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[Question] [ General Urk is commanding an army of orcs in a pseudo-medieval low-magic fantasy world. Orcs are basically like humans in terms of smarts and toughness and equipment, but with one key difference: culturally, and biologically, they are completely okay with cannibalism and anthropophagy. Eating victims, eating each other, it's all fine. No worries about prion diseases or whatever, their immune systems can just fight that right off. Urk isn't necessarily evil, but he wants to win wars, and he's ruthlessly pragmatic in that aim. How might he best leverage his troop's culinary predilections to that end? Would it make much of a difference to his campaign plans? [Answer] There are moments in historic warfare, where commanders leave their logistic supply chain, and operate without resupply. What they gain is they move faster. What they loose is resupply. The hope is that with an imminent combat victory you capture your enemies supplies, and feed and equip your army. The risk is you don't win a battle and don't resupply. Suddenly your going to starve, and need to win a battle now. You enter a battle not because its tactically sound, but because you have no choice. If your eating the soldiers you kill, capture, or your own wounded. Making the decision to go without your baggage train is a lot easier, because you resupplied off the battlefield dead. It means that you can break off from your supply lines, with more certainty that combat victory will 100% resupply you. How might he best leverage his troop's culinary predilections to that end? I would expect that an Orc Commanders are more aggressive in their willingness to leave their resupply lines, knowing they will eat the enemy post battle. They would be more aggressively seek battle to maintain resupply. I would expect that a Human Commander are less aggressive in their willingness to leave their resupply lines, knowing that Orc don't carry as much supplies and rely on combat casualties for resupply. They would avoid combat until the Orc army is desperate for resupply, offer up a battle on unfavorable terms to the Orcs, and exploit your advantage to win. Would it make much of a difference to his campaign plans? If the enemy know about this, they probably prepared in some way (scorched earth, poisons, baiting them as above, predict the Orc will move quickly). I am not sure that eating battle casualties will be much different from eating the enemies supplies in the real world. Its hard to see its game changing, particularity if its common knowledge and the opposition adapt around this strength. [Answer] It depends on population density. Humans / humanoids to be eaten will not be available in the same quantity in all scenarios. Of course war dead can be eaten but it will be difficult to move an army on this sort of food - it is an occasional windfall. The question is whether the army intends to feed itself on the noncombatant populace of the region. Population density has everything to do with this. If you are out in the countryside fighting moving campaigns in open land, the natives will be few and they will scatter. It will be hard to round up enough of them to eat. If however you are like the Mongols and are attacking walled cities in populous areas then you are set. Your orcs round up the populace outside the fortified city and make them serve as slave labor to build fortifications, make arrows etc. Those who misbehave or do not work hard enough will be eaten. For the city and region generally, if your goal is colonization then eating all of the original inhabitants is fine; you want to genocidally clear them out for your colonists and the only reason not to massacre (and eat) them is if you want refugees to stress the neighboring areas not under your control. If, however, you want to conquer the city but some citizens have value beyond their calories then you might need to be careful about who you kill. Or not - if you conquer a city and make jerky of its entire populace, neighboring cities will be eager to come to terms and you can capture them intact and without a fight. [Answer] If their cannibalism and anthropophagy is obligated, you are doomed. After the first campaign where they show their feat of eating humans, what will take to starve them will simply be to evacuate the invaded land. With no humans to serve as food to support them, they will either starve, retreat or eat each other in short time. None of those options ensures holding the conquered land. If they can opt for other foods, they will be subjected to the same strategy anyway: if it helped defeating Napoleon, scorched earth will surely beat them. Therefore you are forced to have a well developed logistic to ensure supplies for long campaigns, or limit yourself to raiding neighboring countries without prolonged permanence. Considering the poor logistic that you can have in a middle age scenario, you are forced to use them for raids. [Answer] Assuming the orc army is on the offensive (as one would imagine orcs would do) as opposed to garrisoning fortresses and being on the defense, the troops are going to spend a large amount of their time on the march, building fortifications and other strenuous activities. The amount of calories needed by a soldier on the march can vary between 5000-7000 per day depending on the distance, amount of equipment, etc. I'll take 5000 as it is a round figure. Assuming orc bodies are similar to humans nutritionally, the body of an orc will contain around 80,000 to 120,000 calories. I'll use the midpoint as the average nutritional output of an orc. That means that a single orc can feed 20 orcs on the march for a day, which is a fairly decent amount. The impact this would have on the army's campaign very much depends on the population density they are marching through, the number of captured prisoners etc. For a 100,000 strong host, they would need to consume 5,000 orcs a day on the march (or probably around 2,000 a day when garrisoned) to meet their daily calorie requirements. This is obviously quite a large amount, so cannibalism could never replace a proper supply line, only supplement it. However, in situations where they have little access to supplies (e.g. a retreating army enacts a 'scorched earth' policy to leave no food behind for the advancing orcs, the army is besieged, with no hope of resupply etc) this would probably make quite a big difference, and allow the army to hold on for as long as possible. For example, if a garrison of orcs is besieged and has run out of food, they could eat the wounded- and then each other- to last as long as possible. If we say that when rationing, 1 orc can keep 50 orcs from starving for a day, they would have to cull 2% of their population a day. The population of the orcs then follows the trend 0.98^x, where x is the number of days after running out of food. If we solve for $0.98^x =0.5$, that tells us that the orc garrison could survive around 30 days using this strategy until their numbers dropped to half the initial number, or around 70 until they were at a quarter strength. That's a pretty significant increase in how long they could last, and gives them a much better chance of surviving until relief arrives. ]
[Question] [ To put it simply. How would the color an eye affect what one could see? I ask this due to watching some of an anime called, "Somali and the Forest Spirit" If I remember correctly in episode 2 the main characters come across two members of an Oni clan. Now, these two Oni visually had eyes similar to humans, but their sclera was not black, but white. That is when I began to wonder how would changing the colors of different parts of the eye affect what one sees, assuming this change isn't merely cosmetic, but in one's DNA, similar to how nocturnal animals' eyes reflect light at night. Please let me know if you need further explanation by commenting. This is the first question that I have asked. Thank you! :) [Answer] Let's go by steps: Size: bigger eyes mean more light can go in, which is why it's common for nocturnal animals to have larger eyes, along with other mechanisms to maximize the amount of light hitting the retina, like the [tapetum lucidum](https://sciencing.com/animals-tapetum-lucidum-8541210.html), which gives the appearance that they're glowing when light is directed at them. Shape: I assume you mean the pupils, unless you mean to talk about the owl's eye "tubes". Here's an image that sums up well: ![enter image description here](https://i.stack.imgur.com/we1N9.jpg) Color: the color of your iris doesn't really change how you see, but it might change how others see you. Colors tend to have psychological effects, so you could say red eyes have a chance of inspiring anger while baby blue might inspire calmness (which is one of the reasons why many monsters are drawn with red eyes). The presence of a large black iris can also be an advantage if you don't want others to know where exactly are you looking at, but can be detrimental in social species, in which the eyes orientation are important to signal certain messages. Commenting on the black (?) sclera (ours is white so I assume you inverted by accident) , I have little to say. I've failed to find animals or humans with similar conditions, but the closest I found was a condition whee the pupil simply covers a large portion of the eye, making it look black. The black sclera might be so due to special pigmentation in this part of their eyes, and I doubt it'd actually change their vision, as the sclera's main purpose os keeping the shape of the eye. [Answer] There is some evidence that brown eyes are better at tolerating bright sunlight and blue eyes give better night adaptation, but it's not on the level of superpowers. The fact that nature hasn't evolved specific different colour schemas suggests there may not be much advantage compared to things like the camouflage effect of having eyes matching your fur colour. ]
[Question] [ So in my fantasy world, my Emperor has recently come into control of a declining empire and managed to restore its control over the continent he lives on. This empire, a continuation of previous empires, has had a long history of its armies. This Roman-style army has existed throughout since the founding of the first empire and continued to exist even when the empire was dissolved/fractured. Now here's the problem; this army while powerful had suffered major losses during the Emperor's war to control the empire. The Emperor can restore the army back to its previous numbers however he wishes to reform the army's organization. This is due to the fact that the empire was on a decline against a rising power and was only able to defeat it due to the Emperor's own powers. Thus he wants to reform the army in a way to where it can deal with any situation that it faces whether it be guerrilla forces, mages, monsters. It can adapt quickly to its confines. What should the Emperor do to move his force's in this new direction? --- Now there are some parameters the Emperor must work in: * He has 100 years to work with as he plans to invade another continent * He has no political or social impediments to his changes due to his popularity and his own power * The most soldiers he can possibly have as a standing army is 400,000 * The max tech level that can be achieved is comparable to 15th century Italy/Germany These are the current characteristics of the army: * It is organized in the tactics of the Roman army during the reign of Augustus however there are no slaves * Weapons and equipment are the same standards during Augustus though infantry don't carry pilum * Promotion is meritocratic but there is some bias towards nobles * The gender makeup is 65% men and 35% women * It is considered honorable and righteous for citizens to join but the pay is about just enough to get by in life * 5% is made up of mages/ soldiers proficient in weapons and magic The current organization also as follows: * The army is organized the same as during Augustus up to a legion and then divided between the 9 regions of the empire; each region has a head General of all the legions in a region * The regional generals respond to a General of the entire army who in turn responds to the Emperor * Communications are handled through a magic spell that works like a Star wars communicator; only those from a Legate to the Emperor have access to such a spell either through themselves or from a mage within their units * Supplies are carried over baggage trains of horse wagons or mages levitating them over rough terrain And finally to what the Emperor can't do: * No guns or cannons due to how versatile the magic is * No full-on mage armies as there are spells that prevent magic from being cast * He also does not want to copy the organization of the rising power he defeated; it relied heavily on skirmishing and magic [Answer] "More flexible and adaptable" actually has a name -- professional. You get professional fighting forces through a combination of factors: * Money: Professional forces aren't cheap. Used correctly, though, they tend to justify the expense. * Professional Education: All leaders, from Generals to Sergeants, need academic education throughout their careers. They need to fully understand the tools (units, equipment) that they have available and how to employ them properly in common situations. They also need to understand likely enemy strategies and tactics. * Professional Development: Skill training, combat training, leadership training, unit exercises, staff rotations, evaluations, etc. Leaders need to make their learning mistakes in a training environment so that they are proficient on real battlefields. Promotion should be based on merit and potential, obviously. * Staffs: A proper staff coordinates and synchronizes the fight, conducts intelligence preparation, ensures proper logistics and good order, and prevents the commanders from getting swamped by irrelevant information. Rotating officers through staff positions broadens their experiences and makes them better leaders. They turn the overarching strategy into detailed operational plans with lines of effort and lines of advance. * Specialization: Corps of skilled experts in intelligence and logistics and medicine enhance combat power. They enable smaller units to move faster, strike harder, and to be punch above their weight at being decisive. They focus combat power on useful objectives to further the overall strategy, and identify the weaknesses that the enemy is trying to conceal. * Depots: Stores of replacement equipment and personnel make replacement operations (handled by those staffs) easy, keeping combat power high throughout a campaign. [Answer] The emperor needs to introduce a staff college for training centurions of all ranks to give them a better understanding of strategy, tactics and a wider range of important military matters that could be learnt from a number of selected centurions who had encountered such situations. The training would probably need to last a year or more. In this way new centurions would be better equipped to deal with a wider range of military situations that might be encountered such as sieges, river crossings, logistics, field manoeuvres, assaults on fortified positions, naval transport, communications, under mining enemy positions, construction of marching camps, use of auxiliary bowmen and artillery, etc etc. The emperor also needs to listen to some of his most senior fighting soldiers (such as the Primi ordines) to find out what difficulties they have been experiencing and to address these issues head-on and correct them. There would also be merit in establishing a wide range of auxiliary units from across the empire for specific specialist duties such bridging rivers, night attacks, defensive works, horse archers, heavy cavalry , light cavalry etc. These could then be used in conjunction with the legions by the trained senior centurions to good effect. [Answer] Leave it to his generals Sun Tzu's Art of War is considered one of the defining manual on tactics and strategy, and was written a few thousand years ago. Seeing as that's the case, it's definitely good enough now. To quote the venerable Sun Tzu: > > There are three ways in which a ruler can bring misfortune upon his army:-- > > > (1) By commanding the army to advance or to retreat, being ignorant of the fact that it cannot obey. This is called hobbling the army. > > > (2) By attempting to govern an army in the same way as he administers a kingdom, being ignorant of the conditions which obtain in an army. This causes restlessness in the soldier's minds. > > > (3) By employing the officers of his army without discrimination, through ignorance of the military principle of adaptation to circumstances. This shakes the confidence of the soldiers. > > > (The Art of War, Attack By Stratagem, 12-15; if you're curious. Though I'd recommend giving the entire book a quick read, it's not that long.) The best thing the Emperor can do is to set a stable and meritocratic military, ensure that the generals are loyal, and then permit the generals themselves, who are going to be individuals of substantial military might and knowledge, the autonomy to give all the orders that are necessary. [Answer] Apart from the weapons/'tech-level', when you're working with the army of the late Republic, it's already as flexible as it gets. [The Marian reforms](https://en.wikipedia.org/wiki/Marian_reforms) were implemented exactly to have a standing army, which implies an army that is quick to react, and consists of standard units capable of multiple tasks. Among the weaponry and cycling discipline of soldiers during battle, which helped to keep the soldiers alive and provided the Republic with victory over numerically superior opponents on a routine basis, the army also mastered the skill in altering battle field conditions. Altering the battle field conditions was done via the corps of engineers, that were part of every legion. They would build forts, walls, ramps, blockades, everything to gain maximum advantage over the enemy, which was an important part of the army flexibility. For Romans this altering of battle-field conditions became such a natural way of preparing battle, that often no battle would be given, until a desired set of fortifications/blockades was constructed. This led to sometimes slightly comical situations, where for example, during the Caesar's civil war, Caesar and Pompey would race to build the longer wall for tens of kilometers in an attempt to enclose each other and cut off supply-lines and escape routes at the [Battle of Dyrrhachium](https://en.wikipedia.org/wiki/Battle_of_Dyrrhachium_(48_BC)). The republican army was designed with flexibility in mind. So while you certainly can implement some improvements, when analyzing their defeats (for example at the battle of [Carrhae](https://en.wikipedia.org/wiki/Battle_of_Carrhae)), just copy-pasting them you would already start with something very capable. [Answer] Wargames. Both the tabletop variety, and actual soldiers fighting with blunt swords / nonlethal spells. It allows commanders to try out tactics, it can force people to deal with unexpected circumstances (perhaps with a gamesmaster who comes up with unusual scenarios for them to face), and it can suggest who might be worth promoting. ]
[Question] [ This is a question regarding my little critters that hijack of their victim. By doing so they get direct access to a steady flow of nutrients through the bloodstream and get shelter with optimal temperature and humidity with the added protection of a ribcage. What's terrifying about these little bugs is that you can't get rid of them, because they've highjacked the one organ that keeps you alive. What kind of physiology would a heart parasite have? This question is not asking "would this evolve" as this creature is already very complex, it performs a risky procedure as part of its life cycle on mere instinct, which is not something your typical leech or tick does. A more pertinent question is what kind of body they should have to make this work? They must first burrow into a host without inflicting a life threatening injury. Then they must attach to a still beating heart and drain sustenance through the blood. They might go through multiple life stages like a larva for burrowing and a crab for latching on the heart. What do you think? Edit: The definition of hijack is "seizing" something, in this case that would be the heart. The parasite does not replace the heart itself, but laches onto it. [Answer] Burrowing through safely isn't impossible (though god help the person feeling it). It just has to miss major arteries and release chemicals that will mitigate the damage (blood parasites tend to use anticoagulants which would be a nono here). Once it reaches the heart though, that's when the challenge develops. It needs to anesthetize/sedate its host-victim so that their heart stops completely. It probably only has 2 minutes at most to then consume the heart and attach itself to the large arteries and veins without significant leakage. At this point it can start pumping blood again (perhaps now with some anticoagulants to help with some of the clots that might have started to develop... don't want the host-victim having a stroke). It can also probably wait for the sedation to wear off, there's no need to immediately wake the host-victim. Given the size of a human heart (roughly the size of that person's fist), this still a pretty big hole for the host-victim to heal. They may die of sepsis within the week. It might be a better adaptation if it makes ingress while small... say, the size of a dime or smaller. It then would gestate internally until it was large enough to take over. I would imagine that this is going to be a hellish sensation. If it were to happen to you, the "heart" would no longer obey your nervous system. If you wanted or needed to run, and it decided that it wanted you to commit to a walking pace, too bad. It might even infiltrate the Vagus nerve and alter your apetite or sense of stomach-fullness. It could use it to cause the host-victim intense pain if it wanted to punish it (not necessarily intelligently, just as an instinct). And given how other parasites worked, its method of reproduction would only be more horrific still. All of this is highly implausible from an evolutionary standpoint. Just like all other real parasites. [Answer] As @vodolaz095 mentioned, this isn't something that could happen quickly - @John O's answer points out a lot of the issues that show up there. There is a parasite that does something marginally similar - [Cymothoa exigua](https://en.wikipedia.org/wiki/Cymothoa_exigua). This lovely parasite will sever the blood vessels in the fish's tongue, causing it to die and fall off, at which point it attaches itself to the nub and becomes the fish's new tongue. Obviously, this approach can't work 100% with a heart. Sever the blood vessels to it and you get death. However, a similar approach could work. The parasite, small-ish, enters the host's body, where it finds its way to the heart. At that point, it attaches itself to one or more blood vessels, where it grows. At some point, it is attached to all of the blood vessels, and begins constricting the blood vessels of the heart, which will then atrophy and die while the parasite takes over. This would be a gradual process - I'm guessing weeks, maybe months, instead of days or hours. And it would likely be highly painful - A modern society would have someone go to the hospital for heart pains, get a CT scan or MRI, and it would likely be early enough to remove it. Earlier medicine probably wouldn't be able to do much about it - And eventually, the pain would probably go away as the heart died. I'm not a biologist nor a doctor, but I think that the creature might even be able to react and adjust heart rate depending on things like oxygen levels in the blood, removing or reducing the need for interacting with the nervous system. Additionally, the way this creature pumps blood could be entirely different to how the human heart works, leading to a different sounding heartbeat or even a different-feeling pulse. In the end, once the creature is there, it's in the interest of both it and the host to maintain the host in a healthy way, so beyond the initial pains of heart implantation, it would likely not be noticed and the person would be able to live a normal life. Depending on how you want to go, it could even offer a boost to the host's immune system against things like other parasites and, specifically, blood-borne pathogens. [Answer] First, i recommend to read about [real world parasites](https://en.wikipedia.org/wiki/Parasitic_worm), but, reading it can be quite creepy. If your creature is something like real world worms, it can inject itself into muscle tissue, consume muscle cells and than act itself as [muscle fibre](https://en.wikipedia.org/wiki/Muscle). So, this worm have to link itself to nervous system and blood vessel systems of host, to fully emulate muscles in terms of acting on nervous system signals (constricting, like real muscle fibre) and consuming nutrients in a way muscle fibres does. After some time, this parasite can inject itself in all muscles (including heart) and become main component of muscular system of host. Or, probably, this parasite directly goes into heart. I think, if we took any helminths, and apply some forced artificial evolution for them, its possible to make them evolve into parasites, that can highjack and act as heart after few years they entered host. But highjacking process will be far from dramatic. Possible symptoms - high temperature (immune system tries to deal with parasites), weakness (because parasite eat peripheral muscles' fibres and it have not fully integrated itself into muscles - acting as temporary shelter before parasite enters heart), muscle shackles (parasite is trying to properly bind to nervous system), than - [Arrhythmia](https://en.wikipedia.org/wiki/Arrhythmia) and various issues with heart ( because parasites are slowly consuming and integrating into heard muscle tissue). So, infection process for this parasite is not dramatic, but once its finished, its nearly impossible to remove it from human - >80% of muscle tissues are parasits, if you kill it, human will become paralysed for best outcome, or, simple die of heart malfunction. UPD1: imho, if parasite replaced >80% muscle tissue in heart, and its host organism is still living, we can say parasite "hijacked" or "seized" heart, yes? UPD2: parasite can release various hormones, or act as better muscle tissues giving it host greater strength and prolonging livespan, so, there will be few people who would want to become infected with it, like Olympic athletes in search for new, undetectable doping? [Answer] There's a [species of eel](https://en.wikipedia.org/wiki/Snubnosed_eel) that's been known to burrow inside fish and nestle in their heart as a parasite, long enough that the blood vessels remodeled themselves to pass blood around the fish. They are thought to do so by tunneling into the ciculatory system or entering through the gills and making their way to the heart. Their gut contents suggest they had been living on blood the entire time, and that's how they get nutrients and oxygen. What killed the fish was being caught, not the presence of parasites within them, and there didn't seem to be evidence of an immune response. However, there's evidence that the fish in question were starting to get poisoned by the eel's waste products, so it's debatable how long they could live. It's thought that these eels more frequently do it to dying fish than healthy ones. A more specialized parasite may have a way to get rid of waste and stay attached to the host longer. [Answer] I don't think the energy equations make sense for replacing the whole heart and doing all it's work. You're basically taking up the most stressful job in the body. I'm imagining something like the mistletoe haustorium. Have it creep along the nerves of the heart, slowly devouring and replacing the myelin around them and eventually becoming the hearts nerve structure completely. From there it could use a technique cancer cells use to induce angiogenesis to cause arteries to grow around it, giving it a huge supply of oxygen rich blood to either chow down on directly or to absorb the nutrients from and re-circulate. Many parasites are extremely good at hiding from the hosts immune system and this one has the advantage that, hypothetically, antibodies towards to might cause a horrible demyelinating autoimmune disease like ALS. As a defense mechanism the angiogenesis could create an impossible to untangle mass of blood vessels around the heart that would result in certain death if severed. Other ideas: * It could hypothetically offer some kind of advantage. Maybe it's got better conductance than normal nerves and offers improved reaction time or a heart less prone to ischemic attack. * It could also render its host frail and often breathless or anything in between. * It has the horrible possibility to spread through blood-blood contact, like the contagious cancers that Tasmanian Devils get. ]
[Question] [ Background In a medieval society with minor fantasy elements, a scientifically minded and not-very-ethical character is looking to acquire some strong acid for a "project" of his. He is particularly looking for acids that could burn skin and leave disfiguring scars, such as the concentrated sulfuric or nitric acid used in real-world acid attacks. However, our "mad chemist" villain lives in a medieval period with Middle Age levels of technology, and that means he has two problems: 1. Concentrating the acid into a sufficiently harmful substance. The scientific equipment to safely manufacture and concentrate acids (at least in the way a modern society would do it today) is not readily available at the current technology level. Glassware and common simple tools - such as flasks, medieval-style distillation equipment, and vials - are feasibly available in his lab, but titration equipment, digital measuring equipment and other complex modern tools are not. He could feasibly just boil an acid over a heat source, but the question is whether that would make the acid become strong enough to cause the effects he wants. 2. Getting the materials. To acquire a sufficient amount of material for the concentration process, our chemist would need to find some setting-appropriate creature or animal that produces acidic or basic chemicals naturally - or locate some other natural source that would make sense to exist without being too fantastical, such as a geologically accumulated post-volcanic acid lake. The question Given the details above, how would this character go about: 1. acquiring a source of acid (or the materials to manufacture acid) in a way that is believable for the setting, and 2. creating and concentrating a sufficient quantity and strength of acid - to the point where the acid could burn or physically scar a person - using only basic scientific tools and the equipment that would be available to him in the time period? I am tempted to just handwave this bit of the plot as "he just finds a magical creature that has super strong acid glands and uses that to make the acid," but I want to come up with a clever way of producing it that shows the character's malicious ingenuity and scientific prowess. [Answer] Nitric Acid I mean, this is just one choice among many, but I like the Latin for it (aqua fortis, literally 'strong water'). It's got a pH of 3.01 and is very, very dangerous. Though Latin isn't quite the right language, as this was discovered in the 800s by an Arabic Alchemist, [Muhammad ibn Zakariya al-Razi](https://en.wikipedia.org/wiki/Muhammad_ibn_Zakariya_al-Razi). Preparation is rather easy - superheat a mixture of saltpeter, aluminum salt, and copper sulfate. (I mean, that's one way among many, but that's how Muhammad did it, so that's the one I would recommend. Also, please don't try it at home.) [Answer] If you really want to handwave away all the details, have your character hire or blackmail an alchemist, who already has the knowledge and equipment to make pretty strong acids. Making strong acids was one of the hallmarks of a skilled alchemist, and passed down from master to apprentice. See for example <https://www.thoughtco.com/alchemy-in-the-middle-ages-1788253> . You're not showing off the protagonist's scientific prowess, but you are showing off other skills, such as identifying the right person to go to for help. (Many alchemists practiced in secrecy, especially after their profession was [banned by the Church in 1317](https://en.m.wikipedia.org/wiki/Spondent_Pariter). But of course a secret known by two people only stays a secret if one of them is dead... ]
[Question] [ In a story that I am building, I want to have an elite force of cavalrymen who are totally mute. In typical fantasy settings, soldiers in an army loudly announce their presence on the battlefield (The Ride of the Rohirrim in LOTR, for example. Theoden's army blow horns and yell and scream as they thunder across the battlefield towards their enemy). What I want is the exact opposite of this. In this fictional Empire, soldiers who distinguish themselves are picked out and are offered the honor of joining an Elite Cavalry Force (still haven't decided on a name for them). If they accept, their vocal cords are slashed or otherwise removed/paralyzed to keep them from making any noise. They are dressed in armor that hides their faces and resembles the servants of the God of Death in their religion. The basic idea is that this cavalry force would enter the battlefield, fight, kill, and die, in total silence. The fact that their faces are concealed further removes any hint of humanity, and my hope is that all of this produces an extremely damaging effect on the morale of any enemy forces they might face on the battlefield. What I want to know is mainly 2 things: 1. Given medieval technology, is it possible to slash/remove a man's vocal cords without threatening his life? (The vocal cords are located in the larynx; would not cutting them out also incur the risk of massive blood loss during the procedure?) / Are there other ways to make a man completely silent other than simply training him to be? 2. Is there historical precedent for a similar strategy? I have personally never heard of silent soldiers, and it seems like it would go against the ethos of chivalry/bushido/other regional versions of a warrior's code. Edits: I see a couple different counters to my question, and I'll try to answer them as best I can. 1: Why not just a vow of silence instead of cutting their vocal cords? > > The idea of a vow of silence did cross my mind, but I thought it might be possible that a vow of silence can be broken by a cry of agony. I mean, people can barely win don't laugh challenges, so I would think a "don't scream in pain when somebody stabs you" challenge would be much more difficult. > > > 2: Soldiers need to make noise by yelling and screaming to make them aggressive. > > A fair point. I think the way I would work around this is by using only instruments. The important thing is that the soldiers are silent so the enemy thinks they are almost supernatural beings. Instruments such as war drums and horns could be used to amp up morale before a fight while still maintaining the illusion of the cavalrymen's inhumanity. Plus, you might be able to psychologically condition your soldiers to actually believe that they are the servants of the God of Death. > > > [Answer] 1. Humans can speak without using their vocal chords; it's called whispering. Technical note: sounds produced without vocal chord vibration are called unvoiced. In English, the sounds /p/, /t/, /k/, /f/ and /s/ (and others) are unvoiced; the major difference between them and their voiced counterparts /b/, /d/, /g/, /v/ and /z/ is that the vocal chords vibrate for the voiced sounds. When whispering, the vocal chords don't vibrate, and all sounds are pronounced unvoiced. Try it yourself: whisper "bid" and "pit", "zit" and "sit" and try to hear a difference. (Whispering is not normal speaking at a low volume. It's specifically speaking without vocal chord vibration. One can speak normally at a low volume, but that's not whispering.) Humans without vocal chords are not mute; they just cannot speak loud. 2. The standard medieval way of ensuring that a slave could not speak was to cut their tongue. They were quite good at it, and were perfectly able to cut a person's tongue with very little risk of killing them. 3. Mute slaves, that is, slaves with their tongues cut, were pretty common, especially in the Ottoman Empire. The goal being that, of course, they wouldn't be able to reveal secrets. (It didn't actually work.) Mute executioners were also not uncommon, also especially in the Ottoman Empire. I've never heard of mute soldiers. 4. In western Europe it was not uncommon for monks to take vows of silence. No need for surgery when devotion can work as well. 5. Humans can make noise without using their phonation apparatus, for example by clapping their hands. [Answer] > > The fact that their faces are concealed further removes any hint of humanity, and my hope is that all of this produces an extremely damaging effect on the morale of any enemy forces they might face on the battlefield. > > > Frame challenge: As pointed out in many comments, a band of mute knights is going to have a terrific effect on a battle field, but not in the direction you hope. Funerals are silent, celebrations are loud. When the supporters of a team want to protest against the team, they usually stay silent within the stadium. If you have seen 300, you probably have felt the chills over your spine when Leonidas' soldiers shout their war cry. Shouting, taunting, making noise, is an effective way of attacking the enemy without physical contact. Silence is a sign of submission, why would you want to give your opponents the psychological advantage of feeling superior? It would be different if it was a group executing a covert operation: in that case the silence play at your advantage, because the enemy sees casualties without noticing any sign of attack, and panic can ensue. But that's not the case for a group of knights riding horses which are, already on their own, noisy. [Answer] We had a Japanese-Americans unit in WW2 who in order to invade a very dangerous base had to do so climbing up a steep cliff in total silence not an issue until you factor in it's night time and the cliff face was very prone to give way and they'd also need to fall to their deaths in silence. They vowed to do this and take the fort. As one by one they fell not a sound beyound the crumbling rocks was heard. Those who made it to the top succeeded in taking the occupied fort from the Japanese. The point? As others have mentioned you don't need to cut your men's vocals to keep them silent give them vows, dishonor, and other things they can speak in the base or at specific times and use sign language, taps, or other things if writing isn't allowed. I get the idea that these people are suppose to be super stealth so muffle the horse's hooves with sacks and if you have carts do the same to them that is a viable stealth method of old. The soldiers are either killed by their CO for speaking or something else is done to mar them and toss them out of the force. Its basically what incentive is there for these people to be in this group as opposed to others? How does this benefit their families more then just pride? These people are also scouts, infiltrators, and the like I'd say not the best for front line combat unless you're also doing the immortals army strategy as well which breaks somewhat the Knight Company aspect. Your war spooks have a limited use and what happens if direct fast combat occurs? They can't shout to one another for aid, cover, or encourage or direct others to coordinate their attacks is their plan in case of discovery to always go after the goal? Or is it whomever has the opportunity is to go forth and complete the goal? Leaving those pinned down unaware the goal has accomplished or failed? It's not impossible to do this unit its just those details and the missions they undertake need to be well constructed. Do they need/have back up plans if things go horribly wrong and what is the rules for how or when they can or must break their silence? [Answer] Would it be safer to precisely cut the nerves controlling the vocal cords, rather then cut the vocal cords themselves? A small an precise cut is easier to manage as an injury, than the risks in wriggling a sharp blade down someone's throat. Your leaders could have discovered this with a lucky survivor of an arrow or blade to the throat. ]
[Question] [ So, here's the premise- in this alternate 'woodpunk' historical timeline, primarily focused upon Japan, someone stumbles across this development far earlier on, in the mid to late 19th century (as opposed to only doing so in the last few years, as they did in real life)- first, through the discovery of 'nano-wood' (or whatever it's known as in this timeline- see below for further details), with further experimentation resulting in the consequent discovery of the other derivative 'super-wood' materials before the start of the 20th century. How massive an impact do you feel that the discovery and patenting of these industrial process, and the production of these 'super wood' variants, with all of their remarkable properties, would have had upon the world? How radically different might the technological and historical development of this 'Woodpunk' Alternate Timeline be, compared to our own? And with this discovery either made by, or patented and exploited to its full potential by, one of the Satsuma Fifteen students (besides the only member of the group to achieve lasting success and fame in our timeline, Godai Tomoatsu), who got scholarships at UCL courtesy of Thomas Glover facilitating their trip in 1865, how much could you envision this changing the course of world history? Last year, scientists at the University of Maryland reported the development of a simple and effective industrial process, purportedly capable of directly transforming bulk natural wood into a high-performance structural material, with a more than tenfold increase in strength, toughness and ballistic resistance, and with greater dimensional stability; as strong as steel, but six times lighter (comparable in weight and density to aluminium). First, natural wood is boiled in an aqueous mixture of sodium hydroxide and sodium sulphite ('white liquor', the same mixture as that used to convert wood chippings into wood pulp for paper in the Kraft process, and its precursor process, developed and used in England during the Napoleonic Wars), before being heat-compressed; resulting in the total collapse of cell walls, and the complete densification of the natural wood, with highly aligned cellulose nanofibres. This relatively simple, low-tech and inexpensive two-stage process has been shown to work on practically all varieties of wood; and the finished material, which the scientists dubbed "super wood", isn't just strong, tough, and light, but is also impressively dense, resistant to compression, hard and scratch-resistant, as well as even being inherently flame-resistant, and protected against moisture. And it can also be bent and molded at the beginning stage of the process, into whichever shapes may be required. Regarding the limitations, the most comprehensive report on the material's capabilities and limitations can be found here: <https://www.researchgate.net/publication/322991664_Processing_bulk_natural_wood_into_a_high-performance_structural_material>. They reported a maximum tensile strength of 587 MPa (placing it in the same bracket as materials like stainless steel, CrMo steel, aluminium alloy and brass in this regard, and presenting a massive increase from the 46.7 MPa strength of the natural untreated balsa wood samples), and a linear-elastic fracture toughness (KIscc) of up to 41 MN/m3/2 (higher than those of aluminium and aluminium alloy, and around 82% that of 4340 Alloy Steel). It's also got an impact toughness of roughly 11.4 J/cm2 and ballistic energy absorption of roughly 6kJ/m. The scratch hardness and hardness modulus of the densified wood are respectively 30 times and 13 times higher than those of natural wood. In its weight, density and impact resistance, the 'superwood' is comparable to the toughest grades of polycarbonates, which is the material of choice for bullet-proof glass and shields IRL. But it's also roughly ten times stronger, harder and tougher, and more fifty times as scratch resistant, as well as having a substantially greater resistance to temperature fluctuations- especially at extreme low temperatures, but with a far higher combustion/melting point as well. With far less warping and deformation caused by impacts, and of course, far cheaper (since it literally grows on trees and all). Along and perpendicular to the grain, the flexural strength of the densified wood's about 6 times and 18 times higher than that of natural wood respectively; and while the compressive strength of the densified wood's about 5.5 times higher than that of natural wood along the growth direction, this increases to become 33–52 times higher than that of natural wood perpendicular to the growth direction (translating into a relatively consistent compressive strength of roughly 300-350MPa regardless of orientation, roughly twice that of mild steel). We do know that the treatment process begins by removing the lignin from the wood, before the wood is compressed at boiling point (roughly 100 degrees Celsius), compressing its cellulose into closely aligned anisotropic nano-cellulose fibers, and reducing its thickness by as much as five times in doing so. The key in the entire process, the paper explains, limiting said material, is the concentration of lignin; “too little or too much removal [of lignin] lowers the strength, compared to a maximum value achieved at intermediate or partial lignin removal. This reveals the subtle balance between hydrogen bonding and the adhesion imparted by such polyphenolic compound. Moreover, of outstanding interest, is the fact that that wood densification leads to both increased strength and toughness, two properties that usually offset each other,” At the end of the process, the compression of the fibers catalyses extremely strong hydrogen bonding, which is what gives the super-wood its super strength. And there were also a couple of variations of the same process, which yielded similarly lucrative end-products. For instance, by increasing the length of time they soaked the wood in the aqueous mixture of sodium hydroxide and sodium sulphite, thereby removing all of the lignin and most of the hemicellulose, and by cutting out the thermal compression stage, reducing the industrial process to a single stage, they created another material which they dubbed 'nanowood'. Lignin is an excellent conductor of heat, and without it, the 'nanowood' became a super-insulator, providing slightly better thermal insulation than Styrofoam. With an anisotropic structure and the nano-cellulose fibers bundled together in parallel, just like the 'super-wood', heat can travel up and down the fibers with ease, but can't easily cross them, particularly because of the air gaps left after all the woody filler (lignin and hemicellulose) was removed. It also turns pure white, allowing it to reflect incoming light rather than absorb it (which also helps to block heat). On top of that, the 'nanowood' was also far lighter than the untreated wood, and while markedly weaker, only retaining roughly 25-30% of its strength, it could still withstand pressures of up to 13 MPa- making it into the compressive strength range of regular concrete, 50 times higher than insulators like cellulose foam, and more than 30 times higher than the strongest current commercially-used thermal insulation materials, making it one of the strongest super-insulating materials known. Yet another derivative material was created by immersing the nanowood in acrylic or epoxy, allowing it to soak in and fill the empty channels; resulting in a material that was almost completely transparent, whilst still retaining most of its super-insulative properties, as well as being 5-6 times stronger than the unimpregnated nanowood (1.4-1.7 times stronger than the original untreated hardwood), and completely shatterproof. So, any thoughts? [Answer] The most obvious alternative history difference with these two types of lignin-reduced woods would be: It would replace fiberglass. Especially the "nanowood" as insulation, and as a resin-filled shock resistant building material. Since wood can not be poured, extruded, moulded, drawn, blown, welded, or cast, it would have a disadvantage to materials that can be, when these construction techniques are called for. However, wood can be cut, joined, drilled, routed, nailed, screwed, bolted, and, in the case of densified wood with its higher strength and heat resistance, even riveted. It would have a clear advantage in these circumstances. It would also allow for larger wooden ships. Trans-oceanic travel would be more reliable. Perhaps the Titanic would have been built from densified wood, and built a decade earlier. The fire in its boiler room might have raised more concern, though. Not as much concern as a ship built from non-densified wood would have raised; densified wood is more fire resistant than modern treated woods, but it's still hydrocarbon based, so it will eventually burn. (Titanic's boiler room was on fire from about a week before its maiden voyage to the day before its collision with the iceberg.) Aluminum might not be the big building material that it is now, but it has properties that aren't found in wood: Electrical conduction. Yes, it's terrible compared to copper, but aluminum is highly resistant to the elements. In high voltage, long distance cables, aluminum works good enough and is low maintenance enough to be more cost effective than anything else. Aluminum will be put to work in aerospace industries, as well; especially when the material can't be porous at all, such as the skin of a space capsule. Densified wood also wouldn't replace aluminum cans for carrying drinks or many corrosive materials. However, it might be used to contain materials that react to aluminum, such as mercury (though I suspect that plastic or less porous hydrocarbons would be a better choice). Once people figure out how to produce aluminum in bulk, it will be just as cheap as it is today. It might take a little longer for the technology to reach that level, due to lower demand, but the space race and electrical grids will have solved the most major technological hurdles for refining aluminum cheaply. The main competing building material to wood is concrete; the mixture of aggregate (loose stones) with water and cement (often powdered lime). Concrete has been around for over 2,000 years, and is partially responsible for the wealth of the Roman Empire. Concrete has a compressive strength that surpasses even low-lignum densified wood... however, concrete has a poor tensile strength. With a ready source of densified wood just before the steel boom, reinforced concrete could be made with densified wood dowels rather than steel rebar. Rebar is easier to bend in the field than wood is, and so could be turned into a supporting mesh for very high strength construction like skyscrapers and bridge pylons. However, in construction that does not need specially shaped rebar, densified wood could be a cheap alternative to steel. Concrete does have one major advantage over wood products (and every building material): The raw materials are everywhere that there are humans. Humans love to build population centers around rivers, and riverbeds (whether current or historical) are great places for cement deposits. Wood is a bit harder to get everywhere, as many people live in desert, tundra, and grassland biomes. Artificial forests can be planted near cities, much as farmland tends to ring cities, but the further any building material has to be transported, the more expensive it is to build with that material. Low lignum wood probably wouldn't affect plastic production much, as wood can't be moulded, cast, or extruded. Nanowood could be used with plastic for various lightweight applications, though. It would be especially superior to styrofoam in this respect, as nanowood is heat resistant, so could have plastic moulded or extruded directly onto it, unlike styrofoam. One final effect, and this is far more speculative than the rest of this answer: Forests would have switched from an exploitable commodity to a precious commodity much sooner. There would still be logger barons making deals with corruptible politicians, but public sentiment would have turned sooner. The result would be a quicker turnaround on reforestation efforts, and sustainable forestry initiatives. If the rest of the world develops much the same, then the extended use of low lignum woods could have a (small) offset on global climate change: Increased usage of new wood would lead to more logging. In a tree's full lifecycle, it is a net carbon sink only for its quick growth period, during the first 10 to 20 years, depending on species. After this, a tree is carbon neutral until its death, when decomposition or a forest fire releases its carbon back to the environment as CO2. By harvesting a tree when it reaches maturity, the carbon is sequestered from the environment and, in low lignum wood, this carbon is much less likely to be released in the form of CO2, as it would likely find its way to a landfill, offsetting the carbon released by burning fossil fuels. Admittedly, this is a small offset, probably in the factor of single-digit percentage points. As far as patents are concerned... It's only since the advent of modern global free trade, where significant numbers of goods can be produced in other nations and find their way into the daily lives of the majority of your nation's population, that governments were able to enforce patents beyond their borders. The single largest possible patent enforcement before global free trade could have been: The British Empire might have granted a monopoly to the East India Trading Company, so Commonwealth nations might have a harder time trading these products beyond their borders, but they would be largely free to exploit the technology once they have learned of it. [Answer] The most obvious difference between OTL and the "woodpunk" world would be the importance of forestry and the handling of forests. In the 19th and early 20th century, forestry was more akin to strip mining, with enormous lots clearcut and then left to regrow on their own, often with little or no attention paid to the process by the loggers. This was somewhat mediated in forests that were actually owned by forestry companies (they had incentives to reforest), but government land or land being leased would be stripped of forest cover and then left. This would have some obvious problems with erosion and related problems with watersheds, wildlife, farming and so on, but so long as the "timber barons" could buy and sell legislators, they would not really be very interested in solving these problems. The other obvious issue would be that all the easily accessible forests would be rapidly cleared, leading to such possible contrafactuals as companies making overtures to the Russian Empire to clearcut Siberian timber on a scale vastly larger than happened in OTL, with a concurrent increase in both population and infrastructure to support these logging efforts. This might also have some interesting side effects further downstream. When Elizabethan England reached "peak wood" in the late 1500's, the resulting shortages in good quality timber for ship building, charcoal production (charcoal was the preferred fuel for smelting metals) and other construction impelled a search for substitutes. Coal mining rapidly expanded through the 1600's to replace charcoal, and England sponsored expeditions to settle the New World partially to exploit the forests for shipbuilding timber. A similar process might take place as forests are stripped away and people begin to realize that it will take between 50-100 years to regrow the forests. Aluminum production would likely have been stalled for decades as inexpensive wood products filled that niche, so the widespread introduction of Aluminum might not begin until the 1920's or 30's. Until then, Aluminum might still be as expensive as gold (an Aluminum pyramid topped the Washington Monument to symbolize its value, and aluminum utensils were sometimes found in the sideboards of very wealthy people to demonstrate their wealth). Aluminum aircraft, lightweight aluminum stampings or engine blocks would therefore be pushed back several decades as well. Other mining industries might suffer the same effects. The use of wood for other puropses like paper and furniture might also be affected by the high demand for structural super wood. Finally there would be a surge in interest and support for the forestry sciences, so in places where industry owned the forests, or places where governments derived much of their revenues from timber, advanced forestry techniques, hybridization of tree stocks and other innovations would be supported. This would gradually spread, as land owners and other governments sought to remediate areas that had been clear cut. [Answer] No Major Differences Would Occur Here's the important thing - both nanowood and superwood are not inherently better than other materials for building things. They don't posses any qualities that aren't present in other materials, they just happen to be cheaper to make. And then we have the fact that deforesting is a problem we're currently facing (and making decent headway on in some places) and that was without the ability to basically turn trees to iron. And then there's your stipulation - it was discovered by a Satsuma student and taken back to Japan. If that did happen, it should be noted that it's unlikely anyone else would know it - even the Meiji era government, which was fairly tolerant of foreigners comparatively, wasn't that willing to share secrets, especially something with that power. And it wouldn't even cause a war either, seeing as this just a way to produce basically iron by other means. (And insulation is useful, but there are other ways to produce insulation.) It'd probably be held a secret until WWII, at which point the Japanese might use it to help construct weapons (the iconic Zero fighter would now be wooden, for instance), but again, it's no better than aluminum, and it wouldn't win them the war, not against the Allies' atomic bomb. The information would be traded, and then you'd have an economic war in the 1950s between the lumber industry and the metal industry as the lumber industry tried to expand. Judging by modern prices, iron rebar is about twice as expensive as the equivalent length of a 2x4, but that price isn't wood treated with sodium hydroxide and sodium sulphate and then heat treated, so superwood would honestly just be too expensive to work with. Now, cost-effective aluminum didn't exist until 1889, but since Japan would hoard this information, I don't see how it would affect any developing technologies not in Japan. And, if this existed far earlier, when iron was hard to produce, it might have more consequences. But as it is, this really wouldn't change that much. ]
[Question] [ One of the plotlines, I'm currently working on, is about a dragon who is forced to serve a settlement to "pay" for some of his past "crimes". For clarity's sake, we call the dragon Gyvaris. Gyvaris is a roughly horse-sized, six-limbed creature with both reptilian and avian features. His intelligence is human-level. His primary weapons are the spurs on his wings and his tail (half of the total body length) with an arrowhead-shaped spade at its end. He also has a flexible neck and a jaw that can crush a human skull like it's nothing. Dragons are fast and nimble but are actually physically weaker than most horses (except for the wings) in the long run, meaning they're optimized for burst strength but tire quickly. They also have enhanced senses (eyesight of a golden eagle, the nose of a canine, etc...) along with echolocation and tetrachromacy. That being said, on the local power scale, Gyv is squarely in the middle. I mean, he starts out his story with a punctured lung, several broken bones, and torn tendons. All of that damage was done by a single human, by the way. --- So, Gyvaris is now in the service of this town. On paper, he's supposed to be some kind of a protector, but I couldn't figure out what role would exactly suit him. Since we're talking about a, more or less, standard fantasy setting, there are lots of monsters wandering around. Most pose little threat to a dragon, the upper echelon, however, are much tougher and most likely trigger Gyvaris' fight or flight response. It probably has something to do with their AA ( ~~anti-aliasing~~ anti-aircraft) capabilities. It doesn't help that they tend to show up randomly. Gyvaris is kept on a leash by a spell. Basically, if he doesn't do as told, the spell will take over his consciousness and does it instead of him. However, when in extreme fear (like wanting to run for his life), Gyvaris can overpower the spell and disable it for 12 hours. During that time, he's considered a loose cannon and a potential threat, regardless if he's just weeping in a corner. What guard role would make the most of Gyvaris' natural abilities, while minimizing the threat of his leash breaking? [Answer] Reconnaissance. Gyvaris spends the days catching thermals like a big vulture, flying large lazy circles high in the clouds. This suits his temperament fine, and making it even more suitable is the fact that since he is a captive, he must be fed by his captors so he doesn't have to hunt. If Gyvaris sees something interesting, he will (eventually) report to the town what he sees. Sometimes he will stay aloft and collect a few things to report before heading down. It is a lot of work to get up that high! --- As regards natural abilities Gy has an ambitious coach in town who had this idea that the dragon might learn to use a lance, capitalizing on the great speed he accumulates on descent. Using his own claws, teeth or tail at that speed results in a lot of energy imparted to the dragon's own frame, which is less than ideal. A heavy lance, however, can be released on impact and the dragon retains enough speed to bank upwards and away from whatever the target does next. That is the idea, anyway. When times are slow Gy is obliged by his coach to practice using the lance and hay-stuffed dummies. [Answer] If he is weaker than a horse then combat should not be his thing. Horses survive battle by smart usage and tactics from their commander. Even the best cataphracts in the world would turn into shredded paper against a line of phalanx/spear men if they insisted on a headlong attack. With that being said I think the best usage is a special unit doing odd jobs for the town. First thing is reconnaissance. OH what a commander do to be able to see from the eyes of a bird scanning the battlefield and seeing all in absolute clarity. Well. Maybe they won't be marching 2 legions and need a place to pitch camp. But he can at least circle the town and roads daily to spot large formations and dangers. Is fire breathing an option? If so I direct his ability to the reserves of the enemy army, to the supply wagons, to the forages...etc. Basically any place not so well protected and guarded to the point that he is in great peril. You don't have to get a video games 100 destruction rate. In reality if an army of 10000 men is attacking you and you cut of their supply line, and what better way to do so than a dragon, then they are at your mercy. Assassinations. If he can manage to get the drop on the enemy commander then he can do a lot of damage with one fell swoop. Stalk the army, wait for a low visibility conditions, then drop on the commander, kill the commander, fly off. Repeat. Organize: maneuvers, marching, linking up... Ok. We tend to think of things with the birds eye view in 3d real time instant communication style of modern warfare. Well. here we have none of that. March Divided, Fight United. Easier said that done when you can't communicate with the other columns of the army. Introduce your dragon and you can see how that works. Same with complicated maneuvers. Keep a strong cavalry force a long distance from the battlefield guided by the dragon. At the right time it can guide them how best to simply materialize on the battlefield to deliver a decisive blow. Obviously now I don't think of his combat prowess as anything special. His ability to fly and see and report that is much more valuable. I'm certain that every single pre-radio general would prefer a smart talking hawk or eagle to an extra 2000 men or even more. ]
[Question] [ In a setting where hundreds of scientists and engineers from around the world embark on an international mission to colonize a distant Earth-like planet (the ethics thereof are out of the scope of this question), and the unifying language happens to be Esperanto, to what extent, in what manners, and at what rate can/would the language deviate or evolve differently from terrestrial Esperanto over time? My intent is not necessarily to create another language or dialect that has branched from terrestrial Esperanto, but to illustrate the effects that may occur when a language evolves separately from its parent in such a setting. Firstly, I would imagine that such an "international" civilization would be an interesting "superculture", but I'm not sure what effect it would have on a language like Esperanto, which is already intended to be pretty unifying. Secondly, the setting is explicitly disconnected from terrestrial civilization, and nearly everyone here is a scientist, engineer, or a child thereof. What effects might this have? Thirdly, and most obviously, neologisms, idioms, and quirks that have developed since their departure from Earth obviously won't appear in their setting (unless they somehow coincidentally come up with the same things). As a slightly more meta question, to what extent can I, as a writer, make their language a little different? Surely, I'm not going to start arbitrarily making up new words or messing with the grammar, but perhaps introducing little nuances, such as, for example (and this is just an example), the tendency for adjectives to come after nouns as opposed to the norm on Earth. Ideally, this extraterrestrial Esperanto should still be valid terrestrial Esperanto. Another concern I have is to what extent linguistic and cultural nuances can differ in terms of what could realistically happen. For example, in this setting and culture, all things, animate or inanimate, are considered objects (in analogy to recognizing both humans and non-humans animals as animals). If the gender-neural pronoun "ri" was not conceived prior to their departure, they perhaps could have used "ĝi" (the pronoun meaning "it") as the notion of "object" differs from what it may imply in a language like terrestrial English (i.e. "humans aren't objects"). Given that the scientists departed at around 1995, and it is now 2047, to what extent could the language have evolved? What could happen in the future, given complete isolation and completely separate societal and cultural development from Earth in such a setting? Addendum 50 years is quite short, as mentioned by John. It is this short in timespan because I did not want to situate the setting too far in the future. I now ask instead how long it would take for a non-negligible amount of differences to develop, and what could possibly happen in such a timespan (in addition to the above, but much further in the future than a measly 50 years). [Answer] In a period as short of 50 years the language is not going to deviate significantly in its structure, especially since you're dealing with a literate population. Widespread literacy will tend to lock in major aspects of the language. There are real-world examples of this; French Canadian became essentially isolated from Metropolitan French following the British conquest of Quebec in 1760 (and even before then migration from France had essentially petered off). Québecois retained older pronunciations and created some vocabulary differences, but even 200 years of separation didn't create any significant difference in grammar. Where you're going to see possible changes in shorter periods of time are in things like accents, which isn't something that comes across in written dialogue very well. To use real-world examples again, vocal fry is becoming more common among younger North American women, and it's easy to imagine that becoming a dominant form of pronunciation, but that doesn't come across in dialogue without the writer explicitly describing the voice of the person speaking. Yet, were you to hear different generations speaking, you'd instantly pick up on the difference. Another example is the Mid-Atlantic accent that was taught in the early-20th century in the United States (that's the "old-timey movie accent" you'd recognize immediately). Again, instantly recognizable as being different, yet the vocabulary and grammar--putting aside differences like slang and such--would be no different from the same film shot a few decades later. [Answer] On one hand, (1) there shouldn't be much change; but on the other hand we are speaking about (2) a small community, and specifically a small community (3) speaking Esperanto. 1. For a normal language, there shouldn't be all that much change. Realistically, for a reasonably sized community speaking a normal language all that one could realistically expect in 50 years are (potentially significant) vocabulary shifts, some pronunciation shifts and maybe, just maybe, the beginnings of a handful of grammatical shifts. * Vocabulary shifts are inevitable, and in 50 years it is not impossible to see massive change. It is rare, but it does happen. My own native language, Romanian, went through a massive vocabulary shift from about 1830 to about 1880, most by borrowing a staggering number of words from initially Italian and then from French; the English language went through a very massive vocabulary shift from the during the 12th, 13th and 14th centuries, mostly by borrowing a very very large number of words from French. * Shifts in pronunciation are also inevitable, but they usually tend to become noticeable over longer periods of time. But all hope is not lost, because ... We have a well-documented historical example of an absolutely dramatic [sound change](https://en.wikipedia.org/wiki/Sound_change) happenning in about 200 years: the [Great English Vowel Shift](https://en.wikipedia.org/wiki/Great_Vowel_Shift), responsible for making English so much different from Dutch and Low German in general. Now the thing is, the Great English Vowel Shift was a [chain shift](https://en.wikipedia.org/wiki/Chain_shift), which means that if the entire chain was complete in about two centuries, then individual stages must have happened very quickly, maybe as quickly as one or two generations. * Grammatical changes tend to happen ever slower than sound changes, and they are quite often pushed by sound changes. And we are speaking about Esperanto, a language which doesn't have all that much morphology to begin with. 2. In a small isolated community language changes can happen very much more rapidly than in large communities. The question states that the community of interest has only a few hundred members, meaning that it is relatively easy for linguistic innovations to spread out. 3. And then, this is specifically a small community speaking Esperanto. Esperanto has seldom, maybe even never, been used as a full-time, full-scope language for any significant length of time. My impression is that if Esperanto was forced to take on such roles it will be put under enormous pressure to adapt and develop into a real human language, replete with nuanced meanings, frozen metaphors, set phrases (a.k.a. [idioms](https://en.wikipedia.org/wiki/Idiom)), not to mention an enormous expansion of vocabulary, be it only to make Esperanto a practicable language for science and engineering. For example, [look up akvo](http://vortaro.net/#akvo) in the Plena ilustrita vortaro, and you will get half a page comprising six definitions including some very pedestrian and made-up examples of use; look up water in the Oxford English Dictionary and you will get dozens of pages, with 32 definitions, the vast majority of them with several subdefinitions, with hundreds of examples of use taken from actual literature. [Answer] After the Second Anglo-Boer war in 1902, in what is now South Africa, a fairly large community (600-650 people) of Afrikaans speaking people immigrated to Argentina, South America rather than be subjected to British rule. This community was fairly isolated at first but around the 1950's they increased their interactions with the local spanish speaking communities and became fully bilingual and eventually Spanish becoming the First language spoken by the newer generation. Today about 300 descendants can still speak the Afrikaans language, mostly the older generation. So while in total this situation spans over 100 years, the main evolution of Argentinean Afrikaans could be considered to have only really "evolved" for around 50ish years. What is really interesting is that this isolated community retains elements of the language from before the main larger South African language and dialects were reduced through standardisation. I've seen a clip of a documentary where an older Afrikaans speaking South African comments on how lovely it is to hear Afrikaans spoken "properly" like "back in the day" (this was after a younger Afrikaans speaking person had commented on how the Argentenians weren't speaking proper Afrikaans). What I suspect for your situation is that your space community of speakers will retain alot of older speech patterns that will have been erased in the larger earth community through standardisation, interaction with a large variety of other languages etc. I reckon the only real new words will be for things that aren't yet included in the language before they leave. Such as words for space phenomena only encountered by actual travellers (nit earth observatories), spaceship maintenance, social words evolving from living in a tightnit community with no escape outside the limits of the ship etc. [Answer] Almost an unnoticeable amount, 50 years is barely a generation. a large percentage of your population will have learned their native language on earth. [Answer] 50 years is plenty, but the extent depends on how their history develops and how it influences their culture and technology. Here are two examples: Culture A and B both make similar discoveries, but they are not in contact so those discoveries are done by different people. Depending on how crucial those discoveries are treated by each civilization different names could become of importance to either of these cultures. Calling someone an Einstein would mean nothing if the discovery was made by someone else, or if it was made at all. Memes are a another way to affect language, they are not anything new since the dawn of the internet. The internet is just a platform for them to spread wider and faster. Memes are often derived from current events, and their success depends on how viral they become through reaching an audience that resonates with the ideas presented. Culture A and B may have common ground, but that 50 years separation is a lot of time for memes to develop which influence culture B's language and be completely alien to culture A. However, that isn't to say that in 50 years their language would change so much that they would not understand each other. It would just become another dialect that requires context for words and phrases. Perhaps there would be a few grammatical differences too. [Answer] The North/South Korean [language divergence](https://en.wikipedia.org/wiki/North%E2%80%93South_differences_in_the_Korean_language) is probably the best real world analog to the scenario. The two countries have been pretty much sealed off from each other (and in North Korea's case, the rest of the world) for about 50 years. ]
[Question] [ For a story I have, modern civilisation must be destroyed by a worldwide disaster. The objective is roughly something that: * Could be man-made or aided (if not now, maybe in the future) * Decimates, but not eliminates, land-based life * Directly destroys most buildings and technology, traces ok * Allows survivors to rebuild over hundreds or thousands of years * Doesn't affect the inhabitability of large parts of the world long-term Something like nuclear war would be inappropriate, as it have too much widespread long-term impact. However, if floods could have worldwide impact then that would work. [Answer] I'd go with the traditional option: bioweapon (natural or man-made). It would have following properties: * no symptoms until activation (so low probability of detection and no panic) * highly virulent even before activation (so you have most of the world population affected) * activates by a singular world-wide event (e.g. massive solar flare) * turns most of nitrogen in human body into nitric acid (so their corpses will corrode cement under them). While this wouldn't destroy buildings that don't house a lot of people, most of those either require constant maintenance (e.g. dams, nuclear reactors), or would be impossible to destroy without a cataclysm that wipes out most life, human or otherwise (nuclear bunkers, autonomous lighthouses and retranslation stations, etc.). [Answer] A nearby supernova might well meet your requirements. Such an event occurring within 50-100 light years of Earth might well have adverse effects on Earth. If the distance of the supernova were just 30 light years the effects would likely be devastating. In fact the close the event the worse the effect, so you can dial up whatever level of destruction you wants. The Sun won't turn into a supernova but if it did it would sterilize the Earth and boil away the oceans. There are no type II supernova candidate stars within 50 light years of Earth, but there are expected to be several hundred type I supernova candidates, however they are very dim and hard to find before they turn supernova so it is reasonable to speculate as to their location. <https://earthsky.org/astronomy-essentials/supernove-distance> [Answer] I can think of a couple options: ### Gray Goo An unstoppable swarm of nanites, or maybe even larger (e.g. insect-sized) creatures that destroy all non-bio-associated metal, would probably do the trick. Ancient stone buildings (and wood buildings with all wood joining) will mostly be unaffected, but many modern buildings will collapse, and the economic disruption (especially because this will take out pretty much all transportation) will lead to mass starvation. Wild animals, however, will be almost entirely unaffected, and the only plants that will be affected are those that were in human-built structures or otherwise depended on humans (e.g. for cultivation). ### Massive storms A biblical, world-wide flood most likely would have affected an Earth that is very different from today's. Much deeper oceans, much more sub-surface water, much shorter mountains. Repeating this on modern Earth is probably not practical (not to mention all the Christians you'll upset because it would be God breaking a promise). However, you might be okay with some sort of planet-wide storm. Buildings are built to withstand wind, but if you throw in enough debris that you're effectively sand-blasting everything over a long period of time, that might have the desired effect. If your "sand" (which can be any loose objects that break or wear down buildings) supports plant growth, the biome should be able to recover. Hard-core survivalists will probably be able to weather this, although I'm not sure how much plant or animal life you'll have left. ### Plague Any sort of medical what-have-you that kills off most people will satisfy some of your points. Whatever happens, you'll most likely have some survivors (at least, readers aren't likely to question that). The main problem here is it doesn't satisfy your criteria of "directly destroy[ing] most buildings and technology" (emphasis added). If you've killed off enough of humanity, nature will do the job for you in a few hundred years, but it sounds like this isn't what you want. --- In any case, I suspect a key part of your regression is going to come from economic disruption. This works well, because it will tend to kill humans, and only humans. Most wild animals are not dependent on humans and would get along just fine without us. [Answer] Some kind of super-hurricane would do the job. The wind plus flooding would wipe out most people, animals, plants and buildings. (Not sea life though, if that matters.) Only those at high elevations would survive, and maybe some by pure luck. You could create such a hurricane by heating ocean water which feeds hurricanes. You would probably want to have a "hurricane generator", which would create hurricanes with warm water, then send them in random directions. Once you stopped and the water drained the earth would recover rather quickly, plants would grow from random seeds. Animals would slowly replenish, as would people. But all the buildings would be gone. [Answer] In my mind the hardest criteria to meet in what you posted is wrecking all the buildings. It's actually a lot easier to kill off most or all of the human population and leave them standing. The thing about the human population is that it's maintained through a really terrifyingly fragile infrastructure, and the more developed and urbanized the population is, the more true that becomes. Anything that sufficiently disrupts the developed world's ability to distribute resources the way it does currently for more than a few months could easily kill off most of the global population, but wouldn't affect the rest of the ecosystem all that much at all. One simple way to do it that's been mentioned a few times is disease. Whether natural or artificial, if you kill off enough humans quickly enough, the infrastructure keeping most of the rest of us alive grinds to a halt and now we've got nowhere near enough food and clean water. The bigger the city, the worse the death toll would be. Populations in rural agricultural areas would make it through with the greatest survivors. Big cities would turn into mass graves that survivors would avoid (literally) like the plague. The other way that's closer to Slarty's answer is a massive solar flare or Coronal Mass Ejection. You totally don't need another star going supernova, our own sun could do it with a big enough fart. Something close to this [actually happened in 1859](https://en.wikipedia.org%20%E2%80%BA%20wiki%20%E2%80%BA%20Solar_storm_of_1859). We got hit with a massive blast of solar radiation that caused northern lights to be visible as far south as Florida and put so much power through telegraph lines that they caught on fire. Something on that scale today would be spectacularly destructive. The entire electrical power grid, everywhere, would be damaged or destroyed. Almost everything that RUNS on electricity that doesn't have mil-spec EMP protection would be damaged or destroyed. The solar flare itself wouldn't kill that many folks. Anybody on the ISS would be pretty screwed. Civilian aircraft in flight would be in pretty severe peril depending on where they were, how much fuel they had, and how skilled their pilots were. The sudden destruction of the entire global economy would have a massive death toll though because most of the population of the developed world now only has maybe a few weeks worth of food, and no way to easily get more, and no way to rebuild the infrastructure quickly enough. And that's assuming that some trigger-happy nutjob somewhere doesn't react to the business by starting a nuclear war on top of it, which WOULD get most of your buildings destroyed, but it's hardly necessary. [Answer] I would go for massive earthquakes over just about all of the earth. You'd be guaranteed to destroy almost all infrastructures, a lot people will die, but a lot of data and ressources could be safe enough to start rebuilding soon after. An interesting development after such a global scale natural disaster would be large floods, landslides, plagues etc that would slow down rebuilding. I'd expect some elites to form after acquiring left over weapons, but they probably wouldn't last for very long. What caused these earthquakes? Perhaps a massive shift in our tectonic plates, that would also rearrange our continents and mountain ranges. Plenty to work with! [Answer] "What disaster could wipe out civilisation worldwide, but allow for immediate rebuilding? What would be the side effects?" Any disaster that would permanently alter the environment won't do. So no supervolcanos or asteroids. You have to keep the ecosystem intact, so the disaster has to target only the humans. The easiest disaster for it would be plague. A plague as deadly as the ones that killed the native americans, killing 80% of population, but saving the elite technicians and equipment. Due to fast communications the killing would be quite fast. The survivors need transcontinental planes, ships and offroad vehicles to gather the survivors. 20% of population is still quite a lot of people and if you gather them in a smaller territory you can achieve the population density to keep industrial civilization working. Maybe gather the survivors around the North Sea (oil, iron, coal) or the United States (farmlands, almost all resources that a society needs). It will need planning but it is doable, i think. In a generation the population will start growing and resettling the abandoned lands, resources will be abundant: many cities to scavange. [Answer] Your buildings don't have to be consumed in the event, they can be dismantled by the survivors for their new homes like Rome experienced once it totally fell apart. Or else these buildings collapse through neglect as the reduced population rebuilds on what is local and after hundreds or thousands of years of neglect buildings that aren't stone or brick will be really bad off. Watching 1000 years after humans will help you visualize this. Yes flooding could work but you need a Noah situation. Flash freeze/mini ice age killing off many who are outside or you could combo this with an emp, famine, and then mini ice age. Grey goo or rogue helper bots but this is cliché The Happening movie could replay in your world aka the trees did it causing everyone to go psycho and commit suicide and the few that didn't die were in the right place at literally the right time to avoid catching what triggered everyone else. Eating GMOs causes the cells to commit immediate suicide so now only a very very few people who avoided the GMOs like the plague or consumed 1% or less are the last survivors to them people just dropped dead so they didn't know what had occurred. Technology did it take the Happening but do it digital. Hackers or a mass world wide government planned plan to add more spy ware on their own citizens from around the globe goes horribly wrong. The signal suppose to be some software hack program instead communicates directly to the subconscious mind in an unhearable wavelength that basically causes the death note to the body and everyone sitting in front of any smart device, TV, laptop, and iPad die with brain hemorrhaging or such so the bulk of many nations are dead in one moment including the very government officials who signed the order to make live the secret spy program. Super bugs/ Plague this is slower but if they can't find a cure either it will kill most people. And finally the plants did it again! This time it's so hot due to man geoseeding their world that the plants and trees stop working and instead of pumping out CO2 they switch over to pumping out carbon monoxide and killing everyone survivors will need to be on oxygen already, not on the surface, or in say the arctic and maybe select desert regions. ]
[Question] [ The premise here is that a government is already secretly using satellite imagery to record every surface of the Earth and automatically catalogues probable military assets and movements using image recognition software. Given the below constraints, could this technology already exist and be in use as of 2020? The following constraints apply: * It must be able to record all of the Earth's surface frequently enough to reliably detect fleet and convoy movements. * It must be able to process imagery fast enough to keep up with what it is recording. * The satellites must be able to cache and transmit enough data to a central data center to keep up with what it is recording. (It can either send all the raw data to the center to be processed there or pre-process the data in spaceand just send its findings to Earth. Whichever is easier.) * It must record and save in high enough resolution for a human arial image analyst to be able to verify any findings. * It can only use currently existing technologies. A best answer should also address the following: * Whether or not the project would be within the military budget of any modern nation or military coalition. * Whether or not there is an adequate timeframe between when the required technologies were invented and now to complete the project. * Whether such satellites could actually be kept secrete. * Any technological barriers that would prevent this project from existing yet. Clarifications My understanding is that surveillance satellites can already track these things in real time in places you are looking for them, and over time in a more global since, but I am asking about global real-time tracking. [Answer] Short answer: If something like this does not exist now, it will soon. The exact specifications of military-grade satellite imaging quality is kept vague on purpose however we can assume with a high degree of certainty that [the US military has at least some satellites which are capable of sub-decimeter imaging resolution](https://www.washingtonpost.com/news/politics/wp/2017/04/21/heres-why-the-resolution-of-satellite-images-never-seems-to-improve/). If we extrapolate and make some safe assumptions, I'd guess that under optimal conditions, the modern military spy satellite can identify what people are doing from orbit and possibly even if they're armed with weapons. If there was say, a table set up with rifles laid out on it, someone reviewing the images would be able to identify that there are weapons present. The problem with these satellites is that they're somewhat rare and are usually used to look at specific targets. In the commercial sector, global surveillance already exists. [The company called "Planet" owns a fleet of microsatellites which it calls "Doves"](https://en.wikipedia.org/wiki/Planet_Labs) and which are all in a sun-synchronous orbit. Each Dove is around 10 by 10 by 30 centimeters and consists mostly of a camera and solar panels. Right now, around 150 Doves and other Planet satellites are active and in orbit. Due to their sun-synchronous orbit, the swarm (or "flock" as it's called by Planet) can image the entire Earth once per day. This scan usually occurs sometime in the morning, between 10am and noon local time everywhere on Earth. The photos that this swarm produces are around 3 meters in spacial resolution with the newer generation reaching sub-meter resolutions (around 70 cm). This means, right now, anyone with the means can buy imagery of the entire Earth that's less than 24 hours old. Still a 24 hour refresh rate isn't quite fast enough to track military moments "live" while you could identify military bases, grab snapshots of convoys, and locate ships, you wouldn't be able to tell where they are going. Still, this is quite good despite the fact that Planet is a commercial company. If the military desired such a capability (and does not already have it), it would be quite easy for them to deploy such a system. It wouldn't even break the bank or even be that significant compared to the USA's military budget. If they wanted to, they could probably push such a satellite system without anyone noticing. As for the questions about data storage and image analysis, those are all doable. While the amount of data that would need to be worked with and stored would be enormous, there is precedent for the Military to build supercomputers. It would be expensive but there's no technological or practical limitations that would prevent such a system. [Answer] # No way. Not enough satellites to do that. I think the biggest barrier to this is the number of satellites required to do this. It also depends upon the kind of resolution you'd be looking for. If we're talking about Google Maps full-zoom level of detail of the entire planet, you'd need a number of satellites that can't possibly exist in the time since they've been invented. Nowadays, satellites are used to take pictures of or track very specific locations in high detail. Doing the whole world in close to real-time is just not possible. # The amount of data couldn't be processed with the computers we have now. (at least not in real-time) The total surface area of the Earth is 510,072,000 km2. Even if we had one pixel per square km, that would roughly equal a 22,584 x 22,584 square image, which might not seem too large in terms of processing at first. An image like that, completely blank and compressed as a JPEG is still about 7.6 MB. As you increase the resolution and add detail, it would go up exponentially. This means the amount of data is going to be many orders of magnitude greater than a measly 7.6 MB. --- UPDATE: It is true that the question did not explicitly ask for "the whole surface of the world" to be monitored and only asked for "the whole world's military movements". Here's a hypothetical: If you have a satellite pointed at a military base, and two trucks full of weapons leave that base and move in different directions, how do you track them both with that same satellite without redirecting another satellite? What if this were to occur at nearly all bases at the same time? The answer is *you can't.* The question did not ask to monitor individual bases, but their movements, which requires tracking on all of the locations where military movement might occur. Which could be anywhere the government decides them to go. [Answer] I think Overlord's answer is wrong. I think some big governments already have things in place like this. First of all, we already have enough satellites to cover the entire planet. Look at google earth. Not enough for real time perhaps, but that is because Google is a company looking for profit. If they wanted to, they could assign satellites to this. But, you do not need to cover the entire planet. After the start up phase, you will have a location on all military personnel, equipment and locations. And then it is a matter of tracking those. You can assign more satellites that cross the earth and scan it, to look for movement you have not logged yet. Aggregate this data with intelligence data, and adding any new movement to the network will be rather quickly. I also want to point out that the images we see on google maps' satellite view are artificially made of a lesser resolution. The original images are so good that you could very well see a person in their home, through the reflection of a car mirror parked in the street. And these images can further be cleaned by software as well. The reason we do not see this is privacy laws and such. We also have the infrastructure to process things like this. You just need to be smart about it. If you send all imagery in a data stream to a central point where it will get processed, it won't be possible. But such a system needs to be split up anyway. You will have cells of satellites working together, covering a certain area with their camera's overlapping each other's view. these satellites will have a small computational centre, in space or on ground, that will cover their images, tie it in a single feed AND perform calculations on that. Again, you do not want to track every square meter of earth. You want to track specific locations and targets. That is what these cell's would do. Since these things are known beforehand, they simply need to track these. If stuff is not moving, there is probably no reason to notify anybody either. So the feed only needs to ring a bell if there is movement or activity happening. This simplifies the system greatly already. Now all these cells will probably send their data to a bigger hub, which will send it to a bigger hub and so on. Somewhere all this data will be stored, but not in its entirety. Only the relevant bits. Next to this you would have a separate network of moving satellites that are not in a stationary orbit. They will move across the globe and provide images this way. You can use software to let them look for certain things (and believe me, the stuff we can do with image recognition these days in commercial and hobby projects is amazing. What governments can do is always miles ahead of this.) and flag these. Another system will check these flags (with or without human input) and if desirable add them to the tracking network as a target to keep track off. You can feed intelligence data to your second network and use that to look for certain things in certain places. eg a spy tells you about a secret base on some island in the pacific at these coordinates. Make network 2 search and locate it, flag it and then add it to network 1 to keep track off. All of this would cost billions and you will need a large infrastructure. But this is certainly possible. The NSA alone would have the computational infrastructure to process this kind of data and they are only one of many intelligence and security agencies the USA have. If an entire country works on a project such as this; this is possible. If multiple countries (say the UN or an alliance of sorts) work on this, it becomes even more easy. Heck, if Google or Amazon wanted to, they could do this probably. If you are curious you should look up what people can do these days with image recognition software. I saw a tech talk from a CEO of a company that is using the windows UWP platform on vending machines in Africa, where they use small camera's to image recognise globally listed criminals. This is image recognition done on vending machine computers. The hardest part was not the image recognition either, it was sending the data over shit internet in the middle of nowhere. So they actively pushed all the processing and such to the machine. With smart algorithms this was possible. And to get a feel of the difference in tech between what we civilians can use and what governments have, look up the difference between night goggles you or I can buy, and the stuff soldiers have access too. They have optics that can turn a pitch black night into a day light scene. This applies to almost any technological industry. [Answer] In my opinion Overlord has it right. This is not possible (using only satellites). Okay, let's tick them off: > > It must be able to record all of the Earth's surface frequently enough > to reliably detect fleet and convoy movements. > > > Repetition is an issue. Modern satellites can cover the same area within 10 to 14 days, if they take images continuously. Some platforms offer fast repetetions of about a day, but this is due to them being able to shift sensors to an area they passed over the day before. Also, optical satellites are limited, since they rely on sunshine and can't see through clouds. You can remedy this by using radar mostly and shooting up a lot more satellites. > > It must be able to process imagery fast enough to keep up with what it > is recording. The satellites must be able to cache and transmit enough data to a central data center to keep up with what it is recording. (It can either send all the raw data to the center to be processed there or pre-process the data in spaceand just send its findings to Earth. Whichever is easier.) > > > Not an issue actually. This is how it is done today: take images, save them, burst signal to ground, repeat - but it can't be done in realtime, since the satellites need a line of sight to a ground station which receives the data. You'll have a delay of at least several hours - and don't forget about the processing and analysis of the images. > > It must record and save in high enough resolution for a human arial > image analyst to be able to verify any findings. > > > Here's the main issue: Resolution vs. repetition. You either can get a high resolution, or a high repetition. Not both. The better the resolution, the smaller the area covered by the image, since sensors on a satellite only can be that large. But the smaller the ground area covered, the longer it takes to cover all area of interest, thus leading to a longer repetition cycle. Still, you'd wonder what a trained eye can see on a blurry satellite image with 2x2 m resolution. Which is why many military installations have hangars in which aircrafts or tanks are parked. But this would mean that every image has to be analysed by a human - software still isn't up to the task (which is why captchas ask us to identify cars or streetsigns). > > It can only use currently existing technologies. > > > Basically, if you plaster Earth's orbit with enough satellites, you could achieve this goal. But the amount of data would be tremendous, and the manpower needed to sift through all the images immens. Also, you couldn't keep it a real secret with all the rockets you'd have to launch. What you could do: * Create a database of the really interesting areas (as mentioned in the comments) using satellites and update that database regularly (at least once a month) * launch some more satellites to increase your repetition (maybe every 4 days) * use drones and/or AWAC to increase your monitoring of the really interesting areas (as the US does today) - this would give you almost real time data * this still would leave you with a lot of data to sift through [Answer] The technical answer is it would be possible if you devote an improbable amount of resources to it, as in tens of thousands of satellites in orbit and supercomputer farms with clusters of supercomputers wired together. Not to mention massive numbers of ground stations to handle the date streams coming in from space, and armies of analysts to interpret the data. As the OPFOR, knowing this, I enlist my countrymen with an email. They report to training by taking the bus to the factory or office, and are escorted to the basement where a gym, range and classrooms are set up. They also have a social media account with us as well, to receive orders, pass on information and so on. They never wear a uniform in public, and after your three year enlistment you leave their "job" at the factory and go on to regular employment and remain in the reserves. Want to invade a country? They receive a ticket via email, take the bus to the airport or train station and travel to your destination. We have already been preparing for years by smuggling in small weapons and equipment via diplomatic pouches, straw purchases in the local economy and so on. They and their fellow "vacationers" rent cars and travel to your destination, with a stop or two on the way to certain hotels or tourist destinations to pick up "items" they might need. The nation being invaded might even have Air B'n'b accommodations for lots of the "vacationers"... So what is your satellite system going to tell you about my military or where or where they are operating? ]
[Question] [ A radical shift in the Earth's orbit has made the Earth much colder, with all the oceans freezing over, and the atmosphere liquifying and falling as rain. Humans live deep underground in areas of high geothermal potential, such as the Ring of Fire around the Pacific. Apart from tunnels, they also want to use submarines in the deep ocean to transport people and goods around the world. Assume that the depth of freeze is currently at around 1 km. Physics Question First, with 1 km worth of ice pressing down on the liquid oceans, that's around 100 atm. In reality, I assume it would be somewhat less. First, water expands when it freezes, so it will be more like 90 atm of pressure. Second, I assume there will also be a "bridge" effect, with some of the weight of the ice mass being held in place by adjoining ice as opposed to "floating" on the water. I have no idea how big this "bridge effect" will be. I assume it's not going to be big, considering that the oceans are thousands of kilometers across, but that's just a guess. Are there any better estimates? And approximately how much pressure will the water be under where the ice meets the sea floor at e.g. the California coast? In other words, if you were to drill a hole down to the liquid ocean, how high would the waters rise - halfway to the level of the old sea level; almost all of the way; won't rise at all? (I'm guessing to perhaps 80-90% of the old sea level?). Engineering Question Second, am I correct to assume that harbor construction/operation will be potentially very dangerous for an underground civilization? As I see it, there are three potential harbor designs: * Docking system (as in space): Submarine sidles up to a hatch, screws itself on, goods/passengers are exchanged. Failure mode: Hatch breaks/is breached. * Lock gates (as in canals): submarine enters a chamber, gate behind it is locked in place, water level is reduced, submarine cruises to the next chamber. Failure mode: gates break. * Compression chamber: in which there are no gates/barriers at all, but air is kept at a very pressurized state e.g. 80 atm to keep the water in place (this may be just about doable, as humans can work in up to 70 atm environments with the right gas mix). Failure mode: Decompression. Of course, failures in any of these systems - assuming that the water is highly pressurized - will have an absolutely catastrophic outcome, as the pressurized water roars upwards and floods all the tunnels in the system... unless they are collapsed or otherwise blocked in time. Is this correct? If so, what kind of safety measures will be required to operate harbors? I can think of just two obvious ones: * Constructing the tunnels leading to the harbors in such a way that the lowest point at which they connect with the main network is above the old sea line (e.g., via a large elevator or funicular). So, even if worst comes to worst, only the harbors themselves will be flooded, not the entire tunnel system. * Having many more redundant gates that can be slammed shut in an emergency on detection of flooding, explosive charges, etc. Are there any other good, practical, not too costly (submarine travel would still need to remain competitive with tunnel transport to be of any use) safety features? Or will this civilization deem harbors too risky and completely forego deep oceanic submarine travel? Thanks in advance for your feedback. [Answer] Physics question Converting the sea/atmosphere to different states of matter will not affect their mass or the pressure they exert. So the pressure at 1km below the surface would remain roughly the same. Engineering question I suggest that the best option would be via an underwater tunnel cut from the bottom of the ice sheet (or a bit further down to allow for additional freezing over time). The tunnel should extend horizontally into the continental land mass until it is below a mountain range for insulation purposes. At that point the horizontal tunnel would meet a vertical shaft also filled with water which would rise to a point roughly level with the top of the ice sheet or a bit below. Water pressure from the liquid ocean would force the water into the tunnel and up the shaft until the point where the column of water in the shaft matched a similar depth of ocean/ice/frozen atmosphere outside. The top of the shaft inside the mountain would be protected from freezing by several km of rock and would also be heated from the interior of the Earth in the same way that deep mines are. At the top of this water shaft a floating harbour could be constructed with maintenance facilities for the submarines. The floating harbour could be linked to the main habitat by a lift of arbitrary length depending on the safety margin required. The level of floating harbour would change due to tidal influences assuming that the Moon was still in orbit around the Earth at this point and might also change over time in the thickness of the ice changed due to volcanic activity or additional freezing. In summary no lock gates, no high pressure airlock (if the sea level rose or fell would compress or decompress the air above the shaft a little but the change would be small and easily accommodated) and no pressurised environment. A high pressure air lock would be the next most suitable solution although as you state it would be subject to failure. Least optimal would be a high pressure environment. In fact a 100 atm pressure habitat would kill the inhabitants by [nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis) and [oxygen toxicity](https://en.wikipedia.org/wiki/Oxygen_toxicity#Underwater) [Answer] Physics Question: I do not think the pressure underwater changes when the surface freezes. Pressure is created by weight, and freezing does not change weight. You could say that liquid gases of former atmosphere add to weight, but again, turning atmosphere into liquid does not change its weight, or the pressure it creates. For engineering problem, Compression chamber is the answer. If everybody is living at 1km depth, then everybody stays at the same pressure as water. It works fine as you said, saturation divers live in pressurized state for weeks. Decompression is only a risk if you go to the surface, but you have a nice solid sheet of ice preventing that. Now I have a concern for you: food. There is very little light that gets to 1km underwater, so most of life there relies on food coming from the surface. now the surface is frozen, so no life and no more food. Your people will have to grow food in artificially lighted greenhouses, or breed extremophile bacteria that feed on underground chemicals. ]
[Question] [ In my fantasy world, unicorns have pearly horns, teeth, and bones. I didn't write it, but I am hoping to write a fanfiction in which it is explained. [Answer] [![enter image description here](https://i.stack.imgur.com/kSI38.jpg)](https://i.stack.imgur.com/kSI38.jpg)You could do it the way bivalves do it with mother of pearl, or nacre. <https://en.wikipedia.org/wiki/Nacre> > > Nacre is composed of hexagonal platelets of aragonite (a form of > calcium carbonate) 10–20 µm wide and 0.5 µm thick arranged in a > continuous parallel lamina.[2] Depending on the species, the shape of > the tablets differ; in Pinna, the tablets are rectangular, with > symmetric sectors more or less soluble. Whatever the shape of the > tablets, the smallest units they contain are irregular rounded > granules.[3] These layers are separated by sheets of organic matrix > (interfaces) composed of elastic biopolymers (such as chitin, lustrin > and silk-like proteins). This mixture of brittle platelets and the > thin layers of elastic biopolymers makes the material strong and > resilient, with a Young's modulus of 70 GPa (when dry)... > > > Nacre appears iridescent because the thickness of the aragonite > platelets is close to the wavelength of visible light. These > structures interfere constructively and destructively with different > wavelengths of light at different viewing angles, creating structural > colours. > > > Your unicorns lay down microscopic plates of calcium carbonate and biopolymer, ocating these various structures. Horns, teeth and bones are all made of different stuff but just as the molluscs coat their shellstuff with nacre, so too your unicorns coat all their various hard parts with their nacre equivalent. [Answer] Iridescence is caused by a diverse range of microstructures, so there is no reason they cannot. Your best bet is to have [photonic crystals](https://en.wikipedia.org/wiki/Photonic_crystal) as they are fairly easy to make biologically (they pop up all over the animal kingdom). They are structural more than material so you can make them with a wide range of materials. Teeth and horns are fine and in theory bone could be used to make photonic crystals so you could have it in the bones as well. The real question you need to answer is why they have these structures. Horns could be for simple sexual display, everywhere else becomes problematic however. ]
[Question] [ If a planet were to have a gravitational acceleration of .7g, how different would it be from walking on earth, assuming this is not someone born outside of earth. Would it be a slight bounce in your step or more noticeable than that? Sorry if this has been asked, I couldn't find anything when searching, just about super low or no gravity. [Answer] Here is what happens when you walk: there is one horizontal frictional compnent, and another vertical Normal component to the walk. [![enter image description here](https://i.stack.imgur.com/938bn.jpg)](https://i.stack.imgur.com/938bn.jpg) When the gravity goes from `g` -> `0.7 g`, this is going to effect on the counterbalancing of `N`, the Normal component. However, there will not be any effect on the frictional component (assuming point landing). So you will see a distinct hop in the walk (as you will go little higher than usual). [Answer] Definitely noticable, but not "I have superpowers". Basically, it'd have the same effect as someone who was pretty overweight going on a heck of a diet. I'm 6'2 and 240lbs on Earth right now, on your world I'd feel like I weighed 170, which was about thirty years ago for me. So yeah, pretty noticeable, and older people would notice the difference a lot more since it wouldn't just be "Hey, I'm feeling stronger", it'd be "Wow, all this stuff doesn't HURT anymore." ]
[Question] [ The year: Sometime a long time from now The place: Mars Little Bobby Colonist is going to play out in sand dunes beyond the edge of the domed city where he lives. Terraforming efforts over the last century have made the Martian atmosphere livable, but the air is still pretty thin and it gets deathly cold at night. But Little Bobby can hang out in the dunes as long as he's back by nightfall. Today though as he's traipsing about kicking rocks, one hits something hard and metallic. Leaning down to look at it, he sees some sort of ancient wheeled device perhaps three feet long. It has some sort of scratched up reflective paneling and six wheels- well, five wheels, but a spot where a sixth would've clearly gone. Inscribed on the side in a very old dialect he can't read is the word `Opportunity`. Though he doesn't know it, Little Bobby has just discovered the remains of a long-forgotten mars rover, launched from the Earth-that-was in the 21st century. And, because it's that kind of story, his entire world is about to turn upside down. Questions: * What year could this be? How long would a modern-day mars rover remain identifiable as such to some future-martian colonist? Might pumping large amounts of oxygen into the atmosphere and raising the temperature change this? * Little Bobby doesn't recognize the rover and there certainly isn't a memorial or museum of any kind at the site. Is it realistic to say that humanity has established a permanent colony, started terraforming, and forgotten about it's past exploration efforts in this amount of time? [Answer] As Mars stands now, probably centuries. Maybe millennia, or even indefinitely. Mars lacks most of the weathering mechanisms Earth has: there's no oxygen so nothing oxides (rusts), there's no water, and [while dust storms are fast](https://space.stackexchange.com/a/2644) and kick up a lot of tiny particles, the low atmospheric pressure means that there's simply not a lot of force behind those winds. (It's said on Earth that it's not that the air is moving, it's what the air is moving. On Mars, "what" doesn't amount to much.) [Meteorites on the Martian surface](https://space.stackexchange.com/questions/24651/why-doesnt-the-perchlorate-on-mars-surface-oxidize-metallic-meteorites) can persist for millions of years and still be recognizable. So, assuming that you're after the bulk structure of a rover and not its electronics (the plutonium core of Curiosity's [RTG](https://en.wikipedia.org/wiki/Multi-mission_radioisotope_thermoelectric_generator) will be long dead, let alone previous rovers' solar panels), it can last quite a long time indeed. By the time they've landed, the rovers have faced the biggest mechanical stresses they're ever likely to. Maybe the biggest threat is that, over the course of millennia, they end up on the downwind side of a rock and become buried in dust. But, your Mars is terraformed. What effect will that have? Surprisingly, for all the intricate detail about what goes into Mars landers, the basic construction of the chassis doesn't come up much. However, it seems reasonable to assume that none of materials that would be on the short list to send to Mars are all that volatile. Plastics don't do very well in low-pressure environments, and there's no reason to send nice oxidizable iron and steel when there's plenty of aerospace-grade aluminum and titanium to go around. Assuming the rover body is rustproof, it shouldn't be unduly affected by oxygen in the atmosphere, or by increased pressure. (Rovers undergo [engineering tests](https://space.stackexchange.com/a/5918) on Earth, so they can handle Earthlike pressure, and gravity for that matter.) If it can avoid being physically weathered (read: hit by a rock) it should be good for a prolonged period, possibly into the centuries. Incidentally, I would use **Curiosity rather than Spirit or Opportunity, partially because it's about five times the size, but mostly because it has [a signed plaque](https://upload.wikimedia.org/wikipedia/commons/a/ab/PIA15883-Mars_Curiosity_Rover-President_Obama_Signature_on_Plaque.jpg) and, according to [this article](http://www.collectspace.com/news/news-112611a.html), was also signed by the student who named it. Whether these would survive the elements is less certain. (If they were laser-engraved, the signatures should last a fair amount of time if not worn down by dust.) However, I think it's neat to think about. (Little Bobby should not tamper with the aforementioned RTG. As long as it's in its housing, he's safe, but if he opens it up he may end up inhaling plutonium dust which is, I should stress, not good for you.) As for whether it would be well-known*, probably in general terms but maybe not by sight. At least in my experience with public school history, "how we got here" is a major topic, and rovers as a whole* probably played a vital part in establishing a Mars colony. Individual rovers, however, might be less important - especially since we don't know what missions may be launched in the future. There were a number of lunar rovers that were important and impressive in their time but have already been overshadowed by the dramatic accomplishments of our current crop of Mars rovers; the future might hold more of the same that would obscure this particular wreck's place in history - at least for awhile. As an example: you probably remember, as I do, that Columbus's flagship was the Santa Maria. You might remember that it was a design the English call a "carrack", larger than his other exploration ships. But could you pick it out in a lineup of sailing vessels? [Answer] Hundreds of (Earth) years at least Reasonable quality solar cells on earth are likely to still be able to produce some electricity after one hundred years. NASA would not skimp on a critical component which is comparatively cheap, so I suggest that Opportunity's solar cells are very likely to be still functional in a hundred years if the dust were cleaned off, definitely still intact. This puts a lower limit of a hundred years on the "recognisable" aspect. Even with terraforming increasing the water content of the atmosphere, a 180 kg robot designed to survive dust storms is not going to corrode away to nothing in the immediate future. However, the question posits that it must have a legible inscription remaining identifying it as Opportunity. If it remains exposed with dust scouring its surfaces, even the most durable surfaces are likely to be abraded into illegibility after a few hundred years. Alternatively, it may have been buried by dust around the time NASA lost contact with it and only been uncovered a day or so before Little Bobby Colonist kicks a rock at it. In this scenario it could have survived for thousands of years almost undamaged, as have objects on Earth buried under ideal conditions. However, the answer to the second part of the question makes neither scenario plausible. The first colonists on Mars will be busy building lives there to allow the colony to survive, but within 50-100 years of colonisation, long before terraforming has got well underway, someone will have sought out Opportunity, Pathfinder etc in order to build memorials. Given ground-penetrating radar and the detailed knowledge of their last position, they will find them. It may even be a high priority within a few years of arrival, as Opportunity offers a prime opportunity (pun semi-intended) to examine how well these man made objects have lasted under Martian conditions. As for future Martians "forgetting" the history of space exploration that allowed colonisation to occur - that would take intentional erasure of history by an omnipotent dictatorship. It is not going to occur "naturally" given the level of documentation of the current era. [Answer] It can last some millenia. The eletronics will be long gone, the plastics will be brittle and the plutonium core won't work (but it can still kill you, plutoniun hates you). The solar panels will be broken and it's pieces will be somewhere nearby. The things that can destroy the rovers are stones moving around, dragged by water as the water cycle reactivates. Mud and being buried won't destroy it, it's made of aluminium, made to survive the chemically active martian soil and the dead martian geology won't crush the sedimentary deposit and turn it into some kind of arenite with a funny metallic aluminiun laced with plutoniun. ]
[Question] [ ## Parallel-Universe Portals A solid material has been discovered that, when shaped into a ring and activated (by lowering its temperature below some critical point, let's say), it forms a parallel universe on the other side. This isn't a gateway into an existing alternate universe, but rather a duplicate of the host universe, identical in every way at the time of activation. However, over time (on the order of minutes), the two universes will desync due to slight quantum-scale differences that the portal produces on each side. (It’s the same type of parallel universe generation described in [this previous Worldbuilding SE question](https://worldbuilding.stackexchange.com/questions/31046/portals-to-parallel-earths-economic-effects), but I’m interested in a special case) As long as a portal is active, it must be in the same position in both universes. If you move the portal from one end, it moves in the other. This means that a portal can never be used to cross distance or time. When I say that it is in the same position, I also mean that it faces the same direction. So if you walk into a portal, moving north, you will exit in another universe, still moving north. Walk south again? Back in your universe, moving south. Walk around the portal and walk north through it again? Back in your universe, moving north this time. (Moving through the portals isn't really relevant to this question, but I just wanted to give some examples so that what I'm describing is a bit clearer.) Notably, portals duplicate existing portals. To illustrate this, imagine that you have an active portal linking your universe, universe 0, to another universe, 1. [![enter image description here](https://i.stack.imgur.com/vUPQ1.png)](https://i.stack.imgur.com/vUPQ1.png) After a few minutes, when the universes are desynced, your copy in universe 1 decides to open another portal (since it’s after the desync, you're able to choose not to open another portal in your universe). The end result is shown below, with 2 copies (joined by a blue portal) of your previous 2-universe system (joined by a red portal): [![enter image description here](https://i.stack.imgur.com/ppedZ.png)](https://i.stack.imgur.com/ppedZ.png) ## The Question What happens if your copy doesn’t wait for a desync before opening the second portal? Suppose once the red portal opens, she waits only 1 second before opening the blue portal. Since you're both still synced, you'll open a portal at that time as well. So there are 8 universes, right? I don’t think so. I think what happens is a “hall of mirrors effect.” Consider the two copies of you at the ends of this 8-universe chain. Why do they only have a red portal open? Shouldn’t they have also opened blue portals, since that’s what you did and they’re synced to you? By induction, the chain of universes should be infinite. The question is: does the “hall of mirrors effect” produce a truly infinite chain of universes, or does something break the chain? My current answer: the chain is infinite. Reasoning: There’s some incredibly slight amount of desync that happens in that 1 second between the portals opening. If a limit exists, it probably depends on that. Let’s assume that 1 second of waiting causes a desync of 1 nanosecond (that is, that 1 second of waiting between portals cause you and your copy to behave almost the same, but with one of you on a 1-nanosecond lag). So the second blue portal opens 1 ns after the first. I initially thought that this would make the chain finite, since each layer further from the starting layer would add time, until eventually the desync would be so large that the copies on the ends would be in a completely different state of mind and the hall of mirrors would be broken. But no, between 0 and 1 ns apart, the multiverse would resemble the second diagram, with 00 and 01 about to open their blue portals at the same time at t = 1 ns. Any role the tiny desync plays in the chain is gone by the first iteration. Am I right? I’m not as sure about my answer as I’d like to be, and it feels a little wrong to have an actual infinity come up in this problem. After all, these portals are remarkably well-behaved in every other scenario I could think of. You can move them through each other and intersect them like chain links, all without making the multiverse implode or anything. I’m interested to see if this case has some subtlety I’m missing. Answers could involve: * The desync between the portals * The time that light takes to travel between the portals * The absurdly small probability of a quantum fluctuation causing, say, the portal to stop working, on a human timescale Answers should not involve: * Handwavium / built-in stopping mechanisms (i.e. the portals are designed not to work if another portal was opened less than a second earlier) * The portals causing the universe to collapse (for General Relativity reasons or otherwise) * Any assertion that the chain of universes doesn't exist at all (or at least think about it a while and draw some diagrams before posting. This is very easy to misunderstand. After a lot of thought, I'm confident that the chain starts, just not that it ends.) [Answer] Let's pretend I have 2 doors. I am the first state(A) [![enter image description here](https://i.stack.imgur.com/pQxUG.png)](https://i.stack.imgur.com/pQxUG.png) I make a copy, then I have 1 door left in each of 2 universes. My second state (B) is linked by door #1 [![enter image description here](https://i.stack.imgur.com/G3n7o.png)](https://i.stack.imgur.com/G3n7o.png) Then using my second door, I make a copy creating resulting in 2 universes with 1 available door, and 2 with none, My third state (C) is now connected to (A) by the second door [![enter image description here](https://i.stack.imgur.com/rPgXB.png)](https://i.stack.imgur.com/rPgXB.png) At about the same time, (B) is also opening his second door to make state (D). [![enter image description here](https://i.stack.imgur.com/QaGsl.png)](https://i.stack.imgur.com/QaGsl.png) (B) now makes both ends. Here is where the infinity thing happens. In the exact same quantum of time as they are made, they also copy themselves. [![enter image description here](https://i.stack.imgur.com/Ype7L.png)](https://i.stack.imgur.com/Ype7L.png) And [![enter image description here](https://i.stack.imgur.com/W0drE.png)](https://i.stack.imgur.com/W0drE.png) etc... So, with this visualization we can see it is infinite because no matter how many times you "unfold it", the ends will always have a copy of the 2nd state (B) with an unopened door. For this to be an eventually terminating pattern, your outside copies would need to be 3rd, then 4th, then 5th generation copies, but you will never generate more than a second generation copy that still has a door to open. EDIT: You can also see from the visualizations that the duplication process never causes an overlapping of portals as I originally hypothesized. This means that you will not get an infinite energy buildup; so, the mirror effect should not destroy the lab causing a forced termination from a run-away interaction between the dimensions. [Answer] Of course this is all theoretically suspect as it is impossible (according to the rules of quantum physics) to create an exact copy of an existing state. Thus it would be impossible for your mystery portal material to form an exact parallel universe. But putting that argument aside, your portal appears to act like a mathematical operator with an inverse. To illustrate: if you construct a portal $A$ then going through it once takes you from your universe $x$ to a parallel (initially 'identical' but now divergent) universe $y$. Passing through it again does the inverse operation - taking you from universe $y$ back to universe $x$. That is fine as lots of operators are their own inverses (for example multiplication by -1). So mathematically $y = Ax$ and $x = A^{-1}y$ . This is consistent as $A^{-1} y = A^{-1}(Ax) = (A^{-1}A)x = Ix = x$ But now consider adding a second portal $B$. To simplify the argument imagine constructing both of them simultaneously in universe $x$, so now you have a choice of going through portal $A$ to universe $y$, or through portal $B$ to universe $z$. Note that as you constructed them simultaneously, both $y$ and $z$ will have 'copies' of $A$ and $B$. Here is where it gets interesting. Going back and forth through portal $A$ just takes you back and forth between $x$ and $y$. Similarly going back and forth through portal $B$ takes you back and forth between $x$ and $z$. If you go through $A$, then through $B$, then back through $B$ and back through $A$, you will find yourself in $B^{-1}BA^{-1}Ax = (B^{-1}B)(A^{-1}A)x = IIx = x$, so you end up back home again. But if instead you go through $A$, then through $B$ and then 'back' through $A$ and then 'back' through $B$ you will be in $B^{-1}A^{-1}BAx$ and if $A$ and $B$ are [non-commutative](https://en.wikipedia.org/wiki/Commutative_property) operators then $x = B^{-1}BA^{-1}Ax$ $\ne$ $B^{-1}A^{-1}BAx = x'$ If you repeat the path again and again you will get from $x'$ to $x''$ to $x'''$ etc. so you will cascade through an infinite hall-of-mirrors of alternate universes. If you want things to be that way then fine, but if you don't want this to be a problem, all you need to do is define that in your universe 'portal-operators' are commutative operators (via some mysterious property of the portal material itself), which would dismiss all recursive loops as then $x = B^{-1}BA^{-1}Ax$ $=$ $B^{-1}A^{-1}BAx = x$ by definition. [Answer] Let's assume you don't open the two portals at exactly the same time. You always have 2 universes that have only 1 portal. Opening a portal in one of them gets rid of a 1-portal universe, but doubles the other one. The rate of the doublings depends on the desync rate and the difference in portal-opening times. In your example, the second pair open a portal 1 second apart. That means your two clones have 1 second to desync. In that 1 second, how much do their opening times/probabilities change? Then, consider the product of the probabilities of opening at each step. This infinite product is the probability of your infinite hall of mirrors. [Answer] I'll add to this letter number festival: We have the starter universe where you have two buttons, one on your left and one on your right. The one on your right is A and the one on your left is B. This looks like this: (1) 1[-] One universe with no portals inside. You create portal A which links to another universe that is perfectly identical to the starter universe: (2) 1[A]<>1[A]' Note the apestrophe at the second universe "boundry" as upon creation the universes are absolutely identical! This changes almost immediately with quantum rippling effects through the universe but at the exact time of creation they will be identical! Now you immediately open portal B with one nanosecond before the second one opens: (3) 1[B]'<>1[B+A]<>2[A] The first paralel universe is now a different one, so its changed from 1[A]' to 2[A]. But thats not as interesting as 1[B]', which contains two exactly identical portals inside it... which means that even before 2[A] creates its second portal you have to write (3) like this: (4) 1[B+A]'<>1[B+A]<>2[A] But wait... since all A portals in universes 1[ ]' and 1[ ] are PERFECT COPIES of each other upon creation they can only lead to the exact same point, universe 2[ ]! Tangent: if you do not accept that the identical portals will reach in the same universe than portal A inside 1[B+A]' would lead to universe 1[B+A]'', which would lead to 1[B+A]''' etc in an infinite loop that would happen even if you desynced before opening simply for having 2 portals simultaneously. Tangent over. Then we move 1 nanosecond further and portal C opens while the other univers desyncs: (5) 3[B+A]<>1[B+A]<>2[A+C]<>2[A+C]' Again we see that upon then moment of creation 2[A+C]' will have the exact same portals at the exact same positions open, meaning that the A portal in it will lead back to the original unless you use the tangental interpretation which causes an infinite loop no matter if you open them synced or not. Edit: testing if you have infinite universes. Activate portal A. Press the button for portal B, an automatic system fires a gun that will pass through portal B to portal A and activates portal B just before the bullet reaches it. This means that a bullet is in flight at perfectly the same trajectory and speed as the one in the other universe. Both bullets pass through portal B and end up in each others universe, making it seem like nothing happened at all from the side-view. They then both pass through portal A simultaneously... In an infinite portal universes the bullets simply hit whatever is behind portal A, a small target for example. In a looped universe both bullets simultaneously try to exit portal A in the exact same position, speed and trajectory. A few things can happen: The bullets coordinate systems function like a combined [3d+1]+[3d+1] coordinate system, the bullets simply collide with each other and fall to the ground. The coordinate systems dont line up and each part of the bullet exiting will do so and occupy the exact same space as a perfect copy of itself. If string theory is right you might get lucky and the vibrations that make up the bullets information just double in size, transmuting the bullet to whatever its new vibration is. Otherwise you now have not just fusion but actual particles down to the smallest gluon or whatever is smallest currently trying to force itself into the same position. This will likely mean it creates micro black holes that instantly evaporate as the bullet passes through (and the resulting explosion pushes back). Dont be there. But perhaps the most interesting question... if you throw something through portal A in universe 2 it will have to exit in BOTH the other universes... What happens? Are they divided or copied? Gag reel: Schrödinger comes along and places a measuring device. Portal A is created, making both universes essentially a quantum-entangled entity. Portal B is opened and at the same time Schrödinger measures his own universe to be up or down. Universe 3 flips upside down. In an infinite portals universe number 2 also flips. In a looped universe, everything not yet desynced inuniverse 2 now has to be both up and down and cannot be up and down. [Answer] There isn't enough desync for one portal to open and not the other.... so you can still treat A and B as a single unit, so when AA and BB open, they are a mirror of A/B. Meaning AA and BB end up linking to each other leaving you with 4 universes, not 8 or infinity. [Answer] There's no definitive answer, following is a few possible explanations. ## Trying to hold strictly to "syncing": 1. Open a portal from universe A to universe B, portal is called A0<->B0 (bit to designate portal location) 2. While synced, universes A and B each open a new portal. Since they are synced, these new portals are in the same location and go to the same universe, C. We now have A0<->B0, A1<->C1, B1<->C1. We have overlap at universe C's 1-location, with portals going to A1 and B1; we also have overlap at A0 and B0, since on C's 0-location must be identical to A's and B's 0-location. You end up with 3 universes and the portals A0<->B0, A1<->C1, B1<->C1, A0<->C0, B0<->C0. ## Without really holding to syncing (it generally breaks immediately): 1. You create the first portal, ending up with universes A and B, with a portal A0<->B0 (again using bits to denote which portal location we're looking at) 2. While synced you and your B-universe double create new portals. Presumably in the same place, since you're synced. 3. Couple possibilities here: * This new pair of portals could either be another portal between universes A and B, so you have A0<->B0 and A1<->B1 (which means we de-synced immediately, because our 1-location portals go to different places; or each portal opens to both itself and the other universe's 1-location) * Or, this new pair of portals both go to new universes, so you've got A0<->B0, A1<->C1, and B1<->D1. (This would also appear to de-sync A and B immediately, since they have different portals in their 1-locations; or each portal could open to itself, and to both new universes (A1<->A1, A1<->C1, A1<->D1, B1<->B1, B1<->C1, B1<->D1)) 4. In the second case, universes A and B both have two portals, and we know where they both go. However, universes C and D each have a portal we haven't determined yet. And there again seems to be two options (there's more, but I'm ignoring the strict-syncing cases): * Portals C and D are literal copies of their parent-universe's portals: which means that in universe C, in the same place as universe A's A0<->B0 portal, universe C also has a portal to universe B. Same thing in universe D (based on universe B this time). So, we've got: A0<->B0, C0<->B0, A0<->D0, A1<->C1, B1<->D1. This is scary, because I don't know what happens when there are two portals to different universes in the exact same place (explosion? walking into a portal means you walk out of both other portals?). * The new portals go to new universes and we have A0<->B0, A1<->C1, B1<->D1, C0<->E0, D0<->F0. Now we have universes A, B, C, D with two portals each... but E and F with undetermined portals. 5. Repeat 4 infinitely many times, instantaneously. This happens since these are simply copies of portals that already exist. So, you end up with 2, 4, or infinitely many portals. There may be other solutions, trying to be strict with syncing is complicated. [Answer] For the chain to be possible, there would have to be a some delay in the creation of a parallel universe. In the case that the other universe is instantly created, it would be more like holding a mirror up to the existing reality. If there was a ‘pulse’ from the ring that created the other universe, the creation of a new portal would occur every time the pulse reached where an existing portal was. This chain would be infinite, or practically infinite. If portals act as a way to create a mirror copy of current reality, no chain would form. Clarification Desync times would not have an effect in the case of a pulse as already existing portals are affected. Unless a ring was destroyed at any point in the chain during the formation(which would take an endless amount of time) the chain will be cut off at the mirror of that universe as each portal mirrors current connected reality. I will post reference images later if you need clarification ]
[Question] [ I'm no scientist and my poor brain box is on its last legs; I was wondering if any of you smart beans out there would be able to help me figure this out? Here are the specs of my system; Kereiol is a 2 billion year old quiescent carbon-rich M star with a temperature of 3,100 kelvins. If it flares at all they are tiny. It has four orbiting planets, only one of which, Liskuel, is within the goldilocks zone. Liskuel is 0.15 AU from Kereiol and has an orbital period of 58 days. Liskuel is a tidally locked (0% obliquity) wet, rocky carbon-born planet with an active core. The surface is 70% deep water and 30% dry land. It is a similar size and mass to earth, with a strong magnetosphere and thick atmosphere. Liskuel is tidally locked in a synchronous rotation with its sun. One of the biggest obstacles to life evolving on a red dwarf planet is the short distance at which the planet must orbit its sun in order to remain in the goldilocks zone. This close orbit almost always leads to tidal locking, which creates extremes of temperature at either pole. A strong atmosphere would be needed to regulate this and render the planet habitable. Unfortunately, even the older Red Dwarves are prone to volatile solar activity such as flares, which produce torrents of charged particles capable of stripping off sizable portions of the planet's atmosphere, as well as starspots which dim the stars emitted light by up to 40% for months at a time. In addition to providing a barrier against solar activity, increased atmospheric pressure would also decrease the thermal contrast between the polesby virtue of retaining more gases, meaning smaller forcing and lower wind speed. (which would be great.) In summation, temperature regulation is an issue, one that would be helped by a dense atmosphere. But, as I have learned, just increasing the size of the planet wouldn't help, sooo.... My question is, is it possible to have a planet with earth-like mass and size but double the atmospheric pressure? If so, how? (Without reference to terraforming or advanced technology). [Answer] Trivial real world case: Venus is about 98% of Earth's mass, and has roundly 100 times the Earth's atmosphere. This extreme atmosphere is mostly carbon dioxide, with the famous clouds composed mainly of sulfuric acid droplets. Interestingly, at altitudes just above the cloud tops, the environment is the most Earthlike to be found anywhere in the solar system off Earth -- pressure and temperature are very similar to Earth at sea level, though there's no free oxygen -- but it's probably the only place in the system where a human could survive with just a breathing mask and air bottle. The mechanism that gave Venus such a deep, massive atmosphere was probably (unless planetologists have changed their minds again) thermal outgassing of surface rocks as the runaway greenhouse took over a couple billion years ago. ]
[Question] [ I'd like to create a story in which a genetically modified man has Aromatase Excess syndrome. For example, if a man has a genetic mutation where he produces a lot of aromatase that turns 10% of his testosterone levels into estrogen (specially estradiol), what would happen to his body? Consider that the fictitious man in this case has a testosterone level of 500 ng/dl or 5ng/ml and aromatase is turning 10% of his testosterone into estrogens. A healthy level of estrogen in a young woman is between 80-200 pg/ml of blood, then 10% of 500000pg (500ng) is 50000 picograms or 50nanograms of estrogen. What would happen if a man had 50000 pg of estradiol, which is many times higher than the average level of estrogen in a woman? [Answer] These men would become obese and infertile. [The Effect of Aromatase on the Reproductive Function of Obese Males.](https://www.ncbi.nlm.nih.gov/pubmed/28679145) > > The expression of aromatase is proportional to body fat mass and > causes more fat accumulation, thus forming a vicious cycle. Excessive > aromatase activity in adipose tissue leads to increased conversion of > androgens into estrogens, eventually results in a reduction of > testosterone levels and is the underlying reason for obesity-related > infertility. > > > As aromatase levels rise, an increasing proportion of testosterone is converted into estrogen. The estrogen causes feedback which tends to suppress testosterone - otherwise estrogen would rise and rise as the body tried to reach normal testosterone levels that the aromatase prevented. These men would become fat, infertile and have gynecomastia. Various other metabolic and endocrinology problems would ensue. This is not especially edgy science fiction. ]
[Question] [ How could a mammal produce milk which resembles blood? The blood milk should keep as many properties of milk as possible, curding for example, while resembling blood as much as possible. The mammal does not have to exist or eat earth food, but if it doesn't what would that food be like? By the properties of mean I mostly mean: * The ability to feed babies (lactose) * Curding (Cheese) * Liquid at room temperature * Preferably not poison to human-like species By the properties of blood I mostly mean: * Red * (Very) slightly thicker [Answer] The creature in question eats foods rich in natural red dyes Most of these plants require boiling to get the dye, but the acid bath of digestion is enough to get to that point. The problem, of course, is that the mammal would need to eat this stuff almost exclusively (or at least a whole lot of it). But methinks it would create the color you're looking for. * Autumn red leaves (seasonal) * Bamboo * Bedstraw Root * Beet Root * Brazilwood * Canadian Hemlock * Choke Cherries * Crabapple Bark * Elderberries1 * Hibiscus Flowers * Madder Root * Portulaca * Rose Hips * St. John's Wort (a bit harder, requires mixing with isopropyl alcohol) * Sumac Fruit * Sycamore Bark (Found from [this source](https://www.thesprucecrafts.com/make-natural-fabric-red-dyes-2145745)) But what about the thicker fluid? I believe you'll need to live without this. Mammary glands are designed to create and pass a relatively specific fluid thickness (not unlike the kidneys or liver). If you try to force something substantially thicker through the glands, they get all clogged up (not unlike the kidneys or liver). Getting something the thickness of blood that didn't hurt the lady would require a physiological change to the glands. You could thicken the fluid somewhat by consuming high-starch foods, but I believe that's the best you'd get. --- 1 "It is by my will alone that I set my mind in motion...." Sorry, I had to include a gratuitous "Dune" reference. Eating enough elderberries to turn milk red might turn the whole blooming cow red. [Answer] There is blood in the milk. [![bloody cow milk](https://i.stack.imgur.com/xoJFg.jpg)](https://i.stack.imgur.com/xoJFg.jpg) <https://www.researchgate.net/publication/283120356_Causes_Diagnosis_and_Treatment_of_Blood_in_Milk_Hemolactia_in_Cows_and_Buffaloes> Milk comes from glands. Glands have blood vessels. There are various reasons a blood vessel might burst and bleed more or less blood into the milk. <https://www.researchgate.net/publication/283120356_Causes_Diagnosis_and_Treatment_of_Blood_in_Milk_Hemolactia_in_Cows_and_Buffaloes> > > Dairy farmers frequently approach practicing veterinarians for the > treatment of cows or buffaloes producing milk which is reddish or > pinkish due to the presence of blood. Farmers suffer from the economic > loss because bloody milk is often rejected by the consumers. The > condition is usually sporadic in occurrence but rarely several > lactating animals may be affected at a time... > > > The main reason is that the animals are being milked a lot, but I took away that some animals idiosyncratically are more likely to have this happen. Evolution could totally work on this. Suppose an animal were born with a genetic variation that led to more vessels in the milk glands and they were prone to bleed. The nursing young get benefit from this and are more likely to grow to adulthood - maybe they get more iron, or more antibodies from the added blood. The genetic variation has improved reproductive fitness and it spreads through the population. Generations later, all the mammals of this sort have blood in the milk. [Answer] > > Blood is red from the protein, hemoglobin. Hemoglobin has a molecule called a "heme" which has the metal iron in it. When the iron is oxygenated, it becomes red. When the iron is deoxygenated, it becomes darker red. > > > [Source](http://scienceline.ucsb.edu/getkey.php?key=2419) I would say the animal would probably eat food very high in iron, be it red meat, or spinach (a lot of leafy greens have high iron content). Add some sort of clotting agent when it comes out. For example, [Lipids](https://chemistscorner.com/thickening-agents-for-cosmetic-formulations/) which gets thicker when it cools. I could be wrong here, but I believe that if you increased the fat content in the milk this could cause this... Also, I would say that milk straight from a goat (the only example I have seen in person) is a similar thickness to un-clotted blood. Although (from the same source) you could add a gum thickener, which has the added benift of making it slightly sticky. ]
[Question] [ This question is similar to [What would happen if there was no wind?](https://worldbuilding.stackexchange.com/questions/61267/what-would-happen-if-there-was-no-wind), but the lack of wind is confined to a small portion of the planet. To make things concrete, the affected region is roughly circular with a radius of about 150 km. The entire region is affected by magic that causes the wind outside to flow around the edges of the circle as if the whole area were covered by a glass dome. To make things concrete, here are the details on the affected region: * It's roughly circular, with a radius of about 150 km. * Magic causes the wind from outside to flow around the edges of the circle, more or less as if the whole area were covered by a glass dome. * The clouds follow the path of the wind, so there's no rain and the skies are perpetually clear (which also means the area around the perimeter gets more rain than it normally would). * The terrain is plains and rolling hills, with rivers flowing in from outside the affected region. The question is, do the rivers and other processes distribute enough water throughout the area to prevent most of it from becoming a desert in the absence of wind and rain? Or are we inevitably left with small fertile areas around the rivers and desert everywhere else? I was specifically envisioning the area as a place for small nomadic hunter-gatherer societies, so it wouldn't need to support agriculture, irrigation, etc. [Answer] They will not need to be very nomadic. This aside from the fact that 150 km is not very big. Life in your magic circle will be next to the river. As an example here is the Amu Darya between Turkmenistan and Uzbekistan. [![Amu Darya](https://i.stack.imgur.com/6dMzF.jpg)](https://i.stack.imgur.com/6dMzF.jpg) Life is clustered by the river because there is no rain in the desert. In your windless land there will be no rain and it will look like this. Your nomads can go up and down the river hunting and fishing. Or stay in one place near the river - they can use the river for irrigating crops and make fish pens. Another difference is that all plants will be insect pollinated. Those plants will not get competition from wind pollinated plants (like grasses) and so will do great. Some wind pollinated plants might be able to use the river to carry seeds and so colonize the area from upriver. [Answer] I believe the nomadic society could survive, but further details may need to be addressed to determine their approach. 1. Can clouds pass over the dome? If they can, at what altitude? The [type of cloud](https://www.weather.gov/media/lmk/soo/cloudchart.pdf) could impact what types of weather and [albedo](https://en.wikipedia.org/wiki/Cloud_albedo). 2. How exactly is water vapor dispelled? If water vapor is pulled from the area rather than vanishing, this would probably cause more clouds, high humidity, and rain. If this pull is not instantaneous, this could cause some sort of humidity gradient, with the driest point being the origin. 3. Can it rain in or above the area? If the rain can indeed fall through the dome, the increased water vapor and new cloud routes may maintain the humidity, or even over saturate the area. 4. How does [erosion and weathering](https://sciencing.com/difference-between-weathering-erosion-8212886.html) play? The interior of the dome would lack signs of wind erosion and weathering. If rain precipitated down the sides of the dome, the edges would show greater signs of water erosion and weathering. 5. How would technology complement a nomadic lifestyle? If rain is sparse within the area, they could create water basins on border. This would give them intensive to travel from each basin rather than settling down around a river. They may consider ditches or primitive types of piping, such as bamboo. This irrigation wouldn't necessarily be agriculturally focused, as it's not for the propagation of crops, but rather the maintenance of land and ecology dependent on the water. Aesthetically these ditches could double as religious or culturally relevant symbolism (such as the [Nazca Lines](https://sciencing.com/difference-between-weathering-erosion-8212886.html)). 6. Is animal ecology and evolution considered? What are the new niches to fill, and how are they resolved? Do animals start retaining more water? Do they utilize primitive fans to maintain wind-based plant pollination? Do plants adapt their seeds to be sticky, adhering to hairy animals to either be displaced elsewhere or begin some sort of symbiosis? [Answer] I think without any wind to bring in moisture, and no rain falling, you will only get a desert area with rivers running into, as suggested by Willk. There is a good example of a group of people living in a desert who follow a nomadic hunter/gatherer lifestyle, the Khoi-San of Southern Africa. Even to this day they remain in the Kalahari desert and continue their nomadic cultural way of life. As another idea for a group living in a desert type biome, you could have them be herdsmen like a lot of the indigenous tribes of Southern Africa. With a large enough herd of animals to sustain the group of people, grazing will easily become a problem if there is only vegetation along the banks of the rivers, so it would be beneficial to rather be nomadic, and move along the river with your herd once the grazing starts to disappear. Bonus is that as a river has two banks, for half the year they can move down one side of the river, then cross it at a narrow/shallow point, and move back up in the opposite direction, allowing enough time for the vegetation to recover. [Answer] If the 150km circle is at the bottom of a crater with gentle walls climbing up on all sides and if the intensified rainfall just outside the circle slides off those walls and flows down towards the center, then the enclosed area could be anything from a desert to a swamp to a lake depending on how much rainfall naturally occurs in the area. ]
[Question] [ In my world, officials dealing with sensitive information have their tongues amputated. Naturally writing and a special, government-only sign-language are the main forms of communication, but creating complex audio signals may also be very practical. What sounds may they use to communicate? The dependence on instruments is not permitted; it would help to have sounds described in IPA where applicable. Edit: Writing and signing (the signing in my world being very precise and nuanced) require fine-motor skills which work very well in daily life but are impaired by intoxication or injury, preventing the well-known "get him drunk and see what he leaks" and physical torture. This serves as a means of preventing accidental leakage of information. Additionally, only highly-trained and trustworthy individuals 'sacrifice' themselves to the procedure of having their tongue removed. The 'spoken' language would be even further limited and constructed to prevent easy decoding, with only simple and emergency signals being taught to all tongueless personnel. [Answer] With substantial training and practice, a [tongueless person can learn to speak again](https://www.ucsfhealth.org/patients/brown_kate/). Intelligibly. Your characters may choose not to do that though. Also, I frame challenge your assertion that people who are drunk/high enough to have fine motor ability impaired can not use sign language. If you're so impaired that you can't sign at all, then you're unconscious (or close to it). Remember, signers can slur their words just like speakers do. In fact, speaking requires more fine motor control than signing does. This is why bilingual children learning both a signed and a spoken language will learn the signed one first. And why children with motor impairments are often taught basic sign language. But to answer your question directly, there are various sounds that one can produce without a tongue. For consonants, there are 3 basic parameters for every sound: 1. Voiced vs unvoiced 2. Placement 3. Movement Voiced vs unvoiced refers to the involvement of the vocal cords. Put your hand lightly on the front of your throat. Make a long "s" sound. Now make a long "z" sound. Feel the difference? The "z" is voiced; you will feel the throat buzz as the vocal cords engage. Removing the tongue will not affect voicing. Placement means where the sound is being made. No tongue greatly restricts the possibility of most consonants because they are made by the tongue (the tip, the middle, the back) in contact with various parts of the mouth. But several are made without the tongue. * Labial sounds like "b" and "p" (the first is voiced, the second unvoiced) * Labial-dental sounds like "v" and "f" * Some glottal sounds like a glottal stop Movement is another characteristic of consonants. * Stops are quick sounds like "b" and "t" * Fricatives are prolonged sounds like "z" and "sh" * Liquids are semi-prolonged but where the contact is pretty minimal, like "l" * Clicks are faster and harder than stops. They are not present in English, though all English-speakers can produce them (super simple versions) as they are used for other forms of communication and play. Again, placement is paramount. Labial clicks won't be impaired. While the tongue is involved in most of those movements, it really depends on placement. They can also be made with the lips, the lips in conjunction with the teeth, and with the throat. Vowels are more complex. They all involve the shape and placement of the tongue during voicing. They're prolonged and don't have substantial contact with other parts of the mouth (beyond just fitting in the mouth). Even without a tongue though, the mouth can change shape. This can approximate many vowel sounds. Enough for basic communication. Ditto for some of the consonant sounds. --- To sum up...and to offer a massive frame challenge. While your question about the sounds produced without a tongue is straightforward and reasonable, your premise is full of holes. A lot of "sensitive information" is vulnerable to someone who can't do anything but nod "yes" or "no." Drugging someone with "truth serum" or whatever won't stop them from signing or writing. Slurred signing or writing will still give away secrets. And removing the tongue doesn't stop people from speaking to some degree. It would be enough to compromise security in many cases. While it's true that removing tongues is used in some fiction as a security measure (the Song of Ice and Fire series has a few cases; though these are people who don't know sign language (one is never mentioned as part of the society) and who are illiterate). Even so, they could give a lot away if motivated to. They don't because they're afraid of losing more body parts or their lives. It's just not as effective as you think it is. You can't take someone fluent in one or more human language, remove their tongue so they don't involuntarily spill secrets during interrogation, teach them a coded spoken language, then expect that only the coded version will come forward if they're too drugged to control what they say. Honestly, I can't even imagine this. [Answer] In Hindi language (India), the alphabets are arranged in order of the way they are pronounced using a combination of tongue, teeths, lips, mouth roof and nose. Refer [this](https://dhavaldalal.wordpress.com/2016/02/14/intensive-sanskrit-workshop-day-1-second-half-sri-aurobindo-society/) link for pronunciation details. As per the details present in this link, the sounds described as "Guttrals" and "Labial" are the sounds that one can make without a tongue. They are: 1. a, aa 2. u, uu 3. ka, kha, ga, gha, ṅa 4. pa, pha, ba, bha, ma The third row is tricky (ka to ṅa) as to make this sound the root of the tongue comes in contact with the soft palate and obstructs the air flow. ]
[Question] [ A launch loop <https://en.wikipedia.org/wiki/Launch_loop> is a proposed way to put lots of things into space at lower unit cost than rockets (only need to pay the energy cost in electricity for each payload) without needing very strong materials (the exoatmospheric-height structure is supported by electrodynamics, not the strength of materials). Postulating a setting where the technology and economics are up to designing such a thing and manufacturing all the components, how would you go about building it? In a half-built loop, the rotor is not circulating, so no support. The obvious answer is static scaffolding, but if you could build static structures that high, you could just let that suffice for the final structure and avoid all the trouble and expense of the circulating rotor. [Answer] It is built and raised in one of 'a few' ways, but both use the same force that makes it work: Built "In Full" on the ground, then slowly powered up. The forces that you're using to keep it up are what raise it, and the end stations down on earth move closer together. [Building over an ocean is probably handy to avoid clearly too much space...] Built "Live, in segments", where a core station is put in place, and a small scale loop is started. This smaller loop is then slowly expanded by adding more and more segments until it is grown to the final size. * Segments could be added in different ways, such as being brought up as wedge shaped pieces that fit in/outside the ring they're destined for. Somewhat like tunnel boring machines laying pre-cast concrete segments that fit through the tunnel already laid. [In short, adding links to a bicycle chain while the chain is being flung through the sky... No one said sci-fi engineering was easy or graceful.] * "Hoberman sphere" like expanding structures are also another option for the segments. <https://en.wikipedia.org/wiki/Hoberman_sphere> But in ring form. Connect the edges of a contracted ring to the inside of two existing segments at a joint, then expand the new segment as the previous joint is released. A third potential option would be to just build the entire structure in a "Hoberman sphere" like nature, where it is compacted for initial on-the-ground form, and is then telescoped/expanded during power up. Neither option is really all that easy, but the "Live, in segments" design is a solid demonstration of how to conduct maintenance and repair. This is not a structure you want to power down and lower back to earth every other month to change bearings... [Answer] You could consider using alternative megastructure/launch system engineering methods to raise your launch loop if you can't build and raise it in place under its own steam. Given the technology required to build a launch loop, one such bootstrapping system would be the [space fountain](https://en.wikipedia.org/wiki/Space_fountain) which uses magnetically accelerated pellets to impart force to the top of a tower via deflector coils, so it isn't entirely unrelated to launch loops. The fountains on their own are handy for space launch purposes, but unlike a launch loop don't provide any speed boost, only a helping hand up in the atmosphere. Fountains have the advantage that extending and contracting them is much simpler as the pellets are connected together into a single giant rotor. Build a series of fountains along the length of your loop to help push the structure into place whilst you're getting it ready, or to provide maintenance later in its operating life. An alternative would be the colossal magnetic levitation system proposed for the [Star Tram gen 2](https://en.wikipedia.org/wiki/StarTram#Generation_2_System). This is intended to be a launch system in its own right, so you'd need to decide what advantages the launch loop brings over the startram (and there are one or two, and in the limit, launch loops start looking like [orbital rings](https://www.orionsarm.com/fm_store/OrbitalRings-I.pdf) which are all sorts of interesting and useful). Basically you use a whole bunch of giant superconducting cables to generate magnetic fields that repel each other, and some dumb tethers to hold the levitated structure in the right altitude and angle. Astonishingly, you could apparently get the business end the rquired 22km up this way. Scaling to 80km and the weight of a whole launch loop may be rather difficult, but might be enough for assembly and partial raising. To be honest, I think a Star Tram type system is much easier than a launch loop, and somewhat more straightforward to make and a lot easier to maintain, even if it isn't as cool or powerful. YMMV, of course. > > The obvious answer is static scaffolding, but if you could build static structures that high, you could just let that suffice for the final structure and avoid all the trouble and expense of the circulating rotor. > > > Scaffolding of any kind is going to have some serious limits... even aside from the issue of ultimate material strength and whether you could build a static structure 80km tall, it would require a colossal amount of materials and have a vastly greater environmental impact than a dynamic structure (it would affect weather patterns like a mountain range, and you might need to find an asteroid to provide you with enough metal at a reasonable price and minimal environmental damage). It may actually be easier to build a launch loop, and that's not something you get to say very often. Whether dynamic (like a fountain) or static, a tower also only gets you up, not out. You still need to achieve orbital speed, and a launch loop provides a means to help you with that in a way that also supports its own weight, killing two birds with one stone. ]
[Question] [ I need an explanation for how one could be immortal and still age. If one was truly immortal one would remain an infant forever. How could this be explained? I'm working on a character who is supposedly immortal, but is also in his later years (an old man). How would that work? Keep in mind he's been immortal since his birth and was not bestowed this attribute by anybody during any point in his life. [Answer] Eternal youth and immortality are two completely different superpowers. Eternal youth bestowed at the moment of birth is a curse. While the person could learn things, the lack of motor control and the lack of pruning in the brain would be permanent (unless you change the specifics of the curse). Eternal youth bestowed at, say, age 20, is something most people would consider a blessing (with caveats). Someone with eternal youth can die like any 20 year old (or whatever age the body is) can die. The body's functions and ability to heal will stay consistent with a 20 year old's but injury and infection kill young people all the time. Someone with eternal youth won't get age-related disease and will have the healing power young people have, but even 20 year olds in the real world get Type II diabetes or heart disease or have strokes because of poor nutrition or chronic drug use, etc. Immortality has different definitions depending on the author. In some cases, you simply can't die. Look at Captain Jack Harkness from Doctor Who and Torchwood. He can be encased in cement for 1000 years, or exploded into a million pieces, but he always comes back. The Doctor is immortal in the sense that he can in fact die but it takes an awful lot, since his species is long lived and can regenerate. In other cases beings are called immortal even if they can die from injury or disease because they don't die from aging and generally they have more time to heal from things that would have already killed a regular human. In other words, you as the author get to choose. If you want immortality to go hand and hand with eternal youth and both are bestowed at birth, well then you end up with a society filled with intelligent worldly infants who can't hold their heads up or articulate words very well (some real life adults are like that, see My Left Foot, and adaptive equipment might become very popular). [Answer] Immortal does not equal ageless. That said, for convenience's sake, I'll abuse the word "age" in the same way you were below. I've seen a number of answers to this question. Most of these concepts can be combined: 1. The character ages at a slower, possibly much slower, rate. 2. The character stops aging when they become immortal. (Not your case, but I'm including it for the sake of completeness, since SE is all about making a comprehensive Q&A site.) 3. There's a difference between aging and growing. The character grows through a normal maturation process, but they just don't age as we normally think of it. (So they keep the healing power of a baby, rather than slowing down to the healing power of a teenager.) 4. The character's aging slows down as they get older. 5. The character ages as normal, they just don't die from it. This option results in extremely serious decrepitude after the character is effectively hundreds of years old. 6. [At any point in the character's aging process, they can reset to a younger age](http://www.egscomics.com/comic/2010-06-30) 7. At some point in their lifecycle, the character just dies and immediately starts over. I've seen this method done with both starting over at birth and starting over at conception. [Answer] *Actually, the movie Star Trek: Insurrection* provides interesting insight into this very question.** In the movie, the Baku are a people who live in the "briar patch," a patch of space littered with radiation, etc. What it does for them is give them incredibly long lives having basically stopped aging. From the novelization of the movie we read: > > Anij unwrapped her arms and leaned forward. "There's an unusual metaphasic radiation coming from the planet's rings. It continuously regenerates our genetic structure. You must have noticed the effects by now." > > > Picard gave her a small, sheepish smaile. "We've ... just begun to." He took the cup proffered by Artim, and inhaled the steam: it smelled of pomegranates and flowers. He looked up at the boy and said wryly, "I suppose you're seventy-five." > > > Artim blinked at him, then with charming childlike candor said, "No. I'm twelve." > > > The adults smiled. "The metaphasic radiation won't begin to affect him until he reaches maturity," Tournel explained. ([Source](https://books.google.com/books?id=4x_Srqsc__kC&pg=PT80&lpg=PT80&dq=star+trek+insurrection+%22no,+I%27m+twelve%22&source=bl&ots=hAqB-0qCj6&sig=ACfU3U2j79r6jCAA1mTQtfp8uahTpNrzsg&hl=en&sa=X&ved=2ahUKEwjuj9qw6NPgAhUl5YMKHRsZAIYQ6AEwAXoECAQQAQ#v=onepage&q=star%20trek%20insurrection%20%22no%2C%20I%27m%20twelve%22&f=false)) > > > The usual requirement for achieving the goal you seek is to declare whatever it is that grants immortality to be ineffective before physical maturity. Yeah, but what if I want an old man? You have two ways of thinking about this one: * The first is the Insurrection method, but rather than the immortality triggering at physical maturity, it triggers at a point of old age. The human body has several stages of development. Simply: childhood to puberty (0-12ish), puberty to physical maturity (12ish-25ish), physical maturity to middle-age (25ish-55ish), middle-age to golden years (55ish-75ish), golden years to venerable (75ish-death). There are actually more, very distinct stages, but these will suit. You can pick any one of them and simply stop the aging process when the body goes through it's chemical changes for that stage. * The second is to not really be immortal, but to age really, really slowly. This is kind of the "Elf" solution to the problem. You live thousands of years — but your aging process is linear through that period and you eventually die. But, none of this is exactly what I want If those solutions (or another provided by one of our other community members) doesn't suit, then you need to choose. You aren't going to find a scientifically sensible way of describing this because it doesn't exist. You need to come up with a narrative mechanism that explains the situation and allows you to move on with your story.... Rats... I just realized your question is primarily opinion-based. OK! You got lucky! You're a new user, so please take a moment to read up on what [primarily opinion-based](https://worldbuilding.meta.stackexchange.com/questions/6436#6437) means. You might also be interested in the difference between asking for an [infinite list of things](https://worldbuilding.meta.stackexchange.com/questions/6130/catalog-of-question-types/6139#6139) (off-topic) and a [finite list of things](https://worldbuilding.meta.stackexchange.com/questions/6130/catalog-of-question-types/6138#6138) (on-topic). Cheers! [Answer] If by "in his later years" you mean that he has the external appearance of an old man, that's easy: only his innards are immortal, and he hasn't molted in a while. The other answers explain maturing to adulthood. [Answer] I have seen this handles one particular way in fiction and mythology, a person is immortal but ages either normally or at a slower pace. But a sufficiently destructive injury (one that would normally be fatal to a normal person) restores the person to their prime as the body repairs the damage. Basically they age and reset over and over again resetting to their prime every time they "die" sometimes the "death" and reset are periodic instead of traumatic, often both. Alternatively they age to some arbitrary point then age in reverse until they are back in their prime then start aging normally again. Some versions or merlin use this method. [Answer] To further other people's points, the main difference here is the difference between growing and aging. Growing is a "deliberate" (in as far as a natural process can be deliberate) process the body undergoes to get from fertilised-egg to physical maturity. This process stops at around age 17-18, AFAIK. As you may have noticed, 90 year-olds are not giants compared to 18 year-olds. Aging, on the other hand, is caused by faults in cell replication which causes the body to slowly deteriorate in quality. While others have said your immortals are not necessarily ageless, I would think these faults would have to be eliminated or somehow worked around to facilitate immortality. So if you follow this logic, then your immortals would be stuck at around young-adult / old teenager stage, not infants. Though you want someone in their later years, so physically elderly. You could say they still age to a certain degree, and whatever biological mechanism allows for immortality halts the aging at a certain point once it "adapts" - kind of like the way the immune system takes a bit of time to figure out how to stop a disease. [Answer] Know how your mental state can affect your physical well-being? At the simpler and easily observable end, stress from work can induce migraines; joy can put an extra spring in your steps; etc. At the extreme end(which may not necessarily be backed by science), despair and hopelessness can kill, and a strong determination to live on can bring the critically injured back from the brink. From there on I'll extrapolate: Your mental state/age is your primary or even sole determinant of your body's condition The character's body develops along with his mind as he goes through the usual process of growing up. However, he stays in his physical prime for far longer than non-immortals do. After all, people don't necessarily define their mental self image as busy working people in their 30s and 40s, it's more like something life inflicts on them. The successful career man who has climbed to the top of the ladder is usually middle aged; he may wish he was in his 20s and try to act like it but his body will tend to dispel that illusion. For your character it simply doesn't work that way, as long as he thinks "I'm an adult at the top of the world" he will be at his physical prime. What would really cause the character to age is world weariness, the mental burdens of life in general piling up. This would be in stark evidence when the people who he's connected and would normally be his peers begin to pass away. Loneliness is a silent killer that saps the elderly in our real world, and I'd think your character would feel it too. ]
[Question] [ I'm no rocket scientist, but I've been reading up on some basic concepts of rocket science (including some great talks here). As far as I've gleaned, there's two extremes of rocket thrusts: high speed/low mass (like ion engines) and low speed/high mass (like chemical rockets). While an ion engine, fer instance, could get you going really fast in space, it doesn't have the mass ejected to lift you out of a gravity well. A chemical engine can do that, but unfortunately requires a much higher mass of fuel to be taken on the trip. My hypothetical scenario for my fictional world is spaceships equipped with ion drives (or similar) for space travel with most never intended to land on a planet. Those that are, however, (like shuttles or my hero's small trader ship) have an additional set of chemical rockets to do the landing and taking off from a planet's surface. My question is, is that an efficient idea? In very broad strokes, could there be a saving of space and fuel by having smaller rockets and fuel just for gravity evolutions and the more efficient engines for space? Or is space travel such a non-thing compared to the power needed to lift off, that you might as well use the chemical rockets in space too? [Answer] # Split the two types of ship completely Take your idea to its logical extreme. Most ships are large, built in space, and stay in space. They are powered by advanced ion drives, or some sort of nuclear propulsion that you couldn't take into an atmosphere without irradiating the planet. Then to transfer to and from the planet, the big ships can either make use of local ships that ferry cargo from planet to orbit, or they carry their own shuttles to do that job. Alternately, use a more advanced surface-to-space transfer, like a [skyhook](https://en.wikipedia.org/wiki/Skyhook_%28structure%29) or [space elevator](https://en.wikipedia.org/wiki/Space_elevator). [Answer] Have interchangeable modules You specify shuttles and trader-ships. If the planets being visited are set up for interplanetary trading then presumably you park in orbit in a designated zone, fill up with fuel and sausage and chips (fries). Then you head to the rental office and hire a rocket-drive module for descent to the planet's surface. This saves unloading your craft and reloading into another one. Undock your space-drive, put it in a secure storage facility and hook up to the rocket drive. Bingo! If you're visiting a far-flung planet with no facilities then it's going to depend on a lot of factors such as gravity, atmospheric density and so on. Probably specialist vessels will be needed for these outposts. They will be designed specifically to cope with the conditions at their destination. It's quite likely that they will be larger vessels with a smaller planet-going ship in the hold. [Answer] What your asking is entirely possible, you can fit multiple different types of engines onto a spacecraft, from liquid fueled, solid rockets, on ion engines Your a space trader, you visit Space Stations orbiting the Earth and other planets where most trade and space commerce occur, but occasionally you need to fly down to the surface to pick up goods, so you have a shuttle. a craft that can travel between the surface and orbital stations, AND between planets. And thanks to that you can be the best space trader in the system if not the galaxy... except You're broke! Alas yes it is entirely feasible, but is it practical? Humans have tried the shuttle idea, and while it was indeed a monumental success of engineering. it was a horrendously expensive way to get anything to and from orbit, that's why NASA have switched to the disposable SLS, and companies like SpaceX have the their own rockets like the falcon, both are far cheaper to build and run then the shuttle, then consider that during launch you'd have to drag some (presumably) big ion engines off the ground and into orbit which means extra weight and therefore more fuel needed to reach orbital velocity. then once in orbit, you switch to your ion engines, but are now dragging along your big heavy liquid fuel engines which means extra weight and therfore extra fuel. Simply put having someone do it with two separate vehicles, one to reach orbital velocity and then offload it onto one to go between planets is far far cheaper then a single multi-use craft. The less fuel you use the less fuel you need. I know that sounds like a grass is green water is wet sort of comment, but if you have a spacecraft that weighs X needs to reach orbit then you need Y amount of fuel, simple put that fuel in... ah but then your craft now weighs Z (X+Y) so you need to add more fuel to get that craft and its fuel despite it always getting lighter moving. thats why the Saturn V was as big as it was. Now consider that you need to take off, carrying extra fuel and extra engines, but thats a lot of extra weight which means needing to spend more on fuel, which you'll need to incorporate into the tendering process of when you price for work. And before anyone comments what about the fact that the Saturn V had loads of different engines that was staging, the spent stages were dsicarded as it climbed, this is no where near efficient enough on an SSTO [Answer] I'm uncertain of the exact size of your spacecraft, but it is possible for a [plane to fly into space](https://en.wikipedia.org/wiki/Spaceplane). The basic answer is to fly as a plane to a fairly high altitude, switch to rocket engines to accelerate to orbital velocity, then swap over to more efficient ion engines. Landing depends on the kind of atmosphere. If it has a thick enough atmosphere it can be approached and used to aero-brake. It might take several passes to reduce overall velocity to safe levels to attempt full re-entry. The final approach would work like a space shuttle. Angle up to 40~ish degrees slow down as you descend. At some point swap over to powered flight (if possible). Or land it like a space shuttle. If there isn't any atmosphere, hopefully you brought enough fuel to actually perform a safe deceleration and landing. [Answer] It all depends on weight The initial planners of the Apollo missions considered all sorts of options. For a while, a 'direct ascent' vehicle was considered. It is basically a large rocket that takes off and lands on the lands on the moon in one vehicle, which could still be staged at lift-off. An early artist example: [![enter image description here](https://i.stack.imgur.com/Bh3SD.png)](https://i.stack.imgur.com/Bh3SD.png) However as they investigate the implications, they found that a Lunar Orbit Rendezvous (ie. have a separate vehicle to launch, a separate vehicle to orbit, and a third vehicle to land and lift-off from the moon) was much more efficient. This is mainly because of weight. More weight = more fuel, and already the enormous Saturn V launch vehicle or even a Nova class was required to launch a relatively small payload (just 3 crew). In the vacuum of space, you do not need atmospheric shielding as your launch vehicle or command module do, takeoff and re-entry into atmospheres is a violent process. By using the Lunar module, you could save enormous weight by having paper-thin walls, lightweight engines and minimal fuel. They even discussed having 3 legs instead of 4, but thought that they needed the redundancy of 4. A lightweight craft was also much easier to handle and control. Encasing the module in the takeoff/reentry stage cylinder meant it was protected during this phase, meaning a command module / lunar module docking procedure needed to be done in space, however this complication was deemed worth it for the weight and fuel saving. In comparison, this early diagram compares the relative size between DA and LOR: [![enter image description here](https://i.stack.imgur.com/67xFR.gif)](https://i.stack.imgur.com/67xFR.gif) Even the Soviets, with their independent space agency, went through all the options and reached the same conclusion. So to answer your question, combining the two doesn't make sense when a simple [docking / undocking procedure (which was accomplished easily in the 60's and 70's)](https://en.wikipedia.org/wiki/Lunar_orbit_rendezvous) could enable you to save enormous weight and fuel expense, reduce spent engines and shielding and be much more controllable. ]
[Question] [ So let's say someone has telekinetic powers. He can move a bunch of things at once with his mind as long as the objects aren't too heavy. One day he's walking through a dark secluded alleyway and, oh no, he gets shot, and even worst the bullet hits a major artery. After snapping his assailant's neck with his mind, he falls to the ground. He's now in a puddle of his own blood still bleeding profusely. Within minutes he'll almost certainly be dead. Unless... Suddenly our fellow has a bright idea, he could use his telekineses to prevent the blood from leaving his body, right? Moreover, could he not draw the blood that he's already lost, back inside of him? Kind of a self-transfusion sort of deal. He might potentially be able to do so and just get back up. Walk over to a hospital on his own two legs after having sustained an extremely severe gunshot wound, keeping his vital fluid within him by sheer force of will, now wouldn't that be a sight. --- Could this actually work? Is there something I'm missing? --- A few notes: Firstly, the ground is obviously not sterile and so neither is the blood that's in contact with it, would this be an issue? Next, this telekinetic can only use his powers while he is conscious, would the shock of losing so much blood so quickly, or perhaps the pain of being shot cause him to fall unconscious before he has time to reach a hospital? Is recovering from blood loss as simple as putting the stuff back in? [Answer] He will live IF ... He should not have lost more than 30% of his blood in order to mantain his consciousness and be able to think clearly and focus his telekinetik habilities properly (Source: healthline newsletter): <https://www.healthline.com/health/how-much-blood-can-you-lose> No, the blood on the floor should not be put back in his body. The blood is now full of bacteria. unless he had mastered his telekinetik habilities to the point he can kill individual microbes without damaging the red cells in the spilled blood. And yes, it could be possible for him to close the wound. BUT he will need to mantain the concentration all the way to the hospital, because although he is supporting the hole with his mind, the wound is not healed yet, and if he looses concentration, the hole will open again because the platelets have not finished working yet. If he was shot in a vital organ, he may need to extract the bullet first and perform a deeper telekinesis healing process (not only in the blood vessels, also in the organs) but if the shot was in the hearth, he may not have time for that (he will die). If he manages to arrive to the hospital without loosing more than 35% of his blood, in the hospital they will "refill" him and will eventually be ok. If he looses the concentration at any point in the way and starts dripping additional blood, then at some point he will enter in a shock state, will loose the concentration and die. [Answer] It seems he is unlikely to faint unless he loses too much blood, or so forensic scientists say. Luckily the body is good at staying alive, so it has several self defense mechanisms to protect itself from system failure. I would personally apply telekinetic pressure as tourniquet, stopping blood flow to the injury. The bodies natural reaction to the blood loss will keep his body functioning and although the pain will be hard to push through, he'd possibly make it to a hospital if not to far away. Stuffing blood back into his veins seems unlikely to work and not that important if it did. [Answer] If he stays conscious and doesn't go crazy from the pain he's most certainly capable of keeping his wound closed. I wouldn't attract the blood unless you assume you'll lose consciousness and bleed to death, as an infection is guaranteed and if you accidentally scoop up dirt and push that your veins you are in massive trouble. That said, he's likely going to be in shock and even if he gets the idea, he's likely not going to have the precision to do anything more than clamp down on his arteries and hope he clamps hard enough/not so hard he does more damage to himself. Gunshots Hurt, and bleeding heavily is extremely unpleasant and terrifying. [Answer] I agree with the idea of using the powers to keep body in the body or by clamping arteries, and not attempting to reuse blood on the ground. Even with IV antibiotics and filtering equipment, it's likely to trade a quick death for a slow one. Perhaps he could also use his powers to bring items to him in the alley that would allow him to slow the bleeding in more conventual ways (though he might not be able to locate them easily). Like surgical clamps or even locking pliers or binder clips. Pressure bandages. Or he could grab a pen or chalk from afar and write a message to someone to come help. ]
[Question] [ Could humans permanently live off a single food-like block, made of various edible materials, which contains all their daily requirements of calories, vitamins, and minerals? Preferably is there a way for this food block to be in a dehydrated state, allowing it to be as portable as possible (only requiring the person to add water for consumption)? How long would the shelve life be, preferably while being stored unrefrigerated? What would this food need to be made of? [Answer] Observe: <http://www.nestlenutritionstore.com/products/Digestive-Nutrition/VIVONEX-PLUS.html> It's a powder rather than a block but for your purposes a binder could be used to make it into a block. Some people with damaged digestive systems have to use this for life. [Answer] Kinda but it wouldn't be something that you'd be able to live on long term. Looking at modern day survival food it would be possible to create a single food block that could keep you alive. While these blocks supposedly last for 5 years after manufacture, the main issue I can see is their limited protein content (9g for a 250 caloric block for example). You could solve this by adding additional protein sources but that would compromise the shelve life of the product. The real killer would be the micro-nutrients from real plants that can't be replicated/supplanted very well and which has a major effect on health. Ultimately food blocks of various types could make up a viable diet they would have to be supplemented by real food as well. [Answer] We know what macro- and micro-nutrients are needed, and it what amounts, per day, for infants, children, teens (male and female), adults (active, sedentary, male, female, pregnant, nursing, etc). Thus, someone just has to actually do the work of making such a food block. (This all ignores the fact that it would soon become very boring and the vast majority of people would really start to grumble.) ]
[Question] [ ## I have a town, the capital of an empire. It covers 560 Hectares. ### What kind of natural barrier conforms to the following requirements: * Is both heavily defensible and does not hinder trade all too much. * The technology is of 1200 AD Europe. * A large (Rhine sized) River either runs through this town or starts in/adjacent to the town * Only has 2 or 3 passages into it from the land (used by everyone daily to get in and out of the town, they should be wide/tall/open enough to have main roads on them and can be natural or artificial), however these passages are not very large (1-2 miles long) * Last but most important, the barrier with only 2 or 3 passages through must be strategically implausible to circumvent. This town should not be able to fall by way of force unless you swarm the passages with thousands of men. I wish to know what type of natural barrier I could use to make it realistic both geologically (it must be able to be explained how it naturally formed) and strategically (it must not prevent trade or be too easy to overcome with an army). [Answer] An "Oxbow Lake" may be what you are looking for. Formed when the river makes a bend, then cuts its self off. Basically you get a moat around a sizable chunk of land. <https://en.wikipedia.org/wiki/Oxbow_lake> [Answer] The river itself is the best barrier. Your city is built on an island in the middle of the river, and there are only a couple of bridges on each side. Imagine something like the [Île de la Cité](https://en.m.wikipedia.org/wiki/%C3%8Ele_de_la_Cit%C3%A9), the original location of Paris, but on a larger scale. [Answer] A peninsula jutting into a deep lake or a spit of land on a river bend seems to have most of the attributes you are looking for. The neck of land is narrow enough to fortify and garrison with a relatively small force, and the water provides a means of hindering approaches from that side. [![enter image description here](https://i.stack.imgur.com/zf9QF.jpg)](https://i.stack.imgur.com/zf9QF.jpg) Fort Senneville. If the peninsula were narrower, the approach to the rear would be much more defensible During the American Civil War, Vicksberg was built overlooking the bend of a river (for reasons of geology, it was actually opposite the land jutting into the river, the garrison had a powerful battery of artillery to close off the river and was mounted on a high bluff), which illustrates most of the points. In the Civil War, Grant found getting either near or even around Vicksburg very frustrating as the terrain was very difficult to manoeuvre armies and artillery through. So building on a high feature overlooking a bend in the river, and ideally one with difficult terrain behind it and a narrow approach (like a finger sticking into the river) will provide a defensible position. Your main issue is actually going to be the ability to store enough provisions to endure a long siege, or having a powerful enough fleet to force passage to and from the city to relieve them and provide supplies. [Answer] It could be on the edge of a fault line, surrounded by deep bodies of water with active underwater volcanoes which cause the water to boil, and frequently release toxic gasses which would make crossing by boat unreasonably dangerous even if the boat was able to sustain the heat. Not to mention, the steam from the boiling water makes the traversal really scary, because nobody knows what freaky creatures are living in that hot water. In a few places, natural land-bridges have formed which people can get across. The land-bridges are wide enough that they aren't too hot to walk on in the middle, but if people stray too far from the well-trodden path then the land becomes hot and unstable, leading to potential for cave-ins and more releases of gas. If you're near an ocean then maybe it rains often enough to replenish the boiling water in your barrier-ponds. In the above scenario, I suppose your river would be warm and yellow, but the people might be able to filter it and make it drinkable... Idk if you plan to have fish in that river, but in this scenario they would have to be fish unknown to the real world. [Answer] What about a crater like those left from a volcano like Aogashima, Japan or Diamond Head in Hawaii? That would offer protection around the perimeter and depending on the size/depth of the impact there could be access to water. The residents could also easily control any paths/tunnels in or out. Because of the steep terrain it would be very hard to get any sort of siege weaponry along the peaks and any attempts would be noticed long before they reached the top. Especially if lined by watch towers. [Answer] Why wish for this city to be built on the continent when it cuould be an island? Your City is built either in an island in the middle of an easily acessible ocean or in a stream. The river or sea around the island would provide protection against almost any large land based army, as they require boats to cross the waters. Adding city walls you have a hard to break line of defense, while a port accessible through one or more sea lanes provides a perfect basis for trade. [Answer] [Dikes](https://en.wikipedia.org/wiki/Dike_(geology)) are your friend, large magmatic dikes can be many metres thick. Most are linear or curvilinear features but they also form full [enclosures](https://en.wikipedia.org/wiki/Ring_dike) around large areas of land. There are three realistic formations * The city is completely within a ring dike, in this case the river would have to either cut through a ring dike, it could then be the main avenue of entry and exit from the city with tunnels cut through the dike forming the landwise entries. * Alternatively a curvilinear dike could define a pocket with the river cutting along one side like the straight side of a capital D, this would give a natural, curved, landside wall that again could be cut for landside access. * Lastly the city could be in a triangular space formed by intersecting linear dike walls on two sides and the river along the remaining edge. In all cases the tunnels cut through the dikes have to be carefully sized and placed to ensure their defensibility but should easily be filled or blocked by dropping large debris from above, inside or out. ]
[Question] [ In my world, zombies are quite common, and are considered a part of the wild life. Most of the usual flora and fauna are similar to those in IRL. I have three key questions, but I'll put the other two on their own separate posts to prevent being too broad. This post's question is: * how could the wildlife have an immunity defense against a zombie infection/prevent their species from all becoming animal zombies? Feel free to lend me constructive criticism, or letting me know about any spelling errors and such that I make. [Answer] For every infection we have an initial uncontrolled spreading of the infective agent, until some individuals with the right antibodies are found, and the infection is contained. This can very well be the case for your zombies: some individuals have immunity against the zombovirus, and can keep the infection under control, while just a few are effectively zombified (you need your zombies to be generated, don't you?). You may want to have a system where some individuals are fully asymptomatic, some are wildly zombified and some are latent zombies, meaning that until their death they do not show symptoms, but then they awake. [Answer] Model your zombies on other introduced, invasive, poisonous species. The cane toad would be a fine model for zombies. [![cane toad](https://i.stack.imgur.com/m9m0L.jpg)](https://i.stack.imgur.com/m9m0L.jpg) <https://www.nambuccaguardian.com.au/story/5320897/biosecurity-zone-proposed-for-cane-toad-infestations/> <https://en.wikipedia.org/wiki/Cane_toads_in_Australia> > > The long-term effects of toads on the Australian environment are > difficult to determine, however some effects include "the depletion of > native species that die eating cane toads; the poisoning of pets and > humans; depletion of native fauna preyed on by cane toads; and reduced > prey populations for native insectivores, such as skinks." > > > Things that touch cane toads do not become cane toads. But things that touch cane toads die. Cane toads eat anything that moves, so things that compete with cane toads starve. The number of cane toads increase and increase. In places like Bermuda they have become gigantic. So your zombies: these are parasitized biological creatures of some sort, not the purely fantastic Walking Dead version that live indefinitely and do not eat or drink. You will need to figure out what your zombies eat. Whatever else eats that will have less of it. You need to figure out what might think zombies are food. These things might become zombies themselves if they try to eat zombie. Finally you will need to think of ways that environmental organisms might evolve to capitalize on the food resource represented by zombies. Diseases, for example - the end run around the immune system produced by the zombie fungus might be exploited by other fungal pathogens that just want to eat rotten meat. Or predators that can deal with zombies - I have read of crocodiles that eat cane toads by first vigorously washing the dead toads and so clearing off the poison. [Answer] Many species don't need to immune to the zombie infection itself, they just need keen senses, an enlightened sense of self-preservation, and to be slightly faster than the zombies chasing them, or able to eliminate zombies chasing them without risking infection. Most birds fall into this category, horses and many other large grazing animals do as well; the problem really is with predators, they don't run as a first response to threats and their weapons expose them to more body fluid than is useful. Immunity to a virus or bacterium that is adapted to target humans is a given for a great number of species due to the vast differences in body chemistry, one of the interesting things about [Max Brook's](https://en.wikipedia.org/wiki/Max_Brooks) Solanum Virus is that it makes infected flesh toxic and kills everything it touches but only turns humans into undead horrors. Fungi are a bit different, their targets can be very specialised or very broad so immunity can be harder to justify. In a world where zombies are a permanent feature the only species that are still active in the landscape are zombies and species that either 1. don't become zombies because they're cautious or 2. can't become zombies because the infectious agent won't effect them That's pretty much a given, you just have to think about which category a given species falls into and you can justify any species you need to as any of: 1. evasive, they don't ever come in contact with zombies 2. naturally immune, their basic chemistry makes the infectious agent ineffective 3. acquired immunity, zombies have killed off that part of the population that could be infected. This will tend to leave a small genepool meaning that, for example, all the remaining leopards are in fact panthers or similar oddities. [Answer] First of all: There are so clarifications that would make this easier like what exactly are the properties of your zombies? For how long have zombies have been around? However I can take a stab at this.. How Could Zombies fit in a natural ecosystem? Well the biggest problem I see is that zombies are "reanimated" humans and that comes with a set of problems. Zombies wouldn't be around for very long! The process of putrefaction will happen to zombies! With some handwaverism you can explain that away with " the process of reanimation kills bacteria and the like in the corpse. That would be the criticism... As to the wildlife! We already have corps-eating animals. Wolves and vultures generally have an immunity to the disease that plague dead creatures. > > the pH scale goes from 0 to 14, with 0 representing a highly acidic > substance, 7 representing a neutral one and 14 representing a highly > alkaline one. While the pH of human stomach juice can vary quite > dramatically depending on what you’ve eaten, it tends to stay between > 1 and 3. The stomach acid of a turkey vulture (one of the hardiest > members of the vulture family), on the other hand, has a pH of almost > 0. Just to highlight how ridiculous this is, the pH scale is logarithmic, which means: “Each whole pH value below 7 is ten times > more acidic than the next higher value.” > > > In other words, in the extreme a turkey vulture’s stomach acid could > technically be almost 1000 times more acidic than yours at a given > instance. In fact, it’s so acidic that it can dissolve many metals. > For further reference, battery acid has a pH of about 0.8. > > > I think that some animals would not be infected by eating them given the info above. So they are a food source! They would be force into the food chain however they are not on top! The Advantage we humans have is our organization (and throwing things) and zombies lost just that! A pack of wolfs would decimate a group of zombies! Given some time wolves would come with strategies, much like dogs herding sheep. And birds!?!?! Well a group of zombies is basically a feast for crows.... Zombies aren't that much of a threat for the wildlife! Cities is where they are dangerous in the wild....not so much! [Answer] L. Dutch has it exactly right in terms of immunity. The alternative is just natural avoidance. Every animal has a pretty healthy self-preservation instinct, and this especially gives it caution around unknowns. Even alpha-predators like bears or wolves, with no natural predators to worry about, will run away from a loud or unknown noise. It's pretty reasonable to assume wildlife would be wary of zombies from the get-go. Assuming these are the classic, shambling zombies, they wouldn't be much of a threat to healthy animals, since they can only move at a walking speed. Instead, they would just become a new scavenger in the ecosystem, targeting sick and old animals that would have died anyway. They are essentially worse versions of hyenas. One way to conceptualize this would be to just consider zombification as a final life-cycle of animals. Every creature is born, goes through childhood, adulthood, infirmity, being a zombie, and then non-existence. [Answer] A) Predators and parazites feeding on zombies Altough your zombies are not walking corpses, they are probably weaker than the healthy specimen of their species * The Zombie pathogen has to bring down the host's immune system and keep it repressed. That would mean excellent oportunity to many other bacteria and fungus to attack them. These diseases, being essentially a complication to the Z infection, could decimate the Zombie population. + To seize control, the Z pathogen has to either destroy or block most of the host's central nervous system. So new Zombies would probably suffer from poor motoric coordination, reduced ability to identify objects and situations, and loose part of their memory. (they would eg not remember the liars and hiding places they had before) \\ These effects make them ideal prey\\: I envision hyena like canines that hunt zombies. They have the ability to digest inflected flesh, and limited immunity allowing them to sustain minor wounds without contracting the disease. And if one if them still catches it, its peers promptly devour him. B) Evolutionary pressure on the Z pathogen to become less deadly. For the reasons aforementioned, the harder the Zombification is, the more likely that the new Zombie dies before it could procreate or infect others. So I imagine that in a sort time many new Z strains would emerge that give up on fully controlling thier hosts. One could devolve into a simple STI, becoming chronic in the genitals, but allowing the host to mate with non-Zombies. Another could allow predators to function normally, not destroying their brain, but camping close to it (say in the nasal cavities). This would only activate itself when the host catches prey, and in one tenth- of the cases, stun the host to allow the infected prey to escape. C) Competition between rival Z variants. As the non- zombie population decreases in the wake of the first epidemic, most of the newly biten hosts would be already infected. Traditional zombies usually ignore their fellows, but realistically some Z strains would start concentrating on catching Zombies of other variants, and either eating or infecting them ( trying to wrestle control from the initial invader) ]
[Question] [ Let's say a group of people live on icebergs. They want to shape them - e.g., let's say they want to add a pier to their iceberg, how do they "grow" the ice. Prefer a primitive answer, but if there is no "primitive" way, then get as advanced as necessary. [Answer] Those people can "harvest" ice from nearby Icebergs (ideally if they are uninhabited, that is). They could also harvest the ice from their own iceberg, extracting it from parts they don't use or they don't need. At night, when it is colder, they can leave water on "cases" shaped as they need so it freezes and they can get the desired part or shape. Getting more fancy, if there is magic in your universe, they could have some sort of "water-bending" skills (think of it as The Last Air Bender's water tribe). These ice wizards play an important role in their community, as they are in charge of making the ice needed for construction. Ice wizards are instructed since young to master their skills. [Answer] Many cultures already live in arctic environments and shape their environment to comfortably live. [![enter image description here](https://i.stack.imgur.com/4rEKS.jpg)](https://i.stack.imgur.com/4rEKS.jpg) An igloo is a prime example of simple structures that can be cut from ice. If the temperature is below zero, it may be possible to 'glue' ice together using water - you can further shape your environment to suit to create many additions to your iceberg. All you need to do these things is to have a primitive saw (to cut the ice), and a helping hand or two. [Answer] Icebergs are (at the moment) pretty damned big - seems to me it'd be much easier to chip away at the edge to sculpt a pier than it would to grow more ice in the shape of a pier. Chipping away at big things to make small things is about as primitive as you can get. [Answer] They'd need to find some way of raising the freezing point of the water where they want to pier to create new ice. There are a number of compounds you can add to water to lower it's freezing point, salt is a major one, that's why they use it to de-ice roads. I there are also compounds that do the opposite; the hormone Testosterone, no one knows why, and long chain alcohols. I feel that the odds of striking on such a compound through accident or experimentation would be extremely low, long chain alcohols are hard to even produce without a modern high pressure chemistry set, ditto isolation of testosterone. Fine dust as from powdered clay will raise the setting temperature but only slightly. If the ocean is cold enough, salt water brine can get below the fresh water freezing point and still be liquid, pouring fresh water out onto the surface in a slow controlled fashion may work. [Answer] Important info: * Pure water freezes at 0° Celsius, but saltwater has to be even colder to freeze. The more salty the water, the lower the freezing point drops. The freezing point of the water in Earth's oceans is -2° Celcius. * Ice can get even colder than the freezing point. This is obvious to some people but sometimes people's intuitions about phase changes get mixed up, and they think ice is always at the same temp it froze at. Ice can get much colder after freezing. If you make a glass of icewater with very cold ice, it is possible for the whole mixture to end up frozen. The ice was capable of absorbing plenty of heat without melting, and the heat it took from the water brought the water below freezing. This is what happens when you handle ice cubes with wet fingers and they seem to stick to your fingers. The ice cube is colder than freezing. It can absorb some heat without melting. It absorbs the heat of the small amount of water on your hands, causing the water on your hands to get colder and freeze. * If the climate starts to get cold enough, seawater (saltwater) will start to freeze. As it does so, it will leave behind the impurities. It will separate into salt crystals and icebergs of freshwater. * Oceans take a long time to freeze. Even if the air temp goes below -2°, it will take a long time for the massive ocean to dump enough heat into the air for all the water to chill to -2°. If your climate is cold enough that the sea is gradually freezing, then the simplest way for your people to grow the iceberg is to wait. Gradually ocean water will freeze onto the side and bottom of the berg. Perhaps if your people can move the iceberg, they could sail it north to colder seas when they want growth. They can harvest blocks from the growth at the waterline, then 'weld' those on by applying a little heat when they place them. If your climate is in that middle zone below the freezing point of freshwater but above the freezing point of saltwater, then simply any fresh water left on the berg will freeze overnight. The temps are no longer cold enough to spontaneously freeze seawater, but your people can desalinate (remove the salt) from seawater to make some freshwater, through various processes, then either let the freshwater freeze into blocks that they then 'weld' to the berg by wetting the place where they put them down, or they could simply repeatedly pour the freshwater on a spot, letting some freeze and collecting the runoff. If your climate is above the freeezing point of freshwater, then a berg is not a sustainable or even safe place to live. When icebergs get to warm climates, they melt unevenly, with the top melting the most. This changes their bouyancy, causing them to [roll over](https://youtu.be/ypNpDEsTg4g), sometimes suddenly. Your iceberg would melt and eventually flip over. [Answer] Dark sky cooling effect (surroundings fully absorbent of all radiant energy transfer based on raycasting from higher temperature surfaces to lower temperature surfaces or spaces) in combination with convective cooling across all exposed surfaces mean that basically you'd be best off making thin walled water-tight formwork the shape of the items (think bricks or gradebeams), adding both reinforcing elements (like seaweed - think kelp) and seed ice - ideally crushed and scattered all placed into your ice formwork (or cases) which are set up to be sitting well proud of the groundplane - say on rocks. Possibly the simplest most effective answer is that there are setup areas where your natives routinely create 2" thick ice sheets, sitting on layers of kelp or similar vegetative matter, then cut these into rectilinear shapes, then "weld" those together with a slurry of crushed ice and ice water to form brick forms and gradebeams... reinforcing the corner conditions of those forms with lapped kelp and ice slurry. They then take the individual brick elements and assemble them together into larger elements on more layers (or the same layers re-used) of kelp... once they reach the greatest size and mass your residents can maneuver, they are then assembled onto the final construction just before nightfall, with again a slurry of crushed ice and icewater with shredded kelp as the mortar. As others have stated above, freshwater's freezing point is lower, but I'm betting that with proper use of the dark sky cooling effect, you wouldn't need a lower freeing point to work as needed: *this is why* all those kids who enjoyed spraying water on their dark coloured tarmac asphault driveways got a great ice sheet forming there before other nearby lighter-coloured surfaces: black body radiation and dark-sky cooling. ]
[Question] [ Previous parts here: [Creating a scientifically semi-valid super-soldier, part 1: Skeleton](https://worldbuilding.stackexchange.com/questions/106292/creating-a-scientifically-semi-valid-super-soldier-part-1-skeleton?rq=1) [Creating a scientifically semi-valid super-soldier, part 2: nervous system](https://worldbuilding.stackexchange.com/questions/107365/creating-a-scientifically-semi-valid-super-soldier-part-2-nervous-system?rq=1) [Creating a scientifically semi-valid super-soldier, part 3: Physical shock resistance](https://worldbuilding.stackexchange.com/questions/107635/creating-a-scientifically-semi-valid-super-soldier-part-3-physical-shock-resis?rq=1) [Creating a scientifically semi-valid super-soldier, part 4: respiratory system](https://worldbuilding.stackexchange.com/questions/108558/creating-a-scientifically-semi-valid-super-soldier-part-4-respiratory-system?rq=1) [Creating a scientifically semi-valid super-soldier, part 5: Heart and circulatory system](https://worldbuilding.stackexchange.com/questions/109503/creating-a-scientifically-semi-valid-super-soldier-part-5-heart-and-circulator) [Creating a scientifically semi-valid super-soldier, part 6: Radiation protection](https://worldbuilding.stackexchange.com/questions/111275/creating-a-scientifically-semi-valid-super-soldier-part-6-radiation-protection) As you move through the world, hearing is a particularily handy trait. It allows you to hear approaching traffic, know if people are around you, allows you to commmunicate and if you are a soldier you'll be able to hear danger and get an approximate location. Modern day soldiers also carry a lot of hearing protection to prevent lasting damage. So if the hearing protection is pretty much mandatory it would be better to build it as standard in super-soldiers. The goal is that these solutions are growable, maintainable and repairable by the biological body of the soldier in question. My own idea's: Localization: Ears can localize a sound, but Human ears for example have their limits. If a sound is coming from directly in front or behind you, it becomes almost impossible for your brain to tell if the sound is either in front or behind you. Barn Owls (<https://www.barnowltrust.org.uk/owl-facts-for-kids/barn-owl-hearing/>) use ears that aren't symetrically placed on the head to counter this, not only are they asymetrically placed on the vertical plane, but also on the horizontal plane allowing them to pinpoint a rodent under the snow better. Perhaps there is also room for another set or (rudimentary?) ears on the body for both redundancy and better localization. Or maybe just place 2 earholes per ear if that works. Hearing protection: I have little idea how to protect the ears continuously without impairing the hearing. Preferably whatever protection is used should automatically kick in when a soundwave/pressurewave reaches a certain threshold to protect the ear. Or perhaps the vulnerable parts of the ear that get damaged could be replaced with something sturdier. A build-in hearing protection like those musicians use which filter out/reduce lots of sounds above a certain threshold seems like a pretty good start but it won't be enough for a battlefield. [Answer] Well, I hope they don't need to be good-looking... I think your idea about additional ears is right on the money. With a bit of tweaking, I think it can accomplish what you're looking for. As you've said, barn owl's asymmetrical placement is great for localizing sound, so that's step 1. Move the existing ears a bit off center. For improving hearing, you've gone in the direction of dampening sounds, which is very important for a soldier, certainly, but with additional ears, we can add another benefit - the ability to hear quieter sounds. In pursuit of this, we need 2 big changes to the "natural" ears. First, make them more sensitive. Not a lot more - the eardrums need to not burst when someone nearby speaks a little loud - but as much more sensitive as you can get without everyday sounds being a problem. We can add better frequency range on these ears, too. Check out owls, bats, and dogs for examples. Second, we need to protect those delicate instruments! Have you ever used your tragus (google image search is the best way to see what that is. I had to look up the name for it) to plug your ear by holding it in with your finger? I would bulk that up with layers of soft and hard tissue and add a muscle so that the soldiers can close it at will rather than needing to hold it closed. Basically this is a biological ear plug. If this isn't too much of a stretch, I would also add the ability to regrow parts of the inner ear in case of damage. Now that that's done, it's on to the big change - a third and fourth ear! These should be off-centered, also, for localization, and I don't think they need the outer ear, (the visible part) since they're not going to be delicate in the least. They could share the existing outer ear or just be slapped on the head somewhere. The idea behind these ears is hearing while under fire, so you want a very tough eardrum. Listening with these would be like listening with ear muffs on, but less... muffled? Hard to say since no human has ever had this experience, but I imagine it would be like a television turned down low - quiet, but perfectly clear. It may become hard to hear quieter sounds, like teammate communication, but you can use these ears for your communication devices, and turn the volume up until it's good and audible. Alternatively, if this isn't too much of a stretch, you could add the tough ear drum as something that can be opened or closed over the delicate eardrum. In that case, the tough ear drum isn't an ear drum at all - it's more like the biological ear plug from earlier. Most natural "seals" like sphincters and eyelids can't seal perfectly on their own, so maybe let your soldiers produce a thinner, more viscous ear wax on demand that could complete the seal. They may also need something like tears to flush the wax out when they're able to safely use their more sensitive hearing again. Yuck, this has gotten gross. Like I said, I hope attractiveness is not an issue. These guys are not going to be good at seducing an enemy operative. I hope that helps you grow your ideas further! [Answer] Experiences From a Modern Battlefield Frankly, hearing is of pretty limited use in modern combat. When you have multiple automatic weapons firing, explosions, screaming, vehicles, aircraft coming in low and hot, more explosions, and more gunfire it becomes apocalyptically loud. I remember my gunny grabbing me by my helmet, yanking my head down and screaming in my ear that we needed to call in medieval and being totally unable to hear him, he ended up just having to shove a radio and a 9-line evac template card into my hands so I could understand what he was saying. We had to move the radio back from the engagement area by a few hundred yards to be heard by battalion over the noise. An no point during 2 combat tours totaling 18 months in total duration between the two was my hearing ever a factor in locating an enemy beyond "oh crap, machine gun fire from over there!". When both parties have high powered modern weaponry they tend to not get very close to each-other to engage. The idea that combatants are stalking around silently straining their ears to hear a nearby hidden enemy makes for good drama but it just doesn't really happen. If the enemy were ever within 200 meters of us it was essentially a point blank engagement and things got very loud and very messy very quickly. The worst part of combat concerning hearing wasn't that I wished I could hear better, but that I could somehow have hearing protection that would filter out what I didn't need while still allowing me to communicate to my squad. In movies everybody had neat little radio headsets, in reality there's two radios for the whole squad, and a headset is less that useless because now you are carrying around about 20 pounds of batteries to power something that isn't even useful once you actually need it. I did do a "non-combat" deployment into Ramadi where our squad was attached to a Navy SEAL team to "instruct" local Iraqi army recruits how to fight, in reality we just raided ISIS explosives caches and obtained intel for airstrikes. The SEALS had this neat headset thing that amplified sound when you were wearing it but would shut off amplification when things got loud, and it had a radio built into it that also boosts radio chatter volume when it detected high noise. The SEALs had them because well, they're SEALs, They get the best gear without question. At $2500 a pop the military doesn't see fit to hand said headsets out to everybody because contrary to popular belief, main battle fighting groups are issued the most economical gear, not the latest gear. I have no way how you would obtain this functionality from genetic modification, that's really not my area of expertise. All I can say is what requirement I would have liked to have on my battlefield and that a technological solution exists already, its just not included in the regular Infantry's general gear issue yet. [Answer] Re-engineer the outer ear and canal to include intricate musculature controlling banks of different-density veils, flaps and apertures. With these structures, the soldier should be able to limit which frequencies reach the ear drum. Add more musculature and ligaments to allow the outer ear to rotate on two planes, allowing the soldier to also chose which direction is being listened to. Make the musculature and control nerves very fast with hardwired instincts to snap closed whenever environmentally necessary. Now re-engineer the larynx. After all, what good would selective frequency filtering be, unless you could simultaneously produce those frequencies audibly. Now super soldiers can speak clearly to each other despite ambient battleground noises. They just have to choose a quiet frequency to speak at and filter out all other noise. Finally, re-engineer the auditory portions of the brain. Model it after the naturally occurring circuitry from the brains of bats. Give your soldiers a gift of echo-location. ]
[Question] [ Okay, so I was working on making a sapient creature that lives underwater ended up with what was basically a two-hundred pound crab. They have human level language skills, and I decided to justify this social skill by making them build structures to protect themselves and their young from predators. Over time, these structures would grow larger and branch into storehouses, temples, castles, and other specialized buildings. To teach new generations to build these things, or to keep building the things their progenitors started, this species learned complex language and writing. Basically, its the old tool-use-leads-to-civilizations idea, except with architecture instead of handheld tools. The problem is what kinds of construction methods could a crab use underwater? All the methods of building I know of require some form of mortar or specially cut stone, neither of which seem possible for a underwater creature without fingers. Just making rock igloos wouldn't work either, as large predators could just knock them over. Two important details: In addition to their crushing claws, this species has a "beard" of sensitive, octopus-like tentacles for more dexterous work, but are only little over a foot long. Secondly, they can go on land, but need to be submerged or sprayed with water in order to avoid drying out and risking health problems (other than their legs and arms, they have soft shells covered in skin). They can comb beaches and travel a little inland for useful materials and farm undersea plants to turn into ropes, but they can't really use tools other than their claws and tentacle-beard. Metallurgy and building mortar are right out, but they can find and transport stone easily enough. I'm not sure if they would be able to mine, as that would quickly were down their claws. Any ideas or suggestions? [Answer] You don't need mortar to build in stone. Check out [dry stone construction](https://en.wikipedia.org/wiki/Dry_stone) for examples of things that a mere predator would never be able to knock over. (Waves are another matter - you'd be wanting to build below the depth of wave action). They can wield a chisel to shape the stone (remember a lot of the things in the above article were built by people without metal tools), or maybe they live somewhere that the local rocks splits naturally into slabs. Use biological mortars. * Barnacles secrete a glue to stick themselves to rocks. [article on the science](https://www.ncl.ac.uk/press/articles/archive/2014/07/naturesstrongestgluecomesunstuck.html) * Mussels spin byssus threads to anchor themselves to rocks (and to pin down enemies like dogwhelks). [Wikipedia summary](https://en.wikipedia.org/wiki/Byssus) * There are a whole bunch of encrusting organisms like bryozoans, coralline algae, corals and things which you can encourage to grow over your structure and hold the stones in place. In fact stopping them from growing on everything you build will be pretty much impossible! Google 'shipwreck' and 'encrusting organisms' and see what happens even to things which were painted with anti-fouling chemicals to prevent the encrusters growing. [Answer] Corbelling [![enter image description here](https://i.stack.imgur.com/6kWof.jpg)](https://i.stack.imgur.com/6kWof.jpg) This is a monastic "beehive hut" on Skellig Michael, an island (More of a large rock, to be honest.) off the coast of Ireland. For over a millennium, it has withstood winds of over 20mph on average and the kind of waves that can, and do, claim lives. [![enter image description here](https://i.stack.imgur.com/rWC3D.jpg)](https://i.stack.imgur.com/rWC3D.jpg) Waves just off Skellig So how did hermits build such resilient, yet crude-looking, structures? They used a technique called corbelling. Flattish stones are stacked on top of each other, gradually getting closer and closer to eachother, until the slabs meet in the middle. The gaps between the stones are so small that you couldn't fit a knife edge between them. Stupid tourists have thrown rocks at the hut and tried to kick the walls in, yet the structures remain 100% stable. All the crabs really need to do is pick up stones, so I wouldn't put it past them to build structures like these. ]
[Question] [ The civilization I've built has developed the technology for near limitless, sustained power generation. Through this advancement it's been possible for them to solve for Alcubierre's Bubbles and traverse short distances (less than 1 light year) through artificial breaches into subspace largely through a greater understanding of Casimir Effect / Pressure and to traverse far greater distances through naturally occurring wormholes. Would it be theoretically possible to apply the principles behind the Casimir Effect and Casimir Pressure as it applies to zero-point-energy / negative energy density to do the following: * Reduce the size (length) necessary for a railgun to be used in space (see other articles/questions on railguns in space) by taking advantage of Casimir Pressure as the primary accelerant or more likely as a catalyst for the creation of the EM Acceleration Field? (Also potentially using this at both ends to cancel out recoil). Essentially asking, can the Casimir pressure and negative energy density (which has been studied as it applies to tiny spaces) be used to reduce the size requirements of a railgun by acting as a catalyst or even the main driving force behind the creation of the EM Acceleration Field. I realize this is purely theoretical and am mostly looking for someone with more understanding of physics than myself to say "technically yes" or "absolutely no." No need to answer in great detail (unless you want to), I'm honestly considering just hand-waving this due to how many bits of data that do apply are still purely theoretical to us now. Additional Assumptions: * Power generation is not a factor, assume it's near infinite and can be applied as needed. * Computing power is not a factor, assume it's near infinite and can be applied as needed. [Answer] Regarding the Casimir Effect, I'd give a pretty hard no with a pretty simple reason - the Casimir Effect is an attractive force between two uncharged plates. If you want to create a gun using it, you're going to run into the issue that these two plates are going to hit each other. If anything, the Casimir effect will actually decrease the power of a railgun, as it will work to "suck" the projectile back into the barrel. But even putting that aside and getting to the math, the Casimir effect is really very weak. Its strength is given by $F = \frac{\pi h c}{480 L^4}A$, where $h$ is Plank's constant, $c$ is the speed of light, $L$ is the distance between the plates, and $A$ is the area of the two plates. [This site](http://math.ucr.edu/home/baez/physics/Quantum/casimir.html) gives a quick example to demonstrate just how weak the force really is. Using plates 1 meter square, placed 1 micron apart we get $F=\frac{\pi \* 6.6 \* 10^{-34} \* 3 \* 10^8}{480 \* 10^{-24}} \* 1$ $F = 1.3 mN$ 1.3 micronewtons is not enough force to do anything at all really, so I'd say forget about it. ]
[Question] [ If all the power plants of an industrialized country like (Germany, France, Italy, Korea) are destroyed how long would it take for the country to rebuild its power grid and get back to normal functioning? Under assumption that foreign countries are willing and able to help the devastated country with both with technology and credit [Answer] Power plant != power grid. If you mean only all the power generation plants where destroyed, than it take really little time to rebuild the grid since, all the national grids are already connected (Italy for example already has connections to all the neighboring nations power grids). In this case the power grid will be up and running again in some days, but the nation will be 100% dependent on imported energy for many years If you mean that only the power grid is destroyed, than it takes months, if not years, to rebuild it, depending on the level of destruction: if only the large transport lines are destroyed, then, in a couple of years, it is possible to rebuild them (but not assured you will do it), if you mean 100% of the grid, which is all of the above, plus the small line that arrive to your home, than you are out of luck, it'd require many years. If you mean that all the power plants and distribution grid is destroyed, you need years (at least a couple of decades) to return to the previous level, assuming you will be able to survive such an event without other problems: no energy -> no food conservation AND production -> you need to import also the food, for example. Think like a "Berlin Blockade" in the 1948 extended to a nation to have a hint of what it means. [Answer] Rebuilding more than a relatively small number of power generation plants is a very slow process. The plants are like any large industrial building and would take at least a couple years to build as a crash project. The generators themselves are not off-the-shelf items. There are only a few companies that can build them and they are ordered years in advance. There's a certain amount of slack in the system -- generators which are under construction for other countries -- and if the rest of the world tightens its belts and stops new power plant production for a while and diverts those generators, there's some hope of a quick fix. But this diminishes rapidly the larger the number of generators that must be replaced. Large transformers are another long-lead-time item and have essentially the same timing issues as the generators. So, for a small country, we're talking a few years and the larger the devastated area, the longer the delay. [Answer] A few years ago, I would have given an answer like Mark Olson's. But while batteries are not included, they can be added. Look at Puerto Rico. The grid was essentially destroyed. Tesla and other companies, Tesla being the most highly reported for various reasons, have brought in a lot of solar power with battery backup. Battery backup is no longer just for the occasional big power outage. It is also enables solar, wind & other intermittent power sources to be used 24/7. It also enables more and more users to go off-grid, or even better to be off-grid when necessary but use the generally cheaper grid when the grid & the power plants supplying the grid are working properly. End result: In the near future it is possible that Tesla, the US government, etc. could step in and air-drop enough small systems (small generators, solar power systems, small wind turbines - all with battery backup) into another country to get at least key infrastructure (hospitals, schools, water treatment, military) up and running long before the traditional power plants can be rebuilt. [Answer] The mean construction time of a nuclear power plant is 7.5y. As of 2015, 18 out of 441 reactors worldwide were completed in 3y. – [euanmearns.com](http://euanmearns.com/how-long-does-it-take-to-build-a-nuclear-power-plant/). Construction time for a coal fired plant is around 4y. – [www.iea.org](https://www.iea.org/textbase/npsum/ElecCostSUM.pdf) You can't handwave money in this situation. Offer the supplier $1M for a part that costs 100k and it will be on your doorstep tomorrow morning if you order it before 5pm. It doesn't matter if manufacturing and the supply chain can't keep up. Somewhere in the world the needed part exists, however it's likely installed and in use, but like absolutely every commodity on the planet, it's just waiting for some sucker to exchange it for 10x its worth. Anything on Earth can be somewhere else on the planet in 24h, with 24h notice... and your checkbook. Equally implausible is the US parking every nuclear powered craft in their fleet just off your coast. It depends on how long it takes to hook up to your grid and convert it to your country's power type, but they can all be there in less than 24h too. ]
[Question] [ From a climatic point of view, what if Earth went through a radical polar shift that would place the geographical pole right where the Himalayas and Tibetan Plateau are? (No matter if southern or northern pole.. let's say southern). These are some of the driest regions in the world, so I wonder if there would be enough humidity to form an ice sheet. Would that result in a polar cap with a dry area in the middle? Note that if I’m right the opposite pole would lie somewhere offshore of Chile. Here's a handy map i did :) [![:O](https://i.stack.imgur.com/Fam7P.jpg)](https://i.stack.imgur.com/Fam7P.jpg) [Answer] Since it's not too different from the polar position to you had showed us. Quoting from the article of "XKCD whatif" in question: "The climate on the rotated Earth would depend heavily on the details of ocean and atmospheric heat circulation. We'll guess at some of that, but for now, let's assume this world has extremes which are similar to ours." [![Horse Latitudes](https://i.stack.imgur.com/ok0iC.png)](https://i.stack.imgur.com/ok0iC.png) This map shows the air movement with horse latitudes with the equator provides moisture from the oceans, which then gathers into rain. Then the water from the rain maintains the tropical fertility of the area. Areas near the equator get seasonal monsoon cycles. Which would be similar to the map provided: [![Hurricane Basins](https://i.stack.imgur.com/StQy7.png)](https://i.stack.imgur.com/StQy7.png) the red areas show where hurricanes might occur. In temperate zones, they have more variety in weather. They are dominated by the movement of the jet streams, fronts, and on the geography. Climates can be hard to exactly predict completely but you'll get the picture when you test it out yourself. But at least this likely the closest map I could get to the Himalayas being the north pole/south pole. I take no credit for any of this information, I just thought I'd share it since it can help explain some things. [Answer] # Dry-ness won't stay the same due to differing wind cycles [![enter image description here](https://i.stack.imgur.com/SoPev.jpg)](https://i.stack.imgur.com/SoPev.jpg) The Earth, due to its rotation, generally has three 'cells' of circulating air. The Hadley cell, Mid-latitude cell, and Polar cell. Due to the patterns of rising and falling air, these cells cause the same general climate patterns to emerge around the Earth (assisted in large part by oceanic currents). I'll describe some of the general effects briefly. The Hadley cell generally causes wet conditions at the equator and dry conditions at 30 degrees. You can see this on each continent with the tropical rainforests near the equator and the worldwide bands of desert around 30 N and S. The Mid-latitude cell generally features Mediterranean climates (wet winters, dry summers) on West coasts of continents at lower latitudes, but cool wet climates on West coasts at higher latitudes. Examples are [Spain](https://en.wikipedia.org/wiki/Seville#Climate) vs. [England](https://en.wikipedia.org/wiki/Bristol#Climate); Los Angeles vs. [Seattle](https://en.wikipedia.org/wiki/Seattle#Climate); [Santiago](https://en.wikipedia.org/wiki/Santiago#Climate) vs. [Valdivia](https://en.wikipedia.org/wiki/Valdivia#Climate) in Chile. The East coasts of continents in the Mid-latitude cell are generally much hotter and wetter in the summer. Compare the summer conditions of [San Francisco](https://en.wikipedia.org/wiki/San_Francisco#Climate) and [Washington DC](https://en.wikipedia.org/wiki/Washington,_D.C.#Climate), or [Lisbon](https://en.wikipedia.org/wiki/Lisbon#Climate) and [Seoul](https://en.wikipedia.org/wiki/Seoul#Climate). The Polar cell is generally devoid of moisture. Rainfall north of 60 degrees is generally very low; for example look at [Yakutsk, Russia](https://en.wikipedia.org/wiki/Yakutsk#Climate) or [Barrow, Alaska](https://en.wikipedia.org/wiki/Barrow,_Alaska#Climate). # Conclusion The polar ice caps are dry! In fact, Barrow is significantly drier than Tibet. Yet it still snows there every month of the year, and sees almost a meter of snow a year. Antarctica is drier still, and has miles of ice in places. All in all, your poles are going to be dry, but as long as they are cold enough, they are going to develop ice caps over time. [Answer] Such a shift would dramatically change Earth's climate and ocean currents... so it's very difficult to predict if -and how fast- a new ice cap would appear. One thing you should really think about is ocean currents. Antarctica is extremely cold because it's surrounded by cold water. The antarctic circumpolar current is a permanent cold stream around Antarctica's landmass, and it prevents hot water from reaching the land, and warming it. In your example, such a circumpolar current should not appear. A warm current may even come from the Indian Ocean and have an impact on your new polar region. See how the Gulf Stream is warming Scandinavia... So, there should be ice in the mountains, but it's hard to say how far it would expand, and if it will cover Taklamakan desert. It depends on the new climate this polar shift will create on Earth... A new ice age ? A new warm age ? It's up to you. ]
[Question] [ Suppose NASA, SpaceX or any other aerospace company has managed to build a technology that allows them to fire a rocket to the moon, from "space". Basically, they have created a huge weather balloon that can reach altitudes so great that atmospheric pressure is effectively zero compared to ground-level - "space". Considering that the shape of the rocket does not matter (it doesn't have to be shaped like a cylinder with a nose cone etc.) because it isn't affected by air drag, what would a rocket launched from "space" look like? Note: The highest point where the weather balloon (launch site) can reach, still has gravitational force on the rocket. Approximately as much as gravity would affect it at ground level. [Answer] We actually did it. Six times we went to the Moon, and six times we launched a rocket from the Moon's surface into space, to return the astronauts to the Command Module waiting for them on Lunar orbit. It looked like this: [![Lunar Module ascent stage](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Apollo_17_LM_Ascent_Stage.jpg/498px-Apollo_17_LM_Ascent_Stage.jpg)](https://en.wikipedia.org/wiki/Ascent_Propulsion_System#/media/File:Apollo_17_LM_Ascent_Stage.jpg) Apollo 17 Lunar Module Ascent Stage. Picture by NASA, available on Wikimedia. Public domain. [Answer] First, a balloon cannot get to 0% air pressure. Balloons float in the air. But you can have a ship built from small pieces in orbit, either by using materials shipped up in a space elevator, or harvested from asteroids, or salvaged from derelict satellites. So I will assume one of those scenarios. You are right that lack of air drag means no need for a smooth aerodynamic shape. But you will still need to deal with acceleration from the ship's engines, which has an effect similar to gravity. Your ship will have to be like a house or tower - the (main) engines are the foundation, and everything will have to be on top of that, or supported so it does not fall off or cave in when the engines fire. You cannot have airy-looking sprawling solar arrays. If you were to take the current ISS and accelerate it with a single engine, the solar arrays would fall off, followed by modules on the sides. If you look at lunar landers from the Apollo program, they did look a bit like a pyramid. You can have multiple engines supporting a sprawling structure, maybe like a castle with multiple towers, but then you would need to balance the thrust from each engine to the weight of the module that it pushes. Finally, you can have very weak acceleration, e.g. from ion thrusters or a solar sail. Then you can have "airy" structure with weak supports; I wouldn't call it a "rocket" anymore, though. [Answer] Orbit is a function of velocity as well as altitude The Reason balloon/rocket orbital launches aren't made is because no matter how high you get your rocket, you still have to get it moving with enough velocity along the proper vector to circularize an orbit. To be sure, balloons with sounding rockets attached are a great way to break out of the atmosphere, but they are a terrible way to achieve an orbit. Achieving a high enough altitude to leave the atmosphere is actually quite easy, but if the proper velocity is not gained in doing so then the object will simply begin plunging back to earth in a ballistic trajectory. About 9.4 km/s delta-v is the minimum required to establish a stable orbit. This means that even if you float it up there on a balloon your rocket isn't really going to end up any smaller or cheaper than a regular ground launched one, its going to have to burn nearly the same amount of fuel (not enough less to offset the cost of your gargantuan balloon) except now its for the purpose of gaining velocity instead of altitude. So, to answer your question, unless you achieve enough velocity to establish an orbit a rocket launched from a balloon will look like this: [![enter image description here](https://i.stack.imgur.com/dEL4V.gif)](https://i.stack.imgur.com/dEL4V.gif) If you DO have enough velocity to establish an orbit it will look the same as a regular rocket launch, it will just have a higher altitude for its starting point. ]
[Question] [ In this mostly hard-science universe I am using a theoretical "Hyperstable Gateway" to travel between planet X and Y; The wormhole has a ~5m diameter, The "Bridge" itself is negligible and a physical ring is used to seal it for use, and there is no "Barrier" or other film over the edge/plane or other obfuscation. How do you solve the time travel issue between 2 rapidly diverging (~0.08c) bodies? Would there be visual lag across the gate? How would I treat the difference in gravity across the gate? Is potential energy maintained across the gate? Is there anything I'm forgetting? P.S. I made this account for the sole purpose of asking this question, I hope I worded it clearly! [Answer] Let's define time travel through a moving worm hole. This is something I found that is credited to Kip Thorne (or the idea is) > > Kip Thorne takes his wormhole and puts one end in his living room, and the other aboard a spaceship parked in his front yard. Thorne's wife, Carolee, hops aboard the spaceship to prepare for a trip. The two don't have to say goodbye, though, because no matter how far away Coralee travels, they can see each other through the wormhole. They can even hold hands, as if through an open doorway. > > > Carolee starts up the spaceship, heads into space and travels for six hours at the speed of light. She then turns around and comes back home traveling at the same speed — a round trip of 12 hours. Thorne watches through the wormhole and sees this trip occur. He sees Coralee return from her trip, land on the front lawn, get out of the spaceship and head into the house. > > > But when Thorne looks out the window in his own world, his front lawn is empty. Coralee has not returned. Because she traveled at the speed of light, time slowed down for her: What was 12 hours for her was 10 years for Thorne back on Earth. > > > Now, as Thorne and Coralee hold hands through the wormhole, they are each traveling in time. Coralee has landed on Earth 10 years after she left, and there she will meet Thorne, 10 years older. But she can still reach through the wormhole and find Thorne, who is only 12 hours older. Thorne can step through the wormhole and find himself 10 years in the future, or his future self can step back 10 years into the past. > > > At first this sounds possible, but this makes the assumption that the perception of time will be the same to the observer no matter what side of the worm hole they are on. This breaks down if when Thorne looks in the wormhole he sees Carolee moving very slowly, not only her but everything on the other side of the worm hole. When she is looking through at Thorne's world, she will see everything moving very rapidly. > > But she can still reach through the wormhole and find Thorne, who is only 12 hours older. > > > If his time was speed up when she looked in the wormhole, she could not find him only 12 hours older as he would have aged at an appropriate rate. If she waited 1.2 hours then went through the wormhole, he will have already aged apx 1 year. > > Thorne can step through the wormhole and find himself 10 years in the future > > > If her time was slowed when he looks in the wormhole, stepping though after 12hours would be only minutes after she left. If he wants to step though when she arrives on earth he has to wait the 10 years. This is where the fundamental assumption takes place > > Thorne watches through the wormhole and sees this trip occur. He sees Coralee return from her trip, land on the front lawn, get out of the spaceship and head into the house. > > > If his view of her through the wormhole was slowed in proportion to her speed, this would never happen. In order to see her finish her trip and land he would have to wait 10 years, because everything on her side of the wormhole moves at an incredibly slow rate. Now there is no reason to think time would appear to move at a constant rate from the point of view of both observers looking through the wormhole. Well unless I missed something. In fact we know the opposite ,which is that the perception of time can change. As to what happens across the interface of the wormhole, that can get very sticky. There are many different ideas about that, I would suggest to be consistent in whatever you choose. * Would there be visual lag across the gate? This would depend on the speed of the wormholes relative to each other, as I describe above. It might also depend if it takes some amount of time to cross the wormhole. I could see how that is useful in a story. You would be at a slight disadvantage when crossing. Say it takes 15 minutes to cross, you would be working off information 15 minutes old. * How would I treat the difference in gravity across the gate? Gravity in GR is a feature of the geometry of space time. A wormhole is a topological feature of space time. I think one could argue that a wormhole can cancel out differences in those geometries (from one side to the other). If it couldn't then it probably wouldn't exist. * Is potential energy maintained across the gate? This is different then conservation of energy. But If you talk about energy (just in general), I can see some things where stuff could get weird. Say you put a wormhole on the floor and it's other end on the ceiling (or some combination of wormholes). Then you drop a ball into it. It would pop out on the ceiling and fall picking up speed go back in the wormhole, pop out on the ceiling and fall picking up an infinite amount of speed. Basically you have a perpetual motion machine (you actual have better because it's accelerating). You could probably harness this unlimited gravitational potential to generate unlimited power. Honestly only way I can think how to square that is that you could put a limit on the energy something has when it passes through the wormhole. Maybe if it has to much energy it can deform space time enough to disrupt the wormhole. This might have implications on moving a wormhole at high speed, because the more you deform space time the more unstable the wormhole would become. In reality you can do whatever you want, whatever fits your need. You just have to be consistent and come up with a plausible reason. The big thing is thinking of other ways those rules can affect things, like I just did. [Answer] The time travel issue isn't an issue. The two planets, I presume, are moving apart at 24,000 km/s (0.08 c), which is remarkably fast for two planets, but we can take that as read. This means there will be an extremely small amount of time dilation relative to each end of the hyperstable gateway. In fact, the amount of time dilation will be effectively miniscule. Although it will increase with time. But it is small enough that it can be ignored for practical purposes. Gateway engineers may be concerned about it, but only in terms of precision engineering. Will there be a visual lag? No the gateway has a diameter of five metres. The only visual lag will be the same lag in the time it takes light to travel a distance of five metres. Effectively, in ordinary practical terms, it's non-existent. Difference in gravity between the two ends of the gateway will need to be accommodated by placing each end of the gateway somewhere on the surface or even under their surfaces where the gravitation at both ends is the same. Two planets with the same surface gravity practically solve this for themselves. Let's assume there is a corridor through the gateway. If there are differences in gravitation between the two ends of the gateway, then depending on which direction someone passes through the gateway they will going up or down hill. Basically the same as walking up or down an inclined floor over a distance of five metres. The query about potential energy cannot be answered unless we know what potential energy you had in mind. Gravitational potential energy has been dealt with in this answer's previous paragraph. But to clarify this further. Each end of the gateway will subject to the local gravity of either respective planets this will create a gravitational potential difference between the ends. That's why it is necessary to place at locations where the potential difference will be low. ]
[Question] [ From what I've read, planets orbiting red dwarf stars would most likely be tidally locked. Under what circumstances might this change? For example, if a planet had been the recipient of some kind of large impact over the course of its existence? We theorize that in the Solar System, Venus's reverse orbit might have been caused by a big impact. If such a thing were to occur on a planet orbiting a red dwarf, could it spin on some kind of "normal" rotational period (e.g., 5-100 hour days). [Answer] 1) A possibility to make a planet less tidally locked would be libration. Luna, the Moon, has libration that makes it seem to wobble very slightly as it orbits the Earth. Tidal locking means that the period that the Moon takes to revolve or orbit 360 degrees around the Earth is exactly the same as the period it takes the moon to rotate 360 degrees. So one side of the Moon always faces the Earth and one side always faces away from the Earth. This is because the average orbital speed and the average rotation speed of the Moon are identical. But the speeds at any particilar moment are not exactly identical. The orbits of all astronomical objects are elliptical and thus deviate more or less from perfectly circular orbits. Thus objects speed up and slow down as they orbit other objects. So the Moon sometimes travels faster and sometime slower than it's average orbital speed. But the Moon cannot speed up or slow down its rotation, it has to always rotate at its average rotation speed. So a total of 59 percent of the Lunar surface is visible from Earth, instead of fifty percent. So if your planet orbited its sun in exactly 3 Earth days or 72 Earth hours, it would orbit at an average rate of 120 degrees per Earth day or 5 degrees per Earth hour. And if tidally locked it would rotate at exactly 120 degrees per Earth day or 5 degrees per Earth hour. And if the planet's orbit is highly eccentric the planet's variable orbital speed would sometimes be faster or slower than it's exact rotation rate, thus making for a lot of libration and for a lot more than 59 percent of the planet's surface to sometimes be in daylight. In our solar system the planet Mercury has an orbital eccentricity of 0.2563 and is 1.5177 times farther from the Sun at Aphelion distance than at Perihelion distance. If Mercury was tidally locked to the Sun its libration would be 23.65 degrees due to its eccentric orbit. <https://en.wikipedia.org/wiki/Mercury_(planet)>[1](https://en.wikipedia.org/wiki/Mercury_(planet)) [Orbital period of a tidally-locked Earth-like planet around a red dwarf](https://worldbuilding.stackexchange.com/questions/50688/orbital-period-of-a-tidally-locked-earth-like-planet-around-a-red-dwarf?rq=1)[2](https://worldbuilding.stackexchange.com/questions/50688/orbital-period-of-a-tidally-locked-earth-like-planet-around-a-red-dwarf?rq=1) Of course the same tidal forces that would tend to lock the planet's rotation would also tend to make its orbit more and more circular with time. 2) Maybe, like Mercury, its orbit and rotation might become locked in a 2:3 resonance. Mercury has an orbital period or year that is 87.9691 Earth days long. It has a rotation period relative to distant stars (or sidereal day) 56.646 Earth days long. That means that it's solar day, it's day relative to the sun, is two Mercurian years, or about 176 Earth days long. If another solar system had a much smaller scale version of Mercury's orbit and rotation, each might be, for example, one twentieth as long as that of Mercury. The hypothetical planet could have an orbital period or year that is 4.398 Earth days long, with a rotational period period relative to distant stars (or sidereal day) of 2.8323 Earth days. That means that it's solar day, it's day relative to its sun, would two of its years, or about 8.796 Earth days long. So divide those figures by three to get a year 1.442 Earth days long, a sidereal day 0.9441 Earth days long, and a solar day 2.932 Earth days, or 70.368 Earth hours, long. Can a star have such a close habitable zone that a planet would have a year only 1.442 Earth days, or 34.608 Earth hours, long? Here is a discussion of distances of habitable planets from their stars: [How far away does a planet need to be from its star to have Earth-like conditions?](https://worldbuilding.stackexchange.com/questions/76391/how-far-away-does-a-planet-need-to-be-from-its-star-to-have-earth-like-condition/76418#76418)[3](https://worldbuilding.stackexchange.com/questions/76391/how-far-away-does-a-planet-need-to-be-from-its-star-to-have-earth-like-condition/76418#76418) Apparently K3-137b has the shortest known year of any know exoplanet, 4.31 hours, orbiting a red dwarf - except that PSR J1719-1438 orbits a pulsar every 2.2 hours. But they are not listed as potentially habitable planets. The list of known exoplanets in the conservative habitable zone includes ones with years 12.4, 9.2, 6.1, and 4.05 Earth days long. They orbit TRAPPIST-1, a M8V type star. I don't know if a M9V typed star could be enough dimmer to have a planet orbiting it in the habitable zone with a year as short as 1.442 Earth days. For a solar day 100 Earth hours long, a habitable planet with Mercury-like resonance would have a year 2.0492 Earth days long, a sidereal day 1.341 Earth days, long and a solar day 4.0984 Earth days, or 98.3616 hours long. It is possible that your planet could orbit in the habitable zone of a brown dwarf, intermediate between a planet and and star. Thus it might have a year and a solar day shorter than a planet orbiting even the dimmest red dwarf star. But it seems very likely such a planet would be tidally locked. <https://planetplanet.net/2014/10/09/real-life-sci-fi-world-4-earth-around-a-brown-dwarf/>[4](https://planetplanet.net/2014/10/09/real-life-sci-fi-world-4-earth-around-a-brown-dwarf/) I may point out that the apparent movement of the sun in Mercury's sky is sometimes very odd, and that different places on Mercury's equator will have significantly different temperatures during their noonday periods. If this planet planet orbits a red star in the habitable zone the tropics and the temperate zone would be divided by longitude as well as latitude. <https://en.wikipedia.org/wiki/Mercury_(planet)>[1](https://en.wikipedia.org/wiki/Mercury_(planet)) Why does Mercury have a 2:3 orbit: spin resonance? Scientists are still coming up with ideas and computer simulations to explain it. For example, some scientists have proposed that Mercury was once tidally locked to the Sun but a massive asteroid strike changed its rotation period, similar to what paltrysum suggested. <https://phys.org/news/2011-12-evidence-large-asteroid-mercury.html#nRlv>[5](https://phys.org/news/2011-12-evidence-large-asteroid-mercury.html#nRlv) Other computer simulations suggest that a 2:3 resonance is a more natural situation and likely to occur a lot in extrasolar planets. <https://phys.org/news/2013-10-explanation-rotational-state-mercury.html>[6](https://phys.org/news/2013-10-explanation-rotational-state-mercury.html) You should look for other questions and answers about habitable planets in 2:3 resonances. [What's the longest plausible orbital period for a habitable planet with a 3:2 spin-orbit resonance?](https://worldbuilding.stackexchange.com/questions/75513/whats-the-longest-plausible-orbital-period-for-a-habitable-planet-with-a-32-sp?rq=1)[7](https://worldbuilding.stackexchange.com/questions/75513/whats-the-longest-plausible-orbital-period-for-a-habitable-planet-with-a-32-sp?rq=1) There is also the suggestion that a habitable planet could actually be a habitable moon of giant planet in the habitable zone of a red star. Thus the habitable moon would be tidally locked to the planet instead of to the star and would have periods of daylight and darkness. It should be noted that it has been calculated that the orbit of a moon will not be stable unless its month is one ninth or less the length of it's planet's year - the length of the planet's year should be at least 9 times the length of the moon's month. If it is desired that the day on the moon, equal in length to the moon's month, should be about 5 to 100 Earth hours, the length of the planet's year should be at least 45 to 900 Earth hours, or 1.875 to 37.5 Earth days, and it can be several times as long. Thus the length of the planet's year can be made to fit into the the possible length of a year in the habitable zone of a red dwarf star. You should look for other questions and answers about habitable moons of giant planets in the habitable zones of red dwarf stars. [Making a slow orbit around a large gas giant](https://worldbuilding.stackexchange.com/questions/79003/making-a-slow-orbit-around-a-large-gas-giant/79106#79106)[8](https://worldbuilding.stackexchange.com/questions/79003/making-a-slow-orbit-around-a-large-gas-giant/79106#79106) [Captured Earth-Like Moons around Gas Giants](https://worldbuilding.stackexchange.com/questions/82415/captured-earth-like-moons-around-gas-giants/82594#82594)[9](https://worldbuilding.stackexchange.com/questions/82415/captured-earth-like-moons-around-gas-giants/82594#82594) [Answer] ## Are you talking about planets in the goldilocks zone? If not, simply have the planet be further away from the star. The reason it is thought that planets in the goldilocks zone (the band around a sun where liquid water is possible) of a red dwarf would likely be tidally locked is because they'd have to be so close to their parent star, since red dwarfs are small and dim. If you remove this constraint, you can just move the planet away and it would be able to rotate freely. In this case the planet wouldn't be terrestrial, but it wouldn't be tidally locked. --- If so, and you are in fact talking about planets in the habitable zone, then one proposed solution ([which I found on the astromony stackexchange](https://astronomy.stackexchange.com/questions/19039/is-there-any-way-for-a-planet-orbiting-a-red-dwarf-in-the-habitable-zone-to-not)), would be to have the planet be part of a [double system](https://en.wikipedia.org/wiki/Double_planet) with the other member either being a very large moon or even a fellow planet (depending on your definitions). Systems like these exist in the real world. The Pluto–Charon system being one such example. In this fashion both bodies would be tidally locked to each other (much as the Moon is to Earth), but not tidally locked to their star. ]
[Question] [ How would the human eye have developed differently on a planet with two suns? One sun will be a yellow star functionally the same as Sol and the other will be a red dwarf. The planet will be earth-like and orbit around both stars. I am curious about the impact to: * Eye and component part size * Eye and component part shape * Functionality (inner workings) * Impacts to seeing depth/dimension Additional notes: * The two stars are .5 AU apart * 20% more luminosity falls on the planet * Don't worry about the planet being too hot [Answer] The simple answer is: not at all Consider eyesight, not just in humans, but across the creature spectrum. You have eyes of different design and makeup all over the place, from the multifaceted fly to the curiosities of cats, frogs, and goats. Add to this the variety just in the human eye including light sensitivity (something I'm very, very familiar with), acuity, the protection of lids and fluid, etc. There is such a wide variety of eyes on the Earth that I find it unlikely a second sun would change the eyes. But, for the record, when comparing your world to Earth: * A substantially brighter world may evolve pupils that can close more than a human's or a decreased sensitivity to light, which would blind them when visiting darker worlds. This would require them to wear light-enhancing lenses just as we would require sunglasses to visit their world. * Alongside the decreased sensitivity to light is the possibility of a second, translucent lid (like a cat's) that could be used as natural sunglasses. * There could be a radiation issue depending on how efficiently your world's radiation belts filter both solar winds. Though I have strong doubts about whether or not this would change the eye substantially, it could be used as an argument to rationalize changing the shape of the pupil or the color of the iris. * More photons could mean smaller eyes generally as fewer rods/cones are needed to "see" the same object. That's all I have. A second sun really only does two things: add more photons to the mix for, potentially, a longer period of time. More photons for more hours doesn't really change the nature of ocular perception. [Answer] One thing that having a second smaller sun in the sky does is make the days seem longer. As the two stars orbit their center of gravity in a period of several hours, days, or weeks, sometimes the smaller sun will eclipse the larger one, sometimes the larger sun will eclipse the smaller one, and the majority of the time they will be seen side by side in the sky. And sometimes as the planet turns only one star will be visible in the sky. James specified that the stars orbit each other at a distance of 0.5 AU. If the planet is at a distance of 1 AU, the stars can look as much as 30 degrees of arc apart in the sky of the planet. So when the two stars are at their maximum separation, The brighter one will be visible without the dimmer one for about 0.08333 of a planetary rotation period, the dimmer one will be visible without the brighter one for about 0.08333 of a planetary rotation period, and both should be visible together in the sky for about 0.416667 of a planetary rotation period, if my calculations are correct. Thus when the two suns are farthest apart, the day should last for about 0.58333 of a planetary rotation period and the night last for about 0.41667 of a planetary rotation period. If the planet has no axial tilt, of course. When the two stars are closer together the periods of only a single sun being visible will be less and less of the total rotation period. It is possible that the animals and humanoids on James's planet may have adaptations to see better during the light of only one of the two suns. If James wants to make his system scientifically probable, he should significantly reduce the distance between the two suns. Astronomers have calculated the stability of possible planets in binary systems, including S type orbits, where the planet orbits only one of the stars, and P type or circumbinary orbits where the planet orbits both of the stars. Wikipedia says: > > For a circumbinary planet, orbital stability is guaranteed only if the planet's distance from the stars is significantly greater than star-to-star distance. > > > The minimum stable star to circumbinary planet separation is about 2-4 times the binary star separation, or orbital period about 3-8 times the binary period. The innermost planets in all the Kepler circumbinary systems have been found orbiting close to this radius. The planets have semi-major axes that lie between 1.09 and 1.46 times this critical radius. The reason could be that migration might become inefficient near the critical radius, leaving planets just outside this radius.[6] > > > For example, Kepler-47c is a gas giant in the circumbinary habitable zone of the Kepler-47 system. > > > <https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems>[1](https://en.wikipedia.org/wiki/Habitability_of_binary_star_systems) So if James wants to be more scientifically plausible he should move his planet a little bit (but only a little bit or it will be too cold) farther out from the suns and move the suns closer together, or simply move the suns closer together. I would make the suns less than 0.25 AU apart (which is still up to 23,000,000 miles) if the planet is exactly 1 AU from the center of mass of the two suns. Thus the maximum possible separation between the two stars in the sky of the planet would be 15 degrees or less, and there would be less need for the animals to evolve better vision in the light of only one sun. Another factor is the different frequencies of light emitted by the two suns. Each would emit almost the entire range of electromagnetic radiation from gamma rays to radio waves, but some frequencies would be many times more common than others. James's original proposal callied for a white dwarf. Most white dwarfs have higher surface temperatures than the sun, some much higher, so their light is the more energetic blue white light. Thus looking at a white dwarf might be more painful than looking at a G type star at the same distance, despite the white dwarf having a much smaller total luminosity. James modified his question to ask about a red dwarf as the dimmer sun. Red dwarfs have much cooler surface temperatures than G type stars, and the most common frequencies of light they emit are less energetic orangish and reddish frequencies. So if Earth type eyes can handle the yellowish light from G type stars they should have no trouble with the reddish light of red dwarfs, right? Not exactly. The Sun has solar flares that are very impressive. If red dwarfs had similar sized stellar flares, they would change the overall luminosity of the red dwarfs much more than solar flares change the overall luminosity of the Sun. Many red dwarfs are flare stars, that have flares many times larger than any solar flare, which make significant changes in the luminosity of the flare stars. The most intense stellar flare recorded may have been up to 10,000 times as strong as any solar flare. Thus if the red dwarf in the system is a flare star it could easily double the luminosity of the red dwarf for a short time. But since the red dwarf would have only a fraction of the luminosity of the G type star that would not make much of a difference. But the stellar flares of flare stars might often have high energy light rays that might be painful to the eyes of the animals on the planet. Especially when the red dwarf is the only sun in the sky and the eyes have switched to a method of seeing better in the dimmer light of the red dwarf, just as human eyes switch to night vision for seeing in the dark. Thus it is possible that if the dimmer star is a flare star the animals on the planet might evolve to tolerate occasional intense light from stellar flares, possibly an eyelid or membrane that would instantly shut when detecting intense light, leaving the animal temporarily blind but preventing long term damage to its eyes. So Jame should decide whether he wants his dimmer star to be a flare star or not and whether he wants the animals and people on his planet to be adapted for occasional flares from the dimmer star. ]
[Question] [ After circumstances make the shallow water in the oceans uninhabitable, great white sharks retreat to the deeper parts of the ocean, about 600 feet down (182 meters) to survive. The sharks can not go more than 450 feet up, as the water up there is uninhabitable. My question is, could sharks adapt to survive in this new environment? [Answer] # Yes. There are sharks that live quite deep in the ocean; the [goblin shark](https://en.wikipedia.org/wiki/Goblin_shark) and [frilled shark](https://en.wikipedia.org/wiki/Frilled_shark), for instance, have been known to live over 1,000 meters below sea level ([Wikipedia](https://en.wikipedia.org/wiki/Great_white_shark#Distribution_and_habitat) claims great whites have been found at this depth, too). This is off the edge of the [continental shelf](https://en.wikipedia.org/wiki/Continental_shelf). Your depths (~180 meters) puts you only just off the shelf - and still certainly in the [photic zone](https://en.wikipedia.org/wiki/Photic_zone), where there's a good amount of sunlight. This means that your sharks will still be in an ecosystem similar to their old one. They'll still have some of their old food, and they'll be living in temperatures that aren't terribly low. Deeper into the ocean, you have three issues: * Food. Sharks are used to a certain lifestyle, with a certain amount and type of prey available. Different organisms frequent the lower areas of the ocean, and so sharks would see less of their favorite fish. Adapting to a new food supply wouldn't be too hard, but having less food overall would. * Pressure. At depths on the order of a kilometer, pressure becomes an issue, although compounds like [TMAO](https://en.wikipedia.org/wiki/Trimethylamine_N-oxide) can mitigate it. Deep-sea creatures do have adaptations like TMAO to help them survive. At less than 200 meters, pressure might be a bit of an issue, but not a large one. * Temperature. Below one kilometer, in the [bathyal zone](https://en.wikipedia.org/wiki/Bathyal_zone), mean temperatures hover just above freezing - not good for fish, although certainly not inhospitable. That said . . . I don't see any of these being problems at the depths you give, for the simple reason that your sharks won't be living in deep water at all. [Answer] ## They are already adapted to such depths [From the wiki:](https://en.m.wikipedia.org/wiki/Great_white_shark) > > The great white is an epipelagic fish, observed mostly in the presence of rich game, such as fur seals (Arctocephalus ssp.), sea lions, cetaceans, other sharks, and large bony fish species. In the open ocean, it has been recorded at depths as great as 1,200 m (3,900 ft). These findings challenge the traditional notion that the great white is a coastal species. > > > According to a recent study, California great whites have migrated to an area between Baja California Peninsula and Hawaii known as the White Shark Café to spend at least 100 days before migrating back to Baja. On the journey out, they swim slowly and dive down to around 900 m (3,000 ft). After they arrive, they change behavior and do short dives to about 300 m (1,000 ft) for up to ten minutes. > > > White deaths are opportunistic and adapt well to a large variety of prey. They have been seen eating sunfish and other sharks. If the top of the water column becomes inhospitable, many other fish will also dive under 450 feet and the white deaths will follow. [Answer] Many species of sharks can live for longer or shorter periods in various depths of water. Sharks that are sometimes seen at the surface can sometimes be found thousands of feet or meters below the surface. Great White sharks, for example, are usually found from the surface down to 825 feet, but have been found as far down as 4,200 feet. Greenland sharks, which have been found in relatively shallow rivers and dived among by scientists, have also been found as deep as 7,200 feet, and the closely related pacific sleeper sharks have been found on the surface, have also been found as far down as 6,500 feet. <https://sharkopedia.discovery.com/shark-topics/the-sharks-of-the-deep/#how-deep-do-sharks-dive>[1](https://sharkopedia.discovery.com/shark-topics/the-sharks-of-the-deep/#how-deep-do-sharks-dive) There is no problem with some shark species that are well known to the public because they are often seen at or near the surface spending part of their time below 450 feet. I am not sure how well they would survive if going above 450 feet was always fatal. And most of their food supply would be gone if all life above 450 feet died. ]
[Question] [ I'm writing a story that involves the protagonists opening the gates of a medieval city to allow an attacking army through - and I need to know how long it would be before the city's garrison realizes what is going on and arrives with enough troops to stop them. Here are some details: * The gate will probably be defended by around 25 men. * The protagonists have 50 armed knights and 50 assassins with them. * Their plan is to sneak up on the watchmen and silently take them out - however, one will escape and go alert the city's garrison. * The city is massive, based on Volantis from Game of Thrones. So basically, there will be a brief fight at the gate, and then it will be opened. As soon as they begin to open the gate the escaped soldier will set off to alert other troops as to what is happening. But: How long would it be before he arrives back with enough troops to stop them - or until someone else realizes what is happening and comes to put a stop to them? [Answer] The entire setup is wrong, as in, it just doesn't work. It is good enough for a Hollywood movie or for a fantasy adventure novel, but it makes no sense in a serious setting. The problem is the attacking army. Medieval armies were slow. Glacially slow. The city would learn that an army was headed towards it at least weeks if not months in advance. And an army cannot be hidden: it is big ugly thing moving slowly through the country, devastating everything in its path. Once the city learned that an army is coming, it would naturally adopt a defensive stance; hence our modern "[state of siege](https://fr.wikipedia.org/wiki/%C3%89tat_de_si%C3%A8ge_(France))". So in practice, the city would already be prepared for defense; there would be no need to raise the alarm. The gate would be closed, towers and ramparts would be manned, regular patrols would sweep the approaches. Most likely, the city would also be in diplomatic communication with the attackers! For example, in 1682 (yes, Early Modern, but still a great example) the Ottoman Empire [decided to take Vienna](https://en.wikipedia.org/wiki/Battle_of_Vienna). War was declared in August 1682. They managed to assemble a great army at Adrianople by March 1683. They arrived in Belgrade in May. The 200,000-strong army arrived at Vienna in July. During this time, the Austrians evacuated the city, leaving only a force of 15000 volunteers commanded by Ernst-Rüdiger von Starhemberg, emperor Leopold established a set of alliances and coordinated strategy with king Jan Sobieski of Poland. (Spoiler: the Ottomans failed to take Vienna.) So in the normal course of things a medieval or early modern army cannot take a city by surprise. To take a city by surprise, some other factor must be in play; for example, it helps if the army is already in the city as supposed allies, or if the people of the city riot, or if the rulers flee and leave the defending forces without commanders. Or maybe decades of neglect have left the walls of the city unmaintained and indefensible. Or maybe the garrison consists of badly paid and untrained mercenaries who couldn't care less whether the city is taken or not. Now, this doesn't mean that taking a city by surprise is not a worthy plot point. That such a feat is not actually reasonable in actual warfare is immaterial: we read adventure novels to be entertained. So make the timing suitable for your purpose; explain away the incompetence or treason of the defending military commanders; and so on. Basically, make something up, and just take care to avoid glaring impossibilities. [Answer] That depends entirely on how much the city expects to be attacked. If the city was designed to repel an attack then the main barracks would be build in close proximity to the gates, simply shouting or maybe ringing a bell should be enough to raise the alarm and bring defenders running within a matter of minutes. If the city is mostly at peace there might be no reinforcements ready to go, which would result in a significant delay while defenders don their armour and collect weapons [Answer] The problem is that when the city gate is opened there is no need to move any soldiers there. You just roll everyone behind wall number two patiently waiting for the incoming army to fall into your well-crafted fortifications and bottlenecks. And you just need one person to open the gate: The gate commander. You do it this way: Anywho commander, here is a nice sum of money equal to all the gold you could ever wish. And here's a safe-conduct for you and your men after we seize the city. Just remember to open the gate on the third night of the second month. Storming the gates is the worst idea of an attack. Gate is designed, crafted and built to be a cool place to what you youngsters call "camping", even when open. You just stay in recess and poke everyone with a pike through small openings. You tear down the wall, blast it, make excavation but you don't go through the gates. [Answer] Let’s assume that the city is well prepared and the guards well trained. It is possible that the events will occur like this: ## Alarm * The escaping guard remembers its training and know exactly what to do: Ring the closest alarm bell! How close is it? You can chose. But maybe if you have one in each church, plus some others to fill the gaps, you could assume 500 meters. So time before ringing the bell: + 500 meters at 4 m/s (good running speed with an armor, adrenaline probably helped) => 2min and 10 sec more or less + Add one minute to climb the bell tower + The bell is ringing about 3 minutes and a few seconds after the attack. You can make it earlier or later by moving the bell closer or further * Sound of the bell travelling to the guard house: you can neglect it :) ## Response to alarm * Once the reserve soldiers hear the bell, they will put helmets on, grab their swords and run toward the bell. (They don’t know what is happening, neither which door is under attack.) Again, we don’t know how far this might be. Let’s assume 1 kilometre, you can change this distance to make it faster or slower. + If they were not sleeping, but rather in a “ready for action” mode: grab helmets, swords ang go! 1 minute. + 1000 meters at 3.5 m/s (they don’t have adrenaline, they have to run for a longer distance, hence are slower): Nearly 5 minutes. ## Planning defence * At the bell the guard explain them what’s happening, they decide of which plan to use (they are trained, they have plans ready for many situations, they just need to find the one that fit the best to this particular situation). Let’s count 30 seconds. * They run to the door. Again 500m, 3.5 m/s because they want to be cautious when getting close. 2 minutes and 20 seconds. * In total 1mn + 5mn + 30s + 2mn 20s = About 9 minutes. ## Total If we sum it all, we have nearly 12 minutes between the attack and the guards arriving at the door. ### Tricks A few tricks might make it quicker: * The guard, after ringing the bell could run toward the incoming soldiers to lead them directly to the gate * Some kind of watchman could stay close to the bell, so that the soldier could yell at him when he gets close enough and so avoid climbing the stairs * The bell signal could convey information about which door is under attack, so the soldiers would go there directly. (one Booong: door one, ...) In summary: you can make it much longer or much shorter. But around ten minutes seems reasonable in a big city, especially if the attacking army did choose on purpose a door which is far from the bells and the guard house. Final note: This answer is more of a hint on how to calculate it, so put your own numbers in it if you have some. Mines are just guesses. ]
[Question] [ I'm currently working on a semi-aquatic humanoid race of aliens, the Soliil. The majority of the race has proportions, anatomy and heights close to that of humans, however, I am working on a much younger subspecies that grows significantly larger than the average Soliil while retaining almost the same proportions, sometimes growing tall enough that they can no longer stand unsupported. Unfortunately I haven't been able to find a consistent answer with the few I found varying between 10ft and 20ft. They still need to be capable of surviving on land, even if loosing some mobility, and able to swim. Preferably, I'd like them to remain close to the same proportions of their smaller cousins, albeit towering above them, but any minor internal changes that could push their maximum height further would be interesting. [Answer] There are two issues: the capacity to bear weight and the ability to stand upright. * WEIGHT How tall did the two-legged dinosaurs get? [Wiki records the estimated heaviest theropod](https://en.wikipedia.org/wiki/Dinosaur_size#Theropods) is the Spinosaurus aegyptiacus: up to 20.9 ton. Estimated sizes compared to a human: [![enter image description here](https://i.stack.imgur.com/aRWnm.png)](https://i.stack.imgur.com/aRWnm.png) Obviously the skeletal structure is diffent, but the fact remains that all that size rests on two ankles. Redistribute the weight on a stand-tall frame (of equivalent bone density and size) rather than a bent-over frame and you could have 40-50 feet (based on guestimating from the pretty picture). What's good for the Theropod is good for the hairless monkey. * LEVERAGE Theropods have a low center of gravity while a 50-foot human wouldn't. [What a strong gust of wind would do](https://www.youtube.com/watch?v=rKUipxR3bDc) to a creature that tall on two feet isn't pretty, and there's only so far you can lean over before your center of gravity shifts so much you can't keep your balance. * CONCLUSION My pull-it-out-of-my-left-ear guess is this: the practical maximum height for a human (true bipedal) might only be 9 feet lest the winds common to Earth make standing any taller a royal pain in the rumpus. What are the winds like on your world? [Answer] Humans have proven to be able to reach about 9 feet high, but that's pretty much the limit due to blood pressure issues. The human heart simply can't provide enough pressure to get much beyond that, simultaneously having too low pressure toward the head and too much pressure in the lower legs. However, if you postulated internal differences, multiple heart-like structures say, you could theoretically get greater height before you necessarily start getting into issues with bone strength due to the square-cube law. Giraffes, for example, are much taller than elephants but have thinner bones due to lowered mass. Humans, proportionally, would likely split the difference in terms of limb thickness. So I don't think it's unreasonable to think you could have a humanoid, with similar proportions to a normal human, at 4.5 meters/15 feet. I would suspect that much beyond that you'd start needing a different body type. [Answer] Meh. It depends on the elemental makeup. Is this a species with the same C:N:O:H:S:P ratios that humans are made of? Or is silicon allowed? Or could metals be incorporated into the bones? Can the heart be stronger because it is bigger? Etc. What is the gravity on your world? How do they get nutrition? How often are they in water, and how long do they need to be on land? Lastly, how tall do you want them to be? There are probably ways to get you there, playing with the ideas you are getting here. ]
[Question] [ I was thinking about how we differ from crocodiles and sharks in terms of teeth. Now of course we don't have carnivore teeth but we also don't grow new teeth unless you are talking about a young child losing his/her baby teeth. But it seems like an omnivore diet, especially one that includes bones would be better suited to growth of new teeth than a carnivore diet. I mean, there are all kinds of things that would wear down an omnivore's teeth. Here are just some of them: * Hard fruits * Nuts and Seeds * Bones And these 3 would wear an omnivore's teeth down the most, assuming no crispy processed foods are included. And wouldn't wearing down of the teeth be a major factor into evolving the ability to grow new teeth? So, since my Kepler Bb Humanoids are omnivores and they eat bones, especially during these circumstances: * Pregnancy * Breastfeeding * Growth spurts And they don't get more frail with old age, why wouldn't they evolve to grow new teeth? [Answer] Growing new teeth endlessly is the norm, everything with teeth can do it except mammals. Mammals kinda traded out that ability for more complex teeth. more complex teeth is a big advantage for insectivores, (insects need to be cut apart to get the most out of them) and all living mammals are descendents from the small insectivorous mammals around turing the time of the dinosaurs. Being small and short lived the limited number of teeth was not much of a problem so the mutation that swapped/transformed the genes for making more teeth into genes for creating more complex teeth was an advantage. Now us as their descendants are stuck with that evolutionary baggage. \* I would not expect that weird fluke of evolution to occur against in an unrelated evolutionary history. So your humanoids should grow more teeth continuously (Polyphyodont), it does not need an explanation, having a limited number would be unlikely and would need an explanation. Now if you are continuously growing new teeth it is a little harder to get them to fit tightly, since they are constantly dropping out an leaving gaps. But dinosaurs found a way around that, just grow lots of little tiny [interlocking](http://blogs.plos.org/paleocomm/2016/09/14/all-the-better-to-chew-you-with-my-dear/) teeth where you need a chewing surface, and normal shaped teeth everywhere else. It is called a dental battery. [![enter image description here](https://i.stack.imgur.com/EIy4o.jpg)](https://i.stack.imgur.com/EIy4o.jpg) The few mammals that have more than one set of replacement teeth (elephant,kangaroo, and manatee) still only grow a limited number, and eventually stop making more. They are not true Polyphyodont they do run out of teeth. They basically don't produce all their teeth in one or two rounds but make them two or four at a time till they run out. [Answer] If you're able to bend your humanoids anatomy, you may consider giving them open rooted teeth. Essentially they are teeth that don't stop growing, and must constantly be worn down. This is usually an adaptation seen in herbivores eating grass, leaves, and hay. I think it's usually just front teeth with this trait, but it would probably help increase longevity of the rest of the teeth by grinding tough foods before the back molars get it. It would be a good reason for your humanoids to chew on bones, since failure to wear down teeth leads to painful dental problems. [Answer] I had an extra set of adult teeth (four front uppers) and later found out I also had two extra wisdom teeth (upper one on each side). Its called hyperdontia. ]
[Question] [ In my post-apocalyptic iron age world meant to be a sci fi twist on fantasy tropes, wyvern like creatures simply known as fliers were said to have been originally created by a crazy billionaire as a gift to his son, but later modified by bioterrorists to instill fear in the population. Some things to note: * They are considered reptiles, but are actually warm blooded as it's theorized some dinosaurs were. * DNA from many different sources, namely a large variety of mammals, birds, and reptiles. * Wild dragons are even more rare than captive ones. Genes inserted by the interlopers have become dominant over the years. * Cannot breathe fire but the bioterrorist genome added the ability to spit venom. While it is most likely just blinding, similar to a cobra's, I'd like some insight as to if it's possible for victims to get chemical burns from an animal's venom, hence the bombardier beetle DNA. * Typically they grow to be slightly larger than a horse, just the right size to ride comfortably. * Can fly, but adheres to laws of both biology and physics. Requires open space to take off. Fully grown individual can usually fly between 6 and 8 hours on energy alone, longer if there is good wind. Requires high food intake to fly. * Need some insight on their bones. Hollow avian bones would reduce the weight, but are easily broken by a human rider. However, conventional full bones of other animals might be too heavy. * Usually found in various shades of browns, grays, oranges, and greens. Black is often a sought after color as it's believed those dragons are healthier. A very recessive gene originating before the fall of civilization is the color changing skin granted by optional chameleon DNA, which cost an extra million on the customization website. What I need to know is how long is the wingspan required to fly, and several other questions listed above. [Answer] The largest known flying animal which ever lived on Earth belonged to the [Pterosaur](https://en.wikipedia.org/wiki/Pterosaur) family. They came [in all kinds of sizes](https://en.wikipedia.org/wiki/Pterosaur_size), but some of the largest sub-species had wingspans of over 10 meters. It's hard to tell how heavy they were from fossil evidence alone, but most paleontologists assume that in spite of their impressive size they weighted only a few hundred kg. Still, with the right genetic enhancements, carrying the additional weight of a human seems plausible. Note that riding a bird might be different than riding a horse. First, it would be important to be near the center of gravity of the animal, and that would usually be just between the wings. Second, aerodynamics are far more important. So the ideal riding position might be laying down, not sitting upright. [![Source: Wikipedia](https://i.stack.imgur.com/hVvpM.png)](https://i.stack.imgur.com/hVvpM.png) [Answer] To be able to fly, the wyverns would need more than just a large wingspan. For example, a human would need a wingspan of about 6.5m to be able to fly, but humans do not have enough body strength to be able to support wings of such size. (See here for more information from Yale: <http://www.yalescientific.org/2013/03/qa-why-cant-humans-fly/>). Basically, birds have air sacs connected to their lungs, which makes it easier for them to pass oxygen through their body during flight - plus the hollow skeleton, which reduces the weight they have to lift with their wings. If an average human (say, 65kg) needs 6.5m wings to fly, an average horse (of anything between 300kg and 1,000kg) would need to generate a lot of lift, and have an adequate strength-to-weight ratio in order to actually have functional wings. Somewhere between 10-20m would be enough to (theoretically) lift a horse, and the wings may require a number of elbow joints if you want the wings to be able to fold. I'm less sure about the bone structure required, but if the musculature of your wyverns is strong enough, you wouldn't need hollow bones to make them lighter; they'd just need to be stronger to compensate. [Answer] A wind is not going to make flying easier. It makes taking off easier, but that is it. Flying is relative to the air. So, wind may boost or lower your speed versus the ground, but it doesn't affect flying once you are airborne. Soaring is probably possible. It is actually possible for a very strong Bicyclist to get airborne and remain airborne by pedaling. <http://www.telegraph.co.uk/news/newstopics/howaboutthat/10177573/Bicycle-powered-helicopter-wins-Canadian-inventors-250000-prize.html> Of course, gliding/soaring itself isn't a problem given the popularity of hang gliding. Aspect ratio is the ratio of the length to width of a wing. An albatross has an aspect ratio of more than 10:1. High aspect ratio makes for a more efficient wing. Increasing the aspect ratio reduces the sinking speed of the wing when soaring. In terms of wing loading, N/m2 large birds are in the 75-100 N/m2 range. Let's say the beast has a weight of 150kg (or 330lbs). There are 9.8 N/kg. Let's call it 10 N/kg for simplicity. We have 1500 N. 1500 N divided by 75 N/m2 equals 20 m2. If we approximate the wings as rectangles (which they wouldn't be all the way to their ends), 10x\*x=20m2 is their area just to get this airborne let alone with a rider. x=1.42m. That is a wing width of 4.65 feet at the wing's base and a wing length of 46.5 feet for both wings together or 23.2 feet per wing. That is unmanageably long. Of course, soaring alone (which is what fixed wing aircrafts do) is not enough. Powered flight by flapping is required at least occasionally. Birds usually create small puffs of air they force downward with each stroke. These are discrete cylinders of downward moving air when the bird is moving slowly, and the cylinders start to overlap and run together when the bird is flying faster. Assuming we somehow get around the muscle strength issue, there is an addition problem: the Reynold's number. This is a dimensionless number that describes how reality change as you scale up or down in size. Air moves smoothly over streamline bodies until the Reynolds number hits about 2,000,000. Air moves smoothly over non-streamlined bodies (such as the body of a rider) until a Reynolds number hits about 200,000. Once you are above this cutoff number, air starts to move chaotically around the flying object. Drag is doubled, and eddies (turbulence) form. Basically, it is not at all clear whether it is possible to reliably push a significant quantity of air downwards in the direction you want it to go while air is moving around the flyer chaotically. It is really hard to study the reasons why something isn't possible, but I looked a while back during my own research. I couldn't even find robots that were able to flying by flapping their wings above this cutoff. It isn't even a matter of being stronger than normal animals. An albatross with a streamlined body of length 1 meter long flying at 15m/s has a Reynolds number of about 1,000,000. The Reynolds number is proportionate to speed and length of the flyer (so take the 1,000,000 number and multiply it how much longer and faster you want the creature to move). The creature we are talking about is 2 meters long at a bare minimum (the wing width is 1.42 meters without a rider). So, we are talking a Reynolds number of 2,000,000 at very least without a rider and flying very slowly in ideal conditions with ridiculously long wings. So, barely flying by flapping regardless of its strength. Make the wings bigger to accommodate the weight of a rider plus riding gear and plus the weight of stuff you might want to carry with you, and this reptile isn't flying. Also, the rider reduces the Reynold's number cutoff simply by being non-streamline and so probably doomed the endeavor right out of the gate. The larger pterosaurs didn't necessarily violate this limit. We don't know if they could do powered flight at all or what weight they were. There are even questions surrounding their supposed wingspan. ]
[Question] [ Is it possible for an asteroid belt to form around a sun? Think of our asteroid belt, but instead of where it is now, it would be where Mercury is. Also, and I didn't have enough room to put this in the title, but what effect would this have on the solar system? How would this affect eclipses, astronomy, etc.? Please note the asteroid belt is in a stable orbit around the sun. [Answer] Anywhere a planet can orbit with stability, an asteroid belt can orbit with stability. Depending on the [orbital inclination](https://en.wikipedia.org/wiki/Orbital_inclination), the effect would vary from drawing a line across the sun to having a thin "halo" around some or all of the sun (not that I've ever heard of an incination of 90 degrees, but that doesn't mean it's not possible. That effect would change as your planet orbits around the star. You might want to research how we see Saturn's rings as the two orbits move, the effect would be similar. As for eclipses, the "halo" (if it exists due to inclination) would be more pronounced. Like looking at a dude with an old "arrow through his head" gag but the face is blacked out. [Answer] The thing you are talking about here are [Vulcanoids](https://en.wikipedia.org/wiki/Vulcanoid). They are theoretically possible but none have yet been discovered. The fact that astronomers continue to look for evidence perhaps give us some idea of just how little effect they have on the solar system. ]
[Question] [ I am writing a sci-fi novel, set in a 1984-style dystopia, so a society which is obsessed with order and surveillance where non-predictable behaviour is punished. My protagonist is a person with a mild form of autism: 1. How would such a society treat people with this and other mental illnesses? I assume that it will find subtle ways to isolate them, but other suggestions are also accepted. 2. What are the ways in which a person that does not want to conform to these norms (i.e. does not want to live in a room without a window for the rest of his life) could escape such treatment, and hide his illness from society? The novel is set in the near future. One symptom that is particularly developed in the text is his very bad (but still existing) episodic memory: so, for example, he remembers the people who are close to him, like his landlord and his friends, but he does not remember particular conversations with them. To combat that, I gave him Sherlock Holmes's style deductive powers which allow him to deduce the things that normal people remember. If you are interested, you can read the first few chapters of the novel [here](https://boris-marinov.gitbooks.io/the-case/content/). Some of clarifications and personal thoughts (not essential for answering the question): Upon hearing the word "dystopia", many people assume that I mean that my protagonist will be persecuted - in the past there have been a lot of violent and inhumane treatments of mentally ill people both in totalitarian and non-totalitarian societies, however, this was at a time when mental illness was way less understood and talked about, therefore I don't think that the same treatments will be used in the future. Also, many people asserted that no special treatment is required because a mentally-ill person does not pose a direct threat to the regime. That is not entirely true - running a (dystopian) society is not as simple as "punish those who are a threat and reward the others". Such societies are, for me, much more fragile than people generally think and keeping everything in its right place is crucial for the whole thing to work. I will give you one example, this is a story of how writers were treated in Soviet Russia and its satellites (I know this to be particularly true in Bulgaria). Many people know that they were persecuted and jailed but that is actually not the whole story. Another option for a writer was to join the "Writer's Club", situated at a glamorous building at the city centre with a bar and restaurant that were free for members. There he/she could meet other writers and members of the country's intellectual elite. Every member of the club could also publish his work with no effort in one of the state-owned publishing houses. The money was very good and there were very few topics that were censored. However once a person became a part of the elite he/she could no longer produce a decent critic of the regime, even if he/she wanted to. And most members had no desire to do criticize the regime either. That meant giving up on their privileges, financial stability, and social circle and substituting that for the life of poverty and persecution. [Answer] As you novel is set in near future, I would guess they would refrain from controversial physical isolation, as modern drugs could achieve the goal of controlling unpredictable behaviour so much better. This would be promoted as "treatment", and, if potential for damaging behaviour considered high, he would have become ward of the state, and be assigned visiting "caregiver" whose responsibility includes ensuring he takes drugs and does periodic visits to psychiatrist for regular assessment and providing authorities with observations and recommendation as to further actions. So to achieve his goal of staying free your protagonist would have to use his deducing abilities to play cat-and-mouse with both caregiver and doctor. Or, if by some miracle his condition was not discovered yet, he might want to play this game with AIs of facebook-like social networks that in your society likely will be tasked to identify "risky" behaviours and flag at-risk individuals. I would not worry too much about handling suspicious neighbours, as today you can avoid in-person contacts almost completely. [Answer] You are mistaken about autism; my grandson has it. He has no problem with memory at all; in fact one aspect of his autism is difficulty in learning language (he did not start speaking until about 4 1/2); in essence the "natural" part of language development is missing in many autistic children, and they have to learn language as you and I might have to learn a second language in adulthood; but without any tutors and a restricted form of rationality. As a result, even at 11, my grandson continues to use "scripting" as his primary communications method: He watches children's shows on TV (meant for children half his age), apparently remembers hundreds of hours of it, and when he wants to say something he repeats verbatim and in the same tone and volume what one of the characters has said. This is usually appropriate usage: One example; in a children's show one character accidentally drops something and says, "Oops, that wasn't supposed to happen!". My grandson, trying to pour himself a glass of milk from a full gallon, spills a lot on the counter and floor. He goes to his mother and says "Oops, that wasn't supposed to happen!", which has become his script for most minor accidents. She knows this and asks him, "What wasn't supposed to happen?", and he takes her hand and brings her to the spilt milk. He uses another script, another character on the same show: "We have to clean up this mess!", and his mother says, "Right. I'll get the paper towels." (she does not stay on script, but he talks almost entirely in them). Because he mimics his TV characters, his speech is clear; he doesn't slur or make errors. Despite this apparent inability to form his own sentences, on paper he understands grammar, and he clearly understands spoken commands. He laughs when appropriate if his mother is playing with him and says something funny. He is sad when scolded or told he cannot do something or go somewhere. My grandson has an awesome memory for people, places and things. He remembers their names and uses them (as single words). If you ask him what he wants at a restaurant; he will say "taco", "burger", even "enchilada". He just can't seem to string these together into a sentence; I suspect even his scripts are the equivalent, in his mind, are not ten words, but just one very long word: His word for "accident" is "Oops...that..wasn't..supposed..to..happen", longer than "Supercalifragilisticexpialidocious". My grandson's primary difficulty isn't language; but imagination, and theory of mind. He does not understand motives. He doesn't think of new things. He is stuck on the children's shows because he cannot understand a plot, or that one character knows something and another doesn't. He does not understand implications of some event. He does not understand "money," if you hand him a \$100 bill he will just drop it on the floor. He doesn't get the multi-step process of getting money, holding it, then spending it on something. (His mother has tried: He loves smoothies, she has given him \$10 to give to the clerk at the counter. When she said, "Now you give her the money," he had a \$10 bill in his hand, but dropped it on the floor so he could go through the motions of handing the clerk money.) ### Where would a person like this fit in? Before political correctness (which I endorse, BTW) I suspect all these people were lumped into the "retarded" category. Originally that was not a pejorative at all; it was a medical description meaning delayed development. It became a pejorative because the people thusly labeled are, indeed, not very intelligent by normal standards; they fail to understand things a normal person understands without effort. Such people, in the past, were relegated to laborer and service jobs that they could memorize. If they were autistic, they may well have had near perfect memories for their tasks and executed them flawlessly. They could be quite useful on a farm, or as a worker for blacksmith. My grandson can clean his room flawlessly (and put every single building block in exactly the same place every time, and all his picture books in exactly the same order on the shelf). In a dystopian society with no public care, I suspect that is how they would get by: Working for a living and being housed, fed and cared for by parents, siblings or lacking those, by profiteers exploiting them as "labor for food". --- Problems with the plot: Sherlock Holmes deduction relies *very heavily* on memory, of how things should transpire but did not. A person with memory problems cannot do this! An Autistic person generally has either no theory of mind, or an impaired theory of mind: This means they cannot understand why other people are doing things; they struggle with the idea that others know things they do not, or they know things others do not. The idea of secrets is difficult for them to grasp. This prevents them from having deductive ability about even the most minor of motives or how what they do affects other people. My grandson again: When he is looking through a picture book, he doesn't like noise. So if his mother turns on the TV to watch the news, he will walk to the coffee table, see that his mother has the remote, then walk to the TV and press the mute button and walk away, all without saying a word. He doesn't realize she wants to hear what she is watching, he just solved the problem of the TV mysteriously coming on and making noise he didn't want to hear. Here is how that transpires: He mutes it. She calls his name, and says, "I'm going to listen to TV." He calmly says, "No." She calmly says, "Yes." He sighs, she un-mutes the TV, and he takes his book to the furthest back room and shuts the door. My grandson is not the only autistic child I know; because of him I have exposure to about a dozen. Although that is a small sample, I can report that not one of them has "episodic memory" or Sherlockian deductive powers, their inability to emotionally understand other people (or even grasp that other people have intents or desires) prohibits that. Although your character could be made plausible; Attributing these traits to "autism" will be both implausible and an insult to the autistic community. It is like confusing "tuberculosis" with "lung cancer". I suggest you attribute your character's traits to something simple, like brain damage due to a physical accident, brain surgery to remove a tumor, or brain damage suffered due to an inadvertent or accidental medicinal overdose as an infant; perhaps in response to a seizure event. [Answer] Provided that autistic people, once placed in an environment they like, will never ever put effort in changing it, I see no problem for a dystopian a la 1984 society. If they like yellow, paint their room yellow and let them enjoy their room. He will be the rightous example of a citizen, enjoying the sober apartment the government provides to all. If they dislike green food, savings for your artificial coloring in the kitchens. If he likes having any set arranged in perfectly matched rows and lines, appoint him as organizer for the year Joy March! Paranoid governments are more afraid of unpredictable people than of methodical routine obsessed people. Once they know the routine, they will be sure it won't change. [Answer] I won't speak to the autism. It's merely the "why" you're using to separate your protagonist from the world around him/her. You could use almost anything to do that, so I recommend (a) that you find a reason to use one over the other (even Sci-Fi stories should have a purpose) and (b) that you research the snot out of it before using it. Illnesses and disabilities are sensitive issues to the many people affected by them (both the sufferer and those around them). Since we live in a world were anger over a perceived disrespect is often instantaneous and virulent, it's worth every second of your time to be absolutely sure you're representing your choice correctly. Question #1 Maybe subtle, maybe not. Most people don't realize that Nazi Germany was a nearly perfect example of a dystopian society that dealt with everything different from the ideal norm (including illness and disability) with brutal efficiency. How did they do that? Euthanasia. Forced sterility. Violence. (See [here](https://www.ushmm.org/learn/students/learning-materials-and-resources/mentally-and-physically-handicapped-victims-of-the-nazi-era), [here](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2800142/), and [here](https://en.wikipedia.org/wiki/Nazi_eugenics).) One of the problems of a dystopian context is that it requires both an excuse and the ability to devalue humanity. Anything that can devalue an entire society requires a fair amount of power. The Nazis used fear through secret police and the simple removal of anything not supportive of the cause. Question #2 Dystopian books are ususally stories of redemption where the dystopia is the framework for the conflict to be overcome. In reality, escaping the destypian influence means resistance groups and "underground" networks to hide or move people away (think Anne Frank or the various Jewish underground railroads during WWII). The despair caused by dystopia is a critical concept in such a story. Our modern YA novels cheat the power of these societies in that they all have ways to overcome the powerful influence. We must suspend our disbelief to enjoy the story. Indeed, allow me to give you a quote from a friend of mine that describes the fundamental flaw that's necessary for a YA book to be popular: > > We write stories about children saving the world for our own sake. We realize as adults that the world is lost to us and we well know no child has the resources, education, or wisdom to overcome this fate. Our stories are our fantasies that the world can be made right by the innocent. – *E. Keith Howick, Jr.* > > > Therefore, to offer insight beyond the two ways to escape already mentioned (hiding and an underground railroad), let me suggest that any mental disability would need to be almost inconsequentially light to avoid society's distaste without help. So, I would begin with asking, "how can others assist the weak to overcome their tormentors?" If you are set with the idea that the afflicted individual overcome the dystopia him- or herself, then you'll need a wonderful story to help people suspend their disbelief as that seriously increases the difficulties. Note that you're suggesting to escape treatments — remember that dystopian societies are usually interested in removing, not assisting. What would be the point of a treatment that further dibilitates the dibilitated? Such a person would be seeking illicit treatments that would help him/her hide their limitation. They would seek employment or other social integration that did not make demands that would exceed their limitation. They would seek partnership with people whose educational or social skills were equal to those imposed by the limitation. These all would work so long as no one suspected their situation and turned them in to avoid a similar fate themselves. ]
[Question] [ It seems to me like one of the major obstacles to terraforming a planet is to give it a magnetosphere. In our solar system, this is accomplished naturally either by a hot iron core (for example, Earth), or by a heavy, thick atmosphere (for example, Venus). Neither of these things are easy to produce on a planet that doesn't already have them. A workaround I've considered for this is to position an object in between the target planet and the star, to block out harmful rays while letting through the necessary light/heat to support human life. I want to think this would be as simple as fitting a large craft with a series of mirrors, and positing it to 'follow' the target planet as it goes around the star. But since I haven't heard about this kind of idea I'm guessing there's something I'm missing. So, would this idea work? Or if not, what would go wrong? [Answer] The biggest threat to the atmosphere is not the visible light, but the streams of [charged particles](https://en.wikipedia.org/wiki/Solar_wind). To protect against high energy particles, a [smaller magnetic field](https://www.universetoday.com/134052/nasa-proposes-magnetic-shield-protect-mars-atmosphere/) between the planet and the star would work just as well as a planetary one. Placed at the $L\_1$ point of the system and sized accordingly as shown in the picture. [![enter image description here](https://i.stack.imgur.com/HrPRO.jpg)](https://i.stack.imgur.com/HrPRO.jpg) [Answer] The obvious flaw of the idea is timing. There are 2 possibilities - you are too early, or you are too late. If a planet has an atmosphere, let's say if mars had an atmosphere, it will take millions(hundreds) of year to noticeably change the composition. If the planet hasn't significant atmosphere, let's say as mars today, there is nothing to protect and current losses of mars atmosphere are minimal and it will take billions of years to noticeably change the current situation. So if you discover some planet and it has an atmosphere, it means it has it since about star system formed and the planet was formed and initial processes of forming of the system gone in its stable state. And there will be reasons why the atmosphere is still there and those reasons will not change soon in most cases. If a planet you discover has no atmosphere and you would like to create one there, then there are 2 important factors to consider. The speed of a planet atmosphere loss is slow compared to the amount/mass of the possible atmosphere. The second, if you able to create the atmosphere at any reasonable rate years, hundred years, thousand years, million years(timescale of optimists and pessimists) then you have no problems to replenish the losses. However, if you concerned to reduce possible losses, just because you can or other reasons. Yes, a construction in L1 point could help you to do so. However, it less likely to be a set of mirrors, and most likely to be transparent solutions, electrostatic solutions, magnetic solutions. ]
[Question] [ I've been looking for information on this, but I haven't come upon an answer that could actually help me figure this out: Imagine a planet, inhabited by somewhat "human" beings, that has one sun-like star (a source of light and such) and two moons. Now, that "Sun" and one of the moons work in cycles kind of similar to ours, that being 15 hours of sunlight and 15 hours of night, during which, this moon appears in a roughly opposite cycle to that star. Now, the second moon has played a crucial part in the disappearing of an ancient city, that being either floods or drought. It may not be directly related, but those living, sentient beings think there is a direct relation between that. The idea is that this moon used to appear during the night for centuries, only to keep changing its span and coming out slightly earlier everyday. The difference of the time it came out from day to day was so small it couldn't be noticed until it started appearing at, what we could call, midnight. To keep it simple: this moon kept appearing earlier and earlier, and by the time it first came out at the same time their "Sun" did, a natural disaster came to that city. This happened nearly 1000 years ago, and the theory states that "Every thousand years, this moon switches between day and night". Some of the people who got to abandon the city on time think they can still come back to it, because (they assure), since so many years have passed, the moon comes out at night again, and so, the place must be habitable again. I'm terribly sorry if this makes no scientific sense at all, my knowledge on physics, planetology and English are quite not as good as I wish they were. [Answer] You don't need acceleration at all to see the effect you mention. In fact, our moon does exactly what you describe, only on a 28 day cycle instead of centuries. It's why sometimes you can see the moon during the day. A highly eccentric orbit would indeed cause an acceleration. The [Molniya orbit](https://en.wikipedia.org/wiki/Molniya_orbit) is a great example. These orbits are designed to reach an appogee over Russia while moving very slowly and then accelerate around the Earth to get back into position over Russia again. They're used for Russian communication satellites -- you only need 3 to guarantee that one is over Russia at any point in time! However, I don't know how well that particular orbit scales to the thousands of years that you want. [Answer] From the question it is not clear to me whether this moon made a sudden switch in its behavior or if its orbit gradually changed over 1000 years. The gradual is not so wacky I do not think. The sudden ""Every thousand years, this moon switches between day and night" requires more thinking. I found that Saturn has two moons that switch position. From <http://www.planetary.org/blogs/emily-lakdawalla/2006/janus-epimetheus-swap.html> [![enter image description here](https://i.stack.imgur.com/OVGTU.gif)](https://i.stack.imgur.com/OVGTU.gif) An orbiting body with a period of 1000 years would have to be something like a comet. Comets take their time. From <https://www.spaceanswers.com/solar-system/which-comet-takes-the-longest-to-orbit-the-sun/> > > As far as the longest period comets go, the current leaders are Comet > Hyakutake with an orbital period of 70,000 years, Comet C/2006 P1 with > an orbital period of about 92,000 years and Comet West with an orbital > period of about 250,000 years. > > > A comet with a period of 1000 years would be hustling right along compared to these. Suppose the comet showed up and when it did, it played the role of Epimetheus, altering the orbit of the second day/night moon then zooming off for another 1000 year circuit before returning and altering it back. [Epimetheus](https://en.wikipedia.org/wiki/Epimetheus_(moon)) weighs 5 x 10^17 kg and comet [Hale-Bopp](https://en.wikipedia.org/wiki/Comet_Hale%E2%80%93Bopp) weighs 1 x 10^19 kg, so a body with the mass of a small moon and the orbit of a comet is possible. [Answer] It sounds like having your evil moon be an evil sibling planet instead would solve some of your orbital mechanics. ## Problems with your moon ### 1. appearing at night In order for a moon to only appear at night, it would need to constantly be on the opposite side of the sun, which would preclude it from orbiting the planet. Note: You could account for this by having it orbit in the opposite direction of the planet's rotation in a geosynchronous orbit (not to be confused with a geostationary orbit) such that it appears in the same position at the same time each day for a ground based observer, and then limit your narrative only to people who live in an area on the planet where the moon is visible at night. (People on the other side of the planet would see the moon during the day, but perhaps they're irrelevant to your story.) ### 2. long orbital period If you were to have a moon orbiting a planet with a period of a thousand years, consider that it would need to be extremely distant from the planet-- either all the time, in the case of a nearly circular orbit, or most of the time, in the case of an elliptical orbit. Making that work with a tertiary orbital body (that is, a moon orbiting a planet that is in turn orbiting a sun) is very difficult. ## How a sibling planet would work You still can't have another planet only appear at night, since the farther out you go from the sun, the longer a body will take to orbit the sun. Eventually any planet orbiting closer to the sun will "lap" an orbit farther out; which means that at some point, the sun and the other planet are guaranteed to be in the same general direction (from the first planet's perspective). In order for a planet to appear on the nighttime side of another planet for 1000 years, the inner planet would need to "lap" the outer planet no more quickly than every 2000 years. Assuming concentricity, the evil sibling planet will necessarily spend more than 1000 years on the daytime side. [![enter image description here](https://i.stack.imgur.com/BmKh7.png)](https://i.stack.imgur.com/BmKh7.png) Keep in mind that the picture above models a gradual desynchronization... The inner planet revolves around the sun 1000 times with the outer planet struggling to keep up, before finally, on the 1000th circuit, the outer planet passes from the inner planet's nighttime side to its daytime side. ## Outstanding problems with the sibling planet approach The biggest problem I can see is that the evil sibling planet would have the greatest gravitational effect during the 1000 years when it's visible at night. During the 1000+ years when it's visible during the daytime, it will be more distant from the planet (at times it'll be on the complete opposite side of the sun) and while its gravitational influence will be cumulative with that of the sun, it will also be relatively minor due to the distance. If the appearance of the planet during the day doesn't actually foretell any astrophysical destruction, and it's just idle superstition, then this approach works fine. ## Potential reconciliation: Have the evil sibling planet wreak havoc at night If you flip the scenario so that the evil planet appears at night and then causes destruction, it resolves a few problems. First, with a concentric orbit, it can spend 1000 years harmlessly on the daytime side of the earth analog, then spend less than 1000 years buzzing by in a closer orbit. Second, its greater proximity during the night period facilitates greater tidal extremes that can cause destruction befitting your plot device. [![enter image description here](https://i.stack.imgur.com/CFkkf.png)](https://i.stack.imgur.com/CFkkf.png) The closer you make the two planet's orbits, the shorter the period of time during which the evil sibling will appear at night and the greater you'll make the gravitational effects. Sometimes these things are easier to model [in two dimensions](https://jsfiddle.net/thriggle/cbzx83md/). ]
[Question] [ Let's say we came across a new species of moderately intelligent birds. Like [Alex the parrot](https://en.wikipedia.org/wiki/Alex_(parrot)), these birds are able to learn a few words and simple concepts. But once we teach these birds the words for different numbers, we are astounded by the fact that... ...these birds can already count (to at least 100) and do simple arithmetic. What evolutionary pressures could have possibly led to this scenario? [Answer] There's a very simple answer to this one: Mimicry of flora/fauna with number-specific differences. Consider the 13-spot ladybird: ![ladybird](https://news.bbcimg.co.uk/media/images/53894000/jpg/_53894765_13spot_peterbrown.jpg) Next, consider the 16-spot ladybird spider: ![ladybird spider](https://3.bp.blogspot.com/-Ym7pOT2pXqc/ULzu8kpKOJI/AAAAAAAAA10/11Hi2ypG8K8/s1600/ladybug+mimic.png) In an environment where predator or prey is a mimic with a subtly different number of spots or other distinctive feature, counting can become increasingly important. Or else if variants with a certain number of spots were poisonous, evolution would select for the birds able to distinguish one from the other. Of course you can create subtler differences in your prey species - perhaps the edible ones all have multiples of seven spots which are added every time the creature moults, almost like the rings of a tree. In a similar vein it wouldn't even have to be about prey - if there was a deadly plant or another threat which was number-specific, such a trait would probably select relatively quickly. [Answer] Social behavior, we know for instance that social primates will not accept extremely uneven sharing. Anything more than about a 3/5th diffrence is rejected. Being able to tell how many of your social group are present can be equally important. Especially if comparing your group to another group. math becomes especially important one you have the ability to communicate. Turn left at the many trees is not as good as turn left at the three trees. More basic keeping track of predators or dangers could be useful, how many wolves went into the cave vs how many came out can be important. The bbc has nice little article about its uses among animals <http://www.bbc.com/earth/story/20150826-the-animals-that-can-count> [Answer] I recall a demonstration of a dog that could count up to n, where the trainer threw a bunch of practice dead animal dummies into the tall grass some distance away and gave the command to fetch. Each time one was returned, he repeated the command. If the number of objects that were thrown was ≤n, then when the next (excess) command was given, the dog would walk around the seat and sit, indicating "I'm done with that, ready for next command" without going out and doing any searching. If the number of items was larger than the dog could count, then he would head out to search for more, even though there were none present. Being able to remember how many prey animals are hidden saves the futile work and also increases confidence that you got them all. How much extra time would you spend working an area just to be sure? It also means they can calibrate their idea of how well the prey hides, rather than supposing a certain amount of work is good enough. This saves work in general, when deciding if an area is finished. So, imagine an evolutionary arms race where prey animals can hide, burrow, or whatnot, when they see the predator coming. How much work they spend digging deeper or hiding better can vary depending on strategy, if they are making the predator work harder as well and waste work and waste time. Knowing how many are hiding will cut out that game and give them an advantage. Perhaps the mental capacity to count to n increased a bit at a time, until it somehow reached a general point where instead of 7 or 9 they could handle on the order of hundreds, because the mechanism had an increment/decrement feature and internal state. [Answer] Let's assume: The bird has x baby birds, each baby needs y worms to survive. So the bird perceives somehow that after y worms babybirds stop to cry. If the bird as fed all babies, he perceives the amount of worms he fed to the family. One day the family need more, the next day less. They perceive that 5 eggs are less than 4. Of course they don't count! I'm talking about being able to abstract reality to put things into relation. Basic counting is understanding >,< operators and arranging the elements of a set in the right order(4>2<3>1)->(1<2<3<4). Now if you teach him the name of relations he is able to grasp, like <,> and values(numbers) he could figure it out and count, because the relation is already in its mind. Teaching the relation is way harder, than just giving tools to apply know things to. Pressure to develop this ability: Don't go for prey bigger than you, don't pick up more than you can carry, build the nest higher than last time, or the fox will get the eggs again. It is in the nature of our reality that most living things can under stand relations like this. This could be a reason why he can count, no one knows why for a fact. Another possibility is he was just very well conditioned and good at mirroring humans. ]
[Question] [ I'm imagining an intelligent race of beings with only one major difference from humanity: that they share one mind. Biologically speaking, they're identical to humanity, and their world is, by all practical means, identical to Earth as well. However, each of these people have access to every memory and thought of every other person of their race. This is essentially the same as this race being a single superorganism that shares a mind. In practice, there would be no war in this race. No cultural differences, no conflicts, no need for things like "rights", and most importantly: no need for communication technology. Exploration technology and transportation would also become less important. Things like cameras or entertainment also wouldn't be useful. My question is in asking "What might this race focus on developing technologically, without our human limitations?" [Answer] One goal of the hive-mind might be growth. This growth could be in two ways: 1. Quantity. The more drones the hive-mind consists of, the better its survival chance. Even better if they are spread out over the whole planet, so a single natural disaster won't cause much damage. So the hive-mind will have its drones mate as much as possible to create more and more of them and have them spread out geographically. In order to keep all these drones healthy and well-fed, it will have to acquire resources. First food and water, then material for shelters and clothes and energy for heating in order to colonize the less ideal climate zones. In order to do that it will need to develop agriculture. When the hive-mind colonized its whole planet, it still won't be satisfied. It will want to expand vertically by increasing the population density. That means it will have to develop more advanced technology in order to tap all the available resources of the planet. That means that the hive-minds scientific interest will focus on industrial resource exploitation and processing. When there is no room for improvement here, it will figure out interplanetary spaceflight in order to exploit the resources of other planets. 2. Quality. Maybe unbound expansion isn't a valid strategy for the hive-mind. Maybe its natural resources are too limited to sustain a population of more than a few million drones. Or maybe its thought processes have an upper limit on how many drones it can control. If it breeds too many of them, it risks to fracture into multiple independent hives. In that case the solution is to not create more drones but to create better ones. In this scenario, the hive-mind will focus on biotechnology. The hive-mind will do selective breeding experiments in order to make smarter, stronger and more resilient drones. It might also try to create drone strains optimized for specific tasks. By evaluating its breeding methods, the hive mind will discover genetics and might develop the technology to replace manual breeding with direct genetic manipulation. This leap will allow the hive-mind to create highly specialized organisms capable of duplicating feats other civilizations can only achieve by using machines. The motivation behind developing spaceflight (likely in form of fully organic ships) might be to find other lifeforms as an inspiration for developing even better genetic traits. [Answer] Your species will likely have little value for life. As a single death means nothing to the hive. Why do we fear death? Because it's the end of our existence. When we will live on in the hivemind that fear is removed. It's interesting what that would do to religion. Perhaps the hivemind will feel alone. Without talking, there will be no script, no writing. The hive will remember everything. However I see that as an obstacle to exploring higher math. When you never explore written numbers, how can you get to equations? Couple that with another issue I see. Survival is the mother of invention. Wether it's another man coming to kill you or nature itself. Without adversary there is no drive to invent. For the hive it's hard to die, the insentive isn't there. Sure it would make progress, after it exhausted every available resource. And then it will go slowly I think. Hiveminds are considered smart, because they overcome problems for the hive. Each worker does his tiny task for the greater purpose of the hive. If the hive is all, why would a worker ever be 'smart'? Anyway, with no math, no writing you have no 1's and 0's. How do you come to a computer without script? And that, that severely limits your species. [Answer] I think the first technological development, perhaps equivalent to humans developing language, will be methods to interfere with or cut the hive-mind into smaller clusters. Because survival. As a single group, as a single species, the hive-mind is, nonviable. Much of history has been, well, less conflict for the sake of conflict and more a struggle for resources. All people being equal (as your question has it) will simply mean everybody dies, when there isn't enough for everyone, and no mechanism to treat people unequally to decide who would go without, who would die for the others to have a better chance of survival. Looking at hive species, ant colonies or beehives, two things are very clear - one is a very clear hierarchy, those crucial to survival (like, say, queen or other necessary-to-survival-and-reproduction individuals) are elevated above others who are merely drones... and so, when there is not enough for all, those expendable are sacrificed to maintain survival of the whole hive. Your human species has no queens, no way of designating essential-to-survival individuals, and any attempt to force unequal treatment of otherwise equal beings will lead right back to conflict and struggle. This happened in humans, too, with some cultures giving most food to hunters (even if it means the sick, weak, or elderly die) because they have to be strong to get more food for everyone, other cultures privileging warriors (because being overrun by predators or outfought by competiton is the end), in other cases it might be healers, or wise-folk, or leaders, who got the nod as essential enough to be worth preserving at the cost of other lives. Though I guess, in a human body, we can't really sacrifice individual bits - oh, wait, we do. Sacrifice extremities to frostbite to protect the core, sacrifice fat cells and then muscles to starvation, to allow the major organs (heart, lungs, brain) energy enough to survive longer, throw up an arm to intercept a blow to the head or curl around tender organs to protect them at the expense of the sturdier musculature. No hierarchy means everything dies together, instead of some lasting long enough to find a way to survive. The other thing that we see in hive species, that is missing here, is multiple colonies. Because a too large colony cannot sustain itself, and two colonies too near each other are in competition - its likely only one is going to win, and the other may not survive losing. If the distance the hive-mind can reach is practically infinite, then they will all act together - so there's no backup, no way for any survival of the species given any failure of the hive-mind. It would only take once for equal distribution of the food to leave everyone starving because hunters don't have enough strength to hunt or everyone vulnerable to predators because the warriors don't have the energy to fight, for the hive-mind to learn about the dangers. But, with only one hive-mind, well, it loses and there's no second chance to be had. If the hive-mind survives those first, crucial failures - I expect it would be by physical isolation of a group/tribe/family, which was not close enough to distribute resources and starve together, or was not vulnerable to predators when they came, or something. So the hive-mind splits up into tribes, which are self-sufficient-ish, and physically separated so resources are not overtaxed. Except then there will be competition for resources when tribes get too close, or too big, and unequal distribution, and those tribes closer or more individual (who can think of the survival of their tribe rather than the other tribe or the greater whole) will survive much better. Mental distance, not just physical, as a survival mechanism. And, thus, either natural evolution towards smaller distance/multiple hive-mind clusters, or the rise of mental technology (like meditation, probably, remember the parallel technology is language) that will let a fragment of the hive-mind slowly learn to cut themselves out, to close itself off from the greater whole for the survival of one tribe over another, or bring specific outsiders into a group for assimilation or expansion. Thus my prediction that communication technology is going to be vital, even if in the opposite direction, interference rather than increased communication. Of course, once interference in the built-in hive-mind communication has been explored, technological adaptions may rise in significance again to bridge the new gaps. Beyond that point, depending on the evolutionary triggers and mechanism of the ability, we might see either evolution towards a loose coalition of minds instead of total merge, that is, individuals (and then mostly human technological development), or towards discrete hives with adaptation towards classes of distinct, hierarchical roles. In the latter case, there is a small, outside possibility of one hive out-competing others too the point of, eventually, assimilating or eliminating any other hives. If that happens, then we are nearly back to your original question But, in this case, the hive would not be of individuals nearly identical to our own species, it would contain separate classes physically adapted to specific roles. This will have a not insignificant impact on how technology progresses. I would expect somewhat slower or lesser use of domestication or tools for certain tasks, with the gap being filled with those classes or castes which were already adapted to those tasks. Each class or caste would probably develop its own technology nearly independently, since they are looking for things specialized for their own task rather than broad applications. It might be harder to initially cross-adapt discoveries or techniques, since each caste (and thus the hive-mind) will think of their discoveries only in terms of their own work - though once any cross adaption is discovered for a technique, other adaptions will probably spread rapidly across the whole hive as the hive-mind thinks about looking for any other possible uses. Additionally, with the high value of specialization, I think the hive would be somewhat better at finding a single answer or solution to a problem or thoroughly investigating all variations of a tool or theory, rather than broader and more abstract discoveries or intuitive jumps. Still probably lots of both, but a bit more of a conservative lean and tending towards steady progression rather than large or luck-based jumps. Lots of people working in concert and with full knowledge of each other's work, instead of off on their own making all sorts of individual jumps and trying things others deemed unlikely, with unexpected success. [Answer] Anything and everything. With no effort wasted on fighting, they can apply their efforts to whatever advancements they choose. They might not choose technology and science, but religion, art, or collecting beetles. Without communication tech needed, they won’t have servers and huge databases available remotely. They might not develop this synergistic technology, which holds them back in other ways. [Answer] Oh so this is the human species where the group is the individual. Well this hive mind is still human it still has the human desire to know things and to Explore that may motivated it to discover new technologies maybe even space travel given enough time. Some technologies though they would not need to develop Technologies it wouldn't develop 1. They would have no need to develop computers there a hive mind made up of billions of people. A billion human working perfectly together can outpace any computer we've yet developed. 2. A communication technology that would have no need why would you need to communicate with yourself that's what this hivemind essentially is it's the human species if where the group is the individual. 3. Writing again no need for it see above. Technologies it would still need to develop Transportation: maybe a hive mind but it's still a human hive mind so it has human emotions such as curiosity and I need to explore. Even without this it would still need to gather new resources as hivemind members grew. So it would need ways of getting to places faster then just walking. Construction Technologies: still needs shelter as its members are still human. Art base Technologies: as mentioned earlier this hive mind is still human and has human emotions it still has a need to create things and a sense of beauty. So would still the art and the tools to create art. Scientific instruments: Again as stated earlier this is a hive mind but it is a human hive mind, it's not a robotic hive mind. Assuming that the human brains that make it up are mostly the same as our own the hive mind probably has the same emotion is that we'd have. This includes our desire to understand the world around us and how it works so it would still develop scientific instruments and maybe even the scientific method. ]
[Question] [ Alien AI DoomFleet has a mission: Destroy threats to their creator. They do this by detecting the signature of FTL drives, going to the system, and blowing everything up, up to and including the homeworld. For thematic purposes, I want the worlds to be stripped of their atmosphere. I'm not sure where to even start with this. "Simply" bombarding with explosives, even anti-matter explosives, seems like it would take far too long to be worthwhile. So my question is: How do you go about removing the atmosphere from a planet? I'm not particularly interested in what would happen afterward, as that is pretty well discussed in [this question/answer](https://worldbuilding.stackexchange.com/questions/22937/what-would-the-earth-eventually-look-like-if-it-was-somehow-stripped-of-its-atm) - I'm looking specifically for mechanisms to remove the atmosphere. Preferably fairly quickly. Notes: Time, while not extremely restricted, is not unlimited. We can't necessarily park something in orbit and wait several years. There's other planets to be exterminated, as the DoomFleet's FTL is relatively slow. Additionally, we want to strip the atmosphere and be done with it. We're eliminating threats, not establishing beachheads, so we don't want to worry about maintenance and the like. [Answer] One possibility is to heat the surface. This is "comparatively" easy since the bad guys could for example deploy an enormous solar sail (the term is apparently mega-[statite](https://en.wikipedia.org/wiki/Statite)) and use it to cook off the planet. It would double up as an extermination weapon, rendering the surface uninhabitable. Exciting and focusing some kind of coronal mass ejection to the extent of stripping the atmosphere away is also efficient, provided these Berserkers - or Amadiros? - have the technology to pull it off. It would probably be difficult to strip off all of the atmosphere in a single go, but nobody says that once overwhelmed the system's defenses - they should do that in any case - they can't install themselves near the sun and start taking pot shots at the planet. This is the strategy preferred by the Ekhat of [The Course of Empire](https://books.google.it/books?id=6PqgMGh6MGAC&lpg=PT247&dq=%22The%20Complete%20Harmony%20will%20attack%20by%22&hl=it&pg=PT247#v=onepage&q=%22The%20Complete%20Harmony%20will%20attack%20by%22&f=false). Another relatively low tech possibility, with the advantage of being very hard to defend against and the disadvantage of only working against oxygen-nitrogen atmospheres (and requiring terrifying resources), could be to bombard the planet with magnesium pellets. The problem is of course to procure the magnesium in the first place: that much metal (the mass of Earth atmosphere is 5.1480×1018 kg) would be equivalent to almost a tenth of the maximum estimated mass for the [Chicxulub impactor](https://arxiv.org/abs/1403.6391). The DoomFleet would need to mine magnesium from somewhere and bring it along from system to system. Then the reservoirs could be placed in space in such positions and with carefully adjusted speeds to hit on the victim planet from all directions, at the same time. The first pellets would burn violently in oxygen, forming magnesium oxide powder and raising the atmosphere's temperature enough to allow further reaction of magnesium with nitrogen (actually this wouldn't even be needed - the reentry heat would suffice to that). The resulting magnesium nitride is solid, but it would quickly react with water vapour from the now boiling surface of the oceans to form magnesium hydroxyde and ammonia, which would mostly dissolve in the remaining water while the dissolved oxygen would get outgassed (completely depleting the oceanic oxygen would take a long time). A large part of the available oxygen would be consumed by the fires engulfing the planet, though - forests, cities, all kinds of organic matter. After a comparatively short time, the atmosphere would be replaced by a boiling fog of low-pressure water vapour and ammonia, and the planet would see its albedo significantly increased. I expect this to lead to a rapid cooling of the atmosphere (and the surface). After that, without the greenhouse effect from the atmosphere, the surface cools down to about -18 °C and we are left with a very thin, sterile atmosphere - carbon dioxide, ammonia, nitrogen, water vapour, argon - on a frozen surface. The remaining organic matter would capture what little oxygen still seeped from the oceans. It's unlikely that any life form could survive the firestorms, the nuclear winter, the change in the environment and the subsequent onslaught of UV radiation after the disappearance of an ozone layer. However, a more efficient way of destroying the planet would be to let the atmosphere alone (directly) and locate instead a suitable asteroid (or more than one) to deorbit and smash into the target homeworld. It would take the same energy as to move a comparable mass of magnesium metal. This is the preferred tactics of the Achuultani of [Empire from the Ashes](https://en.wikipedia.org/wiki/Empire_from_the_Ashes). Now that I've thought on this a little more, so large a quantity of almost anything arriving at several kilometers per second would either burn in the atmosphere or contribute to its heating by friction, and make the planet uninhabitable no matter what. [Answer] If your fleet has a very powerful anti-gravity device, simply suspend the planet's gravity for long enough for much of the atmosphere to exit the planet's gravity. If your fleet doesn't have very long, you could drop a device to do this onto the planet and leave. If you don't want somebody finding it, give it a self-destruct after the atmosphere is gone. If you don't have anti-gravity, you may have to do this on a gas specific basis. I'm going to assume an earth like atmosphere, so you have mainly nitrogen and oxygen to deal with. Nitrogen could be destroyed using a biologically engineered [nitrogen fixing bacteria](https://www.britannica.com/science/nitrogen-fixing-bacteria) to do this at an extremely fast speed. You would have to leave this on the planet because even with an extremely effective bacterium this would take a while (years, not millennium though). Next the oxygen. It's really hard to get rid of oxygen. The boiling point is around -180 degrees Celsius, so that's out. The best way I could come up with is to have your bio-engineered bacteria also somehow react the oxygen into a solid/liquid compound that would then become common on the planet. Iron oxide would make your planet look like mars, with red dirt and sand. It would likely have to mine this substance, so it would be an interesting organism. Maybe include it attacking people/developing sentience/something cool as a plot point? [Answer] As long as you are not against killing all life on that planet in the process, by means others than suffocation, there are some reasonably fast options. One option would be to use relativistic bombardment. Checking <http://www.projectrho.com/public_html/rocket/usefultables.php> (which is by the way, really great site if you are considering writing s-f) Boom Table, you need around 3.2\10^26J to strip Earth-like planet off atmosphere. Assuming you can get impactor running at 99.99% c, it would take around 100000 ton of asteroids (better having number smaller ones than one big in this case). I wouldn't rule away antimatter bombardment - you would need around million tons of antimatter, but you don't need to accelerate it to 99.99% c :) And million tons is not that much on cosmic scale - we are talking about 100x100x100m cube of anti-water, or a bit less of anti-rock. Another option, using locally-sourced material, would be to ask the local star to become more violent. This goes a lot more into handwavium department, but having huuuuge solar flares could do the trick (this was explored for example in <https://en.wikipedia.org/wiki/Commonwealth_Saga>). If you could do a magic space warp thingy around the sun, 1 second of directing all its output toward the planet would be also enough. [Answer] ## The sun can already do this and has done to mars Our magnetic field keeps solar radiation from stripping away our atmosphere. Without a magnetic field [the sun seems pretty effective at it](https://arstechnica.com/science/2015/11/how-mars-lost-its-atmosphere-and-became-a-cold-dry-world/). So we need to find a way to remove the planet's magnetic field. There are two methods of this: Cool the core: This would result in not only the loss of a magnetic field but also the a massive drop in temperature on the planet making it much more difficult for those in underground bunkers to survive. * Slow the planet's rotation: It isn't clear how long it would take for this to remove the magnetic field but the molten core would slow over time and stop producing the magnetic field. Slowing the planet could be achieved by moving the moon (increasing it's angular momentum and so, to conserve it, slow the earth's rotation). The benefit of this is that you don't need to know the composition of the atmosphere before going there. [Answer] The Alien DoomFleet only has to tow a gigantic parasol or [space sunshade](https://en.wikipedia.org/wiki/Space_sunshade) into place above a planet blocking its insolation from its primary star. Once no ambient stellar radiation is warming the planet its temperature will fall until the atmosphere freezes out and the planet's surface is covered in a frozen layer of its atmospheric gases. The DoomFleet sends in armies of robots and evacuation equipment to scrape the frozen atmosphere off the planet's surface and transport to wherever they want to transport it. Perhaps to planets the DoomFleet's creators want to terraform. Freezing planets in this way is also an excellent way of exterminating the inhabitants of planets. Freeze, scrape and shift and a planet's atmosphere is gone. Not as spectacular as some methods, but guaranteed effective. ]
[Question] [ In my story, there is a city which has fallen from grace and is embroiled in gang wars, drug cartels, and other generally high crime rates. How can I plausibly explain this transition? What causes these conditions? If my question is too broad, I am most interested in this: how can I explain the formation of large-scale drug cartels and wide-spread drug addiction? What causes these things to arise? [Answer] # What cities have high crime rates? Here is a list of US cities by [crime rate](https://en.wikipedia.org/wiki/List_of_United_States_cities_by_crime_rate). I can't find anythign specifically drug related; instead I'm going to focus at two statistics, overall violent crime rate, which is mostly robbery and assault, and murder. There are four cities that are in the top 10 for both categories: Detroit, St. Louis, Memphis, and Baltimore. # What do those cities have in common? (All stats from [American Factfinder](https://factfinder.census.gov/faces/nav/jsf/pages/index.xhtml)) First is population decline. Since 1950, three out of the four cities have lost half their population...or more! Detroit dropped from 1,849,568 to 677,116; St. Louis from 856,796 to 315,685; Baltimore from 949,708 to 621,849. Memphis bucked this trend, but several other cities that score highly on the above list have lost a lot of population, as well: Buffalo (580,132->258,071), Cleveland (914,808->388,072), etc. The second is poverty. Of those first four cities Detroit has 40.3% of its population below the poverty line; St. Louis 27.1%; Baltimore 23.7%; Memphis 27.1%. Those numbers are abnormally high. Compared to the states they are in, Michigan is 16.7%; Missouri is 15.6%;Maryland is 10%; and Tennessee is 17.6%. All those cities are 10% or more above the state average. Third is concentrated poverty. Not all areas of those cities are super dangerous or decayed. Johns Hopkins in Baltimore is nice, as is CORTEX between Mid-town St. Louis and Forest Park. But, for example, Zip Code 63106 in St. Louis has a median income of \$13,000 with 60% below the poverty line. Zip code 38106 in Memphis has a median income of \$17,000 and poverty rate of 53%. In Baltimore, 21217 has an income of \$27,000 with 36% poverty; A mile away is the nice Roland Park district in zip code 21210 with income of $83,000 and a poverty rate of 9.6%. # Conclusions Many of the most crime ridden cities in the US have followed a similar pattern. First, automobiles became common and interstates were built connecting all these cities with their sparsely populated suburbs. Second, industry in particular decamped from cramped and expensive cities to cheaper sites in the suburbs. Other industries just folded as a result of the gradual loss of manufacturing jobs in the US. Third, the lower-middle class factory workers that packed these cities in 1950 started leaving. The ones who could afford it left for better pastures, leaving only the poorer behind. As customers left the city, small businesses went under; their owners left too stripping the middle classes of those cities. Fourth, crime started ticking up in the worst neighborhoods. Therefore the rich isolated themselves in their rich people enclaves and left the rest of the city to rot. Fifth, as the rest of the city rotted, there became basically no reason for the middle class to be there. The cities became divided between the richest people in the country, and the poorest. This dichotomy between rich and poor in the most successful cities in the US is obvious: Manhattan is the [richest county in the country](https://en.wikipedia.org/wiki/List_of_United_States_counties_by_per_capita_income) by per capita income; the Bronx is 2710th, around the 12th percentile. [Answer] In my limited experience of drug culture, I think it's a bit like a cult. Once a person becomes involved with drugs, they become marginalized as drugs are illegal. They associate and empathize with other other marginalized people and find it harder to associate with people not involved with drugs. When things go wrong with drugs, there is no means to seek justice via the police or justice system. This in turn means that people involved with drugs are more likely to take risks, to take the law into their own hands.... The good old war on drugs! It didn't work for alcohol and it certainly hasn't worked for narcotics. [Answer] Legal commerce occurs within an artificial environment which can be called "civilized life". In this environment, negative actions have consequences based on a mutually agreed upon set of laws and regulations. Police are employed to enforce these laws, and in a perfect setting, are provided with enough manpower, armor and armaments to incarcerate any law breaker or law breaking group. It is a system which provides opportunity for the vast majority of citizens who abide by those governing laws. This system can break down in a number of ways... * Funding difficulties at the governing level can leave the police undermanned or underequipped. This mandates that sections of the city are left either underpoliced or entirely unpoliced. * Latent prejudices can lead to underpolicing of the minority enclaves and neighborhoods, in favor (and defense of) the wealthy neighborhoods where non-minority citizens live. * Active prejudices can lead to events which foster an understanding in which minority youth are not allowed to participate within civilized life. This can lead normally law-abiding minority and impoverished citizens to side with the criminal organizations, making policing more difficult or even impossible. * A sudden increase in available weapontry in the hands of citizens can change the entire dynamic of police work, making some areas too dangerous to adequately police, no matter how much funding is thrown at it. The list is endless. Anything which leads to a proportional decrease in adequately equipped police on the streets in a neighborhood, will provide an environment in which criminal activity will grow. Without the active enforcement of laws, hunger and ambition will lead individuals to crime. Then seeking either strength in numbers or economies of scale, individual criminals will gather together into gangs; doing this for the same reason that individual workers gather into corporations on the other side of the legality line. The process is inevitable and proven across history; though for most of history, we called the resulting cartels "young nations". Nobody ever built a new empire while obeying the rules prescribed by the current king. [Answer] The cartels and crime rates are caused by a government trying to eliminate the use of drugs. See the current news re the so-called "War on Drugs", or FTM the earlier experiment with Prohibition (US specific), alcohol & tobacco smuggling in places where they're highly taxed, &c. If you have ANY good that people want, and government tries to artifically restrict the supply (or raise the price greatly), criminal-by-definition cartels/gangs will spring up to supply the vacuum. And they will resort to violence to settle disputes: since they are criminals, they don't have access to courts. Meanwhile, the risk to the illegal suppliers means the cost of the goods will rise well above the cost of production/supply in an open market. Those who don't have sufficient legal income to afford them are likely to turn to to crime to supply their wants. As for the why of drug use, you've got me. I found such as I've tried rather boring at best, though I suppose that without some fulfilling career or other outlet, life in a city could be so stultifying that any escape would be welcome. [Answer] economics, drugs are often expensive due to the high risk in manefacturing and selling, but if you have a relatively lawless slum, you can make drugs easily, which brings in your cartels [Answer] The #1 Cause of Addiction is Childhood Trauma([reference](http://www.dualdiagnosis.org/unfortunate-connection-childhood-trauma-addiction-adulthood/)) And this means trauma in relationships with carers - kids seem to bounce back from war, poverty, etc pretty well if they have good emotional support from their family. So if you want a bunch of addicts, have the traditional extended family break down. Place ridiculous pressure on parents isolated in nuclear families to both work, and make childcare so poorly paid that the people who would do it best have to get work in other industries. Keep adults stressed, busy, exhausted and burned out, so that there is nobody around to hang out with the kids, create emotional safety, and process their traumas with them. Remember that rich addicts can maintain a facade of respectability, sometimes for life, but in truth, they are just as traumatised and addicted as the street junkies. Gangs and Cartels When the government goes bankrupt, organised crime will almost immediately take over the role of maintaining "law and order" (as, for example, in [Russia in the 1990s](https://www.stratfor.com/sample/analysis/organized-crime-russia)). Of course, it will be for the benefit of the crime lords, not the community as a whole, but some order is better than anarchy in the minds of most people. ]
[Question] [ So. This has been something I've been tossing up for a long time. Let's say you have a world that has a broad availability for magic power and mages are a normal part of life. Like DnD 3.5 worlds or what have you. Not everyone has magic, but you'd know someone who does to some extent. This includes stuff like telekinesis, teleportation and stuff like that. Realistically speaking, wouldn't most magic combat in a world like this be instantly over the moment one magic rips the hearts of the enemies out of their chests with a small telekinetic pull, or incinerates their lungs, or reverses the electrical polarity of their brains, or makes all the water in their bodies jump one centimeter to the left? Human's are fragile, and in these worlds people through incredibly deadly powers around like hotcakes. So my question has always boiled down to. Wouldn't all combat involving even minor powers be a MAD scenario. Where you either defend with shields and magical shielding or kill everything while they kill you. (In life or death combat that is. I know people can be sensible and do mexican standoffs). So as a result, wouldn't shielding be a major priority in almost all spheres? [Answer] A world like that would already find its balance. I mean, if magic users are around like hotcakes, there would be an animals/ prehistoric animals in that world somewhere on its branch of evolutionary tree that lead to homo magiens that can use magic. When there's a zebra that can do instant teleportation the lions in that world would develop something to survive. Same situations would be developed in its human. Lets just say that their magic attack happens instantly without drawing symbols on the ground, saying spells, or waving a wand. Although the magic user still minority it would be expected that the rest majority population would evolutionary develop some kind of defense while it can stay a subtle one. Maybe you got a tingling sensation (like spiderman have) in your head every time there will be a magic cast to you on a minutes in the future, just an ability like this would increase survival rate of the population and bring some balance in nature. If all of the above didn't occur, and magic user just born randomly like x-men mutant. We will have a society that kills or isolate them from infant stage. [Answer] As you cited D&D, here are some classic limitations used in role-playing games and medieval universes overall. * Line of sight. In order to use magic, you need to see your target. This limitation will exclude all of your examples of unpleasant things a mage could do to internal organs. * Magic costs a ressource. It can be time (think about magic in Pratchett's universe: the time to learn the spell is equivalent to the time you need to so it by normal means). It can be energy (using magic is extremely tiring, drains the lifeforce ...). It can be an outside energy that you need to channel to cast a spell (which is not always available). * Finally, magic can be ruled. There could be some kind of broad ban on "brutal" combat magic, and anyone who would use specific kinds of magic against man would be prosecuted and sentenced to death. This would be akin to Geneva's convention on chemical weapons, middle-age version. Any of these limitations would mean magic is not allmighty, and would make classic combat legit, not only defensively but also offensively. [Answer] Of course there would be a lot of defensive magic. As there are bulletproof vests and armored cars today. First, let's assume that "killer magic" is common, but not commonly used. Because in that case the rules of society would no longer apply. So if i rip a shopkeeps heart out because he charged me 2 silvers more than i liked, i am still a murderer, and will still be prosecuted. Then, let's assume there are powerful mages in some kind of police force that WILL bring you down most likely. Only the most legendary, powerful mages should have the power to "do as you please" without consequences. So even if killer magic is common (like.. guns in some countries, or knives or fists), 99% of the time people won't use it because it's against the law. I was in the military for a while, and we sometimes did security for festivities, and i was walking around with a loaded submachine gun. And i still didn't shoot anybody. Because: a) why should i? b) it's wrong. and c) there would've been negative consequences. Now let's take this to the point where lethal conflict is ok. Law enforcement or wars. In that case, yes, a lot of magic will be defensive. You will have shields and absorption and magic resistance spells, while trying to remove the enemy protection and blasting them to hell. And everyone who is not capable of magic will try to stab or shoot you to death before you can magically spread them across the room like marmelade on a toast. But both forms of combat have something in common: you plan and prepare for it. Magic users will be a 100% requirement for armed forces, be it only to protect against low-ranking hostile mages. But i see no reason why there shouldn't be several mages in a team, some defensive, some offensive. Or why a single mage couldn't upkeep a shield spell while blasting fireballs at the enemy (that's what you do in D&D). But since combat is so deadly, once i break the enemy defense, they are instantly dead. If my shields hold just a tiny bit longer than theirs, i win, no MAD. So, to sum it up and give an answer: No. Defense will be very important to keep the combatants alive, but a difference in skill and ability will allow one party to win by breaking enemy shields and killing the enemy. ]
[Question] [ Ok, quick overview of the situation: An alien planet, reaches basically the same stage we are at now in regards to fossil fuel reserves and environmental loss, a major war breaks out, and after both sides suffer basically equally, they decide to merge forces and revert their damage on the planet. buildings are ripped down, power-plants dismantled, holes filled, forests replanted (relatively) and any damage they can reasonably reduce is acted upon. Most of the population then leaves the planet, now with plans of colonizing a new planet, with a sustainable economy. The odd 2-3 billion or so remaining population then create a great city, far underground, to let the planet heal and periodically (as in every few years) monitor its progress. Thousands of years pass, forests and other environments are basically completely healthy, and humans orphaned of their planet colonize this alien one. After that wall of exposition, here's the problem. In this story, the humans only realize the planet is inhabited about three generations into colonization, and this is only because the natives noticed them. How, after mining and building their own civilization, do these humans not notice the scars created from mining and past cities? Things to note: * The humans came on a makeshift craft, a last minute escape if you will, the economy quickly crashed within the first two generations due to competition with agriculture and alien weeds/pests * Pests are beginning to be controlled at present, as well as development of alien crops, so the economy is slowly rebuilding, but the civ is basically scattered towns and villages with one main capital city. This means the civ is actually quite small, and most of the planet is unknown exploration-wise. * Humans don't really have resources to expend on expansion or exploration (someone already mined most of it) and instead focus on military, agriculture and infrastructure. This means any satellites are cheap and specifically for communication, not thermal imaging or the like. * The mothership isn't an option, it is still in orbit and has been completely stripped of parts and energy reserves. * The city being hidden isn't the focus, this is specifically about the mining and infrastructure scars, however feel free to add such information to your answer, as long as it's a side note. I might make a new question for that topic in the future. [Answer] ## 1. Why did no one notice any of the "scars" when they first arrived in their mother ship? This is already kind of tricky I think. Your settlers were on a desperate, last-hope kind of mission to survive and given the ratio of inhabitable planets to the size of space... Well, finding this planet is like winning the lottery time 1000. So, when they arrived, they scanned the planet for atmosphere, climate, fresh-water supply, flora and fauna to gauge a general human-survivability, easy to miss any kind of shadowmarks, but they would also need to do different kinds of visual scans to determine a landing place. I guess a spaceship on a long and desperate journey through the universe could be kind of bruised, with all kinds of systems destroyed or malfunctioning, including life-support, which would make a rushed departure without proper checks plausible... Some kind of "Either we make it to the ground on this planet, or we die anyways" situation, which would also make people blind to any clues since their whole focus lies on survival. ## 2. Why did no one notice once on ground? Well, I guess your settlers just hit a once remote, almost uninhabited spot on the planet - think a former dessert or jungle - which became a good settling point after the climate changes the locals caused (I guess they would have had a similar fosile-energy focused technology as we do). If you would transform the Sahara to habitable land, you would have a hard time finding any traces of a former civilization there, since there already are almost none and erosion in desserts or plants in jungle areas are very good in destroying structures. Now, after a few years, someone should be like "guys, this is a nice spot, lets see whats over there, a couple hundred miles west", because human nature is that of an explorer... We could have the settlers place be something like australia, with a huge dessert and cities only on the coast line. After the poles melted (yeah, that would have happened...) and the sealevel rise, the cities are now gone, some kind of golf-like stream turned and the once uninhabitable dessert turned into a nice garden. That would give your people a small continent with almost no signs of civilization to explore. [Answer] There is no need to hide the signs of previous mining, industrial, urban or technological activity on the planet. After thousands of years most of the obvious signs would have been overgrown or degraded by natural forces. The surface will look more like that of a previously inhabited planet, but not a currently inhabited one. Basically there's no reason to suspect the planet is occupied by a civilization of sapient creatures. The lack of any native inhabitants by itself will suggest the local sapients have abandoned their planet. After all, that's what they mostly did. Apart from those living deep underground in their great subplanetary city. With this set of circumstances, the human colonists will assume that the planet was inhabited in the past. Wars and runaway consumption ruined the planet. The native sapients moved to another planet elsewhere. Also, this is comfortable story that fits in with their belief they had arrived on a planet suitable for colonization. People do tend to belief what they want to believe. So when native aliens emerged from deep below this would have been a nasty shock. [Answer] If the situation on the alien world is comparable to present-day Earth, it can't be hidden. * Consider [cropmarks](https://en.wikipedia.org/wiki/Cropmark) and [shadow marks](https://en.wikipedia.org/wiki/Cropmark). Of course they show best on planted fields, but modern buildings are so much bigger. They will show on meadows. * If they fought a war, there is the issue of [unexploded ordnance](https://en.wikipedia.org/wiki/Unexploded_ordnance). * Refilled mine shafts will last for millions of years. [Answer] They were aliens. A group of them might easily identify traces as proof of the past but the humans don't recognize what they are looking at. Maybe they mine using rivers, or creating fault lines, or digging up from below. Their cities could have avoided straight or even continuous lines making identifying marks look random leading to the conclusion they aren't marks. The stewards might also be good at their jobs. After recycling almost everything to build their massive post war projects, and burying the remaining evidence under 10's of meters of soil they triggering volcanoes to obliterate even the toughest stains. Much of this rests on the assumption that a billion person city far underground implies these people are really really good at manipulating earth and rock. [Answer] mining could easily be covered by reclamation laws and erosion, and not everyone is going to realize an old mine hole is actually a mine and not a natural formation. holes turn into lakes fairly quickly, and the longer they have been left alone the less obvious they will be. Ones in very dry areas will stick around the longest, of course maybe the humans did not go to the deserts. cities are a lot harder, they tend to stick out. ]
[Question] [ Imagine you've somehow tranquilized or tied up Superman with a kryptonite rope or something, and the military wants to do a stress test so they can start building a series of anti-Superman bombs. So they drop increasingly large nuclear devices on him, upping the yield until they can noticeably injure Superman and thus determine the upper limit of his invulnerability. But there's a bigger problem here than mad science or pissing off Superman. It's the limits of our weapons technology. Which leads me to ask. What's the practical limit for building bombs with today's technology? And I don't mean practical as in efficient or cost-effective. As long as the bomb works and works reliably, that'll do. All it's designed to do is injure a single superhumanly durable target, so it doesn't matter if using it in war on a soft civilian target would be excessive or impractical. Also, saying "antimatter" is forbidden. It has to be doable right now. [Answer] ## Yes. Note: Your Challenges will Include Transportation and Assembly. The only limits to what we have built and plan today are delivery logistics. ICBM's can only handle so much weight, and even large transport planes have limits. However, if you were able to build and detonate a nuclear weapon in the same place transportation becomes a nonissue. The specifics of nuclear bomb construction are not in the public domain so it is hard to comment on more specifically, but I would strongly expect to run into a construction issue. At a point you need to put a LOT of uranium in a limited area, which is going to probably make robot workers a requirement. That seems within the realm of current technology though, so it probably could be overcome if we really wanted to. Here's an [interesting statement](https://en.wikipedia.org/wiki/Nuclear_weapon_yield) on the topic... > > Because the maximum theoretical yield-to-weight ratio is about 6 > megatons of TNT per metric ton, and the maximum achieved ratio was 5.2 > megatons of TNT per metric ton, there is a practical limit on the > total yield for an air-delivered weapon. Most later generation weapons > have eliminated the very heavy casing once thought needed for the > nuclear reactions to occur efficiently, and this has greatly increased > the achievable yield-to-weight ratio. For example, the Mk-36 bomb as > built had a yield-to-weight ratio of 1.25 megatons of TNT per metric > ton. If the 12,000 pound casing of the Mk-36 were reduced by 2/3s, the > yield-to-weight ratio would have been 2.3 megatons of TNT per metric > ton, which is about the same as the later generation, much lighter 9 > megaton Mk/B-53 bomb. > > > [Answer] The ever useful [Atomic Rockets](http://www.projectrho.com/public_html/rocket/spacegunconvent.php) website has a section on theoretical yields for nuclear weapons, and some very interesting figures come out of it: > > Or, to take another tack, and returning to the initial impetus for me looking at this topic, we know that the famous “Tsar Bomba” of the Soviet Union weighed 27,000 kilograms and had a maximum yield of 100 Mt, giving it a yield-to-weight ratio of “only” 3.43 kilotons/kilograms. That’s pretty high, but not for a weapon that used so much fusion energy. It was clear to the Atomic Energy Commission that the Soviets had just scaled up a traditional H-bomb design and had not developed any new tricks. By contrast, the US was confident in 1961 that they could make a 100 Mt weapon that weighed around 13,600 kg (30,000 lb) — an impressive 7.35 kiloton/kilogram ratio, something well above the 6 kt/kg achieved maximum. By 1962, after the Dominic series, they thought they might be able to pull off 50 Mt in only a 4,500 kg (10,000 lb) package — a kind of ridiculous 11 kt/kg ratio. (In this estimate, they noted that the weapon might have an impractically large diameter as a result, perhaps because the secondary was spherical as opposed to cylindrical.) So we can see, without really knowing much about the US had in mind, that it was planning something very, very different from what the Soviets set off. > > > So it seems there is an avenue to approach to create gigaton and and larger weapons. As an aside, on the [NEOFuel](http://www.neofuel.com/inhabit/inhabit.htm) site, Anthony Zuppero writes of an experience he had as a young man being asked to design a hypothetical way to eliminate all of Russia's missile fields at once. His recollection of this project was doing calculations to loft a 5000 megaton bomb to Western Russia in 2 minutes, so he designed an ORION nuclear pulse drive rocket to do the job. There are remarkably few details of size or mass of the device or the total assembly, although the USAF had proposed a 4000 ton ORION Battleship during the Kennedy administration, so there is no theoretical limit to how large the thing could be. The bomb itself, if it worked near the theoretical limit of 11kt/kg would be @ 460000 kg (hopefully didn't drop a decimal somewhere), so it would be a freaking huge rocket overall. [William Black](http://william-black.deviantart.com/art/Doomsday-Orion-504250808) has this theoretical reconstruction: [![enter image description here](https://i.stack.imgur.com/lyMSz.jpg)](https://i.stack.imgur.com/lyMSz.jpg) So short answer is it has been possible since the 1960's to create gigaton yield warheads, but there is no practical reason to do so, nor is there a practical means of delivering them. To put it into a final perspective, the former USSR is reputed to have had a regiment of SS-18 Satan ICBMs armed with a 20 megaton warhead each, who's wartime mission was to convert Cheyenne Mountain and other hardened command centres into lakes. [Answer] Yes, but the other answers are missing the point. The basic design of an H-bomb isn't a secret anymore. Stage 1, you crush a Pu-239 ball with conventional explosives, it goes boom. Stage 2, the energy from that detonation (of course you won't capture it all) is used to crush a chunk of lithium deutride axially. There is a piece of heavy material between the initial atomic explosion and the lithium deutride to slow down the direct crushing, thus ensuring the axial crushing happens first. Stage 2b, the heavy material can't provide much time, the axially-crushed lithium deutride now gets crushed in the third dimension. There's a Pu-239 rod in it that's crushed by this step, it goes supercritical and ignites the fusion burn in the lithium deutride. Now, there's a limit to the energy available for crushing and the lithium deutride takes a lot of crushing in order to sustain a fusion reaction. Thus there is a ratio of the input energy to the size of the fusion stage of the bomb. If this were the end of the story there would be an upper limit on the size of an h-bomb. (The numbers are of course not disclosed!) However, there are two ways around this. First, note that the fusion stage did not capture all the energy from the initial a-bomb. You can mount multiple fusion stages (how many????) around the initial a-bomb, each explodes independently but at the same time. Second, while normal thought is that you use an a-bomb to set off an h-bomb there is nothing about the fusion stage that cares that the initial blast was an a-bomb. Anything with enough energy will do--and the detonating h-bomb certainly qualifies. You can pile another, bigger h-bomb after the first. (Note, though, that the second h-bomb must be in the shadow of the first so the energy from the a-bomb doesn't tear it apart. ]
[Question] [ The concept of concealed carry of weapons has been with us since ancient (prehistoric, even?) times, and is a common trope in medieval-fantasy universes as well. Characters in various stories have used a wide variety of means of concealment, and there are several common tropes surrounding placement of concealed small blades; however, it is not touched on how effective these tropes actually would be. So, what are the pros and cons of the various places on one’s body one could conceal a dagger of modest size (blade of 10–15 cm minimum, total length 30 cm max)? Assume this is a mid-to-late medieval fantasy setting — thin blades are forgeable, but gunpowder is but an alchemical curiosity as elemental sulfur and/or saltpetre/nitre aren’t available in the quantities needed to make it useful. Also, the wearer is only needing to evade casual searches, not a determined “find-the-hidden-dagger” effort. Last but not least — you can consider three different concealed-carry applications: * The thug, trying to sneak a weapon past casual inspection for a quick draw in the heat of the moment * The merchant, who wants something unobtrusive but available to deal with the occasional bandit * The lady, who hates how open carry spoils her looks but has to have something on her for safety’s sake [Answer] The thug * Caneswords; a thin rapier can easily be hidden by using the cane as a sheath. * In the Boot; since it is only a light search, a large knife could be hidden in the boots. * In the trousers; a small, sheathed knife can easily be hidden under a belt buckle to avoid detection. * Prison; If the blade is small enough, you can "easily" hide it by hootering it in the anus. The Merchant * Under a cloak, simply equip the sheath underneath a cloak or coat * Caneswords; a thin rapier can easily be hidden by using the cane as a sheath. * In the Boot; since it is only a light search, a large knife could be hidden in the boots. The Lady * In the Boot 2.0; high heel boots are practically built to conceal weapons. * Under the dress, a small knife can easily be strapped onto the thigh. * [Japanese war fans](https://en.wikipedia.org/wiki/Japanese_war_fan); just like normal fans, but made of sharpened steel. [![enter image description here](https://i.stack.imgur.com/5VeMO.png)](https://i.stack.imgur.com/5VeMO.png) [Answer] Artificial limbs make excellent hiding places. I've seen historical exhibits of wooden legs that had hollows inside of them. The best recommendation I can think of is to see what modern clothing is doing with cell phones -- extra pockets, hidden folds, under arm and belt holsters... Cell phones are about the same size as daggers, the person needs to have them in all the cases you listed, and there are plenty of times when they need/want to be smuggled into somewhere. [Answer] I thought there was an accepted answer already for this question, but I see now that there isn't. So, what's the best way to carry a weapon unobtrusively in the mid-late Medieval period? The answer is surprisingly simple: The knife. Unlike today, people in the medieval routinely carry knives everywhere with them. Knives weren't weapons per se, although they could certainly have been used that way. The reason was that knives were versatile tools. You can use it to eat, open crates/packages, cut stuff, pry stuff loose, dig (somewhat), etc. etc. As such seeing a merchant, or a commoner, or even a nobleman walk around with a knife sheathed on their belts were very common and would not attract attention. An assassin wishing to assassinate someone would be much better off using this because: a) It doesn't attract attention (unlike something very specialized like a thrust dagger) and b) The wound it causes is so common that (with medieval technology) Camelot CSI couldn't begin to tell you which specific knife caused this specific wound. I suppose for ladies there were always the 'bosom knife' or 'bosom dagger', which were knives/daggers concealed in the..well..bosom to be pulled out in case some inbred noble decided to get fresh. [Answer] A belt. An ornamental belt buckle could hold a small dagger or punch dagger, that wouldn't be removable without unlatching it. This would be a simple stabby weapon. For the more skilled martial artist - something like an urumi, I can't find a decent photo of a regular version but here's a [video of them in use](https://youtu.be/fMz_Z0Xq-2I), while they need an expert to use, they're flexible and might be hidable in a belt. A short version might be usable as part of a corset or stay, or as part of a design of a purse. A sheathed thin wire garotte might be a reasonable weapon as well, could be used to tie down hair, and be used to ensnare limbs. And of course Trained attack squirrels. Adorable pets. Then they go for the nuts. [Answer] A [folding blade](https://en.wikipedia.org/wiki/Penny_knife) would probably be impractical. It will be more fragile than a fixed blade, and without a [spring](https://en.wikipedia.org/wiki/Assisted-opening_knife) mechanism it will be slow to use. That means a fixed knife. The length of the handle will add to the length of the blade. * For stabbing and slashing, look at the [WWII SAS dagger](https://en.wikipedia.org/wiki/Fairbairn%E2%80%93Sykes_fighting_knife). The total length is almost 30 cm. * A [throwing knife](https://en.wikipedia.org/wiki/Throwing_knife) may be somewhat smaller, but the total length will still be much longer than the blade itself. Hiding either one against a determined, hands-on search will be impossible. At best, your character can hide it from a visual inspection. * I expect that a scabbard will prevent injuries. It will also increase the bulk. * Depending on cultural assumptions, females may be extempt of hands-on searches by male searchers. Female searchers may or may not exist. For a mixed party with non-traditional gender roles, hiding the weapon anywhere on a female may be effective. * If heavy boots are worn, the knife may be hidden in the boot. * The scabbard may be carried on the inner thighs. How accessible that is depends on clothing. [Answer] The answer depends very much on the clothes and fashion of the people in this world. Generally the larger and more fluffy clothes the easier it is to conceal something. If the fashion is the same in your world as it was in medieval Europe the clothes would often be tighter trousers or breeches and more loose and larger jackets or doublets. I would suggest you do some image searching on 15th or 16th century clothing and look for good places in the clothing to hide your dagger. Places I would recommend for men: - In the boots, if the boots are tall. - At the hip, if the blade is short and flat, and the person is wearing fluffy pantalons. - Vertical on his back with point up or diagonally upwards, if his wearing a cloak or a mantel. Places I would recommend for women: - Inner calf if wearing a long dress (easier to draw from then thigh). - Under (or in) her hair and veil, if the blade is shorter. As I said it is entirely dependent on the clothes, but something to keep in mind is that in a situation where people generally don't carry weapons (e.g. after being searched at the entrance to a ball or the like) a small weapon is as deadly as a large one. [Answer] Let's start with the easy one - the lady. Hair pins, necklace dagger, anything hidden around or in the bust area. Umbrella rapier, purse dagger, etc., etc. A woman has so many places to hide something. The most effective locations will be those on the outside of the clothing, like the hair pin. For men - thug or gentleman, the best concealed location is right out in the open. Consider the tactical pen. It looks like a standard ball point, but is hardened steel casing for quick retrieval and stabbing. I sincerely doubt a ball point pen will be common place, so it would have to be something else that is - a belt buckle for instance or a cane. A thug might have a beer stein with a removable handle or leather wristbands. A gentleman might carry a book - easy to hide something in there - or a satchel. [Answer] The two rules of thumb are the better hidden it is the harder it is to get it in a hurry, and the better a weapon it is the harder it is to hide. nearly every place on the body is an option, the back between the shoulder blades, under the arm in the small of the back, on the forearm, on the upper arm, the belly , on or inside belts, inside girdles and sashes, the crotch, inside and outside the thigh, the shin or calf, inside the side of a boot, inside the heel of a boot. Then there are the off the body options blades have been hidden in all sorts of objects: umbrellas, brushes, makeup and sniff tins, canes, buckles, jewelry, candles, lanterns, hats, even inside food and drink. but consider that you were expected to defend yourself and carry a weapon in most societies, plus you needed a knife for everything and it was often the only eating utensil so not carrying one was weird. If anything Not carrying a knife openly might make people suspicious of you, after all they knew you had one so why were you hiding it? so consider having a open carry weapon and making concealed ones back ups. a merchant in bandit country is likely going to have a weapon openly carried and available, a belt knife at least, why hide it? Plus merchants often wore layers of clothing and would have to carry a money purse and scales so hiding things is easy. Consider a jambiya, they were popular in the middle east for both the one handed draw and being unobtrusive. As for your lady consider a purse knife or sash knife also remember you were expected to bring your own utensils to meals (they were not provided) so even to a dinner party she would still be expected to have a knife. As for your thug unless he is in prison he would be allowed a knife, it might be partially hidden by putting it inside the belt instead of on top but that's about it. A thug would likely have little more than simple pants and tunic which does not provide many hiding places so he might be stuck with the boot knife if he has to hide something. ]
[Question] [ If your blood pressure ever falls below the ambient atmospheric pressure would it be possible for you to bleed. Because if blood pressure was less than that of atmosphere air would move in if you get cut, bleed or something rather than blood moving out as it normally does. So ultimately will it be possible bleed if blood pressure falls below atmospheric pressure [Answer] For the sake of answering the question I am going to making a couple of assumptions. * Blood vessels in this “human” don’t collapse do to external pressure being greater than internal. * The blood of this “human” does not move because the heart pumps it. It moves because of some other organ that shoots the blood through the non-collapsing blood vessels. (maybe it works similar to a Magnetohydrodynamic Drive: <https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive>) If this organism were cut, the wound would quickly fill with air. This would bring the pressure in the creature up to atmospheric pressure. If this sudden increase in pressure does not cause any harm to the organism then as blood passes the wound, some would exit the wound. TL:DR, under the right condition yes the “human” would bleed. [Answer] # You cannot bleed — or live — with zero blood pressure. The absolute blood pressure must be at least 1 atmosphere of pressure or the atmosphere itself would clamp down on all your limbs like a [blood pressure measuring sleeve](https://en.wikipedia.org/wiki/Sphygmomanometer) and restrict blood flow. The blood pressure must overcome the atmosphere or blood cannot flow. So a blood pressure of absolute zero is not possible. But I suppose what you meant was "blood pressure of zero compared to the atmosphere", which is what we normally mean. I am sorry but that too is impossible. There are [100 000 km of blood vessels](https://skeptics.stackexchange.com/questions/15582/are-there-60-000-miles-of-blood-vessels-in-the-human-body) in the human body, and getting a fluid to flow — especially a fluid as viscous as blood — requires a force to push it through all of these tiny tubes. Blood vessels always offer resistance — a kind of friction — to the blood, and this must be overcome to make the blood flow. You cannot have blood flow without blood pressure. If you rupture a blood vessel however, then you have a path for the blood that offers no resistance. So simple physics say that this is where the blood will go, literally taking [the path of least resistance](https://en.wikipedia.org/wiki/Path_of_least_resistance). So you have two incompatible demands here. In order to not bleed, you need zero blood pressure, but then no blood is flowing through your body. It goes without saying that this is very bad for you. Or you have non-zero blood pressure, but then you will bleed if any of your blood vessels are ruptured. ]
[Question] [ Could a chemical compound change a human body in a way that a regular quantity of that compound is needed to stay alive after the first dose? The short answer would be yes, there are already such chemicals (and they are more common than I thought, for example alcohol), however those chemicals require an extended period of time in which they are abused. Similarly, there are substances that replace human biological mechanisms and after a long "training" time those substances may cause the body to stop production of important substances (alcohol is one, but also insulin, benzodiazepines, opiates). To get inspiration I also asked a similar question on [Health SE](https://health.stackexchange.com/questions/5775/any-drug-wich-withdrawal-is-fatal-and-thus-require-regular-assumption-after-the) However all those substances take a long period of time before taking effect, so is there any real drug/medicine from which I could take inspiration that needs a long detox period (with medical assistance) even after the consumption of a relatively small dose? Such a drug/medicine would be used (for example) to control special agents; instead of poisoning them and holding the antidote against their good behaviour, a secret agency may simply just give a known substance once, after which the agents need that substance to avoid death. The fictional drug should be based on some mechanism already present in real medicines so that it has a plausible explanation. The afore-mentioned substance may have lethal withdrawal, however, a medical assisted detox period should enough to avoid death; in my case I want avoiding death to be non-trivial, while the easiest way to avoid it is simply maintaining regular doses. [Answer] ## Antibiotics The effect is probably not as direct as you are looking for, but any substance with strong antibiotic properties (especially if it strongly affects white blood cell creation in the bone marrow) will leave a longtime regular user with a weakened immune system that may well lead to death from an infection. ## Hormone replacement drugs Another option I could see is long term use of specific hormones or regulatory chemicals to push the body to greater performance. Over time, the body itself would produce less and less of the hormones in an attempt to restore the natural balance, until it's all artificial hormones. If their use is then stopped, the body's own system may not take over in time to prevent a collapse of the metabolic and/or nervous system. The responsible glands may even have atrophied, making death a certainty. [Answer] It would be simple enough to create a drug (or more likely a compound of drugs) that has two effects. The first would be to nuke your bodies production of an important hormone or vitamin or similar. For example lets say it makes it impossible for you to take in vitamin C. The second effect would be a temporary fix to the first that allows vitamin C to be taken in but only while it remains in your system. Now unless the first problem is somehow fixed you need the second effect to survive, and that's a permanent change. Fail to take the drug and your body stops working. Keep taking it though and you feel fine. If this is designed to control people then you don't need any further explanation. If you do need it then you can say that the first step is a side effect that is either rare or unavoidable for something that you do need to take. For example on an alien planet you might need to take immunoboosters to not die from the local microorganisms but those have the unfortunate side effect of meaning your body can't X any more. So now you need to take Y for life or die - but you died anyway if you didn't take the drugs so it's still worth doing. ]
[Question] [ Assume there is a point in time when every planet in our Solar System consists of colonies. Each colony is inhabited with civilians that primarily serve the purpose of its colony. Some colonies may specialise in manufacturing, some in resource extraction, some in research etc. Technology would exist to allow travel between colonies in a reasonable time, and comparable to travel times experienced on Earth. For example, Mercury to Pluto would take 10 hours but perhaps a journey between Earth and Mars would take an hour or two. Rough calculations would suggest at best it would be possible to go as fast as half the speed of light, although probably around 1/30th for most travel. Each colony will have various sports teams. For example, 1 or more soccer teams, 1 or more American-style Football teams, and so on. Just like the traditional teams in modern times, each team will be subject to: * Player/Staff contracts (i.e. players sign contracts to play for a team, with the process subject to specific rules such as wages, player rights and so on) * Team stadiums (locations where the team plays) * Team ownership (who owns the team, being a single person/entity or even a "national" governing body) * Organised leagues/competitions (i.e. teams play in organised competitions) How would a sporting body oversee all the sport in a Solar System (note: a Football body would oversee just Football, i.e. I am not referring to a single body overseeing ALL sport)? What kind of measures would be put in place to normalise conditions, so that a match played between 2 teams in one colony would be in the same conditions as a match in between 2 teams in another colony? What kind of organisation steps would be required to make sure a fixture between 2 colonies occurs (e.g. a Mercury vs. Pluto colony fixture)? [Answer] Our current Earth sports would be vastly different on other planets and moons, to the point where most would either be non-competitive or near impossible. Think of soccer/football, where a good player has fine ball control. In a low gravity environment, all of their small ball movements are instead sending the ball flying all over. In American football, every pass and kick would go 6 times as far on the Moon. This would make the game...interesting. Barring some gravitational controlling technology, I think the most obvious solution would be to have competitive sports take place in microgravity. Every colony would have a valid location relatively close to them in orbit (compared to interplanetary travel). Since our descendants have populated the whole solar system, they have no doubt perfected launch techniques. Launches would also be exponentially easier from low gravity moons. Pickup games could still occur on colonies, with some modifications. Most "habitable" moons have a surface gravity of about .15g, which could be light enough to support practice matches. Remember, the enemy's gate is down. [Answer] I've thought about that, and the first problem I stumbled upon is gravity. Each planet has a different gravity. That is a very real problem unless you can manipulate gravity at a local level. I can see three ways to deal with that fairly. A) Have pairs of matches, so that everybody plays home with home gravity once. If the two teams win their home match, you could break the tie by looking at the numbers of goals/points while away, or combined score of the two matches. B) The match happens on a third, neutral planet. Said planet should be picked at random. C) Alternatively, the entire season could be played on one planet. Say one year everybody plays on Mercury, next year Venus, etc. That's assuming players are physically able to play on different planets, but then again if they weren't you wouldn't have a system-wide federation. --- As for the legal aspects, it wouldn't change compared to how it works today. You have one body that edits the rules of the sport. You have one body that organizes international competitions. Ideally, these are independent instances, though obviously they'll need to talk to each other from time to time. Below that you may have national (I say national, you can replace with planetary/continental/local/whatever) bodies that oversee the national leagues and competitions. If these bodies are members of the higher ruling body, then all the teams adhering to the national body get accessing to international competitions. A good example of that is basketball. FIBA and NBA have different rules on quarters: FIBA quarters last 10 minutes, NBA quarters last 12 minutes. As such, NBA isn't a member of FIBA, and doesn't have access to international competitions organized by FIBA. On the other hand, the Spanish or French national leagues are FIBA Europe members, which gives their teams access to European and international FIBA competitions. At least that's the general idea. [Answer] Maybe I'm risking being simplistic here, but we already adress these same problems in a smaller scale if you swap each colony for a continent or country here on earth. Fifa for instance, is headquartered in Switzerland but oversees its more than 200 member nations. Divide and conquer is possibly the best approach choice for solving this kind of problem. Each colony would have its own minor representation body that would answer to this central one and a representative on the headquarter planet. As for the rules, the central body would have its own rules, but they could be changed and extended to some extent, subject to the Solar System body's approval. For games between teams from different colonies, I would suggest having tournaments held in only one colony each time, and no team from that colony could compete. That way you could design a ground that would be fair for every team. Besides that, colonies from afar could send even kids to solve the problem about traveling speed for great distances. These kids could be seen as promises for the colony team, and would be praised for their position. Smaller tournaments between nearer colonies could be held too, to increase popularity and the number of matches played in a season. In fact, matches don't need to be all carried out in the same conditions. They can still be fair without this rule. If a comparison is needed between games in different conditions, you could weight each different possibility of each characteristic of the game. For example, games played in grass could be considered easier than those played on sand, and so games won on sand would increase points more than those won on grass. [Answer] Several posts have mentioned different gravity and other conditions that would make interplanetary sports difficult. This can be overcome to a certain extent if all space colonies are standardized. Rather than living on the surface of the Moon or Mars, people may prefer to live in rotating colonies in free space where sunlight, radiation exposure and artificial gravity are all controlled to resemble Earth. Rotation and shielding are pretty straightforward (all colony will probably be built using the same template to incorporate 5m of shielding material and be the same size so the rotation needed to create a simulated 1 "g" is the same). Standardized templates for building colonies makes all colonies cheaper, and removes a lot of complications. for example, if every colony is the same size and rotation, then automated systems on spacecraft can easily dock with any colony in the Solar System. Indeed, the only difference between colonies would be the size of the mirrors directing sunlight inside to illuminate the place, colonies in the outer solar system will need massive mirrors compared to ones in the L4 and L5 positions in the Earth-Moon system. This also makes most sports competitive as well, since every athlete grows up and trains in the same sort of environment. Even allowing for the Coriolis effect on a rotating colony will be the same between colonies, and the only people disadvantaged would be those from planet Earth, who are not naturally inclined to account for this effect in their day to day lives. This even allows for "new" sports to be developed, since the interior spaces of the colonies will have variable gravity, so "zero G" sports might be invented for the axis of rotation, and "half g" sports take place halfway up the end caps, etc. ]
[Question] [ All work and all play makes Jack a distributed boy: Jack is at the hotel reception with his wife. Jack is also in the office, meeting with unspecified forces for inscrutable purposes. Jack is also in his smithy, forging a perfect Damascus-carbonite blade. All at the same time. The basic question here is simple. I have successfully digitized a mind, now I want to give it the ability to control multiple instances of bodies in multiple physical locations simultaneously. I don't care whether the bodies are flesh or robotic. What I care is to hear some plausible explanation of how the brain architecture would have to be restructured to enable one entity to be successfully active in multiple locations simultaneously. I think this would involve, at the very least: * allow a person to focus on dozens of things at the same time, instead of just one or two; * allow for balance and proper orientation of multiple bodies simultaneously; * enable coordinated movement and speech by multiple bodies in multiple places; * enable the person to remain(/appear?) recognizably human to the subjects of its flesh-based interactions; and * the same entity must maintain control of all these instances at the same time, in a relatively synchronized fashion (i.e. no running separate un-synced instances). In a recent question, I brought up the idea of [markets for digital uploads](https://worldbuilding.stackexchange.com/questions/38876/selling-your-uploaded-copy-of-yourself), so feel free to visit that question for more details on how I envision the process of digital uploading working. [Answer] What we're looking at is a computer architecture that is derived from the architecture of the brain. Since it is a computer architecture, it could take advantage of all kinds of optimizations and extensions that computer architecture does. Given that, let's take a look at how real low-level computer networks work. In a modern automobile, for example, there are dozens of computers that have a specialized task. One might control the seatbelt light. If the seatbelt isn't buckled and there is someone sitting in the seat, illuminate the seatbelt light. May not sound like much, but consider that there are plenty of microcontrollers on the market meant for embedded applications that can be purchased for pennies to a few dollars in bulk, and what's the downside? Other systems make use of a variety of processors that all work toward the same goal, sometimes with specialized purposes and other times just to achieve concurrency. One example is the common CPU/GPU setup. But looking more closely, both a GPU and a modern CPU are designed for concurrency via parallel processing. I'm no expert on the human brain but from what I do know, it seems like it functions--at least on some level--similarly. There is a basal ganglia which offloads commonly-repeated tasks from the conscious mind, hence the famous human ability to walk while chewing bubble gum. Even though consciously doing more than one thing at a time is often difficult, it becomes "mindless" (so to speak) to perform common tasks like walking, so these can be performed concurrently with other tasks. My thought would be to give each body its own equivalent to a basal ganglia loaded with many routines--even some complex ones such as speaking--and have the conscious part of the brain control it remotely, giving it tasks in much the same manner that the human brains relegates tasks to its own basal ganglia. Another problem would be input. At a certain level, we humans seem to have the ability to process input sub/unconsciously, such as when something is so ordinary that you don't even take notice. But this only proves the idea that our ability to focus on input is limited. This can be easily observed anyway by trying to read a book with too much background noise. This matter of unconsciously filtering out unimportant input can be relegated to the bodies too in order to offset the load to the conscious brain, but... The problem with all of this is that this is what our brains do anyway. They already offset these tasks to the sub/unconscious, which means that they only deal with what requires conscious attention for one body. So even by doing all of the above, the bottleneck would still appear to be one body. Beyond that number, we would have the same problems we already have with multitasking, only now the problem is even greater since we have multiple bodies. Simple things like deciding where to walk next would have to wait in queue while we tell a different body where to walk next. We would need to handle each task in rotation. This is actually exactly the function of an Operating System. I think it would be too much of a stretch to introduce parallel processing to the conscious mind, as that would bring into question whether or not the individual really has one mind or several (actually, this could be an interesting philosophical direction to take your story if you wanted), so the only real solutions are either to increase the threshold for consciousness or to increase the processing power of the brain. In the first case, your drone bodies would handle much more on their own. This means things that would have otherwise grabbed your attention will now escape your detection and your basal ganglias will just autopilot through them, for better or worse. An increased incidence of "brainfarts" will occur. In the second case, the already massive processing power required to simulate a human mind in a single thread has to be increased further, leading to astronomical clock rates, which raises a whole new set of problems with computer engineering, including cooling (fast clock rates cause lots of heat; [see this article](http://www.zdnet.com/article/worlds-fastest-processor-is-an-overclocked-beast-video/)) and relativity (light itself only travels 1 foot per nanosecond; the physical size of these processors will have to be tiny). [Answer] ## Entirely plausible and this is a well understood problem As of 2016, humanity has a long history of distributed computing. MMORPGs, Hadoop clusters, thin clients, and thick clients are all examples of where control of a distributed system system is spread across multiple locations then synthesized into a coherent whole. Sometimes this occurs on very long time frames such as days, sometimes it happens in millisecond long slices. Humans are getting very very good at this kind of problem. Working with brain meat as the computer adds additional complexity but doesn't change the fundamentals of distributed control. ## Thin Client Approach If you have sufficient bandwidth to transmit back visual, audio, and tactile information back to the central brain, then that brain should be able to control all those bodies at the same time. This assumes that the central brain is a super brain capable of processing that much information and returning the appropriate instructions in a hard real-time way. Personally, I think that's a crazy way to run this because if you have any significant break in transmission, in either direction, something is going to fail and fail hard. You wouldn't want to have a transmission glitch that causes you to fall into your forge when the command to stop yourself as you walk up to the forge fails to arrive or arrives a 1/2 second too late. Typically, a thin client approach is used when you have a single high powered, expensive brain and lots of cheap low power brains. ## Thick Client Approach In contrast to the thin client where all processing happens at a central location, a thick client maintains a considerable amount of local processing power to maintain functionality. In this scenario, a thick client would maintain local visual, audio and tactile processing and go back to the central brain only for questions like "I've finished making the sword, what should I do now?". Short term planning of where to put the next hammer blow stays local. Thick client architectures are used when there is no central brain and/or all the brains are roughly equal to each other in terms of processing/storage power. ## How thick should the client be? It depends on a couple of things: - How powerful is the primary brain? Is it capable of synthesizing the sensory input and sending out commands to all the other brains? Is there a central brain at all or are all the brains equal peers? - How often do all the brains need to synchronize themselves? If it's every 1ms then that will have some severe limitations on how far apart the brains can be and the methods by which they can synchronize themselves. At 1 second intervals, synchronizing can happen over the open internet (though that's a security nightmare if one of your brains gets hacked). If it's every day, then a distributed version control system like Git would work perfectly. ## Why Git Git is a distributed version control system. It is wildly popular because of its ability to maintain many separate versions of a data structure (usually text files) then efficiently merge changes back into a single cohesive document. In addition, it is very cheap to make "branches" from a base-line copy. For example if you have document A and give it to persons X, Y and Z, Git will allow you to merge the changes made by X, Y and Z back into a single version of document A. How this magic is performed is both beyond the scope of this answer and plentifully documented else where. For our purposes, we will assume that Git is able to magically merge multiple competing versions of a data structure back into a single data structure. ## How it all goes together Let's assume that the various bodies only need to fully synchronize their data sets once a day in a thick client model. If more timely information is needed, then they can push and pull data at will. This approach supports when the clients are working in close proximity to each other but also supports bulk data exchange when new data can wait. 1. Assume that there's a magical translator that takes human brain function and creates a high resolution simulacrum implemented in BrainLang (a computer language I just invented that executes on commodity x86 hardware as well as typical human brain matter. Yeah, it's indistinguishable from magic). This program will be known as MeOS. The combination of the executable code in MeOS and all the things this person knows are known as Me(TM). 2. In the thick client model, the current version of Me(TM) is distributed to the various bodies to be used that day. 3. Throughout the day, small update messages are sent between the various bodies. 4. At the end of the day, each body uploads its current data set and whatever new code they added to MeOS. (During the day, a person will pick up new capabilities or refinement to capabilities in addition to all the things they know.) 5. Git merges all the datasets and MeOS code together (this may take a while) to formulate a new Me(TM). 6. Next morning (or whenever) the new Me is uploaded to the various bodies and they go out to do their thing. Since each version of the Me(TM) running right now is functionally identical to "You", you are in multiple places at the same time. [Answer] Have each version operate independently, and only send updates to the main consciousness when either: ``` A) That thread has run its course B) Something completely unexpected and off-script occurs. ``` For example, the Jack at the reception is a thread of the main consciousness. He chit-chats with his wife, signs into the hotel, etc. - nothing special. Eventually that thread will merge back into the main consciousness and update it on what's been happening. Another version of Jack meets with his mysterious associates. It's only a routine meeting, so Jack sends a thread in his stead. However, a snag happens. These guys reveal a major threat to your plans. Uh, oh! This thread instantly alerts Jack that something's wrong, and that the primary consciousness should get involved, which he then seamlessly does, quickly reviewing the meeting data and taking the thread over. His blacksmithing operation can then be relegated to a thread or abandoned altogether. In John Ringo's *Council War* series he explores a similar concept where the "Councilors" need to be in many places so they send out holographic Avatars to collect information and meet with people, and then "merge" the information back into their main consciousness when each Avatar returns. [Answer] There are several ways you could go about this, depending how autonomous you want the bodies to be. You'll probably be using [distributed or parallel computing](https://en.wikipedia.org/wiki/Distributed_computing) of some sort. [![Distributed Computing](https://i.stack.imgur.com/qTnfr.png)](https://i.stack.imgur.com/qTnfr.png) --- 1. (a/b in the diagram) Bodies can think for themselves and share information as requested. Basically you have Jack clones with a telepathic connection. Each clone could request and receive information from every other one, but it would be done on demand. Each clone also thinks "independently", though using the same process as every other clone. This could potentially be the "simplest" solution as you don't have the input overload that occurs in other scenarios. This would also be the most optimum if there any significant delay between bodies. A disadvantage would be if any body was damaged, their memories would not be recoverable by the other bodies. 2. (c in the diagram) There is one centralized memory location, either JackPrime or a server box somewhere. In this solution, every body has access to the experiences of every other directly. However, each body processes the data independently. This is how most multi-processor machines work. 3. All (or most) processing is done by a centralized CPU. In this solution, the bodies act strictly as input/output devices (think [computer terminals](https://en.wikipedia.org/wiki/Computer_terminal)). This has the advantage of housing most of the hardware in a stationary location, leaving the bodies potentially more optimized for movement and interaction. Another advantage is that the "brain" doesn't have to expend resources on bodies that are idle. The disadvantage is that any telepathic delay means the bodies with have a delayed reaction to everything, as they can't "think" for themselves. ]
[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. As per the title, given * A billion ($10^9$) dollars. * Present day technology. * A year of time (including making projects and testing), (preferred, not compulsory) * No restriction about maximal nor minimal size of the object nor its orbiting altitude. Build and put into orbit a satellite that will have the greatest possible [apparent magnitude](https://en.wikipedia.org/wiki/Apparent_magnitude) when seen from the surface of earth. I am interested both in details about the satellite and estimates of its apparent magnitude. There is no minimum shining time The device may be visible for any amount of time, you should maximize the average apparent magnitude. For example, if X works only half of the day but the apparent magnitude is more than double than Y that works all day, X is better. There is no minimum area to be visible from It does not matter how concentrated the light is, but if it can be seen from just one 'point' it should be adjustable to fire at other locations. Monument to the future humans I intend this light in the sky to be a sign for future humans (or whatever intelligent life will develop) that past space faring lifeforms existed in their planet. So it should last millions of year (I thought all orbits lasted forever, hence the lateness of adding this requirement) [Answer] The first problem we have to solve is power: where does the light energy come from? Our options are the same as for every other spacecraft: * Nuclear thermal: Although this option provides a lot of power, there are two strikes against it: nuclear reactors are very heavy, and they are currently not ready for spaceflight. You'd be looking at a decade-long development program, which does not meet requirements. * [Radioisotope thermoelectric generators](https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator) (RTG): These are a common choice for deep-space probes since they provide long-term power with high reliability. New Horizons and the Curiosity rover both use plutonium RTGs. However, they are not efficient (typical powers are around a hundred watts), and they are very expensive. (NASA is paying the US Department of Energy over a hundred million dollars to restart production at the level of about a kilogram per year.) * [Fuel cells](https://en.wikipedia.org/wiki/Fuel_cell): These can provide high power by consuming a fuel and oxidizer. These consumables limit the lifespan of fuel cells, so they do not meet requirements. (I'm making the assumption that you want the spacecraft to remain visible for at least a month.) * Solar power: [Solar photovoltaic](https://en.wikipedia.org/wiki/Photovoltaic_system) is an OK option. However, we can also use the incoming sunlight directly by reflecting it at the Earth. This eliminates the need to collect, process, and re-emit all of the light power, replacing that equipment with a simple reflective surface. The idea of beaming power from a 'generator' satellite in high orbit to a 'lightbulb' satellite in low orbit is a good one which draws on technically plausible concepts. However there are a couple reasons that I'm avoiding it in my design: * Microwave power transmission is nowhere near mature, and would require a development period of many years. * There is a lot of inefficiency. Even assuming very high efficiency solar panels (30%), LED lights (40%), power transmission (90%) and conversion (95%), the overall efficiency is only about 10% (and the transmission efficiency is likely to be far lower), compared to around 95% for a reflector. * Solar panels are far heavier per area than reflectors (on the order of 100 watts per kilogram). Add to that the cost of launching that weight into high orbit and the project quickly becomes infeasible. Choosing the passive reflector, our initial design looks something like a [solar sail](https://en.wikipedia.org/wiki/Solar_sail). The next problem is the structure of the spacecraft. Unfortunately the reflector can't be tensioned by centrifugal force like a solar sail, because the rotation would interfere with the pointing (since the reflector is not an isotropic radiator, steerability is a requirement). I envision a folding truss structure like [SMAP's antenna](https://www.youtube.com/watch?v=gNMSq7VbMvE) (Note that SMAP's budget was around 900 million dollars). The structure doesn't need to be as "dense" since the flatness of the reflector is not as critical. Now we should determine the reflector size. Assuming that the reflector is very close to flat, it will appear (to an observer within the reflected beam of sunlight) to have the same surface brightness as the Sun. (To put it another way, it looks like a window showing a small part of the Sun.) Thus, the total apparent brightness is equal to the apparent brightness of the Sun times the reflector's apparent size relative to the Sun. To get some rough numbers, I'll assume the reflector has $90\%$ efficiency. The apparent magnitude of the reflector is: $$ m\_\text{sc} = m\_\text{Sun} - 5\log\_{10}\left(\frac{d/r}{32'}\right) $$ The quantity in the logarithm is the angular size of the spacecraft (it's diameter $d$ divided by distance to the observer $r$) divided by the angular size of the Sun (in minutes of arc). The apparent magnitude of the Sun is $-26.74$. Putting this into a plot, we get: ![enter image description here](https://i.stack.imgur.com/WFjDh.png) We can see that this rough estimate has good agreement with the magnitude of [Iridium flares](https://en.wikipedia.org/wiki/Satellite_flare#Iridium_flares), caused by reflective antennas 1–2 meters in size. Assuming again that the reflector is close to flat, the width of the reflected beam will be around 30-40 arcminutes. The diameter of the beam at the surface will be about one percent of the reflector's altitude (from a 4 km spot in low orbit to a 350 km spot in geosynchronous orbit). However, we need to maximize not the peak magnitude, but the average magnitude. This is affected both by visibility of the spacecraft from the ground and shadowing of the spacecraft by the Earth. I performed some simulations to determine the optimal altitude. I took into account four factors: * Visibility: If the spacecraft is below the horizon, it is not visible to the observer and its relative brightness is $0$. * Viewing angle: Imagine extending two lines from the spacecraft, one to the Sun and one to the observer. Call the angle between these lines $\theta$. If $\theta=0$, the Sun is directly behind the observer as they look at the spacecraft and the relative brightness is $1$. If $\theta=\pi/2$, the reflector must be turned at 45 degrees and its apparent size (and apparent brightness) is only $1/\sqrt{2}\approx 71\%$. If $\theta=\pi$ the spacecraft is directly in between the Sun and the observer; in this configuration the spacecraft can't reflect any light towards the observer and its relative brightness is $0$. The relative brightness is $\cos(\theta/2)$. * Distance: The apparent brightness of the spacecraft is proportional to the inverse square of the distance to the observer. * Shadowing: I assumed that the Earth's shadow is perfectly sharp, so the spacecraft is either fully illuminated (brightness $1$) or fully shadowed (brightness $0$). Surprisingly, the simulations indicate that you want the reflector to be in as low an orbit as possible. The decrease in brightness with altitude dominates the increased visibility. However, our orbit can't be too low, since with a large, lightweight structure drag becomes an issue. Let's spec a 1000 kilometer orbit. At this altitude, even a 100-meter reflector would drop by only about ten kilometers per year. The inclination should be a little higher than the latitude of the northernmost (or southernmost) location you want it to be visible from. The reflector will cast a spot about ten kilometers wide on the Earth's surface. At 1000 kilometers, we could make the spacecraft as bright as the full moon with a 20-meter reflector. This size is easily within the realm of plausibility; [JWST's sunshield](https://www.youtube.com/watch?v=PVAe9Ovca5Q) is close to this size at 18 meters long. [Answer] A metallized mylar balloon or light sail can be amazingly brilliant via reflected sunlight, although it would only be visible when the sun is illuminating it (so from twilight to dawn). If you are satisfied with that, then the builder will happily take the money, pay SpaceX $50 million for the launch and a few million more for the balloon/lightsail and pocket the change. In terms of "how" brilliant it could be, Nazi scientists (who apparently had nothing better to do with their time) worked out the parameters of an orbital mirror made of sodium which was designed to focus sunlight on hapless targets on the ground (much like a child uses a magnifying glass to burn ants). Some details can be found here: <http://www.worldatwar.net/chandelle/v1/v1n1/ww2space.htm> <https://en.wikipedia.org/wiki/Sun_gun> > > Later during World War II, a group of German scientists at the German Army Artillery proving grounds at Hillersleben began to expand on Oberth's idea of creating a superweapon that could utilize the sun's energy. This so-called "sun gun" would be part of a space station 8,200 kilometres (5,100 mi) above Earth. The scientists calculated that a huge reflector, made of metallic sodium and with an area of 9 square kilometres (3.5 sq mi), could produce enough focused heat to make an ocean boil or burn a city.[1](https://i.stack.imgur.com/8FcVN.jpg) > > > [![Sonnengewehr ](https://i.stack.imgur.com/8FcVN.jpg)](https://i.stack.imgur.com/8FcVN.jpg) Now to make this visible all the time, use something like the Sonnengewehr in high orbit as a power generator, and beam the energy to a satellite in LEO which has IMAX projection lamps on board. A single IMAX lamp on Earth pointed into space is supposedly visible on the Moon: > > The lamphouse on top of the IMAX projector utilizes two 15,000-watt liquid-cooled, short-arc xenon lamps. The lamps weigh 10 pounds each, and are nearly two feet in length. Costing more than $6,000 each, the lamps have a life expectancy of only about 1,200 hours of operation and are replaced 4 times per year. Because of the extreme high-pressure xenon gas inside the quartz glass envelope of the lamp, projectionists must wear ballistic safety gear when changing out a lamp. If dropped, the xenon lamp would explode with the destructive force of a hand grenade. > > > The average luminance of one of these xenon lamps is approximately 1.6 billion candles per square yard--about equal to that of the Sun as viewed from the Earth's surface! The lamp has a light output of approximately 600,000 lumens. NASA uses this same type of lamp at the Kennedy Space Center to illuminate the Space Shuttle at night on the launching pad. > > > During normal operation, the clear quartz glass envelope of the lamp has a surface temperature of about 1,300 degrees. To prevent the lamp from overheating, it has coolant "jackets" that allow cool distilled water to be pumped around the electrodes at the flow rate of 8 gallons per minute and a pressure rate of 100 psi. In addition, an exhaust fan removes 1,200 cubic feet of air per minute from the lamphouse. The xenon lamps operate at 37.5 volts DC, and 400 amperes of current. > > > [![IMAX projector bulb](https://i.stack.imgur.com/74RNu.jpg)](https://i.stack.imgur.com/74RNu.jpg) So if we take 50 million/launch from SpaceX (X2), use 100 million to build a solar power station in high orbit with a microwave energy beam then we have 800 million left to purchase IMAX bulbs and build the satellite. (Lets put aside 100 million for the satellite body). So we can use 700 million to buy IMAX light bulbs, for a total of 166,666 bulbs. This will produce 99999600000 lumens of illumination until the bulbs start burning out. I'm pretty sure you might need sunglasses to look at it from the Earth's surface. (Use SPF 100 sunscreen as well.....) [Answer] A square kilometer of [metallized PET is available at retail prices for about \$4 million](http://www.mcmaster.com/#7538t11/=111jq8a), and at a density of [1.4 grams per cubic centimeter](http://www.wolframalpha.com/input/?i=density+of+polyester+film), weighs about 71000 kilograms. SpaceX can put that into [low orbit for around \$330 million](https://en.wikipedia.org/wiki/Falcon_9_full_thrust). For \$1 billion, you get 16 Falcon 9 launches, putting three square kilometers of highly-reflective material into orbit. At an altitude of around 200 kilometers, it will have an angular diameter of 34 minutes of arc, slightly larger than that of the Moon, but it will be much brighter, with an albedo close to 1 (in contrast to the Moon's graphite-dark 0.13). With careful angling of the surface, it will be visible day or night, only disappearing when it enters the Earth's shadow; a 10% reduction in size will let you put it in polar orbit, making it visible at all times. Overall brightness will be around -14 (compare the full Moon at -12), flaring to around -27 (the same as the Sun) when the angle is right for it to focus sunlight somewhere. [Answer] ## A nuclear shaped charge aimed at specific point should do the trick. Nuke shaped charges are an idea invented in the 1960s to improve the efficiency of projects like [Project Orion](https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)). Instead of a spherical blast produced by conventional nukes, where much of the energy from the explosion would uselessly radiate away, nuclear shaped charges focused the energy into a relatively small area, namely the pusher plate of a Project Orion spacecraft. The brightness from a blast like this is very short, a few seconds at the most. In order to meet the "fire at different locations" requirement, the spacecraft will require multiple charges be deployed into orbit. ## How to spend the billion * Get some geosynchronous launch services from SpaceX for a few tens of millions of dollars. * Build a launch vehicle. Total production costs are likely to be below $100M. + The vehicle will basically be a axial bomb launcher that can dispense and detonate as many shaped charges as possible within the available space and weight constraints. * Make fusion powered nuclear shaped charges. This is the highest risk portion of the project because no one (to the knowledge of Google) has ever made one. The math is well understood but the actual manufacturing techniques are not. Testing such devices in the current regulatory/treaty environment will be tricky at best (though this can be easily handwaved away). + Fissile materials can be appropriated from existing nuclear stockpiles (US or Russian) so the arduous and tedious process of making plutonium or fissile uranium can be avoided in whole or in part. + The costs of producing these weapons may be very cheap, <\$1M or more expensive at \$20M. These costs will determine how many you can put into orbit, obviously. + The cost of the explosives may be considerably less than the cost of the aiming mechanism attached to the charge. Careful attention will need to be paid here. It is possible that the explosion angle and the distance from Earth may make it so that each charge is able to illuminate an entire hemisphere. ## Discussion Conventional explosives don't pack the punch required to make a really bright new "star". Fission charges may provide the power necessary but if going fission, go fusion and pick up another two to three orders of magnitude in power output without too much more weight. The most powerful US nuclear weapon was the [B-41](https://en.wikipedia.org/wiki/B41_nuclear_bomb) with a yield-to-weight ratio of 5.1 megatons per ton. Note that the Russians did make a 50 megaton fusion weapon at 27,000 kilograms (60,000 lb) for a yield-to-weight ratio of 1.6. [Project Rho](http://www.projectrho.com/public_html/rocket/spacegunconvent.php) reports that the minimum aiming angle for these shaped charges is 0.1 radians all the way up to 0.39 radians (6 degrees to 22 degrees). The angle depends on the material in front of the charge as well as the thickness of the plate. The only other place to find energy yield greater than fusion weapons is to use anti-matter reactions, but those aren't available in the budget provided. Large solar energy concentrators may be available in the time and budget allocated, but no one has launched anything approximating a solar lens larger than 1 km². ]
[Question] [ This question already has answers here: [How do I keep a language shared by two separate peoples, static for as long as possible? The lower tech-complexity the better?](/questions/29908/how-do-i-keep-a-language-shared-by-two-separate-peoples-static-for-as-long-as-p) (9 answers) Closed 7 years ago. They begin as one country with one language, but then a small contingent of people are suddenly blown off course. They land in a land that is much hotter, dryer, and harsher. 750 years later they reunite. How different are their cultures? How different are their languages? [Answer] Depends on what stage they are split and what conditions they each have to live with. However, most likely they are going to be quite a bit different. Look even at any part of Europe at two points 750 years apart. The same culture generally wouldn't recognize each other, much less being separated. Even if you take something similar, the vikings invading and settling Britain, they still had some contact with the homeland but 750 years later they were completely different in many respects. Language is always evolving and it is likely they would diverge a lot over 750 years. Look at English even since Shakespeare! And he was about 500 years ago. Two cultures that had no contact for 750 years likely wouldn't be able to understand much at all of each other. Only having some basic words in common, since even pronunciation tends to drift too. In China there are communities on the opposite sides of mountains that can't understand each others dialect. [Answer] I don't think there's a clear-cut answer here. There are so many factors in play with how languages evolve over time that you can convincingly take it into either direction. While most answers seem to suggest that the two groups wouldn't understand each other, you can also find real-life examples supporting the other side: # Ancient Greek being intelligible to modern Greek users Greek is considered to be the oldest recorded living language, with ~35 centuries worth of written artifacts. While the language underwent evolution over the ages, the changes are said to be comparatively minor, due to lucky historic circumstances (Roman Empire was effectively bilingual, Byzantine Empire was clearly more Greek than Latin). I've seen people claiming that while Homer (30 centuries old) might require a dedicated study, Thucydides's writings (roughly 25 centuries old) are generally understandable to modern Greek speakers without any special preparation. Still, Wikipedia quotes one source saying that "Homeric Greek is probably closer to demotic (modern-day Greek) than twelfth-century Middle English is to modern spoken English." See [here](https://en.wikipedia.org/wiki/Greek_language#Historical_unity). # Friar Julian's expedition Present-day Hungarians are descended from Magyars, a nomadic tribe that settled in Carpathian Basin in late 9th century, converted to Christianity and established the Kingdom of Hungary. Fast forward to 1235, one Friar Julian left with a group of Hungarian monks in order to find Magyar tribes that were supposedly left behind in the east. He found them and despite the 300-400 year gap, during which there was virtually no contact between the two groups, was able to communicate with them in his own tongue. Interestingly, other than the language, the culture of both groups went two separate ways - Hungary was already an established feudal European country, while the eastern Magyars were likely Tengrist and led a lifestyle similar to their shared ancestors. See [here](https://en.wikipedia.org/wiki/Friar_Julian). So if you want your two groups to be able to understand each other - it's something that can plausibly happen. [Answer] According to this chart [![http://language.cs.auckland.ac.nz/media-material/](https://i.stack.imgur.com/8Y3UH.png)](https://i.stack.imgur.com/8Y3UH.png) from [this paper in sciencemag](http://science.sciencemag.org/content/337/6097/957.full?ijkey=9/I0UU0.eTrdQ&keytype=ref&siteid=sci) They would be different languages. Isolated groups tend towards conservatism in language so the group blown off course would most likely have the older usage. [Answer] I read an article\* once about a group of fur trappers from the Hudson's Bay Company. When they arrived at the trapping/hunting area, they set up their camps on either side of a river, so one group hunted to the north of the river, and another group to the south of the river. Because the river was so big and treacherous, there wasn't much contact between the two communities. Anyways, long story short, after a very short period of time, like less than a decade or two, the languages spoken by each of the communities had diverged enough that they were completely difference dialects. The isolation and social order on each side of the river was enough to cause a drastic shift in the development of the spoken language of the people. So basically, after 750 years, and being completely isolated from each other in completely different environments, I'd wager the two groups would be very different to each other in not just language, but culture, social development, core values, diet and attitudes. \*I'm trying to find a link to the article I'm talking about. If I dig it up I'll post it here. [Answer] Try reading [The Canterbury Tales](https://en.wikipedia.org/wiki/The_Canterbury_Tales) in its original [olde English] form. An excerpt: ``` 'Wepyng and waylyng, care and oother sorwe I knowe ynogh, on even and a-morwe,' Quod the Marchant, 'and so doon oother mo That wedded been. ``` For reference, that was originally published in 1475, only 545 years ago, and of course, we have not been completely isolated from contact with England (or the Middle English language). Seems safe to me to say that two cultures and languages would be different enough as to be completely different and would not be able to understand or relate to each other anymore. [Answer] Language-wise, I believe there is at least decent understanding among modern speakers of [Athabaskan\_languages](https://en.wikipedia.org/wiki/Athabaskan_languages) which had been separated for at least that long, some under circumstances very similar to those you suggest (eg the Navajo moved to the what is now southwestern US which is much hotter and dryer than what is now Alaska). There's some more information for this case [here](https://en.wikipedia.org/wiki/Navajo_language). [Answer] They would probably be able to understand each other with great difficulty. American and British have diverged from each other for a long time, and they are still relatively similar. And these two groups have been in contact with each other for only 200 years. However, these groups have had differing external influence as well. Britain is close to Europe and especially France. America is composed of a lot of differing ethnicities and is close to Spanish speaking countries. I'm assuming without much external influence then these two groups of people would be able to understand each other. (I mean, seriously, I used to think it was still the Middle Ages in Britain because they still use torches, and don't have flashlights. As for culture, their culture will likely be very different. To the point where they don't recognize each other's culture as being what their own used to be. Their culture is greatly affected by external influences, so if here groups are in different areas their culture will be very divergent. ]
[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/19083/edit). Closed 8 years ago. [Improve this question](/posts/19083/edit) Considering how drastic our clothing has changed over time, how might a distant (let's say 50 years) society dress? I know that our tastes in clothing have changed, but that is much harder to predict. Instead, how has/will humanity's developments in technology influenced our dress wear? Overtime, religious beliefs have changed (resulting in more liberal clothing), our ability to keep warm has improved (thinner clothes), and our access to global trade has increased (resulting in a different quality of fabrics). For this near-future, how might technology like 3d-printing, wearables, and nanotechnology shape fashion? [Answer] Clothing does three things, 1. Indicates and forms identity (class/social status/'tribe'/gender 2. Sexual and status signaling 3. Increases comfort Sometimes, these things are at odds with each other. For example, opulent ball gowns, some cos-play costumes, fetish wear fulfill the first two but are not comfortable. As social identity continues to fragment, trying to indicate belonging becomes more important. Fabric technology will begin catering to these sub cultures, helping them make their identity part of their everyday life. Developments in health and nutrition will eventually determine the ideal body type for different ethnicities and maybe go further, able to determine the platonic body shape for each individual. In the past, clothing (at least for women) were designed to emphasize What society considered ideal. In the future too, clothing will be made to emphasize this ideal. It could also have tech to help people realize this ideal - like ability to limit food intake and correct back posture... Disabilities are increasingly being portrayed as a unique ability. It is here that the largest change in fashion tech will be noticed. Artificial limbs have become over the past few decades from clunky things of embarrassment to beautiful, practical, things that have the possibility of enchancing individual performance. Ultimately it would be limited by the fact that we are human and need to see, eat, pee and go about performing some sort of work or leisure activity. The only exception to this is when wearing clothes to peacock (look at me, I'm so wealthy I can afford this ridiculous dress that prevents me from being a functional human being). Even as clothing becomes more practical, we could see tech that would create the completely impractical... A one time wearable dress that is printed on the person, maybe? [Answer] I think that "business suits" are fading after a good long run: not too long ago men wore suits to any office job, and before that (if old movies and TV is accurate) just about always, if not a different work uniform. Now "business casual" is taken hold. Some ideas for you, which may not be right but are plausible for your story: Men's clothing will become more varied. "Nice" attire will be much less formal looking to our eyes, but will be (e.g.) not torn or distressed, not have logos or slogans, and be more complex than strictly comfortable clothes. Being "formal" will seem like arbitrary decisions on which colors, styles, or other attributes are more or less formal. Probably not bright colors for "formality". Clothing will be "smart", with wearable electronics. Clothes can be reactive and adaptive, such as changing color or warmth. There have already been some products that uses nanotechnology to make cloth seem like plastic sheeting when liquid is spilled on them. I expect that will be perfected, or so cheap that you don't care if it can't survive being washed. Maybe cleaning will involve re-initializing the repellent technology. And with all the difficulty in washing something that repels water and oil, you also have it not needing to be washed because it doesn't get dirty. Maybe have an "air" treatment that blows out adsorbed odors and trapped molecules, without getting it wet. New materials like carbon fiber. Not sure what good carbon fiber is for normal clothes, but aerogel fabric is already available for insulating. Just like arcticware was revolutionized already with modern 20th century materials, that can have another round: the warmest coat anyone can ever need would be as thick as a moderate winter coat today, and normal winterware looks like today's light jackets. T-shirts will light up and have active displays, not just static printed art. How about new forms of fasteners? We've seen the invention of the zipper, more recently shoelaces give way to velcro, and velcro cuffs for gloves and such. Maybe stretchy elastic that doesn't bunch up but looks neat across a large range of length stretch. But could some new form of fastener catch on? What about magnets? Something as strong as a rare-earth magnet but flat embedded into the cloth could replace some buttons and snaps, especially in "formal" clothes where you like the clean unbroken appearance. For adding to the story, think about specific fashion trends. Hats have come and gone, and could come again. Perhaps neckties will be replaced with cravats that are comfortably loose, with style in different ways of tying it. Here's a thought on form-follows-function. I notice how a vest (wastecoat) has little pockets meant to hold a watch. That was a practical design originally, now frozen as style. Today just about everyone needs to wear displayed ID, often using a lanyard. Could that evolve into a functional element of business attire? A clear pocket to hold the ID card, perhaps? [Answer] Tech that changes clothing will involve several different (and competing) agendas, outside of signalling status, membership of a group or sexual attractiveness: 1. Speed of manufacture. Most people will want to be able to access fashion trends as part of status/signalling behaviour, so when something comes into fashion, the vendors need to be able to access it right away. Waiting for a container ship to arrive from Bangladesh, clear customs, get trucked across country etc. takes a lot of time and ties up money and resources in a notoriously cut throat and low margin industry. Robotics, automated manufacture and even potentially using 3D printing technology to rapidly assemble clothing made from downloadable patterns in plants close to (or possibly even inside) the store will become common. 2. Higher tech fabrics. Materials that can wick away sweat, or are water repellent on one side are common today (think of "Underarmor" T-shirts and underwear, or Gore-Tex jackets). In 50 years, fabrics will probably become "active" materials which can change their properties according to various rule sets built into them. This will be relatively limited (one example might be "warm" and "cold" setting where fabric fibres change spacing for insulation value) and powered by body heat or something similar so people don't have to consciously adjust their clothing. Think of this as "passive high tech". 3. Integration with active high tech. Clothes will be close to your skin, so can have sensors and electronics to monitor your health woven into the fabric. The clothes will have enough on board processing power to do monitoring and notifications to yourself or your health care provider. With enough circuitry built in, the shirt you wear might replace a lot of the current electronics we carry, like smart phones, ID cards and so on. Displays will be fed into a pair of glasses or a monocle, inputs will most likely be subvocalizing or speaking, the tie might survive as a handy place for the subvocal microphone (concealed in the knot). Since the clothes will be performing the work, there is less need to carry items like keys, watches or smartphones, so pockets will become smaller and fewer in number (maybe a pair of pants only has one pocket). Finally, although clothes will become more "functional" in the sense they perform multiple functions, these functions will still have to be integrated with fashion (for status, display and sexual signalling) as well as basic human needs like the ability to use the bathroom (Zippers may be replaced by some magical fastener, but pants will still have a fly) [Answer] Obviously no one can tell how styles are likely to change or what tech might find its way into clothing. However, we can guess at what tech is available for inclusion into clothing. @Thucydides has several good ideas. To his I would add the following: Remember that all of these things depend upon bringing the cost of manufacturing the goods into the price range of the consumers. So although some of the ideas available below we can do now, we can't do it and make the clothing cheap enough for it to be regularly seen. Passive These capabilities will be inherent properties of the clothing / fabric and not require any sort of extra energy, electricity, or active control (by person or computer) to make happen. * Fabrics with the ability to repel most (any?) stains. * The above capability extends to repelling water so the clothing is waterproof to rain, etc. * But it'll also possess the ability to wick sweat away from your body and transport it outside the clothing. * It'll perhaps include the ability to adjust its absorptivity to radiation depending upon temperature (warms you when it's cold, cool you when it's hot). * Glasses with the ability to provide full color vision to people with color deficiency (a condition in which the person possess 3 color receptors but a mutation changes the frequency of one of them making it more difficult to distinguish color). * Tougher materials (e.g. carbon nanotubes) make embedding bullet proofing into clothing easier and less conspicuous. * Color changing clothing depending upon body temperature, air temperature, sunlight or other unspecified environmental factors. Active These are capabilities that require active control by a computer or the wearer or electrical or wireless connections. * Color or pattern changing clothing depending upon prespecified logic or the user's whim. * Embedded clothing sensors which monitor body temperature, heart rate, respiration, blood oxygenation, etc. Especially look for this as a medical device which diffuses into the general population (e.g. starting with performance athletes, moving into the general athletes, and from there into the general population). * Clothing able to provide some first aid depending upon programmed contigencies (e.g. detected blood loss leads to the clothing constricting around the wound to suppress the bleeding). This might start with the military or astronaut core and leak into the general population. * Wearable wireless connections for our hand devices which lead to wearable wireless for our implanted devices which lead to wireless direct brain connection to the internet. * Wearable or implanted devices like Google Glasses that allow recording and HUD type information display instant information about every object around you - probably controlled by an AI that you program so it provides the type of information that you most often want to know (e.g. what WOW classes do they play and what is the level of their highest character or information about their professional experience during a job interview). * Wearable sensor net that extends and enhances certain sense (probably sight will be last because our sight is already better than what most hand devices can do). As additional background you may want to read the books / stories by Charles Stross [Accelerando](https://en.wikipedia.org/wiki/Accelerando) (featuring Manfred Macx) and Vernor Vinge [Rainbow's End](https://en.wikipedia.org/wiki/Rainbows_End). Smart (HUD type) contact lens ![Smart (HUD type) contact lens](https://i.stack.imgur.com/g0Bji.jpg) What that HUD might show ![What that HUD might show](https://i.stack.imgur.com/Mpn7w.jpg) How it might appear Camouflage / Chameleon suit It uses sensors on one side of the suit to detect the the background appearance and make the suite take on that appearance in a given direction. Useful for the military and other very special situations. ![enter image description here](https://i.stack.imgur.com/46BuD.jpg) Desert Survival suit Uses passive nanomaterials to condense water out of the air as well as allow sweat to evaporate keeping the body cool. Also uses passive color changing to reflect heat back into the environment during the day. Uses passive color changing to warm the body during the night. Uses nanomaterials to keep a static charge facing out to keep sand and dirt off / away from the suit wearer. [Skinsuit](https://en.wikipedia.org/wiki/Space_activity_suit) Uses material elastic properties to maintain positive pressure on the body. Wicking ability allows the wearer's sweat to carry heat away from the body. Passive color control helps reflect the heat from direct sunlight away from the wearer. Built in electronics provide sensor suit and radio / data reception to the suit wearer. Space skinsuit ![Space skinsuit](https://i.stack.imgur.com/sTfgE.jpg) Combat suit Uses some of the previous features (e.g. chameleon features) as well as encrypted communications and sending & receiving $C^3I$ information. Helmet with HUD allows the wearer to know where his enemies are even when he can't see them. The $C^3I$ suite identifies objectives and specific targets and prioritizes them. Suit notifies nearby friendlies using FFI (friend or foe identification). Suit sensor readings shareable with other soldiers and command. Built in carbon nanotube fibers provide inherent bullet stopping protection. Optional exoskeleton with power assist increases soldier strength and stamina. [Answer] Once again, comment becomes an answer just so I can make paragraphs :-( First, you need to think about just who the "us" is in your question. Lots of different societies in history and the world today, and fashions worn by different groups in society. As for how things might change in (a mere!) 50 years, not much at all, judging by how they've mostly not changed in the past 50 years. Of course there are changes in fashion: bell bottoms and tie-dye are out, I think. Artificially 'distressed' fabrics are in, or were last I bothered to look. Some groups wear baggy pants with belts below the hips and reversed baseball caps, others don't. But that's just fashion: what exactly has changed technically in those 50 years? Not much, as far as I can see. Polyester is pretty much out, hemp fabrics are available. There are some better snaps and buckles, mostly on outdoor gear. Otherwise, the only thing I can think of that's changed in a way apparent to the casual eye is the running shoe. [Answer] Over the last two centuries men's clothing has become less elaborate. The tailcoat was replaced by the tuxedo in less formal uses, then in formal uses. The tux lost the waistcoat. The lounge suit replaced the tuxedo in many uses and now sporting clothes are replacing the lounge suit in some situations. I wonder how much of that is due to fashion and how much is due to the decline in the availability of butlers and valets. Today few people have domestic help, so they need clothing they can manage for themselves. Would improved robotics reverse this trend? On another note, some professional women's clothing has come closer to men's clothing in recent decades. This trend might continue if workplace equality gets better or backtrack if it fails. ]
[Question] [ In this world I'm building, a bunch of previously inactive genes in humans have started expressing, and changed newborns' metabolic system dramatically. As a result, a portion of population cannot digest regular food, but can eat synthetic food (let's call this population Type S, as opposed to Type R, regular humans). For clarity, regular food can be of plant or animal origin, and synthetic food can only be produced in lab-like settings. The world's population is now divided into two groups, with their food sources not overlapping. The proportion of Type S and Type N people in population change gradually. * What kind of chemistry and biology can be behind this? * How can synthetic food differ chemically, so Type S human body can feel the difference? And how can it be so different, Type R humans are unable to digest it? * What are the raw materials for this synthetic food? [Answer] It’s difficult to imagine how the human body could suddenly be unable to digest naturally occurring organic compounds, but its a little bit easier to imagine that humans could find them toxic. There is a rare genetic disorder in humans called Phenylketonuria (PKU). Individuals with PKU lack a specific enzyme called phenylalanine hydroxylase which is responsible for breaking down an important amino acid called phenylalanine and helping turn it into another important amino acid tyrosine. As a result, if people with PKU eat too much phenylalanine it won’t be converted into tyrosine and will build up as a toxin in the brain and cause numerous problems. An additional problem is they need to supplement their diet with tyrosine because they can’t make enough of it. Fortunately for people with PKU, all they have to do is limit their intake of phenylalanine and supplement their diet with tyrosine and they do just fine. I think a similar sort of metabolic disorder could come close to your desired outcome. Imagine if some humans lost the ability to properly metabolize an organic compound found ubiquitously in all life. It could be a carbohydrate, or a lipid, or an amino acid, but whatever it is, anyone who can’t properly digest it will slowly die from its accumulation. However, the compound is also a precursor for another essential organic molecule (in the same way that phenylalanine is a precursor for tyrosine), and those people lacking the ability to digest it also suffer from a lack of this compound. But, this second molecule needs to be finely balanced, too much of it will also cause toxicity as it doesn’t occur at high levels naturally. So, now we have our setup. The people who are unable to metabolize this organic compound must eat food devoid of it so it will not accumulate and be toxic, but the food must also be supplemented with the compound that the first one is normally metabolized in to. Laboratories will be capable of creating this synthetic food with the precursor removed and the product supplemented, but anyone without the disorder who eats this synthetic food will build up toxic levels of the product. So people with the disorder will find normal food toxic, and people without the disorder will find the synthetic food toxic. It’s a little complex and it’s not exactly what you wanted. The people can still technically digest the other food, it just slowly kills them. However, I think the chemistry is reasonable. I don’t know enough about human physiology to suggest a specific enzyme, precursor, product group but there are potentially many that would work. Of course, as to how a fraction of the human population developed this change, I leave that to you. [Answer] Note that one way to make everything incompatible is to use a mirror image of all the sugars and proteins. Those people would also be immune from disease. So, some awful plague caused people to take the drastic step with their children, ensuring their future by taking the DNA out of the fertilized egg, synthesizing an exact copy made from mirror biology, and inserting that into a mirror egg-surrogate. Meanwhile, when these mirror kids were 10 years old, the plague was finally beaten. Now there are two kinds of human that are totally incompatible biologically, who breed true naturally but can use synthesis to recode the father's contribution for in-vitro fertilization. You can have a lot of storyline concerning these "races". The mirror kids were initially elite and humanity's best hope. Many were born to families with power (who would pay their own way, in addition to the program to produce them over a diverse population), so would not be immediately abandoned. But over generations, their disadvantage creeps up and they become oppressed. [Answer] Instead of thinking about how the body changes, I propose you think about how the food might change. In your world, there could have been a cataclysmic event that removed digestive enzymes from existence (what event that might be is the subject of another question...). This means that humans can no longer digest things because the enzymes that usually do it are nonexistent. The synthesised food, then, can be seeded with digestive enzymes in it. It would have to be eaten rather quickly to avoid the enzymes dying off, but it could be done. Alternatively, if you're fixed on a biological difference, you can simply have a group of humans who weren't affected by the cataclysm - perhaps they were in bunkers, or out colonising Mars when the cataclysm happened. Your type S humans would be those who were affected, and have to have their food seeded with enzymes, and the type R is those who weren't and can digest normally. Enzyme-seeded food could damage the type R humans by giving them stomach ulcers through a digestive overload - having too many digestive enzymes is a bad thing because they starts to digest your stomach lining and cause ulcers. [Answer] I recall a story that featured junk food vitamins, where small evolutionary changes allowed utilization of newly available substances. A few people who shifted to a "helthier" diet got very sick, and it turns out that one lad had a slightly more efficient enzyme for something or another and it needed the caramel coloring in soda drinks to work. Think about how that might happen: the mutation spreads and eventually someone has copies only of the new form. Look at history: humans can't make vitimin C, and it's readily available in our diet. If done intentionally through genetic engineering, new metabolic mechanisms can be invented that are highly desirable. And to save on engineering more pathways to synthesize various parts it is decided to supply that ready made. Maybe some stuff can't be readily made with normal metabolisms, but is synthesized at high temperatures or with toxic feedstocks. Now lets make that new required thing be toxic to unmodified humans and most animals. As for whole scale nutrition, note that food is made of the same stuff as our bodies. For normal proteins, sugar, etc. to not work, the body would have to be very different. Perhaps transhumans add more features to themselves over time. Something better than collegen that doesn't wear out and is stronger, used in skin and other places; bones are totally reingeneered chemically. They will need more materials innthe diet, perhaps including titanium instead of calcium. Now it seems odd that old-style biology food would be not tolerated. Even if some constituents are useless, what's wrong with it? There needs to be some reason why something common in normal food woukd be dangerous to them. How about: the digestive system is changed to handle the wierd feedstocks needed by the upgrades, which are things that are non-biological and normally toxic. Something common in normal food interferes with the new pathways. It's hard to make them coexist since in digeation everything is mixed together: how do you keep A moecules away from B processing and vice-versa? [Answer] I have a friend who is hyper allergenic to almost everything. She cannot eat eggs or diary products, thus letting us having a delicious Bearnaise sauce that contains both eggs and milk (butter) was a difficult process. But she told us that she could eat the canned version since there was a substitute for eggs and the butter was replaced with oil and taste products. I think that story could relate to your dilemma. Where in synthetic food some of the products that causes allergies would be replaced with cheaper, more non allergen products. Also and this is total speculation, people who has been eating synthetic food had their stomachs gotten used to it, have a had time digesting "ordinary food", this is based on my wife being vegetarian and most of our food is vegetarian but when i go to enjoy meat, my stomach is not used to the meat bacteria and sometimes reacts badly. [Answer] As to my understanding (please correct me if i'm wrong), different isomers of the same chemical formula have different properties, and metabolised in the body through different metabolic pathways. In this way it fits the requirement of body to feel the difference. But it's not that simple as "there's two mirror versions and we can only use one". Some isomers (like Isoleucine, an isomer of Leucine) are an essential nutrient (are not synthesised in the body, and must be ingested), and are important for human health (e.g. muscle tissue). Others, like D-glutamic acid, are present in tissues, but when ingested, largely escape most deamination reactions (unlike L-glutamic acid). Yet another isomers, like L-isomer of Glucose, cannot be metabolised by human body at all, and only a bacterium, Burkholderia caryophylli, contains the enzyme which is capable of oxidising L-glucose. But what if some genetic changes made S Type people capable of metabolising isomers which previously were not metabolised at all, or make them have other physiological consequences, so the body can process it as normal and recover important nutrients? Moreover, what if these changes made their metabolic system isomer-dependent? Now only opposite isomers can be used to fulfil their diet. ]
[Question] [ How do I define the Classical Elements with Science so that it agrees with science? According to a single property of a substance. So, no Fire = Energy, Water = Liquid, Earth = Solid, Air = Gas... as I'm quite sure that Energy is not a state of matter... --- For example, > > Specific Gravity ranges for each type of element. > > > Which is something like: > > Water Users have control over materials with a Specific Gravity between 20 to 50, inclusive. > > > Earth for materials with specific gravity higher than 50, > > > Air for materials with specific gravity between 20 and 10, inclusive of 10 > > > Fire for materials with specific gravity lower than 10 > > > --- From [Plasma Manipulation](https://worldbuilding.stackexchange.com/questions/14894/how-to-make-plasma-manipulation-powers-on-equal-power-with-phases-of-matter-wi) I can't do Plasma, Solid, Gas, Water... as: > > See [Fire is not plasma](http://www-spof.gsfc.nasa.gov/Education/FAQs7.html#q97). – DJMethaneMan Apr 21 at 18:02 > > > @DJMethaneMan The specific question asked in your link is if burning wood, paper, or gasoline is hot enough to produce plasma. Fire can easily be hot enough to produce plasma. – Samuel Apr 21 at 18:06 > > > However, not ALL Fire is Plasma... [Answer] TL;DR - For this one, you'll need to define hard limits on what these people can and cannot manipulate, and I think the breakpoints will be around bond energy and kinetic energy. Honestly? I think you were better off using the phases. The Gas phase guy would be most capable of starting and controlling fires. Plasma comes out to a kind of electrical thing. Liquid and solid are pretty self explanatory from there. Except for the whole magic thing, if you want hard-science, people controlling classical elements has some problems - since fire is an ongoing process with multiple possible constituents, things get weird. I mean, what is this guy, a Gasoline mage? Rant over - Now let's see what we can do to make this happen. Each of these classical types have certain recognizable patterns. Liquids bond poorly, solids bond well, gas (very generally speaking) isn't bonded at all, and fire is a self-sustaining chemical reaction consisting of the ongoing decomposition of other material into flammable gasses. In order to have any hard science basis for a classical elemental magic scenario, these people have to be able to recognize, manipulate, and/or create these arbitrary patterns. The Earth guy can arbitrarily reshape the bonds of existing solid without breaking them. Water guy can arbitrarily manipulate forces inside a liquid to cause it to take different shapes. Air guy isn't so much different than water guy, but he can only do it to gases - if you need a reason, then all I can offer is that Water guy can't track the gases fast enough to manipulate the particles, and Air guy can't summon enough force to change the bonds of solids and liquids. Perhaps Earth guy can only control bonds he is physically touching through other solid matter, and can't get a lock on anything that is moving. Now we have to design the fire guy. This is harder, but we're already handwaving the fact that these people are doing impossible things. In that case, I offer that Fire users can only detect and manipulate hot particles - that is, particles that are free to move and contain relatively large quantities of kinetic energy. In order for this guy to not just be Air guy, there must exist some point of exclusion. On this point, I suggest that perhaps Air guy cannot find and use gas particles above a certain energy threshold. The Fire guy must then also not be able to use anything heavier than hot combustible gases that are already burning, or risk just being Uber Air guy - this may or may not be desirable in your work. Minor edit: I just looked back over this and realized that this creates a spectrum, involving how much force a person can bring to bear on a particle and its bonds, and how fast that particle can be moving and still be manipulated. If you want, now, all magic users are basically [Molecule Man](http://en.wikipedia.org/wiki/Molecule_Man) with varying degrees of skill and power, and creating the ability for mages to use multiple classical elements. [Answer] The problem is that in modern science and chemistry, we've found that these 4 things (water, fire, air, and earth) are not very similar, and by no means all-encompassing categories, so they there's no neat way to define them in similar ways. Because of this, you're going to have to choose if you want to stick close to the ordinary meanings of these terms, and have individual and somewhat arbitrary criteria for each element, or if you want to use the classical elements as a metaphorical basis for a more systematic classification (like in the "states-of-matter" example you give) and have the users be controlling things that don't correspond to our everyday definitions of these four things. You can't have it both ways. In the rest of this answer, I'm going to outline the most effective individual and arbitrary physical criteria for each element that I think would get you closest to the everyday definitions. Water = H20. This one is simple, since it is the only one that is a defined chemical compound with essentially a homogeneous composition. Usually in these kind of setups, water-users can also manipulate ice and water vapor, but if you don't want them to be able to you can just restrict their control to liquid water. Fire: one of the things we have learned is that fire is not a substance. It is a process. In general, fire is characterized physically by the chemical process of oxidation, and the release of energy (exothermy). Clearly, fire also has a close connection, both physically and metaphorically, with heat. So a fire-user might be able to control things like oxidation and heat-transfer. One interesting fact is that only gases, not solids and liquids, are capable of sustaining a flame. When something solid or liquid appears to burn, it is really being vaporized and then the vapor is what catches on fire. [Edit: vaporization does occur for burning solids and liquids, but the [overall situation](http://www.sciforums.com/threads/do-solids-burn.79002/) seems to be more complicated than I originally stated in this post.] Air: The most obvious criterion you can use for "air" is simply "substance in the gas state of matter". [Earth's atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Earth) is mostly composed of nitrogen and oxygen molecules, which are two distinct chemical elements that otherwise don't have any special connection, and that can also be found incorporated in solids and liquids, so it's impossible to define air in terms of chemical composition. This could possibly overlap slightly with water-users with regards to the substance of water vapor; you'd have to decide how to resolve that. I suppose you could restrict "Air" manipulators to control of monoatomic and homonuclear diatomic gases: this is a bit arbitrary, but it would include nitrogen, oxygen and argon (the 3 most common atmospheric gases), as well as a number of trace gases, and exclude water vapor (and also CO2; I don't know if that would be a problem). Earth: this one is the hardest to define, as it's rather vague. However, in general, [rocks](http://en.wikipedia.org/wiki/Rock_(geology)) are composed of [minerals](http://en.wikipedia.org/wiki/Mineral), which are solids with an ordered crystalline structure that are inorganic in composition (the chemistry definition of this is a bit tricky, but it basically means that the structure doesn't contain carbon backbones). An earth-manipulator might have the power to affect only things with these kinds of crystalline structures. (As with air, this would lead to overlap with water-users, in this case for the category of ice; you'd have to decide which way you want to assign it.) You can see that each element has a different type of definition. I don't know if this has to be a downside: if you emphasize how the elements contrast rather than how they fit together, this could inspire some unique extensions for each type of power (for example, fire manipulators might gain the ability to manipulate their metabolisms, since this involves a different type of oxidation, while air manipulators might gain the ability to use sonic attacks, and earth manipulators might gain the ability to change the molecular-level structure of crystalline solids, like turning graphite to diamond). [Answer] Bond structure. Earth = Structured bonds Water = Non Structured bonds Air = No Bonds Fire = Individual atoms So if you interact with an individual atom it will vibrate in place, like a point, causing heat. A Gas manipulated creates flow like a line. A liquid manipulated has a surface like a plane. A solid manipulated has structure, like a cube. And then you can either work your way up from fire to stronger elements, or you can have people only able to manipulate energy a certain way. Or you can do Fire as transitions of bonds, since heating and cooling changes elemental states. [Answer] (I think) I just got an awesome idea inspired by Mikey's post. So basically the issue here is that each of the four elements have many unique traits that can't necessarily be sorted by any hard-science forces. What if, based off of each individual's DNA, some kind of structure is formed that bends the forces of science in some way. Each tiny change in DNA could result in a completely different structure that may tend toward another element, or have no change at all. These structures seem to form patterns that allow specific manipulation of similar physical things, such as fire, water, earth, or air. Although Alice (and her previous ancestors) all in the past have only been restricted to fire, Bob, the next generation, may have a somewhat dissimilar structure resulting in him getting earth instead. The last, more fun, part is that, although you don't have to, you can easily add more elements in whenever needed due to the absolutely massive combinations list DNA provides. [Answer] I'm not sure I fully understand your goal. You'll also need a little bit of 'fake' or 'speculative' science, here. First, there's a bit of good news. As Einstein showed, matter and energy [ARE the same](https://www.youtube.com/watch?feature=player_embedded&v=q74suqg5pCk). In your story, in your universe, you can suppose that your characters can convert energy into mass, or mass into energy. In a very cheeky way, you can suggest Hairy can manipulate energy to produce wind, Walter can do the same with water, Dirty Mike can do the same with earth & soil, while Burnadette can manipulate great amounts of energy to create fire. We're daily surrounded by tremendous amounts of [electromagnetic energy](http://www.dailymail.co.uk/sciencetech/article-2016302/Powered-air-Researchers-discover-gadget-extract-energy-sensors-us.html), and it just takes your characters having the ability to scavenge it, store it, and use it. Now, I am going to hide from (1) the real scientists who are going to guffaw when they read this, and (2) people who didn't like my cheesy puns in the third paragraph. --- EDIT, as requested: Why does Dirty Mike have the ability to manipulate dirt, for example? It turns out that each 'type' of person with the ability is connected very closely to the element at birth. Atoms frequently exchange electrons. In your universe, however, a person dwelling in the foothills has developed very strong bonds with elements in the soil. Walter, on the other hand, grew up by the sea. Occasionally a rare cosmic event creates very strong bonds between one person and the element they're closely surrounded by. ]
[Question] [ I'd like to know if a planet without any animals except humans can exist. The cause of this absence of other species could be anything but the humans should not have any social interaction with something else than humans for centuries. What would be the effects on the society? I guess that humans can live without any animal nutrients but can the global ecosystem be rich enough for humans without interactions with other species? Do Humans have to be highly developed in order to live in this kind of planet or do you think people from Middle Ages could live in it? How would this kind of world affect our personality? Humans tend to feel close to the animals. Would a lack of other animals cause us emotional distress? [Answer] Not having insects would be a big problem - a lot of plants rely on them for pollination for example. That can be worked around, but plant life would be very different - definitely no flowers. For anything big enough for humans to really interact with, you just need to fill those roles with humans. A human slave isn't as strong as a horse, but enough of them will get the job done. Actually caring what happens to animals (or most other humans for that matter) is a very recent innovation in our society. [Answer] This is a very good question. In my opinion, humans would definitely die off eventually without animals. Animals play a big part in our society. Here are some notes that I made on this topic: * Some animals that we cannot live without are bees, bats, butterflies, fish, worms, plankton, wasps and rats * The connection between humans and animals is one of the most fundamental bonds that human beings experience * Humans have interacted closely with animals for thousands of years * Animals provide many beneficial things to humans and without them, even with plants, humans would eventually go extinct because the ecosystem just lost a huge chunk * The human-animal connection is: “A mutually beneficial and dynamic relationship between people and animals that is influenced by behaviors that are essential to the health and well-being of both. This includes, but is not limited to, emotional, psychological, and physical interactions of people, animals, and the environment. The veterinarian's role in the human-animal bond is to maximize the potentials of this relationship between people and animals.” * Animals are part of almost everything that we do * Pets are good for people. Pets give people a loving companion to care for. They encourage conversation and laughter. They cause us to exercise and offer an antidote for loneliness. They teach children responsibility. By caring for pets, pet owners benefit, too. * Pets can also boost infant immunity to infections, help with mental health disorders by affecting brain chemistry, and lower blood pressure. * Animals and humans are a powerful two way bond. * A con about animals would be that wild animals are unpredictable and there have been many deaths with wild animals before in the past [Answer] It just came to my mind that that situation can happen. I guess that lots of sci-fi stories tell about humans landing on some planets that flora would consist of plant-like beings. Given that all of these 'beings' are coexisting together filling every step of ecosystem ladder (whatever it may be), then human 'invaders' would start living in such world. Now, let's see what the outcome will be: * at first humans must to adapt to new ecosystem and find what these 'plants' will consist of; * second step would be identifying proper species that would serve as food and what it will be like to live on this kind of food; * if we assume that previous step is sufficient for our humans to survive, they will live that way as long as this 'new food' would not harm them; * as decades and centuries pass, human gastrointestinal tract would change and adapt to this new diet; planet's ecosystem would also change (in what way?) as there is a 'new player' in the game of life; Of course, all of this can be possible and valid as an answer to Your question IF we would classify 'native plants' as plants. For human newcomers they may seem static, rooted to the ground, in various sizes, colors, scents. The way of reproducting can also be not-requiring other 'animalish' species (like bees for that matter). They don't need to be hunted down (they don't move), they do not defend themselves - these can impact on less-aggressive social behaviours in human community. *Simply put, I would say that in world given above* humans may not need that effort of tooth-and-claw and therefore may result in smaller amount of physical aggression between people.** [Answer] Ditto comments about pollinators. The impact of large animals on ecosystems is profound. It's been found that their feces of large mammals are crucial to recycling nutrients in terrestrial and marine ecosystems. Also, I think humans would be sad and if we are ever forced to leave earth we will bring whatever animal species we have not destroyed with us. [Answer] Many people in large cities already live without interacting much with animals, so psychologically it wouldn't be too big of a deal. Maybe some people would be slightly less happy and not know why but on the grand scheme of things it wouldn't be that noticeable. Ecology, on the other hand, has to be completely different, many many plants coevolved with animals and insects and rely heavily on them for seed spreading, fertilized and so on. Many (if not most ) Earth plants will definitely die if animals disappeared, and humans will follow them. Nut on a different planet it should be possible. [Answer] We use a surprisingly large amount of animal products in industry. Wool, leather, fat, tallow, glue, [gelatin](https://en.wikipedia.org/wiki/Gelatin). Maybe our advanced early 21st century industry can adapt the production to a world with no animals, but in medieval times they would have been totally stimied. They simply did not have anything which could replace wool, or animal glue, or animal fat, or leather. Nothing. There were no artificial fibers, no plastics, no epoxy glue, no kerosene lamps... On the other hand I cannot understand a world without cows and pigs and sheep and chicken. We raise them in the billions -- why would we stop? When we colonise an alien world we bring our domestic species with us. If we can eat the local plants then so can a pig... ]
[Question] [ What would happen if an extremely advanced race removed the metal (everything beyond H and He) from a star. Would the star still function? Would it change in appearance or properties at all? [Answer] Unfortunately, there is no good way to give particularly accurate comparisons to the real world with this situation. If current cosmology is even close to correct, the earliest stars in the universe (Population III stars) should have contained almost exclusively hydrogen and helium (and a teeny weeny bit of lithium.) We have yet to discover any of these stars, so it is assumed that they were quite large and exploded in massive supernovae shortly after they formed, very early in the universe's history. The effect of removing the metals from a star would depend very much on how large that star was. Red Dwarf: A small, relatively cool star like a red dwarf almost exclusively undergoes reactions among protons, deuterium, and helium-3 to form helium-4. Removing any metals would only make the star slightly lighter, so its core would decompress very slightly and it would become slightly cooler as a result. Yellow Star: Stars like the sun are large and hot enough to use their metals in fusion processes, if only sparingly. If the aliens removed all of the metals from the Sun, it would lose approximately 2% of its mass and one minor branch of the stellar fusion process would disappear. If the aliens continuously removed all metals from the sun as they were formed, it would cause the sun to dim very slightly. About 15% of the fusion events that occur in the sun use one of the affected reactions, but these particular reactions are the final steps in a longer process that has already liberated a large fraction of the energy it will produce. Further, some of the material that would have reacted in these branches would be available to react in the more typical processes. Another set of processes that I'll cover more thoroughly in the next section would disappear entirely, causing the loss of ~1% of the Sun's fusion. In short, the Sun would dim very slightly, which would not have a massive impact on us but would be measurable and would likely have small, long term consequences to the climate. Wikipedia has a nice diagram of the processes that occur in the sun if you're curious. ![nice diagram](https://upload.wikimedia.org/wikipedia/commons/a/ac/Proton_proton_cycle.svg) Blue Stars: Hotter stars derive more of their energy from a process called the carbon-nitrogen-oxygen (CNO) cycle, which is more strongly temperature dependent than the proton-proton cycle. The CNO cycle relies on the presence of carbon-12 to act as a catalyst for the fusion of protons into helium (via nitrogen and oxygen.) The two processes are largely independent of one another, so ending the CNO cycle would not free up additional material to react in the proton-proton cycle. Thus, if all of the metals were removed from a large, hot star, its energy production would drop dramatically. A star like Sirius derives nearly all of its energy from the CNO cycle, so it would see an enormous decrease in heat production in its core. Once the carbon-12 was removed it is likely that it would be replenished after a (long) time via the triple alpha process unless the aliens continuously removed all of the metals from the star. This process is extremely slow in normal stars, but in the weird high density conditions that would exist here it might be more prevalent. Other comments: The core of any star is utterly opaque to electromagnetic radiation, so any change in heat production would not be observed as a change in brightness immediately. It takes about 100,000 years for the energy of any given fusion event to escape the Sun, for example. Instead the balance between thermal energy and gravitational contraction would be upset, and a large star would contract significantly. The proton-proton cycle is linearly dependent on density, so its frequency would increase as the star's core contracted. Eventually a new stable state would form, with the star smaller, cooler, and denser than it previously was. ]
[Question] [ In a sci-fi world that I am making, an infantry held launcher is one of the many weapons developed to counter increasingly tough armor protection, brought on by the advent of advanced materials and systems that could tank a modern 50. multiple times while keeping the user alive and functioning. What makes this launcher different from others that, say, fire hypersonic projectiles or HEAT rounds, is that it fires a solid 100 cm long, 8 mm wide tungsten (though sometimes alloyed with depleted uranium) "arrow" that is yeeted to Mach 1.5. For simplicity's sake, let's just say that why anyone would think this is a good idea is left to be world specific, and the resulting recoil is dealt with through a combination of advanced recoil dampening systems, enhanced biological soldiers and an exoskeleton. Spring and elastic propulsion have various issues at pushing a projectile to such speeds. Arrow guns require a hollow tube which these arrows don't have, and I'm unsure if rail- or coil-guns could work in this scenario. In short; how could a launcher accelerate a metallic arrow to supersonic speeds in a format similar to a modern arrow gun and not a tank? Clarification: * This is an infantry carried weapon. Either carried on its own or in combination with another weapon. * Advanced materials like CNTs are available. * This weapon does not have an extensive barrel, as the arrowhead either sticks out of the weapons nozzle or is just behind it. [Answer] Mach 1.5 at STP is roughly 500 m/s. That's not particularly exciting... consider that a [Barrett M82](https://en.wikipedia.org/wiki/Barrett_M82) has a muzzle velocity of nearly 900 m/s, and a [General Dynamics KEW-A1](https://www.gd-ots.com/munitions/large-caliber-ammunition/120mm-kew-a1/) (a real-world [APFSDS](https://en.wikipedia.org/wiki/APFSDS) antitank round) manages 1740 m/s. Your arrow is so slow that the various armor penetration calculators and algorithms I could find online refused to accept it... anything lower than rifle-like velocities of 8-900 m/s was considered too low for the equation to reasonably work. This strongly suggests to me that your projectile design is wrong... "long rod penetrators" work at significantly higher velocities than your design, so you probably don't get nearly as much benefit from that style of projectile as you might have thought. Your projectile is 1 m long and 9 mm in diameter, giving an L/D ratio of ~111:1. That's a significantly more slender shape than typical antitank rounds... the largest L/D ratio I kind find in [120x570mm NATO tank rounds](https://en.wikipedia.org/wiki/120%C3%97570mm_NATO) is 37:1. Given that manufacturers of antitank rounds are well aware that armor penetration is a function of the length of the penetrator, you can assume that they worked out the longest aspect they could get away with before some other effects started impairing ammunition performance... maybe at the point of shooting, maybe in-flight, maybe at the point of impact, I'm not certain. In whichever case, your "arrow" is almost certainly too long, and even if it were travelling at significantly higher velocities your skinny aspect ratio will probably impair its ability to use its full length for armor penetration. Your projectile masses approximately 1kg. To accelerate that projectile to that speed over its own length requires an average acceleration of 125000 m/s2, which isn't completely unreasonable by gun standards. If pressure in the barrel were constant, you could pack your arrow in a 20 mm diameter [sabot](https://en.wikipedia.org/wiki/Sabot_(firearms)) and use a conventional propellant to get a chamber pressure of ~400 MPa which is similar to that in the Barret M82. Problem is, pressure in the barrel isn't constant, as it rises quickly to a peak and drops off, and it is sufficiently complex to compute I'm not going to try. If you used a chemical propellant for your gun, you might need either a much wider barrel or a much tougher one to withstand the shot (and that means weight). Note that conventional weapons throwing a ~1kg round include 40 mm autocannon, that have quite a chunky barrel that tends to be 50-70 calibers long (eg. 2-2.8 m), which eases performance requirements slightly (and probably helps accuracy a lot). Admittedly they have a much higher muzzle velocity, because 500 m/s is too slow to be useful to anyone, really. If you used a coilgun to throw your round, then [Luke Campbell's approximation](https://www.projectrho.com/public_html/rocket/spacegunconvent.php#id--Kinetic_Kill_Weapons--Coil_Guns) suggests you'd need a field strength of ~80 T, which implies some serious high-temperature superconductors on top of all your other material requirements. --- You should consider that your design is problematic on multiple fronts, and you're attempting to overcomplicate something that has already been solved using much simpler and more practical technology. Consider that things like the [M18 recoilless rifle](https://en.wikipedia.org/wiki/M18_recoilless_rifle) or even the classic [bazooka](https://en.wikipedia.org/wiki/Bazooka) offered economical and readily human portable antitank weaponry with armor penetration exceeding that of antitank rifles (which in turn were often more powerful than the .50 rounds you mention, eg. [Lahti L-39](https://en.wikipedia.org/wiki/Lahti_L-39), a 20mm rifle) over 80 years ago. Even the ubiquitous [RPG-7](https://en.wikipedia.org/wiki/RPG-7) is 65 years old, is straightfoward and cheap to manufacture, robust and easy to use and offers up to 750 mm penetration (though 300 mm seems more likely) of [RHA](https://en.wikipedia.org/wiki/Rolled_homogeneous_armour)... vastly more than your arrow could be capable of. Lighter futuristic equivalents could have more compact projectiles offering higher velocities and longer ranges and armor penetration suitable for lighter targets, and they could use other projectile types (fragmentation, thermobaric, whatever) for other targets making them much more versatile. (you could even look at modern [high-velocity 40 mm grenades](https://en.wikipedia.org/wiki/40mm#40%C3%9753_mm_HV_(40_mm_high_velocity)), which can penetrate ~50-80 mm of RHA using a shaped charge warhead, and are smaller, lighter and more versatile than your arrows, as another option) ]
[Question] [ Q:Can EM waves naturally create sonic waves? For example, could a natural antenna (e.g. a seam of conductive metal or the right kind of rock)receive em radiation and through thermal/mechanical or piezoelectric effects re-emit low-volume sound? Background: In some esoteric internet rabbit holes the Schumann resonance is mentioned as fundamental to some psycho acoustic effects (including 440vs432 conspiracy theories). As a plot point in my next book, I am considering a subterranean chamber of the right dimensions able amplify harmonics of the Schumann resonance which are naturally generated in the correct geology. Edit 1: Better fit this community's guidelines. Edit 2: Telluric currents [Answer] Yes, if the air becomes [ionised](https://en.wikipedia.org/w/index.php?title=Ion_wind&oldid=1149430005), either by the power of the antenna or through some other means. All you need then is to modulate your high-frequency carrier with an audio-frequency signal and you've got yourself what's basically a speaker made out of air. P.s.: This is a [real thing](https://cordis.europa.eu/project/id/816414) by the way. ]
[Question] [ While researching [Kwak'wala](https://en.wikipedia.org/wiki/Kwak%CA%BCwala), because I think the languages of the Pacific Northwest have this amazing aesthetic I want to mimic in some languages in my world, I came across the fact that the Kwakwak'awakw built [clam gardens](https://en.wikipedia.org/wiki/Clam_garden), which are these artificial very shallow lagoons that are designed to allow clams to grow and multiply in controlled and optimal environment, so they can be harvested more easily and in greater abundance than catching them in the wild. I thought this was a cool idea and wanted to add it to the cultures of my world, but the part of my world I'm working in is sort of a stand-in for Europe, and this got me wondering why aquaculture didn't seem to ever take off in Europe before the modern age, in the way that it did for the PNW or Polynesia or even East Asia. I mean, the Baltic Sea has molluscs, right? So why didn't e.g. Estonia ever develop clam gardens as far as I know? Is it just pure historical happenstance that it never occurred to them? Or is there some reason it wouldn't have worked? Or would it have just been too unproductive compared to agriculture to be worth it? Basically, when deciding whether or not to include this in a culture in my world, is there some objective measure that would tell me whether a culture would or would not practice aquaculture, or is "because they just do(n't) lol" as good an explanation as any? On that note, is there any reason you couldn't likewise have mussel gardens or marine snail gardens? I suppose the spirit of the question also extends to e.g. fish farming and seaweed/kelp farming. It seems like Europe had access to seafood but just didn't bother to extensively farm it for some reason until recently, and I would like to know if there's a particular reason for this beyond just "because they just didn't idk" that I should keep in mind when worldbuilding. [Answer] If you have a good amount of cultivable dry land, you wouldn't start putting effort in cultivating the sea. And before giving up on farming, you would try looking around for available places. In Europe this meant that civilizations would either farm the land they had or started colonies reachable with not too long travels, with the intention of getting more resources. This was done for example by Greeks and Phoenicians. Polynesia, on the other hand, had very little farmable land in the islands, so looking at the sea was more or less a forced choice. [Answer] Frame challenge, don't say they didn't practices aquacultivation if you haven't done the research. Europeans during the middle ages practiced aquaculture. Different from the methods pacific islanders used.. and mostly focused on fresh water aquaculture... But it was still aquaculture. Europeans gathered wild juvenile mussels and [moved them to safe places to mature](https://onlinelibrary.wiley.com/doi/10.1111/raq.12465), sounds pretty similar to a clam garden to me. Europeans traded all over the world with records from one monastery that date [back to 700 A.D](https://www.researchgate.net/figure/Sophisticated-aquaculture-engineering-of-a-monastery-pond-in-Medieval-Europe_fig2_361193934) and include trading with Asia for fish stock. King Philip II (16th century) introduced invasive species park, common carp, tench, and the Italian crayfish to the Iberian peninsula when he decided he wanted his fish ponds stocked with those species. Castles throughout Europe had fish ponds which were managed and stocked with fish (Fresh Fish was highly desired...). There were eel ponds throughout Europe, often located in mill ponds (though whether this was intentional, or accidental, eels can migrate overland). And some mills paid their taxes in eels. They passed laws to promote sustainable fishing. Outlawed fishing during spawning seasons, set minimum net hole sizes to prevent the capture of fish below a certain size, outlawed types of fish trapping deemed too destructive to the fish populations. Limited access to beaches depending on the season. Created fish sanctuaries. Created eel sanctuaries. Limited catch sizes. .. The list goes on, and on, and on. ]
[Question] [ Humans are stranded on a world with .75 Earth gravity. How would that affect their physical evolution? Specifically, would they be taller, thinner, and have less bone mass? [Answer] This is similar to the following closed question: [How can lower gravity affect evolution?](https://worldbuilding.stackexchange.com/q/107338/40609). There would definitely be less bone density, it's a [known problem already](https://www.nasa.gov/mission_pages/station/research/benefits/bone_loss.html). But taller and thinner? Not necessarily. In fact, probably not. At issue is the wondrously wide variety of humanity today. We already have short and tall, thin and thick, athletic and not so much... and every combination of those things. The only real guarantee you'd have is that their leg, hip, and back muscles would be underdeveloped compared to their Earth counterparts. ~~Maybe, maybe, the average would shift to thinner (not taller, though).~~ (See addendum below.) But that's the average, lost within that wondrous variety previously mentioned. *Addendum: Now that I've thought more about it, it's more likely that the people of your low-gravity world would be fatter than their Earth counterparts. Unless their behavior changes with the low gravity, they're arriving with the same predilections for sugar, carbohydrates, fats, and, well... BBQ... that humanity has had since time immemorial. With a lower gravity, they're more likely to become fatter. If they became thinner, it would be due to cultural changes that set them apart more from their Earth counterparts than what any evolutionary changes did ("What? You don't eat BBQ? What kind of alien invader are you? That's so un-Texan! I mean, un-American!... I mean...* You're not from Earth, are you?"). Finally, remember that evolutionary changes take a honking long time. [Answer] ## It Could Possibly Effect Our Developmental Morphology There is a difference between developmental morphology and evolution. There may be morphological differences between a human who develops in normal vs lower gravity without a single change to thier genetics. However, it is hard to predict exactly what these changes will be since there is no real experimental evidence to suggest what long term slightly reduced gravity will do. We know about all sorts of issues with long term zero G living for adults, but nothing about long term exposure to .75G, or what effect lower gravity has on developing children. Since we don't know, then any conjecture is equally valid. It is possible your humans will land on this alien world, and the very next generation of humans will be noticeable taller and skinnier just because they developed under different environmental factors than thier parents did. It's also possible that colder temperatures, higher atmospheric oxygen, or the nutritional qualities of the local food sources could cause similar changes in the next generation having nothing to do with gravity at all. ## Evolution Is Much Less Probable The issue with pretty much every "Will X cause humans to evolve Y?" question is that modern humans experience very little natural selection the way that animals do. Evolution does not happen just because some new trait would be nice to have, it also requires than the existing trait be so unfit for genetic survival that people with it are noticably less likely to raise surviving offspring. Because we modern humans have medicine, advanced defensive technology, and don't just let each other die off for being a little bit slower or weaker, then your short humans and tall humans will both have the same basic chance to pass on thier genes. Even if short people for whatever reason had a distinct physical disadvantage, humans have a way of overcoming physical disadvantages through specialization of labor. This may lead to increased genetic diversity in the future with more people of both exceptionally tall and short frames, but not a general push to evolve in either direction. As to comments about sexual selection, there is actually a lot of reason to believe that this is not a major evolutionary factor in civilized humans either, because we are a generally monogamous species. The kinds of species where sexual selection overpowers selective fitness are generally Harem Polygamies. In a Harem Polygamous species where you put together 10 males and 10 females, the #1 male gets all 10 females. This emphasis on being #1 means that not being sexually ideal is not an option. But, in a monogamous or polyamorous species, The #1 male generally pairs with the #1 female, the #2 male with the #2 female, etc. In fact, the #1 male will generally refuse to mate with the #10 female, even if given the opportunity. This means that even the least desirable of the males (in this case, the shortest) still has a good chance of securing breeding rights. Normally this means that sexually unfit characteristics get paired with selectively unfit characteristics for removal from the gene pool, but going back to modern humans being less likely to ever be selected against, it means that sexually undesirable traits are much more likely to be passed on than in other species. So, the most likely reason you would see for humans to Evolve to be taller is if your world introduces something that selectively kills or sterilizes your short people or if civilization on this world collapses for a really long time so that the alien predators or constant warfare get to have enough generations of killing off the shorter slower humans to impact the gene pool, or if major and extraordinarily long lasting cultural changes were to take root. ]
[Question] [ So, humans have colonised this planet. It is of Earth-mass and volume and so has Earth-like gravity. They are now building a dome to accommodate the population. The question is, how big can they make it? ## Background info: The dome is made from three-inch thick panes of synthetic diamond (built by nanotech). There are two layers of these panes, one on top and the other beneath a steel latticework. This double-layer design is to retain heat, rather like a gigantic thermos. There are no supporting pillars or struts. What is the maximum size a dome of this nature could theoretically reach? [Answer] There is no theoretical limit based on loading/stress. Geodesic domes get stronger the bigger they get. There may be other limiting factors such as: * Availability of materials, though if it's just carbon this won't be a very limiting limit. * The lay of the land – whether there a river, canyon, bog that makes it hard to build there If you are writing a civilisation with diamondoid nanoassembly, that's saying they have extraordinarily high technology. A large dome isn't going to stretch credibility further than making diamonds out of dirt. The steel will act as a 'thermal bridge' conducting heat out, like metal bolts do in a mundane roof. [Answer] This calculation might not be 100% accurate, but let's give it a try: The maximum size of the dome would be limited by the strength of the material used to construct it. In this case, the dome is made of synthetic diamond, which has a high strength-to-weight ratio and can withstand significant loads. However, even with synthetic diamond, there would still be limits to the size of the dome due to the laws of physics and the weight of the dome itself. The final size would depend on factors such as the dimensions of the panes, the strength of the steel latticework, and the load that the dome would need to support, such as the weight of the atmosphere inside the dome. Let's assume the dome has a height of "h" and a radius of "r". The volume of the dome can be calculated as: > > V = (2/3)πr^2h > > > The mass of the dome can be calculated as the product of its volume and the density of synthetic diamond, which is approximately 3.52 g/cm^3: > > m = ρV = (3.52 g/cm^3)(2/3)πr^2h > > > The compressive strength of synthetic diamond is approximately 4.5 GPa. The compressive force on the lowermost layer of diamond blocks can be calculated as: > > *F = m \ g > > > where "g" is the acceleration due to gravity (9.8 m/s^2 on Earth). The compressive stress on the lowermost layer of blocks can be calculated as: > > σ = F / A > > > where "A" is the cross-sectional area of the lowermost layer of blocks. If this stress exceeds the compressive strength of the diamond, the blocks will fail. Setting the compressive stress equal to the compressive strength and solving for the mass "m", we get: > > m = F / (σ / ρ) = (4.5 GPa) \* A / (g / ρ) > > > Finally, we can use the volume equation to calculate the maximum height "h" of the dome: > > h = (3m / (2πr^2ρ)) = (3 \* 4.5 GPa \* A / (2π \* r^2 \* g \* ρ^2)) > > > Note that this is a rough estimate and the actual size of the dome would depend on many other factors, such as the distribution of stress and the presence of any internal loads or stresses. To get the maximum size of the dome in meters, we'll need to plug in numerical values for the variables. Let's assume a compressive strength of 4.5 GPa and a density of 3.52 g/cm^3 for the synthetic diamond, and an acceleration due to gravity of 9.8 m/s^2. Using the formula we derived above: > > h = (3 \* 4.5 \* 10^9 Pa \* A) / (2 \* pi \* r^2 \* 9.8 \* 3.52^2 g/cm^3) > > > We can simplify this further by assuming a certain cross-sectional area "A" for the blocks. For example, if we assume each block has a square cross-section with sides of length "s", then: > > A = s^2 > > > Substituting this into the formula and simplifying: > > h = (3 \* 4.5 \* 10^9 \* s^2) / (2 \* pi \* r^2 \* 9.8 \* 3.52^2) > > > This equation can be solved for the maximum height of the dome for a given radius "r" and block size "s". The maximum size in meters will be the maximum height "h" for a given radius "r". Plugging in the values of r = 10000 m and s = 10 m into the formula:** h = (3 \* 4.5 \* 10^9 \* 10^2) / (2 \* pi \* 10000^2 \* 9.8 \* 3.52^2) h = (3 \* 4.5 \* 10^11) / (2 \* pi \* 10^8 \* 9.8 \* 3.52^2) h ≈ 473.9 m *So for the given values of r = 10000 m and s = 10 m, the maximum height of the dome would be approximately 473.9 meters.* ----------------------EDIT----------------------------- For a hollow dome it's a bit more tricky to exactly determine a maximum height but we can try: Formula to estimate the maximum height of a hollow dome: > > h = (F\_total \* t) / (pi \* r^2 \* E \* A) > > > Where: h is the maximum height of the dome F\_total is the total force acting on the dome ( total compressive force that the dome is designed to support ) t is the thickness of the dome's walls r is the radius of the dome E is the Young's modulus of the material used for the dome's walls A is the cross-sectional area of the dome's walls Note that this is a simplified formula that assumes the dome's walls are uniform in thickness and composition and that the load is evenly distributed over the entire structure. The maximum height of a hollow dome would likely be limited by the weakest point in the structure, which could be influenced by a number of factors such as the composition and thickness of the walls, the size and shape of the interior space, and any internal loads or stresses. This formula is intended to provide a rough estimate of the maximum height of a hollow dome, and a more detailed analysis would be necessary to obtain a more accurate result. There are several factors that limit the maximum height of a hollow dome, including: 1. Strength of the material used for the dome's walls: The walls of the dome must be strong enough to support the weight of the dome and any additional loads it may experience, such as wind, snow, or earthquakes. The maximum height of the dome will be limited by the strength of the material used for the walls. 2. Cross-sectional area of the dome's walls: The cross-sectional area of the walls will affect the amount of stress that can be borne by the walls. A larger cross-sectional area will result in lower stress and a higher maximum height. 3. Internal loads and stresses: The dome may experience internal loads and stresses due to changes in temperature, humidity, and pressure. These loads and stresses will affect the maximum height of the dome. 4. Shape and size of the interior space: The size and shape of the interior space will affect the distribution of loads and stresses within the dome. 5. Design and construction: The design and construction of the dome will play a role in determining the maximum height. Factors such as the thickness of the walls, the size and shape of the interior space, and the presence of any internal loads or stresses will all influence the maximum height. Let's assume that the synthetic diamond has the same resistance as a natural one and the walls are three-inch thick as OP mentioned ( the thickness will limit the height a lot, if we could increase this value we could achieve higher heights ) A, the cross-sectional area of the dome, can be calculated as follows: > > A = (pi \* t^2) / 4 > > > where t is the thickness of the dome wall (3 inches or approximately 0.0762 meters). Plugging this value into the equation, we find that > > A = (pi \* 0.0762^2) / 4 = 0.00451 m^2. > > > Since we can't know for sure the exact value for F\_total in this example, I'm assuming values comparing to the world's tallest building, which could be in the range of millions of tons ( it's built to resist wind loads, seismic forces and the weight of its structure ) Assuming F\_total as 100.000.000 tons ( had to go this high because of the thickness of the walls, may be a good idea to increased the thickness ) Using the formula > > h = (F\_total \* t) / (pi \* r^2 \* E \* A) > > > With the following values: F\_total = 100,000,000 tons = 100,000,000 \* 10^6 g t = 3 inches = 0.0762 m r = 10,000 m E = Young's modulus of diamond = 1,000,000 N/m^2 A = cross-sectional area = pi \* r^2 = pi \* 10,000^2 = 314,159,265 m^2 Plugging in these values, we get: > > h = (100,000,000 \* 10^6 g \* 0.0762 m) / (pi \* 10,000^2 m^2 \* 1,000,000 > N/m^2 \* 314,159,265 m^2) > > > h = approximately 213.82 m BUT, if we can't get our F\_total ( total compressive force that the dome is designed to support ) that high , our height is drastically reduced. Example: Using F\_total=1.000 tons and other values as follows: t=0.0762m (thickness of the diamond panes, which is three inches) r=10000m (radius of the dome) E=1050GPa (Young's modulus of natural diamond) A=1 (assumed area) we can calculate the maximum height of the dome as follows: > > h = (F\_total \* t) / (pi \* r^2 \* E \* A) > > > h = (1.000 \* 0.0762) / (pi \* 10000^2 \* 1050 \* 1) > > > h = 0.114m So, with these assumptions, the maximum height of the dome would be approximately 0.114m. Well, I don't think we can go further than this in especulations and calculations, I hope it helped in some way! Also is worth saying that i'm not a mathematician or physics specialist, some things may not be 100% accurate. [Answer] There was a question a few weeks ago about the size of a dome on the moon. The limits for us are probably set by economics and risk analysis rather than by engineering. If you have a giant dome, and a steady supply of raw materials, then the time taken to build a dome will go as (roughly) the square of the dome area. The risks of the dome being penetrated by a meteorite or some other random event go as the square of the area. if all the air escapes, the costs of the damage might go as the square of the area. We are already up to the sixth power of radius, and we could go higher. The advantages of building many small domes are enormous. You might design one a mile across to win an architectural award, and let your client pick up the tab. This is not entirely silly - think of the glass cupola of the [Albert Hall](https://londonist.com/london/secret/behind-the-scenes-at-the-royal-albert-hall-part-2) in London. For more info, ask [Tom Scott](https://www.youtube.com/watch?v=q3LuZeekVX4) <https://londonist.com/london/secret/behind-the-scenes-at-the-royal-albert-hall-part-2> [Answer] One key parameter is the atmospheric pressure. If it's significantly less than on Earth the mass of the dome might partially be supported by internal pressure. If the pressure is very low like on Mars the entire dome could be supported. One big issue with a dome on Mars is containing the pressure, but in a truly massive dome 15lb/sqin could support a lot of heavy structural elements. If supported by internal pressure in this way there need not be any limit to the size of the dome based on the mass of the structure of the internal pressure. ]
[Question] [ As of 2021, global electrical production was [about 7 TW](https://www.statista.com/statistics/267358/world-installed-power-capacity/). And the largest single power plant is the [Three Gorges Dam](https://en.wikipedia.org/wiki/Three_Gorges_Dam) at a capacity of 22.5 GW. My hero needs a single power plant with 50 times more capacity. What types of generation are possible? * Is there a large enough river for hydropower? It would need to be 50x the scale of the Three Gorges Dam, or 15x the size of the largest proposed [Grand Inga Dam](https://en.wikipedia.org/wiki/Grand_Inga_Dam). * The [largest coal plant](https://en.wikipedia.org/wiki/WA_Parish_Generating_Station) is 3.5 GW. Could it be scaled up 300x? * Nuclear options? Uranium fission or D-T fusion? The latter would require a solution for tritium supply. * Solar and wind are out because the required area would be too large. * Some kind of geothermal megaproject? [Answer] If you want a single plant, and don't want wind/solar (which technically are many smaller plants), these are the possible solutions in order of least practical to most practical: Hydropower comes close: The Atlantropa dam could have generated up to 0.4TW at perfect efficiency. I doubt there is a bigger source of hydropower than the entire Mediterranean sea drained by 200m, but with some clever megaproject-engineering, it may be possible. Geothermal is unfortunately not very energy-dense per m^2. It's technically possible - the earth's core produces 44TW of energy every year via nuclear fission - but to capture even just a single terawatt of that would require encasing the entire land area of Russia in a massive thermo-electric blanket of some sort. I do not know enough about nuclear to comment on it with much confidence, but it seems like nuclear fission plants have relatively small (1GW) power outputs. To get more power, you would link many of these together - this is already commonly done, as in the largest nuclear plant, Uljin NPP: a power production of ~7GW, from 6 reactors. Fusion is more speculative, as no plants exist yet, but I believe that the power density is expected to be smaller than fission, which makes very high-power designs even more unlikely. But if the story requires it (does it really require it?) a large collection of reactors is entirely possible. Space-based solar power is something that you might consider, especially if the setting is sci-fi. In the late 1970's, NASA conducted a very thorough study on this topic, with a proposed system design of 30 3GW power stations orbiting earth in GEO. By increasing the size of the station from 5x10km to 16x30km, 30 stations would give ~1TW. Further increases could result in a single station with TW capacity, at about 120km square. However there is no need for each space-based station to have its own ground station - all 30 or more satellites could point at a single ground station. See also Willk's answer for a lunar variant on SBSP. Note that the required size of the rectenna (energy collector) on earth for a Lunar SBSP will be about 10 times bigger (~100km diameter) than for GEO based SBSP (~10km diameter). It is possible to use the land under a rectenna for farming. Coal would probably work. But it would not be very nice. Currently, the world's generation of electricity from coal is almost 1TW, and has been higher in the past. There are enough coal reserves (and most coal is not used for electricity) that doubling electrical production from coal would not significantly change the estimated end-of-supply for coal. HOWEVER, if it was all at a single plant, it would be a disgusting industrial complex - black with soot, etc. Even with strict cleanliness rules, fires and explosions would likely be common due to coal dust. But this might be beneficial to the setting. Depending on what setting will best enhance your story's message, you could probably pick any of these. [Answer] # Hydrogen Fusion Sure, Deuterium-Tritium fusion is really is impressive. But what if we look for something even more powerful? Something that is much more cleaner, i.e. doesn't release a b\ttload of neutrons during fusion? Behold, I present to you, Aneutronic Fusion (Hydrogen Fusion). In simple layman's terms, ordinary hydrogen has just 1 proton in its nucleus and 0 neutrons. This makes it the lightest element in the universe. This element is also extremely abundant. The Milky way is composed of more [than 70% hydrogen](https://en.m.wikipedia.org/wiki/Abundance_of_the_chemical_elements), for reference. Pound for pound, [fusing hydrogen](https://en.m.wikipedia.org/wiki/Energy_density) releases nearly 50% more energy than fusing Deuterium and Tritium atoms together, and 10% more energy than simply fusing only Deuterium. This proves to be an advantage. You can find hydrogen anywhere. Stars, nebulas, gas giants, you name it. Heck yes, you can just get it free from the oceans. Just dissolve some lye or a strong base in water, pass some electricity through it.... BOOM! There you have it, simple hydrogen. Deuterium on the other hand constitutes only [0.015%](https://en.m.wikipedia.org/wiki/Deuterium) percent of the Earth's crust. This isn't a problem, as this is sufficient enough for us. But tritium.... well, it is, two words, EXTREMELY RARE. At any given moment, there is just 15 pounds of tritium naturally occuring on Earth. This is because tritium is radioactive, with a half life of 12 years. Tritium is also extremely hard to synthesize, requiring a ton of complex fancy apparatus and bombarding Lithium with neutrons and stuff. In other words, it is a PITA to synthesize tritium. Fusing 1 kg of hydrogen (Protium), releases nearly 640 TJ of energy, 2% of which is lost due to neutrinos, but the loss is so insignificant that it is easy to ignore it. 640 TJ of energy is basically enough to boil 2 billion liters of water. Using a conventional steam turbine, you can convert this heat energy into hundreds of terawatts of electricity, something that your hero will be very pleased with. However, there are multiple drawbacks to this: Protium/hydrogen fusion requires temperatures and pressures that are beyond what we can generate in a lab. You need hundreds of billions of atmospheres of pressure and millions of kelvins (The temperature part is easy, the pressure part is really hard) to create conditions suitable for fusing protium to generate energy, which is a reason why most fusion reactors favor D-T fusion over P-P fusion reactions. But this can easily be ignored, considering that this is your story and you can simply handwave the issues away. * Making a fusion reactor requires vast amounts of money, but that can be ignored, assuming that your hero is some trillionaire guy to whom money isn't a money. Overall, hydrogen fusion reactors should be something that your hero should consider building to generate not just 1 TW but a power plant that generates hundreds of terawatts of electricity, and also, completely neutron-free. [Answer] ## Multiple Smaller Linked Plants Consolidating from a few comments on the question -- to quote @AlexP, "a watt is a watt is a watt". Get enough smaller generators to meet your power needs and network them together, and that will look like a single 1 TW source to whatever's plugging into them. Keep in mind that basically all major power plants work this way already, including the ones you mention in your example. Hydroelectric dams have multiple turbines all working together, nuclear plants usually have several individual reactors, fossil-fuel plants have multiple burners and turbines, solar farms have hundreds of separate panels, etc. This is important both for scaling and for redundancy, since you can shut the various components off individually as needed for maintenance or to manage output. Granted, networking the plants to provide 1TW of power to a single point that your hero can tap into is going to be an engineering feat of its own. I'm curious to see what a power cable rated for that sort of capacity looks like! [Answer] 1 terawatt? 1 measley terawatt? Sure you can have a terawatt. Let me introduce you to Luna Ring <https://www.engineering.com/story/could-a-lunar-solar-array-power-the-entire-earth> [![luna ring](https://i.stack.imgur.com/B18P6.png)](https://i.stack.imgur.com/B18P6.png) > > Dubbed the Luna Ring, the project is “a large scale concept [looking] > to create a new form of energy infrastructure”. As imagined by the > Shimizu Corporation, the Luna Ring would be composed of thousands of > solar panels arrayed along a 400km (250 mile) stretch on the Moon’s > 11,000km (6,800 mile) equator.Using microwaves and laser light, the > Luna ring would beam power back to Earth in a continuous stream, > creating an “almost inexhaustible amount of energy.”According to the > Shimizu Corporation, if their Luna Ring project were built on the side > of the moon that consistently faces the Sun the entire system could > generate around 13,000 terawatts (TW) of power. For the sake of > scale, global power consumption reached 16 TW in 2006, meaning the > Luna Ring could provide over 800 times more energy than we currently > consume. > > > Yeah your hero can swipe a terawatt here and there. Luna Ring will not even notice. Chump change. [Answer] ## Time for some solar power satellites (SPS) As the area required is in space, I don't think the objection for area required really applies in their case. Problem is the cost to lift materials into orbit is prohibitive - so don't do that. Plan on capturing a convenient near-earth asteroid and converting it into about 10,000 sq. kilometers of SPS - enough for 1 TW. The microwave or laser receiver you need to be based on the earth will still be considerable, but much less than the equivalent area required to collect 1TW of land-based solar power. I have just the asteroid you need, Apophis - as described in this article about [converting Apophis into a SPS](https://web.archive.org/web/20111212205647/http://www.nss.org/settlement/asteroids/capture.html) From the article, there is sufficient material to convert Apophis into about 750 GW worth of SPS. You would be advised to capture a few smaller (150 m) asteroids first to get experience converting them into 50 GW worth of SPS each before converting Apophis. As a bonus, you also have over 100K worth of space habitation that would be immensely value for industry, research and tourism. Elon Musk will be jealous. ]
[Question] [ For purposes of realistic, but otherworldly visualisations of foreign worlds I'm wondering what the fastest speed is that a moon will track through the visible sky, as observed from the body of a planet (or other moon). As in, the moon rises, the observer watches it move across the sky, and the moon sets on the opposite horizon. My intuition says that there exist a bunch of limits here... Orbital (angular) velocities depend on orbital height, and there are limits to that depending on the masses of two bodies. Then the rotation of the observers planet/moon plays a role too, but I assume there are limits here as well in terms of what is realistic or physically stable for celestial bodies. How quickly could a moon appear and disappear after tracking once through the sky overhead? Hours? Minutes? Less? Assume: * The planet/moon the observer is standing on can support... well a human observer standing on it. At least in a spacesuit - so this gives certain upper/lower bounds in terms of g-force/size/mass. * The orbital system is stable (more or less) - so no rogue moon flashing by. * Assume the moons track in the sky traverses through the zenith (so not just shortly peeking over the horizon for a second, as the sun does in arctic fall/spring). [Answer] Somewhere in the area of an hour, for large moons. If you want a nice cinematic view with a large moon, it has to be orbiting relatively far away otherwise it'll be destroyed by tidal forces. Orbiting far away means it orbits slower, and so it moves slower. The Moon moves across the sky primarily because the Earth rotates, and not really because of the Moon's orbit as it's orbiting so slowly. For a large satellite, the planet can rotate a lot faster before centrifugal force pulls it apart than the satellite can orbit closely before it gets ripped apart. Using Universe Sandbox (which is a fantastic tool for mostly accurately simulating systems like this), it shows that the Earth would need to spin approximately once every 70 minutes or so to rip itself apart. The Moon at just above the Roche limit would only orbit every seven hours; much slower. This is similar for most bodies I tried out. Whilst a planet spinning at close to its own escape velocity would be... an experience, to say the least, it's definitely survivable especially at the upper latitudes. [Answer] I am misusing the prefix "geo-" to refer to this other planet rather than earth. assuming this moon is natural and not the result of a geolocically recent event it is at or above geosynvchronous altitude, this puts an asymptotic lower limit on orbit time at 1 local day as observed. Below geosynchronous orbit tidal drag would decellerate\* the moon causing it to spiral down and crash over geological time. * by decellerate I mean apply a force in opposing its relative motion, not make it go slower, orbital mechanics is perverse. [Answer] Consider [Jasen's answer](https://worldbuilding.stackexchange.com/a/239212/21222) for a limit on systems that are stable for billions of years. The stable limit will have you see the moon go over the sky in about half a day. Also consider [Lura Skye's answer](https://worldbuilding.stackexchange.com/a/239217/21222) for a lesson in cruel astrophysics. If your day lasts a few minutes, well... Let me add a different scenario, one that we have in the real world. [Phobos orbits Mars really fast:](https://en.wikipedia.org/wiki/Phobos_(moon)) > > Phobos orbits 6,000 km (3,700 mi) from the Martian surface, closer to its primary body than any other known planetary moon. It is so close that it orbits Mars much faster than Mars rotates, and completes an orbit in just 7 hours and 39 minutes. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day. > > > For reference, a Martian day lasts just 37 minutes more than an Earth day, Since Phobos orbits Mars below the synchronous limit, its orbit is decaying. According to some estimates it will reach the Roche limit and be destroyed in 43 million years. The wikipedia article I linked above elaborates further on this. [Answer] Short answer: A few hours seems to be the lower limit regarding air resistance I feel like your observer is probably fine, assuming the masses of the earth and its moon. The gravity of the earth is always higher than the moons gravity, even if they would touch each other. The observer might not want to live there and experience a few strange moments and spectacular tides, but should be fine otherwise. I would guess that air resistance is actually the limiting factor. Low-earth-orbit Satellites and space stations orbit the earth roughly 400 km above the surface and take ~90 min for it. The main problem here is air resistance. Even at this height, they have to accelerate occasionally, to compensate for it. The orbit of the moon at this height would not be stable since the velocity would decrease over time and it would fall. Honestly, I don't really know at which height the air resistance can be neglected so the orbit would be stable for the foreseeable future. A very close moon will also cause "atmospheric tides", so the atmosphere will be thicker at the side facing the moon. A few thousand kilometers (wild guess) distance might be enough to have a stable orbit for a while, this would correspond to a few hours per cycle. I'm intentionally vague here, since this is so speculative. [Answer] Frameshift: What sort of "world" is permitted? I'm thinking of a "moon" that's actually a planet orbiting just inside a ringworld. Flyby velocity will be in the ballpark of .001c. ]
[Question] [ I am trying to create a boreal, alien ecosystem loosely based on Northern Siberia. Liquid rain never falls here, since snow and hail fall instead for most of the year, and the short, hot summers- the only time temperatures rise above freezing- are arid and without any precipitation whatsoever. Terrestrial organisms in this ecosystem can either get water from snow directly, drink from unfrozen patches of lakes and rivers, or take their fill when the snow melts in the summer. Water (at least in liquid, drinkable form) is often scarce. Since liquid rain normally never falls, the native creatures are mystified when sudden global warming causes drinkable water to start falling freely from the sky instead of snow. Is it feasible for this environment to exist in a state that allows for complex life? [Answer] You can get rid of the Summer altogether. Just make it "very freezing" to "just freezing"; so it is not possible for rain to fall. But as was mentioned by JBH, sunlight can still heat the ground, when it is "just freezing", enough to melt the snow. You can also make your plants evolve some thermoconductivity so leaves can absorb and store heat from the sunlight, and then snowfall on the leaves will melt and be absorbed. To do that, make the leaves pitch black, and salty; both dark colors and salt are very good at absorbing and retaining heat from light. If you don't like Black leaves, maybe Red, if you must reflect a color red is a low energy color, you want to absorb the higher energies (frequencies) in the color spectrum. Conduct the heat to internal salty sap for storage, that is what keeps the leaves from freezing too solid. So the idea is, you have intermittent snowfall (not every day, and it doesn't have to be year round), a snowflake falls on the leaf, it melts, the water is absorbed. During the day with sunlight, the leaves get recharged with warmth by the sunlight. But it never rises above freezing, and never rains: It just gets close. Then some sort of global warming may push it above freezing, so liquid rain starts falling. That shouldn't affect the forest too much I wouldn't think, the leaves had to melt the snow to absorb the water, now they don't but could still absorb water. They would not behave differently. But now you have issues with runoff and such. Also I did not address snow accumulation; but it might be reasonable, as JBH said, for sunlight to also warm fallen snow enough to melt it into the ground. You just cannot have it snow every day; you need some sort of cycle to deal with the snowfall, or it will literally build up to be tens of kilometers thick, as it is at the Earth's poles. The tallest tree in the world is only 380 feet tall (about 116 meters), and constant snow can accumulate much faster than a tree can grow. You need to average near zero snow on the ground in your snow/melt cycle, or perhaps an inch a year. [Answer] No axial tilt. Seasons are due to eccentric orbit. Earth seasons are because of axial tilt. The poles take turns being closer and farther from the sun. <https://www.weather.gov/lmk/seasons> [![seasons and axis diagram](https://i.stack.imgur.com/GLuW2.png)](https://i.stack.imgur.com/GLuW2.png) > > The earth's spin axis is tilted with respect to its orbital plane. > This is what causes the seasons. When the earth's axis points towards > the sun, it is summer for that hemisphere. When the earth's axis > points away, winter can be expected. Since the tilt of the axis is 23 > 1/2 degrees, the North Pole never points directly at the Sun, but on > the summer solstice it points as close as it can, and on the winter > solstice as far as it can. > > > With no tilt there is more uniform heating of your planet at all times of year. The equator is still warmer and the poles cooler because the planet is round and so the equator bulges closer to the sun. The no axial tilt thing is because alternating seasons on the poles might make one of them warm enough for it to rain. --- Your planet has seasons. It is the same season everywhere on the planet. Your seasons are because of orbital eccentricity. Earth's orbit is nearly circular. The planet is about the same distance from the sun at all times of year. A small increase in eccentricity leads to large changes in solar energy delivered over the year. <https://www.sciencedirect.com/topics/earth-and-planetary-sciences/eccentricity> > > Earth's orbital eccentricity e quantifies the deviation of Earth's > orbital path from the shape of a circle. It is the only orbital > parameter that controls the total amount of solar radiation received > by Earth, averaged over the course of 1 year. The present eccentricity > of Earth is e ≈ 0.01671. In the past, it has varied between 0 and > ∼0.06. The eccentricity value can be used to compute the difference in > the distance from Earth to the Sun between their closest and furthest > approaches (perihelion and aphelion); presently, this amounts to 2e ≈ > 3.3%. At maximum eccentricity, the annual variation of solar insolation due to eccentricity is thus 24%. > > > Your planet has more eccentric orbit such that solar energy delivered in summer (closest approach to star) and winter (furtherst from star) differs by 300%. <https://en.wikipedia.org/wiki/Orbital_eccentricity> [![eccentric orbits](https://i.stack.imgur.com/BIS1m.gif)](https://i.stack.imgur.com/BIS1m.gif) It does not rain in summer because as the planet heats in its entirety, the ability of the atmosphere to hold moisture increases. The moisture evaporates and stays in the air. Hot air holds more moisture, which I remember because your breath is hot, and it holds moisture, but in cool outside air the moisture in your breath condenses out as it cools, and you can see those droplets as fog. At the poles a lot of melting snow makes it into the ground. Plants can grow at the poles during the short summer and into autumn. Because of the equatorial bulge and distance from the star, day and night temperatures differ most at the equator. As summer ends and the planet moves away from the sun, at night it cools enough that the air cannot hold all the moisture it accumulated in the day. It rains a lot at the equator in autumn. This pulls moisture laden air from the poles and so precipitation there is delayed until later in the year. By the time the autumn storms settle down the situation reverses. It is cold enough at the poles for most of the year that little water evaporates. The equator is still warm enough for water to evaporate and moisture laden air moves north and drops off its water as snow as it cools. Thus: 1: Homogenous seasons planetwide. 2: Warmer at the equator, cooler at the poles. 3. Water cycles: Dry summer everywhere. Rainy equatorial autumn. Snowy polar winter and spring. [Answer] There are ecosystems in which there is essentially no precipitation ever. This is why Egypt is the "Gift of the Nile." Snow and ice make it easier. The geology of the land has to be such that the water does not just run off when it melts. Ideally there would be places that were positively soggy after the snow melt, but as long as enough is retained to live, life will do so. In that brief season, there are plants and animals that seize the day and do all their living. This can be quite strenuous; in North America, the skunk cabbage is capable of melting the snow to break through and start its very early flowering. ]
[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/235164/edit). Closed 1 year ago. [Improve this question](/posts/235164/edit) In my world, there is a species of squamates from the Toxicofera clade named dragons (their scientific name is Draco draco). Some of their characteristics include: 1. In comparison to human beings, they have a better sense of smell, a better sense of eyesight (they are tetrachromats), and a better sense of taste, but they have a worse sense of hearing, and a worse sense of touch. 2. They have the ZW sex-determination system. 3. They are adolescents all their lives, in the sense that they never stop growing (the record for the longest dragon is 12.75 meters long). 4. They are oviparous, and they have between one and eight eggs by offspring, the average is 3.4. 5. They are 0.25 meters long when they are born, and they start reproducing when they are 2.5 meters long, this length happens when they are at least 25 years old. 6. They are facultative bipeds like chimpanzees (in other words, they can walk bipedally but not often, and they have a hunchback gait). 7. Their wings are their arms, and juveniles can fly as well as wild turkeys, but adults only glide like colugos, but, when they are at least 5 meters long, which happens whey they are at least 100 years old, they do not fly or glide at all. 8. They are almost immune to cancer like naked mole-rats. 9. They have human-level intelligence when they are juveniles, but elephant-level intelligence when they are adults. 10. Adults have gorilla-level strength. 11. They are as social as emperor penguins when they are juveniles, but when they are adults, they are almost never found in groups larger than five individuals. 12. They are sequential omnivores: juveniles are omnivores with carnivorous tendencies like raccoons, and adults are omnivores with herbivorous tendencies like squirrels. 13. Juveniles are as warm-blooded as polar bears, but adults are lukewarm-blooded like great white sharks. 14. Juveniles are as aggressive as wild boars, but adults are as peaceful as basking sharks. So, I wonder how could a species of tetrapod have a radical change of multiple things (including control of body temperature) when becoming an adult? [Answer] The answer is point #14. Being ectotherms their metabolism level is linked to their body temperature: the warmer they are the more active they are and thus more aggressive they can be. Because the juveniles are very aggressive they have evolved to be semi-endotherms and generate extra body heat by some mechanism such as muscle vibrations or whatever to boost their metabolism level to support their high aggression. But this uses up a lot of energy, so as they mellow out as they mature they no longer need to do this and so they gradually revert back to their full ectothermic mode. Also, as they grow the square-cube relation will mean that they no longer need to generate much internal heat to maintain a reasonable (but not as high as juveniles) body temperature, because they lose less heat to the environment compared to their body mass even as full ectotherms than the smaller juveniles. [Answer] # Stoking the Flame Being an [endotherm](https://www.washingtonpost.com/lifestyle/kidspost/ever-wondered-about-warm-blooded-and-cold-blooded-animals/2015/11/27/575d30ca-6c57-11e5-aa5b-f78a98956699_story.html)([warm-blooded](https://biology.stackexchange.com/a/7080)) means that an animal generates warmth by raising its metabolism for the purpose of generating heat in order to maintain a constant body temperature. Your dragons are simply endotherms in the traditional sense constantly maintaining their own body temperature. They won't turn [ectotherm](https://en.wikipedia.org/wiki/Ectotherm)(reliant on outside factors for heat, which is often called cold-blooded), but their average body temperature lowers with age. They generate too little warmth to sustain themselves using movement, or it might cost them more warmth than it creates. Instead, they got a unique organ("flame") somewhere high up in their torso that generates a lot of heat. The heat is spread around their body by way of their blood. This causes their blood to be warm. When the dragon grows, its "flame" does grow too. It is, however, very costly to keep their "flame" burning, becoming far worse when they grow because of square-root shenanigans. The answer to this? Burn less hot. They simply lower the activity of their "flame" to be able to keep up with demand, which also lowers their body temperature. As a side effect, lower body temperatures lower the activity of other organs, which further lowers energy expenditure. Largely Lethargic As above, their level of activity, or energy level, scales inversely with size. This can be because they are becoming less hot-blooded (and hot-headed) when they grow up. Their blood being cooler when larger causes large variants to become sluggish, and even lethargic at larger sizes. Young dragons can feed themselves on prey animals. As their size increases, so does their need for food. At a point, a dragon won't be able to sustain itself hunting and will be pushed to use less and less energy hunting to offset its relative lack of energy gained from food. This has them go from actively hunting, to waiting in ambush, to just slowly eating whatever is in reach of their mouths. Once they are of a large size, nearly no prey is worth catching because becoming more active requires stoking their "flame", which costs a lot of their reserves. More than most prey would offset. Their intelligence and lethargy combined make them learn this somewhen when transitioning to herbivorous meals. Dragons may still hunt extremely large prey, eat carrion they stumble across, or eat meat that walks directly into their mouth. End result Dragons become colder-blooded and less aggressive when growing in size. That said, if a dragon is threatened, it will stoke its "flame" to fight back. Even if it means dying of starvation/hypothermia later. PS: This can cause fun side effects. * Dragons like living near sources of heat(volcanoes) so they can lower their energy expenditure even more. * Very large dragons hibernate for long periods in times of scarcity because sustaining their flame becomes nearly impossible otherwise. (hibernating wasteland dragons) * The "flame" can also be used as a breath weapon, but using the breath weapon too much will cause them to die of hypothermia. [Answer] ## I can see two options Your best bet is that have not really evolved to live as long as they do, surviving past adulthood is something that only started recently perhaps with the extinction of their only predator. As their metabolism winds down and they get too overgrown they survive but not well, they are literally suffer from severe aging. Another good option is something like human menopause, old individuals stop reproducing and instead take over guarding nests of their offspring's eggs. Too big to fly their diet changes, its not that they stop wanting meat, they just can't catch it. The brain degenerating is still tricky, intelligence is a huge survival advantage, but maybe their lower food intake just can't support the same brain volume. Maybe loosing some intelligence is necessary to make them single-minded enough to watch nests for most of the day all day without getting bored, although that would still be very boring for an elephant. And this only works if they are only passive UNTIL you get too close to the nest, then they should be very violent. Lots of animals have different behavior as juveniles vs adult you age just adding another stage. T-rex and in fact many dinosaurs are known to be far more social as juveniles than as adults, but dinosaurs produce a LOT of eggs because most don't make it to adulthood. . In both cases this means "adults" are not really the adults but past the adult stage. ]
[Question] [ I'm creating a sort of fantasy world that I'm still trying to keep scientifically accurate (it's more alternate history than anything since I'm having it take place in our world with a few points of divergence) and I want to justify the evolution of mermaids from hominids, which gives me a time frame of only about 6 million years, a lot of questions regarding mermaid evolution have already been answered so I'm really just looking for some justification that it could happen so quickly. edit: My mermaids are tool users so they still have the evolutionary incentive to maintain a relatively human upper body. [Answer] You're not the first person to ask this sort of question. To crib from one of my own answers to one of those other questions: Your timescale seems pretty brief, but might be doable. Australopithicines diverged from the rest of the hominins about [five to eight million years ago](https://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_common_ancestor#/media/File:Hominini_lineage.svg). Looking at the [evolution of cetaceans](https://en.wikipedia.org/wiki/Evolution_of_cetaceans), five million years is enough time to get from something that's basically [a land-dwelling quadruped mammal that can dive for food](https://en.wikipedia.org/wiki/Pakicetus) to an [obligate aquatic and unambiguously whale-like animal](https://en.wikipedia.org/wiki/Protocetus) with all of the major physiological changes along the way that would require. Similarly, the [ancestors of modern seals](https://en.wikipedia.org/wiki/Pinniped#Evolutionary_history) evolved from an otter-like Puijila to a very seal-like Pteronarctos over a similar timescale, though the changes weren't quite as dramatic as those that whales underwent. Ending up with something that looks like a classical mermaid is another matter altogether, but there has been plenty written about them and your question doesn't go into any details about the nature of your mermaids, so I won't make any assumptions there. Unlike KerrAvon I'm not quite so down on the mermaid bodyplan, though their objections aren't unreasonable. Many human groups have successfully managed to hunt and forage in the sea (most notably the [Ama divers of Japan](https://en.wikipedia.org/wiki/Ama_(diving))) so the human upper body and head is not entirely useless so long as you can use tools. Having a lower body that's largely useless on land hasn't hurt seals and walruses and sealions too much, either. That said, if your mermaids aren't tool users, then something much more seal or manatee like would be the more likely evolutionary outcome. [Answer] Problematic The thing about evolution is that it is the result of organisms with favourable mutations having an increased chance of surviving long enough to reproduce, and the next generation likewise and so on. The problem with mermaids (assuming that the term refers to both male and female individuals with a human-like body and head but a fish-like lower torso and tail) is that the upper and lower portions of the body are favourable mutations for completely different environments. Let's look at the upper body first. There is a head which naturally orients to look in a plane perpendicular to the axis of the spine, with both eyes spaced apart but looking in the same direction to give good depth perception but poor all-around vision. The arms and hands are adequate for climbing in conjunction with legs, good for tool use, and combine with the eyes to make humans the best throwers of rocks and spears on the planet. Now let's look at the lower half of the body. It's a fish-like tail. It can presumably propel the mermaid through the water fairly quickly, and it is completely useless for anything else. Put the two together and you have a creature that is fairly bad at everything. In the water: * the neck needs to bend at an awkward angle in order for the creature to see forwards when it is swimming * the mouth and nose are badly positioned for breathing without breaking out of the water completely (there's a good reason that whales and dolphins have blowholes and other mammals have nostrils at the front of the head, not the underside) * the body and head are unstreamlined, with arms that are poor at underwater swimming and cannot effectively throw objects underwater. On land - well, it can flop about a bit, but the arms are unable to propel it effectively due to being too far forward of the centre of mass and the head is again at the wrong angle to see where it's going without straining. It's climbing-and-throwing optimised arms are pretty useless with a fluked tail down below. The only real advantage of the hands, arms and head arrangement is that the mermaids would have the tool-using ability to make seashell bikini tops, which only helps them survive predation by modern film censors. Put another way - if the hominids need to spend more and more time in the water, eventually becoming almost fully aquatic then they are likely to eventually end up looking like dolphins or dugongs (the latter having been suggested as a possible source of mermaid myths). It is only if they stay on land that the upper body and head will look "human", but then they must have the legs to go with it. As for timeframe - you are quite correct that 6 million years is not very long for such a radical change, it is about how long it took humans and chimpanzees to diverge from a common ancestor (5-10 million years). Changing from having two distinct legs to a fluked tail is pretty much what happened with the [evolution of the Sirenians](https://en.wikipedia.org/wiki/Evolution_of_sirenians), which took close to 50 million years. In order to knock an order of magnitude off the required time there would need to be very strong environmental pressure (at just the right rate of change to be survivable by evolving) combined with an increased rate of mutation, whether as a result of radiation, chemical pollutants or viral action. Given that most mutations are disadvantageous, greatly increased reproductive rate and shortened generations would be necessary - which unfortunately means that the mermaids probably aren't the sharpest tools in the shed intellectually in addition to their other disadvantages. In short - the timeframe is barely manageable by ramping up the environmental pressure and mutation rate, but unfortunately I cannot see any justification for the contradictory upper and lower body elements being a survivable evolutionary path. ]
[Question] [ There has been a fair bit of previous discussion about how high mountains could get. I'm currently thinking about a different question: assuming the existence of a very tall mountain, how high would it be feasible to climb? In all of this, I'm assuming gravity, atmospheric composition and sea-level atmospheric pressure are the same as on Earth. I think it's trickier than it sounds. The limiting factor is oxygen supply. Everest, 8848 m, is already borderline in that regard: it is barely possible to climb without carrying an oxygen supply, but only at severe risk of permanent brain damage. Let's say anything over 10 km or thereabouts is flat-out impossible to climb without supplemental oxygen. Okay, so you carry supplemental oxygen, right? But that runs you into a different problem: there is a limit to how much you can carry. The obvious solution is to set up additional camps at high altitude with stores of oxygen for further ascent, but this is an instance of the [Jeep problem](https://en.wikipedia.org/wiki/Jeep_problem) where the most important conclusion is > > However, the amount of fuel required and the number of fuel dumps both increase exponentially with the distance to be traveled. > > > The key word in that sentence being 'exponentially'. That's going to set a theoretically soft but practically pretty tight upper limit. I don't know enough about mountaineering to know what the parameters would be, to estimate an actual maximum altitude. Maybe around 15 km? It would be tempting to think okay, you need to cheat, bring in a helicopter. But helicopters have altitude limits, too. I don't think they can actually go much higher than mountaineers. Airships can, but they cannot cope with strong winds... though now that I think about it, you could use an airship to drop supplies onto the high slopes. If the wind prevents the airship being precise about position, that's okay; the climbers can move to where the supplies are. Okay, so there is a technological cheat. If one is unwilling to cheat, and everything has to be carried on the backs of climbers, what would be the practical altitude limit? Would anyone ever climb, say, a 20 km mountain? [Answer] TL;DR: 12-15km Earth-equivalent altitude, because you start needing spacesuits and pressurized habitats instead of a nice warm coat and a tent. You might be OK if you could launch rockets to drop pressurized accomodation for you at high altitude, but you might consider that cheating. --- Firstly: * You need a low-gravity world to keep very high mountains. * Mountains on low-gravity worlds are easier to climb than mountains on high-gravity worlds (cos you can carry more, and jump higher) * Low-gravity worlds have a larger [scale height](https://en.wikipedia.org/wiki/Scale_height) so the air pressure drop (and hence oxygen [partial pressure](https://en.wikipedia.org/wiki/Partial_pressure) drop) is lower for the same altitude gain on a high-gravity world. There's wiggle room in all those statements though, so they aren't strong arguments alone. > > Okay, so you carry supplemental oxygen, right? But that runs you into a different problem: there is a limit to how much you can carry > > > The supplemental oxygen used by mountaineers is inhaled via an open-circuit respirator. This means that any oxygen that is not taken up by the body is exhaled into the atmosphere and effectively wasted. This means that they end up carrying a lot of oxygen but rather less of it is actually used in metabolism than you might initially expect. There is a technological solution to this in the form of [rebreathers](https://en.wikipedia.org/wiki/Rebreather). These are more commonly associated with diving, because they let users spend more time at depth without having to carry huge amounts of additional air. As a very brief summary: rebreathers scrub excess CO2 from exhaled air, and keep the oxygen partial pressure constant by trickling in oxygen from a tank as needed. This ensures that all the oxygen in the tank can be consumed by the user. Using rebreathers for high altitude mountaineering isn't a new idea: [The Use of Closed-Circuit Oxygen in the Himalayas](https://www.researchgate.net/publication/7579535_The_Use_of_Closed-Circuit_Oxygen_in_the_Himalayas) > > Two days before the first ascent of Mt. Everest in 1953, Tom Bourdillon and Charles Evans climbed to within 90 m of the summit at unprecedented speeds. By breathing pure oxygen from a closed circuit, the pair were able to obtain an enormous physiological advantage. Unfortunately, due to a malfunction in Evans's circuit, the pair abandoned their attempt on the South Summit. For many who used the circuit in the 1930s and 1950s, the device proved too heavy, uncomfortable, and tiring for mountaineering. > > > You will not be surprised to learn that rebreather technology has advanced considerably since 1950, and rebreathers used in low pressure air (rather than at high pressure under water) are a little simpler and safer than their conventional underwater cousins. A modern mountaineering rebreather would be much lighter and smaller and more reliable than their primitive 50s forebears, and would make oxygen supplies go much further. There would still be technological hurdles to overcome (because operating rebreathers at very low temperatures is probably not something that's done very often) but there's no reason they should be insurmountable. (note that rebreathers form a part of the [primary life support system](https://en.wikipedia.org/wiki/Primary_life_support_system) of modern spacesuits, for an example of their use at low pressures) You're still subject to exponential losses, but when the exponential term is small enough then your maximum altitude increases considerably. The practical gain from a rebreather might be a tenfold reduction in O2 consumption. > > It would be tempting to think okay, you need to cheat, bring in a helicopter. But helicopters have altitude limits, too. I don't think they can actually go much higher than mountaineers. > > > This is true, but given your example of "Elon Musk" budget you can consider the use of a small rocket driven lander, assuming suitable sites can found to put it down. Maybe the thing could be dropped from a plane and glide to its destination using a parafoil, and use rockets at the end of the flight to fine tune its landing zone. It'll still be vulnerable to "weather windows", and making it robust enough to keep its cargo safe and in place during bad weather might be a problem too, but again: not necessarily an insurmountable one. And it is something that can be tested ahead of time and validated before any climb. > > Would anyone ever climb, say, a 20 km mountain? > > > At a certain point, external pressure becomes low enough that simply being exposed to it is unhealthy even if you have a good supply of oxygen. On Earth, high-altitude pilots wear [pressure suits](https://en.wikipedia.org/wiki/Pressure_suit): > > The physiological-deficient zone extends from 3,600 m (12,000 ft) to about 15,000 m (50,000 ft). There is an increased risk of problems such as [hypoxia](https://en.wikipedia.org/wiki/Hypoxia_(medical)), trapped-gas [dysbarism](https://en.wikipedia.org/wiki/Dysbarism) (where gas trapped in the body expands), and evolved-gas dysbarism (where dissolved gases such as nitrogen may form in the tissues, i.e. [decompression sickness](https://en.wikipedia.org/wiki/Decompression_sickness)). Above approximately 10,000 m (33,000 ft) oxygen-rich breathing mixture is required to approximate the oxygen available in the lower atmosphere, while above 12,000 m (40,000 ft) oxygen must be under positive pressure. Above 15,000 m (49,000 ft), respiration is not possible because the pressure at which the lungs excrete carbon dioxide (approximately 87 mmHg) exceeds outside air pressure. Above 19,000 m (62,000 ft), also known as the [Armstrong limit](https://en.wikipedia.org/wiki/Armstrong_limit), fluids in the throat and lungs will boil away. > > > That last one is worth a deeper look: > > The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body > > > This means that at some point between the altitude of the top of Everest and 15000m your climbers start needing spacesuits to provide counterpressure simply to let them breathe at all. At 20km they need a spacesuit to stop exposed fluids boiling away, which is likely to be an unpleasant way to die (unless their air supply was damaged in which case you just [pass out in a few seconds](https://web.archive.org/web/20141014072430/http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970603.html)). More designs for [mechanical counterpressure suits](https://en.wikipedia.org/wiki/Mechanical_counterpressure_suit) for use on Mars would probably do an excellent job, though I don't relish the idea of carrying a complete spacesuit up to the top of Everest and then having to put it on and climb another Everest and a half! The need for a spacesuit, and a positive pressure respirator suggests that 12km altitude on Earth (or an equivalent atmospheric pressure on another planet with different gravity) might be as high as you'd reasonably want to climb because of the problem of eating and sleeping safely. You can have food-tubes in a space suit or pressure suit, and a clever vent system could allow you to pee and poop too. Damage to the suit might be very serious, and injuries are effectively untreatable unless you were able to bring a pressurized habitat with you (like a cross between a [Gamow bag](https://en.wikipedia.org/wiki/Portable_hyperbaric_bag), a [TransHab](https://en.wikipedia.org/wiki/TransHab) inflateable space station and a [portaledge](https://en.wikipedia.org/wiki/Portaledge)). This probably means that even if human mountaineering activity above 12-15km is possible, the fact that small accidents or kit failures can kill you in a quick and very expensive fashion probably limits climbing at that altitude (contrast with climbing 8000m peaks, where accidents kill you in a few hours in a merely expensive way, and sometime people get rescued). edit: Here's a big problem: time. Climbing is hard work, especially at high altitude, even with supplemental oxygen. It takes [11 hours](https://en.wikipedia.org/wiki/List_of_Mount_Everest_records#Fastest_ascents) to climb Everest from a base camp using supplemental oxygen, which is a rise of <3500m. The round-trip time to base camp was [18 hours](https://en.wikipedia.org/wiki/Lakpa_Gelu). For higher peaks, you'll simply run out of time and energy and you're going to need to camp high on the mountain. No-one camps in the "[death zone](https://en.wikipedia.org/wiki/Death_zone)" at 8000m+ because the chances of you surviving your nap are slim. At 12000m peak basically demands a camp unless the climbers are superhuman. Napping in a pressure suit might work, and your oxygen demands are reduced, but those long and unproductive sleeps will cost you dearly in terms of the amount of food and oxygen you have to carry. Permanent and pressurized high-camps would probably be needed... imagine the effort required to construct a sealed building at the summit of Everest and maintain life support systems up there. Imagine the fun you'd have providing power, given the low levels of oxygen to run combustion engines or fuel cells (and the effort required to refuel). Wind turbines and solar cells might have problems with the weather, to say the least, but might be the only practical options. This may also be considered cheating, but it is hard to see what you might do instead. ]
[Question] [ In our world [bark beetles](https://en.wikipedia.org/wiki/Bark_beetle) can bring serious damages to forests which they infest, by killing the tree which they attack when they feed and breed between the bark and the wood of their host. I am trying to design an alternative bark beetle which, instead of damaging the tree, actually brings benefits to it, so that attacked trees get an advantage from this with respect to a non attacked tree. Which mechanism could explain such advantage? * this beetle still feeds and breeds between the bark and the wood of the host * the host is a tree, similar to those we have on Earth. I have not yet decided on a specific biome for the tree to be in. * the effect has to be proportional to the rate of infection: the higher the number of beetles in a tree, the higher the advantage it gains [Answer] ## Trees need to "shed" bark. Beetles help with that I am going to quickly design a new type of tree. This does not need to be the trees you have but can serve as an inspiration of how to design other ones: The tree has an outer harder bark during the drier seasons. It helps protect it from the elements. However, during the more peaceful seasons it will attempt to collect water (or sap, if you wish). The inner part of the bark and the outer trunk is more malleable and can "bulge out" with the stored resources. Which is where the old bark is a problem - it is hard and inflexible like armour. Left in place, it means the tree has a harder time storing more supplies for later. With this setup, bark beetles can eat the outer bark. This helps the tree to loose the outer bark sooner and sooner start collecting supplies. Which in turn helps the tree grow and develop further. --- This does not need to be the setup in your world but there can be any number of reasons trees would not need the outer part of the bark and thus beetles eating it would help out. It could be that other insects nest in the outer layer of the trunk and bark beetles keep them at bay from borrowing further. At any rate, the premise is some variation of: * Tree provides beetle with food * Beetle gets rid of bark for the tree Where the reason the bark might not be needed can vary, depending on what the story or the world needs. [Answer] You could make the beetles do normal symbiotic things with plants [like ants do](https://www.kew.org/read-and-watch/ants-and-plants-a-very-natural-love-story). Seed dispersal, protection from parasitic insects, and fertilization. They could also be pollinators like moths and bees, or like [fig wasps](https://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/fig_wasp.shtml). Fig wasps only lay eggs inside figs and die inside the fruit. Their entire life cycle revolves around the fig. Your beetles could pollinate certain pods that grow on the bark or branches of your tree if the tree is able to self-pollinate. If self-pollination is not available, there could be a mating season in which all the bark-beetles leave the trees and meet up in swarms that would exchange pollen between beetle colonies and thus plants. [Answer] Your beetles eat fungus. Chestnut blight wiped out the American chestnut forests in the early 20th century. <https://en.wikipedia.org/wiki/Chestnut_blight> > > The fungus enters through wounds on susceptible trees and grows in and > beneath the bark, eventually killing the cambium all the way round the > twig, branch or trunk.[30] The first symptom of C. parasitica > infection is a small orange-brown area on the tree bark. A sunken > canker then forms as the mycelial fan spreads under the bark. As the > hyphae spread, they produce several toxic compounds, the most notable > of which is oxalic acid. > > > Your beetles eat the fungus. The more beetles, the more protection the tree has. Usually there will be an equilibrium with a certain amount of fungus and a certain amount of beetles per tree. ]
[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/223624/edit). Closed 1 year ago. The community reviewed whether to reopen this question 1 year ago and left it closed: > > Original close reason(s) were not resolved > > > [Improve this question](/posts/223624/edit) Instead of being spread by a virus or the temporary effects of a voodoo-induced trance or paralysis, zombies are created by a magical curse that causes the person to rot while remaining relatively cognitively present until they reach an advanced state of decay (a state in which I imagine they'd basically look and act like the zombies on The Walking Dead - they're still conscious but are either too cognitively decayed or too numb from trauma to do much besides bumble around and groan or just be dead). Granted, the journey from fresh and mostly-intact to rotting and less-intact is not a smooth journey and their cognitive abilities will not be as sharp on day 28 as they would be on day 1, but through their gross journey of decay they would generally be cognitively present enough to think "This sucks." So, my question is essentially "What would it feel like to be mentally conscious while your body rotted?" E.g. Would chunks of you fall apart like in comical presentations of zombies? Would your senses fade away? Would you experience pain or would your ability to feel pain go away after a few days? Etc. Factors/other questions you could consider: * What if magic kept the body animated while they rotted? What would it be like to experience their symptoms while still capable of moving? Maybe they try to stand up to make a coffee and their leg (painlessly?) breaks, or maybe they catch a knot brushing their hair and rip a chunk of hair and scalp off, or maybe this action causes most of their head and face skin to slide off! * Could magic make it so parts of their body decay slower than others? For example, could things such as their heart, brain, or other organs remain somewhat functional while their skin, muscle, bone, or other systems become excessively unhealthy? (I understand a functioning heart obviously prevents cell death so I'm not totally sure how this specifically might work but there's magic involved so everything is slightly flexible - maybe the curse causes blood to circulate through some parts of the body and not others) * Bonus points if some kind of timeline is loosely included [Answer] # Do not google for images of this if you are faint of heart > > So, my question is essentially "What would it feel like to be mentally conscious while your body rotted?" > > > You would feel like a person with a case of opioids abuse, but involving a very specific drug that is 10x more potent than morphine. What you describe in the question kind of exists in the real world, without the magic component. There is this sedative called [desomorphine](https://en.wikipedia.org/wiki/Desomorphine). It is as addictive as most opioids and the version people buy on the streets (called krokodil, the "zombie drug", or the "flesh eating drug") has impurities which make it more toxic. According to the link: > > Gangrene, phlebitis, thrombosis (blood clots), pneumonia, meningitis, septicaemia (blood infection), osteomyelitis (bone infection), liver and kidney damage, brain damage (...) are common serious adverse health effects observed among users of krokodil. Sometimes, the user will miss the vein when injecting the desomorphine, creating an abscess and causing death of the flesh surrounding the entry-point. > > > Some pictures of addicts show their arms or legs so rotten that you can see their bones. Again, don't google it.if you can't handle it. And since this is a potent analgesic, users will be quite numb, apathetic and not in their best shape mentally for long spans throughout their days as long as the addiction lasts. But they won't be completely mindless, even as flesh falls off of their limbs. They may also have episodes of anger and rage, specially when withdrawal symptoms hit. This is as close to Holywood zombies as real life gets. [Answer] ## Actually, we have done a lot of research on this - Look at Acute Radiation Syndrome. Although you tag Magic, the zombies still experience the real world, and for the data of what you describe you need look no further than [Acute Radiation Syndrome](https://en.wikipedia.org/wiki/Acute_radiation_syndrome). One could argue that your zombies are in fact humans that have been given a short burst of a very large dose of radiation, starting at around 0.7 Grays but can go up to beyond 30. This dose is enough to 'kill' you. In essence, your immune system is destroyed. What happens next is the stuff of horror movies, but has been carefully scientifically studied intently when it occurs, for example at the [Nuclear Disaster at Chernobyl](https://en.wikipedia.org/wiki/Chernobyl_disaster), or the effects of the [Atomic Bomb at Hiroshima](https://en.wikipedia.org/wiki/Atomic_bombings_of_Hiroshima_and_Nagasaki). Without an immune system, it is arguable if you really are alive as we constantly live in a soup of bacteria and viruses and even have them inside us when we live, which our immune system constantly fights. Without it, all resident pathogens already within our body, and external ones, can now eat without hindrance starting with your gastrointestinal system, followed by the blood and other internal organs. So the following experiences occur, all the while you are 'conscious': 1. Hemotopoietic: No / low white blood cells causes aplastic anaemia, and red blood cell count also, basically your blood cannot repair any wounds or effectively deliver any immune response, meaning weakness, scarring, fatigue and Leukopenia. This also prevents skin cell repair and hair follicle adherence, and depending on dose [burns on the skin](https://en.wikipedia.org/wiki/Radiation_burn), and [hair falling out](https://en.wikipedia.org/wiki/Hair_loss), within a few hours. 2. Gastrointestinal Tract: Immediate internal bleeding throughout the entire tract, causing nausea, diarrhea vomiting, abdominal pain, and loss of appetite. 3. Neurovascular: This process also affects brain function, as pathogens consume your brain and loss of body functions also cause High fever, Dizziness and disorientation, Headache and Shock. After the above, your major body organs start to fail, causing skin cells to detach, hair connections to fail, hearts to become arrhythmic, lungs to be scarred, and complete body function failure is unfortunately assured. In terms of timeline, for an acute dose of more than 30 Grays: * Less than 10 minutes: Nausea and Vomiting * Less than 1 hour: Diarrhea, Headache and Fever, Tremors, Seizures * Less than 48 hours: Fever, Dizziness, Disorienation, Hypotension, Hemorrhage, skin lesions and hair follicle detachment * 48 hours: Actual shutdown of a major organ, such as the heart, lungs or brain, causing body failure. (in your case, the zombie would not be able to do useful work at this point). There is data available on this process in many resources - as those that deal with radiation must be aware of symptoms and dangers. Your zombies would not be enjoying their experience, as Acute Radiation Sickness is considered one of the most painful and inexorable experiences you would hope never to have. [Answer] ## Chilblains, itches and phantom pain The zombie will ignore it, at first. The zombie is used to feel the persistent itch of rotting, because it is dead and already rotting. When it gets worse however, the zombie will start to loose toes, fingers and eventually, entire limbs. Keep your house clean If you want to keep your loved ones alive as zombies, make sure your house stays clean. House flies and fungus thrive on zombies and will accelerate the rotting. Make sure you cut its nails Scratching will make things worse. The itch will make zombies scratch themselves to the bone. It will be a mess and you won't like the smell. Best way to prevent that is to cut its nails regularly. Loosing body parts When the rotting proceeds, your zombie could start loosing body parts. It remembers having legs and arms and now they are gone. Phantom pain kicks in, which is far worse than the itching. <https://en.wikipedia.org/wiki/Phantom_pain> When this happens, it's time for your zombie to return to the grave, to reinforce its life cycle. Kill your darlings, bury your zombie remains and let magic do its work. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. In my question [What is the largest achievable oxygen-atmosphere world?](https://worldbuilding.stackexchange.com/a/217108/75), my [answer](https://worldbuilding.stackexchange.com/a/217352/75) suggests an atmosphere of standard terrestrial air with a sea-level pressure of 20 ATM and platforms at an altitude of 25,250m above sea level. This world is a water world, with a deep global sea. At the 1 ATM altitude, humans live on a number of suspended platforms. Surface gravity is 1g. If an unprotected human was to fall from one of the platforms - or indeed from any other height between 5,000m and 31,000m, and didn't suffer from Nitrogen narcosis or Oxygen toxicity on the way down, would they be able to survive the fall into the ocean below? Would their potential survival depend upon maintaining a correct posture to minimise terminal velocity and to transition to a diving posture just before impact, or could they survive even if unconscious and falling in entirely the wrong postures? What physical condition might they be in after such a fall? In other words, disregarding other environmental factors, would the terminal velocity of a fall through such an atmosphere be sufficiently low that a human might survive a fall into water? [Answer] Entering water at high speed is [serious business](https://www.sportsrec.com/7662906/the-dangers-of-jumping-into-water-from-heights) already before reaching terminal velocity. > > At what height is it dangerous to jump into the water? Although risky, competitive high divers can enter the water from as high as 27 meters without injury, states Swim England. From this height, divers can reach speeds up to 60 miles per hour. However, serious injury is possible, even when jumping from much lower platforms. From a 10-meter platform, divers still hit the water at speeds of 36.6 miles per hour, according to an article published in the September/October 2017 issue of Current Sports Medicine Reports. > > > These speeds cause divers to hit the water with incredible force. While water may offer a softer landing than the hard ground, it still exerts a tremendous amount of force on divers' bodies, slowing their speeds by more than 50 percent in only a fraction of a second. > > > With proper form, the body can absorb the pressure from the impact. High divers typically enter feet first, allowing the feet and legs to absorb the impact. Many other divers enter with the hands and arms extended to protect the head and neck from impact. Even with correct form when entering the water, divers may experience overuse injuries in the joints, especially the wrist and shoulder. Moreover, the position which allows minimal terminal velocity is not the one considered proper form while entering water. > > > Note that those height are far from allowing reaching terminal velocity, and having a proper form after sky-falling for 20+ km is challenging. Even considering the increased density of the atmosphere, let's not forget that the terminal velocity in inversely proportional to the square root of the density, so for example a 4 time denser atmosphere would only half the terminal velocity. The square root of 20 is 4.47, and in the optimal position, human terminal velocity at 1g, 1 ATM is 200 KPH. In a head/foot down scenario, terminal velocity might be as much as 290 KPH at 1g, 1 ATM. That makes it an impact velocity of about 45 to 65 KPH at 1g 20 ATM. As divers can safely enter the water at up to 96 KPH with good form, it sounds survivable to me. ]
[Question] [ The Leviathan is an ancient deity that exists outside the mortal plane. It seeks to enter the human world, which is separated from him by an all-enclosing barrier protecting it. However, the Leviathan is not just another typical demon or eldritch god bent on world domination. It is formed as the manifestation of the tension between the modern world and the premodern world and the rage it creates. Originally it existing as the concept of there being something greater than man, such as gods or the supernatural, that could not be controlled or reasoned with. Modern ideas spurred on by the scientific revolution and the enlightenment encouraged humanity to understand their surrounding environment with a new perspective that focused on rationality and proven facts based on trial and error analysis. The new relationship between humanity and the world began to displace older ideas like religion and superstition. This has led to a time of increasing religious indifference, where people are more concerned with their number of likes on social media accounts and only token tribute is paid to old practices of worship. This concept of the Leviathan was then shaped by the encroachment of modernity into the old world and the clash between the two. The Scarlet King solidified into a sentient entity after it was defined as such by the SCP Foundation, a group devoted to securing anomalies in the interest of protecting current civilization and sustaining its normalcy. An organization known as "The cult of the Leviathan" seeks to reincarnate their deity on the mortal plane directly in the form of a human child with Leviathan's soul. The group seek to return the world to its premodern age where humanity feared the unknown and looked to gods and deities for their sustenance and continued survival. While the cult is powerful and has access to resources, it is small and operates in secret to avoid persecution by governmental forces who see them as dangerous madmen. After being born into the world through mortal means, he will grow up to become the living manifestation of their god and subjugate humanity to his rule, with the cult at the helm of power. As the Leviathan became real, so too did a history of its existence reaching back to the Dawn of Creation, altering history to include it. The cult has essentially created a reality warper who can retroactively rewrite the world's timeline, inserting itself into various points of our history's past. As a result, several cultures and empires have risen and fallen in the revised history, displacing important events with new ones and essentially being the narrator of its own story. As this being has the ability to control the timeline, it stands to reason that it can manipulate things to make itself the winner of past events, establishing the cult as a far more prominent group in the modern day instead of a small organization forced to operate in secret. It could even make itself an already summoned entity who has already achieved world domination and humanity's enslavement. What could prevent a deity who can alter time from making itself the winner? [Answer] ## Leviathan is who we said he is Leviathan only has the power to alter the timeline in so far as is required to make himself real. Before Leviathan entered our world, who he was, what he did, and what he is yet to do was already written into the collective consciousness of man. When he became real, time was rewritten to make his entire mythos became real (past, present, and future), but this does not mean that Leviathan is in total control what the new reality is, he is only becoming what he is already meant to be. There are variations of the Leviathan myth in almost every mythology of European/Middle Eastern origins, but they all basically go something along the lines of there being a great sea-monster that was defeated by God/Baal/Zues/Thor/etc. at some time in each civilizations pre-history. But would return to reek havoc on the world before being defeated again at the end of days. By becoming real, Leviathan's defeat is not only possible but guaranteed because he can not make himself real without also making real the deity who is destined to destroy him. > > The group seek to return the world to its premodern age where humanity feared the unknown and looked to gods and deities for their sustenance and continued survival. > > > Given the mission statement of the cult of Leviathan, this also gives them a sort of motivation for summoning a massive world threatening horror into existence. By summoning Leviathan, they believe they will also be summoning the gods into our world. [Answer] It isn't control over the time line History might be rewritten, but one thing is certain. The god becomes real at a certain point. The way that happens can alter, but the point when it happens can not. That means some events cannot be altered, as they are requirements for the god to become real. This goes much further. The god doesn't really control time. It is merely injected into the time line. Like a complicated equation on one side has an answer. Now the god is real, the answer changes, so the equation has to change. Some things are fixed, others are variable. An example below. The X and Y were fixed to give 8, but have been changed to give 9 the moment the god entered. * (7 \* X) / (1 - Y) = 8 * (7 \* X) / (1 - Y) = 9 In the end, the god has only a limited control over the time line, making her/him not all powerful, yet still giving it great power. [Answer] ### History Isn't Real The past is gone, and all that remains of it are memories, and the stories by which we rationalize the present state of things. Your god cannot actually control the timeline. Once your cult brings him into existence, only history needs to change to accommodate him. History is not the past. [Answer] > > What could prevent a deity who can alter time from making itself the winner? > > > If the Tralfamadorian [view of time](https://www.sparknotes.com/lit/slaughter/quotes/character/tralfamadorians/) would be true, not even a deity could alter it. Simply said, time flow is the consequence of our incapacity of experiencing all at once. > > To them, all events in time have happened and are happening simultaneously. Nothing can be changed, and nothing matters. > > > "The creatures can see where each star has been and where it is going, so that the heavens are filled with rarefied, luminous spaghetti. And Tralfamadorians don’t see human beings as two-legged creatures, either. They see them as great millepedes—“with babies’ legs at one end and old people’s legs at the other" > > > [Answer] /establishing the cult as a far more prominent group in the modern day instead of a small organization forced to operate in secret./ The small organization does not realize that it is a tiny subset of the far more prominent group. The small group bringing the Leviathan into the world succeeds. It brings the Leviathan into being at the start of the world. The Leviathan has always been. The persons who think they are planting a seed that will grow into a sapling do not recognize the ancient forest around them as their own doing. The success of this small group is hugely, tremendously, inconceivably beyond their own small ambitions. Their success is so large as to now be irrelevant for the members of that small group, except in that they exist in the world they made. The world is what it is now because of their efforts. The far more prominent group is everyone and everything. [Answer] # The Leviathan Can't be Controlled or Reasoned with: The Leviathan exists because it will exist, and that necessitates that it always existed. But the very nature of its power is such that conscious goals and self-serving behavior are irrelevant to it. Despite it being the embodiment of human angst and ignorance, it has no desire or motivation - it simply is an elemental force. It will either cease being a child once it incarnates, or it being a child will be irrelevant, because it's mortal existence implies it is limited by petty concepts like "before" and "after." So history distorting is irrelevant. Leviathan may distort history infinitely, like the concept of primordial chaos it comes from. Perhaps when all possible realities have existed, one will be incompatible with Leviathan, and it will cease to exist, replaced by a reality where Leviathan could never have existed. So after a moment and eternity, things will settle down into a reality that always was defined by Leviathan never having existed except as a concept. Despite everything having changed, it will all be as it was before and always would be. Maybe. [Answer] # Control of the flow of time (as opposed to control of the timeline* that you used in your exposition ...)* Leviathan simply takes note of everyone who attempts to alter history, and sets their flow of time to inordinately slow (1 second for offender = 100 years for the world). They freeze in place, and by the time they realize anything has happened, the history they were trying to alter is the dead past again. ]
[Question] [ Would pleopod-based swimming locomotion seen in animals like giant isopods work at much larger sizes, or would drag (or something else?) be too much of a problem? The pleopods, also known as swimmerets, are the paired olive green flaps shown lower right: [![Pleopod model showing dorsal and ventral sides](https://i.stack.imgur.com/buwUHl.jpg)](https://i.stack.imgur.com/buwUHl.jpg) [This video shows the pleopods in action from below, timestamp 0:00–0:28](https://www.youtube.com/watch?v=NbbZxYPhesE), with a side view later. Imagine a creature, roughly the same proportions of the isopod, with pleopods running most of the length of its ventral side, perhaps 20–25 pairs. Anything from 5 to 30 metres long will do – that's about 12x to 80x the size of a giant isopod. Each pleopod would therefore be between half a metre to five across, and I would guess tens of centimetres thick. This type of aquatic propulsion is called drag. Drag propulsion is so named because part of the swimming cycle, the recovery phase, has the swimming surface moving against the direction of motion to reset its position. This form of swimming is less efficient than lift-based swimming. Drag can be reduced by changing the profile of the surface in the recovery phase so it is less than the surface in the thrust phase. In the video above it's the clapping-like motion as the pleopods come together and swing forward. My concern is that such large overlapping surfaces would, during the recovery phase, severly offset the forward motion, or be too small relative to the bulk of the organism to push it forward, or some combination thereof. Or something else I haven't accounted for. The largest organism known that may have used pleopod-based drag swimming was the [Aegirocassis](https://en.wikipedia.org/wiki/Aegirocassis), but the only specimen we have is only a little over two metres long. Contrast that with the largest swimming organisms, all of which swim or swam with lift-based biomechanics. Perhaps there is an upper limit to how effective this form of locomotion can be. Ignore all the usual square–cube law problems with scaling up arthropods: I'm only interested in the biomechanical swimming action. The organism itself doesn't need to be arthropod-like in any other way. While I have tagged this [science-based](/questions/tagged/science-based "show questions tagged 'science-based'") and not [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") I am expecting some number crunching will be necessary to show whether this would scale or not, and sketch the size and/or speed limits would apply. [Answer] ## Drag swimming There seems to be a lot of confusion about what drag swimming is. drag swimmers use a variety of inefficient methods to generate thrust, usually backwards. And use the position of the body, so thrust water is only on the underside, to generate lift offsetting the lack of control in how they generate thrust. A lobster swimming is the classic example. you get a sort of burst followed by a recovery and reset of the mechanism. If there is an obvious clapping motion you are looking at a drag swimmer. example of drag swimming [![https://64.media.tumblr.com/0a6d6a8ad0a3f10842eecf08316fb5fe/5fd155a2a394a5cc-fb/s500x750/65aed5740698d85214b406cc0ae6ba7415fef391.gifv](https://i.stack.imgur.com/o0eEw.gif)](https://i.stack.imgur.com/o0eEw.gif) Pleopods are using drag swimming the forward direction but the mechanism is the same, again thrusting water against the body to products forward thrust, we see this in your video. There is not a upper limit so much as it is favored by animals that are not primarily adapted for swimming, but for swimming and crawling/walking. its just better to develop efficiency and to develop more control if you are a obligate swimmer, these are lacking in drag swimmers. It will work just as well for a large swimmer as a small one, it just does not work great overall. Drag swimming is good enough for a get away but for a habitual swimmer it is awful, so it depends on what you want for your creature. if it spends most of its time crawling along the bottom it is fine, if it is a open water swimmer it is awful. ## Big swimmers today use Body-caudal fin swimming Lift swimming is a problematic term it is a vague term that gets used to describe a lot of different things, some would body-caudal fin swimming is lift based others will say it is not. Today the largest swimmers use the classic fish system, Body-caudal fin form of swimming, sometimes called undulatory swimming, were the main propulsion is produced by a undulation producing thrust via the normal force. Whales use the same method, it is just turned 90 degrees on its side compared to fish. You can read more about this form of swimming in the link below, there are several forms of it. <https://www.researchgate.net/figure/Schematic-diagram-of-thrust-generation-and-propulsion-produced-by-body-caudal-fin-BCF_fig2_299414011> [![enter image description here](https://i.stack.imgur.com/FWaBt.png)](https://i.stack.imgur.com/FWaBt.png) think of fish as walking, while the drag swimmers are frog hopping. the first is way more efficient for long distance travel because losses are much smaller since the motion is continuous, and there is little slowing down. while a frog use high energy acceleration followed by slowing to a near stop requiring repeating the high energy accelerating stage. accelerating is expensive, better to just maintain. pleopods have pushed their system as far as it can go efficiency wise, shortened the "drag" phase and extended the "thrust phase with extra thrust surfaces, but there is still a distinct two step process with a thrust and reset, so it is nowhere near as efficient as an oscillating swim stroke. the pleopod users (isopods and lobster) also have to rely on the body shape evening out the odd angle of thrust, because thrust is not symmetric. this is done through drag, hence the name, which adds more losses. While fish end up with more even thrust because thrust oscillates back and forth, meaning they can minimize drag as much as possible while drag swimmers need a lot of drag to have any ability to steer. ## Big arthropod swimmers mostly use Body-caudal fin swimming. Some extinct arthropods may have use a similar form of propulsion (see images below), or the more eel like form which is also Body-caudal fin propulsion. Although some of them may have uses something closer to hydrofoils (what some call true lift based swimming) swimming. this is the same form seen it in some large extinct animals like pliosaurs and plesiosaurs, penguin and sea turtles also use this method. Any of these would be more likely of you intent to make a habitual swimmer, with little no use for its legs, something closer to how a whale swims if you have a hard time imagining how it works. [![![enter image description here](https://i.stack.imgur.com/9iIxR.jpg)](https://i.stack.imgur.com/9iIxR.jpg) [![enter image description here](https://i.stack.imgur.com/n2F7Y.png)](https://i.stack.imgur.com/n2F7Y.png) [Answer] Ducks and other water birds propel themselves in water with a similar mechanism. Even underwater swimmers can use breaststroke to move underwater, which use a similar mechanism. It might not be the most efficient, but as long as there is a way to fold the propelling appendix during the recall phase, in order to reduce drag, it can work. [Answer] The con-rit. [![con rit](https://i.stack.imgur.com/fp2hM.jpg)](https://i.stack.imgur.com/fp2hM.jpg) <http://karlshuker.blogspot.com/2014/02/contemplating-con-rit.html> In his comprehensive study of sea monsters, Bernard Heuvelmans called this type the "great sea centipede". Con-rit is the Vietnamese name for this rare cryptid. Karl Shuker has a discussion about this type of sea monster on his web page and quotes Heuvelmans with a description. > > The most prominent of these is the 150-ft-long monster spied for about > 30 minutes by a number of sailors on deck aboard HMS Narcissus on 21 > May 1899, after the ship had rounded Algeria's Cape Falcon... > > > "The monster seemed to be propelled by an immense number of fins. You > could see the fins propelling it along at about the same rate as the > ship was going. The fins were on both sides, and appeared to be > turning over and over. There were fins right down to the tail. Another > curious thing was that it spouted up water like a whale, only the > spouts were very small and came from various parts of the body." > > > The only major problem is the con rit's immense length - far beyond > anything recorded so far by science from a known modern-day (or > fossil) crustacean. It is well-known that the spiracular system of > respiration utilized by insects (involving a vast internal > ramification of minute breathing tubes) prevents them from attaining > the gigantic proportions beloved by directors of science-fiction > movies. However, crustaceans breathe via gills, and their bodies are > buoyed by the surrounding water. Hence the evolution of a giant > aquatic crustacean is not wholly beyond the realms of possibility and, > to my mind, offers the only remotely feasible explanation to Vietnam's > anomalous con rit or sea millipede. > > > The con-rit is a giant isopod. It is plausible to me. Isopods have conquered just about every environment on earth, and in the hadal zone of the deep seas, deeper than fish or molluscs can tolerate, they are the main macro-organism. The con-rit is a giant elongated isopod dwelling in the deepest ocean. Only very rarely does one come to the surface. [Answer] The method of drag swimming which you describe is similar to paddling, or even better for the purposes of this question, similar to the swimming style of turtles and pliosauroide, groups which reach to really big sizes, to 5 meters in the case of turtles and 15 meters in the case of pliosauroidea. OF course can be easily seen that the mentioned creatures had just two pairs of fins in difference with the 5-10 pleopod pairs of the isopods. Now, I know your question is not based on plausible evolution, but it is safe to think that a massive creature using this type of water propulsion would specialize just some pairs of its limbs to an specific activity, who knows how many, but while animals turn bigger each movement becomes more costly energetically and the limbs and all the movements that they involve are quite a notorious cost for any organism and even more with the drag swimming style which is more energetically expensive than other swimming methods. Therefore, although it is not safe, it is quite probable that a creature like the one you describe ends up specializing a few pairs of pleopods to propel themselves in the water and that the others end up atrophy and disappear or specialize for another purpose. So this answer does not take much into account the physical calculations necessary to determine the energy expended with each movement, the horizontal momentum or the drag generated by the water, but is based on the deduction that smaller animals can usually maintain a greater limbs than larger animals. Edit When investigating a little more, it seems that this answer becomes completely useless for the purposes of the question, since it turns out that the anomalocarida to which the Aegirocassis mentioned in the question belongs, did not use a swimming method similar to the pleopod drag method of marine isopods (at least not significantly or observably). Here some videos of the Anomalocaris, an strechtly related specie with the Aegirocassis, showing a swimming method which was possibly very different of Isopods. <https://www.youtube.com/watch?v=Ep_zpUa4p1w> <https://www.youtube.com/watch?v=Fpmw9EJmSlw> ]
[Question] [ A bit of a further expansion of my last question. I am looking for alternatives to regular bone of earth (hydroxyapatite) because my superearth would have about 50% more gravity than that of earth. While 50% probably isn't enough to force animals to use other bone compositions, I'd rather take an "odd" route with my creatures instead. Bones would have to be: - Regeneratable - Biologically possible - Compatible with the organism's immune system - Have weird traits, color, formation, impact on the body etc! I was thinking something akin to dentin, being found in our teeth. Density doesn't matter for me, as long as it doesn't reach lead-levels. Along with that, I'd rather use something that has some interesting properties, like pyrite, which oxygizes in a matter of days, or silica, which is rather transparant. Heck, even some biological "plastics" would work! If you do however, have a more speculative material/composition, please note where/how organisms could utilise/find it! The atmosphere is rather earthlike in composition, although it is quite a bit denser if that makes a difference. If possible, it shouldn't be something too earthlike, but it should still be viable and common throughout other worlds. Thank you in advance, feel free to ask any questions! [Answer] Hydraulics. I am going to recycle an answer! But as regards weird skeletons this is a good one because instead of bones your creatures are full of juice. from [Would biological hydraulics be worth evolving in tetrapods?](https://worldbuilding.stackexchange.com/questions/111528/would-biological-hydraulics-be-worth-evolving-in-tetrapods/111532#111532) Velvet worms are terrestrial animals that use hydraulic legs. Model your creature on them. [![velvet worms](https://i.stack.imgur.com/hj5PN.jpg)](https://i.stack.imgur.com/hj5PN.jpg) <http://www.abc.net.au/science/articles/2011/09/05/3306983.htm> [![on the hydraulic skeleton of velvet worms](https://i.stack.imgur.com/50TfF.jpg)](https://i.stack.imgur.com/50TfF.jpg) [Periodic Tables Unifying Living Organisms at the Molecular Level:The Predictive Power of the Law of PeriodicityNov 8, 2017 by Antonio Lima-de-Faria](https://books.google.com/books?id=lUNBDwAAQBAJ&pg=PA107&lpg=PA107&dq=VELVET+WORM+HYDRAULIC&source=bl&ots=ybZdJVUwbv&sig=cCdccpDQGF02UY23qgP7azmdDJ4&hl=en&sa=X&ved=0ahUKEwjGkbaPsPLaAhVW_oMKHVgKCYwQ6AEIczAL#v=onepage&q=VELVET%20WORM%20HYDRAULIC&f=false) Velvet worms have legs but do not have a skeleton. All of the functions of the skeleton are done via hydraulics. If you are dead set that your creature will have an endoskeleton, hydraulic appendages are still very much an option. You may be familiar with a method vertebrates (including humans) use to produce a temporarily rigid organ using only hydraulic pressure. [Answer] Do you know why toothpaste contains fluorine? Because it replaces the OH group in hydroxyapatite and form [fluorapatite](https://en.wikipedia.org/wiki/Fluorapatite) > > Fluorapatite, often with the alternate spelling of fluoroapatite, is a phosphate mineral with the formula $Ca\_5(PO\_4)\_3F$ (calcium fluorophosphate). Fluorapatite is a hard crystalline solid. Although samples can have various color (green, brown, blue, yellow, violet, or colorless), the pure mineral is colorless, as expected for a material lacking transition metals. Along with hydroxylapatite, it can be a component of tooth enamel, but for industrial use both minerals are mined in the form of phosphate rock, whose usual mineral composition is primarily fluorapatite but often with significant amounts of the other. > > > Fluorapatite is found in the teeth of sharks and other fishes in varying concentrations. It is also present in human teeth that have been exposed to fluoride ions, for example, through water fluoridation or by using fluoride-containing toothpaste. > > > It's practically behind the corner in terms of biochemistry. ]
[Question] [ This is the first of two questions. Same introduction. A civilization on Earth has just begun expanding with a Dyson swarm, which is a [Dyson sphere](https://en.wikipedia.org/wiki/Dyson_sphere) but made with many satellites, to prevent structural problems a sphere would have. This will generate a lot of electricity for the population. I was reading some articles about solar flares and it got me thinking. How would a Dyson swarm react to solar flares and coronal mass ejections? Solar flares, Coronal mass ejections, and the like can cause havoc for electrical systems. This is because an abundance of energy is pushed onto the electrical circuits thanks to mostly magnetic induction, with a great potential to cause damage. On Earth and a lot of the orbit we're relatively well protected from the direct effects of a solar flare thanks to the magnetism of the Earth, but closer to the sun not so much. A Dyson swarm is relatively close to the sun and has no Earth magnetism to rely on. How would you defend a Dyson swarm against Coronal mass ejections, solar flares, and the like? In some other threads, I saw a lot of ideas with water or simply protection with a lot of dirt. To make sure it is well understood, the Dyson swarm is meant to make a lot of energy as efficient as possible. That is why the best answer tells the most efficient way of protection against big coronal mass ejections and the like. That means the satellites are preferable as light as possible, with as little complexity as possible, with as little loss of energy gathering efficiency as possible. 'Protection' can mean that you replace parts or satellites if they get damaged if you can support this with why it is most efficient. I'm well aware that this is a depth not suited for my short story, adding problems that aren't there for most readers, but I'm very interested in it anyway. Even if it's only mentioned in passing, I would like it to be correct. [Answer] # Acceptable Losses It's a Dyson Swarm, a prototypical megastructure. You're churning out millions (or tens of millions) of satellites. Why bother avoiding or hardening against coronal mass ejections; collect the roasted satellites for materials and launch replacements. It's basically the [datacentre drive replacement problem](https://xkcd.com/1737/). Rather than make things more durable/able to avoid CMEs, just accept that a portion of your satellites will be knocked offline at regular intervals, build redundancy into your network, and have a steady stream of replacements. [Answer] Individual magnetic fields. Each satellite protects itself the same way that the earth does: with a magnetic field. The individual satellites generate magnetic fields all of the time through their normal operation. If there is predicted to be a huge outpouring of charged particles from the star, the satellites strengthen their fields. These fields extend out some distance from the satellites and divert charged particles entering them. During this process the satellites might transmit less energy home. Do not begrudge that energy, fat and sassy Earth folks! Your hardworking satellites need it to stay safe. [Answer] Why not designing the swarm to take advantage of that bonanza of energy being tossed at it? Solar eruptions are bound to happen, so if one designs dedicated circuitry to capture that energy instead of avoiding it, it will make for a nice bonus on the produced energy, and will surely compensate for the added complexity to the overall architecture. Compare this with adding what is basically passive ballast and waste that energy. [Answer] ## With magnets, of course! You can protect the Dyson sphere the same way you can protect the planet. While it doesn't have a magnetic field by default, nothing stops you from generating one artificially (furthermore you can generate fields much stronger than planetary ones). Even more, CME is basically the sun throwing matter at you for free. Use magnets to channel the plasma into your starlifting facilities to turn it to use. One of the proposed starlifting techniques actually relies on creating a constant unending coronal ejection spot, by heating the surface of the star with lasers. ]
[Question] [ Closed. This question is [opinion-based](/help/closed-questions). It is not currently accepting answers. --- Want to improve this question? Update the question so it can be answered with facts and citations by [editing this post](/posts/201120/edit). Closed 2 years ago. [Improve this question](/posts/201120/edit) I'm struggling a bit in my worldbuilding on justifying the creation of different cultures on my land, when all originated from the same ancestors. So on my continent I have a group of humans that migrated thousands of years ago, and let's say they had a culture similar to ancient Greeks or Romans. This group expanded on the land, and killed or exiled any natives they found who were more primitive. They created the first Kingdoms and also had their own religion, of a pantheon of deities. So, many years after, I'd like to have a few groups migrating from them, towards various regions further to the west, and establish different cultures; more French let's say or others maybe more Celtic. And some of them keep their original religion. Another case is that I want a kingdom which was established by the first group to change into a different culture after many years. Keep the religion and the kingdom's name, but change their namings and cultural ways. As I have no clue how such things work, is any of the above possible and in what ways and circumstances I can have them justified? If not, then maybe any suggestions on a different approach? Thanking you all in advance! [Answer] Culture adapts to region. Your immigrants find themselves in very different circumstances. Some are in hostile areas with productive oceans and make their living from the sea. Some are in a dry steppe and become pastoral herdsmen, moving their herds from place to place. Some find themselves in agricultural land and turn into farmers. One of these farmer groups has found the natives unwilling to go easily and so live in a state of constant vigilance to defend their farms. Some find themselves in rainforest and live off the forest as hunter gatherers. Some become itinerant mimes, earning their keep by entertaining persons in the other tribes with their bawdy burlesque mimery. You can mold the culture of your peoples by varying the circumstances under which they live and how they put food on the table, and what sort of threats and problems they encounter in their regions. [Answer] The time scale you're talking is in the order of a couple of hundred years; I don't think you need to do anything special, there are enough real examples that what you're suggesting is plausible in real-world history. Take the Americas as an example, they were first landed at ~1500 in Brazil, the natives were steadily forced out and by ~1700 roughly 4 European nations pretty much dominated both continents. Another ~200 years later and there are very distinct subcultures, you certainly can't say that the culture of Brazil, Barbados, Kansas, and New York are very similar at all. You also begin to see that the culture(s) of the USA begin to strongly influence Europe and, following the World Wars, American culture is firmly rooted both in Europe and around the world during the late-20th Century. There are surely many other examples you could use from history, such as the Islamic expansion in Middle-East/North Africa/Southern Europe, or the Soviet expansion into Europe in the late 20th Century. [Answer] Children always diverge from their parents - especially when running into a new situation. Thus, teenagers today do not listen to the same music as the boomers. The words they use are different also. That is a cultural change within two generations. The dynamics are people moving into an area, meeting new challenges, solving them, and making new words to describe that situation. All you need is separation so that people are not traveling back and forth between the two areas. (If they did, then they would change the language together.) Many years ago, I was in rural Germany. In that area and at that time, people stayed in their villages enough that there were words different between villages a mile apart. A third village was in the area controlled by a different prince and people talked about how different their dialect was. Few people traveled to that third village from the first two. Often, things change enough that only the name of the religion stays the same but the content changes radically. Simply look at how Baptist churches in the US can be so different from each other today. [Answer] As mentioned already in other comments, the main thing is to keep different regions separate for extended periods of time. The natural differences (especially geographic) will result in different cultures. There's another major factor worth considering: NATIVES You wrote > > This group expanded on the land, and killed or exiled any natives they > found who were more primitive. > > > Even when the natives are being eliminated, they can still have an impact. For reference, think about how much of a cultural and linguistic impact the Native Americans had on the USA. So you could have some regions where the natives had extensive positive interactions (and possible extinction through assimilation), other areas with extended conflict, and a third with minimal interaction (say the natives fled upon learning of the new nation's arrival). In addition, each local native group would have its own cultural identity. The American Indians had very different cultures, even though they alo shared certain commonalities. So a large cultural variety, with varied interactions, could lead to vastly different native influences on your new nation. ]
[Question] [ I'm writing a fantasy story with a race of intelligent dragons who can increase the growth rate of/manipulate plants. If we pretend this is possible, what methods could these creatures utilize to keep the ships alive despite the lack of available soil nutrients and constant exposure to high salinity water? consider also they would be using plants that can tolerate salt to some degree, such as mangroves and sea grass, kelp, ect. [How would dragons utilize ships?](https://worldbuilding.stackexchange.com/q/199939/84593) [Answer] ## Yggdrasil: Plants live in the sea, even small plants floating in the sea, so there's no real barrier. Your tree-boats aren't different than a mangrove with the roots on the insides. Grow a hull on land, and solar (plant) power desalinates water. The plant skin can be cactus-like but for the reverse reasons. Waterproofing keeps out salt water instead of keeping water in. The "anchor" (a modified root with a weight on the end) can sample the bottom and net soil to add to the supply if it has needed nutrients. Leaves and branches supply a self-renewing set of sails that can be coaxed to deploy and retract like leaves do in real life in response to varied stimuli. Carry soil in the hull, or a premade enriched nutrient mix. Go fishing to provide supplement nutrients for the plants (or eat the fish, and use fecal material/bones as compost). Native Americans would bury caught fish in a mound with corn to provide nutrients for the corn to grow. Freshwater fish absorb salt, saltwater ones excrete salt, so there would be no significant difference. The ship can even grow it's own bait (fruits) and could even do the fishing Venus flytrap-style (grabbers or modified root-hooks). The plants can grow vitamin and micronutrient-rich berries to fill in the nutrition of the crew (no scurvey here!) Magic druidic plant charming fills in the gaps. If the sea-foresters can coax the boat into growing into whatever shapes they want, this is a self-healing adaptive vessel that will help feed the crew while they work to get the tree the things it needs. Other than an occasional stop on land to replenish easier supplies (dirt and fresh water would still be easier if you can get it on land) you could have a whole culture that would hardly ever need to touch land. Smaller boats used to row up to shore can be immature versions of the plant that are later shaped into full ships, but otherwise carried aboard or towed. ## Addendum: You could have nesting interconnected symbiotic relationships here, where an insect that might have a close relationship with trees (like termites) have evolved to shape and manipulate the trees and wood. What was once termites growing their own nests has become a three-way symbiosis. [Termites](https://www.termiteweb.com/termite-nests/) are capable of some extremely sophisticated nest engineering, and in this scenario, they are also guided by intelligent beings. Your ship's captain is in a deep interconnected relationship with the termite queen (this could be mind control, or it may be physical, like a symbiote that is biologically joined to the captain). The captain of the ship can consciously control the termites, who lay down hormone trails the plants grow along. The termites can regurgitate wood pulp to directly reshape the ship, digest the parts you want to get rid of, and so on. The relationship would be very close, and a good captain would be amazing. A bad captain would leave the ship out of control and possibly kill everyone. The death of the queen or the captain would be a very traumatic event for the entire ship, with much reshuffling (possibly even physical reshuffling) until the new relationship was worked out. Such termites could serve a variety of critical functions. The termites might be useful as food, or they might produce a secondary food stuff useable by the crew. They could manage the compost, feeding it to the tree. The tree might produce food directly to feed the termites so they don't need to eat their homes to live. The reproductive flying caste could pollenate the trees, and they could even be used as scouts or to communication between ships. They could root out worms trying to eat the wood of the tree. Every nifty function you can think of insects doing could be carried out by your termites. Who knows? Bioluminescent lighting? Maybe they even work in defense of the ship, repelling enemies with poison stingers. Why not? [Answer] They could use a 3 shells system: * the inner shell would be "dead" material, like wood, * the middle layer would be nutrient carrying material, sort of a compost, * the outer layer would be made of a lignin producing, genetically engineered variant of kelp or posidonia oceanica, which would use the nutrients from the middle layer to grow. They would periodically "shave" the outside of the outer layer to keep a decently hydrodynamic profile and to harvest material for repairing, improving the inner layer, while the outer layer would be taken care by its growth. ]
[Question] [ As humans, we're incredibly lucky that we only see in three primary colors. It makes the development of color displays quite easy. We only need to squeeze three subpixels into a single pixel! What if, instead, our eyes had evolved to be more like an optical spectrometer than a CCD camera, so each photoreceptor could tell what wavelengths were hitting it? A green leaf would not be green, but would contain hundreds of distinct colors even at the same point, with green merely being the most prominent. A modern RGB display would look to us like three monochrome displays of different colors superimposed on top of each other and varying in brightness only, not wavelength. How might development of the color television changed in this situation? Would we still be watching in monochrome, or are there any promising techniques that might have allowed a color display to exist that would satisfy our superior vision without being prohibitively large or complicated? [Answer] 1. you should look at squid eyes and shrimp eyes for other ways to achieve color vison. 2. combining colors still works fine because every cell in they eye either has to take take the sum of colors hitting it or the eye ends up with ridiculously low resolution. either the cells detect a tiny margin of the spectrum and thus have very low resolution, or they detect a larger part of the spectrum and get an aggregate signal or it splits the light at the point of each cell which again makes for very low resolution. The more subdivided and discreet the spectrum being sampled the more cells you need just to sample them all or the cells have to be much larger to divide the light entering it, either way you have the same problem they are competing for space and drastically reduce the resolution. Also because of the speed vision needs to work at and how nerve impulses work a cell either needs to be sending a binary or intensity signal, anything else requires chemical signaling which is too slow. A spectrometer's signals is limited by how many discrete colors your sampling can get for a given beam of light, an image is limited by how many discrete sample points you have per surface area, the two are competing which each other for surface area in the eye. You can't sample a single unit area of light for everything unless you make that area very large. Light from the environment is not clean if it has passed through and been reflected by many media before reaching an eye, and these variable are constantly changing. so having something like a spectrograph also makes little sense since it won't tell you anything useful. To put it simply you can either see the shape leaf, or see all the individual spectra being reflected by the leaf and everything around it, not both. You would really need to figure out how such an eye could work before any kind of answer can be given, because using normal biology it can't exist and form a decent image at the same time. [Answer] This just being pure conjecture, and not entirely related three primary color displays would and could still be feasible in us e, but could be better described, to use a direct t analogy as equivalent to black and white displays. Black and White tv was still a medium for entertainment,so a three-color, or five-color display COULD still end up being used in the same way, and I would imagine, not being an expert with regards to anything yet that it would end up sticking around for longer due to the difficulty of creating a display which would simultaneous emit several different bands of light. And a secondary question, are you an alien?(Sorry, now that I look at the question I see that it doesn't really make much sense. I should have given the question a bit more consideration) [Answer] Not only television, but "colo(u)r" photography and moving pictures development in such a world is difficult. I imagine black and white would dominate for quite a long time, at least the chemically produced pictures. As for TV - it would probably start with low-resolution (Baird-like) electromechanical attempts, then move to fully electronic system, still monochrome - no difference from our technology until 1950 or so. Then it depends on the exact mechanism of eye sensitivity to the spectrum. Evolution would not favour total discrimination of the wavelengths, because then leaf (or predator) would look very differently on a sunny day and when it is overcast - and you definitely do not want this (see also quite fantastic automatic white balance of human vision). Much like we have psychoacoustic models (much used in sound compression), there would be a spectral response model. And that means you can approximate the spectral response with a function with some parameters. Analogue transmission means you have to sample three dimensional picture (where the 3rd axis is the spectral one), which increases the bandwidth enormously to have any fidelity. So the true "color" broadcasting would have to wait until say the 2000s, with digital transmission, advanced compression methods and a lot of CPU power (and a fine LCD grid to reproduce enough points of the spectral response). [Answer] For chemical photography, at least, there is at least one process (perhaps two) that produces color in a manner your "full spectrum" vision would perceive as full color: Lippman plates. These are made by using an emulsion in direct contact with a reflecting layer (historically, liquid mercury), which is then developed in a conventional manner and produces a direct positive, full color reflective image due to the interference effects of different light wavelengths within the thickness of the photo emulsion. This was (in our timeline) an accidental discovery based on similar (but not color-accurate) effects that occur on overexposed Daguerreotype plates, and was possible as soon as dry plate emulsions were available (ca. 1870), though the actual process was discovered after tri-color had been demonstrated. Once the Lippman process is known, it's "just" a matter of inventing a display that can use interference in the same way to display color. We haven't tried, because we don't need it (with our four-color -- two sensor types with two colors each) eyes. Your spectrographic-sighted race may decide they do need this. [Answer] You could achieve your goal of television (or indeed cinema) that is not based on combining primary colors using a modified form of DLP ([Digital Light Processing](https://en.wikipedia.org/wiki/Digital_Light_Processing)), a technology that is currently found in movie theaters and some consumer products. A conventional DLP projector uses an array of thousands of microscopic mirrors that pivot under digital control such that they either reflect light along the optical axis or dump light into a black heat sink. As digital devices, each mirror (pixel) is either "on" or "off". Conventional DLP uses light sources in the three primary colors or one white light source and a rotating color wheel. That won't work for your species, so . . . For your spectrally advanced species, instead of each mirror element being a plain mirror, each could be a mirrored [diffraction grating](https://en.wikipedia.org/wiki/Diffraction_grating) that would refract and reflect a specific pure color from a white light source depending on the angle of reflection. (Such diffraction gratings already exist, but perhaps not so small.) Likewise, instead of the microscopic mirrors being designed to have just two states, on or off, each mirror in this device would have to assume any angle within a certain range and could therefore produce any color of the rainbow from the white light source. To prevent color smearing, there would have to be a "[shadow mask](https://en.wikipedia.org/wiki/Shadow_mask)" similar to that used in color CRTs. [Answer] This seems to be a 'Can we see the trees for the forest?' type question. There are three distinctly different things happening in human vision. One is to differentiate the colors, and the second is to resolve the details of the shape and form. Then, there is the original vision systems, such as that still used by the fly, that senses neither color nor detail, but just motion. Basically, all it resolves is a moving shadow across the vision sensors. If there is no movement, there is no 'vision'. In humans, our monochrome vision can resolve high detail, as in seeing the trees. Our color vision resolves the overall background color, as in the forest. It seems our eyes map the the overall color detail on top of the detailed monochrome image to create, in our mind, the final 'color' high-res picture. That is, we do not stop using our monochrome sensors just because the light is bright enough to resolve colors. Our color vision adds to the monochrome vision. I could imagine the eye of this hypothetical being would have to be very similar. That is, monochrome non-differentiated spectrum sensors to determine detail and movement, and the more general spectral image processors to define the color. In terms of pure survivability, the faster monochrome detail and motion response would be a first-alert system, and the slower (I suspect) spectral image processor would provide more information after a very brief lag. In our first televisions and other image capture media, we generally either used black-and-white images, or color images, and did not combine the two. That is, the original CRT screens were either monochrome or color phosphor screens, but not both. After all, the same color signal activates both the monochrome and color sensors in our eyes. I suspect the televisions of this society might have developed a different dual-process form of television - one that produced very fine monochrome detail imaging, and a second system that mapped color onto this monochrome image. Maybe filters that went over the screen, cycling through the color spectrum, in synch with the monochrome image. That way, the monochrome projects the detailed trees, the color filter device fills in the forest color. ]
[Question] [ So this is something I've recently started to think about lately and it's honestly a case of genuine curiosity more than anything else. Many fantasy/adventure-oriented video games usually feature a level defined by flowing rivers of lava, active volcanoes and long stretches of barren, rocky land to trend through. Hell, Star Wars: Revenge of the Sith featured an entire planet themed around this exact same concept. Since these type of environments don't actually exist in real life (well, on Earth at least) my question is, what conditions would need to be met in order for an environment like this to exist in real life and function like they do in video games? How hot would the lava need to be in order for it to be as viscous as water (which is what video game lava basically is)? Could you hop across large rocks situated on top of lava flows like makeshift platforms? Assuming you had both a gas mask and the right kind of getup, could you even set a single foot in this place without burning to a crisp, blowing up or suffocating? Could any sort of life at all adapt to living in an environment like this (this as in, the space between the lava flows and rivers, not the actual lava itself)? Also, key note. I'm not interested in HOW this environment came to be, only the way it would function. [Answer] Lava rivers exist in real life, especially in volcanic areas where the lava is basic, thus very fluid, like Iceland, Hawaii and all over the globe where a rift is open (bonus, those are mostly underwater). Viscosity of lava is mostly dictated by its chemical composition: the more acidic it is, the more viscous it is. And viscous lava tend to explode, because of the gas it traps. Due to the scorching heat radiated by the molten lava there is no life which can survive in the immediate proximity of a lava flow: apart from heat damage, any water would be quickly dried away. And even humans would not fare well in those environments. Volcanologist wear protective gear to not get charred by the radiant heat, but it's far from being pleasant. Top it with the risk of suffocating. Far from being the funny stunt that you see performed by Lara. [Answer] > > Since these type of environments don't actually exist in real life > > > They do exist in real life. The word "lava" was not invented by game writers, it came from the real-life phenomenon. Videos 1. [Video shows man WALKING ON LAVA and now scientists have explained exactly how he did it.](https://www.youtube.com/watch?v=e57D4oGoh5s) 2. [Watch A Man Run Through A Scorching Lava Field And Try Not To Wince](https://www.huffpost.com/entry/man-runs-through-lava_n_57a172bfe4b0693164c33ba9) (scroll to bottom for short version) 3. [This guy putting his foot on Molten Lava](https://www.sociolatte.com/2014/12/this-guy-putting-his-foot-on-molten-lava.html?spref=pi) --- > > what conditions would need to be met in order for an environment like > this to exist in real life and function like they do in video games? > > > Live near a volcano or move to Hawaii. [![enter image description here](https://i.stack.imgur.com/P9eAL.png)](https://i.stack.imgur.com/P9eAL.png) ]
[Question] [ I've been reading up on coilguns and railguns, and it got me to thinking about space combat with railguns or coilguns. I assumed that such space combat would involve ships in somewhat circular orbits around each other. Such ships would experience angular momentum. To keep combat distances plausible, I assumed angular velocities of 8 km/s, which is typical of earth orbital velocities. Assuming angular momentum of 1g, this results in an orbiting combat radius of 6400 km. As such, I've assumed the combat distance a coilgun shell would need to traverse is 6000-12000 km. I've further assumed a meaningful maximum time to target of 60 seconds. That means the coilgun shell needs a dV of 200 km/s. For this purpose, I'm ignoring the incredible energy or technology this would require. The velocity imparted on a coilgun round is related to the length of the barrel and the acceleration it experiences. I've assumed a coilgun barrel length of 100m; EVE Online invisages such skyscraper sized railguns. For a 100m length at a dV of 200 kps, the acceleration experienced is 20,000,000g. A USN railgun experiences about 50,000g. So my question, what is the maximum gs a railgun or coilgun shell could experience without disintegrating while being launched? [Answer] Very high G are possible. But not efficient or easy. A coilgun projectile is just a hunk of matter, there is no part of it that is more or less breakable than another part. Correctly designed, the forces acting on the projectile act on the whole projectile, equally. In effect the projectile would not "feel" any acceleration, it would just be accelerated. The limiting factor in coilgun acceleration does not arise from the acceleration forces on the projectile, but from the acceleration method used. A coilgun works by creating a hugemongous magnetic field, which pulls the projectile along, by inducing an equally hugemongous magnetic field in the projectile. But there is such a thing as [magnetic saturation](https://en.wikipedia.org/wiki/Saturation_(magnetic)). However, as magnetic saturation merely makes further increases in acceleration inefficient, not impossible, this also does not impose a real limit, merely an efficiency limit. The last limit is that the projectile gets heated up, somewhat, by the induced electrical current flowing through it. Pretty soon it will melt, then vaporize. So, yeah. There are no fundamental laws of physics preventing acceleration of the magnitude you want, but efficiency and material science will chicken out a long time before you achieve your desired 20 000 000g. A coilgun that does manage this sort of acceleration would not manage to shot a solid projectile, but rather a diffuse spray of ultrahot plasma. And if you are going to shot that stuff, rather start with a charges particle accelerator in the first place, it is much easier. It is for this reason that Railguns and Coilguns (i.e. ballistic material projectiles) are not considered good weapons for longrange engagements such as you envisage. Not against mobile targets, in any case. For example, in The Expanse, the absolute maximum distance for projectile attacks is some 1000km, with 20-200km being the preferred distance. For longer range, you should use propelled weaponry. Missiles, basically. P.S. If you have a ship capable of 1g of acceleration. And the enemy shoots an unguided chunk of metal at you, regardless of the speed, that takes 60 seconds to reach you, then you will have the ability to detect and dodge the projectile. By applying lateral 1g acceleration, you can be 17.6 kilometres away from the original target point. Which I'm sure you will agree makes a longrange unguided projectile useless. That exact same projectile, from 500km away (2.5s travel time), only allows 30.6m of dodging. And at 50km, maximum dodge is only 30 cm, utterly useless! ]
[Question] [ I want to know if this is scientifically possible in the real world. When you take vast expanses of deserts (the sandy hot ones, not the icy ones) like the Sahara, life in general is restricted to near whatever small rivers or oasis/lakes there are or close to the oceans. But these places can become vastly different with just a bit of steady rain. Take India or mainland southeast Asia/ southern China for example which is on the same level as the Sahara from top to bottom on the map but is much greener and can sustain high population and produce lots of food and even rainforests similar to the amazon thanks to monsoons and tropical rainstorms. The only way to make it rain is to get cloud systems to make their way into the Sahara, but as is evident this doesn't happen. So maybe a way to fix this is to bring massive quantites of water inland where they can evaporate away and then rain down somewhere else in the Sahara (which is HUGE so the rain clouds won't make it far enough to escape the desert). This could be achieved by making massive, deep canals (dimensions can vary) that run through much of the interior of the Sahara (like the veins of a leaf) bringing Atlantic and Mediterranean water inland which evaporates in vast quantities and bringing more water in. Dams could be built to control flow and generate power. Endoheric basins could be expanded on or completely built from scratch to create inland seas like the Aral or Caspian. Rivers like the Congo which already have a high elevation and is second only to the amazon in the water it produces could be diverted easily from higher to lower elevations in the Sahara. Dams again could generate power for new settlements along the new river banks. The salt which collects at the bottom could be a problem and block the canals but they could be mined away or made into building materials and coated to prevent water from dissolving them and this could be used to make at least a few small scale houses. Other industrial uses escape me but must exist. The threat of rising sea levels is non existent as these canals could be made deeper and narrower to prevent flooding. if built on a large enough scale it may even lower the sea levels worldwide. The lake chad basin alone is bigger than a quarter of the US and is mostly desert. Mining could make it deeper. The Massive amounts of materials generated could be used to reclaim new land from the ocean or build flood barriers like the Netherlands is doing. Could this turn the Sahara green? Or at least make it more inhabitable? [Answer] You have rediscovered the [Sahara Sea](https://en.wikipedia.org/wiki/Sahara_Sea) idea. [![Qattara Depression Project map](https://i.stack.imgur.com/1SlRQ.png)](https://i.stack.imgur.com/1SlRQ.png) Its a good 150 years old, so you can sea that people have been thinking about this sort of idea for quite some time now. Proponents of the plan think it has all the good points that you mentioned. What doesn't seem so obvious is any consideration of the bad effects of having a non-draining hypersaline lake. They also didn't worry about the opinions of the locals, because colonial types with grandiose ideas seldom worry about that sort of thing. It is worth remembering that the people who live there will have strong opinions about such a project, have their own economical and political woes, and a significant amount of suspicion for anything coming from former colonial powers. Maybe have a read of this [XKCD What If?](https://what-if.xkcd.com/152/) about flooding death valley, which talks about the [Salton Sea](https://en.wikipedia.org/wiki/Salton_Sea), not very enthusiatically. Of course, the Salton sea is never refilled in the way that a new body of water connected to the ocean would be, but some of the underlying issues will be shared. Dealing with the salinity is unlikely to be as easy as mining a bit of salt and building some pyramids with it, alas, especially when you consider the sheer scale of the enterprise. It may be that the local climatic changes caused by this new body of water might be beneficial enough to warrant the risks of the creation of the sea, and the huge amount of destruction it would cause. I wouldn't want to bet on it, though. [Answer] Backfire Although moisture is one of the important building blocks of life, you can't just throw water on it repeatedly and hope for the best. To make something green, you also need the following: * Water needs to be retained. * Good soil must be available. A desert often misses one or both of these things. Good examples are temperate and arid deserts. Few things grow, as there isn't enough to retain the water that has fallen. In addition, without plants and trees the nutrient rich soil is washed awayby rain, the very thing that should help. There is erosion. More rain in the sahara specifically will not work directly. Left alone it might grow fully green with enough rain, but it would take a long time. And I say 'might', as I don't know how much soil is washed away and how easily the sand holds the water. You can still increase the speed and range of this process though. In China they've experimented with planting diamond shapes throughout the desert. Thise are just plants on the edges of the diamonds, while the inside is untouched. The plants start holding both the soil, the water and cool down their surroundings thanks to vaporising water. This will increase the chances of rain and vegetation to grow in the diamond shapes. In a year it looks green. In three years it looks like a wild young patch of forest. To my knowledge this isn't location specific, although I do fully expect you need to have a basic amount of rainfall. Your idea to evaporate more water and in closer proximity will help with more rainfall and cooling, although the saline properties can be difficult close to the water source as well as building up salt levels like the red sea, potentially stoppimg water flow. It has many other possible problems as Starfish Prime is stating. But in essence, you can increase the rainfall. Still, more vegetation would be a great help. [Answer] The whole idea is not particularly practical. However some progress could be made. I suggest that salt water canals into the interior of the Sahara would be a very bad idea. It would cost a fortune and they would contaminate the existing deep water aquifers making them unusable. To make matters worse the salt would soon start to crystallize on the surface and sides of the canals and some would be blown across the land. Operations to remove salt would undoubtedly also spill salt water onto the land increasing the problem further. It would be far better to pump fresh water into specific areas of the desert than salt water. Also it would be beneficial to ensure that what little rain does fall is utilized to the maximum extent possible, either captured and stored for use in cisterns underground or directed through a series of overflow channels into areas where plants and trees are being grown. The cost would be huge you might want to try getting some top end multi billionaire like Elon Musk to redirect their energies into greening the desert (fat chance). But assuming sufficient funds were available it would be possible to build a lot of water purification plant on the coast and pipe the water inland. With the high temperatures and large scale of operations some sort of massive solar plant could be built. I doubt it would be possible to green more than a small fraction of the Sahara in this way but it depends on how much time and money is involved. Note the practical problems would also include a myriad of political issues. Once a few hundred square miles or more of greenery had been established fighting would likely start over ownership and water rights (regardless of who agreed what initially). [Answer] ### There's a 21st century solution to this So as pointed out by Both Willik and Starfish Prime, we've been planning to build a channel into the saharah for nearly 2 centuries. The issues are: * It'll accumulate salt. Salt is very bad when you want to grow things. * It'll accumulate agricultural run off, so it'll become poisonous. * It'll probably stink real bad, ala Salton Sea. * You'll need to dredge the channel and lake constantly. The Sahara desert is 9.2 trillian square meters, to water it with 250mm of yearly rainfall (A common definition of a desert) you'll need 2.3 \* 10^15 liters of water per year. That water needs to be salt free and pumped into the Sahara. [This desal plant](https://en.wikipedia.org/wiki/Adelaide_Desalination_Plant) can produces 1 \* 10^11 liters of water per annum, so you'd need to scale this up by 23,000. It cost \$1.83 billion for 1 plant, so you're looking at back of envelope \$42 trillion for the upfront desalination plants. Desalination is pretty expensive; You're looking at about 3.5KWH per KL, so 8.05 \* 10^15 Watts of power per year. 8 PetaWattHours of power per year, or 920 GW of average power throughput. This is 92 times larger than [the worlds largest solar/battery power plant](https://www.pinsentmasons.com/out-law/news/worlds-largest-solar-farm-to-be-built-in-australia), but not entirely impossible. Looking at about \$1.2 trillion for power, which would include 2.7TWH of battery storage allowing it to run overnight. You'd probably want to spent that much again on wind turbines too to avoid draining the batteries every night, which is bad for their longevity. The total of the project is looking at about \$45 trillion, lets round it up to \$50 to include piping, pumps, buying land from people who are going to be flooded, and everything else I'm forgetting. Earths GDP is about 80 trillion, so funding this would be hard, but not impossible. I'd suggest a global 30% wealth tax on anyone with over [3 million USD in wealth](https://en.wikipedia.org/wiki/Millionaire), and a 99% wealth tax on anyone with over [1 billion USD in wealth](https://en.wikipedia.org/wiki/The_World%27s_Billionaires). The tax is so small relative to their fortunes they won't even notice - they'll all still be multi-millionaires at the end. ]
[Question] [ Okay, so here's the deal; every time dragon blood is shed, it hardens on contact with the air, forming crystals of 'bloodstone.' Bloodstones are infused with the magical essence of the dragon it originates from, and due to humanity's connection to the Earth element, they can absorb bloodstone and by extension, it's magical properties. However, there is a caveat; only two kinds of people can absorb bloodstone. Those who have slain a dragon, and those who have been eaten by a dragon. When someone slays (or grievously injures) a dragon, magical energy is released, "marking" them and forming a (rather dark) connection. Similarly, since digestion forms a link (you are what you eat has some basis in fact in this world, for reasons I will not disclose unless necessary to avoid erecting a wall of text), those who have been inside a dragon and subjected to its "juices" have a connection to that dragon. Only people who have slain (or grievously injured) a dragon, or been eaten by him or her, can absorb his/her bloodstone. After one ingests bloodstone, they are enchanted, gaining special abilities; bloodstone from a Sky Dragon allows one to fly and manipulate the wind, bloodstone from a Fire Dragon makes one fireproof and allows them to manipulate fire, and so on. Bloodstone consumers are also enhanced; not only do they gain greater energy and stamina, but their senses, strength, speed, (as well as their survival and combat skills) are all enhanced. The level of these enhancements depends on the dragon's power, as well as its type; Fire Dragon Bloodstone grants greater strength than anything else, while Sky Dragon Bloodstone grants greater speed than anything else. However, two problems have convinced me that I need to put checks on this. Number one, there's nothing stopping a Dragonslayer from slaying dragon after dragon, gaining more and more power each time, or a reckless (or rather smart but unconventional) princess from going out and getting eaten by dragons and eating their bloodstone after they've been slain. Number two, bloodstone can only be absorbed by those connected to a dragon because of the species gap. However, after being infused with draconic energy through bloodstone ingestion, humans generate bloodstone naturally (AKA just like dragons do). This bloodstone can be absorbed by blood relatives (siblings, parents, children) or anyone who manages to grievously injure or kill that individual. Considering the two above factors, my question is: How Can Bloodstones Be Better Balanced To Avoid Creating Overpowered Individuals Or Increased Murderousness In Society? \\Please Note:\\If at possible, I would like a balance method that allows someone to absorb more than one bloodstone while preventing them from becoming godlike through sheer number of absorbed bloodstones. This is because some ancient dragons, lying dormant far away from civilization, are so powerful that if they awakened there needs to be dragonslayers capable of handling them. However, no one dragon in the current age holds enough power to create such a dragonslayer. Thank you for your input and feedback, I truly do appreciate it. If you choose to VTC or downvote, please give me an explanation so I can improve this question and post better ones in the future. [Answer] Diminishing returns for balance. I suggest diminishing returns across the board. The more dragon stones one consumes the less benefit they gain from each, or perhaps the diminishing returns only applies to a type of dragon stone, so after consuming a fire stone you get full benefit from consuming an earth stone, but consuming a second fire stone will give far less benefit, and consuming more then 2 gives negligible benefits. In addition the power of a stone is based off of the power of the person who produces it. A Dragon is very powerful, the stone they produce is thus equally strong. By comparison the power one gains from a first generation dragon-slayer is lower, but still useful. a second generation dragon slayer (say the son of a first gen who consumed their father's stone) creates a comparatively weak stone etc. Thus diminishing returns limits the upper bounds of power. This would also imply a dragon stone from one of your ancient dragons could make an uber dragon slayer. If you go this route you would have to decide what happens if someone consumes a 'weak' stone only to later consume a 'strong' stone. You could either have the order of the stone taken mater, once someone consumes a weak stone they will gain less from a any subsequent stone, meaning a strong stone may still give minimal benefits due to diminishing returns, and thus meaning becoming a dragon slayer by taking a 2 gen stone means your have put an upper bound on your potential power you will ever achieve (which could be useful, if you want a group of elite-mook types, strong enough to be some degree of a threat to a 'real' dragon slayer, but weak enough that your hero can take on multiple at once. Alternatively the amount of resistance gained is based off of the strength of a dragon stone consumed. Thus a user gains just about the same amount of power by consuming a weak stone followed by a strong one as they would by using a strong stone followed by a weak stone, since the weak resistance gained from the weak stone doesn't interfere too much with gaining of power from the strong stone. If you do the later though that begs the question why 2 gen dragon slayers don't go around consuming lots of stones from other second gen dragon slayers, until they built up enough power to rival 2 gen slayers since their upper limits are roughly the same. You could say that once you eat a weak stone other weak stones don't gain much but weak stones aren't as good at interfering with strong stones potentially if you want to prevent that. Hello, my name is Smaug, you killed my father, prepare to die! I imagine dragons don't appreciate people torturing, or killing, their kin, and aren't too happy about humans gaining dragon slayer powers if humans are likely to use it to kill more dragons for more power. Thus dragons, if they are sapient, have a pretty strong incentive to preventing dragon slayers from existing. This may mean that dragons go out of their way to kill dragon slayers, and act as a strong incentive to not become a slayer lightly. Maybe dragons can sense the magic of a dragon slayer, making it easy for them to sense when one is near and causing them to go out of their way to find and kill the slayer. This idea particularly works well if you use diminishing returns, with 2 gen slayers being weaker then 1 gen. That way dragons likely will feel safe to kill 2 gen slayers, as their too weak to defend themselves from a dragon usually, but they may think twice about attacking a 1 gen slayer, as their already proven to be a threat to the dragon. Similarly dragons may go out of their way to kill anyone they have 'eaten' (since apparently eating them doesn't kill them?) just to make sure that person will never become a dragon slayer and threaten to kill their kin for more power in the future. Dragon based threats work as a good counter to individuals wanting to become dragon slayers in secret out of pure desire for power, though it would likely want to be combined with a more political reason that large governments don't train up entire militaries of dragon slayers. So basically the threat of dragons hunting you should be a partial answer for why there aren't more slayers, with some of the more political options suggested by other users also being part of the reason. [Answer] Pyrotechnics accidents. These bloodstones you describe offer vast magical power, associated with dragons, such as fire. The more of this power a person has, the easier it is for them to inadvertently release a bit too much and combust, explode, tear themselves apart flying in multiple directions, teleport into a wall or nearby person, etc. [Answer] The first problem is subject to an easier solution than the second. # Dragons Are Immune A dragon who kills another dragon and eats its bloodstone doesn't gain its powers. Similarly, when someone slays a dragon and eats its bloodstone to gain its powers, they also gain its inability to gain other dragons' powers. A bloodstone recipient gets the first set of powers and no others. As for the second problem: # The Law of the Land Local royalty and most of their nobles are bloodstone-infused, from generations past, their power the reason they were able to achieve domination over the realm. As a result, any new bloodstone-infused individual who cannot present proof of the dragon they have slain are themselves put painfully to death, a law of self-interest preventing would be regicidal individuals. [Answer] How about a social solution? Nuclear weapons grant the state that wield them immense power geopolitically, so it makes sense you’d want to have more of them, right? There’s nothing stopping nuclear superpowers from making an ever growing arsenal of nukes and so gaining more power. It’s just that these superpowered states would, in exercising that power, destroy the world as they know it and also be subject to immediate counterattacks from other nuclear superpowers. So in reality the nuclear arsenals of the world have, by mutual agreement, been reduced from their peak. Nobody wants to be the one to start a war, and if they did they know that the best case scenario is pretty much the end of the world. So too with Bloodstone users. They know that a war between two or more überpowered bloodstone individuals is just going to lead to vast swathes of land ruined and not actually achieve anything, so they have written up some accords limiting the amount of power any one individual can be allowed to acquire, along with some extra rules on how powers can be transferred legally. In the accords there is a line about all signatories immediately coming together and turning against any bloodstone user who breaks the accords or refuses to sign. This keeps all the bloodstone users balanced in power by common agreement, because the alternative is Uncivilised. Of course, this is a fragile state of affairs, but that’s where you get juicy plot points from. You might have an emerging superpowered extremist threat that refuses to sign and must be stopped before they gain too much power, or an order of superpowered knights dedicated to upholding the accords, or a handful of pre-accord individuals who are in a constant Cold War style power struggle. Final thought: You might say this will never last because one party will eventually break the rules, but the world hasn’t ended in nuclear fire yet! [Answer] The human body naturally places limitations on itself. Breaking those limitations causes things like Hysterical Strength. After a Bloodstone is absorbed, the Slayer's body is not accustomed to the increased speed, strength, etc. This can easily lead to soreness as a lower bound and the muscles ripping themselves apart as an upper bound to the awfulness. How do the Slayers overcome this? Simple. Living a normal life for a while. Reacquainting the brain with the power of the muscles will take quite a while but eventually they will be able to exercise without risking harming themselves. Additionally, this has to sink in far enough to affect the reflexes otherwise the first punch thrown at them will cause them to dodge subconsciously and rip some muscles. So there is a natural limit to how many Bloodstones you can consume based on several factors. The strength of a Bloodstone determining how many you can consume before ripping yourself apart. The recovery time of consuming a Bloodstone determining how long until you can effectively fight again without self-injury (this is increased by the strength of the bloodstone as well). Why don't they murder for Bloodstones? The Slayers can easily kill a normal person on accident until the power is under control. A Slayer who hunts another person's bloodstone is in the recovery time for a good while after making them vulnerable to a manhunt or retribution. Bloodstones are a valuable but risky business. [Answer] Pain and sadness aplenty. 7, when you die all your body fluids turn into bloodstone. 8, it starts to destroy your DNA on massive scale(think your entire hand having all it's cells DNA fragmented). 9, you get massive cell wall collapse and turn into a puddle of goo instantly. ]
[Question] [ In my story's world, dragons have been living alongside humans for some time now. Of course, there are hospitals and other medical facilities variable to them. Now, as some of the staff of said facilities are humans, how can they protect themselves from aggressive/panicking/delirious patients? An upset child who is terrified of that needle you're holding is bad enough, but when a (dragon) child is extraordinarily strong and can breathe fire, ice, acid, or poison gas, how do you cope? What can human medical staff handle draconic patients? I've already figured that staff would probably have various methods of restraint on hand: sedatives, physical restraints, with help from parents and bribery with treats for young ones. Do you have any other ideas for protective gear or magic? EDIT: It's been brought to my attention that I forgot the time period. This story is set in the BattleTech universe, circa 3135 on an original world that has well-studied and functional high fantasy style magic in addition to all the tech. EDIT 2: Dragon sizes. An adult dragon weighs an average of 10 tons and is 55-60 feet long from nose to tail tip laid out. Wingspan of around 70 feet. A wyrmling weighs about 40 pounds, is 8 feet long from nose to tail tip, and has a wingspan of 20 feet. Juvenile and young adult examples would be in between the two. [Answer] *IRON DOCTOR!* As a health care worker, I hate to say it, but nurses and doctors suffer a lot of workplace violence from abusive patients, family members, and even associates determined to do violence.Intelligent species aren't going to tolerate being sedated all the time. If humans were being treated by pixies, do you think the human would be okay with it? Since we're talking battletech-level science, why not med suits like in Starcraft? It incorporates environmental protection from toxins, diseases, and plain old physical abuse. You could have a species-specific set of medications built in as a pod, depending on who/what you were treating. A giant can crush you, but an ammonia breather is toxic to work around, a venomous lizard can poison you, and you never know when someone's newborn is also a face sucker from ALIEN. The Ytterbian plague is going around, and armored PPE is just the thing to keep it out. Hose it down at the end of the shift with sulfuric acid and hard radiation. All this assumes you don't want to skip a biological doctor and just use robots. The "human" touch is important in medicine. [![Starcraft Medic](https://i.stack.imgur.com/vbvDj.png)](https://i.stack.imgur.com/vbvDj.png) [Answer] In the real world veterinary doctors treat horses, cows, gorillas, elephants, orcas and other such large animals. Some of those patients can kill people and/or deal a lot of damage to property with ease. Check how these animals are treated and you'll have the info you seek. Elephants and orcas specially are very smart and can be very moody. Sedation is mandatory in cases of raging or delirious patients. For lucid yet aggressive patients, you need to gain their thrust. It's just like handling large male human adults in a psychiatric ward, really. The only difference is the amount of danger you're in for in this line of work. [Answer] Not entirely sure what battletech means, but from your comment it seems like they're pretty advanced. Just off the top of my head, I'd recommend sedation, but that's a lot of drugs. So I came up with this stupid idea- immersive VR. we already can make VR look pretty real, and I'm sure you could handwave in this tech that makes the dragon think he's not there until you finish setting the leg/stitching the wing/whatever. not entirely sure what this system would look like, but maybe it's helpful. A secondary option, if you're tech is advanced enough, is to do a very localized drug that shuts down the pain receptors of the brain while you're operating or whatever. if you can do this, you might also consider just turning off motor controls as well so it won't try and swat the doctors away. final stupid option- sometimes, all they need is a good distraction, so maybe set up a tv playing despicable me or something for the patient. not a failproof method, but it would probably help some. ]
[Question] [ This is going to take some explaining, but the basic idea is thus: In the world I'm creating, if matter is exposed to enough magical energy it ceases to respect the laws of physics and becomes known as "eldritch matter." Eldritch matter vaguely retains it's original shape and but on a microscopic level it's essentially a solid with the properties of a liquid (and floats) that retains a shape at a general level, but no complex structures are able to be maintained as the matter constantly shifts. There are some animals that have become eldritch matter, and when they do they survive, and become and eldritch entity, a creature that defies the laws of physics but in return has no neurological function because their neurons are not able to be maintained, so they are essentially reduced to the lowest form of intelligence possible, a mindless beast that does nothing but endlessly seek magical sources to suck dry to maintain it's existence. Since they are essentially immortal so long as more magical sources can be found, people have tried multiple times to become eldritch matter, the basic idea being maintain the structures of the brain while all else becomes eldritch matter. This almost never works, as eldritch matter tends to spread, but one person has achieved it. They now take the form of an amorphous mass that has been crafted to resemble their previous form, but their brain structure has been maintained so they can retain control over it. However, over time their neurons very slowly turned into eldritch matter, destroying the structure and sending them essentially mad. This is (very roughly) equivalent to a neurodegenerative disease, as parts of the brain slowly become useless, but it would be attacking every part of the brain at once, albeit extremely slowly and from the outside. I was wondering what irl disease is the closest equivalent so I can model their behaviour on that of sufferers of that disease? p.s. i have no basis to know if any of this is correct or plausible [Answer] The affected person would die long before neurodegeneration begins. The human body depends on the harmonious interaction of many different complex systems and intricate organs. If the lower portion of the human body is affected before their brain, many of these vital processes would quickly cease to function, resulting in death. Take the circulatory system, for example. Suppose just one of a human’s appendages is affected by this “eldritch disease.” All of the blood cells that flow through this appendage will lose their structure and be lost. Thus, the brain will quickly run out of oxygen and die. [Answer] I'm going to assume that, since the rest of the body is Eldritch Matter, the rest of the life functions are somehow intact and the brain can survive in its current configuration. Neurodegenerative diseases (ND) are typically categorized by the damage to the brain, but usually not in the way we're discussing here. As opposed to actually destroying and removing brain cells, NDs typically involve some kind of protein growth that renders the cell communications useless in some way or physical damages them to the point that they no longer communicate. This should effectively be the same thing as removal of the cells, though, so this an adequate starting place. The most fitting ND subtype would be [Alzheimer's Disease](https://en.wikipedia.org/wiki/Alzheimer%27s_disease#Neuropathology) (AD). AD is associated with formations occurring in the brain that damage it and cause it to atrophy. [Unilateral brain atrophy](https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FBrain-Atrophy-in-Advanced-Alzheimers-Disease-41_fig2_273768877&psig=AOvVaw1eNTfMus1Y_gTNkqUQes-k&ust=1596298835380000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCKCkyN7y9-oCFQAAAAAdAAAAABAD) might be the most similar to the slow-brain-destruction scenario you've expressed, and thus this seems fitting. This disease progresses somewhat slowly, with the common expectancy being 3 to 9 years. That's slow enough for the changes to occur in a timeline wherein this character is still viable, but almost demonstrably being affected by the loss of brain tissue. Various early symptoms include reduction of short-term memory and learning capacities, loss of vocabulary, and a decrease in word fluency. Mid-term symptoms can include increased language deficit, irritability, episodes of uncontrolled laughing or crying, outbursts of aggression, and resistance to care. The late stages do seem to reflect the other entities you mentioned, where the brain structures associated with higher-function are completely destroyed and the Eldritch Matter takes over, so to speak. Of course, there are other physical symptoms, but the Eldritch matter appears to be responsible for physical actions in this case and I'm going to handwave and assume that the brain can communicate with that matter as long as it is conscious and capable of higher thought. Which does raise an interesting question, what happens if this character "falls asleep" or becomes unconscious for a period? [Answer] > > Closest real neurological disorder to the state of being an eldritch entity? > > > > > There are some animals that have become eldritch matter, and when they do they survive (...) > > > Ok, so far so good. > > (...), and become and eldritch entity, a creature that defies the laws of physics but in return has no neurological function because their neurons are not able to be maintained (...) > > > If the animal is a sponge or a member of the placozoa phylum, then it becomes a super version of itself. Any other kind of animals becomes a dead animal. [Even simple animals such as jellyfish](https://en.wikipedia.org/wiki/List_of_animals_by_number_of_neurons) depend on having a huge amount of neural connections (not simply many neurons) in order to function. --- Then you mention a human that survived, but: > > over time their neurons very slowly turned into eldritch matter, destroying the structure and sending them essentially mad. > > > [Alzheimer, Parkinson, Huntington, ALS and Batten](https://en.wikipedia.org/wiki/Neurodegeneration#Specific_disorders) destroy specific parts of the brain. For a more generalized and homogeneous form of slow destruction, you're looking for spongiform encephalopathy. A very well known disease of this kind is [Kuru](https://en.wikipedia.org/wiki/Kuru_(disease)): > > Kuru is a very rare, incurable and fatal neurodegenerative disorder that was formerly common among the Fore people of Papua New Guinea. Kuru is a form of transmissible spongiform encephalopathy (TSE) caused by the transmission of abnormally folded proteins (prion proteins), which leads to symptoms such as tremors and loss of coordination from neurodegeneration. > > > > > The preclinical or asymptomatic phase, also called the incubation period, averages 10–13 years, but can be as short as five and has been estimated to last as long as 50 years or more after initial exposure. > > > The clinical stage, which begins at the first onset of symptoms, lasts an average of 12 months. The clinical progression of kuru is divided into three specific stages: the ambulant, sedentary and terminal stages. While there is some variation in these stages between individuals, they are highly conserved among the affected population. Before the onset of clinical symptoms, an individual can also present with prodromal symptoms including headache and joint pain in the legs. > > > In the first (ambulant) stage, the infected individual may exhibit unsteady stance and gait, decreased muscle control, tremors, difficulty pronouncing words (dysarthria), and titubation. This stage is named the ambulant because the individual is still able to walk around despite symptoms. > > > In the second (sedentary) stage, the infected individual is incapable of walking without support and suffers ataxia and severe tremors. Furthermore, the individual shows signs of emotional instability and depression, yet exhibits uncontrolled and sporadic laughter. Despite the other neurological symptoms, tendon reflexes are still intact at this stage of the disease. > > > In the third and final (terminal) stage, the infected individual's existing symptoms, like ataxia, progress to the point where they are no longer capable of sitting without support. New symptoms also emerge: the individual develops dysphagia, or difficulty swallowing, which can lead to severe malnutrition. They may also become incontinent, lose the ability or will to speak and become unresponsive to their surroundings, despite maintaining consciousness. Towards the end of the terminal stage, patients often develop chronic ulcerated wounds that can be easily infected. An infected person usually dies within three months to two years after the first terminal stage symptoms, often because of pneumonia or infection. > > > You can taylor your eldritch scrapies to last a shorter or longer time on your character as you wish. [Answer] Alzheimer's is characterized by the degeneration of gray matter (the outermost layer of your brain); so, by the time you get that far, those will be the symptoms you observe... that said, our behaviors are not guided by our brain alone. While our brain is where the thinking happens, most of what we feel comes from our endocrine system. You Adrenal glands are located by your kidneys, your thyroid is in your lower throat, your genitalia are located... well you know... So with these organs rendered useless, your subject matter will have several other significant complications from the moment he first pulls off his experiment. Even with most of your physical body made immortal, you'd still feel the neurological effects of improperly working glands such as: [Hypocortisolism](https://en.wikipedia.org/wiki/Addison%27s_disease): Confusion, psychosis, slurred speech, severe lethargy, and difficulty remaining conscious. [Hypothyroidism](https://en.wikipedia.org/wiki/Hypothyroidism): Fatigue, Feeling cold, Decreased memory and concentration, ad Abnormal sensation (which might be intensified by the fact your body's been turned into jelly). [Castration](https://en.wikipedia.org/wiki): Lack of sex drive and reduced aggression. By in large, your person will never be able to think straight even with a fully preserved brain, because the systems that keep you awake and active will all be compromised. --- ## A different perspective might help? Frankly these side effect are so bad even after hand waving away the instant death issues that, I would like to propose something very different which might get you a mental disorder without scrambling your brain at all. If eldritchism were explained by a warping of your underlying reality, then your body and mind could continue to function normally with blood and neurons all doing what they do in your own reference point, but flexing your reality would from your point of view flex everything around you which would be extremely disorienting. We humans learn things like balance and proprioception through conditioned observations. We know this because of experiments which have shown that people who wear visors that flip or distort images can be acclimated to, but once you do, normal vision becomes harder to navigate. Your flexible immortals in this case do not go dumb per se, they just stop being able to understand what they are seeing and feeling as their bodies constantly shift and change. They will need to work very hard to keep their reality in familiar shapes but over a relatively short period of time, finding what is familiar will get harder and harder as your brain tries to constantly adapt to the unpredictable nature of your new senses. The only thing they are able to understand after awhile is magic because it is already formless and therefore just as easy to see and interact with regardless of your perceptions. So, your hero? May have instead of stabilizing his brain, learned to stabilize his eyes and ears, and his deterioration could begin as small distortions in his perception like having [astigmatism](https://en.wikipedia.org/wiki/Astigmatism) that gets exponentially worse over time. After a while shapes will become harder and harder to make since of resulting in something more like really severe [dyslexia](https://en.wikipedia.org/wiki/Dyslexia) or [visual agnosia](https://en.wikipedia.org/wiki/Visual_agnosia) until finally your world just descends into totally nonsensical perception like static. ]
[Question] [ I'd like to create a realistic starscape for an extant planet, ideally with seasonal tilt change like on Earth. While I realize I can just make it up (and will probably do so if I can't figure out how to do it for real), I'd really enjoy a re-creation based on known star data. Is there a way for me to do this with a reasonable amount of effort, and what would be an efficient way to do so? Note: I have checked existing resources (including googling 'constellation simulator'), and none of these address my issue, as I want a simulation of what the real-world stars would look like from a specific real-world planet (let's say Kepler 442B for the moment). All of these resources either assume that either I am making up a universe from scratch, or that my desired viewpoint is from some point on Earth. [Answer] [Celestia](https://celestia.space/) is the program that first comes to mind — it's a free, open-source 3D planetarium engine allowing you to travel around the local stellar neighborhood and view the sky from other locations. Search for your intended vantage point with the enter key, hit "G" to go there, and note down where the bright stars are. If your intended vantage point doesn't exist in the program, it's not too hard to [write up an .stc file](https://www.classe.cornell.edu/%7Eseb/celestia/addon-intro.html#2) with your star's celestial coordinates and distance from Earth. Adding an exoplanet with an axial tilt takes some more effort, but I believe it can be done — then just head down there to your preferred latitude and longitude on the surface to see what might be visible on a given date. [Answer] Celestia is awesome, as [parasoup noted](https://worldbuilding.stackexchange.com/a/180763/627), and it might be your best option. That said, you could do this yourself (and . . . I did - see below) by simply performing the right coordinate conversions. Stars are typically listed in databases by their equatorial coordinates, right ascension $\alpha$ and declination $\delta$, and their distance from Earth $d$ - a spherical coordinate system. If you know the location of the exoplanet you're interested in seeing the sky from, it's a simple enough matter to recalculate those positions by simply shifting your point of reference from Earth to that planet. Let's say that our exoplanet lies at equatorial coordinates $(\alpha\_p,\delta\_p,d\_p$) as viewed from Earth. Consider any star with coordinates ($\alpha,\delta,d$). Its location in Cartesian coordinates is then $$x=d\cos\delta\cos\alpha$$ $$y=d\cos\delta\sin\alpha$$ $$z=d\sin\delta$$ Similarly, the location of the exoplanet is $$x\_p=d\_p\cos\delta\_p\cos\alpha\_p$$ $$y\_p=d\_p\cos\delta\_p\sin\alpha\_p$$ $$z\_p=d\_p\sin\delta\_p$$ Now we simply shift the star at $(x,y,z)$ accordingly to the Cartesian coordinate system with its origin at the exoplanet, $(x\_p,y\_p,z\_p)$: $$x'=x-x\_p$$ $$y'=y-y\_p$$ $$z'=z-z\_p$$ Finally, we convert back to spherical coordinates as seen from the planet, to get a new $(\alpha',\delta',d')$: $$d'=\sqrt{(x'^2+y'^2+z'^2}$$ $$\alpha'=\arctan\left(\frac{y'}{x'}\right)$$ $$\delta'=\arcsin\left(\frac{z'}{d'}\right)$$ If you do this for all of the bright stars in the sky, and carefully pick how you'll display them all, you can generate a view quite easily. # My implementation I saw an opportunity to throw something fun together, so I wrote [a Python script](https://github.com/HDE226868/Extraterrestrial-skies) that performs the above conversions on [almost 120,000 nearby stars](http://www.astronexus.com/hyg), given a desired exoplanet's coordinates. Currently, stars are displayed as white circles on a black background, with size proportional to their apparent magnitude as viewed from the planet. It projects everything onto a rectangle, so it's not great at the celestial poles or if you're viewing large swaths of sky. However, it's simple enough and works well for something I threw together in a couple of hours. ``` #!/usr/bin/env python import numpy as np import matplotlib.pyplot as plt #Coordinates of planet shift_ra = 0 shift_dec = 0 shift_dist = 0 ralist = [] declist = [] idlist = [] new_ralist = [] new_declist = [] new_distlist = [] new_maglist = [] #Data from the Hipparcos, Yale Bright Star and Gliese catalogs data = open('hygdata_v3.csv', 'r').readlines() for i in range(1, len(data)): #Basic proprties of stars line = data[i].split(',') id = line[0] hip = line[1] ra = float(line[7]) dec = float(line[8]) dist = float(line[9]) absmag = float(line[14]) #Convert to radians ra = (2np.pi/24) ra dec = (2np.pi/360) dec #Spherical to Cartesian x = distnp.cos(dec)np.cos(ra) y = distnp.cos(dec)np.sin(ra) z = distnp.sin(dec) #Coordinates of target exoplanet x_shift = shift_distnp.cos(shift_dec)np.cos(shift_ra) y_shift = shift_distnp.cos(shift_dec)np.sin(shift_ra) z_shift = shift_distnp.sin(shift_dec) #Shifts coordinates based on exoplanet new_x = x - x_shift new_y = y - y_shift new_z = z - z_shift #Cartesian to spherical new_dist = np.sqrt((x - x_shift)2 + (y - y_shift)2 + (z - z_shift)*2) new_ra = np.arctan(new_y/new_x) new_dec = np.arcsin(new_z/new_dist) #Some fiddly bits to display nicely new_ra = 2 (360/(2np.pi)) new_ra + 180 new_dec = (360/(2np.pi)) new_dec new_ra = new_ra - 270 if new_ra < 0: new_ra = new_ra + 360 if new_dist != 0: #Size of star is related to apparent magnitude appmag = absmag + 5(np.log10(new_dist) - 1) lum = 50 10*(-appmag/1.5) idlist.append(id) new_ralist.append(new_ra) new_declist.append(new_dec) new_distlist.append(new_dist) new_maglist.append(lum) fig = plt.figure(1) ax = fig.add_subplot(111, facecolor='black') ax.scatter(new_ralist, new_declist, s=new_maglist, color='white') #Adjust the limits as needed ax.set_xlim([0, 360]) ax.set_ylim([-90, 90]) ax.invert_xaxis() ax.set_aspect('equal', adjustable='box') plt.show() ``` As an example, here's Orion (looking a bit squashed because of projection issues): [![Orion as seen from the Sun](https://i.stack.imgur.com/jG7VQ.png)](https://i.stack.imgur.com/jG7VQ.png) Now, if I travel $d=10$ parsecs in the direction of $\alpha = 0$, $\delta = 0$, I see that looking toward that same group of stars, "Orion" looks a bit different (assuming I did the coordinate conversions correctly): [![Betelgeuse after shifting 10 parsecs](https://i.stack.imgur.com/EDX6I.png)](https://i.stack.imgur.com/EDX6I.png) We'd expect to see deformations of a few degrees if we traveled this far away, so it seems* reasonable. It's possible there's a mistake in my code, though. Similarly, here's how the script renders the night sky as seen on Earth: ![Night sky on Earth](https://i.stack.imgur.com/SNr7r.png)][3](https://i.stack.imgur.com/SNr7r.png) Here's how it renders it as seen from an exoplanet $d=10$ parsecs away at $\alpha=0$, $\delta=0$: [![Night sky on this exoplanet](https://i.stack.imgur.com/bxrag.png)](https://i.stack.imgur.com/bxrag.png) Of course, it's one thing to go from the celestial sphere to a night sky - any observer on an exoplanet only sees a portion of the celestial sphere, and of course it differs by latitude and time of year. But if you're looking to construct constellations, you might be okay with using this as a starting point. ]
[Question] [ My story has a group of androids that have enough processing to split their focus and exist in multiple VR simulations, this will then lead to them being able to control multiple battle droids in the real world. At first the battle droids will accompany the original androids into battle and almost work like a superpower of controlling clones, then later I want the original droids to be able to focus on more important tasks or even relax and socialise whilst they send their battle bots to do some of their missions. The speed of light will always limit how far the battle androids can be remote controlled from, as too far will lead to staggered communication and during the lag time they could be attacked or easier destroyed. Another option other than remote controlling is copying their personality into each of their battle bots this will allow them to travel further away from the original droids but giving them a close to full copy of their originals mind could lead to issues by giving them a choice, they could have less thinking capacity but this could limit their efficiency of doing the missions Is there a different solution or maybe a combination of the two options that could work well to allow the battle bots to be alone and quite some distance away from their higher androids and still be as effective as if they were being remote controlled? [Answer] In between real time remote control and full autonomous consciousness, there are a spectrum of semi-autonomous modes. Some of these modes can be thought of as macros or series of commands which can be stored in the remote battle droids and triggered by single commands. Through the use of these macros, the command droid can act like a football quarterback, instructing multiple warriors into complex synchronized actions which then get performed simultaneously upon a triggering signal. Beyond the synchronized attack modes, longer macros containing conditional logic can define general operating modes such as "search and destroy", "conceal and observe", "deep conceal" and "kamikaze berserker". These more complex behaviors can be used during times when the battle droid's distance or bandwidth constraints prevent direct remote control. Also, the remote control protocol can use extremely dense information protocols based on massive shared vocabularies. A single phrase in a battle droids report back to its controller may define the strength, distribution, readiness and general awareness of an entire enemy battle group. For example, "Custer's Last Stand" could inform the command droid that a battle droid is surrounded and outnumbered by a highly mobile enemy force which is aware of the droids presence and exact location. That the enemy is armed with inferior weapons but makes up for that disadvantage in numbers. That tactical retreat is not an option. The command droid could then respond "Butch and Sundance" which means activate all weapons systems and charge the enemy with a goal of doing as much damage as possible while insuring ones own total destruction by enemy counterfire. [Answer] If you want this not to be a problem at all, then go the stargate/star trek route and use some sort of "subspace" communication that's virtually instantaneous. People will scoff but ultimately they won't mind as human beings don't have much comprehension of these effects anyway. If you want this to be a feature, then embrace it; If the androids are supposed to be superintelligent then maybe they account for the time distortion? A master chess player isn't playing "in the moment", they're several moves ahead. Maybe the androids pend their actions and make slight corrections as the battle goes - If distance is not a problem maybe they're only a few seconds behind and corrections are simple. If they're millions of lightyears away, maybe they can only watch as their plan falls apart, their controlled droids now long-dead. A third option could be that the controlled droids do have some level of autonomy and the controlling androids only make high-level plans, the actually nitty-gritty of each bot is left to them. [Answer] /the original droids to be able to focus on more important tasks or even relax and socialise whilst they send their battle bot/ This has the makings of a great story with its roots in the world. You are a skilled leader and when you are in the field things go well. But you have been doing this a long time and you want to pursue your other interests. Have you not earned that? You cultivate underlings. They receive direction from you and do your bidding. It is better and works just as well in the field. But this too becomes onerous; even though you are not there you need to pay close attention and stay engaged. So you teach them your tricks and skills so they can be more autonomous. As they develop, they need less and less direction. Some of them are much like you. Used to be. And the day comes when you wade in to give direction, and it is not taken. You have been replaced. [Answer] There actually is a way around this information speed problem, that is already discovered (although we have no idea how to utilize it as of now): Quantum entanglement If one of two entangled particles (electrons, photons ...) changes in it's properties e.g. the spin flips, so does the corresponding property of the second one. As far as we know, this happens instantaneously no matter the distance. If you combine this with something like a hivemind of sorts, your armies would be set. (Just watch out that the hivemind doesn't get out of control) ]
[Question] [ I would like to create a world with a temperate habitable zone as well as very hot and very cold zones. The hotter and the colder the better, but I don’t want it to be tidally locked. How can I do this? [Answer] How about having a planet with an extremely high degree of obliquity/axial tilt- say, 75-85 degrees of axial tilt, comparable to that of Uranus in our solar system (which has an axial tilt of just over 82.2 degrees), perhaps with a large moon to stabilize this obliquity in the way that Earth's moon did? That way, you'd have a relatively thin 'temperate habitable zone', situated at its equator, whilst its Southern and Nothern hemispheres alternated between extremely hot summers and extremely cold winters on an annual basis. Effectively, you'd be compressing said planet's 'habitable temperate zone', with room for temperature climate extremes vaguely resembling those of Earth, into its equatorial region; whilst effectively turning its polar regions into nigh-uninhabitable zones. Effectively, you could have a 'Urania' style planet, as postulated by Neil Comins as one of the alternate scenarios in What If the Moon Didn't Exist? Voyages to Earths that Might Have Been- one where Theia struck the Earth at a different angle, both forming an alternate version of the Moon and stabilizing the axial tilt of Earth/'Urania' at a far more extreme angle than it did in our timeline. The polar regions of this alternate version of Earth, in mid-winter, would be far colder than any part of our Earth ever has been, even during the 'Snowball Earth' period; meanwhile, the summer side would presumably equally be far, far hotter. Spring would foster enormous storms, as all of the ice (both water and other forms of ice, including dry ice/frozen CO2) in that hemisphere rapidly melted, a week or so after sunrise. All this water and heat being pumped into an entire hemisphere would foster gigantic storms, buffeting the small temperate zone near the equator with super-cyclones. Meanwhile, the hemisphere moving toward winter would rapidly cool once the sun went down, with all of the water there freezing solid within a few weeks of sunset, and much of the atmosphere itself beginning to sublimate and solidify into a huge polar icecap shortly thereafter. As a result, not only temperature extremes, but CO2 levels, atmospheric pressure, and humidity levels, on said planet would also likely fluctuate wildly over the course of the year, with the atmosphere in the temperate, habitable equatorial region reaching its thinnest and driest extreme shortly after its summer and winter solstices (due to a large portion of the atmosphere itself being frozen into surface deposits in the seasonal, winter hemispheric icecap, and removed from circulation), and reaching its thickest and most humid extreme shortly after its autumn and spring equinoxes, during the height of the planetary storm season (when it'd all be melted and released back into the atmosphere again with the thaw ending on the bright/summer hemisphere of the planet, before commencing the process of circulating over to the dark/winter hemisphere, and being sublimated into dry ice once more). What do you reckon, then- could the 'Urania' scenario, with your Earth-like terrestrial planet possessing a similarly large moon to our own to stabilize its axial tilt at a far more extreme angle, effectively spinning on its side like Uranus does, offer the kind of non-tidally locked, extreme-temperature, extreme-weather world you're looking for? [Answer] If we want to avoid tidal locking, we need to find alternative mechanisms for heating (or cooling) particular regions of the planet. Heating is fairly simple: simply inject energy into a particular region. Observations of hot spots on several planets (unfortunately, gas giants) have shown that there are a couple of ways we could accomplish this: * Have strong aurorae heat the upper atmosphere through x-ray spectral line emission (e.g. C VI, O II and O III), as observed on Jupiter ([Dunn et al. 2017](https://www.nature.com/articles/s41550-017-0262-6)) * Take advantage of shocks or gravity waves produced in the upper atmosphere of planets close to their parent stars, as may be the case on Upsilon Andromedae b, producing a hot spot not on the daytime side but nearly perpendicular to the star ([Crossfield et al. 2010](https://ui.adsabs.harvard.edu/abs/2010ApJ...723.1436C/abstract))$^{\dagger}$ Though these effects have been observed on gas giants, presumably similar phenomena could be achieved on terrestrial planets. I wouldn't be surprised if interactions between stellar and planetary magnetic fields could also transfer energy into a spot in the atmosphere; this is know to lead to synchrotron emission in one or two cases, presumably accompanied by some heating. Forming a cool spot is trickier. Jupiter has a cool spot, thanks (ironically) to the aurora, but it exists only at high altitudes, above a warmer atmosphere ([Stallard et al. 2017](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071956)). Perhaps there could simply be an area where air easily circulates with the polar regions but not with lower latitudes near the equator; a lack of circulation would be useful for both hot and cold spots, to maintain temperature differentials and prevent heat from diffusing outwards. I'll admit that I'm a bit stumped on the specifics, though. In general, it's easier to find a way to dump a large amount of energy in than to siphon the same amount out. --- $^{\dagger}$While Upsilon Andromedae b may be tidally locked to its parent star, I believe tidal locking is not necessary in general to produce gravity waves or shocks, though many models assume tidal locking (see [Watkins & Cho 2010](https://ui.adsabs.harvard.edu/abs/2010ApJ...714..904W/abstract)). [Answer] There is a world like this in Asimov's Trilogy of the Foundation, 2nd book, chapter 16. The world's name is Randole. Here, the planet's axis of rotation is always pointing towards the star (partially tidally locked?), and it has a dark side, where "oxygen runs liquid over the surface", and a light side, where lava might be a common sight. It has a habitable zone in the twilight equator and "it has almost transformed into a producer of luxury articles". . The only alternative to this that I can think of, would be a planet similar to Earth but with the rotation axis perpendicular to the orbital plane. There wouldn't be any seasons depending on astronomical events, but maybe depending in the positions of the continents and seas. [Answer] The planet is slightly larger than the Earth, 34% more massive and 15% larger at the equator. The planet's average gravity is just 1% above, negligible. The planet orbits around 1 AU and has an eccentricity comparable to Venus. Your planet had a formation similar to that of Earth, with a strong impact like the [Big Splash](https://en.wikipedia.org/wiki/Giant-impact_hypothesis). Unlike the cradle of humans, your planet kept the mass of debris in a disk close enough that it precipitated again along the equator, forming a mountain range that, as it eroded, gave an unusual flattened shape. The composition of the planet as a whole is slightly lighter (87% of density) than that of the Earth. These lighter materials form a much thicker solid crust similar of the Venus, that is still covered by the debris from the Big Splash. The planet has neither a moon nor tectonic activity. The balance of the planet also means that there is no inclination of the axis of rotation. The atmosphere is similar to that of Earth, perhaps a little richer in carbon in its early days. As a whole, it must also be more massive, in order to have a similar pressure on a 33% larger surface. The flattened shape of the planet makes gravity stronger at the poles than at the equator, attracting bodies of water. The planet has two polar oceans and a long mountain range at the equator, similar to that of [Iapetus](https://www.space.com/15195-saturn-moon-iapetus-ridge-formation.html). In addition to the water bodies, the heavier cold air is also trapped at the poles, the surface of the oceans near the poles freezes and makes the air dry. The albedo at the poles prevents any absorption of heat making the temperatures quite low. A possible problem that such a planet can have for the formation of life is that the poles can become sinks of carbon dioxide. The gas would condense and be deposited on the glaciers, stack and interrupting the carbon cycle. Then the ice layer at the poles contains both water and condensed carbon dioxide from the atmosphere. The edges of the glaciers are eroded by the winds, sublimating carbon dioxide and melting the water. The deposition of the elements inside the glaciers is slow thanks to the circumpolar winds separating the air masses over the ice shield and over the ocean. In the equatorial regions, intense solar radiation, added to the high altitude, forms a very hostile desert, with very high temperatures during the day. Heated wind currents in the daytime travel easily over the desert and prevent low temperatures at night. Near the coastal regions in the middle latitudes where the polar and equatorial air masses meet there is intense condensation, creating conditions for the water cycle and an environment friendly to life as we know it. Without seasonal variations, the planet's temperatures intensify. A long strip of clouds runs along the middle latitudes near the coast in both hemispheres. ]
[Question] [ I am trying to figure out how large the population of supernatural beings can be in a stereotypical urban fantasy setting before their numbers stretch the suspension of disbelief. I.e., your standard setting where supernatural beings live among humans under some sort of masquerade system. Figuring out how big your supernatural society can be is obviously important for plot purposes. Make the supernatural population too large (say, 1 in 25), and it becomes ridiculous that the supernatural could be kept secret because everyone would know at least someone who is supernatural. Make it too small (say, 100 people worldwide) and you dramatically restrict the possibility for narrative conflict because you have at most one vampire/werewolf/whatever per large city. The World of Darkness gives an oft-cited statistic that there is about 1 vampire for ever 100,000 humans. The best I could figure for a reasonable estimate would be a population ratio comparable to the prevalence rate for a rare disease: something rare enough that almost no one knows someone personally that fits the criterion, even though the disease itself is real. I realize that in reality there is probably no way the supernatural could keep a reliable masquerade from humanity for any length of time. There have been [studies](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147905) that suggest even the best-kept conspiracy (which would be analogous to, in this case: insta-fail if any evidence of supernaturals got out, complete unity by the supernaturals in wanting to stay hidden, and no supernatural-hunting organization of muggles that want to expose them, all of which is highly unlikely) could only last a few decades at best. Even in these situations the best-kept secrets would be at best like the mafia: everyone knows the mafia exists, but few people know who the individual members of the mafia are or their rank within the organization. I am more looking for an estimate of the largest population possible that would not also break the reader's suspension of disbelief because there is no way a subpopulation of that size could be completely unknown to society at large. Additional Parameters: * The supernatural beings have both a distinctly inhuman form (or cover-blowing superpowers) and can also pass for human to most people. Think your standard urban fantasy vampires, werewolves, wizards, faeries, djinn, etc. Or even better, the Wesen from Grimm. So it's not a case of "they can pass for human even when using supernatural abilities". * The supernatural beings in question do not feed on humans. Therefore, their population is not constrained by the availability of prey, like it would for [something like vampires](http://spiff.rit.edu/classes/phys317/buffy/vampecology.htm). * Similarly, because they can reproduce with humans or can reproduce non-sexually (i.e., vampire or werewolf bites) inbreeding or difficulty in finding mates to continue the species is not a concern * There are no "secret hidden cities" or "town where everyone is supernatural but they pretend to be normal to outsiders" that the supernaturals can set up in the boonies, they are intermixed with the human population. * *For the purposes of this question, it only matters that the general public* be unaware of the existence of the supernatural*. [Muggle Best Friends](https://tvtropes.org/pmwiki/pmwiki.php/Main/MuggleBestFriend) or family members are allowed to know, the existence of the supernatural just can't be common knowledge. The government is also allowed to be aware of supernaturals and complicit in aiding the masquerade. Obviously if the government did* know about supernaturals and was abetting in hiding their existence, it is only a matter of time before government corruption/incompetence/international realpolitik or WikiLeaks spills the beans to everyone, but still. If you want to go ahead and give separate estimates for population sizes if the government is abetting the masquerade (and hence can make evidence disappear) be my guest, but you don't have to. * No mind whammies, glamours, or [flashy thingies](https://www.youtube.com/watch?v=cGZQqhaU4gA) to make people forget about the supernatural. If muggles see evidence of the supernatural, the only way the supernaturals have to make the evidence disappear through begging, bribery, vandalism, or threats/murder. * There is no [magical "weirdness censor"](https://tvtropes.org/pmwiki/pmwiki.php/Main/ExtraStrengthMasquerade) that will make humans just plain refuse to believe in the supernatural to the point of active denial. The ability of humans to disbelieve the supernatural is about the same as it is in real life. An isolated paranormal event will be written off. A single person spouting nonsense will be seen as crazy. Repeated sightings of a creature in the woods will draw in cryptid enthusiasts. But strong enough evidence that can't be dismissed by a dedicated skeptic won't be ignored and people will notice when things are going on, even if they can't peg it as supernatural. What constitutes failure in this scenario is the supernatural being treated as "real" and common knowledge by your average person, rather than just an urban legend. * The majority of the supernatural community wants to maintain the masquerade. Individual exceptions that believe the masquerade is oppressive exist, but they're a small number and are mostly taken out by internal self-policing by the supernaturals (read: staked in a dark alleyway). The supernatural community is mostly unified on this issue. [Answer] "There are no 'secret hidden cities' or 'town where everyone is supernatural but they pretend to be normal to outsiders' that the supernaturals can set up in the boonies, they are intermixed with the human population." I think you might want to re-evaluate this restriction, since it has an extremely large impact on how your supernatural population develops and thus how large could be reasonable. It also affects the potential quality of life of your supernaturals in a very large way. If your supernatural people reproduce in some controlled/intentional fashion and they all want to remain hidden, then it's natural that they will come together to form communities where everyone is "in the know". Both because it's much easier to keep things hidden collectively, and because if they're anything like baseline humanity in terms of social desires, then they'll naturally want to build a community and culture with other supernaturals. This might not wind up as an entire "hidden city", but a smaller town in a less densely-populated area certainly seems plausible, or a particular neighborhood in a larger city. We certainly see this in the real world, where many cities have neighborhoods with large immigrant populations from the same part of the world -- think of how many cities around the world have a "Chinatown", as one example. Or as a closer parallel, many cities also have neighborhoods that are centers of their local LGBTQ populations. If you allow for this sort of community-building, that not only lets much larger populations arise, but also allows for more relaxed use of their supernatural abilities within that community. If your three-year-old tries out their new wings by flying out the front door and doing loops in the front yard, it's not nearly as big a problem if your neighbor flies off after them instead of plastering videos all over their Instagram account. Also, if the government is assisting in the masquerade, that would encourage the formation of supernatural communities or enclaves. Living in an all-supernatural community might even be mandatory, with varying levels of coercion involved depending on the government. On the other hand, if your supernaturals arise spontaneously--at birth or via random chance later in life--that pushes the likelihood of discovery much higher, and thus the possible population that could remain hidden much lower. Especially in modern-day society, even a relatively small number of slip-ups can become well-publicized, and thus the possible usage of supernatural abilities is very curtailed. Every single supernatural that manifests becomes another possibility for word to get out. What if a world leader takes werewolf form for the first time in front of a giant crowd during a live, nationwide broadcast? What if the latest media darling's baby is born with blue skin and dragonfly wings? Could these be covered up? Sure, but only so well. And if they are randomly-scattered like that, it becomes much harder for them to find and form any sort of community or shared culture, and thus it's more likely that some supernaturals might ignore or deliberately breach the masquerade before their fellows could intervene. In the community scenario, I could imagine hundreds or even thousands of supernaturals within a single mid-size city--even if the overall prevalence within the general population is small, they'd be concentrated in specific areas. In the scattered-individual scenario, I'd be surprised if more than a few thousand could exist worldwide before someone managed to breach the masquerade in dramatic enough fashion, whether deliberately or mischance. There might not be more than a few hundred even in major countries. Really, it all depends on the story you want to tell. If you want to tell a story where supernaturals live their lives in a normal-if-supernaturally-enhanced fashion, either separate from the general population or within it but still interacting with other supernaturals on a regular basis (like a certain series of Wizard School books), then let them form their own separate communities. If you want oppressed loners trying to eke out some connection to others of their kind while constantly on guard against discovery (A certain mutant-focused comic book franchise comes to mind), then keep them scattered. [Answer] This is actually a very interesting question! As I am writing a story which also includes this same type of super powered population, I think I might have some advice Firstly, let's actually look back into history. These dreams of having powers and supernatural abilities are actually as old as humanity itself. With witches in the Medieval ages, to Gods, tales about miracles, and all of these supernatural legends told throughout generations. In real life of course, we know these aren't real. In a fictional world, people also think just like us: they think it's not real, that they're just legends. But what if in this fictional world, these events were actually real? What I mean by this is that it's impossible for an entire population to completely hide their nature. There obviously are going to be several people leaking the secret. Yet, if throughout history humans still don't think they exist, then that means that they were able to maintain the secret. The human psychology The human psychology is quite a complex thing, and it's pretty clear that people are afraid of the unknown. And if people do see supernaturals use their powers, no one would believe them; they would be called crazy, heretics, or attention-seekers. However, if government officials come across such powers, things might get tough for the supernaturals. However, I don't think the government would deliberately tell the public about supernaturals, as it would cause panic, and so this information might be classified. However, this still isn't good for supernaturals, they could be experimented on in labs for example, or taken away by the government for unknown reasons. Another problem would be if a supernatural uses their powers in public, with enough witnesses to make it believable. This is probably the worse case scenario, since both the people and the government would know. Average Population Take for example New York City, with around 8 million inhabitants. I think a good number of supernaturals in that city would be about 100 supernaturals. Now take that, and compare it to other big cities, who would also have about 100 supernaturals in them. Of course, some small villages might have one or two supernaturals in them, or maybe none at all, depending on the size of that village. Supernaturals are rare, but there are more than people think. Hiding from humans If realistically most supernaturals wanted to hide their powers effectively, it would be better for them to live in small villages, where there aren't enough witnesses to make a sighting go viral. I think that in order to hide their powers, supernaturals wouldn't really be able to have the most normal of lives. Maybe getting a simple job would be better than being a celebrity, since there are less risks of getting discovered. Children should not be sent to school until they can effectively hide their powers - or not even be sent to school at all, but be home schooled instead. For marriage, it would be a lot safer for supernaturals to stay together and not mix with the humans, even if they can reproduce. If it means hiding their powers at all costs, these are probably the best safety measures. [Answer] The limit is less about how many people can keep a Masquerade that they want to keep, but about at what point is there enough people to create an organized resistance to the cover-up that will ultimately succeed. ### The Masquerade Itself The key thing about this Masquerade is that its primary tenet is essentially security through obscurity. As the supernatural entities in the world can do just fine without humans, they can choose where they want to exist on the slider of isolation versus integration personally. So the first main thing to decide is WHY there needs to be a Masquerade in the first place -- I didn't see a reason in the question. There needs to be a motive for the dwarfs, vampires, and fey to want to stay generally hidden from the world at large. It might be an outdated reason, but it needs to exist. Without a reason to hide, most people will not bother, and the veil will be lifted. Next is how to deal with myth and legend. In our world, we already "know" that werewolves and vampires exist -- we have them in stories. We have tales of trickster fey, and angels and demons. Spirits of the world in various forms also pepper literature from ancient times. We already know, but I bet that most of us do not go looking for it and that is the key -- to keep people from wanting to look for it. Also needing explaining is why your supernatural creatures wouldn't gravitate towards each other. Humans do it all the time -- we call them cities and towns. So is there any reason why after a few decades of codewords and conspiracies, there wouldn't be a Supernatural Quarter in a city or a town with a prominent werewolf population? Not that it is advertised as such of course -- that would be a disaster, but a neighbourhood with a higher population of X is certainly handy when a parent needs a sitter for a youngster without full control. Basing it on today's world, Social Media and superpowered conflicts will be the biggest threats most likely since the former only takes enough slips for many to put it together starting a cascading failure of the whole thing, and the widespread presence of CCTV means that it will be difficult to hide an epic fight once the human guises come off. That and certain injuries from beings will be distinctive, as would the weapons needed to kill them. Bullets are not often made from or with silver or cold iron. ### Your World What kind of story are you telling in your world? If you have factions at each other's throat in a secret war that kills many, then that is going to drive that threshold population down as opposed to a story of beings that just want to live their lives and happen to turn into a implacable furry hound when the reflective orb reaches maximum visibility. Governmental assistance might allow this number to be higher as they have more power to arrange things to the being's benefits without tipping off the public. The trick is to not have a Ministry of Supernatural Affairs, but still work with them to make sure they fit in the frameworks of the laws. I will toss a base number of 0.01% to 0.1% for this -- making a range of 300 to 3,000 for a city of 3,000,000 on average (the rough size of Toronto, Ontario). I would also expect some clustering of populations, with groups gravitating to the environment best suited to them unless everybody is absolutely territorial about their lands. The distribution will not be even, but at the same time, everyone won't be in one neighbourhood. I don't have any facts, research, or articles to support this, because the correct answer is potentially that two people can keep a secret of one is dead. Note this is just the supernatural population. There is probably that many mundanes that are aware of things, either through marriage or research, or shady deals with people that live way too long to be healthy. Also this will probably require modern governmental intervention if there are groups that live an exceptionally long time -- a 500 year old vampire is not likely to have a valid birth certificate or social insurance number from a country that exists today. If they did, who would believe it when they go buy something big? That should also be enough people in the know to have enough that want to threaten the Masquerade but not necessarily enough to make a organized coalition that will inevitably take it down without a massive amount of help. [Answer] > > can also pass for human to most people > > > I don't get the problem. As long as they can pass for human for 9 hours a day in daylight then they can move among the population and have a normal job. "When in Rome" as they say. "The Masquerade" is for vampires. The reason vampires need it is that: 1. They prey on humans 2. They can't pass for human in daylight 3. They need to be in contact to maintain their social status and make sure new vampires know who is in charge Your supernaturals' ability to pass entirely for human (?at will) means there's no need for a masquerade, they just get a job and get on with life. > > because they can reproduce with humans or can reproduce non-sexually (i.e., vampire or werewolf bites) inbreeding or difficulty in finding mates to continue the species is not a concern > > > This means they don't even need to identify themselves to each other. Each can be an anonymous person alone. ### In summary: Your fundamental setup has negated the reason to have a masquerade at all. Each can act alone in human society and is responsible for their own anonymity. There's no basic requirement for coordinated action. You have created no practical limit to their population, it could even be everyone, humans having died out centuries earlier, and nobody would know. Nothing to see, so nothing to hide. ### What they need is a weakness They need a reason to have a society of their own. They need some set of circumstances where they are involuntarily exposed and need a group responsible for cleaning up the mess before it's uncovered. Some varieties will need to be able to reveal themselves to others to reproduce. Perhaps there should be competition for some resource between varieties so they have reason to act against each other in groups while all covering up the existance of all of them. [Answer] Answer: Close to 3% of population is the max, in order to hide anomalities caused by unique patterns of consumption of economic goods caused by their non-human nature. Imagine society where all population is isolated from one another(probably with exception for the closest family members, like children and their parents. They would be living under the same roof until their child becomes mature enough), all interactions are online, over the Internet. From the youngest age you're indocrinated to believe only information from trusted government-apporved sources (sites, electroinic books, electronic films, etc), which are heavily moderated to delude normies into thinking that supernaturals don't exist and that their existence is impossible. The rest of the mediaspcace (i.e. sites, books, films, etc, not approved by the government) is filled with alleged trolls, insane people, liers, foreign propaganda bots, etc (probably the government will pay people to fill it with nonsense and trolling in order to make aura of untrustworthiness stronger). The reputation of this part of the media is extremely low. And to make it even lower there are secretely paid by government, heavily moderated, forums where "skeptics" "debunk" information from unapproved parts of media space. If an average normie will see, let's say, a blogpost that tries to prove that supernaturals exist, then at the best they will think that it's some kind of an intricate lie that can be debunked by "skeptics" anyway, so why bother reading it? If it will have videos or photos, then the normies will think that these videos and photos are fakes. If it will be just a text with a witness testimony of existence of supernaturals, then normies will think that the person is a troll or a mentally ill person. Also there will be government-paid "crackpots" that will preach that supernaturals are real with bogus logic, weak evidence (so "skeptics" would be able to "refute" them), and also belive in obviously insane things, like that the Earth is flat, in order to create assosiation of existence of supernaturals with with crazy ideas ("So, you believe that supernaturals are real? Then maybe you also believe that the Earth is flat?") [Answer] The part about the goverment aiding or at least not interfearing could be solved by some kind of anchient aggrement. The supernatural don‘t interfere with „the system“ and „the system“ leaves them alone. This aggrement came about in the long ago, after both side clashed horrible and came to some kind of mutally assured destruction. This aggrement is only in peril in times of unorderly change, like the russian revolution. Then the new rulers need to be „convinced“. When there is an orderly change of power, like the german revolution of 1918, then old and new rulers will take care of this because it is in their own best interesst. Hidden population What means hidden exactly? More then the more private parts of the sexual deviant, a community that exists but usually only the in-group knows about. But the general public is aware, that these groups exist. To change that, you‘ll need some kind of trick. My suggestion, the existance of the supernatural is a conspiracy story. There are people believing in this, and have been for centuries but if the society treads them as lunatics, the supernatural are safe. The biggest problem with this is, that we have good vision capturing systems (cameras) for something like 30 years. So you need a way to make videos and photos disbelievable, maschine learning could provide the usual „fake“ excuse. Just make computers in your world faster sooner, so that what is now hot science becomes established tech available to everyone with a gaming computer. Voila photos and videos mean nothing. ]
[Question] [ I want to have Washington, DC have a militarized defensive wall (called the Federal Wall) somewhat similar to the Hoover Dam but with artillery, air, and infantry support stationed on its (imagine something like this from Fallout (<https://vignette.wikia.nocookie.net/fallout/images/d/db/FNV_concept_art_Hoover_Dam.jpg/revision/latest?cb=20100504192604> (<https://images.app.goo.gl/4gApVLP3QVW5N45Y7>))). My original idea was to have the Federal Wall basically take up I-495 (<https://hobnobblog.com/wp-content/uploads/2013/06/beltwaymap.gif> (<https://images.app.goo.gl/6B66h5MHvisd24o6A>)) in order to make Washington itself a very well defended area but after some thinking, I realized that making the wall go around I-495 was impractical and would be a poor us of resources and manpower. So instead, I’ve decided, I’ve decided to have the Wall protect and encircle Capitol Hill, the Southwest Federal center, the entirety of the National Mall, most of Foggy bottom, West End, DuPont Circle, U Street Corridor, Shaw, Truston Circle, NoMa, and Near Northeast (basically the center of Washington with all of the important buildings). The wall itself won’t be anything super crazy like the three walls from Attack on Titan. Imagine a slightly bigger/wider Great Wall of China that’s able to service aircraft, howitzers and mortars, trucks/support vehicles, infantry, etc. Although the District of Columbia has greatly expanded its territory to basically directly control the entire DC metro area as well as large swaths of northern Virginia and bits of southern Maryland, the Federal Wall will be used to still act as a last ditch defensive structure in order to defend against both potential marauders and bandits as well as near-peer enemy militaries. But in a modern (or rather, post-apocalyptic) context, how well do walls work? I know that walls are considered impractical in today’s day and age since modern military hardware and technology like aircraft and artillery can bring down any wall but would they still make sense as a physical protective barrier in a post-apocalyptic setting? [Answer] As I understand your question, your main faction controls all of DC, and has built this wall around the governmental 'hub'. They also control some of the surrounding states, so have a fair decent sized buffer around there wall (My knowledge of American geography isnt great so I probably don't fully appreciate the entire lay of the land). I'm assuming here that this wall is several miles long based on google maps. That would take a lot of building resources and manpower that could be used to kuch greater effect elsewhere (like farming, constructing defences on the frontiers of their territory etc). While it would be a substantial obstacle for a post-apocalyptic military, provided Virginia has combat engineers (or even just enough artillery), they would be able to make an entry point eventually. The defenders need to protect the entire perimeter, the attackers only need to be successful in a few points. More than anything else, however, if Virginia manages to push Columbia back to the wall they will have already lost, whether or not Virginia is actually able to breach it. Without any farmland to sustain them and no allied forces that could help them break out they would cease to be any genuine threat, and could just besiege the capital until their surrender. It would make more sense for Columbia to focus on defending further afield. [Answer] As I'm sure you're aware, DC, during the Civil War era, was littered with fortifications, including an outer, "last ditch" ring of forts. You're kind of looking for the same thing. I'm sure that in your scenario, you'll probably want the outer perimeters watched over by sensors & drones & mobile units. You mention the Beltway. That would be a great military highway, a veritable ring fort of its own. Just space out a number of mobile units that will make use of both directions. Anywhere a potential threat is located, at least two units will be close by. You could also create a ring of outer forts at all the Beltway's 40 intersections. As for the "last ditch" wall around the government sector, I think that's viable, though more useful as a matter of propaganda than anything else. Basically, because once you actually have to rely on that wall for defence, the rest of your territory is most likely lost and you're just hopelessly and vainly staving off the final defeat. You could make it relatively cheap and effective by simply choosing a large thoroughfare, like K Street, starting at the boundary of Georgetown City, and bulldozing all the buildings for two blocks north of the road. Push all the rubble into the one block area just north of the road. Continue over to 4th St NE or so, then hang a right and do the same on down to the water, in the vicinity of the old Navy Yard. Close off "non essential" streets with rubble and erect watch towers and gates at intervals. You could make it look more impressive with concrete veneer walls on both sides. Main gates could be made to look nice with brick and fancy guard posts. Turn the cleared block into a long strip of grass. This would give you an area of good visibility plus a reasonably lethal and ungothroughsome region that personnel will find extremely hazardous to cross and vehicles won't be able to access and would also find impossible to cross because of all the loose rubble, stones, jagged steel beams and rebar sticking everywhere. [Answer] Tall wars are still effective but pointless in modern war: a wall only has to be high enough to stop ground vehicles and/or personnel. Even then, in modern highly mobile warfare it's seen as extremely retro. These days defences are more likely to comprise sensors and suitable covering munitions. If you're building a higher wall, you must have some specific threat you need to keep out. Low-flying drones might be the problem. Perhaps your wall needs to be high enough to force attackers out of ground clutter and into a zone where they can easily be picked out and destroyed by radar-controlled machineguns. [Answer] Sure walls are useful - regardless of the apocalyptic state you find yourself in Walls surround some complexes and houses today - people build them mainly to keep out opportunistic criminals, or even to 'delay' or 'be aware' of anything undesirable that is approaching. In any societal collapse scenario, these issues become more common. This allows your city to 'exist' more securely even without being actively attacked. Physically to attack a city with a military force walls only become a minor hindrance though, however once inside the attackers need to contend with 'urban warfare'. Although walls nowadays are too restrictive for our growing economical powerhouse cities, in a post apocalyptic world Urban Warfare may be unpalatable enough to an attacker. Development of the city would be contained, whereas with no wall the city is spread out and easily penetrable. A wall is also a physical/intelligence holding point - it's more than just useful during battle, it is also useful during 'peacetime' during your apocalypse. A major component of conflict is reconnaissance and intelligence. Your city still needs to trade, get supplies or have immigration. Without a wall, anyone can walk in. With one, you at least have some form of barrier that filters traders/citizens prior to entry giving you an opportunity to screen them. [Answer] Lets start with the easy part, a wall would most certainly be effective against raiders and bandits. It doesn't even have to be incredibly substantial, just pose enough of an obstacle that opportunists are going to see significant risk for any reward they might be getting. A well patrolled chain link fence might meet that requirement for all but the most determined. For a more organised foe that's a different matter, on the tactical level no fixed fortification is insurmountable assuming modern technology, but that does not mean that a wall has no value. The idea is to make it strategically unfeasible to achieve that tactical victory. Such a wall increases the requirements for an attacker. For something like a chain linked fence it means that you have to provide your forces with wire cutters. For a fortification like what you are proposing the attacker would have to train, equip, and supply a significant cadre of combat engineers as well as a decent sized breakthrough force to take advantage of any holes they make. That's doable for most major powers today but in a post apocalypse where you have likely got far more limited industrial capacity and manpower it might be too much of an outlay of manpower. The enemy may be able to break the fortifications but the more formidable they are the more they risk ruining themselves to to break them, and it takes a lot of fanaticism to get people to commit to a battle where they know the best case scenario is a Pyrrhic victory. Based on this it sounds like the smartest response for the attacker is just to ignore the walled area and take the rest of the territory, leaving the defender to rot. As a counter to this there needs to be mobile military forces based behind the walls. This forces the attacker to place the city under siege lest the defenders sally out to raid the attacker's supplies and ambush detached parties of men, bleeding the attackers dry. Again we come to the risk of a Pyrrhic victory as a prolonged siege can be as destructive on the attacker as the defender. But there is a massive issue with all of this. Walls big enough to say to a roughly comparable power, "you may win but you will destroy your economy to do it" are quite likely to destroy your own economy. Which is why I would suggest something different from a monolithic single wall. My recommendation would be defence in depth. Put in a simple patrolled chain linked fence (other fences are available) where you want the wall, that will stop your opportunistic raiders. For facing a proper military foe build a series of small fortresses around and out from the city (preferably all across the defender's territory but budget constraints will likely limit these to key areas). These fortresses should be in range to support each other with artillery and at least have the capacity to host a small raiding force that can sally out to strike at the attackers. As an addition you can pepper the area in between with pillboxes and bunkers. This means that the attacker is tied down slowly and methodically breaking open these fortifications and clearing them while the defender is free to launch raids and bombardments from any of the fortresses not yet under attack. These strong points can be as temporary or permanent as you want/your nation can afford, trenches, sandbags, and building ruins can work as well here as an armoured concrete bunker network. ]
[Question] [ If you took a giant drill (~one hundred meter circumference) and bored down two kilometers into the moon, what would it look like (assuming the lighting was good)? Is there a gradient, or is it a uniform type of rock? Assume the viewer is inside of the hole, at some point in the middle, floating and looking around. [Answer] ## It would be uniform. The crust of the Moon [is, on average, about 50 km thick](https://www.lpi.usra.edu/exploration/CLSE-landing-site-study/ScienceConcept2/). There is indeed some stratification in its composition, with upper layers composed largely of feldspar and a lower layer composed of more mafic rock ([Arai et al. 2008](https://ui.adsabs.harvard.edu/abs/2008EP%26S...60..433A/abstract)). The upper feldspathic layers appear to be $\sim$10 km thick, meaning that the composition at the bottom of your 2 km-deep hole will be fairly similar to that at the top. You'd have to make it about 5-10 times as deep to see significant composition changes - and even at that point, you'd still be far from the mantle! That said, the properties of those rocks would change as you went down - though it's not clear how drastically. For example, it might also be interesting to consider the subsurface temperature gradient, although [that's not well-known throughout the entire crust](https://space.stackexchange.com/q/14422/5963). To at least 20 meters below the surface, the gradient is roughly 1-2 Kelvin per meter ([Krotikov & Troitski 1964](https://ui.adsabs.harvard.edu/abs/1964SvA.....7..822K/abstract)), presumably slowing down considerably after that (possible as low as $\sim$1 Kelvin per kilometer at some point). You'd definitely see some sort of significant temperature differential immediately after the hole was finished, although I'm not sure what effects that would have. There would also be increases in density and pressure with depth. (I should note, of course, that the crust on the far side of the Moon and the crust on the near side of the Moon differ slightly in thickness and depth, but not enough for this answer to be particularly location-dependent.) ]
[Question] [ So, in my previous question, the two most popular weapons for a dragon were wings and the tail. The core concept is that my slightly-larger-than-a-draft-horse dragon, who still only weighs a mere 500 kilograms, uses his tail as a whip. Dragon tails are long, but usually sleek and laterally compressed, sometimes dragons use them as rudders. As you can see in [this video](https://youtu.be/ctaA4iFnITg?t=37), this model tail has enough power to it to shatter a jawbone. However, this isn't enough, you can never overkill, when it comes to natural weapons (as long as the animal doesn't uses it on their kin). Dragon bones are similar in composition to limpet teeth at the molecular level, granting them significantly more strength, albeit for only one direction. They're analogous to carbon fiber and other short-fiber composites. Since between each other, dragons either wrestle like water monitors or compete on who can stay in the air longer, the most likely targets will be armored ~~skeptics~~ knights. The knights are almost always dismounted as dragons can startle trained horses from a distance. Given these, how can the dragon's tail whip be even more deadly against armored, human enemies? [Answer] Quills. A part of the very tip of the tail forms quills that can be expelled at will upon a tail whip. This will would then have the velocity of the snapping tail, being supersonic, or at the very least trans sonic. It'd go through any armor like a hot knife through soft butter at those velocities. It would be comparable to a bullet from a pistol, or worse if it expels multiple quills or large one. These could also be venomous, in case just having super/trans sonic projectiles isn't quite deadly enough for you yet. [Answer] They can [explode their tails at will](https://worldbuilding.stackexchange.com/q/29377/21222). That will leave a mark! Then they can [regenerate the tail like a lizard or a salamander would](https://en.wikipedia.org/wiki/Regeneration_(biology)). For added fun, they could have loose, spiky bones around the tail vertebra, which will act as shrapnel when the tail blows up. Those might also be loaded with a venom similar to that of the [brazilian hardon spider](https://en.wikipedia.org/wiki/Phoneutria#Danger_to_humans). Now there are two things you need to know about this spider's venom: * It is always cited when you google for "most venomois animals" or "most potent venom". The wiki above states that while it is lethal, the animals isually doesn't deliver a lot and only ~2% of bites pose a danger. Nevertheless, your dragon may simply produce a lot of it. * The wiki also grossly mistranslates the meaning of the spider's name in brazilian portuguese, maybe out of naivette. It's name does not mean "armed". At the very least a literal translation should be "armer" or "weaponsmith". The contextual translation is "she who gives you a boner". That's because [the bite will cause lasting erections on men](https://www.livescience.com/4429-natural-viagra-spider-bite-erection.html). It's not like viagra, which restores sexual function and allows an otherwise limp penis to go hard; if you have boy parts and get this venom in your system, you will have an erection that is painful, can last over a day, and can cause your penis to go gangrenous even if it is not the site of the bite. Of course, this will lead to all kinds of legends and myth. And since [boys will be boys](https://www.bmj.com/content/349/bmj.g7094), this will draw a lot of knights to an early grave. [Answer] Scales with sharp ridges: [![enter image description here](https://i.stack.imgur.com/lUZ7q.png)](https://i.stack.imgur.com/lUZ7q.png) You can see that some of the scales on this crocodile have small ridges on them. Now what if the scales on the side of your dragons tails are very sharp and spiky? Against unarmored targets they will be quite dangerous and used to create nasty cuts, expeically if the power of the whips isn't strong enough to break any bones. But of course your knights are armored and the scales aren't likely wounded by the spik. Here the ridges work as lots of tiny hooks. They will hook onto a knights armor and make it easier for the dragon to throw them of their feet. [Answer] I hope I'm understanding this correctly. My first thought would be spikes on the whip. :) ]

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