that sort of knowledge. So after 200 years, you might have a couple communities who are able to survive, but not enough for a story. Your events are plausible if you relax your starting conditions. People have a large variety of hobbies and you need farming/growing plants and cooking to be popular enough that after 70% of people die + sickness/disease + bandits + wildlife occur that those skills are still there. That way those groups can develop into communities over time rather than slowly dying off due to lack of accessible resources. I didn't mention this before but I just thought about it, childbirth might also be a really big issue and you will need people with knowledge about this to survive. As society grows more advance you will likely have a higher dependency on machines, drugs and surgery to make sure the baby is delivered and survives its first few months rather than traditional methods. [Answer] I will start with structuring the aftermath of such an apocalypse into stages how things are going to happen (i may be wrong): Stage 1: Immediately after the End Society comes to a halt. Communication breaks down. Food storages will be looted by marauders. Police, national guard and military (if exists) will try to preserve some kind of order, but will fail as soon as they realize that all their precious tech is not working - remember, nearly every modern military is relying on high tech. You are saying that everything invented after the Middle Ages is not working. Engines, gears, pumps, and so on and so on won't work. But what could maybe work? Simple guns. I do not mean semi-auto or full-auto, but old hunting rifles and single-loader guns. The technology for those existed in medieval times (except cartridges). Who can be expected to die first? The old, small kids, those who altered their body (they became cripples). In this turbulent time alot of panic, confusion and violence is to be expected. Stage 2: Marauding bands of survivors Every know organisation from before the End is gone. What's left are survivors who will band in small groups of about 20 to 30 individuals. These groups are quite mobile, food can be gathered/ looted on the way, they can defend each other and wild animals, even if agfressive, will hesitate to attack a bigger group of victims. Remember, a hunter has to survive the hunt with no or only minor injuries. If to straving bands meet, there will be alot of hostility and caution - the other group could attack you, steal your stuff, or make your life a living hell in some other way. Stage 3: First small settlements At some point, when the first women get pregnant, the first of these groups will look for a place to settle down. A settlement can be easier defended, houses can become home, and if they got enough experience in the wilds on their journey, they may now start some form of simple agriculture. Learning those things will be hard, every relevant information is lost due to the libraries being electronic. These settlements will either use old ruins/ existing infrastructure, or be placed in a suitable, easily defended location near running water. This reduces the available sites dramatically. Stage 4: First contact with others After some time, hunters, gatherers or explorers may stumble upon another settlement of survivors. The reaction to one another may vary alot, depending on the character of the societies that grew in the new settlements. Maybe they do not want to have to do with eacht other, maybe they will engage in trade. Stage 5: Rise of a new society It may take a while, but more and more settlements will come in contact with each other. They may agree to some kind of laws, rules or code how to handle meetings, and soon after build roads again between them to ease trading and traveling. Some of them will have ressources others don't have, maybe there will be fights, maybe trade will set in. Conclusion: How long will each stage take? This depends heavily on the first two. If there are proportionally more survivors in stage 1, it may be a positive or negative thing: More people fighting for the same ressources, or a faster processing to stage 3 due to cooperation. Leading characters of those groups will play an important and deciding role. I would estimate that in the best case, you can encounter the first settlements after 5 years. Why? Well, if some groups band together, you will pretty soon have a population that can't be sustained by hunting and gathering while wandering the land. They will have to help each other, and thus reach stage 3 alot faster. My worst-case estimate is 25 years. Let's say some groups band together, and a fight breaks out. Vital members of these groups get injured or killed, and the survival chance of each group gets diminished so far, that they will have a hard time surviving. The loss of written knowledge is a defining point. If your civilication relied completely on automation and servant-bots, the future will be dark. Alot of them will die in the aftermath of the apocalypse, and only very few will survive. If your civilisation is high-end and takes learning as a pastime, the chances may stand better. Tl;dr: 200 years are more than enough to rebuilt into something resembling society. It may not be a nice future, but one where your people can survive. ]
[Question] [ In my fantasy world, which lacks a name currently, there is a race of what looks like a series of interconnected worms or maggots that is known for growing in and around skeletons using its own body to act as the skeletons muscles. Basically using the skeleton as both a shell and transportation (basically my, I think uniquish, skeleton hoard). Now I'm wondering how would this creature reasonably bind the bones together? Bonus points for a way that would allow fluid motion. Note: The feasibility of this race will come as a later question. [Answer] More or less what you find in social insects, where there are the workers, the soldiers and the egg layer, in this species there are different specializations: some individuals are better suited to mimic the muscles, some other the tendons and ligaments, some other the skin. (At the end you don't want them to dry up in a sunny day, don't you?) They know more or less how to arrange around bones to keep them in place, and then they mimic the organization of tendons and muscles to be able to enact movements. [Answer] If the worms claimed recently deceased hosts, they could east up the muscle and other soft tissue and replace them, but keep the tendons, cartilage etc intact. This may also deal with the feasibility of how they know how to organise themselves - they just copy the old host. [Answer] It sounds like you could use some sort of specialized secretion. I get the impression you want the worms to be fairly small. With that in mind, something like mucuous or silk might work. Seeing as his muscles are normally attached to bone with tendons, you could have these worms use a silk-like material as a substitute for tendons. I suggest picking a natural base like one of these and tweak it to suit your needs. (P.S. This is my first answer, so apologies if I missed any bits of etiquette.) [Answer] You could say that the worms or maggots produce a gooey sticky slime which acts as an adhesive to bones. not only will it be bonded strongly but also will be very flexible. As for the control, there can be a main queen worm which acts like the head and is responsible for just control, while other worms take care of the other functions or you can even have a certain kind of neural signals with a feedback which can transmit over their skins, helping them in coordination and control. ]
[Question] [ I have a race of mainly insectoid aliens known as the Erepo who have virtually bioengineered a ecosystem around themselves. Now I currently have them using either organic systems they can "grow" or materials those constructs create(ex: metal created spheres secreted by slugs). Would it be possible to have a organic creature that could generate electricity and then have a way to transfer it to other systems or organisms to power them? Note: Power generation in the 1000s of joules or if possible a megajoule is what I was thinking this creature could produce. [Answer] So, you're asking if you can have a living battery? Yes, it is not impossible: if you wanted to expand the concept of [organic solar cell](https://en.wikipedia.org/wiki/Organic_solar_cell), you could have your bioconstruct to absorb solar energy to be 'milked' for all purposes. Optimal transfer should work via a direct plugging -even though energy can be moved wireless, there would be a lot of dispertion, not to mention the hazard factor. Instead, if the construct looked like an enormous insect with frontal 'horns' that could be used as plugs, then you can use it to transfer energy safely. This kind of solution would work just fine for, say, small communities or emergency interventions anywhere near the walking range of the big crawler. [Answer] You could engineer the [Sodium channels](https://en.wikipedia.org/wiki/Sodium_channel) in the cells to feed the circuits. > > Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's plasma membrane. > > > With (Na+) ions you can build up a difference of potentials, which can be then used to induce a current in a circuit. In this way you could use the usual metabolism to feed the cells and keep them charged. ]
[Question] [ In my book there are occasional battles between space ships or fleets which can span hours due to the distances involved. Most of the combat is done using missiles which can accelerate at e.g. 750g with enough fuel for 30 minutes, which means they have a range of about 40 lightseconds. Ships move with 200g and are pretty much constantly accelerating in various directions to change their momentum. This becomes fairly complicated over time, because I have to keep the momentum of all ships and missiles in mind when calculating things like time to impact, distances and all of that. I'm currently doing all the calculations manually, which is extremely tedious and time consuming, not to mention error prone. I've tried to find a tool where I can say "Ship A is at X,Y,Z and is accelerating at A gravities. Here is Ship B. Now step through it second by second, occasionally changing the vectors or adding new objects (missiles)." I have yet to find a tool like that and if I program it myself, I don't have time to write the book. Does anyone know a tool (free or not) I can use to simulate my space combat? [Answer] If you are not afraid of some hacking, [Kerbal Space Program](https://www.kerbalspaceprogram.com/en/may) may be your answer. It's a game, but with physics reasonably close to what you have in real life. It has time warp option and good trajectory and time calculations. You will need some add-ons: * [HyperEdit](http://www.kerbaltek.com/HyperEdit) to put things where you want them to be. * One of the "infinite fuel" mods or tricks, unless you actually want to care about that. * [MechJeb](https://kerbal.curseforge.com/projects/mechjeb) or something similar if you want autopilot, and for your purposes you probably want. * One of the "real solar system" or planetary system editors, to set up a scene. * Mod that allows acceleration of not focused ships. I have one installed, with solar sail or ion engine, will fill this bullet point when I'm near my computer. This should do a reasonably good job to simulate movement in space. Note about relativity: 750 g acceleration for 30 minutes gives us merely [4.4% of speed of light](https://www.google.pl/search?q=(9.81750m/s%5E230min)/c). This is substantial, but too small for most readers to notice difference. Thus, KSP being Newtonian only does not disqualify it. And OP asked for Newtonian anyway. --- Of course, [Cort Ammon reminded me](https://worldbuilding.stackexchange.com/questions/114400/tool-for-simulating-newtonian-acceleration-based-space-combat/114406?noredirect=1#comment350281_114406) of Obligatory XKCD! [![Webcomic about XKCD teaching orbital mechanics](https://imgs.xkcd.com/comics/orbital_mechanics.png)](https://xkcd.com/1356/) [Answer] [Children of a Dead Earth](http://childrenofadeadearth.com/) is a space combat game with near-future technologies with a big accent on actually simulating what would happen. Now, it may be a bit too realistic for what you want, and the focus on near-future tech may limit its scope compared to the more fantastic systems generally found in SF. However, there are great insights to be found in it. Note that the simulation isn't perfect: it has been developed by one person, so its scope is necessarily limited and some elements are not quite as finely modeled than others. Still, it is probably the most advanced space combat simulation tool available on market at the moment. As a side-note, its newtonian simulation is more advanced than in KSP, as it always simulates the influence of all bodies instead of only the closest one. KSP is easier to handle and more adapted for sketching long distance travels with no combat (say, the Voyager probes), while CoaDE will give a more exact result. ]

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