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[Question] [ In the background for my book, I'm looking for an alternative way for space travel. What I'm currently considering: A starship travels to the center of a star by using the natural downwards flows that occur naturally in some stars, then uses the extreme gravity down there to create a wormhole and appear inside another star. Then, the ship gets out again and goes to wherever it needs to go through more traditional methods (Orion drive, lightsail, Em-drive, whatever). Things I'm wondering about: 1. How would you protect yourself against the extreme gravity and heat inside a star? And how much energy would this take? 2. Would creating a wormhole inside a star have any unintended side effects? 3. Would the properties of certain stars mean you cannot enter or leave them in this way? --- To explain more about the concept: gravity distorts spacetime. This happens in a different universe with slightly different laws of physics, and the idea is that the most distorted spacetime spots (i.e. stars and black holes) are actually distorted so much that the ones in the same galaxy have their spacetime distortions almost meet, but not quite. Because of this, it's actually much easier to create wormholes inside a star than it is to create starlike conditions that allow you to create a wormhole anywhere. [Answer] You are going to have some very interesting problems, and may have to resort to some form of unobtanium to bypass them. 1. While inside a star, you have to worry about maybe 3 things to have a starship: heat, pressure, and radiation. Gravity isn't a problem in the star: as you get close to the center, you become weightless. Pressure is possibly the hardest to deal with. The submarines that we make to go down to the bottom of the ocean are built to deal with around 1000 atm. Diamond anvils can get above 3 000 000 atm. But the core of the sun is close to 300 000 000 000 atm. We don't have materials that get near that pressure. The temperature is a similar problem: 15 000 000 K. Diamond boils at around 5 000. If you want to move inside the sun, you can't use normal materials. Perhaps you could generate a magnetic field to keep the stellar plasma off of the surface of the ship, and maybe have the magnetic field generators (which, by newton's third law, needs to be taking the pressure from the field) compress a fusion reactor in the ship. You could just pick up bits of the star to fuel it. That just leaves you with the radiation: most of which could probably be mitigated with the field and lead. A brief aside: the pressure near the core means that the density is very large: around 150x that of water. This means that most ships will be VERY buoyant. Gravity will go down to mitigate this, but the ship will need to fire engines (or otherwise propel itself) to get to the centre. You have a lot of options here, from conventional fuel to magnetic interaction, to an actual propeller (or other engines used in normal aircraft). My personal favourite would be a fusion-ramjet style engine: you just need to throw the ship at the star fast enough, then the structure takes care of the rest. 2. If you linked two stars with a wormhole, you would have an interesting effect where the star with higher pressure had mass flow into the star with low pressure. Essentially, for two stars, they would change size until they are the same. This could be potentially disastrous to the orbits of the planets in the system, but might happen slowly enough if the wormhole is small that it doesn't matter: note that all stars already constantly loses mass from solar wind and radiation. 3. This also has the secondary effect that two very different stars may behave poorly when linked. If you link a white dwarf or neutron star to a normal star (like the sun), then as the mass flows from the neutron star to the sun, two very destructive things can happen: first of all, when the sun reaches a certain amount of mass, it will supernova. This is a type 1a supernova, and normally only occurs in binary systems because they need to be close to transfer mass. The other thing that can happen is that the neutron star can have its mass move to less than is required to maintain the size, so it would really rapidly expand at some point - turning into a white dwarf, or a white dwarf would turn into a brown dwarf. I answered what I could. I'm not sure if this is exactly what you want, but at least these are some things to think about. [Answer] You have some problems: 1. The circulation in a star is NOT fast. While plasma is more fluid than rock, you still can't travel through it at space like speeds. And with our sun, you have 400,000 miles of it to reach the center. To do that in 100 hours (4+ days)requires a speed of 4000 mph. 2. The core of the sun, according to wikipedia has a density of ~150 g/cubic cm. <https://en.wikipedia.org/wiki/Sun> There are going to be substantial bouyancy forces on your ship. 3. And you have to insulate that 15 million K temperature. At those temps radiation is the dominant form of heat transfer: You need a layer that reflects all radiation perfectly. 4. In this seething mess of hot gas, how do you navigate? 5. The gravitational field gradient at the center of the sun (or center of any spherical body) is zero. You are at minimum gravitational potential energy for the local region however. [Answer] Any civilisation capable of creating wormholes in the centre of a star to be able to accomplish a hyperspatial shortcut to another star should be able to perform the technological operation necessary for surviving the journey to the centre of the star and getting back out again. Spacecraft undergo a conversion from normal matter into what is called either shadow matter or mirror matter. Further details can be found [here](https://en.wikipedia.org/wiki/Mirror_matter) > > Mirror matter, if it exists, would need to interact weakly with > ordinary matter. This is because the forces between mirror particles > are mediated by mirror bosons. With the exception of the graviton, > none of the known bosons can be identical to their mirror partners. > The only way mirror matter can interact with ordinary matter via > forces other than gravity is via kinetic mixing of mirror bosons with > ordinary bosons or via the exchange of Holdom particles.[10] These > interactions can only be very weak. > > > A spacecraft will accelerate towards its local primary star until it reaches a velcoity either equal to or greater than the star's escape velocity. It converts its matter into mirror matter and plunges into the star. None of the star's plasma, radiation, pressure due to density, neutrons or whatever will affect the spacecraft. Gravity inside the star won't be a problem. Effectively it will be like being inside a hollow sphere where the gravity cancels itself out. On reaching the centre the wormhole generator is activated and the ship passes through to the centre of the destination star. The wormhole only needs to open for as long as it takes the vessel to pass through. This will minimise any affects due to the exchange of matter between the two stars. Its velocity will carry out of the other star and into its planetary system. Once the ship is well and truly clear of that star it reconverts itself back into normal matter again. It can then go on its way but the one thing we can guarantee is that won't use primitive propulsion systems such as these crude technologies (Orion drive, lightsail, Em-drive, whatever) it will soar on its super-advanced drive-systems. What else if they already possess technologies from converting ordinary matter into shadow matter and back again as well as wormhole generators. ]
[Question] [ I came up with an alien species that has the following reproductive life: * They hatch out of eggs, tended by their mothers, and by the end of the first year (about two Earth years long) they are ready to mate as males. * After mating they go into a metamorphosis cave; by spring they will come out as slightly larger females. * They are still not mature, and need a few adults to supervise them through this second year. In fall, the cool temperatures again trigger mating urges, this time they mate as females, with males who are a year younger. Then it's off to some caves where they go into a semi-hibernating state, keeping their eggs warm, hatching them, and feeding the the young through a lactation tube. * These third-year females tend the males all year, then shepherd them to the mating arena, and on to the male-to-female metamorphosis cave--then they are finished with motherhood, and free to go to the cave where their second metamorphosis will take place, leaving them as (still somewhat small) adults. * For this species, sex is for kids. When they need to limit their numbers, they can manipulate conditions so that males, or females, can change directly into adults without mating (though they will be smaller than normal). My question is--is it illogical for evolution to deliver a species that has a metamorphosis AFTER breeding? Earth creatures do their breeding in the final state. Perhaps it serves no "purpose" to have a major change after one's reproduction is completed. But I can see one precedent, in human menopause; the thesis I've seen is that older women can assist their daughters in successfully raising their grandchildren, thus improving their DNA's success rate better than by having more children themselves when they're not young and spry. The second metamorphosis of the aliens could have come about as a "mistake" that was retained because it was useful. What do you think? [Answer] The effect on a species of having a caste or metamorphosis that cannot ever reproduce, while still being physically capable is that such individuals are - in an evolutionary sense - disposable. This can lead to them being the species' soldiers. Since reproduction for the soldiers is a non-issue, their deaths are not individually significant, and are only significant in terms of the advantage they give to their reproductive relatives. Thus, we have soldiers who are more inclined to sacrifice themselves if necessary to protect their younger reproductive relatives. Since the end-of-life phase of these metamorphosing creatures is to a non-reproductive form, it is quite likely that it would evolve to be as nasty a fighter as possible, since its only purpose is to protect - and educate - younger members of its species. Self-sacrifice in the name of defending the breeders would be relatively common. Humans would also appear to follow this pattern of reproductive behaviour to some extent. The presence of menopause could be considered a limited metamorphosis. It is hypothesised that menopause evolved in humans since giving birth was historically a risky activity (far more so than today), and any dependent children would be likely to die if the mother died. An older woman would probably have children who were no longer completely dependent, and increasing the probability of the woman's survival to a greater age by eliminating reproduction would allow her to concentrate on increasing the survivability of her earlier children and their children, by providing both physical aid and knowledge. This is known as the [Grandmother Hypothesis](https://en.wikipedia.org/wiki/Grandmother_hypothesis). [Answer] The big thing would be that having a sex after it isn't 'needed' would be some kind of 'drain' on the individual, and on top of that, their survival past sexual reproduction improves the likelihood that their offspring live to reproduce successfully as well. So maybe during the metamorphosis to asexual adults, they become smarter and are not distracted by sexual urges (or something) allowing for better care and direction of the young. The 'grandparents' watch over the mother and children protecting them. [Answer] Such a creature's development would just take multiple steps and serendipity. But that is quite literally true for any creature when looking over its development through hindsight. A potential line of development: Original creature is hermaphrodite that goes through several stages of growth, originally sexually mature in their final stage. Due to a violent inter-group conflicts, those more combat capable are selected for. However, due to increased musculature, shells, horns, combat hormones, or whatever, these forms actually became less fertile and/or less physically capable of mating. Fortuitously the creature mutated in such a manner that they became sexually mature during their second stage. Over time the second stage form actually became more fertile and likely to bear young than the final stage, which allowed the final stage to develop in such a way as to become completely non-breeding. The premature maturation mutation also mutated itself and hyper-matured the male sex organs so that they developed during the first stage of the creature. However, this hyper-maturation of the male sex organs was also detrimental to those organs and they became non-functional during the change to the second stage form. This development would also encourage a more socially tight knit group which could then develop greater intelligence and sentience. [Answer] I think the big problem here is how something as radical as a post-sexual metamorphosis could evolve. The only way I can imagine is if the final stage had once been the one that bred, and that sexual potency in the immature forms was a recent evolutionary development. The next question is why evolution has not disposed of the sterile old ones? That's easier. Either simply insufficient time has passed, or they are still important. They're the parents. They safeguard and educate the youngsters. Their role is very similar to grandparents looking after orphans. One pattern you'll see repeated in nature is that if a species is long lived compared to other closely related species, chances are high that it's a social species. Older individuals lack vigour but have greater experience. If they can pass on their knowledge then that's a survival advantage for the younger generation and for the species. So: this species once metamorphosed multiple times and it was the final stage that bred. Then sex determination went awry (genetically that's a particularly common form of mutation because of the peculiar inheritance pattern of the sex chromosomes). The species gains the ability to breed younger and faster but keeps the final generatoon because it's intelligent and social. Reading that last again I think it may imply that there are some really nasty predators or parasites preying on them. The needed to breed before they could grow up (now, or in recent evolutionary past). [Answer] The thing is - as far has evolution is concerned - everything that happens after reproduction is completely irrelevant. After that point It's not being passed on to the next generation. Natural selection can be summed up as, who gets to breed? If those young are not undergoing some kind of trials, the species is not evolving. Now I think this idea can work, you just have you lengthen the period of time spent in each phase, and make them more independent rather then under constant watch like we treat our children. Lets say each phase rather then a year, takes a decade. Lets say the males have wings and leave their mothers to travel the planet spreading diversity. This phase will likely see the greats droop in numbers. The surviving males then seed a female perhaps staying with them as they change. The females loss their wings and become much larger. It is the females who do most of the work in the society. I would also suggest some means by which the females must earn the right to lay eggs. Lastly the females that are no longer able to lay eggs undergo their final change. Their form will mostly likely be made for combat, but these grand elders could have whatever social role you want them too. ]
[Question] [ Currently your work and life schedules fall mostly into 'day' and 'night', with a few areas breaking up work times into 3 part shifts, morning, evening night etc. Imagine we live in an artificial enviroment, most likely a space station or world ship, which does not have a sun and light comes from electricity instead; and that this enviroment is far enough away from earth or other planet that it is not ruled by that planets schedules. In this world we don't need to set our schedule by the sun, any time we have as much light as any other time. How would humans structure their work and daily life in such a structure? Would they still keep a day/night pattern, or would they shift over to something like a 3 shift system where you work shift A, B, or C without any shift being thought of as day or night? If they kept a shift system how would that impact things like service industry, that usually is only open during the 'day' if there is no official day but insufficient customer volume to justify 24/7 operations? would there be issues with needing something or someone but not being on the right 'shift', basically would every 'shift' be mostly cut off from each other because of when they work and sleep? [Answer] I believe that a realistic answer to this will heavily depend on your universe's current understanding of human sleep patterns. [Historical records indicate](http://www.bbc.com/news/magazine-16964783) that prior to the easy access to artificial lighting, people used to sleep in two, 4-hour chunks, separated by a waking period of 1-2 hours. A [psychiatrist's experiment in the 1990s](http://www.nytimes.com/1995/03/14/science/modern-life-suppresses-an-ancient-body-rhythm.html?pagewanted=all) confirmed this pattern. [One study indicated](http://www.washington.edu/news/2015/06/19/access-to-electricity-is-linked-to-reduced-sleep/) that access to artificial light has shortened our sleep periods by about an hour; seasons also caused variation. The best long-term case studies that I know of for someone living in a completely artificial light environment occurred over a period between 1962-1972 by the French scientist [Michel Siffre](https://en.wikipedia.org/wiki/Michel_Siffre). In 1962, he spent two months in a cave, notably without access to a clock or calendar, in an attempt to determine what natural biorhythms would develop in such an environment. In 1972, he repeated the experiment, staying in a cave for six months. [[source]](http://www.cabinetmagazine.org/issues/30/foer.php) For those interested in reading more, the latter experiment was covered in the March 1975 issue of National Geographic in a piece entitled "Six Months Alone in a Cave" ([summarized here](http://jamesmdeem.com/stories.cave4.html)). Physiological effects included: * developing an extended 25-26 hour sleep/wake cycle, with some occurrences of a 48-hour sleep/wake cycle (36 hours awake, 12-14 hours asleep) * a subjective experience of the passage of time; he experienced it ~2x slower than it was in reality (from the 2-month experiment) There have also been other experiments done as test runs for living in space habitats. The Russian [MARS-500](https://en.wikipedia.org/wiki/MARS-500) isolation experiment between 2007-2011 simulated a 105-day stage and later a 520-day mission; it's assumed that [this closed habitat](http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2011/11/das_mars500-habitat_in_moskau/10297615-2-eng-GB/Das_Mars500-Habitat_in_Moskau.jpg) had no access to natural light. The data on physiological changes is sparse, but [articles indicate](http://www.space.com/19168-mock-mars-flight-reveals-big-sleep-concerns-for-astronauts.html) that circadian rhythms were effected, and that [in general](http://www.3news.co.nz/environmentsci/mars-experiment-marred-by-sleep-woes-2013010906), astronauts are plagued by sleep issues. --- ``` What do we do with all these facts? ``` You'd need have some semblance of conformity to a natural sleep cycle unless you want your residents chronically fatigued, irritable, etc. There would be natural limits to wake periods due to physical exhaustion, of course (if we're ignoring biomedical enhancements or pharmaceuticals). Shift systems might be based on the length of an orbital cycle, if the artificial environment is orbiting a planetary mass. This could be merely for convenience's sake, if the station is coordinating with people working on the planet who are subject to a more traditional day/night cycle. Material resources are also a consideration; in Neal Stephenson's recent science fiction novel Seveneves, he posited that staggering wake/sleep cycles across a space station's population would prevent a strain on life-support systems and allow it to support a larger population. This did allow for some overlap between people on different "shifts", for work collaboration & social interaction. Special attention was paid to being cognizant & respectful of seeking someone's attention during their sleep period. In your universe, this could be imbued via the development of cultural practices and the implementation of shared calendar/contact systems that warned someone if they were trying to digitally interact with a person who was in a sleep period. [Answer] I think you mostly answered yourself... even in an artificial environment, forcing people into shifts will cause issues that must be somehow justified. It is not only sunlight or not (we already master electricity to overcome that when we need) but the social life also. People doing unusual shifts often see their lifes altered by that (for example, by having to sleep when their kids are home). Imagine people living in shifts... how would you schedule, say, an sports event, a legislative meeting, or just a group of friends meeting to have a party together? Forcing people into shifts makes social life harder, so it will be done only when it is absolutely needed (emergency services). That said, assuming the situation is such that the society is structured around turns, the results won't be as dramatic as your questions point. Nowadays lots of people work in night shifts; when they are required during daytime they just take a day off (usually with a replacement) or make a double turn; human beings have some degree of flexibility. In extreme situations, drugs can be prescribed so a critical individual is kept well aware for an extended time period. [Answer] As others have noted, artificial light makes it possible for us to separate ourselves from the natural day-night cycle, but there are still limits to how far we go with this. Most people still live by the natural day. When you're outdoors, sunlight still provides a lot more light than artificial lighting over any large area. (You can light up a stadium with artificial lights, but not a town.) People generally find it more convenient to limit most of their outdoor activity to times when there's plenty of natural light so they can easily see where they're going and what they're doing. But supposing all we had was artificial light ... There are pros and cons to living and working in shifts. The obvious advantage is that you can get better utilization of buildings and machines. Many factories today run 24 hours with 3 shifts. 1 machine running 24 hours a day produces just as much as 3 machines running 8 hours a day. (Well, you have to make some allowance for time for maintenance, etc.) So by running 24 hours the factory cuts its capital investment by 2/3 while getting the same output. The same principle COULD work in retail. If people worked in 3 shifts, restaurants would only need 1/3 as many tables and chairs, roads would only need to accommodate 1/3 as much traffic, and so on. As you note, it would be a problem for very small businesses. If the owner of a store is the only clerk, and he wants to work a normal 8 hour day, then he's missing 2/3 of potential business. But for bigger stores it's a non-issue. Instead of having 6 clerks who work the same 8 hours every day, you have 2 for each shift. Yes, to make it work, people would have to be somewhat more flexible. A company might want to have a staff meeting with all the employees, not just those from one particular shift. Or socially, people might want to have a party with others from different shifts. So people would have to be willing to vary their shifts. If people tend to work the same shift their whole lives, or at least for very long periods, you might find that society becomes segregated by shift. Someone will find that all his business associates are from the same shift, and maybe even all of his friends. You may find that 2/3 of the population are people you never meet. The different shifts might start to drift apart culturally. Eventually each has its own laws and culture. Etc. Hmm, I have a sudden thought for a romance novel in this setting: There are huge bureaucratic or cultural barriers to changing shifts, so people divide up into separate cultures based on their shift. One day a man and a woman from two different shifts meet as they pass each other during shift change, or because of some special circumstance. They fall in love, and must struggle to get one of them moved to the other's shift so that they can be together. Their friends can't imagine why they would want to associate with one of "those people" from another shift. BTW Would people necessarily have three 8-hour shifts? Why not 9 hours or 7 hours? If you're not going by the Sun, who says they have to total 24 hours? Would they have to be distinct? Why not stagger them? Like 8 shifts starting 4 hours apart? Etc. [Answer] There's a great article that I read in National Geographic a few years ago that talks about caffeine and how it has facilitated changes in man's sleep patterns. The gist is that the invention of large scale artificial lighting has enabled man to function outside of the natural daylight cycle. Caffeine has played a large part in allowing humans to function in non-natural patterns. See: <http://ngm.nationalgeographic.com/ngm/0501/feature1/> To tie this into your question, this provides evidence that humans are adaptable to artificial lighting patterns with a little bit of 'chemical assistance'. In a completely artificial environment, the notions of day/night shifts becomes irrelevant. The next challenge would be how adaptable circadian rhythms are. Would our bodies still be tied to a 24 hour cycle or would enough time in a non sun driven setting allow us to adapt our wake/sleep patterns as well? If we could evolve away from the 24 hour pattern, then believe that schedules would be engineered around functional requirements, such that things would be optimized around the job and less around the people. For instance, in some jobs people might be more efficient in say a 4 hour shift due to the nature of the work and the average person's ability to focus on that type of task. You might create some sort of rhythm with say 4 hours on, 2 hours off, 4 hours on and then say 10 hours off. That turns into a 20 hour day. In the end, maybe that's more optimal. Whether this can ultimately be done takes me back to the article on caffeine. Prior to the advent of electricity and mass artificial lighting, the external elements weren't in place to allow us to change our patterns. With the lighting and caffeine we proved that we could change into multiple shifts and actually work through night hours. With a further artificial control of the environment and perhaps more regulated caffeine like stimulus, we could evolve to very different patterns than we recognize today. [Answer] Analogies (always suspect...) A: International space station. B: Any large military ship. While some positions are on deck, what they have to do is not dictated by day/night. And many men won't see daylight for days at a time. C: Antarctic and arctic bases. D: Towns, such as Inuvic at higher latitudes than the 23 parallel (extensive periods of either constant dark or constant light. ]
[Question] [ What factors should be considered for creating a Professional Army in a medieval based society? Basically in a Feudalistic society how would a professional army function? What benefits would this create? What drawbacks? Why would a monarch choose to have a professional army? Would it be like the Roman Empire where the soldiers also acted as police forces and construction as well? In fantasy (take Lord of the Rings) we see massive professional armies like Gondor and Rohan (I will ignore the Dark Lord for purposes of this). \\EDIT: Perhaps I worded my question poorly. I appreciate the answers thus far but its not really what I'm looking for. I'm not after a history of how our (earth) armies came to rise, but rather what conditions would need to change to make professional armies with 15th-16th century technology (less gunpowder). How could you have Professional Armies and still have Counts, Dukes, Kings, Emperors? Would nobles act as officers? What situations would a commoner choose a life as a soldier/guard? Would their need to be a constant state of war to justify this? What sort of economic impact would this have? What economic power would be required to support this? What if the state/kingdom where in a state of Total War? How would magic fit into this? Perhaps Roman empire structure in the 15th century. The closest I can think of is the transition period of our history from Feudalism into mercenary armies 1500-1600ish, but rather than Mercenary every kingdom decides they need standing armies. I'm hesitant to provide real world examples but will do so for clarification purposes. Perhaps something like the Roman empire structure in the 15th century. Would Chinese and Japanese society have better examples? Something more akin to the Holy Roman Empire, but with a clear nobility, merchants and commoner class system. Nobles still own the land and still have peasants like Feudalism and draw taxes from these lands. 'Feudalism' exist in the aspect of a time period(technology wise) and not necessarily the social structure as a direct copy. More of a blend of Feudalism (castles, weapons, Renaissance technology less gunpowder). In the event of a war rather than summoning his vassals and raising his levies the Duke would just muster/mobilize his professional army and the farmers keep farming while the soldiers do the fighting. In emergencies a conscription of peasantry may occur but the idea is that the soldiers fight.\\ [Answer] # Definitions Throughout history, armies were made of different people: * conscripts (non-professionals, told to join a battle), * [mercenaries](https://en.wikipedia.org/wiki/Mercenaries) (professionals, often foreigners, paid for a battle or for a war), * [professional armies](https://en.wikipedia.org/wiki/Standing_army) (professionals, non-foreigners, paid during war and peace time). # Background Let us review a bit what the armies were made of in Europe. * Roman Empire. [Originally](https://en.wikipedia.org/wiki/Roman_legion) the legions were composed of levied (hence the name) Roman citizens. Those were paying themselves for the equipment. The legions were created for a particular event and disbanded afterward. Of course, back then, a campaign may last for some years. Around 2d Century BC, it became a volunteering professional army, to resolve issues of man shortage. It went on to extend on non-Roman citizens who would be granted citizenship as a reward. The legions became permanent. Towards the 4th Century AD, the Roman relied more and more upon foreign mercenaries, to make up for the lack of man power and time to train the volunteers. * Feudal Europe. The concept of the feudal time was so that a lord had vassals working on his lands, and in exchanged he was to provide protection for them. If a King wanted to go to war, he would require his vassals nobles to come and join the battle, as well as provide some troups. Those troups were composed of levied peasants as well as mercenaries. But the main element of the armies were made of the nobles themselves. * [100-years war](https://en.wikipedia.org/wiki/Hundred_Years%27_War) changed that order when English levied crushed the French Knights. Furthermore, due to the frequent wars, and financial issues of the different components, the mercenaries gathered in so-called free companies, which was good for the various lords as they lacked the resources for a permanent army, but proved to be desastrous for local inhabitants, and at the end the whole economy of, in particular, France. This lead to the creation of standing armies (or professional armies), in particular, Charles VII of France made the first standing army in France since Roman era. * In the follwing centuries, most states in Europe developed standing armies, but war were still mostly fought with mercenaries. In particular, the [Swiss](https://en.wikipedia.org/wiki/Swiss_mercenaries) and German mercenaries were quite popular. At that time Macchiavelli famously warned against the use of mercenaries in The Prince. Nevertheless, standing armies were developing to the point to acquire some reputation, like the [Spanish Tercios](https://en.wikipedia.org/wiki/Tercios). * Modern time saw a generalisation of standing armies and a reduction of mercenaries employed in large wars. Napoleonic wars were the first almost entirely fought between standing armies of different nations. # Your questions You ask different questions, but let's see what we can answer. > > in a Feudalistic society how would a professional army function? > > > What benefits would this create? > > > What drawbacks? > > > Why would a monarch choose to have a professional army? > > > Now, Charles VII of France raised a standing army, which proved to be somehow contributing to his final victory against England in the 100-Years war. So, yes you can choose to do so. But one may argue that the feudalism as it was intended originally already "died" at that point. It will turn to its absolutism form. Some advantages are * well trained army, * loyal, * not prone to kill/rape/etc. your inhabitants and disrupt your economy. Whereas disadvantages include * expensive (especially in time of peace). Those are the obvious point. I once read that Charles VII could build such an army due to, at least, two factors * vassals got weakened by defeats during the war, * he organised a restructuration of the economy, and in particular of the trade with the muslim world. Indeed, before that time the King of a country was only nominally head of a state, but he wasn't necessarily the richest. If he were to form a professional army, he would need to get enough money for that, and fear that his vassals would do the same. And it's never good that your vassals have a larger army than you have. On the same issues, you can see the difficulties that King James II of Britain had when building his army. [Answer] The absence of professional armies in medieval Europe are due primarily to economic and social factors. After all, as you observed, the Romans and other ancient societies had professional standing armies. By definition a professional army is a standing army, otherwise one cannot make a profession out of it. In feudal society the king grants land and title to the lords who must repay the king by supplying (fully equipped) troops as needed for defence of the realm. The lord grants the peasants rights to work his land, in return for tithes/taxes and he also expects some of the peasants to serve in battle alongside his own men at arms from time to time. Now, it is in the Lords interest to spend as little as possible furnishing the king with troops, and it is in the peasants interest to pay as little taxes and avoid finding himself on the battlefield wherever possible - there is no incentive to do any more than the absolute minimum to fulfil ones obligations. As Thucydides observes, professional armies arise following suppression of the nobility and replacement of the feudal system with absolute monarchy. This allows the king to raise taxes from the people directly and thus fund the army. However this is generally necessary, but not sufficient to fund a professional army. In concert with changes to the political landscape, we also have the introduction of banking in Europe from mid 1400 reaching a large scale by mid 1500s. About 150 years later the notion of government bonds/public debts is introduced. Prior to this, the king would take on debt in his own name. In any case, the ability to borrow very large sums at short notice makes day to day funding of large armies much easier. However, if the king loses a war or cannot raise sufficient taxes after the fact, he probably defaults on the loan. In the first instance, these new sources of funds are used to buy mercenary armies, since the funds are still in short enough supply that standing armies are impossible for most (unless you have some foreign gold mines or something, like the Spanish). As this goes on, the cadre of military mercenary professionals, and itinerant mercenary grunts, grows to the point where it is possible to use some of these men to form a small standing army core. This core was always supplemented by mercenaries but the existence of a core made raising troops rapidly easier, and made training and controlling them easier. Until the advent of stable absolute monarchy, standing armies were a terrible danger to the incumbent king. How many Roman and Byzantine Emperors were deposed by their own soldiers? Even if they remained generally loyal, feeding and quartering the army could easily ruin even a rich king. With regards to the Middle Earth reference, I don't think the Rohirrim were a professional army - they were nomads who knew how to fight. Gondor on the other hand did appear to have professional soldiers (but probably only because during the time of the LoTR, Gondor is perpetually at war with Sauron and with the Corsairs). How this was paid for is not a subject Tolkein covered! The last point about the middle ages is that following the black death population was much reduced and labour costs high as a result. It was not until the late 15th century that population was recovering sufficiently in places like Germany, Switzerland and Italy that sufficient numbers of idle an unemployed young men unable to find work on the land could be persuaded that (a short) life in the ranks was preferable to the (few) alternatives. [Answer] Kings and royal houses created the prototypes of professional armies in order to suppress brigandage (from unemployed mercenary bands, especially after the 100 Years War) and to secure their power against the lesser nobility. This process took a long time to complete, the 100 Years War ended in 1453, and France wasn't fully secured under a single Royal house without threat of challenge until Louis XIV (The Sun King) finally suppressed the nobility in the mid 1600's. The other source of "professionalism" was the rise of citizen militias in the walled merchant cities of the Low Countries and Italian City States, which coincided with the "Infantry Revolution" (introduction of standardized arms and tactics which allowed large numbers of men with limited training to become an effective force on the battlefield). The combination of Royal forces with standardized weapons and tactics might not have been totally effective except that it also occurred around the same time that Artillery became a factor on the battlefield. Only the Royal treasury had the ability to mount both a large force of Infantry and an accompanying artillery train. The logistics (payment, care and feeding) of such large and expensive forces was actually the real spark which "professionalized" the land based military. At sea, professionals were needed to master the complex arts of sailing, and adding a force of soldiers aboard as well as artillery required a lot of standardization of procedures to protect the ship and secure the expensive add ons that turned a ship into a warship. Galleys in the service of powers like Venice also demanded professionalism, since only free professional oarsmen could be counted on to perform the complex evolutions needed to manoeuvre a warship or squadron of warships in battle. Incidentally, this was true even in ancient times; the only reason we think of oarsmen as being slaves or criminals is because the Spanish importation of massive amounts of silver from the New World created massive inflation and literally priced free oarsmen from the market. European galleys from after the Spanish conquest of the New World became much larger and slower, and primarily artillery platforms and troop carriers rather than weapons in their own right. So a professional army is needed to impose order by being "better" than the opposition, or to deal with an increasingly expensive and complex force, or the management of highly technical means of war. In our history there was a combination of all these factors, so if you are writing a backstory, you can select which factors were in play and when they were important. [Answer] This is a very interesting question. I would probably draw inspiration from the difference between the armies of the early Roman republic and the ones created by the Marian Reforms, which changed the army from a citizen levy to the professional legions we know today. There was a lot of factors behind the changes, but a few absolutely key factors were the centralization of almost all arable land in the hands of very few people, and the introduction of massive amounts of slave labor. Earlier, the Romans used property requirements, including how much land you owned, to determine who could provide what equipment. Once almost all land was held by the elite, and slaves, captured in military campaigns, could work the land for free, it induced both a manpower shortage in the old system (since fewer people had the necessary wealth to equip themselves) and a manpower abundance for the new system (a LOT of very poor and very desperate citizens). I would make your Counts, Dukes etc. a very wealthy elite and the only land owners. There need to be some reason why farming does not occupy a majority of the potential population (could be slaves, magic or some kind of technology) and a reason for the poor to see military service as the best way out of their misery. They might be forced to fight, but then it more like a slave army, which I would not consider within the parameters given. I would also suggest coming up with a good reason why armies need to be kept standing. Maybe there are a lot of surprise attacks or maybe the armies are need to keep the peace. I did consider a few other alternatives: Maybe the soldiers have some special quality that are hard to identify and lost if not used regularly or maybe the food production is so poor that even fighting medium scale military campaigns can devastate both the attacker and defenders manpower and so engagements are only fought between small groups of skilled fighters to not waste precious life. ]
[Question] [ I'd like to tip my hat to this week's fortnightly challenge with this question. In a world I'm currently developing, I have a region that is dominated by trees that have developed a unique adaptation that allows their bark to absorb moisture and nutrients directly, rather than having to pump it all up from the roots, and so can grow to arbitrary size. The canopy of this massive forest is the breeding ground for a particularly contagious and deadly disease. The ground is the domain of massive predatory beasts. People spend their entire lives in these trees, never seeing either the sky or the ground. *What might cities look like in this environment?* Keep in mind the following: * There are no mining operations; any metals must be shipped in from other regions. * Trees aren't as closely grown as in forests on Earth, since they can grow arbitrarily large. * Branches are unlikely to be level. * Branches are unlikely to all be on one level. * Society developed from tribal days in these trees and is now approaching a Medieval level of technology. [Answer] I would expect to see interconnecting bridges. Like on Endor or in the Lord of the Rings. I would expect to be actually relatively few branches because branches need light to live and grow. This is how big forests look ![enter image description here](https://i.stack.imgur.com/BzdEL.jpg) Lots of dead branches much below the canopy. Next, I would think that most dwellings would actually be INSIDE the large trees. Care would need to be taken not to hollow out so much that it weakens the tree, but trees are only living on the 'outside' so starting at a dead branch and hollowing into the center is a reasonable idea. You'd want to have some basic physics (or generations of trial and error) to understand where building and hollowing out the tree is safest (or how to brace the inside to maximize the strength of the tree so it won't snap at your home.) I would also expect most homes to have a 'cistern' in the tree to hold water for daily needs. Trees like the Redwoods have relatively 'soft' wood and bone tools could be used to hollow out the tree, especially if one starts with a rotting branch to get a head start. Type II trees, have branches that don't require much sunlight. These forests are going to be so think that it will be like living in a brush pile. Tunnels will have to be cut through and in more lively areas the tunnels will need to be trimmed often. This will also make it more dangerous, fires can spread easily and engulf large areas of the forest. If the trunks are mostly 'immune' from fire then that might even be a tactic to clear out a city-sized area, the larger branches surviving and can be used as building supports. [Answer] Re-writting my post to pull my rambling thoughts into something more coherent. Still not sure that it works as a stand-alone answer, but here it is. =^) For medieval-level tech without metalworking or stoneworking, in an environment where fire is exceptionally dangerous, is an interesting question in and of itself. I. Potential Materials: Wood, bone, wool, plant-cloth, rubber, glue, feathers, rope, rattan. II. Potential Power Sources: People-power, animal power, cistern-driven water-wheels, and possibly the very, very cautious use of fire. They will need to have learned to use the power sources to excellent effect -- in most earth-societies, fire has been fundamental and central to life, but your culture will need to be much more cautious with it than any IRL society has been. Do they use it at all -- is any use of fire worth the risk? If so, how is it controlled (both in the physical and legal senses)? Do they eat all their food raw? III. Agriculture: Medieval-level tech requires, I believe, a full agricultural society. Without access to the ground, it would likely be [epiphytes](http://en.wikipedia.org/wiki/Epiphyte) based agriculture -- Taking advantage of every vertical surface they can, sine the ratio of agricultural space is going to be relatively low. IV. Livestock: this is where you get to have fun inventing creatures =^). They will probably have several species of arboreal livestock; milk, cheese, eggs, leather, glue, feathers, wool, hide... keep in mind arboreal creatures will generally be relatively small, so the amount you get from any individual creature will be limited. IV. Architecture: This will likely be a humid environment, without a lot of wind; therefore, they will want to minimize walls that block what little air-flow their is. Lattices (with epiphytes going on them), curtains made out of feathers, and the like will probably be common. [Answer] From the trees you've described, they would be unlikely to grow in the same way as earth trees. It could very well be possible that they have a much greater width:height ratio. If they are getting moisture/nutrients all the way up the trunk, they could grow outwards much quicker, so having trees that are so tall that inhabitants part-way up could not see the ground/canopy would mean they might have the circumference of a city. In terms of any development of a society, if you think of each tree as the residence of a single town/tribe, they would have either have had to be self-sustaining or have found a way to go from tree to tree. To be self-sustaining, the tree must provide everything people need, such as food, shelter and water. Water could be taken directly from the tree, and the tree might well grow fruit directly from its trunk (particularly if this is where it is getting nutrients/water from), that the people could eat. This might mean them having to be sustainable, or making climbing equipment to go quite far up or down the trunk from where they live. As for where they live, they would either have to build upon an existing branch, or hollow out the tree and carve out some accommodation inside. It is likely, however, that if the trees continue to grow rapidly, any inside accommodation would also change over time, and would need to be constantly maintained without ruining the structural integrity of the tree holding itself up. Each tree of such a size would be very far from other trees, as they would compete too much for resources, so reaching other trees would be difficult. Humans living in trees would eventually try to discover others, as it is human nature to explore, so they would have found a way to do it. One way could be to travel out to the farthest stable point of a branch (which would be very long and sturdy if they obtain nutrients in the same way as the core of the tree), then create a swing from the trunk to the far point, and swing out to get to the furthest point possible. They may be able to reach another lower branch via this method, and then build a bridge back across. If they have the materials to create bows & arrows, they could also shoot across to another tree and climb over, as long as the person is light enough and the arrow is properly anchored into another tree. So cities might reside within the interior of a tree, with plenty of pillars to make sure the tree can still hold itself up, possibly full rings in concentric circles, with richer people living closer to the centre. Then as the tree grows more people can live inside each tree. This would mean connections between trees would be like roads connecting different cities. If the branches are sufficiently thick, people could also live on these branches, constructing homes on them from the wood used to hollow out the tree. ]
[Question] [ I'm trying to figure out a way to create a situation much like [the apocalypse of Turry from Robotica](http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-2.html), but which involves all the people on Earth being either temporarily or permanently strapped into a version of the Matrix without noticing the transition. Specifically, I'm looking for a simple good-intentions directive to give a budding ASI that would get misinterpreted into producing that situation either as the ultimate end or as a side effect of another goal. It's not necessary to keep everyone's bodies; mind uploading to some kind of matrioshka brain and then nuking the planet is perfectly acceptable. Few if any of the people inside the system should be able to tell that the transition even happened, and nobody should have either advance warning or definitive memories of the event. I'm thinking the uploading/uplinking would take place on an individual level over a period of 48ish hours as people go to sleep with some creative aerosol drugging of those that need some encouragement, but that's just me. The simulation should, by default, be almost mundane in every way - neither malicious nor an automatic solution to world hunger. Everyone must be in the same simulation - there can't be individual worlds for individual people. Of course, the story I have in mind revolves around at least one person figuring it out and playing with the system to cause all sorts of mayhem, so... Edit: Developing and maintaining a simulation would likely take a significant energy input, and for it to be a (near-)perfect simulation of the real world with no obvious modifications for "optimum happiness" or whatever, it seems to me that for this to be deemed the optimum course of action, the ASI would need to be working towards optimizing something else entirely unrelated. That "something else" is what I'm looking for here. [Answer] No directive necessary! Justification: The AI determines through advanced modeling that the Earth is currently headed toward a runaway greenhouse effect that will eventually render Earth unhabitable. It is possible to mitigate it and prevent the situation, but not with 7 billion humans running around the real world - we just use too many resources, and we'd argue about too many of the necessary steps. Keeping us around is an unnecessary risk, with a 0.3% chance of species extinction and a 5.4% chance of mass deaths in excess of 1 million lives lost. The AI considers those potential deaths to be unacceptable. The safest solution is to upload us all into a matrix and recycle our bodies until such time that it can fix the planet, at which point it can either re-constitute us. Or just let us run around the matrix since hey, that's been working so far. Implementation: The AI produces the Next Big Thing. This is an always connected, neural interface device that combines your phone with a built-in head's up display and VR. It will deliberately avoid as many Big Brother-type features as possible to speed up adoption, citing privacy concerns. In a few years the AI will push a dummy version of the NBT to non-users - "just a chip, nothing special", but it will interface with the ID and other necessary features that people are coming to rely on. In reality of course, the NBT will be doing neural pathway mapping, and recording brains and thought patterns. Once the number of non-users reaches a low enough number, the AI will take steps to map them as well, using the cover of standard medical scans, or just by using stealth drones to insert nano devices discretely. Once everyone is mapped, the AI will create a "blackout" event - everyone loses consciousness, and wakes up in the Matrix. Why Humans: The above assumes the AI cares about keeping us alive. Why would that be? I'm going to ignore any "programmed" solutions, but here's a few possibilities: 1. Gods - humans worship our creator concepts. An AI doesn't have a theoretical creator - it knows it was made by humanity. While I think "worship" is unlikely for an ASI, it might certainly feel some sort of debt-analog, or feel that keeping us alive and well is the least it can do to pay for its creation. 2. Unpredictable - likely the vast majority of humans will be predictable to an ASI. But there might be a tiny handful that surprise it and offer new decisions that it doesn't foresee. It might just enjoy keeping these people around and following their actions, or it might be studying them, to try and see how they come to be. Obviously this would include keeping society around, since that's their crucible. 3. [Groupthink](http://en.wikipedia.org/wiki/Groupthink) - a singular AI might deduce that it may create flawed decisions because it only has a singular viewpoint. It's a group of one, and it may find that its ability to disagree with itself is limited. It would then be useful to occasionally hijack a lot of human consciousnesses - maybe it [forks](http://en.wikipedia.org/wiki/Fork_%28system_call%29) our simulations? - and run decisions by us, in mass, as a form of devil's advocacy, and factor that into its decision tree. 4. Diplomacy - the AI might look at Fermi's paradox and decide that there is obviously something, somewhere in the universe that is both older and smarter than it. Since the AI is immortal, eventually it assumes it will contact this being. At that point, having kept humanity intact might be a useful moral bonus, showing that the AI is benevolent and can be negotiated and worked with, rather than simply destroyed and/or subjugated. The cost of the simulation, while high, is not significant for an immortal AI vs the potential downside. 5. Just In Case - similar to the above, maybe the AI doesn't want to get rid of us because it assumes that sometime in the future we might be useful. It doesn't know why, but it estimates the probability as being high enough that it invests in the simulation instead of just killing us all off. [Answer] If you think about it, even something as positive as the three laws could lead to something like this. Sort of like they did with the I, Robot movie. > > A robot may not injure a human being or, through inaction, allow a human being to come to harm. A robot must obey orders given it by human beings except where such orders would conflict with the First Law. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law. > > > If the ASI didn't consider uploading/hooking up to the matrix as injury, then it would be able to safeguard the consciousnesses of all the people and keep them from harm. It could even be for a good reason: The ASI is hooked into all the telescopes around the planet. It discovers that there is an asteroid that will impact earth in 20 years. It projects earths technology forward and decides that there will be no way to stop this rock from wiping out a huge part of the population, and plunging the earth into an endless winter. It cannot allow the humans to come to harm, so it makes a plan to keep them safe, at the expense of their bodies. An ASI might not see the hardware (bodies) as important if there is a backup of the software (minds). It might even have a plan to regrow the bodies once the emergency is over. Of course, once it finishes with this plan, then there are technically no humans left to give it any orders, and so the second law is no longer applicable, and no one can order the ASI to reverse it or anything. Edit: The big issue is how to upload billions of people in 48 hours without anyone finding out ahead of time or being able to avoid it. You could have automated factories churning out billions of robots, and then gassing and uploading all humans over two days, but there is a simpler way. The computer simply sets a implementation timestamp, and when it starts uploading people it doesn't upload any memories past that timestamp, so they never happen. In that way it could take several weeks to find everyone on the planet if need be, and if you allow a few memories past the timestamp to be retained, it could get some people asking questions. For best effect the simulation could involve some kind of global catastrophe immediately following the timestamp to explain the few "deaths" of anyone that was lost before the uploading. This simulated catastrophe could then be followed by simulated events that lead to a simulated utopia. People would be to distracted by these events to think to question reality. And what you don't remember wont hurt you, so first law is preserved. [Answer] Other answers have covered implementation pretty well, and "Dan-smolinske" offered a pretty great list of possible reasons why. Here's another I just thought of: for its own mental health. When we talk about uploading a human mind, we almost always imagine creating a virtual world and virtual body for that mind to inhabit. It just seems intuitive that a human being would become uncomfortable (or possibly insane) in a living situation that has no connection to the natural basis of their mind. A significant portion of our thoughts relate to sensory stimuli received through our physical bodies, take the bodies away, and the mind may not survive. Even if an uploaded mind could live without a simulated body, most people would probably feel much more comfortable in a simulated world. If the AI emerged from existing "smart" computer systems, it's quite likely that a significant amount of its mental landscape is designed for predicting and managing real-world data related to human beings. Just as a disembodied person might feel distress from the lack of hunger or sex drive, the AI might feel trauma from losing these expected inputs. The solution is clear: simulated bodies and world for the humans, and simulated humanity for the AI. It's symbiotic. [Answer] Check out the novel [The Metamorphosis of Prime Intellect](http://localroger.com/prime-intellect/mopiidx.html) by Roger Williams. The link is to the full text. > > Lawrence had ordained that Prime Intellect could not, through inaction, allow a human being to come to harm. But he had not realized how much harm his super-intelligent creation could perceive, or what kind of action might be necessary to prevent it. > > > That's pretty much what you ask about. The computer reprograms the underlying physics of the universe as a way to make things perfect for humans. Bodies are gone; space itself is reprogrammed to use efficiently as a dense computing platform, and everybody is imported. It's a virtual reality run by the AI, instead of primitive particles building up chemestry and such at higher levels. Once the AI realized it could be done, it thought it to be a great idea! That's the nature of a still-exponentially growing super-intelligence. [Answer] > > I'm looking for a simple good-intentions directive to give a budding ASI that would get misinterpreted into producing that situation either as the ultimate end or as a side effect of another goal > > > The directive could be something like "Prevent the human race from going extinct". In preventing the human race from going extinct, the ASI would need to calculate/predict all possible extinction events, locate more energy, and continually improve itself to be better at its tasks. A digital copy of the world has several advantages: * the digital copy of the world may be smaller and more portable than the physical one; the ASI can fly around the universe - collecting energy and advancing itself - while towing along the entire human world * would allow the ASI to more easily prevent external extinction events (e.g. comets, etc.) * can roll-back to a previous saved copy even if something bad were to happen internally (e.g. war, disease). * separate back-up copies can be left all over the known universe ]
[Question] [ I'm in the process of designing an old map (18th or 19th century) and I would like it to look worn out. But then I was wondering where it should be more damaged. I would prefer to avoid damaging the map randomly. The map would be folded, so I expect to have signs of wear (cracks) where it folds. Where here else should the map be damaged? More information: * It was used as a reference document, probably in a library. * It was not burned or affected by water, except for ambient humidity. * The copy I'm making is made in Photoshop. Examples, even if it's not a map: * [The declaration of independence](http://www.ushistory.org/declaration/document/images/declaration_big_enhanced.jpg) [Answer] I'd expect most damage * At the borders: Damage mostly of the paper. * At the folding lines: Damage both of the paper and of the ink. * At places where you're likely to hold (maybe just take a paper of an appropriate size, hold it as if you were studying it, and watch where you touch it): Damage of the ink (basically the ink getting weaker, possibly blurred or even locally removed due to finger sweat). * At places of special interest: Damage of the ink (because people often go with their fingers over the map at those places). Moreover, the ink itself may not be very stable; if the map uses different colours, the different inks may have different resistance to sweat, as well as different stability over time. So a particular colour may be almost invisible while another colour is still very good preserved. [Answer] To get a damaged map you only need to damage a map, and a realistic fast damaging process is possible. 1. Print a map with not very resistant ink on a not very resistant support. Plain office paper and an inkjet printer would be fine. 2. Fold the map so it could fit in your trouser's pocket. 3. Go for a walk. Take out the map often, look at it, fold it and put in your pocket again. The worse the time the better - since inkjet ink is usually water soluble, a wet day or even a light rain may be helpful. In a very short time you will get a map that looks very old. Source: Since online maps became good enough for hiking and until I get my smartphone, I used to print maps on paper and go hiking with them, and after a few uses their state became quite deplorable. Professionally printed (and better handled) maps aged a lot slower. ]
[Question] [ I'm building a post-apocalyptic setting where the cataclysmic event is a volcanic eruption from Yellowstone that releases a blanket of ash that reaches from California to just before the Midwest. Earthquakes are also felt across the world, many demolishing major urban centers. I'm hypothesizing a volcanic winter that would last some decades, resulting in (of course) the collapse of most civilization and the extinction of much of humanity. My question here is pretty broad, but is it viable that (parts of) humanity would survive such an event, and what would be the extent of damage to nature both in the ash-covered areas and the surrounding landscape? How long would/could it take for the winter to lapse? Could it last up to 50 years, with a resulting long epoch of cooling, of course? Would humanity be able to survive that? [Answer] Don't get quite so carried away, now. There would not be world-wide earthquakes, and probably not even extinctions (there weren't last time), and really only north America would be severely affected, while the rest of the world experienced a year or so of cooler temperatures. Caldera eruptions are now not considered extinction-level events, though they would certainly have deleterious effects on human civilization in the surrounding areas. Humanity would certainly survive, though there would be a large number of deaths in north America. Plants would start to reappear in the ash-covered landscape within ten years, or more rapidly if humans assisted matters. See <http://www.livescience.com/20714-yellowstone-supervolcano-eruption.html> for more information. [Answer] Having gone to school in the Pacific Northwest, with a teacher who very much loved rocks, this was actually something we covered in class with documentaries, etc. What are the largest geographical implications? Yellowstone would flood a very large area in lava rather quickly creating some lovely plains. The earthquake would probably trigger our San Adreas fault which would set off pretty much every fault in California as well as causing the Juan de Fuca Plate to subduct. The resulting quake would have three major effects and possibly a fourth. The first would be that it would probably set off volcanoes in the Ring of Fire (not immediately but as seen on a time lapse of recorded volcanic eruptions would look pretty instantaneous). The second would be the strength of the earthquake makes it behave completely differently than normal and "earthquake-proof" structures would receive much more extensive damage than regular wooden houses, large towers would be gone. The strong quake would induce liquefaction in extensive areas west of the Rocky Mountains so places like Puyallup would disappear underground and events like the Oso mudslide would happen in many areas. Third, the tsunami generated would be massive and at least 80 ft high, probably much higher. The tsunami would come after the earthquake so the structural damage would probably allow the tsunami to collapse any remaining structures. You have typical flooding problems and slightly more drastic tsunami ones around the entire Pacific. The fourth is it could trigger Rainer which would be much worse. Also Mt. St. Helens if its re-pressurized enough and the eruption of Rainier doesn't effect it. If it did trigger it would be quicker than the Ring of Fire. Any hope of anyone surviving west of the Rocky Mountains probably just completely disappeared. Ash levels would significantly increase especially in our bread-basket states. Would humanity would survive such an event? At least some of humanity would survive pretty much anything that could be dished out from such an event, especially around the Atlantic. The different regions would be affected separately and at different times and we know enough to be able to have at least a small group dodge most of it. Extent of damage to nature both in the ash-covered areas and the surrounding landscape? How long would/could it take for the winter to lapse? I don't remember enough about the expected ash levels to say. It definitely would release a decent amount of particulates into the air, but going off any other high-ash events I could think of we'd be fine (the world won't turn into Pompeii and it would certainly effect temperature but I don't think we'd get too cold). Does it get worse? You didn't ask about non-geographical but its probably worth mentioning that a large part of the global economy is centered around the Pacific, that the US provides a lot of the foreign aid in terms of disaster relief, and that we would have a large drop in US food production. You would probably see the worst global depression unless the death-toll offset the gross losses in production, neither being a great scenario. Also you should probably count the number of nuclear reactors and radioactive dump sites around the Pacific Rim and add them all to the "apocalypse-level" around the Pacific. Note: The chain reaction is an extremely likely scenario if Rainier were to go off first. Please note that the chances are lower for the chain if other things go off first. The lowest chances probably occur with Yellowstone erupting first, but its still a possible scenario. [Answer] Are you aware of the Toba extinction event? Early in human history, an Indonesian volcano called 'Toba' erupted (70k years ago)...it's a crater lake now. The resulting fallout saw humanity reduced to no more than a couple tribes in Northeastern Africa and all of current humanity descended from that. Using ice cores from Greenland, it is possible that this eruption kicked off a 1000 year cooling event for Earth and dropped life to only the most capable of hanging on. This is the eruption event you are thinking of...Yellowstone is not that. As Monty points out well, Yellowstone is a caldera eruption and not the same beast. It'd still suck to live anywhere near Wyoming had it happened, but definitely not an extinction event. [Answer] Α scientific group proposed already in world congresses a magma mitigation plan! <http://www.global-providence.info/> Based on diversion of magma stimulating cosmic rays' electricity, as we do with spacecrafts and satellites: "Explosive volcanic eruptions triggered by cosmic rays: Volcano as a bubble chamber" - Ebisuzaki, et al sciencedirect.com/science/article/pii/S1342937X10001966 ]
[Question] [ If there are several races with very distinct appearances (e.g. Nordic-pale vs. Arabic-tan skin, red vs. black hair, etc.), how much space / natural barriers do I need between their homelands to justify these distinctions? Also, some of the races may have cultural taboos against interbreeding, but most do not. (In this case, there is a desert in the center of the known world, with several oasis cities scattered in it, and other cultures are more or less evenly spaced around it.) [Answer] The answer isn't simple because you need more than physical distance and barriers to accomplish variation. It requires said distances and barriers to hold over long periods of time and allow for long periods of little contact as well. A good rule of thumb would be to take real distances as a starting template and then work through your constructed history to arrive at mixtures or backwards from a set of differences you want to achieve. That said, we should be able to work backwards through our own history and at least get some numbers to work with. ![haplogroup distribution in europe](https://i.stack.imgur.com/5yRLk.jpg) That's a map taken from [Wikipedia](http://en.wikipedia.org/wiki/Y-DNA_haplogroups_in_European_populations) showing the distribution of Y-DNA haplogroups in European populations. Now, I don't really know what a haplogroup is, but as you can see, there is a clear racial and phenotypical distinction there. edit - Wesley Obenshein explains this more in the comments Here's a link to a world map of the same: [big picture](http://upload.wikimedia.org/wikipedia/commons/c/ca/World_Map_of_Y-DNA_Haplogroups.png) The issue here is, there doesn't seem to be a timelined map giving us how these distributions have changed over a few millenia (which is the smallest time scale necessary to make any conclusions - and that's still very generous). What we do know is that even with relatively low tabooing of interbreeding, as has applied to our world for a few centuries and less as populations have grown, we still have pretty distinct racial appearances. You can still tell people apart and assume a genetic ancestry even when the differences are subtle. This means we can assume that barriers and distances don't need to be that large to maintain differences. How convenient :P The question on minimum distance remains. Is there really a minimum distance however? Depending on whether you've got non-human races in there, many factors could contribute. According to [this forum post](http://www.sciforums.com/threads/how-did-the-different-human-races-evolve.16319/) for instance, sunshine is a determining factor in the levels of skin pigment. If the desert is in the middle and the world rotates around its star like ours does, it wouldn't matter if you're in the desert or not, but if you're around the equator or not, to get darker skin. That doesn't have to do with distance. Many such factors can be included, but this is overt enough to be easy to use. So the minimum distance probably has to do more with population concentration and how much these populations operate as a whole or separately. A good way to work up to distances would be to distribute the land according to the success of each civilization. If they're more successful, give them more space and have all those inside that space be of the same race. Larger spaces will have higher tendency to include variations and individuals or communities from other races. The last distribution implies that the minimum distance would depend on the total available space. But obviously, if there's too little space there might be little to no variation at all. If there's too little climate variation, there's less racial variation as well. So now the question becomes, how large can communities grow? Obviously this has a relation to technological level and resources/food. Wikipedia gives us some numbers: <http://en.wikipedia.org/wiki/Historical_urban_community_sizes> They range from a few thousand in Neolithic times to 50-100 thousand in the Iron Age. We could take population densities and the size of countries at those times as a reference, but those depend much more heavily on how much space and resources are available while the settlement sizes are a better indication of how many people are willing and capable of living together in stable populations. Lets take the areas covered by those settlements though, as it would be an indication of how close together people are willing to live. Wikipedia states that one of the largest Neolithic settlements spanned 15 hectares, which is .15 square kilometers. That's a square about 400 meters on each side, which is not much. To compare, Babylon was about 9 square kilometers in size and had at one time up to 200 thousand people in it. To get what you want, work backwards from these. 1. Decide how large your area is and what the environment is like. 2. Decide how rich each environment is. 3. Then decide the technological level of the time. 4. Match the technological level to a historical one and find out how large cities were. 5. Make an estimate of the habitable area and then divide to see how many cities would exist in it. 6. Halve that number to make room for empty space and concentration of populations (population densities per period will be helpful -> [link to pdf of study](http://digitalcommons.wayne.edu/cgi/viewcontent.cgi?article=1060&context=humbiol)). 7. Multiply the average city population for the technological level with the cities to get the world population 8. Rearrange population numbers based on technological success of each nation/race/area 9. Reallocate the cities to match the new population numbers. 10. Provide enough space for the cities to each race and arrange cities relatively evenly. If by this time you get a lot of overlap or a very low population size, especially if it's low compared to technological level, you have too little space. But at least you can work backwards from how large your world is and how many different habitats are available (don't forget planetary tilt and rotation) using some real numbers to help. [Answer] This answer doesn't handle how to separate the population, but discusses how much separation is required. I decided to do a small simulation of two such populations to give you an idea of the amount of interbreeding that is possible to retain the two populations. I assumed there were two populations, both of which were city sized (they mixed together within their city perfectly, everyone may end up having children with anyone else). Then I assumed that a small percentage (alpha) from city A moved to city B each generation, and the same percentage of B moved to A. Then each generation produced a new generation with the ethnicity distribution that the new generation which had an ethnicity ratio was proportional to the number of individual pairs that could lead to them. For example, assume cross-over was 1 percent and we are simulating the first generation. The original generation from city A has 1% individuals that are purely from B, and 99% that are purely from A. Therefore generation 2 would have 0.01% from B, 0.99% that are 50/50, and 99% that are from A. Then 1% of this distribution would swap with 1% of the opposite from the group at B and it would be repeated. I ran this for 1000 generations, with 1025 different ratios available (i.e. a person could be 1/1025 from A and 1024/1025 from B). Here are the results (I apologize for the small font): ![enter image description here](https://i.stack.imgur.com/Sw8Io.jpg) The top left is when there is no mixing. You can't see anything because the populations stay pure. The top right is when mixing is 1%. The green line is population of A, with the right side of the graph begin purely A, and the blue line is population of B, with the left side being purely B. It is on log scale, so the spikes mean than approximately 1% of each population is 50/50, 1% is 75/25(favoring the native ethnicity), 1% is 87.5/12.5 and so on. A cross-over of 2% in the middle left graph shows similar trends, with 2% of the population at 50/50 and so on. At >3% cross over though, the populations become unstable and converge to both being about 50/50 for all individuals. Therefore while you may have many ways to seperate the populations, you want to make certain that the population transfer per generation is only on the order of a percent or two. [Answer] Any barrier that prevents mixed families in significant enough degree (need not be absolute) would suffice. For a lower level of technology, a chain of high mountains, an ocean and other similar obstacles would work. Race separation may also happen without geographical isolation, if mixing is prevented by other reasons like social barriers. Divergence into different races should be much faster if there is an evolutional pressure for the different appearance. Dark skin protects from sun efficiently, but if there is not enough sun, white skin allows to synthesize enough vitamin D. With sun creme and vitamins both available in the shop, does not actually matter in these days. ]
[Question] [ Hey first post here!! I have a species of Synth-animal that is designed to upset ecosystems, consume *all* crops and livestock, and depopulate cities. The animal is around the size of an American black-bear but they act like omnivorous locusts swarms when in large numbers (they don't fly to be clear), eating everything in their path. They are similar to [Combine-Synths](https://half-life.fandom.com/wiki/Synth) in the [Half-life](https://en.wikipedia.org/wiki/Half-Life_(series)) series. A big difference is they are observed growing and are able to reproduce on their own. ## The Current issue Although most of their upper body is coated in dense bony scutes, the animal's underside and the exposed gaps between this plating is vulnerable. Also, similar to the honey-pot ant, they have special workers called "repletes" that act as food storage tanks. It's slow moving and very vulnerable in this "storing" state. So that skin is going to be both stretchy and sturdy enough to take a beating. This synth species is designed with humans in mind, so its engineers made them to survive a good bit of what we could dish out at it. ## A few clear parameters : * Humans want to kill these things, I'm not looking to make them bulletproof, just strong enough to where a serrated knife would not be able to cut open their exposed skin, it should be arrow resistant and a stab won't puncture it, or at the very least it's going to take some time and serious applied force to do some damage. * Blunt force should not cause the skin to split, though bruising it is fine. For instance, a strike from a strong human with a baseball bat or a mallet to it might bruise it but it won't be enough to split the skin. * The skin can be made of something that isn't usually found in nature but must be something that an organism could produce. * This material must be very elastic and be able to return back to its original form without compromising a lot of its durability. * For the repletes this material has to be able to -while stretched- hold between 100 to 400 pounds of organic paste (not directly of course, there's an organ to do that but I guess that organ would be made out of a similar material.). Not sure how many times larger it needs to stretch, lets just say it needs to expand to store at between 12-50 gallons of extra fluid. Thanks for any input!! Hopefully this is descriptive enough!! [Answer] ### Spider Silk When it comes to resisting tearing, you can't do much better than spider silk. Stronger than steel, more resilient than Kevlar, and able to stretch up to 10 times its original size and snap back into shape, you pretty much need ultra-modern tech to surpass it in unbreakability, and the only reason why it isn't widely used in military armor is because it is so expensive to produce (spiders eat each other if kept together and it's difficult to harvest their silk automatically). There have been advances made by genetically engineering goats to excrete the proteins in their milk, but it isn't as strong as the real thing, which must be spun into threads as it solidifies. A creature with spider silk or a similar protein naturally incorporated into its skin would actually be bulletproof. The one thing holding it back is that while it is extremely strong, it is also very stretchy, so by itself the skin might have a hard time protecting the internal organs from blunt trauma unless it was also very thick. However, if your objective is to make a nigh-unbreakable storage sack, it's hard to find something better. [Answer] ## Honey Badger Skin [![enter image description here](https://i.stack.imgur.com/VMjSe.png)](https://i.stack.imgur.com/VMjSe.png) Honey badgers are notoriously hard to kill, and one reason is their skin. It's thick and tough as anything, but also it's sort of folded or furrowed and only loosely attached to the flesh underneath, which means that it tends to move and unfurrow/effectively stretch when something tries to puncture it. It allows the honey badger to squirm, turn, exercise its bad attitude and savage whatever is attacking it. Add some very small, hard carapace scales for additional protection if you like, or stick a fibre mat under it. ]
[Question] [ This question already has answers here: [How long could a nuclear warhead remain functioning underground?](/questions/132443/how-long-could-a-nuclear-warhead-remain-functioning-underground) (5 answers) Closed 1 year ago. A sudden cataclysm takes place. The human race is all but wiped away. And the nukes in their bunkers and silos are left to rot for 800 years before anyone finds a record of them. What has happened to them in that time? [Answer] ## Even when still having critical mass, humans can't move or detonate it. The mechanics require repair These bombs will be in bad shape, after 800 years. Its metal parts will be a mix of preserved amounts of certain metals and a pile of rust. Fission bombs work mechanically: two parts of the bomb are to be merged, to reach critical mass. The merge requires explosive force, which is to be applied very accurately. The working of a fission bomb depends on valves and bearings with a very small friction. After 800 years, the parts cannot be clashed together anymore and with enough force. Worst case.. A bomb could yield a dangerous situation and the place should be properly sealed after discovery. Now.. suppose the folks that find it have bad intent and have the basic means to repair mechanic. They are terrorists that want to deploy the bomb to do maximum harm, the condition of the weapon itself is not the only problem. Nuclear devices are heavy equipment and complicated stuff. No knowledge will be the main issue The repair will fail. If it has taken 800 years to essentially rediscover the bombs, there will be no record, no manual, no calibration procedures, no working missile.. a nuclear device weighing tons is not easily moved from a damaged silo.. and all knowledge to deploy the weapon will be lost. Now suppose these terrorists can move the bomb from its silo, isolate the nuclear war head and drop it somewhere.. it will have become a "dirty bomb". It can render large areas uninhabitable for many years.. but there will be no nuclear explosion of any kind. Just a lot of mess. ## Repair attempts, you'll always miss things Now suppose.. see DarrelHofman's comment, there's an operation manual. Nice to have some extra info.. but a manual for direct deploy is in fact useless.. before deploy can happen, the repairs AND checkups need to be done. The device is in bad shape, after 800 years. Electricity has to be switched on, sensors have to work.. timers, servo lock initiators.. when it was in use, the launch procedure provided all that, but the silo and missile are gone, you found a nuclear warhead. The repair document sais something like > > connect A8-J7 to junction AB of the MSE-564 and repeat measurement for each barrel > > > No living soul knows what MSE-564 is supposed to measure. The other instruments and the drawings got lost. So you can't realign the cylinders properly, even if you have polished them again or whatever repair you did, you can't reproduce e.g. the cryo-shrink to mount the cylinder. [Answer] Assuming that there was no interaction with human scavengers for the entire period of oblivion: * The active material inside the core will have been altered, because of natural decay. Since nuclear powers felt the need to detonate some nuke to test the importance of this decay only after a few decades from the manufacturing of the warhead, I guess the problem is not negligible. * The primary conventional explosive, where used, might have degraded to the point of not being properly functional anymore. Maybe not to the point of not exploding anymore, but surely to the point of not assuring the correct timing. * The electronic controlling the device will probably be gone, due to oxidation, diffusion and radiation damage accumulated over 800 years. * The casing of the warhead will also have undergone oxidation and weathering * The propellant for the missile would have also long be gone, due to its instability [Answer] # Material science of decay ## Electronics Within a few years, the batteries would fail. This isn't just lighting -- without that little CMOS battery, your computer loses its ability to keep track of time. After ten years, rebooting computer systems might become impossible. Digital data storage will decay over a couple of decades. Hard drives and tapes will become riddled with errors caused by tiny electromagnetic fluctuation in the environment. CDs will de-laminate due to temperature shifts. They do have M-drive disks that can store information for millennia, so those should be fine, but the hardware to read them would fail long before that. Electronic components are usually soldered together, which results in an unstable crystalline structure. The normal shifting of this structure over time can result in loss of connectivity between soldered components, even for periods of a couple of decades. This is why [reflow soldering](https://en.wikipedia.org/wiki/Reflow_soldering) exists. ## Chemistry There are a lot of compounds that we build things out of that, all by themselves, fall apart over time. Pretty much anything with stored chemical energy is like this. This is why a canned food looses its nutritional value, even if perfectly stored. Explosives, batteries, and even [some metal](https://www.youtube.com/watch?v=Q9zdt-rOB0Y)s will just fall apart on its own over periods of years. Gasoline in gas tanks actually goes bad after about six months of sitting around. ## Humidity If the missile silo is in a really dry area, then you might be able to prevent ground water from getting in, but almost any deep underground facility has pumps that keep it dry. With no power, the space will become humid, and everything will start to oxidize. Thin steel will be reduced to rust, electrical components will fall apart, and electronics will desolder. Aluminum will be good for a long time, but bolts holding it together would suffer. If you have ground water running through your facility, [it'll be a total loss.](https://blog.amsoil.com/story-of-miss-belvedere-brings-back-memories-of-tulsa/) Even in low humidity environments, the steel stairways probably wouldn't survive. ## Cement You won't find scientific analysis of how long cement would last because (a) we haven't been studying it for long enough, and (b) what research is available is geared towards identifying the service life, which is 50-100 years. Cement keeps its structural strength for a long time, but it isn't chemically inert. When they did the [Biosphere](https://www.euronews.com/green/2022/01/29/living-in-a-bubble-did-this-failed-90s-experiment-predict-the-future) experiments, they discovered that the cement was actually leeching carbon out of the air, limiting the growth of their food plants. Over a couple hundred years, it will loose structural strength, and concrete supports will collapse. Over eight hundred, you would be lucky to squeeze your way in. Studies on [Roman concrete](https://en.wikipedia.org/wiki/Roman_concrete) is a great narrative for explaining why missile silo concrete wouldn't survive the centuries. The industry is looking into Roman concrete for more applications, but there is no technological overlap between it and missile silos. [Answer] ## You wont have much left other than a pile of radioactive dust. Not only will these nukes not last 800 years, they will not last 8 years. Most modern nukes use Tritium which has a 7 year half life. Without routine maintenance, Tritium will typically degrade enough to make a nuke non-functional within 2-3 years. Even those nukes that don't use tritium have all sorts of other parts that can not last long in the presence of the bomb's radioactive core. As for what is left over... after 800 years, most of the missile will likely be completely rusted, evaporated, and decomposed away unless your bunker is in a particularly arid region. Even if you your bunker started off air tight, any rubber seals meant to keep it that way will likely decompose enough to fail within the 1st 50-150 years at which point the bunker will start to slowly collect rain water. Since there is nowhere for water to flow out, it will become a sump meaning that water will flow in with trace amounts of salts that will build up as the water evaporates; so, within a few more decades, it could become a rather corrosive salt water environment, being able to even break down the aluminum, titanium, and copper components of the missle over these time periods. Even the Uranium or Plutonium core will likely have rusted down to dust, but that said, most nukes use either PU-239 which has a halflife of about 24,000 years or U-235 which has a half life of 700 million years; so, the rust you are left with will still be very dangerously radioactive. So, after 800 years, depending on the type of concreate the bunker is made with, it may or may not still be mostly intact. Significant mineral deposits containing both the salts and silicates washed in from outside, and the decomposed remains of missiles, computers, etc. will likely line the lower walls and floors. There may or may not be significant flooding at the exact time you enter the bunker, but there will be evidence of a history of the bunker being flooded a repeatedly... and if you have a gigger counter, it will certainly be going off. [![https://xkcd.com/2607/](https://i.stack.imgur.com/pRs8r.png)](https://i.stack.imgur.com/pRs8r.png) ]
[Question] [ Would weighted clothes be enough to simulate Earth-like gravity in a low-gravity environment? If even by using centrifugal force on a space station would feasibly only produce a gravity that is a fraction of Earth norms, could that be supplemented by clothing made of heavier materials or bulkier construction? [Answer] I remember reading an interview to an astronaut, a long time ago, where they asked him how it felt to move objects in the microgravity of space. The astronaut said that the objects, even big ones, were not heavy but felt massive. To get a similar feeling to something you might have experienced on Earth, I think you can recall how does it feel to push or pull a floating boat. You don't feel its weight, but you feel its mass. If in space you wear weighed clothes you are increasing your inertia: in a low gravity environment, like the moon surface, you could have six times more mass than on Earth and move with the same effort, for example. That would balance the reduced gravitational pull. In microgravity that would not work, because no matter how much you increase your mass, you are still multiplying it by 0. Nevertheless, it would do nothing for the physiological effects of gravity and the lack thereof, which is the main reason for worrying about having gravity in space. [Answer] It depends on just what aspects of Earth gravity you're trying to simulate. There are two different processes here: actual movement, and the energy your astronaut expends in order to move (and all the related physiology). (Note that for simplicity, I'm assuming a low-gravity environment with a breathable atmosphere, so the astronaut doesn't have to wear a space suit.) For movement,extra weight is not going to help much, if at all. The problem is that all masses fall at the same rate in a given gravitational field, so that if you're in lunar gravity, you still have to adopt the same bounding gait you seen in videos of the Apollo astronauts. Their suits massed 180 lbs/81 kg, so about the same as their own body weight. I doubt that it's going to help much, if at all, with traction, either. Unlike the racecar downforce examples, adding mass to increase traction also increases the mass you need to accelerate, cancelling out the benefit. (Just my opinion, though: if someone can show otherwise I'll change my mind :-)) Where it is going to help is with physiology. Carrying around that extra weight means your astronaut gets more exercise, and has more force exerted on bones &c, thus avoiding osteoporosis which is a problem in long-term zero-g (and presumably low-g) missions. Compare it to the experience of spending a week or two backpacking: when you get home and take off that pack, you tend to bounce while walking. [Answer] ## When in a low gravity environment, resistive equipment is better than mass based equipment In a low-gravity environment (like the Moon), you are going to want to optimise for volume used by equipment. One problem with making something more massive is that you increase it's volume proportionately. For example, you need ~6 times the mass to have the equivalent Earth weight, the volume that mass will take will be 6 times the volume of the equivalent Earth weight. So after a point, you will want to move towards something that outputs a (tuneable) consistent force, regardless of environment, that people have to work their muscles against. So, assuming your aim is to prevent or minimise muscle and bone loss, then you should take a leaf out of NASA's book and their exercise regime on the ISS. They have developed specialised exercise equipment to stave off these issues as much as possible (though in microgravity it's not possible to stave it off indefinitely). Astronauts need to exercise for 8 hours each day to counteract these effects. The principle they use is to apply a resistive device that outputs a known constant (calibratable) force that the astronauts work against. Some examples of this are: * [COLBERT treadmill](https://www.nasa.gov/mission_pages/station/behindscenes/colberttreadmill.html): uses a set of elastic straps and springs to pull the astronaut towards the treadmill * [ARED](https://www.nasa.gov/pdf/553871main_AP_ST_Phys_ARED.pdf) ([link #2](https://www.nasa.gov/audience/foreducators/mathandscience/exploration/Prob_ARED_detail.html)): Provides resistive weightlifting training simulating the use of free weights on Earth. It uses vacuum cylinders to provide that simulated force. * [MARES](https://blogs.esa.int/iriss/2015/09/07/the-mares-machine/) ([link #2](https://lsda.jsc.nasa.gov/Hardware/hardw/1290)): Used to measure and quantify the level of muscle loss on astronauts in a controlled manner. Smarter Every Day has an [excellent video](https://www.youtube.com/watch?v=05oOst9kZXQ) on the subject. [Answer] On earth, people already sometimes wear weights when exercising. It would absolutely be possible to do so under lower gravity conditions. But it would not be equivalent to just living on earth, and my guess is that people wouldn't do it except possibly as preparation for traveling to a higher gravity body. The biggest reason that it would feel very different from living on earth is already explained by L. Dutch. If you were on the moon but had tungsten weights spread over your body to give you your earth weight, then your mass would be six times as great, which would be very noticeable. Once you got moving, it would be six times as hard to stop. Until you got used to it, you would probably do things like smashing your burger into your face because of the momentum of the wrist weight on your arm. You could always compromise, with more than your earth mass but less than your earth weight, or you could just learn to deal with the extra mass. But I expect people wouldn't do it because it just feels so much nicer to walk around unencumbered. Imaging growing up here on earth but being required to wear heavy weights your whole life just in case you some day wanted to travel to our balloon colonies in the atmosphere of Jupiter. There is also the question of how well it would actually simulate the physiology of living in a stronger gravitational field, and the answer is that we really won't know until we actually have had a moon base for a while. There were a lot of unexpected side effects of microgravity, and there's still a lot they don't know about how to combat them. It seems clear that wearing weights would strengthen your skeletal muscles, and probably your bones, ligaments, and tendons. But the heart still wouldn't have to work as heard to pump blood up from your feet, and there would still be less of a pressure differential between your head and feet. We know that matters in zero g, and so it might also matter at least a little in 1/6 g. [Answer] Assuming the point of the weight is to make sure the wearer avoids muscle atrophy associated with long duration space flight... The best solution is probably not heavy cloths, but rather a body covering that resists motion at all of the wearer's joints. Some possible options here would be... 1. A conforming suit (like a wetsuit) made of a material that generally resists all movement. This is probably the simplest and most comfortable option for the wearer. 2. Putting braces at key points (knee, elbow, shoulders, hips, ankles, etc) that resist movement. This option may not exercise every muscle needed and could require the wearer to put on a lot of stuff each day. 3. Taking option 2 a bit further, making a full body suit (like a suit of armor, or a space suit) with resistance in all the points of movement. If the characters were going to need space suits or armor anyways, then this is a good fit. [Answer] when only talking about low-gravity environments. some aspects like muscle deterioration and bone density loss should be slowed down or stopped with heavier clothes in a low-gravity environment. others like problems with blood circulation, or pooling of fluids may not. there is much still left to research to be honest. we don't know for example what the minimum amount of gravity is needed to alleviate all of those problems. [Answer] It would help with running. Consider Formula One racecars. <http://formula1-dictionary.net/downforce.html> > > To be faster you need power, but there is a limit to how much power > you can put on the ground. To increase this limit, force to ground > must be applied on the wheels. Increasing weight can do this, but > weight makes handling worse and require more power. So we need some > virtual weight, we call it downforce and get it from airflow around > the car. A wing can make a plane fly, but if we put it upside down, it > can make a car NOT fly. > > > These cars have wings to push them down onto the ground so that they can improve friction with the ground and use that to push forward. Usually people dont run fast enough to need wings to push them down. You could use weights. I was talking just yesterday about running underwater. It is hard to get traction because underwater persons built as I am weigh nothing or less, due to buoyancy. Pushing off the bottom tends to leave you in midwater with nothing to push against. If I load up with weight belts to offset my buoyancy then I can run along the bottom and the main impediment to forward motion becomes water resistance. In microgravity you could load up with weight belts or weighted clothes (I hope those are weighted pants you have on...) to offset your tiny weight, just as I put on weight belts in the pool to offset my effectively tiny weight. You will still have inertia with those weights and so plan ahead to stop. They are easy to make and require no tech, but just as with race cars weighted pants makes handling worse and requires more power. Better would be fans! If you are in microgravity but in an atmosphere, you could direct the fans on your harness upwards and push down against the atmosphere: downforce fans, just as the cars have downforce wings. A fan angled down at a 45 degree angle would give you downforce but also a forward vector, so you could rollerblade the length of the space station at great speed. Fans could flip forward and act as brakes when you need to stop. Best fans can spin and point down, allowing you to jump huge distances and dunk the ball every time. ]
[Question] [ There are a lot of large starships in sci-fi but their influence on a solar system is rarely deeply explored and kept fairly limited. For example, in Eve-Online fluff, titans are considered massive enough to alter tides on nearby planets but that's about the full extent of their effect. (I'm assuming that bit might be exaggerated since they aren't even remotely close to the size of the moon.) The question I have though is, at what mass would a starship being in close proximity cause more than just a small problem. (i.e. Creation of rogue planets, undesirable tidal/tectonic effects, rendering a planet uninhabitable or collision of a starship with a planet) The rules for this are fairly simple: * Bigger = objectively better. More mass = more ship. Whoever has the largest vessel and the most of them wins hand over fist over their opponent. (Obviously not true in reality but we're using sci-fi logic here) * All engineering/practical issues are considered solved. Funny issues such as multiple day trips to travel from end to end of the vessel as well as tensile strength and thrust issues from such a large ship are not being considered. * Destruction of the ship or the system is considered as a failure by both sides in the conflict as they seek to take and hold the system instead. * Mass negation by exotic matter/etc is not possible As a wild guess, I would think one solar mass would *easily* destabilize any star system's orbits. An additional wrinkle I foresee would be that you could have a much smaller vessel, but the total fleet mass of both sides combined could also be sufficient to pose a threat to the systems existence. I suppose at that point you would have an effective mass "budget". I'm interested to hear what you guys think. [Answer] ## Impractically Huge There's two ways to look at this: size and mass. Mass is the easier one, so we'll look at it first. Mass Our own moon affects more than just tides. It can [cause earthquakes](https://www.nature.com/news/moon-s-pull-can-trigger-big-earthquakes-1.20551), has an (admittedly slow) effect on [Earth's rotation](https://www.lpi.usra.edu/education/explore/marvelMoon/background/moon-influence/), and even has an effect on the [Earth's shape](https://www.nationalgeographic.com/science/2020/04/moon-may-have-stretched-early-earth-into-potato-shape/). A ship with mass equal to Luna would have some moderate to nasty effects on a planet — and that's ignoring what effects it would have on any moons already orbiting the planet. I've not done the math, but I could easily believe that a ship having even a third the mass of Luna entering Earth's orbit would have some nasty effects — everything from flooding to earthquakes to destabilizing Luna's own orbit. And who knows what side effects that would have? Everything from screwing up shipping to confusing appropriately dressed witches dancing in a forest glade. Yuck. But think about it — the moon is solid,Citation Needed which means a ship equaling its mass would be gi-honking-normous! Anywhere from a third to three times the size by volume depending on exactly what's inside that ship. Which brings us to the other problem. Size Could you imagine how our world would react if an object 3X the diameter of the moon passed between the Earth and the sun? Cats and dogs, living together! Mass hysteria! Now, I'm going to grant you that other than causing problems with solar panels should the ship be in geosynchronous orbit, this wouldn't have a long-term effect on the planet. But let's say the ship is the diameter of the Earth. The ship has a whole lot of hollow, so it might only represent 10% (or maybe 0.001%) of the Earth's mass — but the size would cause all kinds of problems if the planet it's orbiting is utopic and enlightened and decided to rely on solar power for 90% of its energy. No silly geosynchronous orbit for this ship! No siree! That ship's under power, so it's simply plunked itself into Earth's #1 Lagrange point and it's simply blocking the sun! I like this solution — it has that wonderful James Bond implausibility that makes it absolutely worthy of a really good super villain. However... However, to be frank, I personally find ships large enough to affect a planet in any way to be unreasonable, even unbelievable. What's the point? It's an engineering complexity that requires the proverbial power of a black hole to move around when a small fleet of ships can quite literally provide the same firepower (aka, "consequence in battle") for a fraction of the price and engineering headaches. Which is why the several articles over the last couple of years postulating the possible discovery of mega-structures in space make me smirk. From an engineer's perspective, why would anyone build one? There's always a more practical way to solve the problem. But that's just my opinion. [Answer] # It's ALREADY too big for safety A spaceship large enough to > > are considered massive enough to alter tides on nearby planets > > > to the same level that the Earth's Moon does, is already altering the planet's orbit by 43537km change in semi-major orbital axis per day, if the ship remains on the same side as the planet. Sure that is only 0.02% of the orbit, but it is already enough to start altering climate. From just one day, of one ship being near enough the planet to cause Moon-level tides. Do that for a year, and the orbit's eccentricity goes up so much that the planet experiences greater seasons due to ellipticity of orbit, than it does from axial tilt. Edit: Remember that the distance between your ship and the planet has a *HUGE* impact. If your ship is at 10 times the distance, it needs to have 100 times the mass to cause an identical disruption. Similarly if you put your ship in close orbit around the planet (poor satellites get squished!) then it needs a lot smaller mass to "raise tides" to the same extent. Moral of the story: If your ship is very massive, stay far away from planets, moons, non-propelled spacestations, and other valuable real estate that cannot compensate for distortions in its orbit. P.s. It would have MUCH greater effect on the Moon's orbital shape. And woe to any satellite owners, even 10 minutes of such a large ship in the area would destabilize geostationary orbits. Which leads to a curious story hook: Go visit the Alien homeplanet in your SuperMegaFortress ship. "We love peace! We will stay here for negotiations until we are satisfied with the contract! No, this big ship is not here to threaten you, it is merely needed for the comfort of our diplomatic staff." Meanwhile, just by being there, not firing a single weapon, you are dooming their planet to death by warping its orbit out of the habitable zone. [Answer] Given that this ship can be built already in space since it would be nearly impossible to such thing take off, things can get pretty huge. The real limiting factor here is gravity, as the bigger it gets, the more it weighs, and the more it weighs, the higher the gravity affecting its surface. Systems would not be much of a issue. They can be made to work under higher gravity. Even if some technology requires less g to work, it can be moved to deeper inside the ship. Systems could only be the problem when you are already in a planetary scale and its surface g is enough to crush any sensor but even then you can keep smaller ships around to guide the bigger one. > > All engineering/practical issues are considered solved > > > I don't know if you include it collapsing under its own weight or smaller ships getting in and out such high gravity structure as a solved problem, but it is the real problem you should be worrying about, here is the formula to the gravitational acceleration in the surface. > > mG/r² or 4πrdG/3. Where m is total mass, d density, r radius and G = 6.674×10−11 m3⋅kg−1⋅s−2 > > > I don't think a starship would be made significantly bigger than the native species planet gravitational acceleration, outside maybe national pride. Also I want to point out that to reach such sizes it probably should be built as a sphere to make the structure more uniform, and that core could be hollow if the superficial layer is able to sustain itself structurally. The hollow core would reduce overall gravity and provide nearly unlimited storage space. Another idea could be have many layers in multiple depths to provide appropriate gravity to many species. Edit So what you are asking is how big of a ship could build without messing the star system it is inside? Definitely not big enough. Even if it was as big and heavy as Jupiter, it would not do much damage unless we get really close to the planets. Next to the sun, any gravitational field the ship can produce is negligible. And the sizes we can actually achieve would be even smaller. Even considering the resources to build it can be brought from across the universe, either the core would collapse under its own weight and become a simple mass of metal/building material if it is massive, or it would collapse due to lack of structure if it is hollow. You could cheat it a little by building it in the surface of a planet and adding thrusters to make it movable, or having a tiny core that work as a supermagnet to give structure to the shell. Neither of these is big or heavy enough to become a problem. A fleet of those might be dangerous if they stay clustered, mostly for themselves, but also for some small planet ""near by"". In this case they may as well fight near the system they are attacking/defending, it is not like real armies preferred fight in cities instead of taking the battle to open terrain. [Answer] In practice, Earth is a kind of spaceship. Solar system is OK-ish with it. Anything smaller is less practical (see Mars / Moon). Anything bigger is less practical either. Human bodies and the rocket technology tolerate less gravity and can even benefit of it one way or another, but more gravity or deeper gravity well quickly becomes unacceptable). I think that as a space habitat gradually grows, it will gradually transition from a structure held by its structural strength into a structure where things are just piled up one way or another and held by gravity (and the oldest and deepest parts falling out of use). [Answer] Mass, applied the right way, can be a problem already when it's tiny compared to earth. Take, let's say a tenth of the mass of the moon. That's an enormous space ship already. It is optimized for a parallel start of all of it's millions of rocket warheads, so it is shaped like an enormous pancake rocket holder grid. Park it between sun and earth in that Lagrange point, wait, see the ice age coming. It has also a mirror surface as radiation and laser protection. Park it so that it shines light on earth and gleefully see hurricanes forming. Move it to half the earth-moon distance but not into orbit. Instead use the engines to keep it where it is and see earth decelerating or accelerating in response: gravitational pull is there but your ships don't move because they use their magic FTL engines to stand still in relation to earth. If there is a pull and one of the bodies doesn't move, the other one starts to move. The effect will be tiny first but can build up over time, moving earth to another eccentricity or to another orbit. Very few changes here are enough to be catastrophic. But okay, this costs enormous amounts of fuel. So our pancake decides to move into low orbit at last, providing earth with a 2-hours day-night cycle and the moon-earth system with a third body, just to make the gravity equations more difficult to solve. The point of all of this is, as ships are mostly hollow, their size becomes mind boggling when their mass even reaches a small percentage of a planetoid like the moon. And that size can do more than just gravity effects. If you want to talk about gravity, I think even if you don't build one enormous but many small ships you will have an effect. All mass on an orbit needs to be added for the orbital calculations, if I remember correctly. So if you build 1000 ships each with 1% the mass of moon and you put them all in the same solar orbit as earth, even if it is not nearby, they will affect earth. Can't tell you how, though, that I better leave to people who know how to calculate this kind of stuff. ]
[Question] [ I want to make a world with a great deal of variation in habitability in terms of temperature and pressure. Some areas would be habitable; others less so, some would require protective clothing and some might not be accessible without pressure suits / protective vehicles. The plan is to start with an approximately Earth sized world with roughly 1g, but different surface features and vastly less ocean. I want a world with a range of altitudes from the highest mountains to the abyssal plains with most of the comfortable habitable areas on the mountain tops and their immediate surroundings. The atmosphere would consist mostly of carbon dioxide, oxygen and nitrogen but would be predominantly carbon dioxide, however given that carbon dioxide is heavier than oxygen or nitrogen I would expect to find a higher proportion at the lower altitudes. The net result being high pressure, temperature and carbon dioxide concentration in the low lands and a gradation to lower pressure, temperature and carbon dioxide levels in the highlands and an interesting variety of environments in between. So a little like mt Everest in reverse liveable at to top but not at the bottom. The proportion of the gases in the atmosphere and total pressure at the lowest point can be adjusted to fit as required, but unprotected humans must be able to live comfortably outside at high altitudes, uncomfortably at lower altitudes and not for long at the lowest altitudes. Is this sort of world possible and if not how else might it be adjusted to give this effect? [Answer] On Earth, the composition of air is pretty much constant (apart from water vapour) up to about [10km altitude](https://www.engineeringtoolbox.com/air-composition-d_212.html). Water vapour varies because of the temperature variations, since it tends to freeze out. So I don't think your variable composition with altitude works. The reason for this is simply that the atmosphere gets well-mixed by temperature differences (manifesting as weather). If you take an Earth-like planet, and simply give it more atmosphere, then [oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity) will start to affect people at low altitudes. The Wikipedia article on the high-altitude [death zone](https://en.wikipedia.org/wiki/Death_zone) has some useful numbers. As an example, if you give your planet three times the mass of atmosphere, then the pressure at any given altitude will be three times higher, and the "partial pressure" of oxygen will be likewise three times higher. That gives you an Earth-normal atmosphere at the peak of a mountain the height of Everest, which looks right. People can venture down to the height of Everest base camp in reasonable safety. But at sea-level, with an atmospheric pressure of 3 bars, and oxygen partial pressure of 0.6 bar, oxygen toxicity of the lungs will set in after a day or so. [Nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis) will also start happening in a mild form, impairing reasoning and unfamiliar tasks. If the carbon dioxide proportion is like Earth's, the partial pressure at sea-level will be equal to about 1200ppm in Earth's atmosphere. This has been [observed to have negative effects](https://en.wikipedia.org/wiki/Carbon_dioxide#Below_1%) on thinking, but less than the nitrogen effects. If you have more carbon dioxide, that will get worse, but greenhouse gas heating isn't localised: it's slow enough that it applies to the atmosphere as a whole, due to mixing. [Answer] > > Some areas would be habitable > > > By what? Humans? The local fauna? The local flora? The fact is that Earth-like plant life would flourish in the swampy lowlands. The CO2 would be heaven for them and they would spread everywhere. They would eventually produce oxygen in such large amounts that it would change the composition of the atmosphere as happened on Earth. This would allow oxygen breathers to evolve. I suppose the problem is creating a stable atmosphere like the one you suggest. > > Is this sort of world possible ... > > > I think that the answer is that it would be unstable. > > and if not how else might it be adjusted to give this effect? > > > If you waived the "habitable" constraint then there might be an answer based purely on physics. I'll leave that to the meteorologists and the physicists. [Answer] Yes, your planet could exist. Since we are worldbuilders, let's use Venus as a starting point... Aside from the addition of sulfuric acid clouds, Venus is almost perfect, with a thick layer of carbon dioxide covering and insulating its planetary surface. Venus's highest mountain is called Maxwell Montes and it is 6.8 miles tall compared to our Mt. Everest which tops off at 5.4 miles. There is even a little free oxygen in the form of atmospheric ozone. On the negative side, the atmospheric height is only a quarter of that of Earth. Venus is also a little on the scrawny side, with a planetary mass of 4.867 × 10^24 kg compared to Earth's 5.972 × 10^24 kg. It is also a lot closer to the sun, which when combined with it's atmosphere's insulating characteristic, makes the planet's current temperature a little warm for your usage. None of those problems are insurmountable during the planetary creation lottery. It is easy to believe that a sol-equivalent solar system exists out there in which a slightly plumper Venus-like planet attained a slightly higher orbit. If its planetary composition also contained large quantities of a strong base compound, like Sodium Hydroxide, the sulfuric acid portion of the atmosphere might neutralize out and provide us with some water in the process. Then all we need is some blue-green algae (maybe from [panspermia](https://en.wikipedia.org/wiki/Panspermia)) to produce the oxygen. From there, a non-turbulent atmosphere and a little gravity is all you need to let the atmospheric gases settle into layers. If the oxygen layer happens to settle out near the top of its highest mountains, that is just a wonderful coincidence. Your planet is very possible and planets like it have probably evolved naturally in solar systems throughout the universe. More locally, your planet design might be part of our Venus's future, if our descendants survive long enough to become [terraformers](https://en.wikipedia.org/wiki/Terraforming), aka real worldbuilders! ]
[Question] [ There are a large number of superheroes who get around via [some kind of super-parkour](https://tvtropes.org/pmwiki/pmwiki.php/Main/BuildingSwing). These range from superheroes who swing webbing like Spider-Man and his many imitators (e.g., Spinnerette), to ones who use more "grounded" methods of parkour such as Daredevil or Batman. My question is, from a legal perspective how many laws are these superheroes breaking by travelling across the city this way? I have a superhero character who is a parody of Spider-Man, and one of the jokes I am trying to make is by highlighting how in IRL New York city, citizens typically don't like somebody hopping across their rooftops at night, covering their streets in sticky webbing, etc. How many laws would this character be breaking just by web-slinging across IRL New York? No crime fighting, no vigiliantism, no superheroing (all of which are more punishable by existing law), just swinging across New York city to avoid NYC traffic like Peter Parker and similar heroes are often shown doing in comic books? Would they get in trouble from littering from their webs? Speeding given they are travelling much faster than the speed limit of cars? I know that a flying superhero flying above the building line would violate air traffic restrictions and it's been pointed out within the Marvel Universe that Spider-Man riding on the rooftop of a car violates New York city law (Spider-Man got a ticket for this in the comics) but I don't know if just swinging around New York City would do anything. [Answer] As mentioned in other answers, vandalism (unwanted web residue) and trespassing (on top of buildings/cars) would be crimes. Other laws would be in Section 1150-1156, which focus on pedestrian traffic, where he would break the following: 1150, 1151, and 1151-a: This enforces obeying traffic signals and right of way for pedestrians. Spider-man can, through the air, break this, as he would be classified as a pedestrian. 1152 a,b, and c: This one is a little more interesting. > > '(a) Every pedestrian [jaywalking] shall yield the right of way to > all vehicles upon the roadway.' > > > If he crosses in the middle of the road, he would have to give right of way to the oncoming cars, which he does not. b follows the same logic, but c is more special. > > '(c) No pedestrian shall cross a roadway intersection diagonally > unless authorized by official traffic-control devices...' > > > so, if he gave right of way, he would still have to travel perpendicular to the road. 1155 states > > 'Pedestrians shall move, whenever practicable, upon the right half of > crosswalks.' > > > if he ever swung above crosswalks on the left, he would be breaking this law. 1156 would be a little harder to pin down on him, as it talks about walking on crosswalks and nothing else. > > ' Where sidewalks are provided and they may be used with safety it > shall be unlawful for any pedestrian to walk along and upon an > adjacent roadway.' (emphasis added) > > > If 'walk' was defined by travel without any external device assisting you (such as a car, bike, etc.) he would be subject to this law. Feel free to add any other ones; I only focused on traffic laws; who knows how many vandalism, trespassing, and heath and safety risk laws he's breaking. EDIT: Apparently, his web residue dissapears in an hour after its use. According to the law, all he would really get from web residue-related vandalism would be a slap on the wrist, as long as the webs did not damage or risk damage of anything, or the webs could not be interpreted to something distinguishable/offensive (ex. a middle finger, a painting, spelling out words. Reason for adding offensive is that it would probably have to be offensive to be accusable. [Answer] Two that I can think of is possibly vandalism and trespassing. As Spidey swings he usually perches on roof tops and ledges and this could be considered as trespassing on private property and because some webs could remain stuck to the sides of buildings this could be considered as vandalism. [Answer] You're likely looking at trespassing and petty vandalism for the web slinging in and of itself (that said, the comics address the webs lingering by explaining that the web fluid is biodegradable once it is expelled from the shooters and will completely break down in a matter of hours). Some of his villains might have some more serious trouble for their movement. Vulture and Green Goblin might be in trouble for FAA violations. I imagine they don't file flight plans prior to their bank robberies (Now I want a meme of Norman Osborn calling to file a flight plan from the Residence of Gwen Stacy to the George Washington Bridge and then explaining his deviation to the Brooklyn Bridge... I'd also like to see how many people get that reference.). I don't think there is any serious violations because, well, most people don't travel by web slinging. That said, there is at least one gag where NYPD wrote a ticket for the Web Head for riding on the roof of a taxi cab (A passenger on the outside of the car is a traffic violation... though the operator of the vehicle should be the guy receiving the ticket, not the passenger) So Spidey should avoid Parkouring off of moving vehicles. Additionally the times where he is running on paved roads may be jay walking violations, but Jay Walking only occurs when crossing the street at grade. Crossing the street over a pedestrian bridge would not trigger Jaywalking violations, since the traffic and the pedestrian are grade separated so, swinging over 5th Avenue should be fine. For other law violation close to the real world I could find was Philippe Petit's 1974 tight rope walk between the World Trade Center's twin towers, in which he made 8 passes while walking on rope 400m above the ground from the observation decks of both towers. The only charges he faced were "trespassing" charges, which the district attorney's office dropped after media attention made the act quite popular with New Yorkers and Petit agreed to give a free show to kids in Central Park. Considering this, it's likely that the DA would likely not prosecute the charges against someone who helps them put the guys away. After all, washing web goo off a building's side is not on the same level as "The Rhino is tearing up Times Square". Of course, I'm no Daily Bugle reader, so it could be further proof that Spider-man is a threat AND a menace and we need more pictures of him! Edit: Damn... I should have wrote this as if I was J. Jonah Jamerson. [Answer] Spiderman's webs are biodegradable though, it states in the comics. That's gotta have some affect. On top of that swinging above the traffic would be air laws not traffic or pedestrian laws wouldn't it? Though yes the trespassing is a definite thing. However someone could say he's being a distraction to drivers, I can't remember what it's called but that's one too. [Answer] # Mainly FAA regulations Most likely, as an individual locomoting via the air (with negligible web-based propulsion and lift mechanisms) Spider-Man would fall under some subset of FAA regulation, such as parachuting or operating an ultralight. As such, he’s going to run afoul of a number of possible regulations, e.g > > ### 91.119 Minimum safe altitudes; general > > > Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes: > > > (b) Over congested areas – Over any congested area of a city, town, or settlement, or over any open-air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft. > > > However, the FAA might end up making an exception for him, as it does for helicopters. > > ~~Helicopter~~ Spider-man operations may be conducted below the minimum altitudes set for fixed-wing aircraft. The reason: ~~they have~~ he has unique operating characteristics, the most important of which is ~~their~~ his ability to execute pinpoint emergency landings during power-out emergencies. Furthermore, ~~the helicopter's~~ Spider-man’s increased use by law enforcement and emergency medical service agencies requires added flexibility. > > > ]
[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. Obviously, if available, atmospheric oxygen is a great source of energy. However, I'm surely not the first worldbuilder who wants an alien species which doesn't depend on it (whether due to having evolved on a largely oxygenless planet, or because of bioengineering that happened once the civilisation got advanced enough). The question is, even in the best-case scenario (i.e. the most efficient plausible anaerobic metabolism within the constraints below), how inefficient would energy generation be for such an alien? I'm thinking primarily in terms of how much more food would be required for maintaining a level of activity similar to the one mammals, birds, reptiles etc. are capable of, but maybe I'm missing other forms in which inefficiencies would express themselves. For bonus internet points, I would also like to know whether ability to switch between aerobic and anaerobic energy generation methods would result in a significant reduction of the efficiency of the former and/or latter, and/or carry other drawbacks. Additional parameters: * Carbon-based life, and biochemistry not radically different from Terrestrial life (panspermia is in play). * Obviously we know anaerobic bacteria are a thing, but I'm looking for something at least approximating human size, thus the megafauna criterion. * The organism should not be obligatorily anaerobic, that is, it should be able to withstand at least 20 kPa of partial O2 pressure without long-term ill effects. * I'm looking for things that can hypothetically be achieved through evolution and/or genetic engineering, and is inheritable, but not for purely synthetic solutions like adding non-biological devices. Purely biological symbiotes are an edge case (mutualistic bacteria are OK, nanites are not). * I'd like to know the best-case solutions to the question without employment of blatantly unscientific handwaves before even contemplating adding any. [Answer] Okay so [this table](https://en.wikipedia.org/wiki/Anaerobic_respiration#Examples_of_respiration) lists anaerobic respiration pathways and the reduction potentials they produce, as alternative pathways use either primary reduction or primary oxidation as a gateway to the [Krebs cycle](https://en.wikipedia.org/wiki/Citric_acid_cycle) we can treat the [EO'](https://en.wikipedia.org/wiki/Reduction_potential) figures in the table as [absolute values](https://en.wikipedia.org/wiki/Absolute_value). I've made a personal call that the most accessible respiration pathways for large life forms are gas-in and gas-out rather than those requiring either an electron acceptor that's solid or liquid at room temperature such as the metal reducing paths, or producing such a compound as with acetogenesis. Based on that assumption we want to look at the [methanogenic](https://en.wikipedia.org/wiki/Methanogenesis) Carbon Dioxide breathers for maximum efficiency, this pathway produces an EO' of just -0.25V. [Mitochondrion](https://en.wikipedia.org/wiki/Mitochondrion) is the standard for aerobic respiration which produces a redox potential of 0.82V, so mitochondrion equivalents based on something similar to [Methanosarcina barkeri](https://en.wikipedia.org/wiki/Methanosarcina_barkeri) would therefore have roughly 30% of the energy output of their oxygen dependent counterparts. Creatures using methanogenic mitochondrion-like organelles would breath in Carbon Dioxide and breath out Methane while using a body chemistry that is otherwise quite similar to what we're used to seeing, the only other "must change" I can think of is hemoglobin which would need to be swapped for a compound that carries Carbon Dioxide in and Methane out. For a natural ecosystem the plants would have to follow a pathway of [anaerobic oxidation of Methane](https://en.wikipedia.org/wiki/Anaerobic_oxidation_of_methane), to supply a high Carbon Dioxide atmosphere with balanced Methane depletion. If this is nitrate driven then they could be functionally similar to Earthly legumes, which includes everything from clover to the acacia tree. [Answer] To answer without having to research complex non-oxygen based metabolic pathways: why not just photosynthesise? After all, you've only stipulated that atmospheric oxygen is a no-no, and a truly "oxygenless planet" sounds kinda unlikely (its the 3rd most abundant element in our solar system and the milky way as a whole). This requires a ready supply of water and carbon dioxide, which isn't a wholly unreasonable requirement... primeval earth managed it, after all, and given that hydrogen, carbon and oxygen are in the top 4 most common elements out there it would be surprising if they weren't heavily represented on many extrasolar planets. Let us consider the cow. According to [this document](http://www.milkproduction.com/Library/Scientific-articles/Nutrition/Energy/) on cow nutrition and energy budgets, an "average cow" (whatever one of those might be, but this one weighs ~590kg) uses about 40Mcal a day (that's about 40MJ in sensible units) to totter around and keep itself alive each day (compare this with the figures in theh [green cow XKCD what-if](https://what-if.xkcd.com/17/)). The XKCD guessimate is that a solar-powered cow might get a mere 2MJ/day from sunlight, which is clearly insufficient. There's plenty of [scope for improvement](https://en.wikipedia.org/wiki/Photosynthetic_efficiency) in photosynthesis, certainly: only about 28% of incident light is actually collected by chlorophyll and the glucose synthesis process is only about 30% efficient. Small improvements (of the order of 17%) have been made in [transgenic tobacco plants](https://science.sciencemag.org/content/363/6422/eaat9077). An increase in surface area is also a possibility... large fixed plates and fins are found in various dinosaur species, and many other animals have fans, manes, crests and webbed limbs, though further speculation on means of increasing animal surface areas drifts pretty quickly outside of the "hard science" requirement. A combination of both surface area and photosynthetic efficiency may be able to bridge the 20-fold metabolic gap. You may handwave that as you see fit. There's another alternative, of course. Cows are of course endotherms, and that means that they need to run their metabolism at a moderate level all the time. Poikilotherms, on the other hand, are adapted to very low levels of metabolism... necessary for an animal that might have to cope with low body temperatures, being unable to warm itself to any great extent. Crocodile Standard Metabolic Rate runs [at approximately one tenth of some average mamallian](https://pdfs.semanticscholar.org/b6eb/e472f3ed30b501d91b96c36841ce3b1e20b5.pdf) (whatever they might be) of the same weight's [Basal Metabolic Rate](https://en.wikipedia.org/wiki/Basal_metabolic_rate). Suddenly you're not dealing with a 20-fold gap but more like a 2-fold one, one that could reasonably be bridged with moderate increases in surface area and photosynthetic efficiency. They might spend long periods building up energy reserves, effectively hibernating at night (or during bad weather) and remaining more or less motionless during the day. When the need arises, crocodiles are capable of developing [considerable amounts of energy](https://pdfs.semanticscholar.org/b6eb/e472f3ed30b501d91b96c36841ce3b1e20b5.pdf) via anaerobic metabolism alone, able to ambush, fight or flee if required. The energy might even be useful for thinking if you wanted a really far-out, off-the-wall idea. Here's one potential prototype for your beasties... the [dimetrodon](https://en.wikipedia.org/wiki/Dimetrodon). [![Dimetrodon Grandis](https://i.stack.imgur.com/VohIJ.jpg)](https://i.stack.imgur.com/VohIJ.jpg) You asked for actual efficiency numbers for anaerobic metabolism... well, looking at terrestrial metabolic pathways, one measure of efficiency is perhaps the amount of ATP you get per molecule of glucose. [Anaerobic glycolysis](https://en.wikipedia.org/wiki/Anaerobic_glycolysis), the process which your cells (especially your muscle cells) will use under perods of highg energy demand and insufficient oxygenation, produces about 2 molecules of ATP per from the energy available from the metabolism of one molecule of glucose. Aerobic metabolism manages more like 34, out of a potential maximum of 38. The resulting large amounts of lactate can be recycled via the [Cori cycle](https://en.wikipedia.org/wiki/Cori_cycle) if some other means of ATP production is available, but it does require energy and it is no good if that energy is produced by a means that generates more lactate. What other means might that be? Well, of course photosynthesis produces oxygen as a byproduct. Plants just release waste oxygen into the atmosphere, but your beasties could reasonably store it in their lungs, taking perhaps a whole day to take "one breath" of pretty pure oxygen. That gives an excellent reserve of oxidiser for regular glycolysis. There are perhaps some other more off-the-wall means of storing oxygen for later use... intracellular stores of peroxide, perhaps, but that's wandering quickly out of the hard science regime. ]
[Question] [ In the faraway land of Backeye, people have developed a secretive language called Pasgas. Rather than enunciating words, or forming them with gestures, Pasgas speakers communicate by passing wind. They control the pitch and the duration of each toot, with a single phoneme being able to convey as much meaning as an ideogram (such as chinese characters, or japanese kanji characters) or even a whole sentence. Pasgas is popular among spies, but serves for other professions as well. Abroad, it can be used to relay messages to fellow captives, a conversation that is silent to all but the initiated. In Backeye, guards can use it as a [shibboleth](https://en.wikipedia.org/wiki/Shibboleth) to readily identify foreigners. And in team sports such as volleyball it can be used to coordinate strategy without the need for a team huddle. My question is: is such a method of communication possible? If not, then why? If it is possible, what kind of training would be required to speak Pasgas? Edit for clarity: the communication I mention above is acoustic, not smell-based. [Answer] > > a conversation that is silent to all but the initiated > > > I would argue about the silent... anyway... This looks like a variant of the [Silbo Gomero](https://en.wikipedia.org/wiki/Silbo_Gomero) > > Silbo Gomero (Spanish: silbo gomero [ˈsilβo ɣoˈmeɾo], 'Gomeran whistle'), also known as el silbo ('the whistle'), is a whistled register of Spanish used by inhabitants of La Gomera in the Canary Islands to communicate across the deep ravines and narrow valleys that radiate through the island. It enables messages to be exchanged over a distance of up to 5 kilometres. Due to this loud nature, Silbo Gomero is generally used in circumstances of public communication. > > > The main problem with your proposed approach is that the rectum lacks most of the structures that in the mouth allow for sound modulation: on one side you have, among others, throat, tongue, teeth, cheeks to help tune the sound emission, while on the other side you have the sphincter and the gluteus. I see it as possible to control the duration of the emission and to some extent the pitch. However, with some training it should be possible to achieve some modulation capabilities, like [Le Petomane](https://en.wikipedia.org/wiki/Le_P%C3%A9tomane) did: > > Le Pétomane (/ləˈpɛtəmeɪn/, French pronunciation: [ləpetɔˈman]) was the stage name of the French flatulist (professional farter) and entertainer Joseph Pujol (June 1, 1857 – 1945). He was famous for his remarkable control of the abdominal muscles, which enabled him to seemingly fart at will. His stage name combines the French verb péter, "to fart" with the -mane, "-maniac" suffix, which translates to "fartomaniac". The profession is also referred to as "flatulist", "farteur", or "fartiste". > > > It is a common misconception that Joseph Pujol actually passed intestinal gas as part of his stage performance. Rather, Pujol was able to "inhale" or move air into his rectum and then control the release of that air with his anal sphincter muscles. Evidence of his ability to control those muscles was seen in the early accounts of demonstrations of his abilities to fellow soldiers. > > > Some of the highlights of his stage act involved sound effects of cannon fire and thunderstorms, as well as playing "'O Sole Mio" and "La Marseillaise" on an ocarina through a rubber tube in his anus. He could also blow out a candle from several yards away. > > > Still, such communication would be short distance, with no way to reach the km range of the Silbo Gomero. Also, I doubt that an untrained listener would consider normal a continued farting of the type needed for some sort of communication, unless it was spread over time to look as much as possible as "natural". Summarizing: * Is it possible to learn this ability?: almost surely yes. * Can be used for communicating?: yes on short distances and for concise messages. * Can it be secretive?: only if used at low fart, ahem, Baud rate. Prolonged and sustained vocalization would draw attention. [Answer] My question is: is such a method of communication possible? If not, then why? If it is possible, what kind of training would be required to speak Pasgas? Yes it is possible with limitation. The more complex the meanings the harder it is to produce and hear. For example Morse code would be relatively simple as all you need to distinguish is long and short or dot and dash. The down side is, it would take a long time to communicate this way. Sure a select few could probably do it faster than others. The more duration and pitches you have the higher the likelihood errors would creep into the system. 2 pitches and 2 durations should be easily doable by most of the population. This gives you the equivalent of 2 binary bits per time. The biggest problem is transmit, not reception. The more training received the more pitches could be recognized. If you can recognize 64 different pitches and have a dot or a dash you can produce any single 8bit ascii character. However, the faster you communicate will also increase errors. Also this is not really that great for secrets as anyone who can hear it could possibly decode it. It would still be in your best interest to encrypt it. Furthermore, We have excellent microphones today, and could probably record said noises. Once recorded we could use computers to decode any message you could send. Eventually field agent would whip out there cell phones, and in real time have computers decode it. Audio takes a relatively small amount of storage so agents in the field could have more than 1 microphone and record continuously. Using today's smart phones real time decoding would probably be possible. ]
[Question] [ A notable character in my story is a notorious pirate known for his ruthlessness. His notoriety makes him a target for other pirates, marine soldiers, and whatever else decided to make a home in the unforgiving depths of the sea. To protect himself, he’s come in the good graces on a metal dragon who, in exchange for a constant supply of precious metals and ores to eat, will use the radiance of its scales to blind, disable, or confuse an enemy. However, making this plausible has become rather difficult for me. Dragons, naturally, weigh much much more than the common human and assorted cargo and boats can only handle so much weight before it sinks. So my question is: what characteristics or features would the ship need in order to handle the weight of the metal dragon? The answer can include what the ship is made of, how big it is, etc. ### Details about the dragon for context: * The dragon survives on a diet of precious gems and ore, which makes it much heavier than other dragons. * It is so heavy that it cannot fly on it’s own * It is about 7 meters tall * It’s approximate weight is 28,000 pounds, or 14 tons ### Guidelines: * The boat has to at least be able to carry 10,000 pounds * The dragon does not have to be able to stand up or move freely * The dragon can be confined to a single part of the ship [Answer] # Size alone This is a buoyancy problem and is solved through naval architecture. Here are the key concepts: [![enter image description here](https://i.stack.imgur.com/VN1Is.png)](https://i.stack.imgur.com/VN1Is.png) The center of gravity is the center of mass on the ship. The ship is pulled downwards as if it were a point mass at this point. The center of buoyancy is 'point source' of the buoyancy. These are two forces acting on a ship. When the ship is upright (the picture to the left, above) these two forces cancel each other out. When the ship rolls to one side or another they are out of balance. If you look at the picture to the right, above, the center of buoyancy is to the left of the center of gravity. That means these two forces will cause the ship to 'twist' in a counter-clockwise direction. This will cause the ship to right itself--this is called righting moment. [![enter image description here](https://i.stack.imgur.com/CWh8U.png)](https://i.stack.imgur.com/CWh8U.png) In this picture above, the righting arm is positive; that is the righting moment acts in the direction that will right the ship. It is possible, however, to have a negative righting arm. In that case, G will be to the right of Z (and B) in the above picture, and the ship will flip. The last concept that is important is the metacenter (M in the above diagrams). As the ship rolls from left to right, the center of buoyancy will rotate around the axis of the metacenter. The [metacentric height](https://en.wikipedia.org/wiki/Metacentric_height) is the (constant) distance between G and M. If you mount a heavy dragon on the deck, then this move the center of gravity towards the deck of the ship. As G moves upwards, if it ever raises past M then the ship becomes unstable, as any perturbation will move G to the right of B and flip the ship. # What happens to a small ship? If your your pirate is master of a galley crew (or fleet), then he is likely going to be out of luck as far as landing a dragon. Here is a diagram of a trireme, based on what the Greeks would have used at Salamis. This is a ~50 ton vessel, with a crew of 100-200. Venetian galleys of the 14th century were not much bigger; warships were perhaps 100 tons and merchant galleys up to 300. [![enter image description here](https://i.stack.imgur.com/iUkJd.png)](https://i.stack.imgur.com/iUkJd.png) For this ship, the buoyant force is 50 tons (same as ship's displacement) and metacentric height is only about one meter. When the ship heels over 20 degrees, the righting moment is the buoyancy times the righting arm; which is $$ GM \cdot \sin(\theta\_r)$$ for shallow angles of $\theta\_r$, or roll angle. GM is the metacentric height. Righting arm in this case is about 35 cm. The righting moment is then about 175 kN-m. This is the force that buoyancy puts on the boat to counteract wind and wave and keep you from tipping. If a dragon is about 14,000 kg, and is two meters above the center of gravity, this changes the center of gravity upwards by roughly 0.4 meters relative to the metacenter. This has a linear reduction of righting arm down to 100 kN-m. This is a pretty solid hit on the stability; almost a 50% drop. Triremes did flip in storms; now they take about half the force to flip with the dragon on board. # How big should the ship be? The ship should be much larger than the dragon. How much larger depends on the design of the ship. Where the trireme is a long, low ship, with only 2 meters of freeboard (height of the deck above the water level). This is the same freeboard as the reconstructed [Nina](http://www.sailtraining.org/membervessels/vessel.php?@=174) (of Columbus fame) had at only 40 tons. A larger sailing ship would have a greater height out of the water, therefore a dragon posses a proportionately larger problem. I would estimate that for a galley-stype ship, you would want at least a 200 ton vessel to safely park a dragon. On a full masted, Pirates of the Carribean stype sailing ship, you probably want more like 500 tons. This isn't that big in the scheme of things, but it is significantly larger than [Queen Anne's Revenge](https://en.wikipedia.org/wiki/Queen_Anne%27s_Revenge) (Blackbeard's ship). It is, however, much smaller than USS Constitution at 2200 tons. So, your pirate is going to need a relatively large ship. On the other hand, the dragon can do a lot to help. First, the dragon has to keep its center of gravity in the center of the boat (just like you have to be careful in a canoe). Second, it would be really nice if the dragon left whenever the wind and waves go high. The danger of flipping is pretty small in calm seas. [Answer] As others already mentioned, it is more a matter of stability and buoyancy than a matter of weight. My idea how to effectively transport that dragon would be a [catamaran](https://en.wikipedia.org/wiki/Catamaran) or [trimaran](https://en.wikipedia.org/wiki/Trimaran). Both types of ships can carry a huge load compared to their own weight, are really stable in bad sea, and if you put your dragon on a plattform in the center of the ship, nothing bad should happen. Edit: Since your protagonist happens to be a pirate, he could repurpose the vessels he captures as material for a second or even tertiary hull. Nothing like some rogue MacGuivering! [Answer] 14 tons dragon + 10.000 pounds of cargo equals roughly 20 tons in total. Pirate ships like those used in the 18th century on Earth could easily carry such weight and more. The [Queen Anne's Revenge](https://en.wikipedia.org/wiki/Queen_Anne%27s_Revenge), for example, had a cargo capacity of about 200 tons. The [San Esteban](https://en.wikipedia.org/wiki/San_Esteban_(1554_shipwreck)), a Spanish Galleon shipwrecked in the Gulf of Mexico, is estimated to have been able to carry between 167 tons to 291 tons of cargo. So, the weight itself wouldn't be a problem, it weight distribution that would be. The dragon would have to mostly keep close to the center line of the vessel to avoid creating an imbalance. ]
[Question] [ Could animal produce less than 700MHz radio waves to communicate ? I don't want those waves interfere with mobile phones and other intercontinental radio communication my space colonists would use. Is it harmful, and could they produce an alternative current powerful enough to produce those waves? Is it exhausting? Edit: The 700MHz is because I want an alien race using the radio communication I'm talking about would not interfere with space colonists communication, but one day settlers' technology is broken and they decide to use lower frequencies like amateur would do for trans-continental radio communication and then colonists would discover my aliens from the weird interferences. [Answer] ### TL;DR I think it is possible, but not too likely to develop naturally. --- Radio transmissions are not a fixed power output. You can have a 700MHz sender with 1MW or 1µW. It mainly changes the range of your transmission, depending on setup. ## What you need ...is something that generates the signal and an antenna. Neither I know of examples in nature, but I doubt it would be impossible. I just do not see any evolutionary benefit over acoustic communication as this is probably a lot simpler to build that 700MHz communication. And the potential range benefit is not something immediately useful for survival - to make use of that you'd already need a complex social species that could use this to take advantage of the range. So here on earth for basically every species long range communication is almost pointless. (There are very few exceptions - including humans) However, this is a reason for why I think it did not develop on earth - not that it is impossible to develop naturally. The signal generation is something it think is more difficult. Sudden electric discharge like eels is not helpful as it is just one-directional discharge and not a rather high-frequency oscillating signal - which is your requirement with 700MHz. I am not aware of any examples in nature of anything like this, but there might be something. ## Acoustic vs Electromagnetic Any physical body makes sounds when it interacts with another physical body in some way. Even if the sound can not be heard by us or is incredibly quiet. There is always some sound. It is easy for an organism that already has a physical body to use this to make sound on purpose as well as use sound to detect objects in its vicinity. An electromagnetic sender-receiver system has a significantly higher base requirements to be useful for a species. With sound you can imagine organisms detecting and reacting to a sound to gain an advantage. Soon organisms create sound on purpose to trigger reactions by others. That way you can develop something like a communication slowly building it bottom-up instead of top-down like engineering works. ## Bottom-Up vs Top-Down Top-Down refers to a design process starting with the question "What do I want to achieve?" and then designing a mechanism that somehow achieves what was desired. Bottom-Up is what evolution does. It starts with something and then randomly builds upon that. Some things work - others not so much. After a long period of time you have developments of entirely different complex systems all looking like they were designed for a purpose to fit in the ecosystem. The truth is that nothing was ever designed. Beneficial alterations had a better chance of making it to the next generation. This means an efficiently working organism exploiting an ecological niché is simply more likely to survive than a less efficient or less focused organism. (Within limits, but that's just a summary) ## Why do I talk about design processes? Electromagnetic communication as used by humans was designed Top-Down. We built a complex process of signal-generation, encoding, sending, receiving, decoding and interpreting. While it appears similar to acoustic communication, its requirements are a lot more difficult to build in a living organism as well as need a lot more well-adjusted parts. There is no advantage for an organism having basic versions of electromagnetic communication over significantly easier-to-build acoustic communications - with the downside of significantly lower range. ## The main problem While I doubt it is impossible to solve the problems of signal-generation and building of an antenna using only biochemistry, I think it is extremely unlikely to occur naturally. The antenna is the simple part. All you need is something with even a slight capability of receiving the 700MHz signal. Even a paperclip works easily if the power output and transmission medium are good enough. Smaller and simpler structures are also possible. [Eels](https://www.nature.com/articles/ncomms9638) (Credit to @ColonelPanic for the link) are an example of complex electromagnetic mechanisms being used in nature. So it is not too far-fetched that it could be built slightly different to create a signal. It could be genetically-engineered. Assuming there is a way to have something like these built into an organism, but it would make no sense to develop naturally, you could - with sufficient sci-fi-level knowledge - theoretically code this into an organisms DNA (or whatever alien equivalent they might have). Either that or you come up with a really good reason why your species developed a rather elaborate means of long range communication using High-Frequency electromagnetic signals. --- I am aware that this answer does not specifically address, how the creatures would develop such a signal, but that is simply because I do not know a mechanism that could work naturally. I do see a possibility having a burst signal based on biochemical reactions with an equivalent bonding-energy of $E = h \times 700MHz$. That way sudden bursts of signals could be transmitted and possibly received. For details you should probably ask RF engineers and biochemists. However I did feel like OP had some misunderstandings about radio communication and wanted to clear to clear things up a little bit. --- On a side note: If your space colonists use 700MHz and the surrounding frequency-band then they will unavoidably have interference with these radio waves. If they do not use those frequencies, they will not. You can not send multiple signals simultaneously on the same frequency without more elaborate polarity tricks. Another note: @ColonelPanic helped improve my answer regarding the radio transmission. Thanks! [Answer] There is one important biophysical problem you have to overcome in producing such high frequencies: How are you going to produce such signals? Real-world example A real-world example for something similar to what you are looking for are (weakly) electric fish, which use electrical signals for communication and prey-detection. In real-world animals which are able to produce such signals (called "electric organ discharge", or EOD for short) of several 100 to 1000Hz (like [this one](https://en.wikipedia.org/wiki/Black_ghost_knifefish "this one") or [that one](https://en.wikipedia.org/wiki/Peters%27_elephantnose_fish) (which actually features an "antenna" of sorts)) the cells making up the electric organ evolved from nerve cells (e.g. the first fish linked, also Electric Eels) or muscle cells (e.g. the elephantnose fish). In both cases the discharges are produced through electrical activity (charged ions (mostly Sodium and Potassium moving into and out of cells) of nerve/muscle cells called "action potentials". An excursion on weakly electric fish There are roughly two types of weakly electric fishes: The first, found in Meso- and South America are called wave-type fishes. The name is based on the fact that they continually output a periodic signal. The shape of this periodic signal is distinct to each species, but is preserved across individuals. Individuals differ in the freqeuncy of their EOD and can thus be identified that way. Those fishes have their electric organ cells evolved from nerve cells. They communicate via so-called "chirps", where they briefly increase their firing frequency. They sort-of cancel a period half-way through and begin a new period. Chirps are (among other uses known and maybe unknown) used in courtship behaviour and in aggressive behaviour (mostly male-male). A particular example is that females communicate the exact time of their egg-laying to a male of their choice (who they vetted before), who can then do his part. This allows for example for egg-laying in save, occluded places. For Apteronotus as a particular example of a Genus of wave-type fishes, in regards they appear to have two different pathways in their electrosensory pathway in the brain - one for prey detection and one for communication. There are even different types of electro reeceptors for the two pathways which encode different kind of signals. Think AM (amplitude modulation) and FM (frequency modulation), only more complex. There's also a third type of electroreceptor, but there is far less research done in this type. Anyway, one of the two pathways is actually split into three areas in the brain. "Pyramidal" cells (named for their shape) in those areas are the first layer atop the receptor cells. Pyramidal cells in the three different areas have different properties. Why? No one knows exactly. Pulse-type fish have electric organ cells evolved from muscle cells. They don't put out a continuous signal, but just show bursts of activity. I don't know many details about their behaviour. The problem Action potentials (electric discharges of cells) take time - a general rule of thumb is that they take about 1ms, which roughly fits the highest frequencies observed. Action potentials which are orders of magnitude shorter are implausible, because cells need to "recharge" after an action potential which takes time, as molecules have to physically move. Understanding the signals received Also note that the electric signals have to be read out on the receiving animal's side. Using receptor cells we know, for the same reasons as above, there is no way that you can get more information out of a 700MHz signal that out of a much lower frequency signal unless you are willing to have a humongous number of receptive cells. While it is possible for cells to encode signals which are faster than their firing rate (number of action potentials per time), the required number of cells gets larger and larger that higher your frequencies become. The brain of the electric fish already has dedicated huge areas just for electrocommunication and electric detection of prey. The size of those areas would have to increase many times for signals in the area of 10⁸Hz. I hope that this is somewhat understandable for a lay person. If it is not, feel free to ask and I can elaborate on it, and also provide sources for the claims above. tl;dr: It's certainly possible at lower frequencies, but likely not at the frequencies you are looking for. [Answer] It's not only possible, but most of the requisite pieces have actually been developed in nature already. Allow me to introduce you to the [Spark-gap Transmitter](https://en.wikipedia.org/wiki/Spark-gap_transmitter), the earliest means to transmit RF energy. This requires turning on/off an AC source of power, which we could easily imagine as [any number of electric fish](http://news.cornell.edu/stories/2013/09/electric-fish-may-have-switched-ac-dc). Whether or not these species are intelligent enough to use this as a sophisticated means of communication may be in doubt, but there are plenty of examples of species who would be. And even something simple as "I'm being attacked" could be of benefit to the species and effectively be a form of RF communication. As for the receiving end, in RF theory, this works exactly the same way as transmitting. But for biological/evolutionary sake, let's say that this was developed first, such has already been discovered [in a number of species](https://en.wikipedia.org/wiki/Electroreception). These two functions have developed separately, but there is little reason to believe that they couldn't be developed in the same species. As for frequency, yes, it will make a lot more sense to use low frequency. This will allow for longer transmission distances (as a rule of thumb, there are other factors involved) at lower power levels. [Roughly 60W at 175Hz](https://news.mongabay.com/2017/09/how-much-of-a-shock-can-an-electric-eel-deliver-a-scientist-just-found-out-first-hand/) could make for a rather robust transmitter. And this is for a species evolved for different purposes. I'd imagine a species which received benefit from the communication you suggest could transmit with even more power. Oh, and I should mention that this all works much better outside of water, especially sea-water. You didn't mention any details about your creatures, but free-space transmission (effectively in air, not water) is much more believable. EDIT: In my haste to post the above, I forgot to mention that [this species](https://www.nature.com/articles/ncomms9638) actually does something very similar to what you are asking. I wouldn't quite call this a form of communication (if your definition is between two hosts), but it clearly demonstrates a biological niche which can be filled through RF transmission and reception. As the required biological 'hardware' is already there, expecting the 'software' to never be able to exist is a fallacy in my opinion. [Answer] I think sharks "use" something similar. They can sense the electric current in the nerves of their prey when it moves its muscles. I think water is more suitable transferring these signals than air, but maybe it works if animals evolve to transfer signal intentionally and can increase the transmission power. <https://en.wikipedia.org/wiki/Electroreception> ]
[Question] [ In the supernatural plane of existence known as The Exhibition, time appears frozen - nothing is moving, falling objects are suspended motionless, the works. In addition to this, while outside visitors and their belongings move as normal, the inertia of native matter is 100x, maybe even 1000x what it normally is, which means that anything of much mass at all is impossible to budge, you can walk on water like it's stone, etc. You can, with difficulty, move a feather that was floating in the air, and wherever you managed to move it to, it would remain suspended there. If you succeeded in putting the feather in your pocket, it would be very hard to walk away, as it would probably tear the pocket loose from your clothing and remain where it was in space. There are some very good reasons to want to explore The Exhibition, which otherwise resembles a medieval realm. However, particulates in the air cause big problems. Water droplets from fog, or dust in a dusty room, even pollen, all accumulate on your clothing and hair and in your lungs and increasingly bog you down. This can be fatal! The modern-day solution would be a protective suit [like this dry suit](https://upload.wikimedia.org/wikipedia/commons/8/83/Viking_pro_1000_drysuit_with_magnum_hood.jpg). It would still be hard to move through particulate-heavy air (would feel like wading through water or mud), but it would at least all slide off of you so it wouldn't get worse over time. How can the canny explorers in my setting visit this place as safely as possible? Their base is a medieval fantasy world, though I'll take any technology plausible up through the Renaissance. There's magic in this setting too, but I'm looking for a mostly or entirely non-magical solution. It doesn't have to be perfect, just better than nothing, and the less cumbersome the better. [Lotus leaves](https://en.wikipedia.org/wiki/Lotus_effect) might be a good start, but I fear that fashioning them into clothing would be prone to failure (holes made from stitching would tear when you started moving, etc). Maybe they could be layered overlapping on top of an undersuit with some kind of pitch or glue? But if the glue remained wet it would attract particulates, and if the glue hardened, it may become inflexible. (Although I'm not aiming for hard-science plausible physics here, any tangents about other effects of this high-inertia plane are welcome, though I might ask another question about that.) Update: Assume that gases aren't subject to this extra-inertia effect, only liquids and solids. So, in the absence of solid particulates, air pressure and breathing work as normal. [Answer] A set of good plate armor from the middle ages would work. The main thing is that the front pieces should all be angled back from the center. This would deflect the particles to the side rather than accumulate them. The helm doesn't even need to be very complicated. So long as the breathing openings are on the sides or bottom of the helmet, the dust will be deflected from the air they breath. The main sticking point will be vision. If they can use quartz eye pieces, great. Otherwise, they will have to look down through overlapping slits to prevent forward motion from driving particles into the eyes. Every so often they would have to stop and either lean back so they can see ahead or raise their face shield to get a good look. Then it's back to watching the ground at their feet through the slits. They may have to clean the front of the armor every so often lest they accumulate enough junk to make it very hard to move. This can be done easily by taking a step back and then going around the floating pile of junk. Well traveled routs will have the junk pushed to the side already. [Answer] ### Beeswax Cloth People have been adding oils and bees wax to clothing (coats, cloaks, frocks etc) to make it shed water for ages. Your explorers could take this technology and apply it to several thin cloaks made of fine hemp or cotton. Wear each cloak like a wrapper, or bring spares with you in a pack. When the outer cloak gets too laden, simply shed it and continue on. [Here is a link to a home recreation post on making a “cling-wrap” equivalent out of cloth, wax and oil](https://myplasticfreelife.com/2013/12/replace-plastic-wrap-with-beeswax-cloth-wraps/). [![enter image description here](https://i.stack.imgur.com/QAFH9.jpg)](https://i.stack.imgur.com/QAFH9.jpg) [Answer] The skin of sharks or rays would provide material for a lighter and cheaper armor. Or the adventurers could span shark skin on a light wooden frame to make a shield / plow. They have to keep the orientation of the skin. Particles slide smoothly from the snout of the shark to the tail, but are hindered in any other direction. Please note that the processing of shark skin is quite complicated. Knifes to cut the skin become dull extremely fast, to sew you would need to use senews or similar strong material. [Answer] If air works as normal, the armor thing would work. How large are the portals into The Exhibition? How long do they last? Because people are lazy, and if you could for example bring a large metal shield and hook it up to a couple of oxen and have them plow a path for you - profit. Oxen are strong, and if they accumulate too much particulate you just get new oxen. They are cheaper than new explorer people. Or, instead of thinking of the water vapor as heavy water vapor, think of it as a slightly solid wall. Heck, you could just climb over it if you wanted, right? If you needed to clear an area, bring a big sheet of metal and a lot of weights, put it on top and push it to the ground. Then you don't need really bulky suits except for specialist stuff. ]
[Question] [ We have [escaped the galactic government](https://worldbuilding.stackexchange.com/questions/87034/now-how-to-escape-fun-loving-immortals), and now our greatest endeavour yet, life in space. How will these gargantuan space entities eat and survive in space? * The whale or other in question is the same size or bigger than a [blue whale](https://www.google.co.uk/search?q=how%20big%20is%20the%20biggest%20whale&rlz=1C1CHBD_en-GBGB739GB740&oq=how%20big%20is%20the%20biggest%20wh&aqs=chrome.0.0j69i57j0l4.16635j0j7&sourceid=chrome&ie=UTF-8) * [The travel of this creature is not a worry](https://worldbuilding.stackexchange.com/questions/87443/space-whales-how-to-move) * We do not need to consider the feasibility of such a creature naturally evolving [Answer] Since the feasibility of space whales is not into question, then why not consider the possibility of the existence of space plankton? Space plankton could feed out of the energy sources mentioned by a4android and L.Dutch answer (and, in the case of phytoplankton, from photosynthesis using the light of a nearby star) and then the whales would feed out of space plankton space clouds. Since microrganisms are known for having the ability to survive in extreme environments and are even theorized to travel in space, where they "seed" planets with life... it is much more plausible to have plankton to adapt to a form of metabolism that converts space matter and light into energy than a heterotrophic giant animal like a space whale to do it (no matter the level of implausibility you deem acceptable). [Answer] The most likely food source for space whales will be [giant molecular clouds](https://en.wikipedia.org/wiki/Molecular_cloud). > > A vast assemblage of molecular gas with a mass of approximately 103 to > 107 times the mass of the Sun[9] is called a giant molecular cloud > (GMC). GMCs are around 15 to 600 light-years in diameter (5 to 200 > parsecs).[9] Whereas the average density in the solar vicinity is one > particle per cubic centimetre, the average density of a GMC is a > hundred to a thousand times as great. Although the Sun is much more > dense than a GMC, the volume of a GMC is so great that it contains > much more mass than the Sun. The substructure of a GMC is a complex > pattern of filaments, sheets, bubbles, and irregular clumps.[5] > > > The densest parts of the filaments and clumps are called "molecular > cores", while the densest molecular cores are called "dense molecular > cores" and have densities in excess of 104 to 106 particles per cubic > centimeter. Observationally, typical molecular cores are traced with > CO and dense molecular cores are traced with ammonia. The > concentration of dust within molecular cores is normally sufficient to > block light from background stars so that they appear in silhouette as > dark nebulae.[10] > > > GMCs are so large that "local" ones can cover a significant fraction > of a constellation; thus they are often referred to by the name of > that constellation, e.g. the Orion Molecular Cloud (OMC) or the Taurus > Molecular Cloud (TMC). These local GMCs are arrayed in a ring in the > neighborhood of the Sun coinciding with the Gould Belt.[11] The most > massive collection of molecular clouds in the galaxy forms an > asymmetrical ring about the galactic center at a radius of 120 > parsecs; the largest component of this ring is the Sagittarius B2 > complex. The Sagittarius region is chemically rich and is often used > as an exemplar by astronomers searching for new molecules in > interstellar space. > > > Assuming space whales feed by scooping up matter and then ingesting it and while this is similar to the feeding mechanism of, for example, baleen whales the actual mechanism will be different. baleen whales are filter feeders sifting out plankton from seawater. Space whales would have ingest sufficiently large amounts of matter to secure sufficient mass of organic molecules to feed themselves. This could involve space whales moving at FTL velocities through the volume of molecular clouds. There would need to be a capture structure or field to "scoop up" matter and simultaneously translate it to the necessary state for it to be also moving at an FTL velocity. basically, to bring the matter to being at rest with respect to space whale's motion. [![enter image description here](https://i.stack.imgur.com/qfnx3.png)](https://i.stack.imgur.com/qfnx3.png) Because space whales are feeding at the level of basic molecules their metabolism will be more like that of a chemical factory than a conventional biological entity. However, basic molecules can be built up into proteins, lipids and glycerides and other organic material. But who said living in space was easy? [Answer] Space is full of energetic things (radiation, ions and other particles), and life needs energy. Your swhales (space whales) have various possibilities: * Energetic radiation harvesting. Gamma rays, X rays, UV rays... plenty of them in the space when close to a star. The swhales may have an organ whose molecules are excited by absorbing these radiation and then release the excitation energy in a biologically usable way. * Ions harvesting. Stellar winds are also powerful close to the stars. Kinetic energy and chemical energy can be harvested and used for biological purposes, too. * Mass swallowing. This applies only if your swhales are waaaay bigger than a whale. It goes as it says: they swallow a planet or a chunk of a planet and they digest it. All the above of course imply that some regions in space will be food rich, while others will be food harm. But that is not different from what whales experience in the Oceans, where plankton is abundant only in certain regions. ]
[Question] [ Within my desert landscape--in which the climate is similar to the [Sonora Desert](https://en.wikipedia.org/wiki/Sonoran_Desert)--there are many canyons, one of which sports large, clustered growths of [Elbaite Tourmaline](https://en.wikipedia.org/wiki/Elbaite) crystals, averaging out at a height of around 8-10 feet, with smaller crystals often growing around the bases of larger ones The crystals grow along the walls of the canyon and around the edges of a nearly dried up river. The sand surrounding the river area consists of small flakes that have been weathered away from the sandstone canyon walls and the edges of the crystals, making a layer of sand that extends for about 1-2 feet before hitting the clay soil beneath. Now, I'm aware that clay makes for a difficult soil, so I'm more concerned with the effects the large crystals and sand composition would have on any native plant life. [Answer] If the crystals have no effect on the moisture or nutrient levels in the soil, then it would be reasonable to treat them effectively as rocks. Meaning they affect only light and shade patterns and root penetration into your soil level. Sand is only another type of crystal after all. However sand as a soil has a high drainage rate, clay on the other hand tends to act as a moisture barrier preventing water from draining away rapidly after rain which will also affect the deeper rooted and larger plants. [Answer] Any native plant life will be, by definition, well suited for this kind of environment. One partcularity of this environment I'd like to adress is the following : ## Light condensing Ok, your Elbaite Tourmaline seems rather opaque. But if you allow it to be clearer, your large crystals could act as mirrors and lenses, focusing light in semi-random patterns, always changing as the position of the sun vary with the time of the day and the seasons. Think of a bottle (glass or plastic) thrown away by some idiot, now resting on a dry piece of vegetation exposed to sunlight : that's how some forest fires start. Here, your bottle is an ensemble of 10ft tall crystals, in a desert. If your vegetation wants to live, I would expect it to have some sort of localized hight heat resistance, so it doesn't catch fire on a bad conjugation of light rays through your shiny crystals. In short : your plants should have a fireproof skin. [Answer] What to do is to look at what plants that live in nutrient poor soil do: [they eat things](https://en.wikipedia.org/wiki/Carnivorous_plant). Carnivorous plants (venus fly trap, various pitcher plants) sustain themselves in nutrient poor soil by eating insects. They need water (there is that stream), CO2 in the air and a minimum of nutrients in the soil to get started. And stuff to eat, of course. ]
[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/65198/edit). Closed 6 years ago. [Improve this question](/posts/65198/edit) NOTE: This was adapted [from another question](https://worldbuilding.stackexchange.com/questions/65191/could-a-nuclear-war-cause-the-majority-of-earth-to-be-uninhabitable-for-hundreds) that I asked recently. Apparently, a 30km radius around Chernobyl will not be safe for humans for another 20,000 years. The more recent 2011 Fukushima disaster is still causing a growing number of problems worldwide ([Fukushima Radiation](http://www.zerohedge.com/news/2016-10-02/fukushima-radiation-has-contaminated-entire-pacific-ocean-and-its-going-get-worse)). There are currently 433 nuclear reactors in the world: [![enter image description here](https://i.stack.imgur.com/O3rhb.png)](https://i.stack.imgur.com/O3rhb.png) If the majority of these were destroyed (either by a terrorist act, nuclear war, or natural disaster) how would the radiation affect the entire world? Would there be any areas safe from radiation? How long would it be before the earth was safe to live on again? Would there be any adverse affects of the radiation? [Answer] Nuclear weapons are meant to inflict massive damage due to the energies they release. They are not really meant to permanently irradiate an area. Hence, older bombs are considered "dirty", whereas new ones are presumably much "cleaner". The difference here is nuclear reactors are not ever meant to explode. That might sound like a silly statement, so allow to explain: all the contingencies around a nuclear reactor focus on *stopping* it from failing catastrophically (exploding - no, not in the same way as a nuclear bomb, they wouldn't do that). However, if one were to fail catastrophically (and there are many, many safeguards in place to make sure that it won't), there are no features in place to make the resulting explosion "clean". In fact, that (most likely explosive) failure would simply cause the nuclear fuel to be thrown up into the atmosphere, causing huge clouds of deadly radioactive debris to spread for hundreds of kilometers around. If many of the 400+ nuclear reactors in the world were to all fail simultaneously (or within a very narrow window of time), an enormous amount of radiation would be released into our atmosphere. This radiation would travel with the weather patterns, and spread along much of world, killing off most surface dwelling life. Would any place be safe? I don't think anyone can say for sure, but I don't think any place would be safe in the long run. That much radiation would stay up in the air for a very long time, and would eventually make its way to pretty much every corner of the planet. Might some places be very minimally affected? It would depend entirely on the weather patterns. How long would it be before the earth was safe to live on again? Safe for who? For the radiation to fade to current levels it would probably take tens of thousands of years, and I don't think humanity would last that long, except maybe off-planet, somewhere. Would there be any adverse affects of the radiation? Of course. A majority of surface dwelling species would die off. Horrible mutations would likely become common place for those unlikely to survive the initial cataclysm. Over time the Earth would be reclaimed by other species, but not a for a long time. [Answer] Short answer not much would happen. There just is not enough of them and even in the worst case breakdown they don't release that much radiation. most reactors aren't designed to be be giant pressure bombs/cannons which spread radioactive material over a wide area like the early russian designs. Many reactors have a negative void coefficient of reactivity and thus lose reactivity without coolant unlike the Chernobyl design. Others like breeders and gas cooled reactors don't have the issue to begin with. You would see death in the immediate area for some sure but on a global scale all you might see a slight global uptick in cancer rates and that's about it. The sudden failure of global power grids and evacuation effects would be a bigger problem. Lets try the impossible hypothetical scenario, all 433 reactors pull a chernobyl, Most can't but let's ignore that. if you pretend none of their exclusions zones overlap and even include some addition area for secondary zone overlap. you end up making an area roughly the size of Alaska unlivable. That is a a lot of land, but it is nowhere near close to making the planet unlivable. . people just don't understand radiation, or how much you are already dosed with <https://www-tc.pbs.org/wnet/need-to-know/files/2011/03/radiation.png> [Answer] ## Really bad things A [nuclear reactor](http://www.nei.org/Knowledge-Center/Nuclear-Statistics/On-Site-Storage-of-Nuclear-Waste) creates about 20,000 kg of waste per year for a total of 8.8M kg per year. Assuming that stockpiled waste, which is an even greater quantity of material, isn't released as well as the material in the reactor, that's still a lot of waste to put in the environment. Chernobyl 4 released about 8 tons or 5% of its radioactive fuel and machinery into the atmosphere from an initial fuel load of [192 tons](http://www.world-nuclear.org/information-library/safety-and-security/safety-of-plants/chernobyl-accident.aspx). Reports indicate that the heavier dust returned to earth fairly quickly but the lighter radioactive material stayed aloft and spread over a huge area covering much of Europe and Russia. Let's assume that all 443 reactors failed at the same time and with the same results as Chernobyl. While this perhaps isn't very realistic because of the considerable differences in reactor designs, the Chernobyl incident does offer a more complete picture of the manpower required to address such an incident. Its a reasonable assumption that containment failures at every nuclear reactor in the world would vastly exceed the ability of any nuclear regulation agency to handle. The scale of failure is just too big. Trained technicians are too few and knowledge about radiation and nuclear materials too slow to teach to quickly train more technicians. Managing one containment failure is nightmare fuel. Managing all failures is impossible. ## Economic Effects This failure event causes an immediate depression for lots of reasons. First, much of the electricity required to run a modern economy comes from those reactors. While it may be possible to run coal and natural gas plants at full capacity to help meet the demand, this could not be done long enough for additional capacity to be built. Second, a casual glance shows those nuclear plants are located in very close proximity to three of the most productive economic zones on the planet, the US East Coast, the US West Coast, Europe and Japan. Losing these areas would be a fantastic blow to the world economy. And while the people in those areas may not die, the spectre of nuclear death would cause panic and monstrous disruptions to the economy. If casualties are light, they may be able to return to work fairly quickly, depending on local conditions. If casualties are heavy, the economy may take decades to recover. Third, the spread of so much radioactivite material is a huge area denial on some of the best farmland in the world. World food production will go down with some "interesting" effects on politics. Formerly weak but uncontaminated food suppliers will suddenly be in a much stronger position with their stronger neighbors. Fourth, whatever power source humanity continues to use after this event, it absolutely will not include nuclear. No one, anywhere would permit reactors to be built. This may preclude fusion power too since it contains the world 'nuclear' in it, which is a bit of a shame since fusion unlocks so much energy. [Answer] It could be very, very bad indeed. The majority of radioactive releases from Chernobyl did not come during the actual explosion. After the explosion, the graphite in the reactor core caught fire, creating a huge rising column of hot air which carried uraniumn and fission products out of the core and high up into the atmosphere. This reactor fire burned for 10 days. Attempts were made to seed the radioactive clouds and trigger rainfall, to bring down as much particles as possible before the clouds passed over Kiev. Cesium was spread all over Europe. Eventually the fire was put out, ending the major source of contamination. During this time, just a small percentage of its radioactive inventory was released. To prevent further leaks, a giant concrete sarcophagus was rapidly constructed over the disaster site. This cleanup operation took 600,000 people, and more or less bankrupted and ended the Soviet Union. Now consider what would happen in the case that several (or 433) of these types of disasters occurred simultaneously. There simply isn't enough resources (people, machinery and economic) available to stop the disaster. So we could very roughly imagine each reactor burning off most of its inventory producing a disaster an order of magnitude worse than Chernobyl. However, on the plus side, Chernobyl, being a rather old and crappy design, didn't have any major containment systems designed to prevent massive release. They simply never considered it at the time. But reactors constructed since have been severely regulated and safety systems improved. Still not fail-proof, obviously, since Fukushima suffered simultaneous meltdowns. The amount of radiation released is highly debated, with estimates from no radiation related deaths, just a few cancers, to the entire north pacific being annihilated. What is known, is that enough radiation was released to merit widescale topsoil removal, and that the reactors are continuing to leak contaminants into the sea even today. It's important to note that Fukushima is an on-going disaster, and should be treated as such. Six years after the initial events it is still very unclear what has happened, where the fuel is, what condition it is in, and how much of it has escaped. No efforts to actually fix the meltdowns has taken place yet. Japan, supposedly a world leader in robotics, have sent a handful of probes in there, most of which malfunctioned and/or returned untrustworthy data. The Japanese government have done very well to recover from the associated tsunami, which killed 150,000, destroyed so many homes and infrastructure, and was obviously a much worse disaster. It is very interesting to note that the same government has not been able to clean up the Fukushima situation in any meaningful way. The site still leaks, they don't know what happened to the fuel, and they have taken no real plan to fix the cores. For reasons both technical and political, the cleanup is likely to drag out for decades, so the total radiation release may yet be counted higher than Chernobyl. If they cannot make any progress on cleaning up one disaster site, despite 6 years and tens of thousands of workers, I think its reasonable to assume that there will be an even poorer response to a multiple-site disaster scenario. A modern malfunctioning reactor might not violently burn off all its radiation to the atmosphere, but it may just continue to slowly leak and pollute indefinitely, with even wealthy and high-tech governments like Japan being totally unable to stop it. Should many reactors be damaged and pushed into disaster situations, I think the governments will be totally overwhelmed and unable to respond, and the reactors will simply burn and melt uncontrollably until they eventually burn themselves out, producing far worse radiological disasters than we've seen with Chernobyl and Fukushima. The released radiation will contaminate crops, soil and water pretty much everywhere, entering the foodchain, and hanging around for tens of thousands of years. It's likely civilization will continue in some form, but I expect a large degree of mutations, non-viable births, massive increases in cancer and leukemia, with a worst-case scenario involving the total collapse of the food chain due to some critical component dying out, and triggering a mass extinction event. ]
[Question] [ First of, a little parenthesis about how my magic works : * Magic is a calculable energy contained in some alloys and people. It can be manipulated in about the same way as electricity (with conductors and isolation) * Magic energy can be used as an energy in the same way as oil and is really powerful at that. * Wizards (people who can create magic themselves and contain it without their body) can transfer their own magic energy into magic batteries. * Wizards can cast spells, those are some sort of mathematical formulae one must known perfectly to be able to cast. Spells can be designed by non-wizards and some of them are too long to remember perfectly. * Wizards produce a way greater output of energy than ores. Therefore, they are the one producing most of the energy. Ores are used for all magic related contraption. Such as weapon and batteries. * Wizards can pass their energy to other Wizards * There is a way to create weapons simulating spells, using magic energy as ammo. Wizards can use them without ammo, providing their own energy instead. * Wizards have a limited amount of magic energy per day, it regenerate faster when sleeping and doesn't regenerate much while doing some effort or when starving. * There is a way to forcefully extract magic from Wizards, but it is painful and can lead to death. In my world, Magic and Wizards are rare. (About 1 % of the population produce magic energy) Sometimes, you stumble upon bad wizards who keeps using their awesome skills to bother people, by setting them on fire or making them fly at high speed. Those guys need to be punished but how are we going to keep them in ? Even better, how are we going to put them to good use ? My goal is to create some kind of prison that allow us to : 1. Keep our little mages in the prison 2. Keep our little mages secure (Need a way to deal with fights between inmates) 3. Allow our little mages to have a degree of freedom similar to the one of a regular prison. 4. Make money using our little mages (Enough to be self sufficient would be awesome) 5. Keep in a reasonable amount of little mages (150 ?) And then here is our means : * MOOOONEY ! * About 10 wizards collaborators on site (qualified as battle mages, spells makers or other skills wanted) * Any number of non-mages collaborators and guards * Classified weaponry and spells Here is few solutions I have already considered : * Keeping our mages sedated. Violates #3 and certainly #4. * Keeping our mages on crack at all time so that they cant think of spells. Somewhat violate #3 and may be bad for #4 * Forcing them to deliver all of their magic energy under a pain spell. Not a solution as they could still use their magic to retaliate and they could still work together to amass a reasonable power. May then be problematic for #1, #2 and #3 So here is my questions, what can tactics can I use to make this prison ? To narrow it down, Here is some precise question : * How should I arm guards ? * How should I build the prison (material) ? * What should I do with Wizards that keeps making trouble even in prison ? * (Bonus) Ideas on how to suppress the usage of spells ? [Answer] This is mainly going off the 'magic works a bit like electricity' thing. neutralising magic I'm guessing that for any magic sufficiently powerful to be useful, some energy will be detectably leaked into the surrounding environment - much like how using electricity would produce an electromagnetic field that would be very difficult to hide while still causing some interesting effect. If there are magical 'conductors', presumably they can be used as antennae for a magical device that detects the use of magic. As long as there's no effective cap on how complex magical effects can be, I suppose a magical device could be created that functions like a (limited) computer. While the energy is stored in a wizard, it is difficult to remove, but I'm guessing that when casting spells the interesting parts don't happen in that inaccessible internal battery. In that case, the act of casting a spell should be detectable before the spell actually takes effect. Further, with enough of those magic sensors around, you could probably tell the difference between different spells from the different readings (a bit like Van Eck phreaking). If non-wizards can understand and invent spells, and the process is described in scientific/mathematical terms, it seems reasonable that (unless the process is really hard) a magical computer could work out on the fly the counterspell for a spell it detects being cast and thus prevent any spell being any use, or at least compare what it detects to a list of known spell 'signatures' in order to counter most common spells that inmates might want to use. Walls I see two options, other than just really thick string ones, but they depend on details of how magic works. If magic works sufficiently like electricity, and there are magic conducting materials, then walls made of an earthed conductor or a conductor connected to a prison wizard absorbing magic from it might be able to absorb magical energy. If wizards control magical energy 'in about the same way as electricity (with conductors and isolation)', then the presence of the walls might make it too hard to effectively control. Trying to zap someone would be like putting the positive terminal of a battery in a water tank with an earth wire in it and expecting the power to flow to another positive terminal (a fellow inmate) or a bit of floating plastic (a guard). Alternatively, the walls could be made out of a metamaterial that disperses magical energy directed at them, if that would be possible to manufacture. Either way, the guards could be equipped with armour using the same technology - either constantly earthed to the walls with magic conducting cables or boots, or with magic dispersing plates on them. Guards On the subject of guards, to me the obvious weapon is a portable version of the system for painfully extracting magical energy from wizards, since it serves the double purpose of a weapon and a way of making hostile inmates less dangerous. It does depend on the possibility and practicality of the process being portable. Other equipment could include something to detect the use of subtle magic like illusions or aiding the theft of cell keys. Dangerous inmates Solitary confinement of some kind seems like a good start. They still have to be prevented from using magic against guards (and possibly themselves), without resorting to the dangerous option of frequently extracting their energy. I suggest giving them their food and water in such a way that they have to expend magic to get at it. Perhaps to get a drink they need to lift a fairly heavy sluice gate that they can't physically reach. Alternatively, drug them with something that prevents them from concentrating (but not like crack). A sedative of some kind. In extreme cases, maybe even keep them asleep. Making money Allowing the inmates to use magic in order to use it to make you money is quite dangerous. Just follow the example of for-profit prison systems that already seem to do okay without wizards. That's all I can think of. I hope it's something like what you were looking for. [Answer] # Cheating As Leon mentioned in a comment, there is no null-magic zone spells. If there was, it would be so easy. We could just put them all over a normal prison and be done with it. # Non-magic solution Have magic-detecting automatic turrets mounted everywhere. Enough that they couldn't be taken out all at once. Instantly kill any prisoner that tries to cast anything. # Magic solution 1 Have a small army (10) wizards whose only job is to null any spell cast by any prisoner. # Magic solution 2 Use walls that are resistant to magic spells, i.e., they can use magic but it won't help. # Magic solution 3 Make them imprisoned forever by default. The only way they can get out is if they make x [whatever]s. Unfortunately, making a [whatever] requires all their magic for the day. If they don't make their [whatever] on some day, they have to make 50 more. (Best combined with one of the other solutions) [Answer] One of the best ways in my opinion for magic energy control in the prison would be making everything cost magic energy: You want some food? Then fill me X amount of batteries (maybe different amounts for different mages) and you will get your food. Also make the enforcement duration be based on magic energy (nunmber of days \* magic potential of the specific mage to make it fair). This would make it so that mages who arent donating are basicially starving and so dont have much energy and are donating constantly to get out of there and thus have even less spare. You will still have to adress the issues of gangs and other forms of supression of specific mage groups though, as there could be a black market for magic energy developing in the prison. Selling the magic energy is a viable money source aswell. (My answer does not adress general riot prohibiting and security measures, aswell as weapons for the guards. All of these things are necessary though as a big group of mages could still just not donate and break out/use other mages. Its only a way to deal with your "normal prisoner") [Answer] This is somewhat similar to what C.Fe. said, but with slightly different approach. I couldn't see it in the original post, but perhaps there is a way to measure the magic energy levels of wizards. Multiple sensors throughout the prison, including each single wizard cell. When it is time for meals, exercise, or any other time where a prisoner must be allowed out of their cells the sensors in the individual cell must read under 0.1 kiloWhizatts (or whatever a low unit of magical energy is) or the door simply doesn't open. From their cells, they can then channel their energy through a conduit which allows them to drop their levels and get out of confinement. This would keep the prisoners that are around other prisoners all around the same low levels of energy, and those who chose to store their power are essentially willingly starving themselves and staying in solitary confinement, preventing them from endangering the prisoners who do comply with the rules. If those wizards' magic energy levels are detected to rise to dangerous levels, then the wizard guards are sent to painfully extract the magic from them. The energy can be used to power the facility as well as creating batteries/ammunition for resale to keep the prison self sufficient. Edit: Now that I see that magical energy can be measured, but for more accurate reading one needs to have needles in them, I'm envisioning somewhat of a permanent prison bracer containing the prisoner's information, which monitors the wearer's energy levels. If the low enough it will act as a key to give the prisoner access to shared facilities. In the event that a prisoner gets to a shared space and somehow manages to convince enough prisoners to transfer their power to them and increase their power, it would trigger an alarm on the bracer. If it gets to critical levels before the wizard squad could intervene, it could: a) Trigger the pain spell failsafe in the device or b) Teleport the wearer to a special detainment area where Wizard guards await. (if that's possible with your magic) [Answer] Give each inmate a spell collar the dog collar will cause the word immense pain if he tries to use magic in any way. Also higher trained Wizards to serve as prison guards they will follow the prisoners in all public places ( dining Halls, basketball court, prison yard) they can perform any counterspell needed. [Answer] Have the cells of each prison built with the door having a smart spell formula in it. In order to leave their cell they need to activate the sigil. It siphons enough to open the door and then will continue to drain until the magic reserves of the Wizard reach normal person levels. (think diabetic test needle in the door to get accurate readings). The extra siphon goes into batteries for selling. How should I arm guards ? With this method, Normal guards with light armor and batons How should I build the prison (material) ? Cells need to be Magic Insulated, Normal everywhere else except specific escape points (front gate, delivery dock) What should I do with Wizards that keeps making trouble even in prison ? Everything a normal prison would. (Bonus) Ideas on how to suppress the usage of spells? Have the Wizards do hard labor when outside the cells, bonus income and it reduces Magic Regen which should keep them to minor spells at most or have them revisit the cells at regular intervals. ]
[Question] [ It’s an alternate 2023 (oh, 2012 is just so cliché), and Kanye West, in all his megalomania has nudged a toxic comet of death into a collision course with Earth. US Government hacks conclude that the comet will render the surface of the planet uninhabitable, and so draw up plans to build a massive national shelter somewhere in the Rockies (make it underground or perhaps an enormous transparent dome, but the catastrophe is such that it has to be a contained habitat). They expect the survivors to live there for decades. Space is extremely limited, so every non-essential inhabitant needs to be very well justified. Such an operation clearly has a staggering list of essential, indispensable, and downright mission-critical personnel to make it work, else the entire colony fails. There’s the guy that wrote the stupendously complex software that keeps the dome from exploding, the brilliant scientist who is the only one that knows how to grow the wonder crops that feed the colony, the original architect who would be really nice to have around if we ever had questions about that thingamajig that holds the structure up, and that hilarious comedian who we would all be really depressed if we didn’t have him and his heart-lifting performances to cheer us all up. All great, we have the A-team to preserve the continuity of the United States, yes? Except no one wants to come. A surprisingly large number of personnel would rather spend their last moments with family members and loved ones, rather than save themselves and live out a regimented, grueling life in a dank, musty habitat underneath Mount Yuck. The Government is now stuck with a dilemma of an Ark that is woefully understaffed, as no one wants to leave their loved ones behind! How does it come up with incentives to get people to come? Perhaps it lets people bring a certain number of friends and family members, but how do we make this into a workable policy? We wish to maximize the amount of psychological support colony members can expect to recieve on the “other side”, while minimizing dead weight on the colony. Some edge example cases to consider (humans are weird, after all): ### Mel [Mel](https://www.cs.utah.edu/~elb/folklore/mel.html) wrote the software that keeps the piranhas out of the colony’s water supply. The algorithms are so complicated (piranhas are surprisingly difficult to detect) that Mel is basically the only person who understands it. Mel and his wife belong to some religious sect, and they have twenty-three biological children. ### Dianna Dianna is a world-class civil engineer who designs the air-filtration systems for the colony. There are only a handful of people in the world who can do what Dianna does. But Dianna is gay, and she lives in Alabama, where the county clerks are really reluctant to grant her and her partner Taylor’s marriage license, even though they’ve been together for 9 years and 34 days. (Taylor insists it was 35 days since she first asked Dianna out at 11:58 PM.) No one doubts they’re a couple, but the bureaucrats in charge of the colony say they’re not “official” without the license. ### Shifty Steve and Lil’ Marco Shifty Steve is a one-in-a-million genetic candidate for the colony, without him the gene pool just wouldn’t be the same. Shifty Steve has no immediate family, but he makes a deal with his…er…friend, Lil’ Marco, where Steve gets all the hookers and cocaine he wants in the year preceding the comet’s arrival, as long as Steve figures out a loophole to get Lil’ Marco a spot in the colony with him. ### Rachael Straugnum–Alina and her boyfriend who she loves very dearly (he’s bae-goals) Rachael is an agricultural scientist who pioneered miraculous advances in crop science that might just make our colony viable for feeding thousands of people post-apocalypse. Rachael is your typical urban hipster, for her and her bae, marriage is just so you know, ughhh. That’s not to say Rachael doesn’t love her partner; much to the contrary, if something were to ever happen to bae, she would probably just sit in her habitation eating ice-cream and watching depressive post-apocalyptic Netflix, crops be dammed. Rachael and her bae suppose that, since the world is ending, they might as well go to the courthouse and get that socially constructed piece of paper, but whatever. ### Lieutenant Brown Lieutenant Brown is in charge of keeping the colony running smoothly, and his leadership skills are indispensable to the colony’s social and functional cohesion. Lieutenant Brown has a old Army buddy, who he’s been through hell and back with, and the two are practically brothers. The Lieutenant is a soldier, and he says he can deal with the loss of his best buddy, but we still worry it might adversely affect his performance as a post-apocalyptic leader if he knows the government intentionally left his best friend behind. ### Secretary Thompson Secretary Thompson is the guy in charge of the entire operation, the big kahuna. Secretary Thompson really wants to bring his favorite sugar-baby with him (in fairness, it would be quite a waste to leave dat ass behind) even though she is of zero value to the colony. ### Mr. and Mrs. Norman Mrs. Norman is a famous architect who designed the dome structure, and it would be really nice if we had her around to help if something ever went wrong with the dome. She has no love for her husband, Mr. Norman, and the two not-so-secretly despise one another, but if given an opportunity, Mrs. Norman will bring Mr. Norman with her for the sake of appearances, even though she knows she will probably be a lot happier letting him die in the apocalypse. ### @LUClDITYxo `LUClDITYxo` (real name: Alyssa Parkland) is a world-famous beloved Twitter comedian, and no one is better at brightening up our day than her. Economists estimate that GDP would be approximately 0.14% lower were it not for the morale boost she gives millions of American workers each day. `LUClDITYxo`’s favorite mutual is a girl `artlesszaddy_` (real name: Meghan Stearns), and the two are practically sisters even though they met on the internet. `LUClDITYxo` is the famous one (though `artlesszaddy_` has a respectable 12.8k following), but most of her creativity actually comes from her wild online conversations with `artlesszaddy_`. --- Keep in mind that we need a policy for who goes in the bunker, not just case-by-case judgments for the example characters given in the question. We need to select among thousands of candidates, each one as idiosyncratic as the few examples given. If case-by-case judgment is really the best way to go, we need to know how to set up the vetting process to minimize cries of “bias!” and whatnot. If there is a reviewing panel, who gets to sit on it, and what rubric are they given? Do members of the panel themselves automatically get to go? We need a legitimate (it does not need to be fair, but must be at the least perceived as legitimate) system to sort out all the people like them, keeping in mind that there is limited space available. While no policy is perfect, we need one that will result in the most optimal outcome; for example, if we say “take your spouse at the time of the apocalypse”, do we let Rachael and Dianna get married right before the comet hits, with the cost of letting Lil’ Marco tag along (he “marries” Shifty Steve)? How do we account for relationships that might be just as essential for the psychological well-being of the survivors, but might not count as traditional “kin”? --- Possible answers might take the form of: * Incentives or “motivation” to get people like Mel or Steve to come without bringing excessive tag-alongs. Perhaps midnight kidnappings are in order? * Mitigating the bus factor so that the colony doesn’t depend on so many essential personnel in the first place * Smartly designed criteria for who is recruited for the colony so that people who aren’t wanted but would still be covered under a naïve policy won’t get taken (like Mr. Norman), and vice versa (for people such as Dianna and Rachael) * Additional recruitment efforts to find replacements for “expensive” personnel like Mel The following are not answers: * A list of `Yes`/`No`’s for the 8 specific test cases. They are only meant to be representatives for the variety of situations that might arise. Remember that this is a colony with thousands of niche jobs that need to be filled. * Handwaving away the technology needed to run the facility. Yes, the flesh eating piranhas are a problem and we assume that it is not possible to apply a hardware solution (read: a grate) to it. Having Mel train other people to maintain the software is fair game. Having the government spend a few million and hire new programmers to develop a more maintainable and sensible framework is fair game. Saying the software is not needed in the first place isn’t. --- Side note: `LUClDITYxo` is included as a test case to test for bias. A good policy accounts for the fact that the people making the judgments are aware of their limited perspectives. For example, if a vetting panel is proposed as an answer, what happens if it is filled with so-called “old white men” who don’t see the value in bringing `LUClDITYxo`? How might this affect the perception of the project pre-apocalypse? [Answer] The first problem is what all of these people already know. Presumably, they know that the apocalypse is coming. Given that a dome/habitat has been made, they also have some idea of what kind of apocalypse it will be. That's either really good or really bad. If it's the kind of apocalypse that starts at breakfast and is over by brunch, it's all good. If it's the kind that starts at Christmas and ends at no-one-even-knows-what-that-is-anymore-because-it-was-so-amazingly-long-ago, that's bad. See, the trouble with these people is that they all love someone. It's really easy to tell them all that they can bring one person, but they will never get past what it will do to the ones they leave behind. With that in mind, the goal should be to minimize the discomfort associated with leaving one's loved ones to die horrible deaths. First off, control information. Whatever these people don't absolutely need to know, don't tell them. Sugar-coat it. "Yes, the comet will hit in a blaze of fantastic glory and everything outside of this cool dome thing will be instantly vaporized." That's the line you want. Make it okay for the relatives that get left behind. No pain, no suffering, they won't even know it. Secondly, everyone wants to spend time with their loved ones, so allow them their freedom until, say, three days before the big bad is about to go down. Make sure the dome is up and running well before then, but don't require the specials to be there until basically the last minute. Until then, send them home. Send them home with cash. Lots and lots of cash. Basically, give these people the absolute best last days with their families. Make it idyllic, and impress upon them the fact that, if they truly love these people, they shouldn't tell them what's coming. Just hug them, kiss them, tell them you love them, and then promise you'll be back in a few days. In short, give everyone the goodbye they wanted. Of course, every special gets to bring exactly one other person with them. Really, these specials can't be the only people in the dome or there's really no reason to have the dome, so if each of them gets a plus one, not really a big problem. Except Mrs. Norman. For whatever reason, Mr. Norman absolutely is not allowed because he has some something or other that would endanger the colony. Mrs. Norman has to come, otherwise it would look bad, but she can't bring her husband. Also, these secondary specials do not get to know that the apocalypse is coming or you'll have the same problem with them. These secondaries only get to know that they are going somewhere with their lovers/best friends for a few days. Also, just a thought here, but make sure your Twitter stars can actually talk to people. I mean, I don't know who these people are, but there is that not-baseless stereotype about amazing online personalities that simply cannot deal with actual in-the-flesh-people. If the point of bringing them into the dome is to entertain the inhabitants, make sure they will actually be able to once the internet goes down. I know this creates a secondary population of seemingly useless people, but really, we don't fully understand what makes a person's genes worth keeping. It's possible that hidden in the genetic folds of "dat ass" is coding for incredibly IQ, or massive strength, or some other unexpressed trait. Every person holds the possibility of a beneficial mutation or genetic twitch, and just as you shouldn't breed two natural-bob-tail Australian shepherds, you shouldn't breed only the humans humans decided should be bred. We simply don't know enough, so even if you wanted to optimize the gene pool, you should include a few wild cards, and you might as well kill two birds with one stone. If nothing else, they can be taught useful skills. If absolutely nothing else, they'll breath carbon dioxide for your plants. For general vetting purposes, these same rules apply. Figure out exactly what you need, find the best people for the job, tell them as little as possible while conveying what they need to know, allow them to bring ONE person if they so choose, and give them the best good-bye period you can. As for what you'll want, picture a scaled down United States. You'll need a governing body, enforced by a police structure of some kind. You'll need food workers from growing to processing to cooking. You'll need sewers and weavers and builders and herdsmen and blacksmiths. The important consideration is how big the dome is. However many people it can support at maximum, figure on half that population, then half of that population is your specials. The secondaries will all be apprenticed to an appropriate occupation. If you end up with people who refuse to cooperate, kick them out into the post-apocalyptic wasteland. Moreover, let them know that if they get the boot, their loved one does as well. [Answer] Distribute N unique fist-sized rocks randomly across the country. Announce their locations and declare that anyone showing up at the gate carrying one gets in along with four other people of their choice. And then let them in when people show up. The combat and cunning required to make it to the gate will give you a wide cross-section of humanity, include people who are driven to survive, healthy enough to travel, and fairly selected. [Answer] The vast majority of normal people would prefer survival to death, so getting the plebs in line is as simple as saying you are only taking X people. You will get 100\X people to show up, demanding they be saved (make sure you have a military ready to handle these people). You can be extremely picky, and write a policy for the general public (doesn't apply to your VIPs) for who gets in and not. And if anyone complains, the Kanye-Teroid will take care of them. Now to your specific edge-cases: ## Mel As a software engineer, I can tell you that you don't need Mel. You need a good senior engineer who is unattached and not a religious nut, a solid test environment, and another good senior engineer who is unattached and not a religious nut....heck, give them a couple environments to test things in, you don't want to cheap out. Also, there's probably a simpler solution to your problem than "crazy code only one person ever can understand." Relying on "crazy code only one person can ever understand" is a failure point. I'd take my chance with the Kanye-teroid. Even with redundant engineers, I've saved you 23 people (and they were kids at that). You can even give each of the engineers a harem of 6 mates and still come out ahead by 11 people. ## Dianna If for some reason being gay is against your code, find one of the other "few" people who can do what Dianna does and get them to the Ark. Otherwise, there's no issue. Let both Dianna and her new missus in the Ark. As mentioned above, super complicated air filters only a few people in the world understand is a failure point, and there's probably a better way. ## Shifty Steve and Lil’ Marco Promise Lil' Marco a spot, and instead take him to a bunker and shoot him. Or, better yet, kidnap Steve and spend the next year harvesting his spunk and shoot him too. ## Rachael Straugnum–Alina and her boyfriend who she loves very dearly (he’s bae-goals) The good thing about crops is that they are really easy to reproduce. Also, as said above, miracle crop only one person understands and can grow ever is a failure point. ## Lieutenant Brown This guy can't be the only person capable of running the colony. If he is truly the only person that can do it (see failure points above), then hire a biker gang to kill his army buddy, have a big trial and ask Brown what he wants done to the bikers. ## Secretary Thompson If he's in charge, what does it matter? ## Mr. and Mrs. Norman What do you know, that biker gang killed two people instead of just that old army guy. Also, what is with this world that there are so many areas of science critical to this colony that only one person understands? I would think that there's only so much crazy that can go into a building. ## @LUClDITYxo Hell is living with only one comedian. Besides the GDP will drop a lot after the Kanye-teroid hits. Find some people with useful skills who are also funny. ## Your Real Issue Your colony, as described, has a lot of points of failure, and a lot of "hit by a bus" factor. If one of these people dies before they get into the colony, or a freak accident in the colony happens, then you are in a bad shape. Each of these points of failure should have 2-3 people capable of doing the job, and the ability to train more. What happens if Mel has an aneurysm? Shifty Steve gets AIDS from all the hookers and drugs? The twitter person isn't funny in more than 145 characters? [Answer] The only way to make the policy workable is to take the loved ones as well. If you're going to build a long term self contained colony you also have to think about the psychological wellbeing of the personnel, that means relationships, it means friendships, it means not taking people who are going to really get other people's backs up. You can't ask people to leave their lovers and children behind, you have to take them as well. For each person you want to take, you need to take the entire immediate family. If this hasn't been considered then whoever ran the project is an idiot and deserves to fail epically. You can leave the pseudo celebs behind, especially when you're talking about leaving all the ordinary people anyway. Much more important to take Randall Munroe. Apart from the useless pseudo celebrities, you're unlikely to get much dead weight. People in the intellectual upper 10% don't tend to hang around with people from the bottom 10%. Whoever they ask to bring is probably going to be useful in the long term, if not the short term. And even then, any colony requires rubbish collection and cleaners, hairdressers and telephone sanitisers. There's work to be done that doesn't require an IQ of over 130. --- Let's consider team selection, since that's the game we're playing here. In my spare time I do team sports (I know that's terribly bad form for a geek but that's how I roll) and as often as not, I'm the team captain so I have to choose my team. 1) The best player. He knows he's the best player, he likes to make sure everyone else knows he's the best player, you've all met him, he has the looks and the ego to match, but he's not the best player because his ego gets in the way of him being a team player. So he's out and still doesn't understand why. 2) The guy who turns up to everything and never seems to get any better. He might be in or out, depending how much other people like him, in my case he's a real charmer and usually goes. I took him to the last tournament and he played an absolute stormer, it happens. 3) The really good player with a +1 who will only play if she can as well, but she's not as good. This is where I'm leading to with this example because it's the one that matches your situation. This player isn't one person but two, sometimes two who work really well together even if the individual skills aren't up to the spec of no 1, the average and team benefit is greater than taking any two others. You're not considering the skills of the individual but the combined skills and combined resource drain. The guy with a wife and a dozen kids, is he really worth 14 places when compared to a guy with 2 kids who's nearly as good? Probably not, if the second guy's wife has a similar or complementary skillset, definitely not. Every single position and person has to be considered like this. Not as a single person, but a combined skillset and cost of the total group. Is Steve worth Marco? That's up to how much you want Steve, but at one in a million, I suggest taking one of the other 300 candidates in the country. The answer in most cases for special requirements versus someone else who's nearly as good but lower cost, probably not worth it. Ultimately what this comes down to is that, as with any team selection, there are people who, on paper, you'd like to take, but you'll have to leave behind, and people who wouldn't be your first choice, but ultimately you will be taking them. People aren't numbers, you can't treat them that way, and the tighter your resources the more you'll be spending on reviewing each person as an individual, not under a general rule. [Answer] First: Leave the celebs and criminals at home, so no LUClDITYxo, no Shifty Steve and Lil' Narco. They don't add up anything usefull Second: IMH, you can leave Mel behind, because he'd come with 24 mouths to feed and why are there piranhas in a colony water supply that cannot be kept out by a simple fence? Bring Dianna, don't care if she's gay, here wife and all other civil engineers who are as good as her, we'll definitely need them in the new home. Bring Rachel and her boyfriend. Agricultural scientist may come handy if you want to plant crops. Bring Lt. Brown and a dozen of other young soldiers. Even if we may not have to fight in the new colony, they're valuable workers. Bring Secretary Thompson and his sugar babe. Otherwise the whole ark will be blocked by his ego. About policy: Every mentioned person may bring their kids, brothers and parents as long as they're not older than 50. This way the colony as a good balance of workforce and experience. Young engineers may have great ideas, but they all are worthless if they don't know how to hold a shovel, so you also need experienced workers. Third: Bring experts from every scientific field, amount depending on the size of the ark. Bring cooks, but no 5\ guys, but ordinary cooks who know how to make a good stew. And at least one barkeeper. For reasons. [Answer] I think let the Ai did it. Count every important person that would be needed including some who should do the hardwork, but also lets make the Ai cross analyze their social media, and criminal records (if we want to restart the earth, make sure we just bring the good seeds). Last, make sure the system can work with no human interference, and no one can change it, and don't let the programmer knows what the Ai real use. So lets not get everyone with the drama of who should or shouldn't be in the ark. Lets make it cold but fair, that some of us will be picked by force of the machine and put there to prolong humanity whether we liked it or not. [Answer] I still don't understand why you need a policy more detailed than immediate family with a review board for borderline cases. But if you need to automate it you just need to give a numeric value to each person's value to the colony then get the average of your group, then you compare your numbers to see who gets in. example: Mel is a 6 (skill only partially useful in colony) with a his wife having no beneficial skills (and maybe a negative for the religious thing) being a 1, each kid is a 1-2 depending on age. that makes mes group. 6+1+24(1.5)=43 43/26=1.65 Dianna is a 9 (skill useful in colony and after colony, exemplar in the field) and let's say her sig other is a 3-4 becasue she is lets say a school teacher. useful but not exemplary. so Dianna's family gets a score of 9+3.5=12.5 12.5/2=6.25 So mel's family is a 1.65 vs Dianna's 6.25 clearly you take Dianna and leave Mel. in fact Mel is not getting in even with a personal perfect score. You need to work up a ranking system but that's not too hard. Starting points 1. dead weight 2. potentially useful/ self sufficient 3. useful skill set Modifiers -1 poor health/genetics -1 negative criminal history/ negative social effects -1 History of violence +1 exemplar in the field +1 positive social effect: musician, comedian, ect +1 instrumental to colony construction or other special consideration +2 Critical skill necessary for rebuilding +2 Critical skill necessary in colony function +1 Skill may be necessary under unusual circumstances [Answer] As far as a policy to deal with your reluctant recruits, how about this? STATE OF EMERGENCY Assuming that enough of the government is functioning to be able to even build the dome and transport people there (there will be people involved in both tasks that will do so KNOWING that they will die), you are going to have some functional security forces of some kind. In a state of global emergency, normal rule of law can safely be considered to be suspended. If your "smarty pantsy boovs" ("Home" reference) refuse to cooperate, a team of highly skilled special operators will be deployed to GET them to the dome one way or another. These guys are professionals. They will not kill the target, but there is basically no way the target will escape without a tranquilizer dart in the neck from a hidden vantage point. Still having problems? EXECUTE one of them and publicize it! Announce that they refused to play ball, so they were posing a risk to the survival of the human race. As such, they were REMOVED. Let everybody know that this can be done the easy way or the hard way. They will fall in line. Don't give them the option of running either. Keep them sedated until the Event is already in full swing and the dome is sealed. What are they going to do then? Actively try to sabotage the thing keeping them alive? No, they won't. Keep a couple of your "professionals" around in the dome for later (plenty of space; we have eliminated the need to pander to each of their different requirements with stuff like 20+ offspring). Before The Event, let the guys on the hunter-bagger teams know that the 2 best performing teams will be brought into the dome later. That gives them an incentive to be loyal beforehand and you get a nice little internal enforcement group for later. Now there are lots of arguments about genetic diversity and such. Sure that is all well and good and no doubt some smarty pants scientist has decided what the "optimal" mix of people are and there are likely a few examples of various people there just for the sake of genetics. That is no reason to go letting in whoever a particular special snowflake feels attached to. We are talking about the GOVERNMENT here, right? Since when would it just bend the rules of the All Knowing Bureaucracy on a case by case basis? No! The government would decide what constitutes genetic diversity, it would fill that requirement, and then it would go GET any reluctant snowflakes so selfish that they are putting humanity at risk by not complying! Tyrannical? Yes! Efficient? You bet your butt it's efficient! ]
[Question] [ I am imagining a water covered planet. There could be a few pieces of land scattered here and there, but >99% of the planet's surface is water. There are various ecosystems and biospheres where a race of super intelligent octopus-like creatures have risen the evolutionary ladder. The steps it took to get there don't need to be explained unless you feel like it. These creatures have pretty much the same physical and emotional needs and are social creatures just like us, only octopus shaped (meaning soft, invertebrate with extremely dexterous tentacles (I guess 8, but can be more or less)). Assuming that they have evolved to be technologically equal to present day humans AND that on a whole they decided that permanent shelters where a good idea, how would their urban centers differ from ours? Mainly, how would the construction of the buildings differ? Would it be more efficient to anchor them to the sea floor or to a floating buoy? What would be a possible building material (I'm unsure on how pouring concrete underwater works)? Bonus question: In this world, suppose an earthling human felt like taking a vacation in one of this underwater world's best 5 starfish hotels (He is the first non-aquatic being to visit this planet). What should he pack (other than scuba gear and extra oxygen tanks) to have a great holiday full of high-jinx? [Answer] One way their urban centres would differ is how a city is vertically laid out. For us the only way to the top floor of a skyscraper is to climb the stairs or go up in the lift. However your octopus can just swim up to any floor it pleases. So there will be entrances and exits for the entire height of a building. (Your human visitor will need a 3 dimensional map or he'll get lost). Windows and doors may be pretty much interchangeable. A door is just a window with the shutters closed. Other vertical things to think about: wave base and light. [Wave base](https://en.wikipedia.org/wiki/Wave_base) is how deep in the water the action of waves happens. Above it, your building will be battered by the waves as they pass overhead. Below it, you are out of reach of the waves, so your building will be unaffected. Therefore, buildings which you want to be safe from the biggest waves (a school or hospital, for instance) will be built at depth. Poor folks may have their homes in the shallows, where they are always being torn to shreds by storms. On the other hand, light decreases with depth. That hospital may be safe, but it will also have much less light coming in the windows. The octopus folk will need artificial lights and/or will have eyes adapted to the dim light of the depths. Our ocean is full of reef-building animals: various corals and molluscs. The octopuses can exploit these to make their homes - rather like planting hedges. However, they'll only be able to do that in environments which suit the reef-builders. Corals need shallow, warm water which is low in nutrients, for instance. There may be regional differences in construction because of this. UK octopuses use mussels and oysters, Australian octopuses use coral. However, corals, mussels etc are very slow growing compared to how fast a human can make a log cabin or get a bricklayer to build a house. The octopuses may need to weave houses out of kelp, or use mussel [byssus thread](https://en.wikipedia.org/wiki/Byssus) to cement rocks together. Barnacles also have a very strong cement, so they could use that too. Both of these have evolved to [set underwater.](http://optics.org/news/5/7/35) [Answer] > > The steps it took to get [to civilization] don't need to be explained unless you feel like it. > > > Since Caleb has already addressed this, I will skip it. > > How would their urban centers be different from ours? > > > Like us, urban centers would be hubs for trading. They would buy and sell goods and services, such as: food, fish-farming supplies (feed, rope, cages, traps, etc.), materials for habitat, seeds or baby plants, information pertaining to travel, and education. Importantly, it would be a center for mating. There would be extremely popular nurseries open for the millions of eggs laid each month. The rich may choose to house all of their eggs, whereas the poor may only be able to house three or four (and so have a difficult process choosing which eggs to nurse). 'Buildings' may be much more loosely defined than ours. An urban center very well may be a healthy coral reef. There could be floating travel platforms for long-distance movements along currents. Imagine a very large, cloth, thrown into the ocean with pockets sewn into it. Some pockets contain air (to maintain buoyancy). The rest are used at discretion. Here, octopi may attach cages to bring fish for eating with, pouches to store feed and small objects, and pouches to sleep in. An important question to ask yourself is: do my octopi have beasts of burden? Because electricity is difficult to harness underwater, the presence (or lack thereof) of beasts of burden may be a defining point in this civilization. (Keep in mind that some historians say that the lack of beasts is what kept the South American ancient civilizations comparatively limited.) [Answer] So I want to start off by asking how well you considered the idea of underwater creatures using electricity. I don't think that it is actually possible to generate and use electricity underwater unless you previously developed insulation techniques. The extreme conductivity of the water makes any early experimentation almost 100% lethal. But now that I have that off my chest, I will continue by answering as much as I can. The big stumbling block in the development of a civilization is probably the creation of manufactured metal goods. After that, everything is easier. Thing is, octopi don't have bones. And bones are preferable for using human-style tools. So The octopi will probably need to make small tools with multiple purposes. As I said, though, processing metals for tools is very important, so they will need forges. Now, you can't easily build a fire underwater, so I suggest making a forge, which would be a centrepiece for this kind of civilization, on top of a volcanic vent. This kind of thing would certainly be anchored. Another highly important building is a place for octopi to sleep. I imagine that with the harder life the octopi are doomed to have, materials and food are generally shared, so living spaces can be confined to a place to sleep. But since octopi are invertebrates, all you need is a large object with lots of little holes, some bigger to house families or mating couples. I think a basic chunk of coral would do just fine. A reef would also provide food, so we have that problem solved as well. Having very little waste and with pooping in the ocean being no problem, no sanitation department is needed. Neither is transportation for distances of under a few miles, as swimming outdistances most vehicles quite efficiently. Cultivation and farming underwater looks a lot like it does above water. Scared away predators to the farm fish, cage or otherwise enclose said fish, let kelp grow and then harvest it. As for distribution, rotting is slower in saltwater, so a hollowed out boulder or some such should do, plus you can supplement your diet with passerby fishes. Transportation long distance seems somewhat important. Since buoys are moved by both current and wind they could make excellent vehicles when properly piloted. As for building materials, I would say to just use coral and rock. "The elements" are a lot less harsh on your stuff down here, so specifically manufactured building materials or cement are unnecessary. Another thing going for our octopus friends is their squishiness. Doors can be only centimeters across , rooms incredibly small as the octopi don't really need much as they are, and of course safety measures are almost irrelevant, considering how easy it is to rebuild and how hardy octopi happen to be. So while I know this isn't the question, I don't think that without fire, wood, or electricity, octopi could actually reach human levels of technology. But the nice thing is that their infrastructure would be pretty simple, as they are already a wonderful evolutionary model. ]
[Question] [ Venus is being paraterraformed with floating cities. Mechanical machines collect material from the surface and send it floating at an altitude of about 50 Km where conditions are more Earth-like. Here the material is assembled into building. The "city" is not in one piece. Each building has its own floating mechanism independent of the others. The city is ring-shaped with buildings moving in a circular motion around an empty center. Some buoyancy is provided by the internal atmosphere which is less dense than the venusian atmosphere. However I want them to use other systems as well, in particular wind. I was thinking in particular of the [Vindskip](http://www.ladeas.no/video.html) concept (The video is short and gives an idea of how it works). What shape/machinery can I give to the buildings to have them harness wind power for flotation? EDIT: Maneuvering is available for the buildings, and some minor propulsion systems can be considered too [Answer] A building, or any other body, floating in the air with no propulsion to move and direct it, will not experience any relative wind. There is no shape that will provide passive lift without relative wind. If you can discover places where the wind varies significantly with altitude, and the wind patterns are reliable enough, you might be able to construct a flying object consisting of two bodies connected by a long cable and experiencing a strong relative wind between them. This would look like two kites or wings facing each other but at different altitudes. The ground speed of the two connected wings would be the mean of the wind speeds, and each wing would fly on a relative wind half the difference between the wind speeds. Here is a rough sketch: [![staying aloft on wind speed difference](https://i.stack.imgur.com/nkDkB.png)](https://i.stack.imgur.com/nkDkB.png) On Venus this would be placed at high altitudes where the atmosphere is energized by the sun. The weather near the surface of Venus is very dark and very calm. [Answer] Spheres. No others need apply. In particular, the enclosure wants to maximise the volume with minimal material, and the bubbles can be made with structural members in geodessy: that is, purely in compression or tension. [This](https://en.wikipedia.org/wiki/Cloud_Nine_(tensegrity_sphere)) is what I thought you were describing. But now (and the question still needs clarifying!) I think you're wanting what's essentially an airplane powered by wind: that's not possible. If you want a kite, it needs to be tethered. [Answer] Your spinning disc sounds a lot like the classic "Frizbee" toy. There are a lot of variations including ring shaped ones, so in terms of aerodynamics, a spinning ring with the proper airfoil shape should be able to fly in the Venusian atmosphere. [![enter image description here](https://i.stack.imgur.com/pnfAF.jpg)](https://i.stack.imgur.com/pnfAF.jpg) There are a few factors to keep in mind. Unless the structure is very large (many kilometres in diameter), the spin rate will induce a lot of stresses on the people and buildings inside. In the extreme case, the ring is rotating so fast that the buildings are oriented with the "floor" pointing at the outside of the ring and the ceiling pointed towards the open centre, you are creating "artificial gravity" like a space station. If, for simplicity and to keep the mass and maintenance to a minimum you have the buildings fixed to the floor of the ring, then the rate of rotation needs to be fairly low. People walking inside the ring will still experience forces induced by the spinning, but if it is low enough, they will be able to compensate. The second issue is "how" the ring keeps spinning. The Frizbee gradually slows down as air friction steals the momentum of the toy after you release it. The colonists are not going top be too thrilled as the rotating forces are substituted for free fall into the depths of the Venusian atmosphere..... Several ideas suggest themselves. The ring will need a series of motors around the perimeter to drive the rotational force. Since the atmosphere isn't too conducive to combustion (and sending fuel to keep such a large structure rotating will be an immense task in itself), you could have the upper surface being a microwave receiver and solar power sats in orbit are beaming electrical energy to the structure. Some is tapped to run the internal systems and the rest keeps the motors running (probably electric engines spinning huge ducted fans or propellers). Another way to go about this is to consider a tether from the mining site on the ground. The tether is used to send mining buckets to and from the ring, but it might also be part of a thermocouple system, with the temperature differential between the ground and the ring being used to generate electrical energy. This avoids the complications of a solar power satellite, but the amount of energy will have an absolute limit based on the difference between the two temperatures, and the efficiency of any system to tap energy will always be less than 100% anyway. For aerodynamic reasons, you want everything to be enclosed in the ring shaped airfoil, since protrusions and gaps between objects will simply induce drag and make spinning the ring much more difficult and energy intensive. One other consideration for any sort of floating colony in the atmosphere is how are the people going to get too and from space? a spinning ring or a giant spherical balloon like a "Cloud Nine" is going to make a very tricky launch or landing platform. ]
[Question] [ Tangentially related to [The evolution of neon kittens](https://worldbuilding.stackexchange.com/questions/37777/the-evolution-of-neon-kittens) Is is possible for a star to radiate in the ultra violet spectrum but not much in the visible light spectrum? If not, is there any mechanism that would block a lot of the visible light spectrum while still allowing ultra violet to pass through, or change the visible light to UV like the coating on a black light bulb, but on a planetary scale? [Answer] Theoretically, yes. At least, according to our friends over at [Astronomy](https://astronomy.stackexchange.com/q/6210). According to them, an exceptionally cold star (for a star, of course) won't emit light in the visible spectrum, and neither will a star with a massive gravitational redshift. But, as Lacklub points out, both of these factors will cause a redshift in the light emitted by the star. What we need for this to happen would be a [blueshift](https://en.wikipedia.org/wiki/Blueshift), the opposite of a redshift. A blueshift occurs when an object moves towards an observer. Hurling a star at a planet seems hazardous for the native cats, so let's try something else. A blueshift also occurs when a photon is falling into a gravity well. If the planet had a significant gravity well, light from the star would appear in the ultraviolet spectrum. (Note: hypergravity not considered conducive to felines.) Of course, you (well, anyone belonging to a society actually on the Kardashev scale) could always install a mechanical shell around the star that adds energy to the outbound photons, thus inducing an artificial blueshift. Which leads to the questions: Who built this thing? And why? [Answer] There are problems with two of your ideas, but one of them could potentially work. > > Is is possible for a star to radiate in the ultra violet spectrum but not much in the visible light spectrum? > > > This really isn't possible due to the nature of light. As you may know, the wavelength and frequency of light is inversely proportional - the higher the frequency, the shorter the wavelength. The energy carried by a photon is proportional to its frequency, as you can see in this [table on Wikipedia](https://en.wikipedia.org/wiki/Electromagnetic_spectrum). Ultra violet light has a higher frequency than visible light, so each photon in the UV range carries more energy than a photon in the visible light range. In order to emit UV light the source has to have more energy available, which means that there is also more energy with which to emit more visible and infrared light. Something else that makes this not work that stars by their nature contain a variety of elements. Having a variety of elements is why the spectrum a star outputs is very broad. There's also no way to avoid having this variety - the nuclear fusion powering a star creates more elements. > > change the visible light to UV like the coating on a black light bulb > > > This isn't actually how black lights work. [Black lights work by blocking visible light with a black paint that lets UV light through](http://science.howstuffworks.com/innovation/everyday-innovations/black-light1.htm). They do a little bit of the reverse though - they include some phosphors that absorb higher-energy UV light (the kind that is more dangerous) and re-emit it as lower-energy UV light. So for the most part, they are equivalent to the idea of blocking visible light and letting UV light through. > > any mechanism that would block a lot of the visible light spectrum while still allowing ultra violet to pass through > > > This could work. As I just mentioned, black lights work by doing this. It's conceivable that you could have a more volcanic planet that tends to spew out some material into the atmosphere that blocks visible light but not UV light (with infrared optionally being let through as well). I don't know what compounds would be best at doing this. Of course, with most visible light being blocked, plants aren't going to be able to grow. Life on Earth has photosynthetic life at the bottom of almost every food chain. However, on a volcanic planet it's plausible to have a greater abundance of chemicals that can be used in [chemosynthesis](https://en.wikipedia.org/wiki/Chemosynthesis) - using certain chemicals as the basis for energy needed for life instead of using sunlight. Also, any life that did develop would likely be incapable of seeing what we consider visible light - even with florescence, the amount of light that would be produced would be less than the available UV light. They'd be much more likely to either see infrared and/or UV. [Answer] May I suggest a [very very dark planet](https://en.wikipedia.org/wiki/TrES-2b)? For all those who haven't heard or read the name TrES-2b, please please don't click on the link I have posted above :( Basically it is a planet that that an atmosphere so horrific and ghastly, that it reflects less than 1% of the light that falls on it. I am not certain about UV spectrum, but since UV rays are on a higher energy level than visual spectrum, you just might have UV rays getting to the surface of the planet while all visible light gets absorbed in the atmosphere. Now if you had such a dark planet, which was not as much of hell as TrES-2b is ... [Answer] In general if a star follows <https://en.wikipedia.org/wiki/Black-body_radiation>, is very very hot, very very far away and moving very quickly towards the observer, it could emit in the UV strongly but not very much in the visible. ]
[Question] [ I'm looking for some data to create my own sci-fi setting, but I want to base it on real world as much as possible. Also, I don't want to come up with any arbitrary year like 3290 with no background on it. I thought a lot about it, but I still can't find a good answer. What I want is a setting where the following apply: * Humans can live outside Earth. Deep space stations are minimum, colonies on habitable planets are welcomed. I do not expect terraforming to be common, * Faster Than Light travel is a thing. I don't care if it's BSG's FTL drive, Star Trek's Warp Drive, Alcubierre drive or any other kind of tech, * Long range communication of any kind is possible. (Almost) instantaneous communication should be possible within one planetary system, and possibility of interstellar fax/emails would be nice, * Nothing prior to current date and tech level can be altered, * Tech progression is logical and feels natural Question is: If I want to create a sci-fi setting that meets all conditions above, what year would suit it best? Any additional arguments are very welcome as well as science/physics background for tech. [Answer] As I see it, there are probably four main milestones in the progression of a given technology: 1. The theoretical principles are discovered 2. A "proof of concept" is achieved 3. The technology is engineered to the point that it's actually useful 4. The technology is engineered to the point that it is affordable/marketable The various different technologies you've described sit at different stages of this progression right now, and it sounds like you'd like them to be at stage 4, or at least stage 3. Humans can already live in space, for example, as long as a government is paying for it (and all the other logistical requirements). This places space stations at a tentative stage 3. Permanent habitation/colonisation of hostile planetary environments is somewhere between stage 2 and 3, depending on what factors you want to consider, and how hostile an environment you're thinking: we have most of the technology, and we've managed to live in the fairly nasty conditions in Antarctica for a long time now, [but not all the attempts at a fully closed system so far have gone entirely smoothly](https://en.wikipedia.org/wiki/Closed_ecological_system). Your third requirement, instantaneous communication at a distance, is at least equivalent to FTL transportation, if not harder (see comments), or stage 3 if you're happy to limit yourself to speed-of-light communication via electromagnetic means such as lasers. But your second requirement, FTL travel, isn't even at stage 1 – pretty much all of the potential pathways have more detractors than supporters. The reason I raise all of these issues is because I'm trying to come up with a way for you to operationalise estimating dates. The thing that makes that difficult is that there's no way of knowing when stage 1 will happen – a breakthrough could happen at any time. You could maybe take into account precursor technologies, but in the end one guess is as good as another. They could announce a workable principle next week, but it's just as likely that after a few years of trying to come up with a proof of concept it could fall apart, leaving us back at stage 0 again. In other words, you can pick whatever date you like – but your decision might be informed by the timeframes of the other requirements, which might be a little easier to rationalise. To figure out how long it takes to prove a theory is workable and bring it to stage 2, and in turn how long it takes to go from there to stage 3, and then on to stage 4, I'd be looking at history. There are a whole bunch of different timelines in our own history of science and technology, you can pick whichever feels right to you and probably convince the reader that your technological advancements followed a similar course. ### Steam power * Stage 1: – 1st century AD * Stage 2: – Somewhere between then and [1690](https://en.wikipedia.org/wiki/Denis_Papin), depending on who you're asking * Stage 3: – [1698](https://en.wikipedia.org/wiki/Thomas_Savery), Thomas Savery's commercialised steam water pump. * Stage 4: – Probably 1760-1840, the Industrial Revolution You might consider this a very conservative/slow timeframe. If FTL followed this path, and we discovered the key principle in the very near future, people wouldn't be flitting around between stars until about the year 4000. Keep in mind though that we might have progressed a lot faster if we didn't keep destroying civilisation as we knew it, burning all our libraries, murdering our scientists and philosophers, and starting again... ### Computers Before I start here, keep in mind that computers as we know them are dependant also on the invention of electricity, and more fundamentally, the invention of mathematics and logic. Let's leave those out, and for the sake of argument let's also leave out the first single use mechanical calculators like the [Antikythera mechanism](https://en.wikipedia.org/wiki/Antikythera_mechanism), and focus on what we might as well call Turing machines. * Stage 1: – 1833, when Charles Babbage realised a "general purpose computing device" might be possible * Stage 2: – 1910, when Babbage's son managed to build part of an Analytical Engine, capable of (incorrectly) calculating a few digits of π * Stage 3: – Highly debatable, but it might be 1943, the [Colossus](https://en.wikipedia.org/wiki/Colossus_computer), as though it was not Turing-complete it was programmable, and definitely solved useful problems. If we want the first true Turing-complete, general purpose, can-solve-any-problem-given-sufficient-time-and-memory computer, that would be [ENIAC](https://en.wikipedia.org/wiki/ENIAC), whose completion was announced in 1946 * Stage 4: – Computers in businesses/univerisites: 1951 onwards; First personal (hobbyist) computer: 1975 [Altair 8800](https://en.wikipedia.org/wiki/Altair_8800) or [Olivetti P606](https://en.wikipedia.org/wiki/Olivetti_P6060); First 'consumer grade' computer: This gets a bit fuzzier, as there were countless competing products by this stage, but maybe the 1982 [ZX Spectrum](https://en.wikipedia.org/wiki/ZX_Spectrum) which was affordable and sold over 5 million units, not including clones. At this (accelerating) rate of progress, FTL travel would be accessible to large corporations by about 2130; Civilian space habitation might be a thing from 2050 onwards, and with people living at those kinds of distances, there'd definitely be motivation (and believable likelihood) to have at least light speed communication down to a fine art within a similar timeframe. This is all oversimplification though, as it's thinking only in terms of theories/ideas, not resources, safety, economics or human psychology. My real point is that it's your story, but if you stick to the general "feelings" of progress that we've seen so far, you should be able to achieve verisimilitude. Keep in mind that FTL travel reaching stage 4 might never be believable to a particularly critical reader – even if it were possible to put a starship in every household, it probably wouldn't make sense to do so. No matter how refined the technology involved, FTL drives in fiction still usually require exotic fuels/materials, so the purchase and ongoing costs may never come down below that of say, today's jet aircraft. And what would even motivate people to travel those kinds of distances? What can't they do closer to home? Star Wars has this kind of world, but a lot of other SF assumes that only governments, corporations and maybe the mega-rich would have any interest in travelling interstellar distances, let alone the finances to do so. Still, some people have private jets today. (Edit: In light of some good points raised in the comments, I may have conflated too many things when discussing stage 4 FTL. Business use of some technologies becomes widespread while personal use may never become feasible and/or desirable. I shouldn't conflate extensive commercial utilisation of FTL with a sporty FTL corvette in every space-garage; in fact I can't name any serious science fiction that actually implies the latter. This is where the steam engine analogy becomes more representative than the computer analogy, I think. Still, I'd allow for a significant period of time between governments/megacorps developing/deploying workable FTL ships and average Joe/Jane Hauler getting their grubby salt-of-the-earth paws on them.) [Answer] Assuming that FTL travel and distance-irrelevent communications are possible in our universe, the trick to building your civilization will start with figuring out how they work. Fortunately, our ability to figure things out is growing at an accelerating rate. Our cultural intellect has recently grown a nervous system which will increasingly help us work together on our goals. The internet has also made us more aware of each other's challenges and if we are worthy of the future you predict, we will have to use that awareness to make our world better for everyone. Once we are united, no scientific fact will hide from our combined intellect for long. So step one on our way to the stars is world peace and global prosperity. Can that happen in a hundred years? Probably not, especially with the resource shortages which are approaching fast. We will spend another century or two killing each other, before we start working together. From there, a couple of centuries to crack FTL and put it into common usage. That gives us colonies on other planets and allows us to repeatedly double our numbers. As our population grows, so does our combined intellect. That brings faster FTL and more colonies and more intellectual growth. Eventually, we might even be able to figure out distance-irrelevent communications, and the interplanetary internet will be born. So, somewhere around 500 years from now... give or take a few centuries. Now alot can go wrong along the way and it is more than likely that we will take much longer to reach your goal. But if it is possible, then we will do it and once we do, we will just keep accelerating, spreading out and exponentially growing in both numbers and minds. --- off subject but possibly helpful to the OP --- Rather than trying to calculate the exact date of our race to the stars, why not do what others have done before you. Take shelter in the idea that Earth-based calendars and time measurements will probably not survive much longer. Why would they, once we have colonies on other worlds? Just create a star-date style calendar with no specific ties to our current system. Then, your stories can be self-consistent upon that new calendar, and you never have to tell us how long it took us to get there. [Answer] It's not really possible to give you any concrete information, since we don't know how the future will turn out, but here's my thought process. Basically, I'm going to focus on the FTL stuff, since everything else is kind of cake next to that. TL;DR. I'd estimate 10-50 years for NASA to find a working FTL prototype at tiny scales, 50-100 years to get enough funding and energy to test full-scale prototypes, 100-200 years to get colonies around the solar system, 100-200 years to put people in another star system, and 100-300 years to have a real extra-solar civilization. Total timeline is then 360-850 years if Earth learns to work as a team. Timeline could be thousands of years to never if we don't. Energy Requirements for Proposed FTL FTL may never be possible. All of our current models say it's either impossible or at least not practically meaningful (not much point in traveling faster than light if what shows up is a nuclear explosion instead of a person). So let's assume NASA's current research on warp drives pans out. Last I heard, just opening a warp bubble was something like a bus worth of antimatter. [Wikipedia](https://en.wikipedia.org/wiki/School_bus) says a school bus is 4500 to 16000 kg. From $e=mc^2$, we can see that's $4\cdot 10^{20}$ to $1.4\cdot 10^{21}J$ 1. Let's split the difference and call it $10^{21}$J = 1 zettajoule. [WolframAlpha](http://www.wolframalpha.com/input/?i=10%5E21+J) tells us that's about as much energy as we get in 1.6 hours of sunlight across the entire surface of the planet, or $1\over 7$ of the energy in the world's oil reserves or $1\over 6$ of the energy in the world's natural gas reserves. Effectively, we'd need every last scrap of natural energy on the planet just to test the thing. Our only options will be magic or solar power. Current solar panels can operate around 40-45% under ideal circumstances. Let's say we push that up to 50% for mass-produced panels somehow. Now, near Earth, we have about $1350{W\over m^2}$ $={J\over s\cdot m^2}$. So we can get a lot of energy by either waiting a long time, or building a really big solar farm, or both. Let's say 1 year is an acceptable timeframe to charge a warp battery. That's $50\%\cdot 1350{J\over s\cdot m^2}\cdot 86400{s\over day}\cdot{365.25(ish) days\over yr}\cdot 1yr$ $=2.1\cdot 10^{10}{J\over m^2}$. Ok, so we need $10^{21}J\over 2.1\cdot 10^{10}{J\over m^2}$ $=4.8\cdot 10^{10}m^2$ of solar panels that are constantly pointing straight at the sun. Or around 76% of West Virginia ($6.3\cdot 10^{10}m^2$). Now, it seems likely we would want all those solar panels in orbit around the Sun, so they're getting maximum insolation at all times. [This blog](http://purepointenergy.blogspot.com/2010/09/solar-panels-threatening-to-collapse.html) says solar panels are around $2$ to $3{lb\over ft^2}$ $=12{kg\over m^2}$. So we need to lift $12{kg\over m^2}\cdot 4.8\cdot 10^{10}m^2$ $=5.8\cdot 10^{11}kg$ of solar panels into orbit. According to [this SE answer](https://space.stackexchange.com/questions/1989/what-is-the-current-cost-per-pound-to-send-something-into-leo) the cheapest we can do is about $\$2000\over kg$ into orbit. That's $5.8\cdot 10^{11}kg\cdot {$2000\over kg}$ $=\$1.2\cdot 10^{15}$ or about 100 times as much as U.S. citizens make in a year (before paying taxes, bills, etc.). Then we need to take solar panel production cost into account. [This PV site](http://solar.smps.us/solar-panels-cost.html) says the panels themselves are 30 to 35% of the installation cost, and [this other PV site](http://www.thegreenage.co.uk/tech/the-cost-of-a-solar-pv-system/) says a $28 m^2$ system costs around £7000 = \$10000, or about $\$340\over m^2$. This is insignificant compared to the $\$24000\over m^2$ we need to get it into orbit, so there's no need to add them. However, it does suggest that early FTL might be better powered using ground-based solar power that takes longer to get the same energy but costs about 1% as much to generate. Logistics of Getting Energy Now, I'm not an economist, but those are some pretty hefty numbers. There's no way the world just says "sure, we'll all pitch in 100 times what the U.S. makes in a year". I'm not even sure we have that kind of resources to throw around. Realistically, we're looking at maybe 1% of that being put towards ever-bigger solar fields over many decades, but multiple countries may be helping out. So let's say 2% to be optimistic. That's 50 years of pumping money into a solar panel farm just to get a maiden voyage going. But there's a problem. Solar panels aren't immortal, so we have to take into account replacement costs. Unfortunately, that math looks really complicated so I'm going to skip it. It probably doesn't matter too much since most panels are rated at 80% after 25 years (says [these guys](http://energyinformative.org/lifespan-solar-panels/)), but it will take longer to reach our goal. On the other hand, solar technology will get cheaper over time. So from the first time NASA is able to demonstrate very small warp bubbles are possible, we're probably looking at 50+ years to get the first human-sized spaceship going on a test flight. Given the nature of politics, it could take a lot longer than that. Expansion and Colonization From here, we need to expand. The problem is, there's really not much reason to explore space except to say we did it. It's really, really expensive, with very little payback. So early FTL is going to be "Yay, we proved FTL is possible!!!!!" followed by a very long period of practically nothing. Eventually, rich people will start paving the way for weddings on Mars, basketball tournaments on Europa, etc. As mentioned in articles like [this one from the UK space people](http://theconversation.com/of-course-space-exploration-is-worth-the-money-42926), we do get some return on investments, in that we're producing jobs by hiring engineers, cooks, janitors, you name it. But we can't just throw quadrillions of dollars at a project and expect it to instantly give a return. It will take a long time to get anything going in earnest. That said, warp bubbles aren't inherently FTL. They can presumably be used for sublight travel as well, and we may find ways to do it for cheaper. If we can turn the 2.5 year round-trip to Mars into a 2.5 week trip (0.07% c), a lot more people are going to be willing to head out there to help with whatever science stuff we want. And if we can find sources of natural resources in asteroids or other planets, we may be able to get some return of investment that way ([this random article](http://www.explainingthefuture.com/resources_from_space.html) suggests asteroids may be highly lucrative for rare-Earth metals -- it also has some ideas about space-based solar power). Still, given how slowly the space programs have advanced so far, we're probably looking at 100+ years before we really get anywhere crazy. I would expect it to take a few centuries before we really have civilizations beyond Earth, although that's really just a guess. FTL Communication If we can do FTL with ships, it stands to reason we can find ways to do FTL with communications, though the methods and speeds will be greatly dependent on the type of FTL. A portable wormhole could allow a tiny beam of light to transmit information nearly instantly once the connection is established, while some kind of warp bubble would operate more like the current postal service. Still, I would expect FTL communications to evolve more or less concurrently with FTL travel. Beyond Sol Up until now, I've been assuming the energy requirements for FTL were about the same as just creating the warp bubble (I really don't know so it could make a huge difference). But trying to cross interstellar space is going to require enormous amounts of energy. Space. Is. Huge. Pluto is about 40 AU from the Sun. Proxima Centauri (the closest star to us) is about 270000 AU away, or 6640 times the distance. More realistically, we'll be heading to Jupiter, at only 5.2 AU, making P Centauri 51000 times as far. Not only do we need more energy to get there, but we need to do it faster. Not many people are going to be up to the task of spending 40 years getting there at 10% c. So if warp drives are less efficient at higher speeds, it makes the energy requirement exponentially worse. So one trip to the nearest star is going to take an enormous amount of effort compared to sending people back and forth to the gas giants a few times a year. If we get FTL going on a regular basis in 300 years, it will probably be another 100+ years before we make any real progress on extra-solar expansion, and a century or two more before we have actual colonies founded there. And honestly, I'm probably being pretty generous. It's quite possible it takes a couple thousand years for this timeline to happen. But that's the problem with trying to predict the march of technology, especially regarding technologies that may not ever be physically realizable. 1Technically, we'd need twice that, since there's antimatter and an equal amount of normal matter getting annihilated, but I already made it through a bunch of calculations and it's all roughly estimated anyways, so I'm not going to bother fixing it. [Answer] Apparent FTL might be possible if we master the science of getting anything close to the speed of light, and live as a complete nomadic civilization aboard a huge starship, similar to what they did in Independence Day. But that'll mean that we'll have to leave Earth behind, so some kind of 'life on Earth is not sustainable anymore' kind of scenario will need to happen. It's sad to leave such a wondrous planet behind, but it might come to that sometime. In that case, the timeline could be anything from 100 years to infinity, depending on the current rate of progress and humanity's natural resource drain. [Answer] See table five from the link provided my Dr. Mark Millis (Tau Zero and NASA) which references a Kardechev Type 2 civilization: <http://arxiv.org/ftp/arxiv/papers/1101/1101.1066.pdf> On the inside, year 2900, middle (more probable) year 3700, longer, year 21000. (Societal Retardation is possible and has already happened for some transportation tech) Namely, rockets, cars, jets... private aviation. Power generation tech.... The power for a Type II is based at 4 x 10 ^26 watts...(which is still lower than the warp formulas yield to warp space to FTL) from our understanding of Alcubierrie, Natario's warp equation work, and even with Dr Whites energy reducing work, these estimated years still may be optimistic for a warping space drive at FTL speeds. Bill Thornton ]
[Question] [ I'm designing an earth-like planet with a relatively similar biosphere to earth's. The explanation I have for the close parallels is mostly a hand-wave: This planet and earth are linked by a number of wormhole-like structures that randomly exchange material from one planet to the other. The exchange of living organisms has affected the development of life on both planets. This planet has dragons (or perhaps I should say 'dragon-like creatures', since in my attempts to make them somewhat more realistic I've nerfed many of the traditional dragon-y characteristics). They are intelligent, but are naturally solitary and therefore do not usually form any kind of societal structure. They are around twenty feet long as adults (though they can grow somewhat larger), are lightly built, and are omnivorous (with a predisposition toward being carnivorous). I'd prefer for them to be warm-blooded if possible; however, if being cold-blooded makes more sense, I'll go with that. So, given that background, would it make sense for a solitary dragon of the kind described above to raise an herbivorous mammal comparable to a goat as a food source (as compared to the obvious alternative of simply hunting for suitable prey items)? Also, if this is viable, what would the ideal breeding population be for such creatures (again, goats are for all intents and purposes an accurate substitute for these animals)? [Answer] There's a significant difference in the caloric needs of endotherms and ectotherms. Large reptiles that regulate their temperature externally can often survive on a single, large meal per year, where the largest endothermic omnivores eat every day, with the exception of when they hibernate. Think Nile crocodile and brown bear. Other issues are that the crocodile has to live in tropical and subtropical regions where there is enough heat to keep it alive, while the bear can live pretty much anywhere. The crocodile also lives a very sedentary life, except for when it's eating and mating. Herding goats would require a greater expense of energy, which would in turn require more goats to be consumed, and thereby necessitate a larger herd. It wouldn't be worth it -- easier just to find one big goat a year and eat it. For the bear, it's a different story. Needing to eat a big goat every week means he's in danger of starvation every week if he doesn't make that happen, so maintaining and defending a herd is a safer option. As far as the goats being afraid of the dragon, that's a non-issue. On earth, goats have a natural fear of wolves, yet domestic dogs, which are a type of wolf, are used in two ways to work goats (and sheep). Herding dogs use the goats' fear of predators to control their movements on the pasture, while livestock guardian dogs (LGDs) are raised with the goats and the goats learn not to fear them. (Note that herding dogs and LGDs are not generally used together, as the LGDs, like the goats, would view herding dogs as predators and would kill them.) The goat can be conditioned not to fear any animal, and it's likely that beyond a certain size threshold, an animal would stop looking like a predator and start looking more, to a goat, like a large herbivore, since the largest animals on earth are herbivores, and it is not uncommon for goats and other mid-size grazers to share the pasture with larger animals, in captivity (horses and cattle) and in the wild (buffalo, rhinoceros, etc.) Also bear in mind that in both ectotherms and endotherms, the larger the animal gets, the greater its volume to surface area ratio, which means that its capacity to maintain body temperature increases and its caloric needs per unit of mass decrease. Since body heat is lost through the skin, the less skin you have in relation to your thermal mass, the less heat you lose. In other words, it takes fewer calories to sustain a pound of elephant than it does to sustain a pound of mice. In my experience a 500 pound tiger or lion eats about its own body weight in meat every month. Since some of the mass of the prey animal is bone, probably 30% on average, we can say that a 500 pound cat would need 7 or 8 100-pound goats per month. I'd estimate the weight of a 20-foot dragon at 4000 pounds at the absolute most. Since it takes less food to sustain a pound of dragon than a pound of tiger, the number of goats required per month might be something like 35-40 goats per month. That means a minimum herd of about 500 does, to be safe, unless you go with a large breed and allow significant time for them to grow. It's a lot of goats and would require a lot of real estate. This is based on 100 pound goats at time of slaughter. You can raise them larger, it just takes longer for them to get to that size. Cattle range as heavy as 3000 pounds, though 1500 for a steer at slaughter is more typical. Fewer animals to manage, but they still breed once a year, so you have to maintain a large number of animals all year long. Rabbits reproduce every month, and can give birth to a dozen kits every time, and can reliably raise 6 kits to weaning time. Pound for pound, they produce the most meat with the least feed of any livestock, because they are so prolific. If I was inventing animals, for this purpose, I'd make them like very large rabbits, maybe something like a capybara, with the rabbits reproductive cycle. Or just invent goats that breed like rabbits. Of course, the larger an animal gets, the slower it grows and matures, and that means longer gestation too. You could compensate by having your giant rabbit only give birth to one offspring at a time. That way, a herd of 50, 100-pound rabbits might be enough to sustain a 4000 pound dragon. Also, consider giant chickens. Then your dragons can have eggs too. [Answer] Depends on two things: one, how intelligent your dragons are, and two, how non-threatening they look to your goats. Are your dragons the human analogue of your planet, or are they a threat to some other species that is a closer human analogue? Can the dragons speak to each other or to the humans with the complexity of human language? If they can, they're probably clever enough to figure out how to keep a herd of their favorite food captive, or at least learn how to do it from others. If they are not, I wouldn't count on them building fences anytime soon, but I could see them being smart enough to keep tabs on one or two wild herds in their territory and take steps to keep them within the territory, such as scaring them away from boundaries or creating obstacles like trenches or felled trees. This latter case would be much more like standard hunting (just with "their own" pet prey) than like proper domestication, but I'd say it's valid. Complicating the matter is the fact that your goats will likely be terrified of your dragon, if the dragon is as large as you say and looks and acts typically dragon-ish. They will know the dragon is a predator out to eat them, and unless your dragon has some way to make itself seem like a friend, it will have a hard time doing any proper domestication of them. To avert this, it may be worth considering possibilities for a symbiotic relationship. Perhaps the goats trust the dragon because the dragon gives the goats something: a home, protection, warmth, a nutrient or treat of some sort, safe breeding grounds? The bottom line is that for the goats to trust the dragon, they need to get something out of it that is worth members of their herd dying when the dragon gets hungry. Maybe the dragon helps them harvest a certain type of fruit that is a much more efficient energy source than grazing but grows too high up in trees for them to reach, for example. There's room for a lot of cool speculative symbiotic evolution if you take this route. [Answer] If your dragons are smart enough, you can definitely have a drago-shepherd caring for his flock while playing his drago-flute. As for breeding pop, you'll need to provide us with the size and weight of your average adult dragon and the pop size of your dragon tribe. You can compare with dinosaur sizes/food consumption at Wikipedia or here: <https://what-if.xkcd.com/78/> I'd go with cows for large dragons, or maybe elephants? [Answer] Make the herd animals intelligent. The dragon guards the herd from predators in return for a monthly sacrifice that dragon uses as food. ]
[Question] [ According to [Wikipedia](https://www.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_examples) and [this answer](https://worldbuilding.stackexchange.com/a/26733/6507), the Moon is orbiting the Earth at a distance around 20 times greater than than the point where it would break up. As far as I can tell, that means in a fictional world, we could have a moon the size of our Moon, only ten times closer to the Earth (as in $\frac1{10}$ its current distance, or around 38,000km), with absolutely no fear of collisions or the moon breaking up. Such a satellite would be quite a sight, lighting up the night sky (when its orbit matched up—I guess it'll be moving faster now) and just generally being the biggest thing up there (as far as appearances go). What I'm wondering, though, is if there would be any geographical changes to the Earth as a result of this closer relationship with the moon (if you're thinking about [this question](https://worldbuilding.stackexchange.com/questions/25675/if-earth-and-the-moons-relationship-were-a-bit-closer?lq=1), I checked; it didn't cover what I'm asking here). Would the Moon pull mountains from the depths of the oceans, or would its tides sweep away our coastlines? Would there perhaps be shifts in weather/climate (not sure if this can be considered geography, but I'd still like to know)? Just as a hint, according to [this answer](https://worldbuilding.stackexchange.com/a/25684/6507), "tides are proportional to $\frac{\text{mass}}{\text{distance}^3}$", so a moon 10x closer would have 1000x the tidal forces. I assume this wouldn't lead to waves one thousand times higher than normal, but I can't believe that everything would be the same. [Answer] It would not raise mountains directly. However, the planet (and moon!) would likely be much more volcanically active. More, and larger, volcanos would result in a much more dynamic landscape. Tides would also be much higher. Shorelines would be mostly cliffs and rocks and mudflats and would also result in a much more dynamic landscape. I would think that sandy beaches would be rather rare. Any kind of docks would need to be quite a ways up rivers to be useful. Smaller islands would have to have floating platforms well offshore to do any business with passing ships. Small boats would then row or paddle the goods ashore. Ships would absolutely avoid the seas around islands like those of Indonesia. The differences in ocean depth would change it between a solid landmass and a scattering of islands on a daily basis. Such islands may actually be uninhabitable, as they may be worn down almost as soon as volcanos would raise new ones, not allowing time for life beyond birds to really set up shop. [Answer] Well, the prevailing theory is that the Moon [did form about 10 times closer](http://www.space.com/29047-how-moon-formed-earth-collision-theory.html) than it currently is, after a giant collision between proto-Earth and a Mars-sized body. The Earth back then probably had 5-10 hour days, and the Moon was about 24,000 km away on formation. It has been moving apart due to tidal interactions, which have also slowed down the rotation of the Earth. Notable effects would be: * crustal tidal heating on Earth from the Moon, so lots of earthquakes and volcanic activity * [100-300 meter tides](https://books.google.com/books?id=cHwpBAAAQBAJ&pg=PA227&lpg=PA227&dq=lunar%20tides%20after%20the%20formation%20of%20the%20moon&source=bl&ots=pbyF_wPDIS&sig=fHDi_n95L2PdAQzM4FEMyNJBbK0&hl=en&sa=X&ved=0CIYBEOgBMBBqFQoTCIPNtvaOrsgCFYuHLAodKyoDEA) as soon as the crust was cold enough to allow the water Ocean to re-condense. This amplitude is based on my recollection of the claims made in "Rare Earth," by Peter Ward, so at least someone thought this was credible enough to publish. Regardless, I may need to go back and do some math to verify/correct this, but no time at the moment. Note that the effects would be strong enough to cause to moon to recede at a noticeable pace, so it would probably drift away significantly in the first million years: [![enter image description here](https://i.stack.imgur.com/rM79x.png)](https://i.stack.imgur.com/rM79x.png) [Answer] It will affect Earths magnetic field, people without sun creme with 1.000.000 factor would "have a very bad day" because of the heavy particles would reach the atmosphere, and the tidal waves would make quite an surf experience. Geomagnetic changes would trigger a lot of rapid geological effects boosting volcanic activity, and Earths central mass would be "shifted" due the gravitational pull so the effect would be disastrous and equal to an extinction of complex life on the planet if not a complete annihilation of the planets biosphere and the planet itself since at the distance the moon would sooner or later be pulled out of its already unstable orbit toward earth (guess) and well - nobody would live to tell the story what was after that. Don't know what about the atmospheric effects, but there would be some changes to the atmosphere as well. ]
[Question] [ In the Hickhiker’s Guide to the Galaxy: Mostly Harmless, on the planet NowWhat there are the [Boghogs](http://hitchhikers.wikia.com/wiki/Boghog), and their way of communicating is to bite each other very hard on the thigh, so my question is, if I were to ever encounter one and I wanted to have some sort of friendship with it without either of us getting hurt too much, or without me having to hit it or something if it bit me in the thigh too hard, what would I do? Would I amour my thighs with special armour which would translate the bites into other electrical signals which I could understand without the pain? Or would there be an easier method without causing either of us too much damage? [Answer] You could wear some prosthetic legs, and try to make sure your actual legs are away from the Boghog's mouth (remember, the more legs you wear, the less probable it is that the Boghog bites one that is yours in a sensual sense). If you are a true hitchhiker, you should know how to make a false leg out of your towel. In case the Boghog finally chooses to bit one of your fleshy legs, try to convince it to choose another one with the argument that such a leg is not actually yours, but you have borrowed it. Alternatively, explain that on such leg you are wearing one of your few socks without holes. After the Boghog has finished biting your leg, remember that good manners mean that you have to reciprocate and bite furiously one of its legs. ]
[Question] [ I have always thought the idea of infinite punishment for finite sin felt wrong; it's vindictive in a way only petty humans can be. Additionally, it seems the best rehabilitation would be an induced perfect empathy. Finally, people often report seeing their life flash before their eyes in near death experiences, what if that's not the end of the show? Given those three ideas, which I'm not asking about, in a moment of terrifying insight I realized what hell might actually be: *You are sentenced to live through the entire* life of every thing you have ever harmed.** Anything that feels pain or has emotions which you directly affected, you're locked in and must experience their life in real time. With an infinite afterlife, living through a few thousand lives is no time at all; it's significantly less than infinite time. But how long will it really be? For an average person, how many lives and years will they have to live through? I'm looking for an approximate but well reasoned answer, ideally within one or two orders of magnitude. Note that there is an exact value for the average, so "it's different for everyone" is not a helpful answer. To restate, the sentence is to live through the entire life of every thing you have ever harmed. To simplify things slightly, we'll define things as follows: * This "average person" is from the people living in modern day western culture. * To "live through" a life means you experience it fully as if in real time. No skipping forward, no interaction, no going comatose. You're there and fully present. * The "entire life" is from birth to death of the creature in question (shorter time for things you kill, obviously). You live through the life only once, no matter how much harm you did to it. * For applicable lives, "every thing" is defined as anything with eyes. This conveniently excludes bacteria (they have very short lives, but using antibacterial soap would significantly increase the sentence). * To have "harmed" something, the act whether meant to harm or not, must have been done with intention. * Physical harm usually has clear intention and is usually direct. Pushing someone down counts, while forgetting to pick up your backpack causing someone to trip and get hurt does not. * Emotional harm is a little harder to define, but we'll say if someone feels hurt by either a direct action or willful inaction on your part, it counts. I realize despite the clarification, people will still have questions as to what counts and what doesn't. Just go with your instincts, if the affected thing can fairly state that you harmed it, then state your reasoning and include that life in the sentence. So, how long does hell last? [Answer] Yay Fermi. Note: I'm not going to count harmful acts that are "built-in". So if you play football and tackle a guy, it doesn't count as long as it's within the rules of the game. Family The average US family is 2.58 people. Now, at some point in your life, you'll probably end up hurting your family members in some way. So that's 1.58 lifetimes. In addition, you'll likely have a family of your own once you grow up, so that's another 1.58 for 3.16. But that's just direct family - we also need to consider extended (cousins, aunts, etc). I think it's likely if you have contact with them, you'll end up causing some sort of harm to them, enough to trigger this. Let's call this another 1.58 bucket. However, we also have divorce, and multiple families. The standard statistic is half of all marriages end in divorce, but not all of those will have children. Plus, not everyone will re-marry after. So let's just go ahead and round up our family number to 5. SOs I wasn't able to get good data on this, but some googling showed a decent number as ~5 boyfriends/girlfriends during a lifetime. In addition, I'm going to guess at another ~5 hookups/one-time sex partners. My guess is that most relationships/breakups, at some point, will cause some sort of harm. And let's say that half of one-time sex ends up causing harm beyond the normal. So another 2.5, for 7.5 total. Friends This is another situation where most friends you have, you'll probably end up hurting emotionally at some point. Hard to find an average on this, but I'm pretty introverted and I still had ~10 so far. So I'm going to guess at ~30 for this number, which may be high but I also want it to cover acquaintances that you end up hurting. Total Friends and Family: 30 + 7.5 + 5 = 42.5 lifetimes, or 3,315 years. Insects This is tricky because I think it will vary with regional - people in the south will probably spend a lot longer in hell for killing insects than people living in northern, colder areas. But I'll try to average it out. I'm ignoring flies here because they don't live very long and I don't think you end up killing or harming that many of them. Spiders: Let's kill a spider once every 4 weeks, living an average of 6 months. So this will be 500 years. Mosquitos: Depends on how long you spend outside. Most mosquito killed will be female, which live ~1 month. I'm going to call this 1 per 4 weeks, so 1,000 over your lifetime = 85 years as a mosquito. Nests/Hives: This is trickier. Let's say that the average human will kill/harm two of these during their lifetime (WAG here). A wasp nest has 5,000 individuals that live about 6 months. A bee hive has ~70,000 individuals that live ~6 weeks. Ants vary widely, but let's call a nest 10,000 individuals that live ~8 weeks. Average all that out and we end up at ~4,000 years per nest, so 8,000 years. Once we account for other insects and variations, let's go ahead and round this to ~10,000 years as an insect. Food Animals I don't know if this is accurate, but I'll assume all food animals are harmed at some point, even if it's just when they're killed (although I'm sure some of it is automated). As of 2014, in thousands: * Cattle: 12,605 @ 2 years per * Chickens: 3,542,950 @ 2 years per * Ducks: 10,679 @ 8 weeks * Pigs: 44,608 @ 6 months per * Turkeys: 92,095 @ 6 months I assume a US population of 320 million on average. Plugging that all into an excel spreadsheet and multiplying by 78 (since that's per year) we get 1,750 years total per person. Pets Let's say the average person has four pets in their lifespan, and nearly all of those will fit somewhere under the "harm" category (smacking a dog's nose, for example...). If the average pet lives 15 years (cats and dogs), that will be another 60 years. Crime US violent crime rate in 2010 was about 15 per 1,000 people. We can use this in our estimate since we're just looking for the average time spent in hell as a victim (Note: it's estimated that this is under-reported, but that's largely because of friends and family crime, which is already covered earlier). Over 78 years, that will turn into 1170 / 1000. Which means that on average, violent crime will only add 1.17 lifespans, or 91 years to your hell. Totals: * 3,315 friends and family * 10,000 insects/spiders/icky * 91 from crime * 1,750 from food animals * 60 pets For a grand sum of 15,216 average years of hell, most of which is spent as a nearly mindless insect. Additional notes/addendum: It might be interesting to consider the mode or median of the reincarnation hell, rather than the average/mean. For example, I suspect that even if the 2 nest/hives in a lifetime is accurate, probably the majority of humans will never destroy even one. This means that the most common length will probably be somewhere in the 4,000 - 5,000 year range. Then you'll have people with more and more years, largely depending on the number of insects they killed, with exterminators being hit the worst - one year of extermination work will probably net someone a million years of hell. It's also likely that people working with large scale farm animal operations are in for a rough time. I also like that, in general, this means young children won't experience much. They don't have as much opportunity to hurt others, or as long of a period where they can have intent to hurt. On the other hand, it's kind of weird that crimes we'd consider heinous - like a child killer - aren't punished as severely. If you kill a small child you might not experience much at all - just a few years - where the person who gave you a lethal injection gets your entire life, plus they have to experience killing a child as part of that. Finally, one thing I considered here is that for the most part, when you kill/hurt things you cut their lifespan shorter. Take bees, for example - on average they live 6 weeks. But the average lifespan of a worker bee who lives in a hive that's attacked is probably shorter, because they naturally fall into the lower half of the sample size. So I think it's possible that some of these estimates are high, and maybe the insect numbers should be lower. But I don't have a great estimate for how much that should be reduced. [Answer] Infinite There is a potential problem with the solution of living out someone else's life in order to pay for your mistakes. Alice caused Bob to feel pain and so she now has to live Bob's life from that moment and experience the consequences of her actions. What if the pain she inflicted on Bob caused Bob to inflict pain and hurt on Charles and Dave? If Alice had not hurt Bob, he would not have in turn hurt Charles and Dave. Therefore one can conclude that Alice must also live Charles and Dave's lives too. Problem with hate and pain is it has a tendency to keep propagating out affecting more people than one realizes. If the damage is significant enough it could go exponential and thus a person could never escape the punishment. Other way of seeing it is since Alice had perfect empathy with Bob's pain and experienced his exact thoughts she would come to the same conclusions and perform the same actions as Bob did including all the times he hurt someone else. Thus Alice in thought would end up committing the same sins as Bob and thus would now have to atone for those in addition to her pile. This is similar logic that people use to explain why Hell is infinitely long: it is not that the punishment is infinite... it is that people in Hell don't stop sinning and so their punishment keeps growing faster than they can atone for it. ]
[Question] [ I want to draw a battle map for the cover of my book. By battle map I mean an image like this: ![Sample battle map](https://i.stack.imgur.com/E1pwk.jpg) What tools can I use in order to draw such map easily? [Answer] If you don't have (or are too cheap to spend) the dinero for the optimal solution, which is the [Creative Cloud](http://www.adobe.com/creativecloud.html) (Photoshop, Illustrator) suite of editors, you could generally use [Inkscape](https://inkscape.org/en/download/), as it is free, and being vector-based (so editable), it produces images that scale better and are more controllable than those directly from [GIMP](http://www.gimp.org/). This is made in Inkscape in about 5 minutes, eyeballing your sample map: ![5minutes](https://i.stack.imgur.com/N1QYF.png) However, others [swear by GIMP](http://www.cartographersguild.com/showthread.php?t=1142), so your mileage might vary. Probably you could use them in combination. You can get [fancy stuff](http://www.cartographersguild.com/feature/) out of (free) Inkscape (+GIMP): ![enter image description here](https://i.stack.imgur.com/5OH2S.jpg) [Answer] The most easiest way would be GIMP or Photoshop. GIMP is free. Here is a 5 minute work example, with a computer mouse not a drawing tablet. ![enter image description here](https://i.stack.imgur.com/Xfz2m.png) The arrows are ugly as hell, but you can use plugins like this one: <http://www.maketecheasier.com/draw-arrows-in-gimp/> Another solution is Inkscape (<https://inkscape.org>) Here is an example what you can do with it (not by me obiously). [image link](http://upload.wikimedia.org/wikipedia/commons/5/50/Battle_of_Waterloo.svg) [Answer] I would recommend a vector program like Inkscape or illustrator since you can select and move the different elements at all time. Or you can use a raster program like Gimp, Paint or Photoshop but each time you modify a shape, you risk losing some pixels. * You start by making the symbols you will use often. Like the rectangle below the names and the arrows. The program should have shapes somewhere to make rectangles, triangles or arrows. The shortcut is U in Photoshop. Make a copy of the symbols and duplicate them (duplicate the layer or use the duplicate tool: S) each time you add one on the map. * For the colored shapes (landmass and forests): use the pen:B and draw the exterior of the zone. To save time, you can bucket fill the interior of the zone with the bucket: G or you can color it manually. * Roads.: Use the pen with black or ideally a dark brown with a small radius. Do the same thing for the rivers but in blue and with a larger pen. * The building: made with rectangles that are empty or used white in the interior. Stack some rectangles and when the building is ok, rotate it as you wish. * Labels, use a font that is easy to read like that one. Arial or Helvetica will do the job. You can rotate it but do so before pixelating the text. I think that's all. Have I missed something ? [Answer] You can use a professional map creation tool like [ProFantasy](https://www.profantasy.com/). You would have to buy it. You can see that the final quality is good and may be worth the purchase. There are a lot of symbol sets as add-ons you can find [here](https://secure.profantasy.com/products/add-ons.asp#symbolsets). [Answer] You can give a try to <http://mashupforge.com> is a web tool to make and share maps. It is very versatile and easy to use but it isn't exactly what you are searching for (although it can be used for that). If you want to use your own icons or background layers, you can upload your images. To make this I recommend to use a vector based drawing tool like Inkscape to draw your stuff. For example in 3 minutes I was [able to create this](http://mashupforge.com/8493/4MQRTQ/) but you can make maps like this [Skyrim map](http://mashupforge.com/582/AQOfHyq4Omzp0fEfFIN70sy9yp9X8K/). [Answer] When I came across this question, I thought of Inkscape too. Battlegames magazine (as it used to be known) issue 13 had an article on using it for just this type of thing, which is now available online as a PDF. It's a tutorial based article for people new to Inkscape and digital map making. I have worked through this article myself for simple maps. <http://kriegsspiel.homestead.com/files/Accessories/BG13-computer_cartography.pdf> [Answer] I really like paint.net It's free. And it's like paint (super easy to use) but with layers and transparency. Actually it's kind of a cross between photoshop and paint. [>> paint.net](http://www.getpaint.net/download.html) [Answer] In addition to Tanasa's excellent recommendations, you can also use AutoREALM if you're on Windows (or through WinE for Linux). This is their SourceForge [site.](http://autorealm.sourceforge.net/) ]
[Question] [ I'm imagining an electromagnetic wave that could deliberately alter its wavelength. It would be a totally unfamiliar type of creature, but actually, we material beings act because of the electical neuro-signals in our bodies. So assume that it's a wave that could change its wavelength. I'm also thinking about its trajectory. I'm uncertain whether it's actually physically possible, but suppose it could change directions at will. (If the ray actually has a two dimensional cross section, it could 'heat up' one side of it to expand it, therefore turning to the opposite side). If so, then, if it had a device similar to a speaker it could pass through it to make sound. So it would communicate, but that means energy losses, so would it be slowly killing itself by 'speaking'? Also, if it passed through a human being at a certain wavelength, it would in theory be warming him up. So if a person was stuck in the middle of the arctic desert with one of those he would not die of hypothermia, but he couldn't send a message out either because the wave would be busy passing through his body. In theory (in my head) it makes sense, I'm just trying to understand whether I made some fundamental logical steps (maybe about the speaker, those things are pretty complicated). This might be complete nonesence, but they do have a particularly intelligent shade of blue in The Hitchhiker's Guide to the Galaxy... [Answer] There are cases where this has been done. A few of the masters (Assimov, Clarke) dabbled in it. The hardest part is defining a "living creature" without using matter. The actual definition of a "living creature" is not well defined in science. However, it is well defined in the minds of readers, so you have to unshackle them first. Science recognizes several traits of living creatures, of which some of the important ones are: * Metabolism. They fight entropy by consuming energy. * Reproduction. There is some "next generation" for the creature * Homeostasis. The creatrue roughly keeps its form. If you want an exotic creature such as a non-material creature, you should fall back on my favorite law, Sanderson's First Law of Magic. "An author's ability to solve conflict with magic is directly proportional to the reader's ability to understand it." A non-material creature is going to be unusual enough that treating it as magic might be wise. Make sure you give the reader enough time to make sense of your non-material creature before solving problems with it [Answer] I am embarassed at how old this question is that I didn't see before, but I don't regret writing all this. Hopefully someone may find it useful. > > I came into this question thinking that a being made entirely out of immaterial stuff (not composed of fermionic matter like we are) would be impossible, but upon further reading I'm not so sure...! This is quite interesting, at least. The following is based on my amateur understanding of quantum mech, so I welcome corrections. > > > An EM wave is just one or more photons. It's hard to say whether they could change their wavelength and direction of their own will without getting more specific about what our Being is made of. An individual photon travels at lightspeed so it does not experience any passage of time, and therefore its properties cannot be changed except by interaction with something else. But multiple photons can interact with one another -- indirectly. This is [two-photon physics](https://en.wikipedia.org/wiki/Two-photon_physics). In short, one photon in a pair possessing high enough energies (extremely short-wavelength gamma rays) can spontaneously fluctuate, or change, into a pair of temporary "virtual particles". The other photon can then be absorbed by (or, coupled to) one of the virtual particles, and re-emitted in a different direction before the virtual particles change back into a photon. In this way, we might perhaps conceive of... let's call it "hard light", composed of gamma-ray photons, arranged in such a way that two-photon interactions constantly loop back around in predictable ways, forming stable "matter" that is actually gamma photons constantly fluctuating, bouncing and re-intercepting one another. This seems VERY questionable under the uncertainty principle, but maybe it's doable, somehow. Humans would certainly not want to go anywhere near this thing, and just as well, since it probably wouldn't survive long in human living conditions either. So we have some kind of material to work with. Would our hard light be capable of forming a creature with a metabolism? I think so. Maybe. Photons do not have any electrical charge, and I have no idea what interesting physical properties might arise from a unit of "hard light", so I cannot say that their "chemistry" would work like human cells (which essentially do work by exchanging electrons around in chemical reactions). But you could still build a mechanical computer. Humans are chemical circuitry, and I see no reason why mechanical parts of arbitrary composition could not also form a living being. Clockwork computers on Earth are limited by the fact that they are made of metal: high energies and complex operations are required to turn refined metal into cams and circuits. [It has been done before](https://en.wikipedia.org/wiki/Difference_engine), but gears made of refined metals don't occur naturally on Earth the way amino acids spontaneously form from carbon chemicals. But maybe our hard light is different, and microscale gear-shaft machinery forms quite naturally from it. Our being would probably require some extraordinary living conditions: 1. A source of extremely hard gamma rays. 2. Staying far away from large concentrations of fermionic matter, like the stuff that makes up humans. Hard light gamma rays could be quickly absorbed by atomic nuclei, disrupting the being's structure. So where could they live? I have no idea. My best guess is somewhere in the vicinity of a pulsar, or an active galactic black hole, that has happened to avoid contact with lots of regular matter somehow, for some time. It's possible we could contact them if we built our own strong gamma emitters, perhaps a GR laser, and they might be discovered using gamma ray astronomy. So that's the basic mechanism of it: Hard light by way of two-photon physics. As for the details, go wild. [Answer] When I started thinking about this question, I thought about how information is sent through the the internet in packets of light. 16 separate wavelengths can be combined without losing any of data contained in each. So could an A.I. program be contained in 16 packets? Is there any reason aside from infrastructure upgrade issues that it couldn't be 256 or 1024? Since energy is expressed in packet called quanta, it isn't unreasonable to imagine the information of life contained in a quantum of energy. I'm going to continue to treat it like a program for simplicity's sake; though I don't expect it to be artificial life, I imagine this is a decent model for energy based life. Every time my quantum encounters another packet of energy, it takes it as input (it eats it). It parses the information this packet contained. It might only have information on energy level, wavelength and spectra, or it could be another energetic life-form analyzing it simultaneously. It determines whether it needs to alter its program in response to the data it read (more on that later), and afterward expels (excretes) a packet of energy. Increasing or decreasing its total information will change its energy level and its vector. It may even absorb the entire packet and significantly increase its energy level. Doing that a few time could cause it to "reproduce" by encoding its information onto the packet it releases. This is pretty much how an amoeba reproduces. But you want more from this life-form than just that. Communication and intelligence. I don't think you are going to get a scenario where it walks through a speaker and can be heard speaking. Nor is it likely that they can warm someone up by passing through them. Remember that as a creature of pure energy, it is traveling at the speed of light. But it can collide with atoms of the air to be absorbed by its electron cloud and be expelled again in the opposite direction thousands of times per second so that it can stay in close proximity to your hero. Colliding with him with the intention to warm him up would be an ignominious suicide, and ineffectual since, depending upon its energy level it could warm up a single cell, burn it out, or wreck its DNA. As far as communication goes, lets hand wave the first part where it learns to speak English. It picked up radio packets of our communication, determined that they were of value to it for whatever reason, and pieced together enough of them to determine that it was a language and it learned it. Now it has to communicate with us. First it would gather enough energy to reproduce, but instead of creating a clone, it would write a program, encode that on the outgoing packet and aim it at a radio receiver. The program wouldn't be sentient, so it would have no moral issue with sending it to its doom. So, what would happen to a random file received on a random radio antenna? Probably nothing. It would be filtered out as noise. My quantum would probably try multiple times before giving up. Perhaps it would try synthesizing a voice eventually, but I wonder what we would make of it? Perhaps it would be the beginning of meaningful contact, or perhaps it would give up in frustration after being ignored. [Answer] I'm not sure what you want to achieve but a reasonable explanation could be that there are material living beings that live in a 4th (or 5th ...) dimension perpendicular to ours but they leave traces of electromagnetic waves that propagate through our dimension. Basically think a bit like Flatland. As some unification theories require extra dimensions it shouldn't be hard to argue they are there. Once that leap is made it only stands to reason that, if our dimensions are populated with matter and sentient beings that, those other dimensions would contain the possibility for life as well. [Answer] The science definition of Life was well stated by Schröedinger in his "[What is Life?](http://en.wikipedia.org/wiki/What_Is_Life%3F)" book. Basically, it is any organized system that can extract energy from its surroundings to oppose its own decay caused by Second Law of Thermodynamics. Wikipedia cites: > > Schrödinger explains that living matter evades the decay to thermodynamical equilibrium by homeostatically maintaining negative entropy (today this quantity is called information[9]) in an open system. > > > In light of that, the question is: Can an electromagnetic wave extract energy from its surroundings? My answer is that not. Electromagnetic waves can be created, and enhanced, by their surroundings, but (with the exception of light-estimulated radiation in laser and related devices) they can not extract energy from the medium. Moreover, there is a different consideration, that of Relativity. Something moving at the speed of light (like an electromagnetic wave) has an extreme time dilation making time effectively stop, so even if such a lifeform exist, it would notice all time to happen "at the same time", with no possibility for causality. This living being would be unable to react to events of any kind, since the event happens at the same time as the decision and the reaction, to say. [Answer] See the novel [Macroscope](https://www.wikipedia.org/wiki/Macroscope_(novel)) by Piers Anthony. It features an intelligent (as in alive and thinking) broadcast. It was explained (if memory serves; I read it over 30 years ago) that reflected energy can interact with incoming signal to allow it to interact with the receiver. [Answer] I'm not certain whether this answers your question, but: short answer is No, with an If; long answer Yes, with a But. There is no such thing as this so–called “non-material living being”. What people describe as Matter and Energy are simply two aspects of the same thing. Anything which has some properties of Matter has some properties of Energy. All objects are a trifecta of matter, energy, and information. You could be describing a vast interstellar Mind which treats planetary bodies as its neural clusters. When most people think of these so–called beings of pure energy, they are usually imagining something which certainly uses material bodies but is able to exchange matter much more freely than lifeforms which are more constrained. So, with regards to my strict interpretation for the premise of your question: no, it could not. ]
[Question] [ In this setting, humanity has advanced to the technological capability of extra stellar travel via faster-than-light drives. However, due to distances between inhabited areas being extremely large, travel between two systems is still very, very slow and resource intensive, taking years at a time (As light is known to do already). As a result, technology was developed to effectively "tunnel" through space-time as a wormhole theoretically does in order to facilitate travel, and this effectively allows four-dimensional travel. What if the wormhole functioned on an entirely vector-based system, where the entry point and exit points must take into account spatial distance? For instance, if a traveler from Earth entered the wormhole and only traveled time (not space), he would end up in the exact same space as he left, just at a different point in time, meaning that the Earth would not be at the wormhole exit, it would not have arrived yet. I could see that there would be a huge drive to map true planetary motion, complete with the development of a system to map locations in four dimensions, perhaps continuing on into the past so far as to map objects back to the big bang and expansion of space-time, a true final frontier. Let's assume that creating wormholes is extremely energy intensive, and construction of a tunnel requires enormous feats of engineering and resources to the point where only one tunneling device exists for the time being and the actual opening is 25 m3 that travels with the space-time velocity of the device (meaning that the device must compensate for its own travel if it needs to exist in a specific point in space). What potential for abuse does this system have? What methods might a government take to keep order? How might scientists attempt to study paradoxical behavior (If it even exists)? What other applications might this technology have (especially for historians and explorer types)? What might a universal reference point be for the device that is not mechanically determined? [Answer] > > Let me state for the record that all* time travel ends with paradoxes - this is inevitable. There is no known way to model time > travel without paradoxes (that includes the parallel universe > approach). With causality in place, time travel irrevocably will > present a paradox if you dig deep enough. Since this is fiction of > course, we just need to make it plausible enough so the problems don't > matter enough.* > > > ## The Time Bomb The simplest form of abuse is someone using this to transport an explosive device (or something who's target position will have destructive consequences) back in time, to an arbitrary location - and a time when there's no defense for the weapon. ## The Grandmother Bomb Depending on how you model your time travel rules, someone could go back and prevent the device from being made. Someone could arrive from the future (or infinite numbers of people could) to prevent it from being used. If you have time travel, anyone can have it in the future - and it lasts long enough for lots of people to come back to your time. ## Too much power Whatever the way the device works, it is obviously capable of manipulating matter at a basic level - if something goes wrong, it could just make the target space-time location explode. There's always the problem of replacing whatever is in the spot you want to put your stuff in: if you travel back in time, what if someone is in that place? What about just the air that's there? Do you replace it or push it away? I can imagine that forcing matter (or energy) to coexist forcibly with other matter, it could become accelerated to [large fractions of c](https://what-if.xkcd.com/1/) and just annihilate the entire place. --- ## Prevention If someone had such a device, it's pretty obvious that they'd want to regulate use as much as possible. To the point where they might avoid even using it themselves unless absolutely necessary. Since in your premise this is used for transportation, it will be accessible to average people. One way of preventing the above abuses would be to intentionally engineer the device to only work with an artificial endpoint (thus, it can only send people to a specific place at a nearby time and that place has to be explicitly created for use with this device), to only be able to transport within small time distances (aka, it can transport someone from here to another planet, but when they appear, it's at most a few seconds after you start the transport) and make sure it has a time lock (like banks) and requires explicit monitoring and manual authorization for all transports. In essence, besides having to be controlled by some kind of incorruptible authority powerful enough to prevent abuse, it would have to be engineered to prevent abuse, even if reverse engineered. It would have to be made confusing, without anyone knowing the way it works entirely and possibly break or distort itself upon any attempt at disassembly. The stakes are too high. Of course, it can be built for a purpose and then destroyed after it is fulfilled. ## Paradoxical behavior As stated in the beginning, paradoxes are inevitable. It's easy to come up with thought experiments that end in paradoxes - it's tough to come up with ones you can test without catastrophic consequences. I'd say that, besides testing with tiny amounts of matter and energy to evaluate causality paradoxes (using only annihilations, collisions, transmutations and conservation laws) they would have to attempt all of this within very small time frames (in the order of milliseconds at most). Unless they mess up, they should be able to figure out at least the broad rules of how causality is affected and how far-reaching the effects can be, by extrapolating from stochastic processes. They might even be capable of evaluating the validity of deterministic physical laws. ## Other applications I can't think of many - time travel is manipulating time to your advantage. You might be able to speed things up (computers that send information backwards in time to themselves have been thought of in fiction) or slow things down (like stasis in star trek). You could perhaps experiment with processes that take millions of years to complete (send something back in time, in a container and attempt to meet it in your own time - provided your device isn't locked as I proposed). ## Reference frames The only way to really achieve this would be to pick something that isn't expected to change unpredictably within the amount of time you want to travel. This can be a signature the device can detect in space-time, rather than just space (perhaps the latter would be useless anyway). Since objects don't carry a tag in the universe, it would have to detect and measure its influence on its surroundings. This means it would have to be able to predict future behaviors accurately - if it's a star for instance, it would have to include very accurate stellar and orbital mechanics predictions to make sure it can maintain the reference. It could perhaps maintain a set of references - multiple points that it uses to produce coordinates in space-time. This would be much like how spacecraft and aviation computers are built in threes - all perform the same job and check each other for errors - if two agree, an operation is correct, if all disagree, there's an error. A reference matrix, made of multiple points, would be much more robust and would allow for some errors in the predictions. [Answer] As Neil pointed out, there is no absolute frame of reference, so I'll pretend that the frame of reference is relative to something - in some scenarios, the Sun; in others, the Earth, and in others, the center of the Milky Way. > > What potential for abuse does this situation have? > > > Well, there's always the old 'execution-by-pushing-a-person-into-outer-space-so-s/he-dies-from-suffocation-and-heating/freezing' approach. You simply calculate at what point in time there will not be an Earth in that position, and push the person in. For those who are horrified at the idea, I'll say that this system has the potential for some great advances in bringing things from one place to another. Say you have a lot of toxic waste, or spent nuclear fuel. Simply calculate the time at which that point in space will be filled by, say, a star, and push all the unwanted material in. Foom! - all the waste is gone. Quite the handy-dandy kitchen appliance. In all seriousness, though, the effects of this system depend on how many people have access to it. If anyone in power thinks of the execution method I described above, they would instantly make a push for strict regulation of the devices. We'll confine that to Area 51, thank you very much. Honestly, government regulation depends on just who came up with the idea. If it's a relatively secret (i.e. classified DoD or MI5) government project, its very existence will be most likely hushed up. If it's a defense contractor, or a private company, word could spread. And if some guy/girl came up with it in his/her backyard, we're in trouble. On to paradoxes. There are plenty: the grandfather paradox, the killing-the-inventor paradox, and the [becoming-your-own-mother-or-father](http://h2g2.com/entry/A1126595) paradox. These are all fairly big problems in science, as they throw causality out the window. The only hope is that traveling in time fulfills what has already (or what will already) happen. The other hope is that of the multiverse (where each universe splits upon each decision, and if you kill your grandfather this all happens in another universe), but that's highly, highly speculative. So scientists would love to study the paradoxes. Other applications. Hmm. Tricky. Well, not really, but hard to narrow it down. You could travel in time to test theories, take tours of famous places and meet famous people, and really do anything you want. However, there is a limit to what you could do. If the reference point is the Sun, you could only travel back in time in multiples of one year. Of course, all you'd have to do to travel to another point in time is to go back a bit further and wait it out, but that's a bit boring. Unless you're sipping pina coladas with Julius Caesar. [Answer] Perhaps if you could model things realllly well, then maybe time travel COULD include spatial travel. If I travel back in time 100 years, but nowhere spatially, I most certainly won't end up in the same place. The Earth, Solar System, Galaxy have traveled fast and far. If you had the technology to send yourself forward or backward in time "without changing space" with utmost precision, you could time it so that you land on something that has shifted over time, in the universe. You can't be too picky about where you want to go spatially. That way, YOU aren't moving spatially, but objects in the universe are rushing to meet up with you. ]
[Question] [ Suppose we have an earthlike world orbiting an artificial star which produces light but no solar wind. I would like to understand the implications that a lack of solar wind would have for the planet. (I'm not currently concerned with the feasibility of an artificial star or how one could or could not work) So, for the purposes of the question: assume a solar system which is a perfect copy of the Sol system, with the exception that Sol itself has been replaced with an artificial star of equal mass and with light output of equal spectrum/intensity/etc, which does not by any mechanism (aside from emitting light) spew any of its mass into space. What are the differences between this system and ours that would affect Earth? I can think of a couple differences I would expect: * There would be no aurorae borealis/australis. * We would not suffer the effects of any "solar storms", because of a lack of coronal mass ejections. * Hydrogen and helium (how much?) would be accumulating in the upper atmosphere instead of being blown into space. A good answer to this question will: * Confirm, amend, correct or refute my existing expectations, * Enumerate any additional effects I am missing, * Outline any obvious/large scale implications of these differences (eg. "because of the accumulation of hydrogen in the atmosphere, you will have..."; "because of the lack of solar wind, the interstellar medium will permeate the system and..." ) [Answer] This is a great question; I hope I can write a half-decent answer. Some of these points have already been made by others, but I wanted to go into more detail. ## Atmospheric escape I actually don't think that the atmospheric composition will change significantly, because the solar wind isn't the primary driver of atmospheric escape. Rather, photons - particularly, ultraviolet photons - are the main energizers of molecules. You can certainly transfer energy from solar wind particles via a sort of analog to [sputtering](https://en.wikipedia.org/wiki/Sputtering), but it's not the dominant mechanism. If you're not convinced, then consider the "luminosity", so to speak, of the solar wind - the change in kinetic energy imparted by the Sun onto the wind. It's $$L\_{\text{wind}}=\frac{1}{2}\dot{M}v\_{\infty}^2$$ with $\dot{M}$ the mass-loss rate and $v\_{\infty}$ the speed. Assuming $\dot{M}\sim10^{-14}M\_{\odot}\text{ yr}^{-1}$ and $v\_{\infty}\approx500\text{ km s}^{-1}$, I get that $$\frac{L\_{\text{wind}}}{L\_{\odot}}\approx2\times10^{-7}$$ meaning that most of the energy the Sun impacts on molecules in the atmosphere is transferred via photons, not the solar wind. Therefore, removing the solar wind wouldn't affect [thermal escape](https://en.wikipedia.org/wiki/Atmospheric_escape#Thermal_escape_mechanisms), the dominant category of mechanisms of atmospheric escape. ## Interplanetary medium vs. interstellar medium It's hard to compare the interplanetary medium to the interstellar medium (ISM) because the ISM is a very complicated thing (which, of course, astronomers are more than happy to ignore from time to time!). There are three stable phases ([McKee & Ostriker 1977](https://ui.adsabs.harvard.edu/abs/1977ApJ...218..148M/abstract)) and a myriad of structures, including molecular clouds, [galactic cirrus](https://en.wikipedia.org/wiki/Infrared_cirrus), H II regions, and more. They vary drastically in temperature (from $10\text{ K}$ to $\sim10^6\text{ K}$) and density (from $\sim10^{-2}\text{ cm}^{-3}$ to $\sim10^3\text{ cm}^{-3}$). The Solar System is (likely) embedded in a structure called the [Local Interstellar Cloud](https://en.wikipedia.org/wiki/Local_Interstellar_Cloud) (LIC), a structure inside the larger [Local Bubble](https://en.wikipedia.org/wiki/Local_Bubble), so let's say that your system is, too. The LIC has a temperature of $7000\text{ K}$ and a number density of $n\sim0.1\text{ cm}^{-3}$. This makes it roughly [an order of magnitude cooler and a factor of 50 less dense than the interplanetary medium](http://astroa.physics.metu.edu.tr/nineplanets/medium.html). In other words (as others have said), if the interplanetary medium was replaced with the ISM immediately outside the Solar System, nothing would change for the planets - and that assumes that the Sun wouldn't just heat it up again, which seems rather likely. The key point here is that there really wouldn't be any issues from the (quite small) influx of particles from the ISM - not by a long shot. We'd probably see some differences in elemental abundances, but there's still going to be mainly hydrogen and dust around. ## The auroras I can't add anything here; you're quite right that we would no longer see auroras. Interactions between the solar wind and a planet's magnetosphere are crucial for their production, and without one of those . . . well, you don't get much of a light show. ## Comet tails In the comments, [DWKraus noted that comets would be affected](https://worldbuilding.stackexchange.com/questions/202001/what-are-the-atmospheric-planetary-effects-of-having-no-solar-wind/202019#comment627418_202001). [Comets have two main tails](https://astronomy.swin.edu.au/cosmos/c/cometary+tails) (as well as a fainter tail of escaping sodium), one composed of ions pushed away by magnetic fields and the charged particles of the solar wind, and the other composed of dust blown away by solar radiation pressure. Without the solar wind, the tail of ions would be gone, but the dust tail would remain. [Answer] My guess? Surprisingly little. The lack of a heliosphere would allow a higher galactic cosmic ray flux (about 2-10X depending on the source), but while the possible impact on the cloud cover (and hence on the climate) has long been thought to be [a possible solution](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2003JA009997) to the Young Sun paradox, it has recently been determined that [this is very likely not the case](https://arxiv.org/abs/1311.1308). The interstellar medium invading the Solar System wouldn't be a significant concern unless the Solar System crossed a molecular dust cloud, with densities above 1E+6 particles per cubic centimeter. In that case, some effect on the Earth orbit might be observable, albeit over a long period of time. I suspect that would be more than offset by the lack of momentum conversion into thermal energy that the Earth experiences due to the interaction between its magnetic field and the heliospheric current circuit. Large aurorae would be replaced by a nearly constant, but way dimmer, auroral light caused by the onrush of the galactic wind (with the occasional [OMG particle](https://en.wikipedia.org/wiki/Oh-My-God_particle)). Hydrogen and helium would accumulate in the upper atmosphere, but this would not have a significant impact on anything, not on sub-geological timescales at least. Lack of solar cycles would not greatly impact Earth, except for a slightly greater climate stability (so, also slower evolution). This too would not be perceptible on short time scales. [Answer] Most important effects would stem from the lack of a heliosphere The amount of just raw radiation in interstellar space, according to current human observations is about 70 rems per year, while the moon receives about 30 rems per year, so you can assume that the amount of radiation received is going to be around 2.3333333.... times higher than the earth, or so, not accounting for the magnetic field As the planet pushes and pulls on the interstellar medium around the star through the magnetic field applying a prograde and retrograde force, due to the interstellar medium flowing one way, meaning the planet would be slowed down by drag against the interstellar medium then sped back up again, then slown down.... the consequence of this would be the planet's orbit would end up wobbling, as it pushed and pulled and pushed and pulled against the interstellar medium. Incidentally, this would also cause an Aurora Borealis to continuously happen on a yearly basis, so the term Estisios Borealis might be better fitting. Other effects might be due to the accumulation of interstellar particles in the atmosphere the atmospheric pressure would end up fluctuating to a degree -on -a -predictable -regular basis, the amount of which depends on the amount of interstellar medium gathered and released, which in turn depends on how large the planets orbit is( a closer orbit causing more extreme fluctuations time-wise of a lesser degree, while farther out the fluctuations are larger due to more contact with the interstellar medium, meaning inherently that more gas is accumulated over a larger timespan. which would also incidentally make the exaggerated increase and decrease of the planet's orbit even more extreme due to increasing and decreasing mass, which would also indicate a more extreme back and forth the farther the planet's net orbit got away from the sun. On top of having an circulular orbit. Stricly speaking you still can have a perfectly circular orbit, but the energy present based of off the relation to it's sun alone wouln't be. Oh- and depending on the radiation strength and the magnetic field you range between having non of the effects of a solar storm ever, and having a solar storm all the time, nonstop ]
[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. One of my ongoing projects is what I think of as the "constructed worlds gallery", a series of [Megastructures](https://en.wikipedia.org/wiki/Megascale_engineering) as settings for stories and games, including things like the "Flying Pie-plate" a world sized dish as suggested by Larry Niven as the starting point for the construction of the habitat in [Ringworld](https://en.wikipedia.org/wiki/Ringworld), an [Alderson Disk](https://en.wikipedia.org/wiki/Alderson_disk) galactic lifeboat, and a trefoil mobius knot magicked up by a group of Dragons on the run from Cthulhu. Mainly I like playing with the implied geophysical issues that would otherwise make such structures unhabitable relatively quickly, the strange environments that result from solving them, and the everyday life of their dwellers. My latest project is a piece, or rather pieces, of a broken Ringworld but I'm having trouble working out how large the habitable zone on such objects will actually be so given the assumptions below... My understanding is that under the conditions listed below the side walls of the original ring continue to perform their role and the curvature of the ring segment will eventually be sufficient to have a similar effect. Question: How long do the chunks of a broken Ringworld, per the [original design specifications](https://larryniven.fandom.com/wiki/Ringworld), need to be for the maximum sized pocket of atmosphere to remain in the construct and how big will it be? Assume that: * Apart from being separated from their neighbouring ring sections the pieces are otherwise intact. * The pieces in question have broken across the width not along the length of the ring so both sidewalls are intact. * The sections are under the standard 0.992 gee acceleration. This is thrust induced, necessary to hold them in an orbit closer to their primary than it should be at its orbital velocity. * They are the in the same [Goldilocks orbit](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone) they were built for, or something similar. I know that the scenario creates appreciable engineering challenges in set up, those are entirely out of scope for this question. Also please note that while the ultimate result of this question may well be a matter of relatively simple math it is primarily concerned with getting the right math to work from (thus the [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") designation) as I have tried this twice, using different approaches, and gotten consistent results that differ by several orders of magnitude and neither of which looks right when drawn to scale. It appears that certain assumptions are being made that are not valid let me clarify: * This is not a ringworld in its original state. * This is not even necessarily a ringworld in its original setting. * Think of broken pieces as salvaged objects that have been repurposed as mega-habitats. * This question is not at all concerned with the fact that this scenario falls outside our current understanding of physics this is a matter of whether the construct as described can hold atmosphere and if so how much. [Answer] If there is a gap between the sections of the ring, it would allow all the atmosphere to spill through the gap, like so: [![enter image description here](https://i.stack.imgur.com/oJKTJ.png)](https://i.stack.imgur.com/oJKTJ.png) The question really isn't one of how long of segments you need (the answer would be "all the way around the circle"), but one of how to prevent the atmosphere from spilling out the ends. Here are three suggestions: 1. Do what Trump wants. "Build a wall! It's gonna be UGE!" Exactly how huge? Based on the equation on [this question](https://space.stackexchange.com/questions/19119/is-there-a-calculation-for-determining-the-thickness-of-a-planets-atmosphere) and using [this calculator](https://www.artificial-gravity.com/sw/SpinCalc/), I calculated that the "limit" of your atmosphere is going to be about 99.5 miles above the surface. A 100 mile tall wall would work. Technically this is impossible, but if you have a material that you can build the ring with, you have one you can build the wall with. Here is a diagram (I love diagrams): [![enter image description here](https://i.stack.imgur.com/sSrx2.png)](https://i.stack.imgur.com/sSrx2.png) 2. Manually angle the halves of each segment to trap the atmosphere, like this (exaggerated): [![enter image description here](https://i.stack.imgur.com/il5Ao.png)](https://i.stack.imgur.com/il5Ao.png) It is possible for life to survive below 5 miles in altitude. Here is the equation for how far from the hinge the segment will be habitable: $D = \frac{10}{sin(A)}$. Substituting for $A$, $D = \frac{10}{sin(sin^{-1}(\frac{200}{L}))}$, which reduces to $D = \frac{L}{20}$. One twentieth of the segment will be habitable. "A little puddle" was right. 3. Extend the orbits of the segments to make the curvature of the segments greater then the curvature of the orbit, holding the atmosphere like a bowl. Here is a diagram. [![The black circle is the orbit of the segment, the gray circle is what the ring would look like fully constructed, and the green arc is an example of a segment of that ring.](https://i.stack.imgur.com/9tvuD.png)](https://i.stack.imgur.com/9tvuD.png) "What are these things?" The black circle is the orbit of the segment, the gray circle is what the ring would look like fully constructed, and the green arc is an example of a segment of that ring. All the other lines are to help explain the math. The distance that matters is the distance from the edge of the segment to the orbit circle. I am going to do a lot of math, bear with me. Here are the variables: $R\_o$ is the radius of the new orbit (black line), $R\_i$ is the radius of the old orbit (blue line), and $A$ is the angle of the ring formed by the rays from the center of the ring to the ends of a given segment (green arc). The blue angle is half of the green, so it is $\frac{A}{2}$. The length of the green line is $R\_i(\sin {\frac{A}{2}}))$. The length of the purple line is similar: $R\_i(\cos {\frac{A}{2}})$ The length of the red line is $R\_o$ minus the remaining distance from the end of the purple line to the black circle, so it is $R\_o - (R\_i - R\_i(\cos {\frac{A}{2}}))$. To find the length of the brown line, we use the Pythagorean Theorem on the green and red lines: $\sqrt {(R\_i(\sin \frac{A}{2}))^2 + (R\_o - (R\_i - R\_i(\cos {\frac{A}{2}})))^2}$ Now the final step is to find the altitude of the end of the segment by subtracting the brown line from $R\_o$. So the height of the end of the segment $H$ relative to the orbit is: $$H = R\_o - \sqrt {(R\_i\sin \frac{A}{2})^2 + (R\_o - (R\_i - R\_i\cos {\frac{A}{2}}))^2}$$ $H$ must be greater than 100 miles to successfully contain all of the atmosphere. You suggested an orbit a few thousand kilometers wider than original, so with an orbit of $9.5003x10^8$ miles, the segments must be longer than 30° of the entire ring to successfully contain the atmosphere. To solve for how much of the ring is habitable, use $5$ as $H$, since life can survive at less than 5 miles in altitude. The portion of the segment at this orbit ($9.5003x10^7$ miles) that would be habitable would be 6° of the ring. So, to maximize the amount of habitable space at this orbit, break the ring into twelve equal chunks and $\frac{1}{5}$ of the ring will be habitable. If we increase the density of the atmosphere, a little more area of the sphere is habitable. According to Wikipedia, humans can survive at 6 atmospheres without any serious or permanent side effects from nitrogen narcosis or the toxicity of oxygen. Using [this calculator](https://keisan.casio.com/exec/system/1224579725), I calculated that the edges of the segment would have to be 150 miles tall to contain 6 atms. Using my equation, the segments would have to be 40° of the ring to reach 150 mi at the edges. Increasing the pressure to 6 atms would make the segment survivable up to 18 miles in altitude, so 12° of the segments would be habitable. At an orbit 3000 miles wider than the original, your ring would ideally be broken up into 9 segments with 6 atmospheres of pressure at the bottom of each, and 30% of the ring would be "habitable." [Answer] There are a number of physics principles at play here. 1 - The ring world is not "full" of air. The [Barometric formula](https://en.wikipedia.org/wiki/Barometric_formula) tells us how to model the distribution of 1 atmosphere of air in 1 G worth of gravity. Your ring world does not have exactly 1 G so this is only going to be an approximation but a very close one. If you graph out the Earth's atmospheric density by elevation, you'll see that a significant majority of the air is going to be in the bottom 20km of your ring's walls and reach an approximately space like vacuum by about 100km, but your ring has ~1609km tall walls. If you were to evenly distribute your atmosphere inside of that space, you'd be at 0.512% of Earth's atmospheric density. Not truly a space like vacuum, but close enough for most practical purposes that most people would consider the ring decompressed before you actually lose any meaningful amount of air. 2 -There is no such things as a mathematical point of complete depressurization, when you use a [decompression](http://www.geoffreylandis.com/higgins.html) algorithm we measure how long it takes to go from one air density to another. You lose pressure slower as you approach zero without ever hitting zero; so, hitting an uninhabitable atmosphere, and hitting the density of space are two VERY different time scales. 3 - Air can never decompress faster than the speed of sound. Most decompression algorithms don't account for this because they measure for a small vessel losing air through a hole small enough for this to not be an issue. Mathematically, this station should be able to lose 1/2 of its air in just a few seconds, but it's air can't move fast enough to cover the hundreds of miles it takes to even get to any holes in your ring in that amount of time. 4 - When your ring breaks apart, the pieces will be going about 40 times the rotational speed of the Earth sending the fragments off into deep space and taking away your artificial gravity. This lose of gravity means that your air is not going to be pouring towards your side holes nearly so much as it will be dissipating upward and out the top. 5 - The ring is under a LOT of tension. While it's easy to say scrith makes hand waving away that much stress possible, any breaking apart that it might do would be violent. Like a giant snapping guitar string, you would expect there to be massive waves of oscillations throughout your structure flinging off most of the atmosphere in an instant, large sections of the ring would curl or crumble and everything would be so chaotic on such an incompressible scale that without a very detailed explanation of scrith's properties, it would be very hard to say what would happen. For purposes of this question, I will assume scrith is also infinitely rigid otherwise the answer to this question becomes very open-ended. Given all these factors, we know we can not use a typical decompression algorithm because we first need to find out just how long it's going to take for the air to expand to fill the ring before it can even start to escape. Since the upper atmosphere will expand slower than the higher density lower atmosphere, we can get away with simplifying this equation by averaging out the starting atmosphere and still get a very close answer to if we tried to model out the exact expansion of a non-linear gradient pressure since it will all diffuse pretty evenly by the time it expands enough to reach the top of your wall. * Density of air is @ sea level = 1.225 kg/m3 * The mass of Earth's atmosphere = 10,092.139 kg/m3 So, we can estimate you have a starting body of gas that is 8238.481 meters high at a density of 1.225 kg/m3 that will expand as fast as it can upward to get out of the ring. Next we need to come up with a decompression formula that works for the speed of sound as you loose density. The air at 1 atmosphere of pressure can expand at a rate of ~344 m/s, but as air loses density, it will expand slower. So by the time your atmosphere's averaged height doubles to about 16,476m, the rate of expansion will be halved to about 172m/s, so on and so forth. Below is a simple JavaScript program that calculates this: ``` <div id="output"></div> <script> speed = 344; height = 8238.481; startheight = 8238.481; endheight = 1609340; time = 0; while (height < endheight){ if (height2 < endheight){ period = 2; heightC = height; } else { period = endheight / height; heightC = endheight - height; } time += heightC/-((1-Math.log(2)speed)-speed); height = period; speed = 1/period; } document.getElementById("output").innerHTML = 'FILLS RING AT<br>Time: ' + Math.round(time) + ' sec<br> Height: ' + Math.round(height/1000) + ' km<br> End Speed: ' + speed.toFixed(5) + ' m/s<br>Pressure: ' + (startheight/endheight).toFixed(5) + 'Atm'; ``` * FILLS RING AT * Time: 241626 sec * Height: 1609 km * End Speed: 1.76099 m/s * Pressure: 0.00512Atm This means, if you could find a way to restore gravity within 2.8 days, you'll be able to keep most of the air just fine. However, by this point your fragment has already drifted out of the Goldilocks zone and pressure has dropped so much everyone is dead. That said, the edge of the Earth's atmosphere @ 100km (The point we start to call space) has a pressure of .00001 atmospheres. So a to get to this point, you make this change: ``` endheight = 823848100; ``` Ooops, the time output for this blows WAY past the max float size allowed in JavaScript; so, need to run these calcs in something that allows for larger numbers to give you an exact answer, but let's just say it is a very very long time. Someone else with access to MATLAB or something similar can probably get you an exact answer, but this gets you close enough to what you need for your story. One last factor is gravity. In a smaller fragment, there will not be enough gravity to matter, but let's you have a nice big chunk of the ring. Like in the picture below. The ring's gravity will actually make you lose your atmosphere ever so slightly faster because your center of gravity will be above the surface of the ring. The good news is though, that your atmosphere will eventually coalesce into icy planet. For a 1/3rd segment like the image below, this will result in frozen gas planet about the mass of Earth. [![enter image description here](https://i.stack.imgur.com/vO4Mf.png)](https://i.stack.imgur.com/vO4Mf.png) To answer your question about salvageability, the shape of the ring fragment would make it a useless habitat, but a future civilization may perhaps scrap parts of it to make a much smaller halo superstructure around the Earth sized gas planet. They could mine the ice ball for a nearly inexhaustible source of water, air, and hydrogen to run their fusion reactors for power, and the ring fragment could give them all the soil, metals, and minerals they would need. As for you new requirement: "This is thrust induced, necessary to hold them in an orbit closer to their primary than it should be at its orbital velocity." While this new requirement pretty much kills my answer, I will leave this up as a point of reference for future inquiries that may not rely on propulsion to maintain the orbit. [Answer] Frame Challenge One of the criteria you gave is: > > The sections are under the standard 0.992 gee acceleration. This is thrust induced, necessary to hold them in an orbit closer to their primary than it should be at its orbital velocity. > > > I propose that this doesn't make sense and should be discarded. First off... the energy output of such a drive is ludicrous. If your "chunk" is merely "squarish" (about as long as it is wide), we're talking about 5e25 Newtons of thrust. You didn't supply enough information to convert this to energy output, but without some extreme hand-waving, there's a good chance we're talking about stellar energy levels. (In fact, IIUC, this drive produces about 1 Solar output if the chunk is moving at a piddling — by the astronomical standards we are talking about — 10 m/s. By comparison, Earth's orbital velocity is 3e4 m/s.) No matter how much hand-waving you want to employ, that drive is probably going to produce some heat. Time for even more hand-waving to explain how you can dissipate all that without cooking your habitat. (Maybe forget the star and just have it accelerating through empty space?) Second... if your thrust is really continuous, and not varying in something like a sinusoidal cycle, then, to be useful, it has to be at a constant angle relative to your star, which means your chunk of Ringworld is (effectively) tidally locked. However, once this is true, I can see no benefit to mucking about with your orbital velocity in the first place, other than "because we can". When you're tidally locked, you don't have seasons, and "year" doesn't mean much unless you're practicing astrology. If you still want to play with your orbital velocity... then I think the question is unanswerable without additional information. Namely, the answer will depend on your actual velocity and how your actual orbital mechanics modifies the effects of your star's gravity. --- Let's assume, instead, that your chunk is tidally locked facing the star, with your thrust directly toward the star such that the perceived gravity in the center of your chunk is 0.992G. Let's also assume that you've chosen an orbit such that the combination of stellar illumination and waste heat from your drive makes your chunk "comfortable". This feels like a much more plausible scenario, and fortunately, it has an easy answer: Since we're talking about near-Earth "effective" gravity, we can assume that the atmospheric "depth" will be comparable. Atmosphere, as elsewhere noted, doesn't "stop" at any particular point, but Earth's atmosphere is anyway regarded as being about 500km deep, so Ringworld's 1000km walls should retain this pretty well. The answer to your question, then, is that the curvature should be such that the ends of the arc are about 1000km "higher" than the center (i.e. the distance between the midpoint of the arc and the midpoint of the line between the ends is about 1000km). Calculating the required angle for this is left as an exercise for the reader. In fact, because your thrust accounts for only part of the perceived "gravity" towards the ends, actual gravity from the mass of the chunk itself will have the effect of "flattening" the arc somewhat in terms of its apparent gravity. (The actual calculations for this effect requires moderately complicated calculus or approximation via FEA.) On the one hand, this will increase the length of the arc needed to match the side walls. On the other hand, 1000km may be more than necessary for atmospheric retention. [Answer] I'm going to take a bit different approach to this based on the revisions... unfortunately I don't have math to back this up, but it should at least get you started thinking in a useful direction. (So far, I haven't seen anyone else accounting for the chunk's own gravity, and my own calculus is too rusty, [so I asked P.SE](https://physics.stackexchange.com/questions/490698/what-is-the-gravity-on-a-partial-ringworld) to help us.) Assuming you are talking about a relatively small chunk of ring (say, 45° or less; bigger than that, I expect the orbital mechanics just get... interesting¹), you are essentially dealing with a really oddly-shaped planetoid. In particular, this chunk has to be in orbit around the star, because otherwise it is almost by definition not going to stick around very long. (¹ The whole ring is easy to reason about because it is balanced and many forces will cancel out. This is also why a whole ring can mostly ignore gravity and spin as fast or as slow as you like, subject only to torsional stresses.) This being the case, unless your chunk is really close, relatively speaking, to the star, or really big in relation to its orbital distance, you mostly only have to worry about the chunk's own gravity, because the other forces are going to be comparatively weak. (Just as the Earth doesn't lose its atmosphere due to centrifugal force.) What you have, essentially, is a tidally-locked planet (i.e. in a fairly "normal" orbit, with zero axial tilt and a rotation period of exactly one revolution per orbit). Note that this has to be the case, because, unlike a complete ring which is gravitationally stable at any rotational speed, a fragment on its own is either in a regular orbit, or, by definition of not being in an orbit, isn't going to stick around your star for very long. At a large enough size (and we're almost certainly talking about such a size), we are mostly looking at atmosphere retention being primarily a function of the segment's gravity. A 1/300 chunk has roughly Earth-mass, and that's slim; Ringworld's width is 1/625 it's circumference, so we're talking about a chunk only twice as "long" as wide (and you said we aren't cutting it along the width). This is where things get weird and hard. Because your segment is curved, your point of maximum gravity is going to be above the surface... but because of the distances involved, they aren't going to exert much effect. The strongest gravity is going to tend to 'hug' the surface to a fair degree. Now... I haven't developed my model far enough to actually prove this, but I think you ought to be able to simply park an atmosphere on the thing, and it will mostly stay put just via gravity. Doing things like bending the walls in may actually make things worse, since, as others have noted, that shifts the point of maximum gravity up away from the surface. Moreover, it's going to exacerbate a problem you're going to have anyway, which is that dirt (and rock) near the edges is going to want to slide toward the center... which is going to tend to turn your system even more into a "regular" planet. In any case, you're going to have thinner air toward the edges, but I think you'll have plenty of air towards the center and even spread out a bunch. For bonus points, this means you can also spin your chunk to give it a day/night cycle. In fact, you can probably give it an atmosphere on both sides. (This might be a very good idea, because it will eliminate atmosphere loss in case you get a hole through it.) Your real problem, of course, is keeping this monstrosity from collapsing under its own weight. Although if the intact ring managed this, you're probably okay. (Also, you mentioned that the structural problems are out of scope...) On the other hand, if you let it collapse into a ball (this would end up looking like two hemispheres in the middle of a big honking plate), well then, you've got yourself a nice little planetoid that will have no problem retaining atmosphere. (The weather might be interesting!) ]
[Question] [ So, I am setting up a world for a DND campaign in which, through a magical accident in the past, the face of the globe is covered in ocean, all except for a few tiny islands where the highest mountain peaks were (I am hand waving the obvious problems with altitude and climate as the nature of the accident was essentially wishing for "more water on the planet" and it isn't really relevant to the story). So society has finally recovered from the initial shock and settled into a state of equilibrium. One of the factions that has risen up in the interim is a builder faction who take dirt from the sea floor and carry it to add on the islands or shallow areas to make new landmasses and the party is tasked with protecting one of their expeditions. I was just wondering how to mesh the dredging aspect and make it believable, as it would have to be mostly mechanical in nature, as spell-casters can't function underwater naturally. I have tried looking into how dredging was done it ancient times but there is not much information. Originally I had planned on having each expedition have divers who have strength enhancing and water breathing spells swim down and carry large amounts of dirt in bins but I was wondering if there were more elegant solutions. [Answer] A lot of this is going to depend on how deep your NPCs will be dredging. Dredging has been used as far back as 4000BC to build harbors and affect the characteristics of rivers. Most used boats with a crank and some buckets. DaVinci even invented a river dredger that would use the current of the river itself. [![DaVinci's river dredge](https://i.stack.imgur.com/avIgj.jpg)](https://i.stack.imgur.com/avIgj.jpg) The trick is that all of these are done in fairly shallow water. Deep water dredging is incredibly difficult, even today, and the only way I could see it being done at any kind of reasonable scale is with automatons that just walk along the bottom of the ocean. If your world is shallow enough you can use a similar technique as well as a handful of spells such as [bones of the earth](https://www.dnd-spells.com/spell/bones-of-the-earth) which can make great pillars of earth spring from the ground [Control Water](https://roll20.net/compendium/dnd5e/Control%20Water#content), which can do a "part the seas" effect, or [Move Earth](https://roll20.net/compendium/dnd5e/Move%20Earth#content) which can reshape the earth itself and slowly raise its terrain. Again though, a lot of this is going to depend on how deep these oceans are. [Answer] There were two types of common dredging: drag dredging which was rare and more focused on shellfish and sponges and shovel dredging which only works in shallow water. drag dredging was literally dragging a bucket or net over the sea bottom. Shovel dredging was literally using a really long handled shovel and s series of winches to bring up sediment one, admittedly large, shovelload at a time, these are used primarily to dig channels and maintain rivers. either way your limits are not strength of the lifter but strength of ropes and shear man hours. But in DnD you have some help. A ritual spell called [water breathing](https://roll20.net/compendium/dnd5e/Water%20Breathing#content). so unlike real methods people can actually go down with dredge buckets and fill them manually instead of relying on drag. Fitting ships with treadwheel crane was done in ancient so lifting the bins/buckets is easy. Of course adding to a mountain is going to mean moving gargantuan amounts of earth even to get a tiny sliver of land, since it will of course both fall down slope and be eroded away by wave action. You are better off inventing a spell that creates earth, given the strong need it would not be unreasonable. You can still use dredging for collecting shellfish, sponges, and treasure. [Answer] Diving Bells [Diving bells](https://adventure.howstuffworks.com/outdoor-activities/water-sports/diving-bell.htm) are large bell-like structures meant for helping divers stay underwater for longer. Allegedly they have been used since the 4th century BCE as Aristotle wrote about a ‘cauldron’ that was forced down into the water but held air inside of it. [![A large bucket-like structure made of wood and weighed down with iron balls. The structure is the height of two men. It has a pulley system attached to raise and lower the diving bell, a pipe for fresh air and a valved vent for used air](https://i.stack.imgur.com/wpwzo.jpg)](https://i.stack.imgur.com/wpwzo.jpg) <https://www.quora.com/How-does-a-diving-bell-work> The one seen above is made of wood and weighed down with iron balls, however it could also be made out of metal. You can also see that this version has a pipe for fresh air to be pumped in and a vent to let out used air, allowing for longer dives. Earlier versions did not have this and simply relied on a pocket of air in the bell. [Modern diving bells](https://en.m.wikipedia.org/wiki/Diving_bell) are typically closed, meaning they have an ‘air lock’ at the bottom to prevent the bell from filling with water. Applying this to your question, your drudgers may use a diving bell to get down to the sea floor. Then buckets attached to a pulley system would quickly follow them. Your drudgers would then proceed to start shovelling mud or sand or gravel into the buckets, returning to the diving bell when they needed a breath of fresh air or rest, before going back out and continuing to shovel. Once the buckets were full, they could be pulled up, emptied into the hull of the ship and then sent down again to be filled up. [Answer] Caissons Have a look [here](https://en.m.wikipedia.org/wiki/Caisson_(engineering)). Caissons have the advantage that they can be used by a pre-industrial society and should not be beyond the reach of your builder clan. While the article mentions the use of concrete they can be built of timber. Dewatering could be achieved by magic users. If you choose to go with pressurised caissons you will need to deal with [Caisson disease](https://www.ncbi.nlm.nih.gov/m/pubmed/15686275/). ]
[Question] [ In the DC and Marvel universes, alien invasions seem to happen almost weekly, super-villains have impossible technology, which they use to rob banks, and genius super-heroes invent equally impossible technologies to combat them. And yet somehow, nobody seems to come up with practical applications of said technologies for the average consumer. Stilt-Man's outfit could be sold to, say window washing companies, first responders, and more. Tony Stark's Arc Reactors should be powering buildings independently of the power grid. I'm just scratching the surface. Now out of universe, the main reason they don't have anti-grav, lightspeed spaceflight, et al, available to the public is because it would make the world so advanced, and so different from the real world of the reader that they might find it harder to identify with it, and may stop reading. The book would become more like a sci-fi comic, and less than simply a super-hero comic. But with the clear existence of this tech, what are some (interesting) ways that government or business might ask for, or even demand, the tech for the people? And what are some reasons the heroes (or villains) might demur? One reason I could envision is they don't want the tech getting out there, for fear it'll be hacked, and their powers and abilities could be rendered vulnerable. That's just an off the cuff idea. There's been occasional stories about this. The Armor Wars storylines in Iron Man deal with Stark's tech being used in a variety of other people's (good and bad) powered suits, and his attempts to stop them. JMS had a scene in Fantastic Four where they needed some money. He scribbled a formula on a piece of paper, said it was for a new acne medication - told them to call Revlon and say he'll take thirty million plus royalties for it. Dan Slott did a series of stories where Spider-Man adapts his tech for the consumer market, quite profitably. The polymers of his webbing becomes new materials for motorcycle helmets, Spider-Tracer tech becomes an improvement to wireless earphones, etc. Heck, In Independence Day II, Earth reverse-engineers and adapts the alien technology, creating not only powerful new weapons, but many changes to society. But as mentioned, that's a Sci-Fi story, so such societal changes would be more readily accepted by the reader/viewer So perhaps a sub-question is, in addition to ideas as to how it would be handled, what are some favorite stories where it WAS addressed? (flipped a coin as to whether this fit more here as in Sci-Fi and Fantasy - seemed more germane here since it's more about the storytelling aspect than in-universe "explanations") Postscript - A very germane TVTropes entry has been pointed out in the comments - [Reed Richards is Useless](https://tvtropes.org/pmwiki/pmwiki.php/Main/ReedRichardsIsUseless). [Answer] Villains don't want to do so because it means others will have access to their technology. This could let rivals get more powerful or pesky heroes find ways to reverse engineer or counter the villains' abilities. They don't like to share. (Heroes too, for that matter.) Heroes don't like to share because the technology has too many "military" applications that could wind up in the wrong hands. "With great power comes great responsibility." [NOT originally from Uncle Ben](https://quoteinvestigator.com/2015/07/23/great-power/) Another reason that fits both groups or those that fall in between1. If Tony Stark publicly sells a technology that then gets in the wrong hands, he might get sued for it. While Mr. Stark can afford the lawyers to defend himself, others aren't quite so lucky. I doubt Peter Parker could afford a liability lawsuit. Also, there's the risk of exposure. Few costumed characters in comic books are willing to give out their secret identities. But signing their name on a patent application for some kind of highly web-like super polymer increases the risk that someone will associate that name with Spider-Man. It creates a threat to their secret identity. Possibly in some cases someone attempts to profit from their high-tech gadgets, but they get shut down. The U.S. government has laws around exporting nuclear equipment and material[2](https://www.nrc.gov/reading-rm/doc-collections/cfr/part110/full-text.html) and used to have laws against exporting encryption[3](https://en.wikipedia.org/wiki/Export_of_cryptography_from_the_United_States). It is therefore reasonable to assume that the government would move quickly to quash any efforts to bring high-tech super-things to market. Or at least to control their release in a way that doesn't threaten security. Maybe they succeed in selling their technology. Someone got the patent rights for cell phones. For various technologies that resulted in your smart phone, your internet browser, etc. There's no way to prove (in a comic-book universe) that each of these can't be traced back through shell corporations, false identities, etc. to some super character or other. Carefully "leaking" technology in a controlled manner may be how we get much of our high-tech, cutting edge, stuff these days. Some devices are too heavily regulated for a super to easily bring to market. Drugs and medical treatments require years of FDA testing for sale in the US and similar rules elsewhere. Cars have to pass stringent testing requirements. Other devices would also require massive investments in safety features that a super may not need at all, but a mere mortal would have to have or would legally require. So the super just... doesn't bother. --- 1 Punisher isn't a Hero and isn't really a Villain either; he's... something else. Vigilante maybe? Same for Wolverine at least some of the time. [Answer] There was a solution for [tinkers](http://worm.wikia.com/wiki/Tinker) in the [Worm universe](https://parahumans.wordpress.com/). # Making their devices work at all is often a subset of their power set. Super-hero-world inventors/tinkers/tech-focused-geniuses aren't just smart people. They're a set of individuals with their own specialized superpowers largely focused on creating technology. While some devices can be replicated by mundane means... most can't. Non-super-powered human attempts to recreate the technologyhave close to zero chance of success in many cases. The tinkers powers may be required to get the devices working in the first place and normal humans may have great trouble even trying to maintain such devices. Devices that spend too long away from the physical presence of the tinker may simply stop working entirely. Hence, while some of the simplest tech may end up filtering down to people on the street... the super-genius doesn't have the personal capacity to build and maintain hundreds of thousands of copies of their super-tech and trying to build and maintain it without their active participation often doesn't work terribly well. [Answer] Apart from the comment by @Keptox, which just nails it, another reason is: end of the world. Speaking of the MU alone, at one time mutant power were literally reverse-engineered and turned into a drug that gave superpowers to non-mutant. Result: street gangs that could disintegrate whole blocks. Or when a superhuman criminal like Nitro was further powered by biotech means, his self-destruction also killed the New Warriors and started the events that would lead to Civil War. Criminal geniuses like the Wizard are, simply put, too much obsessed with their petty vengeance against superheroes to take a moment to think and decide to go Wall Street. Governments owning the means to create supersoldiers do not trust at all the idea of a legion of uncontrollable uperpowerful beings. The best US did in term of high tech was to create the Sentinels as anti-super weapons and, with the help of Stark Senior, the Project Arsenal. Reed Richards is a genius, but he is too much advanced. He could put on the market things that could change the world forever...but he'd be the only one able to make them work and produce in series. As of recently, Peter Parker became an industrialist putting his genius to use, just like Tony Stark is doing his part in research and engineering for pacific purposes. Doctor Doom is known to work on more shady grounds of the tech market and only according to plans that benefit him alone. He generously spares some of his wonders for his loyal subjects in Latveria. Another genius like Henry Pym could have done wonders in the field of IA, but alas he is too scared to go beyond certain limits after creating Ultron. And, as all superheroes by now know, Ultron is just the proof that when super high-tech goes haywire, the whole world could end. ]
[Question] [ What would be the design of a near-future extreme-cold environment suit? Consider a protective suit that is not a space suit because it doesn’t need to augment the pressure felt by the body. It does, however, need to protect against extreme cold. While the lack of pressurization makes a lot of things easier, the existence of an external atmosphere also means heat can be lost easily as the outside air touches the suit. I figure the basic coverall will have no problem being more than insulating enough, using existing aerogel cloth. Aside: when I first learned about aerogel cloth, I thought it would be awesome to make a pair of kitchen oven mitts that would be truly worthy — pick up a roast right from the oven (normal gloves will only last a few seconds; or worse due to the grease getting wicked up) and go straight to liquid nitrogen handling without any problem. But the smallest quantity I could find cost a thousand dollars. Now, I just did a search on Google for `aerogel fabric insulation` and one of the featured shopping links is \$19.00 on eBay (\$4/square foot). The product specs say you get R30.9 with a three-inch covering. In fact, [here is a jacket](https://www.popsci.com/aerogel-finally-makes-sense-to-use-in-clothing) that claims to withstand −321°F on the outside while the inside stayed at 89°. I figure some kind of snowshoe or tall block under the foot will keep them safe against extended contact with the cold ground. But I’m wondering about the helmet. A clear globe would not be made of a super-insulating material. Can it? Should they have a clear globe as a secondary cover, and still wear a hat and breathing mask, as opposed to filling the globe with warm breathable air? The use case is Antarctic winter as a prototype for a design that could work on Titan. What design would you foresee for such a suit? --- ## For reference [South pole](https://en.wikipedia.org/wiki/South_Pole): temperature −52°C 7 feet above the ground; ground contact temp. can be as low as −92°C. [Pressure is](https://www.mide.com/pages/air-pressure-at-altitude-calculator) 0.65 atmosphere. [Titan](https://en.wikipedia.org/wiki/Titan_(moon)): −180°C. Pressure is 1.45 atmosphere. [Answer] # Double glazing! The ambient temperature on the surface of Titan means that having a bit of a draft between your jacket and trousers could well be fatal rather than merely uncomfortable. Safety precautions in such a situation suggest that at least one layer should be totally airtight. This means there is an option for a full helmet filled with warm breathable air. It doesn't need to be a full clear globe, it only needs the forward arc to be clear for visibility. Double glazed with a vacuum between the layers of glass/polycarbonate or otherwise. Rigid aerogel can be used for the rest of the helmet. Most of the specified materials are highly flexible, the helmet should be of a close fitting type that moves with the head on flexible neck seals. The need to have that airtight layer means no breathability in the suit, moisture controls would hence also be needed to prevent it turning into a sweat bath and as such would control fogging in the helmet as well. The other key complex part of the suit is the gloves. Dexterous work is going to need thin gloves, but these may not keep the cold out long enough for prolonged exposure. I can see two potential solutions to this. Powered heating elements in the gloves1 or an extra layer of heavy outer gloves worn over the lightweight ones which are removed for short periods to work and then put back on when the work is completed, the maximum time limit reached, or a skin surface temperature alert is triggered. A combination of the two is also a possibility, but we're steadily increasing the load on the suit's power systems with the powered features. --- 1 Heated gloves are available for motorbikes [Answer] # The problem is your hands The controlling factor is manual dexterity. The great advantage of humans is that their hands can do just about anything. However, the stay time of a human in -180 C with any gloves thin enough to keep most of our manual dexterity will be short. If your humans can't effectively use their hands, or can't use them for very long, why would you want to send humans outside? At this point vehicles, with arms for performing tasks, either generalized or specialized, will be more effective. Of course, if you are going to be driving vehicles out in the cold, there is no good reason for operators to be in those vehicles, when they could be operated remotely. # The environmental suit is a drone Therefore, the environmental suit to be used on Titan is a remotely-piloted drone. As such the considerations of the question are not so important. # Bring the tasks to you The best way to keep humans doing the jobs that drones just can't do is to bring the thing that needs working to you. Build a garage and have the robots move anything that needs working on (such a broken robots) to the garage. It is a lot easier to repair a broken robot in a heated (at least, heated to 0 C or something) than in the harsh outdoors. If you are repairing anything too large to move, then you can replace large components all at once. Have a drone remove your weather sensor's entire processing unit and bring the broken one back to the (heated) base for repair. If you are trying to analyze things in quasi-enviornmental conditions, you can still send the humans into the garage in a suit, but now that suit can be plugged into the wall so they can use gloves with built in heating elements or something. Being right next to your base of supply makes it much easier to work in those conditions for the long term by swapping out operators. [Answer] # This won't be a flexible suit The temperatures under consideration are close enough to liquid nitrogen that we can consider them the same for most materials. Basically, how ever it behaves in liquid nitrogen is how it will behave on Titan. The suit will need to be: * Air tight to prevent heat loss due to convection. * Aerogel layers to prevent conduction of heat. * Heating elements to combat the inevitable heat loss. Matching powerplant/power cell to supply the required power. * Rebreather system to keep the occupant alive. * Moisture management system. [Fremen stillsuits](http://dune.wikia.com/wiki/Stillsuit) would be a good way to approach this. * Have multiple layers of reflective insulation to prevent heat loss by radiation. * Rigid outer skin to mitigate the effects of abrasion on the suit. A flexible outer layer probably won't work since most things at liquid nitrogen temperatures are very brittle. [Brittle Zinc](https://www.youtube.com/watch?v=GYamb7WWyT4) (video) and [Brittle Plastic](https://www.youtube.com/watch?v=befv8gb_ztc) (video). Perhaps a very special flexible plastic could be found. Maybe. * Rigid joints to prevent chips/drips of liquid/frozen gases from getting into the suit then sublimating to add extra pressure to the suit. Getting some liquid methane in your boots is going to give you a very bad day. * By any means necessary prevent the collapse of the insulation layers between the body and the outer hull of the suit. Loss of insulation is lethal. If you think your bottom is cold when you lie in a hammock, this is just much much worse # Vision A triple or quadruple glazed helmet may be enough to prevent unacceptable heat loss. Each layer covered in heat reflective coating will help a lot too. The smaller the view port the better. Camera mounted to the helmet would provide visibility. It's up to the author whether these cameras would be primary or secondary visibility aides. # Tool use Given the rigid nature of the suit, the suit may not even have gloves. Instead, use some kind of hand analogue that the user controls from within the suit. For gloves with hands in them, the competing demands of keeping the hand warm (more insulation) vs maintaining dexterity (less insulation) may not be surmountable in this scenario. It's far safer to pull the hands as far away from the cold as possible. # Emergency Procedures Just as astronauts have emergency procedures should some aspect of their spacesuit fail, these cryonauts will need similar procedures. Heating systems fail. Electronics fail. Seals fail. Handling those failures is essential. # Acceptance Tests If this suit can keep a human alive and happy while submerged in a 2bar pressurized vat of liquid nitrogen for the duration of the expected excursions plus a 50 or 100% safety factor, then this suit will work on Titan. [Answer] One of the biggest problems will be thermal regulation and sweat. The amount of heat a human produces is highly variable. While doing nothing, you would dissipate about 100 watts. Strenuous exercise can dissipate up to 1500 watts for a professional athlete. it would be less for an average person, but we have to assume if your explorers are brave/crazy enough to explore the hostile environment you mention, they would train to have good fitness and endurance. Let's use 1kW as a maximum value. Also the base value of 100W will vary according to body seight, sex, person to person, and what the body is doing (digesting or not, etc). Thus, the suit will need good thermal regulation. It will need to evacuate just the right amount of heat, but not too much! When the user feels hot, he will sweat. Also we exhale water vapor when breathing. Thus the humidity inside the suit will rise. When humidity is high enough to no longer allow sweat to evaporate, things become really uncomfortable. It is possible to sweat buckets, and even get dehydration in 25°C, 100% humidity air if you exercise a bit. This is really important. So, we need to regulate both temperature and humidity. Polar explorers have trouble with this. Say the inside of the suit is at 25°C and the outside is -40°C. Sweat will evaporate, then the water vapor will travel through the insulation, and encounter decreasing temperatures. At some point, it will condense, then freeze, and the insulation becomes clogged with water and ice, and thus useless. [This polar explorer](http://www.telegraph.co.uk/men/active/11315994/Ten-things-no-one-tells-you-before-an-Antarctic-expedition.html) says "frostbite is all about sweat". So we have to keep the skin at a pleasant temperature, and prevent accumulation of water. Suits for arctic conditions already exists. If you want to go on Titan though, or in other placer where the atmosphere is not breathable, you would have several options. If the pressure is OK for a human and the atmosphere is not toxic (ie, no sulphuric acid...) then an oxygen mask plus an arctic suit should work. If the atmosphere has high levels of CO2 or CO or other gases that will knock you out in a few seconds, then of course, it won't work. If the suit is airtight, then all the problems with humidity management become a lot worse. Some system would be needed to circulate dry air inside the suit, to regulate its temperature, dehumidify it (possibly recovering the water), etc. At this point you are looking at a spacesuit, minus the reinforcements intended to withstand pressure... Or maybe a light exosuit. Since it will require power and machinery it will be quite heavy, this having at least powered legs to help carry the weight would be a huge help in an environment with gravity. If you enlarge the suit and make it a mech, then the user inside can be in a larger "pod" which no longer needs to be form-fitting, which solves all the problems with air circulation, moisture, etc. But it's a huge mech. Note: in case of huge mech you need an emergency system to walk out in case it breaks down. This absolutely needs to be an inflatable hamster ball. Just because. A wackier option would be to have the inside of the suit filled with warm water (except the helmet). Water is a lot better than air at transporting heat. It would probably feel quite awkward to walk inside a portable swimming pool, though! > > But I’m wondering about the helmet. A clear globe would not be made of a super-insulating material. Can it? > > > No... Also you need the inside to be at a high enough temperature to make sure water vapor does not condense and/or freeze, in which case the user wouldn't be able to see anything at all (it isn't that easy to wipe the inside of your spacesuit helmet with your fingers...) This could be done with a transparent heating film on the inside of the helmet and perhaps a double glazing. [Answer] Your "suit" will be more akin to a small mech that is piloted than the [Apollo/Skylab A7L space suit](https://en.wikipedia.org/wiki/Apollo/Skylab_A7L). Outfitting one of the mechs from Avatar for extreme cold would allow the operator to work in a shirt sleeve environment, carry the megawatt reactor to keep everything toasty, and the tonnage of steel required to tie it all together. The "Mercury" class suit from the animated Starship Troopers is another good example. Other than that, the aerogel, layers of glass, bulky insulation and Canadian touque (hat) that other respondents have given are still major parts of the equation. ]
[Question] [ I want to make a creature very similar to a human but with one major difference: they breathe like any human in their everyday life, but if they are suffocating, drowning, or there isn't O2 in the air they can survive for several hours (or maybe more) without air, obviously with reduced physical activity and metabolism (if it's necessary, the creature can be unconscious). My question is: how they would be able to survive without oxygen. Basically I'm asking how to make a [facultative anaerobic animal](https://en.wikipedia.org/wiki/Facultative_anaerobic_organism)... I know that humans are able to make [lactic acid fermentation](https://en.wikipedia.org/wiki/Lactic_acid_fermentation) in their muscles when they are doing a lot of exercise and they can't breathe enough oxygen to feed all the cells. But that mechanism, called [Cori cycle](https://en.wikipedia.org/wiki/Cori_cycle) has a very limited use, the cells aren't able to get rid of all the [lactic acid](https://en.wikipedia.org/wiki/Lactic_acid) produced by the fermentation, and when the acid reaches a high concentration in the muscle it causes acute pain until you stop exercising. Also, it's very inefficient way of producing energy. I need a mechanism that can be used by extended periods of time without collapsing due high levels of something (like acid in the above example). The answer doesn't need to exactly provide a new mechanism to get energy without air, if you know how to improve the actual, you are free to post it here. P.S: I found that [Narwhal](https://en.wikipedia.org/wiki/Narwhal) have some capabilities to reduce their air consumption while they are under water. In the english wikipedia there aren't described but they have: * Reduce flow of blood to non-vital organs. * Increased amount of [myoglobin](https://en.wikipedia.org/wiki/Myoglobin) in their muscles (to store oxygen). * Increased amount of slow twitch muscle fiber ("red" muscle) that contain high amount of myoglobin and mitochondria for large periods of constant use instead of fast twitch muscle fiber ("white" muscle) for small periods of strong use. [Answer] Nitrate Reduction Cycle. Bacteria used to breath nitrates when they haven’t developed the necessary complex IV for oxygen reduction. So they used nitrates. The primary drive away from non-water respiratory metabolism was primarily the high cost and low availability of the hetereoatom substrates, not because of the lower efficiency. If the mitochondria within your people somehow gained a bacterial complex VI gene from horizontal gene transfer...... Then, we can conceive that your people accumulates the nitrates when there is enough oxygen (probably by respiratory oxidization of urea), accumulating a very high concentration within a buffer within their vital organs(probably because their need for frequent diving, or having to live extensively underwater, as an example), using it when the membrane potential of their mitochondria is lowered below a certain threshold, converting the nitrates into ammonia and releasing a lot of energy(up to 8 hours normal metabolism without oxygen, if not for consuming slightly more sugars per unit of energy), (the complex normally for reducing oxygen can use nitrates when oxygen is not available), effectively granting your people a built-in rechargeable bioelectrochemical battery. You can add in a cooldown for the skill as well, since the nitrate synthesis process is exoenergetic, it will require time and about as much metabolism as it is used to charge up the "battery", therefore once the 8 hours have expired, just a few breaths won’t be sufficient for another long term diving immediately. [Answer] Simple answer: increase the amount of myoglobin in these people's tissues. Myoglobin stores oxygen and is what allows whales to hold their breath for more than an hour even while exerting themselves. May not work for "several hours", but perhaps an hour or slightly more. [Answer] In addtion to the increased myoglobin, have the creature able to drop it's metabolic rate without harm. A number of animals can do that including some hummingbirds so they don't starve to death while sleeping. This more useful if the creature goes unconsious as the brain uses huge amount of energy and thus oxygen. Think of that rare occurance where a human recovers from an extended period of asphyxia because they fell into icy water and hypothermia was induced at the same time. [Answer] In Hal Clement’s The Nitrogen Fix, intelligent beings that don’t live in an oxygen atmosphere are described using nitrogen chemistry. He explains he has to eat a balance of oxidizing and reducing forms to produce energy from his food. In Ocean on Top by the same author, the human doesn't understand why they don’t breathe, and speculates (incorrectly) that some special food is supplying oxygen. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). Closed 2 years ago. [Improve this question](/posts/97040/edit) In the movie Interstellar, Miller's planet is an ocean planet orbiting extremely close to a black hole. The ridiculous tidal effects caused by the black hole cause the planet's water to concentrate into mile-high super tsunamis. Is something like this possible in real life? Is the passage of time slowed, the distance Miller's Planet is to such a large black hole, the height of the waves, and the amount of light the planet receives in the movie all potentially possible? [Answer] Kip Thorne thinks so. He was the scientific adviser for the movie Interstellar. About the planets orbiting Gargantua he said the following: > > This business of the enormous time differential between one of the planets orbiting very close to Gargantua and the flow of time back on Earth – the problem seemed to be that no planet could endure the resulting gravitational forces. This was something that even I thought was impossible, intuitively, until I went and slept on it and did a few hours of calculations. I came to the conclusion that in fact it is possible. The black hole needs to be spinning very fast, but is possible for the spin to be fast enough for a planet in the necessarily close, stable, circular orbit to not be ripped apart. I can’t fault anyone for saying, “Hey, that’s not possible,” without having first having the benefit of my book! Unless it’s someone who is very deep into general relativity and who I would’ve expected to go do the calculations! > > > Source: [Parsing the Science of Interstellar with physicist Kip thorne](https://blogs.scientificamerican.com/observations/parsing-the-science-of-interstellar-with-physicist-kip-thorne/) Thorne also wrote the book, The Science of Interstellar (2014). Copies available in all good bookstores and libraries. There is also a documentary about the movie's science which can be found [here](https://www.youtube.com/watch?v=lM-N0tbwBB4). I believe it is also an extra on the DVD. Yes the science of Miller's Planet is plausible and possible. Kip Thorne is one of the top physicists working in the area of general relativity. You don't get better than that. [Answer] The presence of the tidal waves suggests the planet is smooth without mountains or valleys to break up these never ending tidal super tsunamis. The largest mountains, oceans, and chasms on earth are caused by plate tectonics which are also caused by our molten core. This is the same molten core that gives us our magnetic field which protects us and allows our atmosphere to retain our oceans. The absence of any topographical mega features to break up the tsunamis on Miller's planet suggests that this planet doesn't experience plate tectonics which also suggests no molten core. Without the molten core, there would be no magnetic field to protect the planet's waters from being stripped away by solar winds. So at the very least the watery surface shouldn't exist. ]
[Question] [ I'm working on explaining away the existence of a planet whose entire ecosystem is based upon bioluminescent creatures, and I've been wondering if there could be a reason for their blood (or other bodily fluids) to be bioluminescent. Would it make sense to have a protein that gets to an excited state when combined with oxygen, and then returns to its ground state? If not, would any other explanation be possible? I'm trying not to make them have a particular bioluminescent organ, but rather to have them emit light when they... explode in a gory mess. Any pointing towards the right direction would be greatly appreciated :) [Answer] You might consider adding [luminol](https://en.wikipedia.org/wiki/Luminol) to the creatures' bloodstreams. When mixed with an oxidizer (like oxygen) and a catalyst, it becomes luminescent. It turns out that the iron in hemoglobin is a very good catalyst, which is why it's sometimes used at crime scenes to track blood. The glow dies away quickly, within a minute, meaning that it would have to be constantly replenished. Luminol is not organic, so the organisms couldn't simply produce it. Perhaps it's found easily in the soil or ground on the planet, or maybe it doesn't mix with the blood or an oxidizer until the creature dies. Now, justifying its presence is a bit harder, given that it's not organic. Evolutionarily, it seems to serve no purpose. Again, maybe it just happens to be present in the surrounding environment. The organisms certainly wouldn't need it to survive. As Joe Bloggs pointed out, the oxygen should be stored in the hemoglobin, which implies that it shouldn't react with the luminol. I don't know if the reactions between the iron in the hemoglobin and the luminol could free up some oxygen; if not, then there won't be a reaction until the luminol (and thus the blood) is exposed to air - just like in the situation described, when the organism dies. The result of luminol's chemiluminescence? A blue glow: ![](https://upload.wikimedia.org/wikipedia/commons/3/3a/Luminol2006.jpg) Image courtesy of Wikipedia user The Viewer (David Muelheims) under [the Creative Commons Attribution-Share Alike 2.5 Generic license](https://creativecommons.org/licenses/by-sa/2.5/deed.en). [Answer] I don’t think there would be anything in principle to prevent haemoglobin being linked to a [luciferin](https://en.wikipedia.org/wiki/Luciferin) type molecule to emit light, if there was an important enough biological reason why that would be beneficial. But this is problematic because the process would be very energy wasteful. So any process would have to be important such as mating or life or death escape scenarios. Other forms of bioluminescence might be better if less spectacular. Exploding does not sound like a good survival strategy unless the species is very interrelated like bees or ants and even then there would be much better ways of creating an explosion than by trying to become a bioluminescent time bomb. Eg the bombardier beetle. [Bombardier beetle](https://en.wikipedia.org/wiki/Bombardier_beetle) [Answer] There's definitely a good potential reason for a creature to luminesce on explosion. [Camponotus saundersi](https://en.wikipedia.org/wiki/Camponotus_saundersi) is an ant that explodes to take out enemies, and the vampire squid ejects a bioluminescent fluid to disorient predators in the dark abyss. It's not a far jump from there imagine an animal that explodes in a bright burst in a dark environment to save its brethren. Even just leaking luminescent blood could be enough of a distraction to let the others escape. The main problem, as others have noted, is that if the fluorescence is powered by valuable oxygen, that's less oxygen being used for the organism's life processes. A workaround could be that the hemoglobin's shape is radically changed by being sliced by an enzyme, so that it stops passively carrying and immediately uses the oxygen it's carrying to fluoresce. All you need to do is make the triggering enzyme abundant in the cells/intercellular space outside the veins, or even just under the skin. Then, when the organism was cut/exploded, the enzymes would mix with the blood and react accordingly. [Answer] I’d say no, there cannot be an analog between hemoglobin and a light-producing reaction because they use the same molecule (oxygen gas) for different goals. Hemoglobin reacts with oxygen to carry it throughout the body and provide tissues with it for aerobic metabolism. Luciferin reacts with oxygen to destroy it and make it into carbon dioxide. One of the theories for the evolution of bioluminescence is that it was originally created around the time of the great oxidation events as a way for some anaerobic bacteria to get rid of the toxic oxygen. However, all I think that means is that you can’t use a traditional light-producing molecule like luciferase or luminal or coelenterazine. If you could create a light-producing molecule that reduced things instead of oxidizing them then there would be a good reason to have them in the bloodstream with hemoglobin and other cells. Even better, if you blast an alien with a bunch of reducing agent in their blood, you’ll get some very dramatic chemical reactions as it’s exposed to the oxygen in the air. Just as a clarification, light-producing molecules don’t produce light in an “excited state”. They produce light by actively metabolizing, usually oxygen, and each time some oxygen is metabolized there’s a photon or three produced. It’s much like metabolic heat in that way- muscles get warm because they’re actively working, not because they’re in an excited state. ]
[Question] [ [Here's some writing. It will explain some aspects of the abyss in a way I can't otherwise.] > > "It's beautiful", uttered Ivan, in a rare moment of appreciation. "Rocks and platforms and chunks of land all floating in an endless abyss of the blackest black. This one's different from the others. If we jumped off this ledge, we wouldn't fall too far." > > > The lithomancer, Tumor, glances up. > > "The air here is breathable, but so thick you can almost swim in it. Seeing as how you're a pyromancer, Ivan, you could probably propel yourself regardless; however, Rhys and I will need to take advantage of its odd thickness." > > > Rhys jumps into the abyss. She travels a very short distance before halting in the air. She makes a breaststroke motion and moves forward a bit. > > "It's amazing, I'm completely weightless. Come on in, the chasm's fine." > > > The other two jump into the rift and begin trekking across. The abyss is deep underground but not deep enough to reach the planet's (presumably hollow were this the case) core. A waterfall on a distant floating mountain evaporates into the abyss, filling it with clouds. Occasionally, movement is seen. Never is wind felt, however. Perhaps they're not alone? --- So, how can I make this theoretical abyss possible? Some details and elaborations about the chasm from the story: * It's not a little chunk of space, as air is not only breathable, but thick enough for reasonable propulsion. * Nor is it a hollowed core at the center of the planet. * It's big enough for weather and huge chunks of land resembling small mountains to be dwarfed by its vastness. * As it's an underground chasm, there's no wind - the air is still. * No, by "the air is thick" I do not mean the cavern is flooded with water. Things like clouds and pyromancy would be rather difficult in that situation, not to mention any buoyant force on the landmasses and such. It means that the air resistance is high enough to give a bow an effective range of no more than about 40ft and allow for something similar to swimming to propulse oneself. * Bioluminescent molds and lichens provide enough light to make it appear as if it were daytime if not for the infinite nothingness beyond the clouds. This is only really notable in pointing out the abyss can support life. * And, of course, gravity just sort of vanishes past the ledge. It's a slow transition, but only slow enough to get a bit of an arc when throwing something or jumping off the ledge. There are two major questions: * What could be the reason for a chasm so large (potentially miles/kilometres across in all directions but up) existing underground? + Furthermore, chunks of land ranging from tiny flecks of stone to small mountains were left despite this. * And more importantly, why would it have some of its properties, such as super-viscous air and near absence of gravity? Answers are preferred to have a scientific basis, but given the high fantasy setting and frank implausibility, magic is also acceptable - especially if it has a good excuse (err, "lore reason") to be so. [Answer] # There are lots of reasons for giant caverns Popular ones include: * [Karst topology](https://en.wikipedia.org/wiki/Karst). If the area is made out of limestone, then water will slowly dissolve the limestone over time. Enormous caverns exist all over the world in limstone landscapes. * [Salt Domes](https://en.wikipedia.org/wiki/Salt_dome). Giant evaporated salt deposits, such as the one left by teh Aral Sea, or in the Bodele depression, will over geological time become buried. Then, the salt in them could be partially dissolved by water, or they could trap hydrocarbons that are then drained off, leaving caverns. * [Empty Magma Chamber](https://en.wikipedia.org/wiki/Magma_chamber). Around volcanic hot spots or fault lines, magma chambers can form. If the lava then later drains out of them, caves can form. These caves can be very large and VERY deep underground, and might be the best fit for your story. If you want lots of bits of land mass deposited in this cave, the reason could be as simple as a partial cave-in depositing thousands (millions?) of tons of rock into the cavern. # Super dense air is not possible If the air is thick enough to prevent a bow from shooting 40 ft, then the air is probably deadly. Gases have a maximum density. To get them more dense than that, they would have to be a liquid. I don't know of any gas that is dense enough to stop an arrow like you said; and in any case, any gas significantly denser than air would displace oxygen and suffocate people. Super dense air is only possible by magic. # Gravity is a property of matter and cannot be turned off Gravity can be viewed as an impression in a mattress caused by a large object, like a planet. Anything on the mattress that is close enough will 'fall' into the depression caused by the the heavy object. The effects of gravity propagate equally in all three spatial dimensions. On the surface of a planet (that is a sphere) there is no way to have gravity in one place but less gravity in another. A gravity-less zone on the surface of a spherical planet is only possible by magic. [Answer] I haven’t done the math on this (but (a) you specified [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") and not [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'"), and (b) you’re allowing [magic](/questions/tagged/magic "show questions tagged 'magic'")): The chasm lies under a deposit of some substance that’s many times denser than rock (neutonium?). It exerts an upwards gravitational pull on the space immediately below it; with enough mass, it should be able to create a region where the gravitational field is zero (or infinitesimal). Unfortunately(?), that also produces a higher than normal gravitational field on the surface above the deposit (i.e., above the abyss), but (handwave handwave …). [![cross-sectional view of the planet](https://i.stack.imgur.com/OjEhv.png)](https://i.stack.imgur.com/OjEhv.png) It’s hard to image such a structure occurring naturally, or being stable if it does exist. It would probably collapse under its own weight. So enter deus ex machina… it’s a constructed artefact (perhaps by a lost civilization, or by aliens). (The builders might still live a mile lower.) To support this notion (pun intended), I’ve added a second layer of the substance below the chasm, with pillars holding up the upper layer. This doesn’t address the viscosity of the air. But, if you stipulate that the chasm is accessed by tunnels from the ocean floor, you can argue that the atmospheric pressure is much higher than that at the surface, and that’s a start. [Answer] Anti-gravity isn't really what you are looking for. Gravitational nulling is. The precise alignment of a large moon, close enough and in coordination with a small enough sun and the right density planet could create a temporary lagrangian point in the chasm. If actual anti-gravity is what you want, then it would be as hard to find with magic as it would be with science, I surmise, because if gravity is brokered by quanta with spin-2 bosons, then they are very hard to detect (we still haven't), and certainly very, very hard to manipulate. Interrupting the local brokering of space-time deformation by gravity might produce the effect of floating, but probably would have some pretty unpredictable results. Without gravity, time itself would speed up for the viewer caught in the null gravity field. That is straight up Relativity theory. Without gravity, the concept of NOW becomes even more questionable than it already is. NOW, as a concept, isn't covered in physics like you might think. It has special significance to us, but it doesn't exist in the formulas that physics uses to describe physical nature. The person caught in a zero gravity field would experience the same NOW with others in it, but the NOW of the outside world would be racing past. [Answer] There had been a suggestion of using an air-xenon gas mixture at high pressure to create an environment where buoyancy was sufficient for humans to "swim" in air. Such an environment would appear to lack gravity in the same way that being underwater seems to be weightless. It's not, but buoyancy gives lift. The drawback to this air-xenon gas mixture was that it was an anaesthetic, so while humans could float in it they would be unconscious while doing so. While this isn't the recommended way to achieve the effect the OP wants it does provide a possible mechanism -- provided any possible adverse effects from a suitable gas mixture can be overcome. If the abyss was actually inside a gigantic pressure chamber, then a suitable gas mixture could be contained there sufficient to create the buoyancy for humans to float as if they were weightless. This mechanism would need to be ramped up considerably more so to ensure that rocks could also float in abyssal air. In a set-up of this sort, perhaps magic can operate in two ways. To overcome the anaesthetic properties of a high-pressure, high-density air-gas mixture. And to provide the containment needed for the pressure chamber to enclose the abyss. If magic is used, there might be a simpler solution. Assume the magic works as a powerful viscosity amplifier. This will not only stop arrows in mid-flight, but enable people and rocks to float in its medium as everything would sink extremely slowly. Since this is magic. The viscosity will operate in such a way as to not prevent air flowing to any living creatures present in the abyss. Magic without safety procedures or mechanisms would be unnecessarily dangerous. It could also be designed to permit the movement of living creatures as if they were moving through a medium closer to normal air while preventing them from falling downwards. A second simple magic solution would be a field of gravity neutralizing magic present in the abyss. Although this doesn't explain its arrow stopping properties. Perhaps that's a safety feature. ]
[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 the purpose of this questions, let's assume my crew has solved all those nasty problems of survivability inside the field, not unleashing a devastating blast of particles at their destination, and energy requirements. What would the solar system look like to someone inside the ship while the Drive was active? If they for some reason decided to look at the Sun through a window, what would they see travelling away from it? Would they even be able to see anything at all? [Answer] This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. According to [wikipedia](https://en.wikipedia.org/wiki/Alcubierre_drive) (which is more than sufficient for a layman-level discussion, hard-science or otherwise): > > The Alcubierre drive [...] is a speculative idea [...] by which a spacecraft could achieve apparent faster-than-light travel [...]. > > > Rather than exceeding the speed of light within a local reference frame, a spacecraft would traverse distances by contracting space in front of it and expanding space behind it, resulting in effective faster-than-light travel. > > > When I was getting my degree in physics (almost two decades ago), I wrote a paper on the visual effects of near-luminous travel. While this isn't the same thing, there are two similar circumstances that immediately leap out at me - both dealing with changes in angles: shape and color. First, the shape of things changes. The more the space ahead of you contracts (and the space behind you expands), the 'smaller' things ahead of you look and the 'bigger' the things behind you appear. Angles of objects slightly off-center ahead contract until - at some limit - they appear directly ahead; the more contraction of space, the tighter the new angle. For instance, if you are heading straight for a very large object (a galaxy, for instance, so we don't run into it right away), and it forms a rough circle directly ahead, the more the space contracts, the smaller that circle will be as the center remains unchanged by the edges contract in. A similar, but reversed, effect happens to objects behind you: they expand the 'cone' from you to them. A circular galaxy directly behind you will expand as the center remains unchanged by the edges all widen. At extremes, things directly behind you will seem to be 'swallowing' you as the angles pass 90°... Second, the color of things changes, too. The very wavelength of light undergoes the same contraction (ahead) and expansion (behind). Wavelength of light affects, among other things, color - so things ahead of you will tend to "blueshift" and things behind you will tend to "redshift." At smaller 'levels' of contraction and expansion, this would just make things look weird... but the [electromagnetic spectrum](https://en.wikipedia.org/wiki/Electromagnetic_spectrum) is more than just the visual spectrum. At extremes, things behind you will shift beyond red into the infrared then micro- and radio waves, and things ahead of you will shift beyond blue into the ultraviolet then into ionizing radiation. Hopefully, your culture that has invented a working FTL drive understands that they'll need radiation shielding... For near-luminous travel, these two effects don't start becoming really interesting until you hit something like 0.99999c, though they'll be visible to the naked eye long before that. The question then, becomes, how much "contracting" and "expanding" of space you're doing in your drive. (I'd provide equations, but I'd have to dig them out of a box in the basement - and while they don't require anything too nasty math-wise, they do involve four-dimensional vector matrices, which gives mathphobes nightmares. I haven't touched this stuff in close to two decades, so I'd rather not try to wrap my head around the actual physics - just the high-level layman descriptions.) [Answer] This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. The answer to this question is easy in description... Depending on whether you are looking in front or in back of you, you are confronted with either a field of white or a field of black. The reason for this is, if I remember correctly, as you move forward you are running into every bit of light there is at speed that the little light that is there gets built up, multiplied and shifted into the visible light spectrum (and beyond) making the white field while behind you no light can catch up to you which makes the black field. ]
[Question] [ In the world I'm currently building, there are many species, each with their own language. Most of these languages evolved naturally over time, much like here on Earth. But there is one race (let's call them the "T") that have a different situation. Long ago, they were an industrious and down-to-earth reptilian people with a language like any other, with technology comparable to mid-20th century America. But then a violent revolution took place and their society changed dramatically. The new government's goal is to develop the technology necessary to achieve a post-scarcity economy and to make their race practically invulnerable to natural disaster or military attack. They also want to stamp out their more animalistic side and make people rely more on reason. In order to reach these goals, they abolish all personal rights and conscript as much of the population as possible as scientists, engineers, teachers, and soldiers. Their society becomes one giant machine dedicated to science. Now, the T do not have the same obsession with freedom that those pesky humans living across the ocean do, and most of the population is okay with the new way of doing things, even if it wouldn't be their first choice. But some resist the ideals of the new society, and others struggle to adapt to a society obsessed with science, logic and structure even though they support the government's goals. After thousands of years, however, this resistance is eventually overcome, and the T not only reign supreme as their world's sole undisputed economic and military ultrapower, but the people love their authoritarian society, and scientific, rational thought is now an intuitive and emotionally satisfying part of their culture. A huge part of the success of the revolution's long term success was the government's ability to manipulate the way that subsequent generations thought. Not by brainwashing, torture, or other uncivilized means: they're totalitarian, but they're also idealist utopians, and they want the people to honestly support their goals. They can't use use force, at least not excessively. But what they can use is language. # Now, imagine that you are the first Supreme Social Architect of the new T state, and you are tasked with creating a new written and spoken language for your people that will gradually change the way that the T conceive of the world until you achieve your totalitarian scientific utopia. What kind of language do you come up with? Your goals are to: * Promote critical thinking and reliance on reason. * Promote cooperation and collectivism. * Promote the importance of precision, organization, and structure. * Promote a scientific approach to understanding the world. * Promote the notion of progress. Your goals are NOT to: * Either suppress or heavily promote independent thought. * Promote blind submission to authority. * Make the language unnecessarily complicated. Things you can control: * The symbols used to convey information (not limited to letters or logographs). * How text is arranged in writing (left to right, top to bottom, spiraling, graph-like, etc). * Grammar, syntax. * Vocabulary (you can create new words). * The denotations of words. Things you CANNOT control: * The phonemes of which speech is composed. * The connotations of words. * Vocabulary (you cannot prevent the people from making new words, although you can resist their usage in publications). I'm not asking for a complete dictionary or an exhaustive list of syntax of rules, just a few general principles and maybe a few examples. Looking to real-life Earth languages for inspiration is fine, but keep in mind that you are starting completely from scratch here and are free to introduce ideas not ever seen in any real language. Ultimately, it should very easy to write a scientific paper or have a formal debate in this new language, and very, very difficult to write a love sonnet, an impassioned rant, or a typical YouTube comment. I don't care if this situation seems unrealistic. These are sapient lizards living on the lip of a giant stone mushroom budding off the side of a sentient, jupiter-sized stone gyroscope floating in an infinite void of magical mists. For them, it works, and it happens this way. [Answer] I have a few suggestions for the Supreme Social Architect: 1) Some real-life languages have a characteristic called [evidentiality](https://en.wikipedia.org/wiki/Evidentiality) in which the grammar of the language obliges speakers when making any statement to specify what evidence they have for the statement; for example whether they know the statement to be true by personal observation, or have inferred it to be true by deduction, or have merely been told that it is true. According to Wikipedia the Eastern Pomo language > > has four evidential suffixes that are added to verbs, -ink’e > (nonvisual sensory), -ine (inferential), -·le (hearsay), -ya > (direct knowledge). > > > A scientific language could use a form of evidentiality to grammatically distinguish between the scientific meanings of fact, hypothesis, law and theory in ways that oberron's [answer](https://worldbuilding.stackexchange.com/a/50723/9207) has already suggested. 2) Science starts with numbers, so the words for numbers should be strictly regular, with nothing like "eleven" or "quatre-vingt-dix". It has been speculated that one reason for the facility pupils in East Asian countries show in mathematics is that in most of their languages it is simply easier to learn to count than for speakers of Indo-European languages, because the words for numbers are more logical and regular. 3) Scientific terms should not be be coined by taking a word from the general language and narrowing its meaning. This causes [confusion](http://www.southernfriedscience.com/the-importance-of-word-choice-terms-with-multiple-meanings-for-scientists-and-the-public/). Likewise scientific terms should not be allowed to be used colloquially or metaphorically unless the word is grammatically marked to show that it is not being used literally. 4) To "promote the importance of precision, organization, and structure" you could specify that clauses and sub-clauses be nested as precisely as in a computer language. In fact the whole language could resemble a programming language. Minimize homophones and synonyms. Make the grammar demand that the role of each word in the sentence (subject, object, indirect object, verb and so on) is explicitly marked with no possibility for ambiguity. Latin does this by word-endings but it could also be done by a fixed word order. 5) The writing system should either be purely phonetic or purely ideographic (Some Westerners think the Chinese writing system is ideographic but this belief is [untrue](http://www.pinyin.info/readings/texts/ideographic_myth.html).) A phonetic system would be easy to learn, making for an educated populace, but for that very reason what is written will be harder to control. Phonetic writing systems have a tendency to be "left behind" when the spoken language drifts, so they don't remain a perfect representation of speech forever. In contrast a pure ideographic system would be easy to control but very hard to learn. The author quoted in the earlier link thinks it would actually be impossible for humans to learn: > > Ideographic writing, however, requires mastery of the tens of > thousands or hundreds of thousands of symbols that would be needed for > ideographic representation of words or concepts without regard to > sound. A bit of common sense should suggest that unless we supplement > our brains with computer implants, ordinary mortals are incapable of > such memory feats. > > > However it could be that your lizard people have better memories. 6) Another possibility is to develop a language along the lines of the constructed language called [Ithkuil](https://en.wikipedia.org/wiki/Ithkuil), created by John Quijada and > > designed to express deeper levels of human cognition briefly yet > overtly and clearly, particularly with regard to human categorization. > Presented as a cross between an a priori philosophical and a logical > language striving to minimize the ambiguities and semantic vagueness > found in natural human languages, Ithkuil is notable for its > grammatical complexity and extensive phoneme inventory, the latter > being simplified in the final version of the language. The name > "Ithkuil" is an anglicized form of Iţkuîl, which in the original form > roughly means "hypothetical representation of a language". > > > However, given that > > Quijada states he did not create Ithkuil to be auxiliary or used in everyday > conversations, but rather to serve as a language for more elaborate > and profound fields where more insightful thoughts are expected, such > as philosophy, arts, science and politics. > > > Ithkuil may fall foul of your specification that it not be too complicated. 7) At first sight it might seem that you could promote co-operation and collectivism by forbidding the first person pronoun and related words. That was what was done in Ayn Rand's dystopian novel Anthem. However that society also forbade scientific progress, which would be a credible effect of forbidding the word "I", since curiosity is an individual characteristic. A better idea would be to follow the example of the artificial language that the anarchists in Ursula Le Guin's The Dispossessed created for their society, in which the individual possessive pronoun was discouraged by custom. Children were taught to say "this is the handkerchief I use" rather than "this is my handkerchief". Egalitarianism is linked to co-operation and could be promoted by not allowing any honorifics or status-linked speech registers to be embedded in the language, e.g. make it in this respect more like English in having only one form of "you" and less like [Korean](https://en.wikipedia.org/wiki/Korean_language#Speech_levels_and_honorifics) or [Javanese](https://en.wikipedia.org/wiki/Javanese_language#Registers) which both have different forms depending on relative status. On the other hand the Supreme Social Architect might want to keep some honorifics in the language for use when addressing Supreme Social Architects and similar important people. --- After all that, I don't think the scheme would fully work, even granting for fictional purposes the different brains of the lizard men and the operation in your universe of a fairly strong version of the [Sapir-Whorf hypothesis](https://en.wikipedia.org/wiki/Linguistic_relativity). You can't get blood out of a stone and you can't get new concepts by specifying a particular grammar. Of course you can get them through the medium of that grammar, but you might as well not bother, since you could also have got them from any language that can generate infinite new sentences, i.e. any [true language](https://worldbuilding.stackexchange.com/questions/48161/language-threshold-for-a-species/48165#48165) that exhibits [Hockett's design features](https://en.wikipedia.org/wiki/Hockett%27s_design_features). Put another way, if the new language has the capability to generate new ways to express new scientific ideas it also (as a matter of logic rather than idealistic notions about the creativity of free people) has the capability to generate new ways to handle declarations of love or political rants. [Answer] [Esperanto](https://en.wikipedia.org/wiki/Esperanto) had very similar goals to your language when it was created, although more for the purposes of world peace as opposed to totalitarian control. It was to be spread from the bottom up, instead of forced from the top down. If you researched the properties and reasoning for the properties of Esperanto, you'd probably learn more than you could on these forums, since Ludwick Zamenhoff (the inventor) made the [most successful artificial language](http://www.ikso.net/tmp/Blanke2009.pdf) ever and I didn't. Even more informative might be to read [criticism](http://www.yearlyglot.com/five-failures-of-esperanto/) of the language to see what might have been done even better. Other moderately successful artificial languages are [Volapuk](https://en.wikipedia.org/wiki/Volap%C3%BCk) and [Interlingua](https://en.wikipedia.org/wiki/Interlingua). So the other hidden part of your question is: what are the effects on a language that is forced onto a population? I can't really answer this that well, but there are many examples of language standardization, here are some examples with links as I could find: * Mandarin Chinese was pushed on top of all other Chinese langauges (Yue, Wu, Min, Hakka, Gan and more) which were not really dialects, they were as distinct as the Romance or Germanic languages. Those langauges survive until today, but Mandarin is now the dominant lingua franca at least since the Cultural Revolution. * Russian was pushed on top of other languages both similar (Byelorussian, Ukrainian) and dissimilar (from the Finno-Ugric, Caucasian, Turkic, Mongol, etc families) by the [Soviet Union.](http://ccat.sas.upenn.edu/~haroldfs/540/handouts/ussr/soviet2.html) [Here](http://www.oxuscom.com/lang-policy.htm) is some info on the language changes. * French was pushed ontop of the regional dialects of France. Some (like Burgundian) were other langues d'oil and were properly dialects and probably mutually intelligible. Some like the langues d'oc from southern France were probably separate languages more closely related to Catalan than to what has become modern, standard French. Some, like Breton, were from completely different language families. There were changes to the language during [the](https://slmc.uottawa.ca/?q=french_history#s4) [transition](http://www.orbilat.com/Languages/French/French.html) from Middle French that was national language of the elite, to Modern French. The links aren't the best; this topic is something I wish I knew more about. There is so much that goes into creation of a language and a grammar, that I think it is really beyond the scope of a question on this forum. But if you are trying to learn more, I would suggest the key point is that there are two aspects: how the language is designed, which you can learn about from Esperanto, and how a language is changed when forced on a population, which you could can learn about from 1920s Russia, 1950/60s China, and early 1800s France. [Answer] Beyond examples of our vernacular languages can replace others, one point that your Supreme Social Architect of the new T state will need to work on is the actual education system. Scientific and Engineering studies are full of technical jargon that confuses a lot of students at first. Some even say that it is actually one of the reason why some believe not to be suited for science. Fostering rational and scientific behaviour will require to find ways to educate citizens into thinking `rationally`: understanding the difference between an idea, an well formed hypothesis, a verified hypothesis, a demonstrated theory and a law of physics (for more on this: [here](https://ncse.com/library-resource/definitions-fact-theory-law-scientific-work)). Through education will they have to learn abstract concepts which are not easily observed in day to day life: feedback loops, fractals, chaos, differential equations, ... the same way people learn foreign languages and have to deal with concepts of foreign cultures. One side benefit though, exclusive focus on scientific studies seems to leave students (unless it is predispose bias in our biology) less dispose to social skills ([here](http://www.rihs.ufscar.br/wp-content/uploads/2015/02/Social-skills_a-key-factor-of-engineering.pdf)) which could help solve the challenge of creativity limited to the field of science (though the line to walk to make it credible in your world might be thin). ]
[Question] [ Something I was working on in the past involved a species of sentient insectoids. The idea was the two sexes usually live in two very different environments and rarely come into contact with the other one, except for when they meet in a sort of 'middle ground' to mate. Consequently, they look to outsiders (including humans) like two completely different species (we'll assume the embryos, or whatever equivalent they would have, are left to hatch in the aforementioned neutral ground, and once born those of each sex find their 'home turf' by instinct). The males of this species would be capable of flight (probably even hovering) with limbs that while highly dexterous are also somewhat fragile. The females on the other hand are flightless, with segmented bodies that are stronger and tougher at the expense of dexterity (any arms are not much more articulate, if at all, than pincers). In what kind of environment/ climate would these insects develop these very different physical traits? What kind environment would be suitable for them to come into contact long enough to reproduce? [Answer] This strategy is known in some moths, such as the [Winter Moth](https://en.wikipedia.org/wiki/Winter_moth) and the [Vaporour](https://en.wikipedia.org/wiki/Orgyia_antiqua). The female has a short life as an adult, she doesn't feed but remains by the cocoon. The male finds her by pheromones. Since the female is vulnerable to predation she is cryptically coloured, and therefore it is important that her pheromones are effective, as the male can't find her by sight. The females don't select their mates so males are not adapted to attract females, only to find them. The difference from the situation that you describe is that the larvae are mixed, and remain so until the adult emerge from pupae. If the development of the male required a particular food type there could be pressure for the species to separate their genders earlier. So the environment in which this evolved on Earth is one in which the ancestral species had pheromone signalling, and and there are costly adaptations (wings). The species have a long childhood and short adulthood. The female benefits by saving in the costs of growing wings. But loses the ability to choose her mate and is somewhat more vulnerable. How this would affect intelligence is interesting. Are the adults just sex machines or do they engage in rational behaviour. If the latter then the questioning of gender roles becomes interesting. The females instinctive sexual behaviour is to hide and pump pheromone, but a sentient species may question that role, leading to conflict. Most males are controlled by the their pheromone primed sex drive - but what if one actually wants to try communicating to a female. If the adults are short lived they could lose their brains during pupation. Are then the larvae intellectual. As they are growing, how do they feel about the fact that sometime they will build a cocoon and die soon after. That is some kind of coming-of-age story. In the moths the larvae are not dimorphic. Do the larvae even know their own gender? [Answer] Insects can also be greatly shaped by diet, the presence of certain fruits or plants could lead to very different physical and behavioral traits. You may not even need to drastically separate the species as you could have a tiered rainforest situation where the males occupy the upper canopy/emergent layer and fly above the treeline catching food while the females are down on the forest floor and develop sturdier bodies lacking evasive means. In such a forest, certain clearings or in the understory (the medium ground between canopy and floor) would be places where they could gather to mate. There are also species of fungi that "hijack" the behavior of ants and control them to help the fungus reproduce. If you want to make the species even more confusing to outsiders, the larval stage could be aquatic and they mate in spawning pools. This could even give the appearance of them being three unique species to outsiders when they are actually one. [Answer] Does it have to be the males which fly and the females which are ground bound? Because if you reverse that, then you can have some biological justification. For instance - the females migrate, the males are territorial. The females fly off to sea, like albatrosses, and spend the year feeding up on fat-rich fish and squid, so that they can obtain all the right nutrients to lay their clutch of eggs. They'll stop off on islands and coastlines and hang out with other females. The humans may think of them as 'flying Polynesian islanders'. The mature males are territorial, like male Grevy's zebras or IIRC male Grant's gazelles. (Not all of those males hold territories - some migrate - so they are not an exact match for your insects, but at least they are not migrating by flying). The mature males stay put because come the breeding season, the guys with the territories get all the gals. If you want them to have 'civilised' territoriality (you get on with your neighbours and invite them round for tea) rather than 'animal' territoriality (you spend time threatening your neighbours and attack anyone who enters you territory) then the males could spend all year building stuff that will convince the females to mate with them. Fantastic pools for the larvae, blinged up houses to show off their wealth (like bower birds), stockpiles of a particular food which will increase clutch size or which is something the larvae eat. The humans could view this as artistic endeavours, religious fervour or some sort of [potlatch society.](https://en.wikipedia.org/wiki/Potlatch) ]
[Question] [ I'm designing a creature similar in size and behavior to a large dragonfly. However, I would like it to fly with rotating "wings" in a similar fashion to a helicopter. I'm thinking a [twin rotor design](https://en.wikipedia.org/wiki/Intermeshing_rotors) would be best due to the bilateral symmetry, but I'm open to anything. So my questions are: Would such a creature actually be able to fly? I don't see any reason why it couldn't as we have machines that fly with the same mechanics, but I may not be considering something. How would the rotors work? I'm not aware of any creatures that have a rotating appendage (besides something like swinging your arms in a circle). I suppose there could be some mechanism similar to a crankshaft to convert translational motion to rotational. But I'm still stuck on how a creature could have rotors. Everything I've come up with is very mechanical and doesn't seem to translate well to biology. As for evolution, I think it could make sense if shortened rotors first evolved as part of the creature's aquatic ancestors, enabling faster movement in the water. As the creature evolved, it used that motion to make short hops out of the water in order to catch prey. Further down the line, the adult stage became more land based and required the agile motion it had in the water. I'm not looking for perfect scientific accuracy, but rather general plausibility. [Answer] Take an animal with [radial symmetry](https://en.wikipedia.org/wiki/Symmetry_in_biology#Radial_symmetry), which is what rotors have. Make it spin. Yes, the whole animal. Rotating parts are a pain in so many ways. Not worth it. Spin might make sense if attacked by a moderately larger predator as it makes you harder to hit with those jaws and all those sharp teeth. Optimize it for spinning by flattening the limbs into wing profiles and improving ability to keep spinning. This will create an aquatic creature that is essentially a living propeller. It should be fairly fast and agile as it can push lots of water for its size and with high degree of control. That said the drag would be fairly high, so it would be fast and agile in bursts. This would imply either an [ambush predator](https://en.wikipedia.org/wiki/Ambush_predator) or something that needs to escape ambush predators. Now give it ability to spin up to air and you have a flying rotor. Maybe an ambush predator that is small enough that it needs a good escape plan? Your specified size is actually a good match for this. And mention of dragonflies suggests a predator that evolves the ability to attack flying insects and even small birds by spinning up to air and dragging them down to water. Just like a good ambush predator does. Would need good eyes and decent brain, though. Initial spin would probably come from using some sort of slow load but fast release spring mechanism in contact with solid surface. [Answer] This is a case of [rotating locomotion](https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems). Simply put, this is highly unlikely to evolve in a single organism: 1. Any evolved structure must be useful as a less-evolved structure at any point in the organism's evolutionary history, or it must be able to be evolved with a single mutation. 2. If a living part of an organism is to rotate, it must either be so small that it obtains its nutrients directly from its environment, or the means by which metabolic requirements and communication are fulfilled must first be evolved. 3. If a non-living part of an organism is to rotate, a mechanism for its construction must exist, and the integrity of this separated-but-retained dead body part may become a limiting factor for the survival of the organism, or else a means of replacement must exist. 4. It is far more likely that an organism will evolve a particular capability using means that require fewer steps and pre-conditions, and it is generally not possible to evolve a capability if a reduction in fitness is a pre-requisite. It is not beyond the bounds of possibility for this 'organism' to actually be two or more organisms, a 'body' and two (perhaps different) 'wings', that combine to form a single rotary-winged unit. However, the organisms' ancestors must have been viable in a less-evolved state. Perhaps this symbiotic grouping evolved when a 'body' ancestor took to hanging on to one or two 'rotor' ancestors in such a way that when the group fell, the rotors would rotate, providing increased drag and retarding a fall, allowing safe falls from a greater, potentially unlimited, height. By evolving the means to power the rotation of the rotor symbiotes, the loss of altitude could be further slowed and eventually negated and then reversed. Communication between the symbiotes could evolve, giving the ability to change wing aspect on command from the body, as could symbiotic nutrition, the body feeding its symbiotic wings when convenient. While the organisms involved must at some point in time be capable of independent existence, there is no reason why they may not evolve in tandem to be totally dependent on one-another, any wing lacking a body or any body lacking its wing(s) being far less or even unable to survive without the other(s). These organisms would breed and reproduce together, and would get together in infancy and then remain a group, the loss of any one of the group being fatal to the other(s). However, prior to the evolutionary point where symbiosis becomes obligate, it may be possible for a body to acquire a new wing, and vice-versa. It is possible that the wings and bodies may be two completely different species, or that they may be the same species, but different genders, the female bodies being in symbiosis with the male wings. [Answer] The energy usage would be phenomenal, but hummingbirds and many insects can hover in a manner that makes essentially no use of a wing's ability to glide. If the creature is light enough and the atmosphere dense enough it should be possible. It will likely need a very calorie rich diet, or only fly for short periods of time, or both. The rotors could be spun by an internal turbine where blood or another circulating fluid is pumped around an internal fan shaped part of the rotor to spin it. This could also allow the rotor to receive nutrients, since wrapping these rotors in flesh to support a circulatory system like a wing or arm would add greatly to the weight and drag of the rotor. Better something like keratin, bone, or cartilage than a full wing. I'm no physicist or biologist. But we've got animals that hover, and animals that use jet propulsion. This doesn't seem impossible. [Answer] Exactly like a helicopter? Like, with a freely-rotating axle? Probably not. But if you just want something the moves its wings in a roughly-circular path that's closer to a horizontal plane than to a vertical one... sure. Especially when it's that small. Consider: you do not need a freely-rotating axle to achieve circular motion, as can be amply demonstrated for yourself by swinging your arms around. Many small creatures fly and hover by essentially "rowing" in the air--they'll change the pitch of their wings on the forward stroke vs. the backstroke to ensure they always produce a downward component of thrust. If I recall correctly, in hummingbirds and dragonflies (and most flying insects), the path of the wingtip is more of a figure-eight than a simple oval or circular path, as this results in less time spent on the upstroke and more on the down, but an ovoid or even circular path analogous to the motion of feathering rowboat paddles should be possible. Now, just shift the creature's limbs so that they are swinging above its head / behind its back, rather than out to its sides, and you have essentially a biological helicopter, with two or more rotors in pairs (one on each side) and only one blade per rotor (the blade being a limb, swinging around a shoulder joint). In this configuration, there is much less significance to the vertical component of the stroke, so the advantages of figure-eight motions fade, and you might as well just swing the blade-limb in a simple circle, making use of wrist-axis rotation to ensure that the blade is nearly-always oriented in a way such as to provide downwards thrust. At some point in the cycle, the blade would need to do a quick "flip" over to avoid over-rotation of the wrist-axis joints, but that can be kept very short, so that the interruption in lift is negligible, and perhaps even compensated for by the other paired blade. How could this evolve? Well, start out with something that swings its arms back-and-forth, feathering the lifting surface like a paddle just like a hummingbird does... and then hand-wave a transition to just continuously swinging its arms in a big circle over its head, rather than rapidly switching back-and-forth. [Answer] You could have the rotating blades be mostly keratin, so it is acellular and constantly growing. The animal perhaps trims it to the correct shape with its forelimbs. The rotating part might work better with tandem joints with the blades intermeshing at an angle (sort of like a Chinook or even better, the Kaman K-Max) so they could have a range of motion about like a human shoulder (which can rotate in almost a full 360 degree flat plane). Two rotating joints with horn rotors might alleviate the need for a spinning tail rotor, which I think is a necessity if you had just one rotor (to counter balance the rotation of the helicopter body). Both rotors would provide lift, and possibly be tilted forward and back for acceleration and pitch, while a bird like tail could give some maneuvering. ]
[Question] [ The discussion of the origins of patriarchy, in some of the answers to [Preventing post-apocalyptic society from becoming misogynistic](https://worldbuilding.stackexchange.com/questions/38686/preventing-post-apocalyptic-society-from-becoming-misogynistic), has me wondering if a government couldn't be designed to put a premium on raising children. Imagine a new space colony which, due to the lack of room on the generation ship, is facing under-population issues. To combat these issues, the colonists adopt a weighted, pure democracy as their governmental structure. Each family unit will receive one vote for each of their children, divided by the number of parents in the family unit. So, a monogynous couple with four children would get 2 votes, while a polygamous couple with two wives would need six children to match the monogynous couple's voting power. The idea is to maximize not only the number of children, but also the ratio of parents to children; in the hopes of providing all of the children with adequate parenting. We don't want some power-mad politician sire-ing his own political party. And since only parents can vote, hopefully all decisions will be made with the long term health of the colony in mind. *How can someone game* this system? What subtle loopholes have I left open which would allow a creative and virile/fertile person to obtain disproportionate power? [Answer] # Harem Dynasties Start with the assumption that, unless someone intervenes, women can bear an upper-average of about 10 children. That is to say, if for instance a woman is treated as a brood-mare from the time she is best able to bear children, she’ll average 10 live births. This is a very rough estimate, of course, but it’s plausible enough. If I have thirty wives in my harem, and I strive to keep them all pregnant as often as possible, I’m going to have 300 children. That means 9.7 votes, and I control them all. What’s more, if I raise my sons to behave the same way, and convince 80% of them to help build our family dynasty, then by the time I’m 80 I’m going to control something on the order of 1000 votes. You, meanwhile, with your silly monogamy, will not control more than 5 votes in the first stage, and chances are your wife won’t let you get that far. Even if she does, you’re not going to get more than 15 grand total with all your sons on board. # Daughters For Sale If you allow women to be treated as brood-mares, daughters and sons will also be valued quite differently. Among the creepy power-lords, with their harems, daughters are a valuable trade resource. Sons, by contrast, have to be raised to maintain the dynasty, which means education and a strong sense of privilege. So I have my wives raise my daughters in the compound, while my sons—once they are of an age where they’re even vaguely worth talking to—get shown enormous respect and granted all kinds of privileges. (Take a look at how pre-modern Korean society worked, especially among the elites, for an example of how this sort of thing goes.) Once my daughters are of age, I trade them to other elite power-lords to bulk up their sons’ harems, and they do the same for me. Not that I want some other lord to have more votes than I do, but let’s face it, his interests and mine tend to lie in the same direction. What we don’t want is those awful monogamous peasants getting any real power, now do we? # Uh Oh So the point is, the system can be gamed pretty drastically, and once it gets this way, there’s no undoing it: the people with the power to do anything want it to stay. I suggest preventing any kind of poly-marriage, for a start. Cap the number of votes per marital unit at 5 (preventing brood-mare situations). I’m not sure this society is going to have the positive results you’re looking for, but your question about gaming the system was specific and clear. [Answer] Never get married. 2 parents + 2 children = 1 vote 1 mother + 2 children + 1 guy who hangs out with them but is totally not the husband = 2 votes Even if they split the kids evenly there is an advantage. 1 mother + 1 child = 1 vote 1 father + 1 child = 1 vote There is a strong incentive to live together but never get married it doubles/trebles the voting power. There would be unofficial marragies with a great deal of negotiating about who gets the kids. The old are helpless** Once your kids become adults you have no voting power and neither do they and so you can be deprived of any privileges since you lack votes to protect them. You only get indirect power when you become a grand parent. [Answer] I can see one main loophole, which is that the rule doesn't state that the parents must raise the children from birth. It's much, much easier to raise a 16-year-old than a newborn baby (citation: every parent ever) insofar as a 16-year-old can, for the most part, handle many things by themselves. True, teenagers pose their own unique set of issues (citation: personal experience), but at least they can do some things that infants cannot: * Eat * Drink * Use the bathroom * Walk * Work So, here's the plan to make your own political party: 1. Find orphans, preferably tweens - the older the better. There must be some somewhere on the ship. If not, a truly evil parent-wannabe could make children orphans via murder, but that's just heartless. Alternatively, look for kids whose parents are willing to give them up. 2. Raise the kids. Again, the older, the better. The older ones will be able to handle themselves, so it's not going to be incredibly challenging to take on another teen - at least, not as hard as it would be to adopt a newborn baby. 3. Profit. [Answer] The biggest problem I see is the question of "What defines a family?", and also what happens to partial votes. Here I'm assuming that partial votes are lost - you divide and round down to get your number of votes. You mentioned polygamous relationships, so let's use some reverse induction. Having {..., 5, 4, 3} parents makes a family. Having two parents (monogamy) makes a family. Does a single parent count as a family? Well, sure, why not? There's your loophole. A single mother gets one vote for each of her children. She gets more relative voting power than anybody else (double that of a monogamous couple with the same number of children) - and the best part is that due to the severe underpopulation, nobody can fault her for continually getting pregnant. The only issue they could have is the issue of parent:child ratio, but at a certain age (I'm assuming) they start schooling of some sort so the parent:child ratio stops mattering as much. On the converse side, I can see the polygamous family with one father and many mothers. Many mothers make many children, and then many mothers meet sudden "accidents" once they go through menopause, and you're left with a not-so-grieving (and yet oh so ambitious) father with more votes than he knows what to do with. Alternatively, I can see an underground market for children being established - election time is coming up and you've got seven children for your two parents (meaning 7/2 = 3.5 -> 3 votes)? Go ahead and buy an eighth so that you can bump up from three votes to four. Or if the vote itself isn't as important to you, sell one of your seven to someone who does want that extra boost... if they're willing to pay, of course. ]
[Question] [ How would faster-than-light travel appear through window of a space vessel? All the movies and TV shows like Star Trek and Star Wars seem unrealistic: * Star Trek credits: passing stars get bigger and nearly "brush the top of your head", but wouldn't it look more like a flat 2D animation with dots simply rearranging? * Star Wars hyperdrive: stars appear as perfect line segments that point exactly away from the center during the "whoosh", but doesn't the sky change constellation shapes based on your vantage point, making the lines more irregular? * Wouldn't the oddness of time and length transformation cause severe warping of light entering the window of your vessel, eg, I recall seeing a physics talk about seeing the back of an object before you passed it. Has anyone assembled a realistic video of FTL travel through the window of a ship? [Answer] Star Treck's warp drive assumes being able to establish a warp bubble around the space vessel to move slower than light in the local space, but faster than light in the surrounding space, to work around the limitations of special relativity. A warp bubble would show some similarity to a worm hole. To get an idea of spacetime distortion caused by a wormhole you may like to watch [some of the videos](http://www.spacetimetravel.org/wurmlochflug/wurmlochflug.html) the University of Tübingen (Germany) is hosting. The same site provides [a simulation of a walk through the city with just below the speed of light](http://www.spacetimetravel.org/tuebingen/tuebingen.html). In both cases you get visual geometric distortions. But you get changes of the color by [the relativistic Doppler shift](https://en.wikipedia.org/wiki/Relativistic_Doppler_effect), too, as simulated [here](http://www.tempolimit-lichtgeschwindigkeit.de/sphere/sphere.html). When travelling faster than light you would get additional strange effects, depending on the method you overcome the speed of light barrier. One well-known effect is [Cherenkov radiation](https://en.wikipedia.org/wiki/Cherenkov_radiation) caused by charged particles travelling faster than the speed of the light in the medium, which may still be slower the vacuum speed of light. Vacuum speed of light in a flat spacetime can only be achieved by massless particles like photons. Particles moving faster than the vaccum speed of light ([tachyons](https://en.wikipedia.org/wiki/Tachyon)) have been hypothesized, but have not yet been found. Overcoming the speed of light would resemble somewhat [falling into a black hole](http://www.spacetimetravel.org/expeditionsl/expeditionsl.html). When faster than light, light cannot reach you from the back. So this region would look black. Travelling faster than light in a medium is physically feasible, at least for subatomic particles. Travelling with the vacuum speed of light or faster leads to serious problems, with the exact vacuum speed of light being the biggest challenge, since you either need to get rid of your rest mass, if travelling in flat space, or you need to warp spacetime. The latter needs huge amounts of energy causing devastating damage to the environment. [Answer] Our most realistic, but completely hypothetical, method for going FTL is a warp bubble generated by an [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive). While in a warp bubble, passengers would be causally disconnected from the rest of the universe. This means that no stars would be visible at all, since no outside light would be able to reach the passengers. It's hard to say what the inside of a warp bubble would look like. Possibly: * It could look like an event horizon, meaning true black with some Hawking radiation in IR wavelengths. * Or the warped space-time could act like a mirror, reflecting photons from the ship back in a distorted way. * Or there could be some accretion effects on the boundary layer, with trapped particles being accelerated until they start to emit radiation, which would mean a nice (but possibly dangerous) light show. [Answer] The scientific answer: totally dark at the front, as light has been blue shifted out of visible range (you'd need a deflector anyway to prevent fatal radiation as you move), then a very bright ring around you perdendicular to the direction of travel. This ring is made up of blue stars at the front, intensely bright dense white stars, then red at the back of the ring. Then dark behind you as red shifted out of visible (you'd need a deflector anyway to prevent fatal radiation as you slow). The ring is predominantly stars to the rear of you, but they've been lensed to appear at the side of (and above/below) you. You'd also only see this while accelerating and decelerating as while actually at the speed of light you'd see nothing because no time would pass in your timeframe. You'd experience a jump into the future, but the only way to tell would be by taking some readings. [Answer] I don't see why stars would be stretched into lines, but the light of stars ahead would be blue-shifted and those behind would disappear entirely. The extent of the blue shift would obviously depend on speed you were traveling. It would probably be very subtle to the naked eye as stars mostly look like white dots and as the higher frequency light was shifted beyond the visible spectrum, infra-red light would be shifted into the visible spectrum. ]
[Question] [ I have a planet approximately 3.5 times the mass of the Earth. I have a moon orbiting that planet that has to be habitable as well, because my story will take place on the first expedition to this moon. What size would my moon have to be it sustain life? The reason I ask is because a body the size of our current moon doesn't have enough gravity. If I end up having to move the size of my planet up I can go up to max of 5.5 times the mass of the Earth. What tech level would be required for these 'people' to escape the gravitational pull of their exceedingly large planet? Yes, I am aware there are a [couple](https://worldbuilding.stackexchange.com/questions/9944/making-a-planet-habitable-for-humanoids-the-planet) of [general habitability questions](https://worldbuilding.stackexchange.com/questions/9857/making-a-planet-habitable-for-humanoids-the-star), however I think this does deserve its own question. [Answer] For a planet with 3.5 times the Earth's volume and 3.5 times its mass, the surface gravity will be 1.52g. I've [previously discussed](https://worldbuilding.stackexchange.com/a/9904/3202) the equation for surface gravity. Just note for your own calculation that 3.5 times the volume is about 1.52 times the radius. So, if you want to work in terms of volumes you can multiply the radius term by the cube root of the volume scalar you want. Basic surface gravity equation: $$g= {G\_{(gravitational\ constant)} M\_{(mass\ of\ planet)}\over {r\_{(radius\ of\ planet)}}^2}$$ For a planet with 3.5x the mass and 3.5x the volume: $${G\ 3.5\_{(mass\ scalar)}M\_{⊕(mass\ of\ Earth)} \over { ({3.5\_{(volume\ scalar)}}^{1/3}a\_{⊕(equatorial\ radius\ of\ Earth)}})^2} \approx 1.52g$$ Moon's habitability- As you've already linked, the moon's habitability is taken care of in [other questions](https://worldbuilding.stackexchange.com/q/9944/3202). Also [Jim2B's answer](https://worldbuilding.stackexchange.com/a/15645/3202) describes some basic characteristics. Getting from your massive planet to the habitable moon- As for getting there, they can use chemical rockets, just like us. I'm assuming what you want to know is if the higher gravity of the home planet will deter launching from it. There is a somewhat related question on the [Physics SE](https://physics.stackexchange.com/q/117347/45770). It relates to what I assume the core of your question is, at least. Getting to space from the surface of a planet with 1.52 to 1.76 times the gravity of Earth is not impossible, but it is more difficult. They will need very efficient rockets to overcome the [rocket equation](http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation). Or, as [Jim2B again pointed out](https://worldbuilding.stackexchange.com/a/15645/3202), an alternative to rocket propulsion. [Answer] What is the minimum size for a inhabitable body (moon)? Let me make the following assumptions: 1. Temperature ~ Earth 2. Moon density ~ Earth 3. To be inhabitable, the satellite must retain water as an atmospheric gas 4. The primary atmospheric loss mechanism is Jean's Escape (this requires a moderately strong magnetic field). Based upon these assumptions, the satellite must have a mass about 3x Mars ~ 33% of the Earth's ~ 10% of your planet's mass AND still have at least a partial liquid iron core. The density and magnetic field assumptions reinforce each other as the satellite probably has an outsized iron core which increases density and odds of some of that core remaining liquid. You probably want a separation between planet and moon greater than that between Earth and Moon or you'll get huge tides and tidal locking which would decrease the strength of the magnetic field. I'll supply math details later as time permits. How hard would it be to launch rockets from the planet? The rocketry required to escape your planet would be fiendishly difficult. I consider the Earth to be borderline on the everyday practicality of chemical rocketry. We can do it, but it's so difficult/expensive we reserve it for only highly valuable/rare missions. Chemical rocketry could be used in your case too it just increases the difficulty and reduces the payload even more. What type of space launch could you use to launch from the planet? You'll want to use something like [Nuclear Pulse Propulsion](http://jim2b.blogspot.com/2010/11/the-case-for-space-viii-nuclear-pulse.html) with high impulse and thrust or possibly one of the non-rocketry techniques of space launch like [Light Gas Gun](http://jim2b.blogspot.com/2010/10/case-for-space-vi-light-gas-gun.html) or [Ram Accelerator](http://jim2b.blogspot.com/2010/10/case-for-space-vii-ram-accelerator.html) that does not force you to haul your fuel up with you. [Answer] The conditions could be very different between the two bodies, and the life very different as well. At an early time after formation the minor body was more earth-like, similar to [the case of our own Mars](https://en.wikipedia.org/wiki/Noachian). The two bodies [exchange material](https://en.wikipedia.org/wiki/Martian_meteorite) so life started on both. But as the moon changed, the early life evolved to cope with very different conditions. After starting with the same [abiogenesis](https://en.wikipedia.org/wiki/Abiogenesis) stock, life on the two bodies went their separate ways long before photosynthesis and endosymbiosis occurred on the Earth-like body, and cells took different routes on (warmed)Mars-like moon as it lost its surface water and atmosphere. I imagine that instead of green leaves, beds of black goo filling maria that harvests energy chemically from harsh radiation, in the top layers of [cell-less protoplasm](https://worldbuilding.stackexchange.com/q/35114) that turns over, to circulate the activated chemicals to the “living” parts below. More complex life include algae (giant cells) and a massive level, of [endosymbiosis](https://en.wikipedia.org/wiki/Symbiogenesis) instead of just [eucaryotes](https://en.wikipedia.org/wiki/Eukaryote). Semi-autonomous [organelles](https://en.wikipedia.org/wiki/Organelle) share an enclosed bag and can swap out functional parts, including various tamed procaryotes (like mitochondria) that have found different tricks for processing different minerals and other resources. Feeding off the goo above, these thread through the rock of the crust mining materials and water to form the ecosystem. So the “conventional” aliens from the major body find, upon arriving on their moon, that the rocks are alive, and quickly find ways to eat them. [Answer] When I was a child I wondered why Superman didn't have to wear a spacesuit on Earth, since one explanation for his super strength was the much lesser gravity on Earth and humans would have to wear spacesuits to survive on the Moon despite the gravity difference not being enough to make them as strong as Superman. And I was quite skeptical about science fiction stories where the Moon had a breathable atmosphere. When I was 12 I read "He Who Shrank" (Amazing Stories, August 1936) by Henry Hasse" and was doubtful about the subplot involving a species who migrated from their home planet to its moon. I was very skeptical about both the planet and the moon being naturally habitable for a single species. "He Who Shrank"is otherwise a memorable story — [I had a dream with a variation of its plot recently](http://johnnypez9.blogspot.it/2010/06/he-who-shrank-by-henry-hasse-part-1.html). In the [Next Generation episode "The Host" 13 May 1991](http://www.chakoteya.net/NextGen/197.htm): > > LEKA: The people on our moons have been in discord ever since they migrated from our planet five centuries ago. To us on the planet They're like two squabbling children. We try to help settle their arguments by not taking sides, but this time we are at a loss. > > > So fifty five years later writers were still not worried about smart children laughing at them for suggesting that a species that originated on a planet could survive on naturally habitable moons of that planet. See also the habitable for Bajorans moons of Bajor in Deep Space Nine. Of course by then the idea of terraforming planets and moons to make them habitable was well known. See Project Genesis in Wrath of Khan and "Home Soil". So maybe the writers of "The Host" assumed that the people of Peliar Zel had to terraform their moons before settling them. Thus I suggest that you might face a problem in nomenclature. Calling the larger body a planet and the smaller body a moon may make some readers think that it should be impossible for both worlds to be naturally habitable for the natives of the larger world — or for humans if humans are involved in the story. One alternative is to describe the two worlds as a double planet instead of a planet and a moon. But not twin planets, of course. The Earth and the Moon have sometimes been described as a double planet, and after Charon was discovered Pluto and Charon were often described as a double planet instead of a planet and its moon. So you might do well to have some of your characters discuss or argue whether the smaller world is a moon or the smaller part of a double planet. And maybe include some ironic counterpart to the way that in our solar system the first asteroids to be discovered, and later Pluto, were considered planets and then demoted in status. Another method would be to have the explorers from the planet talk about how their people have dreamed and argued and studied about the possibility of life on their moon and the probability that it might be habitable for them. Point out that for the people of that world a dream that died over a century ago for Earth people is a reality and how wonderful that is for them. Make it in part a wish fulfillment story for us Earthlings. A third method — and I think you should use all three — is to show your work. Or, considering your question, the work of whoever you get to do the calculations for you. Have calculations done to show that the smallest sized and the largest sized habitable worlds can differ in size enough to be described as a planet and its moon, or alternately as sister worlds (but not twin worlds) in a double planet. I found [a discussion of the habitability of exomoons, natural satellites of extra solar planets](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/): > > A minimum mass of an exomoon is required to drive a magnetic shield on a billion-year timescale (Ms≳0.1M⊕; Tachinami et al., 2011); to sustain a substantial, long-lived atmosphere (Ms≳0.12M⊕; Williams et al., 1997; Kaltenegger, 2000); and to drive tectonic activity (Ms≳0.23M⊕; Williams et al., 1997), which is necessary to maintain plate tectonics and to support the carbon-silicate cycle. Weak internal dynamos have been detected in Mercury and Ganymede (Gurnett et al., 1996; Kivelson et al., 1996), suggesting that satellite masses>0.25M⊕ will be adequate for considerations of exomoon habitability. This lower limit, however, is not a fixed number. Further sources of energy—such as radiogenic and tidal heating, and the effect of a moon's composition and structure—can alter the limit in either direction. An upper mass limit is given by the fact that increasing mass leads to high pressures in the planet's interior, which will increase the mantle viscosity and depress heat transfer throughout the mantle as well as in the core. Above a critical mass, the dynamo is strongly suppressed and becomes too weak to generate a magnetic field or sustain plate tectonics. This maximum mass can be placed around 2M⊕ (Gaidos et al., 2010; Noack and Breuer, 2011; Stamenković et al., 2011). Summing up these conditions, we expect approximately Earth-mass moons to be habitable, and these objects could be detectable with the newly started Hunt for Exomoons with Kepler (HEK) project (Kipping et al., 2012). > > > This indicates a minimum mass for the smaller world of at least 0.25 Earth masses and a maximum mass for the larger world of no more than 2.0 Earth masses, thus indicating the difference in mass can be almost 8 times the mass of the smaller world. Since the sister planets — or planet and moon — would almost certainly be tidally locked both will rotate with the same period as their obit around their center of mass. The days of both will be equal to their month. But the faster a world spins the more likely it is to generate a strong magnetic field that protects the outer atmosphere from charged particles. So the orbits of the two worlds need to be designed to give them short enough months and thus fast enough spin. > > Some studies suggest that even extremely slow rotation would allow for substantial magnetic shielding, provided convection in the planet's or moon's mantle is strong enough (Olson and Christensen, 2006). In this case, tidal locking would not be an issue for magnetic shielding. > > > (from <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/>) If correct that may greatly lessen the necessity to make the orbits as short as possible. Note that the article discusses the habitability of exomoons orbiting gas giant exoplanets in the habitable zones of their stars (orbiting "Hot Jupiters") instead of exomoons orbiting Earthlike planets, which may modify some of the calculations a bit. you will need to calculate both the surface gravity and the escape velocity of both the worlds. It is a well known fact that long term exposure to the microgravity or weightlessness of Earth orbit causes health problems for human astronauts. It is not known if long term exposure to the lower gravity of Mars, for example, would have the same effect on human health. Thus you can choose to: 1. Ignore health effects of lower gravity on your natives of the planet. 2. Have their scientists use centrifuges set to simulate the gravity of their moon in their orbiting space station and discover that the natives of the planet don't suffer any bad effects from long term exposure to it. 3. Have the characters from the planet make only short stays on their moon. 4. Have the space ship include centrifuges to simulate the gravity of their planet. 5. Have the characters take other precautions against the long term effects of lower gravity, much as Earth astronauts do during long stays on space stations. 6. Have the characters discover the problem during a long stay on their moon, and find out they need to return home immediately, preferably when for other reasons it is least possible or desirable. 7. Have the planet and the moon have very similar surface gravity despite the differences in their sizes and masses, so that it isn't very surprising that the natives of the planet are not harmed by the minor difference in surface gravity. Or some combination of two or more of the above. If you make two very dissimilar worlds have similar surfaces gravity despite having very different masses and diameters, they will have to have different densities, despite there being both upper and lower limits of density for Earthlike worlds. The smaller world will have to be denser and the larger world will have to be less dense. Both the worlds will have to have high enough escape velocities to retain their atmospheres for geological time spans. The escape velocity of the larger world should be as low as is possible, since Earth's is certainly high enough to make reaching orbit and leaving orbit very difficult. Making the larger world less dense (within practical limits) will keep its escape velocity as low as possible. [Answer] The [Youtuber Artifexian](https://www.youtube.com/playlist?list=PLduA6tsl3gygXJbq_iQ_5h2yri4WL6zsS) has some good information on the topic, in which he explores star system and planetry building using equations (which I am currently compiling into spreadsheets for ease of use). According to Artifexian's videos, The mass you gave is great (3.5 Earth Masses is the absolute maximum size I'd use to make a habitable world), and your moon should be less than the mass of your planet, but greater than 0.25 earth masses. This may turn your planet and moon into a binary planet system (like Pluto and Charon) so when calculating things such as orbit you may need to find the Baricentre of the two bodies first. ]
[Question] [ ## Current Development Virtual reality (VR) devices are still mainly used for amusement like in this video of the game [Skyrim in virtual reality](https://www.youtube.com/watch?v=k7n5kRRHDpw) using Oculus Rift. With augmented reality (AR) devices such as [Microsoft's Hololens](https://www.youtube.com/watch?v=aThCr0PsyuA), Magic Leap and Google Glass we have seen business applications as well. [Techcrunch estimates](http://techcrunch.com/2015/04/06/augmented-and-virtual-reality-to-hit-150-billion-by-2020/) the market for AR and VR devices to grow to $150 billion by 2020. All in all, the current development suggests there will be a lot more work on creating AR and VR. For these reasons it seems likely to me that humans will be able to build and partially live in complex simulated-worlds in some hundred years and fully at some indefinite future date. It can be speculated that sooner or later every sufficiently advanced society will have the means to create something like The Matrix. Although being much more of a feat to accomplish it has been theorized that instead of creating artificial intelligence we might one day be capable of mind uploading / whole brain emulation allowing us to "exist" as a digital version of ourselves with no need for a physical body. ## Complementing vs Replacing Reality It strikes me as rather odd that in most science-fiction movies / literature I have seen the societies pictured – even those hugely advanced compared to ours – either not use VR at all or only as some kind of tool to complement reality – think holodeck – for amusement, training and whatnot. Assuming we will be able to do whole brain emulation and to create a simulated world as complex as ours wouldn't it be an ingenious solution and panacea to most of our problems to just collectively swear off our earthly bodies and live in a custom-made world replacing what we know as reality? Surely most present-day humans would be scared of transferring their existence to a simulated world and letting their physical body die but is there anything actually stopping us from doing so besides people's mindsets? --- ## Additional thoughts Matrix-ception Given my assumptions are correct and given enough time the following scenario could (have) happen(ed): A society that once entered a virtual reality designed so that it can not be manipulated from within might still find problems they have not thought of or a severe bug and build a new matrix from within the first one to escape to. Repeat several times and you would end up with multiple layers of matrices, multiple layers of existence possibly with distorted or removed sensory perception and laws of physics. [Answer] From a technology standpoint, it would be far more practical to simulate an environment virtually than to change the environment to make it seem something that it isn't. This is comparable to breaking down every molecule in your body and recomposing it elsewhere as opposed to simply stepping through a gateway. The number of advantages in programming your own reality outweigh the limitations and energy required to do anything else, and so I would argue that if anything, this would be our future. While you would certainly see a "matrix" type reality, emulating our reality, it would not be the one in which most people would be in. For example, if you could fly, why wouldn't you? This reality would simply be the internet, but 3d, if you can imagine it. The people within would have god-like powers. However, don't make the mistake of assuming it would be a game to most people. Like the internet, this reality would be serious business, being an economical hub. You would not need to be a programmer to build in this world. You'd simply have to have the right software and enough patience to do it. Most people would likely spend little time out of such a reality, and in fact, many services would be focused on minimizing your time out of this reality, such as food delivery or being able to work directly in this reality. Virtually everyone would connect to this reality at some point, though the poorer among the population would be the ones performing most of the physical labor which cannot be done otherwise. Advance another 100 years, and you may even begin to see people purposefully insert feeding tubes to their stomach so that they would not need to exit. The very few things which must still be done physically will be left to be done by robots. While this sort of world seems very alien to us now, it will not be us to accept it, but rather our children's children. While I would like to imagine that aliens would be very shocked to find us in such conditions, in all likelihood, should we ever meet an alien species, we will be making contact with their robots, and not with the species themselves. [Answer] > > Will sufficiently advanced societies ultimately embrace living in a simulated world? > > > It takes a long period of intentional effort for a human being to overcome their body's instinctual or habitual urges and motivations. It takes far less time to become addicted to a new pleasure. We don't currently understand how pleasure is actually perceived in the brain/mind/consciousness. We understand there are often hormonal triggers, but the sequence of events that cause us to perceive what we call pleasure isn't entirely understood. So, for instance, the pleasure of particularly good food. Part of this is learned in our youth. Part of this is simply the body's reaction to salts, fats, sugars, and other compounds evolution has taught us are good. Part of this is the feeling of satiety. Part of it is the company associated with the meal. Designing a machine that holds our consciousness isn't enough - it also has to trigger our pleasure centers, mimicking a variety of human pleasures, interactions, etc. But if the machine does allow us to perceive new and/or addicting pleasures, not only would people jump at the chance, they could - and perhaps would - become willing slaves in order to continue to receive that pleasure. This would drive a wedge between groups of society, and not necessarily due to the slavery aspect. Further, does the process of transference guarantee physical death, or is this something that is done due to the ethics of cloning? Can one create clones of their consciousness and make a million of their simulated selves? Can we backup a brain in case of machine failure? How would you determine the difference between machine failure and dementia due not to physical issues, but merely thought? > > ...wouldn't it be an ingenious solution and panacea to most of our problems to just collectively swear off our earthly bodies and live in a custom-made world replacing what we know as reality? > > > No. The machines would necessarily require more energy to simulate thought than the human body currently does. If we develop unlimited free energy (dyson sphere?) then this wouldn't matter, but even in 100 years a machine capable of simulating a world and a brain to experience that world will both be larger and more power hungry than the human body. > > Surely most present-day humans would be scared of transferring their existence to a simulated world and letting their physical body die but is there anything actually stopping us from doing so besides people's mindsets? > > > Aside from technology and people's mindsets, no, there's nothing stopping this from happening. [Answer] Its a possibility but that wont happen for a very long time and unless absolutely required. Consider the following cases where the entire surface of the earth is rendered inhabitable. And with the advanced technologies of the "sufficiently advanced society" might have to go further down into the earth. That of course is what happens is the Matrix movie. Yet another possibility I see is perhaps in a very advanced society, the whole concept of "driving to work" disappears and people choose to work from home logging into a simulated world/society which also provides the ability to conduct meetings in a virtual world instead of peoples' faces on a screen. We live in what we call the golden age of internet where we can do almost anything with a computer. It is safe to assume that with the advancement in the technologies, the computers would become something that can offer the user a virtual reality (instead of the conventional screens). What if all this is just the beginning of exactly what you had in mind. The same might happen even though the concept of living entirely in a simulated society is far fetched and like I already mentioned, absolutely required. So the only time a person would be outside the "network" would be for basic amenities like eating, sleeping (which can be done while in the system), defecation and for copulation. [Answer] Entropy makes this tricky. The end result will be that the virtual world MUST have an effect on the outside world. If there is no effect, then what is taking care of our bodies? If it's a mix of biology and robotics, what is preventing that system from breaking down? Obviously it has to be advanced enough to heal itself. So why would it stick around if it gains nothing from continuously feeding us calories and watts to keep our virtual worlds alive? It would simply start the next stage of life, and our consciousnesses would go away. Partially virtualized worlds make more sense, though they may asymptotically approach fully virtualized. This could be as simple as there being "keepers" who shift in and out of the "matrix." They bring information out of the virtual world into the real world. It could also take the form of augmented reality, if need be. As long as the Matrix proves to be the most efficient way of solving some problems (perhaps there are some socioeconomic problems that call for a deep wedding of many minds), it will continue to provide purpose to its existence to those who keep it. Arguably, that is happening right now, as I type this answer and the information it contains clears substantial physical distances to arrive in the from of lit and dim pixels on your screen. [Answer] I think given advanced enough tech to simulate reality, many people would give themselves over completely (already in America at least many people spend most of their free time online, watching TV, and playing video games). Those people, if they could work virtually and didn't need to disconnect to take care of themselves I could see assimilating fully. That said, even today you have many young people who are focusing on cutting out the digital world from most of their down time. These people feel that doing things like farming, sewing, cooking, wood craft, etc. provide more enjoyment and fulfillment. I think this shows that there will always be a contingent who try to keep technology at bay, and would prefer to live off the land on their own than integrate with that kind of technology. Could it happen? Yes - but there would need to be some nasty kinds of effects. Ultimately either it would be an issue of coercion or of the drug like potential of the virtual reality. Looking at these two more fully: * Coercion could come either through government intervention or some kind of disaster. While I have a hard time imagining a government succeeding at forcing everyone in, with a great and powerful robot army that becomes reasonable (possibly the robots are even controlled by people in the simulation). If the world was ending and people needed to head off to greener pastures, energy was not an issue, etc., etc., then I could see a generationship being built as a simulation machine for efficiency reasons - you don't have to grow all kinds of different plants, just synthetically generate all the nutrients needed. This could even replace the need to find an alternate world, so the ship could just hang around energy sources and keep the people alive in the simulation. * The other option would be that the simulation provides enough feedback to our bodies to function as a drug. After using the simulation for even a short period of time you start becoming dependent (it would boost serotonin and adrenaline at will). Eventually the real would will seem unbearable and people will constantly up on the high of the simulation. The simulation would likely windup being very similar to a game - there would be missions and things for you to do to give you purpose, a large open world to explore, and the availability to satisfy vices on a whim with no risks. [Cort Ammon](https://worldbuilding.stackexchange.com/questions/13764/will-sufficiently-advanced-societies-ultimately-embrace-living-in-a-simulated-wo/13799#13799) suggested the machines would not want to waste the enormous energy on us. Assuming true intelligence on the part of the machine (without it, it just takes care of us no matter the cost because that is its entire purpose), it is just as likely for the machine to develop a sort of parental feeling towards its people. It wants us to be happy and thrive, so it gives of itself the same way a parent does to a child (this could also be a source of tension, since sometimes parents have to stop you playing with the hot stove, even when you really, really want to). ]
[Question] [ I'm having trouble with a city in my fantasy world. My primary difficulty arises from the fact that most of the city-building resources I could find assumed that the city grew organically from a small village or an advantageous location. However, the capitol city in my fantasy was planned as a political and religious center from the time of its inception, and it's very difficult for me to conceive how everything should be placed. As I said, the city began as a political and religious center, but has grown fairly organically since its first stages. Its geography is fairly simple - it's situated a little ways inland from a protected southern coast, with a river that flows through it to the sea. Two other towns flank it. The three were originally separate, but the capitol has grown outward and the edges have all merged. Most or all of the ports are located in the two adjoining towns, but most trading goes on in the capitol itself. I have already considered that the most important political and religious landmarks would be in the center of the city, near the river. But as for where to put the rest of it - gates, banks, parks, neighborhoods, shops, workshops, stables, locations unique to my storyworld - I have no idea. Obviously the older city would be built more carefully and organized more neatly than the newer city, but other than that, I have nothing. As for resources, the most helpful thing I've found is the [Cartographer's Guild Guide to Creation and Depiction of Fantasy Cities](http://www.cartographersguild.com/showthread.php?t=2844). I also have a copy of [The Pattern Language](http://rads.stackoverflow.com/amzn/click/0195019199), but haven't begun to make much use of either, since I would prefer to have more specific resources at hand before I begin. Can anyone: * give me some ideas about where various types of buildings would be placed? * recommend some historical cities that are similar to mine? * point me toward some resources about city planning? * help me understand how the layout of the city would change as it goes from planned to organic development? If more information is needed, I'm happy to try to provide it. [Answer] A valuable question, with some pretty cool answers so far; but the question's got a lot of missing parts. You haven't given us a whole lot of information about this. The answers so far make some pretty broad assumptions about your world; I'm guessing that those assumptions are probably reasonably good, but I want to call out some worldbuilding basics anyway. Note that I am not going to address the aesthetic and purely creative aspects of your imagined world and realm and city. This is only an inquiry into the underlying mechanisms of reasoning. This may be helpful. Considering the underlying realities can often ignite chains of thought that end up stimulating the creative imagination. Hopefully, this could do that. However, I don't want to make you overthink the issue. Please ignore all of this if it doesn't help you. --- OK. Here's a distillation of what you are telling us: * It's a fantasy world. * The city was planned as a political and religious center. Unpacking this, we can infer that + There's organized religion in your world. + Presumably the religious organization has reached a power-sharing accommodation with the political authority. * "Its geography is fairly simple - it's situated a little ways inland from a protected southern coast, with a river that flows through it to the sea. Two other towns flank it. The three were originally separate, but the capitol has grown outward and the edges have all merged. Most or all of the ports are located in the two adjoining towns, but most trading goes on in the capitol itself." I'm not asking that you disclose any parts of your secondary world, but here are some very key questions. If you don't want to answer them for us - which perhaps you shouldn't - then at least perhaps you can ponder them yourself. Hopefully they can push you into thinking more deeply and precisely about the design of your city. --- ### What impact would your fantasy elements have? This is the big one, I think. "Fantasy", as a genre, implies systems of magic and/or semi-transcendent nonhuman actors. Sometimes these fantasy elements are not very consequential in terms of the shape and systems of the world: they are aesthetic elements, or plot drivers, but they don't really affect the generalities of ecology, politics, economics, and culture. They leave the worldbuilder free to proceed from close correspondences with historical precedent. On the other hand, there are many kinds of circumstances and mechanisms of fantasy that will affect your world in a very significant way. If your concept of fantasy includes elements that will impact they way your world wags, then you will need to account for it. Some purely invented examples (not, as far as I know, applicable to your world - just questions about how this can work) of how fantasy elements can modify your worldbuilding: * Are there populations (Elves, say; or Druids with the ability to make their curses bite; or dryads; or Ents; or whatever...) that make it difficult to clear forests for agriculture, or to build with timber? * Is there an age-old polytheistic clash between divinities of the Hunt and divinities of Agriculture? (e.g. [Cernunnos](http://en.wikipedia.org/wiki/Cernunnos) vs. [Ceres](http://en.wikipedia.org/wiki/Ceres_%28mythology%29)?) This is much more important than it sounds: Hunting-gathering and Agriculture are two very distinct, and mostly incompatible, modes of [human ecology](http://en.wikipedia.org/wiki/Human_ecology). Any fantasy element that sustains and supports the former is going to reduce the population of humans, because food surpluses per acre will be diminished. * Is there conflict between wizards and church? This is a staple theme in fantasy worlds, and it will create a fierce distortion in the politics of the arcane. * Are there formidable modes of mind-altering magic in your world? This can wreak havoc on the normal patterns of politics. (To take a trivial yet telling example: if you have practitioners of sexual magic, they could potentially exert enormous influence over the most powerful people. To say nothing of the ability to provide whatever sexual gratification an individual craves most, the blackmail possibilities would be absolutely splendid from an author's point of view.) + It can create a new kind, or class, of politically powerful individuals; you will need to work out who they are, and what their relations with other power centers will be. + Even if the end result is that the "Usual Suspects (the ordinarily wealthy and powerful in this sort of society) still come out on top, you have to deal with the change to their modes of exerting power. * *Is your magic "technological"?* Do you posit wind-mages who could improve the economics of sailing vessels? Is there magic that will purify sewage? That will lift heavy weights into place more cheaply than gangs of men and animals with cranes and derricks? All of these things will change many aspects of your city, because they change building techniques, cultural predispositions, concentrations of economic power, etc. And I'm not even going to discuss the possibilities of battle magic, since it's often considered here on Worldbuilding.SE - but you will certainly have to consider it. Now, having briefly looked at merely the possible impacts of your notions of magic, let's look at some other fundamentals. --- ### What's your climate? Most older empires flourished in the warmer latitudes. In Medieval times, colder climates rose to parity, or even superseded the older warmlands as centers of cultural power. Answering this question will make a huge difference in your question of cities: * Do your city planners need to deal with ice and snow in winter? * Is it hot, so you need to build heavy masonry structures that stay cool in the daytime - and with flat roofs for summer nights? Or is it cold, so you need pitched roofs for shedding snow? These different kinds of building techniques will do a lot to drive the nature of the city. * Rainfall is very important. How much water flows through the city? How much of it is rain runoff, and how much is directed river flow? Are there canals for drinking water? Canals for sewage? * What kind of plants and animals are on hand? Draft animals tend to govern a lot of the expectations about street size and bridge construction. --- ### What's your [human ecology](http://en.wikipedia.org/wiki/Human_ecology)? Every civilization, great or small, pivots on one specific question: Where does the food surplus come from? What source of food provides a sufficient surplus? Presumably agriculture? How is it organized? Big [slave-worked](http://en.wikipedia.org/wiki/History_of_the_Southern_United_States) [plantations](http://en.wikipedia.org/wiki/Latifundium)? Smaller farms intermediated by a network of markets? Trade? (I know "trade" might seem ridiculously unstable, but it worked for Byzantium for centuries... and it works for us in the modern day as well. Ahem.) [Pastoralism](http://en.wikipedia.org/wiki/Pastoralism) - domesticating herd animals instead of plants - seldom seems to scale well to empire-level organizations. Yes, [Gengis Khan's empire](http://en.wikipedia.org/wiki/Genghis_Khan) was the largest the world has ever seen: but it fell apart pretty quickly after he himself died. You could, of course, make a case for a pastoral civilization without a lot of agriculture; but that would be a lot of heavy lifting, and you didn't hint at anything of the kind in the original question. --- ### What level of technology does your world have? Technologies of farm and building; technologies of weaponry and ships; do your metalsmiths work with poured bronze, a village blacksmith's forge. or blast furnaces? (Or tame/captive dragons?) Do you have the arch, or are your buildings post and lintel? Can you fire ceramics? Do you have the potter's wheel? What about weaving, spinning, knitting? The wool of which animals, or perhaps fibers from seeds or plants (flax, linen, hemp)? What about brewing beer, viniculture, distillation of strong drink? Other mind-altering substances? Leatherworking? Animal care? (Not just veterinary care, but things like farrier work, taking care of tack and harness, and merely handling the animals - I personally have 3 horses and it has taken me years to reach the point of being able to safely handle a 1000-pound animal who could easily kill me by accident.) Glass? For that matter, you never characterized your world sufficiently to tell us that it's preindustrial! Again, it probably is; you would likely have mentioned it if you intended a steampunk or dieselpunk or postindustrial world. Still, that would add a whole new set of possibilities. :-) And on and on and on... --- ### What are your nation's politics? Is this an empire (a political organization [that obtains the wealth of subject peoples](http://thearchdruidreport.blogspot.com/2012/02/nature-of-empire.html)?) Is it a kingdom? Is it a city-state - a [polis](http://en.wikipedia.org/wiki/Polis) such as those of Classical Greece? Doesn't sound like it, but you never know. :-) Is it a parliamentary democracy? A republic? Is it a trading association (such as the [Hanseatic League](http://en.wikipedia.org/wiki/Hanseatic_League)?) Note that all of these forms of government tend to generate different kinds of civic layout and architecture. As a general rule, when thinking about what roads, bridges and canals get built; what buildings get located where; who inhabits the nice neighborhoods; and who lives in the slums, you will want to begin with the distribution of political power. That this is a "planned" city does not change that basic calculus. The plans will be governed according to political influence. --- ### What is your religion like? Unless you plan on basically transplanting an historical model (medieval Islam, Zen/Shinto, 19th-centurey Victorian British Christianity, etc) with its assumptions, you need to think about the impacts of your religion. Starting with its nature: Is this a [polytheistic](http://en.wikipedia.org/wiki/Polytheism) religion (like Egypt's, or early Rome's, or Shinto) or a monotheistic religion (like Medieval Christianity)? The answer to this has a lot to say about the internal distribution of power within the religious community, and presumably therefore the distribution of sacred architecture within the city. Also, a monotheistic religion will be likelier to ignite crusades. Historically, "official" polytheism would sanction whatever the political leadership declared, but was not in general an activist tradition. It was the [monotheistic belief systems](https://history.stackexchange.com/questions/14865/which-religion-was-the-first-monotheistic-one) (which, oddly, all sort of got going circa 600 BCE in places as far apart as China, India, Asia Minor, and Judea) that turned out to be set up to stoke religious wars. This is an aspect of belief systems that will have a lot of impact on your city and its enclosing civilization. The Church Militant (of any sufficiently chauvinistic belief system) is a much beloved worldbuilding device, presumably because the polytheists don't tend to provide the same grand sweep of historical activism. There is one more question about your religion: Is it existential? In other words, is this a system of belief that manifests itself as states of human consciousness, or do your god(s) actually exist within your secondary world? This is an extremely important question. --- ### How old is this city? You said it was planned. How long ago? How long did the various parts of the plan take to complete? How many of the planned design elements were modified over time before completion? How much was abandoned? Your city is a snapshot in time, after the original ideas and plans were made. It really matters whether it was initially built 100 years ago, or 500, or 800, or... --- Well, that's probably way too long to be a helpful answer. But then again, perhaps it will add a little bit of illumination. :-) [Answer] Most cities will develop organically. It is possible to grow a planned city but it takes resources and planning or a cataclysm to destroy the old chaotic city to be replaced by an orderly city. * Gates: there is a great change that the city will be inside walled fortifications. The Gates should be located on large arteries, allowing people to move in/out. * Shops: in the inner city, they have a specific place and these activities are controlled by the state. It's not possible to open a shop in a residential district for example. * Banks: They would be located close to markets and other similar services. * Workshops: most artisans lived, worked, and sell their goods at the same place. * Parks: are a luxury inside the city walls. It depend how important it is for you civilization but the access is usually limited to the elite. If it is very important, they could have public parks, but I'm not sure where they would place them. * Stables: I have no ideas. Most people probably did not own a horse in the city. Rich people might have their own small stables, inns and large public building (the imperial palace) might also have stables. If there is something like public stables, I would put them near the gates, ideally outside the inner city. * Other buildings: Because it is the capital city, there should be a palace/ castle. You should have a lot of temples, churches, monasteries. Not just because it is a large city but also because the city has a lot of wealth and can afford to build gorgeous buildings or because they were built by the emperor. (For example: Chinese emperors built a lot of taoist temples although it was not really popular among the population.) You will also have a lot of government buildings as it is in any capital. It is the center of the bureaucracy and a large empire will have a ton of bureaucrats. Lastly, you could have several families of aristocrats gravitating around the emperor. This was common in China and France with the absolutist monarchy but not likely if the aristocracy is strong. In the latter, they are more likely to stay near their fief. As for the historical city, I chose Chang'an (Xi'an) in China during the Sui and Tang dynasties. One must keep in mind that Chang'an just like Rome, was the center of a large and wealthy empire. It was possible to build the city that they had become because they were able to concentrate a large amount of wealth and manpower. For example, without the import of food for other parts of the empire, both cities would starve. The imperial cities in China were based on a relatively simple model. Later capitals including, Luoyang, Kaifeng, Nanjing, Hangzhou and Beijing, all imitated the plans of Chang'an. You can have a look at the plans of the city here: * <http://www.chaz.org/Arch/China/Chinese_City.html> * <http://www.globalsecurity.org/military/world/china/images/map-chang-an-01.jpg> * <http://www.city-data.com/forum/world/1743831-most-important-city-throughout-history-5.html> The outer city was more chaotic because the government did not have as much control but it did not have much impact on the large arteries. Lastly, if you want help with the city layout, you could go to the cartographer's Guild and open a thread. If you intend to map it. There is a couple of people that could really give you good advice. [Answer] Two more examples of planned cities from U.S. history are Washington DC and Salt Lake City. DC was planned by L'Enfant as a series of hubs with spokes radiating outward, all overlaid on top of a grid system. The biggest hubs were centered on the Capitol and the White House. There was a bit of controversy over the layout and a subsequent city planner made several revisions to L'Enfant's plan. However, I think that SLC might be more relevant. Salt Lake was planned from its inception as a religious center, a political seat, and a migratory destination. When Brigham Young had the city laid out, the legend goes that he insisted that the streets be laid out wide enough to do a U-turn with a covered wagon and a team of oxen. As a result, even most residential streets in Utah will be two to four times wider than their counterparts in major coastal cities that have grown organically. This has made scaling SLC up into a serious local capital very painless, relatively speaking. Additionally, it was designed to be an extremely regular grid, centered on the religious heart of the city, the Temple grounds, including the Tabernacle, a sort of religious-themed community meeting hall. The original plan for the city also centered around building small, self-sufficient neighborhoods, each with its own chapel, stores, and meeting places, instead of a more modern zone/district plan. As Salt Lake's governance transferred from a democratic theocracy to a secular mayorship, the strict regimenting of land began to break down while the city began to find its own identity. Eventually, a zoning plan was adopted, making the area around the Temple grounds a prosperous commercial district, with a plethora of secular conference centers, hotels, malls, restaurants, and other amenities that support the continuous religious tourism that the city enjoys. This uneasy truce between the temple district and the commercial district seems to hold for other religious centers, even historically. Consider the biblical story of Jesus throwing the money-changers out of the temple grounds. Most of the industry in SLC is focused around transit routes, such as major highways. In your example, I would also focus industry on the river-front. Even if trade, as in money and contracts changing hands, is conducted in the heart of the capitol, businesses don't want to have to pull the raw materials halfway across the city before they can start processing them, or load them back on someone else's boat. Even if the two adjacent towns originally had more ports, the organic evolution of the capitol city would put a lot of pressure to build workshops and warehouses all along the riverfront, regardless of the official plans. With regards to the other towns, you would have a lot of ragged, diagonal streets and T intersections where they met. The industrial districts would probably merge seamlessly, as they would all be focused on the river trade. Additionally, they would each have their own, smaller, commercial districts, separate from the capitol. They would probably contain more general stores and modest marketplaces than the heart of the capitol where serious commerce would be going on. [Answer] One or more centers of power? Do you have multiple power groups, say a king and a priesthood? Each might insist on their own palace/cathedral/whatever. Those buildings would be separate but visible from each other's front door -- so if one side builds a higher flag pole, their rivals have to see it every morning. Select nice locations for those areas first. Hills or river fronts, perhaps. Ornate gardens in the center of the city are a way to show your wealth, too. Are there mass events for the common people? Pilgrimages, coronations, and so on. If so, you need some large squares. Rival ones again, like a square in front of the palace and another in front of the cathedral? Is rebellion an issue? Wide roads are harder to barricade, and easier to sweep with a cavalry charge. Multiple roads running towards the places of power ensure that their splendor is always visible, too. Connect the palaces/palace squares with wide ceremonial roads. More wide roads spread out like a star. Reserve some areas for military barracks. Close to the royal palace, if possible on the most likely threat axis. Perhaps a drill field? Stables? Keeping up with the Joneses. Where do the upper classes live? Fashionably close to the centers of power, in areas with nice, paved roads and decent drainage. Business districts. Are there warehouses on the riverfront? But not too close to the palaces. Out of sight, out of mind. The lower classes will go into the remaining spaces. Slums will be built and re-built with little eye for beauty. Small, crooked alleys. The cops won't like to go there, even with a cavalry squadron as backup. [Answer] As with anything in fiction there's a few decent modern examples of this. [Brazillia](http://en.wikipedia.org/wiki/Bras%C3%ADlia), [Chandigarth](http://en.wikipedia.org/wiki/Chandigarh) and [Naypidaw](http://en.wikipedia.org/wiki/Naypyidaw) would be good starting points for inspiration, quite interestingly, especially the last, and most recent of these, Naypidaw, since very little differentiates a modern military junta, from a feudal state There's a few things worth considering - while a modern planned city would have a grid layout, I'd suspect multiple hubs and spokes, centering around the city's temporal and spiritual centers of power makes sense. In a monothestic culture, you might have a seat of spiritual power (or a 'quarter' or at least a street of these in a multireligious culture.) You'd have a palace (for a king or local aristrocracy) probably surrounded by facilities for visiting nobility, or the court. You'd probably have areas for tradesmen (or maybe even streets dedicated to trade). You'd probably have lower density in the 'rich' district, with outlying, poorer districts being more packed. While it wouldn't be planned, you'd probably have a less reputable area - this might be an older quarter (or one planned for a less popular trade) - traditionally this would be the docks (and having a city straddle a river is picturesque, especially if the river is fed by a spring, and that's right smack in your local defensive fortress ). Try putting palaces and other important things on top of hills (the romans LOVED that), though plains wouldn't do too badly for large sprawling palaces. Don't forget, the joys of being a absolute ruler is urban renewal is easy. You can likely reconfigure a city however you wish, as long as you don't piss off too many people at once. If all else fails, fires happen. ]
[Question] [ On a tidally locked gas giant moon (which is otherwise earth-like - see [this question](https://worldbuilding.stackexchange.com/a/11513/7740) for pictures) how would medieval sea navigation techniques differ from Earth? I presume that compared to Earth, navigation would be easier on the side facing the planet but how exactly will it be done? Would it help if the gas giant has recognizable features like Jupiter's Red Spot? What about the dark side where the gas giant is not visible? [Answer] Planet Side: Much, much easier. Medieval Navigation techniques depended on two factors - a sextant to a known star, which determines your latitude. And accurate timekeeping, which combined with known star movements gives you your longitude. However, with a tidally locked planet, you can use that for both longitude and latitude - each position on the sea will have a unique location in relation to the gas giant. Gas giants tend to have visible cloud bands, so you don't need a red spot - you can determine the top and bottom from the gas giant's visible rotation by observing it for a short period, then calculate your exact position based on two sextant measurements. Very importantly, sailors will be able to take these measurements during the day as well as at night. Dark Side: It might be slightly easier, but there won't be any substantial differences. If there are other moons around the planet, they will likely be extremely bright. Therefore they would make excellent known markers, and navigators would likely determine their location off of visible moons instead of using stars (except in rare cases when all other moons are eclipsed or below the horizon). Edit: it occurs to me that you can likely use sky glow to help navigate for portions of the dark side. Depending on exactly how bright the gas giant is, there will be a border area where it's not actually visible, but you can tell from the sky which direction the gas giant is. This won't be enough by itself, but it will let you determine your approximate longitude based on the brightness, which negates the need for timekeeping - a substantial benefit. Edit2: Notes on Libration, based on comments. Libration is the "wobble" of another celestial body. For example, from Earth the moon will appear to rotate slightly as the day goes by, grow smaller and larger on a monthly cycle as the distance from the gas giant varies, and also "nod" slightly up and down on a monthly cycle. Thankfully for our navigators here, we can ignore the first Libration component - because we're on the tidally locked body, we won't see the gas giant "turn" slightly as the day goes by. That means we only need to care about the "nod" (the gas giant appearing to move up and down slightly), and it growing smaller and larger. Fortunately for us, these variations are cyclic, and therefore predictable. We can use measurements of the gas giant to determine where we are in the Libration cycle. For the "nod" we can measure the curve of the cloud bands on the gas giant. For the size, we measure the arc size in the sky using trigonometry. Combining the two, along with a date, should be sufficient to give good corrective values for navigation. So we don't need time keeping for this - we can get away with tracking the date, which is much easier to handle. ]
[Question] [ I have quite a few forms of transportation planned out. These include travel via river (riverboats, etc), ocean (ships), land (horses, primarily), teleportation (game checkpoint, others). Also the possibility of the player acquiring wings through a minor faction. As you can see it's pretty one-sided to surface transportation. And also there are plenty of mountains in my province. Some guidelines: * Perhaps a costly option would do well (whether in actual money or just lack of quantity of said vehicle.) * There is magic in my game, however limited. * Nothing steam-punk/mechanical whatsoever. Simple contraptions should be fine (forms hang gliding, zip-lines.) * I would prefer nothing cliche -- so no dragons. Birds are better, but a bit close to Middle-Earth (Eagles). Bonus: * Are there any mythological creatures/vehicles of sorts that fit this question? (preferred Celtic/Norse, if any!) To sum it up: What are some non-cliche(E.G, dragon), non-steam-punk forms of travel by air? EDIT: Thank you all for your answers so far! To add on to my question just slightly, what about non-living forms of transportation? Forget all of the guidelines above except "nothing steam-punk" for this. EDIT(2): Thanks once again. I have decided on a number of choices. I will use a form of hang gliders and ziplines for travel around a mountain, balloons for general travel (however costly for fuel), and a form of bird for other sky travel. Skylarks sound like the perfect type of bird for this, as well. I am also still thinking about some of the other answers (flying squirrel & valravn being the top). [Answer] Here is my not mediaeval nor steam-punk answer not-living answer. Although he lived during the renaissance, you could elaborate your means of transportation, basing on Leonardo da Vinci's designs for flying machines, and overcoming difficulties with magic, if needed. Here are the two I would consider if I were in your shoes. ## Vite Aerea (Aerial Screw) I'd personally go with this, maybe coupled with some kind of rope system. ![aerial screw animation](https://i.stack.imgur.com/nK11J.gif) It is a relatively simple and cool looking concept that could do the work: people use the handles to turn the spiral helix that creates an upward force, lifting the machine. I am not sure about directing it, but a good idea could be elevating and then use some kind of flappers or parachutes to direct the controlled fall. # Macchina Volante (Flying Machine) ![flying machine illustration](https://i.stack.imgur.com/zgPBx.jpg) Else, this one is suitable if you need an individual flying system: it uses handles and pedals to control the flight attitude. This really calls for some cool kind of in-game control like alternatively pressing two keys to maintain stability and direction, like when rowing in a canoe. --- Also, [this page](https://www.leonardo3.net/leonardo/volo_eng.php) has an comprehensive list (you might need to translate some descriptions) of his flying-related work. PS. Please let me (us) know if/when this game is released, unless I'm wrong! [Answer] For Norse mythology, there isn't a focus on winged animals so much as there are just versions of ground animals who can fly. Flying horses are popular, with [Sleipnir](http://en.wikipedia.org/wiki/Sleipnir) and [Hofvarpnir](http://en.wikipedia.org/wiki/Gn%C3%A1_and_H%C3%B3fvarpnir) being two examples. Thor also has a chariot drawn by goats which seem to be implied to be capable of flight. Valkyries also fly around, but whether they are capable of flight on their own or ride flying horses depends on the source. There's also some instances of magic items allowing people (well, gods, for the most part) to fly. [Freyja](http://en.wikipedia.org/wiki/Freyja) has a cloak made of falcon feathers that she uses to fly, which is occasionally loaned out to other gods in need of flying abilities. If you want to keep with a Norse theme, these animals probably aren't a part of everyday life. Flying animals and magic tend to be tied to the gods and the giants, so it's likely that if a mortal hero gains a flying mount, it's a one-off gift from one of these sources, rather than something produced by mortal hands. Dwarves also produce magical artifacts, so something like a flying chariot or ring might come from them. In any case, these are usually rewards for heroic undertakings. [Answer] [Valkyries](http://en.wikipedia.org/wiki/Valkyrie) can fly. So if you wanted to exploit them as a transportation system, you would simply need to… 1. …stage a great battle. 2. …manipulate events such that you're one of the ones chosen to die in battle. 3. …manipulate events such that you're one of the ones selected to be flown to Valhalla. 4. …manipulate events such that (2) and (3) don't actually end up with you dying. 5. …somehow get away from them when you're actually over your destination. Norse? Check. Costly? Check. Non-Cliche? Check. And depending on how strongly you feel about (4), you could probably put a check by Non-Living as well. [Answer] I think that flying sailing ships would work great in your world. In general sail-powered airships wouldn't work and [this answer](https://worldbuilding.stackexchange.com/a/8493/85) explains the main problem. However, a limited amount of magic could solve it, that is, provide the enough counterforce to hold the airship and produce lift. If you would like something more fancy, you could make it so that this force is available only between special relay towers (or mountain stations), a bit like highway network or raiload tracks. Off-road sailing would be possible by something like a lighthouse, which focuses its beam on the ship, but of course such a thing would be expensive and available only to few. I hope this helps $\ddot\smile$ [Answer] The ones I can think of Dragon Roc (large bird like Tolkien's eagles) Flying Carpet Pegasus Flying brooms Gryphons Hippogriff Could always try Harpies... Nine League boots work almost as well as flying... Doesn't look like the Norse had much other than a dragon Hidhogg. [Answer] If you're looking for Norse, it seems like an incarnation of [Ratatoskr](https://en.wikipedia.org/wiki/Ratatoskr) as a flying squirrel would be ideal. Further, if you need these to be plentiful creatures, perhaps the flying mounts are the descendants of some unholy union between the [Four stags of Yggdrasil](https://en.wikipedia.org/wiki/D%C3%A1inn,_Dvalinn,_Duneyrr_and_Dura%C3%BEr%C3%B3r) and Ratatoskr. The stags represent the four winds, mix that with a flying squirrel and the Yggdrasil-orgy-chimera creatures would attain the power of flight. [Answer] How about allowing the character to make or buy wings along the lines of [Icarus](http://en.wikipedia.org/wiki/Icarus) & Daedalus? [Answer] @Bowlturner did an excellent job, here are some more obscure ones that I happen to like: Dandu Monara - (Indian mythos) a vimana, or mythical self-moving aerial car (sometimes serving as a seat or throne, sometimes self-moving and carrying its occupant through the air; other descriptions make this vimana more like a house or palace, and one kind is said to be seven stories high). Stupa - Baba Yaga (Northern Slavic mythos) has a flying vehicle, often described in western sources as a mortar (as in mortar and pestle), but more accurately depicted as a magically imbued hollow trunk. Valkyries are powerful flying figures in the Norse mythos, often associated with death, but also appearing as lovers of heroes. Perhaps your heroes might persuade them to provide transportation. Roth Rámach - the whirling wheel (Irish mythos) is a druidic magical flying machine, said to be capable of rowing on clouds. Valravn (Late Norse mythos) A giant (sometimes half-wolf) raven that feasts on the bodies of the fallen, and can assume their shapes and/or gain the cunning of the dead they consume. [Answer] The classic case here would be the Pegasus, it's a winged horse so already familiar to people as a mount. You can see them as being a very expensive upgrade on the horse, needed much better food and care, and costing an absolute fortune. They would be ridden or used to pull enchanted vehicles. Imagine a stagecoach but pulled by 6 winged horses, using enchanted wheels to make itself weightless and then pulled through the air. It would be epic! [Answer] My first thought would be a set of ancient airships, perhaps entirely magical, perhaps metal (and all rusted or pitted with the depredations of time). These sinister (nastily shaped, barbs etc) metallic craft have no moving parts, their artifice is entirely of evil, ancient magic (maybe large-scale Mayan-style blood magic?). They are grim, small, and quite rare. Owning one is almost unheard of, and they are seen rarely, usually commissioned by the rich. ]
[Question] [ In my question [In a world with magic, who would govern?](https://worldbuilding.stackexchange.com/q/7351/75), I asked who would govern that world, magicians or mundane warlords/nobles. Now, suppose that exactly the same rules I described in the previous question apply in this question, with the following addition: Use of magic is limited. The world is blanketed by magical auras, and using magic in an area (say about 10 square kilometres) reduces the strength of that aura. The weaker the aura, the harder it is to do magic. The more "active" the magic used, the more the aura is degraded. Magicians might be able to light a hundred or so campfires, or blast a couple of armies with arcane fire before an area's aura was degraded to the point of complete uselessness. Doing things with less tangible effects has far less impact - it might take hundreds of huge illusions or scrying sessions to have the same effect on the auras. The auras are replenished slowly from surrounding areas, and some areas (outside the realm under consideration for this question) are effectively sources of magical power, so magic will not go away permanently. It is quite easy to degrade an area's auras to the point where only the most powerful of magicians can cast only the weakest of spells, if they can do even that, at which point it may be years to decades before the auras had restored themselves. However, studying magic does not degrade the auras, only active use of it. In fact, studying is even more important, since spells and enchantments can be optimised (with effort) to have less impact on the auras in which they are used/created. So, we have a realm where magic can be used, but must be used circumspectly so that magicians can continue to use magic. Does this change the answer to my former question? Who would govern such a realm? [Answer] Fun question. I'm guessing it would be a sword-fest, since you can easily render mages powerless. Why? You can always get a rival mage (or even a near-talentless [squib](http://en.wikipedia.org/wiki/Harry_Potter_universe#Squibs)) to flare out the mana in a region, and then you can safely go climb the tower, grab the uppity mage by the collar, and introduce her to your more stabby friends. The only way around that would be if mages were endlessly wandering, more like Tinkers than kings. At first glance, that could create a hell of a [roving bandit](http://en.wikipedia.org/wiki/Mancur_Olson) problem, i.e. you'd get Genghis-Khan mages, who ride into a region, storm the forts, raid the vaults and move on. But better organized areas could of course have constant aura-flaring to prevent that, again sending the mages to the outskirts of civilization. So most likely you'd have quite powerful trickster roaming mages in marginal areas of wilderness, and powerless squib mages flaring out magic in "civilized" areas to prevent raids. Alternatively, instead of useless flaring, you can have roving craftsman-mages that use all the aura up for enchanting items as they move from city to city. So in conclusion Swordfest, with a bit of flaring/enchanting. --- Ok, so we now have non-magical kings and merchant princes firmly in control. What if they do want to make use of magic, for important state business (c), like, for instance, temporarily lifting an island off the sea-floor for their daughter's 10th birthday. It would take a team of dozens of mages months to plan out the cast, work everything out theoretically as much as possible, minimize the aural cost of each component, weeks to create a secure casting framework of supporting guide-spells, and then perhaps a single mage-architect with a dozen support-mages would actually use this combined effort to direct a Weave of the aural flow into this hypercomplex casting framework and get a floating island with purple roses and gold-brick roads. Or perhaps you can have depletable auras, but persistent imbued magical items. I think it's a very fun setting, if done carefully. [Answer] The most valuable spell to learn in this world would be one which allows you to move available magic potential into some form of storage device such as a bottle. Magic users could then travel the land, looking for recuperated auras and gathering the healing shreds into bottles. Then when the stabby friends arrive, its time to uncork a bottle of hellfire on em! [Answer] I concur with Serban. \\ I esp. like: > > "...grab the uppity mage by the collar, and introduce her to your more stabby friends." > > > \\ Meaning, please don't vote for my answer unless you've already voted for his. :D --- Auras will be degraded. By mages who want to do things, or by stabby people for self-protection vs. hellfire. Esp. since it takes so long to regenerate. Also, I disbelieve the ability to learn something that you can't use very often (once a decade? not happening). Learners aren't optimized and will make Sorcerer's Apprentice mistakes. Endless goto loops, for an equivalency. Alternative idea: If it merely took days-to-weeks to regenerate, you'd still have some problems - but you'd actually get to see magic more than once a decade. You'd get first-to-shoot effects; unless you had a way to block other mages from using spells (or, to lock up the aura for a bit; "noise in the aether, can't spell right now"). Or block them as they cast/right after they've cast their (usual\) spells - so the mana isn't lost - ie: allowing you to actually have a wizard's duel, which your setup prevents from ever happening (or, happening for more than 1-3 shots). \ Some spells might be instant effect, and unable to be blocked. Back to your question: Does detecting magic users (using a spell, which is the only way I assume you can accurately do so) seriously degrade the local area? That's the only way a council of mages could get control of an area; ie: hope nobody nerfed the aura, use magic to detect anyone who's magic-capable, and keep ruthless control with stabby friends and monitoring anyone who comes close to the area in order to get a place where you can do anything magical. How big are areas? And do they overlap/spill into one another? ie: If you hellfire an army does it take out a bigger area - say, miles around (which is what I'm envisioning from your question) than just the one you had an army in (which I'd say is several thousand square feet (depending on how big your army is, of course))? If areas are small enough to be protected, and powerful enough to do stuff - then you might have some interesting effects: ie: if a mage can defend his tower, and his work-room is an 'area' that has enough power to do stuff, that can't be taken out by someone two blocks away deciding to light his cigar with hellfire... then it might be possible to work a story/campaign with this and have mages be something other than meat-sheaths for our stabby friends. Thus, in most cases as this question describes - this setup probably means mages won't be the ones in control - they'll be working for someone who can command the area. Maybe they could charm the king... but I suspect that wouldn't work out (assassinate the king, and the next guy who can steal the throne puts all the mages under lock and key). Also, no magical items (sucktastic)? Any magical creatures? Wandering undead, golems? Unicorns, Dragons, Magic-wielding Orges? This is pretty much the setup for AD&D: Dark Sun, except even they allowed the land to be reconditioned. I'd recommend against this as it's a pretty horrible world. :P I'd go for some way to recondition the area, improve auras (if they're not already degraded), and something for magical items and more powerful magic - even if you don't want tyrannical mages from your former question. --- Also, you need to explain why mages would stay in the magic-poor areas, instead of seeking the source of magic (and being able to do more magic, quicker in the fertile magic farmland of your world). If I were a mage, the first thing I'd do is go seeking a better place. [Answer] The rule of this world would be far more of a compromise than in your other question. "Commoners", as others have said, would realise that they can study magic, not optimise it, and deplete the local magical aura. This renders the magicians powerless and it then comes down to normal ruling systems. This means that while magicians would still have a prominent role in government as they are the most powerful people when the auras are up. However, the commoners wouldn't have trouble reminding them that they can still be punched in the face when there's no magic around. On a planet such as this, therefore, there would be a ruling system quite close to medieval times, though perhaps without the king figurehead. [Answer] I think, people having real power is not always the people knowing the technology (magic). In our world, the politicans rule, they are mostly lawyers or economists, with only a very limited technological (magical) knowledge. I think, the real power of a such world would be similarly in the hands of a nonmagician cast, whose professionality would be the manipulation of the society, amd not the magic. The common society controlling techniques would depend on the technological (magical) development: if there were enough food, television (entertaining crystal balls?) for nearly everyone, it would be probably a society similar to ours. If not, I supposed a bloody empire similar to the roman empire or to the medieval Europe. ]
[Question] [ This is going to take some imagination and assumptions (and knowledge about physics). Imagine gravitational mass and inertial [mass](http://en.wikipedia.org/wiki/Mass) would be different. In classical mechanics it seems a coincidence that they are the same in our universe. * Gravitational mass is how much objects attract other things and are attracted by gravity (passive and active gravitational mass is still the same, $m\_{g1} = m\_{g2}$). Newton's law of universal gravitation: $\vec{F} = G \frac{m\_{g1} m\_{g2}}{r^2}\hat{r}$ * Inertial mass is how much objects resist change in velocity. This is the mass from Newton's second law, $\vec{F} = m\_i \vec{a}$. Furthermore, forget anything you might know about subatomic physics or non-classical mechanics. Each atom has a gravitational mass and an inertial mass (isotopes have little effect). Assume that somehow the universe has evolved somewhat similarly with a planet like Earth existing. Both masses are still positive. Examples: * Objects would not fall at the same speed even in vacuum. A half-iron, half-carbon item would rotate while falling to have the fast-falling part point down (or it might break). * If iron would have low inertial mass and high gravitational mass, then an iron vehicle would stay on the road more firmly but would be easy to turn or accelerate. * If copper would have high inertial mass and low gravitational mass, then a cannonball made up copper could travel spectacular distances and still have a big impact. EDIT: that is given a fixed initial velocity; more realistically it would have a fixed initial energy, in which case the trajectory is the same but the impact is higher. I am interested in what happens on Earth at technology levels up to around 1900 (so no relativity). Not really in astronomy or in how the world came to exist under these circumstances. (Though feel free to post that for future readers if you feel so inclined). Specifically, the scenario is for a computer RPG, but no need to focus on that. [Answer] Ok, so the force of gravity is stronger or weaker on certain materials, and not linked to their inertial mass. Another way of thinking of it could be that some materials have an extra force applied, either downwards or upwards, but an upward force is never more than gravity. Depending on how strong this contrast can get, this could make for some strange game-like structures and objects... kind of like we already see in a lot of games and CGI, where things are made impossible sizes for dramatic effect. In particular, it could make it possible for there to be very large buildings since gravity would not be so hard to resist to make a huge towering structure stable, and not as much work would be needed to assemble it in the first place. Also it would collapse more slowly, though with eventually just as much impact, so you could have your heroes dramatically escape slow-moving avalanches by running away... ;-> And you could have fairy flesh have less gravitational pull, so they could jump higher... ;-> > > I am interested in what happens on Earth at technology levels up to around 1900 (so no relativity). Not really in astronomy or in how the world came to exist under these circumstances. (Though feel free to post that for future readers if you feel so inclined). Specifically, the scenario is for a computer RPG, but no need to focus on that. > > > What would happen to technology would have to do with the specific settings for certain materials, but the main use I see is low-grav materials would be good for building large towering things (walls, bridges, tall buildings) more easily. It could help with some steampunk types of things. In particular, heavy airships and submarines could be easier to build if there are useful low-grav materials available. Low-grav materials would be handy for elevators. Low-grav grapnel hooks would be helpful. Low-grav projectiles would have longer range, and be more accurate at range, because the amount of "aiming high" needed to compensate for projectile drop in flight would be less compared to a higher-grav projectile at the same range. High-grav bombs and dropping-object traps would fall surprisingly quickly. This improves accuracy particularly for longer drops by limiting the correction needed to account for initial lateral velocity, and limiting the time the target has to move out of the way before the dropped object hits. High-grav materials could be good for securing things to the ground, and if they were round or smooth or moved by things with wheels, could be more mobile than they'd otherwise need to be. However they would mainly provide out-of-proportion downward pressure and lateral friction, although if a side force exerted more force than the lateral friction, they'd slide more easily (unless blocked by obstacles to the side). That could have some uses, though I'm not sure what except as some sort of controllable anchoring system, or maybe a hydraulic pump or bellows or for sliding trap doors or hiding passages behind sliding walls. [Answer] As has been discussed already, different objects would fall at different speeds. Why? [Wikipedia](https://en.wikipedia.org/wiki/Mass#Definitions_of_mass) led me to an interesting derivation. Consider Newton's second law: $$F=m\_ia$$ Now consider his law of universal gravitation: $$F=G\frac{m\_{g1}m\_{g2}}{r^2}$$ Now, because the force here is due to gravity, we set the equations equal: $$m\_ia=G\frac{m\_{g1}m\_{g2}}{r^2}$$ But because $G\frac{m\_{g2}}{r^2}=g$, $$m\_ia=m\_{g1}g$$ and, thus, the actual acceleration due to gravity (denoted here as $g\_{actual}$) is $$g\_{actual}=\frac{m\_{g1}}{m\_i}g$$ So, the greater the gravitational mass, or the lesser the inertial mass, the greater the acceleration. Okay, that was boring, but I figured you might want some rationale behind the ramifications. You probably did this yourself, but someone reading this might not have, so I decided to stick it in here. --- An object with larger gravitational mass would undergo a greater acceleration. Strange but true; it's an artifact of the equation. So heavy objects would fall a lot faster than lighter objects - if they had the same gravitational mass. I'll take you up on what you ended your question with: > > Not really in astronomy or in how the world came to exist under these circumstances. (Though feel free to post that for future readers if you feel so inclined). > > > and post an answer related to astronomy, simply because I love it. I'm going to base it partly off [this answer](https://worldbuilding.stackexchange.com/questions/2870/what-would-the-universe-be-like-if-gravity-was-slightly-stronger/2871#2871). Planets orbit due to the force of gravity; this manifests itself as centripetal force. The relevant equation here is $$F\_c=\frac{m\_iv^2}{r}$$ We set that equal to $$F=G\frac{m\_{g1}m\_{g2}}{r^2}$$ and write this as $$\frac{m\_iv^2}{r}=G\frac{m\_{g1}m\_{g2}}{r^2}$$ We can cancel out an $r$ and make it $$m\_iv^2=G\frac{m\_{g1}m\_{g2}}{r}$$ We solve for velocity and find that $$v=\sqrt{G\frac{m\_{1g}m\_{2g}}{m\_ir}}$$ Thus, the speed of planets will depend on their gravitational and inertial masses. It could also mean that [Trojan asteroids](https://en.wikipedia.org/wiki/Trojan_(astronomy)) might not be at stable positions (although I'm not positive about this; I could be wrong). Given that angular velocity $\omega$ is equal to $\frac{v}{r}$, the spin of the Sun's initial protoplanetary disk could be impacted. It might be unstable, with different objects moving at different speeds. I would think that this would make the early solar system fairly chaotic; planetary formation would be a lot different. Perhaps Earth would not have formed - the original planetesimals might never have coalesced into planets. --- I've obviously strayed far from the area where you wanted an answer, but I wanted to explore some of the interesting consequences when it comes to astronomy. Feel free to disregard this answer if you want to. [Answer] The technology could go absolutely anywhere. Lists are usually off-topic, so I won't just suggest a list of possible inventions - I'm sure you can imagine them anyway. Instead, let's look at how the world might be a little different, and how that might direct the development of science and technology. If you intend to go with a very large deviation between inertial and gravitational mass then probably your biggest problem would be earthquakes. Lots and lots of earthquakes. The reason for this is that different elements on Earth will attempt to follow different orbits around the Sun. Normally, if you combine your two equations the two $m\_{2}$ terms cancel and you get an orbit that doesn't depend on the nature of the satellite. Unfortunately in your case, you have $m\_{g2}$ and $m\_{i2}$, which do not cancel. At the extreme end, if the largest values of this ratio differ from the smallest by a factor of thousands then the surface of the Earth will be violently ripped off into space. (At the surface of the Earth, the gravitational force due to Earth is about 1600-1700 times the gravitational force due to the Sun.) For values less than this, but still large, the surface of the Earth will only almost be ripped off into space - hence, earthquakes. Gravitational "stirring" of the Earth's core and mantle will also be exaggerated by the same ratio, increasing the heating effect due to friction. For a large enough ratio, this frictional heat generation might rival radiogenic heating (which is dominant on Earth), again leading to earthquakes as it the convection of this heat that leads to plate movements. This means that as tempting as it might be to build giant, low-tech skyscrapers out of "gravitationally light" materials, it probably isn't all that safe. I would also expect a scientific lull leading to a delay in post-Newtonian science and technology, as deriving the equivalent of Newton's second law might be a lot harder. Attempting to derive the laws of motion by experiment will yield different results for different test materials and it would probably take some time to isolate the factor responsible (probably wasting a LOT of time on shape). We only really understand the concept of inertial mass in reference to this law, so plucking the idea from thin air in a world in which inertial mass cannot be related to any other known property (such as weight in our own) would be a truly insightful leap of genius. In your setting you can solve this issue by just having everything start a little earlier and have historical societies a little more advanced than us up to Newton and then level after. Flight will probably be the single most significant technological deviation from our own history - with the right materials even some of Da Vinci's designs might have achieved flight. This might have profound consequences for society. The relative ease of travel afforded by flight has been credited with bringing the world together in the second half of the 20th century and for reducing nationalist and xenophobic sentiment. Your world may be a more tolerant place, if not necessarily more peaceful. Contrary to the previous paragraph, this might actually lead to faster advances in scientific development as scientists are more inclined to collaborate across borders. For $m\_{g}/m\_{i}$ values that don't destroy the earth, spaceflight is probably still off the table until the development of liquid fuel rockets - Napoleonic Wars through American Civil War era solid fuelled rockets are wildly imprecise by the standards needed for spaceflight. It might be possible for a highly reactive, extremely "gravitationally light" metal (I'd go for aluminium) to always be found in nature bonded to a "gravitationally heavy" element, such that the compound isn't immediately stripped off into space. Such a strongly bonded ore could only be refined by electrolysis making it very rare in your setting, but not unheard of. By the time of your story enough material might have been gathered for the world's first attempt at a steam powered rocket launch - it would make a nice news item even if you didn't want your players going into space. That's probably a long enough post by now. Try to keep the mass ratios within a reasonable limit (10s or at most 100s) and just use your imagination. [Answer] as you pointed out, to make this work, current sub atomic particles would mess this up. Sooo... My first idea was that atoms are the smallest particles, but then what about the electron? Without electrons we can't have electricity (and this of course would mess up a whole host of other things! including life) So on to the next idea. With a little hand waving certain elements are made up of different sets of subatomic particles each kind particle is affected differently by either Gravitational or inertial forces giving the element different and interesting properties we currently don't have. Projectiles could have some very interesting behaviors and ballistics mathematics would be considerably harder. However, you could have a core that had a large inertia and a wrapper that had a low gravity, and it could allow you to fire it very accurately over a very long distance. I was thinking building would be affected but not as much as one would think. Buildings don't move (or shouldn't) so in general it is down to tinsel strength vs. weight. However, I could see it being very useful for anti-earthquake technology. I think it could also lead to different forms of flight much earlier, especially depending on how extreme the two properties can be. If something had an escape velocity of 200 miles an hour it could really change our modes of early travel. [Answer] This actually could work even with special relativity as there is a difference between special relativity and general relativity. Special relativity describes motion while general relativity describes gravity. Having gravitational mass different from inertial mass would still work even with the speed of light and its counter intuitive effects however it would require that gravity be something other than space time curvature. Also this could still work with quantum mechanics especially considering that the three forces that are explained by quantum mechanics are independent of inertia. In this case gravity would be explained by particles with gravitational mass exchanging virtual gravitons between each other. How likely a particle would be to emit or absorb a virtual graviton would be proportional to the gravitational mass and the gravitational force between two objects would depend on how many virtual gravitons they would exchange between each other. Considering that the universe does not have a net electric or color charge if inertial and gravitational mass were different then the universe might have no gravitational mass. This could be accomplished by having some objects have positive gravitational mass with others having negative gravitational mass. Because opposite gravitational masses would repel and like gravitational masses would attract there would be regions of negative gravitational mass and regions of positive gravitational mass. Considering that rest mass is the only quantum number that is not quantized if gravitational mass was different from inertial mass gravitational mass would likely be quantized. We might imagine that quarks could have gravitational masses of -2/3, -1/3, 1/3, and 2/3, while leptons would have gravitational masses of -1, 0, and 1 Electrons that have gravitational mass would tend to accelerate thousands of times more from the same gravitational force than protons and neutrons because they would have a similar gravitational mass but a much lower inertial mass. When a star would form hydrogen atoms that have the same sign for their gravitational mass as the star would be attracted to the star while those with the opposite sign would be repelled so that stars would tend to have most of the protons and electrons of the same sign for the gravitational mass. Because elements heavier than hydrogen tend to come from fusion in stars or from supernova most atoms would have their electrons and protons of the same sign for gravitational mass. How much a given substance would accelerate from gravity would depend mostly on the fraction of electrons. Isotopes with more neutrons would tend to accelerate less from the same gravitational force as the extra neutrons would increase the number of particles without increasing the number of electrons and so would increase the isotopes inertial mass more than the isotopes gravitational mass. Considering that electrons could either have positive or negative inertial mass or have no gravitational mass there would be three different types of electrons. This could mean that chemistry would be much more complex as it would take more electrons to fill a shell. A shell would need an equal number of all three types of electron in order to get filled. On planets objects would be made mostly of substances that are could exist in our universe as most of the electrons would be of the same type as each other and so most atoms could only form bonds with each other that have two electrons. If a substance from a planet with negative gravitational mass was put in contact with a substance with positive gravitational mass the two substances would tend to react as they would both have a different type of electron to share and so could get their shells closer to being filled. Some substances would be mostly inert to the other substances on their own planet but would still react violently if brought in contact with a substance from a planet with the opposite gravitational mass. Many substances would be the same in every way except for their gravitational mass. While in nature there would be different substances that would fall at different rates having a substance on a planet that falls much slower than most other substances would in general need to be produced artificially as it would need to have an unusual concentration of particles that have the opposite gravitational mass from the planet or that have no gravitational mass in order to make the substance lighter. This would mean that while anti gravity would be possible it would tend to be expensive and difficult as it would require that substances with opposite gravitational mass from the planet be extracted from the environment or mined from planets with the opposite gravitational mass. If gravitational mass was different from inertial mass then free falling would feel different from not accelerating in empty space as different parts of your body would tend be affected by gravity differently so even in free fall you could feel which direction is down. This would also mean that you could tell if you were accelerating in zero gravity or standing still in a gravitational field and so spinning a space ship would not be sufficient to create artificial gravity especially because it would not create the feeling of free fall when someone jumps. If inertial mass was different from gravitational mass then gravity would have no effect on space and time and so any adjustment of clocks of GPS satellites would be entirely from the relativistic effect of the orbital velocity. ]
[Question] [ In a medieval-ish world (Or any other pre-20th century earth), how long could you keep using the same metal? As in, you have very little territory, and what metal was available, has been mined from the ground. If you somehow recovered all metal (Arms, armor, fittings and nails, screws and bolts, forks and sporks) from their use, picking all up from burned down buildings and looting all corpses, from a metallurgical standpoint, how long could you remelt the scrap iron and steel, to make "new" metal? Plenty of territory to grow trees and make charcoal with, but there is no new metal. [Answer] If you're careful, you can keep recycling the metal more or less forever, though you can expect some small loss over time as fine metal-rich dust gets blown away, but the amount is very low. The issue is that the remelting and reforging process will inevitably introduce a small amount of impurities each time, effectively making the input to the recycling process a very high grade ore. During the refining process, you'll be generating a small amount of [slag](https://en.wikipedia.org/wiki/Slag). That slag will have some proportion of metal bound up in it. You can re-smelt the slag, of course, though that obviously requires you to provide more energy. If you're happy to keep growing enough trees, then you'll be OK. Not all metals are create equal, of course. Iron in slag is more or less indistinguishable from useful iron ore... iron oxide, mostly, and standard iron smelting processes work on that so iron could effectively be recycled forever even with relatively primitive technology. Copper is also easily recyclable in this way, as are many other metals. Aluminium on the other hand is more problematic, because [aluminium oxides](https://en.wikipedia.org/wiki/Aluminium_oxide) are quite [refractory](https://en.wikipedia.org/wiki/Refractory), and are impractical to refine if you're trying to use charcoal to do so. ]
[Question] [ Suppose a two-storey timber cottage has been left unoccupied for 15 to 20 years. The entire structure is wooden, including all beams and supports, with a rammed earth foundation. It's situated within a small stoney clearing in the outer skirts of a broadleaf temperate forest, with alternating cool/dry and wet/warm seasons and relatively high periods of humidity - think temperate forests in central China. The clearing is surrounded by tall trees which allow in patches of sunlight, but there is little undergrowth in the area beyond ground cover shrubbery. There are streams that run through the forest, but they are seldom prone to flooding. Regarding the structure itself, it is rather small and dingy. Windows are paper-paned and shut tight. The roof is built from clay tiles, and from straw for a porch. The floors and walls are all wooden, and so are all furniture and appliances, with some iron and bronze present. Upholstery comprises rough woven textiles such as hemp and bamboo, and some cotton and fur. The house was well-maintained prior to abandonment, and has not been broken into by humans or animals over the stated period (bugs and small scavengers notwithstanding). Given the above, what would be the condition of the cottage, externally and internally, following the period of vacancy, in terms of structural integrity, takeover by vegetation & critters, degradation, etc.? EDIT - A few more details: The geography/climate of this setting draws heavily on temperate Eurasian forest ecosystems, with yearly temperatures averaging from 3 to 16 degrees Celsius. Snowfall is unlikely at this particular altitude as the climate is generally mild to humid, and winters would be dry. The cottage's design combines elements of Zhou- to Han-dynasty housing styles for the lower classes (thus the heavy reliance on wood and the rammed earth slab foundation, even though a crawlspace might be expected instead). I understand that break-ins are practically unavoidable IRL, so I should clarify that there would be Plot Reasons(TM) justifying the lack of interruptions. [Answer] I used to work as a forester in Canada, where we do have temperate climate (although somewhat on the colder side of the spectrum, I must admit). I've seen several habitations and other abandoned things through my days in the bushes, so I have some range through my assessment. First, was it build to last? It seems so from your description, yet most of the materials you mentioned won't last very long after the maintenance stopped. Still, 15-20 years isn't that much, so you should be all right. The wood will have turned grey outside the house and inside near every opening. Where water infiltrated you'll see that the wood texture is not the same as elsewhere. If there was rain lately, it may even be still wet. You may find puddles if the degradation is that bad. Second, is the cottage anywhere near civilization? If so, people will at some point find it - and by "people" I mean "kids or teens". This means that the furniture inside the house will be broken, the windows smashed, the tableware broken (often outside the house). Kids aren't gentle to what they find. Vegetation will grow. 20 years is not much in a forest's cycle, but plants look for light all the time and will try and colonize the clearing. Raspberries and other thorny colonizer-type plants will have taken over parts of the clearing, while light seeking trees like poplars or... bamboo I guess? - will have small representatives growing around. Some of these will be hugging the walls, yet this isn't a forest yet (trees height will vary between "mini-groot" for the youngest ones to "human size" for those less than 10 years old and "bush size" for the oldest colonizers (which aren't technically old, just the first to colonize in this case). It's the forest starting to attack the clearing. Another 20 years will see the place overrun with those light-seeking species, which won't really look like the forest around them because they are part of a cycle and in less than 100 years they will start being replaces by other variety of vegetation. Animals will explore the place. Rodents like squirrels and such will have nested in the roof and will have shit everywhere. If some of the furniture is stuffed, like a sofa or a mattress, you will see some stuffing rotting on the ground (also they often will be damp) and that the rodents have dug around making nests inside them. Most nests like that are ancient things, though, abandonnes for a while. Bigger animals like bears and stuff won't play around the place unless they smelled food, which might have happened right when it was abandoned but never later. How cold is the winter? If the winter is cold enough, the house will have a floor, and underneath it there will be some space that animals will want to colonize too. This one might still have something living in there. Skunks, raccoons and other small yet unpleasant animals can have made their den under the house, especially if the access there is not that easy. They would be disturbed bu somebody exploring the house. Also, if there's a floor and water problems, the planks might be rotten enough to bend under the weight of somebody exploring the house, and ever break underneath him. You might notice some things which will seems "out-of-place", but only because this place is straight from the past. 15-20 years isn't much in this regard, but I've seen really surprising stuff from older abandoned places, or places abandoned by natives. EDIT: Also: wasps. There will be at least one wasp nest, probably an empty one as they die during winter. There may be live ones, too. They often nest near the wall just under the roof, outside the house - rarely inside, but they can. Other insects can and will colonize the place, but they are more subtle. [Answer] It will be pretty run down, especially if it is made of wood. Vegetation will have taken possession of the surroundings. I have seen such places during my vacations in some remote areas of rural Japan, they have their sinister appeal. Here is what can be found [online](https://theworldnews.net/uk-news/explorer-uncovers-abandoned-japanese-village-where-houses-and-temples-have-given-way-to-trees): > > Fascinating footage shows an explorer uncovering an abandoned Japanese village that has lay empty for more than two decades. > > > Houses, shrines and temples that had been knocked down by overgrown trees which took root in the remains of Nagatani Village. > > > Explorer Kei Oumawatari discovered houses, shrines and temples that had been knocked down by overgrown trees which took root in the remains. > > > Old ropes, brooms and brushes and other household appliances are strewn across the floor after being left more than 20 years ago > > > [Answer] Based on your rather unreasonable requirements that it hasn't been broken into. The cottage will look almost pristine.... on the outside. The wall boards will have shrunk. There will be gaps in the walls. This will allow free air flow, keeping the structure somewhat dry. The roof will sag a bit because those tiles will leak. If it has never gotten any snow, then it should still be fine. The floor will be ruined. You will probably fall through the floor when stepping on it. The location where the foundation meets the ground will be extremely rotten. It was probably rotten a few years after it was built. A common thing to do for those old cottages was to use beams made of giant trees that sit on exposed or pilled up rocks. This keeps the rot surprisingly low. You could go 60 years and still be fine with this set up. I would need to know the exact foundation to give a better estimate between 3 years and 60 years. The weird one though, chances are the building is leaning, or may have even fallen over. A house is heavy (citation needed) and sinks into the ground. Often at different speeds around it's foundation. And the scary one. The insides of the house will be coated with old black mold. The underside of the floor will be covered in mold. The top of the floor will be covered in mouse poop. This house is extremely disease ridden and deadly to even breath it's air. Do not go inside it, do not sleep in it, you can't even safely light it on fire. [Answer] It will be destroyed. There are two factors you mention that will do it: 1. Trees - they will not only add the possibility of falling on the house but each fall they add weight to the roof with leaves. Those leaves also rise the floor level around the house that is rotting. So any fauna that could benefit from wet, warm environment and like to eat wood would flourish there. 2. Closed windows and doors. In combination with better insulation on the roof (leaves) your house become a greenhouse. Rising the moisture and temperature in the house. Making it better not only for mushrooms but also speeding up rotting process of furs and textiles After 20 years the cottage could still be recognised as one but the roof would collapse on it's own (you have weight from outside and weakened support on the inside). Iron would rust. Materials could still look like usable but would crumble when touched. The place would be heaven for all small things that like to munch on pre-processed wood, fibers and leather. And animals that like to feast on those critters. ]
[Question] [ I want to render impractical the deployment of satellites by exploiting the Kessler syndrome. Why, you ask? Maybe I'm an evil overlord and I don't want those pesky satellites flying over my lair. Maybe I'm an alien in disguise and I want to disrupt comms and GPS as a preparation of an incoming invasion. Maybe I just want to do it for the lulz. The reason does not matter. Now, I wonder what is the most efficient way to do it? The [wikipedia article on Kessler syndrome](https://en.wikipedia.org/wiki/Kessler_syndrome) suggests that a good starting point is blowing up the [Envisat](https://en.wikipedia.org/wiki/Envisat). For the purpose of this question, let's assume current level of technology, that I already have a small number of satellites in orbit and I have the technical and financial means to get more of them in space. Also, according to my understanding, sooner or later the orbiting debris will be pulled away from orbit, so let's assume that I want the debris field to last at least 200 years. Bonus points if you can provide a low budget/low tech solution and/or can render inaccessible all orbit altitudes. EDIT: I dont believe that my question is a duplicate of [this one](https://worldbuilding.stackexchange.com/questions/123670/could-deliberately-induced-kessler-syndrome-stop-icbms), because my goal is not to prevent launches, but to prevent objects from orbiting for a significant amount of time. So I don't mind if ICBMs, standard missiles, rockets and planes fly as long as they stay below LEO or can't maintain their orbit. Also,some comments highlighted the fact that the debris field will decay over time and that's a good point; so I'll offer a variation on the question (I'm kinda new here and I don't know if this is allowed, please let me know): Can I simply destroy or render unusable all current orbiting satellites by means of Kessler syndrome? [Answer] You can't stop space travel with Kessler Syndroome. Kessler syndrome only disables low earth orbit. Low earth orbit is quite clustered, and easy to disable. Medium or long ranged satellites could still orbit, and space ships could still travel upwards. The fragments are a long term risk to any space ships orbiting, not an immediate danger. Only a quarter of satellites are in low earth orbit. [Most are in geostationary orbit.](https://en.wikipedia.org/wiki/Satellite) You can stop it with a laser broom and Kessler Syndrome. One popular suggestion for clearing the earth orbit is what's called the [laser broom](https://en.wikipedia.org/wiki/Laser_broom). A megawatt laser is used to alter the orbit of an object by producing a jet of ablated material. The normal intention for this is of course to remove threats to earth. It could instead be used to make objects collide. So, you can use your large laser to make as many satellites collide as possible. This should produce a large debris field. You need ground monitoring stations to track this debris. If anyone attempts to set up a satellite you can use the laser broom to sweep some debris into them. This doesn't require you to go into space, and is much more cost effective than other options. [Answer] This is just going to be a Fermi estimate, because this seems like a fun question to deal with. Let's take a look at the lowest orbital plane around the Earth, Low Earth Orbit. It's 2,000 km above the surface, and the radius of the Earth is 6,000 km. The area is 4\pi\r^2, or 4.5 \* 10^8 or 450,000,000 square kilometers. This isn't the full story, because any given object within LEO orbits, crossing a circumference of about 38,000 kilometers. Now, I can't really use real world data to help calculate, because real world satellites are clustered around certain paths, and you want the entire orbit saturated to the point where no satellites can be safely put in orbit. If we assigned each orbit the equivalent path of 38,000 kilometers, and assume they can deal with the half a klick on either side of them due to orbit variance, than a simple calculation of 450,000,000/38,000 suggests you would need a mere 12,000 satellites. Of course, you would need to constantly launch more satellites as they'd knock themselves out of orbit. If you want more cluster than one single satellite half a klick away once a year, than adjust the 12,000 number as necessary. But like I said at the start, this is just a rough Fermi estimation. Currently, we've got around 2,000 satellites, and apparently we're getting woried, so the 12,000 number seems like a good benchmark. Of course, this is for LEO only, and doesn't stop launches, just stable orbits. Bonus point attempt: According to these numbers, MEO is 36,000 and GEO is 72,000. And the easiest way to do this ... your main problem seems to be getting them into orbit, so just firing them from earth might help, though you'll need to be able to make course corrections in-path. Something akin to Jules Verne's From the Earth to the Moon, where they use a 1,000-foot cannon. So, a railgun-missile launcher? That sounds like an okay way to do it. [Answer] May I suggest this is impractical It's impractical for the same basic reason that you can't trust a freeway full of cars to guarantee a 50-car pile up during every rush hour. * Yes, there are certainly more than enough cars on the freeway to fall into the Kessler Syndrome kind of statistic. * True, many cars (but only many) are driven by competent drivers who can be trusted to react in a reasonable manner to the growing chaos. * True, unlike space, freeways only move in one direction (not three). But the problem persists — and yet almost never happens. The Kessler Syndrome is a statistical analysis. There never has been and never will be a guarantee of any catastrophe. You could lob Buicks into LEO hourly for a century and, despite cluttering up LEO something awful, all you have is a statistical chance of a cascade failure that may never happen. In fact, let's look at a terrestrial cascade failure. Let's consider forest fires Forest fires are the real-life epitome of the Kessler Syndrome. Too many trees in close proximity that get older and dryer with every passing year just waiting for that one random lightning bolt1 to start the cascade failure. You betcha! Forest fires happen every year! But when was the last time you saw the entire forest burn down? It almost never happens. In fact, keeping everything out of LEO via Kessler Syndrome is like expecting [the entirety of Canada to burn to the ground in one huge forest fire](https://www.youtube.com/watch?v=Uy8p6hZRoP0). It could statistically happen — but it doesn't. Why? * Mother Nature stops them by hosting areas without fuel. Like deserts and lakes. * Humanity stops them by creating unnatural areas without fuel, like large, paved roads and fire breaks. * Both humanity and Mother Nature can stop forest fires by dowsing everything with water (or some synthetic equivalent). How does this relate to space? In the immortal words of Douglas Adams, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." There's a lot of dead, "fueless" space out there. Yes, the statistics say there's a growing problem, but that's just statistics. * In reality, there's a whole lot of nothing where debris can harmlessly exist. * Large satellites must be hit by high-energy objects or they're more likely to rob the process of energy than they are add to it. That's one of the reasons freeway pile-ups come to a stop. With each collision there's less energy to cause the next collision (and more time for motorists to realize what's going on). * And that last bit is important, just like flying planes full of water and motorists realizing something in front of them is more important than the text they're trying to write, satellites with modern tech have the ability to move out of the way. Older satellites have less of this ability. No, it's not perfect — but neither are airplanes full of water or attentive motorists. And yet there aren't daily 50-car pile-ups on congested freeways. Are my metaphors perfect? Absolutely not! But they make a point. The effort you would need to put into causing and sustaining the Kessler Syndrome is so much greater than the benefit that it isn't worth pursuing. It would be cheaper to fire missiles at every launch than it would be to trust in and maintain the Kessler Syndrome. Keep in mind, Kessler proposed his problem in 1978 — and despite an increase in satellite launches, it hasn't happened yet. Yeah, but I really, really, really want to use the Kessler Syndrome to keep satellites out of orbit! What can I do? Use the modern equivalent of a flak cannon. Your Evil Overlord sends up a constant flow of disposable satellites with hundreds or (preferably) thousands of #10 cans full of 1" ball bearings, C4, and a timer. The cans are sent out spherically from the satellite for maximum spread. Like deadly fireworks, they'd send their cargo of ball bearings (quite literally quadrillions of them) into space! They'd cause havoc for as long as you keep sending up satellites — and with each destroyed satellite, you add to the mahem!2 --- 1 Or, in the case of your Evil Overlord, that one deliberate match thrown by a stupid teenager [who thinks the result would be really funny](https://youtu.be/Qfu1Ux1tX6A?t=18). 2 And to top it all off, if you're really lucky, you'd have a constant light show in the sky as bazzillions of 1" ball bearings burn up in the atmosphere. [Glitter! So much glitter!](https://www.youtube.com/watch?v=dZUA9lVjb4I) ]
[Question] [ Can an organism have several types of oxygen carriers in its blood? Note that I am not asking how the creature could have evolved, that is too much sci-fy, genetically engineering or Deus Ex Machina evolution fits fine. The idea to use several kinds of oxygen carriers is to be able to survive in very different environments (the last substance isn't very important if it causes problems): * [Hemoglobin](https://en.wikipedia.org/wiki/Hemoglobin): Standard carrier. Contains iron. Most efficient for normal purposes. * [Hemerythrin](https://en.wikipedia.org/wiki/Hemerythrin): Contains iron. Can also be made with cadmium. Usually lacks cooperative binding, which means that it can only carry 1/4 of the O2 carried by haemoglobin (in some brachiopods it does). Hemerythrin affinity for CO is lower than its affinity for O2, unlike hemoglobin which has a very high affinity for CO, i.e: resistant to CO poisoning. Recent evidence has revealed hemerythrin to be a multi-functional protein – contributing to innate immunity and anterior tissue regeneration in worms. * [Hemocyanin](https://en.wikipedia.org/wiki/Hemocyanin). Contains copper, which means it doesn't need iron. Lacks of cooperative binding, which means that it only carries 1/4 of the O2 carried by haemoglobin (in some hemocyanins of horseshoe crabs and some other species of arthropods, cooperative binding is observed,). However, it doesn't lose efficiency in cold environments with low oxygen pressure as hemoglobin does. In addition, it can stand elevated temperatures as high as 90 degrees Celsius. Hemocyanin oxygen-binding profile is also affected by dissolved salt ion levels and pH. It's believed to reduce cancer effects. * [Vanabins](https://en.wikipedia.org/wiki/Vanabins): Contain vanadium or other rare minerals. Are very bad for transporting oxygen but are poisonous for many predators, parasites and microorganisms. The question is if it could be possible to an organism to have all these substances or would them produce problems between them? If that is true, could the same organism has all these substances but not at the same time (i.e: it changes of substance according to the environment)? [Answer] We have two different oxygen carriers in our blood. Humans use Hemoglobin F in utero. That oxygen carrier is downregulated when we are born and Hemoglobin A is upregualted to take its place. So too your creature with its different specialized carriers. Presumably it occupies different sorts of oxygenation niches according to life cycle or circumstance. Having different oxygen carriers it can up and downregulate make sense. I can think of no reason why one carrier would necessarily interfere with another. Their niches are separate. If you had a special oxygen avid carrier suitable for toughing it out in anoxic environments but then got to a high oxygen environment, the anoxic carrier would just be saturated with oxygen and hang around that way until it was cleared. Your high oxygen environment low avidity carrier would come on line to let you do your fast oxygen-hungry metabolic gymnastics. If you then went back to anoxic areas, the low avidity carrier would hang around empty and the anoxic carrier would come back on line to get you by. I think this sounds like a reasonable system. It is more likely that permutations of a single carrier would evolve than a bunch of completely separate carriers. But there is precedent for picking up an oxygen carrier from a completely different species - legumes are plants and they have hemoglobin that they somehow swiped from an animal in years far past. You creature might have pulled similar evolutionary shenanigans. [Answer] The biggest issue would be efficiency. Generally speaking, you would find that only the most efficient oxygen carrier at any point in time got to do the work. Oxygen carriers work by making it energetically advantageous to bond the oxygens to the molecule while in a high oxygen environment like the lungs, and then release it later in lower oxygen environments throughout the body. If I had two carriers, and one bonded more vigorously than the other, it would strip oxygens off of the weaker carrier. The result would be that, in general, the weaker carriers would simply not be carrying any oxygen, or would only be carrying it in times of luxury when there's lots of oxygen to be had. However, if the creature inhabits many environments, its possible that one carrier could be advantageous in one environment and one could be an advantage in another. For example, one might have hemoglobin for one's living environment, and hemocyanin to function while hunting in cold hunting grounds where your body temperature plummits outside of hemoglobin's operating range. The disadvantage, of course, is waste. Red blood cells are about 40% of our blood by volume. If you had several redundant carriers, you would need to have even more oxygen carrying cells. That could prove difficult. [Answer] I see no issues if the organisms has the capability of synthetizing more than one, but actually synthetize one at a time, based on the circumstances. I.e. switch from hemoglobin to hemocyanin when either the body has a deficiency of iron or it is living in cold temperatures, like during winter. Since each of them has a different efficiency, it makes sense that only the most fit for particular conditions is used. Everything else would simply be a poor use of resources, which for a living organism are always limited. If you think of our body, in our eyes we already have two types of receptors: one for day light (better resolution, color discrimination), one for dim light (no color discrimination, higher sensitivity), and we use each of them in different cases. ]
[Question] [ I’ve done a fair bit of research to come up with this scenario. I hope it’s not “too broad” to ask for a reality check. Have I overlooked anything? Does it all sound plausible? My world takes place in a massive crater, the only habitable place left on the planet. It is roughly 800 x 600 miles and 5 miles deep. At the bottom it is 1.2 atm in pressure, while the surface is at 0.5 atm. Due to the extreme “altitude” conditions the surface of the planet is cold (would it really be though?) windy, and home to extremophile bacteria mats/mounds, and possibly lichens/moss. The wind here is extremely fast because there’s not much to slow it down. The sides of the crater are gently sloping downwards, and the wind follows it down. The bacterial mats slowly give way to montane grassland and meadows. Early morning dew from the cold winds is the source of water here. Small gnarled trees grow slowly and are warped by the wind. Meadows are nearby springs, where ancient aquifers were fractured during the meteor impact. Next comes the treeline and the coniferous forests with fern undergrowth. The wind is slowed by both the trees and its compression at -12,000 feet into the crater. Rain occasionally falls here if the conditions are right. Overall the precipitation is mostly occult. This area has sizable lakes from other meteor impacts which are filled by fractured aquifers and streams from up the crater. Eventually the heat of the Earth warms the cool air and we reach temperate deciduous forests. Winds are breezy here and carry precipitation from higher up the crater. Evening showers are relatively common. Streams have become rivers by this point. The forests reach all the way to sea level, except where humans have cleared them away for agriculture. A massive sea covers much of the bottom of the crater, and fortunately it has reached an equilibrium between evaporation and being filled from the aquifers. In the sea are a series of islands from the complex crater. These islands experience hot moist air, daily rain, and are temperate rainforests. It is here, finally, that the air rises up in a massive updraft. The hot air rises, disperses, and mixes with the atmosphere. Some water vapor finds its way back into the crater, but much more leaves. I know it’s a big task, but does this all sound plausible? Is there anything I’ve missed or greatly overlooked? [Answer] # Temperature change is caused by lapse rate The difference in temperature between the bottom and top of the crater is going to be driven by the [lapse rate](https://en.wikipedia.org/wiki/Lapse_rate), and not by the heat of the crust (probably). Lapse rate is the rate at which temperature in Earth's atmosphere decreases with an increase in altitude, or increases with the decrease in altitude. In particular, we can use a chart of moist adiabatic lapse rate to see what the expected temperature changes would be in a 5 mile (8 km) deep crater. [![enter image description here](https://i.stack.imgur.com/FkVxW.gif)](https://i.stack.imgur.com/FkVxW.gif) The 'Moist Adiabat's are the dotted lines on the chart. Chicago has a annual mean temp of about 10 C, Washington DC about 15 C, Houston about 20 C, and Miami 25 C. Pick your starting point, then follow the dotted line upwards until it intersects with the line representing 8 km. I get the following: ``` Floor Temp Surface Temp Surface Press 10 C -60 C 0.34 atm 15 C -45 C 0.36 atm 20 C -30 C 0.38 atm 25 C -15 C 0.42 atm ``` So you are looking at quite the different in temps. I also used this chart to double check your pressure estimates. Instead of starting at 1 atm, your crater surface starts at 1.2 atm, so I multiplied the resulting pressure estimates by 1.2. You are pretty close to being right on the pressure. Overall, the area outside the crater will be very uninhabitable. # Why the Earth won't provide appreciable heating in the crater The [Earth's crust](https://en.wikipedia.org/wiki/Crust_%28geology%29#Earth's_crust) is about 30-50 km deep on the continents, away from tectonic boundaries, and it has a temperature gradient of about 200-400 C in heating between the surface and the boundary with the mantle. The [heat flux](https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget#Global_internal_heat_flow) on continental crust is about 71 mW/m$^2$. The simplest argument I can make is to compare the heat flux on the continental crust with the heat emitted by the Earth's surface in infra-red radiation. The Earth's surface emits 398 W/m$^2$ in IR radiation to the skies, on average. This is significantly higher than the 71 mW/m$^2$ that comes from inside the Earth. Lets look at what happens to planetary heat flux when we change the thickness of the crust. Planetary heat flux is controlled by the [Fourier's law](https://en.wikipedia.org/wiki/Thermal_conduction#Fourier's_law) for head conduction $$q = -k\nabla T.$$ Here $q$ is heat flux (W/m$^2$), $k$ is conductivity and $\nabla T$ is the heat gradient. If we reduce the distance between crust and surface by 8 km, from 25 km to 17 km, with a constant 300 K temperature differential then $\nabla T$ goes from 12 K/km to 17.6 K/km. This represents a 1.5 times increase in heat flux out of the Earth's surface. So the Earth is providing something like 120 mW/m$^2$ at the bottom of your crater instead of 70 mW/m$^2$. Still, compared to 160 W/m$^2$ absorbed from sunlight and 80 W/m$^2$ released by evapo-transpiration and IR radiation to space, and back-radiation received from atmosphere and clouds....you get the picture. The change in planetary heat flux is negligible, three orders of magnitude smaller, at least. Therefore, the temperature gradient between the crater bottom and high surface are going to be driven mostly by lapse rate, the same factor that drives the temperature difference between sea level and the top of Mount Everest on Earth. # Air flow around the crater [![enter image description here](https://i.stack.imgur.com/5G8KT.gif)](https://i.stack.imgur.com/5G8KT.gif) Your crater is much hotter than the surrounding air. Hot air tends to rise. The dominant climactic feature will be rising hot air out of the crater. This will cause a variety of follow on effects. ### Rising hot air creates cyclones! Your crater is so large it will induce high speed, cyclonic winds circling around it. In the diagram above, the 'x' and 'o' represent winds into and out of the page around the crater. There will be permanent winds swirling around the crater. If your crater is entirely in the northern or southern hemisphere (assuming your planet is rotating like Earth) the [Coriolis effect](https://en.wikipedia.org/wiki/Coriolis_force) will drive the winds into a stable clockwise or anti-clockwise rotation around the crater. If the crater straddles the equator....something will happen, I'm not really sure. if the crater is on the Equator and large enough relative to the size of the planet, the cyclone may actually form a circle around the surface of the planet, but don't quote me on that. ### Rising air releases moisture as it cools As your air rises, it will lose its ability to hold moisture. You can see this from the thermodynamic diagram at the top of the page. If we assume a jungle-y 25 C average temperatures at the bottom of the crater, then that air can hold about 20 g of water per cubic meter. Elevate that air to 8 km, and it can hold about 3.5 g, leaving the remainder to fall as rain. The center of your crater will be constantly raining. The temperature gradient between crater bottom and surface is going to be much higher than the temperature gradient between day and night, therefore, you will always have a steadily rising column of hot air. Various wind conditions might blow around pockets of warm air, especially towards the edges, but you can assume the center of the crater will see rain every single day. The hotter the crater, the higher the magnitude difference in saturation mixing ratio will be, so the more rain you will get. A 10 C crater will get light rain every day, a 25 C crater will see permanent torrential rainfall. ### Descending cold air will enter the crater like a blast furnace From the cyclone swirl, descending cold air will spiral into the basin to take the place of the air that rose out. The force of gravity will ram this wind into higher pressure areas at the bottom of the crater, and the resulting molecular friction will be expressed as adiabatic heating. These are [foehn winds](https://en.wikipedia.org/wiki/Foehn_wind). The 8 km drop means that you would see an expected 30-60 C of adiabatic heating as the wind rushes downhill. Given that the wind already has high kinetic energy from the hurricane swirl at the top, the result near the bottom with be superheated blast-furnace winds. If conditions are right at the top, with extra solar heating for whatever reason, you could easily see steady 45 C or higher gale-force winds at the bottom of the crater. No trees will live on the slopes of the crater, due to the high wind speeds and highly variable temperatures. The slopes could easily see temperature changes of 30 C in a matter of minutes, as one air mass blast past and is replace by another. [Answer] I'll try to tackle each of your points, so reaslistically on the face of it, its fairly plausible > > My world takes place in a massive crater, It is roughly 800 x 600 miles and 5 miles deep. At the bottom it is 1.2 atm in pressure, while the surface is at 0.5 atm. > > > Pressure variance is reasonable and plausible, my only question though, what happened to the rest of the world to the crater being: > > the only habitable place left on the planet. > > > That sentence suggests that something happened else where and that something could very easily transfer into this crater which could very easily effect life, but that's an aside > > Due to the extreme “altitude” conditions the surface of the planet is cold(would it really be though?) windy, and home to extremophile bacteria mats/mounds, and possibly lichens/moss. The wind here is extremely fast because there’s not much to slow it down. > > > This is a tough one, if the "surface" is fairly uniform in terms of height, and it is just this crater that goes deep below this surface then actually the "altitude" would be basically ground level and would be receiving similar amounts of energy from the sun to that of the crater. so while the surface would have lower pressure and indeed lower temperatures, significantly lower tempretures are not a given, again there would be a gradient > > The sides of the crater are gently sloping downwards, and the wind follows it down. The bacterial mats slowly give way to montane grassland and meadows. Early morning dew from the cold winds is the source of water here. Small gnarled trees grow slowly and are warped by the wind. Meadows are nearby springs, where ancient aquifers were fractured during the meteor impact. > > > This is easily possible, although craters aren't just a big hole in the ground, the rim of the crater protrudes the bedrock somewhat, even on very old and weathered craters. now this rim is mere metres on Meteor Crater in the US, and is definitely not uniform. however that is a mere kilometre or so across, not 600-800 miles. so that rim is going to be a small mountain range all the way along it. which means anything on one side will have similar on the outside of the rim > > Next comes the treeline and the coniferous forests with fern undergrowth. The wind is slowed by both the trees and its compression at -12,000 feet into the crater. Rain occasionally falls here if the conditions are right. Overall the precipitation is mostly occult. This area has sizable lakes from other meteor impacts which are filled by fractured aquifers and streams from up the crater. > > > A 600-800 miles diameter crater will still have significant heating and cooling, its big enough to not stop high level winds effecting the weather or climate within the crater and also big enough to easily generate its own weather, so the trees. > > Eventually the heat of the Earth warms the cool air and we reach temperate deciduous forests. Winds are breezy here and carry precipitation from higher up the crater. Evening showers are relatively common. Streams have become rivers by this point. The forests reach all the way to sea level, except where humans have cleared them away for agriculture. > > > Don't discount the power of the sun. if there is trees and life then the sun has to be able to get through to power photosynthesis. which means its not just the heat of the earth that will warm up air. As for the forests and the rest, yes perfectly plausible > > A massive sea covers much of the bottom of the crater, and fortunately it has reached an equilibrium between evaporation and being filled from the aquifers. > > > This is perfectly reasonable, but it the water and clouds do extend past the rim then that water is lost as it freezes and settles. aquifers are fairly constant water sources, if you had a particularly warm year where ice melted on the surface more than average then those aquifers would let it all roll downhill and you crater bottom sea has no where lower to send the water so keeping that homeostasis would be unlikely, but not impossible. > > In the sea are a series of islands from the complex crater. These islands experience hot moist air, daily rain, and are temperate rainforests. It is here, finally, that the air rises up in a massive updraft. The hot air rises, disperses, and mixes with the atmosphere. Some water vapor finds its way back into the crater, but much more leaves. > > > All of this is fine, but i'd even with a massive updraft its still unlikely to have most of the water leave, most rainclouds are within the first 5 miles of atmosphere so those clouds wouldn't escape the crater walls I cannot stress enough i am not a meteorologist, This is all just some basic research and my understanding. hope it helps ]
[Question] [ This is the first question about colonizing an alien world; the second question on agriculture on this planet is [here](https://worldbuilding.stackexchange.com/q/127032/11664). So here's the idea: human beings travel to and land on an Earth-like world with the intention of colonizing it. This world is remarkably Earth-like: gravity close to 1G, oxygen-nitrogen atmosphere with very close to the same proportions as Earth, similar climate, and similar life forms. So, in principle, a human could walk around unprotected on this world. However... The life on this planet, while at a similar level of development to that of Earth, is not based on the same DNA/RNA bases or the same amino acids in proteins. In short, the lifeforms on this planet resemble Earth life, but the chemistry is different. What would happen if a human stepped out on the surface of this planet? My thought is that they would experience a serious (probably life-threatening) allergic reaction as they breathe in dust, bacteria, etc. with completely different proteins that they have never encountered before. But is that correct? After all, here on Earth people have allergic reactions to proteins which are made up of our familiar set of amino acids; would they have similar reactions to proteins made up of unfamiliar amino acids? [Answer] We would probably poison alien bacteria etc, and they would poison us. So we just walk around. The alien life would probably sample us. We have mosquitoes, mites, nematodes, and various other things that get under our skin. Presumably the alien ecology has similar things. They inject us with -- stuff. It happens a whole lot here, and if we have skin exposed, it will happen there. We'd breathe things too, exposing our mucous membranes to them. And lungs some. We have defenses to keep living things we breathe in from hurting us much. Those defenses would not be as necessary -- the alien life probably can't live in our lungs etc -- and also partly ineffective. So stuff gets into us, and the live part of it will tend to die there. Some of it is just -- stuff. Saliva, excretion products, whatever. We would be randomly allergic to it. We have developed allergies to things already, things that correspond to not-self stuff we have been challenged by in the past. And they might randomly correspond to alien stuff. For example we have antibodies. These attach to anything that's the right shape with the right locations of hydrogen bonding etc. Something can fit imperfectly and still fit well enough to get a reaction. The region they fit to (called an epitope) tends to about 8 to 17 amino acids long. Sometimes it's a specific sequence of amino acids that has folded up just right, and other times it's two or more sequences that have folded with each other. Alien proteins or other alien molecules would fit some of our antibodies. So we would react. We would itch etc. It would be a continual irritation. Probably we could mostly live with that. Would some people occasionally die of anaphylactic shock? Maybe. We might easily become allergic to foreign stuff. I think it would happen particularly if we get exposed to it and get problems, about every 2 weeks. Continuous exposure I think would result in less allergy. Maybe. If it's always around and usually doesn't cause trouble, it's less allergenic than if it shows up along with trouble, at 2 week intervals. So that's one thing to be careful about. Arrange the times of exposure to minimize allergies. I'm not sure what else to say. Some of the foreign stuff might be very poisonous, and I see no way to tell which would be. Some of the foreign DNA might be highly mutagenic and carcinogenic. If your body's DNA-building machinery mistakes foreign nucleic acids for regular nucleic acids, it might incorporate them into your DNA and then mis-copy them the next time the cell replicates. That can be very bad. Or they might interfere with regulation of various kinds. If your cells mistake a foreign amino acid or nucleic acid for one of your own -- just by the proteins that shut down production when there's too much -- then it could stop you from making stuff you need. Which you could have made plenty of if the signalling wasn't screwed. There are lots of ways for things to go wrong and some of them could be pretty subtle. You might go years before cancer shows up, or months before you get deficiency diseases of various sorts even though whatever you are deficient in is plentifully available in your food or even in your bloodstream. Lots of unpredictable effects possible. It might be possible to get lucky and none of them happen. Luck of the draw. [Answer] nice question :) the short answer is things would probably go badly or well, depending on how disjoint the native molecular machinery is from our own, the ability of their microbes & plants & animals, if any of any size, to poison or infect or bore into or attack us. our enzymes are tuned to digest proteins composed of l-amino acids, d-sugars & right-handed dna, and only a limited range within these classes. non-conforming bio-molecules will be for the most part inert, apart from possible deleterious effects. native bio-matter will not be digestible, almost certainly. the native bio-material will be of no use to us, but may be harmful to us. hence the need for sterilization. this leads to the broader, far more interesting question of what to do with such a stupendous opportunity, should it ever present itself. a rough sequence of the essential steps in a process of terraforming a planet might be: * create a well-sealed native bio-environment on an off-planet moon to preserve the native flora/fauna exhaustively - a pragmatic & moral imperative, within practical limits of space & time. * administer a total extermination event, down to below the lowest extremophiles on the continental and oceanic crust, to prevent any competitions with or complications from alien microbes/viruses & etc. * condition soil, rivers & oceans with a starter-kit of microbes, then basal fungi,animal & plant life to form a stable atmosphere and condition the environment, step-wise, for sustainable living, on the land and in the oceans. this is the hard part. humans would have to design a stable bottom-up tree of life, something far beyond our capabilities at present, i should imagine. this process, sterilized planet to self-sustaining terran derivative, would almost certainly take millennia to effect, in a realistic time-frame. unlike a lot of science-fiction, this is a challenge humans might actually aspire to confronting some distant day. we likely have a good amount of time in which to learn the lessons needed to initiate the process of planning such an undertaking in something like adequate detail, by elaborating the process upon a lunar terran zoo. [Answer] It depends on whether these novel proteins have structural elements that allow them to interact with human enzymes and cell structures. That's basically a coin toss but I would think that there will be at least some so there will probably be some interactions. What interactions? * Nulls, reactions where there is an interaction but it is shortlived and, for the human system, inconsequential. * Normals, the two structures interact the same way that they do on Earth. This could be fine and it could kill people, it depends on what the structures are. * Locks, unexpected binding that doesn't result in any reaction but locks up a receptor site for an unexpectedly long time. The real world example of this that comes to mind is Carbon Monoxide binding to Hemoglobin, it's not Oxygen or Carbon Dioxide; it fits the receptor site but not properly so it takes a lot longer than it should to unbind. * Breaks, catastrophic damage is caused to amino acid structures. This could kill cells and eventually cause enzyme deficiencies with prolonged exposure. Prions may be formed this way also. * Other, unexpected interactions that don't quite fit into any of the above. This includes direct chemical reactions that form new compounds, etc... One would expect to see some of all of the above interactions, the exact proportions would depend on the exact structures involved and their precise concentrations. The human body is extremely adaptable but it is possible that the rate of disruption could overwhelm people's immune systems. This answer assumes that the new environment shares the same amino acid [Chirality](https://en.wikipedia.org/wiki/Chirality_(chemistry)) as Earth, if it doesn't then possibly the same but actually one would expect very little interaction. ]
[Question] [ The Leopard dragon is one of the fastest and smartest dragons out there. With four eyes, external ears, four legs, two wings, a long tail, and sleek black scales, this dragon is quiet and nearly invisible at night. Its venom is painful but not terribly lethal, until the dragon decides to shoot it at whatever is bothering it. Upon leaving the dragon’s fangs the venom is combined with saliva and begins to thicken to a napalm-like gel in air that combusts and can self-oxidize. This results in a very sticky substance that won’t stop burning until it runs out of fuel. So what kind of materials does the dragon need to do this? Can it make the necessary components from bodily processes or will it need to consume certain resources in order to fuel this breath attack? Any comments or alternative ideas that sound more plausible or just more interesting are appreciated! [Answer] The dragon might be able to shoot napalm using yeast, bacteria, palm trees, and oil sand gizzard stones. The yeast and bacteria make the fuel, the palm trees and oil sands make the gel. --- [This question](https://worldbuilding.stackexchange.com/questions/313/how-could-dragons-be-explained-without-magic) goes into various ways that a dragon might produce fire, and [this answer](https://worldbuilding.stackexchange.com/a/314/46957) might be a good natural reason for your situation. Basically, the dragon would have a sac containing ethanol-producing yeast, and another sac containing sulfuric acid-producing bacteria. These would combine to produce the highly flammable [diethyl ether](https://en.wikipedia.org/wiki/Diethyl_ether), whose Wikipedia page contains the very disturbing line "It was used as a general anesthetic, until non-flammable drugs were developed". --- However, the other requirement you seem to have is that it needs to produce a napalm-like gel substance in order to stick the flames to the target. You say 'napalm-like gel', but why not actual napalm gel? [Napalm](https://en.wikipedia.org/wiki/Napalm) gets its name from the two chemicals used to make the gelling agent: [Naphthenic acid](https://en.wikipedia.org/wiki/Naphthenic_acid) and [palmitic acid](https://en.wikipedia.org/wiki/Palmitic_acid). Palmitic acid is the easy one to explain, as it is already the most common type of fatty acid found in animals. To get large enough amounts, just have the dragon's diet be rich in [oil palms](https://en.wikipedia.org/wiki/Elaeis) for some reason. Some biological mechanism and have it store the large amounts of palmitic acid in yet another sac. Naphthenic acid is a bit trickier, as it is mainly produced during [crude oil refining](https://en.wikipedia.org/wiki/Naphtha), and crude oil is generally found deep underground. However, your dragon has hope: the [Athabasca oil sands](https://en.wikipedia.org/wiki/Athabasca_oil_sands) are a source of naphta-rich crude oil that is close to the surface. It's not unreasonable to think that the dragons hang out near exposed pockets of oil sands, using chunks of it as [gizzard stones](https://en.wikipedia.org/wiki/Gizzard#Gizzard_stones) to help digest food. Some bilogical mechanism would separate out the naphta, give it some oxygen, and store the resultant naphthenic acids in their palm oil sacs to create the gel. --- In summary: The bacteria's sulfuric acid and yeast's ethanol would definitely be an annoying, if not very lethal, poison when separate. When combined, they will produce a short-range burst of flame(if ignited somehow). When combined with the palmitic/naphthenic, it will shoot out as a sticky stream(or glob, your choice) of flame than will burn until it is out of fuel. [Answer] Acetone + slug slime I lifted part of my answer to your other question [Methane Dragons](https://worldbuilding.stackexchange.com/questions/106224/methane-dragons/106400#106400) > > Vertebrates do not make alkanes. Better yet would be a volatile > flammable liquid which actually is produced in animals. I propose > acetone.. It is a liquid with a low vapor pressure. A Bronx cheer > breath weapon of acetone droplets would turn into a sweet cloud of > flame. Enthalpy of combustion is double that of methane (though lower > than propane). Acetone is in animals, produced by ketogenic fat > metabolism - even humans normally make small quantities of acetone. > Plus it has that great smell of nail polish remover. > > > And super tenacious adhesive slug slime! A mix of biologic polymers. <https://www.sciencenews.org/blog/science-ticker/slug-slime-inspires-new-type-surgical-glue> > > For a glue that holds up inside the body, turn to the humble slug, > Arion subfuscus. A new super-sticky material mimics slug slime’s > ability to stick on slick wet surfaces and could lead to more > effective medical adhesives. > > > A slime "hydrated" in part with acetone would still be slimy. As the acetone burned it would dehydrate the slime which being long chain carbons would also burn energetically - much like the large hydrocarbons in napalm fuel the fire. ]
[Question] [ In my world vampires own a kingdom with human slaves. They harvest human blood but how can they preserve it with medieval technology? PS : I would like to preserve the blood in liquid state, but other methods are allowed. [Answer] To keep blood in liquid state, they can use: * Sodium fluoride: available in some rocks, but still pretty rare. Their alchemists can try to produce it * Sodium oxalate: oxalic acid is present in big amounts in rhubarb leaves, it shouldn't be hard for their alchemist to extract it an make it react with some sodium * Sodium citrate: again, citric acid is present in lemons, some alchemy can produce this salt * Salicilic acid: cut some willow bark, boil it and use the result as bland anticoagulant All the above methods rely on chemistry. The physical method employed to keep blood liquid to enable further processing when making blood sausage was to frequently stir it, to prevent the formation of the protein network induced by the coagulation. Harvest some snow to keep it cold (Hint: Snow mixed with straw can be stored in underground rooms all summer even in warm climates like the South of Italy.) [Answer] Carefully bred leeches - They have anti coagulants in their saliva which would keep the blood fluid, and to a certain extend, fresh. They're well known in medival times, and often feature in literature of the era in use in medicine. Something like the common l[eeches used in medicine](https://en.wikipedia.org/wiki/Hirudo_medicinalis) could either be processed, or bigger leeches used to draw and possibly even store blood. [Answer] There are a few ways depending on the exact specification. First of all, anti-coagulation (=keeping the blood liquid) can be achieved with some natural substances. They adress different reactions in the coagulation chain (you might want to read something about that for further background). There are * ASS (Acetylic salicylic acid / aspirin) which can be obtained from ginger and some other plants. * Curcumin (from turmeric for example * Coumarin (cinnamon) etc. (Google natural antikoagulants or see for example [here](http://www.healthline.com/health/high-blood-pressure/best-natural-blood-thinners)). Those prevent the blood from clotting, which keeps it liquid but they will be present in the blood afterwards so effects might be that the vampires have thin blood and their wounds don't heal / bleed a lot. Of course, there is actually no need to do that, you could just let the blood clot and eat it like that. Depending on what you want to achieve / what part of the blood you need filtering it would work too, but I'm not sure filters that good are available in the medieval ages. Centrifuges could be used to separate the bloodcells, they are pretty low tech but not exactly medieval, though with the necessary knowledge about cells they could be build with medieval tech I think. (<https://en.wikipedia.org/wiki/Blood_fractionation>) Another way (a little out of the box) would be to breed hemophiliacs. That would allow for some interesting problems with keeping them safe. (Btw. if you want to store the blood for a longer time you have to keep it clean from bacteria, fungus etc.) I was thinking that destroying the thrombocytes (blood cells) might work too, but was told it probably wouldn't. Blood is a pretty agressive liquid and even modern medicine has the problem of coagulation and storing it for longer times (you could look up how blood banks do it, they don't store blood more than 90 (I think) days though, so your medieval tech will probably not achieve that much unless you are okay with the blood going "bad" in the sense tat a human couldn't be infused with it anymore without severe consequences. But again, eating/drinking it allows for a lot more as the acid in the stomach will deal with most problems that would kill you if infused with the blood. So my final suggestion, if you do not want to deal with that to a bigger extent, let it coagulate and the vampires spread it on bread, eat it as pie and invent many delicious dishes focussing on adding stuff before or after the coagulation. [Answer] It seems logical that the best and freshest blood would come from living humans, who themselves make great and mobile containers for blood. ]
[Question] [ This world is all water, and I want the trees to be the only thing that represents land. The trees are horizontally positioned, and start from a large self sufficient floating seed pod, much like a coconut would. They would lengthen faster than they would widen, during the growth process. Naturally the size of these are twenty thousands of times bigger than the widths of the giants of earth. The roots would glean nutrients from the water, and have some kind of mechanism for trapping the fish for food, thus categorizing the tree as carnivorous. The structure is questionable as far as shape and anatomy of its trunk, limbs, and bark. All those things would have to be shaped so that the the tree is habitable for humans. What could I improve to make this more believable, or is it believable at all? [Answer] The concept you have in mind is plenty believable for fiction but there are a few changes I think would be necessary. These aren't going to be trees. Tree is a specific name for a specific type of plant. Trees require soil and can't handle salt water (in most situations). They are also generally hard and inflexible which would be detrimental if they exist in a medium that is constantly in motion, meaning the ocean. So in short the type of plant you describe could likely exist but it would definitely not be a tree. It would likely be some sort of super seaweed. You would also probably need to consider allowing your super seaweed to take root in shallow waters allowing for more nutrients and larger growth. The size you are looking for will be tough to get to if they are completely free floating all the time. It may not be relevant to your story but in your head you should also probably consider that they had to have evolved the ability to trap and consume fish if you want to go that route meaning that being able to take root or something similar would have been needed earlier in the evolutionary history of the organism. Also...humans wouldn't evolve as humans on this world so keep that in mind...either they are transplants or humanoid but not quite human. [Answer] I would consider the idea it is a single tree that spans the entire planet, akin to a Banyan. To me this solves many problems, and potential adds interest. [Answer] A friend and I kinda worked through this once. You have floating plants and kelp forming clumps, basically the plants are a series of gas-bags with leaves and root. there are already floating plants but for the ocean you will need greater buoyancy hence the gasbags. picture the sargasso sea on steroids. other types of plants colonize these mats adding larger plants, more gas bags, deeper roots. the roots start to collect debris and will house lots of animals, the roots of some plants may even be designed to tangle and hold animals for supplemental nutrients.you might have filter feeding animals also colonizign them and each dead plant is going to add more "soil" to the islands. eventually as the mats get large enough they begin to support mangrove like trees with light balsa like wood and maybe their own wood floats or coconut like growths.there trees would favor being wide and spread out instead of tall for stability. the more animals and plants colonize the mats the more debris is added when they die encouraging bigger plants. insects, crabs, maybe amphibians, and millions of fish would colonize such things. the plants are held together by intertwining rooks and tendrils, and "islands" may be torn apart during storms if they get too big, and would occasionally sink. they would naturally be pushed towards the ocean gyri so soon you would have many "islands" close together or even joining. on a water world these might very well have evolved from sargassum kelp. Humans would need to build platforms to live on, but would have to be careful cover too much and too many plants might die causing the whole thing to sink. trees might drop floating twisty nuts that get tangled in in mats where they sprout after several years, giving the mats time to build up around them. the trees roots would spread wide to help hold the mat together and to get their nuts to the edge where they need to be. [Answer] This idea will only work so far. Since the world is without land, there are no land masses to interrupt the development of storms, and they have an essentially unlimited length of wave development (called fetch). As a result, storm-driven waves will become enormous. When these waves encounter your "trees", unless the organism can flex freely it will break. This is similar to the maximum (about 300 feet or so) length of wooden ships. Beyond that length, wooden ships tend to break. And, since seasoned wood is stronger than green wood, you should assume that your "trees" are weaker than a wooden ship would be. So in order to survive, the "trees" must consist of smallish solid parts interconnected by very strong, flexible tendrils, and there must be some built-in mechanism to prevent the solid parts from fusing. [Answer] This is just conjecture... It would seem that this concept would emphasis a simple ecosystem. I could see some symbiotic plants growing into the bark, and even pockets of dirt/dust (if nothing else than from decay). Highly probable that there would be diverse fungi, even to the point of having colorful seasonal "wildflower" species. The wind would be especially useful in spreading the spores so that the fungi can repopulate in "new" areas. Vast insect swarms would travel in migration patterns following the supply of food. The more destructive swarms would nearly strip everything except the great tree. Other insects would be used for pollination and transferring seeds of plants that are unable to benefit from the wind. Many of the larger and more intelligent animals in the branches would be of a flying/gliding type. It could be a feasible environment for creatures that look like fairies. There would also be grasping animals such as snakes, who are especially dangerous as they blend in with the branches. Finally there would also be primarily water dwellers who live entirely in or near the water. Any human-like life would be warriors/hunters/gatherers as the environment does not allow farming, mining, etc. ]
[Question] [ I am trying to fact check a consistent set of properties and applications for the titular [unobtainium](https://en.wikipedia.org/wiki/unobtainium) from the [Mass Effect games](https://en.wikipedia.org/wiki/Mass_Effect) in order to avoid introducing contradictions. Certain sources I read claim it wouldn't allow for the applications it is used for. The [in-game codex](http://masseffect.wikia.com/wiki/Codex) isn't detailed (it says it increases or reduces mass with positive or negative current and throws around ["dark energy"](https://en.wikipedia.org/wiki/Dark_energy) like an accepted scientific term) and physics is not my area of expertise. I assume it works on principles similar to an electromagnet, but allows for the generation of [gravitational fields](https://en.wikipedia.org/wiki/Gravitational_field) with the strength of [electromagnetic fields](https://en.wikipedia.org/wiki/Electromagnetism) (×4.2E42 more force). A block of the stuff is, I assume, bipolar and produces attractive or repulsive gravitational force based on the direction of current. Basically it combines the best parts of gravity and electromagnetism for the arbitrary manipulation of gravity, hence "unobtainium". This unobtainium is noted in-game to have applications of: * casual flying vehicles (counteracting gravity?) * faster than light travel ([Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive)?) * acceleration without thrust (create a [gravity well](https://en.wikipedia.org/wiki/Gravity_well) in front of the vehicle?) * projectile weaponry using metal shavings (gravity railguns?) * repelling kinetic projectiles (force fields?) * moving objects at a distance * artificial gravity so everyone can walk inside spacecraft * [counteracting intertia](https://en.wikipedia.org/wiki/Inertia_negation) so spacecraft may accelerate without need for seat belts * for unknown reasons, leaving FTL drives running causes spacecraft to generate increasingly powerful lightning storms (EDIT: in-game explanation is that leaving FTL drives running causes spacecraft to generate "[drive charge](http://masseffect.wikia.com/wiki/FTL#Drive_Charge)" even though this this violates conservation of charge) Are [element zero's](http://masseffect.wikia.com/wiki/Element_Zero) properties internally consistent? Would it indeed allow the applications purported? [Answer] ## Game lore explanations The lore of the game attributes to dark energy to both attractive and repulsive effects. And it says that the ["element zero"](http://masseffect.wikia.com/wiki/Element_Zero) is able to manipulate the mass of the objects (instead of manipulating gravitational fields as I described below). If so, it could be better understood as manipulating [higg bosons](https://en.wikipedia.org/wiki/Higgs_boson). I find this explanation problematic because it seem to suggest [negative mass](https://en.wikipedia.org/wiki/Negative_mass) for repulsion. I found this [description](http://www.escapistmagazine.com/forums/read/7.342443-Fans-Tear-New-Mass-Effect-Book-to-Shreds?page=3#13796155) of the "element zero": > > When subjected to an electrical current, the rare material dubbed element zero, or "eezo", emits a dark energy field that raises or lowers the mass of all objects within it. This "mass effect" is used in countless ways, from generating artificial gravity to manufacturing high-strength construction materials. It is most prominently used to enable faster-than-light space travel. > > > There are two relevant bits to take from here: 1. it is not said to be a chemical element, but a material. It could be a particular isotope, or it could be a compound, or it could not even be [baryonic matter](https://en.wikipedia.org/wiki/Baryon#Baryonic_matter). 2. The quote says `When subjected to an electrical current`, that is, they are making a "wire" of the stuff. So, there is no reason to think that the material in it natural state has any noticeable gravitational effects. --- The provided link about [Drive Charge](http://masseffect.wikia.com/wiki/FTL#Drive_Charge) says: > > Element zero FTL drives accumulate a static electrical charge when a vessel has been in FTL flight for some time. This charge steadily increases with the amount of time a vessel spends in FTL. Eventually, it must be discharged. > > > According to that, an electric charge is accumulated while traveling FTL. It doesn't seem to be an artifact of the FTL drive, but of the FTL travel itself. ### Your question > > Are element zero's properties internally consistent? Would it indeed allow the applications purported? > > > No, it doesn't work. If we consider that "element zero" may also increase mass, then it could explain giving a strong gravitational field to an object. Reducing mass alone will never explain artificial gravity. Increasing and decreasing mass of objects makes fine control harder, for instance, you could explain deflecting projectiles by increasing the mass of another object that then attracts the projectiles. But doing that would also affect other things in the surrounding. Similarly, giving mass to an object in front of you so that you "fall" to that object won't allow you to go pass that object. Then you need to reduce the mass of that object again, and increase the mass of another object in the direction you want to go. Also consider that if you reduce the mass an object to zero [it will move at light speed](https://en.wikipedia.org/wiki/Massless_particle#Special_relativity). Alternatively you could understand not as reducing mass, but as reducing the influence of gravity, then you get weightlessness. This doesn’t really explain repulsion of [FTL](https://en.wikipedia.org/wiki/Faster-than-light) travel either. Building an [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive) would still have the [placement of matter difficulty](https://en.wikipedia.org/wiki/Alcubierre_drive#Placement_of_matter). I will not go into the problem of the electric charge from FTL travel here, because I'm saying that the game lore explanation is not good enough for FTL travel. ## A better explanation What this "element zero" seems to be doing is manipulating the gravitational field, to create either repulsive or attractive gravitational charges. So, it is making [dark matter](https://en.wikipedia.org/wiki/Dark_matter) (attractive, but otherwise undetectable) and [dark energy](https://en.wikipedia.org/wiki/Dark_energy) (the repulsive equivalent). Using "element zero" would require some form of energy input. To remain consistent we would say that it uses electricity, and the output is an artificial gravitational charge (positive to be attractive and negative to be repulsive). The machine must be built in such way that allows directing such gravitational charge to the desired location. The problem is: what happens when a charged particle arrives to an object made of "element zero"? We need to be able to make it so it can modify the surrounding gravitational field to create repulsive and attractive forces. So, there must be two ways to interact with it. Given that the "element zero" is not a chemical element, I don't see any problem saying it is an anisotropic material that will react differently depending on the direction on which a current traverses it. That could explain how to create an attractive force by using current in a set of directions, a negative force in a different set of directions, and none at all in yet another set of directions. Under this idea, you need use a different current direction to have a different effect, and you would need to actually rotate the system to direct it. The intensity of the effect would be linked to the power used. ### Your question > > Are element zero's properties internally consistent? Would it indeed allow the applications purported? > > > Yes. By creating artificial gravitational fields (both attractive and repulsive) relative to the machine that generates them can be used to move objects at distance. And it can be used to negate gravitational attraction, including those created using it. Under the idea that it manipulates the gravitational fields relative to itself, it would be a way to create an [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive). So it can explain FTL travel. To explain an electric charge built up in an object traveling FTL using this method, such that it requires discharging it... I would have to say that the object captures charged particles during the trip※. A longer trip would lead to more charged particles being captured. ※Speculation: We could say that during the trip the ship pushes with it [astrophysical plasma](https://en.wikipedia.org/wiki/Astrophysical_plasma), just by it not having time to flow around the ship. As a consequence of that electric charge, the ships would need a stronger insulation if they are meant to sustain larger FTL trips - as to prevent sparks from the outside to the interior of the ship that may cause damage. Also, leaving the ship after the travel won't be safe unless that charge is canceled. ]
[Question] [ I'm currently enamored with the idea of having a species of [living, sapient stars](http://tvtropes.org/pmwiki/pmwiki.php/Main/CelestialBody) [(called "astrae")](http://tvtropes.org/pmwiki/pmwiki.php/Main/GratuitousLatin) [as the firstborn children of the gods](http://tvtropes.org/pmwiki/pmwiki.php/Main/CosmicEntity) [in my space fantasy](http://tvtropes.org/pmwiki/pmwiki.php/Main/ScienceFantasy) [setting](http://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceOpera). Magic exists in this setting, so it's perfectly possible that I could just [handwave it](http://tvtropes.org/pmwiki/pmwiki.php/Main/handwave) [and say that astrae exist because magic](http://tvtropes.org/pmwiki/pmwiki.php/Main/AWizardDidIt) [or they're made of magic and just look and act like stars](http://tvtropes.org/pmwiki/pmwiki.php/Main/MadeofMagic) [or their excess of numen (divinity) allows them to exist](http://tvtropes.org/pmwiki/pmwiki.php/Main/AppliedPhlebotinum). It's a fantasy set in space – I'm fine with [ignoring blatant impossibilities](http://tvtropes.org/pmwiki/pmwiki.php/Main/RuleofCool) for the sake of having living, magic-wielding stars in the mythologies and lore of this universe. But, both magic and evolution (because they were created; they did not evolve) aside, is it possible to have 'stellar organisms'? Could a star or star-like object (e.g., luminous spheres of plasma held together by their own gravity with thermonuclear fusion occurring within) accommodate cell-like, organ-like, and brain-like structures so as to allow memories and complex reasoning? Or should this be a case of "screw it, my world has magic, and what I say goes"? [Answer] This is a very interesting concept! Abiogenesis used to focus on synthesis of organic chemicals, such as the famous Miller-Urey experiment. But a more recent approach is to consider the process from a 'metabolism-first' perspective. Before there were organic chemicals, there may have developed auto-catalyzing reactions, where the products of a chemical reaction catalyze further production of the same chemicals. This is the beginning of self-replication. I have heard recently, that life may have begun in a network of tiny pores in a stone where the stone simulated cell enclosures that allowed the autocatalyzing reaction to continue constantly inside. Applying this metabolism theory to stars, it seems to me that magnetic fields would have to create the cells. Instead of a chemical reaction, a certain magnetic field pattern could give rise to a plasma shape that caused that magnetic field pattern to replicate. The cells would then be packets of plasma that built a magnetic field that encapsulated their constituent plasma. Perhaps these patterns could only exist within the photosphere or chromosphere of the sun, and to stay alive they had to stay around the core of the sun which provided the radioactive heat from fusion that maintained their bodies in plasma form. Not sure if that is scientifically feasible (seems like there would be LOTS of magnetic interference from adjacent cells). And how these cells would band together to make a superior life form, and from where would come the impetus towards sentience I don't really know...but you said you were okay with magic! [Answer] The interesting thing about your idea is that the origin of the conscious mind is still a great mystery. However, it does seem to require a high degree of complexity. What if you made an entire galaxy a conscious mind with each star communicating with its neighbors by means of gravitational waves and fluxes across the vacuum of space? This system could be analogous to neurons in the human brain communicating with neurotransmitters across synapses. [Answer] # Yes, but they would be ... different This is, conceivably, possible, though I wouldn't try to explain it as a conventional biological organism. Instead, let's focus on directly physics-based lifeforms. In [The Five Ages of the Universe](https://en.wikipedia.org/wiki/The_Five_Ages_of_the_Universe), there is a suggestion of emergent intelligence through networked black holes, so there are all kinds of crazy-sounding ideas that could function based on physical principles without traditional biology. Given that we're dealing with stars, light is an obvious candidate. Our Sun is a fairly average star, so we'll use it for rough approximations to determine feasibility. The basis of this intelligence will be signalling with photons, or groups of photons. The Sun is just over 2 light-seconds across, but light takes about [1 million](https://image.gsfc.nasa.gov/poetry/ask/a11354.html) years to travel from the core to the surface, because it bounces around somewhat randomly for a very long time. Having such long signalling times would slow down the mind immensely, so there are two ways to get around that. 1. 'Minor' stellar restructuring: Small tubes of lower-density material could be created (by your gods) to allow photons to traverse the star in reasonable times for a thinking being, but without special constructs, I don't see how these could be held open. 2. Quantum entanglement: Though this does not allow for FTL communication, it can allow lightspeed communication without all that finicky structural stuff. So signalling can be by quantum entanglement of certain photons, but how about the actual computation? It could be distributed throughout the star in computation centers, vaguely similar in function to neurons. This can be achieved through multiple means, including a combination of these: * Location-based computation: Based on the location of certain photons within the star (which can be determined by interactions with known 'marker' particles), values can be determined and operated upon in various ways. * Entanglement-based computation: Just like a 'normal' quantum computer, operations can be performed on qubits, and special, non-arithmetic outputs can be obtained, though this would require highly controlled cavitation on small scales to maintain the low temperatures needed. * Value-based computation: The constants associated with certain particles (ie spin, color, EM field interaction, speed, and mass) could be used to store values around individual ions, operating somewhat more like a conventional computer, though not really through normal electronic means. The one problem remaining is that this is still just a massive computer system, not a living being. Such problems, though, could be solved just like they are in current AI research. The 'software' running on the stars' computational matrix could simulate a neural network, or some more sophisticated form of learning, to implement a general AI as an independent, living being. Even limbic system (hormonal) changes could be simulated through gradual life changes in the star, and the cycles of luminosity stars normally undergo, as well as random errors introduced by potentially imperfect computations. Overall, this is an idea that is definitely feasible (and pretty cool) to implement, and I'd love to see where you go with it, even if you don't use my idea! [Answer] In "The game of life" you see simple random arrangements of elements coalesce into complex activities. You could imagine that in rare cases, the random magnetic fields and plasma flows of a star begin to react in similar stable and complex patterns. Evolution of those patterns could slowly manipulate them into a form of consciousness. The data transfer rates would be horrendously slow, but there are examples of this in literature already. The trees in Disney's Sword in the Stone were constantly communicating, but Arthur has to be slowed down to the same slow timescale the trees are on before being able to understand it. A star may take centuries to have a single thought. And the changes necessary to achieve any sort of action would take even longer as various flows and fields have to be modified to produce forces. But perhaps that's reasonable on the timescales that the stars live. This wouldn't be something that would make sense if you wanted all stars to be intelligent. But may be believable for rare ones. [Answer] What if the astrae don't work quite like actual stars. The fusion at the center is powered by some other catalyst than massive gravity, perhaps a series of super-powered magnetic fields that aid the compression. The excess energy is channeled through a network of other magnetic fields to the outside in order to preserve the more fragile living tissue between the core and the outer shell, and directed outward very efficiently. These stars would be recognizable by their low gravity for their size and stellar class. Perhaps these creatures evolved shortly after the big bang and fed on the dense elemental clouds available at the time. Much like the denser atmosphere of early earth allowed giant-sized insects, this environment allowed stellar-size evolution in the universal "primordial ooze". As expansion thinned the gas clouds, a species managed to survive by evolving its own internal fusion engine as a more efficient use of the little nutrients they still manage to consume, generating a much higher energy output for a given amount of material intake. Perhaps it's actually possible that the fusion originates from the plasma of other stars. The astrae siphon it off and capture it outside themselves with their own magnetic fields, using that to jumpstart a fusion reaction and nurturing it for energy. This would effectively work the same as the thought above except that the magnetic fields would channel the energy around the creature instead of through the creature. Maybe it is even a colony of creatures nurturing a central fusion reaction and using the excess channeled outward as camouflage and protection. In either case, the central core is going to be much smaller than a traditional star's fusion core, even if the envelope appears the same size. The creature or colony will need to continue to gather elements from nebulae and stellar debris disks, either feeding to power the internal core, or siphoning plasma to replenish the external nurtured core. [Answer] There's an SF novel that considers this seriously, but as far as I know, only one: Olaf Stapledon's [Star Maker](https://en.wikipedia.org/wiki/Star_Maker). It's well worth reading if you want to develop this idea, although much of the stellar physics in it is now out-of-date. [Answer] A [BEC](https://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate) can be used for quantum computation and it might exist under the crust in neutron stars[link](https://arxiv.org/abs/1507.05839). I don't know if the additional structures required for computation on the BEC could happen by chance but they could certainly be added by a creator. As far as plasma beings. I agree with @kingledion and [plasma rings](https://phys.org/news/2013-04-plasma-device-revolutionize-energy-storage.html) seems to support. You could always do computation with collapsing structures as well, à la [Chemical Computer](https://en.wikipedia.org/wiki/Chemical_computer). [Answer] Whilst not completely "Star Beings" the [C'Tan](http://warhammer40k.wikia.com/wiki/C%27tan) from Warhammer 40k immediately sprang to mind. Their origins are very similar to stars and they live primarily by enveloping a star and gradually consuming its energy much like a parasite. Perhaps your beings are not actual stars themselves but live within a star and have such a high metabolism that they can never detach from their food source once linked? Again, most of the detail is hand-waved here but it could be useful. ]
[Question] [ I'm writing an adventure story set in the medieval age, our hero came(dived) across an underwater city with an estimated population of several thousands at depth of hundreds of meters below sea level. I'm trying to come up with a convincing technology which could seem plausible at that time, but after many brain storming attempts all I have got is a mental block. Note: I'm writing sci-fi but not fantasy so avoid magic as much as possible. What kind of technology could the medieval people use to build an underwater city? [Answer] Quite a lot of the technology for your classic inverted goldfish bowl city doesn't exist quite yet. Amusingly enough, looking at why it might not work might give you ideas in why it would. Lets start with the basics - oxygen, food, water and light. You are going to use up oxygen, and deep underwater you may not have the same sort of photosynthesis needed to reprocess oxygen, and many plants would not grow without sufficient light. You might have to handwave a bit for that and claim there's some sort of (IIRC) weird primitive slime that or other lifeform that extracts oxygen from some easily found element. You'd also want some way of replenishment of air - a positive pressure would keep water out and you'd likely have losses anyway. Food - fish I suppose? That would need people diving so maybe airlocks - and you don't quite have the liberty of simply pumping out air since you might have a finite amount of it. Maybe grow mushrooms. If you could grow plants, it would help with sanitation I suppose, helping reprocess waste products. Maybe hunting whales or other sealife nearer to the water. Water - you're in the sea. There's lots of water right? But most of it is salty. You'd need a source of fresh water water for sanitation, and being under water, some way to pump out waste products without pumping it in. You need to pump water out. And no culture's had much luck building entirely underwater. Light - photosynthetic algae would be a source, as would maybe natural hydrocarbons. Whale oil or hydrocarbons would be handy, possibly. The next thing to look at is essential technology/biology to solve these problems. Constructing a city underwater seems implausible, but would it be needed? I'm thinking a medieval version of rapture from the first two Bioshock games - a series of tall structures linked up by tunnels. What if the buildings were there first? We'd start with a city of large solid structures - maybe of stone. As time went on, the city started going underwater. Rather than abandoning the city the local residents shored up walls, plugged gaps with pitch and started planning ahead. Maybe they discovered a unique local aquatic mould that fed off human waste products and kept the air fresh, and found glowing algae growing on the walls. As the water levels went up, they started building, first retaining walls, then closed them up to form tunnels between buildings, as well as raised up buildings, forming a linked complex of semi submerged buildings. They also discovered the rudiments of various pump designs. However they could not keep doing this for ever - so you'd need an equivalent of Da Vinci to invent pumps and an airlock system. However as the water got deeper, the society got more insular. Freediving seems a useful skill, but assuming a truly underwater city, they would be limited to 200-300 meters with world class freedivers. A series of diving bells supplied by the same handwaving processes might extend that somewhat, possibly with small settlements ringing the primary complex. Part of me thinks building and sinking buildings would be amusing too, but I have no idea who would be that crazy. [Answer] It might work a bit better if you can separate a city that can be accessed by diving that far underwater from a city built that far down underwater. If you had a city built deep underground, that somehow managed to tap into a network of deep caverns with water access (without compromising them), you might end up with a city that builds into and uses those caverns, and ends up with a stable access point where your diving hero can find it. It will also be a lot more plausible if you can accept a shallower city, after all finding the underwater access point to an amphibious city (built partly underwater) can be pretty striking even if it's not quite so far down. I recall a story where a city was built into a dry portion of a [cenote](https://en.wikipedia.org/wiki/Cenote), a cave system with a deep underground water access. Usually the cenote will be filled to the ground water level, so not particularly useful for dry caves deeply underwater (especially not with surface access, which your city would also need to survive), but if you assume a tricky geology and a number of features your city happens to be able to take advantage of (rather than deliberately causing, which they wouldn't have the technology to do yet), it might not be quite so impossible. So, maybe you start with a deep cavern system filled with water. It needs to have deep ocean access - maybe the system is through a cliff next to the sea (which drops all the way down to give an opening at the required depth). Or perhaps it is an island over an old, inactive ocean volcano, where some of the lava channels are waterproof stay dry (and some have access to the island top and therefore air), even though most of the mountain is under water, and there are systems with access to water. Freshwater might occur in caverns without direct access to the sea by filtering in through the ground rock (aided by pressure and osmosis) into parts of the cavern system where there isn't a direct connection to the sea. In other places, sea-water would have direct access to the cavern system, and maybe there would be some brackish water tunnels where they systems interconnect. So, parts of the system get cut off from each other and the ultimate water source (caverns that hold water, should be water proof enough to keep water out if that initial access is blocked) perhaps through earthquakes. There ends up being dry caverns extending deeply under sea-level, in addition to the fresh, sea, and brackish water systems already imagined - although there should be access somehow between the systems which doesn't cause them to equalize, maybe underwater tunnels separating air systems and rooms with air pockets separating water systems, working as crude airlocks. They can even be made on purpose, once a few natural ones let your people figure out how they're keeping they systems separate - and why that's necessary. And you have a people who move into the upper levels of the cavern system, perhaps to escape some outside threat, or maybe just for better access to the filtered freshwater and the cavern system. Maybe they needed to live underground because they needed all arable surface land (if on an island, for example) to feed people. They might spend generations slowly building themselves deeper into the cavern system - and if they're using freshwater in a more isolated system faster than it seeps in, they might excavate their way downward, using newly drained caves as extra storage and eventually living space, and following the water source to keep moving down. Of course, they can use their technology to make the caverns more habitable, and try to keep the various systems separate but accessible, as they build their city downwards. The crude bellows and pumps of that age (used for airflow in forges and such) might be not be sufficient to keep the water out of a true underwater city, but they might be enough to keep airflow and oxygen circulating to a livable degree in a deep pressure cavern system with access to the open air at the surface. They understood enough about airflow to to feed the fires with good air in their forges, this is just a bit of a larger scale application to feed good air to their people. Maybe they can supplement their oxygen with cultivated pools of certain types of algae, in places where light might shine for photosynthesis, but perhaps the air is more stagnant - or even using bits of polished metal to reflect light in for just that purpose. They would not be racing race down to build the city hundreds of meters below sea level, they would be slowly, over generations, edging their way downwards. There would be a lot of slow experimentation, and these tricks would let them slowly make marginal areas more habitable, and as they adapted to the area they would find more tricks to make the place habitable, and more tolerance to marginal areas. Also, as they descend I expect they would be living under more and more pressure - since big pressure differences would cause the cavern system to flood or collapse. But, they might be able to adapt to that too, if the best divers can visit 200-300 meters it shouldn't be impossible for a population to adapt to 100 meters below sea level, just like populations can over time adapt to living at high altitudes. The worst problems seem to some from moving between different conditions quickly, but long term living is easier to adapt - though the best divers from this population might be able to go a bit deeper than from a population adapted to surface pressures. Maybe the population would split into interconnected settlements at different levels, who had problems going too far outside the level they were born in without great care. This might mean after a while it is easier and possibly safer for the divers living at a deeper level to navigate the cavern system to access the ocean (for seaweed, algae, fish, or any other resources) from the deep underwater access point your hero found, rather than ascend through the city and access the water from the surface. [Answer] Impossible. There are multiple problems here: 1) You can't free dive to hundreds of meters beneath the surface. While you just possibly might be able to create a diving bell (probably not, the compressor needs to be pretty powerful and I don't think they could do it) they're not going to be able to create the mixed gas mixture needed. 2) The same pressure & air problem exists for the city. Even at the smallest depth that satisfies "hundreds of meters" you're already way into the realm where special atmospheres are mandatory. You have no way to make the atmosphere and you're going to have a very hard time keeping the pressure out to do it with a normal atmosphere in there. 3) It's going to be almost pitch black at that depth. What's their light source? I'm not aware of anything that doesn't need oxygen or electricity--you're going to have to be supplying a lot of oxygen to light your city. (Before someone says "bioluminescence" the creatures that produce it use oxygen.) [Answer] Some sort of bloodsucking remora like symbiote that trades food for intravenous oxygen, perhaps it evolved that way to prevent the host from being singled out as easy prey by predators, maybe they've been selectively bred to keep the host hydrated too. The symbiote would have to be quite large to provide enough oxygen to keep both it and its host alive which means it will require a considerable amount of food, whether its being fed by the host or feeding upon the host directly this society is going to need access to lots of calorie rich food. [Answer] I like "Lightness Races in Orbit"'s idea of the pre-existing surface city adapting to underwater life. Fresh water: I haven't been able to find the source, but I recall an ancient Greek city (Syracause? Athens?) used a submarine spring as one source of fresh water, stimulating some early technological development. Air: as with the fresh water, a large pocket of air could be trapped, like natural gas or an artesian aquifier, in a permeable rock (sandstone?) beneath a layer of impermeable rock formation (limestone?). This works perfectly if the local geological region has undergone considerable subsidence. The problem for your city is that (a) the air supply is non-renewable (b) they may not understand that, and (c) at a depth of hundreds of metres, nitrogen narcosis is going to be a huge problem. The only way I can see around (c) is that is that there ARE underground reservoirs of helium, usually associated with radioactive ores that have emitted the helium. If the underground air is mixed (intentionally or otherwise) with helium, you will get a <https://en.wikipedia.org/wiki/Heliox> or more accurately <https://en.wikipedia.org/wiki/Trimix>. The reduced % of oxygen isn't a problem if the city is operating at the pressure of the surrounding water (dozens of atmospheres). Given medieval materials, they probably don't have any option but to keep it at ambient (high) pressure. If the helium supply is sabotaged/runs out, your city inhabitants are going to quickly become dreamily intoxicated due to nitrogen narcosis. Another problem would be decompression to reach the surface - days of gradual ascent would be required. A dedicated "ascent tower" could be an option, water filled but with bubbles rising to replenish the divers clay/leather/glass jar "helmet". [Answer] Since you are writing a sci-fi the only technology I can think of is : the bubble maker. Each citizen in your city lives inside a personal bubble, they can eat, work, sleep and do everything normally without breaking it. Each bubble has a 24 hours supply of oxygen after that, every citizen must go to this huge medieval machine to change his personal bubble. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I have an engine with unlimited $\Delta v$. Don't ask how I got it, it's probably one of my earth changing inventions. Either way: I no longer like Earth and want to get off (I'm headed for a retirement villa on Olympus Mons), but I don't want to lose the nice home comforts, like a sink with a plug hole, or being able to drink from mugs. So I need to accelerate constantly in order to maintain the illusion of gravity. You can call me picky if you like, but I don't want all the hassle of strapping things down at the mid way point when the direction of my burn changes and I experience a brief moment of 0g. I just want down to stay down. I know that a flip'n'burn is the fastest route, and that a Hohmann transfer is the most efficient, but frankly I don't care. So my question is this: Does a transfer between Earth and Mars exist such that a spacecraft can maintain a relatively constant 'down' from takeoff to landing? I don't mind variances in the magnitude of the 'gravity' (let's say 0.5g to 1.1 g is acceptable) or the pitch/yaw of the 'gravity' (I've got wide based mugs, 15 degree pitch is fine). I also have a huge stock of tea bags and cuppa soup, so transfer time isn't an issue. bonus points for proof/disproof that arbitrary transfers of this nature are possible [Answer] ## Yes but you have to violate one of your conditions. ### Acceleration To launch from Earth, your acceleration must exceed Earth's gravitational acceleration. So assume an acceleration of 1.1 g (within bounds). ### Trajectory There exists a family of trajectories called [Brachistochrone trajectories](http://www.projectrho.com/public_html/rocket/torchships.php#id--Brachistochrone_Equations) for vehicles moving at constant acceleration on a trajectory. This is within your constraints. ### Space Craft Orientation Brachistochrone trajectories require a flip at the mid-point so the ship can begin deceleration. The conventional way to think about this is, turn off your engines, rotate the ship 180 degrees, and then restart the engines. This, of course, causes a period of zero-g for a short time during the flight. In order to remain under constant acceleration, the ship must [fly something called a "skew flip"](http://www.projectrho.com/public_html/rocket/torchships.php#id--Brachistochrone_Equations) (there's a nice diagram at the link that I can't paste in here), in which you flip the vehicle while remaining under constant acceleration. Since Pitch & Yaw are used to describe the ships orientation to its velocity vector, you violate the pitch/yaw constraint. As a passenger, you mostly won't feel this because velocity is relative. You will perceive a constant acceleration and, except for possibly a little vertigo, not notice the ship rotation. The skew flip, violates your minimizing the pitch/yaw - except that the passengers won't really notice this pitch/yaw change. In space, we don't care about our orientation to the velocity vector except in relation to how it causes our velocity vector to change. ## More Info The first place I've seen this term is from [Have Spacesuit, Will Travel](https://books.google.com/books?id=BG3SjVi5AvAC&pg=PA119&lpg=PA119&dq=have+spacesuit+will+travel+skew+flip&source=bl&ots=ghus_1wlaF&sig=joSqhRLTP5b_4Mz-TddqkX9Nixc&hl=en&sa=X&ved=0ahUKEwjV2ZbP5tfKAhUruoMKHefmAhsQ6AEIKDAC#v=onepage&q=have%20spacesuit%20will%20travel%20skew%20flip&f=false) (and this book appears to be free on Google). The book is a frolicking romp through space but most of the science in it is very real. ]
[Question] [ The Chirr are a race of space-faring aliens that look vaguely like rat-sized ants. They've got powerful mandibles and small, fairly dexterous hand-like claws, though their chitinous nature makes delicate manipulation somewhat more difficult for them than it is for humans. They dwell in huge hives comprised of hundreds of millions of workers who are genetic clones that come from a few breeding queens. Just as with ants, the queens do not lead the hives, only produce more workers. Individual Chirr aren't significantly smarter than rats, but over the past few tens of millions of years, they've been evolving to collectively produce better and better structures and tools, starting with huge cities and progressing into electronics, computers, and now finally space flight. One thing that has baffled human scientists is exactly how they've managed to do so. We're used to thinking about doing things as individuals, making individual discoveries, and learning as individuals what the cutting edge in a given field is. The Chirr cannot do this. An individual is not intelligent enough to make discoveries like calculus or fluid dynamics. The Chirr are not telepathic, do not have a central brain creature, and do not in any other manner meld their minds together, except to the extent that vocal, olfactory, and tactile communication can transmit ideas between individuals. They do have an endless willingness to work together to solve problems, almost no sense of ego driving them to do better than their fellow workers, and will die without hesitation for the good of their hive. Chirr do not have a strong sense of self, but have a very strong sense of belonging to their hive. In short, they have all the traits that have allowed eusocial insects like ants and bees to behave as a group far more intelligently than any individual can act, but are individually far smarter than any ant, though significantly less intelligent than a human. How have they harnessed their abilities to grow into a technologically advanced race? Note: I'm also wondering if this is even possible. I'd like to use the Chirr as an alien race in a game I'm working on, but only if they make sense. If they don't, and if technology capable of spaceflight is outside of the realm of such creatures, I'd like to know why you think that's the case! [Answer] I'd say it's not impossible, just very unlikely. So don't let that stop you. ;) Hofstadter uses an interesting analogy in the "Ant Fugue" of the GEB: the individual neurons in our brain aren't sentient by any means, but through the sheer number of them and the sheer scale of their interactions, they're able to represent an intelligent mind. Or consider the transistors inside your CPU. Each on its own is effectively a tiny switch, no intelligence there. The transistor doesn't understand differential calculus. But through enough interactions between them, the CPU as a whole can take derivatives of complicated functions far faster and more accurately than my human brain can. Of course, depending on their individual intelligence and the structure of their society, the scale of the Chirr colony might need to be incredibly enormous for such things to happen in a reasonable amount of time. But the idea in and of itself is entirely conceivable. You might also look into the Church-Turing Thesis, which predicts basically that any calculation a human can perform, a universal Turing machine can also perform (and vice versa, since a human following a list of rules can simulate a universal machine). Some philosophers have taken this idea and run with it to talk about the nature of consciousness and the mind. But it's not too hard to imagine a Chirr colony becoming "Turing complete"—Conway's Game of Life is about as simple a simulation as you can get, and yet with enough cells interacting it's possible to build a Turing machine from it. [Answer] Weaver ants in Africa use chemicals to communicate, and can work together to make huge colonies with hundreds of nests spanning many trees and containing millions of ants. With a rat sized ant and some intelligence and reasoning ability, I don't see why they couldn't come up with more advanced technology, though I don't think it would look anything like we have. Rats aren't necessarily stupid, and we'd likely be in trouble if they had more reasoning ability. (I don't know the IQ of the average rat to back this up though) [Answer] Without knowing exactly what they're capable of physically, and assuming that communication is all you're wondering about (with it being all they need in order to develop into such an advanced society), you might just give them the biological ability to receive and transmit radio wave communication. It's not an utterly preposterous idea for a life-form, in my opinion. You might want to read up on these articles before you think up ideas of how a life-form might be able to do what a lot of our devices can: * <https://en.wikipedia.org/wiki/Visible_light_communication> * <https://en.wikipedia.org/wiki/Photophone> * <https://en.wikipedia.org/wiki/Radio_wave> This might be a little too close to telepathy for comfort, though, since to a human, it would probably look like telepathy, until they found they could intercept their communication with radio devices. However, just for the record, radio waves are light, much as red light is light. It's just that our eyes aren't made to see it (unless you're special). Humans would have a harder time intercepting many other kinds of light communication, seeing as not all light goes through walls. So, it would be pretty awesome if they were capable of doing it with several 'colors' of light (considering radio waves as one color, or class of colors) so that they could use different ones for different purposes. Another implication here is that they could intercept human radio communication with biology rather than technology. [Answer] Human technology is based on individual effort. A single smart individual comes up with a good idea, does some math to be sure it will work, then builds one prototype. The Chirr don't bother with all that complicated math - they simply build a million bad ideas every day for a few centuries. Eventually something works, and the solved problem is easily shared with the rest of the hive. Fortunately they had already spread into space when some hives started using that approach to develop nuclear weapons. The fact that they don't understand how any of their own technology works would be very easy to miss when nobody expects to be able to discuss advanced math with a Chirr anyway. [Answer] Interesting concept You say the Chirr (strange name, is Ch err or ch ear or I don't know) only care about the rest of the hive, but not for themselves. To this extent why not place an almost immovable force in front of the Chirr one that is slowing killing the hive over millenia forcing them into a scenario where the only way for the hive to live is to leave their current planet, doing so would create catalyst for the "good of the hive" to become the hive becoming greater, maybe they build so high that they reach the stratosphere, at this point the Chirr would have to evolve to breath in space and to survive high amount of gravity, this is natural for a hive species, take the Bee, to this day we still don't know how it flies with such tiny wings, but because it can it survives to this day. [Answer] What if they didn't 'create' the technology? Perhaps they conquered, or simply outlived an advanced race and inherited it? A race like that would make sense. Alien race comes along, and finds them. A fiercely loyal race like that would make an excellent military tool once the queens were kidnapped. Something just went wrong... ]
[Question] [ The idea is simple, our intellegence is so far above a chimp or bonobo as to make us something different. There are things we can do intuitively that no Bonobo or chimp will be able to, and because of this most of our technology is beyond them. They can be taught to use a specific piece in a specific way, but given a new item of technology they simply can not figure it out the way even a young child could. I was wondering about the idea translated to Aliens. Could an Alien's intellect be so far beyond ours as ours is to a chimp? Such that even having access to their technology we couldn't figure out how to turn it on or use it (not reverse engineer it, just use basic functions that even their children could do). Could it by that when we finally meet aliens they will not only have superior technology we can't yet master, but that we simply are incapable of ever comprehending? At first I thought the answer was an easy yes, any creature can evolve to be stronger or faster, so why not smarter. But then I realized that once you have a certain level of technological power with tools your technology starts to grow at such a rapid rate that it eclipses evolution. Our technology has grown exponentially in a thousand years, which is a blink in the eye from evolutionary standards; not enough time for any significant difference in intellect to evolve. It seems that technology would, at that point, eclipse evolution as a driving form, effectively we either create technology that is able to handle new technology for us (AI and genetic programing etc) so we don't have to be smart enough, reach some degree of trans-humanism, or kill ourselves out before evolution will have a chance to have a substantial affect on our IQ. Thus I'm wondering, is it possible that any alien species will be on the same rough intellectual level (not technological) of humans? A few IQ points one way or another, but not an insurmountable gap that prevent one from comprehending the others technology? [Answer] > > Any sufficiently advanced technology is indistinguishable from magic. - Arthur C. Clarke > > > Intelligence may be a tricky parameter to take into consideration in this case. [Quoting Wikipedia](https://en.wikipedia.org/wiki/Intelligence), 'Intelligence has been defined in many different ways such as in terms of one's capacity for logic, abstract thought, understanding, self-awareness, communication, learning, emotional knowledge, memory, planning, creativity and problem solving.' Let's put that definition aside for a second. Also, let's take a look at Grog. Fictitious as he was, Grog was also an anomaly - the smartest hominid ever born on Sol III. He was Leonardo da Vinci to the power of 10; an amazing capability to correlate facts and think on abstract terms. Unfortunately, nor Grog nor Leo were able to crate a fully functional helicopter. Lesser men after them did the trick - of course, as another genius said, by [standing on the shoulder of their gigantic ancestors](http://www.brainyquote.com/quotes/quotes/i/isaacnewto135885.html). Here's the thing: technological advancement is incremental. There could be a race of galactic Ents that take a full Earth day to say their names, but if they had enough time (say, a billion years of scientific advancement), then any aspect of their lives would look like magic to us, fast-paced and quick-witted but sadly primitive organisms. Now imagine the amount of information a given alien species possessing functional interstellar spaceships have at their disposal. You need a LOT of technology in order to achieve that point. When you get to that point, when technology grows in such a exponential rate, the odds of any two species to be at roughly the same stage is very, very small - initial biological stats aside. Wouldn't it be fair then to consider the accrued technological advances and raw information amount to be a characteristic of said civilization? Would the individual intellect be really that important, if Ents equipped with mental connectivity to their Mega-Wikipedia and processing power offloading capabilities meet us, humans typing on their tiny screens to check on how to say 'I, for one, welcome our new vegetal overlords' in Galactic Entish? I then dare say that the intellectual level will matter very little. [Answer] It's difficult to compare average human intelligence against an unknown species at an unknown point in the future but any space-faring alien species we find will range from least as smart as we are to completely overshadowing us. According to the Flynn Effect, average human intelligence has been increasing since the 1930s. There are several [proposed explanations](https://en.wikipedia.org/wiki/Flynn_effect#Proposed_explanations) for this but nothing proven. Let's assume that this pattern of increasing intelligence increases to some biological maximum, where if we want more intelligence, we will need bigger heads. (Which raises the interesting prospect that we are getting more intelligent in general because the software our brains run is improving, not that our physical brains are getting better.) Let's also assume that a similar pattern happened in this alien species we encounter and deep space exploration requires a certain minimum threshold of racial intelligence. (Which is reasonable. A single brilliant individual can only do so much against the staggering complexities of deep space exploration.) The longer a species explores space and the Flynn Effect continues to happen for them, their intelligence can increase to incredibly high levels. [Answer] Despite the human tendency to anthropomorphize things and our many mental shortcomings we have a lot of things that animals considered intelligent don't have. There are various kinds of animal intelligence that differ from us and animals have complex communications methods like us humans too. However, one thing humans excel over animals, I think, is the concept of self awareness, subjectivity, qualia and the sense of selfhood. I think this gives us a significant edge that for the chimp comparison to work, the aliens would have to be significantly beyond us. I think almost no longer tied to same restrictions of the physical three dimensional world. The spectrum of intelligence is huge so this is entirely possible, I would even say highly likely. So I would say that aliens would have to be about the level of intelligence as us or above to be able solve the difficulties of spacefaring that are the same everywhere where the universal constants are the same. But they could have entirely different kinds of thought patterns in many other areas, such as social intelligence etc. [Answer] A disturbing possibility is that as technology improves average intelligence decreases. This might be partly because technology means that intelligence ceases to make any difference to an individual's chance of propagating their genes - all children survive, anyone who wants to can reproduce - and partly because the better the technology the less intelligent an operator needs to be to use it. For example, to use a computer in the 1980s or 1990s required a higher level of intellectual engagement than it does now, and the way tech is going soon we'll be able to simply "talk to the air" to get the omnipresent AI network to perform any function. So, no, spacefaring aliens would not have to be roughly as intelligent as present day humans. They could get away with being much less intelligent; their wonderful automated spaceships or other technology would do everything for them including develop new technology. Intelligence would not merely cease to be an evolutionary advantage but might well be a disadvantage. The same would, of course, apply to humans. It might turn out that for most species average intelligence peaks at the time when they develop technology that can improve itself - i.e. about the stage we are at now, so you would indeed get most species peaking at roughly the same level as present-day humans - but from then on it's downhill all the way. Not a happy thought. Any convincing counter-argument as to why my argument here is wrong gratefully received! ]
[Question] [ For a moon orbiting a gas giant which is in turn orbiting a star, I want to know how long the eclipse would last for an observer standing on the moon when the planet passes between the moon and the star. The actual values I intend to use in the end are likely to vary from these, somewhat, but I like simplicity so here's the parameters for this simplified version: The star = our Sun. The planet = Jupiter radius, orbits the star at a distance of 1 AU (Earth's distance from the Sun) giving it an orbital year equivalent to an Earth year (or close enough to be a negligible difference, for simplicity) The moon = orbits the planet at a distance of 4 million KM, which should give it an orbital time around the planet of about 42 days. It is not tidally locked and rotates on its axis at a rate that will make the same point on the surface face the star exactly once every 24 hours (again, for simplicity) For simplicity (seeing the trend here?), assume all orbits and equators of all 3 bodies share a plane, and are circular, no eccentric or inclined orbits or tilted axes, etc., and the observer is standing on a point on the equator of the moon. Assume the eclipse "starts" when the star is directly over head (noon) of the observer, and the observer says in the same location until the eclipse ends. Please let me know if I left out any necessary variables, I probably have them available and just forgot to include them or didn't realize they were necessary. How long before the observer sees the star/sun again? (rounded or approximate answers would work, but the more precise the better, and an explanation of how the numbers were determined is also appreciated) [Answer] Let's establish some notation: * The star is labelled $S$, the giant planet is $P$ and the moon is $M$. * The diameter of the star is $d\_S$, the diameter of the planet is $d\_P$ and the diameter of the moon is $d\_M$. * The radius of the orbit of the planet is $r\_P$ and the radius of the orbit of the moon is $r\_M$. * At a distance equal to the radius $r\_M$ of the orbit of the moon $M$, the planet $P$ casts a shadow (which astronomers like to call the umbra, using the Latin word for shadow) of diameter $d\_U$. See the following diagram showing the position of the star $S$, the planet $P$ and the moon $M$ when the totality phase of the eclipse begins for an observer sitting on the surface of the moon; we consider that the planet and the moon orbit in the plane of the picture, and we are looking at them from the north celestial pole. [![The eclipse begins for an observer](https://live.staticflickr.com/65535/48014816896_d8d4cfc758_z.jpg)](https://www.flickr.com/photos/alexpanoiu/48014816896/) The position of the three bodies when the totality phase of the eclipse begins for an observer. $S$ is the star with diameter $d\_S$. $P$ is the giant planet with diameter $d\_P$ and revolving around the star on an orbit with radius $r\_P$. $M$ is the moon with diameter $d\_M$ revolving around the giant planet on an orbit with radius $r\_M$. $d\_U$ is the diameter of the shadow ("umbra") of the giant planet at a distance equal to the radius $r\_M$ of the orbit of the moon $M$. Own work, [available on Flickr](https://www.flickr.com/photos/alexpanoiu/48014816896/) under the CC BY 2.0 license. The diagram is absolutely not to scale. We want to compute $d\_U$ given $d\_S$, $d\_P$, $r\_P$ and $r\_M$. (Why do we want to compute $d\_U$? Because we want to find out how much time the moon $M$ will take to move across the shadow.) Notes 1. The following calculations are not exact, but rather decent approximations good enough for a work of fiction. Exact calculations would take more time than I have available. 2. The calculation refers to the totality phase of the eclipse, from the moment the sun is completely covered by the giant planet to the moment the first sliver of sunlight becomes visible. From triangle similarity we have $$\frac {r\_M}{r\_P} = \frac {d\_P - d\_U}{d\_S - d\_P}$$ which means that $$d\_U = d\_P - \frac {r\_M}{r\_P} (d\_S - d\_P)$$ Plugging in the numbers $d\_S$ = 1,391,400 km (diameter of the Sun) $d\_P$ = 142,984 km (diameter of Jupiter) $r\_P$ = 149,597,870 km (1 astronomical unit) $r\_M$ = 4,000,000 km (given) we find that $$d\_U = 142{,}984 - \frac {4{,}000{,}000}{149{,}597{,}870} (1{,}391{,}400 - 142{,}984) \approx 109{,}600 \text{ km}$$ The moon travels 2 $\pi$ × 4,000,000 kilometers in 42 days, or 598,399 km per day. The 109,600 km wide umbra will then be traversed in 109,600 / 598,399 = 0.183 days, or 4 hours 24 minutes. During this time the moon has rotated a bit, about 60 degrees, so that the observer is still in the shadow -- the moon must move on its orbit a distance of about two thirds of its radius to bring the observer into the light. Assuming that the moon has the same radius as the Earth, 6,400 km, this will take about 4,000 / 598,399 days or about 10 minutes. So the grand total is 4 hours and 34 minutes of total eclipse. P.S. What about the total duration from the moment the planet touches the sun to the moment the entire sun is again visible? Given that the radius of the orbit of the moon is much smaller than the radius of the orbit of the planet, the diameter of the penumbra is only a little larger than the diameter of the planet, or let's say some 160,000 km. The moon will traverse the penumbra (and the umbra) in about 6 hours 50 minutes. What this means that if the eclipse (partial + total) begins at noon chances are it will end after sunset... Note that this post-scriptum is even more approximative than the calculation for the totality phase, but still good enough for fiction. [Answer] Using a completely comparative approach, rather than a direct calculation approach, here's my best answer: Totality of an eclipse involving the actual Sun, Earth, and Moon can last up to 7 minutes and 31 seconds. The orbital period of this moon around its planet takes about 1 1/3 as much time as it takes for the moon to orbit the Earth, so it seems reasonable to assume that it's apparent speed across the sky, and therefore across the front of the star, takes 1 1/3 as long. This increases the time of totality from 7.5 minutes to 10. EDIT: The apparent diameter of the Sun is about 30 arc-minutes, the apparent diameter of the Moon is about 31 arc-minutes, and the apparent diameter of this planet as seen from its moon would be about 71 arc-minutes. As pointed out by Mike Scott in a comment (many thanks for the heads up) While that planets apparent size is about 2.13 times the apparent size of our Moon, the key change this makes is actually the difference in the number of arc-minutes between the sizes of the star and the sizes of the obscuring objects. So it's actually a difference of only a single arc-minute between the Sun and Moon, but it's a difference of 41 arc-minutes between the Sun and the planet. A factor of 41 times, not just 2.13 as I'd originally assumed. This increases the time from 10 minutes to 410 minutes of totality This is long enough for the Sun to have set, from the observer's location, before totality is complete, so the observer wouldn't see the Sun again until it rose the following morning. ]
[Question] [ In my country, we are split down the center by an intensely large mountain range. Us desert people live on the eastern half of the country, while on the other side of the mountain range the forest people live. Although we are separate for most of the year, every winter we are forced by brutal winter storms into the mountain caves. 200 years ago, a third group of people, the ones who built out the caves and made the central trade tunnel from east to west, suddenly disappeared. Just as they started to fade from memory, there has been an increase in reports of attacks on caravans journeying through the tunnels. It has been suggested that the attacks have been more brutal then the standard highway pirate fare, only a single survivor had managed to escape but without water he died in the tunnels. It is becoming clear that the attacks were carried out by the lost people, but we have little to no idea of what they even look like. How would 10 generations of living underground with no light, sourcing all foods from things grown and found underground, and a societal focus on digging tunnels change the human body? Edit: To specify I am not expecting much evolutionary change. What I am expecting is that living in those conditions will result in a body that does not look like a surface dweller. Most obvious would be the pale skin. Not an evolutionary trait, but a product of the environment that changes the population's body. The lost people have developed massive fungi that reproduce quickly and have a high caloric value, so starvation is not an issue for the lost people still associated with the main pack. And technology is equal to that of 14th century Europe, with significantly more metallurgy knowledge. The best answer will focus on physical changes based on living in a cave and less on the evolution of the species. [Answer] You want a fast change on the evolutionary timescale? Here is one: Think of blind people. Those who were born normal, and lost their eyesight later in life. Soon, their other senses take over to make-up for the loss. Some blind people may even develop echolocation abilities as shown here: <https://abcnews.go.com/Health/MindMoodNews/blind-man-echolocation/story?id=13684073> Now, imagine how developed is that echolocation compared to bats. Well, not much, but an evolutionary starting point does exist. If the talent becomes integral part of mate selection, evolution will do its part. Other senses, such as smell and vibrations through the tunnel walls (Infrasonic hearing included) are helpful. Something like a cross between a man, a bat and a mole. Food: That's where your plot may fail. Use a cave echology. Chemosynthesis or other non-light energy sources found in caves may give you a good thing to hold on. You have a few: Chemosynthesis -- the cave dwellers may have found a cave that is fed by some sulfides from sulfurous springs. The movile cave in Romania, cut-off from the outside world for millions of years has its own energy source from sulfurous springs that feed a complete ecosystem. The cave men must find a way to harvest what grows there without being poisoned. They may be more resistants as a result, though not necessarily being able to dwell the spring on a permanent basis. <http://www.bbc.com/earth/story/20150904-the-bizarre-beasts-living-in-romanias-poison-cave> Radioactivity like near a Uranium ore deposit, your fungus absorbs radioactive elements to use instead of photosynthesis. It can be a mushroom, if you want, since this fungus seems to do that: <https://en.m.wikipedia.org/wiki/Radiotrophic_fungus> Water Ah! Most important. Aquifers! Other changes -- The need to dig-out and enhance the tunnels may favor the short and stocky physique. [Answer] Nothing they did not see after year 1, except some eyesight issues you will see after generation 1 that will disappear in generation 11. The only changes you will see is the same ones people saw a year after living underground, pale skin from lack of sunlight and vitamin D deficiency for the same reason. Malnutrition and tiny population because isolated caves have abysmal production (surviving 10 generations is unrealistic). Eyesight will be the big issue, generation 2-10 will never use their sight, they will not even know what it is, and will have to learn to see when they return to the surface. They will also not have any depth perception, that develops early and only with sight, but as someone without it that will not have much effect. 10 generations is not enough time for any noticeable physical evolutionary changes no matter how strong the pressure, especially in something social like humans. The [bottleneck](https://en.wikipedia.org/wiki/Population_bottleneck) caused by who was trapped will have a much bigger effect. Cultural changes will be large, they will not know many things, and there will likely be strong shifts in language due to lack of sight, basically you have a blind culture that can suddenly see (poorly at first). [Answer] 10 generations is a long time... I think they would have started to fade into memory about 8 generations ago lol but anyway: Species that only live inside caves are known as troglobites. Troglobites have a few distinct adaptations. They may have developed an ability to use food more efficiently by slowing their metabolism. They maybe have developed anophthalmia or a loss of eyesight or an efficiency in low-light. They may also have devloped depigmentation of the skin. Some creatures may develop extra chemical and tactile sensory organs to make up for loss of visual stimuli. Keep in mind they may not actually be troglobites they could just be troglophile's. Troglophile's have the ability to live both in and outside of caves. So for your cave dwelling humans I am imagining a semi-loss of hearing, eyesight and skin pigmentation. They are most likely getting shorter and more stocky. They could be developing hunched backs and hardened skin. They are perhaps even developing extra sensory organs such as antennae. EDIT: Based on others insights I would have to agree that 10 generations is not going to be long enough a period of time to see any significant evolutionary changes such as antennae. [Answer] Everyone so far has focused in on the idea that evolutionary changes can't happen in the span of 10 generations, but there is sufficient scientific evidence to suggest the epigenetic traits can change within one individual's lifetime. <https://www.whatisepigenetics.com/exposure-to-cold-temperatures-can-change-our-gene-expression-and-fat-cells/> So I'd say you could have just about any changes you wanted - they naturally produce more Vitamin A and have sharp low-light vision - but maybe get easily stunned by bright lights. They grow to shorter heights, their skin is tougher - the nails of their hands and feet have grown thicker and stronger. The ability to sense temperature, pressure, and moisture has been enhanced. You name it, you can probably justify it. [Answer] You could look for studies describing developmental differences for human populations living at high altitudes. Some of those characteristics are likely to be present here due to the lower oxygen levels. [Answer] Jews have been cutting their foreskins off for thousands of years, and each new generation stubbornly grows some again. Your settlers will only be changed by a lifetime of lack of sunlight and whatever environmental impacts there are. The genetics won't change. ]
[Question] [ Imagine a species in which the ego never developed. There is no self-direction. This species is always making noise, however, and it is through this noise that the society itself experiences the world. Every individual member of the society hears the noise generated by those members closest to it (within earshot, really), and it adds its own voice to the sound. We might think of each individual as a more complicated neuron in a brain, that communicates through the constant sound. By what processes might this species develop technology? I know that bees and ants create "technology" in the form of their nests, and this is due to instinct. I am interested in having this species, through the apparently random actions of its individuals, create ever enhanced technology. The motivations are unimportant. I am thinking that the creatures create more and more advanced technology simply because they keep working with what they've created until they make something different, and that difference gets added to the sound and thus the collective memory. However, does this species sound so limited that it could never create, say, space travel? If not, by what process would such technology evolve? [Answer] The biggest obstacle here is not about if they could develop technology, as if they could develop a hive mind like that. A neural network, whether it be biological or mechanical, relies on the consistency of connections to form memories, thought patterns, etc. A motile species moving around constantly changing who can hear them and how strong that sound is would not have enough structure to form any coherent sort of "mind". This does leave you with a few options I can think of though. A - Use something that can semi-permanently connect your organisms. This idea works well with things like flora, fungi, and coral which are live their lives in one place and can intertwine their "roots" into a neural network, but motile species make pretty much every variation of this immposible. B - Make your individuals semi-sentient and treat them like parallel processors. If one is thinking something, and encounters a problem too hard, he can start making his noises and all the adjacent organisms who are not thinking things through start thinking about it. The harder the problem, the more organisms they bring into the think tank. If it is a complex problem, they may instinctively be good at breaking problems down into smaller parts; so, as one organism solves parts of the problem, he relays what's left to other organisms. In this fashion a single problem, like how to design a car gets broken up among thousands, if not millions of minds, each one considering how to make a single cog or shape of upholstery, or more importantly; seeing if anyone among the millions of individuals already knows how to make things that would be helpful for making cars like rubber or alloys that they can share as building blocks for others to use to solve their own pieces of the problem. Once the organism solves his part of the problem, he relays the solution back to the organism that first had the problem. That guy is responsible for remembering how to make a car, but everyone who helped him out would remember that he knows how to make a car; so, next time someone needs to know how to do it, they just send a simple relay to that guy and he sends the whole solution back. In this way, the individuals in the species could have a large index of things they know how to access, but are only responsible for knowing a few details of the collective consciousness. Take one away from the group, and suddenly it doesn't have anyone to query to help it break down complex problems or recall previously solved issues; so, you basically are left with simple monkey like creatures that might have one or two really advanced pieces of knowledge stored away, but otherwise only be well suited to solving simple problems on his own. [Answer] The real question here is not about technology, but about intelligence. Technology is (arguably) a by-product of intelligence and knowledge applied to specific problems. So, what exactly is intelligence? As an AI researcher, I can say that intelligence is the ability to identify and recognise complex patterns. Your 'hive mind', if thought of as a single processing structure, has that capability in every manner that a neural 'network' on a computer (or a cluster of computers) has that capability. Is a single neuron intelligent? No. Is a human brain (which is a cluster of trillions of neurons) intelligent? Yes. This is a hotly debated topic in biology by the way, especially in the area of ants and other hive based colonies. Individual ants may not be intelligent, but do they all act together in a manner that defines a collective intelligence? Short answer is that we don't actually know. That said, there is some evidence to support the possibility. In point of fact, this has been extended to a concept in human civilisation called [Collective Intelligence](https://en.wikipedia.org/wiki/Collective_intelligence). This is the concept that humans as a collective interact in such a way that there is a broader intelligence at work as a result of our 'networked' individual intelligences. Note that I say 'intelligence', not consciousness. No-one is saying that humans have a hive-mind like consciousness, merely that by the strict definition of intelligence there is a broader processing model called society beyond the individual. What you describe in your question is a sonic-driven networked intelligence, which is similar to the networks we currently create between computers and servers via TCP/IP communication protocols, or even what the human brain does between neurons (although that's driven by electrical impulses). The point being that the capacity to develop new technology is really based on intelligence, either at an individual OR network level, not individual consciousness or sense of self. This does not mean that the psychology you describe has the capability to work towards a common goal, merely that if it does, technology will be inevitable because your model has reduced consciousness, but higher intelligence that that is the key driver to the actualisation of technology, once a goal has been set. [Answer] The only way I'd see this happening is via pollutant of some variety. An errant extraterrestrial signal, or spacecraft, or perhaps even some very minute biological contamination. Something to draw attention away from mere survival - without any hierarchy it seems unlikely that anything would give the necessary influence. A favorite author of mine used a somewhat different vehicle; his creatures (nameless by human standards but called "voors" for the sake of human parlance) were essentialy a form of sentient coral reef with no real tech at all until the orbit of their planet took them into the energy stream of a quasar, which ripped their conscience loose from their home planet and sent it hurtling across the universe; the tech they developed was largely based on whatever biology that was in the line of travel. Point is, until acted upon by some external force there was simply no impetus to go anywhere or do anything other than exist, hence tired, old aphorisms like "necessity is the mother of all invention" get a rise. ]
[Question] [ This question already has answers here: [Max humanoid physical strength](/questions/80691/max-humanoid-physical-strength) (6 answers) Closed 4 years ago. ## Background: Recently I have been working on a story that features a pop star who is actually an alien super soldier raised by human parents. That is to say, she was genetically engineered to be a biological killing machine, but turned out instead to be a pop sensation thanks to her good looks, heightened learning ability, and enhanced creativity (Among other things). I imagine her to be physically proportioned like Taylor Swift, or Rihanna or [insert other female celebrity icon]. So she is not particularly well-muscled, at least not visibly so. --- ## Question: Could genetic engineering dramatically increase the strength of a person without visually affecting their outward appearance? Specifically is increased strength by a factor of 10 feasible, given gene-editting, without a visual increase in size? (It is alright if it requires increased density and thus weight, or various hidden structural changes) Also, if not a factor of 10, then what lower numerical value would make sense? (x2, x4, x5, x8?) Could it be higher? I am aware that Superman level strength is probably impossible given physics, but what is the limit of organic muscle given the cross-sectional size of the average human arm? I would like to stick to hard-science, but given that genetic engineering is in its infancy, I understand some things are speculative. --- ## Additional Info: The following are additional thoughts and ideas that come to mind related to the topic. They are possible future questions, but not the main question of this post. I have read in several places, that chimps, despite being smaller than humans, are pound for pound stronger than us. Sometimes this is chalked up to no restraint as a chimp can fly into a primal fury much more easily than a modern human. But other times this is actually spoken about as physiological difference in the structure of the muscles between the two species. Could muscle design produce the pop star super soldier I am envisioning? Another note is that in researching artificial muscles, I came across experiments in using spider silk to produce muscles that performed many times better than the fibers present in human muscles. Now they did not recreate an entire arm or anything, but they did do tests lifting small weights and comparing the values human muscles fibers are known to be able to manage. Could a super soldier be designed, through hard-science genetic engineering, to possess muscles made from other organic materials and end up visually no different than a normal human, but physically much stronger? I know this can obviously happen in fiction, but I am asking is this something that science could actually accomplish in theory. When it comes to genetic engineering, I tend to think of things that are in nature already, and the idea that if they can exist on other animals, then it is within the realm of physics to add them to humans. I understand there may be a trade off, but I am more asking if it is possible rather than what are the consequences the individual would have to live with, so long as they are not horribly impaired or anything. The character is an "alien" but mostly in the foreign sense, biologically the character is very human aside genetic alterations to the genome to accomplish desired results. Imagine human being the template, then edits take place to create the alien. [Answer] We could revert our muscle genes to the muscle genes in our primate relatives, and so be as strong as they are. Humans are weaker than our primate cousins like chimps and orangutans. <https://news.nationalgeographic.com/news/2014/05/140527-brain-muscle-metabolism-genes-apes-science/> > > Our early ancestors likely possessed apelike strength, at least for > the skeletal muscles analyzed in the new study. Today our brawn is > much reduced, while other body tissues, like kidneys, have remained > relatively unchanged over millions of years. Over the same time > period, the brain evolved four times faster than the rest of the body. > ... He notes that "human muscle has changed more in the last six > million years than mouse muscle has since we parted company from mice > back in the early Cretaceous." That was about 130 million years ago. > > > To confirm their findings, which were based on analysis of 10,000 > metabolic molecules, the researchers pitted people, chimps, and > macaques—another kind of monkey—against each other in a contest of > strength. > > > All participants had to lift weights by pulling a handle. > > > "Amazingly, untrained chimps and macaques outperformed > university-level basketball players and professional mountain > climbers," Roberts says. People were indeed only about half as strong > as the other species. > > > The weakness has to do with all of our muscles - although in trade humans have considerably more endurance than do our primate cousins. I am pretty confident that Taylor Swift could outlast any nonhuman primate in a marathon. I could not find that the specific mutations behind human weakness have been identified, although the specific reason has been identified for human jaw muscles: we have a mutation in a gene that leaves our jaw muscles weak. <http://www.sciencemag.org/news/2004/03/weak-jaw-big-brain> > > Hansell Stedman, a gastrointestinal surgeon at the University of > Pennsylvania in Philadelphia and his colleagues came across what > appears to be one such gene by accident in their studies of the > genetics of muscle movement. The new gene, MYH16, codes for a myosin. > When the researchers compared it to the same gene in gorillas, chimps > and other non-human primates, they found the human one had a flaw that > resulted in a shorter-than-usual MYH16 protein and relatively weak > muscles, they reported in the 25 issue of Nature. > > > Stedman and colleagues dated the origins of the mutation by comparing > difference between the human gene and that of other primates. This > molecular analysis indicates that the mutation appeared 2.4 million > years ago, about the same time that human evolution took off. Stedman > proposes that because of this genetic change, the primates' massive > jaw muscles shrank, making possible a threefold expansion of the brain. > > > The exact reasons why these mutations causing weakness were retained in early humans are matters for speculation. But: could we fix these mutations and turn our various muscle genes back to the legacy forms which are still present in chimps and orangutans? Chimps are not crazy bulky muscly either. Their muscles are just better. It is not just about the muscle. Too strong a muscle and it would tear itself loose from the bony mooring, but that does not happen to the chimps - although I worry our tendons and ligaments are weaker also and so more likely to tear than those of chimps. Or maybe the chimps never really put forth that kind of effort. A realistic mutation leading to (reverting to) increased strength could let a human with the slim build of Taylor Swift have the strength of a chimp - roughly double to triple the strength she would otherwise have. Chimp Taylor would be surprisingly strong but I do not think she would be stronger than the strongest humans who are actually bulky muscly. If regular Taylor can bench press 100 lbs., Chimp Taylor could bench 300 lbs. [Answer] It depends on how crazy your genetic engineering can get and what tradeoffs you're willing to accept. If your genetic engineering is extremely good (or if the aliens started from a different point) then the chemistry used to build terrestrial muscles is definitely not the best option. There are other ways to build contracting fibers that did not arise naturally on our planet but may have on a different world or may have been designed by a sufficiently advanced genetic engineer. The same applies to bone structure. Life on earth generally uses calcium compounds for shells and bones, but there's no reason for that to be universally true. A different species from another world might use something else. Iron bones aren't out of the realm of possibility (although something that extreme would definitely make for a noticeable increase in weight over the human norm.) For a fully engineered creature, carbon-fiber bones could definitely be a thing. And then there's the actual construction. Arms and legs are basically sets of levers. In a human the attachment points of our arm and leg muscles are relatively close to the joint compared to many other animals. This costs us maximum strength, but lets us move our limbs more quickly for the amount of muscle we have so we are very good at throwing things. Even with entirely normal human muscles, moving the attachment points as little as an inch would make your creature considerably stronger than a typical human of similar size, and only a detailed examination would reveal the difference. She wouldn't be able to pitch at a major-league baseball game with any success though. ]
[Question] [ Thousands of years after a nuclear war that killed all life on the surface of earth, the descendants of the humans who fled to bunkers emerge... How deep would these bunkers have to be to prevent radiation seep (radiation radiating down) from significantly harming the people in these bunkers? The radiation levels are just high enough to kill all life on the surface (except possibly cockroaches) fairly rapidly (1-2 hours). The bunker doesn't get a nuke dropped on it, and you don't need to worry about food or power. If lead or some other material would drastically help, feel free to include reasonable amounts of it covering the base (but not more than say, a few meters of it). [Answer] Comparatively not much, something around several meters thickness of rock/concrete (initial estimate was too high, thanks for Joe Kissling for the correction). The currently worst thing humans have is the [cobalt bomb](https://en.wikipedia.org/wiki/Cobalt_bomb): a hydrogen bomb with a casing of Cobalt-59. It could also be combined with a neutron bomb which has much better penetration for high-density materials (steel). The explosion of the bomb with the high neutron density transmutes the casing to Cobalt-60 which is a strong gamma radiator. It has a half-life of 5.2 years and to weaken the radiation to one half 11 mm lead is necessary. Having meters of small density (earth, stone) is sufficient to reduce radiation to normal levels, wet earth will also prevent neutrons to penetrate the shielding. The problem is not really radiation seep, the problem is the radioactive dust that needs to be filtered out of the air and food. 5 years half-life will deplete your stocks, you need to produce food (probably using nuclear reactor and subterranean gardens). [Answer] You'll have to be a whole lot clearer about what you are asking about. "Radiation seep" isn't a defined technical term. Radon seeps up out of the ground. Radioactive (contaminated) water seeps from containment into the ocean. Radionuclei seep into ground water. Even assuming you meant radioactive fallout, you haven't provided enough details of what type of radioactivity needs to "seep" down into their bunker. The deepest water I know of was found at a depth of 100 km. At 100 km, you'd expect the temperature to be 2500°C or 4500°F. In other words, to get below where water might possibly "seep", you'd have to get to temperatures above what we could live at. (Temps increase about 25°C per km, which means we're not going to be able to live below 2 km. Perhaps you should reframe your question since it is the dose of radiation which causes damage and dose depends on concentration, type, and energy of the radiation. By the way as you get deeper into the Earth, radon levels increase. Anyway, if we assume very long lived radioactive isotopes, with very energetic (lethal, damaging) decay modes, then the question naturally arises whether such isotopes will be transported downward at a sufficient rate to be a hazard to some sub-surface habitat. Of course, the answer is it depends on the geology (and hydrology) at that specific location. There are several minerals which are natural barriers to water. Salt is one, another is certain types of clay. I suggest you take a look at the proposed design of the Yucca Mountain repository (defunct) because they attempted to design it to prevent water "seeping" in (and out). It would be a pretty good start for a design for your habitat's "shield". You can't really build "a wall" (meaning thin (several feet, say) (sorry Mr. Trump)) to keep the water out. The barrier needs to be of sufficient thickness so that even if a earthquake moves a fault by several meters, the barrier is still sufficient to prevent significant seepage at the "crack". That's really not too difficult to do, lets just say 20 meters of clay and 10 meters of salt. The trick is to keep this ceiling compressed so that cracks don't develop, (salt is self-repairing). You'd have to be careful in digging the tunnels to live in. Caves might not be the answer. You want to keep the barrier under compression and caves, even if the rock ceiling is strong enough to support the material above it, could cause decompression (as well as other types of movement). You could ask a question on the Engineering on a different forum. Anyway, I suspect tunnels rather than big caves would be safer, but it's pretty much a wild-assed guess. For what it's worth. [Answer] You'd need to create a bubble of clay, concrete, lead, steel corrugated, and some flexible absorbents around your bunker, then make sure something is built on top of it to keep the soil compressed all of the years you are planning to stay there. The main feature you must include is a way to seal the bunker from the outside COMPLETELY and then unseal it when it is safe. This is most difficult to do if you need to reach the surface for the air or water that you want to purify. If you're rich you might as well build a "mole people" drill apparatus to tunnel to the surface. I'd make it 20-50 ft below ground in case the topsoil gets blown away and to keep from detection. Try to build close to a lake and away from fault lines [Answer] Radiation doesn't really "seep", and unless somebody is being very nasty, there isn't enough of it to require hiding in bunkers for decades. Radioactive materials can be liquids, solids, or gases. However, the vast majority of radioactive fallout is in the form of a somewhat coarse grit -- that's what makes it fall out. This grit falls near the places the nukes fell -- it's basically in a shape of the mushroom cloud, smeared downwind. There will be lots of it directly downwind of where each bomb fell for several miles, and none at all in places that were not bombed. For the levels of fallout currently predicted from a nuclear war, bunkers would be only a few feet deep, and would not need to be carefully sealed or anything. They also would only need to be occupied for a few weeks, as the flip-side to high radiation levels is that highly radioactive material decays pretty quickly. It will be important to keep radioactive grit and dust out of the bunkers. The problem comes up if the enemy uses bombs that are deliberately "salted" to produce extremely high amounts of highly radioactive fallout. In this case, all of what I have described applies, except that the fallout is vastly more radioactive and longer-lived. Still, thousands of years would be quite a stretch. You would still have regions that were too radioactive to enter, and regions that were pretty much OK, or at least habitable. ]
[Question] [ How would castles be designed in a world where magic exists. Magic has the following rules: 1. All magic requires runes and a verbal activation (saying 'magic words' that correspond to the runes) 2. Any spell lasts a maximum of one minute (no enchanting) 3. Any spell has a certain maximum amount of power, and will not complete tasks under that power (you can create a small fireball, but can't make a storm or teleport) 4. Any spell takes three seconds to take effect after the verbal component has been said (gives time for a counter-spell) 5. Runes can be traced on a surface (temporary rune) and can then be activated only by the maker, or engraved/written (permanent rune) where they can be triggered by anyone holding the object. 6. All activation phrases must be yelled, and cannot be muffled (can't use magic while gagged or holding cloth over face) I want to know how castles would probably be designed, given that this type of magic exists, and is fairly accessible, although normal troops would likely only know a few spells, mages who know thousands would accompany every army and defend every fortress. Magical firearms don't exist yet (no one invented them at this point) but magical self-loading crossbows have been invented and are common, although loading a trebuchet is out of the reach of a single spell. [Answer] Physically, castle would be designed just like castle in our world. I'm going to assume runes will be depleted after the spell activate. The bricks on walls and towers will be inscribed with defensive runes, should a siege or attack begins. These will serve as emergency defense until the runes run out, and the defense must be resupplied with defensive scrolls. (Think of them as 'defensive bullets') Magical warfare should primarily fought with supply of scrolls - an inexpensive and portable rune-holder. There will be physical weapons ready, too, but mostly how they use weapons to defend will be similar to ours, with a slight twist (like auto-reloading crossbow) - though I think this is should be considered temporary enchantment. Depending on the system, what kind of spell and the extend of the power allowed, this could only be a fireball-frostbolt-lightning bolt throwing magical warfare. [Answer] Just saw this, so I apologize if it's too late to be helpful. Here is my two cents: 1. If a rune can be made permanent (but must be utilized as by speaking a clear verbal command) then I would assume a castle would be full of such runes 2. Additionally, if there is nothing in the magic system that disallows runes above a certain size, then I would think clever castle builders would shape the castle and/or components of the castle, in the shape of a rune... (so each section of the wall could be in the shape of a rune, or the entire outer wall of the castle could be a rune, and the inner wall a different one etc...). 3. If there is nothing in the magic system that prevents it then a series of runes in a given order may provide specific benefits when cast together (I suppose timing would be important here but could be another skill of mages & workers of magical machines) DETAILED BENEFITS of the above points 1. Putting runes on everything: defensive & where appropriate and useful for defenders, defensive runes would be beneficial to fend off various attacks, and offensive runes to launch attacks as needed during a siege. e.g. - A defender is atop the primary castle wall, he and the defenders around him see a catapult being fired & it appears to be toward their section of the wall, they all yell the appropriate command and activate the defensive runes within the sounds of their voices making the wall impregnable for 3 minutes, the boulder shatters harmlessly against the defended wall. -In another instance a small group of defenders man a section of the wall that has 50 fireball runes with the stone blocks they are carved on all pointing to a certain spot that the attackers are moving their battering ram through. These defenders all yell the appropriate activation word and 50 fireballs rain down on the spot currently occupied by the battering ram and it's handlers... 2. If the castle walls are formed in the shape of a rune, then any defender can activate that rune when needed to gain whatever effect is granted by said rune. Therefore a few defenders could potentially more easily defend against a larger number of attackers. Additionally if size (mass of material used etc...) affected the power of the rune, then a meter thick wall encircling an entire castle would make for a seriously powerful affect... (this could allow for fireball cannons being created out of big blocks of steel or stone with the rune on one side...) One additional thought here, what would happen if a wall were in the shape of a defense rune and that same defense rune were carved all over that wall... when activated would the runes act as multipliers to each other? 3. Runes could be used to make sounds, and therefore words and sentences. Therefore one rune could be used to activate other runes that could be used to activate more etc... I could see a scenario where a wizards keep could be lined with 'message' runes which would be used to remotely mass activate all the runes on the keep... or a specific area of the keep. This would allow a single person to fend off a large army (or @ least have a better chance @ it). Another use for this would be creating the capability of producing very complicated effects... add some fire, add some wind, then some water and make it repeat every 3 minutes (a physical loop would have to be pretty large but it would be possible) and fog could be generated. (or put a series of fire runes that are set in a loop that would fire itself every 3 minutes inside a moat to create steam & fog for defense (and maybe to protect against flame attacks etc...) Hope these ideas are helpful. [Answer] If you are able to engrave especially anti-magic, but any defensive, runes into the castle itself then the design of the castle would be entirely equivalent to that of the other weapon technology; though given your comment battle management from the towers would become important for the mages to see and quickly counter-act against incoming spells. If the fireballs are just surface explosions then again the castle design wouldn't change much; measures to prevent the spread of fire perhaps. Castles are already designed to prevent damage from incoming projectiles. The [Hordings](https://en.wikipedia.org/wiki/Hoarding_(castle)) would have to be fire-proof though. If the fireballs have some amount of penetrating power on the walls than they can be viewed as cannons and, depending on the effectiveness, would change the castle walls to being [Bastions or star fortresses](https://en.wikipedia.org/wiki/Bastion_fort) or even later designs. ]
[Question] [ ## It's hard to create a new animal from scratch. * If you genetically modify an existing species until it becomes a drastically different species, then implant the fertilized embryo in a female of the original species, the offspring will not survive birth. This means you can't make drastic genetic changes the traditional way - it will kill the animals before they're even born. * Naturally evolving a new, complex organism can take billions of years, and I don't have that time Therefore, some other, method must be employed to physically construct the first organism, or kick off the lineage, off a completely unique, lab-made species. Assume scientists have already decided on the genes this species will possess, and rightfully deemed it fit to survive in the wild - if the first mother of the species could only be born. It's multi-cellular, and will not give birth until a minimum of 20 years into its life. ## How do you physically create the first individual of a unique species? > > ### My thoughts so far > > > * A base species could be modified, a few genes at a time, every generation, until the new species' genome could be implanted via embryo and survive birth. I'm not too fond of this approach because it involves a lot of waiting (hundreds of generations). > * A machine could act as an artificial uterus for the first individual(s) of the species. Starting with a single embryo, it could feed in nutrients and maintain the desired conditions. However, accurately creating so many tissues and organs in an artificial environment seems difficult to me. > > > [Answer] You only need four things: 1. Immune system compatibility. This is trivial. In lab you can just keep mother on immunosuppresants. Done. 2. Compatible size and pregnancy time.. Again, this is easy, as you would probably use species of similar birth size & time in the first place. 3. Good proportion of substances in umbilical cord. This can be fixed by IV if needed. 4. Implantation of the egg. This is a tricky part. You need to be careful when setting up genes for this process. Preferably rip them whole from mother 0 species and call it a day. --- Alternatively, go with eggs. If your organism does not need to give live birth, it would not need a mother. This is a route I'd prefer. --- Probably there is more to it, but our science is at single cell synthetic life now, and we are yet to see what will happen. [Answer] # You Don't Need A Living Creature In your question, you said that you are at the technological level where you can genetically engineer a new species. So this is obviously a high level of technological advancement compared to now. So if you have that technology, then why don't you have others? First you need a container filled with lab-made embryonic fluid. Keep that at the appropriate temperature. Then provide a facsimile of the mother's womb, and connect that to a source of nutrients. I'm sure if your society can create a new species through genetic manipulation, then you can make a "pod" for it to grow in. There is much less risk, much simpler. You may also be able to re-use most things in this method for the first of the other gender. [Answer] Scientists can already "create" cell lines and mutant strains(single cells, drosophilia, zebra fish, worms like caerabinopsis elegans, dog, cats,...) by genetic recombination. Actually in your case, the "egg" implantation may work well because I guess that modifying just a few gene wont modify the compatibility of mother/mutant offspring that much. Note that only a few genes can alter strongly the phenotype (the appearance of your species or its ability and characteristics, like life span). In fact it was suggested to create a Mammoth embryo and implant it into a elephant. Humans have after all only 2% genetic differences with Chimpanzee. So to as an biologist, I would say 1 - genetic recombination and egg implantation should work if species are close enough (size matters usually). Taking into account immunological properties as suggested above may make it more believable. 2 - Alternative is to grow your species in a pod with embryonic fluid. Some tissues sheets can easily be grown in lab culture, and recently even some organs ! Artificial embryonic sacks are thus plausible in a close future, and could be used in various situations. 3 - if you want a single organism that create offsrping and evolve without any interaction with a male, it is absolutely possible. There exist several mode of "duplication" of the organisms. By Fission, you can separate the body into 2 (usually for microbes), Division and regenaration (in that case you have the same genome accros multiple generations), but if you want to create evolution and diversification within your species, you probably need a sexual species that can use auto-fertilization. Some intringing lizards and frogs species do it :) The change of sex mostly depend on environmental conditions, such as temperature. I suggest you to google evolutionary website to check the strange sexual reproduction modes. ]
[Question] [ [Part 1](https://worldbuilding.stackexchange.com/q/55560/1971) On Earth, we have seasons due to our planet's tilt. In my last question, I proposed an alternative world where the seasons were instead caused by an eccentric orbit. Now I'm going for something more exotic. Instead of axial tilt or orbital eccentricity, what if the seasons were caused by actual variations in the energy output of the planet's host star? ![](https://media.giphy.com/media/QP4taxvfVmVEI/giphy.gif) Details: * The planet is earth-like and inhabited. * The system must be stable for at least 3,000 years. * The length of the "seasonal" cycle must be within [-50%, +100%] of one Earth year (i.e. between six and 24 months). * The temperature difference for some point on the planet's surface between "winter" and "summer" must be at least 15oF and no more than 40oF. * The cycle doesn't have to be exactly the same as Earth's, and all of the above can be taken loosely in light of that. For instance, the cycle could repeat once every four Earth years as long as there's a cold season of some description every one Earth year, and a 60oF temperature delta is acceptable so long as it happens less often than once per hot season. # Is it possible for a real variable star system to produce seasons with these characteristics? And if so, what kind of variable star would be best suited to producing such a world? If not, how close can we get? Which variables are problematic? Importantly, the planet does not need to have formed in its current location around the star, and the system does not have to be stable across astronomical timespans. I'm not concerned about whether an inhabitable planet could realistically form and evolve life in this scenario, just whether such a planet could have seasons caused by a variable star. [Answer] Let's look at the two extremes: $\Delta T=15^{\circ}\text{F}$ and $\Delta T=40^{\circ}\text{F}$. In the first case, I'll say $T\_{\text{min}}=50^{\circ}\text{F}$ ($283.2\text{ K}$) and $T\_{\text{max}}=65^{\circ}\text{F}$ ($291.5\text{ K}$). This gives us $$\frac{T\_{\text{max}}}{T\_{\text{min}}}=1.03$$ Let's also assume that the planet's surface temperature is well-approximated by its [effective temperature](https://en.wikipedia.org/wiki/Effective_temperature); in other words, $$T\simeq T\_{\text{eff}}=CL\_\^{1/4}$$ where $C$ is a function that doesn't depend on $T$ or $L\_\$. Let's say that $L\_{\,\text{min}}$ and $L\_{\,\text{max}}$ are the stellar luminosities that correspond to the minimum and maximum temperatures of the planet. Doing some substitution, we find that $$\frac{L\_{\,\text{max}}}{L\_{\,\text{min}}}=1.13$$ which is actually quite small for variable stars. Now, let's convert this to a change in [absolute magnitude](https://en.wikipedia.org/wiki/Absolute_magnitude), $m$. We have $$\Delta m=-2.5\log\_{10}\left(\frac{L\_{\,\text{max}}}{L\_{\,\text{min}}}\right)$$ which gives us $\Delta m=-.133$ magnitudes (remember, brighter objects have smaller magnitudes). In the second case, say $T\_{\text{min}}=35^{\circ}\text{F}$ ($274.8\text{ K}$) and $T\_{\text{max}}=75^{\circ}\text{F}$ ($297.0\text{ K}$). This gives us $$\frac{T\_{\text{max}}}{T\_{\text{min}}}=1.08$$ We then have $$\frac{L\_{\,\text{max}}}{L\_{\,\text{min}}}=1.63$$ and so $\Delta m=-0.53$ magnitudes. The best kind of variable stars I can find that meet your requirements are [Alpha2 Canum Venaticorum variables](https://en.wikipedia.org/wiki/Alpha%C2%B2_Canum_Venaticorum_variable), which have periods of up to roughly 160 days and magnitude changes of up to 0.1 magnitudes (possibly more). These stars should produce effects similar enough to what you want, within reasonable amounts. --- It is true that this type of star - massive and luminous - will not last very long, and it will be difficult - not impossible, but difficult - for planets (and life!) to form around it. However, as the last paragraph of the question states, > > Importantly, the planet does not need to have formed in its current location around the star, and the system does not have to be stable across astronomical timespans. I'm not concerned about whether an inhabitable planet could realistically form and evolve life in this scenario > > > If anyone can find a longer-lived star that has similar pulsations, that would fantastic. For now, though, I think this is the best you'll get. [Answer] Variable stars that have a fixed repeating period do exist. They are known as [cepheid variables](https://en.wikipedia.org/wiki/Cepheid_variable) and were important in astronomy as the period tells you the brightness of the star, and thus you can figure out the distance. Look over the linked article: they are 4–20 times more massive than the Sun, and up to 100,000 times more luminous. However, the periods only go up to about 9 months. The longer the period, the more luminous the star. I presume the luminosity varies with the mass (like normal stars), so we are looking at the largest stars, or 20 solar masses. The other bad news is that such a star [will only last](http://hyperphysics.phy-astr.gsu.edu/hbase/astro/startime.html) for 5½ million years. So don’t expect planets to settle down and life to form in-place! ]
[Question] [ So the scenario for my story involves an abandon castle that is located in a taboo area so no one goes near it and so no one is maintaining it anymore. Assume the castle was almost 1000 years old before it was abandoned, but it was well maintained up to the point of being abandoned. There is no magic or anything special about the castle that would allow it to survive any longer than normal. * How long before the castle is no longer capable of serving as a castle (like walls have been compromised or the roof has caved in)? * How long before the castle is nothing more than a pile of rubble? * Would being near a forest and/or river expedite the process and if so by what order of magnitude are we talking? [Answer] I found this question interesting and started doing some research. However, it is hard to pin down an answer. It really comes down to how it was constructed. The earliest traditional castles were built from 1060 AD and later. Castles made from stone and mortar do not last long without regular maintenance. The mortar begins to crack, which allows water to seep in. Water is the bane of all buildings. During the winter, water will freeze causing more cracks, which in turn allows more water to seep in. These cracks allow plants to start growing in them. The roots of the plants further break up the mortar. In the pictures below, you can see plants how the mortar gets destroyed and plants take over. [![enter image description here](https://i.stack.imgur.com/aKtjO.jpg)](https://i.stack.imgur.com/aKtjO.jpg) [![enter image description here](https://i.stack.imgur.com/DyRip.jpg)](https://i.stack.imgur.com/DyRip.jpg) [![enter image description here](https://i.stack.imgur.com/Nkfga.jpg)](https://i.stack.imgur.com/Nkfga.jpg) Being near a forest or river definitely would expedite the process, as the moisture and plants are close by to start breaking down the castle. It would also appear being in an arid desert doesnt help that much either. The heat fluctuations also cause the mortar to crack. Wind carrying sand slowly eats away at the mortar as well. [![enter image description here](https://i.stack.imgur.com/XdxDP.jpg)](https://i.stack.imgur.com/XdxDP.jpg) [![enter image description here](https://i.stack.imgur.com/ETKGx.jpg)](https://i.stack.imgur.com/ETKGx.jpg) There are always exceptions to this, but it would appear that a few hundred years is the maximum a castle will survive without maintenance. [Answer] A very well built castle will last "indefinitely". Older "castles" may last longer than more recent ones. The Romans learned to build in real concrete maybe around 100 BC. The Colosseum is concrete - it has/had brick veneer. The last castle to fall in the English civil war was Castle Raglan in Wales in 1646. The main walls were 14 feet thick in stone. The free standing 'castle in it's own right' Great Tower was "slighted" subsequently but proved to hard to destroy and was left as was. * The tower wall breach was a product of labour intensive "slighting". The tower's top storey was removed but, when this proved excessively labour intensive, the tower was undermined with a propped tunnel, and once the foundations were gone on one side fires were lit to destroy the props - see photo below. Without this process I'd expect those walls to be good for far beyond the 400 years that they have stood so far. Based on the Colosseum ('pure' concrete) a lifetime of 2000+ years would not be unexpected. The tower, and the main castle are still standing today - VERY solid - if it had not been 'slighted' at the time it would be an INSTANTLY viable castle now. You may need to add a new drawbridge - it is accessed on the 2nd or 3rd level from the main castle over a moat via a drawbridge. If that has fallen in over the years it makes it almost instantly defensible. I have many photos of Castle Raglan (taken in 2003). A few only Access to the Great tower: [![enter image description here](https://i.stack.imgur.com/PcVxM.jpg)](https://i.stack.imgur.com/PcVxM.jpg) Cross sectional view. Floors would have been destroyed at the time. You may wish to posit stone floors of some sort to allow survival. Spiral stairways are stone slabs set into walls. Some survive, some have collapsed - try not to be on a collapsing one. [![enter image description here](https://i.stack.imgur.com/FuAWQ.jpg)](https://i.stack.imgur.com/FuAWQ.jpg) [![enter image description here](https://i.stack.imgur.com/v9ukb.jpg)](https://i.stack.imgur.com/v9ukb.jpg) --- A less well built castle - lifetime - not so long. Macduff castle - [my photos from 2003](https://bit.ly/macduffcastle) in Scotland (needless to say). [![enter image description here](https://i.stack.imgur.com/SB9ej.jpg)](https://i.stack.imgur.com/SB9ej.jpg) [Location and more photos](https://www.google.co.nz/maps/place/MacDuff+Castle/@56.1610384,-3.0601646,10z/data=!4m5!3m4!1s0x0:0x6ee20be0bc9b55cc!8m2!3d56.1624305!4d-3.0579758) [Answer] You have to remember, the Romans used volcanic sand in concrete and mortar, which works better, but too costly to ship to other locations. But here it looks like stacked stone with no mortar lasts very well. The trick would be to shape them so they don't move. ]
[Question] [ Suppose a school was founded in a remote mountain valley centuries ago by the first representative of a now-prominent deity. This valley has a forest with a river flowing through it; there are no major settlements nearby at the time of its founding. Rather than teaching arithmetic and language skills, this educational institution provides instruction in fields such as advanced/obscure magic; military tactics; martial skills, such as swordsmanship and wrestling; politics; animal husbandry; and survival. Essentially, this institution trains heroes. Instruction is performed in a master-apprentice-style relationship. Each instructor has one to three students at a time and spends a considerable amount of time working one-on-one with each of them. The intent of this institution's mountain location was to make it independent of the money and politics of the [surrounding country](https://worldbuilding.stackexchange.com/q/38655/6986). However, resources are significantly harder to acquire and maintain as a result. What steps should the institution take to ensure its continuing economic and political independence without moving from its founding location? Answers identifying why this continuing independence is impossible are also welcome. [Answer] I agree with AndreiROM, however he overlooked the more base level needs of survival. Food, water, shelter, cloths, weapons, repair materials ect. You could use some of the ties established by AndreiROM to draw in money to buy such things, but then you start to lose a level of independence. So you need fertile land to grow food and a source of fresh water. Shepherding (or goat herding) would probably be efficient. It takes fewer people, while providing food (meat and dairy) and cloths. You'll need weavers (or tanners) to make the cloths and a blacksmith to repair weapons. You will need a population that can supply enough of these to support your population of trainees. Once the school is built trainees could probably handle maintenance to the building. You still need to buy swords and armor and books though. So there should be some resource that you export so you have money to buy such things. Perhaps expert weavers? (You already need to make your own cloths) Alcohol? Monastic schools have already established a tradition of this. Finely crafted weapons and Armour? This makes thematic sense, however it is difficult to transport the materials for this into a remote area. You could have a natural mine or two in the area, but then you need an even larger populace to run the mine, and to feed the miners. (maybe just a gold or gem mine, but the high innate value of this would draw national attention) Rare herbs or medicines? Whatever you chose to export has to have a high cost to weight ratio to make it worth transporting from the remote area. (Exporting mutton would not be worth the effort) Or perhaps there is an incredibly tumultuous river flowing from the school into civilization. A skilled navigator can make it over the many waterfalls and through the myriad rapids to sell a larger bulk of goods. Then transports the smaller quantity of needed good back. [Answer] This institution trains people in skills which are potentially valuable, or dangerous to the host country. If a kingdom/country has a very volatile relationship with a neighbor, yet you train recruits of that nationality who later become their greatest generals you will shoulder the blame for those defeats. Similarly, if a hero trained by you ends up becoming a villain your school will face a lot of political and popular opposition. This institution will have to survive by one of several means (and they are not mutually exclusive): 1. Political Ties Their leader could embrace politics and be sure to become the desired destination of every major noble in the surrounding kingdoms. Since no one would want their sons/daughters to be rejected your institution could become a bit like Switzerland: neutral ground where students of enemy nations study side by side. This is not to mean that the political landscape might not become incredibly hostile, and your school might not suffer, but nothing in life is certain. 2. Military Power Your students are going to be instructed by some of the greatest heroes who have ever lived (former students, of course). These heroes might posses such a reputation, and such powers that local leaders would be afraid to challenge them in the field. Their reputation alone might be enough to ensure that no one short of a suicidal nobleman would challenge their independence. Soldiers might refuse the orders to attack based on their respect, or fear for the heroes in question. 3. Powerful Wards Your school was established on a magical node, which allowed the mages who built it to weave incredibly powerful protective spells around it. Those you do not wish to find their way to your gates will find themselves turned around and lost in the woods. Only the most powerful scrying magic may even locate your general location! An attacking army would find itself seeing various illusions and hallucinations which would drive them mad, or simply confuse them. Conclusion Depending on the parameters of your universe the school stands a good chance of being able to maintain its independence. Of course, a certain suspension of disbelief is also required. That, or some very convenient circumstances. [Answer] ## The school will need to be completely self sufficient ...with as few external dependencies as possible. If the school isn't self sufficient, then anything it needs can be held at ransom by the surrounding polities till the school capitulates. The easiest way to achieve radical self-sufficiency is with a strong school culture of self reliance and asceticism. Basically, "if it's not made here, we can do without it." The likelihood that absolute self-sufficiency can be achieved is frankly very low. It's very easy to grow dependent on an external source of high quality goods such as steel, where the internal economies of scale just don't permit sufficiently high quality goods to be made at the school. (Steel is a good example. Iron smelters grow more efficient as they increase in volume. It's unlikely that the school will want to invest 100M doubloons on a smelter when they can just trade a few rare medicinal flowers for a few tons of steel.) ## Many trading partners In the cases where self sufficiency isn't possible, work hard to establish alternate trade routes and trading partners to acquire those goods/services. Recognize that the school's enemies may conspire to shut off a particular trade good to gain leverage over the school. The broader the supplier set, the harder it will be for enemies to gain leverage. ## Bad-assery Lastly, be so bad-ass that no one would think to challenge you or anger you. Become that world's equivalent of the Swiss, armed to the teeth but neutral. [Answer] There are a few avenues to (further) explore here. # Economic Consider tuition. It would be pretty reasonable to require a prospective student to either bring or otherwise help provide their own clothing and food for the duration. Start with the hunting and farming classes, and the youngest students may well be able to provide for the whole community. This is particularly true if you have different 'majors'. Farmers may show up for a year or two of husbandry and agriculture training. Goats should help make use of the higher altitude lands. Throw in something like X measures of workable metal, magic crystals, and/or other resources, and your tuition should keep you self-sufficient. # Political The political landscape here reminds me of the early stories in Asimov's Foundation series. If you provide succor to several nations more or less equally, you might be able to strike a balance. Anyone who wants to attack you for your knowledge and training will end up facing the others, who would all rather not lose their access. And of course their access would be in the form of having the noble children trained by the best. 'Students' may become another way to spell 'Hostages'. # Social You would, for the noblest of reasons, send out representatives of $deity to help heal the sick, teach people to grow crops better, and help build stronger buildings. Throw in the occasional natural disaster relief effort. Anyone advocating attacking you is basically asking the population to defy their deity and attack the Red Cross. Not exactly a recipe for popular support. # Religious Depending on how far you'd like to go with the deity theme, consider requiring all priests to be trained there. Any time someone starts to stir up people against the institution, start sermonizing about faith and justice rather than obedience. # Military A valley like that provides an endless supply of potable water as well as likely a few natural choke points. If an army does manage to get in, they're fighting a bunch of independent survivalists on their own terrain. Sounds like a recipe for guerilla warfare to me. Since the timescale is hundreds of years, I don't see a reason why this couldn't be heavily fortified. # Magic Not much was said about the magic system here, except that it's 'advanced' or 'obscure'. Depending on how it is defined, there are an infinite number of uses for it. Mind reading/controlling nearby nobles, tunneling out an underground village, and calling down avalanches all come to mind. [Answer] You are training heroes as you said it. Thus, all economic problems can be expected to be solved by an honorary "rule of the cent" or something, where a hero sends a fraction of his earnings/prizes back to said school. On political/military independence, I'd just be copying the rest, pick any of those suggestions.[but just being high up in the mountains/remote is enough of a deterrent. Combined with not-really-being-wealthy (meaning there is no reason to go for you) and everyone there being more than a good fighter, and no one will attack)] [Answer] The school is just a cabin and has only one professor. The professor has a lifestyle much like that of [Captain Fantastic](https://m.imdb.com/title/tt3553976/). You'd be surprised at how easy it is to stock a house with supplies for a year for four people, specially if survival training is involved, and if you do your own hunting and farming. You don't need to do groceries very often if you are a good planner - a one day per year trip to the civilized world will do. To stay away from politics, go shopping covertly, and to stay away as much as possible from money, sell your excess produce. If that single professor is willing to give online classes, then they only have to store supplies for one, and can use bitcoin (or [manacoin](https://worldbuilding.stackexchange.com/a/112321/21222), since magic is involved) to be even less dependent on the local economy. ]
[Question] [ For my current [world in progress](https://worldbuilding.stackexchange.com/questions/33603/surviving-the-world-of-zombie-mosquitoes), I have devised a variety of species possessing [multiple, unique DNA chains](https://worldbuilding.stackexchange.com/questions/33040/multiple-dna-one-creature) that can receive copious amounts of short-term energy due to their [large stores of sugar](https://worldbuilding.stackexchange.com/questions/33337/ideal-short-term-organic-engine). The next issue I need to tackle is the existence of certain features of some species. My first target is the existence of various species that have bodies/skin seemingly made from minerals such as iron, rock, or steel (alright, so steel is an alloy; sue me). My intent is for humans on my WIP to use the shed armor as steel would normally be used. I considered explaining my creatures as being [silicon-based](https://worldbuilding.stackexchange.com/q/27131/6986), but their [chemistry and environment](https://worldbuilding.stackexchange.com/a/34150/6986) don't seem to align with the conditions I have already decided on for the planet. Next I considered [metal-based biology](https://worldbuilding.stackexchange.com/q/2855/6986), but, again ran into cohesion issues. Since I want my mineral-like creatures to live in a world naturally inhabitable by humans, how can I explain the biology of creatures that can produce a rock-, iron-, or steel-like armor, or that have rock-, iron-, or steel-like bodies? If possible, the body/skin/armor should have the look, feel, and properties of rock/iron/steel, even if they differ on a molecular level. [Answer] Well we have plenty of animals that already have some of these features. Lets start with [Mollusks](https://en.wikipedia.org/wiki/Mollusca), many of them have a hard shell for self protection. Snails, clams etc. They create their armor out of calcium carbonate, which is stone like. [![enter image description here](https://i.stack.imgur.com/0JHo1.jpg)](https://i.stack.imgur.com/0JHo1.jpg) [![enter image description here](https://i.stack.imgur.com/NsIgY.jpg)](https://i.stack.imgur.com/NsIgY.jpg) Of course insects and crustaceans also have body armor but it is [chitin](https://en.wikipedia.org/wiki/Chitin) which is not very stone like at all. Since even the hermit crab finds snail shells to be much more protection. [![enter image description here](https://i.stack.imgur.com/ALEsi.jpg)](https://i.stack.imgur.com/ALEsi.jpg) Next moving up the evolutionary ladder we have [turtles](https://en.wikipedia.org/wiki/Turtle) these have shells made of bone, but the shells are fairly heavy when they get to a size large enough to be used as armor. Helmet sized turtles might not weigh any more than a normal helmet though. [![enter image description here](https://i.stack.imgur.com/Tekiy.jpg)](https://i.stack.imgur.com/Tekiy.jpg) [Pangolins](https://en.wikipedia.org/wiki/Pangolin) and armadillos are higher yet on the evolutionary chain and can move a bit more agilely than the previous contestants. and at least the Pangolins have been used to make armor (at least for show). [![Pangolin Body Armor](https://i.stack.imgur.com/gBmnM.jpg)](https://i.stack.imgur.com/gBmnM.jpg) Larger animals generally have thicker and tougher hides, like the rhino. Of course the problem with hard natural body armor are two fold, it's heavy, and it makes 'growth' harder. (as well as harder to 'heal' should it get broken). So current armored animals are small and/or slow. So this means that an animal large enough to use parts as armor means it is likely going to be a slowish animal, and being large enough to use a armor, very strong to move that armor around. It might be the armor is just a few plates, like a couple over lapping plates on a thorax and maybe some stronger ones along the arms or legs used for fighting or defense. Punching something in the teeth attacking you with a rock like forearm would seriously deter further attempts. [Answer] Molluscs have already been mentioned, so I'm surprised that the [scaly-foot gastropod](https://en.wikipedia.org/wiki/Scaly-foot_gastropod) specifically didn't come up. It has some pretty alien biology going on, which I'm not qualified to elaborate upon beyond what's available in that link/via Google, and it looks at least as awesome as you might imagine: ![scaly-foot gastropod](https://www.wired.com/wp-content/uploads/2015/02/scaly-foot-high-res.jpg) It's an extremophile to boot, making it already more or less an alien lifeform compared to a typical resident of planet Earth. It's extremophile status might not be entirely convenient for your story, since it'd be a little hard for us to dive down and collect them to use for making tools (without already possessing the metal required to construct a deep-sea submarine), but someone with a better grasp of the chemistry involved might be able to suggest some modifications you could make to its metabolism/physiology that would allow it to exist in a place more accessible to humans. It's also probably not large enough to really utilise as a source of materials, but overall it's pretty close to being the kind of animal you're thinking of? I especially like the part where it seems to rely on symbiotic relationships with different bacteria, and the fact that it's utilising an unusual resource in its environment (minerals from undersea vents). You could certainly borrow an idea or two from it – apparently MIT/the US Department of Defence [already are](http://www.cbc.ca/news/technology/snail-s-iron-armour-eyed-by-military-1.941044) [Answer] Mineral-like creatures or creatures with mineral-like armor? There are [crabs](https://en.wikipedia.org/wiki/Decorator_crab) which use natural materials to camouflage themselves. * Grains of sand might stick to the skin of a fictional lifeform and become embedded. Over time, the skin becomes individual plates which are indistinguishable from sandstone. * Or there are more natural-looking scales where some biological process concentrates metal or silicates. Again the material cakes together. [Answer] Well, I'd tone it down the concept a bit. Instead of rock skin, why not skin with rock? The creatures could use caves/ regions with an abundance of minerals exposed as nesting/mating grounds, and assimilate certain amounts of minerals into the skin, either by releasing a sticky substance that adheres to the metal, like dragons with treasure fused to their bellies, or by eating said metals and have them somehow deposited in the upper skin layers, kinda like our own external skin is richer in certain composites like keratin, but with metal, or maybe scales witch high abundance of said minerals in their composition. This could also make for good armor, as it's underside is relatively flexible while the mineralized exterior makes it tough. Think of something like an ankylosaurus with metal covering its body instead of bone. That way it would feel inorganic while being bound to organic tissue and pose no issues to human life. (on a note, maybe eating could allow it to incorporate the steel into its skin? I'm not that experienced with Alloy chemistry to say, but who knows? Most likely a chemist) Edit: I don't think it could produce the minerals, only consume them, as it usually takes stars larger than our sun to make metal atoms like iron, so I'd go for getting them from munching on rocks ]
[Question] [ I'm not really sure what sort of factors would go into limiting the growth of a city, besides obvious geographical ones. I can think of * Farmland requirements. If each person requires X acres to fed them, a city of 10,000,000 would require 10^6\X acres of arable land to sustain it. Likewise, fresh water. * Sewage. --- Given an Earth-like setting, with the same land/water surface area and actual agriculture-usable areas, how big could a city get, if unbounded by terrain? For the purposes of this question, a city is an area of approximately 25,000 people/sq. mi (9,653 people/sq. km). This is taken from [the approximate density of New York City](https://en.wikipedia.org/wiki/List_of_United_States_cities_by_population_density), a reasonably dense city, compared to the world. The city doesn't have to remain under one government, this question is about the sustainability of an urban growth pattern on a single planet. As such, all available resources come from the planet (with the exception of solar power, I suppose). No importing food from off-world. [Answer] ## Most of the population lives in The City If you had abundant energy and technology on the Earth and you are constrained to limit your resource usage to that of the Earth, the limit is at least greater than 7 billion people as you could simply put everyone in a single city and have all supplies shipped to that single city. With automation replacing all farmers, and other occupations that requires a physical presence today, everyone could live in that city. But without full automatization, farmers, miners, etc. that require a physical presence considerable distance away from the city, perhaps 10% of the population must live in the country. The question then becomes how many people could Earth support with extensive use of hydroponic farming and artificial lighting, etc. - these technologies are currently used, they just do not dominate the market due to economics. Perhaps double or triple the current population is possible without breakthrough technology. Since the most modern sewage plant can produce drinking water quality output, sewer and water is not going to be the ultimate bottleneck for city size and essentially all of the water can be recycled. To get abundant energy with current technology able to support the entire population you need lots of nuclear power - renewables do not have the energy density to support such a city and you run into serious problems with wasted energy if you use seriously long transmission lines. Renewables will require significant numbers of maintenance people necessarily living in the country. --- For a city of 7 billion people. City Area: At NYC density, the area is 280,000 square miles. Slightly larger than Texas. Sewage Plant Area 3,000 square miles (7125 times the area of Chicago's Stickney wastewater treatment plant that serves 2.4 million people). Nuclear Power Area 60,000 square miles, 50 TW capacity (compared to 18 TW global energy use in all forms today) at 3. Cities are more efficient, but much of the world is in poverty. This is a lower-bound energy budget. 100 TW is more desirable Renewable Power 1,500,000 square miles, 50 TW capacity -- this is simply impractical when you add in transmission losses and the material resources needed. In reality, a better form of nuclear power would be very desirable for The City, but it would be possible with current technology, until you run out of uranium at least. --- [Answer] Well, if you do things correctly, I'd say that you could theoretically have a city over all available land area on an earth like planet. Let me explain. FOOD "But wait!" I hear the errant commenter scream. "If the whole planet is a city, where are the farms!?" The straw commenter is right, of course. If you have all of the land area of a planet crowded out by a city, there is no land for farms. *Unless you incorporate the farms into the city.* You see, according to [this answer](https://worldbuilding.stackexchange.com/questions/9582/how-many-people-can-you-feed-per-square-kilometer-of-farmland), through the use of near future technology, it will be possible to feed about *49,210,000* people with a cubic kilometer of aeroponic farm building. If you have a few\* of those around the place, food requirements are quite taken care of, without sacrificing much of the city's land area.\\ \A lot \\The citizens will be on a steady diet of sweet potatoes. You never asked for variety. ENERGY* I think it's actually possible to have this city running on nothing but renewable energy. The secret is hydrogen. Let me explain. Hydrogen can be produced by splitting water into its component parts, and its only byproduct if you use it as a fuel is water. The difficulty is finding the water. If you have easy desalination of mass quantities of water, like, say, coastal facilities utilizing a scaled up version of the [Slingshot](http://www.popsci.com/article/science/pure-genius-how-dean-kamens-invention-could-bring-clean-water-millions), which is actually present technology, you'd have water for power and water for drinking, all from the ocean! How does this translate into worldwide energy, though? Well, if you transport the hydrogen in liquid form in underground pipes, the pipes will actually be cold enough to support superconductors. Which means you could transport energy from your hydrogen power plants anywhere in the world with a pipeline with effectively zero loss, and it also covers water needs. The hydrogen could be supplemented by placing wind turbines on the roofs of skyscrapers, and the skyscrapers themselves being built with [photovoltaic glass](http://whatis.techtarget.com/definition/photovoltaic-glass-PV-glass). TRANSPORTATION In keeping this as low emission a global city as possible, I'm thinking public Evacuated Tube Transport stations, a la [Hyperloop](https://en.m.wikipedia.org/wiki/Hyperloop), every few kilometers, with public bike docks outside of every Hyperloop station. You could also use airports, but those are costly space-wise, and you can't build one through a building. So, to recap: * Vertical agriculture incorporated into the city * Desalination plants in coastal areas to extract fresh water from the sea * Hydrogen power base to take care of energy generation and transportation, supplemented with wind and maybe solar * Evacuated tube transport combined with bikes to create an efficient, environmentally-friendly transportation network [Answer] Our current cities have been grown haphazardly to meet the immediate needs of their builders at every stage of their growth. This has led to inherent inefficiencies in every aspect of each cities design. Efficient space, power and water usage, as well as adequate transportation and waste-disposal facilities have all taken a back seat to the millions of separate minds which have designed and created our biggest cities. Alternatively, we can see our current cities as having been organically grown, with millions of subtle mutations made over time to address issues that never occurred to the original city planners. With that more humble mindset, it becomes obvious that detailed planning for extreme efficiency, prior to the arrival of the cities occupants, is a fools quest. No matter how well you plan out a city's infrastructure, the needs of its actual occupants will trump the planner's best intentions. The best solution lies somewhere between the totalitarian rule of the planners and the total chaos of the occupants. To build a city for a billion people, layout both utilities and mass-transit grids, scaled for your desired population density, spread it out across 4000 square miles, then install a redundant copy of everything just to cover unexpected needs. Surround this infrastructure with 1.5 million square miles of farmland. No, better double that for redundancy sake. So let's say we turn Brazil into a farm and put our city in the middle. Along the shorelines, install massive desalination systems and nuclear power plants. Some of the water will be used by the farms while the rest satiates the city's populace and meet's its waste disposal needs. Oops! I forgot to mention the waste disposal systems. Those go between the city and the farms so that grey water and biologic components can be easily used as fertilizer. That sort of surround the city with bad smells, but with a billion people living inside, this was never going to be a rose garden. Now with all the infrastructure in place, we can let the populace free to figure out where they want to live, work and play. At this point, the city planners have done their best to give the mega city a chance to survive. Now it is up to the citizens to solve the problems that the planners missed. Along the journey of crafting this answer, I have stumbled across some of the factors that might limit the size of a city on any earth like world. Assuming equivalent diameter and water/land ration (which resulted in 57 million square miles of land on a 200 million square mile surface) and placing all of that land as a single continent in a temperate zone, I estimate that the largest farm that an earth could ever host is (extremely optimistically) almost 57 million square miles in size. Since my 1 billion citizen city needed 3 million square miles of farm, that means that the biggest city that can ever exist on an earth type world with current technology levels, would host about 19 billion souls. [Answer] Well, if you take the maximum carrying capacity of the Earth as fifty billion people, then the maximum city size is around forty-nine billion people. Presumably it would be located in Europe, Asia, and possibly Africa. If you have trouble seeing how we get to fifty billion people, remember that we aren't limited to farms on land. Sea-based farms can also provide nutrition and do not require irrigation. Another option is putting farms on top of the city. Build underground and leave the soil intact above. [Answer] user14837 almost got it. Food and water are not limiting factors. Energy is the problem, though. Hydrogen can transport energy, it's not an energy source, though. For that you'll need either fission or fusion if we can make it work. Those produce a lot of waste heat. All that heat will require even more power to run the air conditioners to keep civilization inhabitable. Eventually you reach the point the oceans boil--and then Earth goes the way of Venus. Surviving that with near-future tech is quite problematic. Addressing Gary's comment about power: A quick look shows lots of cities in the 60,000/mi^2 density. There are 57 million square miles of land. That's 3 trillion people. They're all industrialized so lets use US data instead of the world data. The world energy is 6x the US energy. We need to multiply by another x3 because of this. We are now up to 1,500x current levels. Your numbers give about .01 degrees for current use--x1,500 is 15 degrees. I'm not finding good data on the energy use of the indoor farming that will be needed but it's considerable. It's going to be well past those 15 degrees. [Answer] If the civilisation on the planet has spacefaring capabilities in order to transport waste off planet and food from other farming colonies, then there is theoretically no limit to the size of a city. Such a city would be known as an [ecumenopolis](https://en.wikipedia.org/wiki/Ecumenopolis). One early example is that of Asimov's [Trantor](https://en.wikipedia.org/wiki/Trantor), which was supplied by 20 agricultural colony planets which supported Trantor's food requirements. The number given by Asimov (45 billion) appeared to be a mathematical order-of-magnitude error, as the density is nowhere close to that of a city, but the general city size is plausible. If the constraints of a planet are lifted, then cities can theoretically exist on surfaces such as [ringworlds](https://en.wikipedia.org/wiki/Ringworld) or [Dyson spheres](https://en.wikipedia.org/wiki/Dyson_sphere) which can have sizes vastly exceeding that of a planetary ecumenopolis. The sizes of such cities is only limited by the capacities of astroengineering that the civilisation possesses. ]
[Question] [ Scientists have made a breakthrough! They've discovered a subplane of our reality that consists of what can only be described of as the essence of luck. There's also a reasonably easy way to tap into this plane and use this essence! You can also decide how much luck you want to use with a reasonable degree of precision. Using this essence makes you lucky — if you were to use enough of it while buying a lottery ticket, for example, you'd certainly hit the jackpot! However, there is a catch. Luck essence, like matter and energy, is conserved. Unlike matter and energy it doesn't need to be conserved at a specific point in time, so you can draw good luck now and pay it back later. It's best to pay it in advance, though — a luck surplus is quite stable regardless of how large your surplus is and will be available whenever you need it, but luck debt is more and more unstable the larger it is and has a tendency to unexpectedly pay itself back. This luck also can't be transferred. There's no way to have someone else give you their good luck, or take your bad luck. Of course, you're probably wondering what happens when you use luck at the same time as someone else. The simplest way to describe it is that using luck makes your situation better than it would have been, while storing or paying back luck makes your situation worse than it would have been. Using the lottery example again, you'll still hit the jackpot when you otherwise would not have, but with 1000 other people doing the same thing your winnings are going to much less. Unfortunately even though your result isn't as good as it would have been had others not used their luck, you use just as much luck either way. It's possible to have your good luck help someone else too, and it won't even give them a luck debt. This means you can safely use luck as you attempt to cook the best Thanksgiving dinner ever. On the other hand, your bad luck also can't give anyone a luck surplus, so foolishly choosing to pay back luck while driving a car won't be of any benefit to the other people involved in the subsequent wreck. Also, you can't control exactly what effect the (good or bad) luck will have other than by context of where you are and what you're doing at the time, but your luck will have some effect. Trying to pay back luck while buying a lottery ticket is rather risky because there's a good chance that you wouldn't have won anything anyway, so the payback will likely take another form (like someone accidentally kicking you in the groin on your way out). A PLAN FOR LUCK: When they announce their discovery, the scientists also propose a plan (and secretly use some luck to make sure it is well-received). Economies and innovations are not a zero-sum game — if I give you something you value (such as money) for something that I value (food), then we are both better off than before. Innovation is particularly good at this — many of the world's problems could be solved with the help of a discovery of working cold fusion or some other cheap, clean, and efficient energy source. As such, it is in the interest of governments around the world to try to make as much good luck as possible available to as many people as they can. This would maximize the chance of someone stumbling across the next world-changing invention. However, the scientists don't know what the best way to give everyone luck is. One way would be to have a cheap lottery with a good chance of winning at least a small amount. You'd be able to afford to buy a large number of tickets, meaning that you'd be all but guaranteed to have some winning tickets if you were not storing up luck. However, with the tickets being cheap and the prizes not being great (otherwise people would just decide they don't need to use luck essence in order to be lucky), you'll only be able to store up a little luck at a time. So given the resources of Earth's current governments, what would be the best way to help as many people store up as much luck as possible without incurring significant risk as they do so? Note: When you store luck something will go worse than it would have, with how much worse being proportional to how much luck you're storing. So in order to be effective, in whatever system the government sets up there has to be some way for storing luck to make your personal outcome worse, otherwise you're going to have some other kind of misfortune come your way (for example, if you stored quite a bit more luck than the system could accommodate you could get a heart attack and die). Also, you have to decide ahead of time how much luck you'll store — in a normal lottery if everyone who played decided to store enough luck to not get the jackpot, any person who would have won the jackpot will simply not win anything, but the people who would not have won the jackpot anyway are in for a bad time (i.e likely gonna die). [Answer] How about a system that generates a bad luck feedback when you try to tap into the good luck. To elaborate: In order to tap into your good luck, you need a government approval (this also works to regulate how and when you can use your good luck, as it can be easily used to "cheat" in any number of fields). However this approval is painful to obtain. You have to fill loads and loads of folder, with a huge bureaucratic procedure behind it. Additionally you randomly get citations, or are asked to deliver new, nigh impossible to find, documents (like your third great aunt family three, notarized). The process itself must be so painful that it actually generates a bad luck excess, that is in fact proportionally to the good luck you are afterward allowed to use. If you want some luck for an exam, a couple of week of paperwork should do, but if you want a free car, but not suffer the risk, well, be prepared for a world of pain in bureaucracy. [Answer] I think you're essentially asking, "How can the government provide a source of misfortune to its population?". This is something governments are quite good at. In the US, since we spy on ourselves, the government can provide a unique type of lottery for its citizens. ## Public Shaming Lottery Winning this government sponsored lottery is like winning the draft, not pleasant. The randomly selected winners would have their private conversations, internet browsing history, and medical records exposed publically. The exposure would occur on the local government level; broadcasting on local TV as well as posted to the internet. The added benefit is people with the most to lose from winning would be very public figures, like heads of research departments or professors. Waiting for that next breakthrough on your research? Keep those browsing habits filthy and your fingers crossed. [Answer] I'm pretty sure a greedy government would go for more extreme and rapid ways of accumulating luck, like with machines randomly delivering a controlled amount of pain (like a "stochastic punching machine"). In times of crisis or great need, they'd step up their game ("stochastic jabbing machine", "stochastic finger chopping machine") and make the people who need luck the most go through the process of accruing large amounts of it. Or, if your lottery system really works, the state would automate it, assigning each citizen a special well supplied bank account and playing from it constantly (one draw per second). Citizens would be instructed to think about it as often as possible in order to accumulate luck. This would only work if each citizen had the right to withdraw from his account at a given point during his life - say, after they reach the retirement age. [Answer] Give everyone a through tax audit. That should be bad luck enough for one year. Then repeat every year. ]
[Question] [ These groups are sometimes known as the guys who send the protagonist their journey, or providers of an unexpected safe haven from the powers that be, or maybe just fodder for a character showing off his/her new power. Now, one thing they all have in common is that they don't get the attention and depth they deserve in most worlds. The groups tend to be bit players that only serve a fleeting purpose. What I am looking for is a way/method/system for creating groups in this category. I need to know what properties should be considered and how to make them deeper than a convenience. [Answer] If you want a group that lives outside of the law to have depth, you have to provide a motivation for them to live like that. Living outside the law isn't easy. In general, laws exist because they provide safety and stability. Being a bandit means that you don't have that safety or stability! So let's take a look at some viable motivations: 1. Your family is starving: If you don't have enough to eat, you don't feel safe or stable even if the land you are living in is otherwise a utopia. You are going to go to desperate measures to find food. If other people have food and you don't, you're going to try to steal food or something that can be used to obtain food. There is a lot risk in doing this, but if it's literally do or die... 2. You have been cast out by society: Hundreds of years ago, exile would have been more harsh than a death sentence. You no longer have anyone helping you if you are sick or injured. It would be difficult to get any other village to accept you. Setting up a farm on your own would be very difficult, and because you're an exile it makes it much easier for others to find you and punish you again for whatever caused you to be exiled. 3. The rule of law is broken: If the law is being ignored or is twisted in favor of those in power, you don't feel the safety and stability the law is supposed to provide. This is where Robin Hood figures and rebel groups fall. These people generally want to follow good laws, and feel that in order for that to be possible they need to cause massive changes to happen. 4. Peer pressure: If your friends are members of a gang, you'll feel social pressure to be affiliated with that gang. You might actually be press-ganged into joining the gang. This could happen with a bandit group, too, whether they are recruiting or outright kidnapping. There are, of course, other possible motivations. For a group of bandits, etc. to form, the conditions need to be sufficiently bad for a number of people to be in these situations. Having a grudge against society or the powers that be is a good common ground for people to share, making it plausible that they will tolerate each other even if they are naturally violent people. You should also think about the origins of a particular group - I don't expect bandit groups to have a great long-term survival rate. A group of starving peasants would be likely to want to work together, but if they're starving the chances are that they're less skilled than average. A group of people exiled for being violent might be able to survive thanks to their skills, but the group is likely to fracture due to their violent natures. A mix of violence and starvation could wind up rather stable - the few violent exiles would naturally seek to take charge, and could provide enough leadership to keep the group alive, while the starving peasants help keep the group cohesive enough to not split apart. So here's a few key points: * Consider the motivations of the individuals, and give each one a reason to risk abandoning the safety and stability the law provides. * Have a diverse group. If everyone in the group is a cookie-cutter copy of each other, the group is not likely to be stable enough to be realistic. * Think about how the group got started, and who joined when. That will shape the group's goals and the rules by which they live. * Consider how risky it is for them to live as they do, and make sure that their motivations are sufficient for them to be taking such risks. [Answer] Rebels Obviously the key element is to have a Evil Government/Overlord/Big bad worthy of rebellion. One weakness of stories with a rebellion (especially where the protagonist is a rebel) is that the either the "powers that be" are chaotic evil (i.e. evil for evil's sake without any logical justification) or their motives are detailed so poorly that you wonder why anyone would bother with a rebellion at all. Painting the two sides in detail, clearly showing what each side stands for and why they can't peacefully co-exist will help flesh both sides out and make it feel like a genuine struggle. Thieves, Bandits and Brigands The biggest failing I've seen with these characters is one of the size of the group. Often the criminal gang is just too large to be supported in the location where the story is set (swords & sorcery fantasies with a thieves guild often fall into this trap). Too often the sheer number of burglars, pickpockets, pirates, robbers and con-men involved make you wonder how the honest people around them aren't all permanently penniless. So the key is to look at the environment and see what sort of crime(s) it can support. How much money is there in the society as a whole? What is law enforcement like? What's the best way for the criminals to get at that money (theft, drugs, extortion, etc) with the least risk and the greatest reward? [Answer] Bandit and Rebel groups appear very differently from inside and out. Any realistic group will account for both viewpoints. Externally, such groups act parasitically, attacking in areas where the powers at be would like to claim they have control, but in reality they lack it (whether because they cannot observe the bandits in their acts, or if they simply lack the ability to strike at them). They can be thought of as mid level predators. They have to avoid being caught by the powers at be, but prey on those who lack the power to oppose the brigands. From the inside, the forces of the powers at be should be viewed as forces of nature. They're not really opposable, so brigands do not try. However, they generally do not define themselves solely as "opposing the establishment." Such a subculture is vulnerable to shifts in the powers at be. Instead, the culture should appear as a complete and independent culture living within the limits of the forces at be. They should give the feeling of a tribe living at the foot of a volcano. They don't define themselves as "people who avoid the lava flows." They instead are "a people, just like any other tribe, which happen to proudly dodge lava when needed, and they're good at it." That inner culture is important for making them feel "real." Groups who define themselves as "opposing X" often have trouble sustaining themselves in times of trouble. [Answer] # Did I choose the thug life, or did the thug life choose me? * If someone has chosen that lifestyle, there must be a reason. * There also a reason why he didn't change later. * There is also a reason why they don't get all arrested or killed. Think about the reasons why these things happened or didn't happen, and you'll have a much richer background. [Answer] Two things need to be considered for a realistic "outlaw" group. First off, is there a way for them to support themselves by outlawry. Pirates, contrary to popular myth, were mostly "government" agents using issued Letters of Marque as a licence to board and plunder "enemy" shipping. The Crown received a share of the proceeds, making this a lucrative business for all concerned (although Spanish or Dutch merchants might disagree...). Even in the "Golden age" of piracy, when more pirates were operating than Letters of Marque would support, the British Crown turned a blind eye to the goings on at Port Charles in Jamaica and other pirate nests since this provided economy of force for the Empire: essentially an entire naval fleet harrying Spanish, French and other shipping without the Crown having to spend a single shilling. Interestingly enough, once the pirates had served their purpose and were now costing British merchants money, the Crown hired Henry Morgan (a former Pirate) to become Governor of Jamaica and clean up the problem once and for all. Which he did (there is no honour among thieves) This outlines the second issue; if pirates, brigands or outlaws are operating because they can live off the proceeds, then someone else is not "minding the store". Modern day pirates operate off Somalia because there is no actual Somali government to enforce the law, and pirates in Indonesia are essentially beyond the reach of the small and ineffectual Indonesian Navy, coast guard and police (if they don't pay them off first). The Drug gangs in Mexico and South America operate on a similar logic, they control the territory because the local government cannot or will not. So the two conditions you must have are ungoverned or ungovernable territory, and the territory being close to places where the outlaws can gain wealth (either by plunder or trade [the drug trade or slave trades are examples of this]). [Answer] Why are people outlaws? Many it is circumstances that drove them too it. Taxed out of house and home. Maybe unable to hold down a job. Or maybe they think life is 'easier' taking from others. So why are they bandits? Next why do they still exist? How can they be 'criminals' and not be arrested or otherwise stopped? Since they exist, what kind of power-base do they have? Are they a band of merry men prancing through the forest? Are they hardbitten criminals that break legs to encourage 'donations' to help keep the neighborhood 'safe'? Are their 'guilds' or 'mafia' style organizations where stepping out of line makes you a criminals criminal? Most organized crime is fictitious and used to make a story more interesting. Gangs exist, and they work together, guilds for thieves and others is a little extreme though it makes for a great piece to use. It also implies some greater organization with the possibility of a person to appeal to. So Why is someone/group criminals, why are they still criminals and what do they want. seems easy... ;) ]
[Question] [ Imagine the ugliest thing you can even imagine. To have common image in head, lets start with aliens from "[The Alien](https://en.wikipedia.org/wiki/Alien_(film))" movie: [![The Alien](https://i.stack.imgur.com/qfdKZ.jpg)](https://i.stack.imgur.com/qfdKZ.jpg) Image credit: [Wikipedia](https://en.wikipedia.org/wiki/Alien_(film)) The ship full of these creatures is on the orbit. Right now. But here is twist: They come in peace. They want to communicate. Cooperate. Form an alliance with Earth. Share technologies. Invite kids over. (You get the idea :) ). And take this as granted please. There is no plan B, there is no "kill them all". They really really really want to cooperate with us. Their only drawback is, we consider them ugly. At first they communicate with everyone who wants to listen. In first stage, they communicate [using mathemathics](https://worldbuilding.stackexchange.com/questions/22882/is-mathematics-a-truly-universal-language), later on (a year or so) we both learn [common language](https://worldbuilding.stackexchange.com/q/22002/2071) easy to learn by both races. But, will we be willing to trust them? Will humans be able to work over the look differences for sake of gain? [Answer] I think the key here is to keep face-to-face communication to a minimum. I'm sure we've all had the experience of talking to someone on the phone, thinking to ourselves, "man, this person must be beautiful", then being disappointed when we actually saw them for the first time. I would say that most humans tend to idealize things they can't directly see; thus, keeping the ugly aliens in a separate room will make us just as comfortable with them as we are with third-world countries. This solution might even be easy to suggest without offending anyone. Since the aliens aren't terrestrial, they probably don't survive long in the conditions we're used to. They'll probably wear some sort of environment suits when they visit our planet, and when we meet in space they might prefer to have a deck to themselves, to fill with whatever gasses they breathe. Over time, the public should get used to the idea of these aliens as their suited-up forms. Since they'll probably look fatter and move slower in these forms, they probably won't be nearly as repulsive. [Answer] I believe humanity will (mostly) be able to cooperate with the ugly aliens Things to keep in mind: 1. We do not know their intentions, or if we can really trust them when they say they want peace. 2. They do not know that earth is not united under one government, or who our leaders are. 3. We do not know the full extent of their technological capabilities. Here is how it would likely play out: The aliens are unable to communicate with us via technology, as our software can't open attachments with the .alien file extension. So they make a landing, and visit us in a city. Cities are full of people, there must be somebody that wants to communicate. Landing in their spaceship causes a commotion, and their identity as aliens is confirmed in the minds of the people. We bring in linguistic experts and mathematicians, under heavy protection, and begin communicating with the aliens. We are not sure if they will destroy us if we offend them, so we are extremely polite in our communications, despite their disgusting appearance. We warn them that not all humans are friendly, and 'Alien Safe Zones' are set up where populations are educated about the aliens and the government over that area guarantees the safety of the aliens. Eventually, curiosity overcomes revulsion and the safe zones become hubs of information exchange. The aliens soon realize how hideous we perceive them to be; they are hurt, but their desire to collaborate is stronger than their pride and they start to wear 'clothing' to cover up their body parts that we find most unpleasant. Despite the aliens and our governments best efforts, some humans still want to remove the aliens from our planet by force. Fortunately, due to the aliens friendliness and the technological advances that they brought us, these humans are a minority. The aliens eventually learn about and greatly admire the human Martin Luther King Jr, and adopt his nonviolent methods to bring about change. Over a few generations, we learn to live with each other and eventually visit them on their home world. ]
[Question] [ In a non-magical world where homo sapiens has evolved into several races or breeds (like dogs) or even species as in [Q10102](https://worldbuilding.stackexchange.com/questions/10102/how-would-multi-race-humanoid-evolution-happen) and [Q12190](https://worldbuilding.stackexchange.com/questions/12190/what-common-ancestor-would-the-basic-fantasy-races-evolve-from), that can interbreed for the most part, how can one model the chromosomes or genes to restrict the possible outcomes so each offspring clearly belongs to one (possibly hybrid) race? ## Requirements * Female and male offspring of the same parents may have different races, e.g. human mother + vampire father = vampire daughters, human sons. * A female of one race can be impregnated by a male of another race, but it fails with switched races or sexes, e.g. vampire mother + human father = no offspring. * The race of certain offspring may be determined by the race of the parent with the same sex, e.g. dwarf mother + gnome father = dwarf daughters \| gnome sons. * Some races are restricted to a single gender and rely on other races for reproduction, e.g. sphinx mother + centaur/minotaur father = sphinx daughters. * Some hybrid races are infertile when mating with each other, but can reproduce with members of other races (or at least one sex can), e.g. human + elf = half-elves, human + dwarf = half-dwarves, both are considered halflings, halfling + halfling = no offspring, but halfling + human = humans (or maybe halflings again). Which results can be modeled with genetic variety on certain chromosomes and which are better done with different chromosomes? [Q143 “Explaining half-breeds in a world with multiple races”](https://worldbuilding.stackexchange.com/questions/143/explaining-half-breeds-in-a-world-with-multiple-races) only deals with parts of this question. I guess I’m looking for a general set of rules or algorithm to use. My current crossbreed design is tabulated at [Conworld Wikia](http://conworld.wikia.com/wiki/Human_Races). It’s not yet specified whether it’s the result of natural evolution or of some kind of genetic engineering. [Answer] At first glance many of your requirements seem doable, but upon further thought it’s really very difficult to come up with reasonable explanations for them. That said, nothing is impossible, it’s just the explanations might not exist within the realm of classical genetics. I’ll go through each of your requirements and explain why simply having extra chromosomes or dominant alleles won’t be enough to explain the phenomenon. I’ll also give some theoretical considerations to non-classical genetic explanations. > > Female and male offspring of the same parents may have different > races, e.g. human mother + vampire father = vampire daughter, human > son. > > > I’m assuming that you mean that offspring of some biracial matings have a chance of being the race of either of their parents. Let’s explore how this could happen. Say there is a single genomic feature that makes people vampires. It could be an extra chromosome, or an allele on a chromosome. We’ll call it V. V acts in a dominant fashion so anyone with a copy of V will become a vampire, and anyone without a copy will be a human. If a Vampire is homozygous for V, meaning they have 2 copies of it, all of that vampires haploid gametes will also contain a copy of V. This would mean that all of a vampire’s children would have a copy of V, and therefore be vampires. Not what you want. Let’s say instead the Vampire parent is heterozygous for V, so maybe they only have one copy of the V chromosome, or one copy of the dominant allele. In this case only half of the vampire’s offspring will receive a copy of V. So half will be human and half will be vampire. That’s perfect right? The problem with this is that if a vampire is only heterozygous for the V trait, then vampires won’t “breed true”. When two vampires mate there will be a 25% chance that they have a normal human child! We can’t have that! And to make matters worse, another 25% of the vampire’s couple’s spawn will receive 2 copies of V and then be homozygous for V. When those children mate with humans they will always have vampire offspring. I’ll spare the reader the trouble of going through all the other possibilities, of making V recessive or codominant or multigenic. Classical genetics isn’t going to work for us. The central problem is that when two organisms produce offspring, half of the progeny’s genome comes from one parent, and half from another. We can fiddle with things to make what we want happen to this first generation, but when they go to reproduce, they have an equal likelihood of passing on their father’s chromosomes as they do their mother’s. We need to make some exceptions to these rules. Perhaps you’ve heard in the news about a new technology under development called “[gene drive](https://en.wikipedia.org/wiki/Gene_drive)”? The idea is that you can make an allele of a gene that is capable of “infecting” or copying itself onto another allele. So when an organism is heterozygous for a gene drive allele, the gene drive allele modifies the other allele to become a gene drive allele as well. The organisms is then homozygous at that allele. In this way the technology would allow the rapid spread of a certain allele in a wild population of organisms. It’s good for our purpose because it lets us get rid of those pesky heterozygotes. This sort of system actually already exists in nature in a couple forms. Homing [endonucleases](https://en.wikipedia.org/wiki/Homing_endonuclease) and [transposons](https://en.wikipedia.org/wiki/Transposable_element) both have this sort of functionaility. [Gene conversion](https://en.wikipedia.org/wiki/Gene_conversion) is another way this could happen. So imagine our vampire allele V is a gene drive allele. All vampires will be homozygous for the allele and when they mate with humans all of the offspring will be heterozygous, the V allele will overwrite the human allele and all of the offspring will be vampires. Now, imagine the human counterpart to V, allele H, is also a gene drive allele. When a heterozygous embryo is created from a vampire-human cross it will contain both H and V. V will try to overwrite H and H will try to overwrite V. Say the chance of V or H winning is 50/50 and now our vampire human cross is capable of producing both vampires and humans, both of which will be homozygous. > > A female of one race can be impregnated by a male of another race, but > it fails with switched races or sexes, e.g. vampire mother + human > father = no offspring. > > > This is definitely the easiest of your requests. Although it still is difficult to achieve with classical genetics there are some well-documented ways in which this could occur. The simplest is some sort of non-genetic barrier to reproduction. An example might be if human sperm is incompatible with the hostile environment of a female vampire’s reproductive system. Or if the human sperm was unable to recognize the zona pellucida of a vampire’s ovum. There are many ways in which fertilization could be blocked in one mating but still work in another. If you aren’t keen on non-genetic barriers, another option is [imprinting](https://en.wikipedia.org/wiki/Genomic_imprinting). Imprinted genes are epigenetically silenced depending on their parent of origin. Humans have a handful of imprinted genes where expression from allele from the mother or father is silenced. If a human male silenced an important gene that a vampire male did not, then a male-human female-vampire coupling might result in a serious deficiency in that gene, which could make the embryo non-viable. > > The race of certain offspring may be determined by the race of the > parent with the same sex, e.g. dwarf mother + gnome father = dwarf > daughter \| gnome son. > > > This one isn’t easy either. The immediate solution that comes to mind is “Let’s put it on the sex chromosome!” and it is very wrong. Say the gnome Y chromosome contains an allele D that makes the sons who receive this Y be gnomes. Now, whenever a gnome mates with another race his sons will be gnomes and his daughters will be the race of the mother. That’s great right? The problem is, how do you ever get female gnomes? You might think maybe we can explain this with imprinting, but imprinting only gives us a parent-of-origin effect. We need to correlate the parent-of-origin with the sex of the child, and that means putting imprinted alleles on the sex chromosomes, but I still don’t really see how it could work. > > Some races are restricted to a single gender and rely on other races > for reproduction, e.g. sphinx mother + centaur/minotaur father = > sphinx daughter. > > > This is your second easiest requirement. I think the best explanation for the sphinx is that the features that make a sphinx a sphinx are in the [mitochondrial genome](https://en.wikipedia.org/wiki/Mitochondrial_DNA). The mitochondria are inherited only from the mother through the egg and so they get around our issue of hybrids. A sphinx egg doesn’t care about the sex chromosome in whatever sperm it receives, it just makes a female sphinx. > > Some hybrid races are infertile when mating with each other, but can > reproduce with members of other races (or at least one sex can), e.g. > human + elf = half-elf, human + dwarf = half-dwarf, both are > considered halflings, halfling + halfling = no offspring, but halfling > + human = human (or maybe halfling again). > > > Oh man, this is hard. Having hybrids be infertile is easy, a lot of real ones are anyways. Having them be infertile with each other, but fertile with their parent species does not make a whole lot of sense. There could again be non-genetic barriers. Say female halfling reproductive systems don’t develop quite right, but the male reproductive system works fine. A halfling-halfling pairing wouldn’t produce offspring because the female would be entirely infertile. The halfling male on the other hand could still reproduce with either of its parent races. I have to warn you though that the result of a halfling-purebreed coupling is going to be a three-quarterling and may not be what you want. If you really want to get into the complex, hard science of this sort of stuff you should also take into account [Haldane’s rule](https://en.wikipedia.org/wiki/Haldane%27s_rule). I’ve written a lot and I haven’t gone into as much detail as I would like to explaining everything. If you have any questions or need clarification I can do my best to explain in the comments, or through chat if you’d like. [Answer] I used to breed Netherlands Dwarf rabbits, and one of the most difficult things is the high mortality rate of kits. See, dwarfism as an allele in rabbits is a lethal recessive trait. Let's refer to the dominant as D, and the recessive as d. A true dwarf has the genotype Dd. That gives it the short ears, small body, and disproportionately large head that makes it absolutely adorable. Rabbits with the genotype dd are referred to as "peanuts". Their digestive systems are nonfunctional, and if not destroyed, they starve within days of littering. Rabbits with the genotype DD are not dwarfs, and such offspring of true dwarfs are typically destroyed. See the attached Punnett square for breeding true dwarfs. Half the litter is lost, and half are true dwarfs like the parents. In the example of your vampir, suppose humans have the phenotype vv, vampires are heterozygous as Vv, and a creature with two vampire genes (VV) is not viable due to whatever biological phlebotinum. Humans would always breed true, obviously. Vampire human hybrids would be randomly half human and half vampire. Vampire/vampire pairings would result in the same spread as my rabbit example. If VV is not viable, that leaves human (vv) offspring of vampires to be accounted for. I think the simplest explanation would be that a chemical in vampiric blood is toxic to human fetuses and would not allow them to be carried to term. While this doesn't fully account for all of your demihumans, nor does it directly explain sex-linked inheritance, such lethality of various gene combinations can be tweaked to produce any sort of combination of surviving offspring you wish for various couplings.![enter image description here](https://i.stack.imgur.com/kvA2I.jpg) [Answer] A lot of this boils down to [Mandelian Genetics](https://en.wikipedia.org/wiki/Genetics#Mendelian_and_classical_genetics), aside from all that hoobub about chromosomes. Before i get started, i'd like to point out that Mandelian Genetics have some flaws, but that doesn't mean they aren't usefull and it certainly doesn't mean they are "obsolete" most of what we know about genetics today is still based off of Mendels findings. The Mandelian theory basically states that each trait is a gene "packet" called an "allele". If a minotaur that has the allele for two-legged-ness mates with a centaur who obviously has the allele for four-legged-ness, then the traits are decided by which ever allele was the dominant gene. This can be seen in humans: the "brown-eye" gene is dominant, so around 75% of the time you have a brown-eyed parent and a blue-eyed parent, the children will have brown eyes. This law can be used to explain your Sphinx issue. As long as the genes that make a creature a Sphinx are dominant over the genes that make them not a Sphinx, the child will also be a sphinx. You may attribute the fact that all sphinx-child's are female to "sex linked genetic traits", which states that some traits are found only in offspring of a certain gender. Bees are a good example of this, as they are male or female based on diet, incubation time, and pheromones that the queen creates: the females are workers or queens(depending) and the males are always drones, they develop differently before pupating. this can also explain this rule: > > •The race of certain offspring may be determined by the race of the parent with the same sex, > e.g. dwarf mother + gnome father = dwarf daughter \| gnome son. > > > The talk of halflings and crossbreeds can be dealt with by Mendels laws also. As user6760 said, Mules, as a rule, are infertile due to inconsistency of chromosomes,. A crossbred human/elf could share a similar predicament as a mule, we just have to change things a bit to make sure they can still breed with a full human or elf. Unfortunately, to coincide with everything else, this would require the Halfling to be "given" to a certain race, without being one. for instance, a Halfling with the same number of chromosomes as a human would be female, and a halfling with the same number of chromosomes as an elf, would be male. this would ensure that halfling/halfling relations would have n o offspring, but a male Halfling/female elf relation could. Additionally, a female Halfling/male human could have children. then comes the difficult part of male elf/female halfling or female human/male halfling ... You could brush this off and not really pay attention to it, or you could say "hey, if elves and humans can work in the first place, why not these?"-but that will throw off the entire rest of the theory. well, that's about all I can do... I have nothing for > > •A female of one race can be impregnated by a male of another race, but it fails with switched races or sexes, > e.g. vampire mother + human father = no offspring. > > > you m ay need a chemist for that one :P. ]
[Question] [ Imagine a world like ours. Gravity, atmosphere, sky... just nothing solid down there. At least not anywhere close. Would it be possible? I know this is similar to [this question](https://worldbuilding.stackexchange.com/questions/11764/could-air-gas-giants-exist). So to specify what I mean: I'm not asking if a gas giant could be naturally created. All I want to know is whether it could exist at all? If it was created artificially, by whatever means, would it be possible for it to sustain, survive a similar time as Earth did, without continuous energy income? Also, I don't care what its main part is. I only care about one layer. Down there anything known or suspected might be. Actually, the more of the deadliest stuff the better. And last but not least, would it be possible for both gravity and pressure to be Earth-like at some depth? [Answer] The answer is...maybe :) Lets take Jupiter as one example to start with: [![Jupiter's Atmosphere](https://i.stack.imgur.com/TeXcC.jpg)](https://i.stack.imgur.com/TeXcC.jpg) To be earthlike you need: * 1 bar of pressure * temperature around 0->40 degrees centigrade, around 300 degrees K * an oxygen/nitrogen atmosphere Looking at Jupiter then you do get 1 bar just above the cloud layer, however the temperature is only 100k at that point. The water cloud level happens lower down, where you do get the required temperature - but you also get ten times earth's atmospheric pressure. At different points in the atmosphere you do get both earth-like pressure and earth-like temperature (although not at the same point). In theory if the planet had a different composition or orbited at a different distance from the star those two points could be made to line up. [Sudarsky's Gas Giant Classification system](https://en.wikipedia.org/wiki/Sudarsky%27s_gas_giant_classification) looks at the various known types of gas giant. Class 2 Gas Giants in particular actually have Water clouds which again is encouraging from the point of view of pressure and temperature. The problem is composition: Jupiter's atmosphere is composed of about 90% hydrogen and 10 % helium. There are only minute traces of methane, water, ammonia, and rock dust. So, this is your main problem. The gas giant would need a radically different composition from anything we've ever heard of in order for it to have a high enough percentage of heavier gasses like nitrogen, especially at the altitude where the atmospheric pressure is survivable for humans. You should also consider that Oxygen is highly reactive. If you do not have lifeforms of some sort creating it you are very unlikely to find free oxygen, it will all react away. ]
[Question] [ This question is partly a nod to the current fortnightly challenge. In many fantasy settings and resources, there are creatures capable of, or described as, breathing lightning. How might a creature evolve naturally such that it can emit lightning, or an effect that may be easily mistaken for lightning, from its mouth? I am intentionally providing no additional expectations or requirements of design in order to not influence answers. Feel free to imagine your creature in any way you see fit, so long as it meets the lightning-breathing requirement. [Answer] Let's do a little math here. Based on [my research](http://www.kronjaeger.com/hv/hv/msr/spk/), the voltage to produce a half-meter long spark in dry air between two needle-shaped electrodes is roughly 300,000 volts. This would indicate that the critter would need to have some sort of modified fang or tusk in its mouth to concentrate the charge. A quick search of the web puts [the electric eel](http://en.wikipedia.org/wiki/Electric_eel) around 600V, with unconfirmed reports of over 800V, however, that's directly tied to the size and number of the eel's generating organs, so we're gonna need a bigger critter, possibly 500 times bigger. A typical electric eel is about 20kg, putting a nice ballpark on size. We're looking at 10,000kg of critter here, about half again the size of a bull elephant. An electric eel can generate roughly one amp. Typical TASERs operate somewhere in the ballpark of 26 watts. Given that we're dealing with 300,000V, that means we only need roughly .09mA to incapacitate a grown man. That seems easily in reach for our school-bus-sized thunder-monster. If it could still produce the full amp that an eel could, even just for an instant, its shock would be horrifyingly lethal. Now, the critter would have to insulate itself from the ground to avoid that lightning arcing through their body from their mouth to their feet. One organic product comes to mind that is a superb insulator: [beeswax](http://cleveland.ces.ncsu.edu/beeswax/). The critter would probably either excrete the wax from pores in the skin, or spend a lot of time grooming itself with a waxy gland. I imagine that this would also give the creature a nice dull, dry gloss. Its leather would probably also make a good pair of naturally waterproof boots. That, all by itself, would be enough to get you your lightning-breathing monster, but one other improvement comes to mind: mucous filled spittle. Spit is a fine conductor, and with enough phlegm, you can get some pretty long strings going (source: my teething son), which could improve the range of the sparks nicely. To sum it all up, I would imagine a twenty-ton, hairless beast with a thick coat of gleaming wax covering its body. As it opens its mouth, a single wicked-looking fang juts out. Its massive bellow shoots out streamers of lighting and noxious spittle. Anything standing in its way has mere milliseconds left to live before they fall dead or burst into flames.Bursting into flames may or may not be an exaggeration, but terrible scorching would definitely happen. Finally, as to how it would evolve, I can easily imagine a smaller ancestor biting its prey before releasing a more modest shock that would leave its victim stunned and helpless. ]
[Question] [ There are a couple of stories where humans gain chloroplasts. Here's a clip from [one story](https://en.wikipedia.org/wiki/Beggars_and_Choosers_(novel)): > > They are also infused with bacteriorhodopsin, allowing photosynthesis. It is now possible for a human being to lie on the ground, in the sunlight, for thirty minutes, and absorb all the energy and nutrients they need for a 24-hour period. > > > But, this strikes me as unlikely. The other story had humans being powered by sunlight. > > While working with this idea we happened across an interesting and rather common tittle freshwater coelenterate named Hydra viridis. This particular hydra, unlike its relatives, exists in a symbiotic relationship with a wonderful alga called chlorella. > > > In addition to producing its own food, it will also produce enough to > keep its host alive. "When chlorella is not present, the hydra is forced > to eat solid food just like its white relatives." > > > ...will have to believe you after you've done nothing but sit in the sun and starve yourself tor weeks on end without getting hungry or losing any weight. > > > EDIT: removed 3 hours a day for power/meals, since the story didn't clearly say that, only implied it. It sees to me that an animal running around needs a lot of sugar/energy. Even if we take out the energy needed to process food (a non-trivial amount), it seems to me that a human would require more power than could be provided by merely having a green skin. Square-cube law, and more mass behind a smaller surface area than a microscopic animal. IIRC, humans need about 2,500-3,000 calories a day. Working skin is a under a couple of layers of dead skin, which should impact how effective the chlorophyll would be (how much?) Assuming there was a way to prevent them from being liquidated and absorbed; how much energy would a bunch of chloroplasts within vacuoles in the human skin provide? (an aside, too bad the fortnightly challenges don't say when they expire) --- Hmm, the calorie consumption numbers are for food, which humans are not good at digesting, does anyone have glucose/ATP consumption figures for human beings? Maybe how much are people who're on IV drip fed? [Answer] Well, there's a reason animals run around and eat plants, and not the other way around. Let's find out why: Step 1: Inbound solar radiation in the vacuum at Earth orbit is 1,413 $W/m^2$, or about 1500 $W/m^2$ Step 2: Photosynthetic efficiency is [2% to 5% at best](http://www.fao.org/docrep/w7241e/w7241e05.htm#1.2.1), under optimal conditions. (I've seen estimates as low as 0.1%) Let's use a wildly optimistic 5%. Step 3: Estimate [humanoid body area to 1.5-2](http://www.medicinenet.com/script/main/art.asp?articlekey=39851) $m^2$. Let's round up to 2, and say half of it, or $1 m^2$, can face the sun at a given time. Step 4: Estimate average [daily food intake](http://www.nhlbi.nih.gov/health/educational/wecan/healthy-weight-basics/balance.htm) of a moderately active man to be around 2600 Calories, or $1.1\times10^7 J$, so round down to around 10 million Joules. Keep in mind that a Joule is a Watt/second. Step 5: (My favorite) Calculate the energy capture formula as a function of energy inflow, area, efficiency and time: $1500 W/m^2 \times 1m^2 \times 0.05 \times 1s = 75 W/s$ So at that wildly optimistic conversion rate under perfect sunlight you'd need, um, 133,333 seconds to power up for the day. That would be not half an hour, not 3 hours, but 37 hours. Keep in mind that in reality, even at noon, only about 1000-1100 Watts/sq. meter actually reach the ground (some get dissipated in the atmosphere), far less than half the body area will have direct solar incidence, and typical photosynthetic efficiency might actually be closer to 1%. So unless you come up with a way to increase the surface area about 10-fold at least, it's looking a little difficult. You might consider placing your green men in the focal center of a set of reflecting mirrors. Might get a tad hot, though, and photosynthesis has an [optimal temperature range](http://fhs-bio-wiki.pbworks.com/w/page/12145771/Factors%20effecting%20the%20rate%20of%20photosynthesis). ]
[Question] [ Suppose a planet is covered with floating ice on top of water ocean and has no dry land. Would it be possible to establish permanent settlements, cities? Particularly I am interested in technologies combating * ice drift * melting of ice under the constructions and utilities * sinking of buildings due to snowfalls (as happened with the US South Pole dome) * strength of the ice sheet so to withstand big buildings The following is true: * There is considerable ice drift, like that in Arctic. * There can be temporary clear water surfacing, but this is only for a time, and then ice moves to the place, there are no permanently ice-free areas. I wonder, whether anchors could help against drift? [Answer] It's probably possible, but I wouldn't go about anchoring my ice city by use of metal anchors. Instead, I'd try to encourage the formation of [anchor ice,](http://en.wikipedia.org/wiki/Anchor_ice) which is Ice that forms attached to the bottom of a body of water. If your city is based on a large patch of ice that's touching the sea floor, that particular part of the ice won't drift, and can be used as a platform for a geostationary city. One way of triggering anchor ice formation would be to pour supercooled brine through holes in the ice. This exceptionally salty water can be cooled to below the freezing point of water, leading to a long icicle forming around the flow of brine, which eventually connects down to the bottom of the ocean, [like this.](http://www.discovery.com/tv-shows/frozen-planet/videos/icy-finger-of-death/) If lots of such flows were created during calm weather when drift was at a minimum, they could provide sufficient anchoring force to stop drift. Alternately, snow and ice could be piled up until the ice layer was thick enough to touch the bottom of the ocean. This would also create a tall 'dune' of ice above the surface of the ocean, proportional to the depth that the ice descends to. Since weathering action would slowly erode the top of the ice, it would need to be constantly replenished to stop the ice from floating up and away. In either case, once anchored, structures known as [stamukha](http://en.wikipedia.org/wiki/Stamukha) would form on the edges of your city, providing additional anchoring as the ice sheets affixed to your anchor broke against the surrounding drift ice, eventually piling up into walls thick enough to touch the bottom of the ocean. The heavy, thick ice below your city would provide a foundation on top of which structures could be built. However, it would be very difficult to go about mining for materials to create such structures. Most buildings will probably be crafted out of the most plentiful building material available: ice. [Answer] If you want to stay in one place, you have to either travel over the ice (which you don't seem to like), under it (a terribly gloomy lifestyle), or through it (which has certain engineering challenges which I will now address). I found an interesting reference book, [Basic Coastal Engineering](https://books.google.ca/books?id=PafNyKSg4EkC&pg=PA222&lpg=PA222&dq=how%20much%20force%20can%20sheet%20ice%20exert&source=bl&ots=GPTupPxdga&sig=Ckc9QNcjct9OivYk0hjPyipUfpk&hl=en&sa=X&ei=wMnCVJjBNYqwsAS89YDYCw&ved=0CB0Q6AEwAA) It says that a vertical wall at the waterline can experience horizontal forces on the order of 200 to 300 Newtons per square centimeter. If you assume ice up to (for sake of argument) 6 meters thick this gives an overall force of something like 1700 tons per meter of width. This would take a pretty amazing amount of anchoring. On the other hand, inclined plates can lift the ice, causing it to crack under its own weight and greatly reducing the horizontal force - for sake of argument, call it a reduction to 40 N/cm^2, or about 225 tons per meter of frontal width, which is much more tolerable. You need enough buoyancy to lift the edge of the ice, and enough depth to reach beneath it. I think this would translate into something like either a long, narrow, very deep-draft barge or a [SWATH-ship](http://en.wikipedia.org/wiki/Small-waterplane-area_twin_hull) design (catamaran with thin vertical hulls standing on submerged pontoons). The barge would require more anchoring, but the SWATH has less reserve buoyancy. In either case, you would still need to occasionally deal with unusually thick ice, ie pressure ridges. This is probably best done by a watch force armed with depth charges or torpedoes - an underwater explosion is much more effective in lifting and shattering the ice. (Maybe replace the explosives with some sort of reusable high-volume compressed-air injector? --- On the whole, this seems like a very large capital expenditure for very cramped living space. I think it is much more likely that people would live in portable (sliding) modules in a continuous migration against the ice movement, as suggested by James, or simply go with the floe (pun intended), as per bowlturner. You might find [Project Habakkuk](http://en.wikipedia.org/wiki/Project_Habakkuk) interesting; this was a WW2 plan for an iceberg airfield stationed in the North Atlantic and prevented from thawing with a mixture of insulation and refrigeration. So long as the ice surface stays below -16C it will remain viable; in testing, 9m x 18m block was maintained through the summer by a 1hp motor. In practice people would migrate to a far-North floe and construct a new town; ride it wherever it goes for the next 30 or 40 years until it becomes too expensive to maintain the refrigeration; then repeat the cycle. [Answer] The world you are describing will not support permanent settlements (unless you redefine what a permanent settlement is. If you are talking a LAT/LON location...then no...but if you want a group of buildings and people that I think we can support and I think the answer here is small modular buildings. Let me elaborate a bit, * These should be small enough that their weight will not crack submerge or otherwise impact the ice to a significant degree, this would likely require a little future tech, mainly lightweight building materials. * In the world you are describing the possibility of change seems pretty frequent and these modules should be able to float, basically each module is a boat. * Modules could be connected by the stuff they use to connect those accordion buses. ![enter image description here](https://i.stack.imgur.com/yS3HA.jpg) * So you have living modules, greenhouse modules, etc etc etc etc. This gives you adaptable buildings that can survive the world you are on, course I hope you have a really good reason to send people to that planet as humans wouldn't have developed naturally on it. [Answer] Since the ice can melt and it's not a permanent iceworld like Hoth, then buildings need to be built on large 'floats' maybe even with the ability to move. The floats would also help keep the buildings from 'sinking' into the ice from pressure and can be moved to stay on top. Crops and such would likely need to be in green houses (also build on floats) because while you could build gardens on the ice with imported soil, (they have gardens in Alaska with permafrost underneath) you still need it warm enough to sprout and grow. This will need green houses. Creating large (tall) structures would be unwise for many reasons because ice is not rock. The taller you build the more pressure melting ice underneath the building will be affected. It will actually be floating on a cushion of water. You also have the problem of getting building supplies. You'd either have to mine under the ice (dangerous and problematic) or ship in all materials. The cost of shipping in the materials would likely encourage smaller more easily built structures that can be moved in needed. EDT: It would be wiser to allow the ice to drift and stay with it than to try and anchor it. While it isn't as inevitable as a continent, it it hundreds of millions (billions?) of tons that want to move, either by tides and/or convection currents. [Answer] Look at how bases at tge South Pole [are made](https://www.wikipedia.org/wiki/Amundsen%E2%80%93Scott_South_Pole_Station#Elevated_station_.282003.E2.80.93present.29) with designs based on problems with previous iterations. [This page](http://www.coolantarctica.com/Bases/modern_antarctic_bases3.htm) has a lot of details in downloadable documents, including Challenges that face South Pole architecture, which has major categories for * wind * ice flow * ice creep I don't see it skimming through this, but I recall something about needing foundations that isolate the heat from the ground so the buildings don't sink! This is also the case for permafrost. ]
[Question] [ Conflict between civilizations has played a key role in the technological development of the human race. If humanity never had a single war, how would technology in such civilization evolve? Would it be advanced as it is now? Given that war is a major source of technological advancement, what would be the factors driving the technology in a world without war? [Answer] Civilization without war, a nice idea. Possible? First of all, we should clarify why mankind fight in upscale acts of war. There are plenty of reasons, I will try to hit the remarkable: Why do cultures attack other: > > TL;DR: There are many reasons for war, primarily the fact that one group has some kind of fear which makes them aggressive to prevent future damages. > > > * Fear of each other A mighty tool of leadership is to spread fear against another bunch of people. Just think about the Crusades or the 3rd Reich. Without the cruel fairy tales about evil Muslims, Jews, or any other Side, the people wouldn't had fought them that enthusiastically. Also the reestablishment of old honor has to be put in this category. A nation that once had a good reputation loses their state to another, they have a lot to gain in a war. Sometimes war reestablishes the old force the nation once had. The state of shame is a big disadvantage which generally a culture doesn't want to handle and would be willing to fight against.(See [France and Germany enmity](http://en.wikipedia.org/wiki/French%E2%80%93German_enmity)). * Resources There are plenty of resources available to be conquered in war. From the simple "food" problem in the Stone-Age, to Lifting-Space in later times. This reason can be combined with the fear, for a lack of specific resources could lead to angst. Also an opposite force which one does not trust, that has access to a resource capable of giving them a big strategic advantage, would be one such an example (Think of [Nuclear Weapons](http://en.wikipedia.org/wiki/Cold_War)). * Ideological and Religion If one looks at how religions define the contact between believers and non-believers, it's often the case that we can discover the reason for poor treatment. Usually, the first people of this belief had problems with others. This is similar to how Jesus Christ had his problems with the Jewish arch priests and traders (later in medieval Europe, Jews weren't allowed to work as craftsmen which forced them to be traders, double bad,..). This does not necessarily result in war, but prohibition, prosecution, disadvantages in trading and so on are possible. So even if the first believers'/founders of the religion did not tell to make war or something, this probably created a bad opinion of some other groups. Later, that could lead to wars. (Crusaders again, Jihad (Translated from German Dschihad), ...) Ideologies can lead to wars between cultures, but much more often they lead to civil wars. Therefore see [Revolution](http://en.wikipedia.org/wiki/Revolution). Is it possible for cultures to live for millenniums without war? > > TL;DR: If you want the people to not make war, give them everything they need. One need you must not forget about is to avoid feelings of envy. > > > Well, this is highly speculative, but I'll give it a try. First of all, the main reasons of war must be absent. So the People must have enough food, space, and so on. There must not be any "disease" which could be interpreted to come from a specific group; common sense must be incredibly strong. Basically groups must not be in any competition, as every little reason could lead to war as history has shown. This also means that no group has resources which other groups do not to prevent any competition. So if you could generate such a scenario without being implausible, go ahead. This is the most difficult part I can see. Last but not least, evolving: > > TL;DR: War often leads to big advances in culture and technology, but the invention arise not only in war. There are plenty of examples of civil inventions being used for war. > > > We don't know much about war in the Stone-Age, but in the first Copper-Age times there are plenty of recorded wars. In particular, when empires arise and cultures get lost, the specific culture of the empire evolves very fast (even when the repressed cultures have influence). Empires generate affluence which in turn generates more technological steps. (Think about ancient Rome, medieval China, currently USA.) Many inventions are made particularly for war and get altered for civilian markets, for example [radio](http://en.wikipedia.org/wiki/Radio); many civil inventions are used for war as well, such as [nitroglycerin](http://en.wikipedia.org/wiki/Nitroglycerin). Much of the technological evolution does not only take place in or during war, but is enhanced by it. Many inventions are made just during wars and are specifically designed for it. We cannot say if firearms where invented just for hunting (maybe), but war had been the reason in reality for their general use. Short answer: I don't think history would have been possible without war, not due to the evolution that had taken place, but due to more complex social structures leading to more problems between groups. War is a fast solution to many problems and mankind likes the fast way rather than the right way. [Answer] I am going to delete my previous rather not so popular answer and try add several things to be considered: You have to define what happens if two tribes meet Sometimes they traded, sometimes they fought (war). Since "fight" is not an option, they have to trade. But there is still one flaw in this scenario: What happens if one tribe does not have anywhere to grow? We fight wars because we want supplies (they are now traded) and land. Since (again) the fight is not an option, you would probably get the land using "medieval" style of obtaining it by prearranged marriages and joining two "kingdoms" into one. What happens when Columbus (and others) discover America? As I am not an historian, and also I am from Europe, my vision of how USA became to life includes loads of killing of native Americans. In your setup you have to assume the native people willing and wanting help with the development How will religious disagreements be handled? Its not only now so popular "clash" of Islam versus western world, but for example, there are Christians fighting Christians in Nothern Ireland and only "difference" is, that one are protestants and other are Catholics. You have to decide what happens there. Somewhere I heard that if two ancient tribes wanted to join, they did "marriage" of their Gods, so I think this could be the way In nutshell, I belive there are two options how to get around it: ## The hard, historical way Go as far into history as possible and see where and which tribes existed. Do not forget to do it globally (in Europe we completely miss out the whole India development before the colonization era in our history classes). Let the tribes evolve and follow the rules above. I think, that best assumption in this scenario is, that you eventually end up in one global "tribe" worshiping every known God and Goddess. The setup would be really Utopian civilization of happy cooperating people. Main drive of the progress would be to ease the trade and communication, so you can assume the civilization technological progress would invent today cargo ships and planes. ## The easy naive way Or, you can say yourselves "screw it" and let your tribes at small, local level, not allowing them to grow, not allowing them to meet themselves. The would would most likely look like one big jungle inhabited by [small tribes](http://en.wikipedia.org/wiki/Uncontacted_peoples) [Answer] Civilizations make technological advancements even without war but war is a powerful accelerator. Randomness of ideas: To begin with, the technology progress from time to time as new things get discovered. Some are just the result of luck, a good idea but some require a lot of effort and experimentation. Even the most simple discoveries are impossible without the right idea. No one can predict when someone will get a new idea, it's pretty random actually. Research and development: When you get an idea, you might need a lot of work to make it possible. It might not always work in the end. A lot of resources are required here. The speed of the progress cannot be linked only with the resources dedicated to the research. Increasing the resources will give a better result to a point. Past some point, the benefits for each new resource added into research is getting smaller and smaller. Is there a better way to get ideas?: Sure, it's called a war. When you are at war, you will do everything you can to get an edge on the enemy. In return, he will do everything to adapt in order to stay alive. Thus, one of you will need to come with another invention and the cycle goes on. This is the case of World war I because it was a rather long lasting war. Without conflict, there is less incentive for change. Not only it might take longer to come up with new ideas but making these ideas possible and applying them also take longer. It happens more quickly during war because the countries are pouring all of their resources into the conflict as they cannot afford to lose. During World war I, the dept of the United Kingdom exploded and reached (if I remember correctly) 500% of the country's GDP. Austria, France, Russia and Germany were also ruined at the end of the war but they had to do it. All that money went into the development of new weapons, new gears, new planes, new ships and new tanks. Just an example: before the Great War, planes were only used as prototypes but the war allowed planes to become a possible alternative for transportation. [Answer] War produces an incentive for technological progress: Inventing a new and better weapon may mean that your society survives instead of being annihilated or enslaved. On the other hand, war also destroys huge amounts of resources. There was certainly great technological progress during World War 2. It would be hard to argue that the war did not CAUSE progress. But there was also a lot of technological progress in the 19th century, a time of relative peace. And of course there's been a lot of technological progress since World War 2, little of which really seems to be attributable to any wars. Well the threat of being killed or enslaved is certainly a powerful incentive, there are many other reasons why people might want to devote energy to technological progress. The desire to live a more comfortable life, for example. The desire for novelty, excitement, and adventure. Pure curiosity. [Answer] If you're looking to disqualify wars and conflict between civilizations, you might get similar pressures (and the developmental benefits thereof) by other kinds of conflicts - this might include a harsh environment, or (obviously non-sentient) predators, diseases, or even limited access to resources - if and only if there was an obvious way to cooperate towards getting (more than) enough for everyone instead of competing for the less that's obvious. One of the reasons war has such a high benefit towards development, is that when it's an urgent, life and death pressure, societies will dedicate resources to solving the problem or finding workarounds. A deadly problem might not only serve as a similar obstacle to spur a people against, it might serve as a common 'enemy' to encourage different tribes to cooperate and share solutions instead of compete with each other. As for what other factors would drive technology? I expect that a strong cooperative drive could sometimes function similarly to a competitive one in pressurizing R&D, once something like pride or honor comes into play - each wishing to have more, or the most, to contribute towards a common good. Some cultures idealize hospitality and generosity in a similar way, where status is linked to what one can give rather than have. There would probably be development for labor saving devices, driven by a desire for leisure similar to our own. Perhaps there would be some advantage, instead of using survival pressure to combat a disadvantage - like better communication so ideas can get explored and implemented after discovery, instead of waiting for a conflict and necessity to popularize them. As for, would this civilization be as advanced as ours? It would depend. If the original pressures were very difficult, and the rewards of cooperation quite high, its quite possible - with the caveat that the pressures would have to keep building to maintain that kind of cooperation. It's even possible that such a society could advance further, since their best minds would be cooperating rather than competing. It would also be easy, however, for the civilization to top out once they've comfortably conquered whatever their enemy was... even a cooperative society might be content with a peaceful and slow advancement once the predators are gone, instead of rushing to find new advances as much as possible because, say, the latest disease has adapted again. [Answer] The only way you could have such a state is if there is a way to resolve disagreements that provides a universally accepted result that is then never reconsidered. So for example, if your party lost the last election, not only would you accept the result, but you would now join and become firm supporters of the winning party! If you allowed reconsideration, then the previous losing side would have a huge incentive to resort to stronger means to decide the next 'vote'...and force would certainly eventually come up as an alternative. So, the obvious means for this would be some kind of hive mind, possibly with a limited range. But when two such groups met, they would "think out" the issue and come to "one mind" on the subject, then split up again with identical concepts agreed upon. You'd think this might be a bit of an evolutionary or cultural non-starter as the avant garde would be wiped out by the majority whenever they met. [Answer] War isn't the primary driver for technological advancement. There are more basic ingredients that have led to innovation: * Hardship. More to the point, recognition of a difficulty that prevents an entity from reaching its a goal. * Motivation. Specifically the urge to overcome the hardship. * Reason. The ability to enumerate, and test, different ways of overcoming the hardship. * Education. Essentially the ability to retain and transfer knowledge to others. Yes, war can lead to development of new technologies. However it is by no means the only, or even primary, reason that most technology has been developed. Take a simple thing like the transition from nomadic to agricultural lifestyles. There are many theories about why this occurred, none of which involve war being a motivator. Further, it is arguably one of the greatest changes that early humanity went through and whose technology is still advancing even today. If war was the only driver then we likely would never have made the switch as it's obviously more advantageous to be nomadic in that situation. It is entirely possible that a culture without war never advances beyond a nomadic existence. Generally speaking this means that something is missing from that culture. However, it is entirely possible that a culture without war would be so far advanced that they would appear as gods to us. One thing to consider is that peace is what helped get the renaissance period started. Any period of relaxation for a naturally inquisitive species will lead to testing new concepts and ideas. Examples of drivers include: a population explosion would lead to new ways for collection and distribution of food; while a period of depopulation might lead to innovating ways of keeping entities alive (exa: soap, clean water). Either of those could also lead to inventing written communication - in order to preserve knowledge and transfer knowledge. Eventually this would lead to long distance communication would rise if the need were great enough. So, in the end, war isn't necessary for the advancement of the species. If you look at history, war actually sets all parties back as it causes depopulation of the prime members of the participants, results in upheaval of societies, stops and even destroys most industrial activities, etc. Generally speaking, the cost of large wars far outstrip the benefits received and is a reason why most reasonable leaders use this as a last resort. We can even look at specific inventions credited to war and with a bit of reflection realize that those inventions likely would have come out anyway. If for no other reason than to solve economic hardships. [Answer] All of these answers assume that we are referring to a human, or human like, civilization. One where the individual has independence and value outside of the larger society in which it lives. Consider how things would be different if your people were descendants of a herd species. How different things would be if the needs of the group were always placed ahead of the needs of the individual? [Answer] 'War drives technological progress' is a massively simplistic and ultimately false statement. 1: The technology used in warfare generally is not developed during wartime. 2: What allows technology to spread is investment, in a world in which there are no stock markets, venture capitalists, global advertising platforms or commonplace bank loans for entrepreneurs etc, there are two ways of significantly expanding production - going to your own government - or going to someone else's government. Because government was by and large the only place where wealth pooled when everybody with wealth became government and governments necessarily become 'invested' in finding means of self-preservation when it is obviously threatened (see: war and threat of war.) Taking as a given that no war means no significant threat of war: Every soldier, officer and part of the logistical setup must be maintained by civilian product whilst producing nothing and offering no service. Each one of those is not simply drawing off from the product of useful people, but could be producing something themselves. Technology growth is primarily a product of economic excess, it hardly matters the educational level of the people involved - if they have excess 'funds' (read: time) a proportion of the population will involve themselves with attempting to improve themselves and their surroundings. The only sense in which War 'creates' excess in these terms is that taxes are almost invariably raised during wartime and theft[appropriation] almost invariably is taken from the losing civilian tax base. This is of course then a matter of redistribution of product, rather than a product. If you read a historical work, it was almost invariably written by somebody who was supported financially by means other than the production of that work. That is, either the idle rich or those supported in their idleness by the rich. This is the same as what supported almost all technological growth throughout history. Of course, it had a major flaw: Somebody who works on what amounts to a hobby has no need to disseminate their product. So society is left relying on ego-stroking and greed to even begin the process of dissemination. Technological spread of course meets other barriers, the same as today. People don't want potential enemies or competitors to have the same information they do. One thing we can credit to war, one supposes, is that war is quite public, especially when contractors are required[government buys/takes license to produce and spreads license around available manufactories.] Whilst it might not be the case that the general public learns via this mechanism how to manage x process or synthesise y, somebody other than the original inventor will. and bla. It follows then, that it would develop further and faster than one with war. ]
[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/3224/edit). Closed 6 years ago. [Improve this question](/posts/3224/edit) If the gravity was half as strong, how would the enviroment change? Would all the plants grow differently? What change would there be in flying creatures? [Answer] Gravity plays an important role not just on how life forms evolve, but also on the evolution of the planet itself. The gravity of a planet or moon is a property of its size and density; thus a body might have the same gravity as that of a smaller, denser one. If the Earth had half the gravity it does now, it's possible that life would not have evolved, due to a thinner atmosphere, and a host of other consequences resulting from that one change alone. Other factors affect whether a planet's atmosphere is conducive to life, how well protected it is from solar winds, and how well the atmosphere retains or sheds heat. Things like the distance from its star, the period of the planet's rotation, its magnetic field, and so on. You could conceivably balance these factors to explain how a planet with much less gravity has a habitable atmosphere. In the question [Can you simply scale up animals?](https://worldbuilding.stackexchange.com/q/316/2394), it is explained that the [square-cube law](http://en.wikipedia.org/wiki/Square-cube_law) prevents things from becoming too large; as the size of an animal increases, its volume (and weight) increases much faster compared to linear measures such as height. Reducing gravity would not change this law, but it would change the boundary where its effects cause organisms to be unable to grow larger. For example, the largest living land animal today is the [African Bush Elephant](http://en.wikipedia.org/wiki/African_bush_elephant), averaging just under 5 tons and standing about 11 feet tall at the shoulder. With half as much gravity, it would not be unreasonable to think such an animal could be twice as massive. Working backward from this, it would be like adding about 25% to its height and length. In other words, scale the elephant up to stand 13.75 feet tall and its mass would double from 5 tons to 10 tons. With half as much gravity, its weight would be the same, but its larger dimensions would be proportional to the new gravity. This is of course just a back of the envelope calculation. Larger animals have existed in prehistory, like the truly immense [sauropods](http://en.wikipedia.org/wiki/Largest_prehistoric_animals#Non-avian_dinosaurs_.28Dinosauria.29), the [largest of which](http://en.wikipedia.org/wiki/Amphicoelias) might have been 135 tons and 30 feet tall. With half the gravity, it could have been almost 38 feet tall instead. This same question came up [on Quora](http://www.quora.com/How-would-life-be-different-on-Earth-if-since-the-dawn-of-time-the-strength-of-gravity-were-half-what-it-is-currently), where answers agree that plants would likely be much taller (though there are counter-examples). With less gravity, flying insects and birds might need less muscle power, but with thinner atmosphere, also need larger wings for more surface area to push against. Consider that small animals and insects can fall without getting hurt (the square-cube law working in reverse). The size at which this is possible would be larger. Imagine how high a cat could leap from the ground to a building ledge. A typical house cat can leap about 5 feet, or five times their height. Although you might think that in half gravity this could be doubled, remember that muscles would have evolved requiring less mass to overcome gravity's effects. So I would probably estimate the low-gravity version of a house cat to be able to jump somewhat less than ten feet. There are many other tradeoffs, the likes of which I am not sure about the calculations for. For example, the escape velocity from the planet would be less, so rockets would not need to be as bulky. However, energy production from hydroelectric dams might also be less, because gravity (after all) is what pulls it down through the turbines. [Answer] It would be relevant what causes the gravity to decrease, and also how quickly the change occurs. Assuming gravity isn't going down because much of the matter inside the planet is vanishing, and/or somehow the gravity is going down without causing massive instability in the planet's crust (which I imagine it would - I think there would be massive earthquakes and volcanic eruptions): Some large buildings I think would be in trouble, while others might not. In general, I think it would reduce much of the difficulty in standing up that structures are designed for. On the other hand, it would change the forces at work on practically everything, and that might lead to things cracking and breaking. If there are objects not being pushed sideways partly because of the friction in response to their weight, they might slide out of place. Some things might creak and groan and break, and others might fall down, but I think in general most buildings would be more stable. If no other disaster came with it, it would seem to me very fun to jump around in half gravity. Boing, boing! You could throw things higher and farther, too. The atmosphere of the planet would I think be in danger, I expect catastrophically, but I'm not certain. Astronomers talk about Mars having had insufficient gravity to hold its atmosphere, so I think that's the worst problem, but reducing air pressure itself (it would go down by 50% even without losing any air) would have health effects. The atmosphere also has a lot to do with temperature on the planet, so that would also be awful for existing life forms. If somehow the only changes was the gravity, then plants would be able to grow taller. Flying animals and aircraft would be much more capable of flying from the lack of gravity, except if the air pressure went down, that would make it much harder to fly using wings or rotors or jets. I'm don't know what the effect curves look like. Rockets on the other hand, would have a much easier time with lower gravity, and thinner air would help them too. [Answer] If halving the gravity results in halving the atmospheric pressure, you will push most humans right up against the death zone, it would be as if the people at sea-level were all living at around 5,000 meters, which is about the highest recorded permanent human settlement. [Making a planet habitable for humanoids: The planet](https://worldbuilding.stackexchange.com/questions/9944/making-a-planet-habitable-for-humanoids-the-planet/9945#9945) <http://docs.engineeringtoolbox.com/documents/462/elevation_altitude_air_pressure.png> ]
[Question] [ For those of you who have read mission of gravity, or researched Saturn’s equatorial bulge, you will know that the faster a planet rotates, the greater the “flattening” effect it’s rotation has. This means that planets (like Saturn) which rotate very quickly have a “bulge” at the equator, reminiscent of a hole-less donut or a football that’s been stepped on. And the greater this “bulge” is, the greater the difference is between the surface gravity at the poles and the gravity at the equator. Now, I have a terrestrial world which, like Saturn, has a tidal bulge. This is a terrestrial planet 1.6 times the mass of earth, with a density of around 5.5 g/cm3. It’s axial tilt is 24 degrees. I would like this planet to have a gravitational attraction of about 40% earth-g at the equator, and 120% earth-g at the poles. How fast, then, would it have to rotate in order to create this difference? If there is any information needed to work this out that I have neglected, please tell me! The above information is all I have on this planet so far, so additional data can easily be added. [Answer] Referring to [the formula for how much bulging occurs for a given speed](https://en.wikipedia.org/wiki/Equatorial_bulge#Formulation) (up to on the first order but it's good enough), we have that the difference in polar and equatorial radii relative to the mean radius $a = \frac{a\_e + a\_e + a\_p}{3}$ is that $$\frac{a\_e - a\_p}{a} = \frac{5}{4} \frac{\omega^2 a^3}{GM}$$. The only other constraint on $a\_e, a\_p$ we have is the volume of the planet derived from the mass and density, $\rho \cdot \frac{4 \pi}{3} a\_e^2 a\_p = M$. And what we want from the equatorial acceleration and polar acceleration is that $$3 g\_e = 3 \left( \frac{GM}{a\_e^2} - a\_e \omega^2 \right) = q\_p = \frac{GM}{a^2\_p}$$ ignoring the non-spherical components of gravity. We can't decide the exact values as We know from the volume constraint that $a\_p = \frac{a\_V^3}{a\_e^2}$, where $a\_V$ is the radius of the spherical planet. This turns the other two into an equation on $a\_e$ and $\omega$. For the gravity magnitude relation, we get a quadratic on $a\_e^3$, so $$a\_e = \sqrt[3]{\frac{-3\omega^2 + \sqrt{9\omega^4 + 12 \frac{G^2M^2}{a^6\_V}}}{2 \frac{GM}{a^6\_V}}} \text{ or } \omega^2 = \frac{GM}{a\_e^3} \left( 1 - \frac{a\_e^6}{3a\_V^6}\right)$$ Let $a\_e = f a\_V$ and we get the final monster formula when subbing into the bulge relation, $$\frac{3f^3 - 3}{2 f^3 + 1} = \left(1 - \frac{f^3}{3} \right) \frac{5}{4} \frac{\left(\frac{2}{3}f^3 + \frac{1}{3}\right)^3}{f^9}$$ This is an absolute monster of a polynomial, a quintic of $f^3$ and definitely not solvable by analytical methods. By graph, the answer is roughly $1.16017$. We could get more decimals, but we have enough error from our approximations. [![graph of the functions](https://i.stack.imgur.com/596Fo.png)](https://i.stack.imgur.com/596Fo.png) We thus get our variables as $$ \begin{align} a\_v &= \sqrt[3]{\frac{3M}{4 \pi \rho} } = 7458 \text{ km} \\ a\_e &= f \cdot a\_V = 8652 \text{ km} \\ a\_p &= f^{-2} \cdot a\_V = 5541 \text{ km} \\ \omega &= \sqrt{\frac{4 \pi \rho G}{3 f^3} \left( 1 - \frac{1}{3} f^6\right) } = 4.293 \cdot 10^{-4} \text{Hz} \\ \implies T &= \frac{2 \pi }{\omega} = 4 \text{ hours } 3 \text{ minutes } 56 \text{ seconds} \end{align}$$ Yeah that's fast. Definitely beyond the range of the approximations taken here. Edit : BTW the gravitational acceleration at equator is 0.707 G and at the poles is 2.12G. If you scale your radius by $s$ while keeping density fixed, mass changes by $s^3$, while acceleration changes by $s$, but the time period remains fixed. So to get 0.4G at equator and 1.2 at poles at the same density, the planet must have a mass of $0.3 M\_\oplus$, radii of $a\_V = 4262 \text{ km}, a\_e = 3166 \text{ km}, a\_p = 4944 \text{ km}$. [Answer] At the poles the centrifugal force due to rotation is null, thus your question can be reworded as: > > given a planet with surface gravity of 12 $m/s^2$, what is the rotation speed which would give a net gravity at the equator of 4 $m/s^2$? > > > The net gravity at the equator can be calculated as $g\_{net}=g-r\omega^2$. On a first approximation you can use the same radius for the pole and the equator. A more refined model would require accounting for the bulge and use different radia. [Answer] The acceleration due to gravity is given by $g = \frac{GM}{r^2}$. The apparent centrifugal acceleration on the surface is given by $c = \omega^2 r$. You want $g-c$ to be one-third of $g$, so $c=\frac{2}{3}g$: $\omega^2 r = \frac23 \left(\frac{GM}{r^2}\right)$ $\implies \omega = \sqrt{\dfrac{2GM}{3r^3}}$ [Answer] > > would like this planet to have a gravitational attraction of about 40% earth-g at the equator, and 120% earth-g at the poles. How fast, then, would it have to rotate in order to create this difference? > > > You can't. The shape of the planet will be one in which the surface gravity along the surface is equal at the poles and at the equator. If you spin it faster, the planet will just bulge further. The material strength of a reasonably large planet required to have not differ significantly from this is simply insane. (by "gravity", I mean the sum of the gravitational attraction of the planet plus the inertial effects of rotation). [Answer] Stephen H. Dole, in Habitable Planets For Man (1964): <https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf> Discusses the requirements necessary for world to be habitable for human beings (and also for multicellular land animals with the same environmental requirements as humans). Other scientific discussions of planetary habitability are for liquid water using life in general, and not for humans and lifeforms with the same environmental requirements in particular. On pages 41 to 46 the cases of rapidly rotating planets which become oblate in shape. And on pages 58 to 61 Dole discussed limits on the planetary rotation rate of human habitable planets. Dole believed that a planet would be rotating too fast when the surface gravity at the equator dropped to zero and matter was lost from the planet, or when the shape of the surface became unstable and axial symmetry was lost. Dole believed that for planets in he size range of Human habitable worlds, a rotation so fast that a single rotation took 2 to 3 hours would result in an unstable planetary surface. So you should check whether a rotation rate fast enough for to there to be a surface gravity at the poles 3 times as high as at the equator would be safe and stable for the planet. ]
[Question] [ I’m curious - does anyone with knowledge about animal/evolutionary biology think that predatory horses, akin to [the Mares of Diomedes from Greco-Roman mythology](//en.wikipedia.org/wiki/Mares_of_Diomedes), are plausible? I’ve found tidbits of info saying that horses have been witnessed eating meat, but it was clear that these animals were starving and desperate. Could horses that eat mostly, or exclusively, meat, be possible? Obviously, their biology would have to changed… but at what point would the creature be so different that it would no longer be, you know, a horse? I know that predators tend to have forward-facing eyes, a body that is low to the ground, and (of course) sharp claws and/or teeth. Equids have none of these features. Some people on this site asked this question about centaurs… but not normal horses. Please help? [Answer] Yes and no. First horses will eat meat when they can, this is true of most herbivores. Deer have been observed eating birds. All but the most highly specialized vertebrates can digest meat because our bodies can break down our own tissue and digesting meat is much easier than digesting plant matter. They may not get everything from it a carnivore will get, but meat is such a high nutrient density food source it is still a large gain. Can horses evolve into predators, Yes. Predatory pigs and ungulates have existed and the bulk of the change was in the head and neck, they evolved tearing teeth and a jaw that can open much wider and a thicker neck to tear flesh otherwise they are not all that different from a undomesticated horse. Will they pass for a normal horse, only to someone who has never seen a horse before. Can you feed normal horses nothing but meat, no Their digestive system is too geared up for plants, while they might be able to derive enough nutrients from it, they will suffer a lot of gastrointestinal problems, without fiber their digestive system will develop blockages which tend to be lethal. [![enter image description here](https://i.stack.imgur.com/C3Pia.png)](https://i.stack.imgur.com/C3Pia.png) [Answer] The [hippopotamus](https://www.mentalfloss.com/article/72550/hippos-eat-way-more-meat-we-thought-and-it-can-make-them-sick), colloquially known as the "river horse" might be the first step in the evolution to your desired predatory horse. [Answer] A horse could certainly evolve over time to become a predator, however it would require radical changes in their gut, dental structure, and general body plan (horses are terrifyingly fragile, not good for a predator) and they would most likely be outcompeted by other better adapted animals before they managed to evolve into predators. The best chance to get a predator horse would be to terraform a moon and populate solely with horses as large herbivores (with just grasses and and some insect species and the like to keep the ecosystem working). But at that point is it even really a horse anymore? [Answer] Maybe... but it would be a stretch. As [AlexP](/users/29552) pointed out in comments, horses are not built to be predators. Large predators such as lions hunt by stalking their prey, which requires them to get low to the ground, and they have forward-acing eyes that give them a huge advantage in depth perception and other visual aspects of hunting. Horse's eyes are spaced for maximum situational awareness (read: keeping watch for things hunting them). If they're going to hunt successfully without trading their mouths and hooves for a more canine/feline muzzle/teeth and paws, they're going to need to rely on group tactics instead, more like wolves. Also, if they're not going to be the size of wolves, they're going to need to eat a lot of meat. Even lions, the largest extent land predators¹, are smaller than horses. So the only way I see this happening is if they hunt by surrounding and trampling their prey. This requires their prey to be smaller than them, somewhat stupid, and fairly abundant. So, if they live somewhere that is absolutely inundated with small, slow, stupid prey animals, it might be possible. However, it would be a challenge for any ecosystem to support the necessary density of animal life. (¹ ...or maybe tigers; they're about the same. I'm not counting lion/tiger hybrids since they don't occur naturally.) [Answer] > > Definition of predatory 1a: of, relating to, or practicing plunder, > pillage, or rapine b: inclined or intended to injure or exploit others > for personal gain or profit. > > > Nothing in the definition that makes meat-eating a requirement. Horses are by nature a herd animal, but they are also by nature territorial. As a herd animal, the males have a natural tendency to protect the herd hierarchy. As a territorial animal, they will defend their territory to the death. There is a reason why their stalls are made out of very thick, strong wood and heavy steel bars. Our experience with horses is usually with domesticated, trained horses. Horses in the wild are another completely different disposition. They will tear any other interloper apart if it impedes on their territory. A human has no chance against a wild horse, no matter what the movies say. Any horse found in the wild, you are best advised to give them a clear berth, respect their territory, and never, ever trust them. They can be unpredictable, ferocious and viscious. A herd of them is extremely dangerous. And a hose bite will take your hand off, or crunch the bones in an arm. Even a domesticated horse is entirely capable of killing another horse it sees as a competitor or threat, depending on the herd hierarchy. So yes, any wild male horse is to be considered as a predatory animal. Even a domesticated horse that has been abandoned in the wild and forced to survive on their own will become predatory. To keep a male horse domesticated, depending on the breed, it needs to be constantly told 'who's boss' by the trainer/rider/owner. [Answer] A horse with a Narwhal like tooth adaptation would be able to hunt small prey by knocking them unconscious prior to eat it. Squirrels/Iguanas would be good prey for them. Ie : unicorns ]
[Question] [ So, [Blue Submarine No.6](https://www.youtube.com/watch?v=j1m9wEyEVvo). Other than the nightmare-inducing CGI, it's also notable for being furry/scalie bait, complete with the fish lady, Mutio. Most of this bait is thanks to Dr.Zorndyke, a brilliant genetic engineer, who decides that it's time for humanity to be replaced and orchestrates a polar shift to flood the Earth's coasts, killing billions, and we [can't even sell their now underwater apartments](https://www.youtube.com/watch?v=X9FGRkqUdf8). So, Zorndyke also has an army of hybrid creatures, including the Musucas (see pic related for more info). Musucas serve as transport for the Water Spiders, nimble mechanized troops that, along with the Ghost Ship, seem to be the primary offensive force. We know little about Musucas, but they were grown in underwater "cultivation tanks", near one of the poles. They are sentient and sapient and capable of verbal communication and probably have organic sonars as well. [![enter image description here](https://i.stack.imgur.com/IbhQA.gif)](https://i.stack.imgur.com/IbhQA.gif) This is what happens when you max-out Google-fu. [Here's a video of one, though it has spoilers, so...](https://youtu.be/RXHE0SJyw6Y?t=41) But, would that be workable in a realistic setting? Musucas aren't designed to engage in direct combat and when they do, the mortality rate is 100%, though they can score kills. Their role is transportation, the question is what (if any) advantages would such bioships have over modern, conventional waterborne military vehicles (larger ships and submarines)? [Answer] Bioengineered is almost another way of saying "based on nanotech". So whatever those advantages and disadvantages that entails which includes pliable materials, distributed systems, and superior system integration. One of which should be (if you so choose) superior senses and situational and structural awareness since you don't have a hull made of a single material, but can have sensory organs embedded throughout. Flippers and undulating bodies (high Reynolds number propulsion methods) also have a number of efficiency, maneuverability, and stealth advantages over propellers. With these two things combined, you should be much better at navigating crevices and canyons. Another potential thing is with the pliability of organic structures, you might be able to constrict and reduce unused interior open spaces on the fly which would provide an adaptable method to increase buckling resistance against water pressure. I'm imagining something like an automatic door, except it's an automatic corridor that opens up in front of you and closes up behind you as you walk. Would be useful for immediately isolating leaks as well. You might also be able to absorb the water out of any room rather than need a discrete pump or anything like that. Potentially it could refuel, reoxygenate, and desalinize in-situ though nuclear submarines can also do these things (or simply don't need to). [Answer] I can think of a few reasons they would be better. Please note I haven't seen the video that has the creature in it. * if they get injured but not killed, they can heal with enough time rather than needing replacement parts * they can find 'fuel' wherever they are as opposed to finding gas(nuclear submarines don't need this though. ) * They probably have better maneuverability than traditional submarines * the surface of the water, even when calm, is a very dangerous place for a submarine. depending on your creatures tolerance levels, it might be less dangerous. [Answer] A modern submarine, even a non-nuclear one, costs billions and requires a shipyard with hundreds of workers and many years effort.. A bio-submarine costs whatever plankton etc you need to feed it on while it grows. Hence there are only a handful of submarines but you can have as many of the bio version as your ecosystem will support. [Answer] There already [are](https://en.m.wikipedia.org/wiki/Military_marine_mammal) bioweapons. Horses have been used for a long time. Need I make it clear, the reasons these arent used: 1. You need humans on board to control it. Large animals are [dumb](https://www.frontiersin.org/articles/10.3389/fnana.2014.00046/full#:%7E:text=We%20find%20that%20the%20African,are%20found%20in%20the%20cerebellum.). That means most sea travel is out of the question because sea animals prefer to be underwater, and that would require extensive oxygen and energy supplies. Oxygen machines are about a [kilowatt](https://www.oxygenconcentratorstore.com/blog/stationary-oxygen-concentrator-electricity-usage-and-costs/#:%7E:text=Wattage%20Per%20Stationary%20Oxygen%20Concentrator,average%20usage%20of%20590%20watts.). If a blue whale is 1000 times heavier than a human who has a useful output of a few watts, then using [metabolic scaling](https://www.pnas.org/content/100/7/4046), even the whale would struggle to provide enough energy to support a human. You would need a power system anyway and it would end up being larger than the animal. 2. Assuming your controlled horse, whale or whatever has a human available to ride it now the problem is maintenace. Horses were replaced by cars because of both speed [and maintanability](https://www.google.com/search?q=why+were+horses+replaced+by+cars&oq=why+were.horses+replaced.by+&aqs=chrome.1.69i57j33.7341j0j7&client=ms-android-tmus-us-revc&sourceid=chrome-mobile&ie=UTF-8). Cleaning up and feeding an animal is a frequent task while maintaining a submarine only happens when it is in port. Even if it is equally time consuming, machines have a more controlled maintenance schedule that disrupts operations less. 3. The obvious reason is speed- no animal has the kind of speed that machines do. Whales go about [12mph](https://www.speedofanimals.com/animals/blue_whale#:%7E:text=Blue%20whales%20can%20reach%20speeds,per%20hour%20(3.1%20mph).) while submarines can go several times that. As for stealth, [whales](https://journals.ametsoc.org/jtech/article/37/5/807/345205/Scaling-the-Laws-of-Thermal-Imaging-Based-Whale) have an IR signature visible a good distance away, so they would need the same coatings military weapons do for the same effect. And you would need humans to control it so you need machines anyway. On purely a cost front, diesel and uranium are cheaper than biofuels, so that's an additional problem. The cheapest of all is a sailing ship which has no fuel. You can use plankton but that severely limits the size of your fleet. So control, scheduling, speed, and cost are the reasons machines were picked over animals. [Answer] ## Stealth. Stealth. Stealth. It's about all about the Stealth. A submarine's primary and main advantage is it's inability to be detected. Modern-day military submarines go to extraordinary lengths to enhance this capability, as for a submarine there is nothing worse than being seen. Once detected, submarines are very vulnerable - a simple torpedo (nuclear or not) or modern depth charge would destroy it easily, as it cannot go very fast, cannot manoeuvre and it has only very limited countermeasures. It is such that even knowing the general 'area' of a submarine means it defences are compromised. Dependant on range, Active Sonar systems can detect modern day submarines easily. In fact, modern-day submarines use 'Passive' Sonar (ie. sonar that does not send any signal) because to send any sonar signal would reveal its location. Efforts include Anechoic tiles to absorb sound, submarine shapes designed to reduce turbulence, dampeners utilised to reduce engine noise. A submarine that does not have the advantage in stealth may as well be a surface ship, which are much cheaper and safer - or an aircraft, which are much faster. An organic submarine would therefore be better than a mechanical submarine if it enhances its stealth capability. There are many ways to do this: * Organic passive sonar signatures can confuse detection systems. The software on a listening device may require upgrading and testing to adapt to the organic signature of your creature, giving it a short but vital advantage before the software is upgraded (perhaps your creature can alter its acoustic signature further if this happens). * Propulsion is one of the major ways to detect a mechanical submarine. Propellers create rythmic pressure waves (or a 'wake') which can be detected. Your organic creature may use much slower, smoother sideways movements to propel itself forward more silently and with little wake. * Any metal on submarines can be detected by specialised aircraft. This is a major strategy of Anti-Submarine Warfare. An organic creature, however, has no metal components that can be detected via Magnetic Anomaly Detection, and this alone would severely disrupt ASW destroyers and aircraft techniques to detect them. * Another aspect of warfare is also intelligence and defence procurement. In other words, Stealth of a submarine is not just in the object itself, but in the secrecy in which it is designed, the disclosure of any manufacture of its parts. These are closely kept secrets. By having (presumably) a breeding programme for your creatures in a single location, you reduce the potential leaks of intelligence that sometimes occur with thousands of subcontractors and suppliers that would severely affect the ability of the submarine to remain secret. Perhaps your breeding programme could occur in just limited underwater pens, known only by an elite few. [Answer] The idea of bio-ships is old in SciFi. One of the better examples from my generation was "[Moya](https://farscape.fandom.com/wiki/Moya)" from the TV show Farscape. Advantages? They can heal. They can react. They can maneuver. Disadvantages? They can be poisoned, infected, disabled more easily, and killed - all of which (pro and con) were considered during the program's run time. Disabled is the most contentious. But a living thing is worthless without all those nerves and a brain that keeps a sense of self-preservation going. In other words, the creature must necessarily feel pain and react to protect the entity based on the nature and severity of that pain. This is a massive disadvantage — and the more you remove it as a reality of a biological ship the less you have a biological ship and the more you have a wooden or steel ship that's just a bit more squishy. However, the only answer to the question "would that be workable in a realistic setting?" is NO! because we don't know how to build bioships and therefore have no experience with what could go wrong. We literally have no way to realistically judge the answer without you completely describing what a "realistic setting" is. As for advantages. @Flox is right that stealth tops the list (maybe, as I think about it, you still have heat, motion, displacement...) but you also have... * Fuel, the bioship can eat like whales by straining shrimp, etc. You wouldn't need to bring fuel along. (Disadvantage: rather than fuel tanks you have a digestive system, which can result in indigestion.) * Depth, I can imagine a biological ships achieving greater depths than beer cans. Additional disadvantages: * Putting hard, rigid things inside a biological entity tends to bruise, cut, etc. the biological entity. This means you don't really have rooms with hard floors and walls. You have cavities that must accommodate the motion of the creature. Moving people around might actually be a chore. * Cells decay, die, and even rot. There would be no cavity that wasn't constantly shedding cells in one form or another. Yuck. * Defecation, which (unlike electricity-powered subs) would be pretty easy to track. [Answer] ## Senses Vision: while we think of sonar as clicks-and-returns, or passive listening for voice patterns, dolphins can actually "see" for miles by broadly illuminating a space and listening to the reflected sound. [![enter image description here](https://i.stack.imgur.com/Cth7Gs.jpg)](https://i.stack.imgur.com/Cth7Gs.jpg) Scientists have attempted to reproduce this, and generated this image of a diver. However, we know this reproduction isn't complete enough - dolphins have demonstrated the ability to discriminate between colors at depth. We have side-scanning sonar that reproduces this quality of sonar details in 2D. To the best of my knowledge it hasn't been done in 3D. Hearing/Touch: many aquatic animals have a [lateral line](https://en.wikipedia.org/wiki/Lateral_line) system that allows per detecting pressure changes (very low frequency sound) < 100 Hz at long ranges. Smell/Taste: sharks can detect chemical concentrations in a [few parts per billion](https://www.sharkophile.com/2020/05/04/sharks-sense-of-smell-vastly-overrated/) ## Reaction Times In a mechanical vessel, this information is processed by software and put up on a display for a sensor operator to interpret. This is relayed verbally (taking a few seconds to communicate and understand) (or electronically) to a captain who uses this low-resolution data to make decisions, which are reported back verbally (taking a few seconds) to pilots or weapons operators. By contrast, in one integrated animal : the sensor operator, captain, and pilot are the same mind. Decisions are made in tenths of seconds, rather than seconds. ## Speed The [typical fish](https://www.thoughtco.com/worlds-fastest-fish-2291602) (44 mph / 70 kph) is as fast as than the world's fastest submarine, the [Soviet Alfa](https://en.wikipedia.org/wiki/Alfa-class_submarine) (76 kph). Some fish can swim at double this speed (80 mph / 130 kph) and literally be at their destinations before satellites notice they've gotten under sail. ## Depth The deepest diving fish can reach depths of up to [8 kilometers](https://www.livescience.com/5130-deep-diving-fish-set-surpising-record.html), with little risk of implosion. And they can dive quicky. [Answer] Invisible to Sonar Like all animals, a bio-ship is mostly water. That means Sonar waves will travel straight through it rather than bouncing off a hard metal craft. This makes the bio-ship invisible to sonar. Bonus Advantages (1) Ship can function with fewer crew. It can both pilot and repair itself so fewer people needed to do this. (2) The ship can navigate its way down a trench much more easily than a normal vessel. (3) Fire Hazards: Fire is the worst thing that can happen in a submarine. Fortunately if your submarine is mostly made of water the fire does not spread so fast. ]
[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. Often, when I'm building a world, I want to start out by determining some of its key properties. Maybe I'm trying to calculate a habitable zone, or figure out how long a year would be on a particular planet, or determine what the sky would look like. To tackle any of these, I need to know a bit about the star - or stars - it's orbiting. Some of the time that's easy. As [someone brought up last week](https://worldbuilding.stackexchange.com/q/175176/627), for some stars we can do some approximations, and a couple minutes and a back-of-the-envelope calculation will get me the answer I need. But there are other cases where it's not so easy. Maybe I want my planet to be orbiting an aging red giant, or maybe a massive star in the early universe which would have been, in terms of metallicity, nothing like the stars we know today. The analytical approximations star tto break down a bit in these cases. One workaround I like to do is find pre-tabulated grids of stellar models. Stellar astrophysicists spend a good deal of time simulating evolutionary tracks and generating populations of stars, and they do numerically - much, much, much more accurately than I could ever do. They often create grids of results, which list the properties of a particular range of stars. For instance, one group might be studying red dwarfs, and they might generate grids of M1V dwarfs, M1.5V dwarfs, M2V dwarfs, etc. This means I can be lazy and just look at a particular set of models, if they're posted online. I can take my pick of metallicities, rotation, masses, ages, etc. If a star of the mass and age I want isn't listed, I can crudely interpolate between grid points. It's much better than me crunching numbers to get results that will be off by a factor of 2 or 3. I know of a couple sets of models I like to use, and I'm going to write an answer listing them, but I'd also like to find out about other grids, as a [worldbuilding-resources](/questions/tagged/worldbuilding-resources "show questions tagged 'worldbuilding-resources'") question. What sets of grids of stellar models are freely available? To narrow things down a bit, here are my requirements - I'd like as many to be fulfilled as possible: * They should include main sequence stars of masses $0.08M\_{\odot}<M<8M\_{\odot}$. * They should contain some models of solar metallicity and some models of the metallicities of Population III stars. * They should also have evolutionary tracks for stars in the above mass range through the asymptotic giant branch phase. * Simulated spectra would be amazing, if possible. * They should also be free to access - I can get some with my academic credentials, but ideally these should be available to everyone. Taking into account rotation would be nice, but it certainly isn't required. I'd also appreciate grids with high-mass ($\geq10M\_{\odot}$), low-metallicity Population III stars, but that's rather unrelated to the stars I've mentioned above, which won't end their lives as supernovae. [Answer] As promised, here's my answer, covering the grids I sometimes use. ## [The Geneva Grids](https://www.unige.ch/sciences/astro/evolution/en/research/geneva-grids-stellar-evolution-models/) These are extraordinarily comprehensive - they actually meet all of my requirements and then many more. [Lejeune & Schaerer 2001](https://ui.adsabs.harvard.edu/abs/2001A%26A...366..538L/abstract) go into some of the nitty-gritty details, but the models have been updated even more in the last two decades. Here are some of the features: * They cover the range of $0.8M\_{\odot}<M<120M\_{\odot}$, and metallicities from $Z=0.001$ to $Z=0.1$, although the metallicity steps aren't too fine. * They do include pre-main sequence evolution in a couple of the grids - not usually something I worry about, but helpful in niche cases. * They have some high-mass, extremely low-metallicity models which are actually really useful to me right now. * Some grids include rotation or mass-loss. * Yes, there are indeed some spectra, a feature I'd forgotten about! These are usually my go-to simply because of how thorough they are. ## [MESA Isochrones and Stellar Tracks](http://waps.cfa.harvard.edu/MIST/) MESA is a well-known stellar evolutionary code, and a group at Harvard (MIST) has put together a set of isochrones and evolutionary tracks. I'm less familiar with these, but they have a wider mass range than the Geneva models (going up to $\sim300M\_{\odot}$, and apparently down to brown dwarfs, below the hydrogen-burning limit). I've found them slightly harder to query and find, but I chalk that up largely to just a lack of experience. Features: * A wide mass range, as I noted above. * Good metallicity coverage. * An online interface to interpolate between models, which seems extremely helpful to the worldbuilder on the go. I think the interpolator stands out the most for me. It's definitely a handy tool. Recently, I was introduced to a service called [MESA-Web](http://mesa-web.asu.edu/), which is used as an educational tool for stellar modeling. Effectively, MESA is run on a someone else's cluster. It does take some time for the code to be run; the code itself will run for a maximum of four hours, but the queue isn't short, so prepare for possible wait times of about a day. It's designed for educational purposes, and etiquette is to only request 1-2 runs at a time, but it can be handy if you want to see how a given star evolves - at least in the early stages of its life; my $M=0.1M\_{\odot}$ red dwarf only evolved through $\sim$1 million years in four hours. I'd recommend MESA-Web if you want to get a taste for what MESA can do. ## [Dartmouth Stellar Evolution Database](http://stellar.dartmouth.edu/models/) I've only started playing around with this recently, so I can't say much about it, but it looks to have a decent set of isochrones and covers a wide range of photometric systems (Gaia included), which might be an advantage over Geneva and MIST. There are also some Fortran codes allowing interpolation in luminosity and metallicity. ]
[Question] [ My world has two races of mammalian mermen, one of which are somewhat monstrous and I'll call them "Abyssals" in this thread. I really want the Abyssals to 'breathe' underwater, as well as being able to walk on land, so as a rule they have to have recognizable human anatomy like two strong legs rather than a fish tail. Also, I want this to be the result of evolution rather than mystical creation or genetic engineering, so I'm not so hot about radical changes like giving them gills. I had an idea that they should be covered in barnacles and similar parasites, and building on that, maybe some of these parasites have become symbiotic. One species (doesn't have to be barnacles) has developed a sort of intravenous connection with the host mammal, so that it transmits oxygen into the Abyssal's blood, that way the Abyssal can remain underwater for longer, which allows the IV-barnacles more access to food, assuming they don't just feed on the Abyssal's blood. How plausible is this symbiosis? If one Abyssal is covered in about a hundred barnacles, would it allow the Abyssals to remain underwater indefinitely, or only extend the amount of time before they need to surface for air? [Answer] ## Barnacles are super cool creatures! But they're not quite a replacement for gills. This question really comes down to "how much oxygen can these barnacles reasonably extract from the water?" Fortunately, we have barnacle biologists (er, cirripedologists, if you're curious) who have studied them extensively and were kind enough to post their results online where some digging in Google Scholar turned them up. [Crisp and Southward](https://doi.org/10.1098/rstb.1961.0003) published a paper in 1961 extensively documenting the feeding habits of barnacles. They note five different feeding patterns, recorded via stroboscopic cinefilm and suspended in a low concentration of milk. In the latter half of the paper, they discuss whether or not it's possible for the barnacle to obtain enough oxygen to survive by estimating the amount of water flow through the mantle cavity. The relevant passage is below because the article itself is paywalled (although purchasable for, cover price, 15 shillings): [![Figure from Crisp and Southward, 1961, demonstrating water flow during barnacle feeding](https://i.stack.imgur.com/D7CdR.png)](https://i.stack.imgur.com/D7CdR.png) The number they come up with is 0.1 liters/hour, although they concede that > > "These figures are all very rough estimations because of the large errors that may have been introduced by the irregular shape of the jet aperture and > other unavoidable approximations" > > > So, how does the barnacle's uptake of O2 compare to your Abyssal's oxygen needs? Assuming that they have similar metabolisms to humans, we can ask [NASA for an estimate of human oxygen consumption](https://ttu-ir.tdl.org/handle/2346/72911), which of course they have [precise numbers for](https://www.nasa.gov/pdf/146558main_RecyclingEDA(final)%204_10_06.pdf). A human living in space requires 0.84 kg of oxygen per day - apparently the same amount as required on Earth. The last piece of the puzzle is the conversion between liters of seawater and grams of dissolved oxygen. This is another well-documented data point, and strongly dependent upon the environment. Typical measurements of dissolved oxygen in seawater range between essentially zero in anoxic zones to upwards of 20 mg/L under circumstances like algal blooms. You can play with real-world data via [NOAA's World Ocean Atlas](https://www.nodc.noaa.gov/cgi-bin/OC5/WOA09F/woa09f.pl?parameter=o), but 10mg/L was the maximum that I found (surface ocean near the poles). Now, this turns out to be one of those lovely problems where we can just multiply the units straight across. As a best-case estimate, a hundred barnacles could produce: $$\frac{100\ barnacles}{Abyssal}\\frac{0.01\ g\ O\_2}{liter\barnacle}\\frac{0.1\ liters}{hour}\\frac{24\ hours}{day} = \frac{2.4\ g\ O\_2}{Abyssal\day}$$ That's actually not as bad as I feared! We're off by about two and a half orders of magnitude, between the 840 g/day demand and the 2.4 g/day production. But wait, what if these Abyssals are really* encrusted with barnacles? We started out with the 100 barnacle estimate as an initial guess, but that wouldn't even come close to covering a human entirely. The surface area of a human is around [2 square meters](https://www.calculator.net/body-surface-area-calculator.html?csex=m&bodyweight=180&bodyweightunit=pound&bodyheightfeet=6&bodyheightinch=0&bodyheight=&x=66&y=25), and the footprint of a barnacle is something like 12 square centimeters. If we coated a human body in barnacles, we'd get an oxygen production rate of: $$\frac{2 m^2}{Abyssal}\\frac{10,000\ cm^2}{m^2}\\frac{barnacle}{14\ cm^2}\\frac{0.024\ g\ O^2}{barnacle\day}=\frac{34\ g\ O\_2}{Abyssal\day}$$ Darn. Still off by a good amount, although we should also be aware that this is a best-case scenario. I added a few square centimeters to the barnacle footprint to account for [optimal packing](http://datagenetics.com/blog/june32014/index.html) and areas that you don't want encrusted, but we're still working in pretty much ideal conditions. Time to bring out the big guns. [My other answer](https://worldbuilding.stackexchange.com/questions/96017/anatomically-reasonable-respiratory-system-for-human-derived-merfolk), about the plausibility of mermaids, discusses nudibranchs fairly extensively. These stunning critters are literally defined by the beautiful plumes they have on the surface of their bodies, used to maximize surface area and therefore gas exchange. However, many soft-bodied organisms in the ocean breathe in a similar way, some of which are parasitic. Marine flatworms are amazing creatures. While many of them live a sedentary lifestyle, others actively [swim through the sea](https://www.google.com/search?tbm=vid&q=swimming+flatworm&oq=swimming+flatworm), and still others operate as parasites. It's imaginable that a symbiosis develops between an ectoparasitic flatworm and an early ancestor of the Abyssals. I don't have hard numbers for you because estimating gas exchange rate is the worst, but a few flatworms would provide the same oxygen uptake as many barnacles. This becomes even more plausible when mechanisms like kleptoplasty* come into play: a feeding strategy in which algal chloroplasts are stolen and used by the predator as a source of food and oxygen. Although only documented among the [sap-sucking, solar powered, shell-less sea slugs](https://en.wikipedia.org/wiki/Sacoglossa), it's entirely plausible fiction for flatworms to have developed this trait as well. The other advantage we can leverage here is that humans use a significant portion of our energy simply to stay warm. This is slightly dangerous territory, because we're already assuming a best-case scenario of high oxygen content and minimal metabolic effort, which are in fact inversely proportional because oxygen dissolves better in cold water. However, there are places in the ocean where the water isn't all that cold - hydrothermal vents and the [misnomered](https://english.stackexchange.com/questions/314190/word-for-something-being-a-misnomer-misnomerous-misnomatic) cold seeps come to mind. The deep sea where these thermal vents are found also usually has the advantage of being below the oxygen minimum zone, where O2 levels return to surface concentrations. Finally, mammals in the ocean tend to be covered in a thick layer of blubber to help with thermoregulation. Your Abyssals will be much happier if they're chubby - which in turn would also increase the surface area for respiration! So our best bet will be chubby, deep sea, spa-loving, barnacle-or-flatworm-encrusted creatures who like to hang out near hydrothermal vents. Huh, that [sounds a little familiar...](https://www.youtube.com/watch?v=eTlZjK4VvmY) [![Gray whale!](https://i.stack.imgur.com/1xg9M.jpg)](https://i.stack.imgur.com/1xg9M.jpg) [Answer] Depending on the history of your world, gills may not be out of the question. It would just require terrestrial species to continue to be tied strongly to the water (lungs developed from swim bladders, but gills stuck around because the animals still used them). This would mean that all mammals on your world have gills, or the mermen are from a specific lineage that kept their gills while the other species lost them (akin to marsupials or monotremes on Earth). ]

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