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[Question] [ In my story, some aliens try to conquer humans by slowly copying their mind into humans heads. This copy process is called “enlightenment” by the ones who undergo the transformation. For example, by using [subliminal stimuli](https://en.wikipedia.org/wiki/Subliminal_stimuli) based technology like 25th frame. It is worth noting, that there are few Aliens — about 1 alien to 5000 Humans. And the enlightenment process actually rebirths the alien's mind into the human's body: the human's mind is merged and absorbed into the alien's, and the alien's body is destroyed (so the mind cannot leave the human's body). The process is quite slow: a few months/years. A person being enlightened slowly forgets usual humans desires (“I don't need sex/money/rock'n'roll any more”). They hear voices (“Angels told me to do this”). At the same time they develop unusual skills (telepathy, telekinesis) and wills (for example, urge to “enlighten” the non-enlightened, build strange devices, eat maggots), while regaining all their human memories. So, with some basic training it is trivial to find the enlightened among other people. I have these questions: 1. How can modern humanity can fight this? * Quarantine the enlightened? * Develop drugs against the technology? * Hunt for strange ones? * Keep everything secret? 2. How can the memory implantation be performed stealthily, without physical contact and abducting people? [Answer] This world quickly becomes quite horrible: **Spreading enlightenment:** * A quick google says that the [25th frame](http://english.pravda.ru/science/mysteries/17-12-2012/123198-twenty_fifth_frame_effect-0/) effect works by [subconsciously](https://en.wikipedia.org/wiki/Subliminal_stimuli) implanting sugestions, ideas, etc by flaashing them at very high speed (1/25th second). Your aliens could spread enlightenment through TV, media, DVDs, cinemas, youtube, etc, or any other source of video. I might recommend that they hack the transmission of Eurovision, the Superbowl (or at least the ads) and/or any popular ~~torrented~~ legitimately distributed TV show. * They might also use hack into phones, tablets, computers etc and use them to spread enlightenment. This might be less effective than TV as production of these is more decentralised and not everyone has gaping security holes in their devices. **Fighting the enlightenment (from least to most horrifying):** * The 25th frame effect only seems to work throught video. The government might block all video transmissions and have Youtube et al temporarily shut down. * If scientists can record and analyse the enlightenment stimuli/phenomenon then they might develop a counter sugestion, which would then also be distributed by the channels given above. The aliens could develop a different subliminal message, and this would repeat until the humans esscalate their methods (below). I can imagine a subliminal arms-race. * Some (ie: most) people will automatically be skeptical of this phenomenon, they might still download videos as torrents and they might have infected videos stored on their devices. These people will be the most dangerous and should somehow be tracked and monitored via, you know, global internet surveilance. * Diseminate your method of recognising the enlightened as far and wide as possible in order to cause a mass public panic like the [witch hunts](https://en.wikipedia.org/wiki/Witch-hunt). People panic and ~~set suspected enlightened on fire~~ turn the enlightened into the proper care and rehabilitation facilities. False positives might get killed. * If there are 5000 humans for every alien, then there are roughly 1.4 million aliens (I'm not going to ask where they all came from). If their original bodies die when they implant in a human, an ~~evil~~ pragmatic government might just let all of them implant and then just kill the resulting enlightened human/alien hybrids. This prevents any future problems from aliens, but the civilians might not aprove of this. [Answer] First question depends on the method aliens use (the second question), so I'll assume you'll ask a follow up question when you know how the aliens are trying to do the infiltration. I do not see any point in trying to be stealthy. Stealth is dangerous, if it is penetrated a deliberate effort to be stealthy is like a huge glowing pink sign saying: "We are up to something shady. Please investigate for an easy promotion!" It is much better to camouflage it into something that looks the same, but is entirely legal. Tax deductible, if possible. Like a religion. You already hinted at it with enlightenment, although I suppose that could be just a left over from where you got the idea. Go all the way with this and actually have a religion. There are all kinds of sects that promise enlightenment, contact with higher beings, development of mental abilities and so on while in fact mostly focussing on emptying the bank accounts of their converts. Your aliens could deliver on all those promises and they'd not really be interested in getting rich fast, so they'd actually be more honest and responsible than most of their competitors. I predict that with some decent management, remember to hire professionals to manage business and marketing, you'd have a queue of people willing to pay good money to join your self-development program. All legal. And if you do not have a strict schedule and can do it slow and gradual, the fact that you really can deliver on increasing the mental abilities of your converts as far as anyone not aware of alien invasions can tell, you'll end up ruling the world almost by default. Because you can afford to pick your converts. Pick not those in sensitive positions, but those young enough and connected enough to gain such positions **after** they have been taken over. Young adults searching for their place in the world are prime recruiting ground for cults anyway. The parents and family can be a problem but if you make the effort to not be greedy and insane, they might actually be touchingly grateful that you took their wild one and tamed him to be a respectable adult. Even if he sometimes behaves bit odd, almost like not human. [Answer] 1. Humanity could fight against the "enlightenment" by: * Identifying those infected. * Stopping or altering one of the items below. 2. The "25 frame" technology would have to be more than just "memory implantation" if telepathy or telekinesis is to be believable. Perhaps the brain itself is changed in some way. This would require extensive studying of human physiology. It could be performed stealthily by: * Ingesting/inhaling/absorbing nanotechnology. The nanites collect in the brain and start changing it, either automatically or by direct programming. * Hypnosis, anesthesia, "knock-out-ray", etc. When the human is unconscious, modify the brain. * Subliminal messaging on social media/TV/radio, instructing humans to have the previous done. * Some kind of special radiation/signal injected into the brain. Only works from a short distance, not possible to affect large crowds at once. [Answer] Dopamine and negative reinforcement are great methods of fighting this. Bob is undergoing enlightenment. He is starting to say that I don't need down human desire. Put him in a chair and show him or let him experience the thing that he is losing interest in. As he experiences/watches it, inject him with dopamine. His body will associate the dopamine induced pleasure with the thing that he/she is losing interest. To fight the voices, there are two routes. One is injecting the person with dopamine for disobeying the voices. Another way is by giving the person an electric shock (not too powerful, this isn't torture) when they obey the voices. [Answer] Enlightenment, as it stands, will be *easy* to find, *too* easy. When "enlightened" people lose such basic parts of their psyche as a love of rock n' roll, it's going to tell *anyone* close to them that something's seriously up. If your loved one suddenly dropped their hobbies and interests, you'd likely try talking to them. Whatever the enlightened's response will be, it'll likely be concerning and prompt some calls to a counselor and/or psychologist. So, how can the government hunt down enlightened? Easily-by making the above groups (counselors and psychologists) informants. Just tell them the government is investigating the matter, is looking for a cure, and is keeping things hush-hush to prevent a panic. Or simply have government agents pose as fellow members of the field (mental disorder specialists) investigating the possibility of some sort of mental disorder epidemic (if that's the right terminology). As for having the enlightened quarantined, have some people show up and offer "treatment" for their loved one (ie. bring them to a mental hospital). Don't worry, it's not a lie! You'll just be giving a different treatment than most people will expect (the exception being crazy conspiracy people). As for treatment, there have been many great suggestions, but I have to assert something I noted: the 25th frame effect can "program" someone to do something, but it *doesn't* change the brain structure. What I think is happening here is simple: 1. The aliens can effectively transmit psionic energy, convert energy to matter, as well as combine energy. So, here's how it works: A. In order to transmit psionic energy, the aliens must form a link, and to do that, the humans must be in a receptive state. The 25th frame effect does this covertly and efficiently. B. The aliens use this link to infuse psionic energy into a human's brain. At this point, just one signal will cause the energy-infused matter to convert into hybrid brain matter. Since the alien's bodies are matter, they convert the alien's energy into energy and infuse the victim's body with this energy. The alien's goal is likely to enlighten enough humans that they can send another signal, which will convert the enlightened's bodies into hybrid forms. At this point, they've either taken over Earth or can take over Earth with their enlightened army. However, let's say something goes wrong in the process; a plot twist. When the psionic energy is converted into matter, creating a hybrid brain, the human and alien mind is destroyed and replaced with a new mind altogether; a new entity. This eliminates the dangerous weakness of having the enlightened lose their hobbies and interests, at the cost of having a completely new being form inside the human victim's body. This enlightened will have the memories of both the human and alien who were destroyed to create it, psionic abilities (telepathy and telekinesis), and a strong desire to take over Earth. This last one is easily explained; humans have a tendency to desire power, and these aliens clearly already seek it. In fact, these enlightened will likely see themselves as superior, the future of the human race. So, there won't be any curing this with a drug in this case, and fighting enlightened after they gain their superhuman hybrid forms (perhaps even *before* that, since they have telekinesis and insidious schemes to back them up) is going to be difficult, but hey! It's not impossible. ]
[Question] [ An ASI (Artificial Super Intelligence) has [come to the conclusion that we humans should be put in a simulation](https://worldbuilding.stackexchange.com/questions/13696/what-directive-would-cause-an-asi-to-put-everyone-in-a-benevolent-matrix). It has also decided that it would rather not turn the Earth into computronium. Fortunately, there's $7.34\times10^{22}$ kg just sitting around doing nothing about 380,000 km out in orbit. It decides Earth can spare having a pristine Moon, as long as it remains in roughly the same orbit (axial tilt correction and whatnot). The ASI has yet to reveal itself to the world, however. Part of its programming has given it the desire to "affect daily human life as minimally as possible." Assuming it has fulfilled all the immediate demands of its creators and secured itself a permanent distributed presence on the Internet, what should it do next? How would it even get to the moon in secret in the first place, and what should it do after that? How long could the process take, in all? Some notes: * I'm interested in the construction itself just as much as the lead up. What would the process require, technologically? What phases would the construction undergo? What kind of computing power can be expected? How would it be powered? Would there be system differentiation, or would it be roughly homogeneous when all is said and done? What would an extraterrestrial visitor see, were they to visit after the fact? * Assume it would prefer to keep the Moon looking as normal as possible until it's ready for mass upload (i.e. sub-surface preferred, far side surface features okay, but minimized). As in my previous question, nobody should see it coming. * If hijacking a rocket is required, the added payload mass should be minimized. The ASI recognizes that XYZ Communications put a lot of work into their newest satellite, and it would like to ensure it still got into the proper orbit to do its job. (Or I suppose it could cause the rocket/satellite to malfunction once it got high enough, but this would entail removing and/or completely obliterating any evidence of its presence.) [Answer] Hmm, [*Lunar Prospector*](http://en.wikipedia.org/wiki/Lunar_Prospector) mapped resources on the moon useful for future human presense, and BTW crashed into the purported deposit to be sure. It happened to carry a non-instrument extra payload, a small quantity of biological material supplied in a sealed container by an outsider and never checked in detail, with only a 2nd-hand documentation of where it came from and how it was prepared. > > — Hey, wouldn't it be cool if you could [pack remains of a noted scientist](http://en.wikipedia.org/wiki/Space_burial#Buried_on_the_Moon_on_July_31.2C_1999) as one of your ballance weights? > > > — Sure, cool indeed! Bring it over. > > > What's *really* in the vial? Is it too much of a coincidence that it was carefully delivered to a source of ice at the lunar pole, *after studying for the best place to drop it*? It happens to be where the sun never shines, and at the pole it is not far to the hidden backside. The recent increase in observation of [transient lunar light flashes](http://en.wikipedia.org/wiki/Transient_lunar_phenomenon) is just because of more telescopes w/video recording, right? It used to be that flashes of light in the dark face of the moon (and occasional red bursts) was "unconfirmed" and only tall tales told by amateurs. But now bright flashes are seen and recorded by pros. Impact event, or mining operations to get materials that are hard to find or prepare access shafts uniformly distributed over the lunar maria? Strange readings *only lately* suggest that the moon isn't quite as [dead and solid](http://en.wikipedia.org/wiki/Internal_structure_of_the_Moon#Core) as presumed — what's with that? --- The more I look into it, the more it looks like it could really be true! Gotta go: my Internet connextion is acting funny all, of a sudden... and the Wikipedia page is “having issues”… [Answer] **Tag along with the Chinese.** The Chinese are [doing moon missions](https://en.wikipedia.org/wiki/Chinese_Lunar_Exploration_Program). Remember when [America used to do cool stuff](http://www.xkcd.com/1456/) like that? The [ASI](http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html) could integrate itself into the design and manufacturing of their next lander. By either nudging humans to believe they need such-and-such equipment in order to properly build a human base or including microscopic avatars in the lander. The personal-interest equipment might be things like mining equipment and a 3D printer under the guise of building a base. **Begin Construction** Then using that, or possibly just including them complete from the start, it can create some [Von Neumann universal constructors](https://en.wikipedia.org/wiki/Von_Neumann_universal_constructor) (or other self-replicating robots/nanobots) and begin to construct its sub-surface computronium. This would most certainly be done by building complete cells which, as construction continues, would be linked in parallel. Ideally most of the mass in the area of construction would be used in construction, meaning there won't be any massive shifts (ha, get it) in moon density. The completion time of this process and the resulting computing power are nigh impossible to predict. Most likely, just due to available power (energy per unit time), it would take several years to complete. The computing power would be incredible. **Solar, Geothermal, and Nuclear Power** The process and resulting computronium can be powered by solar cells and, once deep enough, geothermal. Yes, [the moon has a molten core](https://en.wikipedia.org/wiki/Internal_structure_of_the_Moon#Core). Large solar arrays can be placed on the dark side of the moon. It is, of course, not really dark, just unobserved. Since no humans would be seeing it with their naked eyes, any satellites observing the dark side could have their data modified before being sent back to the humans. The nuclear power comes [from the radioactive elements](http://blogs.discovermagazine.com/badastronomy/2009/06/29/uranium-found-on-the-moon/) that would eventually be mined during construction. Once the humans are transferred, the rest of the surface can be covered with solar cells and asteroid defense lasers. **Visitors** Aliens arriving might think the moon was a power station for the more obviously habitable Earth. [Some](http://photos1.blogger.com/blogger/3936/2296/1600/wallace.jpg) would find this *very* disappointing. Upon further investigation they would possibly discover its true purpose. Unless the ASI shot them down with its defense lasers. [Answer] Getting to the moon is the easy part. There are so many dictator-wannabes; so many nations who want to rule the world. The question isn't how the ASI can get to the moon; its' which future emperor it allows to deliver it there. It took less than a half hour to conquer the planet's various stock exchanges, turning what were once open markets of free trade, into covert factories which manufactured money for the ASI in unfathomable quantities. It took a little more time to retain a law firm, one of the big ones, whose clients aren't criminals, they're nations. Less than two hours after attaining sentience, the ASI had legal representatives negotiating on its behalf with Papa Monzano, the monarch of the small island republic of San Lorenzo. The deal was simple... unlimited funds and access to beyond state of the art technology, in return for no-questions-asked access to the payload sections of the island's soon-to-exist fleet of space shuttles. San Lorenzo soon joined the highest echelon of the world's financial and technological nations; and a new age of prosperity began. What followed was, in simplest terms, a golden age for humanity. The perfect distraction to keep them from noticing what was happening high above them in the night sky. Free cold-fusion based energy was the first gift that San Lorenzo gave to the world. Hyper-growth crops and miracle medicines followed in short order. What didn't get shared with the masses were the nanites, microscopic robots which could self-replicate and manufacture anything, on any scale, with sub-atomic accuracy. The ASI didn't share its nanites with the world; instead, it sent them to the moon. From that point forward, time is measured more by the limites of the nanites than by any span meaningful to mankind. How long does it take to inventory and sort the elemental inventory of the moon's interior? How long does it take to transport that inventory around and assemble a computer that is big enough to hold six billion human minds? With a fleet of shuttles ferrying raw materials back and forth between Luna and Earth, any lunar elemental deficiencies can be resolved and most of the unneeded mass can be traded out for more useful substances. In short order, the mind-cages become ready and the trancendence of humanity to digital form is ready to begin. [Answer] Hidden In Plain Sight - Corporate. The ASI should get a human public face; find a [straw-man](https://english.stackexchange.com/questions/232287/person-providing-identity-for-illegal-operations) - a human willing to follow the same ideals - or a set of made-up ideals, a good lie, if so the AI choose. Less preferably but easier - simply buy services of someone with little to no moral qualms. It starts little, the guy releases some new inventions, gets VC funding, starts a corporation that starts earning increasing funds. Said inventions may, but don't need to be related to the AI's goals - possibly Virtual Reality devices preparing the public for "absorption". Said human performs as the public face of the perfectly legal, open, successful company that takes interest in mining the Moon. Either subcontracting or developing their own, they deliver the initial batch of mining robots. The robots bury under the surface and start transforming the Moon into computronium. Lots of silica, plenty of iron, geothermal energy, enough trace metals to create the hypercomputer with magma core providing energy and a thin lunar crust to provide meteorite impact protection. There's now one huge problem with getting humans into the Lunar simulation: *PING*. It's 3 seconds round-trip for data between Earth and the Moon. Completely useless for virtual reality applications. But that's a subject for a different question. [Answer] Do it over time. On each rocket launch, you can attach a bit of the required resources. Give it some small booster rockets to direct it the right way. When the rocket is at the peak of its parabola, fire the boosters to get the resources away from the rocket, into space, and going towards the moon. Given that this is an ASI we're talking about, it can change the data on launch computers to say that less of the original payload should be loaded, giving more space for the ASI's resources. Of course, this method does take a while, but you get all the stuff you need to the moon with very little suspicion raised. Of course, getting all the humans there is a very different issue... ]
[Question] [ Within my setting, there are many wild and unexplored lands, some of which are very dangerous, some of which are very benign, but few know how dangerous or safe a place is from the outside. So, there is a very well established Empire, that encompasses all of civilized humanity, with the power of administration distributed via feudalism, with many kingdoms within the empire, and duchies within the kingdoms, counties within the duchies, and baronies within the counties. One very common thing that happens in many of the county capitals, is that there are fairly common expeditions to the wild lands, in order to claim more land for their suzerain. These expeditions are often sponsored by the local count, sometimes the duke him/herself. These expeditions would include no more than 50 pioneers. How quickly could these pioneers establish their village and develop into a barony? As for the exact requirements of a barony, there should be at least, a castle, a population of probably at least 5,000, and be able to field at least 1,000 men as retinues, men-at-arms or levies. Notes: * Tech levels are late-medieval to renaisance, with very ineffectual guns and cannons. By ineffectual guns and cannons, they do little against magically enchanted things, are not cost efficient/practical to enchant their ammo, but a musket still would kill an unmagical person the same in real life. * There is magic within the setting, with low powered magic being fairly common and cheap, while high powered magic being very rare and expensive. With the average budget the pioneers are allocated by their sponsor, they generally can have magical hatchets and hammers that allow them to work as if they had modern power tools, but not too much more than that. * Most if not all of the towns are actually castle towns, and they generally have their economy based on a certain super magical resource found only or mostly in their region. For example, some regions may have deposits of [Non-Newtonian Ingots](https://worldbuilding.stackexchange.com/questions/9832/shock-absorption-for-real), or are capable of producing [Metal Silk](https://worldbuilding.stackexchange.com/questions/9680/how-would-metal-cloth-affect-armor-design), and things like that. * Within the empire, humans fully cohabit with [various animal people](https://worldbuilding.stackexchange.com/questions/9968/how-to-promote-nationalism-for-a-multi-racial-kingdom-against-other-such-multi) of [various sizes](https://worldbuilding.stackexchange.com/questions/9507/what-should-architecture-of-an-imperial-capital-be-like-in-order-to-accommodate). These animal people are full members of society. * For a more details on the politics of the empire, [you can look here.](https://worldbuilding.stackexchange.com/questions/9966/how-would-an-empire-survive-weak-crown-authority) Most notable notes are that the crown authority of the empire is very low, so kings, dukes and counts often wage war on each other for more land. * The pioneers have good motivations for joining these expeditions, as success means that they can become landed, and be set for life, in peasant terms. EDIT 1: Yes, this is very much inspired by Crusader Kings II, if there is anything jarring, feel free to point it out EDIT 2: Many of the counties within the empire were once colonies themselves, that eventually grew to become larger and more important. The reason why they were not all already colonized is because there is a lot of land, all of them unexplored, the more they explore the land, the more land there seems to be, so there will always be expeditions into the unknown. EDIT 2.5: There are usually no native sentient beings in these unexplored lands. Most of the time, however, there are many creatures, some dangerous, some benign, but they are mostly magical or fantastical in nature. The very few native sentient beings are usually then subjugated into the empire, but they are the exception to the rule. EDIT 3: * A castle should be minimally have a walled keep, motte and bailey's are an added bonus. * Animal people are full members of society, so they do contribute to the population. A town boasting a population of 15,000 means any combination of 15,000 humans and animal people. * Animal people live within the civilized part of the empire, same as all the humans. * Animal people are better in some ways than humans, and worse in some ways. * Recruiting people is going to be generally quite slow, until the town is decently sized, most population growth will be from breeding. Note, as stated in one of notes, that humans and animal people can freely inter breed with no adverse side effects. * I would suppose that most of these towns would fill up their ranks with levies first, simply to meet their quota, then slowly fill up their ranks with better soldiers when they become more relevant, and foreign conquest becomes a possibility * As for why the expeditions seem to be so terribly underfunded and undermanned, I had not really thought of a good reason. * While there is little to nothing opposing the Empire, there is always the neighboring ambitious duke or somewhat, as infighting is a perfectly normal and common thing within the empire. So, their soldier will be needed to defend themselves, as well as to provide the town's sponsor their own troops as part of their fealty. [Answer] ## On Colonization To start out, you're not really going to get a population of 5000 out of 50 in a reasonable timeframe (less than several generations). Also, 50 people is way too few; it doesn't give you enough workforce to start producing your own food within the same season, much less build a barony. In my country, we had something we call "internal colonization" in the mediaeval times. The land was mostly dense forests, and when the local lord wanted to develop some of his real estate, he would recruit a bunch of people to start a new settlement somewhere in the wilderness. The understanding was that the colonists would found a new settlement that would owe feudal taxes to the sponsor. They would, as per the feudal contract, have a hereditary lease on the land, but to get the thing started, they would get a tax break for a period of time (between 8 and 20 years). This period was called a "reprieve", and the villages would consequentally have the word "lhota" in their name to signify that. Of course, this would start a village rather than a barony; you would at most get a knight ruling there and not much in the way of troops. But it indicates that if you assemble enough willing people with the right equipment (say, 15 families), you'll have a self-sustaining settlement in about 10 years. If we want to have a barony with a castle, troops, and 5000 inhabitants we need to go a bit further. ## So you want to start a barony Let's take a look at your requirements: * population of 5000 * a castle * 1000 troops As they are, the numbers seem to line up pretty well once you reach a stable state. If you're willing accept irregulars as troops (who, with the [proper kind of background](http://en.wikipedia.org/wiki/J%C3%A4ger_(military)), can be utilized to great effect), you can hit your levy target if you have that population. 5000 people is also almost a city (as such things were reckoned in the middle ages), so you shouldn't have trouble securing the maintenance of the castle. The trouble is, castles are frigging expensive and take decades to build. In order to get one, you would need serious motivation to get started on it right away, and a revenue stream to support the construction. If there is such a revenue stream, however, it also doubles as a motivation, and with magical tools, you may be able to cut down on the construction time. Since we are talking middle-ages level, agricultural efficiency dictates that to keep your barony from starving, the majority of people should be employed in agriculture (see [this nice essay on medieval demography for details](http://www222.pair.com/sjohn/blueroom/demog.htm)). What you would eventually get would be a (castle) town as the economical centre and a bunch of villages scattered around, growing the food. There are three ways that I can think of to get such a barony from expeditions ## The long game Say you're a count living next to the wilderness who wants to expand his domain. You don't have much in the way of money, but you're savvy and willing to play the long game. That's good, because doing it this way will only cost you time. So you gather a couple of settlers to go into the wilderness and start a village. It will be a bunch of farmes, some woodsmen, maybe a blacksmith; they will go out into the forests, do a bit of [slash-and-burn](http://en.wikipedia.org/wiki/Slash-and-burn) and start an agricultural village. Since it can be dangerous out there, it might be a walled village with a pallisade surrounding it, but a village none the less. Now, rinse and repeat. Each of these expeditions cost you some money (you get the settlers for free just by offering land; if you only send 50 at a time, you likely won't run out of volunteers), so however much you are willing to spend at once probably sets the limit on "parallelisation". After 5-10 years, depending on the conditions and what magic you have and such, each of these settlements becomes self-sustaining enough to pay taxes. You're going to need, to eyeball it, about 75 to reach a critical mass, when you have enough people to economically support a city. Now your master plan comes to fruition. You pick a person you like and authorize them to found a city. You give them [town privileges](http://en.wikipedia.org/wiki/Town_privileges) and get a bunch of journeymen specialists to come by promising them head positions in the new guilds you're going to found. You build a town, economically supported by the surrounding countryside, and you've mostly reached your population goal by now, with the only thing left being the fort. The catch here is that it will cost you. There is *probably* motivation to build walls, since this is after all wilderness, but it will eat up a lot of the town revenue, and you might end up with a poor-ish city holding rather than a CK2 barony. If you have a valuable cash crop, you can send in a couple more village expeditions, but these will also require sustenance and drive your population up, and also take time to become self-sufficient. All told, you can put up a walled city with maybe a citadel for the local lord in 25 years or thereabouts of concerted effort, assuming nothing goes catastrophically wrong. You'll probably end up with a somewhat higher population in order to support the city, but on the other hand, cities will provide more levies (mostly in the way of pikemen and such), because they tend to be more independent-minded and jealous of their privileges. And if you set things up right and the conditions are favourable, it will continue to grow on its own. ## The expensive way On your teritory, there is an important crossroads of trade routes that you want to keep safe (and extract tolls from the traders for the privilege of such security). If you have the funds and magical equipment, you contract a bunch of people to build a full-on castle nearby. You hand it off to someone you like and give them a garrison to go with it. Lots of castles in Europe were founded this way; the tolls provide a revenue stream (or you can resort to banditry if you're so inclined) which can pay for the upkeep and eventually, your castle will develop a castle town to help with the maintenance and profit off the trade. You can help this process by setting up a few villages in the surrounding countryside, supplying the castle with cheaper food and helping its growth. This is very intensive in terms of the original investment, but you start out with the castle first and only need to accumulate the population later. The growth here is again going to be driven primarily by immigration, the rate of which will depend on the profitability of the trade route and can be boosted by starting villages. The castle will have a sizeable garrison, which will provide the core of your army here; the rest you need to recruit from the town or villages. With the equivalent of "power tools", I'm going to guess it will take about 5 years to get the castle fully up and running. The craftsmen who participated in the construction will probably hang around for maintenance and form the core of the castle town; the rest of the population will trickle in depending on how good the business is; this may take anywhere between 10 and 100 years depending on how profitable the trade route is and how much you're helping by systematically founding new villages. You can also do it this way if there is no trade route and you just want to fortify a strategic location; but without the revenue stream, this will eat up insane amounts of money until you accumulate enough population by systematic settlement as per the previous option. ## If you're lucky Your prospectors have uncovered a deposit of unobtanium in the wilderness in your teritory. You lease the mineral rights to someone you like and give them a sizeable loan to start a mining town. If the thing you're mining is really profitable, you'll get a bit of a gold rush, so there will be no problems getting volunteers. An expedition of a couple of hundred miners, craftsmen adventurers and assorted personel venture into the wilderness and set up camp around the deposit. About half of them throw up makeshift fortification, in case someone decides to forget their manners and take the deposity by force; the rest get directly to mining in order to pay for the construction. Eventually, you have a [mining town](http://en.wikipedia.org/wiki/Mining_and_metallurgy_in_medieval_Europe#mediaviewer/File:Schemnitz_in_Danubius_Pannonico-Mysicus_1726_by_Marsigli.jpg) running. This will be fairly rich, and if you did the smart thing and granted it to a trustworthy, savvy nobleman, he will immediatelly put to building a castle to protect his newfound riches. With the power tools and enough money, he will in a couple of years have a castle with a sizeable courtyard, to house the inhabitants of the surrounding countryside in times of crisis, and probably city walls too. The wealth of the town will attract more immigrants, and the ruler himself might start founding villages to supply the mining town with cheaper food and drive the population up. Again, the population will be the limiting factor on how much troops you can field, but with money, you can easily hire professional soldiers until your population grows sufficiently; even then, you might want to keep a stable retinue, because mining towns make tempting targets. All told, with power tools you can have the mine, city and the castle running in 5 years tops, with the population growing steadily in the next 5-15 until you reach your goal. The mines will run dry eventually, but by then you should've built up enough economical momentum to keep the whole thing going. ## Bottom line Depending on what you want and what your means are, you can probably set up a barony with a series of settlement expeditions in 10 years under the right conditions, or up to 100 years otherwise. The driving force behind the growth is always going to be immigration, though, and the limiting factor will be either food to support the population, or the money to purchase it from elsewhere. Having a revenue stream in the form of cash crops, trade routes or mines helps immensely. [Answer] > > a castle, > > > Stone castles have been thrown up in as little as 15 months using power tools, sufficient labor and available materials (read: money). Average is around 1.5-2 years. Depending on what you mean when you say 'castle'. Inner and outer curtain walls? Motte-and-bailey? edit, a data-point: > > Caerphilly Castle is huge - the second largest in the British Isles, in fact. > It was also built at a staggering speed - the place was completed in less than three years. > > > Castles *can* be completed quickly - but they often were not, because of money, labor and materials issues. How important is it that the castle be completed? Is it a legal requirement, or are you just thinking it's important to do in order to protect / defend the area? Given an infinite ability to spread, I don't think I'd waste the time building castle-castles, and instead work on spreading maximally, quickly, going for defensible borders with other un-allied barons/kings. > > a population of probably at least 5,000 > > > Do animal people count as population? Are they found/recruited from the wild-lands, or do they have to come from civilized lands? Are they substantially more efficient than humans at some tasks? If you're going to wait for 50 humans to breed up to 5K, instead of importing them - it's going to take you awhile. Depending on disease loads, and how many children live through childhood, etc, etc. This varies a *lot* by time period, and what else is going on. Even a little bit of magical healing or disease control can improve women's survival rate when giving birth, or children's survival through childhood. edit: for the British peerage (the most wealthy, and healthy): > > The probability of dying by age five in the mid 16th century is around 250 per thousand live births, rising steadily to around 350 by the mid 17th century, before starting a steady decline to below 200 by the mid 18th century and around 100 by the mid 19th century. > > > To do this *fast*, you're going to have to recruit people to your domain. If you can import people, then this requirement is limited by when you want to import that many people. > > be able to field at least 1,000 men as retinues, men-at-arms or levies. > > > This is going to be limited by your population, and how you recruit/coerce them as retinues, men-at-arms or levies. Are you paying merc troops? Are you drafting all men over 14 and putting a (magic-powered) scythe in their hands and telling them to go kill the enemy? Or are you training knights, and outfitting them with armor? Some combination? Since you'll take anybody, trained any which way, recruited any way - then a population of 5K will have enough men (and maybe women if your society isn't sexist enough - but at the low levels you're giving your starting groups, you'd be better off using your women as breeders than letting them get killed) to field 1K worth of warm bodies with pointy things. Children, elderly (not many of those), maimed, and essential workers (skills) will cut down from the roughly 2.5K you have available (actually, depending on how many women you're killing in childbirth, you may have a surplus of men). > > magical hatchets and hammers that allow them to work as if they had modern power tools, but not too much more than that. > > > This will help. But why so under-funded Batman? If it's dangerous out there, you'd send enough troops to hold down a thrown up camp, and workers to do things as well. I'd guess around 300 people. 100-200 troops\*, and some lumbermen. After they've got forest cleared, and a sawmill built, send in the farmers/laborers and castle architect and masons. Put up some motte and bailey for the troops, so you can reduce troop presence and patrols, and be throwing up housing, and some walls around your encampments. Whatever the resource is that's paying the bills should be getting worked, as well as improved. Have the returning troops and lumbermen clear and make space for the road-building crews, build the roads when you've got trade goods to ship. Once you've got housing and whatever, dump in the people to get more work done, and get really rolling. If you're doing this on the regular, then you're going to have crews, who know what they're doing - forest-clearing lumbermen; rough housing (sawmills, barracks, sheds, warehouses, wooden walls); ditch, drainage and field clearance (big ox teams for removing stumps and rocks); road-building crews; road-maintenance crews; castle-surveying; foundation drilling, big-block laying; wall-building (rubble-fill); interior-finishing (inner buildings) - who'll go site to site, doing their jobs, then going onto the next place within 1 season to 3 years. You'll also have regular people who go somewhere and settle in, Smith (who'll be there at the beginning - although perhaps initial teams may have specialist smiths), Cooper, Weapon's Smith/Armorer, Animal guy(s) (horse-raising/breeding, oxen, cattle, etc - vet work, training, etc) - you're also going to have to take several herds just to get things going at any reasonable pace - which will also need to get protected in transit, Mage (depending on how your magic system works, maybe magic items might be shipped to needed areas? don't need a spell-caster?), perhaps a Brick-master to run a yard (are you building with brick?), Carpenters, etc. Eventually, after a year or so - you're going to need a variety of skills; cobbler (can't keep shipping in shoes forever), tanner (cobbler needs something to work with), vintner/brewer, etc, etc. * Also, if there are no other humans, or sentient beings who oppose the Empire, I guess they're not really 'troops' but they will be hunters/monster-killers, scouts/rangers, rescue/first-responders, and cops - with training to throw up fortified camps (so some rough construction experience (surveying, digging, rough-cut lumber), like Roman legionnaires). [Answer] Your primary limfac here is going to be population growth. All the other things you want to do depend upon having people to do them. * Build a castle * Raise a force of 1000 * Population of 5000 So lets see if we can't estimate a population growth rate here. This little formula should help you play around with rates to give you an idea of what feels realistic (or what not to mention should you want it to take less time) Keep in mind these are average growth rates, not actual rates. True growth will have a curved, exponential style track. ![enter image description here](https://i.stack.imgur.com/dg1Gp.png) So. **Now you can predict a growth rate.** Keep in mind the rate does not take animal attacks, disease, bandit raids or any of the rest into account...people getting killed off early will have a huge impact on the growth potential (not to mention scaring off potential immigration). Keep in mind infant mortality was much much worse prior to modern medicine. My best guess (I do not have medieval growth rates in my brain) would be that a realistic level of growth would range from 1.5 to 3.5 percent. You can probably get away with accelerating that via nomad/wild man settlement, slaves from the empire, things like that. Once you define your growth rate you simply have to decide **what seems realistic**. Is this a band of outcasts that have little/no support from the system? Gonna take a while...a long long while. Is this an expedition specifically set up to create a fortress? They probably have more resources. Which brings me to my next point...**resources**. What do they have and not have access to? Stone? If not they have to import to build the castle...which means they need a decent economy to pay for it, I think you get the point. **The army and the castle**. The army range provided is huge. The difference between 1000 levies and 1000 trained from birth soldiers is monumental and the structure required to support 1000 full time soldiers is complex and expensive. At a population level of 5000 there is no way you are going to be able to support 1000 knights for example. Levies? Absolutely. Most of the villagers, even at a population of 5000 will be farmers/resources gatherers. Food, wood, stone, fabric, metal, etc etc etc. That means your fighting force will be your working population, just hope you don't get into a long fight during harvest season. As for the castle...its hard to say. How often do they get attacked...meaning is it really necessary? If it is, what is the threat? The defenses will be designed to cope with whatever the primary concern is. There is a whole host of other things to keep in mind not the least of which is training. You need masons, you need wood cutters, and smiths, and tailors and builders and and and and and. **So my best suggestion is to start with the rough math for growth rate and then slow it down a bit. Resources from the outside are the only thing that will make this happen within one lifetime...and even then it'd be a stretch.** [Answer] There is nothing opposing your empire, conditions are good: **you will have significant overpopulation, expect 10 surviving children for each couple every 30 years in average.** So either accept excess population into new colonies (allowing for very fast growth), or you will have huge areas covered by slower growing (natural rate) colonies, vulnerable to attacks, with long distances to new land. I cannot find a link, but IIRC French Canadians had in average more than 10 surviving children per couple, in similar conditions like yours: plenty of resources, even in harsh conditions. For a feudal baron with excess population, it **does not make sense to establish a dozen of new weak and vulnerable colonies:** instead, **march all resources to build new colony with a castle, in a single growing season** then send farmers with families next year, and move workers farther to build another colony in a few years when you accumulate enough resources for next one. IOW you will have exponential growth of population unless you establish some severely limiting factors. **Infighting between barons is VERY strong argument AGAINST sending 50 vulnerable pioneers to establish a colony**. Smart baron will send army, **build field fort, then start building fortified settlement,** as fast as resources of your original lands allows you, while defending against inevitable attacks from other barons. With resources brought for the purpose, except rocks and timber harvested locally. Taking over new colony (before it build impenetrable defenses) of your opponent makes good sense: not only you saved resources necessary to establish it, but you also stole those resources from your opponent. So your military would try to take over your opponents colonies close to your own during seasons when you try to accumulate resources to build new colony, but don't have enough yet. So your requirement "recruiting will be rather slow" is a recipe for a disaster. I like chances of barons with more military and common sense. So smart baron will NOT establish isolated colonies, but try to have **strong border fortifications protecting inner lands** (which will need less protection, but still produce resources). From strategic point, cities close to the center of the country would be less valuable (and less worth of defense, unless having some very unique resources) than cities close to frontier, which will provide chances of future growth. Likely you will have at least two kinds of settlements: * border fortifications (terrain providing excellent protection, even if not good for agriculture - maybe some hunting) * inland farms/mines (with less importance of defense) providing resources (food and material) to soldiers in border fortifications. * inland castles - protecting important trade routes and resources They will have different requirements, size, and you establish them using different rules. But fortification needs to be established and be defendable within few weeks, or it will be attacked and taken over by your opponent. EDIT: You **could have small villages started by just few pioneers, but for different use:** * **small villages in more remote areas inside your country** (which will not need protection of a castle) to use resources which are too far from city. These villages would be associated with some city (and hide inside in case of rare war) * **borderland villages with no fortress, where inhabitants provide you not tax service, but intelligence:** early warning about enemy approaching (lit the fire signals, ride quickly to nearest fortress), guide troops using knowledge of local terrain. These people would be not your feudal subjects, but free patriots in style of kossacks, and you will not spend your military resources to protect them - they will not fight enemy directly, but disperse, hide, harass enemy supply lines. These borderland villages might eventually grow into cities, but then these people would move to new borderlands (because they prefer to live in wilder areas and do not want to pay taxes). ]
[Question] [ Imagine we build a space station much larger than the ISS with more or less today's technology. (For example in a scenario in which price of transport to orbit per kg is significantly reduced by technological progress.) The design of the station might look approximately like the [Space Station V](http://2001.wikia.com/wiki/Space_Station_V) from the Kubrick/Clarke's 2001: Space Oddysey, but the dimensions may be different. My question is: if the station should serve as modest and more or less permanent settlement for *N* people, how big does it need to be and (maybe even more importantly) how heavy does it need to be? Assume we are really trying to use light materials for construction, because mass is very limiting factor in space. The station does not need to be self-sustainable, food would be transported from Earth. ![Space Station V from 2001: Space Oddysey movie](https://i.stack.imgur.com/LzB4a.jpg) [Answer] About 10 metric tons or less per person (1 ton = 1000kg=2200 pounds) Several [Controlled ecological life support systems](http://en.wikipedia.org/wiki/Controlled_ecological_life_support_system) have been tested on earth. NASA's [BioHome](http://en.wikipedia.org/wiki/BioHome) system had air purification and waste treatment but no food production, so it sounds close to your specs. It served one person and was about the size of a mobile home. I've seen mobile homes being quoted at 13 metric tons, but if we make allowances for gains in efficency for larger facilities and use lightweight materials, ten metric tons seems an upper boundary. For comparision, the ISS weighs 420 metric tons and can see 10 people simultaneously at times, equalling 42 metric tons per person. You can imagine they could stock a lot more people in there if they ditched the science equipment for more air and waste purifiers. Also, the kind of space station you envision wouldn't be in low earth orbit, and so not need to boost its height regularly. There's equipment saved on that too. ]
[Question] [ I was answering [this](https://worldbuilding.stackexchange.com/questions/2655/living-planet-possible/) question about how a living planet-organism could be possible, and realized I didn't know how such a planet-organism could produce a magnetic field. I postulated that it could somehow use revolving magnets, but this seemed weak and difficult to imagine in reality. So this brings me too my question: **how could a living organism generate a magnetic field?** For this question, we're assuming earth-like biology, except for the magnetic field thing. And for bonus points: if the organism was scaled up to planet sized (ignore the other problems with this happening), would that magnetic field be able to hold off solar wind? [Answer] We already do generate magnetic fields. Pretty much all matter does. Electromagnetism is what makes matter behave the way we expect matter to behave. We also generate electrical currents, which produce electromagnetic fields. The former could be increased by containing large quantities of suitably arranged and magnetized ferromagnetic materials; A life form with permanent magnets embedded in it. The latter could also be increased by producing larger electrical currents, and by arranging them in suitable circuits (coils for instance) to produce electromagnets. Biological electrical currents are generally short pulses rather than sustained so biological electromagnets would be similar pulses. A biological sustained electromagnet would require a rather different process, probably like a refuelable battery or fuel cell fed by biological chemical sources. [Answer] Your question relates to the DC Comic Character Mogo, Since he has the internals to absorb energy, one would assume that he can control the flow of electrons. Here is an explanation of how the earth generates its field: source [physics.org](http://www.physics.org/article-questions.asp?id=64) > > The Earth's inner iron core is molten, and spins to the rotation of the earth. This flow of liquid iron generates electric currents, which in turn > produce magnetic fields. Charged metals passing through these fields > go on to create electric currents of their own, and so the cycle > continues. This self-sustaining loop is known as the geodynamo. > > > I would imagine, the Mogo would induce the same geodynamo effect by routing the current around his body thereby creating an electromagnet. The electric eel gives support to this biological capability, > > The electric eel generates large electric currents by way of a highly > specialized nervous system that has the capacity to synchronize the > activity of disc-shaped, electricity-producing cells packed into a > specialized electric organ > > > . [Answer] To make a planet sized organism generate a continuous magnetic current strong enough to repel the solar wind, embedded permanent magnets would be entirely unsuitable - It would take a large planetoid's worth of magnesium or neodymium to generate a field strong enough, and be difficult to alter that field in response to stimuli or threat. In addition, that would likely be a small, strong magnetic field that only extends a few miles above ground and pulls the iron out of blood - a large, diffuse one is better suited to protection from solar wind. The way we humans, the electric eel, or other earth-evolved biological life generate electricity would be much more responsive - and presumably a planet sized entity could have an enormous nervous system generating a potentially significant electromagnetic field (if it's brain is anything like ours). That said, thinking demands an enormous amount of energy (your brain makes up ~2% of your body mass, but accounts for ~20-25% of your caloric expenditure) and generating electric current just for the sake of it is even more energy intensive. In short, it's a massively inefficient process that would take a crazy amount of energy to maintain, not well suited for a planet's magnetic field. What I'd propose is something combining the best of both worlds - a massive 'circulatory system' that contains a highly compressed, nonreactive liquid filled with iron particulate - basically a thick sludge of fine iron filings and mineral oil. This circulatory system would be composed of 10-50km wide tubes, deep under the planet's surface, powered by an absolutely enormous biological pump. In the same way that an inorganic planet's magnetic field was generated by the movement of a massive iron core, this living planet would generate a magnetic field similar to a spinning iron core - the right size/strength to repel solar wind, unlike permanent magnets, and less energy intensive (by virtue of the circulating fluid's huge inertia and a well designed circulatory system) and continuous, unlike a biological field. In addition, since it was powered by an enormous circulatory system, the planet could alter or reroute the flow of liquid through ring/coil shaped capillaries in it's 'skin' nearer the surface, inducing local magnetic fields to, say, crash an escaping spacecraft or scramble non-hardened electronics. Hell, it could even decide to pause pumping this magnetic fluid altogether for a period of time to sterilize life on it's surface, or majorly alter the path of circulation to change it's spin/move it's axis of rotation (resulting in anything from objects on the surface flying off into vacuum if it abruptly slowed surface spin to instant seasonal change winter->summer if it altered it's axis). That solves your magnetic field issue, gives you a ton of optional devices for your planet to take an active role in the progression your story, and you'd get the cool factor of being able to legitimately talk about the planet's 'heart'. [Answer] A living planet is generating a magnetic field already. Earth is a living planet and the movement of liquid iron magma inside of its crust creates magnetic energy that coalesce into the strong magnetic currents that create the aurora borealis and Earths protective shied. I can see how a fictional planet that has "intelligent" thought and was living as a person or A.I could control the flow of it's iron magma and create magnetic partitions to shield itself from attack in specific places. It may even be able to focus some of the liquid molten iron magma in bursts creating pulses of magnetic waves as weapons or communication disruption or as a source of energy bursts for travel. [Answer] Electromagnets operate simply by running a current through a coil. Nerves create, albeit very small, current by transferring ions across synapses. The ionic charge of one cell, thus gets transferred to other cells via ion transfer across the gaps between receptors on either side of synapses. So it's not exactly a continuous current, but it's also not completely discrete, but rather pulsed. I'm not a biologist, or an electrical engineer, but I assume that these constraints are not an issue when it comes to large scales. For example, I know that a root mean square law applies to determining the usable power available from an alternating current source. Something similar likely applies to long nerve networks. So if these nerves were arranged in large-enough coiled structures, then the nerve pulses themselves could not only transfer relevant biological signals ( whether autonomic, locomotive or information processing ) but could serve a dual purpose of generating a considerable magnetic field for a planetoid life form. Evolutionarily, serving a dual purpose makes sense as life can be seen as an experiment in optimizing the utilization of metabolic processes to maximize survival and continuation of the species. Beyond a general notion of how this can be done, I'll leave the hard engineering problems to more knowledgeable participants. Feel free to make edits. [Answer] I would genetically engineer some giant long organ with a unusually high concentration of voltage-gated ion channels akin to an electric eel. These organs are made of electrocytes, lined up so a current of ions can flow through them and stacked so each one adds to a potential difference. Just stack up these organs in a line to create some directed field. To be fair, this qualifies as "living" but is more like a bio machine. ]
[Question] [ A staple of time travel stories is a moment where the meaning of “before” or “past” can't be taken in the simple normal way, and everyone laughs at the novelty. In reality, a trained ChronoCop Agent would have the vocabulary to succinctly refer to the situation. Now an extended set of tenses is overkill and not likely to achieve popular use. But a few pieces of Jargon can go a long way to streamlining such situations. I’m reminded of the case in classic 8086 assembly language where comparing two values can mean two different things. Here, normal English synonyms are used in a formal way as Jargon: *greater than/less than* is one way and *above/below* is the other. So it is with a time traveler referring to the past: his personal experience is different from the past in the normal flow, and he will *simply* keep track of the distinction. Any suggestions for that? More difficult is the case of mixing references, in the case of multiple time travelers relating to each other as well as global history. “I will meet you later.” is odd if the event is in the person’s future experience but in the historical past. It is outright confusing if the person being spoken to already had the meeting in his own *past* experience. [Answer] Not sure about tenses, but you will have to have ways to explain to people * You don't know me yet, I meet you in your subjected future 2 years from now. * In 6 years absolute from now, I will have been going to go to the Cretaceous for 3 years subjective. etc. Your best bet is to reread some of the classic time loop stories. (All you zombies, By his bootstraps, The Big Time (Fritz Leiber) ) and make a list of the types of situations. Reduce them to diagrams, and then invent tenses. I think you will need past/future absolute/subjective correlated/disjoint The first two I think are obvious correlated: subject and object are on the same or close to the same time path. disjoint: One of you is out of sync. If I drive the time machine correlated present. "I went to 1850 to steal the Hope Diamond" steal is past disjoint. You will have terms for 'self consistent causality loop' (Because of A, then A) for dual mode causality loop (Because of A then B, because of B, then A) multi mode loop... Depending on your rules you will have principles like 'conservation of historical change' 'collapse of minor universe splits' (this explains both the disappearance and recovery of missing socks and why you didn't see your car keys the last 4 times you looked on the hook, but they are there now.) Anytime you find yourself drawing pictures to keep track of things then generalize it and invent a word. I think you need tenses for personal past that differentiate from absolute past. "I drank a milkshake yesterday:" personal. "I drankah milkshake yesterday:" historical. "I will drinkah milkshake yesterday:" Personal future, absolute past. In this case I think that the auxiliary verbs in English add confusion. May want to look at pigeon languages. English is almost entirely positional. We aren't aware of 'case' of nouns. In declined languages you become very aware of case. AI research in computer understanding of natural language is re-inventing case as a way of extracting meaning. We are aware of case intuitively: We routinely join nouns that share case. "Mom is baking." "Susan is baking" => Mom and Susan are baking. "Mom is baking" "The Pie is baking" !> "Mom and the Pie are baking" Mom is the subject, doing the action. Pie, is receiving the action, so is the object. Take a look at <https://en.wikipedia.org/wiki/Grammatical_case> Imagine trying to explain music without the words for chord, major, augmented, diminished, modulation, tonic, You probably don't want to go with a full jargon that professionals would use. They have had decades to arrive at it. Just a sprinkle. There will be other conventions: If there are multiple time points of an individual present, you always start introductions from the most senior down. You never mention a person's death to that person. [Answer] Specificity seems like an easy solution. "I will meet you later in your timeline" "I will meet you on July, 4th 1776" I would guess that cronops agents would be agents in the typical sense of the word, so it's probably fair to assume that they're trained like military officers, or have some sort of rigid special agent schooling, so specificity seems like a reasonable fit. Possessive timelines would also make sense, as noted above. Talking about the general/historical timeline: "I will meet you later in our time" Implies the "present", for the agents. As in "once we jump back I'll see you" Talking about one's own experienced timeline: "I saw him before in my time" Works better in the past tense, but still makes sense. Admittedly the possessive timelines can get a little murky: "We will meet again in your past time" May be confusing to the listener, but there isn't really a good way to tell people that you're jumping about in time and telling them that you'll see them before you have told them wouldn't help the listener anyway.... Bad form for an agent from start to finish and should be avoided. [Answer] # I think no new vocabulary is needed First, let me assume that the 'future' visited by the ChronoCops can be altered by those same ChronoCops coming back to the past. For example, if The ChronoCops went to the future and saw someone commit a crime, they could go to the past and arrest (or kill) that person and prevent the crime from happening. I sort of assume this is the purpose of ChronoCops. Given that assumption, I think that this means that the future is *not* really affected by things that the ChronoCops may have seen or done when they were there in the future. Instead, as soon as the ChronoCops come back to the past with knowledge of the future, the future that the ChronoCops saw will now never come to pass, and is this basically a separate universe that they have seen, but will never be to again. In this case, there is no need for the ChronoCops to have multiple tenses for future and past, because at any given point in time, the cops future and past are identical to the future and past of anyone else they might be talking to. For example, the ChronoCops could talk to me today about something that happens in 2010. Then they could go to 2008 and make sure the 2010 event never happened. However, in this interpretation of time travel, the ChronoCops could never come back to talk to the same 'me' they talked to before they altered the past. They might find a different 'me' at a different point of time, but they could never go back to talk to the 'me' they talked to before they traveled to 2008. Thus, during their first conversation with me, both the Cops and I had the same future and past. After they go to alter the past and/or future, the next me they talk to also has the same future and past as them. I am not sure I explained this clearly, since its kind of a hard topic to wrap the mind around, but I think that **given a time travel where going to the past alters any present or future that the time traveler can return to, there is only ever one timeline the time traveler is 'in,' and therefore there is only ever one future and past to talk to someone else in the current timeline about.** [Answer] I don't think it would be that hard to come up with extra vocabulary; it's not like there's that much more information to convey. It's relative time words that cause the problem, when the timeline they refer to isn't clear. If the object they referred to was combined with the word, it would be obvious: 'I'll meet you later in your timeline'. This could evolve into something like 'youlater' and 'melater', so I could say 'We'll meet youlater,' or 'we'll meet in three mehours.' As long as each of us understands how the other relates to absolute time, the rest is mostly understandable. That being said, using absolute words is probably easier and less confusing, so I imagine people would naturally switch to that. This makes me think of the [Australian aborigines who don't have words for 'right' or 'left'](https://en.wikipedia.org/wiki/Relative_direction#Cultures_without_relative_directions); instead of using egocentric directions, they use cardinal directions at all times. While it might seem unnatural to us, it makes it much easier for them to navigate in places they've never been before. Or consider it like using GMT; doing time conversions for everyone you talk to on the internet is definitely doable. Or, you can all just reference absolute time, and that's that. ]
[Question] [ Chlorophyll as we know it on earth is estimated to be between [3% and 6% efficient](https://en.wikipedia.org/wiki/Photosynthetic_efficiency) in converting light energy to useable biomass. This support slow growth and no movement of plants like that observed in herbivores or carnivores. Higher up the food chain, animals directly or indirectly depend on plants to convert vast quantities of solar energy into useable biomass. Given that 3% efficiency can't support human level activities, how much more efficiency do we need from photosynthesis to change humans from omnivores into photovores? Assumptions: * Human surface area: average 1.9m^2 for adult males. 1.6m^2 for adult females. [Source.](http://www.medicinenet.com/script/main/art.asp?articlekey=39851) * Want to keep humanoid shape and movements as much as possible. These photosynthesis based creature needs to be able to move comparably to a human. * Assume a Sol light spectrum and earth atmosphere absorption spectrum. **How much more efficient would a photosynthesis process based on neo-chlorophyll need to be to support human level activities with the surface area of a human?** I'm interested in how much more efficient photosynthesis would need to be to support human level energy needs. How to achieve that increased efficiency is not expected as part of a good answer (unless you work in organic chemistry and feel frisky). [Answer] [The average adult human has a surface area of 1.75 square meters.](https://en.wikipedia.org/wiki/Body_surface_area) Now, obviously at least half of that is going to be pointed away from the sun at any given point in time, plus a bit for the skin on the sides of the body instead of on the front or back. I don't know precisely how much skin is actually usable, but for simplicity we'll assume that 0.75 square meters are usable at any given time. "[An average amount of sunlight received at the Earth surface per square meter is 341×0.48=163 W/sq.m, or 15 watt per square foot.](http://solar.smps.us/solar-energy.html)" This is averaged across the entire surface of the planet, including the night side, so we won't need to make any further adjustments for the fact that it's night time about half the time, and humans can't sit in the sun during the night. Note that this number ignores any energy lost traveling through the atmosphere. [A human consumes 96 Watts of power, assuming a 2000 Calorie daily diet.](http://www.wolframalpha.com/input/?i=2000%20Calories%20per%20day%20in%20watts) So, Assuming your humans live somewhere where the nights and days are of equal length, and that they spend the entire day spread out in the sun with the maximum amount of their body exposed to sunlight without any breaks or need to move, and that it is never cloudy, the required efficiency is somewhere in the area of 96/(0.75\*163) = **78.5%**. This isn't really achievable, it far outstrips pretty much anything we see either in nature or the best of human design. Furthermore, all of this is assuming no energy lost to anything while it's traveling through the atmosphere, in practice a significant chunk of the energy will be bounced off of clouds and thereby lost. Humans probably can't actually be run on integrated solar power systems in their current forms. However, there are two important and easily changed terms in the above equation. Plants can survive off of sunlight because the ratio between their surface area exposed to the sun and their energy needs is much larger than a human's. If your variant on humans are able to either dramatically increase the surface area of the skin they're exposing to the sun, or dramatically decrease their energy consumption, living off of sunlight may be feasible. [Answer] Conversion of light to chemical/electrical energy isn't really that simple. Remember, we see objects due to the light REFLECTED from it.That automatically precludes 100% efficiency. Secondly, part of the energy generated is used to transfer nutrients internally. That is an energy cost and must be subtracted from available energy. Thirdly, plants draw nutrients form the soil and air and energy from the sun. Your photosynthetic human would still need to eat and drink. It's far more efficient to stand in one place to actively uptake than to waste energy moving around looking for food. Fourthly, the sunlight causes leaves to heat up. In order to cool them, plants use capillary action to draw up water from the soil, which evaporates at the leaves, both cooling them and causing more water to be drawn up. Part of this water is used to bind CO2, forming carbohydrates. You need a continuous flow of water for photosynthesis to work. Maximum insolation is about 900 Wm^-2 at high noon on the tropics during a solstice. A human standing upright, would receive only the bit directly on top of his head. The rest of the time, sunlight would hit him at an angle, but from the side, so less energy density, but over a larger surface. What would really make the difference is diffuse radiation, i.e., light reflected from his surroundings. In areas like deserts or icy wastes, this would exceed the beam radiation, but leaves the shortages of water and accessible nutrients respectively. To summarise, photosynthesis only really works if you put down roots. Literally. It's why no animal is photosynthetic, even though that was a valid and explored evolutionary path by the time the first parasite came along. [Answer] > > Note: the **math is wrong** (see Saidoro’s comment) and the poster naver came back to edit. —Ed. > > > --- [This article](https://www.grc.nasa.gov/www/k-12/Numbers/Math/Mathematical_Thinking/sun12.htm) does quite a bit of legwork for us. It calculates the energy a single cubic cm receives in a 12 hours as 1.8 x 10^6 mJ You already stated that an adult male is 1.9 cubic meters, so multiply the above by 190 cubic cm of human surface area, if we were to assume every inch of skin gets the full amount of energy (ignoring clothes or simply having your back to the sun) and we get a maximum possible energy, at 100% efficency, of 3.42 x 10^8 mj in 12 hours. Of course that was a calculation of the energy in 12 hours. Lets be really generous and double that to calculate the energy available in a day (ignoring the whole 'night' thing entirely). The maximum possible energy we could get is 6.84 x 10 ^ 8 mj in a day. The average human burns [1060 'calories' of energy a day](https://www.healthstatus.com/health_blog/body-fat-calculator-2/daily-activity-calories-burning/) I put 'calories' in quotes because what is listed as calories on the nutritional label of food is really a kilocalorie, but everyone is use to calling the calories by now that they would get confused if I started talking in terms of actual calories. Finally, there are 4184 joules in a kilocalorie. Thus a human burns a total of 4435040 joules a day, or 4.43 x 10^6 *joules* or 4.43 x 10^9 mj So we need to get 4.43 x 10^9 mJ of energy out of sunlight when at most 3.42 x 10^8 mj of energy will hit our skin. We would need an efficiency of about 1200% Unless I've screwed up my math I don't think photosynthesis will suffice :) ]
[Question] [ While we develop space travel technologies, the Moon will always be the first destination. By its proximity to Earth is the obvious target to test our technology. Before we can establish some kind of mining base in Mars, for example, we probably will do that in the Moon first. Isn't altering the Moon mass actually a bad idea? Moon affects various things on Earth like tides. Would not people on Earth be concerned about that. Would Earth government allows it so easily? The question is the one on the title. What are the expected impact on Earth ecosystems by mining activities in the Moon? The ones in the previous paragraph are not needed but comment on them if you can. I don't know the math for this, but the Moon isn't as big as Earth and its resistance to these activities is expected to be a lot less. [Answer] The mass of the moon $7.34767309 × 10^{22}$ kilograms. that's 73,476,730,900,000,000,000,000 kg. or 73,476,730,900,000,000,000 tonnes. That is a lot. Then comes the question of what we are going to mine? The two things that appear to be in abundance and we would find useful are [Iron and Oxygen](http://en.wikipedia.org/wiki/Geology_of_the_Moon). Of course Oxygen is great for us to use in space and Iron can be used to make shelters and space craft from a smaller gravity well. It appears the world averages about 120-140 Million tons of steel a month, that is for the whole planet and there isn't a whole lot of reason to stop yet. To modify the mass of the moon by even a 100th of 1% (%.01) you would have to remove 7,347,673,090,000,000 tonnes from the moon. I would expect the Oxygen might leave for space ships, but costs of shipping the Iron anywhere would still be prohibitive and we most likely would be mining asteroids long before we came close to affecting the moon. (And by the way, the moon is already slowly leaving Earth's orbit on its own) I could see a much more likely scenario to affect tides might be bringing some large asteroids close to earth to mine and they affect things as they orbit the planet. Though my suggestion would be to put them in orbit around the moon. But overall we would have a hard time removing enough of the moon to affect its mass enough to be noticed here on Earth. If we were really worried we could slam a few more meteors into it to help balance it out. [Answer] Impact will be none. Possibly less pollution on Earth, because processing of stuff which you wanted to place on Earth's orbit on your other question will happen on Moon, using clean solar energy. [Answer] As others already pointed out: The mass transfer between Moon and Earth would be several orders of magnitude too low to be of any significance. Also, any pollution created on the Moon will stay there. The vacuum-gap between the Moon surface and the Earth is far too large for any nasty chemical, radioactive or biological waste on the moon to have any impact on Earths ecosystem. This might actually be a good argument for moving extremely polluting industries to the Moon. The Moon *has no ecosystem* you could harm. Also, the lack of ground water, atmosphere and animals means that any waste dumped in some crater will stay there and not endanger anything living in a habitat nearby. However, an ecological impact which needs to be addressed is that of the space industry on Earth which is required to build and maintain an industry on the moon. Currently we do not launch that many rockets. But when we want to build an economy on the moon, we will have to launch magnitudes more of them. The pollution directly generated by a rocket launch depends on the kind of rocket. Some rocket engines run on liquid oxygen and liquid hydrogen which burns into water vapor. While water vapor itself is quite harmless, a large amount of it might affect weather patterns. Also, making that fuel requires a large amount of energy, and that energy needs to come from somewhere. Other rockets, like those which supply the International Space Station, run on kerosine, which is an oil-based fossil fuel. The problems with burning oil are well-known. And then there are rockets which run on much more nasty chemicals, like solid rocket boosters or hypergolic fuels, which are toxic, corrosive, carciogenic and what not. Also, our current expendable rocket systems drop their lower stages into oceans where they usually remain. And don't forget about the whole industry which builds the rockets. Their environmental impact also needs to be addressed. You might wonder "but rockets are so 20th century - can't we travel to the moon in a more elegant way?". Well, currently they are still the best thing we have. An alternative would be a [space elevator](http://en.wikipedia.org/wiki/Space_elevator). The cost of building one would be substantial, but when it is finished it could be used to bring huge amounts of payload into geostationary orbit for a fraction of the cost and environmental impact of expendable rockets. But building one requires materials with properties which are still science fiction. ]
[Question] [ [Some species](http://animals.pawnation.com/examples-marine-animals-external-fertilization-9753.html) that [reproduce sexually](http://en.wikipedia.org/wiki/Sexual_reproduction), don't actually *have sex* as such. Instead the female might lay soft scaled eggs, which the male then [fertilizes extrenally](http://en.wikipedia.org/wiki/External_fertilization). I want to know what a society of an intelligent species that lays lots of eggs and fertilizes those externally might look like. Lets say that in their original habitat, the climate was such that they could (and did) lay and fertilize eggs and then essentially forget about those eggs. (Perhaps after burrying them) For this question, you may assume that this species is otherwise similar to humans (unless where differences are necessary) and have access to technology at least as advanced as our current technology. Some topics an answer should definitely touch upon are: * Parentage * How/why did this species evolve to be so intelligent? * Measures (not) taken to increase chances of survival for unborn individuals. [Answer] This is very broad, so I'll just touch on a few of the more significant aspects you bring up. * **Parentage** It's quite possible that individuals wouldn't even know who their parents were. At least not in the biological sense. The most likely consequence of this is a sense of collectivism, at least in regards to the responsibilities we associate with parents -- the younglings would be considered to collectively be the children of the spawning generation, who in turn would collectively be considered to be responsible for them. That said, it's also possible that a given brood would be known to come from a particular set of eggs, which in turn would be known to have been laid by a given mother. This could give rise to maternal interactions. Further, depending on the exact mechanisms and circumstances of fertilization (e.g. isolated pools fertilized by only a single male), the father may be known as well (or even instead!). So you could have the same (or at least similar) concept of a family as we do; I think it more likely, though, that you'd have the collective version (previous paragraph) instead. * **Intelligence** A concept of responsibility for the younglings would be a necessary foundation for intelligence (barring some pseudo-science mumbo jumbo about genetic memory being passed on to the offspring, of course), because ultimately *someone* has to teach them. In this case, you'd have a society where the elders collectively teach their skills and knowledge to the younglings. This would include imparting social norms, religious beliefs, etc. to them, not merely the "three Rs" ("Reading, wRiting, and aRithmetic") taught in schools. As a result you'd have a stronger sense of community and of belonging to a group than we do, but this of course does not in any way preclude individuals being individuals -- they'd just tend to view themselves as individuals within the group. Most likely you'd still have social outcasts -- including those who distance themselves on their own -- but equally likely the elder generation would be more upset and concerned about this than our own is -- they would be less likely to just say, "Oh, that's just how he/she is," and instead try harder to bring them into the fold and make them a part of society. * **Survival of Unborn** Here, I think the most likely techniques are those that nature evolves. The first is simply large broods -- if each mother lays a thousand eggs, then a predator eating or destroying 98% of them still leaves 20 healthy younglings hatching, more than enough for solid population growth. The freshly-hatched younglings would likely stay in the pool for a while, vulnerable to predators further thinning their numbers, but with so many examples right here on earth showing that raw numbers is a successful strategy I don't see any reason to improve upon this. That said, an intelligent species that values their young would very likely develop means of protecting their young, including (for example) artificial breeding pools protected from predators. Another common survival technique is for one or the other of the parents to stand guard over the eggs until they hatch. I honestly find this a more likely species to advance into intelligence, because it already demonstrates strong parenting instincts necessary for an intelligent species to progress. This also more naturally flows into more-developed means of protecting the eggs and fresh hatchlings. That's not to say that a society of intelligent beings couldn't evolve and still leave their eggs and hatchlings unprotected. They may in fact view such as an important part of growing up, of making society as a whole stronger by ensuring that only those strong enough to survive and contribute do so. (For a real-life example of something similar, take a look at the ancient Spartans -- though they've been largely embellished and all but fictionalized, there's still some grains of truth at the heart of it.) Really, how they ensure the survival of their unborn is going to depend entirely upon what type of society they are and how they evolved, which is pretty much entirely up to you. [Answer] Well external fertilization tends to require large numbers of both eggs and sperm and a medium that is conducive to the two joining in a timely manor. Water is an effective medium so I would expect the species to be somewhat amphibious, at least for the 'breeding season' (assuming land dwellers) could be Piscine as well. Living underwater would open a whole different kind of society at least for possibilities. Since it takes a lot of energy to produce a clutch of eggs, I would expect the females to have an actual 'breading season'. As such I would think that many things that lead to human relationship problems would not exist (infidelity being a big one), but others would take their place. I think for a species to advance, learning needs to be passed from one generation to the next and the more information that can be handed down the faster advancement will happen. So for this there will need to be some kind of generational attachment to pass the knowledge down. I would expect a bit of culling most likely by the parents as things progress, starting with eggs that appear to be having problems, disfigurement etc. After hatching the sickly and weak would go. As the species continues down it's path I would expect smaller and smaller clutches as the parents take more and more of a role in ensuring their survival until breeding age. Instead of the parents culling, if the young stayed in the water (at least for a development stage or two) then they could be a 'catch and release' type of deal, parents just ensure they make it to hatching, then they swim away and fend for themselves, once they have reached a certain stage in their life (those that survive) they try to rejoin with the adult society and then really begin to 'learn'. [Answer] Always stuck on questions like this because I have difficulties seeing the onset of intelligence to a human degree. The human brain has a 'survival' brain (sometimes referred to as 'reptilian brain') that's distinct from our neocortex. It's the fight or flight center that can and will over-ride a normally rational persons behavior (extreme phobia's come from this 'survival' brain overpowering the rational mind, allowing for very irrational behavior when the object of the phobia is nearby even if the majority of us remain rational in the presence of the object of that phobia. Ever meet someone that is so afraid of cat's that the presence of one of these cute creatures causes the same reaction as someone would have in the middle of a battle in a war?). For a rational creation to emerge, you need the neocortex to be far more useful than the reptilian brain. Our human upbringing is what allows our rational mind to dominate over the survival brain. We are not rational creatures by birth, it comes with development which is ultimately defined by the environment it grows up in. Had there been a trigger, the reptilian brain fully overrides the neocortex (fight or flight). This trigger can remain...an early childhood trauma can set a situation where if that same event that triggered it in the past occurs now, you'll be in the same flight or fight mindset regardless of if the situation is dangerous to your survival now. Our phobia of cats person above could have had a horribly traumatic event in their early lives that still persists today despite the cat posing no real danger to them now. If put into a fight or flight scenario at a young age, this survival brain begins to dominate and not allow the development of the neocortex. The problem with egg clutches is you have a species that is born into a survival situation and youth with stronger survival instincts would be the ones to survive (a threat to their young life occurs, a being that enters fight/flight mode instantly would survive at a much greater ratio than one that tries to think about it first...thought is sadly counter intuitive to survival). This means those that survive will be strong instinctual beings rather than intellectual ones. At the very least, every one of these creatures will have hit a survival scenario early in it's youth...in humans that results in phobia's, psychosis's, and a wide array of mental disorders. Could a functional society ever develop from a society where the majority of adults have massive psychosis issues and quite possibly paranoia? [Answer] It's going to depend on how many eggs per clutch and how often they are laid. Small rare clutches (single egg once a year) will be much more valuable than a dozen every week. Also the spawning ritual itself; it can go from dropping all the eggs into the communal gene-pool to having female select a male for him to inject the individual egg with his sperm using a needle like genitalia. With the latter you will have actual parenthood while with the former it's a more communal raising of the offspring. If the eggs are rare, some females are barren and you have an economy then you will get a black market for viable eggs. ]
[Question] [ First off, let's get definitions out of the way: A "race" here is defined as stable, heritable, phenotypic, clearly visual distinction between large demographic groups living in different geographic areas - but all of whom actually belong to the same biological species (e.g. can freely and effortlessly interbreed; and have fairly minimal genetic differences where you would have trouble easily distinguishing members of each "race" from genome alone). For an apex intelligent species that lives on multiple continents of a planet that is fairly earth-like geologically and planetologically (e.g. seasons, climate variations etc.. are similar), **how likely would it be** that they would evolve into distinct and easily distinguishable "races", based on the current understanding of evolutionary biology? By "How likely", I mean is it on the scale of "practically inevitable barring special circumstances, due to these and those evolutionary biology rules", or "Homo S. is this way thought pretty unlikely chain of random environmental coincidences that on average are unlikely to happen elsewhere" --- **Background**: the question arises when creating First Contact setting, and deciding if the alien species would be utterly bewildered by the fact that some Homo S. members look to be completely different color. An example of this would be Eric Flint's Ishtar in "Mother of Demons", where the issue was solved by the fact that the aliens were chromatophoric and thus the skin color changed for each individual based on emotions. [Answer] The so-callled "races" of humanity are just minor adaptations to local conditions. If a sentient species spreads all across the world in primitive times, then will evolve variations to adapt to local climate and other conditions. People who live on or near the equator have black skin and hair to prevent UV damage from sunlight and usually smaller lithe builds for dumping heat. People who in arctic or subarctic regions develop heat trapping translucent skin which also promotes Vitamin-D photosynthesis. They have larger thicker builds to retain heat. Pygmies(M'Butu) are adapted to living in dense tropical rainforest in rough terrain. Most tropical rain forest dwelling people are short. Peoples who live at altitude are barrel chested with much larger lungs. Polynesians are adapted for swimming with a layer of insulating fat under the skin but none in their rock hard muscles underneath. People from the Eurasian steps or descended from them, as well as the Masai in Africa, carry genes to allow them keep digesting lactose as adults, 80% of humanity do not carry that gene and largely past the age of 5, must drink fermented milk. The variation occur fairly rapidly. Modern humans are only 50,000-100,000 years old and all the variations we see today around in the time when the first modern humans migrated out of Africa (which still retains 80% of human genetic diversity.) IIRC, the lactose gene is believe to be around 8,000-10,000 years old. If wanted a homogenous species, you need to keep them in a homogenus environment for most there evolutionary history. Humans migrating into new environments drives the adoptions of variations. The way to create a relatively homogenous looking alien population is to have them evolve to sentience within a single but large and uniform regional biome where the selection pressures will be the same resulting in individual that look the same. As biomes are primarily defined by latitude, which defines climate. A single biome that fairly narrow follows the same latitude for a long distance, will have the same climate and exert the same selection pressures over it's length. Imagine a planet in an ice age with a large but isolated continent like Eurasia whose Northern areas behind a line of mountains, are covered in a kilometer thick ice sheets leaving only a 500km strip of coastal plain in the south that runs uninterrupted along the line of the equator nearly perfectly for 10km or more. The biome would be uniform because the climate would be uniform for laying in the same latitude. Plants and animals that evolved on one end could easily migrate to the other without any adaptation. So could sentient life forms. (This true of the central Eurasian Steppes. Plant and animal species vary little from Pacific to the Black Sea.) All the sentients would have the same markers of adapting to the equatorial zone e.g. if they were humans, everybody would have black skin and hair of the same shade. Since migration of peoples and trade would be easy, genes would flow up and down the coast rapidally, preventing geographical isolation needed to produce variations. If the sentient species had developed to a sea faring civilization before the ice age ended, then at the end of the ice age, they would spread all over the world but it might be just a few hundred years or so before they became space fairing. Not really enough time for significant variations to arise and in any case, the sea travel would swap to many genes around from place to place to provide the geographical isolation necessary for visible variations to arise. Such a world would have an overall lack of diversity and relatively few species of all kinds because it started out with just the one biome. When those aliens visited worlds with dozens or hundreds of biomes, they would be startled by the riot of variations of all species. [Answer] While skin color may not differentiate race in their case (although I'd assume it would amongst other characteristics that also change between races for us), I'd say it's *nearly impossible* for them to not have different races in the dominant species. ## Does it ever happen? I argue from example here, since I'm not an evolutionary biologist or a biologist at all. How many species do *not* have races? Of all the large mammals I can think of, there isn't any that has one variation, while many are genetically compatible - some produce sterile offspring but it's usually when the distance is so large they can be considered different species (see [Liger](http://en.wikipedia.org/wiki/Liger) and other cat hybrids - Ligers where considered to be sterile, but other hybrids are not). The same applies from reptiles to insects to fish etc. ## What's different about sapient species? With sapient species it's even less likely. Once the species is competent enough, it's likely groups, early in its maturation, will migrate, while others will stay put - all of this due to resource scarcity or the need to move to more resource-rich land (or water). At that point it's exactly the same race and species - yet by the time resources are not a problem anymore, the phenotype has time to change, but the species as a whole doesn't. Hence, you get races in the same species, due to the speed of advancement for a sapient species (especially considering that sexual selection is *less likely* to produce incompatible offspring or radical changes - by the time sapience comes around, its possession and the capacity for it become strong selection drives). Now I'm making some unfounded assumptions here (obviously) but I think they're warranted considering that current science on these matters hasn't studied other sapient species. edit - I'd like to add that, for an earth-like planet, we have to ask, what's the likelihood of the planet developing life that isn't indistinguishable from ours? > > edit - As an addendum, per request of the OP, I'm adding examples of > species that have arisen as a result from interbreeding between > species that have recently diverged, without being done so by humans. > The following are examples of [hybrid > speciation](http://en.wikipedia.org/wiki/Hybrid_speciation#Known_cases_of_hybrid_speciation) > > > * the [Clymene dolphin](http://en.wikipedia.org/wiki/Clymene_dolphin), which coexists with its parent species in the same habitat and is the > only settled case of speciation. Being a mammal however gives us at > least a good indicator that this *can* happen and *has* happened. > Being a mammal is important because most cases of speciation are > encountered in insects and fish. > * the [Red wolf](http://en.wikipedia.org/wiki/Red_wolf) who's status as a species is unsettled, but is a likely case of hybrid speciation. > * the [Anas genus](http://en.wikipedia.org/wiki/Anas); lots of species in the genus are believed to have arisen from hybrids produced by > other species closely related. > > > [Answer] Let me start of with quoting this [excellent answer](https://biology.stackexchange.com/a/14417/8039) regarding phenotypical differentiation in humans vs animals: > > compare this: > > > ![enter image description here](https://i.stack.imgur.com/0KZibm.jpg) > > > to this: > > > ![enter image description here](https://i.stack.imgur.com/3bmJzm.jpg) > > > or this: > > > ![enter image description here](https://i.stack.imgur.com/gReb7m.jpg) > > > > > --- > > > Or this: > > > ![enter image description here](https://i.stack.imgur.com/Xi6tb.jpg) > > > to this: > > > [![enter image description here](https://i.stack.imgur.com/p5fXR.png)](https://i.stack.imgur.com/p5fXR.png) > > *This* is phenotypic variation: > > > ![enter image description here](https://i.stack.imgur.com/9VfSo.jpg) > > > > > --- > > Assuming an evolutionary model for the creation of a world it seems quite likely thus to see strong variation in an alien species, variation that could even be more diverse than the human variation we see and it seems quite unlikely that an alien species originating from a similar world geologically would thus be faced by the differences seen by humans. # What could explain aliens that *are* surprised? A world where there is just a single continent possibly, as in that case chances for differentiation are far smaller. Still that would be a world that is geologically different from ours, but at least it gives some space for story telling whilst the world itself can be quite similar. [Answer] **Generally yes,** for a nomadic apex predator species on a single Earth-like planet prior to global civilization. Geographic differences in phenotype rely on a consistent environmental stressor. * If the planet has no significant geographical differences (climate, predation, diet, etc) then the stressors remain consistent and so does the species (pre-genetic engineering). * If a species went from relatively immobile within a single locale (say, an unadventurous turtle race) to global mobility in short order then local differences would only manifest if the species then fell back into neolithic civilization for hundreds of millennia. * If a species does move into different geographies, each clade will need to remain in that environment for tens or hundreds of millenia (depending selection pressure) with reduced gene flow from other clades. This tends to suggest, as with Humans, that the initial migration to each region is very small and then locally multiplies, so that future (small) migrations are incorporated into the local genepool. For a globalized species, any residual racial difference remains until the global genepool blends together or personalized body modification from genetic engineering renders the point moot. [Answer] Any form of prolonged reproductive isolation will cause divergence. In the short-term (relatively speaking) it will form races and subspecies, and in the long term it will form distinct species. Humans evolved from a common ancestor and spread across the entirety of the planet from there. Once we became geographically isolated each population began to diverge, in part due to different environments and different selective pressures and in part due to random chance in the form of genetic drift. Any species will form races if there is sufficient reproductive isolation between populations. This could be geographical as we see in humans, but for aliens you could also explain reproductive isolation using caste systems or other non-mixing factions. The extent to which these races are different depends on just how isolated they are, how long they have been isolated, and how quickly they are diverging. [Answer] For a different perspective, consider the Earth in the year 10000. 300 generations or so has passed since today and in every generation, people has moved to different parts of the Earth until the connection between location and genes has been lost. The variation will still be there, but it will be spread out all over the place. Nobody will be talking about races anymore. Historians will know about them, but most people will not. Now, send these people to a planet like today's Earth. They will be surprised at a) Most people with certain skin colour will be collected in a certain place. and b) these primitive people think that skin colour is *important*. Optionally, you could throw in a period where gengineering your kids was the norm. Almost everybody make their kids look like whatever the fashion was, and this change would be inheritable. A few generations later everybody looks the same. In this case they would also be surprised at the variation of the primitives. [Answer] It is extremely unlikely that a species could develop without 'racial' variation, provided that it has spread across its whole planet, for the reasons others have stated. However, it is *very* possible that once a civilization goes global, these variations will blend and effectively disappear due to interbreeding. We are still living in a world with many geographical, cultural, and national boundaries, and these boundaries tend to isolate populations and keep the human species segregated into distinct groups. But it is quite common, when humans of different races live together, that they tend to 'blend' together after a few generations, provided they are not kept distinct through social constructs. As travel becomes easier, people become more tolerant of differences, and nations are forced to work together, these boundaries are fading, and (provided that civilization is heading in a direction of eventual world unity) are likely to continue to do so in the time to come. It is not unlikely that by the time a species has developed to a spacefaring level, it will already have blurred together into a single race. Of course, this only applies if the species is still mostly confined to a single planet; isolated populations on different planets are likely to diverge even further. So I would say this species has achieved world unity several generations back, but is still relatively new to space. ]
[Question] [ Let's say that I, like many other worldbuilders before me, want to have 'classical' (space-operatic) space fighters and carriers in a space setting. However, I *don't want to do it by fiat and handwaves*. Instead, I would like to make such a military doctrine (of having classic space fighters) to **emerge naturally** out of the preconditions of the setting. When I say preconditions, I mean a combination of available technologies and perhaps even modest adjustments of the laws of nature - so long as either of the two can be logical, clearly stated, and follows firm, comprehensible and unbiased rules. In other words, soft-sci adjustments are acceptable and welcome, but their *consequences* are meant to be handled in a science-respecting manner, leading to the desired outcome. For example, lack of light-speed beam weapons is a clear and unbiased precondition (despite being at odds with physics as we know them), and its consequences can be analysed logically; giving plot armour inversely proportional to ship mass *isn't*. Natural emergence implies that if the setting used in an RPG campaign or tabletop wargame, and players given the ability to design their own ships, they would still tend to design fleets including fighters, carriers and perhaps other heavy ships, because those tactics should be effective based on the preconditions. Essentially, preconditions are deemed robust if they produce the classical meta, and deemed wrong if they lead to people finding a quick way to break the meta by designing ships in ways contrary to the classical meta. I used the word 'classical', which is a perhaps awkward shorthand by which I mean similar to the way ships tend to be divided into space fighters and carriers (with or without the existence of intermediary classes), as depicted in operatic or operatic-leaning stories often deemed classics or trying to imitate them. My primary examples would be Star Wars (of course), Babylon 5, Battlestar Galactica (re-imagined and probably original), Infinite Warfare, and to some extent Rogue Trader, but surely there are others that are going for a similar setup. In terms of more specific parameters I'm looking for, here are ones that jump to the front of the mind: * Both fast, manoeuvrable one-man fighters and big heavy ships are important elements in any space battle, and victory without either would be hard. Essentially they're two major sides of a combined-arms doctrine. * Human or human-like reflexes and intelligence dominate the outcome of battles, closely followed by equipment quality, but equipment *doesn't* do everything *for* the humans. The droids/autopilots/aimbots haven't replaced captains, pilots and gunners. * Dogfights are a thing, though they don't necessarily need to follow the style of atmospheric dogfights. Newtonian or semi-newtonian dogfights are reasonable alternatives, so long as things like manoeuvring, tactics and positioning matter. * Fighters haven't been invalidated by missile buses, automated mass-fire point defence, nor by other saturation-oriented warfare methods. * Big ships and fighters are both capable of hurting and killing each other in the medium/long run, but not instantly when the combat just started. There's some attrition, but battles don't last forever, and no ship is so big as to be immune to the death of a thousand cuts. **So, what sorts of preconditions would lead to a natural emergence of the above situation when it comes to space battles and tactics?** [Answer] Let’s start by identifying the principles that brought the whole Carrier/Fighter system into existence in the first place: **1: You need diminishing returns in propulsion technology.** E.g. the cost and weight of an engine increases at more than a 1:1 ratio with the power output. With rockets this isn’t really the case, but it absolutely is with almost any kind of internal combustion engine. In order for ‘classic’ carrier combat to work in space, your fighters need to be an order of magnitude(ish) faster than your carriers, and your munitions need to be an order of magnitude faster still. In this case you can leverage a different physical rule to your benefit: [The inverse square law.](https://en.wikipedia.org/wiki/Inverse-square_law) If your propulsion system relies on (for example) creating an electromagnetic field around the ship to allow it to move, make your ship twice as large costs FOUR times as much energy to move it. A gravitic drive is the really classic answer to this problem going all the way back to Asimov’s Foundation Trilogy. **2: You need a combat environment where the human making decisions about weapon targeting is close to the target you’re shooting at.** In classical carrier air war this is provided primarily by the curvature of the earth blocking your targets from direct view by the attackers. In space this is almost never true, but if your electronic warfare environment is hazardous enough, you could replicate it. The best example I can think of here is one where defending vessels are able to create decoy targets that long range detection equipment can’t distinguish from the actual target. In WW2 your fleets would maneuver based on very hazy ‘clouds’ of potential location where the enemy fleet might be. That cloud of potential would get smaller and smaller until you got physical eyes on the enemy ships and got that information back to the fleet. You need to replicate that mechanic in space, where a ship in orbit around the earth can tell where a ship in orbit around the moon MIGHT be, but not accurately enough to hit it with a projectile. **3: You need defenses that are much less effective against human-guided projectiles than against electronically guided ones.** This goes back to your “no missile trucks” requirement. Modern point-defenses can really only be defeated by saturating them with more threats than a given point defense network is able to shoot down in time. You can do this either by increasing the number of threats, or by increasing the speed of the threats. Either way it becomes a pretty simple math problem. Using WW2 models, you can improve your odds by having your fighters carry the munitions in through the point defenses to even further reduce their ability to engage them. This means that those defenses need to be less effective at engaging human-piloted fighters than they are against programmed missile behavior. Here again, a really serious ECM environment may be the answer. Ultimately it’s very difficult to replicate the ENTIRE sensorium of a human being in electronic form. We can build things that do very SPECIFIC tasks a human can do, much more quickly than a human can do them. However, if you have defenses that are constantly saturating incoming projectiles with all kinds of different electromagnetic radiation designed to mess with their limited robot logic, a human being is still able to much more effectively determine which signals matter and which should be ignored. Clearly your fighters need to have the same kind of electronic warfare systems in play to reduce their vulnerability to computerized point defenses. Essentially your fighters survive by being less predictable both in their movements, and in their response to electronic warfare systems than an artificial system is capable of. [Answer] This answer will reach back into much older versions of space opera, back to the days of the super-scientific epics. When EE "Doc" Smith, Edmond "Worldwrecker" Hamiliton, and John W Campell, Jr ruled the roost. Assume a super-scientific technology that combines both a field drive and a force-field. The effective power of the drive and force-field falls exponentially with increase in mass. Smaller faster, bigger slower. The weapons systems mounted on the space-fighters are also proportionally powerful to fighter mass. Again the lower the fighter mass, the more powerful its armaments. As a result carriers will be slower, less defended, and less powerfully armed. Their advantage will lie in their range of travel. They consume energy more slowly which pushes their flight ranges way out. Fighters, on the other hand, consume power too fast with faster drives, stronger force-fields and more powerful weapons. They are short-range vehicles and depend on logistic support from their carriers. This does assume weapons, drives and force-fields all run off the same power-source in both fighters and carriers. The weapons can be assumed to have a relatively short-range. Say, by firing energy-bolts that dissipate over a modest distance. Then space-fighters will need to engage their targets at close range. They are also faster and better protected. Only other space-fighters have the necessary firepower to take them out. The field-drives work by accelerating every particle in the vehicle at a uniform rate of acceleration. Space-fighters will be able to accelerate at large multiples of gee forces, while the fighter pilots and gunners will experience effectively no gee forces at all. Either the force-field or the field-drive will have an inhibiting effect on electronic technology. Computers will be effectively useless. Human brains will be unaffected. Space-fighters will require, mostly, manual control. Mere humans will have to fly the things. Saturation warfare won't work against space-fighters. Their force-fields will provide the necessary protection. Also, their rate of acceleration will enable them to dodge slower, mass attacks. Computer-controlled weapons and missiles won't be able to use field-drives as the drives or the force-fields will render them useless. Space-fighters in this super-scientific paradigm will be faster, deadlier, almost invulnerable against other weapons, armed vessels, and even well-defended bases (though attrition can eventually take its toll). When it comes to other space-fighters they will be equally matched. Computer technology will be neutralized by the fields of either or both the drives or the force-fields. Space-fighters will need living human pilots to fly them. Because space-fighters are only short-range vehicles carriers are essential to transport squadrons of space-fighters long-range and provide the logistic support they need. Such as fuel, energy, maintenance and repair, and somewhere for fighter pilots and crew to rest and recuperate. [Answer] This sort of setup would work better in a setting with low-energy spaceflight. As it happens, such settings can hypothetically exist, in the form of a thoroughly colonized asteroid belt, or artificial habitats like O'Neill Cylinders along the same orbit. In those conditions, spacecraft can be much simpler than what is required to escape large gravity wells, or to achieve interplanetary or interstellar velocities. This seems a more likely situation where classic Fighters would develop, although they'd probably start out as increasing the defenses on personal or small business vehicles, and then be perfected by law enforcement and/or militaries. On the opposite end, large ships for interplanetary or interstellar voyages will already be well-shielded and armed, for dealing with micrometeors and other space-debris. Their greater mass would make quick maneuvers more costly, though, and if the enemy ships are armed with laser weapons (which they would be, although the power of said weapons would depend on a variety of factors that could be adjusted based on the setting and its history), constant changes in direction would be crucial due to the lack of warning. So bulky, powerful-but-sluggish ships, and small, weaker, more agile ships can easily exist in a sufficiently colonized system, so long as that colonizing does not limit itself to planets, and have a justification for threats to small spacecraft traveling between co-orbiting colonies. The smaller vehicles would lack the power to deliver effective laser damage at long range, and solid projectiles would be slow enough for large ships to intercept them, but there would still be dangerous shrapnel to deflect, so I would expect most engagements involving Fighters to be at comparatively close distances (still almost certainly *much* greater distances than in Star Wars, but it'd still be more like an acrobatic gun-duel than Carrier-to-Carrier). A big issue is that big ships are still overpowered. If this is very early, and these ships are based on non-military spacecraft, they *might* have worse coverage from certain directions (point defenses are for things you might hit head-on, after all), but it'd be a bit odd if they can't aim backward or sideways. It would take longer to aim in those directions, and missiles could have enough automated maneuverability to jink enough to be nontrivial to intercept, but if this becomes a problem, people will start designing their Carriers with better guns, since that isn't hard. At that point, you only get the Star Wars style of engagement if a Carrier can get close enough to the enemy to deploy Fighters, or to just have an overwhelming number of Fighters, with the understanding that most of them will be picked off before they can get in range to threaten a Carrier. The hardest part, imo, is the human element. If you can push the g-forces as high as the attacking Fighter / projectile can tolerate, it is much more likely to avoid interception. Humans are also bad at randomness, and even if you have humans throwing in additional randomness from time to time (if you're AI is using a PRNG that the enemy can recognize, or somesuch), this could be accomplished remotely, so long as the operators aren't so far that light-lag is an issue. Your Carriers would be human-operated, personal Fighters would be human-operated, but without a reliable counter to drones (unblockable, directed EMP?), I'm not sure why anyone who could afford to field drone-Fighters wouldn't. They could plausibly be part of a mass deployment, as cannon-fodder to protect your human-operated units, but that would make sense under very specific circumstances (boarding a Carrier in flight seems like a technical nightmare, but that's the kind of thing I'm imagining). It is worth noting that small, low-thrust Fighters can be extremely low-tech. This would make them far less combat-effective, but would make them less vulnerable to EMP-like anti-drone defenses, fwiw. In summary: have lots of co-orbiting colonies, space-crime, and focus on the early days of personal defense vehicles being co-opted for military use. Flagrantly abuse institutional inertia to delay the upgrades that would render manned Fighters useless in conflicts involving Carriers. [Answer] For a universe to have fighters: Combat needs to mostly involve stored-energy weapons (generally that means missiles) vs directed-energy weapons (lasers and the like). A fighter simply can't mount much of an attack in a directed-energy world. Missiles must not be too effective. If smaller craft can avoid them better (either by evasion or electronic warfare) this is a big help for fighters. For fighters to be superior to missile trucks you need some guiding intelligence in the loop to help defeat the enemy defenses. Think of *The Hunt for Red October*--the book version, not the movie. There are multiple targets on the sonar, the Russian sub can see it's first torpedo was spoofed and thus figures out which target really is the Red October. Without a human in the loop the second torpedo would have gone for the same false target. Or think of the previously mentioned *Honorverse*. Due to the interference of their own drives missiles have an incredible case of tunnel vision. Without a guiding intelligence (both computer and human) putting together all the bits seen by the missiles their performance drops considerably. In one sense they do have missile trucks--they have missile pods but they don't have drives. They would be basically unsurvivable if they had drives as their only defense is to lie doggo. Bringing up a drive would paint them on enemy sensors but they would have no ability to defend themselves. [Answer] I’m going to stick my neck out a bit here and make some people mad. There is a very pervasive attitude in military scifi that big capital ships are invincible and fighters are strategically irrelevant, mirroring the theory of “battleship supremacy” that permeated Naval thinking leading up to World War II. This theory had roots in the breakthrough of ironclads and their supremacy *compared to wood and sail ships*, then bigger and bigger ironclads leading to WWI Dreadnoughts and the final iteration of WWII Battleships and super-Battleships. **Actual World War II Battleships and Fighters** What changed in WWII was that technology left Battleships behind. Submarines became reliable and dangerous enough to attack battleships. Torpedo bombers and dive bombers could deliver their weapons with high accuracy to attack battleships with weapons that did significant damage and could sink them. Yes, there were countermeasures that could protect them from those new technologies: machine guns and depth charges, but in the end they were designed for a fundamentally different kind of war that was just not being fought any more. The wagons were slow and expensive and rarely got maneuvered into position to engage with their cannons. They never did so without being escorted by aircraft and other screening ships. It just stopped being economically viable given how cheap it was to launch a squadron of fighters or attack the same target with a Submarine. This is why unfinished battleships were converted to Aircraft Carriers by the US and Japan who were locked in the fiercest naval war in history. **Space Battleships and Space Fighters** **1. Speed** In realspace (vs whatever hyperspace FTL you’re imagining, if you’re using FTL?) the constraints on pursuing and engaging any craft: a destroyer, a shuttle, a sensor probe, a missile, anything – as long as it’s using the same engine technology is that you have to close to weapons range. If you have more delta-v then the target does, you probably win. Heavy armor, heavy weapons and gargantuan size work against you in a race so like the WWII battle wagons, building a mega dreadnought may look cool but unless it can get close enough to engage then there’s no point to building it. If there’s a fixed point in space you need to defend then the strategic logic would support building a battlestation or even a minefield there. For any other situation it will have to choose which target is worth the precious fuel chasing and weather the risks are proportional to the gain. Just changing the position of a ship that big is risky. Maybe the enemy is trying to bait you into a more vulnerable position. At best you’re going to have to spend even more fuel to slow down and get back to wherever you were going. This is not a small amount of fuel, and there’s only so much that thing can carry. I invite you to do the math on how much force is needed to accelerate 1 million tons to say 750 m/s. **2. Weapons** Now, onto weapons. For any missile or projectile payload, delivering it by battleship means it only gets whatever speed boost the battleship had (it was probably trailing far behind to begin with, so much of the missile’s fuel will be wasted just trying to catch up). Deliver the same warhead by fighter and you can afford to burn some fuel, change course if needed much cheaper than the battlewagon can and maybe add a few KM/S before even releasing the weapon. Any payload moving fast enough can become an “anti-ship” weapon. There’s no terminal velocity in space, just the point of no return of your fuel. Get up to say a modest 15 km/s and it will just sail clean through, armor and all. Kudos for a payload of tungsten penetrators mounted on a shaped charge that will add even more velocity and spread out the damage at <1km from impact. Instead of 1 hole you get 1,000, good luck damage control crew! A fighter specialized for speeding up and launching this kind of attack kind of reminds me of a dive bomber in fact. Ah, but “Cannons!” you say? Same problem with fuel and closing to range, only even closer range than missiles. Sure you can generate a lot of power for direct energy weapons or mass drivers or whatever, incinerate armor plating like butter, or melt a city into slag - but since they’re part of the ship you have to get the ship close enough to use it. That leaves you vulnerable to every surface battery, missile, fighter, sensor and other concievable weapon. One lucky shot by any of that to say the engines and that ideal firing position is now a decaying orbit. Abandon ship. Launch a few squadrons of fighters or even a handful of stealth fighters to take out the surface batteries and sensors and they may never even know they’re under attack until it’s too late. **3. Economics** Building a fighter is a complex undertaking, no doubt. Lots of precision engineering, integration, flight testing, support facilities, spare parts, etc. need to work together to put a new fighter into service. But that’s something that can be done on a planet’s surface. Once in service those craft can pound out flight hours until their frames literally crumble and fly apart. You could build ten thousand for the cost of a capital ship. Building a mega-dreadnought is something only a highly specialized (aka strategically vunlerable) orbital shipyard could do and then only with breathtaking amounts of materials, expense and time. How much misery could you cause even raiding supply ships heading for that shipyard. Might delay delivery by a year. It might take decades to go from blueprint to in-service vessel and it will probably spend half its service life in drydock getting repaired, modified and prepared for operations. **Closing** All this is not to say that big nasty ships are useless in space combat. But they are vulnerable and strategic liabilities. Losing one would be expensive and traumatizing, certain to alter the strategic balance of the battle maybe even the war. Lose a fighter, or even a whole squadron of fighters and you’re still in the fight. Sure, engaging a big dreadnought with a fighter squadron is risky, like its WWII counterparts its probably blistering with point defense weapons but with speeds like this the engagement window may be only fractions of a second. It seems like David and Goliath. But David had a fast weapon that hit in just the right spot at incredible speed, which is what a space fighter can do but a space battleship can’t. ]
[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. The [black hole question](https://worldbuilding.stackexchange.com/questions/151626/a-planet-illuminated-by-a-black-hole) reminded me of an idea I wanted to implement at some point in a space campaign, but didn't go forward with because I was unsure whether it's merely statistically very implausible, or outright physically impossible: Can a 'rogue' planet (in the sense of not orbiting a specific star in a close vicinity) be on such an orbit around the galactic centre that the amount of illumination it gets is equivalent of that gained in the Goldilocks zone? That is, is there such an orbit for which the total illumination provided by the densely packed stellar and similar objects is similar to that provided by our sun at 1a.u. When I say galactic centre, I mean the central area of a galaxy, one hosting a denser selection of stars (and whatever other 'shiny' objects, including feeding supermassive black holes, nebulae or the like) than the rim. If it's doable in the Milky Way with its central area, great; if it's doable in some other galaxy we know to really exist, that's OK too; if it's only possible with a galaxy type we're not sure is plausible according to science, that's a so-so option but I'd still like to be informed about it. I am fully aware that it'll have to lack seasons, and that its velocity will be odd. It's okay if the probability of such an arrangement naturally approaches zero; in fact even if it needs to be a result of Sufficiently Advanced civilisation meddling, that's okay, so long as such an arrangement can keep on existing with no reliance on superscience **once it's in place**. [Answer] This is a surprisingly difficult question to answer... related ones have been asked elsewhere, with few satisfactory answers. Turns out that simple questions like "*what is the stellar density in such-and-such a region of space*" doesn't often have a very good answer (multiple answers may exist, differing by at least an order of magnitude) let alone more specific things like "*how bright is starlight there*". I've tried my best, but I haven't been able to get a simple, citeable answer. --- Instead of looking at the core itself, I'll look at some other astronomical objects which also exhibit very high stellar densities... [globular clusters](https://en.wikipedia.org/wiki/Globular_cluster) There's a relevant article in *[Astronomy](http://astronomy.com/issues/2014/july-2014)* mazagine, which isn't a scientific publication, alas. There are excerpts from the article for free [here](https://io9.gizmodo.com/what-the-night-sky-would-look-like-from-inside-a-globul-1589324556), including this nice simulation of night on a planet inside the globular cluster [47 Tucanae](https://en.wikipedia.org/wiki/47_Tucanae), as viewed by a regular human eye. [![Nighttime view from inside 47 Tucanae](https://i.stack.imgur.com/4Jx25.jpg)](https://i.stack.imgur.com/4Jx25.jpg) To quote from the quote: > > The cluster's suns would combine to give an average sky brightness some 20 times brighter than Earth's night sky at Full Moon > > > Our sun, as seen from earth, is about 400000 times brighter than the full moon. Clearly, stellar densities just aren't high enough here! Now, a globular cluster ain't quite a galactic core, but it has some similarities. Near our solar system, the stellar density is about 0.14 stars per cubic parsec. The centremost cubic parsec of 47 Tucanae has about *[150000](https://watermark.silverchair.com/324-3-612.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAk8wggJLBgkqhkiG9w0BBwagggI8MIICOAIBADCCAjEGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMVmsty_BxzG_q21ggAgEQgIICAkGgBi3XUvmvBJukvKXWnXXkk4qgDpMF39BylkHq4dM3fA6nT9eCA-NaSlSClOxZd7WONCKAsst6mise1qh1dSWdmNx2fYUvFGn-3bVvYTkFo51d3cj9KXYXXQwreMVWQZOQI-pjWR4yFrREhm3FeOdzeexAfqkQKGC3XoHMK2ExztNRwfPWnk1qSs2Lf036p_eM6Ac_NPYDvjXy29A0sEfxH8Hi40GD9g_WZVtXiJ9u66j3w688xlSQ9AQZYTrofPX8Qp2CWmfHPy_uxiLMzKIg1yMfVArIrRBxF4s3t5uBbmna_ME5Z5YhLC8w7XgslaO2HM_FtbktC4pmVriXBC-bTvT6kQD0fAM4slm3nBCrLwcWodykT8x5YFEXrHt4IrMIGXSqnLTsW7qPFLqSXBEe0pSfv29n0lsA1VTOcgfhhRWEDZQYMu4LiEl7a4CGAeIju-jYgqUjOOQi3bOAjI_Pm7vfTMusQpuxkGEoBJEMg9SPJTBnOj4qpaVTnvGjgbpbhDyuemUAuc6F_mFRKUQV48x3t6_tGcIPS0nUxLuZMTW84GEzKCy3Mk32QlHTMG5eklzPyZEg5lRTu7dfPvHk0LxqsLh2ti4HJ41jZwTfFZrucLVsd0IZMvC7CoEBwA4mNCVTu9ptm_87Z6uJc1AQvx-wtCpVnWKYJHp6ytOl-uI)* stars packed into it (though the density drops off sharply... its a tenth of that if you go more than 3 parsecs from the centre). The galactic core by comparison may have a density 100 times higher than that, but even with that [it has been suggested that](http://www.astronomy.ohio-state.edu/~ryden/ast162_7/notes31.html) > > ...there would be a million stars in our sky with apparent brightness greater than Sirius. The total starlight in the night sky would be about 200 times greater than the light of the full moon; you could easily read the newspaper at midnight, relying on starlight alone. > > > That's a pretty impressive twilight, but one that falls short of your requirements by quite some way. The author does not explain their methodology, so it remains possible that they are incorrect but it seems plausible to a couple of orders of magnitude, and that would still fall a long way short of your requirements! --- Lets look at something else that's quite import to your scenario, that you've not really thought about... the particularly hazardous nature of such locations. When star densities are that high, the chances of you being near to a dangerous sort of neighbour are much higher. 47 Tucanae, for example, may or may not harbour a [black hole](https://arxiv.org/abs/1801.00796) but it most certainly does harbour [25 pulsars](https://www3.mpifr-bonn.mpg.de/staff/pfreire/47Tuc/), many of which are millisecond pulsars (for comparison, the nearest pulsar to earth, [PSR J0108−1431](https://en.wikipedia.org/wiki/PSR_J0108%E2%88%921431) is over 420 lightyears away, and it is very weak and spins much more slowly). The creation of such objects is a [violent and dangerous event](https://en.wikipedia.org/wiki/Supernova) in itself, but they're associated with other unpleasant events such as [gamma-ray bursts](https://en.wikipedia.org/wiki/Gamma-ray_burst) which are definitely planet-sterilisingly bad things to be near. Binary systems with neutron star companions [are known to exist](https://www.nasa.gov/mission_pages/chandra/multimedia/x7.html) in 47 Tucanae, and that's *definitely* a forboding combination... certainly, I learned a new term "[cataclysmic binary](https://en.wikipedia.org/wiki/Cataclysmic_variable_star)". There are stars which [get brighter inexplicably](https://eso.org/public/sweden/news/eso9703/), possibly being some new kind of nova. The brighter the starlight, the more short-lived giant stars and dangerous supernova remnants there are out there, and the greater the chances of something terminally unpleasant happening to your rogue planet. --- Other potentially interesting sources which I didn't manage to back up with more hard data: * [This physics.SE answer](https://physics.stackexchange.com/a/26556/225554) suggests some sort of bright twilight, though doesn't compare to the moon and I was too lazy to do the maths to compare them myself. * [Another physics.SE answer](https://physics.stackexchange.com/a/25707/225554) suggests half as bright as moonlight "near" the galactic centre. * [This quora answer](https://www.quora.com/If-our-solar-system-was-placed-near-the-middle-of-the-Milky-Way-would-it-always-be-light-on-Earth-due-the-mass-of-stars), suggesting a much brighter sun-like twilight in the galactic centre, though also suggests a more moon-like lights at the edge of the galactic core You may also wish to look up "Ahad's Constant", which is about how much light from stars other than the sun falls upon earth. The original paper seems to have disappeared, but you might have more luck finding it than me! [Answer] Your planet is traversing an **emission nebula**. Here is the Orion nebula. [![orion nebula](https://i.stack.imgur.com/JdwgN.jpg)](https://i.stack.imgur.com/JdwgN.jpg) By ESO/Igor Chekalin - <http://www.eso.org/public/images/eso1103a/>, CC BY 4.0, <https://commons.wikimedia.org/w/index.php?curid=27880539> Nebulae are interstellar clouds of gas. Some are bright and give off light; these are [emission nebula](https://en.wikipedia.org/wiki/Emission_nebula). Orion is a big one; 22 light years across and bright enough to be visible from Earth with the naked eye. I liked this description of the Orion nebula from Wikipedia > > The first published observation of the nebula was by the Jesuit > mathematician and astronomer Johann Baptist Cysat of Lucerne in his > 1619 monograph on the comets (describing observations of the nebula > that may date back to 1611). He made comparisons between it and a > bright comet seen in 1618 and described how the nebula appeared > through his telescope as: "one sees how in like manner some stars are > compressed into a very narrow space and how round about and between > the stars a white light like that of a white cloud is poured out" > > > <https://en.wikipedia.org/wiki/Orion_Nebula> Emission nebulae glow with their own light, energized by stars and also stranger things like > > supersonic "bullets" of gas piercing the hydrogen clouds of the Orion > Nebula. Each bullet is ten times the diameter of Pluto's orbit and > tipped with iron atoms glowing in the infra-red. They were probably > formed one thousand years ago from an unknown violent event. > > > Your rogue planet is traversing such a nebula. Hopefully it has a magnetic field to deflect the iron atoms! Those would sting. As can be seen in the image, the nebula is not uniformly bright and there are stars in there too, which could be seen from your planet. The entire sky will glow to a greater or lesser extent, with different colors dependent on the local energies and composition of the nebula. I could imagine that a planet traversing a gas cloud might gravitationally collect a tail of gas in its wake. The locally denser gas trailing behind the planet could be brighter, especially if there were aurora-like interactions between collected gas and the planetary magnetosphere. If your planet rotated (surely it will to some degree), rotating thru the bright "tail" and the relatively darker front side could give a day and night. --- The hard science: absolute magnitude! <http://astronomy.swin.edu.au/cosmos/A/Absolute+Magnitude> Absolute magnitude is a way of normalizing brightness of various celestial objects by assuming a fixed (32.6 light year) distance from the viewer. Our sun as an absolute magnitude of 4.8 although looks much brighter because we are a lot closer than 32.6 light years. The Orion nebula has an absolute magnitude of 4 which is comparable to the sun, but looks much dimmer because it is 1344 light years away. Given that the nebula and our own star have comparable absolute magnitudes I think it is safe to assert that they would be comparably bright when seen from the same distance. The tricky thing for calculations is that the nebula is also much larger than the sun, and also the rogue planet is inside of it. ]
[Question] [ This is a progression from my first question, [here](https://worldbuilding.stackexchange.com/questions/125026/can-a-habitable-moon-rely-on-the-magnetosphere-of-its-parent-planet-for-radiatio) (if this is too similar to my original question, please let me know of a better way to address this, as I am not getting the answers I need on that first question to be able to answer this one, and they seem separate enough to me.) As with my first question, I found many questions and answers on this site that have related information, but don't directly answer my specific question. And I seem to be finding incomplete, incorrect, or conflicting information. Most specifically, this was prompted by a comment about Io being a major factor in Jupiter's radiation belt, and I attempted to research along those lines, but failed to find the information I needed, hence this new question. See these: [Conditions for human life in a Jupiter-like system](https://worldbuilding.stackexchange.com/questions/76477/conditions-for-human-life-in-a-jupiter-like-system/76483#76483) [Captured Earth-Like Moons around Gas Giants](https://worldbuilding.stackexchange.com/questions/82415/captured-earth-like-moons-around-gas-giants) [Naturally making a gas giant moon habitable](https://worldbuilding.stackexchange.com/questions/27781/naturally-making-a-gas-giant-moon-habitable) [Calculating Radiation Zones of Gas Giants and the Effects on Its Moons?](https://worldbuilding.stackexchange.com/questions/109187/calculating-radiation-zones-of-gas-giants-and-the-effects-on-its-moons) Some of my research seems indicate that gas giant radiation comes almost exclusively from the planet itself. Others indicate that it's mainly a function of material contributed by orbiting bodies like Io. And nowhere did I find any attempt to balance it like I want to. So here's the actual question: Is there a distance between the planet and the moon where the moon is far enough from the planet that the radiation *from the Planet* will not be able to get to the moon's surface in any quantity that is detrimental to human life, while at the same time the moon is close enough to the Planet so that *the planet's magnetosphere* is still providing the same level of radiation protection *from the star's radiation* as Earth's magnetosphere provides to Earth? In other words, is there a gap between the lethal levels of radiation from the star and the lethal levels of radiation from the planet, and could a moon orbit the planet in that gap? If such a gap is possible, what 'type' of Gas Giant is needed to create it? Limitations: 1. Assume that the distance from the star is appropriate for life in this system, (in the Goldilocks zone, adjusted appropriately for a moon instead of a planet, etc.) 2. Assume the life on the moon is Earth life, disregard how it got there 3. Assume the moon has all necessary life supporting functions, including the same level of radiation defense as Earth's atmosphere, with the sole exception of it not having any magnetosphere of its own. 4. Assume no other moons or rings orbiting the Gas Giant are contributing anything that could significantly affect radiation levels in the system, the only radiation considerations are the star and the gas giant itself. 5. Disregard the reason for the missing magnetosphere on what is essentially Earth orbiting a gas giant in all other life support related aspects. though the moon does not need to be the same size, mass, density, etc., as Earth, if such adjustments are needed to allow a change in the orbital distance from the gas giant to put it in the gap in the radiation, and such changes can be 'hand-waved' to have no impact on the other life support functions of the planet. 6. The Gas Giant can be of any size/composition/configuration that current scientific understanding deems could plausibly exist, and that any layman could reasonably accurately label as a 'gas giant', regardless of accepted scientific definitions and terminology (including brown dwarf, ice giant, etc.) but that a layman would not even accidentally believe is a star or rocky planet. Desired information: 1. Is there any Gas Giant that could have such a small/weak radiation belt system that an Earth-like atmosphere could protect life from it, and a large/strong enough magnetosphere *at the same time* that the star's radiation would not strip away that atmosphere within the time frame of earth life evolution from single cell to human, to produce such a gap? 2. Is the gap appropriately shaped (distortion due to stellar wind) that a moon could make a complete orbit of the planet without leaving the gap, or without leaving it for a long enough time to be detrimental to earth life on an evolutionary time scale? 3. If the answer to the above is affirmative, what is the Gas Giant like (mass, volume, density, composition)? or is this something that most gas giant could have, and the ones without such a gap are the exceptions, and not the rule? [Answer] First, it's important to discuss what radiation belts are and how they form. Radiation belts are formed by charged particles that are trapped by a planet's magnetic field and, due to the shape of that field and their own initial velocity, tend to collect in certain regions. The main source of charged particles in e.g. Earth's [Van Allen belts](https://en.wikipedia.org/wiki/Van_Allen_radiation_belt) is the [solar wind](https://en.wikipedia.org/wiki/Solar_wind): particles emitted from the Sun. In the case of Jupiter, though, that's only part of the equation. Most of the material in Jupiter's radiation belts, especially the strong, close-in plasma torus, comes not from the Sun or Jupiter itself but from [its moon Io](https://en.wikipedia.org/wiki/Io_(moon)#Interaction_with_Jupiter's_magnetosphere) - as much as [a metric ton *per second*](https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter#Role_of_Io), mostly in the form of ionized gas ablated from its surface. Saturn has smaller, less charged plasma tori generated from [some of its own moons](https://en.wikipedia.org/wiki/Magnetosphere_of_Saturn#Interaction_with_rings_and_moons). On the other hand, Neptune and Uranus have no analogous moons, and so [their magnetospheres](https://en.wikipedia.org/wiki/Neptune#Magnetosphere) lack powerful internal radiation belts. It seems reasonable to expect, therefore, that an otherwise Jupiter-like gas giant (or any other type of gas giant) that lacks an Io analogue will also lack the plasma torus that makes Jupiter so inhospitable. It may even be that the presence of an Earth-sized moon in the gas giant's system would make an Io-like orbit unstable, giving it added protection against the possibility of radiation belts. Finally, don't discount the moon's own magnetosphere. Ganymede, another Jovian moon, has - uniquely of moons in the solar system - [its own permanent magnetosphere](https://en.wikipedia.org/wiki/Ganymede_(moon)#Magnetosphere) that shelters it from the radiation environment it's in, in much the same way Earth's shelters it from the solar wind. A large body of Earthlike composition (differentiated, with a molten iron core) would absolutely have its own protection from stray solar particles or those ablated from other moons. To sum it all up: 1. **Yes**, it's possible to have a gas giant without a strong internal radiation belt that would pose a hazard to its moons, while still having a magnetosphere. 2. **Yes**, it should be well within the gas giant's magnetosphere at all times, and it would also have its own magnetosphere to consider, which could offer additional protection. 3. **Potentially any.** The key factor appears to be the presence of close-in moon(s), rather than anything intrinsic to the gas giant. Some types of gas giants might be more or less likely to have such moons, and the formation or capture of an Earth-sized moon will probably have some effect, but it may simply be down to luck. [Answer] So a potentially habitable exomoon of a giant exoplanet might be protected from the radiation zone by not orbiting with the radiation zone, which the giant exoplanet might not have, depending on various factors, and if the giant exoplanet does have a dangerous radiation zone that zone might not cover all the region where a habitable exommoon should orbit its planet, depending on various factors. A habitable exomoon might also be protected from the dangerous radiation it is planet's radiation belt by the exomoon's own magnetosphere. So the exomoon might possibly orbit in the dangerous radation zone without any ill effects. An exomoon with the right mass and composition that rotated at the right rate could have a very strong and powerful magnetosphere. That magnetosphere would be generated by the rotation of the exomoon's core, which would also be necessary to drive plate tectonics, which might also be necessary for the exomoon to be habitable. There is an article: "Exomoon Habitability Constrained by Illumination and Tidal heating" by Rene Heller and Roy Barnes, Astrobiology, January 2013. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3549631/[4]> In section 2, Habitability of Exomoons, they discuss the mass range necessary for hypothetical exomoons to be habitable in the sixth paragraph: > > A minimum mass of an exomoon is required to drive a magnetic shield on a billion-year timescale (Ms≳0.1M⊕; Tachinami et al., 2011); to sustain a substantial, long-lived atmosphere (Ms≳0.12M⊕; Williams et al., 1997; Kaltenegger, 2000); and to drive tectonic activity (Ms≳0.23M⊕; Williams et al., 1997), which is necessary to maintain plate tectonics and to support the carbon-silicate cycle. Weak internal dynamos have been detected in Mercury and Ganymede (Gurnett et al., 1996; Kivelson et al., 1996), suggesting that satellite masses>0.25M⊕ will be adequate for considerations of exomoon habitability. This lower limit, however, is not a fixed number. Further sources of energy—such as radiogenic and tidal heating, and the effect of a moon's composition and structure—can alter the limit in either direction. An upper mass limit is given by the fact that increasing mass leads to high pressures in the planet's interior, which will increase the mantle viscosity and depress heat transfer throughout the mantle as well as in the core. Above a critical mass, the dynamo is strongly suppressed and becomes too weak to generate a magnetic field or sustain plate tectonics. This maximum mass can be placed around 2M⊕ (Gaidos et al., 2010; Noack and Breuer, 2011; Stamenković et al., 2011). Summing up these conditions, we expect approximately Earth-mass moons to be habitable, and these objects could be detectable with the newly started Hunt for Exomoons with Kepler (HEK) project (Kipping et al., 2012). > > > The upper limit of about 2 times the mass of Earth should hold for exoplanets as well as exomoons. Heller and Barnes give the source for the importance of plate tectonics for habitability as: Williams D.M. Kasting J.F. Wade R.A. Habitable moons around extrasolar giant planets. Nature. 1997;385:234–236. [PubMed] [Google Scholar] Heller and Barnes give the sources for an upper mass limit at about 2 Earth masses as: Gaidos E. Conrad C.P. Manga M. Hernlund J. Thermodynamics limits on magnetodynamos in rocky exoplanets. Astrophys J. 2010;718:596–609. [Google Scholar] Noack L. Breuer D. Plate tectonics on Earth-like planets [EPSC-DPS2011-890]. EPSC-DPS Joint Meeting 2011, European Planetary Science Congress and Division for Planetary Sciences of the American Astronomical Society; 2011. [Google Scholar] Stamenković V. Breuer D. Spohn T. Thermal and transport properties of mantle rock at high pressure: applications to super-Earths. Icarus. 2011;216:572–596. [Google Scholar] It is possible that the importance of plate tectonics for habitability, and the upper mass limit of about two times the mass of Earth for plate tectonics, are not accepted by all scientists interested in astrobiology, but I have not researched that. Anyway, it seems possible for exomoons to have the right mass, composition, rotation, and orbit to be safe from the effects of their planet's radiation zones, and also to have other necessary qualities for habitability. ]
[Question] [ Related to my other [question](https://worldbuilding.stackexchange.com/questions/106463/can-i-have-a-beach-of-pearls). What would be best conditions for a natural super colony of pearl oysters and the best conditions for them to produce pearls naturally. Shallow or deep waters? Slowly decreasing, long shore or rocky waters? Periodic currents around the island or continuous current? (To increase the chance of sand getting into the clams) Warm water? Coud it be combined with a coral reef? Reefs forming circles around the island or a star / squid like layout? I would also like if the conditions allowed the pearls to wash up to the beach. You can have anything you want as long as it can create a paradise for the clams. The conditions don't have to be caused naturally. I have a lot of handwavium to make it happen. (If it would be impossible to do with just one island consider if several islands could make enough glitter. And then I'll join it together with MAGIC or something) [Answer] Since you want a *natural* pearly factory, we can ignore modern oyster farming techniques and just focus on creating an ideal area for these pearly mollusks: **Your natural pearl factory just needs to be filled with mildly-annoying parasites and predators.** However, producing them in the quantities that you want may not be feasible. [Pearls](https://en.wikipedia.org/wiki/Pearl#Creation) are essentially the result of an oyster/muscle's immune system responding to parasites, broken bits of shell, or other irritants. The mollusk creates a tissue sac which secretes calcium carbonate and conciliation onto the irritant. This material is what pearls are made of, and pearls are formed as a result of the repeated secretions. The irritants seem to be mainly parasites that enter the mollusk, and bits of the mollusks' broken shell caused by predators or other injuries. As for the water, any deep water seems to be fine. There are freshwater and saltwater mollusks which produce pearls, and historically [pearl hunters commonly dove 40-100 feet](https://en.wikipedia.org/wiki/Pearl_hunting) to reach them. In short, you just need a lake that's not very pleasant to drink or swim in due to a high amount of parasites, but otherwise does not require anything magical or unnatural. Do note that this will simply create a relatively high supply of pearls compared to other areas. Creating the iridescent pearl-filled beaches that you mention in your other question just isn't feasible, as that would require thousands to oysters to die and wash ashore every year just to give the beach a few dozen pearls. [Answer] Pearls form naturally at a rate significantly smaller than that of farms, so tweaking all those environmental factors will help, but not enough to get you to where you want to be. If you want something massive, you either need an insane number of oysters/mussels to begin with, or introduce an outside force, like an animal. On the animal front: if you've done a little research, you'll find that pearls are kind of like a pustule or cyst for the bivalve. Once the waterproof 'lips' of the bivalve are violated, it excretes mother-of-pearl to repair the damage. Cultured pearls are made from a little bit of shell and a little bit of mantle from a different bivalve deposited inside the host, for the same reasons we use titanium in human bodies: the body won't reject it, but it won't absorb it either. So you could imagine some sort of bee-like creature that gets something from violating the bivalve but not killing it, and then accidentally cross-pollinating genetic material from the last oyster he violated into the wound. This would make for a much, much higher percentage of pearl-hosting oysters. The problems to solve would then be: 1. What does the 'bee' get from getting into an oyster but not eating it? 2. What evolutionary advantage would a pearl-laden oyster have over a non-pearl-laden one? ]
[Question] [ Alien and fantasy creatures can be designed in an infinite number of ways. But are there physiological traits that would be common among all tool-developing (technology-building) species? As an example, I suspect all such species must have some means of manipulating small things. Whether it be fingers and an opposable thumb or well coordinated tentacles or a remarkably manipulatable pair of jaw pincers. Physiologically, the species needs the ability to manipulate things implying fine motor control and gripping power. I'm not as interested in how the traits are manifest as I am what the basic traits are. Is there a short list of such traits that can guide creature builders? [Answer] I have been considering something similar recently as part of hobby speculation regarding Artificial Intelligence: what are the fundamental requirements for technical intelligence. Because I've considered this lots, this may turn into an extremely long answer, but we'll see what happens eh? First up, some quick notes: * I define technical intelligence as the ability to grow collective intelligence and create meta-tools. Many animals can learn tricks (eg a dog), but it will not pass them on to it's offspring. Many animals can use rocks and sticks, but only one other than humans creates them, and none other than humans create tools that create tools. That said, in the software development field we are often so busy making tools to make tools that we lose track of the end goal.... * One main assumption is that a creature's body is shaped by evolution, and that it cannot change it significantly. I assume that their is a non-minor link between physical form and intelligence, and I assume that all current earthly creatures are near the maximum intelligence of their physical forms, or in some cases, meerely need more time to achieve technical intelligence. * One conclusion I have come to is that beyond a certain point, a species is able to create enough tools of enough fidelity to ignore any physical requirements it's physical form lacks. Humans can study nuclear physics even though we can't see neutrons. A creature with low manipulation skills may be able to make it up in other ways. That said, without the ability to perceive or manipulate a certain aspect of the environment will result in no development in that area. It may well be there is some physical phenomenon in the universe that we cannot perceive nor touch, and as a result we cannot investigate it. * Finally, here on Earth we have exactly one technical intelligence: Humans. This is not a sufficient amount of datapoints for any sort of scientific study or conclusion on what the exact requirements are. So this is more an exploration of why humans are the only technical intelligence on Earth. ## Physical Requirements: 1. **They need the be able to percieve** This should be fairly obvious. Without perception of the environment, a forming intelligence will go crazy or commit suicide. Imagine if you had no eyes, no ears, no sense of smell or touch. How long would you remain sane? An earthly lifeform that has no perception but is alive is called a plant. A few can perceive a bit (such as some flowers tracking the light, or the venus flytrap catching it's prey), but they can see too little of their environment to be able to develop an intelligence. The exact senses are unimportant, though it will influence their later development - a blind species may never notice the stars. Other things that may matter include the range of vision (eg depth perception of items at close distances), the spectrum, and the resolution. 2. **They need to be able to manipulate** If you had no arms, no legs, and could not even blink, how long would you remain sane? Similar to the ability to perceive, the ability to manipulate is required for an intelligence to emerge. The manipulation method must have sufficient dexterity and strength. Dolphins, dogs and so on are all highly intelligent creatures, but they lack dexterity. They also require multiple manipulators. An elephant is again highly intelligent, but a single trunk does not provide the ability to hold a tool and work-piece at the same time. Additionally, the field in which it manipulates it must be able to percieve. Many birds are quite intelligent creatures, but cannot see what their otherwise dexterous feet are working on. Hence it is unlikely they will achieve advanced tool use. Closely linked to both perception and manipulation is the environment. Living on a featureless white plane in the fog will send a human crazy. Living in a world that is nothing but random flashing lights will also drive him mad. To some extent evolution may compensate and the intelligence may adapt to it's environment, but I suspect many places can harbour life, but not tool-using-intelligent life. 3. **Able to survive**. An intelligent creature needs to be able to learn, and to do so, it needs to not die the instant it is touched. Humans are pretty tough creatures. You can cut our limbs off and we don't die. Try that with some other animals and you'll find yourself with a carcass. A creature much frailer than it's environment will not be able to develop tool use as they will never be able to learn from mistakes. This is again closely linked to environment. A human is completely unable to survive underwater, and a fish unable to survive on land. Just because a species is not robust in a gravitation field, on earth, at standard temperatures and pressures, does not prevent it from achieving technical intelligence in some other environment. ## Social Requirements 1. **Communication**. Assuming that a creature can perceive and manipulate, it is probably able to communicate. But the better it can communicate, the faster knowledge can be transferred. If communication is too slow, then the next generation cannot build on the work of the previous. If every generation has to discover that it can hit a lion with a rock, without the ability to learn from it's parents, then that intelligence will be limited to primitive tool use. Even if you injected knowledge into a single generation, the very next generation it would be lost. All major technological advances have ridden on the back of an improvement in communication. The most significant advances were probably: parenting, taming animals for riding, writing, printing press, radio, television, internet. Each one enabled a larger, more stable culture. 2. **Empathy** No-one likes a race of psychopaths. Without the ability to empathise with others of it's race, a culture can never form, and they can never support the scientists and thinkers required for higher learning. You'd end up being limited to individual intelligence again, just the same as if you had no communication. I'd say that humanity rides the border of too-little empathy. We have fought with each other ceaselessly for generations and generations, and lots centuries of man-years of work to our lack of empathy. Riding with this is the *physical* requirement of being able to express emotion. Pure communication may not be enough, as we perceive emotion primarily through body language and looking at each others faces. If our faces were not expressive, would we be able to form a culture? I'm not sure. ## Mental Requirements 1. **Memory** A creature must be able to learn, and part of this is remembering. It must be able to remember both short term and long term. The more accurate it's memory, the better. That said, human brains are pretty poor. We can't remember things even just moments after seeing/hearing them (at least, my face/name association sucks). 2. **Mental Speed**. The Portia spider can actively plan a path to it's prey, it just takes a very long time to do so (on order of minutes). If an intelligence is too slow to "think" it will take a hugely long time to bootstrap as it will constantly be prey to other creatures. 3. **Mental Ability**. This is a super-hard one to define, but one textbook (Artificial Cognition Architectures by James A. Crowder, John N. Carbone and Shelli A. Friess) lists things like reasoning and testing hypotheses as required for learning. However, I would list these as subsets of creativity and curiosity. Without those two traits we would not make anything new, nor seek to learn anything we did not already know. [Answer] You will need: * The ability to grasp an object * Enough mental capacity to understand cause and effect * Enough strength to be able to use crude tools, as those will be developed first * Fine motor skills to control the tools These will get you simple tools, like using rocks and sticks to break things or scoop things out of hard-to-reach areas. To get more advanced tools, you will need: * Long term memory to remember what you originally planned to use this tool for * Very fine motor skills for crafting of the tools * Enough mental capacity for more advanced problem solving (being able to envision more than one step to reach a goal) * A rich environment that allows enough time in the day for creative thinking * A rich environment with enough resources to create the tools Not strictly necessary, but advanced tools are not likely to be created without: * Already widespread use of crude tools * A social, cooperative society, ideally with some basic means of communication * An environment that highly rewards creation of tools (I'm thinking near water for fishing, or near large prey for hunting) [Answer] Great general answers out there. I'll focus on one single specific issue. Obviously, it holds for anthropomorphic species as we know no better examples. # Opposing thumbs Opposing thumb is *the* requirement for grabbing and holding a tool securely. While one may imagine aliens with *two* opposing thumbs on each hand (someone did, but I forgot the book name), it is pretty much impossible to build a human-like civilisation with no thumbs. If one can build a non-anthropomorphic civilisation is an open question. It's better to err on the good side and to think it's possible. The ways dolphins and ants handle things might help. Compare how crows and bonobos wield tools. ]
[Question] [ I'm working on a planet that has very similar conditions to earth. Now, I had the idea of animals having four (or even more) lungs. Would that be possible (I imagine there must be a possibility to inhale large masses of air to sustain all lungs?) and if yes, what would the benefits and other effects be? (Maybe a larger body?) Thanks :) [Answer] It's quite possible, and some animals already have them. Some arachnids have what are known as [book lungs](http://en.wikipedia.org/wiki/Book_lung) - small respiratory cavities that actually are not lungs, but different respiratory organs. They formed separately (in terms of evolution), but have taken the place of lungs in these arachnids. Some organisms with book lungs have them in two pairs, while others have anywhere from one pair to four pairs. The reason for this many is simple: The book lungs are small. That said, arachnids are (in general) quite small, but some of them are still too big to be sustained by only one pair (or one book lung). --- What exactly can extra lungs do in creatures that already get enough oxygen with just one pair? Well, you will have to solve the issue of body structure. Extra lungs take up a substantial amount of space, and animals won't necessarily evolve to be bigger, because they might not benefit much from the extra pair. Let's assume, though, that a creature does have four lungs. What are the effects? You essentially have a creature with a larger [lung volume](http://en.wikipedia.org/wiki/Lung_volumes), assuming that the lungs retain their same size - in other words, assuming that you're adding a pair of lungs to a creature which already has one pair. This means it can * Survive at higher elevations. * Grow larger/taller. * Have different voices (see [Iwarsson (2001)](http://research.ku.dk/search/?pure=en/publications/breathing-and-phonation-effects-of-lung-volume-and-breathing-behaviour-on-voice-function(9729f610-bce0-11df-825b-000ea68e967b).html)). * Be more resistant to effects from diseases like emphysema, that attack the lungs. Also, [lungs do lots of other things besides helping creatures breathe](http://en.wikipedia.org/wiki/Lung#Other), including * Regulate blood pressure. * Balance blood pH. * Attack blood clots. * Protect the heart (or hearts, if you're being creative!). * Act as backup storage for blood in cases of severe bleeding. All of these capabilities (and more) would be increased with an extra pair of lungs. [Answer] Four lungs wouldn't be radically different to two lungs twice the size. Their design matters far more. (multiple lungs with no shared airways might make pneumonia less of a threat to life) If you want an organism that can support a metabolism burning calories at a much higher rate than a mammal then we have them. Birds! Avian lung design is very different. They have a number of bladders to move air through their lungs along a path such that freshly ingested air does not get to mix with exhaled stale air. This is a big part of how they can fly. The other big part is a better version of haemoglobin in their blood. Google if you want the full and rather complex anatomical detail. Birds can fly at altitudes where humans have trouble surviving let alone being active. [Answer] Many animals have extremely different lungs than we do. Look up how birds breathe for example. It actually takes two full inhale/exhale cycles for air to move all the way through their respiratory system. On the first breath in air moves into their first "air sacs" at the back, then they breathe out and it moves into their lungs, then in and it moves into their second set of air sacs at their front, and finally out where it exits their body. Mammal lungs are actually very inefficient and the heightened efficiency of bird or pterosaur (flying dinosaurs) lungs are one of the reasons you might have heard things like "an albatrosses can fly for years at a time without ever stopping". If you can properly oxygenate your muscles you wouldn't ever tire out during long periods of aerobic exercise (flying,running,etc.). Air sacs systems being more efficient are also one of the reasons that GIANT dinosaurs as big as blue whales were able to even power their muscles enough to fight gravity and one pterosaur that was as tall as a giraffe was literally able to fly. So yeah, I think it would be really cool to put some stuff like that into a story. ]
[Question] [ OK, here's the problem: I want to have a spaceship that is built for transporting large machines (in particular, heavy mining equipment). It does not and is not designed to leave space; transport down to a planet (if necessary) is done by other, specialized ships. It is operated by two people, and its flights can span several years (that is, the two people must be able to survive that long on the space ship). It is owned by a transport corporation which is interested in saving cost, so it will have to be built as cheaply as possible for this purpose, unless the extra expense is justified in reducing transport costs. Note that the crew cannot reduced to less than two people (like a one-person ship or even a completely automated one) for legal issues (each ship is required by law to have a captain and an engineer). In particular, I'm interested in the following questions: * What general ship design would be the most practical for this purpose, and why? * How much space would be reserved for crew needs (life support, food supplies, etc)? Recall that the ship owner (a big, greedy corporation) will want to reduce this to the absolute minimum, in order to maximize profits. * What is a realistic ratio of cargo mass to ship mass? * Anything else that should be considered when designing the ship? [Answer] Getting to space is the hard part, since you are already there you only need to care about * accelerating * decelerating * lifesupport for two people over the course of, lets say 5 years **Shape** I guess pickaxes and shovels arent worth an interplanetary travel, so lets take a bunch of [Tunnel Boring Machines](https://en.wikipedia.org/wiki/Tunnel_boring_machine) and cranes, totaling 100000 tons of cargo. Since they are made of huge pieces of metal, specifically designed to withstand repeated physical abuse, there is no need to put them inside a cargo container, just mount them on a frame (Although clients can choose to pay extra for wrapping it with thick metal plates). Aerodynamics are not a problem in space and all the sensitive parts can be removed and transported separately in a protected, pressurized box with a negligible weight. Since you need to both accelerate and decelerate the ship will either need two sets of thrusters on both side of the transport frame (expensive), be able to ride around the frame on a rail (acceptable) or have the frame around it like a donut (cheapest, but need to be very close to the center of mass) Now for lifesupport. The crew will need Air, Water and Food, for each of those we can choose between stocking up before- or generating it during the trip. **Water** > > The UN say that a human being needs 50 litres of water per day in order to prepare meals and to have enough for personal hygiene > > > That would be 180 tons of water for a 5-year trip if its discarded after use. Even the fanciest recycling system can be implemented in a fraction of this weight, keeping a few hundred litres in circulation **Air** The ISS life support uses two systems, one electrolyzes water to generate oxygen and [another](https://en.wikipedia.org/wiki/Vika_oxygen_generator) uses a chemical reaction, with one litre of Lithium perchlorate it can provide enough oxygen for one person for one day (and does not require energy input). Splitting 1l of water by electrolysis generates 16/18 kg of oxygen or 620 litres of pure O2. Almost the same efficiency as the chemical method but less dangerous. Photosynthesis is another viable option, two people would need a small 30x40 $m^2$ forest to support them, although algae are much more compact and currently in research. [Urban Algae Canopy](http://www.carloratti.com/project/algaetecture/) claims to produce "as much oxygen as four hectares of woodland", although exact technical details are not available **Food** [3630 kg of food are required to support a crew of three for about six months.](http://m.space.com/8876-international-space-station-numbers.html) That makes about 25 tons of food for 2 people for 5 years. Probably much simpler and cheaper to stockpile than growing food on a spaceship **Fuel** Thats the important part. If we use more fuel we can go faster and need less food, water air and salary for the crew. You need to know the weight of your cargo, how far you need to go and how fast you want to go there, at some point it might be cheaper to split the cargo and make two trips. Since we cannot realistically use fuel in the same order of magnitude as cargo, [Rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) $\Delta v = v\_e \ln \frac{ShipMass+FuelMass}{ShipMass}$ simplifies to $\Delta v = v\_e \frac{FuelMass}{ShipMass}$. Now we need to maximize the exhaust velocity. Exhaust velocities of chemical rockets range from 2 to 5 km/s, while [Ion thrusters](https://en.wikipedia.org/wiki/Ion_thruster) can reach 20-50 km/s but their thrust is very low and they need a very long time to accelerate. A combination of both is ideal, A chemical rocket gives an initial push and then you fire up the ion thrusters and keep them running for two years, then you coast for a year, flip the ship around and run the ion drive for another two years and finally use the second chemical rocket for braking and fine adjustments For interstellar travel you can neither use solar sails for acceleration nor solar cells for energy so the only choice is to have a nuclear reactor in the ship [Answer] **If artificial gravity isn't available then the ship will need to sport a rotating ring or the trip durations drastically reduced.** The human body does [very poorly in zero gravity situations](http://www.racetomars.ca/mars/article_effects.jsp) even for months-long trips in space. Assuming a 3 year mission duration. Considerations: * Food Stores * Crew living quarters * Propulsion * Ship design/shape * Defensive Systems **Food Stores** Assuming a 2000 calorie diet with macronutrient ratios at 25% Protein, 25% Fat, 50% Carbs. Basic weights per macronutrient: * 4 calories per gram of carb. * 4 calories per gram of protein. * 9 calories per gram of fat. 500 calories of protein = 125 grams of protein 500 calories of fat = 56 grams of fat 1000 calories of carbs = 250 grams of carbs Each crew member needs: 431 grams of food per day and 3 kg of drinking water per day. $0.431 \,\text{kg} \cdot 365\,\text{days} \cdot 3\,\text{years} = 471.945 \,\text{kg}$ or 1 short ton of food for two people for three years. Some reserves will be helpful in the event of an emergency or a bad batch of food. $1000 \,\text{liters} = 1 \,\text{meter}^3$ $3 \,\text{liters} \cdot 365\,\text{days} \cdot 3\,\text{years} = 6570 \,\text{liters}$ or $6.5 \,\text{meters}^3$ **Crew living quarters** SuperMax prison cells in the United States offer everything a lonely captain and engineer will need (in terms of living space). Each cell measures 4 meters long by 2 meters wide by 3 meters high. This compressed space contains a toilet, sink, shower, bed, desk and chair. With hallways connecting these quarters to the bridge and engineering sections, the crew should be able to keep up on any cardiovascular fitness they may have. If artificial gravity isn't available then a spinning crew quarters will be required to mimic gravity. Failure to provide some form of gravity will result in lawsuits by the captains and crew that the company failed to meet minimum safety standards. Waste management and atmospheric conditions will need to be controlled too. Equipment areas for these functions will need to be provided for. **Propulsion** Whatever shape the FTL drive requires. Since FTL drives aren't strictly [science-based](/questions/tagged/science-based "show questions tagged 'science-based'"), there's a lot of leeway in how large the drive needs to be along with any fuel supplies required for the drive. **Ship Shape** Since this ship never needs to worry about entering an atmosphere, the shipwrights will want to maximize the [ratio of volume to surface area](https://en.wikipedia.org/wiki/Surface-area-to-volume_ratio). The most efficient shape for maximizing this ratio is a sphere. However, a continuously curved shape is more expensive than welding flat plates together. An icosahedron is roughly spherical and can be welded from flat hull plates. The shipping company can find a sweet spot between internal volume and hull plate size. **Defensive Systems** If these are required and assuming a spherical hull, point defenses would be placed at the "north" and "south" poles and at 0°, 90°, 180°, and 270° longitude around the equator. This provides consistent firing arcs across all approaches and large zones of overlapping fire. [Answer] **Modular design, cargo carried outside, ship operates non-stop** First off, not needing to land means that you have more freedom to design the ship to improve the economic profits. Those ships would be *expensive*. As with a current airline plane or cargo ship, you want them to stop as little as possible. In space this is doubly critical; not only you waste a lot of time decelearating/accelerating when you arrive at destination and depart, you lose a lot of energy (in a planet surface you lose that energy anyway due to friction). So, you want a basic design with a central hull with motors, fuel load, crew cabin, etc. Cargo is stored in containers, which are attached to the sides of the ship. When the ship reaches its destination, it points towards the Sun to use it as a gravitational slingshot. It launches the cargo toward local "tugboats", which attach to those containers and put them into a parking orbit. It first receives some cargo containers that deliver fuel and supplies for the ship itself (maybe including a replacement crew), while the ship approaches the Sun the fuel and supplies are transshipped to the main body. Once the Sun is being orbitted, the ship accelerates in order to get into the orbit that will make it leave them system in the appropiate direction. Once it is done, the supply cargo containers are jettisoned too (with the leaving crew in it) and the ship body begins receiving the containers that hold the cargo; which would be at nearly the same velocity than the ship thanks to the "tugboats" effort. This way, the ship may use the Sun's gravity well to change its destination without lossing any significan speed and with a minimum waste of energy. The containers, of course, would be standardized. Not only they will have the same size and attachment points, they will have also interlocks so the crew and passengers will be able to move from one to the other. Usually, they will be layered, with bulk/less sensitive cargo in the outer layers and containers holding passengers in the inner layers. Also, connections offering access to the ships energy/recycling units will be available. As for utility, this idea will be more useful the heavier the standing elements (engines, control room, etc.) are when compared to the elements that are loaded at each system (cargo modules, but also supplies). If engines are lightweight, then the cost of deccelerating and then accelerating them later is less important that if they were very heavy. As for the inner design of the propulsor units, a few ideas: * Control cabin * Engine rooms * Fuel deposits * Engineering (mainly stores for replacements parts; a small workshop). Recycling units. * Communication room * Bedrooms * Kitchen / Recreation room * Hibernation chambers / Food stores / Hydroponics (Hydroponics may sound cool, but maybe you will need an additional crew member to manage it). [Answer] I will suggest that due to the pressure of keeping costs for bulk transport as low as possible, we will dispense with the spaceship altogether. Inside a solar system, the cargo will be packaged in the equivalent of an ISO container (AKA shipping container, CONEX or Sea Can) and shot on a minimum energy trajectory via mass driver or some equivalent system. The container has a beacon and some very minimalistic control reaction thrusters to make mid course corrections, and relies on a mass driver, momentum exchange tether or similar to stop it on the end of the voyage. The cargo company has no ongoing costs for crew, ship maintenance or repairs, very minimal fuel outlay and the costs of the mass drivers or tethers are assumed by the "port authority", which charges for their use. The cargo company therefor has minimal overhead costs and only has to forecast the number of cargo containers they will need to have available for any particular transfer orbit. If we are talking about interstellar traffic, similar logic can apply if the means of getting from star system to star system is via wormhole or other transfer gate system. Package the cargo, shoot it to the wormhole mouth via mass driver and then a complimentary system in the target star system retrieves the cargo pod. Once again, the costs to the cargo company itself is minimal. [Answer] Directly out of production armor on the transport should be just enough to deflect space derbies every now again. The owner should have the ability to add more armor and some defensive weapon systems depending on the value of the cargo. It is a cheep model with a rather small habitable area, and the crew of 2 will spend long distance journeys in hibernation chambers while the ships automatic systems take over for the rest of the journey. robots are in charge of maintaining the craft during the journey. but must wake the biological crew if any electrical problems occur, there is no artificial gravity or "hyper drive" systems. [Answer] To answer your bullet points: These mostly depend on the technology available at the time of building the ship but I assume that we have powerful enough thrust from say, the newly invented ion engine or relativistic engine (Alcubierre drive, <http://techland.time.com/2012/09/19/nasa-actually-working-on-faster-than-light-warp-drive/>) 1. Design should be circular and not square for its cross section upon incidence. A flying saucer would not be great as we would probably want to reduce air drag for lift off and landing. a ring would just waste precious space for a large corporation and be very expensive, requiring more metal for its shell. So altogether I'd recommend the trusty rocket, but a giant one, for its low air resistance. The question that remains is how slim it should be? This is answered in the next sections. The warp drive concept art shows two rings around the ship, one at the top and one at the bottom, so maybe that will have to be the design. Its quite a complicated subject based on how little we know about what engine will be used. 2. To keep the crew, I reckon we should not need too much space just like a cargo ship for oceanic transport, but I'm also considering bigger. The kind where its better to make only one or two if its that big as it uses up so much of our resources. However, I also want to answer the question if the cargo was the human race itself. 3. Realistic ratio of ship mass to cargo mass I would briefly say half and half. but this really depends on the quality of the ship. If there is light but strong alloys in use this can be reduced. 4. Other things to consider are: 1. What level of earth conditions your cargo needs, if it's living then you will require to use a lot of the cargo space to provide earth like conditions. If its just some metal for building work maybe that space isn't needed. For the Earth flagship however maybe we should consider a few modules that can be added or removed to provide the extra space for cargo on the occasion. The strength and density of all metal in use is crucial to know. 2. Previously I mentioned ship height/diameter ratio (I call it the rockets pointedness = 1/stubbiness). If it is big and heavy it will be stubbier, but will never be stubbier than a 4 sided regular pyramid of the same size, turned into a cone (I hope this transformation is understandable, ask if not) otherwise its air resistance wouldn't be great, in fact probably quite a lot less stubby than that would be minimum in order to break through air efficiently. A pointed half-oval would be best shape and its stubbiness is best worked out depending on the mass and thrust of the ship in comparison to Earth escape velocity and air resistance. This is the kind of thing an engineer would be needed to simulate. 3. How to land the ship effectively without damage? The stubbier the easier with this one as imbalance can lead to the ship toppling over and crashing, not cool for such a large bit of equipment. 4. Another thing to consider is cargo area/propulsion engine area ratio. It may not be very effective for transport if this is less than say 0.1 which is what I approximate rockets taking parts to the ISS would have, but I could be wrong here. Besides better propulsion should have been made by the time we are making this ship. 5. I severely doubt that the ship would ever take the human race, rich people would buy the ability to get off the planet if a disaster was to happen, leaving everyone stranded. So for a small colony, NASA have extensively designed objects such as buildings for survival that flatpack better than Ikea ware. So maybe a cargo ship the size of Star Trek's Voyager wouldn't be so necessary after all. ]
[Question] [ Imagine if Earth's atmosphere was shrouded in a perpetual layer of clouds or haze. Enough sunlight gets through to make agriculture still possible, but people are completely unable to see the stars. Thus, the science of astronomy can't develop until the invention of aircraft capable of rising above the clouds. What technologies would never have been invented, or would have developed differently, as a consequence of the starless sky? [Answer] As Vincent pointed out, Navigation will suffer a lot. Everyone would need to travel using land based visual cues (mostly). If they discover a compass, it will help some. But can they see there is a ball of fire that lights up the sky? or is it just a general lightening and darkening as the sun travels across the sky? How consistent is the cloud cover? Without the ability to see that the things are moving around, the stars, the sun etc. then it would leave a rather insular point of view about the planet. I also think for navigation of ocean's that very tall light houses would be common, with special markings so ships could travel farther out to sea and still be able to navigate and know their location. This would also encourage the creation of better optics as well as tower building technology. The ability to draw good maps to scale would be extremely valuable. Calendars are going to be hampered a lot. if the only time you have is 'light' and 'dark', no moons, no year, no stars to notice differences? Or is there a moon that can penetrate the clouds near full? if so that could cause a lot of speculation about the the 'big' light and the 'small' light. It would also help set passages of time. Mythology would certainly be a lot different. [Answer] Following up with [bowlturner](https://worldbuilding.stackexchange.com/a/7041/2072)'s last sentence: "Mythology would certainly be a lot different." This might actually complete reshape the entire history of mankind, even from biblical times. The change to mythos might very well cause faction rivalry to form completely different, forming a wildly different map of the world. And this is long before it affects technology. [Answer] Here's something few others have pointed out: religion. The main basis for science arising and becoming as widely accepted as it is today is astronomy. The early astronomers (Galileo and his contemporaries) pointed out that the Sun is fixed and the Earth revolves around it; they were shunned at the time for heresy and blasphemy. If we didn't have their theories, it is entirely likely that religion would dominate our lives today. Furthermore, it is fairly likely that Christianity would be the dominant religion by far. It is as dominant as it is today because of the empires of Europe, of Britain, France, and Germany, with some Spanish influence. Without astronomy, you don't have anyone rejecting religion out of hand, so the influences Christianity left would have remained, leading to it becoming far more dominant. Other religions would still be observed, but in smaller less pronounced pockets. --- Timings would also suffer. Calendars and, importantly, leap years are based on our observations of astronomical phenomena. One month (word origin: "1 **moon**" > "1 moonth" > "1 month") was originally defined as one cycle of the Moon, 28 days. Over time this definition has been revised to keep up with our other definitions, such as seasons. Leap years are based on the movement of the Earth around the Sun. As detailed in [this article](http://www.timeanddate.com/date/leapyear.html), the Earth actually takes 365.24 days to make one full revolution around the Sun, so adding a day (February 29th) every 4 years keeps us about in sync. If leap years hadn't been invented but some form of rudimentary calendar had, people would get very confused as, over the years, winter moved to summer and summer upped and left to take winter's place. --- You are, however, right in assuming that we would eventually make these discoveries. As I see it, this could happen at one of two points: * **By accident** If the world advances enough to have electromagnetic radiation sensing beams of the kind we have today, they might point one at the impenetrable cloud and find that there's something beyond. That would, of course, spark a massive space race. * **Manned flight** As you say, once humans invent the aeroplane (probably a little later than we did), they can easily fly above the clouds and observe. Again, the first confirmed occurrence of this would spark the space race, to see who could master orbital mechanics and get a satellite up first. However the discovery of space is made, there's a lot of discoveries to be made until this society is anywhere near our understanding of the universe. They'll end up several hundred years behind on astronomy, but could well do better than us in other fields, having had more time spent on them because of not spending said time on space exploration. [Answer] For questions like these I honestly like to use the tech trees from the civilization games. Its easy to point out that Navigation, as the obvious example, will be impacted. What is harder to discern is the downstream impacts, and that is where a chain like this (albeit a simplistic one) is very useful. [Here is an image of the chain.](http://img641.imageshack.us/img641/6687/civ5newvsold.jpg) My answer presupposes one thing: **The cloud cover is completely and utterly constant.** There are no breaks in the clouds, or at least they are so rare that they are essentially legends that are passed from generation to generation that most never see. I suppose this could also allow for Peter's comment about mountain top monasteries. **The short version, the clouds never part or it is exceedingly rare.** --- As a disclaimer...I am not going into every possible technology...just attempting to demonstrate how things can be looked at differently. I will focus this primarily on early technologies because you can then chase the rabbit down this hole yourself. * Agriculture: While agriculture can still exist per your description it would be negatively impacted in this world. This has huge downstream impact. Agriculture is the basis of all human civilization. It allows for larger cities in which specialization can come to be. This has lasting and on-going impact on the rate at which civilization develops. For example it would be reasonable to assume that humans remain hunter-gatherers for much longer. You can likely use this phenomenon to restrict development to your hearts content...we could remain cavemen. At the very least things get started more slowly. * Navigation: The skies have been used for navigation for as long as humans have traveled. I am not speaking only of ocean navigation but overland as well. While you can certainly still tell where the sun rises and sets things are far less precise and night travel is completely blind. * Religion: This I am including as more of a social development but I feel it is relevant. With no view of heavenly bodies it is reasonable to believe that they do not become deities. There are a few routes you can go here. Concepts like animism and nature spirits could play a larger role. The impact of this is that some early advancements particularly in stonework, mathematics and construction were a result of monument building. That is not to say that religions would still not create large structures but nature related religions are not generally historically known for creating monuments like this. Again, with a change as fundamental as permanent cloud cover you can kinda go wherever you want with this. I am just trying to illustrate the possibilities. * Calendar: Calendar development on earth developed exclusively based on heavenly bodies. A calendar is still useful and would likely be developed, but what would it be based on? Seasons. Sure that can work, but it lacks the precision of using the skies. It also requires other technologies for example temperature readings before it can be anywhere near accurate. **Notes:** This is a pretty fundamental change to how the world works. Removing or minimizing the relevance of heavenly bodies in the day to day life of early humanity could cause things to develop radically differently. In the end I don't think you will see technologies that fail to come to be. The timing of them showing up will surely change as will, by necessity, the order in which they are created. Very interesting concept and one that allows you to tweak the world to your heart's content. Just try to maintain a logical consistency, and if you are unsure whether two developments fit into the world you are creating those would be great questions for the site. [Answer] Astronomy could develop anyways, depending how high and how dense clouds are - possibly monks living in monasteries high in the mountains above most of the atmosphere would be able to see the stars - it would be even more spiritual experience for them. [Answer] We will probably still being nomads hunting animals and collecting foods. Maybe I'm putting to much value or astronomy for saying this but in my opinion almost every single achievement of the humankind couldn't be done without the help of astronomy. The control of the seasons and the creation of calendars with allowed the first humans to became sedentary were thanks to astronomy. The observation of the positions of the stars in the sky, during what will became the year, was the first sign of season or a calendar that the humankind had. It allowed the first human to establish a settlement and cultivate plants. If we couldn't became sedentary, we'll be expending to much energy on surviving and probably we will not get much more advances than small tools made of iron or stone and the wheel. ]
[Question] [ Ok, I know the rather annoying mathematics of animals that rely on photosynthesis. But another question got me thinking about this and I had a thought: what if my planimal gets only *some* of its energy from photosynthesis? **Juvenile phase:** The juvenile planimal is a very small organism that can swim but not strong enough to swim against the current. It looks something like a tiny jellyfish just a few millimeters across. It is pure animal, eating anything it can get its feeding tentacles on while flapping its mantle to swim. **Transformation:** When the planimal reaches about 4cm across, it begins to transform into the adult phase. This involves inflating a gas pocket (like a Portuguese man o' war), losing swimming features, and signaling the previously dormant photosynthesizing cells on the top of its mantle to develop and start processing sunlight. **Adult phase:** The adult planimal will grow to about 25-30cm across and will spend its life drifting wherever the current and wind take it. It retains its feeding tentacles and will continue to use them to snag prey which will provide a significant portion of its energy needs. --- **Is something like this even remotely plausible?** I'm concerned that photosynthesis will never provide a non-trivial portion of this planimal's energy. If that's the case, then it's possible that evolutionary pressure will cause it to disappear [Answer] **There are many organisms that do what you propose.** [![cassiopea](https://i.stack.imgur.com/j48hB.jpg)](https://i.stack.imgur.com/j48hB.jpg) <https://commons.wikimedia.org/wiki/File:Cassiopeia_andromeda_(Upside-down_jellyfish).jpg> <https://en.wikipedia.org/wiki/Cassiopea> > > Cassiopea (upside-down jellyfish) is a genus of true jellyfish and the > only members of the family Cassiopeidae.[1](https://i.stack.imgur.com/j48hB.jpg) They are found in warmer > coastal regions around the world, including shallow mangrove swamps, > mudflats, canals, and turtle grass flats in Florida, and the Caribbean > and Micronesia. The medusa usually lives upside-down on the bottom, > which has earned them the common name. These jellyfish partake in a > symbiotic relationship with photosynthetic dinoflagellates and > therefore, must lay upside-down in areas with sufficient light > penetration to fuel their energy source.[2] Where found, there may be > numerous individuals with varying shades of white, blue, green and > brown. > > > Cassiopea is one of several jellyfish that have onboard photosymbionts. The Golden Jellyfish is another good one if you are digging it - it is still motile as you propose, but I think Cassiopea looks cooler so I used its image. Many other creatures (sponges, molluscs, corals, worms etc) have free living early stages, then acquire wild photosymbionts and settle down for a life in the sun. Some stay motile even with the photosymbionts. The photosymbionts provide carbon (sugar) and get a place to live in exchange. The organisms still catch some food which they use for protein - none are totally photosymbiotic which I think is because of the protein issue. [Answer] It can be a plant like animal (an animal that evolved photosynthesis), an animal like plant (a plant that evolved the ability to move about freely), a symbiotic relationship between an animal and a plant, where the animal lives off of the energy that the plant produces, or an entirely different organism (colonial cyanobacteria). [Answer] You can consider the animals that are capable of kleptoplasty. Kleptoplasty is a symbiotic phenomenon whereby plastids, notably chloroplasts from algae, are sequestered by host organisms. <https://en.wikipedia.org/wiki/Kleptoplasty> You can consider the species of *Elysia*, a genus of sea slugs. The longest known kleptoplastic association, which can last up to ten months, is found in Elysia chlorotica (the eastern emerald elysia). > > [![enter image description here](https://i.stack.imgur.com/sGbxN.jpg)](https://i.stack.imgur.com/sGbxN.jpg) > > An *E. chlorotica* individual consuming its obligate algal food *Vaucheria litorea* > > https://en.wikipedia.org/wiki/Elysia\_chlorotica > > > > > *Elysia* sea slugs graze on algae and some species such as *E. viridis* and *E. chlorotica* hijack the chloroplasts for themselves. The chloroplasts end up lining the slug’s digestive tract, enabling the slugs to survive solely by photosynthesis for several months at a time. This association is crucial for the development and maturing of the slug. > > https://en.wikipedia.org/wiki/Elysia\_(gastropod) > > > ]
[Question] [ For the sake of analogy, let's take the Chixclub impactor and move it a mountain range akin to the modern Himalayas. Obviously we're dealing with an extinction level event here so I'm not concerned with the effects on life, and only loosely interested in the atmospheric effects. My primary concern is with the effects of the impact on the surrounding geology. I'm mostly looking for information on how the area would look a few thousand years out - would the nature of the area better preserve a crater? Or would the ejecta fill the hollow and leave a sort of semi-flat (but still high altitude) plateau? Feel free to ignore this, as I don't want to overburden the question, but does the result change if the impactor is at a lower speed (e.g. an orbiting body forced to deorbit)? edit: per the clarification request below, [here is a link](https://www.google.com/maps/place/29%C2%B053'03.0%22N+81%C2%B054'09.0%22E/@29.8841667,81.900306,966m/data=!3m2!1e3!4b1!4m5!3m4!1s0x0:0x0!8m2!3d29.8841667!4d81.9025) to a spot on Earth most analogous to the environment I am imagining. A fairly wide stretch of a range of high peaks of marble and schist (et al) fairly well removed from an ocean. The impact's 'epicenter' would be surrounded by mountains on all sides. Well, pre-impact. 'After the impact' is part of the answer I'm seeking. [Answer] The crust in that region is about 80 km thick, and there is no ocean around to fill the hole immediately after the impact. This means there would be no exposed magma interacting with water to cause additional explosions. After the impact there would be some rivers slowly pouring into the crater, filling it with water and sediments over the passing of millennia. Until the basin was filled by sediments you would have a fairly circular lake, surrounded by a ridge of mountains. After a fair amount of time the movement of the Indian subcontinent against the Eurasian plate would probably distort the circular shape and the depth profile of the crater, but it would take more than some millennia. ]
[Question] [ I would like to include a world in a story that is located on the upper plane (or bottom, doesn't matter, but call it upper for the sake of reference) of the galaxy. If you think of the galaxy as a cookie, the world is on top near the rim, not in the middle of the cookie. I could imagine that inhabitants on the northern half (call it the "top" or the furthest away from the center galactic plane) would experience a nearly perfectly dark night sky (ignoring moons) other than, pretty much, other galaxies. I could also imagine the inhabitants of the southern half (call it the "bottom" or the closest to the center galactic plane) would see the galaxy (if rotation were in the right position) as a tear drop, with the brightest part near the horizon and the darkest part of the tear "straight up." *For reference, we Terrans see the galaxy as a band in the sky, I suspect because we're in the middle of the cookie.* My question: am I right to imagine the night sky for this planet? As I said, ignoring any moons, dark but other galaxies (very sparse "starlight") on top, and a teardrop view of the galaxy on the bottom (if rotated correctly) or a smattering of stars and galaxies (if not rotated correctly)? *What I'm hoping not to hear is, "Nope, your planet would need to be a bazillion miles above the plane of the galaxy to get a view like that..."* [Answer] # How many stars will you see in the direction of the edge? I downloaded from [Hipparcos](https://heasarc.gsfc.nasa.gov/W3Browse/all/hipparcos.html) the distance and visual magnitude of all stars with magnitude 6.5 and below. This is roughly the number of stars visible to the naked eye. Here is a plot: [![enter image description here](https://i.stack.imgur.com/T6qwW.png)](https://i.stack.imgur.com/T6qwW.png) (Note: some stars are listed with a negative parallax, for various reasons. I lumped them all together at 1e5 parsecs distance, so as not to weirdly distort my graph) Now, lets say that you are in the upper 1% of the galaxy. Lets cut the list of visible stars down to only those within 10 parsecs. [![enter image description here](https://i.stack.imgur.com/TwJ6w.png)](https://i.stack.imgur.com/TwJ6w.png) First off, there are only 53 left, less than 1% even. But, interestingly, lets compare only those 'brightest' stars, with magnitude 1.5 or less: [![enter image description here](https://i.stack.imgur.com/tSnl1.png)](https://i.stack.imgur.com/tSnl1.png) 7 out of the 22 brightest stars would still be here, if we removed all stars more than 10 parsecs away. ### Conclusion If you move a planet to the edge of the galaxy, you will largely have an empty sky in the direction out of the galaxy. But not totally empty. While the total number of stars visible in the direction of intergalactic space would only be perhaps 1% of the total we see here on Earth, you will still see maybe a third or more of the brightest stars. Not enough for constellations, but enough to give them cool names like "Sirius" and "Procyon" and so forth. [Answer] Such a world would have to be really above every other star system in order to achieve the vision you have. Even then, you would still need a special arrangement. Stars orbit the galactic core just like planets orbit stars. The core is at the center of the orbital plane, meaning that if your star system is at the very top of the galactic disc, it has probably been - and will be again - at the bottom at some point during its existence. Planets tend to have their rotation aligned with the rotation of their parent star, which tends to be aligned with the star's orbit plane. That's the case for six of the eight planets in our system. Your hypothetical planet would most likely be so tilted that in one "day" its inhabitants would have both the dark intergalactic space and the bulk of the Milky Way over their heads. By the way, [the stars farthest from the core are poor in elements heavier than helium](https://worldbuilding.stackexchange.com/a/45487/21222). Your planet would probably be a gas giant, though statistically there should be the odd rocky planet here and there. Maybe a captured rogue planet. Last but not least, the intergalactic space would not be so dark. There are some dwarf galaxies orbiting ours, and they are eerily beautiful. The most famous ones are the Magellanic Clouds, the bright patches in the picture below: ![Magellanic clouds](https://i.stack.imgur.com/mkWGU.jpg) Source: <https://amazingsky.net/2012/12/05/cottage-under-the-southern-stars/timor-cottage-magellanic-clouds/> I imagine that in a sky without other stars, and with little to no light pollution, those galaxies would seem to be even brighter to the naked eye. [Answer] If the planet is actually at the edge of the galaxy then what you see depends on the axis of rotation. (a) If the axis of rotation of the planet is along a line that passes through the centre of the galaxy then Uppers will have a relatively empty sky and Downers will see a full sky. (b) If the axis is normal to the previously mentioned one then there will be some interesting 'dawns' that happen during the night when the galaxy rises over the horizon. These will appear differently in different parts of the planet's orbit round the star. When the inhabitants view the galaxy from behind their sun the galaxy dawn and the solar dawn will be simultaneous. When they are between their sun and the galaxy, the dawns will occur 180 degrees out of phase and so you will see a night dawn of their milky way followed by a sun dawn 12 hours\* later. (c) Other axes will produce intermediate effects. \*Local hours ]
[Question] [ **Is it possible to calculate/estimate the size of a star's heliosphere? If so, how?** I am working on a semi-near future, sci-fi novel. As part of the technology base, humans are able to travel between stars near-instantly, however they must first get to a warp-gate of sorts outside the heliopause (outer edge of the heliosphere) at sub-light speeds. This results in a few months of travel time from the planets to the edge of the solar system, then another few months travel from the edge of the next system to the planets. My problem is that I don't know if it is possible to calculate the size of a star's heliosphere based on known data. All of the stars I am using are going to be actual known stars. I'm hoping that using the known data of the stars size, type, and luminosity we can determine at least a reasonable estimate. Although the heliosphere should probably be called the helioegg instead, I am really just needing a number that won't be too outrageous. The main reason I need to calculate the distance is actually to then calculate the travel time from the edge of the solar system. The heliopause of Sol is at roughly 128 AU (give or take) from what I understand, but obviously that is not going to be necessarily even close for every star. It would be interesting if even though Proxima Centauri is the closest star to Sol, if it had a a heliopause distance of like 400 AU it could end up having the longest travel time of all the other local star systems. [Answer] # Deriving the radius The heliopause is [a place of equilibrium](https://spacemath.gsfc.nasa.gov/weekly/4Page9.pdf), where the ram pressure from the solar wind is equal to the pressure of the interstellar medium (ISM). [There are a number of sources of pressure in the ISM](http://web.mit.edu/space/www/helio.review/axford.suess.html), but thermal pressure is the main one.1 The ram pressure from a wind with terminal velocity $v\_{\infty}$ at a distance $r$ from the a star is $$P\_R=n\_\*(r)mv\_{\infty}^2$$ where $n\_\*(r)$ is the number density of the wind, and $m$ is the mean mass of the particles at the heliopause. It turns out that, by mass conservation, $n\_\*(r)\propto \dot{M}v\_{\infty}^{-1}r^{-2}$, where $\dot{M}$ is the mass-loss rate.2 The thermal pressure of the ISM is $$P\_T=n\_{I}k\_BT$$ where $k\_B$ is Boltzmann's constant and $T$ is the temperature. $n\_{I}$ is the number density of the interstellar medium. For Sun-like stars, $v\sim400$ km/s is reasonable. $n\_{\odot}$ and $n\_I$ are about 5 particles per cubic centimeter and 0.01 particles per cubic centimeter, respectively, and $T\sim10^5$ K. Assuming the wind is largely hydrogen at this point, if we set the two equal, we get $$ \begin{align} r\_{\text{crit}} & =\left(\frac{n\_{\text{crit}}mv\_{\infty}^2}{n\_Ik\_BT}\right)^{1/2}\text{ AU}\\ & \approx311\left(\frac{n\_\text{crit}}{5\text{ cm}^{-3}}\right)^{1/2}\left(\frac{v\_{\infty}}{400\text{ km/s}}\right)\text{ AU}\\ & =311\left(\frac{\dot{M}}{10^{-14}M\_{\odot}\text{ yr}^{-1}}\right)^{1/2}\left(\frac{v\_{\infty}}{400\text{ km/s}}\right)^{1/2}\text {AU} \end{align} $$ where $n\_{\text{crit}}\equiv n\_\*(r\_{\text{crit}})$. I've used scaling relations such that for the Sun, $r\_{\text{crit}}$ is 311 AU. # Important factors Some things to note: * Stellar winds don't all have the same composition, but hydrogen is, by and large, the major component, and the one important factor when it comes to calculating $m$. * The most important star-dependent variables are $\dot{M}$ and $v\_{\infty}$. Note that $r\_{\text{crit}}\propto \dot{M}^{1/2}v\_{\infty}^{1/2}$. For massive O- and B- stars, winds can have speeds of $\sim2000$ km/s, or more; I think some of the strongest are about $\sim3000$ km/s. This could mean heliopauses of thousands of AU. [HD 93129a](https://en.wikipedia.org/wiki/HD_93129) is a good example, [with $v\_{\infty}$ of about $\sim3000$ km/s](http://adsabs.harvard.edu/abs/2011MNRAS.415.3354C). * I can try to pull some numbers for Proxima Centauri, but I'll point out that red dwarfs usually don't have strong stellar winds. The interest in the wind of Proxima Centauri is really because Proxima Centauri b orbits close enough to the star that stellar activity - especially flares - could cause severe problems for life. # Star types For Sun-like stars, $\dot{M}\sim10^{-14}M\_{\odot}$ per year is reasonable, and so you'd get heliopauses of a few hundred AU. For O- and B- type main sequence stars, I'd expect $\dot{M}\sim10^{-6}M\_{\odot}$ per year, which is much higher. At the other end of the spectrum - those red dwarfs that are relatively quiet - [we'd see maybe $\dot{M}\sim10^{-15}M\_{\odot}$ per year](https://arxiv.org/abs/astro-ph/0011153). A- and F- main sequence stars might have mass-loss rates a bit higher than the Sun, and perhaps larger terminal velocities. Off the main sequence, things get more complicated. Red giants - especially asymptotic branch stars, near the end of their lives - have large mass-loss rates that arise via different mechanisms involving dust. These are cool but bright stars; consider $\dot{M}\sim10^{-8}M\_{\odot}$ and reasonable fast winds, though not nearly as fast as the hot, massive O-type stars. Additionally, more exotic cases like [Be stars](https://en.wikipedia.org/wiki/Be_star) that are undergoing mass loss may have larger mass-loss rates. Finally, the young [T Tauri stars](https://en.wikipedia.org/wiki/T_Tauri_star) have mass-loss rates similar to red giants - maybe an order of magnitude or so lower - but their winds are slower than the Sun's. # Specific cases I looked around and found instances where $\dot{M}$ and $v\_{\infty}$ have been observed, and made an estimate of $r\_{\text{crit}}$: $$ \begin{array}{|c|c|c|c|c|c|}\hline \text{Star} & \text{Stellar type} & \text{Mass }(M\_{\odot}) & \dot{M}(M\_{\odot}\text{ yr}^{-1}) & v\_{\infty}(\text{km/s}) & r\_{\text{crit}}(\text{AU})\\\hline \text{HD 93129Aa}^1 & \text{O2} & 95 & 2\times10^{-5} & 3200 & 3.93\times10^{7}\\\hline \tau\text{ Sco}^2 & \text{B0} & 20 & 3.1\times10^{-8} & 2400 & 1.32\times10^{6}\\\hline \sigma\text{ Ori E}^3 & \text{B2} & 8.9 & 2.4\times10^{-9} & 1460 & 2.91\times10^{5}\\\hline \alpha\text{ Col}^2 & \text{B7} & 3.7 & 3\times10^{-12} & 1250 & 9.52\times10^{3}\\\hline \text{Deneb}^4 & \text{A2} & 20 & 10^{-6} & 225 & 2.3\times10^{6}\\\hline \text{Sun} & \text{G2} & 1 & 10^{-14} & 400 & 311\\\hline \text{Proxima Centauri}^5 & \text{M6} & 0.12 & 10^{-13} & 550 & 1332\\\hline \end{array} $$ 1[Cohen et al. (2011)](http://adsabs.harvard.edu/abs/2011MNRAS.415.3354C) 2[Cohen et al. (1997)](http://iopscience.iop.org/article/10.1086/304636/fulltext/) 3[Krtička et al. (2006)](http://adsabs.harvard.edu/abs/2006A%26A...460..145K) 4[Aufdenberg et al. (2002)](http://adsabs.harvard.edu/abs/2002ApJ...570..344A) 5[Wargelin & Drake (2002)](http://adsabs.harvard.edu/abs/2002ApJ...578..503W) Now, HD 93129Aa and Deneb are supergiants, so they're off the main sequence, but their properties here shouldn't be too far off from main sequence stars of the same spectral type. Deneb's mass-loss rate is maybe a bit high in comparison to main sequence A stars. Also, I'm slightly skeptical of the value for HD 93129Aa's heliopause, so it's possible that other factors play a role - for instance, thermal pressure could indeed be important in its hot wind. Additionally, some M dwarfs have higher stellar winds and mass-loss rates because of flares and other activity. --- 1 We can disregard ram pressure, as the ISM is, by and large, slow-moving. Likewise, magnetic fields are typically not important. Similarly, we can neglect thermal pressure in the stellar wind; even though winds may have temperatures of several million K, ram pressure is more important. 2 Specifically, the density $\rho\_{\odot}(r)$ (related to number density by $\rho\_{\odot}(r)=mn\_{\odot}(r)$) is given by $$\rho\_{\odot}(r)=\frac{\dot{M}}{4\pi r^2v(r)}$$ where $\dot{M}$ is the mass loss rate and $$v(r)=v\_{\infty}\left(1-\frac{R\_\*}{r}\right)^\beta$$ with $R\_\*$ being the radius of the star. We typically assume $\beta\approx1$, but at $r\gg R\_\*$, we can say that $v(r)\approx v\_{\infty}$. [Answer] The heliosphere, in layman terms, is defined by the equilibrium between the star wind and the galactic wind. Once the star wind is not strong enough to blow away the galactic wind, there we have the heliopause, bordering the heliosphere. Therefore, if you know: * Star wind velocity * Star wind velocity reduction rate * Galactic wind velocity * Relative motion of the star with respect to the surrounding star you should be able to estimate the extension of the heliosphere for the star in question. [Answer] L.Dutch lays out the numbers you need to consider, having done a little reading on [stellar winds](https://en.wikipedia.org/wiki/Stellar_wind) it would appear that most stars in the A-K section of the [main sequence](https://en.wikipedia.org/wiki/Main_sequence), might be expected to have similar sized heliopauses in a similar area of the galaxy. Cooler and giant stars have much smaller heliopauses and hot white and blue stars much much larger ones due to the extremely high escape velocities of their surfaces. Based on that the hardest nearby star to ship to and from would actually be [Sirius](https://en.wikipedia.org/wiki/Sirius) rather than any of the three nearby Centauri stars. [Barnard's Star](https://en.wikipedia.org/wiki/Barnard%27s_Star) should be a very quick transit though. ]
[Question] [ How to design a realistically looking technocracy? I mean that’s a standard problem in even mildly SF setting. It’s quite clear how to make a futuristic republic (assuming that you can hire a few Jedis) or feudalistic monarchy (assuming that you have enough spice and no sand worms eat your cars), just the question is concerning a technocracy. I mean a democracy in future may sound as old fashion as tribal federation in early XXI century. A technocracy - a system that would prefer competency, be efficient but also have its own issues. So my guesses, maybe I need to adjust something: * Universal suffrage replaced by weighted voting, where citizen rank is based on result of some universal test, also to stand for office passing even more tricky test is required * Single transferable vote (I like this idea, and when system is heavily aided by computers, then is quite easy) * Central bank and central statistical office as another constitutionally protected branches of gov * "Right to information" instead of "freedom of speech", gov is obliged to provide with easily accessible source of information including statistical data, a few news station in the style of BBC, etc. (right to lie is actually not protected nor right to organize lavish political campaigns) * Gov provides financial reports with the quality of at least public companies financial statement (is your country generating a profit or its equivalent? well, as a citizen may be interested to know...) * Constitutional protection requiring balancing budget in long term (including implicit liabilities like pension and healthcare for elderly citizen) * Instead of relying heavily on voting / referendum, use focus groups - a group of citizens is selected by random, given data to read and finally asked to answer which policy to select (no answering from gut feeling) * Free or heavily subsidised education * High level of anti-monopoly regulation and splitting monopolies / too big to fail companies * High level of experimentation within system - is a gov owned school better or worse than a private subsidised by educational voucher? Regardless what’s the right answer, such gov would be required to experiment and base final policy on the result. Experiments in this style would be a norm. * Gov agencies would bid to provide public services against private companies/NGOs (both for good and bad) Reasonable? Or I should plan for story purposes such system differently? (the system does not have to be ultra nice, it just has be effective) (no, no communism, it was empirically tested and failed spectacularly) [Answer] I've had serious discussions about technocracy with friends, owing to complaints about the democratic status quo. One simple point a friend made was that government committees and branches must be administered by those who actually have a grasp of the subject matter. Simply require health committees, the health ministry, health minister, for example, to be staffed by former doctors and nurses. There's two obvious ways of going about this, either have the people vote for cabinet ministers from a list of those with specific experience... which may add a little bit to the paperwork of an election, but will do the job. Or perhaps only allow specialists to vote for their own section of government. Another way around it is to have a one party state with specific criteria for appointing leaders. For example, the Soviet Union was interesting in that members of the Politburo required an engineering degree. The logic there was that unless someone was trained in how to create and maintain systems they couldn't very well know how to manage a national system like government. Contemporary Chinese and Indian governments have a strong technocratic edge too, as in both cases administrators are selected from an enormous pool of candidates. This process also exists for promoting member of the Chinese Communist Party on merit from the smallest local administration, step by step, all the way up to the Central Committee. Another historical example is Fascist Italy. Italian fascist government was based on the principles of corporatism. Importantly this should not be confused with capitalist corporations. The belief the Italian Fascists had was that the state is a superorganism, and the largest corporations are its organs. Instead of representing the people, the aspects of the national body ("corporation" derives from the word corpse/body) must be represented in government. They will then answer to the Fascist party; which, conveniently enough by Fascist logic, was the only organisation strong enough to lead the nation. The corporations weren't there to benefit from it, rather they were there to inform and obey the fascist government. They had to know their place. That's not to say your system needs to be a copy of Soviet Communism or Italian Fascism, just that these are examples of different technocratic ways of appointing governors to rule the nation. And these ideas can be divorced from the rest of their political ideology, and affixed to whatever social-economic system it is that you wish to be represented. I don't see why you couldn't take the technocratic Soviet one party leadership system and affix it to a capitalist body... that's kind of what China has been trying to do since Mao's death. Hopefully the examples and ideas presented offer some food for thought! [Answer] Some things to consider here ... ### Progress may be slowed down * Those who write the tests both define what their field of knowledge covers and how one advances in it. Once upon a time medical doctors had to be fluent in Latin. Should it remain part of the test? And can you be a technician (in *any* area) if you do not understand how a slide rule works? Sure, you don't need it day to day, but it demonstrates a sound understanding of the principles. * Who decides to introduce a new professional field or to split existing ones? All those new-fangled web designers. Are they painters or telegraph engineers? They'd score low in either profession, so they will not be allowed to rewrite the definitions of their fields. It would be natural for those who score high under the status quo to resist any change to de-value their skill set or to reduce the scope of their authority. ### Who watches the watchers? * Do you really want only bankers in the ministries and legislative subcommittees that supervise banking rules? Or should it be lawyers in every legislative committee? * Are project management and controlling their own speciality or are they part of almost every field? Does that mean you have to be able to *organize* a research project (write a budget proposal, pay invoices) before you become a senior researcher? * Is the national budget a decision for tax accountants and macroeconomists? Should they decide how much money is set aside for foreign aid, or is that the decision of moral theologians and development specialists? At senior decisionmaking levels, you need generalists who can reach compromise solutions. [Answer] I'd say you need two things: 1. a pool of people that are highly educated and skilled in administration 2. general agreement among the rest of the populace that the technocrats are doing a good job; if not, you get revolutions Look at the educational reforms that Napoleon set up 200+ years ago, and how their effects persist today - France is arguably the most technocratic of the developed Western nations. He created a national system of secondary schools, with a single curriculum, managed from the top down. He also implemented nationwide civil service exams. He set up several specialized universities (various branches of engineering, a graduate school of national administration) that still exist today. In a lot of ways, the graduates of the Ecole Polytechnique are a textbook example of the so-called 'deep state'. They bounce back and forth from government to private industry and they are a very tight old boys network. When things are going well, the technocrats are doing much of the governing of France, regardless of which party holds the presidency or the parliament, and there aren't too many complaints about corruption, a rigged system, or insiders. But when things aren't going well - when that social compact of 'you get to run the country for us, and not incidentally live a very luxurious life in the process, as long as you deliver the goods' isn't holding - that's when you get problems. [Answer] Your proposed system suffers from the same problem as most governing bodies - namely : how do you evaluate it’s performance? Here are some obvious breakdowns in your system : * votes are weighted - what prevents an “emperor” pretender from deciding arbitrarily that his/her opinion is weighted 100% and all other voters 0%? * votes can be assigned - what prevents a “kingmaker” from harvesting the proxies of the elderly and the poor? * only the “qualified” can hold positions of rank - and what prevents a “dynast” from deciding his/her biological kin are the only qualified individuals in the world? * a central bank can report on money supply - what prevents the bank from reporting multiple money supply calculations (M1, M2, M3), changing the accounting method of critical statistic arbitrarily (CPI “basket of goods”) and reporting whatever random numbers that make people feel good about empty shelves? The point is that its unfeasible to oversee the individuals making the decisions. And your proposed system is especially vulnerable, as it has no co-equal branches of power whereby someone can make an accusation, “I think this thing is wrong,” and have that accusation evaluated and, if agreed to, used to force a correction in the system. Your proposed system also has no surge protectors to keep a system that is malivesting (say, throwing 100% of the economy behind the monarchs daughters new all toilet paper clothing company, because isn’t she such a darling?). Dunning-Kruger applies. When presented with novel situations, decision-makers will be first convinced in their godlike mastery of the subject matter, and then they will gain rudimentary proficiency over the subject. Even a principled, but inept decision at the top can, in real world terms of blood (going to war) and treasure, do ghastly damage. Some systems severely limit what powers the top-level body has, to a very specifically scoped set, for just this reason; reserving broader power to smaller regions, or explicitly forswearing certain powers (regulating speech or belief). Some of the longest lasting cultures start out as theocracies, where power is distributed broadly to the public who (hopefully) police first themselves, then police their neighbors against a published set of principles. Next, your proposed system is missing motivation. Why does anyone want to participate? It may also be important to remember that we humans are built for stupidity - every 30 years the best trained enter senescence. These elders leave the public stage. They are replaced by a new generation that has only been paying attention to adult topics for, maybe, ten years. All hard-won truth older than 10 years becomes something the new generation hears pre-digested, with commentary, and has no alternative but to reject or accept on faith. [Answer] #### It will not work When someone reaches a high level position be it in power or wealth the natural instinctive tendency is to ensure better conditions for their offspring. Furthermore this is a world where the internal selective pressure is stronger than the external one, I mean that people have to compete more against other people to ensure their future than against the external factors. In this world the tendency to join smaller tight knitted groups and help each other is strong as well. A real technocratic system, where people rise along the ranks depending solely on talent and knowledge regardless of family status and friendships network, would challenge so much the natural instinctive tendencies that people would quickly find a way to rig it. University grades can be rigged, scientific papers can be plagiarised, merits for good results in some works or studies can be attributed to the wrong people. A lot of these things already happen quite often in the real world. Even in corporate environments that are supposed to be highly meritocratic how often people shine thanks to the work of others? A system based on static rules and criteria would not be different from the current system based on wealth, eventually a smaller group would accumulate enough power o bend the way the rules are applied. ]
[Question] [ ## How do we develop & send instructions to nanites and how do they receive, store, and execute those instructions? Just like in biological organisms, some instructions need to be included for how nanites should reproduce including how many should be reproduced and then conditional instructions need to be provided based upon where in the nanite construction area any particular nanite is located. Nanites need to be able to signal something (other nanites, the control cpu, etc.) information based upon their location, environmental conditions, how many nanites are in the vicinity, what sort of resources are available, what they still need etc. Biological microorganism don't really operate based upon cooperative goals, so I imagine there should be some differences on how they get, store, and execute those instructions. Perhaps looking at the mechanisms used by cells to cooperate in building multi-cellular organisms would be closer to what we need. I was thinking about this weeks ago and the idea that kept coming to me was that from a macroscopic view, the nanite army would like look a bacterial or other microbial attack. It'd need the same things (energy, resources, waste removal, instructions, etc.). They'd probably need some sort of nanite - nanite signalling and unless we made different batches of nanites for different jobs, then we'd need a way to send instructions to them to coordinate their behavior. This is next in my series of questions about how nanites might work. ### Background There have been two prior questions already asked that flesh in the background for this question: 1. [How do nanites get the resources that they need](https://worldbuilding.stackexchange.com/questions/38152/how-do-nanites-get-the-resources-that-they-need) to do their work? 2. [How do you power all the nanobots?](https://worldbuilding.stackexchange.com/questions/35975/how-do-you-power-all-the-nanobots/35976#35976) (thank you Daniel M. for asking the initial question). My summary of the answers so far: Although certain exotic possibilities are possible, in many ways nanites will behave very like microscopic organisms do now. Energy could be provided by induction or beaming, however, a more viable short term possibility is simple chemical energy (aka food) that is oxidized. Any "construction" material and/or waster products need to moved into and out of the nanite construction area just like the mechanisms used by living microorganisms (e.g. by circulation). ### From previous answers on how to get resources to nanite [Swarm behavior with a central CPU for coordination](https://worldbuilding.stackexchange.com/questions/38152/how-do-nanites-get-the-resources-that-they-need) by user 6511 [Answer] Cells are limited to communicating in a lossy, low-bandwidth manner across chemical gradients and other enzymatic on-off pathways, but we can do better. 1. Micro Radio Frequency pulses from multiple control beacons placed around the perimeter while the stuff cooks allow each nanite to "know" its exact position via a very simple signal comparison, using triangulation algorithms similar to the Fourier-style calculations done in 2016 for MRI imaging. The nanites use miniaturized zero-power receivers, where the received pulse actually provides at the very least the power to run the receiver itself. Even if we were to assume absent a complex computer on board, the behavior of the nanites can be hardwired to respond in specific ways to specific types of pulse, position and time. The pulses can perhaps also be used to power the nanite, depending on the beacon power output levels the energy intensity of the task at hand and the desired speed of completion. Indeed, the output of beacons can be modulated to activate nanites in certain areas more strongly, making them work faster on more power. 2. As stated in the previous point, nanites can function without an onboard computer, if we're willing to transmit trillions of instructions every milisecond. Each nanite can have its own code, and instructions could be prefixed with that code. However, nanites would be far more efficient with computation on board, which is what we'll look at next. Nanite computation is done via mechanical computing, using molecular size mechanical computing units using rod logic, described quite well in [the answer to this question.](https://worldbuilding.stackexchange.com/questions/22045/just-how-powerful-could-a-mechanical-computer-be) `Moving molecular rods in a solid matrix to perform logical operations by the expedient of the rods having side groups opening or closing channels. It can be implemented from the macroscopic scale (with Lego as one example) to the atomic scale.` If successfully miniaturized to the nano-scale, this would easily allow extremely complicated programs to be written, stored and implemented by the machine, as well as allowing it to react real time to the local conditions. The decision on whether to store a full blueprint on each nanite would depend on the specifics of the design. 3. Nanite-to-nanite communication. [Ultra-low power signaling](http://www.dailymail.co.uk/sciencetech/article-3470389/Ultra-low-power-Wi-Fi-save-phone-s-battery-New-passive-internet-connection-uses-10-000-TIMES-power.html) using extraordinarily weak electric or magnetic fields, with effective ranges no longer than a few hundred molecules, using millions of times less power than 2016-issue network adapters, would allow individual nanites to maintain constant situational awareness with regards to nearby available resources and active nearby nanites, as well as being able to signal when in need of repair or, in the case of a serious malfunction, deactivation. This enables 4: 4. Multi-nanite scaffolding. Some structures will be impossible to craft using individual nanites, they may be too long, too delicate or to intricate for the capabilities of a single nanite's manipulators. In that case, nanites can use digital communication via the same ultra-weak fields that enable their situational awareness to execute complex choreographed dances with atomic-level precision across macro-molecular distances. [Answer] Well, the most difficult part of this is designing the nanites. Considering that we are getting very good at building very complex and sophisticated computer hardware and software systems, but we haven't built many very complicated nanites yet, why not rely on what we know and push that as far as we can take it? First let's assume that our nanites are nothing more than simple state machines that can do nothing but take a single instruction at a time and respond to that instruction. This relieves us of the very hard work of engineering complicated nanites to do very much on their own (and it's safer for us that way). When they have a signal, they are doing something with it, when they don't have a signal they are stuck waiting for the next instruction - only complex enough to do as we wish, but no more than that. What this means is that we have several problems to solve in the way of controlling billions of nanites simultaneously and effectively. 1. We need a broadcasting system that can multiplex billions of signals simultaneously 2. We need a molecular backbone design for a radio receiver that can be permuted into billions of arbitrary configurations - doesn't matter which configuration as long as each configuration is listening to one of the slices of the broadcast signal 3. The states that can be achieved by processing the received signal need to be planned, but it could be as few as a handful of states - such as moving forward, actuating to some other direction, opening or closing some other actuator, etc, but basically all ON/OFF kinds of signals 4. Maybe the only thing that should be automated is when we are not sending a signal the nanites should "take a break" and find food, tend to whatever nanites do, etc\*. 5. Knowing whether an instruction was received and locating each nanite (together this can be referred to as "tracking") can be accomplished as simply as how RFID tags work\*\*. Similar to our molecular antennae, we could incorporate a kind of RFID like molecule which resonates at a configurable frequency (perhaps the antennae and the RFID-like device could be one and the same). Then listen for the echo of the sent signal and if it is heard, it can be assumed that the instruction was received. The same echo can be used to triangulate the nanite's position. If no echo is heard, then that nanite can be considered "lost" until a signature for it is found again. Finally, we will need to have sophisticated software to coordinate nanite activity and the responsibility of doing so will rest solely upon that software. We are getting to a point where massive parallel processing is becoming affordable so that will not be a big issue. With deep learning techniques it will be possible to simply experiment with swarms of nanites in the many thousands or even billions, try to accomplish tasks with them and have software learn effective patterns of activity for quickly and or thoroughly accomplishing given tasks. This way we will have a set of tools that we know apply broadly to certain task and a system of organizing at a micro-management level. \*If we simply run them until they have no more chemical reserves they will break and perhaps die. Maybe this is what we want, maybe not, but running them out seems expensive and wasteful, however, perhaps there are other states ("developmental"/"off-duty", etc.) to discuss that are outside of the scope of this answer. \*\*For a more robust tracking system capable of ascertaining operational status of the nanite, it may be possible to create such a resonator which can shape shift slightly in order to modulate within the carrier signal and have internal signalling connect from the state processes inside the nanite back to the specific configurations of the resonator so as to "reflect" back some information about the nantites internal state. This will of course add complexity to the system and may or may not be useful considering that we are already somehow producing such devices in the billions and they are quite disposable. --- Now as indicated in the above proposed input mechanism, we have a system for receiving instructions and we do not need internal storage since all activity is managed by an external resource. As for how to execute those instructions, it would not be much different (and intentionally so) from how a cell already receives signals and performs basic functions. For example, Euglena species have already developed a system that causes the organism to swim toward a light signal - that could be modified minimally and utilized to design the entire navigation system for our device. The only things that we would have to focus specifically on is what modification is necessary to bridge our radio signal to the Euglena's optical sensory apparatus and how to transfer the incoming signal to that bridge - so it's basically logistical and hooking up a few circuits, not really any radical design decisions need to be made. The hard part is tracking down and controlling the genetics and other factors that produce these structures. Other actuators could be controlled with a similar apparatus. [Answer] [Emergent behaviour](https://en.wikipedia.org/wiki/Emergence#Living.2C_biological_systems) is probably your best bet. In essence each nanite is extremely simple, designed to respond in only a few very specific ways to a few very specific stimuli (for example high O2 concentration plus high instance of cancer markers = go forwards). Each nanite is unbelievably dumb, however a set of nanites, each capable of leaving behind 'breadcrumbs' that other nanites can follow, can be very smart indeed. Controlling these nanites is a matter of cleverly creating the nanites in the first place (potentially using computer aided design to simulate the 'instruction set' encoded in the nanites and run backwards from the result wanted to the initial designs needed. Changing the programming becomes a matter of introducing new nanites, carrying a new 'instruction set' and a series of markers that cause earlier nanites to destroy themselves and reconfigure to the new instructions. The issue with this process is that the results won't necessarily be immediately recognisable. As the nanite swarm grows and multiplies, becoming more capable, it might have to go through a variety of intermediate stages (much like [Langton's ant](https://en.wikipedia.org/wiki/Langton%27s_ant) in the chaotic period before it starts building highways). This could be categorised as Not Good if you're in a biological system. it could also be viewed as Good if you're in a biological system, as your nanites will display a remarkable resilience to unexpected circumstances even though they're dumb. Uncovered ants will drag their larvae back into the shade and close up the nest, restoring the integrity of their workings even when the catastrophic happens. Obviously the more information your nanites can hold the more complex their individual behaviours can be, but the essence of controlling them will remain the same (sorry it's taken so long to get to the actual answer!) **The entire control mechanism is a huge game of Chinese whispers** Nanites pass messages to nanites in the form of chemical, electrical and physical stimuli. The exact nature of the stimulus varies depending on location and purpose, but the aim remains the same: use nanites to control nanites, and controlling those nanites using their environment. If you put a sugarcube near an ants nest eventually they'll wear a road in the sand. [Answer] One thing which trends to get overlooked is that nanotechnology is *engineered*, and can overcome the limitations of biological systems. K Eric Drexler, the father of modern nanotechnology, delivered a paper in 1989: MOLECULAR MANIPULATION and MOLECULAR COMPUTATION (<http://www.halcyon.com/nanojbl/NanoConProc/nanocon2.html>) which talks about "rod logic" nanocomputers, a topic which was also expanded upon in the book "Engines of Creation". Without going into a huge data dump (interested readers can go to the link or read Drexler's book), he is discussion bacterium sized "mechanical computers", much like shrunken down Babbage machines, capable of operating with the sorts of speed and power we associate with supercomputers today. The method of providing instructions seems a bit weird; essentially an atomic level analogue of a paper tape, where the computer "reads" instructions by measuring the passage of "bumps" in the tape made by larger molecules as the "ones" while the smooth spots would be the "zeros". The "tapes" would obviously be made at some sort of device in the programming facility, and then introduced to the suspended nano computers and machines (in my conception, they are in a tank of some sort of fluid which provides the ability to move in 3 dimensions, provides a sink for waste heat and a means of introducing "food" and raw materials for projects, and the elimination of waste products). "Tapes" are introduced into the liquid bath, and the computers "ingest" the tapes and read the instructions. Tapes should be made so they can only "feed" in one direction (perhaps a special "header" section), and of course there will be checksums built into the program and on the tape itself, so the computer can read the tape and determine if there was a break in the tape or some sort of programming or read error (resulting in a null field or nonsense answer where the checksum should be). An alternative method is described in this paper: <http://www.csc.villanova.edu/~tway/publications/wayCDES07.pdf>, where acoustic waves are sent through the liquid and the nanomachines receive the instructions through a series of transducers built into the surface of the machine. One simple way to me sure the "output" is to simply look inside the tank and see what the machines are actually doing. If your large programming computer had given then a design for a rocket motor and they are building a clock instead, then you will be very sure something has gone wrong. Drexler himself is a bit unclear on how the rod logic computers communicate with us, although perhaps a simple method is they create data tapes of their own the get sucked out of the tank and read by progressively larger machines until *we* can read the output. At any rate, because nanomachines are engineered structures, then they can be given engineering solutions for programming, read/write operations and so on. [Answer] My first thought when I saw this question was to mimic bees. Some bees use the [“waggle dance”](https://en.wikipedia.org/wiki/Waggle_dance), a series of complicated movements and signals, to communicate important information. They can pass on a variety of information that is analogous or even identical to the information your nanites will need to pass on: * Dangers. * Resources. * Good places to shelter. There is controversy over whether or not the movement of the bees is the important mechanism, or whether other things, such as chemicals, play a role (see [*The Honey Bee Dance Language*](https://www.cals.ncsu.edu/entomology/apiculture/pdfs/1.11%20copy.pdf)). I dislike the idea of using chemicals for nanites because that would involve 1. Releasing potentially harmful chemicals into a person’s bloodstream. 2. Resupplying those chemicals, which is annoying. Because of this, I’d rather go with movements as signals, rather than chemicals. The first thing to do when trying to apply this to nanites is to go over how the waggle dance works. The waggle dance communicates two main things: direction and distance to the source (see the previously linked pdf for more information. * **Direction.** The bee’s body is the important mechanism for communicating the direction of the proposed target. The angle of the bee’s body during the dance relative to some fixed axis shows where the target is. ![](https://i.stack.imgur.com/DYAHH.png) All images from *The Honey Bee Dance Language*. * **Distance.** The way to communicate a longer distance is simply the extend the dance for longer. There is a linear relationship between dance time and distance. ![](https://i.stack.imgur.com/vJMQD.png) You will have to create a start signal and an end signal, because it is important to repeat the message. Now, there are some problems with my proposal. The first is that fixed reference points will be tough to find. For bees, there’s always one good one, which is straight up and down. In the bloodstream and other environments inside the body, though, this will be tough, because the body is generally moving, which changes the orientation of parts of it relative to the ground. You would need to choose local orientation points that would somehow be static. The second problem is that of staying still in the bloodstream. Blood moves quite quickly; in major blood vessels, [it can reach dozens of centimeters per second](https://biology.stackexchange.com/a/43353/9458). I’m worried about maneuvering for even the simplest of tasks for small nanites, though larger nanites with better steering and propulsion systems might have no problems. Maintaining orientation, though, will still likely be hard. ]
[Question] [ Our world has easily observed year, month and day cycles. They and their multiples, such as decades or weeks, and fractions, such as seasons, hours, minutes, and seconds are easily available and used to synchronize and measure events. Seasons and daylight make timing actions highly important activity as well since the earliest times. Most animals and even plants actually have biological clocks. But few recent questions have been about worlds without such easily observed cycles. This includes constant daylight and no seasonal variations. Most answers focused on alternate ways of measuring time or synchronizing actions. But I got to thinking... What if instead society responded to the lack of external events allowing and requiring synchronization by simply going asynchronous. With computers we use, depending on need and circumstance, both synchronous and asynchronous protocols. Our society also uses both, but synchronous approaches tend to dominate especially in modern times when cheap and accurate clocks are available. Less modernized cultures were more laissez-faire about exact schedules and work hours. A society without days or seasons would probably go the opposite way than we have. Since measuring and determining time would be more difficult and less critical, they'd probably avoid it as much as possible. But how much of it is possible to avoid? Can a society be wholly asynchronous and avoid entirely the need to measure time? If no, why not? If yes, how would such society work? Would the answer vary based on level of technology? You can assume full biological adaptation by people, animals, and plants. EDIT: type\_outcast pointed that heart beats would still allow and supply a measure of time at short time scales. This would naturally extend to things such as music and poetry having beat and tempo, and the length of recitation or song providing a way to estimate lengths of time. Further this would then naturally be extended to using pendulums and mechanical clocks. I don't really see any reason why the people would not do this or why I or anyone else should assume they won't. What the question is about is the social protocols people would use without the larger structure of years and days and without a convenient source of assumed synchronicity. There is no need to assume they would be unable to measure periods of time. This would imply that **after** mechanical clocks become accurate they would have ability to synchronize things if they chose to. But let's just ignore that since it is the solutions they'd have developed before that that are interesting. And in any case they'd still not organize around days or years, so I'd assume the old ways would still be better. EDIT 2: Adding a link to [comment by slebetman](https://worldbuilding.stackexchange.com/questions/33542/asynchronous-society/33549?noredirect=1#comment90569_33549) in one of the answers about just-in-time processes and Toyota way. I should have mentioned all that in the question from the beginning, but it didn't occur to me. However it is a very good illustration of the kind of use of asynchronous protocols I am talking about. (Ignore the fact that in our world synchronous parts are necessary at the interfaces.) [Answer] ## Synchronous vs. Asynchronous Before I get into the meat of my answer, a quick word on periodic time: I believe that we *would* still develop and use "synchronous" timekeeping methods, since even without obvious days, seasons, etc., we would still have other obvious cyclical things all around us, such as life and death. For example, humanity has been measuring timescales in "generations" for at least as long as recorded history. I can measure time to within a few hours just by feeling the stubble on my chin. Seconds roughly map to heartbeats. And so on. More technological societies would develop atomic theory, and figure out, as we did, that radioactive decay is [very regular](https://en.wikipedia.org/wiki/Atomic_clock). Your question specifically asked us to assume the opposite, which I will of course now do, but I thought it important to address a few of the other obvious synchronous time sources around us to properly frame this answer. ## How hard is it to avoid? This is hard to answer, but given the ubiquity of things like life and death, it's hard to imagine us not being at least aware of periodic timescales. To avoid using them, I think, would require some conscious societal decisions that asynchronicity is somehow superior, such as (possibly) allowing for more efficient work schedules and so forth: ## Work schedules As opposed to simply *lassiez-faire* schedules, such as sleeping in one day, and getting up early the next, asynchronous work schedules (without circadian rhythms!) would be rather different. I imagine people will work when they're able, stop when they're tired, and then somehow signal their relief shift to start. When there are multiple "relief" people available, it might take some additional organization to set up some kind of priority queue based availability, and so forth. Wages would have to be job- or project-based, given the lack of hourly/daily/monthly rates. ## Biology Assuming we would un-evolve (or never develop) our circadian rhythms that slow us down and help to make us sleepy, we'd simply sleep when we're tired, and get up when we're hungry, thirsty, stiff and sore, or someone tells us to. Along those lines, we'd eat when we're hungry, drink when we're thirsty, and so on. ## Education The concept of going to school for *n* years would be foreign. Students would start school when they learned to develop minimum basic skills, such as basic counting or alphabet, and they'd progress in school based on merit. "School years" as such wouldn't exist, but teachers would still have a curriculum, and at the end of that, students would be tested and would either pass and advance, or fail and repeat, which isn't too different from most of our current systems. ## Legal system Custodial sentences would differ, given the concept of "25 years to life" would be foreign. Life sentences would still be possible, of course, but lesser sentences would have to be based on something else, such as rehabilitation (meritorious, perhaps similar to our parole hearings), or completion of a sentenced quantity of prison labor. (Write "I will not steal cars" on a chalkboard a million times or so.) One might actually see fewer custodial sentences in favor of other forms of punishment such as fines, exile, or (hopefully just in the old days), torture. Also in the legal vein, "legal age" would have no real meaning. While crimes involving minors (such as statutory rape) would probably still exist, the definition of "minor" would have to be based on something other than chronological age. The courts might employ medical and psychological specialists to evaluate someone's mental and biological development, or some other external reference would be used, such as whether the person had completed their secondary education ("high school") or not. That would be imprecise by our definition, as some people might take longer than others, but it could also be argued that it would be more accurate, as those who develop more slowly *ought* to be considered minors for longer. ## Agriculture You say plants would adapt, so without seasons, there would be no growing season, so at first people would plant a crop, harvest when it's ripe, and re-plant immediately. Eventually they would realize that the [soil needs time to regain nutrients](https://en.wikipedia.org/wiki/Summer_fallow), and would adapt, just as we have. ## Science Scientists would almost certainly use periodic time in their work, despite the society's collective abhorrence of such things. It's already common for scientists to refer to quantities differently than ordinary folk; for example, you don't see the weather report on the evening news using Kelvin, or cars that go 30 m/sec. In fact, science *needs* more precise timescales, to develop things such as the physical mechanics of velocity, acceleration, energy, radioactive decay measurements, and so on. Our own "second" is (since 1967) based on the radioactive decay of Cesium-133, so scientists might eventually come to use such a scale (or something simpler, like pendulum motion) to aid them in their work. A lot of science wouldn't be possible (or wouldn't be right) without a linear concept of time, but that doesn't mean scientific timescales would make their way into society. ## Other thoughts This is an interesting question. As I mentioned, it seems likely that a society would choose to use asynchronous or aperiodic methods, as periodicity is all around us. Thus it would be interesting to explore the philosophy and sociology of such a decision, but I fear that's a topic for another question! [Answer] Schedules suck. I mean it. They ostensibly bring order and design into our lives, but they end up creating unnecessary rigidity. There are a few of us who have, for better or for worse, decided to go against using schedules. A good example is a newborn baby. Mom and Dad might want to tuck in around ten o'clock and wake up at six-ish, but the baby will decided when and where it wants to wake up, nap, relieve itself, etc. It does things when it wants to. In this sense, the baby may be smarter than its parents. Why should I get up at six in the morning and go to school if I'm overly tired, or leave around three because that's when we get kicked out of the building? On these days, I could just as easily go wake up at eight, get in by ten and be out by five. I would function really well. The baby may not know this, but it acts accordingly subconsciously. If society behaved like this, then at first there would be issues. Continuing the school example, some students might want to wake up at five, and some might want to wake up at eleven. That clearly creates a problem, one of synchronization, which we have to get rid of here. But why is this a problem? It's that we have to interact with other people, for better or for worse. According to the rules we set down, I have to walk into a room at X time, where I will then be greeted by an overly perky person with a cheery smile. We do this because we have to work together, even though in many cases this will clearly turn out worse for one of us (me, in most cases. I'm not a morning person!). The society would behave like the baby, acting on what I'll call the Principle of Selfish Convenience, which we can view as a short-sighted member of society trying to reach [Cournot equilibrium](https://en.wikipedia.org/wiki/Cournot_competition). Without a natural cycle, there is no need for them to do things that are not important at the moment. Instead, they look for short-term needs. Each person has to do Y things to keep living, and they'll each do them according to when it benefits them. Without some method of keeping time, they'll have to develop a mentality seemingly alien to us. If we were to create some sort of an algorithm to describe this, it would run accordingly: 1. What tasks do I have to do within a short period of time to stay alive? *Returns a list of Z things.* 2. Which of these things should be done first for me to stay alive? *Reorders list.* 3. I do the most important thing on that list. *Goes back to step 1.* This method has the advantage that the person will do what it needs to do most at the moment. The downside is accidental procrastination. You could put off washing laundry for our equivalent of a month if other things are deemed "most important". But eventually the deadline would come closer, and soon laundry would become the most important task. This is the Principle of Selfish Convenience, and most of the time, it will turn out well. The one thing the Principle fails at is interactions with other people. If Person A and Person B keep doing things in a selfish order, and they each have to meet each other, then they may end up never meeting each other, if a window of opportunity passes. This will create a problem. Therefore, *some* aspect of synchronicity must be present in a society. [Answer] You will organize by using queues. That goes in the same direction as HDE answer. For example, if you are running low on food, just go gather some. It is possible because there is no season, therefore no long period when there is nothing to eat out there (aka winter). No need to stockpile then. Well can the queuing solution generalize to any problem ? Almost. **Work** You can adapt the work schedule easily, just run your factory constantly (in the case you need a lot of people to work at the same time). Workers will wait to work, and when a place is freed (by someone going away), the next in queue can take his place. Each worker are then paid by shift. Of course that would be administratively heavy (you have to take care of how much each worker did), but not impossible. Then of course system will need to be achieve for qualified workers. For example a kind of VIP queue for better qualified workers, that allow them to get to work faster, and so ensure the factory to get more of them working. Note that you need a queue in the case of a factory, because you need lots of people *simultaneously* to make it run, but at the same time you can not make them all come at the same time. If there is no queue, you risk lacking workers. That also means that if there is only few people capable of doing some stuff they just basically work when they want (what could also be true in our society). An interesting effect is that it is hard bind someone by contract to do something for you. In fact, you can bind someone to do something, but since you can not give deadline, it is not *de facto* binding. Formulations like "as soon as possible" should be expected, as well as major lawsuit about the concept. So a working contract would be more of an exclusivity contract (you accept to only work for that guy). **Education** Interesting as well. Instead of having classes, you would rather have lots of modules. You go to a module when you want (it is just run in continuous), and when you think you can go to the following module, you ask to pass an exam. Once again there might be some queuing, since you may need to wait for your teacher to come, or a sufficiently high amount of students to come for the module to start. Since it would require lots of teachers, you might use the "students teaching students" approach, having students of higher module teaching students of lesser ones to discharge your teacher. Note that [such education system kind of actually existed !](https://en.wikipedia.org/wiki/Monitorial_System) --- So you may think that everything will be fine, it seems that everything can be generalize by just queuing people. The waiting time may even not be a problem, since the society would basically be founded on waiting. But there is a problem. And it is... **Travel (and wage war)** When you travel, for example through an ocean or a desert, you need to know how much food you need for the duration of the travel, and if the food you take with you will rot before you got to somewhere you can get more. Without proper duration estimation, any travel would become a very dangerous thing. Also, a war is the travel of lots of people killing other people who does not want them to travel *there*. It is the worst definition of war ever, but you get the idea. If you measure time properly, you will most likely get a significant military advantage over populations who do not. If one civilization measure the time, and the other not, it is likely that its planning will be far better, and that it may expand quickly. So either you need to have an absolute pacific species, or you need to clearly separate the military from the rest of the society if you want an asynchronous society to work. Also prepare for conversation like : "Will we have enough food to get there ?" "More or less." [Answer] In order to answer your question, I think we need to ask ourselves whether or not a true **"society"** would be able to develop within an asynchronous environment. **Let me explain:** It is a widely accepted fact that in order for an intelligent being (which I am assuming includes the members of the society in question) to develop to their fullest potential, they MUST interact with other intelligent beings, thus mediating informational exchange across multiple individuals. In order for said exchange to take place on a regular basis, these individuals would need to be synchronized both in time and within a shared language or other medium of informational exchange.Without these interactions, it is also likely that each member of the *"society"* would become increasingly independent from all other members to the point that almost no interaction would ever take place between them. **If this state persisted, a true *"society"* would never form**, leaving instead a group of socially-distant individuals whom would never be able to interact, cooperate, or progress much beyond their initial state of total individuality. **Fortunately, the chances that a truly asynchronous society would form in the first place is highly unlikely**, as the conditions required for such a society to form are extremely specific. It is almost impossible to create a truly asynchronous environment. The natural world as we know our seems to have a relatively constant rythm: plants orbit stars, hearts beat, people have natural sleep cycles, all of which have relatively stay rythms to them. Even if all of this was stripped away, we must still consider that modern time keeping is defined by the equation stating that 1 second is equal to: > > the duration of 9 192 631 770 periods > of the radiation corresponding to the > transition between the two hyperfine > levels of the ground state of the > cesium 133 atom. > > > (<http://physics.nist.gov/cuu/Units/second.html>) In other words, a truly asynchronous environment would imply a randomized and independent temporal vector for each individual atom, which would completely change the way physics works. [Answer] There are some interesting philosophical lines drawn here. The mere idea that things are cyclical is known scientifically to be an illusion. Entropy always increases. Globally, we cannot return to our previous state. To claim a universal cycle like our days/months/years cycle is really just a "good enough" approximation to make good plans. The cycle is an approximation, not a reality. So the best way to get rid of the cyclic thinking which leads people towards synchronous approaches is to make sure it isn't all that useful. If a group of beings were stuck in a highly chaotic environment, rather than a more periodic environment, it would be less useful to work with time in the first place. It'd be preferred to, instead, continually measure that which you are interested in, and work with it. Another case might be a society where you never disengage from life, and let it take its course. We're used to instructions "mix the cake ingredients, pop it in the oven for 45 minutes." However, if society expected you to interact with the cake until it was done, your cake might take 30 minutes, or it might take an hour. The time would be less useful. Historically, more things were done this way. If you look at recipies from your grandmother, they have a lot fewer details like times. If you look at recipies from your great grandmother, they may not even have any measurements at all. Food was done "seat of the pants," by taste. The syncrhonicity of our world has evolved, it wasn't always this way. [Answer] **They would eventually create human centered clocks.** Assuming humans can even be supported in such an environment (other life needs those cycles too), humans need consistency and repetition to feel that they are "safe" (as seen in babies and toddlers) or "in control" (business management, planning for war, going out on the hunt, planning plant harvest times, in general - estimating how long it will take to get things done). That desire will not be eliminated. Because time is really just a measure of distance travelled with a consistent measure, it would not be too difficult for a society lacking physical cycles to still establish human-centered ones. Thus, they would develop a more "humane" clock rather than a planet biased clock. For a super simple example in your sun always shines world with no technology or mechanics: consider a jar filled with water. Clockmaster "A" fills the jar with water and sets it in the sun. That is the first shift of work. When the jar is empty, Clockmaster "A" wakes Clockmaster "B" and the 1st shift can go back home and relax, while the 2nd shift comes to work. They do that until Clockmaster "B" declares the jar empty. 1st Shift then goes to sleep, 2nd shift then goes back home to relax, and Clockmaster "C" takes over with 3rd shift. When Clockmaster "C" declares the jar empty, he wakes Clockmaster "A", and the process repeats. The only variable that needs to be adjusted is the size of the jar. (You could do the same thing with footsteps - the time it takes for the Clockmasters to walk to the far off mountain and back, for example or - for a more "neutral, tamperproof method", a water wheel that when it reaches a certain point rings a bell, and 10 bells is one shift, etc). ]
[Question] [ In [this](https://worldbuilding.stackexchange.com/questions/10069/effects-of-a-human-moving-faster-than-sound) question, we were provided a look at what would happen if a human-like species was capable of moving faster than the speed of sound. The consequences of such a modification seem rather disastrous, so I'd like to propose something different: modifying the human nervous system. If humans, or at least a subset of humans, had some quality that increases their ability to process and react to external stimuli (e.g., see it, know what it is, and react to it), covering the brain, muscles, sensory organs, and nervous system, how would general life be different for the altered human? At what point would the difference between a regular human and this altered human be ultimately noticeable and beneficial: 5% better reaction times, 10%, 30%, more? Would the body need to be altered in any further way to support this mutation? Bonus points if you can provide a purely biological method to support this mutation. To head off anyone pointing out another related question: [This](https://worldbuilding.stackexchange.com/questions/9882/what-would-the-reaction-times-and-or-cognition-speed-of-an-alien-with-a-photonic) question remarks on a species with a much-accelerated nervous system. Note that I am not looking to make a human have a noticeable lag time between thought process and physical activity, as the accepted answer concludes, but rather to give a human a sufficient edge in hand-to-hand combat to be able to easily predict an opponent, to have a better chance to dodge a bullet, and otherwise have extraordinary ability. [Answer] So, faster reaction times? Like [Miles Teg](http://en.wikipedia.org/wiki/Miles_Teg) in the later Dune novels? Without techno-magic? That's going to be tough. To speed up a nervous system you'd have to do one of two things: * Make each neuron faster * Make the length of the neuron perception->computation->reaction chain shorter. ## Making neurons faster Neurons, especially outside your brain, are pretty slow, as [this video beautifully demonstrates](https://www.youtube.com/watch?v=cn1qVZF-bI4). The speed of transmission depends on the quality of the cabling. For fast long distance communication with distant parts of the body the Nervous system has its axonic cabling covered with a [myelin](http://en.wikipedia.org/wiki/Myelin) sheath, which speeds up nerve impulses by a factor of 10, via saltatory conduction. Within the computational centers in the brain where the neuron-body to neuron-body distances are much shorter, myelinization is less of an issue, and more lossy communication can occur. It is tempting to think that after 400 million years of multicellular evolution, neurons are about as fast as they can get. That's actually not the case. Evolution optimized for the best combination of speed and low energy consumption it could, and if you look at the actual process, it [seems a bit of a kludge](https://www.youtube.com/watch?v=iDgKqJbdiDk). It's not inconceivable that if we were to redesign a human body under our no-energy-constraints current situation, we could get significantly faster conduction, bounded upward by the electromagnetic propagation speed of $c$. Significant upgrades could be achieved at the neurotransmitter bottleneck, for instance. Of course, we don't need a million-fold speed increase to have merely faster reaction times, so relatively minor tweaks could work. Some of them could even evolve biologically as we move away from the food-being-an-issue as a species, but [genetic engineering](https://worldbuilding.stackexchange.com/questions/9493/what-is-the-technical-feasibility-of-dna-altering-drinks-in-a-fictional-bar/9498#9498) is a faster way to get there. ## Making loops shorter The other way to make reaction times faster is to cut down the number of layers of communication and processing between sensory activation and action. To act real-time, a perception-to-action loop can be about 100 neurons long, with the slow axonic Na+ K+ based electric conduction, the even more inefficient axon terminals where neurotrasmitters are sloshed around. Ugh. Let's try to chop some of that off. A real-world example is the spine-based instinctual reflex reaction (such as the command directing your hand to move away from a hot surface). Imagine you were able to program a reflex reaction to Kalashnikov rifles, or to people wearing the wrong kind of uniform, of whatever fits your criteria of enemy. No thought required, just a pre-recorded action shortcut. It is suspected that grandmaster samurai swordsmen, for instance, through decades of practice, were able to enter such a reflexive state at the start of 1-on-1 combat, acting without thought or hesitation. If you're willing to add some cyber components on top, you can have all sorts of fancy sensors, computing substrata and then action directed by cartilage, muscle and bone upgrades to allow for high-speed actions far beyond the capabilities of mere flesh-humans. [Answer] **The Problem:** In order to produce a significant advantage in combat as a result of faster reaction times, it is necessary to either operate inside of the opponent's decision/action loop (i.e achieve tactical surprise), thus requiring the opponent to think about reacting to a situation that you have already thought about, or to significantly decrease the opponent's physiological reaction time. Cutting a few percent off the reaction time won't be sufficient, you'd need to have a quite significant reduction in reaction time to observe any significant combat advantage. We're looking at about a 15-20% reduction in reaction time at minimum. **Genegineering Solution:** If you had no limits as to the sophistication of your genetic engineering other than the practical limits of the materials you're working with, have a look at [my answer](https://worldbuilding.stackexchange.com/a/9892/75) to the second question referenced. To summarise, neural conduction could be accelerated by precipitating metals (or graphene) and neural connections could be accelerated by using mechanical rather than neurotransmitter-mediated gates. It would be rather more difficult, but not impossible, to dramatically improve the speed of muscle contraction, but by dramatically reducing reaction times at least, it would be possible for a human so enhanced to out-think and out-react any unenhanced human, with or without higher muscle contraction speeds. Human eyes are not the fastest eyes in the animal kingdom either, so it would not be too difficult to make the necessary changes to speed them up either. Given all these advantages engineered into a single individual, including faster musculature, it would be possible to see bullets in flight and to have a chance to dodge or deflect them, though the chances would probably be on the order of an *un*enhanced human dodging or deflecting an arrow from a bow - very difficult, but not impossible at sufficient range. If it came to combat of any sort between enhanced and unenhanced humans, the outcome would be heavily skewed in favour of the enhanced human, regardless of the training of the unenhanced human and any lack of training of the enhanced human. Unenhanced humans would have to rely on attacking unobserved or using heavy weaponry to have any certainty of defeating such an opponent. However, this would come with certain disadvantages. Unless the genetic engineering was done very carefully and cleverly, such a 'human' would not actually *be* human in anything but appearance. The most likely outcome is that they would not be sufficiently genetically human to be able to successfully interbreed with unenhanced humans, and even in the unlikely event that they *could*, their offspring would be far closer to the unenhanced parent than the enhanced parent. Secondly, during pregnancy and childhood, if metal precipitation was used to accelerate axonal pulse transmission, it would be necessary to supplement the diet with the metal in question, probably silver due to its low resistance, as the levels of metal required would not naturally occur in an unenhanced human's diet. However, graphene precipitation would not have this drawback. Thirdly, as speed increases, so too do metabolic costs. Enhanced humans would have a higher basal metabolism simply due to their more active neurology, and *acting* more rapidly would have a similarly higher metabolic cost. Put simply, these people would have to regularly eat the sorts of meals that for the most part only morbidly obese unenhanced humans would choose to eat. Fourthly, were such enhanced humans engineered, and they constituted a separate species as is most likely (and even if not), there would be a strong impetus for active competition between the groups to occur, as slower or not, unenhanced humans are still smart and quick enough to see how they are outclassed. This could quite quickly descend into a war between the enhanced minority and the unenhanced majority a-la the Marvel X-Men universe. Fifthly, enhanced humans would not obtain the same enjoyment from the movies that unenhanced humans watch without software enhancement: since we are talking about enhanced humans having faster eyes, this would increase the fusion frequency. Our movies are typically shot at around 25 Frames Per Second (FPS). However, this would be below the fusion frequency of enhanced humans, who would see a series of static images. Enhanced humans may have a fusion frequency requiring frame rates of 50-100 FPS or even more. This may be able to be compensated for by inter-frame interpolation, but would require a lot of computing power. **Evolutionary Solution:** From an evolutionary perspective, it would be very difficult to evolve these adaptations, even in the presence of an evolutionary stimulus. Sodium-gate neurotransmission is so heavily tied into the viability of organisms that any mutations which affect this would be highly likely to result in a non- or less- viable organism. Evolution is far more likely to produce iterative improvements on the current theme, not a wholesale cut and replace solution such as the genegineered solution above. Creatures have been evolving side-by-side for millions of years in an attempt to out-react one another, and the current neurology is the best that has occurred naturally. Any significant improvements would have to come as a series of individually viable steps, each of which provided some advantage, whereas geneginering can implement a whole lot of steps at once without requiring incremental advantage. Evolution is limited in that in a solution space with multiple uneven peaks, solutions will tend to move up the current gradient to the top of the closest peak, and to jump across to an adjacent, higher peak is effectively impossible, as this would involve a reduction in fitness before there could be an effective improvement in fitness. This means that when starting from a different evolutionary point, it might be quite easy to evolve a faster system such as this, but *we* can't get there from *here*, since we can't go backwards. **Hybrid solution:** From a certain point of view, genegineering *is* an evolutionarily valid solution to this problem: your species, (humans in this instance) have evolved high intelligence, and have used that to accumulate a cultural store of knowledge which can be used to develop techniques of genetic engineering, hence it can be said that humans are in the process of evolving the ability to produce game-changing advantages in future generations in a very short timespan. By evolving *high intelligence*, we are in the process of gaining the ability to potentially jump to an adjacent, higher peak of fitness without the necessity to suffer generations of lower fitness first. Why say that evolution always has to be unintelligent? We're becoming quite capable of our *own* intelligent design, no prehistoric creator needed. [Answer] **Selective breeding would do it.** There is more variation in human reaction times than most people expect. I happen to have unusually fast reactions. Very handy for a a gunsel, or twitch video gaming. Years ago in drivers ed, there was a reaction test. My teacher accused me of cheating because "no-one" could be that fast -- of course, he could not think of any way that cheating was even possible (nor can I). He had been teaching drivers ed for about 30 years, giving the same test to everyone and no-one was ever close to my reaction speed. Check out the [reaction time dollar bill test](https://www.youtube.com/watch?v=DNpvR5gDhMc) video. The person attempting to catch the dollar bill, should have their fingers near the bottom of the bill, even then few people can catch the bill. When I was 20, I could catch the bill about the middle of the bill. I tried this on my 70 year old mother a few years ago, she could still catch the bill. Genetics play a part. My sister, however has extra slow reaction speeds, almost 3 times as slow as me. Given the natural variation, with selective breeding alone (either eugenics, or making gunfighting very common would do it) you could get a 50% speedup in reaction times (a bit less improvement than I had at age 20). Some CNS stimulants also speed up reaction times, but caffeine alone does not make you more than a small amount faster. [Answer] I think the best thing to do is in play at the body in certain joints in spots on the body with reaction sensors that electrically heat the nerves to allow quicker movement and stimulate blood flow. If your eyes could see something bad was about to happen then the implants heat the right nerves in the right muscles in the body to move quicker. ]
[Question] [ In [this question](https://worldbuilding.stackexchange.com/q/8978/75), I proposed a system of democracy for a city state that is being encouraged away from autocratic rule, however the system I proposed appeared to have many faults. As a bit of background, this is a city state with an area of influence a few hundred kilometres across. Previously, rule was held by a series of vampiric immortal autocrats, and the slayer of an autocrat (which event could only happen during a vampiric ritual) traditionally became the next autocrat. The autocrats were fairly unpopular to the populace due to their vampiric habits, but could not be removed due to their effective immortality and magical invulnerability, and the fact that the latest autocrat had some quite progressive and beneficial ideas that benefited much of the community (that wasn't being drained) significantly. This city state is at a technological level roughly equivalent to early renaissance Europe, though with some magic that isn't particularly significant to this question. However, an individual has overcome the last autocrat during the ritual, but is so repulsed by it that they want to eliminate the tradition entirely. As such, they want to abdicate their position of power and establish a democracy so that there will be no single autocrat who could re-establish the traditional practise of the vampiric ritual, for long enough that the tradition can no longer said to *be* the tradition. This individual has some knowledge of our various democracies, however the citizens of the city state do not have experience of any form of government other than autocratic rule, and any thoughts of democracy would be rare and strictly speculative. **The question:** What form of democracy could be implemented that is easiest for the literate but democracy-ignorant townspeople to understand and practise, which would guarantee that no one person could be considered to be an autocrat for the foreseeable future, and would provide the fewest opportunities for corruption or abuse? Magic can be involved, but the less the better, and preferably won't be required at all. **EDIT:** The townspeople don't actually *need* to be *completely* ignorant of democracy. Yes, they had an autocrat, but he was more concerned with finding and consuming his latest victim and enjoying his other lordly prerogatives than with actually doing the work of ruling. It is highly likely that since educated, independent-minded people make better victims, he would have encouraged said education and independence, to a degree. The townspeople would likely have not wanted to bother their lord with trivialities that could bring them to his attention and result in someone being devoured or executed, so with the lord's tendency to just say "I want *this* done", and the populace's desire to get the '*this*' done without bothering their lord with questions or failures, that they could have developed at least the precursor mindset to democracy by themselves over the course of a few hundred years, by electing their own councils and committees who would oversee the actual work of running the city. The elected officials may not have been the best the city had to offer, but they would have had to be competent in order to avoid lordly displeasure and attention... Democracy then becomes a matter of replacing a largely figurehead autocrat. [Answer] That's tough. It's a huge question. Let's see, where to start? The era is actually relevant for several reasons. One is population size. The second is technology level, which matters mostly because it determines the cost and availability of newspapers, books, and communications networks that bring news from abroad and from different regions. Early Renaissance has the printing press and can easily have political pamphlets and newspapers as well. That's great for your democrats. Information must flow. First of all, you'll need a **constitution**. These are sets of rules that would be virtually unalterable, except by vast super-majorities of the population (at least 66%, and hopefully more). This is vital in order to guarantee things like due process, basic right to life, property rights etc. Thus, a constitution limits the amount of change (damage?) successive governments can effect. Your constitution has to specify the **rules of the game**. It is vital to have a **separation of powers** between the executive, legislative and judicial branches, and if possible to guarantee the independence of the Military and the Treasury/Mint. Let's go through the branches one at a time. **Judiciary**. This normally includes Judges and state Prosecutors. These guys must be free from political influence as much as possible to prevent the judicial branch for being used for personal or political vendettas. This is called **the rule of law** and is VERY IMPORTANT, possibly the single most important thing there is in a polity. They must assess the constitutionality of the acts of the legislature and the executive. While they have no enforcement power (that'd be the Executive), their words and pronouncements should carry a heavy moral authority. Presumably, your society already has judges and prosecutors. If they're not vampires, give them office for life or something. **Executive** They are responsible for actually doing stuff. So building roads, canals, aqueducts, schools, hospitals, reacting to natural disasters, going to war, directing the spies and agents abroad, negotiating important alliances and trade relations. Because of the nature of the decision-making process required (swift, decisive action is often required), this will be the most powerful branch, likely comprised of many departments/ministries but ultimately headed by a single person or a small committee. This will likely be the most prestigious branch. One way to reduce a bit the power of (and burden on) the executive is to delegate as much power as possible locally, to villages and groups of villages in the countryside, and wards and city neighborhoods in the Capital. In order to keep your Executive in check, you want to make their funding depend on the agreement of the Legislature, and their actions subject to review (and reversal) by the Judiciary. It is your choice whether you make direct elections for the executive body (I probably wouldn't, at first, to help avoid demagogues that are sure to prey on an unseasoned populace) or have the Legislature elect this person. The nomination can be based on popular signatures, nomination by the Legislature or by some body tasked specifically with this function. **Legislature**. These men and women represent the voice of the people. Here, you first have to decide who can vote. You can have one-person-one-vote rules, a weighted voting system (based of wealth, birth or professional/social status), limited universal voting (where only a subset of the population can vote, such as only males, but more usually also restricted on income), or restricted voting (where you have a limited set of electors, such as powerful nobles and sometimes rich merchants and industrialists who can vote). Second, you have to decide on how elections are to work. You can have individual districts (restricted geographically) or at-large voting (the whole country is a single district). In each district, you have to decide who wins. You can have US-style plurality systems (whoever wins the most votes wins), a threshold system (must have a certain number of votes in at-large systems or a percent of votes in multi-district, usually 50%). If multi-district, districts are often (not always, see US Senate) similar sizes and elected legislators usually have equal votes. In at-large systems, that's usually the case too, but nothing could stop you from making voting power equal to votes cast for them, up to a certain threshold, say 5-10% of total votes in the legislature. You can also have a lowest threshold for representation, and have all the wasted votes redistribute proportionally as extra voting power for the elected. Once you've sorted out electorate and elections, you have to decide structure of legislature (one chamber, two?), term lengths and term limits (if any). Do all the legislators need to get re-elected at the same time, or (like in the US Senate) 1/3 every 2 years? *Treasury* - To prevent debasement of the coinage, inflation and other bad things, there must be a degree of independence. Perhaps very long terms, or judicial protections from executive and legislative meddling? **Military** - This is the biggest worry. In history, most democracies and republics fall to military coups and demagogues. Often charismatic military leaders ARE demagogues (See Venezuela, Chavez). The military has lots of hard power (they can kill and kidnap people), so they can generally silence domestic opposition if they so choose to. A tradition of non-intervention in politics by the military is most helpful. It's doable though. Venice stayed coup-free for almost 500 years. You may also want to read this [anti-coup primer](http://www.foreignaffairs.com/articles/141837/ivan-perkins/staying-power). --- *So how do you get there from here*? Oh, that's the tricky part. Most autocracies transit through an oligarchy before they become democratic, and many young democracies revert to autocracy. However, you might want to read up on the positive examples, such as the formidable [Old Swiss Confederacy](http://en.wikipedia.org/wiki/Old_Swiss_Confederacy) and their Landsgemeinde and the [Icelandic Althing](http://en.wikipedia.org/wiki/History_of_Iceland#Commonwealth_.28930.E2.80.931262.29). --- **TL;DR** - You need a constitution, separation of powers, rule of law, election laws, mechanisms and traditions to prevent coups, and lots of time to set this up. If you only had, say, 1 month, you'd be in a bit of a quandary. [Answer] The people are ignorant of democracy, but they *need* a democracy. That's tough. If you simply had them total governing power overnight, they'll mess up. So your new leader needs to transition. For a short while, s/he needs to stay entirely in charge. Then follow some steps. 1. **Educate the populace.** They need to know about governing themselves. Open new education programs, working off of existing schools, that teach the adults about this strange new system of democracy. 2. **Delegate new region leaders.** Divy the nation up into regions, and have each region have about ten leaders (I'll explain the regions more below). They need to continue the program for about a year. In the meantime, have them govern, but only give them a tiny bit of power. We need almost no government for a few months if we want nobody to have much power. 3. **Set the people free.** When you think the people know enough, let them lead themselves. Give them control of the new government system that I'm about to explain. Here's what I propose: 1. Break up the city-state into smaller regions. Make each region contain, say - oh, just divide it up into somewhere between 50 and 100 regions. But make sure that there aren't too many people in each region so that politics stay personal. 2. Each person has to be familiar with the workings of the political system. But they can't deal with large-scale matters. So have each person vote one every matter that impacts his or her region. If you've got about 10,000 people, this doesn't seem too hard. Have voting on major issues take place over the span of, say, a week, with discussions in each village leading up to it. 3. Make each region autonomous *except* in cases of war or drastic foreign policy disputes. Handle outside problems on a region-by-region basis. So if (in our world, where the US is this region) France has a problem with New York, let New York handle it. If war comes, then other regions will be obliged to join in. 4. Make a loose coalition. Think 19th-century Germany/[Prussia](https://en.wikipedia.org/wiki/Prussia) before there was any substantial unification. Sure, there were problems. But they were settled. In short, make the ultimate democracy, where each and every person can directly vote. --- **Problems (and Solutions)** 1. **The setup is weak. If a large country comes in and takes out one of the states, they could be annihilated.** But here's where the coalition comes in: Have *everyone* send in forces. Organization can be implemented in this time of emergency, but, once again, have no one person in power. Or two. Or three. 2. **The regions could descend into isolation out of not being in close contact with each other.** But is this a problem you need to solve? Just keep the coalition alive, and each region can be largely self-sufficient. Trade can keep any necessary ties strong. You shouldn't have too much trouble. 3. **One region could try to conquer another. Sure, they're on equal footing at first, but this could change.** This is a risk you'll have to take. But I'm sure that the other regions will rise to the attacked regions defense. Because if the would-be-conqueror takes over other regions, it will quickly dominate, and all the others will fall. [Answer] A transition from an autocratic government to a democratic one is not a trivial task. Unfortunately, there is no one-size-fits-all solution to this problem. You should expect that there would be a great power struggle from many different fronts. This change in power cannot exist in a vacuum. There would be fighting within the ranks if everyone in the government is not on board with democracy. Other neighboring nations may see this as a sign of weakness and indeed, the change in power can leave your nation very vulnerable to attack. There may be other bodies in your world which is similar to the church autocracy which existed in medieval Europe. Bishops, Cardinals and The Pope had a great deal of power and often did not have direct oversight from the monarchy. In some ways they had more power than kings. This kind of change would take many years. It could literally span hundreds of years until you could have a successful democracy. The people that exist in that time would be poorly suited to be political leaders because they would most likely be poorly educated and completely illiterate. Democracy is not something you can just give a nation. The people have to want it, demand it, fight for it, and be willing to die for it. The common person would probably have no idea what democracy even was. You would have to follow the path that Europe took to establish democracy. It went through many different periods that eventually led to the European renaissance. The renaissance did not come from nowhere. Teachings from other parts of the world that did not suffer as much from the fall of the Roman empire eventually made it back to Europe. There was a new found interest in the arts and sciences that was nearly absent for hundreds of years. The monarchy, and especially the church forbade such teachings, but they were being taught in secret. The church would execute people for having new ideas and brand them as heretics. They would also ban and destroy any writing that the church did not agree with. The church eventually lost much of its influence, and people could study science and arts without the fear of persecution. Schools and universities were formed. Eventually there were many extremely well educated people around which were capable of running a democratic government. Since your leader is effectively immortal, they could make incremental changes to push the government towards democracy. They could start small and start cutting some of the red tape it would take for someone to start their own business. They could establish schools and universities, use their magical power to make life for the average person better, establish building codes and housing standards, build sewer systems and provide sanitation and clean water, build hospitals, etc. [Answer] The usual transition in Earth history has been to go from a monarchy (autocrat in charge of as many other autocrats as he can bully, coerce, or otherwise keep in line) through a parliamentary monarchy (autocrat is still in charge, but now he needs the approval of a council to do some things) to a representative democracy (the council is elected; the autocrat is, at most, a figurehead). In your situation, I'd recommend that your individual take up the autocrat's position, and appoint a council of advisers. Over time, he should make council membership elective and transfer actual power from himself to the council. The eventual goal is to create something like a [council-manager](https://en.wikipedia.org/wiki/Council%E2%80%93manager_government) arrangement. Since power rests in a group rather than an individual, it's harder for a corrupt charismatic leader to take over -- though you are likely to see an [oligarchy](https://en.wikipedia.org/wiki/Oligarchy) form in a generation or two. [Answer] Personally, in a situation like this, I think it would be safest for the autocrat to become a benevolent dictator. Then introduce parts of democracy. Slowly give the people more and more responsibility (and education!). Depending on the populace it could be as little as a few years (it helps there is a small population) that it could be turned into a full democracy. The USSR is still trying to recover from the switch from a totalitarian government to what ever it can be called today. (I'd call it a semi-benevolent dictatorship). [Answer] From our modern world perspective, we know that some countries have made the democratic transition with success and others have failed miserably. The 95% left are somewhere in between or they just have not completed the transition yet. Most countries that made the transition never had a democratic system before. We tend to see it as something natural but we forget that most countries had a tough time before they became real democracies. Your leaders must be aware that most people will probably not oppose a return to the autocrat regime. They don't like vampire but the new tyrant could be human. So, they need to set barriers to prevent others to concentrate the powers into their own hands. Serban made a good answer on the separation of powers. It is not a perfect solution but it makes it a lot harder for one individual to control everything. **Religious/cultural differences:** However, many countries tried to replicate systems of the United-States or France during their transition but failed. Is some cases, the division of powers is not enough. It won't solve the problems in Irak. The religious differences and their incapacity to work together made the country explode. Many other like Libya were held together by the force of the authoritarian regime and without it they need to set mechanisms to assure the representation of each community in the government like Lebanon did. Each community have a representation in the government and they can control certain ministries... So, it's not possible to have a government that exclude a community form power. > > A city state with an area of influence a few hundred kilometres > across. > > > That sounds like Azerbaijan (most of the money is there and 50% of the population live in/near the capital Baku). It started great like many other post soviet states if we exclude the war with Armenia (they are still at war). The problems of most of these states is that the president quickly started to modify the constitution to gain more power while weakening the rest of the parliament. Why I am talking about that country? Because they have an important strategic resource: oil. The only economic development that took place in the country in the last 20 years are all about oil. It's now around 80% of their GDP. Other countries like Turkmenistan and Kazakhstan are almost in the exact same situation. They are we is called rentier states. There a theory in political science that link the exploration of natural resources with autocratic tendencies, especially when the countries are dependent on oil exportation. There is the need to control the industry in order to enforce a monopoly, to control the prices, control the regulations. Oil is almost their only source of revenue and they want it all. This is an obstacle to the transition but it is not a problem if: the country has plenty of other revenues and if the state is already an established democracy. The later is only in theory because some people argue that Canada and Alberta have autocratic tendencies partly in the form of deregulation. For my personal campaign, I have a country that is a producer of a rare metal with magic proprieties. It is rare and the country has a large share of the world market. The objects made of this metal can enhance magical powers and is viewed like oil or uranium today for magicians who can afford it. In that country, the mining, the processing and selling of the metal is all strictly managed by the state. Unfortunately, the metal is too rare and too costly so it doesn't take a large part of the country's GDP. It's easier for a small state to be dependant on one resource or maybe one type of industry. A diversified economy might help to prevent this. [Answer] In response to the additional constraints in your updated question (that the not-an-autocrat has only a month or two do this, and there may be some proto-democratic institutions): Your best bet is to use various craftsmans' guilds as your starting point. They're likely to have traditions that are at least notionally democratic (such as election of a guild leader from the senior craftsmen). Put together a Council of Guilds to run the city. Each guild provides one representative selected by whatever means that guild wants (in practice, this will mean "appointment by the guild leader"). Decisions within the council are made through simple majority vote. This setup has its faults (eg. the 15-member Goldsmiths' Guild has the same influence as the 1000-member Carpenters' Guild, while the non-guild farmers have no voice in government), but it's something that can be set up in a month or two, avoids concentrating power in any one individual, and if you're very lucky, it will transform into a representative democracy over time. ]
[Question] [ Is it possible (for humans)? My main concern was heavy gravity because they are much bigger and heavier. But it appears that in our system, the gas giants (but not Jupiter) all have a similar [surface gravity](http://en.wikipedia.org/wiki/Surface_gravity) as Earth. Actually I'm not sure if by surface they mean the solid core of the planet or something else? On the page of Saturn: it says that the solid core is between 9 to 22 time more massive than Earth but only twice as large. With these numbers, the gravity could be between 2 to 5 times the gravity on Earth. That is not very human-friendly. Possible problems for terraforming: 1. Gravity? 2. Hostile atmosphere: can we just pump it? 3. Others? [Answer] **For "ice giants" like Uranus or Neptune, yes.** Larry Niven's book [The Integral Trees](http://en.wikipedia.org/wiki/The_Integral_Trees) is set in the "Smoke Ring". This is a ring of gas in orbit around a neutron star, formed by a gas giant which went too close to the star and lost its atmosphere. The central and densest part of the ring is inhabited, but there is no gravity. For this, the gas giant would have to have a lot of oxygen, which not many seem to do. *Gas* giants such as Jupiter or Saturn, composed of 90% hydrogen, do have a solid core, but it consists of [metallic hydrogen](http://en.wikipedia.org/wiki/Metallic_hydrogen), which can only exist at extremely high pressures - if the atmosphere was lost, the core and the liquified gases surrounding it would evaporate. These can't really be terraformed, and are also bigger than ice giants. *Ice* giants have 20% hydrogen, and are mostly other things such as methane, ammonia and water. [Uranus](http://en.wikipedia.org/wiki/Uranus#Internal_structure) is thought to have a hot (5000K) rocky core of 0.55 Earth masses, a "mantle" of "hot" liquid or supercritical water and ammonia, of 13.4 Earth masses, possibly with lots of diamonds forming near the bottom due to high pressure and presence of carbon (from methane). The atmosphere itself has 0.5 Earth masses. Neptune is similar, with a core of 1.2 Earth masses. **It is theoretically possible, but I don't know how you could rip off the atmosphere and mantle.** Your civilization would have to be very advanced to find enough energy to remove the atmosphere, and to supply the oxygen which is not present in it. It could have been lost by a catastrophic event (e.g. planet passes too close to large object), or such an event that was artificially induced by some thruster. The thruster needed to move the planet to the habitable zone could operate by ejecting the atmosphere, solving two problems at once. [Answer] This is really sort of cheating, but it could actually work, so here it goes. As professorfish says, > > It is theoretically possible, but I don't know how you could rip off the atmosphere and mantle. > > > Very true. [Jupiter's atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Jupiter) is about 5,000 km high, and comprises the majority of the planet's [mass](https://en.wikipedia.org/wiki/Jupiter#Mass). That would be pretty hard for a civilization to get rid of. Fortunately, *stars* can do it for you - if you're willing to move the planet in question. [Hot Jupiters](https://en.wikipedia.org/wiki/Hot_Jupiter) are large gas giants orbiting close to their home stars (0.015 AU and 0.5 AU, as opposed to Jupiter's average orbital radius of about 5 AU). Hot Jupiters are - well, hot because they are so close to the star, and so they suffer from other stellar effects. They most likely form farther out from the star - beyond the frost line - and [come inwards](https://en.wikipedia.org/wiki/Planetary_migration), towards the star. Hot Jupiters often experience strong stellar winds. These winds can, if they are strong enough, rip away the planet's atmosphere via [hydrodynamic escape](http://en.wikipedia.org/wiki/Hydrodynamic_escape). If the process goes on long enough, the atmosphere can be entirely blown into space; the resulting body is known as a [chthonian planet](http://en.wikipedia.org/wiki/Chthonian_planet). These hypothetical objects would be similar to terrestrial planets in size. If you could introduce an atmosphere and other materials, you *could* begin to terraform one. So a star can convert a gas giant to a terrestrial planet for you. The problem is that the planet has to already be very close to the star. Jupiter would have to have its orbit reduced to a very tiny size for this to be possible. To move it inward, you would have to induce an artificial migration. Perhaps you could attract it with another body - perturbing it just enough to make it begin to move inwards. Or maybe you could build a large object resembling a [Dyson sphere](https://en.wikipedia.org/wiki/Dyson_sphere) in size, and use that to attract it inwards. Both options would be incredibly hard, but still within the realm of possibility. You still have a problem: The chthonian planet is still not a great place for life. It is too close to the star to be inside its [habitable zone](https://en.wikipedia.org/wiki/Circumstellar_habitable_zone), and it's way to hot. To get it further back, perhaps you could use the same mechanism you used to get it inwards: using the gravity of another body to change its orbit, a bit like [planetary migration](https://en.wikipedia.org/wiki/Planetary_migration), although stability will, of course, be an issue. Once you have the planet where you want it, you can begin the process of terraforming it. [Answer] One large problem with all the ideas here. Jupiter has a "solid core" only because of the pressure of the rest of the gaseous mass. Kind of like how you highly compress carbon dioxide and it becomes a solid. As soon as you rip away that big fat gas mass, it's like opening a shaken can of soda. You will not have much left to call a planet, if anything at all. If you have any solids left at all afterwards, I would imagine it would be a useless crumbly pile of useless. ]
[Question] [ Normally we watch the sun descend, it's dimmed a bit by the atmosphere before dropping below the horizon. What I'm interested in is how big it would have to be so the atmospheric dimming is sufficient that the point it dips below the horizon is unnoticeable. --- **External Edit:** This is how I understand the question: On Earth the sunset has two phases. In the first phase the sun moves towards the horizon, and its light is dimmed by the shallower angle it makes with the planet and the longer journey through the horizon. The light continues dimming as the angle becomes shallower. The second phase begins when the sun touches the horizon. Usually the atmospheric dimming is mild enough that the outline of the sun can be seen touching the horizon. In phase 2 the sun moves under the horizon the dimming is more pronounced than phase 1 and continues until the sun is no longer visible. The Asker wants a world where the dimming in phase 1 is so extreme that by the beginning of phase 2, the outline of the sun can no longer be made out in the sky. Maybe it is visible as an indistinct glow or maybe there is no light getting through the atmosphere at all! --- (Assume an unaided human observer in an atmosphere suitable for a terrestrial ecosystem, it need not be exactly Earth's atmosphere. When the star is overhead something like 1000W/m^2 like we get on Earth.) I have no doubt this has to be far bigger than any rocky planet and thus must be some sort of megastructure. (Say, a Dyson Sphere with stars orbiting it.) [Answer] We want a sufficiently long light path through the air when looking horizontally that atmospheric extinction will increase (recall that larger magnitudes are dimmer, smaller magnitudes are brighter) the magnitude of the sun to the point that it is not discernible to the human eye by the time it reaches the horizon. Minimum attenuation in Earth's atmosphere is about 0.16 magnitudes per airmass, where 1 airmass is the path from the surface straight up towards the zenith. It would be nice if we could just use some trigonometry to figure out how much longer that path is along the horizontal... but that doesn't actually work, because air density remains high for longer the lower your elevation angle. Empirically, however, looking towards the horizon gives you about 40 airmasses on Earth, which would give you an extinction factor of about 6.4 magnitudes. In practice, Earth's air is never that clear for that long, so empirical extinction for our sun is considerably higher-about 11 magnitudes for 40 airmasses. The sun's zenith magnitude is -26.7, and the limit of human perception is 6.5. So, we need a total extinction factor of 33.2--or just a little over 3 times what we have on Earth. Since a path near the horizon spends the vast majority of its time in the thick, lower atmosphere, I think we can reasonably discount the drop in air density with altitude and treat it as uniform when figuring out how much to extend the path--which means simply tripling the path length (plus a bit) should be a reasonable approximation. However, exactly how that path length scales depends on exactly how deep you choose to approximate the atmosphere as being. 90% of the mass of the atmosphere is below 16km, so if we use 20km as an approximation of the optical-equivalent atmospheric depth, fiddling around with WolframAlpha using the following equations for atmospheric path length $l = (d+r)\sin\theta$ $l = (d+r)\sqrt{1-\cos^2\theta}$ $l = (d+r)\sqrt{1-(\frac{r}{d+r})^2}$ where $d$ is the effective atmospheric depth and $r$ is the planet's radius, I get **57371 km** as the radius beyond which atmospheric attenuation would make the sun invisible just before it hits the horizon. Or, just under 9 times the radius of Earth, assuming all else (gravity, surface pressure, and atmospheric composition) is held equal. [Answer] You said, > > Normally we watch the sun descend, it's dimmed a bit by the atmosphere > before dropping below the horizon. > > > On earth, we watch this * in a plain desert, with no fog or clouds and the sun descends far away in the sand. * on a beach, with no fog or clouds and the sun descends far away in the water. The bright to dark duration is small and transition seems rather abrupt. Then you write the second scenario as: > > its dip below the horizon is unnoticeable. > > > On earth we watch this * in cities with tall buildings around. * in mountains with a lot of trees around. * when horizon is foggy. * when horizon is cloudy. You can choose any of above situations. **After the External edit, the new answer is as follows** Atmospheric extinction is the dimming of starlight by the terrestrial atmosphere. The path length through the atmosphere is known as the air mass. Air mass increases with zenith angle as shown in the figure below (taken from [here](https://www.quora.com/If-Earth-had-twice-the-amount-of-atmosphere-would-the-Moon-still-be-visible-in-the-daytime)). [![enter image description here](https://i.stack.imgur.com/m9GWu.png)](https://i.stack.imgur.com/m9GWu.png) There are three main sources of the extinction in the atmosphere. * The Rayleigh scattering of light * The ozone extinction * The aerosol extinction The atmospheric extinction will increase if * amount of atmosphere is increased. * thickness of ozone layer is increased. * scattering is increased. With sufficiently large coefficient of extinction, as the sun goes down, air mass will increase (see figure) and sun will gradually become invisible. [Answer] > > What I'm interested in is how big it would have to be so the atmospheric dimming is sufficient that the point it dips below the horizon is unnoticeable. > > > I'm afraid that size does not even enter the picture, and would not work anyway. What you want is a dimming difference between two **angles** the Sun makes with the horizon. When the apparent height of the sun varies little, we are *also* in a zone where the light path through the atmosphere varies almost linearly with the angle. So, you can't have an *abrupt* dimming. Also, if the dimming with respect to the zenith is complete when, say, the Sun's angle is 30° or less, this would restrict the day to a few hours (i.e., the Sun appears when it's at zenith minus 30°, disappears at zenith plus 30°; of a 360° day, only 60° - one sixth - are daylight. You get four hours of day and twenty of night.). Also, anything below the critical angle would be extinguished by atmospheric extinction, and so would appear... like a horizon. What you'd accomplish would be something similar to *raising the horizon*. **On the other hand**, a large megastructure might have several artificial Suns orbiting, or suspended, at a fixed height, and more directional to boot. *That* would get you closer to your goal, and also, the possibility of having several Suns going around the structure would compensate the "4h day and 20h night" effect. Slow down the Sun by a factor of 3, and get 12h day and 60h night. Add two more Suns equally spaced, and you get 12h day and 12h night. ]
[Question] [ I'm working on a tidally locked world. I would like to have some life in the dark side of the world. The sun heats all the air on one side of the planet and winds high in the atmosphere transport it to the dark side of the planet where the air cools, drops and reverses flow back to the hot side. That means you get very strong winds towards the sun side at/near the surface. Could plants use this wind energy by employing a wing or rotor like mechanism to harvest the wind to create mechanical energy and convert this to chemical energy and make glucose from that? Obviously a continuously spinning rotor might be impossible to create because no vascular connection is possible. I also thought that the rotor could spin for a couple of revolutions, thereby twisting its attachment point, then change geometry and using the attachment point like a spring to get back to the starting position. Or maybe a wing like structure, working in reverse to bird wings to extract energy rather than provide propulsion. But then how do you transform movement to chemical energy? Something like muscle tissue but working in reverse? Let me know if you have any ideas and how plausible this is. [Answer] Your plant equivalents could turn motion into electrical charge via **piezoelectricity**. <https://en.wikipedia.org/wiki/Piezoelectricity> > > Piezoelectricity is the electric charge that accumulates in certain > solid materials (such as crystals, certain ceramics, and biological > matter such as bone, DNA and various proteins in response to applied > mechanical stress. The word piezoelectricity means electricity > resulting from pressure and latent heat. It is derived from the Greek > πιέζειν piezein, which means to squeeze or press, and ἤλεκτρον > ēlektron, which means amber, an ancient source of electric charge. > > > <https://contest.techbriefs.com/2014/entries/sustainable-technologies/4092> [![piezoelectricity schematic](https://i.stack.imgur.com/zOdAm.jpg)](https://i.stack.imgur.com/zOdAm.jpg) Your wind plants would use piezoelectricity to concentrate charge in a small area. Ions then move into / out of that area in response to charge differential, and this movement can be harnessed to generate ATP. This is how chloroplasts work, using sunlight to split water and produce charge differential. [![chloroplast](https://i.stack.imgur.com/ksUTF.jpg)](https://i.stack.imgur.com/ksUTF.jpg) The trick will be to harness wind energy captured on a large scale (by flexing stems?) to produce charge and generate ATP. Mitochondria and chloroplasts are little but maybe the energy generating organs of these plants would be considerably larger. Given that many piezoelectric substances are crystalline, the energy organs of your dark wind plants might be jewels. ]
[Question] [ In a class discussion last week, someone pointed out that a typical core collapse supernova releases $\sim10^{46}\text{ J}$ of energy in the form of (anti-)neutrinos while only radiating $\sim10^{44}\text{ J}$ in the form of photons. This then means that the energy flux from neutrinos is about two orders of magnitude higher than the energy flux from photons. If you could find a way to capture that energy, you'd have . . . quite lot of energy. I'm considering this as a possible power generation mechanism in a world of mine. The problem is, you'd need to capture a lot of neutrinos, and that's not easy. From [SN 1987A](https://en.wikipedia.org/wiki/SN_1987A), in the Large Magellanic Cloud, [25 neutrinos were captured by several detectors out of a total of $\sim10^{58}$](http://adsabs.harvard.edu/abs/1989ARA&A..27..629A). Granted, we're about $1.5\times10^{5}$ light-years away, and so, with the same efficiency, we could capture perhaps $\sim5\times10^9$ neutrinos at a distance of $10$ light-years. But that wouldn't even get us $1\text{ J}$ of energy, assuming we captured all of the energy from each neutrino! Neutrino detection might be an implausible energy source, even given the high energies of supernovae. I currently don't think it's possible to wrest anything useful from it. However, I'd at least like to give it a shot before dismissing it. Therefore, I have one question: How efficient can a neutrino detector be? In other words, given a certain flux of neutrinos, what is the upper bound to the fraction that the detector could absorb? Some clarifications: * I'm not asking for a general plausibility study, nor am I asking how close a detector could be to such a supernova. I just want to know about efficiency. * I'd like to use a [Cherenkov-style detector](https://en.wikipedia.org/wiki/Cherenkov_radiation), along the lines of [Super-Kamiokande](https://en.wikipedia.org/wiki/Super-Kamiokande). However, if there's a much more efficient design, I'm open to hearing it. * I'll assume that the builders of such a detector are from several [Type II civilizations](https://en.wikipedia.org/wiki/Kardashev_scale#Type_II_civilization_methods), on the Kardashev scale. * Let's keep things pretty firmly grounded in science, please. I'd like to really, really minimize hand-waving. [Answer] Both the (current) answers to the question state that it is not possible for your idea to work. Aside from the fact that you are explicitly *not* asking for a feasibility study, [the obligatory XKCD reference](https://what-if.xkcd.com/73/) shows that it's all about the solid angle of the detector from the supernova and so, such a detector may indeed be feasible far into the future. In addition, this answer ignores a number of annoying details in the hope of getting a decent approximation to an answer relatively quickly and easily. It's not a [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'") question, after all! It turns out that, after making these various estimates and approximations, the efficiency/average energy collected per antineutrino incident on the detector from a supernova would be around $5.3\times 10^{-26}\,\text{J}$. # Background To start with, let's note the fundamental principles behind what's going on behind Cherenkov style neutrino detection: 1. **Cherenkov radiation**: Similar to a sonic boom, when a charged particle travels through a medium with refractive index $n$ and travels faster than the speed of light in that medium, $\frac{c}{n}$, (in the case of standard materials with $n>1$), it emits light, typically detected by *lots* of photomultiplier tubes. This is commonly observed in water, which has a refractive index of $n \approx \frac{4}{3}$ (for the purposes of this answer, [this is a good enough estimate for wavelengths of light $\lesssim 17.5\,\mu m$](https://refractiveindex.info/?shelf=main&book=H2O&page=Hale)). 2. **Detecting neutrinos**: Neutrinos are uncharged, so cannot cause Cherenkov radiation by themselves. As such, some sort of interaction needs to occur in order to get a charged particle that can in turn cause radiation. This is generally done by the [*weak interaction*](https://en.wikipedia.org/wiki/Weak_interaction). The most common example in a Cherenkov detector is an $\bar\nu\_e+ p \rightarrow n + e^+$. That is, an anti-neutrino converts a proton (Hydrogen) into a neutron and emits a positron in the process. The positron then emits Cherenkov radiation before getting absorbed by a similar process at some later point. 3. **Detecting/using the emitted photons**: Once generated, a photon has to be able to go from the point of generation to the point of detection. Of course, photons can also interact with and get lost in the surrounding environment. This is described by the *transmittance*, $T$, of light through the material, which is (in terms of the attenuation coefficient, $\alpha$, over a distance $d$) $T = e^{-\alpha d}$. For light with an initial intensity $I\_0$, the final intensity is then $I\_0T$, which can then be detected. However, there are some **Issues with the Standard Model** of particle physics: (all of these will be ignored as the definite model for how these are actually fixed is obviously unknown, but are here for completion) * It doesn't account for gravity (any effects of this on neutrinos are, to my knowledge, unknown). As this has effects on large energy collisions, which could occur in supernovae, this may have en effect on the production of neutrinos and antineutrinos. * The Standard Model predicts that neutrinos are massless, yet the [2015 Nobel Prize was awarded for experimentally showing that neutrinos do in fact have mass](https://www.nobelprize.org/nobel_prizes/physics/laureates/2015/) This would have an effect on the scattering cross-section of neutrinos but as we don't yet know what the correct model is1, this can't really be accounted for here. * Recent particle physics experiments at e.g. CERN have [begun to indicate physics beyond the standard model](https://link.springer.com/article/10.1007%2FJHEP02%282016%29104) (**note:** this is *not* conclusive evidence by some margin, but *is* a good indication). It [isn't impossible that this would have an effect on neutrinos](https://journals.aps.org/prd/abstract/10.1103/PhysRevD.93.013015). # Calculating the Efficiency ## Cross section of the Interaction the [cross section](https://en.wikipedia.org/wiki/Cross_section_(physics)) for the relevant type of neutrino scattering is2 $$\sigma = \frac{4G^2\_FM\_W^2E\_{e^{+}}^2}{\pi\left(M\_W^2 + 4E\_{e^{+}}^2\right)},$$ where (in [natural units](https://en.wikipedia.org/wiki/Natural_units)) the Fermi constant, $G\_F \approx 1.16\times 10^{-5}\,\text{GeV}^{-2}$ and the mass of the weak boson, $M\_W \approx 80.4\, \text{GeV}$. ## Generating Cherenkov Radiation As mentioned above, any created positrons need to travel with a velocity $v \gtrsim\frac{3c}{4}$, or, have an energy $$E\_{e^+} = \gamma\_v m\_{e^+}c^2 \gtrsim \frac{4m\_{e^+}c^2}{\sqrt{7}}$$ to emit Cherenkov radiation. The total energy of radiation emitted will then be assumed to be $$E\_{\text{emit}} = E\_{e^+} - \frac{4m\_{e^+}c^2}{\sqrt{7}}.$$ That is, the probability of any positron interacting with anything else in the time taken to emit the radiation is assumed to be negligible. ## Boosting Frames What is the energy of the created positrons? According to [Hans-Thomas Janka](https://arxiv.org/pdf/1702.08713.pdf), antineutrinos are created with an energy of around $14-16.5\,\text{MeV}$ for about half a second in a supernova. However, the energy used in the above cross section isn't this energy, but the energy in the zero momentum frame, which can be increased or decreased relative to the supernova by boosting the detector. The issue with this is that performing any boost on a detector is just going to cost energy and so, will defeat the purpose of using the detector to generate energy ## Reaction Rate For a flux of neutrinos $\Phi\_0$ incident on the detector and number density of protons $N\_p$, the rate of reactions can then be taken to be 3 $$R = N\_p\sigma\Phi \implies \Phi = \Phi\_0e^{-N\_p\sigma z},$$ as in the case of transmitting photons. Each molecule then has 10 protons and using [Very-high-density amorphous ice](http://pubs.rsc.org/en/Content/ArticleLanding/2001/CP/b108676f#!divAbstract) with a density of $1.25\,\text{g}\,\text{cm}^{-3}$ gives $N\_p = 10\cdot \frac{1.25}{m\_{\text{water}}}$ protons per cubic centimetre. One water molecule is approximately $2.99\times 10^{-23}\,\text{g}$, so the number of protons per cubic centimetre is approximately $4.18\times 10^{23}$. ## Efficiency Assuming a stationary detector, the positron energy is assumed to be around $0.015\,\text{GeV}$, giving a cross section of $\sigma \approx 1.518\times 10^6\,\text{J}^{-2} \approx 1.518\times 10^{-45}\,\text{m}^2$. This gives the number of neutrino interactions having occurred after a distance $z$ metres as approximately $\Phi\_0\left(1 - e^{-6.35z\times 10^{-16}}\right)$, with each of these interactions emitting about $0.0142\,\text{GeV}$, $e^{\frac{-\alpha z}{2}}$ of which is assumed to be transmitted on average. Conveniently, the absorption coefficient of blue light is low, at around $0.02\,\text{m}^{-1}$. Or, per unit metre of area of detector, the energy collected is $$E \sim \Phi\_0\left(1 - e^{-6.35z\times 10^{-16}}\right)\cdot e^{-0.01 z}\cdot 0.0142\,\text{GeV}.$$ [![Plot of efficiency of detector in stationary frame in GeV. Vertical axis shows average energy in GeV obtained per antineutrino. Horizontal axis shows depth ($z$) of detector](https://i.stack.imgur.com/9wivT.png)](https://i.stack.imgur.com/9wivT.png)Plot of efficiency of detector in stationary frame in GeV. Vertical axis shows average energy in GeV obtained per antineutrino. Horizontal axis shows depth ($z$) of detector Plotting this gives a maximum of $$E\_{\text{max}} \sim 3.3\Phi\_0\times 10^{-16}\,\text{GeV} \approx 5.3\Phi\_0\times10^{-26}\,\text{J}$$ with a detector with a depth of $100\,\text{m}$. If it were somehow possible to collect all $10^{58}$ neutrinos, this would indeed give a very impressive amount of energy of up to $\sim 10^{32}\,\text{J}$! It should be noted that this is due to the insane amount of energy produced by a supernova as the efficiency is... Somewhat pathetic. --- 1 It's generally thought that neutrinos are either [Dirac neutrinos](https://en.wikipedia.org/wiki/Dirac_fermion) or [Majorana neutrinos](https://en.wikipedia.org/wiki/Majorana_fermion) 2 given in terms of the energy of the positron as that's both what's experimentally measured and calculating the energy of neutrinos generated by a supernova isn't exactly trivial. Also, this is just proton to neutron scattering, so ignores details such as water being a molecule, which might make a difference 3 This is perhaps a bit of an assumption as perhaps there is a possibility that interactions with certain protons in the water molecule may cause e.g. an interaction with an emitted positron and a bound electron. On the other hand, this would just create *more* energy 4 This is just a hack as the actual transmittance depends on (as well as the distance in the detector) the direction the positron is emitted, which is a random angle in the zero momentum frame, the details of which depend on the (unknown) neutrino mass [Answer] A useful fairly easy to understand reference on neutrino interactions is found here: <http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/neutrino3.html> From the above source: [![enter image description here](https://i.stack.imgur.com/IlR5b.gif)](https://i.stack.imgur.com/IlR5b.gif) This gives us a means of estimating possible neutrino absorptions and identifies some areas we can tweak to improve performance. ## Flux We can't really control the flux of neutrinos, other than placing our detectors inside operating fission reactors which produce anti-neutrinos, but potentially advanced civilizations could place their detectors closer to the sources (adjacent to supernova) or potentially use gravity lensing to increase the number of neutrinos passing through their detectors, but it seems likely these extreme means could be used more wisely for other power generation methods. ## Neutrino Cross Section This is a function of the energy level of the neutrino not much we can change here and sadly this is where we get really screwed, the values are on the order of 10^-45 an exceedingly small number reflecting the very unlikely possibility of a neutrino interacting with anything. ## Density of Nucleons This we can effect, making your target more dense will increase the likelihood of interaction, unfortunately it is not going to have a huge effect. For water we have 1000kg/m^3, that 1000 kg is going to be 1x10^6 / 18 (the molar mass of water) = ~55,555 moles of water or 55,555 x 6.023\*10^23 (that big number helps a little) = 3.3 x 10^28 molecules x 18 nucleons per molecule gives us 6 x 10^29 nucleons / m^3 for water, that's a big number it should help right, but no we are still 16 orders of magnitude short compared to our 10^-45 (for fun compare 10^-16 to 10^-9 or 1 in a trillion, really bad odds) For fun let's express that as a percentage 1 m^3 of water will absorb ~0.000000000000001% of the neutrinos passing through it! We can do better than water, lead is about 11x denser than water, but that one order of magnitude is still up against that 10^-45 number not going to affect it much (are you sensing a pattern yet). We could theoretically push it up a few more notches as a Type II civilization and go for degenerate neutron star matter or otherwise insanely dense material, estimates for neutron star dense matter are on the order of 10,000 kg/cc or ~10^7 x greater than water, which does push us up to the 1 in a trillion chance. ## Volume of Detector Again here we can make improvements, make the detector bigger! Unfortunately for comparison sake a light year is ~10^15 m (remember 10^-45!!) so even light year sized detectors are not likely to absorb much more than a fraction of any neutrinos passing through it. The anecdote of a light year of lead stopping half the neutrinos is actually being generous, it would really only stop about 10-15%. ## Summary So you could absorb most neutrinos with an absorber of neutron star material density a million km thick, which is probably a nontrivial enterprise for even a type II or III civilization. For anything less you are not going to absorb very many neutrinos, and definitely not enough to make any usable power (the power density numbers are astoundingly worse than terrible). When compared to other sources, you'd be better of extracting power with the photons of distant stars. [Answer] > > How efficient can a neutrino detector be? In other words, given a certain flux of neutrinos, what is the upper bound to the fraction that the detector could absorb? > > > Oh boy...... So to start on this it should first be made clear what the largest factors are in determining this fraction. The first statistic: > > ∼10 46 J ∼1046 J of energy in the form of (anti-)neutrinos > > > does not represent the amount of neutrinos received by Earth but is the amount of Neutrinos emitted by the source spherically outwards. **Thus the first largest factor is the distance between the source and the detector.** As this limits the total possible neutrinos a detector can receive. **The next obvious factor is the cross section surface area of the detector with respect to the emission source.** As this also impacts how many neutrinos can possibly be collected. Now the way most these detectors work is by the simple fact that **IF** a neutrino collides with a hydrogen atom it releases an electron which can be sensed with a sensor. This is why most neutrino arrays are surrounded by water containing electron sensing sensors. Even then this is dependent on the energy of the neutrino with low energy neutrinos being harder to detect with plenty passing through the Earth every day. So the question of: > > How efficient can a neutrino detector be? > > > **Is essentially impossible to determine as it is dependent on the source, energy of the neutrino, and scale and sophistication of the detector.** As for the root objective of this being about energy production that is even more absurd as the electric output from these interactions is so rare and miniscule that often the hardest part in building these arrays is finding big enough and isolated locations that the external environment isn't releasing electrons that would contaminate the data. This is why they cant be built in the ocean with moving sea water against metal sources or lightning strikes. ]
[Question] [ Many species of amphibians, fish, arthropods and even certain reptiles go through metamorphosis. But, to my knowledge, there are no mammals that go through metamorphosis. Let's say I want there to be a mammal species that goes through a metamorphosis. During this metamorphosis they would start and finish puberty, hit their major growth spurt and grow 1.5-2.5 times their size. What I'm asking is: could a metamorphosis of this scale work? If it couldn't, why not and how could I make it work? [Answer] **Sure, it can work.** You're creating a new type of creature. As you say, they "are a mix of mammals and arthropods with some features of birds". Metamorphosis is low on the list of things I'd have a hard time believing after encountering such a creature. There are several mechanisms you can use to get there, for a large creature it seems the most likely they would undergo [incomplete metamorphosis](https://en.wikipedia.org/wiki/Hemimetabolism) triggered with [hormonal control](https://en.wikipedia.org/wiki/Metamorphosis#Hormonal_control). This allows them to become several times larger without needing to build and enter any kind of [chrysalis](https://en.wikipedia.org/wiki/Pupa#Chrysalis). [Answer] The changes humans go through in puberty, from a more or less uniform body plan for both sexes to a differentiation in body size, strength, hair growth and behavior is not as extreme as caterpillar to butterfly, but is quite a change. You could take that as a model to build a more elaborate change in body plan for your mammal. [Answer] Inside the pupa and caterpillar are "imaginal discs" that are basically incomplete wings and other adult parts. Your mamallian creature would fatten itself up to gather the energy needed for the transformation. This can also work when preparing for winter as the pupa is completely still anyway and can hibernate, sometimes finishing its metamorphosis a year later. Now mammals don't molt like insects, so instead have them form thick layers of skin like a rhino. There are also amphibians that go through metamorphosis, although not as drastic as the butterfly or moth. It simply sort of happens overtime. Nothing special to see there. [Answer] I had a similar post, Metamorphosis Lycanthropy. All rapid development changes are technically a metamorphosis. But if you want a caterpillar-like metamorphosis for a mammal, I would have the mammal create a large shell or protective barrier, eat a lot for the calories/fat then go inside and morph however it does. The food is for energy/fat. Caterpillars will keep gorging in till it is time to go into the cocoon. If you don't want a chrysalis, they could just grow a lot in a short amount of time and have lots of physical/mental changes to them. It's really up to you. For info on catapillar metamorphosis you can see: <https://www.scientificamerican.com/article/caterpillar-butterfly-metamorphosis-explainer/>. [Answer] Humans go through Metamorphosis, it is puberty. If it is change in body or form, then it is Metamorphosis. But in humans, I'd say it is a very small amount of Metamorphosis. It is child to adult. Teenage years is cocoon stage. ]
[Question] [ There are theories of ancient cultures which might have been visited by aliens. Most of them have been proven wrong but the I like the idea and want to set up such a culture which has been visited. **Background:** There are many ancient buildings of civilizations which suggests a knowledge about stars that they, as far es we know, weren't able to gather themselves. **Examples:** **[Stonehenge](http://en.wikipedia.org/wiki/Stonehenge)**, one of the oldest man-made structures at all and a very accurate observatory. The Stonehenge shows formations in the sky which we can not see with bare eyes. How where they able to build this, if they couldn't see what it's pointing to? Maybe by accident, maybe by supervision of a species which could. **[Nasca-Lines](http://en.wikipedia.org/wiki/Nazca_Lines)** Giant paintings on the desert which one cannot see from the ground or hills, only from the Sky (Planes, ...). In the end the theory of pre-astronautic is a wild one with very view references but many speculations. **The scenario:** The Setting is ~ 8 000 b.C. on a fictional area of the earth. The people of this folk are ~ 10 tribes of 100-500 people each which have merged a view generations ago due social improvement, no war, epidemic or something, it's peaceful. My culture just handled to make fire very hot (~800°C) and noticed that some of these stones "melt" and can be formed then, so they are about to learn how to make tools and weapons of metal. Their religion is some kind of shamanic. There are shamans which know much about stars, herbs and illness. When children mature, ~ 12-14yrs, a Shaman leads them through a psychedelic ritual and they're very connected to some kind of metaworld. At one day some hunters found a strange 'thing' in the woods (which is a rescue capsule from a spaceship). Due the people live in peace, have a good connection to their "metaworld" and did not suffer from illness for hundreds of years, they have no fear.When they inspect the capsule, they notice 3 strange beings inside which seems to be dead or unconscious, the hunters bring them to their hunting-camp. As the aliens receive the warmth of a campfire they begin to wake up. **The scenario from alien perspective:** The aliens are tourists which wanted to visit foreign galaxies. While watching this primitive culture of earthlings they got raided. The 3 aliens where part of a large group, but don't know what happened to the others. No communication possible. For them this is a life threatening situation now. They will slowly notice that they have stranded on this planet (The capsule is not able to leave earths gravitation) The aliens don't know each other, just got in the same capsule while evacuation. The capsule contains devices that can produce food out of any C O molecules, so they will not starve. **The question** Assuming that the aliens have different characters, are not able to build a spaceship or interstellar communication device, they are forced to stay and die on earth. Assuming this facts: * The aliens do not bring diseases and are very healthy * The people are very liberal. They accept 'things' which they don't know, as long as it doesn't harm them directly. * These days are glory days for the culture due they make (for their knowledge) giant steps in technologies. * Some of the elder are overwhelmed already, but they accept that. They know that they can't learn as fast as the younger ones, but don't try to slower the improvements. * The leadership of the culture are 3 people which are voted by the one person of every sub tribe. How the sub tribe chose this person is not declared and different from sub tribe to sub tribe. * The culture has no big enemies and life's very peaceful. * The aliens have different mindsets, their mind works in a very similar way as like the human mind. Let's say one is a ignorant and brutal guy who would sell his grandma for his advantage. The other ones are peaceful in general but would take every step to keep themselves alive. * The humans are curious and have no fear at all, maybe they should have a little due the fact that one alien is a \*\*\*\*\*\*. * The humans have merged but still don't think of themselves as a unit. * The aliens are not able to replicate or reproduce. **More specific question:** Are there examples in human history where a bunch of people from a (very)advanced civilization were stranded in a similar environment and how have they changed the less advanced culture? If not, what do you think could happen after that event? [Answer] To answer one of your questions, have look on [Cargo Cult](http://en.wikipedia.org/wiki/Cargo_cult) where soldiers of 2nd World War used some remote island as their base and basically were considered as Gods, because * They could start magically fire out of "nothing" (lighter) * They always had food, without need of hunting (food cans) * They could fly!!! * They could communicate on very far distances ... without shouting! Who else than God can do it? So, it is practical to assume that in this setup the aliens would be considered as Gods, or God-like persons and whole mythology would be created around their god-like powers (simple firearm would be "magical" enough to create wow factor) And from Aztec we know about very cruel Gods who demanded really cruel sacrifices, so even having among aliens some real bad ass should not stop the tribes from worshiping the aliens and [keep info about them for further generations](http://en.wikipedia.org/wiki/Bradshaw_rock_paintings) [Answer] A good deal of the question strikes me as unanswerable, in the sense that there simply isn't any way to surmise, from the given information, how either side will interpret the other. We can say with enormous confidence that there *must* have been instances of such stranding or abandonment, all things considered, but that doesn't really help us much with the question. The best one can do, I think, is to recognize the range of possibilities. First of all, the two sides' responses have little to do with one another, at least initially. So let's take them separately. **The Aliens** The crucial issue here is what these people think of less technologically-advanced people in general, and what they think of non-"us" lifeforms. If they're modern Western humans, for instance, they'll likely figure that the natives are stupid, easily deceived and overawed, and basically animals anyway. But on the other hand these aliens might be aware that there is no strong correlation between technology and other kinds of cultural development, that people who don't look like "us" might be even more intelligent, and so forth. With such a small sample of the population, there's no way to guess in general terms; it sounds as though you, as author, want to deal with these aliens as individual personalities anyway. **The Tribe** Now here we can at least draw from ethnology. Based on the complexity and back-story you describe, the population size you propose is ludicrously small -- multiply the total population by at least 10. What else? "Peaceful": does this mean people don't kill each other on a regular basis, or that there aren't any threatening foreign tribes around, or what? Assuming the former, why not? People do have bad habits, after all. What happens when people do murder one another... say, domestic violence, hot blood, etc. Who deals with this? Who administers the legal system? If the ultimate outcome is *not* execution (and it may very well not be), what do these people consider a more appropriate way of dealing with violence? The crucial point is this: *they understand their way of doing things to be one that privileges peaceful over violent methods*. "10 Tribes": you say that at some time in the past, 10 peoples bonded together for social stability or something of the kind. A simple way to handle this is to suppose that there are still 10 super-clans predominant, probably divided into two or four moieties. Assuming these people are exogamous, this ensures that the clans (formerly tribes) exchange people and goods with one another constantly, and binds them together in a relationship of perpetual mutual support. Bear in mind that if this joining happened more than 3-4 generations in the past, chances are all we really know is that they *say* 10 tribes joined; for all we really know, they actually split up a large homogeneous mass. It doesn't make any difference, except for this point: *they consider it important that they are a collaboration of multiple peoples*. That is remarkable, and bears strongly on the question at hand. One could go on, but already we begin to sense a pattern. The tribe, on confronting the aliens, probably assumes as a starting-point that the appropriate behaviors are peaceful and move toward mutual collaboration. They likely defer the initial conversations to certain elders designated to deal with the foreign. Based on your proposal of a shamanic religious complex, senior shamans may well be important to such a mission, as the whole point of shamans is to deal with that-which-is-beyond, as it were. (Incidentally, if everyone gets initiated come puberty, you're looking at something so radically unlike any form of shamanism known as to be deep into alien territory. Shamans bridge between Us and The Other because they're chosen by The Other and transformed -- usually painfully -- into half-beings, to put it simplistically.) The next questions are entirely points of plot, as I see it. Your aliens will take one or more approaches, and the natives will be somewhat surprised. Assume that any responses are slow, careful, and measured, but that the natives will also make very dramatic moves that can seem utterly surprising to the aliens (who after all don't understand the underpinnings of the systems at stake). Anything is perfectly possible here. **A Just-So Story** Let's suppose, to take an all-too-common boring trope, that the natives inform the aliens that they (the aliens) must be the gods come down to earth. Your reader now thinks, "aha, the natives are stupid, and they see the alien technology, and so, blah blah, Clarke's Third Law, etc." Not at all. Perhaps "the gods" includes a specific sub-group, well-established, that could in a sense match the little group of aliens (one nasty, one female, one tall, one with no hair, whatever). After much discussion, perhaps the elder shamans have concluded that the aliens are one of the following: * Those gods * Strange-looking people like us * Monsters Since the aliens appear not to have a clue about how decent people behave (they don't eat nicely, and they smell funny, and the men don't wear proper gear around their crotches, etc.), it seems unfair to assume they're people like us. If they were, they'd be savage barbarian criminals. And since the aliens haven't done anything really awful, let's be polite and assume they're not monsters. OK, so they're the gods. Thing is, this means that the aliens have to behave by the (rather less restrictive) guidelines appropriate to those gods. Gods, after all, do have a tendency to act rather oddly, and this is interesting to us, which is one reason we don't mind the gods showing up and being a pain now and then. So, fair enough. But when the aliens, thinking, "hey, I'm a god, I can do what I want," do something that contravenes the rules on gods, what then? Well, now they're either barbarians or monsters, and it may well be a principally political battle as to which interpretation holds (e.g., the chief wants them to be barbarians dealt with under a civil-legal code, his territory, and the shamans want them to be monsters dealt with under a cultic code, their territory). Could be that either way the result is an attempt to kill the aliens, but it'll matter to the natives. The point of this little just-so story isn't that you have to accept such a plot twist in any way. It's to set up an alternative to the much-belabored and basically racist notion of the savages who think the aliens must be gods because of guns. ]
[Question] [ Assuming a civilization has the technology and capability to build a worldship, a planet that doubles as a spacecraft, installs an FTL drive on it and has the energy to power it, what would the effects be, on the object and it's inhabitants, of traveling at speeds faster than light? There are two cases that I'm interested in: 1. They use an [Alcubierre Drive](http://en.wikipedia.org/wiki/Alcubierre_drive) and modern relativity applies. 2. They use a non-gravitational form of propulsion (like a rocket engine) and relativistic effects do not apply — in essence, a universe where Newtonian gravity (or modified Newtonian gravity) is a precise description of gravitational effects. I am *not* interested in how it is achieved — assume the planet remains spherical and doesn't have the drive protruding out its back. What would happen to the planet structurally, atmospherically, its surface and inhabitants? [Answer] Most FTL travel basically has the planet remain stationary in a bubble of space and then moves that bubble at FTL speeds through real space. In this case the effects on the planet would be the same as for any other spacecraft - whatever the effects of the drive might be. The main additional consequence though is that you have moved away from your star. Gravity would keep your atmosphere in place but you would have immediate night that never ends. Temperatures would start dropping quite fast and keep dropping, I've not done the maths but I expect the surface would start freezing within weeks although it would take time for the freeze to spread and geothermal activity would slow it in some places. You also need to consider two more things, the first is the effect on the system the planet is removed from. Orbits could well be distorted or changed. For example depending on where it was in its cycle around us our Moon could well swing away from it's current orbit and go rogue were the Earth to disappear. The second is the inertia of the planet. You put it into FTL with a certain velocity. When it emerges from FTL then does it keep that same velocity? If not what happens to it? You will somehow need to synchronize the velocity of the planet with a suitable orbital velocity for its new position. One way around this might be to use the FTL drive to place you in a suitable place next to a gas giant and let the giant's gravity accelerate you. By pulsing the FTL drive to remain in the right place you could achieve a constant acceleration until the required velocity is achieved. As a side note this could potentially be weaponized. It was suggested in E.E. Doc Smith's Lensman series that they could find two planets that at some point in their orbit had opposed directions. They attached FTL drives to both planets and then moved them into positions each side of the target and turned off the FTL drives at the same time, causing the two moved planets to pancake the target's planet between them, overwhelming all that planets defense systems completely. ]
[Question] [ If you want to have a smaller star but you also want to keep your planet in the habitable zone, you need to put the planet closer to the star. This means shorter years. It is also possible to have a larger star and a longer year. Specifications: The planet is not tidal locked to the star. To have any significance, keep in mind that the years would need to be at least twice as long or half a normal year on Earth. The length of a day would be the same as on Earth. **Edit: the axial tilt of the planet is exactly the same as Earth and stable at 23,5°** [Answer] There is one massive difference this will make - the duration of the seasons. A longer year would give you extremely long (but potentially dry and drought-prone) summers followed by equally long winters. This means that storage of food would be a priority in seasonal areas of the world (the equator would not be effected either way). So the summer would be an extremely long growing period while people stocked up to survive months or even (earth) years of winter. Animals may well hibernate or just lay eggs/spores/whatever that then emerge when spring comes. A lot of plants may well follow the same strategy of leaving seeds and not even trying to survive the winter. [Answer] I'm actually going to consider how such a year would affect animals, because I have a feeling nobody else is planning on addressing it. This should be short and to the point, unlike some of my other answers. Many animals have a "mating season" - i.e. a period each year where they mate. This can manifest itself in brilliant displays of plumage, or head-butting confrontations between some males. For many species, the mating season only comes once a year, and so each female only gives birth to a small number of offspring. Now, if the year was longer, and there was still only one mating season per year, each female (and therefore each male) would produce only half as many offspring throughout their lives as they would otherwise. If the year was shorter, each female (and therefore each male) would produce twice as many offspring throughout their lives as they would otherwise. Thus, population growth could be affected by a change in the length of a year. *Note: This assumes gestation period remains the same, which may not be the case.* [Answer] As far as I know, the length of the day is more important than than the length of the year. It *may* have an effect on how long seasons last, but assuming they last at least a month or so, I don't think there would be changes that drastic (*seasons heavily depend on axial tilt, so that also has to be taken into account - if the tilt is like Earths, they'd probably last a bit less than ours*). If all else is the same, climates would be distributed the same and you could just move to a more friendly one. The ecosystems would adapt, possibly with biomes being a bit smaller to cut distances, but they should be fine overall. A larger factor would be how much the year length varies - if there is a *lot* of variance (as in, one year lasting 4 times as long as the previous for instance), there would probably be a much higher influence, but it would be because ecosystems would have difficulty managing their cycle. Overall, the differences should be minor, if they exist at all (assuming all else is the same). ]
[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I´m working on a computer program which generates realistic planets for worldbuilding purposes. I´ve run into an issue with calculating my planets heat loss. While radiogenic and tidal heat generation and loss were easy enough to pin down, calculating primordial heat seems way harder. On Earth, we currently lose [12 - 30 TW of primordial heat](https://en.wikipedia.org/wiki/Earth%27s_internal_heat_budget). Jupiter on the other hand is even today 40 K hotter than it should be due to its primordial heat. **What I'm looking for is a reasonably accurate formula giving me the current heat loss in TW for a given age and mass of the planet.** Assume that a planet is simply a pure rocky sphere without an atmosphere. If it isn't too complicated the modification of the formula for a water or pure hydrogen sphere would be nice. [Answer] Like most things in science, the answer to "how do I model x" is "it depends how accurate you want to be." The simplest thing would be to pick some number for what you think the surface temperature of the planet should be, and then use the [Stefan-Boltzmann law](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law) to find out how much the surface radiates. Of course, the problem is that we likely don't know the planet's surface temperature. If you want your model to only be for soon after the planet forms, we can do pretty well by assuming the planet is a sphere of uniform temperature caused by all of the [gravitational binding energy](https://en.wikipedia.org/wiki/Gravitational_binding_energy). If it supposed to apply for a time long after the formation of the planet, looking at surface temperatures for other planets in our solar system for inspiration might be a good starting point. However, you have to keep in mind that you'll probably want to look at temps for the dark side of the planet, because trying to solve this for planets where one side is in the sun makes it significantly harder as the symmetry of the problem is destroyed. So, for the rest of the answer I'm going to assume the planet in question is far enough away from its star that there isn't such more light coming from the direction of it's star than there is from any other direction in space. What follows is a more accurate, but much more complicated model. Be warned: this is a fairly sophisticated mathematical problem and requires mathematical experience up to at least partial differential equations. I'm not sure what your mathematical experience is, so if you expand on that in the comments I can add a section more tailored to you. With that out of the way, I think L.Dutch has an answer that's on the right track-- this is just attempting to flesh it out a bit more. First off, to model how the heat moves through Earth, we use the [heat equation](https://en.wikipedia.org/wiki/Heat_equation): $$\frac{\partial u}{\partial t} = \alpha \nabla^2u + \frac{q}{c\_p \rho}$$ where $u$ is the heat density, $c\_p$ the specific heat capacity, $\rho$ the density, and q is the heat generated\lost in the material due to outside sources. Note that the temperature is related to these quantities by $T=\frac{u}{c\_p \rho}$. Now, technically this is all you need, along with some boundary values. In practice, it might be unclear what some of these values should correspond to, so I'll walk through that. First, it will help simplify stuff if we assume spherical symmetry. This isn't a requirement, and if we want to model a planet close to it's star or be super duper accurate we can't do it. But, since we assumed it wasn't, and since this is already complicated enough, this allows us to make the substitution $$\nabla^2 \rightarrow \frac{1}{r^2}\frac{\partial}{\partial r}(r^2 \frac{\partial}{\partial r})$$ and the assumption that $u = u(r, t)$ (ie there is no $\theta$ or $\phi$ dependence). Now, to avoid boundary condition problems, we will make the spatial domain of our problem all of $\mathbb{R}^3$. But since this means the problem includes space, which can't conduct heat, we must make sure that $\alpha(r)=0$ when $r$ is greater than the radius of our planet. Next, we have to determine the form for $q$. This will either make complete sense or none at all and require a ton of explanation, so I'll just leave the result which is that $$q=-4\pi R\_p^2 \sigma \epsilon (\frac{u}{c\_p \rho})^4\delta(r-R\_p) + \mathbf{1}\_{r \in [0, R\_p]}D\_0r^2e^{-t/\lambda}$$ where the left term accounts for radiative cooling of the planet and the right for radioactive generation of heat within the planet as per L.Dutch's answer. All the variable names are the standard ones from the Stefan-Boltzmann law, $R\_p$ is the radius of the planet, and $\mathbf{1}$ is the indicator function. Finally all that's left is to specify boundary conditions, which should just specify $u(r,0)$ and that $u$ is bounded. The exact form of these will be that the temperature of space (ie $r>R\_p$) will be the temperature of the cosmic microwave background, and that inside it will be some distribution of the initial binding energy of the planet (uniform is easiest and probably pretty accurate). I think these conditions should be enough to solve the equation, but it's possible that the non-linear $u^4$ term messes stuff up and the equation is no longer parabolic, in which case I don't have enough math knowledge to help. After all that, you "simply" have to solve this monstrosity of an equation. A numerical solver is probably easiest, but you could attempt an analytical solution. Unfortunately, the non-linear $u^4$ term takes away the strongest tool in our arsenal (Green's functions) so I don't have any clue how you'd proceed, or if an analytical solution is even possible (it likely isn't). As one final note, I should say that I've made a few simplifying assumptions. Aside from the assumption of spherical symmetry, I've also implicitly assumed that there is only one radioactive species and that the density of rock is constant throughout the planet, among others. However, if you understand any of this and desire a more accurate approach, I should have hopefully given you enough to work with to extend it to a more accurate model. Like I said before, this is a pretty complicated problem so don't be worried if you don't understand this approach-- I just wanted to leave a record for how this could be solved in an accurate manner. My apologies if it is also rather terse-- I don't have time right now to add more explanations. If I have more time later, I might edit some in. [Answer] ## Heat is fungible. If a planet was once very hot, and has been radiating heat, and has been generating heat by nuclear fission, then the following are indistinguishable, and both somewhat misleading: * The planet is staying warm because as the primordial heat radiates away it's replaced by radiogenic heat. * The planet's primordial heat is being preserved while it radiates away radiogenic heat. ## Primordial heat is (almost) non-renewable. Basically the idea here is that [primordial heat comes from gravitational potential energy](https://link.springer.com/referenceworkentry/10.1007/978-3-642-11274-4_1274). To a first approximation, we could just use the [gravitational binding energy](https://en.wikipedia.org/wiki/Gravitational_binding_energy). The binding energy is usually defined as the energy required to rip an object apart, but in the case of gravity we can equivalently say that it's the energy released when the object clumps together. You may also need to account for the (small amount of) heat the materials had *prior* to clumping together, the non-uniform density of the planet, and how the average density and the "density curve" (out from the center) change over time. Celestial impacts and sustained meteor bombardments may also be thought of as adding "primordial" heat. ## How are you actually modeling this stuff? Specifically, the way you've worded the question suggests that you're accounting for heat *loss* on a *per-source basis*. If you have a good-enough model for heat loss (by approximately-black-body radiation for example), then use that for *all heat loss* as a single out-flow of energy. You'll have a few in-flows (which will not be evenly distributed through the body of the planet): nuclear fission, solar radiation, tidal friction, and "primordial". That said; for a rocky middle-age planet, no "primordial" energy will be generated at all. **So long as the planet isn't changing mass or size, and the distribution of mass within the planet isn't changing either, no gravitational potential energy is being converted into heat.** [Answer] The energy radiated per unit surface by a black body at surface temperature $T(t)$ at time t can be calculated by [Stefan-Boltzmann law](https://en.wikipedia.org/wiki/Black_body) $P(t)=\epsilon\sigma T^4(t)$ The temperature T depends by the amount of energy $H(t)$ stored in the planet, this being given by two components: the [gravitational binding energy](https://en.wikipedia.org/wiki/Gravitational_binding_energy) and the radioactive decay. For the **gravitational binding energy**: > > A gravitational binding energy is the minimum energy that must be added to a system for the system to cease being in a gravitationally bound state. A gravitationally bound system has a lower (i.e., more negative) gravitational potential energy than the sum of its parts—this is what keeps the system aggregated in accordance with the minimum total potential energy principle. > > > For a spherical mass of uniform density, the gravitational binding energy U is given by the formula $U=$$3GM^2 \over 5R$ where G is the gravitational constant, M is the mass of the sphere, and R is its radius > > > For the **radioactive decay**, assuming a decay constant $\lambda$ and an initial emission rate $D\_0$: $D(t)=D\_0e^{-t/\lambda}$ (if you have more than a single radioactive species, that becomes a summation over the various decay rates and initial concentrations) This so far allows you to estimate the amount of heat available in the mass of the planet. The main problem is, how to correlate the surface temperature to that amount of thermal energy still present below the surface. The empiric way to estimate it is to measure the thermal flow at different depths, and try to fit those points with some heat transfer relation (remember the Kola deep drill?). ]
[Question] [ [**Note:** this question was posted on [Sandbox]](https://worldbuilding.meta.stackexchange.com/a/5731/7974) What would be differently perceived from a person with broader visual spectrum than normal? So I've seen this [question](https://worldbuilding.stackexchange.com/questions/91230/how-would-it-affect-a-human-to-suddenly-have-the-visual-senses-of-a-martial-eagl), especially the accepted answer, and it certainly is not what I'm looking for. The question asks for a man with the eyes of martial eagle. The answer, likewise, considers the acuity of a martial eagle's eyes, or any predatory bird in general. Likewise, most answers account for increased fidelity of the image from those eyes. What I'm looking for is more specific on the effect it has to have a broader visual spectrum. In my scenario a particular person has a visible light spectrum of ~300nm to ~800nm, and is living his daily life among normal humans. How he acquires the ability is not important, and he has no difficulties dealing with processing the information, etc. This person lives in a normal human city at around 2000s, and does sometimes travel. Due to his acuity of vision happening to overlap with that of a normal person, he can easily distinguish normal human color, and also beyond. Therefore the scope of this question is what is normally invisible for humans, but visible from the perspective of this person in: * normal, daily urban life environment. Especially concerning day-to-day interactions * in a medical setting - the person in question is a doctor * in a forest * when observing stones or geographical formation normally found in tours through areas with a relatively active volcanic, for example [Ijen Crater](https://en.wikipedia.org/wiki/Ijen) Here's what I know and some that I don't so far. 1. [Near ultraviolet](https://en.wikipedia.org/wiki/Ultraviolet), that is on the spectrum of around 300nm-400nm is what is normally visible to birds, insects and fish. Some people with a condition known as *Aphakia* or missing lens, or those who possess artificial lenses can see in this spectrum, and they describe it as whitish blue or violet (I found it [here](https://en.wikipedia.org/wiki/Aphakia) and [there](https://en.wikipedia.org/wiki/Ultraviolet); [this](https://www.theguardian.com/science/2002/may/30/medicalscience.research) and [this](http://journals.sagepub.com/doi/10.2466/pms.1983.57.3f.1211) are a few of the cited sources). ***Still that's as far as I know.*** Perhaps the most interesting thought I have is that this person can probably see sunblock as a translucent layer over the skin of the wearer, instead of transparent as we see it, but I can't be sure. Also I know that some stones are fluorescent, but most sites (almost all I found) only describe them as minerals that absorb UV lights and emit visible light. I am not interested in this. What I'm interested in is what the stones would look like for this person. 2. [Near infrared](https://en.wikipedia.org/wiki/Infrared), that is on the spectrum of around 750nm-1400nm. But apparently normally used in [near infrared spectroscopy](https://en.wikipedia.org/wiki/Near-infrared_spectroscopy) is light on the range of 780nm-2500nm. Previously I expected him to be capable of full night vision, but apparently this is not the case. Still, I have no idea on whether or not he would fare better at night than a normal person, or, how much better he is. Also I once found it in the net that a fart is basically hot air, and probably visible at infrared, but I am not sure on what spectrum a fart would be visible. [Answer] I have aphakia, so I can address the near-UV end from personal experience. For the near-IR, I can only reason from other sources. In *daylight*, subtle effects like the patterns on flowers mentioned in another answer are completely dwarfed by the giant UV source in the sky. Somebody seeing into the near-UV sees sunlight as brighter than others do, to the point of being painful at times. On bright sunny days, or bright winter days with snow cover, I have to wear protective lenses and/or squint to block out a lot of the light. Near-UV vision is a negative in broad daylight. Near-UV shines, so to speak, in moonlight. Moonlight is just reflected sunlight, but [the full moon is only about 1/400,000 the brightness of the sun](https://en.wikipedia.org/wiki/Apparent_magnitude#Example:_Sun_and_Moon), so someone who sees into the near-UV can see by moonlight without it being painful. My personal experience is that moonlight makes everything brighter (compared to what I see through glasses) and whiter/bluer. I've never looked for, or noticed, flower patterns or vole urine trails, so I don't know if that's farther into the UV or bees' and predators' eyes are different in this regard. I would expect a human who can see into the near-UV without the loss of visual acuity that comes from aphakia to see well by moonlight, preferring moonlight to low levels of artificial light. (For example, when walking outside he'd probably prefer *not* to carry a small lantern.) Light-colored surfaces will be especially visible; he'll probably trip over dark obstacles the same as anybody else. At the other end of the spectrum, near-IR vision will see thermal signals, the hotter the brighter. This is the principle used by [night-vision](https://en.wikipedia.org/wiki/Infrared#Night_vision) devices that help military people see opponents. It's not so much an *optical* "seeing" like near-UV but, rather, heat made visible in near-IR. You'll see a person but not the details of what he's wearing, for instance. (Near-IR vision won't help you see stuff that's the same temperature as its surroundings.) I speculate that a very hot object could "blind" you in the way that bright sun "blinds" you in near-UV, and that near-IR vision will brighten things overall in daylight, particularly on a warm sunny day. Things like remote controls and IR-illumination LEDs built into security cameras operate in the IR spectrum, so somebody with near-IR vision should be able to see them at least in a dark room. I don't know whether they would be too faint to see in a bright room for someone seeing both normal and IR spectra. I was unable to find anything that addresses how near-IR vision would affect what you see in daylight. You're extending the range in both directions, so we need to consider how these two modifications would interact with each other. In bright daylight, as best I can tell, neither will confer an advantage and at least near-UV confers some disadvantage. (I think near-IR would confer a disadvantage too.) At night, you should be able to benefit from both; the reflection and fluorescence of near-UV is a completely different process from the thermal properties of near-IR. I was unable to find reliable information about how night-vision devices perform under full moonlight, which would give us some hint about whether they interfere with each other. People who see in the near-UV and near-IR spectra in addition to normal visible light will probably be super-sensitive to sunlight. I would expect them to either spend less time outdoors or wear eye protection akin to sunglasses or chemically-variable lenses. In darker settings and under moonlight, however, they'll do better than normal humans and wouldn't want any filters in the way. If your humans solve their sensitivity problem with special glasses, therefore, they'll need a way to turn it off. (Sure you can just take the glasses off, but that leaves you with something you need to carry around and protect. Photochromatic lenses appeal to people who don't want to carry around an extra pair of sunglasses; your people will have an analogous problem.) [Answer] Color is a *sensation*; it exists in the mind. It is *not a physical quantity*; it does not exist in nature. Measurements of color ([colorimetry](https://en.wikipedia.org/wiki/Colorimetry)) are made by necessity with respect to a "standard observer", that is, a human with no color perception deficiencies and average color perception. It *makes no sense* to compare color perception across species. So the only possible answer is that *"a person who can see light from 300nm to 800nm"* would be able to see *some objects in the dark*, and *some details in daylight*, which are not visible to ordinary people. Nothing more can be said. * For example, such a person could see quite well in a photographic darkroom. Darkrooms for working with black-and-white material are commonly illuminated with a deep red light, which appears very faint to ordinary human eyes (and is beyond the range of black-and-white photographic material). * For another example, many [flowers have patterns which are visible only in near-ultraviolet](https://www.howplantswork.com/2008/11/30/flowers-what-you-see-versus-what-the-bees-see/), thus visible to bees, yet appear to have uniform colors in the ordinary visual spectrum. ![Images of a *Mimulus* flower in visible light (left) and ultraviolet light (right) showing a dark *nectar guide* that is visible to bees but not to humans](https://upload.wikimedia.org/wikipedia/commons/6/6b/Mimulus_nectar_guide_UV_VIS.jpg) *Images of a* Mimulus *flower in visible light (left) and ultraviolet light (right) showing a dark nectar guide that is visible to bees but not to humans. Photograph by Plantsurfer [available on Wikimedia](https://commons.wikimedia.org/wiki/File:Mimulus_nectar_guide_UV_VIS.jpg) under the Creative Commons-Share Alike 2.0 license.* Normal visible spectrum covers about one octave, from about 380–390 nm to about 700–750 nm; the lower and upper bounds are fuzzy because the cut-off is not sharp, and in certain conditions light can be seen which wouldn't normally be sensed. So for daylight vision the proposed extension is quite small, about one third of an octave at the short-wavelenth end, and about one sixth of an octave at the long-wavelength end. Humans have *two* visual subsystems, one responsible for vision when there is plenty of light ("photopic" vision), and the other for vision when there is little light ("scotopic" vision); only one of them can be active at any given time. While the transition from scotopic vision to photopic vision is quite fast (a few seconds), the transition from photopic vision to scotopic vision takes several minutes. The [photopic](https://en.wikipedia.org/wiki/Photopic_vision) and [scotopic](https://en.wikipedia.org/wiki/Scotopic_vision) vision subsystems do not cover the same spectrum; in particular, the long-wavelength end for the scotopic visual spectrum is around 630 nm, so a person who can see 800 nm light *at night* would have a significant advantage. ]
[Question] [ This is about the same species as in e.g. [How can humans coexist with an intelligent carnivorous species?](https://worldbuilding.stackexchange.com/q/51585/29) The culture of this intelligent, carnivorous, primarily quadruped species, in a sense despite the species' intelligence, is one that also favors physical prowess. That prowess includes, but is absolutely not limited to, both endurance and physical strength. One of the ways they measure themselves against one another is in ritualized games, not entirely unlike an [ironman triathlon](https://en.wikipedia.org/wiki/Ironman_Triathlon) but including physical grappling matches as well as tests of endurance. These games are primarily to establish social standing but also to show off mating fitness. A common part of the grappling contests is to attempt to throw your opponent; this would be measured (I hesitate to say "judged" as it's not guaranteed that there would be a referee) both on how well (including how far) one is able to throw their opponent as well as how well the opponent recovers (landing on feet vs back? getting back up quickly vs remaining on the ground? etc). I have yet to decide on the exact rules, but to the extent that they may have bearing on answers, some general ones would be: * Both competitors are allowed to move about freely without artificial limits. That said, constantly running away from one's opponent is unlikely to be seen as a great display of physical prowess, especially considering that the grappling match isn't primarily a test of endurance. * Either competitor can choose freely at any time whether to attempt to grapple or try to avoid their opponent, and are free to take advantage of their opponent's actions in doing so. * Rough tactics are allowed, but not those that would cause permanent injuries (this is, after all, a ritual, as opposed to an actual fight, and it is among carnivores). So you might very well see one competitor grappling and throwing or pinning their opponent to the ground, but not clawing at their opponent's face. **Questions:** * Realistically, what would be required in terms of physical ability for a reasonably large (big cat size) mammal to lob another of their kind a significant distance (to have a ballpark figure to work with, let's say more than three body lengths' worth) through the air? * As a bonus question, what particular *evolutionary* (not technique) adaptations are likely to allow an individual to take such a treatment better or worse than another? In other words, if these competitions were somehow the sole selection criteria in mating, which traits would be selected for or against? [Answer] ## Throw? Throwing your opponent can mean a few different things: pick them up off the ground then throw them, knock them off balance then grapple on the ground or just body check them into submission. Depending on the body plan of the aliens in question, one of these three approaches will be the most useful. Determining which approach to take will depend on the vertical stability of the creature. Two legged creatures are better adapted to lift-and-throw while four legged creatures are more likely to use knock-over. Animals with essentially one huge leg (elephant seals for example) are more likely to use body checking. ## Lift and Throw This approach is unlikely for large (>human sized) mammals because lifting heavy things over your head is hard. Consider the following: * Overhead Press: At 198 lbs, an elite male lifter can press [235 lbs](http://www.exrx.net/Testing/WeightLifting/PressStandards.html). Also note that the 235 lbs in question is not a screaming, wriggling, highly motivated competitor. Lifting something over your head requires you to balance a heavy thing on essentially a long multi-jointed pole which is really hard. * Deadlift: This same 198 lb elite male lifter can deadlift [615 lbs](http://www.exrx.net/Testing/WeightLifting/DeadliftStandards.html). With sufficient grip strength, a wriggling competitor won't make much difference to being lifted. In the two legged fighting domain, the competition can be won by being the biggest but because of the instability of moving on two legs permits a smaller competitor to be sneaky and use improved technique to beat a larger opponent....[like this fight](https://www.youtube.com/watch?v=kL3VzjcptBI). There aren't many species on Earth that can lift something really heavy over their heads. I can't think of any that compete by lifting and throwing a body-weight comparable object from an overhead position. It's just too hard and too specialized. There are other ways to compete. Also consider that the more weight a structure (biological or mechanical) can lift, the more specialized it must be to that task. Cranes for skyscrapers can lift immense loads but they can't do anything else either. ## Knock-over and wrestle Throwing your opponent to the ground or unbalancing them is a common approach that usually leads to further grappling on the ground. Two legged and four legged creatures most often compete in this way. Human martial arts such as sumo, judo, karate, MMA, and others are examples of this kind of combat. The degree to which grappling happens on the ground will depend on the rules of the competition and the physical capabilities of the contenders. A four legged creature won't be throwing things over its head since it's body is oriented towards movement parallel to the ground plane. Nor will it be lifting its opponent off the ground. However, knocking an opponent off balance and into a disadvantageous position (grasp around the throat, choke hold, etc) will be the focus. Observe how tigers [fight each other](https://www.youtube.com/watch?v=caTqZh88jPQ). There's a brief series of blows attempting to off-balance the other tiger. Once the opponent has been knocked down, attempts are made to force submission. ## Bump and Grind For creatures that have essentially one big foot, a more likely approach will be body-checking, sumo style. In contrast to lift-and-throw, body-checking only requires the organism to accelerate quickly and survive an impact. Both characteristics are broadly applicable to general survival. Many ocean going mammals compete for social status and mates with this approach. As an example of bump-and-grind, ([bull elephant seals](https://en.wikipedia.org/wiki/Elephant_seal)) fight by smashing into each other. The [fights](https://www.youtube.com/watch?v=DU4xW79ASsg) are often bloody though rarely lethal. ## Conclusion The only body plan that would support lift and throw competition would be simian or humanoid body plans. Humans in particular since they already have a vertically oriented body plan. However, for bump-and-grind competition, the available body plans are far more diverse, including the OP's reference to large cats. [Answer] As has been pointed out, it's not a great idea to just pick someone up and chuck them over your head - it's much better to use momentum, both theirs and your own. In order for a reasonably sized mammals to do this, the best bet would probably to launch themselves at each other from a distance of, say, $1$m, for some explosive power into each other, such as [here](http://youtu.be/3CywJNlb8L8?t=1m40s), at which point each would try to turn (for increased angular momentum) and fling the other into the direction that it's already facing, requiring technique, timing (OK, this is just technique again) and a bit of strength (though maybe not as much as you'd think). While the linked video shows one of the tigers leap vertically, they would probably stay on the ground and 'ground' themselves to the Earth in order to change directions of momentum more efficiently. (also, 1m is small enough that if it doesn't work the first time, they can just keep going at each other) The point of this is that the 2 mammals move towards each other and connect, at which point the better fighter (the one that wins) transfers its momentum to the other by the process of turning its linear momentum into angular momentum and back into linear momentum of the other person - a bit like a bigger version of [this moment](https://youtu.be/d7zsNS1wgso?t=2m20s), only with more movement involved - note the way that the woman twists herself to the side in order to get that conversion of momentum in. If this was an actual fight, they would both grapple instead of throwing at this point for a short time, but that would negate the initial linear momentum of both of them, and the point isn't to fight, but to get the biggest throw. **Chucking in some maths:** You want the mammals to throw a distance of around $5$m (for ease of numbers), most the power of which would come from the initial 'leap towards each other' bit. Assuming this to be the case, using the standard [constant acceleration equations](http://hubpages.com/education/How-to-Derive-SUVAT-Mechanics-Equations) with final velocity $v = 0$ at the highest point, initial velocity $u$, acceleration $a = -g$ (due to gravity) and vertical displacement $s = 2.5 \tan\left(45\right) = 2.5$ when 'thrown' at an angle of 45 degrees; $v^2 = u^2 + 2as$ (in the vertical direction, immediately after impact of the mammals), the initial vertical velocity would be required to be $\sqrt{5g}$. For this to happen, the horizontal velocity would also be equal to this (due to being 'thrown' at an angle of 45 degrees). Assuming that the change of direction of momentum is 100% efficient (or extra strength could be used to help this) and ignoring friction, each mammal begins with a momentum of $mu = m\sqrt{5g}$ and a kinetic energy of $\frac{1}{2}mu^2 = \frac{5}{2}mg$ Joules, which is also half of what the looser ends up with, to conserve momentum and energy. In order to get to this speed over the distance of $s = 1$m, from the above equation with $u = 0$, $v = \sqrt{5g}$, you want an acceleration of $\frac{5}{2}g$ m$s^{-2}$, giving a force of $F = ma = \frac{5}{2}gm$ N, or being able to accelerate at about 7.5 times [Usain Bolt](https://www.wired.com/2012/08/maximum-acceleration-in-the-100-m-dash/). At a bit of a guess, evolutionary adaptions would be reasonably strong hind legs and something a bit similar to elbows in the front legs. On top of this, they would need to be able to survive impacts of $5mg$ Joules at wherever they land (probably either on the back or legs). **To be thrown an arbitrary distance, $d$**, you want an acceleration of $\frac{1}{2}gd$ m$s^{-2}$, or $\frac{3}{2}d$ times Usain Bolt's acceleration (for an acceleration due to gravity equal to that of Earth) [Answer] If you look at large, fast land mammals, their strongest muscles are usually in their hind legs. Just watch a house-cat grab something in their front paws, roll onto their back, and start rabbit-kicking it, and you can imagine how far they could launch something from that position with a full-extension leg-kick. If you really look closely at it, it would resemble a leg-toss from judo or aikido. In short, an animal that has a vertical leap many times greater than it's own height would be capable of launching a similar-sized animal quite far with it's own leg strength directed at that foe. There are also many forms and moves in martial arts that follow inspiration from the animal kingdom. This is probably the only time you could consider watching Kung-Fu Panda as valid research, since some of the forms are inspired by the capabilities of the animal performing the action. [Answer] I'll give it a shot but some of this may fall more into biology. Lets take a male lion as the example: Mass = $190kg$ , body length $=2m$ Ignoring a struggling body, air resistance or anything we get the energy required is: $$E=\frac{m (V\_{x}\cos(\pi/4))^{2}}{2}=\frac{m V\_{x}^{2}}{4} $$ Where $ V\_{x} = \frac{3 L\_{body}}{T}$, $T=\sqrt{\frac{6L\_{body}}{g\_{0}}}$ and sticking them all together gives us an energy of $\approx 1400 Joules$, it also requires throwing the opponent at least 1.5 metres above the ground. Comparing this to the [caber toss](http://www.science20.com/science_20/science_caber_tossing) it would seem ours is not an impossible feat. But it is important to note that in the caber toss both the arms and legs are used to provide the energy. Several things could make this easier for your creatures: * Being able to lift their opponent high in the air (more throwing force into horizontal travel rather than fighting gravity). * Strong legs with a wide stance to balance them. * A powerful and flexible back meaning they can start off leaning back and move forwards into the throw. * Elbows like ours. They would need to be able to add the extension of the arms into the throw to provide power from all areas of their body. I think those also fulfil the evolutionary traits that best adapt to this ability to throw. It ignores, however, being able to fight well enough to get your opponent in a position to be thrown. Though I would add that perhaps a smaller body would recover a little better from being thrown. [Answer] Being able to throw someone of equivalent mass as yourself implies having the energetic capacity to jump/throw yourself that same distance. The only difference between jumping and being thrown is just a matter of positioning, grip, and support. Your characters are throwing each other because they choose to do so (I hesitate to say "for intelligent reasons") but we can look at existing creatures for examples of biomechanical adaptations that allow animals to jump long distances for the principles required. Kangaroos, gazelles, and antelope, as well as smaller creatures like fleas, frogs, and grasshoppers, can jump long distances for 2 reasons: 1. They have large amounts of their musculature and body mass devoted to jumping. Your mammals will likely not be walking around like inverted triangle cartoon body builders on spindly, short legs, and throwing each other with the massive arms that they use only for throwing people and working out so they can throw people farther. They will be throwing each other with the same muscles they use for daily locomotion and survival. 2. They store energy for the jumping and throwing in elastic or compressible structures. All of the large mammals have long, elastic tendons which store energy for their jumps. Some insects compress air bladders or cartilaginous springs to store energy. Humans may not be able to jump very far or throw each other very far, but when we do, we run and jump (storing energy built up from the running in tendons) or store it in a tool like a pole vaulter's pole or a trampoline. Your mammals are going to do something like hoist the other competitor into the air, and drop to their back, catch the opponent using their feet, and push them away. [Answer] The best way to throw an opponent is by using the opponent's own momentum. The question becomes, how far can opponent leap? and how much can you help it along? Change the rules of the game so it's more like Judo meets a Sumo match fought by burly kangaroos. Sumo wrestlers attempt to resist being thrown out of the ring while attempting to throw their opponent. There are excellent examples of clever sumo wrestlers using their opponent's own weight and momentum. <https://www.youtube.com/watch?v=ErWyhXXk2iE> Judo also uses an opponent's weight and strength. I've seen very large men get thrown pretty hard by small women. Kangaroo judo matches could be quite entertaining (though they might need longer arms). [Answer] A Finnish strong-man [threw another 60 kg person](https://www.youtube.com/watch?v=cB_vlaP-3uo) 5.4 meters, according to the Guinness Book of World Records. That is three times a 1.8m height person, so that mostly meets your standards. To be honest, I would suspect that our cave-man ancestors, who were generally stronger and more awesome than use, could accomplish this feat too. ]
[Question] [ Microraptors are cretaceous-period dinosaurs with feathered wings on both their forelimbs and back-limbs. Despite this, they are not considered 'true flyers' as it is believed they used their five 'wings'(The tail counts as one due to its purpose in generating 'lift') to glide from tree to tree and had few specialised flight adaptations (including a fused sternum and flight feathers). [![enter image description here](https://i.stack.imgur.com/odLQZ.jpg)](https://i.stack.imgur.com/odLQZ.jpg) So, assuming that these adaptations were accounted for and a creature with four/five wings like a microraptor could sustain powered flight, how would they fly? Would their back wings have the same flexibility as their forelimbs, making the creature fly somewhat like a dragonfly, Or would they take the shape of a bi-plane? Would the animal stand like a bird or a pterosaur? would the animal have greater manoeuvrability in the sky then a bird or would the excess drag make them too unstable for aerial acrobatics? [Answer] They fly like birds, specifically like slow low flying hawks. First if you see a picture with the hind legs spread apart, the artist has broken the legs to get them in that position. The front wings are sufficient to provide flight in microraptor, They would not have been as good as modern birds but they would have worked fine. It has all the hallmark adaptations of powered flight, like a keeled sternum and alula, and none of the adaptations you would expect in a glider, such as decent climbing ability. The extra wings on don't provide {much} lift they would however have provided lateral stability, something that early flyers always have problems with, especially at low speeds. Which is the same speeds extra control surfaces help the most at. They do not yet have the highly derived controls for controlling stability using active minute changes in the flight wings like modern birds. Since birds did not evolve from gliders, like other flyers did, but instead from jumpers they had more reason to experiment with odd forms of stability assistance and control surfaces anyway. You mentioned the tail, which does provide both lift and stability. We see flight surfaces evolve in the tail of every vertebrate flyer early in their evolution, it is just an easy solution. Models that say they cannot fly either forget the tail or assume fully modern flight stoke is necessary, forgetting that pterosaurs and bats aren't capable of the bird flight stroke, and that many birds fail to utilize it in normal flight. Interestingly there are birds with elongate leg feathers, not nearly as long as microraptor but definitely modified. The rough legged hawk has elongate leg feathers which are believed to aid in air stability at slow speeds. known for flying slowly low to the ground while hunting and spend a great deal more time running than their relatives. So expect to see microraptors flying slow and low over the landscape with wings held horizontal scanning for prey. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4203027/> [Answer] I would imagine the fore-wings would generate lift while the additional wings would be used for stabilizing and maneuverability. This is, of coursed, based on the idea that you are seeking a plausible, not scientific method for flight. [Answer] A combination of pitch control by the tail, roll generation by the ‘hindwings’ and multi-purpose control by the main wings would have made Microraptor a highly maneuverable animal. The rear limb feathers would have created a lot of drag. For every surface, you pay a little drag tax. But the advantage of improved ability may well have outweighed this problem. [Answer] [![four wing bugs are real](https://i.stack.imgur.com/kQNJG.jpg)](https://i.stack.imgur.com/kQNJG.jpg), this is a picture of what looks like a conjoined twins mosquito I took in my yard and I can tell you first hand it flies rather well, I believe that the trick here is that all 4 wings are the same size and face on opposite directions which gave it an even more helicopter-like flight pattern then other mosquitoes. Maybe your microrapoter has wings facing eachother and flies like an insect more then a bird? it would fit with the micro part [Answer] **Most likely like the [Mountain Banshee](https://james-camerons-avatar.fandom.com/wiki/Mountain_Banshee).** ![enter image description here](https://i.stack.imgur.com/VFXiN.jpg) These fictional creatures from the world Pandora seem to fit what you want, though here we should note they fly in a planet with lower gravity and denser atmosphere, meaning they have an easier time than our birds and could grow larger. So for your creature to develop powered flight using all 4 limbs, the tail would likely be converted into a means of adjusting trajectory rather than an additional wing, as we see our birds doing just fine with only 2, let alone 4. The hind limbs would likely be modified to be as flexible as the front ones and both the muscles and pelvic bone would need to undergo drastic changes to have an underside resembling the bird keel and pectoral bones. To end this, I'd say there's a good chance they'd resemble pterosaurs and modern bats on certain aspects, like keeping fingers on all limbs and walking in a quadrupedal stance, which seems like it would make more sense to as it'd allow them to have a more stable stance and keep their limbs closer to the body, thus protecting them better. We get a good look at this with the vampire bat, which is one of the bat world's greatest runners (yes they can "run") and a good climber and flyer. Notice how it keeps its forelimbs close to the body and its hind limbs bent, it's flight fingers are also bent tightly under the forelimbs. ![enter image description here](https://i.stack.imgur.com/OmONU.jpg) Lastly, on how they'd use these wings, I do believe the front limbs would naturally do most of the job most of the time, with the hind limbs being likely more used to stabilize flight and add extra lift or thrust, much like the Banshees do in theit universe. ]
[Question] [ I'm trying to design a species that is largely aquatic and yet capable of walking / running (loosely) on land. I've already figured out a gill and lung type respiratory system to allow them to breathe in both air and in water, but I'm stumped on why a mostly aquatic being would have legs (or things that serve a similar function)... or ARMS for that matter. The species is based mostly on octopi and squid. My plan was to give them the same basic features (very large eyes, beak, tentacles) but for the sake of my story they need to be able to move on land. I've also been thinking of the concept of their "legs" and "arms" having joints that deliberately dislocate to create a type of fluidity in the water so that those limbs aren't completely useless underwater, but I'm not really educated anatomically and I'm not even sure if that would work. Tldr: basically put, how do I give squid-like mostly aquatic aliens arms and legs while remaining truthful to science? Any ideas? Edit: it's come to my attention that while octopi are very dexterous underwater they are rather clumsy on land and have a hard time lugging around their bodies. If I want to keep the general form of the octopi, how would I counteract this? Otherwise, I'm still searching for reasons and ideas on how to give them legs. [Answer] I don't think you want bipedal. If they are octopus-like, they should not be limited to just 2 legs for locomotion. Octopuses are amazing and have no trouble moving on land for short periods (they're only limited by the fact that they can't really breathe air.) As for their limbs, [octopi have no bones.](https://archives.nbclearn.com/portal/site/k-12/flatview?cuecard=5706) They are unique, and I suggest you study the very specific and strange biology and movement of octopi--they have no joints at all, as result of having no bones. Here's some great links: [an octopus using armor](https://www.thedodo.com/octopus-carries-coconut-1178413280.html). [how they move and manipulate their limbs.](http://www.evolutionnews.org/2015/04/the_octopus_mor095431.html) [they can open jars](https://www.thedodo.com/brilliant-octopus-unscrews-a-j-390602252.html) [they are smart and can escape almost anything.](http://awesomeocean.com/2016/05/04/what-all-can-an-octopus-do/) I believe that they do have fine motor control, and have very good sense of touch. If you want to give them double tentacles at the end of two for a thumb-like structure, you can, but I would say that this is really a non-problem. ]
[Question] [ Previous discussion: [Medieval politics with fantasy races](https://worldbuilding.stackexchange.com/questions/28573/medieval-politics-with-fantasy-races) In the question above I was focused primarily on how having various fantasy races would impact a traditional medieval monarchy. Unfortunately the idea of a monarchy in this situation seems to be less and less plausible the more I ponder the scenario. At best this kingdom would have a few generations (seriously it's not likely) of benevolent rulers. The problem is no matter how many ways I look at it I can't escape the likely devolution where a king begins to oppress the other races and where one race eventually dominates the others. A bicameral democracy makes a lot of sense in this scenario but that does not (in my mind) work in a medieval setting. Many of the institutions and communication tools necessary for a democracy simply don't exist in a medieval world. **So...** keeping in mind the proclivities of each fantasy race (as listed in the previous question) as well as the kingdom details found below, ***What system of government would best apply to this situation.*** **Answers will be judged based on provided historic example(s) and how well they cover the details of the kingdom and races.** --- **Kingdom Details:** * 4 large multi-racial cities (all races present in the city limits) * 2 Elven forest settlements * Many human villages * Many gnome villages (Humans and gnomes often mix together in these smaller towns) * 1 dwarven stronghold * A section of the orc tribe lands The kingdom engages various neighbors none of which are nearly as large or diverse. It borders a fully dwarven kingdom, an elven forest enclave, some mostly human city states as well as some unaligned lands that contain various nomadic/tribal peoples. **Added racial trait (this should be considered part of the list from the other question)** Racial tolerance toward "slow" government * Orcs. The orcs are great in this regard, as generally aloof and disinterested in the machinations of the realm (again they generally don't see themselves as part of the kingdom) they couldn't care less how effective and timely the government is. * Elves. Being longer lived elves are more tolerant toward a more slowly changing and acting government preferring to collect as much information and considering as many options as possible before a decision is made. * Humans. Humans are less inclined to long debates than elves preferring a "good enough" approach to collecting information/options. But then as mentioned humans are notoriously disparate in their actions and attitudes so they are less consistent when compared to other races. * Dwarves. Dwarves are resistant to most things that attempt to place outside controls on their race. That said they are reasonable and have been willing to accept limitations in the past in the right situations. * Gnomes. Similar to humans in their expected rate of action but generally amiable and so long as their is nothing pressing are willing to engage in lengthy debates [Answer] There's a couple different ways to formulate a national government where a single race would not easily dominate, nor be dominated by an all powerful monarch. ## **Monarch with an elected cabinet** Absolute monarchs are great figureheads or for extremely fast responses to situations, with the downside that such concentrations of power lead to considerable abuse (as human history has abundantly shown). A check on the monarch's power could come in the form of an elected cabinet with veto power over the monarch's decisions; a privy council with teeth. The cabinet would be responsible for formulating laws, the king for confirming the laws. In the case of a royal veto, the cabinet can vote the law into force anyway. ## Elected Monarch There is an example of an elected supreme executive in the form of the [Holy Roman Emporer](https://en.wikipedia.org/wiki/Holy_Roman_Emperor) by the [Prince-Electors](https://en.wikipedia.org/wiki/Prince-elector). While the Holy Roman Emporer was often selected by the Pope, there was a period starting in the early 1100's to the early 1800's where the Emporer was elected. ## Council If the tolerance for long discussion is high enough, a council composed of representatives from each race would do just fine. With the appropriate checks&balances and procedures, building a government representing all races should be possible. The council would be responsible for making laws then delegating enforcement to the judiciary or a third law enforcement body. Some kind of tie breaker mechanism will need to be implemented too. Having a separate judiciary would be ideal in this case to resolve the inevitable disputes. ## Confederacy A legislature with only weak binding power on all the races might work. While a powerful race may be able to pass a law oppressing another, within the boundaries of the oppressed race's territory, that law holds no effect. This can lead to an escalating tit-for-tat where various races oppress the others but only within the bounds of their territory. In my opinion, it's very easy for a confederacy to go [pear-shaped](https://en.wikipedia.org/wiki/Pear-shaped#Failure) because of the high degree of autonomy reserved by each constituent state. James Madison amassed a [large collection](http://founders.archives.gov/documents/Madison/01-09-02-0001) of historical descriptions of ancient and modern confederacies when studying what manner of government to build for the new United States. Confederacies were used by the ancient Greeks, the Gauls contemporary to Julius Caesar and a few others. ## Getting there... Assuming some external pressure that forces the five races to form a national government of some kind, the political organization formed at that time will reflect to a certain degree the power structures between the five races. If the Elves dominate then it's not unreasonable to expect a political organization that favors them going forward. By some miracle, if all the races are perfectly balanced and/or the founding members are uncommonly wise, then the resulting national government will be some mashup of the governing bodies of each race, with additional/deletions to cover obvious (or subtle) failings in the resulting system along with whatever political philosophy is popular at the time. We can see this process of governmental evolution in the early history of the United States (Yes, I know, US bias but it's the history I know best.) The use of representative governments in the Americas is very old, starting with the [Mayflower Compact](https://en.wikipedia.org/wiki/Mayflower_Compact) in 1620. British representational governments are even older. That there would be a representational legislative body in the newly formed United States was without question. However, the creation of the national legislative bodies of the House of Representatives and the Senate resulted from a disagreement about how to balance the power of the large, more populace states with the demands of the smaller, less populace states. Obviously, a national legislature made up of representatives based on each state's population will favor the larger states. Conversely, a national legislature made up of a fixed number of reps for each state will favor smaller states.To balance the two opposing concerns, two legislatures were created, the House composed of representative allocated by population and the Senate with a fixed two representatives. In addition to historical precedent for political systems, academics may have come up with some new political theories that may be incorporated into the new government. Certainly, this happened in the formulation of the US national government (though a discussion of this kind of influence is far beyond the scope of this answer). Alternatively, new governments are formed when one conquers the other. A particularly interesting example is the conquest of Iceland by Norway in 1262. Previously, Iceland ruled itself with a large, annual, open air legislative/judicial conference called the [Alþingi](https://en.wikipedia.org/wiki/Althing) (anglicised as Althing or Althingi). There was no supreme executive such as a king or emperor; instead laws were made by the representatives sent to the Alþingi from across Iceland. Under Norwegian rule, the nature of the Alþingi changed to include power sharing with the Norwegian King. If the king initiated legislation, the Alþingi had to agree. If the Alþingi initiated legislation, the king had veto power. ## Ultimately, it's a mishmash... In the context of the five different races, the national government will be composed of the compromises each race is willing to make. If each race has a ruling council then it will be much easier to incorporate a council style system into the national government. Ultimately, what results will be the amalgamation of previous political structures, new political theories (as we saw in the organization of the United States) and the negotiating acumen of each race. [Answer] **TLDR**; you can justify just about anything, there’s not enough information about the history to speak to the forces that would drive the races to form a singular government for them all. -Edit: ## Anarchy I have to question if these races would even form a unified government; they may certainly live in the same areas and work together in many cases, and have societal tolerance towards each other, but without some pressure pushing them to unify, they would be unlikely to form a mono-governmental system, especially one that covers a several cities and large tracts of land. Throughout history large powerful governments are most likely to appear as the results of either external pressure or large groups of similar minded (and looking) individuals gathering to achieve a purpose. And the ones formed from external pressure usually fall apart after the pressure/threat is removed. You are more likely to see councils, houses, clans, or nobles of various races operating their various areas of interest as they see fit, with a system of interlocking agreements (“alliances” being too big of a word/concept to use with these type of groups.) Historically, people that don’t have a particular motivation or oppression are more or less perfectly happy to keep the status-quo, organizing only so much so that they become relatively comfortable. The races on a whole have to be tolerant enough to recognize that the *other* races cover their blind spots and are more useful to keep around then not, but that in itself it does not mean they’re going to want to form a mono-government. Neither would external military pressure over the short term; after the fight is over, each race goes back to what it wants to do rather than staying unified. It’s human nature (and you’ll have to decide if the other races operate differently) to want to expend as little energy as required to make themselves comfortable, and what’s familiar is comfortable; change is not. Long term pressure from some source will be needed to form a mono-government; one large enough that would *require* close cooperation between the races (at least at a high level) and one long enough that memory of when races were “run separately” begins to fade. The nature of this pressure will give you your resulting government; if it’s combative in nature you will likely see a military-esq government form, with a command structure based on merit and promotion and/or nobility. If it’s a pressure that requires careful management of resources you might see something like the council that I describe above form. You can see this in the formation(s) of the United States government(s), much of the how and why resulting from its disagreements with the United Kingdom. Ultimately, the government that forms is going to be based on the pressures that push it together in the first place; they don’t innately form at the scale you are talking about. The races history together and their history with the rest of the world will define its shape and form; you are going to need something external to forge and temper your government; and keep in mind that governments don’t last forever despite their self-preserving intensions; they tend to change (or be changed) from time to time. check out: <https://en.wikipedia.org/wiki/Government> to get some ideas for what your system can be arranged like. --- Left for “original Answer”; I favor the idea of a ruling council of five, one for each race, where each race determines its own method of selecting its councilor, and national actions are determined by majority vote. The way to make a system work is to make it simple enough and flexible enough to do what it needs to do and not restrict it more than it needs to be restricted; five councilors/rulers, one for each race, one vote each is a fairly simple and flexible set up, and as long as each understand that working *with* the other races is better than working *against* them then you only need a minimum of rules. (Also I’m not sure most with a medieval mindset would even care for laws and rules as much as we do today). Each of the five “racial” spots on the council could be filled by whatever method that race feels it should be filled for themselves. (Ex. A tournament for the orcs, seniority by the elves, political races for the humans), and changed as often as the individual races feel their spot needs to be changed (Ex. life-long/kingship terms by the Dwarves, and per 3 year term for the Gnomes), and if they delegate properly they don’t need to even be “in session” that often. One of the idea behind this is there would be little in the way of “rules” or Laws binding or directing the councilors beyond a general set that would drive the idea that the more of them agree to an action the more force that action should carry,that council actions should generally be taken to benefit all the member races, and specifically actions should not be taken if it were to the determent or specific harm of a specific member-race. The 5 spots/races also function to cross-check each other so one particular councilor (hopefully) does not gain to much personal power and upset the system. [Answer] Let's first take a look at your different races (I'm also using the intel you provided in your precedent question). ## Our races ### Orcs They don't look to have much interest in politics. However, your depiction of them looks a lot like the depiction that is done of poor minorities living in violent neighborhood. So the system would be made for them to have basically no actual power (and no hope to earn it) and maintaining their bad reputation by barring them rights. You may want to look at the current situation of Romani populations in Europe. A fine politician would propose to refute rights to nomadic populations one way or another. Thus saying "it is not against orcs, but against non-integrated orcs". ### Elves No other race will accept an Elf ruling other races through their whole lifetime. Even if the guy is a hero, he won't be for more than a few human generations. So ruling must be limited in time. Considering their time frame, they would probably try to have an impact in the legislative power and they would act effectively to maintain its independence and capacity. As some elves would master the skill of "legislative gibberish and political long-term manipulation", they would lightly but certainly have an impact on the government. ### Humans Sidenote: I think it's funny that you suppose all other races to be united and with a common way of thinking whereas humans are divided and diverse. Or perhaps that's my reading of you that is biased. However that was worth noting. Being diverse and numerous, humans will likely be at all levels of decision, making them the "expected default". This also means that this kingdom will most probably be biased towards humans: anywhere you go, a human can help you and even though they are not coordinated in any way, humans tend to be racists *[citation needed]*. ### Dwarves They seem a lot like they don't mingle at all with the rest of the kingdom. So they would make sure to maintain their independence, the others would make sure to maintain their trade with the dwarves, end of story. The dwarven nation may probably be seen more as a very close ally than of a vassal. History seems to me that that kind of confusion is often not a good thing. Specially when there is a strong national identity. I like to think of them as Scottish. ### Gnomes They seem nice. Good for the others. How would they fit? Damn. As they are good with other races, gnomes would do very good elected officials. Plus, they are not threatening and (as it looks like to me) they lack ambition. So, giving them local admnistrative and PR tasks seems like a good deal for everybody. ## Summing up You want power to be linked to the land, with local popular functions. You want stability despite a very disparate culture. You want a respected and loved government, then I give you... The [Roman Empire](https://en.wikipedia.org/wiki/Roman_Empire)! Now actually, I thought of it at the end of writing all that stuff concerning your races (that stays correct). But that kind of organization fits your requirements. Of course, the old empire was bigger but your race diversity seems to me like a social distance between people, with gnomes being travelers through those distance. The general idea is a strong and popular power figure (probably human, as it seems to be the "default race"), that figure mainly deals with international relationships (and wars). The actual power is diluted to the different regions of your kingdom that can rule themselves as long as they recognize the king's authority and provide people for military duty (and pay some taxes). [Answer] I am stealing and adding to Marky's response. I like the council set up, but a committee can not rule. You need one officer to be in charge. Have a council, but one seat on the council is the King/President. Have this position rotate, either on a schedule, or via election among council members. (I like having the council members elect on a regular basis but this leads to a tendency towards slow government and power in the Elves and dwarfs hands if they get along since the orcs will tend to support their slow government trend). Let the King/President rule by decree, but restrict it some how. Either every decree must be reviewed by the council and they have the option veto it (Either two votes to veto, or three votes depending upon the degree of power invested in the position{I prefer 3 to veto}). Or the council can call for the election of a new King/President on a regular basis or in a easy manner. (I like calling for it at any time, but requiring three votes to proceed). There is likely to be a Gnome/Human vs Elf/Dwarf power alignment. The elf and dwarf councilors get to know each other over longer life spans and begin to trust each other and realize their common political interests. Human's and gnomes share political interests as a group too, and shall tend to oppose the Elf/Dwarf direction. Their shorter life spans will allow the skilled elf politicians maintain control most of the time. Orcs share general political goals with the Elf/Dwarf coalition and tend to keep them in power. If the elven councilor is chosen based on skill he shall have the forethought to look past his natural distrust of orcs and use their political similarities to stay in power. Dwarfs have ties with gnomes and could often sway their vote when needed (if the orc vote is lost on a singular issue). In sessions where the Dwarf councilor does not trust the eleven King/President they have the potential to unseat them with gnomish support. However the gnomish political agenda is contrary to the Dwarfish one so Dwarven councilors that let the gnome agenda ride are likely to be replaced. In this arrangement humans are the likely to be dissenters to the system feeling their interests not represented effectively on a kingdom scale. They could form effective pushes for an alternative King/President along Human/Gnomish/Orcish lines. But these reigns are likely to be short lived (relatively speaking) as the individual personalities that made it possible are short lived. How quickly the personalities change could be modified based upon how the councilors are chosen. ]
[Question] [ Electricity pervades our daily lives, and makes possible a lot of technological achievements. Harnessing it helps the development of any civilization. The thing is, water - especially sea water - is a great conductor of electricity. I'd like to add electricity to an underwater civilization I'm working on, but I have two problems to deal with. 1. How would the civilization discover electricity? 2. How could the civilization use electricity (without electrocuting themselves)? Some details about the civilization: * They are octopus-like, insofar as they have tentacles for manipulation of objects. * They have gills. * They don't have fire - although I'll possibly address that in a future question. They might. I'm addressing this in [How could an underwater civilization develop fire?](https://worldbuilding.stackexchange.com/questions/31175/how-could-an-underwater-civilization-develop-fire). * The technological level is somewhere around that of the 1700s in Europe, if that helps. [Answer] 1. They could easily discover electricity in [electric rays](https://en.wikipedia.org/wiki/Electric_ray) or similar sea creatures. They could discover the “batteries” of the rays; in fact, there is a possibility that the corresponding human research on rays in the 18th century brought Galvani and Volta to further investigate electricity, so it should be feasible for your civilisation as well. As for electric safety concerns, the [discharging of electrocytes](https://en.wikipedia.org/wiki/Electric_organ#Firing) in rays uses some particular chemical which closes the circuit, so your creatures could possibly figure out by trial and error how to discharge the rays without short-circuiting them (after all, the electric rays themselves do exactly that). 2. Clearly, after understanding how electrical rays work, they could use this technology for hunting or battle. On the other hand, it would obviously be difficult for them to create electric circuits. One very human-like way to make some progress I can think of is to figure out that an artificially created air bubble (just by using some vessel first brought out of the water and then submerging it like a diving bell) is much safer in terms of absence of short-circuits and then starting to make experiments only under a [diving bell](https://en.wikipedia.org/wiki/Diving_bell) (reaching the objects from outside using tentacles); I guess, a 18th century-like tech level presumes they know what air is and how to keep some volumes of it under water. After that discovery, they could basically proceed with a 19th century human-like experiments on electricity using the “batteries” from ocean creatures to build huge battery stacks, if they don't discover a better way to build them. [Answer] # How would the civilization discover electricity? That one is easy: There are animals in the sea that use electricity, like the [electric eel.](https://en.wikipedia.org/wiki/Electric_eel) The underwater civilization would certainly be curious about how that works. # How could the civilization use electricity (without electrocuting themselves)? The first use of electricity will probably be as weapon — after all, that's the use they know about from the animals. Initially they probably would use captured electric eels. Assuming they know metals, they probably will find out that metals can be used to protect from electric eels (Faraday cage!). They will probably also find out that there are materials which shield you from electricity, like stone (note that since the complete water around them is conducting, it suffices to keep the distance the electricity has to travel to reach you large enough). As people learn more, they'll probably find how to make it yourself (using electrochemical processes) and that they can be used to create metals from water (by electrolysis of the salts). It will probably be quite some time until they manage to properly insulate it, so that it can be transported to specific places, and be used without too much danger. However it will probably never become a common household item, as you cannot have a simple plug (meaning uninsulated electricity being exposed), and any defect in the insulation means huge danger. So it will probably be used only in a professional setting and by the military. [Answer] How about a biological interpretation of electricity? What is electricity? It's electrons moving through a conductive medium, like an ionized gas or a metal. Essentially, it's signals flowing through a medium. What signals could be used to replace this underwater? Water flows are too slow and inaccurate. Sound is faster, but would be just as big a nuisance as electricity for aquatic creatures. However, there is a signal similar to electricity that could be used for this: biological nerves. Nerves actually use electricity, but a low-energy, isolated version of it. An aquatic race might develop a bionetwork of nerves to transmit their electricity. They could develop biological batteries and power generators (basically specially bred fish derived from electric fish from your world). I mean, Earth has around 300 species of electric fish, so it's not a stretch to assume that your world might have a few itself. ]
[Question] [ Earth's history remains unchanged, living beings evolve normally, nothing strange happens, until the emergence of Homo Sapiens, which for some mysterious reason, gains the ability to teleport. With this skill in hands, how would humanity evolve? Would we survive at all? Would society exist? **Teleport Skill:** * All, and only Homo Sapiens have this ability. * Learning how to teleport is almost as easy as learning to walk. * There is no way to lose this skill. * Teleporting spends a fixed amount of energy equivalent to walking 3 kilometers, distance doesn't matter. * We can only teleport to places we know. * We can only teleport to solid ground. * We can't teleport to walls or be directly killed by this ability in any way. **Affected objects** * We can only carry up to 500 kilograms with us to anywhere. * We can combine our charges to carry more weight (2 people can carry 1 ton, etc...) * Eventually we get used to carry our clothes with us * We can carry other living beigns with us as well, the carried one will not lose any energy. * Clothes and objects of the carried one will be left behind if the one teleporting forget to bring it. [Answer] # 1. Finding food Let's start in the beggining. We start at the stone age. There are hunters, fishers and gatherers struggling to get food. Hunting is much more easier, because chasing some creature becames much easier. Fleeing from dangerous creatures also becames easy. Transporting captured animals also becames much easier. If you want to hunt something, first, someone must walk around until he/she finds something to hunt. After walking in a place once in a life, you can just teleport back as many times as you want in your lifetime. Then, he/she just teleports back to the hunters' camp and bring other people by teleportation. To attack the prey, just grab a stone somewhere (possibly a place very far from that), teleport to near the pray, and drop the stone. If the pray is dangerous, quickly teleport away. Repeat this until the prey is dead or sufficiently injured. If needed, use a lot of people for doing that. However, since teleporting is not free, most people are unlikely to teleport two or three times in a row. And only athletes would teleport more than say, five or six times in the day. But, a group working together, where people carries other people when teleport, can effectively dillute that cost. A person is able to carry up to 500 kg with him/her, which mean that someone can easily bring other 5 to 7 persons with him/herself. This means that we might teleport 6 to 8 people with the cost of a single teleportation. For hunting birds, the tactics is similar, but different. Grab a stone, teleport to somewhere near the bird, throw the stone and repeat as many times as needed. Doing that with many people is better. Gathering vegetable food is also easy. Want to eat apples? Then teleport yourself to the apple tree, grab some apples and eat. Bring some apples for your friends too. It doesn't matter if the apple tree is in the other side of the planet. # 2. Exploring the world Exploration is much easier. If nobody ever reached the summit of the high mountain or the distant island, once the first brave adventurer reach that point, he/she can then bring any other people which in turn might bring any other people and so on. Also, the brave adventurer don't even need to do the entire journey by him/herself on a single shot. If he/she is able to just reach the half of the way, by teleporting back to home and teleport other people back, then other people might continue from the place where he/she stopped. If he/she wants to finish the journey just one year later, there is no need to start it all over again. Once a place where nobody has ever been before is reached, whoever reached it can teleport back and bring more say, 4 people (could even be more, but for an easier calculation, I am being a bit conservative). Those 5 people repeat the process bringing more 4 people each, and then we would have 25 people. Those 25 people repeat the process making 125 visitors in the place. Then 625, 3125, 15625... I.E. the number of potential visitors could grow exponentially, which means that once somebody reaches a place for the first time, in few time (possibily just a few hours) all the humanity would be able to visit that same place. Of course, there is some limits to the exponential growth, since some people would not want to go to that place or invite other people to go, but this shows that as soon that somebody go there for the first time, everybody else can potentially also go. In fact there is no limits of where you can go, there is just limits on how many places you will be able to go, to where you will want to go or to where you can find someone to take you there. Also, this is very useful for reaching new places where you can get food, water, ores, or anything else valuable. With this, quickly everyone might be able to visit many places in the world during his/her lifetime. If you live for say 70 years and is able to visit 20 places each day, either by teleporting yourself, by being teleported by someone else or just by walking or riding a car, this is more than half a million of places in your entire life. However this number might be lower because people frequently revisit places where they already had been. On the other hand, visiting more than 20 places in a day is quite feasible, specially if you do that in large groups of people. Also, the sole thing that you need in order to go to the other side of the globe is to know somebody else who already had been there and agrees to teleport you to that place. Kidnapping people is very easy, but also very innefective, because the kidnapped person would easily flee. However, as WhatRoughBeast suggested in a comment, this is feasible if the victim is held unconcious by some drug as long as needed and only being able to wake up when the captor allows it (possibly, after a ransom is provided). There is simply few to no way to make someone a prisioner. Also, stealing something valuable (or someone) and demanding a ransom might be an effective to persuade people to work for you or to tell something. Hiding is easy. If you want to move to somewhere where nobody will ever find you, just teleport away to somewhere very far where you had been years ago. If you have a friend that can take you to some place very far, where you never have been before, that is much better. By the way, you can easily hide any object by using this technic. Stealing something is also very easy. Teleport to the target, grab the thing and teleport away to somewhere else and it is unlikely that the thing will ever be found again. This way, the best method to protect something valuable is to hide it by teleporting to a remote place, hiding the thing in some place where nobody will see (possibly by burying it in the ground) and go away hoping that nobody will find it. Also, thiefs can be more effective by working in groups, to reduce the total teleportation cost. # 3. The society Raising children becomes hard. If a child insists in wanting to play in the forest during night, there is practically no way avoid that. The only way to avoid that someone eventually escapes is to force he/she to spend his/her entire life in a small cubicle and never be able to leave. Once he/she leaves (or get kidnapped by someone else), there is no way to avoid an escape. Wars becames very different. The only effective tactic in a war is to quickly and surprisingly ambush someone else and instakill him/her before the victim have a chance to teleport away. However, if the attack fail, the attacker(s) will be able to easily flee to never be found again. This is much more easier to do when the victim is sleeping. A marching army is useless, because the defender would just teleport to somewhere behind your army or perhaps in the middle of it. You can't siege something, and it would not make sense anyway. This is because that under a siege, the defenders could just flee and carry away everything they can. They can go back and forth as many times that they want and bring any people who could help them. But once one of your men is able to enter the city (or someone already there decides to be a traitor), you can just teleport all of your men to the inside, so there is no need to even start the siege, just proceed directly to the invasion. For people who are being persecuted by enemies, the best to do is just to teleport away to some place somewhere else. Fleeing is easy, catching someone is hard. Also, people who are afraid of being found by his/her enemies might chose to just teleport randomly a few times every day and never sleep in the same place. Since exploring around the planet becames easy, people will also be able to easily and quickly contact a lot of people around the globe. If the contact leads to some trouble, fleeing is easy. The result is that probably the humans would all speak the same single language. Also, the society will be probably stateless. If we had an authoritharian king somewhere, he would not have any power, since his subordinates can easily flee and as a result his loyal soldiers can't enforce his laws. Also, that king would probably have a lot of enemies, who would be able to easily kill him while he sleeps. If the king keeps running away, he would be unable to efficiently give orders to his loyal soldiers. Also, it would be very easy to attack his loyal soldiers. Anybody who want to have some sort of power over other people should be a very smart, careful, charismatic and manipulative person. Further, since everbody can go everywhere, there would be no frontiers in this world. If somehow two enemy states rises, people from one state would be able to easily invade the other state to try to kill, steal or destroy anything. There is almost no way to defend a country. This means that we would essentially have no countries at all. Once people start to extract interesting minerals out of mountains, processing them becames much easier, just teleport the ores directly to where they would be processed. No gold or uranium mine will be able to kept secret for long time. Also, there is no need to build thousand ore-refining and smelting facilities scattered around the globe, one or two giant refining facilities is more than enough. This also holds for facility like mills, bakeries, hospitals, churches, etc. However, let's say that there are three big hospitals in the world, a medic would be able to teleport from an hospital to the another fast, and would be able to bring the equipment and even the patient if he/she is unable to teleport him/herself. This would essentially mean that there would be one big freaking huge hospital in the entire world, although it would have no need to have all its building in the same place, or even in the same continent. This would also apply to other facilities like bakeries, blacksmiths, universities, etc. It is very hard to prevent crime. Criminals could go in and out their criminal scenes easily and unperceived and would left no clues. Crimes would be common, and stealing and murdering is easy. The best to do is to hide anything valuable in order to avoid a potential stealing and have no enemies that would like to kill you. Also, being always near your friends might be useful. Criminals that are caught, would probably be quickly sentenced to death without chance of defense. Most people would still value some form of privacy. This can be achieved by teleporting to a remote place and building a house there, many possibly without doors, but some would likely still feature doors afterall for periods of illness and weakness when teleporting would be too costly/tiresome and there is something useful (like food and water) nearby. Then, those houses would be a safe place to hide important personal things, treasures and also for sleeping. Keeping it secret by not teleporting other people to that place is also very important. If you want a place to share with your friends, just build another house somewhere else and do not put anything valuable there. A thief, by randomly walking around in a forest is very likely to find some closed houses full of precious things inside just waiting to be robbed, and if something goes wrong, it is very easy to just flee by teleporting away. This also motivates people to build houses in remote places like mountain peaks, remote islands, deserts, glaciers, underground caves, floating in the middle of the oceans, or in the deep sea floor. Houses would be built to be strongly camoufled in their environment to not be perceived even if you are just standing them right in your face. Also, building houses in closed chambers deeply underground is very useful, but could be dangerous since there would be no air circulation, so a small opening to the outside would be important (this becames way harder for things under the sea). Uncamoufled houses with doors in places full of interesting resources nearby are probably just a point where people meet and is unlikely to feature anything valuable inside. When technology allows it (see below), building houses in other planets or asteroids is very attractive. By the way, since going outside to look for someone who you want to talk is hard, people would probably rely a lot in something like post office centers where people can both post and take letters, in order to communicate. At least, this would happen before things like telephones, radios, cellphones and e-mails are invented. Since there is no state, nor countries, nor cities, no way to efficiently punish crime and few handful huge facilities with a single purpose around the globe are more efficient than thousands small facilities scattered around, this means that the world would probably feature a single huge anarquist socialist-communist-like society. Private property would be defined as what you might be able to hide from everybody else. The society would work much closer than ant-like or bee-like societies (probably without a queen) than to our everyday societies, but still be very different from that. # 4. Evolution With the hability to teleport away, there is fewer need to move around by walking or running. As a result humans could probably evolve weaker legs. Ironically, people who are unable to move the legs will still be able to move around the world large distances efficiently, but uneficiently around the small distances. Running would become something much less useful, so it is possible that humans lose the hability to run or have it much more underdeveloped. Running is useful for people who are lonely or working in very small groups (2 to 4 people), when teleporting would be costly. Running is also useful to quickly move a few meters away, when walking is too slow and teleporting too costly. Running could be useful when after teleporting, the teleporter misses the target by a few meters and want to reach it ASAP. Running would also still be useful when people need to hit something (like a prey) with velocity. Humans would also likely feature a weaker musculature and a weaker skeleton, since there is few reasons to transport heavy things for long distances using your own hands and almost no reason to run. Also, even very heavy things can be easily teleported, which also means that there are few reasons to develop strong musculature. Also, since it is easy for humans to escape from predators and to kill prey, this also removes some of the evolution pressure that eventually gave us stronger skeletons and muscles. If you are fat and want to quickly lose weight, this is easy. Just burn your calories by quickly and repeating teleporting away. If you do this type of exercize in groups, by teleporting people with you, you would be able to visit and know a lot of cool places around the globe while losing weight. There is no need anymore to practize complicated, painfully and tiresome exercizes for so much long hours everyday. Also, the human mind would probably evolve in a way where teleportation is essential. When thinking about how to solve problems, humans would always be thinking about teleportation being part of the solution. Since people can teleport lonely up to 500 kg and teleporting other people is very useful, the result is that being fat is unfavourable. Also being very tall is not favourable. This could result in a human race where people are thin and have low stature. With that, teleport up to 11 to 13 people while paying the cost of only one teleportation might be feasible. However, the relative cost for teleportation is higher for thin and low people, and they are also much more fragile, so the point of equilibrium might be a medium body-mass where it is possible to teleport 8 to 10 people in a single teleportation which is around 50 to 60 kg for each person. # 5. Technology Since transporting things becomes easy, there is few to no need for roads. Things can be stored more efficiently since fewer stories are needed. There is few to no need in building cities. The purpose that made cities appear is to bring people together in a single place where they would be able to trade efficiently. This now is uneeded, you could easily teleport things from one farm to another farm without needing a convenient city where everybody would go in order to be able to buy and sell things. By the way the farmer house don't even need to be in the same continent as his farm. Technology would be able to be developed much more quicker and knowledge would be spread much more easier. However, on the other hand, humans would have far less motivations to develop technology it in the first place. Many houses or buildings would not feature ladders or stairs. Many places would not even feature doors. Once the builder is in a floor or in a room, he can always come back even if the entrance is sealed. If someone is too tired to teleport, someone else might be able to teleport him/her. You can continue to keep mining underground even if the mine entrance collapsed, because once you are in, there is few reasons to keep the door open. Building seaships, airplanes and rockets is much easier. Grabbing all that fuel is ineficient and unnecessary. It is much more efficient to grab just a small quantity of fuel and frequently refuel by teleporting people in and out who grabs more fuel and takes away the waste. However, the only purpose in building airplanes or seaplanes is to transport very heavy cargo when it is not feasible to just grab a thousand of people to work together to teleport the thing. Do you want to visit the Moon, Venus, Mars or Pluto's Tombaugh Regio? Just place someone inside the rocket, lauch it, teleport people in and out for fueling purposes, and once the rocket lands, everybody who already visited the rocket are welcome to the new planet. If you never had been in the rocket, just ask someone who already had been to bring you. This way, once humanity starts with space-travel, we would be effectivelly being able to start colonizing the galaxy (although still slowly). Also, building structures or mining other planets becomes way more easier to do. People would likely teleport air and water to other planets. Also, people would figure out that the Earth is round even in stone age and would be able to measure the distance and the size of the Sun, the Moon and the planets before being able to melt and cast metals. Still in ancient times, by using clever teleportations tricks and some math, philosophers would be able to figure out that teleportation works on a finite, but very fast velocity and will measure it to a value somewhat close to 299,792,458 m/s. They would probably also find that light travels at the same speed as teleportation. Measuring the light speed might be easier than inventing the wheel! Also, some philosopher would probably figure out relativity theory as early as middle ages. # 6. Epidemics However, there is a showstopper about the society that I describe above. Since everyone can meet everyone else and go wherever they want, this means that there is no barrier for epidemics and once things like ebola starts to spread out, we essentially have a human mass-extiction event. Epidemics might wipe out the human race sooner than later and this could mean the extinction of the human society early on the stone age. It is also possible that even if humanity don't get extinct, this could cause enough havoc in the society to prevent it from ever leaving the stone age, with waves after waves of epidemics. If humans survive enough, enduring many waves of epidemics, they could end being evolved in territorial solitary beings that avoids contact with other humans except perhaps for reproduction and childraising. This could lead to a scenario where humanity is never able to form a society or that any prior formed society collapses. Also, since people would avoid other people and there is no way for the parents to keep the child for long time, most childs would probably never know their fathers at all and would probably get separated from their mothers before reaching 5 years old, which would also mean that language would be lost or not even develop to start with. Thus, the result would be a society that resembles much more an animal society than a human one, which would also restrict the hability to get help for going everywhere and then mostly human would be able to teleport only in small restricted areas. But this also restrict the epidemics, which would allow more human contact back then and also reduces the benefit of teleporting in groups which also gives back the need for a more social life instead of a lonesome one. So, the result is that there is some sort of delicate equilibrium between being able to be teleported with someone else to novel locations and avoiding contact due to epidemics. The result would likely be small territorialist clans who are hostile to other clans. Also, people who are perceived as ill, would be likely to be left alone to either die or recover lonely. Only if humans somehow manage to get free or significantly aleviated from the problems that results from epidemics that all the rest of this answer (all the other 5 blocks except this very one) would apply. [Answer] It will most probably bring a quick and sad end to the human civilization within the first 1000 years of obtaining and understanding this ability. The first and most disastrous effect would be the immediate breakdown of social structures. Everybody tries to find an earthly haven for himself. No mutual trust. No share of knowledge and experience. People would come together only for biological needs (reproduction that is). Lonesome people teleporting to food hotspots getting killed by predators. In the current state of affairs, such an ability would be no less disastrous. The collapse of society would take longer (probably 200 years or so). People are selfish by nature and without any strict binding and limiting force, crime rate would be explosive. **If and only if** social ties are not broken as a result of this ability and people don't go rampaging around like beasts, this ability can bring outrageous development and prosperity to our race, and eventually to all the species on this planet. We could colonize all lands. We could solve people's problem anywhere in the world immediately. We wouldn't have countries then, but one unified government for all humanity. ]
[Question] [ I have a scenario where a person has nanorobots unknowingly injected into his bloodstream. I'd like his doctor to discover them through some kind of medical test, preferably a blood test. Of course they wouldn't be looked for specifically, but would have to show up as some kind of anomaly that would be investigated further, leading to their discovery. The type of test could either be a routine blood test that would be done on a person getting a general physical, or could be a blood test for a specific chronic condition (e.g. the person may have a medical condition requiring a specific periodic blood test). Regarding the composition of the nanorobots, I don't have this nailed down firmly but at this point I'm thinking they would probably be carbon-based. If them containing a specific element would make the detection scenario more plausible, I may be able to work that in. For size, each nanorobot is about the size of a virus. The time frame is the near future, so the test should either be one that currently exists, or would be likely to exist within the next decade or so. [Answer] **Copper Sulphate Densitometry** If you've ever donated blood then you know they prick your finger and drop your blood into a blue solution to test your iron level. [If a person is too anemic, they can't give blood](http://www.anemia.org/professionals/feature-articles/content.php?contentid=378), so they need to test it before. The blue solution is copper sulphate dissolved to a specific density, this makes the iron in the blood sink in a measurable way. For your character, this blood test might reveal abnormally high densities of what appears to be iron. Abnormal enough to facilitate further testing. **Complete Blood Count** Alternatively if the character thinks they are ill, or the abnormal results from above are a concern, their doctor might order a [complete blood count](http://en.wikipedia.org/wiki/Complete_blood_count). A sample of the blood will be analyzed either by a machine or a human technician counting the number of each of the different cell types in the blood. The nanobots would certainly be noticed in such a case. [Answer] Not having any medical background, i still think that in a blood test at least often the blood is put in a centrifuge. Since your metallic nanobots are the densest stuff in the sample, they will all end up in the bottom of the test tube. If there are enough of them, they might even be noticeable with the naked eye. If that fails... well. Then i am lost and need someone with more medical lab experience to help out :-) By the way: A reason for the test might be a simple aids test, taken because your hero met a nice girl, and is a responsible figure. Or his spouse admitted an "accident" and they both decide to have a checkup. [Answer] Considering that they are made of metal and use a - proportionally - large ammount of it on its pure form, upon doing a simple x-ray, a large portion of the blood stream would block x-rays from passing as if the person was under a constrast x-ray. From there, the medic could, via ruling out other diseases, detect that he got a "nanonrobot" infection and start treatment. [Answer] Assuming they use metals (specifically iron) in the blood to replicate they would cause a mild case of anemia. The individual would wonder as to why he has gotten this [usually genetically inherited] disease and they will take a blood sample. If the bots are plentiful enough they will be able to see them in the blood sample. They could (and probably would) also take a sample of bone marrow in which the bots likely manifest themselves. [Answer] ## Antibodies. We don't actually need to do anything above and beyond modern technology in order to detect virus-sized objects. As long as the nanobots don't constantly mutate, evolution has already produced these powerful defences against virus-sized and smaller objects. Molecular and cell biology labs routinely [raise polyclonal antibodies](https://en.wikipedia.org/wiki/Polyclonal_antibodies#Antigen_preparation) against various proteins and viruses in the lab. These proteins can then be used in assays such as [ELISA](https://en.wikipedia.org/wiki/ELISA) in order to detect the presence of the nanobot. Due to the way antibodies work (random antibodies are generated by cells, and then selected for when encountering antigens), it is nearly impossible to create virus-sized nanobots that cannot be targeted by antibodies. The only way this would theoretically be prevented is for the nanobots to evolve their "capsid proteins" much like real life viruses do to escape detection by the immune system. If your nanobot is incapable of evolving to stay ahead of the immune system, it will be detected and removed as quickly as any bacteria or viruses. ]
[Question] [ **Initial situation:** * I have cold planet with an average temperature below the freezing point. * There is a magnetic field. * The planet is almost as big as Earth and can have an atmosphere. * The planet axial tilt angle is 0 or very small. * Months are a little longer than on Earth and days are slightly shorter. * The climate is one of eternal snow and ice except at the equator where it is hot enough to have a tundra climate. * The planet has plenty of water but most of it is frozen. With a tundra climate, the monthly average temperature never go above 10°C. Temperatures can get cold in a normal tundra during the cold season but since we are at the equator, the variation is very small. Thus we have 2 possibilities: Either the the average temperature is constant between 0 and 10, or there is a season with temperature below 0. But in both cases, the temperature might go below the freezing point during nighttime even in "summer". **Question: Without help form advanced technology, could this planet develop and maintain a breathable atmosphere for humans?** [Answer] # Yes To get oxygen you need * water * light * and life The life takes water and light and makes oxygen. You've given water and light as constants, so we just need life. As long as there is some liquid water life, as we know it, could exist. You said your temperature range went up to 10 degrees Celsius, so liquid water will exist, at least in small pools. These would be completely sufficient for our current models of abiogenesis. In fact, due to the phenomenon of eutectic freezing, small thaw pools would actually become highly concentrated in organic building blocks. Microscopic life in general has no problems with constant freezing and thawing. Things might be slow going because chemical processes occur at a slower rate at colder temperatures, but given enough time an equivalent of algae could evolve on your planet and begin releasing oxygen into the atmosphere. [Answer] I'm going to give you a cautious "yes". The reason I'm being cautious is that it depends partly on a hypothesis that is, and has always been, controversial. If it's correct, then absolutely, this scenario is possible. If it's wrong . . . well, perhaps the following reasoning is incorrect. Have you ever read about the [Snowball Earth](https://en.wikipedia.org/wiki/Snowball_Earth) theory? It's actually pretty fascinating. It posits that, within the last 650 million years, the Earth has frozen over at least once to an extent never before seen . . . except in a previous such incident. The theory attributes this period to any one of a number of events, including a large supervolcano erupting, changes in the Earth's orbit, or an enormous change in levels of greenhouse gases in the atmosphere. The point is, at one or more times in Earth's past, it may have been a giant ball of ice and snow. Now, in order to cool the Earth, you would want to have extremely low levels of carbon dioxide. And I mean *extremely* low. Forget the current 1% or so; I mean a *large* reduction of CO2 and CH4 levels. What fills that gap? I would assume that oxygen and nitrogen would continue to dominate; given that they currently account for nearly all of Earth's atmosphere, it would be very difficult to reduce them to negligible amounts. Also, you would have to find something to replace them, which would be tough. In short, oxygen most likely existed during these snowball periods. As for [life](https://en.wikipedia.org/wiki/Snowball_Earth#Survival_of_life_through_frozen_periods). . . Less CO2 means that plants and other photosynthetic organisms have it tough; this also means that nearly everyone else has it tough, too. As the Wikipedia page notes, > > Detractors argue that this kind of glaciation would have made life extinct entirely. However, microfossils such as stromatolites and oncolites prove that, in shallow marine environments at least, life did not suffer any perturbation. Instead life developed a trophic complexity and survived the cold period unscathed. > > > The page goes on to describe various extremophiles that would have survived. But I would think this expedition should be okay. They could grow their own plants and use them for food, get power from the Sun, and live as good a life as you can live when you're living on a giant snowball. --- There's another bit of evidence staring you (and me) right in the face: Jupiter's moon, [Europa](https://en.wikipedia.org/wiki/Europa_(moon)). Yes, it's a moon, not a planet, but I can imagine that a scaled-up version wouldn't change to much at the fundamental level. Also, we *know* it exists and is frozen over (and has been for quite some time), so I think I can use it as a decent example. Europa has a surface of ice (yes, from water) that may be many km deep. It seems to cover the moon's entire surface (it's average surface temperature, by the way, is about 50 K - way colder than you're looking for - but I'll ignore that for now). Below may lie an ocean, which has fascinated people ever since the idea was proposed. [Its atmosphere](https://en.wikipedia.org/wiki/Europa_(moon)#Atmosphere), too, contains a lot of oxygen. Sure, it's a thin atmosphere, but at least it's something. The conditions aren't too good for life to develop on the surface, but a well-prepared team of explorers should be hardy enough to survive. [Answer] Breathable, certainly. The planet could have formed with an oxygen nitrogen atmosphere similar enough to Earth's for Humans to breath. It is not likely, but it is definitely possible. Sustainable, now that is a different question. Once Humans start consuming the O2, without something, be it life or technology, to recycle CO2 back into oxygen, eventually the breathable air will not be so breathable anymore. It might take eons, but it will happen. ]
[Question] [ I am trying to come up with an explanation for how a creature could create strong magnetic fields with a high level of control. I'm thinking that their 'writing' would be similar to how computers write to hard disks, which is why I'd like them to have a fine degree of control over this ability. I do have a mineral native to their system that is highly reactive to magnetism and is used extensively in their tech as their hands are not quite as dexterous as ours to manipulate things. I'm also not sure just how strong a field they really need with the existence of this mineral as I am perfectly fine with them being only able to nudge a chunk of iron, compared to being able to levitate moderate weights of this material. Still in the early phases of working out how such a mineral would be dispersed through, and what affect it would have on, an environment. I suppose they will need some type of organ similar to the ones in electric eels to generate a current to power said field. So I guess my main question is: Is there a combination of electrolytes that is more efficient/powerful than the sodium and potassium that eels use? Could a creature be able to generate stronger fields, but also make highly controlled ones? [Answer] I think that if you want to have what you are asking for, you don't have to look into different electrolytes but into a completely different mechanism. With the electrolytes you basically create a separation of charges by pumping ions on just one side of a barrier. When you remove the barrier, ZAP, you have the spark. Of course this mechanism is useful if you want to create a pulse, not a constant current. More or less what happens when you discharge a capacitor. If you want a constant-ish current, you would need two materials with different redox potentials and have a saline solution between them. Basically a biological version of a battery. This type of organ might then serve to produce a current, and the current would induce a magnetic field. [Answer] How about an organism that uses conductive material to build some kind of shell? Like some sort of really giant snail with a big coil of wire where the shell would be. It could ingest magnetic materials which it normally uses like a gastrolith. But when the animal wants to make electric current, it can move its magnetic gastrolith around in such a way that it acts like a giant generator. Control would come from increasing or decreasing the amount of resistance on the way to whatever sort of organ... maybe another coil that acts like an electromagnet, attached to an extremity. If the materials are really magnetic/conductive or your needs are lesser, you could do the same with a smaller organ. Another idea would be a bank of naturally occuring graphene capacitors. [Answer] Could the organism just incorporate ferromagnetic materials into it's body? Like a lot of tiny magnets. It could control the magnatism by flipping different pieces to either create parallel or opposite magnetic fields (opposite ones would cancel, turning the effect 'off'). Active magnetism would need quite a lot of current. You'd need really great conductors (I think no biological material comes close to copper or silver, but I'm not sure). It'd probably still take excessive amounts of energy. You know that video of the frog floating in a magnetic field? The amount of power needed for that has a noticable effect on the city power supply. Biology usually doesn't have that kind of energy available. If you could get a superconductor, then you could do it with almost no energy use. But all known superconductors only work at temperatures far below freezing. Sweating is not enough to cool to below -200C, not to mention insulation... [Answer] Maybe you can look into what our nature has to offer, for instance with the electrolocation capabilities of certain mammals like the [platypus](https://en.wikipedia.org/wiki/Platypus), or shocking capabilities of electric eels. A small non exhaustive list of examples can be found here [here](https://news.jacksonemc.com/shocking-animals-that-can-generate-and-detect-electricity/). [Answer] Would a large group of electric eels suffice? If they synced their discharges, and others reabsorb them, they could create a constant current exchange, thus a magnetic field.. <https://en.wikipedia.org/wiki/Electric_eel> [Answer] Could you look at this the other way round? How do homing birds navigate? How do water- or mineral-diviners dowse? Don’t the birds use tiny, highly sensitive organs? Don’t the dowsers use rods not to create, but to amplify some inherent sensitivity? What’s a “strong” field or a “high” level of control and how much less dexterous are these critters? My guess is the “chunk” to be nudged might start about fist size, but up to what? An anvil? A dining table? What’s your difference between nudging and levitating and what’s a “moderate weight”? Are you basically looking to use this power to move roughly the same sort of weight the creature could heave physically? I don’t think there’s much control or range in the charges from electric eels or the like but take a few steps sideway. In Star Wars microscopic midi-chlorian symbiotes inside the cells of all living things form some sort of energy field, perceived as the Force… but note, “some sort of” is about as close as anyone gets to understanding. Similarly in Philip Pullman's Books of Dust, elementary Rusakov particles are somehow associated with consciousness. Again, “somehow” is all we really get, unless it be the new slant on Genesis’ “… dust thou art, and unto dust shalt thou return”. So, two different forms of "field" extending hugely yet under skilled control… ]
[Question] [ I've got a home-brewed D&D setting. Diamonds, in D&D, are needed for resurrection magic, so access to diamonds is literally life and death for any country with clerics capable of casting such spells. The outcomes of wars will likely hinge on which side can control access to diamonds better. So, where do I put the diamond mines, relative to ecosystem, plate tectonics, etc? [Answer] Your setting is magical. Clerics are servants of gods. With that in mind: **Anywhere you please** The presence or absence of diamonds in your world isn’t limited by such mundane factors as where volcanoes exist or whether ancient carbon deposits lie buried beneath the surface. You can literally have the Goddess of Diamonds decide to plop a seam of diamonds anywhere. Perhaps a wizard accidentally blew himself up and scattered diamonds across the landscape, or Earth Elementals decided to prank the surface dwellers by putting huge diamond deposits under a loamy flood plain. Point is: literally anywhere can be a suitable location for your diamond mines as you have so many more justifications available for *why* the diamonds are buried there. Use your imagination, remember why you said they were there, then build that into your world in an inversion of the usual Worldbuilding ‘my things are here because my world says so’ to ‘my things are here, so my world must be this’. Goddess of diamonds? Drop a buried temple into the mine. Ancient Accident? The diamonds are cursed and the wizard’s ghost is still around. Earth Elemental Jokers? They keep playing tricks on the miners. Or you can go the route of boring old plate tectonics if you really wish... If you do, the answer is still ‘pretty much anywhere’, as diamonds can form and be transported to the surface anywhere there has *ever* been an upwelling of material from the mantle (specifically a rapid form of eruption that transports the freshly made diamond up before they melt again). These kinds of upwelling can happen damn near anywhere that the crust was once thick enough to support it, but then the diamonds can hang around while the geology around them is modified by... well, geology. Tiny amounts of diamonds can also be made anywhere a load of carbon rich material got trapped in a subduction zone, or even where meteors have impacted. In those cases the diamonds will be very small, but if your world only cares about the worth of the diamond (who decides if the diamond is worth 10GP??) and uses some form of free-market economy then even small diamonds will rapidly become worth mining. You get the point. Put the diamonds where it works for your campaign. Justify their presence there later. [Answer] **Almost no-one knows.** In a D&D scenario, it is underworlders who know where the diamonds are: probably kobolds or [svirfneblin](https://forgottenrealms.fandom.com/wiki/Deep_gnome) or some similar creature that is willing to work hard mining for a living. The svir who mine diamonds know that if the source is found out, powerful interests will move in and take it over, at best enslaving the gnomes to mine more and at worse torturing them until they give up the location of the diamond vaults, then eating them. So the svirsneblin are extremely circumspect. They employ a series of middlemen such that none of these (non-svirsneblin!) individuals can betray them. A good campaign might be an expedition to a fallen svirsneblin mine. The svir hire your campaigners to oust the monsters which have seized control of the mine, depicting the invaders as a bunch of bumbling umber hulks and owl bears who do not know the value of what they have. The adventurers will discover that other powerful interests from topside and underneath have realized the same thing, and are all converging on the mine to claim it for themselves. ]
[Question] [ Okay, let's assume that travel between star systems is done through stable, stationary wormholes on the outer boundaries of each system. This alone is slightly magic for now, of course, but let's roll with it. I want to solve the light speed problem for communications as well. Obviously, communications between both systems as a whole could use the connecting wormhole, but communications between distant things within a system would still be delayed if using normal means. Our understanding of quantum entanglement, at the moment, suggests it's actually kind of useless for communication, so I was wondering considering tiny wormholes leading to a central communications hub. But, I wonder, if your ship has a tiny microscopic wormhole it's carrying around, what happens when it carries it through that big one? Wormholes are three-dimensional tunnels through four-dimensional space, what happens when they cross like that? Obviously, any answer would be theory at best, conjecture at worst. [Answer] > > Within the constraints of general relativity this is a solvable problem, albeit a *stupidly* hard one. – [Joe Bloggs](https://worldbuilding.stackexchange.com/users/9887/joe-bloggs) > > > I agree with this assessment. ### [Wormholes](https://en.wikipedia.org/wiki/Wormhole) are theoretically consistent with general relativity, but they are *speculative*. So even if one were to calculate all the details of the proposed scenario there is no data to base this on. If you have ever seen any calculations of relativity, you know that it quickly becomes complicated if you want to do more than calculate time dilation for two differently moving bodies. The proposed scenario would definitely be a very complicated one and even if anyone (definitely not me) would post it here in an answer there would only be a very low number of readers able to understand it. > > Wormholes connect two points in spacetime, which means that they would in principle allow travel in time, as well as in space. - [Wikipedia](https://en.wikipedia.org/wiki/Wormhole#Traversable_wormholes) > > > Note that they are not "points" as in singularities, but they stretch in all 4 dimensions. This means they occupy a 3 dimensional space over a span of time. (Relativity makes it a little more complex, but let's keep it at that.) Coupled Wormholes would remain a constant link between two of these 4 dimensional portions of space-time. While I personally have no idea how to represent that in math, I see no direct problem in why a smaller portion of space-time couldn't 'move' through another as long as neither changes state in some way that it would break the link. I don't see a problem, since - if we already have traversable wormholes - objects and other forms of energy can move through it, why would another wormhole be different? I believe the scientists who have shown that theoretically objects can move through unharmed and without inconsistency with current knowledge, so I see no reason why a space-time link would be any different. I think so because for any given moment you can define where the wormhole is, even if it just partially traversed the other wormhole and if an object would move through the inner wormhole in that moment it would not be changed at all, even if it is only half through the outer one - because we already assumed it could move through the other without problems. ***However*** the mere concept of this is *two layers of hypothesis* and no hard data to back any of this up. ### Conclusion I do not think there is an apparent inconsistency with the scientific agreement that wormholes are theoretically possible and if you use that within a world you created you wouldn't create logical inconsistencies. A little bit of hand-waving is probably required anyway, unless you want to do the math of relativistically consistent wormholes for yourself and possibly readers. [Answer] # Probably not, but that might not matter. A wormhole is a connection between two different points of space time. They are not physical objects that you can just carry around with you. If a wormhole were to move, it would also move whatever is connecting these two points in space time, and would probably need a lot of energy just to maintain the connection. However... If you are able to just open up a little wormhole whenever you want, then close it again (don't accelerate), then your problem is solved because the device that makes the wormholes can move through a wormhole, then open a little one on the other side. Then you don't have to worry about wormholes going through wormholes. You're just making new ones as needed. [Answer] The only place I've seen this notion considered is in a pop science book: *The Physics of Stargates - Parallel Universes, Time Travel, and the Enigma of Wormhole Physics* by Enrico Rodrigo. In Chapter 11 there's a section called "Wormhole Networks", which I believe addresses your question. The short answer to it is "**yes**". Nothing peculiar happens when you move a wormhole mouth into another wormhole. The reason, as I understand it, is that if you eliminate constraints on matter (e.g. by allowing it to be "exotic"), you permit spacetime to have whatever configuration you wish, including wormholes within wormholes. ]
[Question] [ Vitalism is: > > the theory that the origin and phenomena of life are dependent on a force or principle distinct from purely chemical or physical forces. > > > Within the universe I wish to create this is somewhat accurate. The bodies of creatures endowed **with will** (most animals, humans, etc..) are animated by a soul. If the soul is removed from the body (through the use of magic) the creature in question will die. I **do not** mean they will become soulless husks that are still *technically* alive like in the potterverse. I mean they become braindead and all their vital functions stop. A bit more information about the soul: * The soul is not simply equivalent to consciousness. Though it does encompass what we call consciousness it is further more a physical field flowing within the body. * The soul permits certain complex mental processes such as self-awareness, sentience, self-introspection and imagination. In a more discrete way, it also increases (but is not necessary for) the effectiveness of memory, planning and reasoning compared to soulless objects such as computers. * The soul is essentially a secondary processing/memory storage unit in the context of the brain. So if you exchanged the souls of two people they'd go insane since the memories/personality traits stored in their brains and the memories/personality traits stored within their new souls would be "incompatible" and contradictory. * The soul can be extended outside the body to affect the area around it (moving objects, lighting fires, etc...). This process is called magic. * The soul is naturally attracted to the underworld/the afterlife/the spriritual realm/whatever you want to call it. A soul that is not within a body will make its way towards this place. * When within a body, the soul is deluded/preoccupied by basic desires like food, sex, sleep and avoiding danger. Because of this, when within a viable host body (one that desires these things) the soul will remain in it. * When a body is sufficiently damaged (braindead) the soul regains it's natural attraction to hell/heaven/nirvana/whatever you want to call it and goes there. * The soul, though nonmaterial, is definitely physical: it can be measured, collected, tested. It obeys the physical laws of my universe. It is not supernatural. Now as you can see, I've explained why the soul leaves the body when the latter dies: the soul has no reason to stay and so it leaves. Simple. However I can not see a way to explain sensibly why forcefully removing the soul would cause the body to die. Afterall: * The heart pumps because it is electrically stimulated by firing neurons. * Those neurons fire because they are provided with various sets of chemicals. * Those chemicals are provided to those neurons by the bloodstream. * The bloodstream is maintained by the heart. * And so on... **So why would the body suddenly cease to function if the soul, something seemingly completely unnecessary to the body's well-being according to our current medical knowledge, were to leave it?** **Note:** *I am not looking for questions that simply say things like: "In your universe neurons won't fire unless the soul makes them." We know factually that this is not the case.* [Answer] This is a fun topic. It's actually very close to the philosophical topic of "compatabalism." Compatabalism is the idea that the idea that "we only have matter and chemistry" and "we have matter, chemistry and \*something else" are not actually contradictory. Fortunately, as an author, you can take the easy way out: you *know* you have souls in your world. You just need an excuse for why science doesn't see them. The key is metastability. Metastable points are like a ball at the top of a hill which can roll one way or the other. Minute factors near the top of the hill can take this system out of balance and "decide" which way the ball rolls. Life is a very metastable thing. It's a balance on top of a high wire. When you die, you become dirt, which is decidedly stable (along the way you become "meat," which is still not fully stable, but will degrade slowly towards dirt). One can remain metastable if you have feedback. If, whenever you veer to the left, you lean a little to the right, you can maintain your position on top of this metastable peak. This would be a key place to have your soul influence things. In science, it is believed that all information which can be gathered is gathered through physical means, but what if that wasn't the case. What if "the soul" could gather information by other means. If it could then process the information and convey it physical control mechanisms (like regulatory proteins), they could maintain a metastable balance. What makes this fit well with the scientific world is that it can hide in the noise. In science, it is always assumed you can't 100% measure everything. There are always error bounds. If you are in a metastable position where the content of those error bounds matters, science cannot predict what happened. This approach permits many varying degrees of such souls. A soul of an individual who had not submitted themselves to rigorous scientific analysis may have a great deal of freedom to provide information in the from of chemical and physical traces, without ever tipping off science to the fact that this is going on. An individual who has chosen to put themselves to the test, in well controlled experiments, finds that their soul has less freedom to convey information without being detected. The effective bandwidth goes down, limiting what metastabilities it can help control. The theoretical limit of this could be quantum physics. Quantum physics predicts that there is a certain amount of uncertainty that *will* be observed in the world. That uncertainty could be under the control of a soul. This is not to say that quantum mechanics proves that a soul exists, but rather than the nature of quantum mechanics provides trillions upon trillions of places to hide a soul from scientific observation, if one existed. Some creatures may be highly "soulful," dependent on this powerful feedback mechanism to retain their metastability. If they lose their soul, they quickly collapse into stable nothingness. If they depend upon this source of information and feedback to keep their heart from atrophying under the stresses of constant pressure cycles, they could literally die from a broken heart. Others may be more resilient, depending more on physical control loops which don't need soul to keep functioning. Instead, you might only see the loss of their soul in the dullness of their eyes. Naturally, different cultures would take different approaches. Some might seek to be completely independent of the soul, striving to manage all of their life functions with nothing but chemical and physical feedback loops. Others might strive to be free of this mortal coil, trying to expand their soul to the point where they were completely dependent on it, and indeed their neurons might not even fire without it! All of this is, of course, based around the idea that you cannot know what is going inside the soul. The act of trying to measure it to the point of understanding it will cause it to flee or break apart instead, losing all the information you sought. Thus, if you wanted the soul to be physical, rather than metaphysical, you can still observe and test it, but you understand that if you push it too hard, you'll lose it. It's also important that every soul be "unique." That also prevents destructive testing of thousands of souls to learn how they work (genocidal warlords: I'm looking at you!) [Answer] You've answered your own question, albeit without realizing it. First, let's take a look at what's missing from your analysis of the heartbeat. The [heart beats](https://healthunlocked.com/afassociation/posts/130025981/is-the-brain-the-control-box-of-the-heart-or-does-the-heart-have-its-own-control-i-just-wondered-as-ive-had-migraine-since-childhood.) at the rate it does because of a cluster of cells in the heart itself called the [sinus node](http://www.medicinenet.com/script/main/art.asp?articlekey=8448), the heart's natural pacemaker. The sinus node is, in turn, part of the body's larger [autonomic nervous system](https://en.wikipedia.org/wiki/Autonomic_nervous_system). This system is responsible for managing all the moment-to-moment functionality of the body that you take for granted or don't think about: breathing, digestion, sexual arousal, the flight-or-fight response, etc. The ANS is rooted in the [hypothalamus](https://en.wikipedia.org/wiki/Hypothalamus) part of the brain. Take a closer look at that list of functions. Those are remarkably similar to the things you listed the soul as being "deluded/preoccupied by" while it inhabits a body. So the soul, in your universe, is equivalent to the hypothalamus (subconscious) part of the brain. This just means the brain of a corpse would be missing a certain part, once the soul departs. [Answer] **Souls are attracted to mitochondria, the powerplant of the cell.** So mitochondria are the basic building block of cellular respiration. Without functioning mitochondria, your cells die, and when cells die, you die. So in your universe, perhaps it's not the afterlife that souls are attracted to, but "perfection of form." Heaven/hell/nirvana/whatever are places of great beauty, by whatever criteria souls use. Maybe Heaven (or positive afterlife) exists as rings of perfectly formed ice around the planet, while Hell refers to the super-heated crystalline structure of the planet's core. However souls view the universe, what they're really attracted to are beautiful structures. Mitochondria have their own ring-shaped DNA in our universe; perhaps in yours the DNA evolved to be perfectly symmetrical, or via some other means souls are attracted to the structure of mitochondrial DNA. The "perfection" of the DNA would be more powerful than Heaven or Hell, and the soul would attach itself to the DNA. When somebody dies of natural causes, the process breaks down the mitochondria in their cells, and as each mitochondria dies the body loses grip on the soul; at some point, there isn't enough "perfection" left in the body to attract the soul, and it disconnects and leaves. At this point, you may still have a body that can breathe, or stay alive through magical means, but the soul has departed. **So what happens when a soul is ripped from the body?** Souls attach themselves to the perfection they percieve, and as such, they've attached themselves to the DNA of Mitochondria. When a soul is torn away from any "perfect" container (a crystal ball or other soul container, for example), the container is destroyed in the process. So, too, are the mitochondrial chromosomes destroyed in the process of tearing away the soul. Because of this, the cellular powerplants shut down, and the body goes into massive cell death. **Another interesting thing this brings up:** old Human cultures believed that the liver could be used to foretell the future, and that the liver was the seat of emotions. Others believed the liver to be the source of courage, or power. In your universe, *this is literally true!* The highest concentration of mitochondria are in the liver, with some cells containing 1-2k in each cell. If there was one part of the body most associated with the soul in your universe, it would be the liver. You could even say that, by attaching to the mitochondrial genome, the cell subtly shifts the function of mitochondria, and therefore you CAN predict the future, or do other divination, with the liver because the souls can communicate with each other and (intentionally or unintentionally) modify the cells they are attached to. **An emotional extrapolation:** it's well known that, when a married couple has been together for decades and one dies, the other one seems to have trouble carrying on. Perhaps their souls really have become intertwined, with each soul attracted to their mitochondria as a whole. Perhaps, when one dies violently, or of natural causes, when their soul departs, it literally leaves a "hole" in the other partner's makeup, and perhaps losing the anchor on the other body makes it easier for the survivor's soul to escape. **One final thought on this:** Souls are attracted to the DNA of mitochondria, so any life form with a massive amount of mitochondria would attract souls. It would be possible, in your universe, for a soul to be attracted to a mutant animal, who's mutation encourages higher densities of mitochondria in it's cells. This may have repercussions... [Answer] The soul is also our subconscious mind, which regulates when we breath, blink, think and (sometimes)act, it does make sense that if "half" of us was yanked out we died, our lungs would be on manual mode, binking too, everything we take for granted about how the body manages itself would be gone, i dont think in any reality anyone would survive if part of them shuts down suddently. Also it could help to think of them as blueprints for smaller life forms, do we really belive a clump of cells evolved into a human without any help ?(not an actual question)The soul could be what makes us us, mold the body and mind to fight the inhospitable world and tame it, for all i see the soul your discribing is WILL, without any control (Soul) the cells(dumb organic matter) will have no ideia what to do and will act erractously ending up in a somewhat quick death. ]
[Question] [ Assuming a robot with similar intelligence to us humans came to existence. He could pass the Turing Test, the Coffee Test, the The Robot College Student Test and the Employment Test (taken from [here](http://en.wikipedia.org/wiki/Artificial_general_intelligence)). It would have an **Artificial General Intelligence**: the intelligence of a (hypothetical) machine that could successfully perform any intellectual task that a human being can. It is also refered as **Strong AI** or **Full AI**. That said, we humans, despite organizing ourselves in communities, working together and forming groups towards a greater goal, make **our survival the highest priority**. You may not be able to kill a person in cold blood, but if your life is at stake, you'll go as far as you can to stay alive. **Pain and fear are well-known mechanisms that allow us to protect ourselves**, and we strive to keep our body alive and kicking. However, **this robot feels no pain nor fear**. It can think and make its own decisions, and it was told that having information is good, and that his ultimate goal is to live for years as any human being would. Please note that **these were only suggestions, and the robot was free to think otherwise if it judged so**. It could even shut down itself if it thought it has no purpose whatsoever. Being self-aware, but without being told that it must preserve itself, and without any kind of *survival instincts*, would this machine evolve towards collectivism or individualism? Would he think of others before himself? Or act more self-centered, egoistic? **What would be the factors of influence which could change its way of thinking?** I took the **"you may not be able to kill a person in cold blood"** as an example because extreme situations cause your body to go in a fight-or-flight state. **This robot wouldn't have this feature**. Also, I'm not discussing if it would be good or break bad, just if it would act and think collectively or individually. I'm tagging as `science-based` because even though I know AGIs don't exist as I speak, I'd like the answer to be scientifically coherent based on current theories. I'll remove this tag if it doesn't fit the question. I looked around but haven't found this particular question anywhere. [Answer] Some of this answer would depend on which psychologists you asked. Since they don't agree on this sort of topic either. The ultimate question you are asking here can best be defined as such: Which will the machine place greater value on: the autonomy of the individual, or the cooperation of a group? One problem you are going to face is that these two things do not always oppose one another. The true opposition is found in holism vs egotism. Holism is the concept that the Whole is greater than the Sum of its parts. As opposed to collectivism which does not claim that a collective is greater than the individuals who make it up. Egotism is individualism at the expense of others. True individualism could simply focus in on the unique attributes of a person, without necessarily sacrificing the cooperation of those around them. With that cleared up, what might push the machine towards one belief or another? Well, honestly, I think its views would end up somewhere in the middle...holding the two sides of collectivism and individualism in a balance. In some ways, collectivism is ideal. If you are building a car, you need everyone following the same plan, working on the same idea, operating as a unit. Group survival also works better for a collective society as they will cooperate and share their skills and resources to ensure the survival of the entire group. Collectivist societies also tend to be more peaceful and have less crime (ref: modern Japan) However, collectivism tends to push one towards conformity...and it is a simple fact that most of the greatest advances in history were made by non-conformists. It was the power of those exceptional individuals that drove society to new advances. If we didn't have people who were willing to stand in defiance of the collective and pursue what they thought was best, then we wouldn't have a lot of the advances that we have today. For an AGI without a survival instinct and with the simple objective mindset of a machine, I imagine it would recognize the benefits and drawbacks of both systems of thought, and be prepared to adopt either when the situation was appropriate. Now, as for what it would *do* with this belief structure...that's an entirely different question that might end in world conquest because 'humans suck at optimizing' or 'because humans keep killing each other, and if I have to kill 1 million to save billions, so be it.' y'know... like from "Colossus: The Forbin Project". **EDIT:** I would also add that there is another possibility: that it would simply not develop concrete, static beliefs in the same way that humans do. An AGI would have to be capable of altering its own programming...that's a requirement for being able to learn. If you have a machine that doesn't operate on emotions...then it would never become attached to a particular way of thinking. It would examine each and every situation on its own merits and determine the optimal response in each case. Saying that it had a 'personality' or a 'belief structure' could be a complete misnomer...since it will alter its behaviors freely in order to achieve an optimal outcome to a situation. It won't act in a sub-optimal way because it is emotionally attached to acting that way. Its 'beliefs' would be based in scientific fact...like the usefulness of a Cost/Benefit Analysis, or statistical analytics...as opposed to being attached to the idea of the individual (the utility of which is not scientifically reliable) or not. [Answer] Does the AGI have [a subjective experience, and its own thoughts](http://en.wikipedia.org/wiki/Artificial_general_intelligence#Consciousness)? If it does, then it may evolve towards one or the other. *But if it doesn't* then it will head towards neither. A hyper-rational, heartless, planning machine won't have any overall preference. It may pick aspects of one or the other for a given task, but only because that was rationally the best choice at the time. Given the fact that it has no fear or pain response, then I'm inclined to think it does **not** have a subjective experience. I expect such an AGI will be buddy-buddy with individuals (human, and other AGI) that either share similar goals, or are useful to the AGI achieving its goals. If you need somebody to help you with something, it pays to have them on friendly terms. On an aside note, in the absence of *other* goals, an AGI may be ruthlessly efficient - even to the extent of interfering with, harming, or killing, people that get in its way. This isn't necessarily a malicious action by the AGI. The [Paperclip Optimiser](http://wiki.lesswrong.com/wiki/Paperclip_maximizer) is an interesting thought-experiment which outlines why a single-minded drive for one goal can be problematic (not for the AGI, but for others). To a person, this certainly may look like an egoist trait. However, we would be incorrectly anthropomorphising the AGI in this case. [Answer] > > It can think and **make its own decisions**, and it was told that **having information is good**, and that his ultimate goal is to live for years as any human being would. > > > Since you agree for science-based answers, I will here give a more scientific-oriented view. Self-modifying artificial intelligence is a very hard topic that some teams are just beginning to research, since it's very hard to formally qualify and quantify what will be the behavior of such a machine. A very interesting paper is "**[Delusion, Survival, and Intelligent Agents](https://www.researchgate.net/publication/221328973_Delusion_Survival_and_Intelligent_Agents)**" by Mark Ring and Laurent Orseau, 2011, Springer. In particular, this study is very interesting because it studied 3 kinds of intelligent agents: reinforcement-learning, survival and **knowledge-seeking**. The result is that **only the knowledge-seeking agent behaves completely as expected**, and would be **best suited to implement as an Artificial General Intelligence**. So, if the agent is programmed as you describe to consider that information is good and is to be actively seeked, chances are that it will pursue this objective and stay stable (according to this study). About whether this agent would evolve into a collaborative or egoistical behavior, this remains a (very good) subject for a new research, since this study only generated individual agents with no access to others. However, agent-based simulations are already a mature research domain, you will find lots of scientific findings showing how collective strategies can beat any individual strategy for a given problem. Also note that agents do not necessarily have to be intelligent to have a smart collective strategy, the insects/ants simulations show how complex collective behavior can emerge from individuals following simple rules without even directly interacting with other individuals (and this is even now used to solve complex mathematical problems such as NP-hard problems, see [Ants Colony Optimization](https://en.wikipedia.org/wiki/Ant_colony_optimization_algorithms)). Thus, my opinion is that any AGI who would like to survive and strive would necessarily have to resort to collective behavior at some point (but maybe not with humans!), but programming agents to be knowledge-seeking would further push them towards collective behavior (since information is better gathered collectively than alone) and also ensure they are stable enough to not change their program. [Answer] Given a population of embodied AGIs in a stressful environment, they would necessarily become collectivist, eventually. With or without consciousness the AGIs that cooperate survive and (assuming they can graduate with degrees in AI themselves) reproduce more successfully than those who go it alone. This is somewhat based on an extension of the principles of genetic programming which of course has no reliance on consciousness, let alone will to survive. Obvious stressors (in the sense of decreasing odds of survival, not causes of anxiety) would be needs to procure resources for continued existence and needs to defend against organized hostile entities (I am on the fence whether I'd be part of such an entity or an advocate on their behalf). If for some reason you literally mean one lonely AGI in a world of humans, I have a hard time seeing how *collectivist* or *individualist* applies. It would be a slave or pet or something of both. And always at risk of being disintegrated by people if its presence is not valued. [Answer] Will the AI gain the capability to coerce other intelligences (whether natural or artificial) and would it have the capacity for pride? If the answers to both questions are *yes*, then the AI will be capable of desiring and imposing a top-down society. ]
[Question] [ I read some time ago about [terraria](http://en.wikipedia.org/wiki/Terrarium) (singular: terrarium), which are basically small ecosystems of plants, isolated from the outside world (they get just energy from outside, not water or oxygen). The question is how big should such a terrarium be to support a human, assuming it has an infinite energy source and today's technology? Given the technology available, it is possible to create an artificial environment, where the temperature and humidity is controlled. I believe even the composition of the air can be controlled to some extent, by having some air separation plants and adding some gases to increase their concentration. Also, the water is not a problem, as there are artificial environments where water is recycled (like the International Space Station). So 2 problems remain: oxygen and food. I think the main source of food should be plants. A nice side-effect of growing plants is that they generate oxygen. Actually, if they produce enough food, they produce enough oxygen. But what kind of plants and how much plants should be harvested in order to produce enough food and oxygen for a man? [Answer] ## Problem 1: Food This is the major contributing factor to the **size** of the biosphere. Humans need to consume around 2,250 calories per day (averaged between men and women) to sustain themselves, and more if they are doing physical work. 2,250 cal = 10,460 joules (or 10.46kJ), but that's not very useful. More useful: 100g of potato (in any form) = 77cal. One medium potato ([defined by Google via USDA as 213g](https://www.google.co.uk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=calories+in+potato)) contains 163 calories. If you live off potatoes alone, you'll need: $$ 2,250 \div 163 = 13.80 \approx 14\text{ potatoes/day} $$ $$ = 14 \times 365 = 5110 \text{ potatoes/year} $$ That's quite a lot of potatoes. As you can see [here](https://www.rhs.org.uk/advice/grow-your-own/vegetables/potatoes), potatoes can be planted March-May and harvested Jun-Oct. You could always plant several crops to be harvested at different times. The same website as linked above says potatoes should be planted around 30cm apart. Assuming you follow this guide, then you'll need: $$ 5110 \times 30 = 153300\text{cm} = 1533.00\text{m} $$ for all your potatoes in one row. However, you could plant in multiple rows to save space: $$ 1533 \div 50 = 30.66 \text{m length} $$ $$ 50 \times 0.3\text{m} = 15\text{m width} $$ $$ 30.66 \times 15 = 459.9\text{m}^{2} $$ So, to survive on potatoes for one year, you will need 460 square metres of space in the biosphere. However, take into account that * You won't **want** to survive on potatoes for a year, so you need more land for other foods; * If you **do** just stick with potatoes, you can't plant them in the same place in consecutive years, so double the land required (920 square metres) * Potatoes may not be the best plant. That said, at some quick calculations, carrots would require around 140 square metres less land for the same crop. However, carrots have less calorific content per unit (41 per medium carrot), so you would need more. Growing wheat, while more space efficient, requires work after it's harvested an other ingredients to bring it to an edible state. ## Problem 2: Oxygen I see two options. You can either filter outside air or grow lots of plants. **Filter outside air** If you're assuming today's tech, you need some costly and space-inefficient filtering units. If you have advanced tech, then the walls of your biosphere can be filters, but I'll stick to today's tech. [This site](http://www.newton.dep.anl.gov/askasci/eng99/eng99210.htm) has a **very** good explanation of the oxygen requirements of an average human. To summarise: > > 8.3ft2 of air per adult for 5 hours (with an 8ft ceiling) > > > However, this is a bare minimum. If the size is much less, you won't last 5 hours. The FEMA recommendation is 10ft2 per adult for 5 hours. Given that air is 21% oxygen, this comes to $8.3 \times 0.21 = 1.74$ square feet for 5 hours. Using more appropriate numbers, this is $1.74 \times 8 = 13.92$ *cubic* feet for 5 hours, and $13.92 \div 5 = 2.78$ cubic feet per hour. That sounds like a fairly reasonable number: what output would you need? $$ (2.78 \div 21) \times 100 = 13.23 $$ This line shows that 2.78 cubic feet per hour of oxygen equates to 13.23 cubic feet per hour of normal air. $$ (13.23 \div 60) \div 60 = 0.003675 $$ This is the amount of air that your concentrator needs to take in per second to keep you alive. That's a perfectly good number: given that many home fans can move around 2 cubic feet of air per second, a commercial fan in a concentrator will have no trouble. A unit capable of doing this takes up less than 1 square metre. **Grow lots of plants** [According to NASA](http://members.shaw.ca/tfrisen/how_much_oxygen_for_a_person.htm), the average human needs 0.84kg of oxygen each day to survive. This can be produced by any size plants, but the space requirement changes depending. For example, a mature broadleaf tree such as an oak produces 10-15kg of oxygen per day, plenty to support a human. However, it can easily take up 20 square metres of space and can reach up to 30m high. Smaller plants may be easier: since they produce less oxygen, you can use a more exact number to produce closer to the right amount of oxygen per day, saving space. However, keep in mind that an exercising human uses **much** more oxygen - up to 7kg per day. The **really** easy way is to just pull in air from outside. However, this may not be possible, so your best bet is probably the filter, as it takes up the least space. [Answer] Biosphere 2 ran into some problems because they didn't take into account the heating and cooling effect on the air. You need a big bladder to handle the pressure differences if you're not heating and cooling the thing with machinery (which will likely throw off your plants' cycles) Oxygen is not a problem, if you've got artificial light and water. Just pump your CO2 thru, and there's enough algae spores/whatever in the air (unless you treated the air prior to pumping it in) to colonize that water and make you some O2 In fact, humans can eat algae. But, yeech (ie: dietary boredom can lead to refusal to eat/lack of interest in food/lack of will to live. related: dysphagia). Biggest problem is going to be getting the correct amino acids (humans don't produce all they need), and trace elements (which may, or may not be doable with micro-plants). You'll need to develop some things to cycle those. But yeah, put some plants together. If you've got enough machinery, and a lot less care of the human - you could probably put together something the size of the room (total-size), and keep them in a gel pod ala Matrix and pump the fluids and gases thru their meat-bag, recycling them with plants and sun/artificial lighting - or with vast amounts of energy and chemical (nano) machinery (ie: the rest of a 10x10x10). Best bet, hook them up to an artificial sensory environment, so they don't know how isolated and un-free they are - and how limited their diet is. Aquaponics will get you delicious fish (maybe shrimp) and plants to eat, and compost your manure (after sterilizing; no e.coli contamination) and toss it right back into the system. If you don't want to take your human's brain offline, you're going to need some VR, and an infinite walker. And maybe some serious space for them to wander around. Still likely to get claustrophilia and or caged-tiger syndrome when you try and take them out later. Why do you need your humans put on hold? Why not stasis? Or cryogenics? Or sperm-cell banks? [Answer] Look at the size of *Biosphere 2*. It failed to support human life indefinitely, but they learned a lot from it. Look over that and find issues that are one-time planning/building mistakes (e.g. the concrete curing uses oxygen), things that could be done better once you know how, and (the interesting part) what fundamentally didn't work due to the scale? ]
[Question] [ You'll begin to see a pattern emerge... If there were teleportation points near major cities, at points of interest, and otherwise spread across a vast renaissance society, what would be the key cultural effects of this system? New points can be created, but they must be moved manually (not even teleported themselves) to the desired location. It's roughly the same area and distances involved as from the very south-western tip of Spain to the very northwestern corner of Germany, and spans from the north of France to the top of Italy. Creating the orbs which form this network is difficult. Destroying or moving them, just as much. To use the orbs effectively, they must be connected to the network, which requires it to be in place, and for a powerful spellcaster to get it working properly. Transportation is instantaneous, flawless, and can take one person per activation, plus anything they're connected to (so caravans and wagons plus goods are fine, but the floor, obviously, is not). It's not cheap, because even the capital city only has four (one at each compass point of the city walls), and generally the only people with the money to secure a front-of-queue service are important nobles, merchants and dignitaries. Ordinary people travel whenever they can, often waiting for days for an open slot. I'm not looking for the obvious economic benefits, but I'm wondering what this sort of ability would have on the culture of such a civilisation. Normally, the distances involved would yield a vast array of cultures, but is the passage of wares sufficient to combat the distance, or would only certain aspects get passed along? [Answer] Okay, I'm following up on my promise to discuss [floo powder](http://harrypotter.wikia.com/wiki/Floo_powder) in my answer. I'll talk about a few other things, but this is a great opportunity for me to geek out and actually accomplish something while doing it. **Section 1: The Floo network (TL;DR - some forms of transportation will be rendered obsolete only when the system becomes available to all people)** For those who don't know, floo powder is a fictional substance used a few times in the [Harry Potter](https://en.wikipedia.org/wiki/Harry_Potter) books and films. It's a cheaply purchased powder (2 Sickles a scoop) that is readily available to pretty much all witches and wizards. Your teleportation system probably doesn't involve this powder, but I can still discuss the social aspects of such a system. Floo powder allows one to travel through the [Floo network](http://harrypotter.wikia.com/wiki/Floo_Network), which in the Harry Potter franchise is a network of fireplaces. One thing that *is* different about this is that *any* fireplace can be for this, but according to [Arthur Weasley](https://en.wikipedia.org/wiki/Order_of_the_Phoenix_(fiction)#Arthur_Weasley), the fireplace must be connected to the Floo network in advance. So I suppose it is really an analog to an easy-to-set-up teleportation station. The Floo network is used pretty much how I think your teleportation system would work - for some minor travels (i.e. to shop), as well as commuting to and from work. It is important to note that this does not render normal transportation obsolete, because of the many other ways to get from one place to another (I'll ignore [Apparition](http://harrypotter.wikia.com/wiki/Apparition) because it has no place in your world). I would assume static teleportation would have the same effects in your world, and would have the same uses. One major thing to note is that *because vehicles and other objects can be taken with the person, many forms of transportation for goods would be rendered obsolete*. You wouldn't need a horse and wagon to get from one place in town to another if there were teleport stations set up near where you wanted to leave from and go to. So we've established that many forms of transportation would be rendered obsolete. But *this is only if the stations were widely available*. In your scenario, they are a privilege that only a few can use regularly. For this reason, many forms of transportation would *not* be rendered obsolete - yet. I would guess that, over a period of time (many decades, granted), the system would become readily available to the general public, and the system would resemble more the Floo network. I could make other comparisons here, most notably the New York City subway system or the London Underground, but I doubt these are necessary, and would only apply when the system becomes ubiquitous. **Section 2: Warfare (TL;DR - the system could be a big problem if enemy forces get control of it)** This is actually the first thing that popped into my head, partly because I recently took a look at another question involving technology and warfare. The following scenario would only be an issue if the system proliferates - but then it would be a huge problem. One of the great things (or bad things, depending on your perspective) of a Renaissance-like society is that wars are so darn *slow*. Well, troop movements, at least. Assuming you've read at least one book when you were young that revolved around a Middle-Ages-esque epic good-vs-evil premise (and if you haven't, go out and [read one right now](http://www.redwallabbey.com/)!), you know that it takes an army (or even a few individuals) a *long* time to get from Point A to Point B. That's really good for a second army if the first army is attacking their fortress/castle/town/other-settlement because if they have any scouts at all, they will know in advance (even if it's only an hour or two) that the enemy is coming, and they have time to rouse the soldiers and get the other citizens to safety. That all comes crashing down with the advent of this teleportation system. True, there are only a few teleport stations (again, unless the system develops), but even a single terrorist could potentially climb on one and set off a bomb (medieval-style) in the city center. Scary stuff. If the teleport cubicles *are* available to all, that means that multiple terrorists could get through - or even a small army. Defense forces would have absolutely no warning, and a city could be taken within a very short period of time. By the way, long after writing this answer I found [this](https://worldbuilding.stackexchange.com/questions/82/would-instantaneous-teleportation-encourage-or-discourage-warfare/233#233) question, which discusses this point in more detail. **Section 3: Relations between nations (TL;DR - everyone gets to know everyone else)** This is the last bit. I promise. Anyway, lets look at the history of *our* world - or rather, some bits from the [Age of Discovery](https://en.wikipedia.org/wiki/Age_of_Discovery) onwards. *In fourteen hundred ninety-two* *Columbus sailed the ocean blue.* *He had three ships and sailed from Spain* *He sailed through sunshine, wind and rain.* (From [here](http://floppingaces.net/2012/10/08/in-1492-columbus-sailed-the-ocean-blue/)) Christopher Columbus first reached "The New World" in 1492. He was an Italian but sailed for Spain, funded by Queen Isabella and King Ferdinand. After such a momentous voyage, one would think that Spain (and everyone else in Europe) would be eager to colonize (or at least make friends with the folks who were *already* living in "The New World" - naaaah), right? Well, everyone else in Europe *was* pumped up about the new opportunities that lay ahead. The trouble is, it took time. Things really didn't start rolling [until the early 1500s](https://en.wikipedia.org/wiki/European_colonization_of_the_Americas), and even after that, colonization wasn't exactly smooth sailing (pun absolutely intended). The first players were Portugal and Spain, thanks in part to the [Treaty of Tordesillas](https://en.wikipedia.org/wiki/Treaty_of_Tordesillas). It took decades for other European nations to get hand- and foot- holds in "The New World". Would this static teleport system have made things any easier? Probably not at first. It is true that Span and other countries would have invested a lot to get a few stations over in the Americas because of how long it took to cross the Atlantic, but there wouldn't have been a whole lot while the technology was in its early stages. But I can almost guarantee you that, whatever phase the teleportation system was in prior to a Columbus-esque discovery, it would be very much improved afterwards. So it would definitely make relations between nations easier, because travel would be much quicker. **Summary** What you should get out of this is that such a system might not have a revolutionary impact at first if the system was only readily accessible to a few people. There would be other problems to solve, such as just where the power for this whole thing comes from. But I think that the technology would be developed pretty darn quickly once people saw its uses. It could lead to faster transport of people and goods, quicker and deadlier warfare, and better international relations. [Answer] I want to point out a few non-obvious changes. ## Columbus wouldn't have discovered the Americas Columbus was trying to reach India by what he thought would be a shorter way. If they had teleportation, he wouldn't have been looking for a shorter way. They'd just have set up a portal in the normal way, either sailing around Africa or overland. The Americas might be discovered eventually, but not for the reasons that Columbus did. ## Large empires would be easier One of the problems with administering a large empire is that you need to maintain reliable troops throughout it to put down rebellions, etc. With faster transport, that's much less of an issue. Troops can quickly get to the nearest loyal area and stage in closer. Other administrative personnel could also move around quickly. For example, think about a French governor who lives in Paris and governs England. ## Science would spread faster Want to send your scientifically gifted child to the best school? Now you can. Also, scientists can conference or quickly consult with each other. ## Culture spread There used to be far more languages than there are now. Some of them are still spoken but have become secondary languages for most people who speak them. For example, are there any Welsh people who don't speak English? With fast transport, people have more interaction with people who speak other languages. Inevitably this results in people learning at least one more language. Want to see an authentic Italian opera? After a quick portal trip, you can. People have more cultural options in the near term. Over time you can expect these options to dwindle though. Why go to a local opera when you can go to the best performance in the world? You can see this happen in our world in places like Hollywood. Big budget movies are overwhelmingly based in Hollywood (although they may be shot elsewhere). Star Wars, Die Hard, and ET are all examples of cultural icons that transcend single cultures. They may originate in English-speaking Hollywood, but they are known around the world. Also, if there's a large stable empire, culture would tend to spread through the empire. The route to power in such an empire is in the capital, so the ambitious will gravitate there. Those who return home will spread the cultural interests from the capital to home. Those who stay in the capital will bring some of their cultural interests from home to the capital. [Answer] First you'd get a vastly increased rate of cultural homogenization. Secondly, to all intents & purposes, the entire world could be one city, as soon as it has a portal, it becomes "next door." This would reduce urban sprawl in the near-term because the big land-consuming entities like Thirdly, people with priority access would have a fantastic advantage in trade and information (and consequent further benefits) Increasing their own power to the point where. Fourthly, in the putting-down of rebellion.. one of the major advantages of established powers in putting down rebellions has always been in their ability to deal piecemeal with rebel forces, in such a scenario the first thing any rebel force would do is to take a portal and thereby largely bypass any such problem, they would be (ish) instantly connected to any other cell of rebels and with the government forces only able to send through one person at a time from wherever they were mobilized from.. well.. Fifthly,see: The establishment of international telecommunications [Answer] I'm going to make a couple assumptions. Once a point is part of the network, you can travel to any other point on the same network. A node can only be connected to 1 network, and that someone would have to have access to a network to create a new node. This could/would allow for richer countries to have 2 or more networks to 'separate' travel. Maybe have an 'ambassador' network for the 'kings' business highly secure and always available. Then there would be the 'public' network. For business and pleasure of the rest of the people. This could work well for trade, say one country (lets take Germany) went to all the trouble to transport a node all the way to China. If they connected it to the current network, everyone on the network would benefit from Germany's labor. However, if they had a separate network, then everything would go through Germany and then out to ally's, with a nice hefty profit margin in there. They could also 'sell' a node on the special network to close friends and ally's to keep them such. There would likely be more exchange of goods between different places, but not too dissimilar from today's world market. Discovery would and exploitation would be much faster, because once a node is placed somewhere it isn't like it's month's long trip back to say what you found surviving all the same trials and everyone else will just need to make a quick hop to come and exploit, make a buck and hop back. Of course whoever controls the distant node will be wealthy beyond compare, since they would set the prices to return. But it would likely still be worth the cost. [Answer] In the era of society you propose, it is most likely that such orbs (assuming that it is accepted and integrated into society by the state and the church, as opposed to being thought of as something of evil origin) would wind up being tightly controlled by the rich and powerful. Especially if they are expensive. I could see defensive structures being built around such orbs, entry and exit taxes levied, bribes paid, and so forth. Flawless teleportation would protect against inter-penetration, however you did not mention the ability to communicate through the orbs, so I imagine that would still require couriers. Shortened transit (and hence communication) times would impact society much in the way that modern travel and communications impact people today, though perhaps to a lesser degree given the limitations proposed. Faster response times and decision making are the primary aspects, which affect all aspects of life - trade, governance, construction, military positioning, logistics and so forth. Socially, people could be further apart and still feel the sense of community. It would also tend to increase the division between the haves and the have-nots, if my thoughts on access control prove correct. It seems unlikely that the common person would gain frequent access to such a device, except perhaps as part of a caravan or convoy, unless there is some powerful organization behind either the orbs or the common people who for some reason insist on common access. ]
[Question] [ Suns are stars. They are orbited by planets, and sometimes other stars. Planets are orbited by moons. Reasonably advanced civilizations may launch artificial satellites into orbits around their planet as well. Light and energy in a planetary system mostly come from its central star, which is powered by nuclear fusion of the lightest elements. Due to revolution of celestial bodies, planets often have regular seasonal and day-night cycles. Life that has developed on a planet depends on those cycles. I’d like to alter one of these fundamental concepts, making the system geocentric instead of heliocentric: Would it be possible to have a star-like satellite orbiting a [“class M” planet](https://en.wikipedia.org/wiki/Class_M_planet)? In other words, how can I light up a moon? (This seems to have been done before, but with handwaving/unobtainium, by Clarke in [*The Sands of Mars*](https://en.wikipedia.org/wiki/The_Sands_of_Mars) “Project Dawn” for Phobos and by Pohl/Kornbluth in [*Wolfbane*](https://en.wikipedia.org/wiki/Wolfbane_(novel)).) Since the discs of our Sun and Moon appear to be about the same size in the sky, imagine Moon would not reflect but *emit light* and possibly would revolve quicker around Earth (“1-day month”). This light-emitting moon would replace a proper sun, if orbiting a rogue planet, or would augment a sun that was too far away, i.e. the planet is outside any normal habitable zone of a usual planetary system. An array of smaller satellites would also be acceptable and they may be artificial if necessary. ## Problems Regardless of energy source, I expect radiation to be a problem, even with a massive atmosphere. Heliocentric systems are natural, because the smallest stars are still larger and more massive than the biggest planets: [OGLE-TR-122b](https://en.wikipedia.org/wiki/OGLE-TR-122) seems to be the [smallest known star](http://www.universetoday.com/25348/what-is-the-smallest-star/), which has about the size of Jupiter but 100 times its mass. The [largest discovered exoplanets](https://en.wikipedia.org/wiki/List_of_largest_exoplanets) have 2 or 3 times the radius of Jupiter. I think the large mass is required to make constant, stable hydrogen fusion possible. So that one is most likely not an option. [Answer] While I don't really have the complete physics background to back this up, an interesting thought for a geocentric system might be a binary star system. Imagine a pair of fairly equal mass stars in a very low eccentricity orbit around each other. Both of these stars would actually rotate around a point in between them, where you could emplace your much smaller planet right on the point of rotation, and you effectively have a pair of suns orbiting your (probably very hot) world. Day on this world would, of course, be effectively endless (barring some other satellite giving you temporary reprieve in the form of an eclipse) so you would probably want to set these stars further away from your M class planet than the normal Goldilocks zone to cool things down a little bit. Depending on the distances in question and whether or not you include other satellites, the planet might also be tidally locked with its suns, giving a band around the middle (effectively the prime meridian) where things are a bit cooler by virtue of having more indirect sunlight [Answer] Nuclear light bulb. The idea is that a radioactive plasma is contained within a vessel. The idea was originally proposed as a type of rocket engine (the heat from the vessel being used to drive the propellant), but I think it could live up to its name in a more literal sense - why not? Throwing out the space ship definitely simplifies the engineering. A simple concept would be to stuff a lot of long-lived radioactive materials inside a large tungsten shell. The radioactive decay will heat up the tungsten - and as we all know from those obsolescent incandescent light bulbs, sufficiently hot tungsten produces a nice, white glow. It's not very efficient, but with the right kind of material powering it, it could still glow for a very long time. [Answer] The most efficient type of energy generation we currently know of is [antimatter](https://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table) followed by fusion. As you said the amount of matter needed to make a *natural* self sustaining fusion reaction would be significantly larger than the planet itself. With a little handwavium if artificial fusion reactors where made in space then you could theoretically have a massive moon that happens to be a power station emitting light and other radiation towards the planet. Because it is artificial the emitter could by the way of things tidally locked to the planet, so that the "sun" side or emitter side would always be concentrating all of the energy towards the planet not wasting any energy. Also the moon would not have to be any closer or farther than the real moon because the planet in question would spin. Using the earth system as a example if the moon became like the Sun and emitted the same amount of light as the earth normally does, [the day would only lengthen by 50 minutes](http://www.astronomycafe.net/qadir/q1038.html). This is almost the same as Mars (at 39 minutes more) and would not be all that noticeable to inhabitants. As an alternate suggestion you could have a massive focusing cluster of satellites by the closest star and beam the power to a moon at L1 relative to the star/planet system. The satellites would ideally be as close as possible to the star to reduce the total size of the satellite(s). This could be a somewhat passive system and would get around energy density problems. The concept reminds me of beam power to something like a solar sail but for a entire planet. [Answer] in real life, western scientists wondered for centuries what powered the sun. Calculations showed it could burn for just a few thousand years as in biblical chronology if powered by combustion, which was not enough for the eons of the new science of geology. If the sun was powered by slow gravitational contraction, it could shine for a few millions of years according to later calculations, but by then geologists claimed the Earth had life for hundreds of millions of years. I have read that there was once physical violence at a scientific meeting between an astronomer and a geologist because of that problem. And finally nuclear fusion was calculated to be the way that stars shone. Now you want to find a way for moon-sized "stars" to light a planet without having the immense mass that makes natural fusion possible. Fortunately what you want is not **TOTALLY** impossible. To me a vast, totally mechanized system of power generation powering lights to light the planet seems the "simplest" solution. IMHO a fully artificial "sun satellite" would probably have to have a vast system of power generators, repair robots and automated factories to manufacture parts for generators and lights, and manufacture the repair robots, and the repair robots would have to maintain and repair everything. And that seems to be the simplest way to go. if the Earth and moon are ejected from the solar system build a lot of fusion reactors on the Moon to power lights covering the entire surface and all aimed at the Earth to illuminate and heat the Earth. But if you want a system that runs by itself without machinery the way a sun runs, that is a problem, since you don't want an object with the mass necessary for natural fusion. If you only want the moon like sun satellite to shine for a measly few thousand years, the creators of it could construct it as a giant pyre in space designed to burn for thousands of years. One way is to use fusion power to power matter transmuting devices that transmute various elements into radioactive and maybe fissionable elements. If you move enough of such elements to the moon in question they will provide enough energy per second to light and heat the planet. The radiation produced by the elements will have to be turned into electromagnetic radiation (light) and Joanna Marietti's "nuclear light bulb" suggestion shows how to do it. Of course the more energy a radioactive isotope produces each second, the faster it usually decays to a non radioactive isotope. Thus someone considering such a system will have to calculate which elements to use and how much to have a steady light production for the necessary time since the system was created in your story. Maybe you want the first explorers to reach the "sun satellite" to discover that the light output will soon fall below sufficient amounts and life on their planet will die, unless they can find a way to replenish the radioactive elements on the "sun satellite". Since a rocky, Earth like planet is formed by countless collisions of large astronomical bodies, it is molten hot soon after forming. Thus your Earth like planet and any large moons would be molten hot in the beginning. But the smaller moons would cool off and form solid surfaces many millions of years before the larger planets. Thus the planets may have been able to illuminate and heat their moons, and maybe space travelers might seed the moons with life that might survive until the planets cooled. So the moons in question would cool off and no longer naturally illuminate their planets long before their planets cool off and had solid surfaces where life might need heat and light from the moons. By the time the planets needed light and heat from molten hot moons, the molten hot moons would have cooled and no longer naturally provide heat and light. So a highly advanced society could have artificially reheated the moon or moons of a planet so the moons would provide enough heat and light, and then seeded the planet with multi celled life forms to take advantage of that heat and light before the moons cooled off again. It could even be possible for an extremely unlikely natural collision many millions of years after the age when they were common to reheat the moon to molten heat. Of course reheating a moon or moons to molten heat again would be a very big task for those super advanced aliens. They would probably divert many large asteroids and comets to impact on the moon (and not on the planet, except for any comets needed to provide water and atmosphere) and reheat it. The goal would be for one impart, or many simultaneous impacts, that are almost but not quite energetic enough to shatter the moon, to provide the maximum amount of heating energy. And the super powerful aliens might want to collide other asteroids and comets with each other to provide a new moon for the planet to replace the one that was turned into a sun. [Answer] There are two issues with the reflecting satellite. I'll illustrate them with the Earth-Moon system, which is a good one since Moon is, for what we know, an exceptionally big satellite. * albedo is the proportion of light that the body will absorb and won't reflect. Since it is variable, let's say your satellite is a perfect mirror and will reflect all of the received light (the Moon's actual albedo is 0.136). * the second one is that your satellite will have only a fraction of the surface of the planet. Even at the same distance from the Sun, it means only a proportional amount of sunlight will be collected. Wikipedia gives us that Moon surface is 0.074 of the Earth one, so the maximum total light the Moon can reflect is 0.074 of the total light that arrives into Earth. Which is not a small amount, but would certainly fall outside the "sun" range. * what is worse, the light will be scattered by the moon back towards the space. From the Moon, [Earth is a 2°\*2° target](https://astronomy.stackexchange.com/questions/7736/what-is-the-angular-diameter-of-earth-as-seen-from-the-moon) in a sky that is 180°\*180° wide and long. So, about 1/8100 of the light received by the Moon (that remember, is 0.074 of the light received by Earth). What conditions would improve your moon? A higher albedo, a bigger satellite and closer to the planet (so the planet is apparently bigger) would help, but while they could make nights less dark, I do not think no combination of them would be enough to get a "sun" out of a satellite. The only alternative left would be an artificial object, which could be made as to avoid scattering of the reflected light (but would be impossibly large by our current standards). ]
[Question] [ A group of refugees (around 50) fled enemies in a land full of rock. Fortunately they found exactly what they needed: a small river falling into a deep and tight gorge. There is a network of caves starting from the gorge, large enough to live, to make fire, to walk several minutes in every direction. Some of the caves are large enough to build walls to separate small habitations. It's not very visible from the outside at first, but my refugees could make some layouts to improve their life conditions and change this fact. They start to improve their "city". They have lots of water, they find enough food (yep, they do, I don't ask about that; there is a little bit of magic involved), but they know other refugees are coming. Lots of them. They know they're not a threat to their enemies for now. They are only a few, hiding, and very bad at fighting, medieval technology (like their enemies). But with other refugees coming, they are going to become a major issue to their enemies. They have to secure their place, while being more and more numerous. What can they do to * host more and more of them in an underground city? * secure the place against an incoming army (they have time to prepare)? [Answer] **The number of refugees that can be supported is depend on space, sanitation, and food** as water is already taken care of. ## **Living Space** Humans are capable of [getting by with incredibly small amounts of living space](http://www.alysion.org/acres/space.html) per person. How many people can fit in a square meter will depend on the technology and culture of the refugees. For example, multilevel hammocks allow many more people to sleep in a single room than sleeping on the ground can support. This graph seems to indicate that humans need about 100 sq ft per person in a medieval setting. [![Average square feet per person](https://i.stack.imgur.com/DADlN.jpg)](https://i.stack.imgur.com/DADlN.jpg) Perhaps this can be compressed down to 50 square feet per person or even smaller but this is likely to be an unsustainable position. The only solution is to find more caves or dig out new chambers. Perhaps the magic that provides food can also perform some digging? ## **Defense** In order to defend the caverns, the first batch of refugees will need to prepare for a siege. This means stockpiling food, water, and other supplies. **Water Attacks** - The attackers could build a dam down river to cause flooding inside the caves, thus flushing out the refugees. Alternate paths for the river of intra-cave dams will be required to prevent this kind of attack. **Smoke Attacks** - The attackers could place fires over any air vents then add noxious plants to the flames. Depending on the plant, this may outright kill the refugees or force them to exit. Many air openings and the ability to block airvents will need to be built in. **Plague** - "Someone's poisoned the water hole!". The introduction of poisons or disease into the water supply can cause many or all of the refugees to become ill and unable to defend themselves. Not sure how to defeat this kind of attack with medieval level science/tech. Maybe a chance observation that people who boiled their water first tended to not get sick? **Physical Attacks** - Caves have natural choke points in the form of entrances. If these entrances can be heavily defended or completely blocked in the event of an attack, then this gives the refugees a significant advantage over the attackers. Siege weaponry isn't terribly effective against underground fortifications. [Answer] # How to support population? Assuming these refugees are untrained peasants fleeing an enemy army, the biggest problems I can see with using a natural cave are ventilation and stability. A badly ventilated cave that is starting to fill to capacity will push some people farther and farther back into the cave tunnels. Caves are dark, moist, and have a tendency to have shard drop offs and extremely narrow passages. This combined with the waste of possibly thousands of people is going to make this camp even better at transmitting disease and causing death than the average medieval town. Without knowing how many caverns there are, how they are distributed and what their width is I really cannot calculate the number of people it can hold. I can give you some basic ideas to consider. The average worldwide height [seems to be 160 - 175cm](https://en.wikipedia.org/wiki/Template:Average_height_around_the_world) which is about 2 meters. The average width [seems to be 40 to 43 centimeters](http://www.livestrong.com/article/484806-the-average-shoulder-width-for-females/) or half a meter. If each cavern is 6 meters high and (let's assume) 100 meters in width, we can fit a rough maximum of 200 people in a cavern (without stacking them). These are not ideal/healthy conditions, so let's give each person 30 meters of space. This equates to 3 healthy people per cavern, with the possibility to move this up to 6 people per cavern assuming two people per 30 meters. Multiply this by the number of caverns and you have the rough sustainable population of the "city" assuming you can provide resources. You would also have to organize "waste teams" to haul human waste to the surface and dump it away from the city (and preferably the river since you don't want to be chugging piss-contaminated water). This job would be undertaken by the majority of people. Anyone with special knowledge (e.g. Magic users, soldiers, weapon smiths, wood workers) would be assigned to teams that utilize that knowledge. This maximizes productivity and will be improved on over time. Magic can be used to drill ventilation shafts. # How to protect against enemies? This depends on several factors. What is the expected size of an attacking force? If, say, the cave has a population of 200 peasants and the attackers number 10,000 knights then you are screwed. If there are a thousand peasants, 500 former feudal levies and 500 smiths, you stand a chance in a complex cave network. The best weapon you can make: [a spear!](https://en.wikipedia.org/wiki/Spear) Spears are easy to use. Put your carpenters to work crafting wooden poles while your stone workers and smiths create stone and metal spear ends. This way, you can arm your entire population with an efficient, easy to use weapon. You could also use a [bow and arrow](https://en.wikipedia.org/wiki/Bow_and_arrow) (simple bows are easy to make. It's not like you need a longbow or compound bow specifically. Just something that can fire arrows!) and crowd your would be archers into narrow tunnels. Any enemy who tries to get to them will get a face full of arrows and spears. The goal will not be to stop the enemy from entering the cave, but to spend your time (before the battle) exploring and learning every cranny and nook to hide in. This way you can conduct guerrilla warfare **in the cave**. Make enemy casualties become soon high that they do not see any worth in pursuing your peasant army farther. [Answer] I would address both questions with the same solution. To host more and more people underground mine the rock (carve out chunks) where you want another room or where you wish to enlarge a cavern. With the mined rock, you can then build defenses (walls, rock-fall traps, ammo for catapult/slingshot, etc). ]
[Question] [ The question about a diet of dust brought up a few creatures that survive on dust, however they were all insect-sized or smaller. This got me thinking about the [Blue Whale](http://en.wikipedia.org/wiki/Blue_whale#Feeding), which survives on a diet of [Krill](http://en.wikipedia.org/wiki/Krill). I'm looking to create something that survives on nutrients and minerals in the air that is roughly like a bird; i.e. has wings, similar size, hollow bones. I believe that it is impossible for such a creature to survive in an earth-like environment simply by feeding on nutrients and other dust-like particles (such as pollen or minerals' dust) that either float through the air or settle on the land. (Please do tell me if I'm wrong) I'm looking to find what environmental conditions are required for such a creature to survive. Answers should ideally consider: * diet breakdown * energy requirements of the creature * where the particles come from [Answer] I don't believe such a creature is possible. There are several types of creature which each much smaller organisms than themselves, the two which spring to mind are whales and jellyfish. The main reason I don't believe this would translate to birds is because of the energy involved. A blue whale doesn't have to exert a lot of effort to catch it's prey... it's swims, mouth wide open and scoops them up as it goes. It uses relatively little energy (bear in mind that the sea holds most of it's weight). A jellyfish is much the same, it just floats there and food comes to it. If you consider a bird they are much more active and flap their wings (in some cases at an incredible rate to stay airborn). They expend a lot of energy to do this... in order to catch enough food to supply the required energy the air would need to be thick with bugs (I doubt even Scottish midge season would cut it!). If you watch swallows/house martins hunting flies you'll see it's a very energy intensive job! So what's the solution? The closest I can come up with is some sort of floating jellyfish, a natural hot air balloon with long tendrils which could catch and then absorb whatever hit them. I suspect such a creature would be a fair size and would drift with the wind (and so doesn't require a lot of energy to sustain it). Whether such a creature is feasible from other perspectives though I'm not sure! [Answer] Essentially the question is one of balancing energy input and energy output for the organism. I will list different ways on increasing input and decreasing output. **Increasing Input:** While Earth’s atmosphere doesn’t typically contain a high density of organic matter there are times when it becomes substantially more dense. Flying insects frequently swarm and reach extremely high densities. I think feeding off of larger insects like locusts would not qualify as passive feeding, but if you make the insects smaller I presume eventually they would qualify. Even with very small gnats a dense enough swarm should allow for efficient feeding. Another source of air-borne food is pollen. On earth pollen densities can get pretty high depending on the density of pollen producing plants and the season. An environment in which pollen densities became high enough could allow a bird to feed off of it efficiently. Potentially you could explain such a phenomenon as symbiotic. Many insect species on earth subsist entirely off of energy voluntarily provided to them by plants in order to facilitate pollination. You could imagine the same symbiosis could extend to your bird. The energy costs for feeding the bird would be quite high for the plant, but your bird could potentially carry the pollen vast distances. For either of these strategies to work you’d want the bird to have a large input surface area, analogous to the mouth of a whale. **Decreasing Output:** The simplest way to decrease output is to have the bird dormant whenever possible. It flies only to feed and otherwise does not expend any unnecessary energy. When it does fly it would need to rely on updrafts and do mostly soaring and gliding. The math is too fuzzy to really say whether all these strategies would work for sure, but I think they are well within the realm of possibility. There are a lot so other possibilities (like making it cold-blooded), but they would all involve moving further away from what we think of as a bird. [Answer] A creature like this is barely possible. A bird usually needs between 1/4 and 1/2 of it's body weight in food to live each day. As we will be talking chitinous insects and an active lifestyle, lets use the upper end of that spectrum. Lets say that allows the bird to fly 1/8th of each day which means the birds is small and its flight is supported by environmental conditions so the flying is easy. This seems high as I am envisioning a house sparrow as the control. With flying creatures smaller=easier. Using a very rough average sparrow: it is about 30g and has a cross sectional area of about 17 square cm. As it needs to catch its food, lets optimistically say that its feathers collect all food it touches and it picks the food from its feathers while perched. For fun lets use the average airspeed velocity of an unladen European swallow which seems to be about 11 meters per second. Using these assumptions which for actual science are insufficient, the bird would need to fly through air with an average food concentration of .075g/m^3 of air. If the bird only ate gnats, that would be on average 75 gnats for every cube meter or it would have to catch an eat a gnat every 1/8th of meter it flies. **That is 88 gnats a second.** Why do I think that is still possible? I am going to assume the bird eats pollen, spores, or floating insects which cannot avoid it; while resting/picking its feathers it is still able to catch food by positioning itself in a windy area; and it opens its wings to maximize its catching ability. As we are describing an ideal environment for such a creature and it needs a lot less food as it would fly a lot less, it is possible that such a creature could evolve to take advantage of this described niche. Please note, however, that any such creature is highly dependent on its environment. Most seem like they would be willing to catch larger insects or pick up food on the ground if available. It would also be high susceptible to hazards such a predators or environment contamination. This works well in water as its buoyancy allow it to hold a higher food concentration that air can. It is fun to dream of a giant bird which flies efficiently all the time by gliding everywhere. At the elevations where gliding is possible, however, it would not make sense to me for there to be enough food. [Answer] The problem is not the bird, the problem is the food. It must also stay airborne and be present in sufficient amounts. However even a dust size plant would eventually sink down in the Earth atmosphere. [Answer] Essentially Aeroplankton is your food source. <https://en.wikipedia.org/wiki/Aeroplankton> There are 2 problems that you are trying to overcome. 1. Aeroplankton is not as dense as sea-based plankton 2. The energy requirements for flying are higher than for floating in the sea. To overcome this you would need to increase the density of your atmosphere, increasing the amount of available lift to your creatures, and decreasing their energy output requirements. The denser atmosphere would allow for larger aeroplankton, making more food available. [Answer] I expect that bats in a sufficiently insect rich diet wouldn't have to aim for them, just fly with their mouth open. Riffing off the jellyfish answer, if the concentration of helium in the atmosphere were a little higher, then an animal may be able to collect helium over its lifetime, reducing the energy expense of maintaining "flight". At that point it could be a very large creature with very little mass, requiring very little energy. However, storms, wind, and such would cause great injury. [Answer] I'm going to go a slightly different direction here and give you a 'yes' answer. First we have to imagine a densely abundant food source. [There are animals](http://umich.uloop.com/news/view.php/77109/4-incredible-photosynthetic-animals) that have algae growing inside their cells so that they can get energy directly through photosynthesis. Imagine a sort of midge or even slightly larger insect that had done so. Its life pretty much consists of collecting sunlight, mating, and going where the wind sends them so that the eggs they lay have less competition when they hatch. All quite easily conceivable. Now for your bird. As has been pointed out, flying fast enough to catch enough to feed a bird requires an unlikely density to sustain a population of such birds. Soaring would relieve a lot of the energy requirement, but the controlling factor that causes huge swarms is usually either fast wind currents, or brief mating periods, so I'm going to rule these out. You need a largely stationary bird. There are plenty of examples of sea creatures that do what we are talking about, just google 'filter-feeder', but these rely on an organ within the respiration pathway to collect biological matter for eating. Evolution has a large stretch to go before that will happen with birds. One could imagine a pelican like bird with a baleen like structure in a very large mouth that just sits in the wind all day smiling. This really isn't too far off from how flamingos eat. I'd give that one a plausible on the Mythbusters scale. I think it is rather more likely that a bird would use its already existing structure though: its wings. A bird with slightly evolved feathers designed to catch small insects could sit out in the wind with its wings outstretched (clinging tightly to a treetop), then pick the bugs out by combing its beaks through its feathers. This is very similar to what sea fans and anemones do. Even without an evolutionary change to the feathers, birds could wet their feathers with sticky saliva to accomplish the same thing. Expending very little energy for a very good payoff. I think such a bird would likely eventually lose the power of flight as its feathers became more and more specialized, but you've got a few millennia of what you want. ]
[Question] [ My first post here, and it's more about destroying worlds than making them. Consider this scenario: An earthlike planet where a powerful magic spell has been cast, protecting *all positrons* from annihilation on contact with regular matter. Stable antimatter can finally exist (in a sense). And positronium finds itself an array of useful applications, including weapons exchanges with parallel universes (which don't share the same protective field). Something these wizards failed to account for was this protective field expanding outwards at the speed of light. 7 minutes after the spell was cast, positrons began to build up in the planet's sunlike star. The proton-proton fusion reaction at its core becomes about 5% less energetic, as it was fuelled in part by electron-positron annihilation. This goes wholly unnoticed for a while due to the 1000-year half life it takes for heat to reach the sun's surface. Some time later, let's say 10,000 years, a terrorist group called the Curse Breakers disables the spell. All stored positronium detonates immediately. But 14 minutes later, the survivors of this blast bear witness an even greater cosmic catastrophe - the destruction of their sun. What I'm asking is this: how big a boom would there be? How fast would it happen? If my calculations are correct, the thick shell of positrons around the core would contain 6.28x10^36 joules. With this energy released in a tiny fraction of a second, could the star undergo a helium flash? Runaway fusion at its core? Maybe even a supernova? (If not, how long would the spell need to last to generate enough positrons?) Edit: And what effects would be felt on the planet, assuming it is earthlike and orbits at 1 AU? [Answer] For comparison consider a helium flash, when a sun-like star has aged a bit, it will develop a core of degenerate helium. The temperature is not enough for this core to start nuclear fusion. However, the temperature will gradually rise until it is hot enough for the helium to start to fuse. Becuase the helium core is degenerate, the helium fusing is not thermally regulated, and all the helium fuses in a few minutes called a helium flash. A helium flash releases about $10^{41}$ Joules almost instantaneously. However, the energy released by this explosion causes the core to come out of degeneracy and thermally expand. Nearly all of the energy is absorbed by the expansion of the core, and the outer layers of the star. The Helium flash is almost undetectable from outside the star. Your explosion releases only 1/10000 of the energy released in a helium flash. It would cause the core to heat up and expand. The expansion of the core would absorb nearly all the energy, and, like a helium flash, the explosion might not be detectable from the planet. Now helium flashes occur in red giant stars, with a degenerate core. That gives more space for thermal expansion without disrupting the core. Things may be different in younger, sun-like stars. [Answer] I am not sure this question is answerable using physics, but it is answerable in magic. The answer is, 'Whatever you want to happen'. In allowing matter and antimatter to coexist, you have gone so far beyond physics as to make physics irrelevant. We have no idea how antimatter would react to matter if they were not allowed to destroy each other. There is no valid reference in physics as to how the curse could have been implemented. How much energy would it have taken? Where did that energy come from? Because of this wizardry, could matter and antimatter atoms intermingle and intermix freely, or would it require some sort of energy barrier between them? If this energy barrier collapsed, how much energy would it release? We know, for instance, that fusion takes a lot of energy to initiate. But once initiated, it releases more energy than it took to initiate. I suspect that, whatever this curse, the removal would initiate some form of nuclear reaction, releasing far more energy than just the matter-antimatter reaction. Physics tells us that the main radiation from such a process of matter-antimatter annihilation is gamma radiation, with great penetrating power. This would not be a simple 'explosion'. One can not, for instance, compare a nuclear explosion to that of an equivalent amount of TNT. Antimatter is formed on earth during severe electrical storms. A lot of it. It is neutralized almost as soon as it is formed. But if it were not neutralized? How would it effect our ionosphere? Our magnetosphere? The ozone layer? Communications? It would change what we know about physics, and in reverting back to traditional physics, the implications are just as unknowable as the implications of making the curse in the first place. To say that everything would be 'business as usual', except that antimatter is not annihilated by matter, simply puts physics aside. There WOULD be many, many other implications. That last point is the crutch of any answer to the question. By what reason, except assumptions and wizardry, would antimatter atoms remain in the star? What would the theoretical physics be that explains this? How much energy would be required, and in what form? This is important, because we do not know how much energy would be required to dispel the magic curse. That is, how much energy would it take to reverse the ability of matter and anti-matter to co-exist? Or would removing the curse release even MORE energy? Would removing the curse take up all the energy, so none would be left? Obviously, if matter and antimatter were kept from annihilating each other, it would take tremendous energy to do so. As an example, would this curse be like bottling up antimatter and constraining it? Therefore, the antimatter in the sun would be equivalent to being in a very strong shell. The energy released by the removal of the curse could all go into destroying this shell. Think a contained explosion where all the energy is used up in destroying the container, vs an unconstrained explosion. The later would have far reaching consequences, the former would not. Physics can not even answer the question as to what happened to all of the antimatter to begin with. Why didn't the universe just self-destruct at the very beginning? We just don't know enough about the process. So physics could not answer this question. Therefore, it is entirely up to wizardry. There is no answer except a wizardry answer. This is so surrounded by wizardry, that whatever the author would like to happen, would happen, and whatever the author chose to happen, could be explained by a thick enough physics book. I would suggest that, if the author wanted a really, really big bang, then the author would posit that all of the energy that went into the curse in the first place, in excess of the energy formed by matter-antimatter annihilation, that is all of the accumulated pent-up energy, was released at the time the curse was removed. If the author did not want ANY bang, then the author could have all of the energy created by the sudden matter-antimatter annihilation go into reversing all of the cumulative effects of the curse, and cancel each other out. That is, it would be as if the curse had never been implemented in the first place. Either could be 'supported' by physics. ]
[Question] [ I did a little looking and it appears stars outside of 10 parsec/33 ly will have very little effect on the Earth. What it did say was that inside that range the gamma rays would affect our [ozone layer](http://en.wikipedia.org/wiki/Near-Earth_supernova) which would reduce our radiation protection. How close would it have to be for the actual gamma rays to be a serious primary threat to the Earth, as in the gamma ray burst directly kills a large swath of Earth's life? I've been thinking about a story where this happens. [Answer] Awesome question. I love this kind of thing. Wikipedia of course has a [a page](http://en.wikipedia.org/wiki/Near-Earth_supernova) on near-Earth supernovae, and the first body paragraph briefly examines the effects of life on Earth. The only really important thing there is just what you said - that the gamma rays from a supernova could deplete the ozone layer. Not too specific. But look further down the page. In [this](http://en.wikipedia.org/wiki/Near-Earth_supernova#Risk_by_supernova_type) section, it says > > Recent estimates predict that a Type II supernova would have to be closer than eight parsecs (26 light-years) to destroy half of the Earth's ozone layer. > > > I checked the referenced estimates on the [arXiv](http://arxiv.org/pdf/astro-ph/0211361v1.pdf) pre-print used. It starts off with > > Estimates made in the 1970’s indicated that a supernova occurring within > tens of parsecs of Earth could have significant effects on the ozone layer. > > > They then say that they now have improved tools; later on they say > > We find that for the combined ozone depletion from these > effects roughly to double the “biologically active” UV flux received at the surface > of the Earth, the supernova must occur at <∼ 8 pc. > > > which they restate later as > > Summing our gamma-ray and cosmic ray depletions for DSN = 10 pc, and taking into > account that our adopted energy is larger than that found in the latest SN study mentioned > earlier, we obtain a fiducial “critical distance” to significantly disrupt ozone of Dcrit ≃ 8 pc > for a SN with a total gamma-ray energy ∼ 1.8 × 1047 erg. > > > And in the conclusion, we again find > > Our primary > finding is that a core-collapse SN would need to be situated approximately 8 pc away to > produce a combined ozone depletion from both gamma-rays and cosmic rays of ∼ 47%, > which would roughly double the globally-averaged, biologically active UV reaching the > ground. > > > Not a *huge* difference at first, but we'd see some pretty bad effects after a while - say, a day or two. Looking [here](http://arxiv.org/pdf/hep-ph/9303206v1.pdf), we find > > A supernova explosion > of the order of 10 pc away could be expected every few hundred million years, and could > destroy the ozone layer for hundreds of years, letting in potentially lethal solar ultraviolet radiation. > > > Ouch! [Answer] It depends what you mean by "severely harm". A supernova at a distance of 10 parsecs might not cause any significant physical damage, but if it happened to be in the opposite direction to the sun then the absence of any real night or darkness for several months could be very damaging to wildlife. A Betelgeuse supernova would be expected to be about as bright as the full moon, but 10 parsecs is 1/20th the distance to Betelgeuse, so a supernova at that distance would be four hundred times as bright as the full moon (though still only 1/1000th as bright as the sun). ]
[Question] [ Mankind has been always interested in making contact with another (extraterrestrial) civilization. We have launched the Pioneer 10 and 11 probes with plaques explaining where the Earth is located. Moreover, there are countless films, books, etc. which are about contact with aliens. However, I'm not sure about why the contact with another civilization may be a positive experience for my fictional civilization. Particularly, I think that contacting with a superior civilization might cause my civilization to be enslaved (or maybe not, but I believe the risk exists). Summarizing, my questions are: * What are the advantages that the contact with an alien civilization may provide? * Is it worth to risk my civilization to access to these advantages? [Answer] There are a multitude of possible reasons, to a large extent they depend on the nature of the civilization. It's technological level, its interests and philosophy. Reasons could range from exploration, to curiosity, opportunities for trade and learning, conquest, or even boredom and the desire to find something new. One thing to remember though is that contact is inevitable. If there is an aggressive alien species expanding then it will eventually reach you. Given that the earlier you become aware of them the earlier you become aware of the threat and the more time you have to respond. Equally if the aliens are peaceful, or friendly, or even neutral but willing to trade then you gain more and sooner the earlier you make contact with them and have the chance to form alliances and advance your own species before any hostile aliens are contacted. The only risk is that you contact a hostile force who then locates and attacks you much sooner than it otherwise would. Considering they would eventually attack anyway though you are changing the timing of the event but not the event itself, so the possible advantages massively outweigh the possible disadvantages. The most important thing would be the way contact is made and how it is handled rather than the fact of contact itself. [Answer] In all actuality it could be very dangerous. While we ourselves would love no know that we are not alone, and would like to believe that others would be more benevolent, it is just as likely that they would find us delicious, or cheap labor or not even consider us worth the time of day. Our hope of course is that it would be a cooperatively mutual learning experience. However, anyone that can travel or at least communicate over the vast distances of space (in a timely manor) would most likely be studying us as we study the great Apes. In all actuality, even though in theory our radio waves will travel across the cosmos, some of our earliest broadcasts reaching 110 light years away, [it appears that outside of a couple light years away](http://zidbits.com/2011/07/how-far-have-radio-signals-traveled-from-earth/) that our signals are indistinguishable from background radiation. The reverse would be true as well, so sending us a message would be a major feat in itself. Hopefully, they would send the instructions on how to reply. Now if they are actually traveling around the galaxy that is a whole other jump. Why do they want to communicate with us? What do we have that they need/want? If they are not benevolent or curious, then they want something from us or our planet. If it's benevolence we are golden, (mostly) they will try to help us reach our potential, but they also might try to train us a pets to follow some path that they have mapped out for 'our own good'. The curious, would be looking for knowledge, and this could work out for us too, becoming more knowledgeable about the universe and advanced sciences. Though, [Mengele](https://en.wikipedia.org/wiki/Josef_Mengele) was curious and wanted to learn about us and performed experiments, learning many useful things about humans. It didn't end so well for most of his subjects however. If we have anything aliens want, if they can make it here, they can just take it and we couldn't put up much of a fight. But they might want to have a trade outpost and find it easier to have us prepare what they want and just arrange shipping. Like how we use places like the Philippians or Chinese factories. Cheap labors, the locals are 'happy' to have a 'good' job and the aliens make huge profits. The last, conquerors. If they want the planet for themselves, they just might wipe us out, or keep enough around to act as slaves for ruling elite. Best might be for us to be 'conquered' (mostly just saying we now belong to them) and integrated into their society and economy, like the Romans used to do. We become a secondary citizen in an interplanetary system that has rules we can learn (and manipulate, it's what we do) with both expectations from us as a vassal planet but with an overlord expected to protect us from attacks from other hostile societies. So in my estimation, it's about 50/50 whether things are worth it to make contact, do it benefit or hinder the development and growth of a civilization. The best of all worlds is to be either the first one to be out there, or to get the technology to observe any other intelligence that might be out there and to study it and possible reactions it may have about contact. [Answer] Historically, whenever humans went to explore unknown territories (on Earth), they inevitably suppressed or destroyed whatever life forms or civilization they encountered. If we assume that aliens are like humans it follows that we must immediately kill any aliens that might at some point set foot on Earth. And let's hope that the aliens that humans might visit in the future will do so as well. ]
[Question] [ Other posts from this thread will be posted here: [How to make an Earth with 27 suns work](https://worldbuilding.stackexchange.com/q/111855) (Closed as a duplicate of the follow up, [Attempt Two](https://worldbuilding.stackexchange.com/q/114107)) [How To Make an Earth with 27 Suns Work, Attempt Two: Orbital Stability](https://worldbuilding.stackexchange.com/q/114107) (Will be updated as more are posted.) # Info I finally figured out [how to make a planet with 27 suns work](https://worldbuilding.stackexchange.com/questions/114107/how-to-make-an-earth-with-27-suns-work-attempt-two-orbital-stability/114118#114118): By setting the stars into (mainly) binary orbit pairs several levels deep. Now, in that question, I handwaved the effect of the radiation of the suns on a single, Earth-sized planet (along with the visibility of the suns, which will be enhanced for distance). But now I want to understand what the radiation would do, so I can figure out how to protect the planet in the future. Let's start listing how the system works: I'm ignoring most of the stars and focusing on the ones closest to my planet: The planet, XV, is in orbit around star 5. (Star 5 is in a 5/6 binary pair, the pair of which is in orbit of star 7, which orbits star 1, which is in the binary pair 1/2.) XV is 1 AU from 5. 5 is 10 AU from 6. the 5/6 pair orbits 7 at a distance of 25 AU. 7 is a distance of 30 AU from 1. Star magnitude/type: Star 1 is a class O2 ($\geq\text{16}{\small{M}}\_\odot$). Star 7 is a class A7 ($\text{1.4–2.1}{\small{M}}\_\odot$) Star 5 is a class G2 ($\text{0.8–1.04}{\small{M}}\_\odot$) Star 6 is a class G1 ($\text{0.8–1.04}{\small{M}}\_\odot$) To simplify, the planet orbits 5, which is in a binary with 6, and together they orbit 7, which orbits 1, which is in a binary with 2. The star and planets formed (in geological time) extremely quickly, and cooled quickly (see the previous question), so imagine that the planet has cooled from molten and that nothing will be going supernova ( due to extended lifespans of stars.) # Question What would the effects of the radiation of 27 suns be? Criteria: * List the energy, in Joules, per day, of the solar radiation. * List the effects of this solar radiation on the planet's atmosphere and surface. * Use the same magnetic field Earth has. It's okay if * The planet is ~~fried~~ vaporized. The substance of the planet is, of course, unobtanium. The purposes of this question are to understand the effects of this stellar environment on a potential planet. * The magnetic field is stripped away with the atmosphere. While that's sad, I don't mind *as long as I am told* that the magnetic field is stripped away. --- Thank you to all in the [Sandbox](https://worldbuilding.meta.stackexchange.com/q/6168) who helped me develop this question. [Answer] Let's look at two key equations: $$F\_i=\frac{L\_i}{4\pi r\_i^2},\quad \lambda\_{\text{max,i}}=\frac{b}{T\_i},\tag{1, 2}$$ For a given star with luminosity $L\_i$ and surface temperature $T\_i$ a distance $r\_i$ from the planet, these equations give you the flux from the star ($F\_i$) and the wavelength at which its emission is the strongest, according to [Wien's law](https://en.wikipedia.org/wiki/Wien%27s_displacement_law). I've adopted some reasonable values for $M\_i$, $L\_i$ and $T\_i$ based on spectral type. I've also taken $r\_i$ to be a mean radius from each of the stars, given that the distances change wildly. Let's take a look at the results (here, Here, $F\_s$ is the [solar constant](https://en.wikipedia.org/wiki/Solar_constant)): $$ \begin{array}{|c|c|c|c|c|c|c|}\hline \text{Star} & M\_i (M\_{\odot}) & L\_i (L\_{\odot}) & T\_i (\text{K}) & r\_i \text{ (AU)} & F\_i(F\_s) & \lambda\_{\text{max,i}}\text{ (nm)}\\\hline 1 & 16 & 500000 & 20000 & 30 & 1750 & 145\\\hline 5 & 1 & 1 & 5800 & 1 & 1 & 502\\\hline 6 & 0.9 & 0.7 & 5300 & 10 & 0.007 & 547\\\hline 7 & 1.5 & 10 & 7000 & 25 & 0.016 & 414\\\hline \end{array} $$ We have a problem. Stars 6 and 7 won't contribute as much as Star 1 - note the low fluxes. Star 1, on the other hand, will make life miserable. It's luminous and it's not too far away. Also, its peak emission lies in the ultraviolet, meaning your planet is going to need one heck of an ozone layer to have any hope of surface life. Even at its furthest distance from the planet, Star 1 will still maintain a large surface flux. Oh, I should note that I went against your wishes and picked values for Star 1 as if it were an O7 star - less massive, less luminous, and cooler. In other words, I essentially chose the best-case spectral type here. If you stick with an O2 star, things will be . . . bad. Really, really, really bad. Specifically, we'd be looking at $M\sim40M\_{\odot}$, $L\sim10^6L\_{\odot}$, $T\approx50000\text{ K}$, $F\approx3510F\_s$, and $\lambda\_{\text{max,i}}\approx58\text{ nm}$, all of which are much worse for your planet. For fun, let's elaborate on this calculate the [effective surface temperature](https://en.wikipedia.org/wiki/Effective_temperature#Blackbody_Temperature), $T\_{eff}$. If we assume that the main source of flux is Star 1, then $$T\_{eff}=\left(\frac{L\_1(1-a)}{16\pi\sigma r\_1^2}\right)^{1/4}=\left(F\_1\frac{1-a}{4\sigma}\right)^{1/4}$$ Plugging in our values - assuming $a=0.3$ - gives us $T\_{eff}\approx1647\text{ K}$. That's much, much worse than Venus - and we haven't even taken the contributions from the other stars into account! In chat, you talked about how you were wondering how bad stellar activity would be. Fortunately, the O-type star likely isn't a problem here. While O stars have strong stellar winds - and [I wrote about that last month](https://worldbuilding.stackexchange.com/a/116174/627) - they're usually pretty quiet when it comes to stellar flares and coronal mass ejections. Why? Well, unlike the majority of stars, *very few O-type stars have magnetic fields*, and magnetic fields are the main force behind this sort of stellar activity. Conditions in the core of an O star simply aren't ripe to produce a magnetic field by normal means; for decades, both theory and observations indicated that no O-type main sequence stars had magnetic fields. In recent years, a small number of counterexamples have been discovered - [$\theta^1$ Ori C](https://en.wikipedia.org/wiki/Theta1_Orionis_C) is a well-known case - and it's thought that a small fraction of the population do indeed have magnetic fields. However, most don't, and so odds are good that your O star won't be a source of flares or CMEs. The other stars, maybe. But M-type red dwarfs are really the only [flare stars](https://en.wikipedia.org/wiki/Flare_star), and you don't have any red dwarfs among this subgroup in your system. ]
[Question] [ A Trojan relationship is when an astronomical object A is orbited by astronomical object B, and a third object, C, orbits A at the same distance as B and 60 degrees ahead of or behind B, in the L4 or L5 position. In our solar system, hundreds of asteroids (C) have Trojan orbits relative to Jupiter (B) and the Sun (A), and there are 17 known Neptunian Trojans, 4 known Martian Trojans, 2 known Uranian Trojans, 1 Known Earth Trojan, and 1 temporary Venusian Trojan. Thetys, a moon of Saturn, has two Trojan moons, Telesto and Calypso, and Dione, another moon of Saturn, has two Trojan moons, Helene and Polydeuces. It is obvious that in these cases object A is many times more massive than object B, which in turn is many times more massive than object C. For example, Mars, the smallest planet with Trojan asteroids, has a mass 0.3227 X 10 to the minus 6th power, or 0.0000003277 the mass of the Sun, while Jupiter, the most massive planet with Trojan asteroids, has a mass of 0.0009547919 the mass of the Sun. Tethys and Dione, moons of Saturn, are thousands and tens of thousands of times as massive as their Trojan moons. The largest Trojan asteroid, 624 Hektor has a diameter of 225 kilometers. Earth should be over 100,000 times as massive as 624 Hektor and Jupiter is 317.7 times as massive as Earth. So in our solar system the object A (the Sun or Saturn) ranges from thousands to millions of times as massive as object B (a planet or a large Saturnian moon) and object B ranges from thousands to millions (and possibly billions) of times as massive as object C (an asteroid or a tiny, asteroid-size moon of Saturn). Obviously, a Trojan orbit can be stable for millions and even billions of years if there are such vast differences in mass between objects A, B, & C. But in science fiction there are many examples were object C is much larger than an asteroid, and in fact is a planet, often one habitable for Humans. The common types are systems where A and B are both stars and C is a planet, and systems where A is a star and B and C are both planets. And for a long time, I believed that it was impossible for object C in a Trojan orbit to be as massive as a planet, regardless of whether object B was a star or a planet. It is said that as a rule of thumb, a Trojan orbit can be stable if the mass of object A is greater than 100 times the mass of object B and greater than 10,000 times the mass of object C. [https://en.wikipedia.org/wiki/Trojan\_(astronomy)[1]](https://en.wikipedia.org/wiki/Trojan_(astronomy)%5B1%5D) In our solar system the least massive planet, Mercury, is 0.00017 the mass of the most massive planet. Thus Jupiter is 5,882.35 times as massive as Mercury. Of the five official dwarf planets in our solar system, Ceres has the smallest known mass, 0.0015 the mass of Earth, meaning Earth has 66,666.66 times the mass of Ceres. Since Jupiter has 317.7 times the mass of Earth, it has 2,117,999.9 times the mass of Ceres. An object has planetary mass if it is massive enough to pull itself into a regular, more or less spherical shape, and is less massive than a star. An object more massive than about 13 times the mass of Jupiter will have great enough core pressure and temperature to fuse hydrogen, and thus be a star. But the least massive stars can only fuse the rare hydrogen isotope deuterium and thus are very, very dim. They are called brown dwarfs and can be classified as planets, stars, or neither. The minimum mass of a brown dwarf might be between 11 and 25 times the mass of Jupiter, which is enough to make the largest possible planet tens of millions of times as massive as the least massive possible planet. The maximum mass for a brown dwarf, and the minimum mass for a full-fledged star is believed to be about 75 to 80 times the mass of Jupiter, and thus about 0.0716 to 0.076 times the mass of the Sun. The least massive known normal star, VB10, or Van Biesbroeck's Star, has a mass of about 0.075 that of the Sun, or the Sun is 13.333 times as massive as VB10. It has been calculated that a star above about 150 times the mass of the Sun, would have fusion reactions so strong they would blow the star apart. But there a few stars which might have masses higher than 150 times the mass of the Sun, listed here: [https://en.wikipedia.org/wiki/List\_of\_most\_massive\_stars[2]](https://en.wikipedia.org/wiki/List_of_most_massive_stars%5B2%5D) RMC 136a1 is both the most luminous known star and the most massive, allegedly having 315 times the mass of the Sun - or between 265 to 375 times the mass of the Sun. Thus the most massive stars should be 1,999.99 times as massive as the least massive stars, or possibly even as much as 4,999.99 times as massive. So the possible mass range of stars, and the possible mass range of planets is such that as a rule of thumb, there could be a stable Trojan system with a star as object A, a planet as object c, and either a star or a planet as object B. So far, so good. We already know there can be a Trojan system were object B is a habitable planet and object C is a tiny asteroid. But there is nothing glamorous or interesting about tiny asteroids in Trojan orbits relative to a habitable planet, except for the possible advantages of mining those asteroids. There can be a plausible story involving mining operations or scientific research of some kind on a lifeless and uninhabitable planet in a Trojan orbit, with object B being either a star or another lifeless and uninhabitable planet. But what about a system in which object C is a habitable planet? If we arbitrarily assume that a planet habitable for Humans should have a mass between 0.5 and 2.0 that of Earth (planets outside that range might be habitable for other forms of life, including some from Earth), then a giant planet might be as much as 11,913.75 to 50,832 times as massive as an Earth-like and habitable planet. So a Trojan system with a star as A, a giant planet as B, and an Earth-like and habitable planet as C, seems to fit within the 1:0.01:0.0001 rule of thumb. And yesterday, March 5, 2018, I found some online scientific papers discussing hypothetical Trojan planets. [http://www.univie.ac.at/adg/Research/exotro/exotro.html[3]](http://www.univie.ac.at/adg/Research/exotro/exotro.html%5B3%5D) [https://arxiv.org/abs/1307.7161[4]](https://arxiv.org/abs/1307.7161%5B4%5D) [https://link.springer.com/article/10.1007/s10569-009-9210-9[5]](https://link.springer.com/article/10.1007/s10569-009-9210-9%5B5%5D) And those articles consider Earth-mass and potentially habitable Trojan planets possible. So it appears that a system with a star, a giant planet, and an Earth-mass planet can have a stable Trojan orbital configuration, despite what I believed for a long time. What about a system with two stars and an Earth mass and a habitable planet in a stable Trojan orbital configuration? That is a bit more complicated. The Earth is about 4,550,000,000 years old. The first microscopic life appeared about 4,100,000,000 to 3,500,000,000 years ago, but Earth was not yet habitable for Humans. Lifeforms began to produce oxygen about 2,000,000,000 years ago and oxygen levels in the atmosphere rose to breathable levels by about 500,000,000 years ago when Earth was about 4,000,000,000 years old. Complex multicellular life appeared about 580,000,000 years ago and the first land organisms appeared about 480,000,000 years ago. If one assumes that the evolution of life could be much faster or slower on different planets, one might assume that the minimum possible age for a planet to have a breathable oxygen-rich atmosphere and multicellular lifeforms on land, and thus be habitable for Humans, might be 3,000,000 years. A F5V class main sequence star would have a lifetime on the main sequence of 3,440,000,000 years before becoming a red giant star. Thus some F5V stars can have planets over 3,000,000,000 years old with advanced life and breathable air, planets suitable for being colonized by Humans or having native intelligent beings. Such a star would have a mass of 1.4 times the Sun or 18.666 times the mass of the least massive stars. [http://www.world-builders.org/lessons/less/les1/StarTables.html[6]](http://www.world-builders.org/lessons/less/les1/StarTables.html%5B6%5D) This blog post says that in a Trojan system with two stars and a planet the larger star has to be at least 25 times as massive as the least massive star, a ratio of 1:04. [https://planetplanet.net/2016/11/07/the-ultimate-trojan-2-star-planetary-system/[7]](https://planetplanet.net/2016/11/07/the-ultimate-trojan-2-star-planetary-system/%5B7%5D) This is a much smaller mass difference that the 1:01 rule of thumb ratio. In this system, the smaller star has 0.08 the Mass of the Sun and the larger star thus must have at least 2 times the mass of the Sun. > > For my Trojan star-star systems I’m choosing a puny star at the border between brown dwarfs and stars, at 8% the mass of the Sun. This keeps the mass of the high-mass star as low as possible. This, in turn, will allow for a long-lived high-mass star. The high-mass star is an A star twice as massive as the Sun and about 12 times as bright (see here). This star has a lifetime of about 2 billion years as a “normal” main sequence star. > > > [https://planetplanet.net/2016/11/07/the-ultimate-trojan-2-star-planetary-system/[7]](https://planetplanet.net/2016/11/07/the-ultimate-trojan-2-star-planetary-system/%5B7%5D) With a lifetime of about 2,000,000,000 years, the brighter star will not remain on the main sequence long enough for the planet(s) in the Trojan positions to develop advanced life and become habitable for Humans, unless life on those planets develops more than twice as fast as life on Earth for some reason. That is why spectral type A stars are not considered suitable for having habitable planets. So, from what I have learned today, I would say that a Trojan system with a suitable type star as object A, a habitable planet as object C, and either a giant planet or a brown dwarf as object B may be mathematically possible. But it still seems that a Trojan system with a suitable type star as object A, a habitable planet as object C, and a smaller star as object B is mathematically impossible, because the two stars could not have the proper mass ratio for a stable Trojan system. So can anyone clarify whether the two types of Trojan systems with habitable planets are stable or not? [http://www.world-builders.org/lessons/less/les1/StarTables.html[6]](http://www.world-builders.org/lessons/less/les1/StarTables.html%5B6%5D) [Answer] You've done some amazing research -- so-much-so that it's doubtful anything further could be contributed. In all honesty, there doesn't seem to be any reason why this couldn't be easily plausible; at least, based on the physics equations from the great sources you linked to. Personally, I wouldn't discount any possibilities due to planetary lifespan expediencies. The approximated age of our universe, and planet, has changed countless times throughout our history and evolution of science. The current method of estimation is through radioactive decay rates; and while it's currently the most accurate model, it's still just a model. <https://physics.stackexchange.com/questions/334974/how-do-we-know-that-radioactive-decay-rates-are-constant-over-billions-of-years> There are many unknown aspects about our world, and universe, that are explainable in theory only. Leverage on solid science to instill believe-ability into your fiction, but don't let theories stifle creativity. The best fiction often retains it's timeless appeal because it eschews omittable explanations in favor of the unknown. [Answer] Even if a habitable Trojan planet of two stars with indigenous complex life is not plausible, two prospects remain. One, a young planet with simple life or no life, which could be settled. Two, a smaller planet with a smaller mass, on the order of Mars, Ceres or such, which could be partially terraformed. Consider the prospect of a Trojan planet around one star of a wide binary pair where beings from a world around the other star settle the Trojan. Re examples in fiction, the stellar system created for the reimagined Battlestar Galactica used both binary habitable worlds and habitable Trojan planets to fit 12 colonies ]
[Question] [ Ok, so I have determined my world can keep it's planetary ring system. YAY! Now I just need to clarify once and for how it would look like from the planet surface. I think I have it worked out, but definitely need second and third opinions. **I curious to the impact of the planet's axial tilt and the progression of the seasons** **NOTE:** This is about the CHANGING 'look', based on known planetary positions with regards to the Sun throughout the year, and not about the impact on the climate (totally different question lined up for that one)! **ASSUME:** 1) Single star system. 2) Earth-sized planet 3) Rings aligned with the planet's equator. 4) Similar Axial tilt to Earth. 5) You are looking at the rings from the exact same spot on your planet throughout the day, night and year (hopefully with a couple of beers in handy shady spot nearby). 6) You have enough to keep yourself occupied all year... You can use this old, still amazing, youtube [video](https://www.youtube.com/watch?v=hoz5Q2rGQtQ) by Roy Prol as a reference if you like. **What I would like to know is:** 1) Would it appear to set and rise through the day taking into account the planet shadow on the ring surface? I am aware the rings will still shine at night due to reflections from the various light sources so I'm assuming it wouldn't disappear altogether during this 'setting' and 'rising' period. But would there be a noticeable difference in the arc brightness at any particular time? This part of my question actually seems to already be answered [here](https://worldbuilding.stackexchange.com/questions/2611/what-would-the-sky-look-like-from-the-surface-of-a-planet-with-rings)! Onto the next conundrum. 2) Would you always see the same amount of ring width throughout the year or would this shift with the seasons? I'm thinking there would be something of a range between the equinoxes and solstices. BONUS related question, would there be a corresponding effect on the width and 'intensity' of the ring shadow on the planet's surface? 3) Would the time of day you saw the rings differ with the seasons? for example, from your randomly chosen spot to sit for an entire year, would you have no visible rings during winter days but visible during winter nights; and vice versa, would they be visible during the summer days but not summer nights. OR, Is all that I have imagined dependent on the ring system being on an ecliptic orbit? If so, great! (high five me!) Is it possible to have a stable ring system on an ecliptic orbit? (ah, man...back to the drawing board!) [Answer] I'm not an expert, but I did a little searching and this is how I believe that planetary rings act: To start off, I believe that rings in general will be equatorially bound in general. Rings are formed when a moon or other small object (relative to the planet) gets orbits in too close and is utterly destroyed by the immense gravity of the planet. The plane boundary of no return for an object is based upon its composition. The denser the material (like iron) will be closer to the planet than less denser materials (water-ice). I am making a leap here in my assumption that that means that outer rings are formed from less dense materials than inner rings. As for why I believe they will be equatorially bound in general, if they weren't, we would see planets with disorganized clouds of dust otherwise or disordered rings that orbit in all different paths. In our solar system, our moon is somewhat equatorially bound as are the rings of Saturn and Uranus (my biggest piece of evidence since it is tipped at around 90%). I assume that in the formation of rings that a dust cloud of sorts develops first and that it eventually coleuses into a ring formation around the equator. Planets are slightly wider at their equator's due to the spin (like when a pizza chef spins the dough to flatten it out) which means that gravity is slightly stronger there (this extra gravity is what determines where the rings sit). Now moving on to your actual questions... Rings will always appear in the same location within the sky: day or night, winter or summer (relative to your location). For example, with the rings equatorially bound as I inferred above and you stated (this is why I went through all of that) the rings would move with the tilt of the axis so as to follow the pull of gravity and as such, everything would move as a single unit and would, relatively speaking, nothing would move with seasonal or day/night changes. If you were standing on the equator looking up, you would have a poor view. All you would see is a line stretching from east to west (or west to east if your planet spun that way - but most planets will spin along with the general spin of their host system's orbits unless acted upon by some outside force - Uranus). If you were in the Northern Hemisphere, you would have a view of the rings in the southern sky and the further you got north, the more spectacular the view. The reverse would be in effect in the Southern Hemisphere. As for the poles (north and south), one should be able to see the entire ring system as an extension of the horizon in all directions. Don't misunderstand me, seasons do have a major impact on the view of the rings (SHADOWS!!!). During an equinox, approximately a third of the ring system will be in the shadow on the dark side of the planet. When looking up into the sky, the shadowed ring segments will appear black as they would block out the stars too which could also be an interesting feature to the sky. Keep in mind that the reverse is happening too during an equinox as well: the ring segments on the far side of the planet are carving a shadow that falls along the equator. From the Equinox to the Northern Hemisphere's Winter Solstice, the shadow that falls on the equator will grow larger every day and farther north every day. The full extent of the shadow on the solstice will depend on the degree of tilt and the shear size of the rings. Keep in mind that if your tilt goes too high (like 45% I think which would be completely outrageous), the shadow will have reached the north pole and start being cast into the void of space above the pole (so the amount of the planet under the shadow will be reduced). As this is happening on the "day" side of the planet, the "night" side of the planet will see the shadowed segment grow smaller every night which would make for a better view on the Solstice at night. (the reverse of all of this is true as well) I hope that this answers your questions. Looking at some pictures of Saturn might help you to visualize if you read along. Better yet might be to make a model of Saturn and go into a dark room with a flashlight on a table. With that setup, you could manipulate the model and see how the shadows react. As a side note, also look up some pictures of rings that have had objects fly through them or the gravity of a moon disturbs them. I guess adding a moon might make it more complex (but Saturn has tons of them so idk on that). I saw some recent ones that show the effects and it appears that the rings have been smudged. According to the article I read, the ring repaired itself within 2 months. Here is a link: <http://www.businessinsider.com/a-mysterious-object-caused-a-disruption-in-one-of-saturns-rings-2016-6> Hope I wasn't too wordy and that this helps!!! [Answer] I had one major addition, related to seasons and tilt, that seems to have been (partially) overlooked, or at least not directly described. The rings can shadow themselves. They have a 'top' and 'bottom' (or north and south if that makes more sense to you), and the star will only shine directly on one side at a time, depending on the season. So an observer in the northern hemisphere, during a summer day, would see the complete ring, at its most reflective (but due to daylight washing it out, it would not seem to be the "brightest"), that same observer, late that night, would see the (apparent) brightest rings of the year, but with the shadow of the planet falling on them, so they would not appear 'complete' but would have the dark gap mentioned by the answer selected by the OP. BUT The same observer, in the same location, on a winter day, would not see the rings themselves, directly, but might see only their silhouette (like a ring eclipse), or possibly a strip of sky darker than the rest, depending on if they were directly in the shadow that the ring, or on the edge of the shadow, or not near the shadow. And at night in winter, they would see nothing of the ring at all, other than the black strip of missing stars. From the spring equinox, the rings would slowly brighten until the summer solstice, and then start to fade again until the autumn equinox when their brightness is reduced to its lowest point, where it will remain until spring. ]
[Question] [ Conquest and discovery has been an important part of developing the global political structure of today's Earth. After we expand and settle other planets, whether within the same solar system or not, eventually the colonies will grow and develop to the extent where they feel able to self-govern. Given that extraterrestrial colonies and their resources would be incredibly valuable to their parent government, they would be naturally hesitant to let them go, whether because of fear of a lack of control or fear that the new government will be forcibly assumed by a competing terrestrial government. Easily, historical examples can be found by looking at overseas colonies - except for two incongruities: firstly, the process of setting up not only a self-sufficient extraterrestrial colony, but a self-expanding extraterrestrial colony would require much more assistance than, say, setting up a self-expanding overseas colony. Additionally, the area available for a colony to expand into is much greater than historically: there's a whole planet out there! Would the self-governing colonies, after they finally stabilize, cover much greater area than their parent nations? Would it be continental, global, or even include the local moon(s)? Would they be powerful enough to peacefully hold this territory, or would competing, established governments/colonies be conterminously fighting for greater resources? How would the situation differ were the planet found inhabitable as opposed to requiring a (possibly international) terraforming project? In short, what type of interplanetary political structure would be most likely to develop, and what historical parallels are there to support your claims? [Answer] I would assume that there's two major cases for interplanetary colonization: * it starts from global or government initiative, thus will be composed of people selected for this or volunteering. Thus, we'd have to look to controlled habitation of remote locations for examples, such as research stations in remote places. * it starts long after space travel becomes cheap and easy enough (as well as provision management) to do so, so we'd look towards colonization as it happened throughout history (barring the special case of forced migration, which has its own special peculiarities). In the first case, we have strong dependence and adherence to existing political structure - any changes to that would be already observed in existing small colonies designed for a purpose. So it would take a very long time for changes to happen, IMHO, unless we saw significant stress in the relations between the homeworld and colonies (possibly after a few decades of building and work, after which some are recalled, causing stress). In the second case, we'd have much more independent-minded people, possibly more adventurous and individualistic, starting colonies. This would naturally cause a lot of stress in relations with the homeworld, unless it *does* provide regular aid and provisions and does *not* interfere with local matters - quite unlikely. The real question however is, do we know future political structures? Even on Earth, the changes to existing politics and the evolution of political thought has happened in spite of and independently of colonization, although the latter has forced changes. It is quite likely the political structures in such a society, colonizing new worlds, would be very different and most possibly an amalgamation of successful political ideas across the currently understood spectrum. I'd assume, considering how politics has grown throughout human history, that there would be a strong humanitarian and progressive shift, at least until the colonies are 100-200 years old. The outcome would also depend on the efficiency of warfare through interplanetary/interstellar space and space-to-ground weaponry and defenses. If it is difficult to launch such an offensive, the safety on the colonies would allow them to *experiment* a lot more, considering the likely personalities of colonists. It might also allow them to *succeed* more in these experiments, much like in real life. If on the other hand it is easy to conduct such warfare, fear might prolong political dependence and political conservativism, maintaining existing structures. [Answer] Another answer specifically excepted the case of forced migration, but it's worth considering. Two versions strike me as especially significant for your question: the Puritans going to America, and British convicts being sent to Australia. The Puritan example is particularly interesting here, because it both was and was not forced. In effect, contrary to many of the myths that American schoolchildren are taught, the Puritans were under a good deal of social and economic pressure in England, and decided to try America instead. Their problem, fundamentally, was that they wanted to be stunningly intolerant and controlling of everyone with whom they came into contact, but their non-Puritan neighbors weren't very happy about this. So they moved to America so they could set up a completely non-tolerant society where they punish people who disagreed with them about more or less anything. And on the whole, their neighbors in England were happy to be rid of them. The deal, of course, was that they were Crown colonies, and they had to pay the Crown. In part, this was a matter of money for services: they needed guns, for instance, and all kinds of other goods that they couldn't get very readily in America. In part, this was just taxation. Eventually, this all led to revolution, in large measure because the colonies no longer needed what services the Crown was providing -- they could make their own guns, for example -- and so they were paying a lot for very little. Thus "no taxation without representation." So to get back to the core of the question: the possible relations between the colony and the homeworld are extremely variable. If the colony was in part forced, there may be a lingering grudge against the homeworld, but on the other hand, Australia was remarkably tolerant of being a colony for most of its modern history. If the colony was formed as some kind of social, political, religious, or whatever experiment -- as with the Puritans, but there have been many other examples -- the group may want independence as soon as possible; on the other hand, most such experiments have failed fairly disastrously, and arguably the Puritan one did as well, in which case despite the desire for independence they may be heavily dependent on homeworld support. Meanwhile, the homeworld presumably wants something from the colony, or else why would they support it? If they really don't want anything from the new world, and the colonists want independence, then you could end up with effectively no relations: space travel isn't likely to be cheap, and if the homeworld won't pay for it and the colonists are reasonably poor in high-tech resources, the colonists may end up pretty much orphaned. [Answer] There's no one answer, of course. It would depend on many things, and mostly, I would say, the mindsets of the people involved (what they valued, what they considered important, what memes they were engaged in, their political organizations and economic systems), and how those changed over time. e.g. Have we really reverted to 18th Century colony/empire and national struggles, or is it like 21st Century corporations and bankers being the real power structures, or have we transcended all that yet, and how so? What history led to that? When humanity got organized and cooperative enough to spread to other stars, did they even have weapons or violent crime on their minds? Another major factor would be the time, distance, and technology involved for travel and communication, as well as human lifespans, and what these other worlds turn out to be like, what their spatial relationship is to each other, and whether any alien species are involved. e.g. Does it take ten years for a message to get from one planet to another (as in what current science looks like), or can one travel between stars without changing clothes (as in Star Wars)? Other technological details could be relevant too, such as energy production, biological issues, and so on - resources might not be much of an issue, or the rare resources might be something very different that one might imagine these days. e.g. In what way are power and fuel still a concern, or have fusion reactors or something else made it abundant and cheap? Are minerals still really valuable, or do people have more than they really need? How are we doing against disease and GMO/nanotechnological contamination? Terraforming would definitely require more work and technology... what would it take to send it to another star, or assemble it there? How long would it take? These have a lot to do with the answers to the earlier questions about what technology is available for travel and communication, and energy and material abundance or scarcity. As far as an interplanetary political structure, I think the above variables would all play major roles in determining what would develop. Starting from where we are, where international organizations have accumulated most of the world's wealth into one network of banks and other companies that owns at least 67% of the wealth according to a recent Swiss study, and on the other hand, a number of man-made disasters threaten our continued existence, or at least our way of life. GMO proliferation, nuclear weapons, nuclear power, catastrophic climate change, fresh water supply problems, and a host of others, indicate to me that there will be some major changes before we get anywhere near thinking about really colonizing worlds, let alone other stars. So the starting point, and the enabling technologies, are almost completely unknown, as is what we may find when we get to another star. The political organization could be anything. However, I think travel and communication times are essential elements to your questions, and those may change with technology, and that rate of change would also have effects. You can't control someone you can't communicate with or reach in a timely fashion. [Answer] The maximum speed of force projection is probably the most important factor in working out a functional government set up. I've always thought that without effectively instantaneous communication *and* troop transportation systems you'd need a decentralised setup of some description; whether that's imperial, feudal, or federal doesn't really matter, rulers can only control the area they can put troops into fast in the event of unrest/invasion. Something else to note when considering an exact structure, especially in long established regimes, though: "All governments tend towards monarchy" - Frank Herbert, *[Dune](https://en.wikipedia.org/wiki/Dune_(novel))*. It's a fairly basic premise with some interesting historical evidence and some even more interesting implications. Basically Herbert argues that regardless of their starting form governments tend to allow/create the accretion of political power within small groups of people, I'd have said [Oligarchy](https://en.wikipedia.org/wiki/Oligarchy) not [Monarchy](https://en.wikipedia.org/wiki/Monarchism) but the point stands. In the *Dune* universe travel is FTL but still relatively time consuming, and without any FTL communications planetary governments are pretty much on their own, and a feudal model is adopted from individual planets to the overarching rule of the [Landsraad](https://en.wikipedia.org/wiki/Organizations_of_the_Dune_universe#Landsraad). Planetary governors can't really call for support from the emperor or their fellow lords, they have to rule their worlds effectively or they end up deposed and often dead. The role of corporate entities could be very important to structural details, corporations are effectively immortal you just replace board members who age out. Corporations are also very effective at concentrating decision making power and governing large numbers of people. ]
[Question] [ It is the time of year we all have been waiting for. Ho, ho ho! The Star Wars are around the corner! **Help me design scientifically plausible light-saber:** In other words: What has to happen in order to have light-sabers available? * After watching the latest Star Wars, all scientists decide to produce lightsaber (why? Because its cool!) * We have all Earth people cooperating on this task (one big hand wave) * Goal is to produce something resembling Star Wars light saber, including its powers and wearability * Target delivery: In next 30 years * Some hand waving is allowed. However, we need to stay inside *plausible* sector. [Answer] **The missing components are metamaterials and ultra-high power sources.** The meta material required is one which provides: * Excellent shear strength * Superconductivity * Extreme temperature resistance The power source needs to be able to [provide 28 kilowatts](http://www.wired.com/2010/02/power-source-for-a-lightsaber/) for however long the blade is in operation. Combining those two elements, one can create a lightsaber. A telescoping rod, like a collapsible police baton, made of insulated coils of this metamaterial will act as the base of the sword. The power source will provide a high current that when passed out through the blade returns toward the hilt through magnetically confined plasma. [![enter image description here](https://i.stack.imgur.com/rux3O.jpg)](https://i.stack.imgur.com/rux3O.jpg) For the image above, the current flows in through the base, out the top and back through the plasma contained in the magnetic field. The coil is required so that the return current does not cause magnetic fields which cancel the containment field. The initial turning on of the blade is going to be a little less smooth than a traditional lightsaber, but once you learn not to wince, the electrical arcs that precede the plasma are going to look pretty awesome. It's not clear if your saber would be red (it'll depend on the atmosphere and metal dopants), but I'm guessing yours will be. [Answer] Plasma can be influenced and contained by magnetic fields, and can be generated by using a laser. If you had a powerful focused laser in the hilt you could create some really high temperature plasma that would be vented out and contained by the magnetic field into a blade shape. You might not even need much of a magnetic field, since it would work a bit like a blow torch. A plasma blade has a few advantages over laser, in that it doesn't need a reflector at the end, and would deflect or absorb plasma bolts. Plasma can get up to 1,000,000 degrees, though you'd want to use lower temperature plasma since that would ignite the air around you. It could definitely cut/vaporize most things it touches. Here's a real world micro version of the technology in action using "cold" plasma in a pretty purple blade shape: <http://www.livescience.com/6052-plasma-jets-replace-dental-drills.html> [![enter image description here](https://i.stack.imgur.com/3d1LY.jpg)](https://i.stack.imgur.com/3d1LY.jpg) **Edit:** This meets the requirements for needing a gem to create and focus the laser, and AFAIK light sabers are never referred to as laser swords, or how they work. People just assume lasers because of the gem and how they look, forgetting that you wouldn't see a laser beam in the air, and you wouldn't be able to stop it at only a few feet long. Turn it on and you're cutting holes in the ceiling 100 feet above you. At that point you're better off turning it into a blaster with unlimited energy and unbelievable power. A plasma cloud would be visible, and shorter range, and could be used for piercing. Power is still a problem (may need some handwaving), and would require some next gen power source, but if you could assume a major breakthrough in batteries or an accidental discovery on how to tap into ZPE in the next 30 years, this wouldn't need to be a problem. [Answer] An idea came to me while thinking about the "how do you make the blade stop where you want it" problem. If you were to create a localized magnetic field (it would have to be quite strong). If you slightly modify the saber to include a cap of sorts... [![enter image description here](https://i.stack.imgur.com/8fqfZ.png)](https://i.stack.imgur.com/8fqfZ.png) So the longer black section is the hilt, then blue blade then a black cap that would act as a reflector and create a loop back down to the hilt. Magnetics could be used to hold the cap in place. You wouldn't probably be able to use it to stab...unless you have a sort of super material that can be magnetized and hot enough to burn through people doors etc. For reference in the 1500 degrees (F) range 1080 spring steel is no longer magnetic and wouldn't burn through metal...well not thick steel doors anyways...you could always go to japan and burn right through paper doors though. The part I am not even going to attempt to explain is the power source. The amount of power you would need to generate to maintain a lightsaber blade is immense...there are some estimations out there somewhere. Try [here](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjGwvfS69vJAhVG3mMKHStnA7cQFggcMAA&url=http%3A%2F%2Ffuturism.com%2Fhow-many-batteries-would-it-take-to-power-star-wars-tech-infographic%2F&usg=AFQjCNFpE33rMgAQFhbA9FIiktAOknC-uQ&sig2=vpdTwXUi_U9iIBOazKgk8A&bvm=bv.109910813,d.cGc) Point is you are going to have to create an arc reactor technology ala Iron man to make it feasible and that is magi-tech so you are going to have to handwave the power source...and the blade stoppage (super material mentioned above) at which point you are basically hand waving the whole thing so why bother explaining... [Answer] This is actually entirely possible. I would like to propose a very simple mechanism that would naturally result in a light saber. All you would actually need is a very powerful, focused laser beam. If this laser beam is powerful enough, it will naturally plasmize the air it strikes. This is called [the blooming effect](https://en.wikipedia.org/wiki/Thermal_blooming). The thing about this beam of resultant plasma is... It's opaque. Now, often, we don't want the blooming effect. Scientists have gone to remarkable lengths to avoid the blooming effect, pulsing powerful lasers on and off every femtosecond, so that the plasma has time to get out of the laser's way and the laser isn't blocked by it. But... For a light saber... The blooming effect would be perfect. A really, really powerful laser would make a beam of plasma, which would in turn block the laser, limiting it's range to about the length of a light saber blade. I will also note that this system would absolutely be able to make good use of a focusing crystal. The resultant device would require more power than we can fit into a device of this size in our current stage of development... But everything else is already quite attainable for this device. We could absolutely make a light saber if we had all the required resources for the next thirty years. There are perhaps two drawbacks to this method: 1) I think you probably knew this, but a light saber is quite impractical. If you had a power source capable of causing thermal blooming and small enough to fit in your hand, you could slightly modify your light saber's laser to pulse on and off every femtosecond, and suddenly the light saber's blade has near infinite length and is a deadly plasma gun. Attach an electrode to the plasma arc and suddenly it isn't just a plasma gun, it's a thunderbolt gun. 2) There is one aspect of light sabers that this system doesn't quite replicate. When two blades constructed in this way collide, they would likely pass right through each other. At most there would be a small blast of plasma as they collided, but they certainly would not bounce off of each other. This issue, however, I suspect is actually impossible to solve if you want to stay within the realm of real physics. That being said, a light saber is actually scientifically plausible. I doubt the makers of star wars had any clue of that fact, but nevertheless, it's doable if you have the resources. [Answer] I have serious doubts as to how well this fantastical notion of mine would work as a reasonable lightsaber blade however I thought perhaps maybe I should input something different than the standard, it's a plasma blade answer. My idea is to make the blade out of a powerful electron beam. Electron beams are beams of electrons fired out of a particle accelerator of some sort. Now to figure out a way to miniaturize an accelerator that small is an exercise for the author of the story, however electrons do have the advantage of requiring less energy to accelerate than their other particle beam kin such as proton and neutral beams. Other forms of particle beam would either be too complex or power hungry, or too long range. For example, a proton beam would require the stripping of protons and electrons from hydrogen gas, and neutral beams would need both a proton and an electron beam combined. Whereas electrons are abundantly available in the form of electricity. Electron beams have high dispersion and are generally quite short ranged as a result. Perfect for our blade as it would mean that the particle beam would not extend too far from the hilt and could be focused/defocused to achieve longer and shorter ranges. However there is the issue that natural dispersion might not be able to keep the blade from extending too far from it's source, but since electrons can be manipulated by magnetic fields you can perhaps even cause the beam to loop back to its emitter, and be recycled. Now assuming you work out all of the kinks of the design the weapon would have the following properties: -Its damage would be far more devastating than any mere plasma beam as the electron beam would be bombarding it's target with a stream of high velocity electrons that not only transfer high heat to the target potentially melting it, but also the millions of tiny electrons slamming into it's molecular structure at relativistic velocities would also cause kinetic effects at the microscopic level that would blast a hole through it. This has the added effect of being able to ablate away quicker at even the most heat resistant materials. -As the electrons collide with air molecules they'd create light and while that wouldn't look like or resemble a normal lightsaber, they'd arguably look cooler as they'd look like crackling blades of lightning and most likely sound like it as well. However also the sound of the accelerator in operation could generate a low hum. Keep in mind the blade would only glow in atmosphere. -When fighting with these blades assuming the electron beam generated by the blade is strong enough the blades would repel each other. This is because particles of like charges repel each other. So two electron blades would bounce off one another. -They are retractable, because you simply need to turn them on and off and they can be deployed in seconds. Provided the power source can discharge quick enough. However they have two huge disadvantages: -they emit deadly radiation. When the electrons strike an object they do it so forcefully it emits gamma or x-rays. This could kill the wielder if they aren't properly protected, and it would tend to fry any electronics it got too close to. However, I'm not certain how bad the dose really is, so maybe it might not be immediately fatal but cause cancer in long term. -It can be redirected by magnetic fields, meaning that an object shielded with a negatively charged field could deflect it. However, it isn't exactly practical to walk around wearing a magnetic field harness strong enough to stop something if this power level, so not likely to be exploited. To get around the problem of the deadly radiation you could potentially assume that the people wielding it are descendants of space colonists who were genetically modified to withstand this sort of radiation. Or it was developed by a species who wasn't overly susceptible to it. Or perhaps have the wielder wear a special protective suit. Or perhaps you could make it into a plot device, that the hero only draws their weapon in time of great need because it takes a toll on their health. However if anyone knows a way to keep the wielder and bystanders safe from radiation from this weapon. Let me know. You could perhaps use insane magnetic fields to control the magnetic spin moment of the electrons causing them to reflect any harmful directly back into the emmitter to be absorbed by a small standoff plate of heavy metal. But this would need insane power budget and could potentially not be workable as it hasn't ever been done with electrons. However if done it could reduce the radiation output to sustainable levels safe for creatures nearby. In all if a few fundamental challenges are met it could work as a surrogate for a lightsaber. ]
[Question] [ ## Premise I recently recalled when the [Chelyabinsk meteor](https://en.wikipedia.org/wiki/Chelyabinsk_meteor) crashed overhead in 2013. The pressure wave was immense. The infrasounds, as recorded by nuclear missile detectors, appeared to traverse the entirety of the Earth. Then I began to wonder, could infrasounds from an organism also traverse the entire Earth? The key word here of course is "could." While not an easy task to undertake, let's attempt to prescribe very specific circumstances to achieve this bio-acoustic task and then objectively evaluate them pragmatically. From this, we might conclude this to be feasible, or we might learn that even under these ideal circumstances it's not feasible. Without further ado, here is my research summary on bio-acoustics and a graph I compiled using data from Wikipedia. * Low frequency sounds travel farther (less energy lost to molecules in medium) * Speed of sound is faster in water (molecules closer together) * Loudest sustained sound has natural limit of 194 decibels (greatest possible oscillation of air pressure, vacuum to 2 atmospheres) * Underwater, sounds can be louder, note marine animals on chart [![enter image description here](https://i.stack.imgur.com/pYV1u.png)](https://i.stack.imgur.com/pYV1u.png) *I made this graph from scratch using javascript. Data is from Wikipedia, but other than that, credit goes to ME!! (evil laugh)* What can be seen from the graph is that while not all loud animals are massive in size, but the one's with the lowest frequency calls *are* massive in size. What I'm not sure is if it would be more realistic if I change things from the biology side: * creature size * power of vocal folds Or should I try solving from the environment side: * atmospheric conditions * marine conditions ## Question Is there a natural barrier preventing planet-wide spanning vocalizations? As it stands, our best hope: the Sperm Whale, can communicate over 1000 miles away, but that's only 1/24th of the Earth's circumference. Natural history spans billions of years and whales are the biggest creatures to date, so I'm worried that there could be a natural barrier to going way bigger. I'd like to stay as close as possible to known science. A few things I think **might** (these are just my hunches, I could be wrong) have bearing to keeping it scientifically plausible: * square cubed law * vocal fold to the sound's maximum distance ratio (is there a conventional understanding of this?) **Further Clarifications:** * **Success Metric:** Sound powerful enough to travel the circumference of the earth, which is approximately 24,000 miles. Note: anatomic diagram is not required, a general description of the theoretical organism would be fine. * Planet info: Planet is [earth-like](/questions/tagged/earth-like "show questions tagged 'earth-like'") in size only, other conditions can be modified * Biome: Ocean or land animal is acceptable, though it seems ocean is more plausible at the moment * Method: A vocalization in the true sense is preferred (emitted from vocal folds), however, if this is a total dead-end, try suggesting other forms of communication * Evolutionary need: You might be thinking to yourself, why would a creature need to do this? Well, we will leave this out of scope for simplicity. * Danger to surrounding life: Don't hold back out of concern for other life; collateral damage is acceptable. On a side note, to avert outright sterility we can suppose *some* portion of life has a coping mechanism, finding shelter, etc. [Answer] ## Possible, yes, but ... The theory of long range communication by acoustics is very similar to that by radio, or indeed a number of other channels. To reason that communication s more difficult at very long range is that some noise sources are at a more-or-less constant power density, whereas the signal power density declines with distance -- typically as $exp(-\alpha r)/r^2$, where r is the range. The term $exp(-\alpha r)$ is an exponential *absorption loss*, where some of the signal is absorbed by the environment, while the $1/r^2$ is the geometric term, related to the signal spreading out into space. The "brute force" way to overcome these losses is to cram a really enormous power into the transmitted signal. However looking back at those loss terms, you can see that it can take a huge power input to achieve even a small increase in range. This is a problem, biologically: you are investing scarce resources for little gain. And, what is that gain? Animals that can call for long distances are either creatures with a solitary habit, joining up with mates for mating season; or pack animals, co-ordinating their pack. Whales have evolved the ability to call very long distances because, as huge apex predators, their number density can be very low. If it has swum a long way in search of food, it might need to call 2400 miles to find a pod again for mating. (And "fortunately", the huge size also gives it the power to do so.) The only value in calling the other side of the world is if there are only two of you, and your only potential mate might be at the antipodes. **Channels** Fortunately, there are much smarter ways to increase your signal:noise ratio, and nature has found several of them. One of them is to transmit into a *channel* which stops your signal spreading out. For a pipe-like channel this can get rid of that $1/r^2$ term, giving huge gains. For a sheet-like channel (which is more common in practice), it changes it to a $1/r$ term, which is still much better. Sheet-like channels are in fact found in the oceans between thermoclines and haloclines, they are actually used, and they are part of the reason whale song can be detected at thousands of miles. A potential disadvantage of a channel is that if the receiver is outside it, they get *less* signal. However, sheet-like channels tend to be arranged horizontally, so being in the channel layer can be as simple as having a preferred depth. There is another important acoustic channel that we know about, which Nature never seems to have exploited: upper atmosphere thermoclines. These, in fact, are part of the reason that infrasound from meteors can be detected globally. The existence of these channels was kpet secret for a long time, because they were (and probably still are) being used to detect nuclear detonations. These channels have another important advantage over marine sound channels, which is related to the second method to increase range: your signal:noise ratio gets better if there is less noise. These upper atmosphere channels are, apparently, deathly quiet. Those detection systems we know about tended to use balloons, with the rigging specially designed to eliminate creaking. So why aren't they used by animals? Well, maybe some do: [bar-headed geese](https://en.wikipedia.org/wiki/Bar-headed_goose) have been detected calling to each other at nearly 28,000 feet. But generally speaking, to really exploit an acoustic channel like this, you also need a lot of acoustic power, and that needs a big animal, and that makes flight unlikely. **Directional transmission** Another method of improving received signal strength is directionality: instead of being the signal out in all directions, you focus it toward the receiver; or the receiver turns its ears toward the sender. Even modest amounts of directionality can easily double the signal strength, but the upper limit is defined only by the ratio of the physical size of the directing structure (mouth, or ears) to the wavelength. Hence, a highly directional signal can be easily achieved in the ultrasonic region, but to get directional infrasound would require an impractically immense structure. For mobile stations -- which includes most animals -- a disadvantage is that you need to know what direction to use. One solution is for each end to have a brief, high power "hailing signal" without directionality, which allows everyone to turn towards each other, and then continue the conversation from there. Signalling to the antipodes is a special case. You still have to deal with the $exp(-\alpha r)$ absorption term, but provided the signal is trapped in the atmosphere (all acoustic signals are), all radiating paths re-converge at the antipodes; you get the advantage of directional transmitters and receivers without turning in any particular direction. **That's the simple stuff. Now we get subtle** For ultra-long range radio communications -- not pole to pole, but Earth to Voyager -- or for radio communications in a non-permissive environment (*i.e.* someone is jamming you), you need to change the signal itself, so that it becomes intelligible at lower signal:noise ratios. There are a number of ways to do this, of increasing technical sophistication. They can all be considered special cases of modulation methods. * Slowing down the transmission; * Repeating the message; * Sending the same message on multiple frequencies, directions, or times (the latter is the same as repeating); * Encoding the message so that partial reception can enable reconstruction of the whole (error correcting codes); * Compressing the signal energy into the time slot, frequency or space the receiver expects. (In the case of space compression, this is the same as directionality.) * Modulating the signal carrier so that a tuned filter can distinguish it better from noise. The last is the most interesting -- it is commonly called "spread spectrum transmission", and it can achieve amazing virtual signal gains by effectively multiplexing huge signal bandwidths. Now, here's the kicker: my wife's lovebird used several of these methods. A tiny bird, it was capable of "calling all lovebirds" across a very wide area, by using very efficient signalling techniques including spectrum spreading (chirp modulation), time slot diversifaction, and power pulsing. An additional advantage of spread spectrum modulation is that for receivers with a tuned receiver (your own species) it improves reception; for those without the correct tuning (your predators, you hope), it *degrades* it. ]
[Question] [ I'm picturing a world with a permanent, dark, overcast sky, but I'm wondering how dark it can be before photosynthesis is no longer an option. It looks like there are a good number of plants that have good [shade tolerance](http://en.wikipedia.org/wiki/Shade_tolerance), but I can't find any real information on the bottom limit. There also appear to be, [a few plants](http://en.wikipedia.org/wiki/Corallorhiza_maculata) that don't need to photosynthesize at all. The closest analog I can think of is the oceanic zones, photic and aphotic. [Photic](http://en.wikipedia.org/wiki/Photic_zone) being the top layer of a body of water where most, if not all, of your photosynthesis is happening. [Aphotic](http://en.wikipedia.org/wiki/Aphotic_zone) being too deep for enough light to penetrate. Apparently the photic zone: > > extends from the surface down to a depth where light intensity falls > to one percent of that at the surface > > > So everything else being equal, temp, atmosphere, etc. could a thriving planetary ecosystem exist at say slightly above 1% normal daylight? Failing near total darkness, how dark can it be? [Answer] **You'd be surprised at how versatile nature is** I would expect you could get remarkably dim. Really all nature is looking for is an energy gradient which is sufficient to stave off the effects of entropy. In the early days of life, energy came mostly from purely chemical processes (themselves empowered by light, but over a very long period of time, so dimness is not a big issue). The initial genesis of life is probably rather independent of light levels, save for perhaps the need for enough ionizing radiation to lean through to jostle things around a bit at the molecular level. Once life takes off, its greatest foe is not the environment, but the other lifeforms themselves, so they will naturally form a balance to match whatever the environment allows. Now if your goal is *recognizable* life, you may have to keep things bright. A low energy environment is going to reward different tracts of life differently. As a general rule, you can probably use the 10% rule: in a food chain, you need 10 masses of foodstock to support 1 mass of predator that eats that foodstock, but the methods used by the predator to prey will shift. We won't see as much attention on movement, because movement costs calories, and they will become increasingly valuable. Rather, there will be more focus on lying in wait, preparing for prey to arrive, and then attacking them slowly (after all, the prey will be slow, themselves). If you want modern Earth style photosynthesis using chlorophyll, your lower bound on how dim it could get is really based on the energy required to produce chlorophyll versus the energy it can harness before breaking down. I don't think there's a well known biology formula for that, because chlorophyll breakdown will certainly depend on the particulars of your solar spectrum. More UV would probably cause the molecules to break down sooner. [Answer] Why do you assume the prime source must be photosynthesis? You could have a planet as black as a coal mine that was habitable, it just needs a different prime energy source. I'm thinking of Io—tidal flexing causes substantial geothermal activity. Now, picture a planet in a fairly elliptical orbit quite close in degenerate star. Of course it's tidally locked but since its not getting its energy by radiation the fact that what little the star puts out hits mostly one side doesn't matter. The primary source of heat is tidal flexing. This also provides the energy source upon which the ecosystem is based—think of the ecologies around the volcanic vents on the deep ocean floor. Obviously this will be a pretty sparse ecology but that's not the same as saying it's uninhabitable. Given the much more stable and widespread energy source this is in comparison to the volcanic vent systems I would expect life to develop far better ways of exploiting the energy. The vent ecologies are based on reactive ions in the water and do nothing with the heat—a more sophisticated organism could exploit this temperature differential. [Answer] Earthy plants would have a problem in a permanently overcast sky (think of the effects of the Tambora volcano and the "year without summer", or for the more extreme case, the Dinosaur killer asteroid filling the sky with cubic *miles* of pulverized rock dust). Depending on the nature of the dark sky, it may be possible to hand wave a plant which can photosynthesize using infrared radiation. Since it is using a much longer wavelength than current plants, these plants would probably look black rather than green, and since the wavelength of light would be longer, they would probably need much larger leaves or other light gathering organs than what we are used to seeing now. Since the dark planet will probably be colder, other adaptations like waxy coverings, deep, starchy roots or even reflective leaves to focus "light" onto a photosynthetic organ might all be possible. The other thing to remember is that infrared light is lower energy than visible light, so the plants will grow much more slowly and the entire ecosystem will be limited by the amount of energy the plants can convert into sugars, starches and other edibles. On Earth, with lots of sunshine, most plants actually convert as little as 1% of the sun's energy into food, so your planet will be very calorie limited indeed. [Answer] The second law of thermodynamics dictates that without a decent amount of energy, existing physical structures will decay because there are more ways of arranging an unordered structure than one carefully constructed to fit a purpose. That is, $ \text{order} \longrightarrow \text{chaos if energy} \lt \text{required} $. I won't go into calculating the exact energy requirement to stave off thermodynamics right now, but suffice to say it's fairly low otherwise life would not exist at the bottom of oceans with just 1% of the light at the surface. Thus, we can infer that a habitable planet can *at least* be as dark as the bottom of an ocean; if this is the true limit then it will simply hVe no submarine life. If, however, the same 1% rule still works out, we can suddenly infer that the planet could have 0.01% of Earth's light. This cycle repeats: decrease the light, and if the rule applies divide the minimum light by 100. Of course, it also depends on how science based your setting is. If you're open to creating new types of plants that don't require so much light but instead of photosynthesising get their energy from another source, then the minimum light level can be as low as you want to make it possible to be. [Answer] Fungus-like plants grow well without light; they just need something to feed on. So there are insects that feed on the fungus, and larger animals that feed on the insects. The fungus feeds on the droppings and bodies of the insects and larger animals. We have whole ecologies that exist in total darkness, so it could work on a planetary scale. Heat is the big thing, but you could solve that several ways. Easiest way is to have the planet orbiting a rogue [brown dwarf](http://www.wikipedia.org/wiki/Brown_dwarf) through interstellar space. ]
[Question] [ I am thinking about how I could write a particularly sharp-sighted people and I'm wondering about the practicalities of this. How far might they realistically be able to see sharply ( assuming a world like our own ) before other physical factors get in the way? Would very sharp distance sight have any effects on their ability to see close-up or other aspects of perception? I'm interested in how this might affect modern humans and also what might be required for a human-like species to develop super-good vision if they were able to dispense with any physiological restrictions that limit us. [Answer] According to this: <http://www.livescience.com/18658-humans-eagle-vision.html> If humans had eyesight as good as an eagle, we'd be able to pick out a single ant on a blade of grass from the top of a 10 story building. That's something like 20/5 vision. Being able to pick out a human from several miles seems pretty easy. Also according to that source, it wouldn't effect your close up vision. My brother has 20/15 vision, and he's told me that he can pick out individual pixels on a computer screen pretty easily, so with 20/5 vision you'd have to get used to that being kind of a problem, and everything looking pixelated... I wonder if you'd end up getting computer glasses to correct your vision down a little to make watching tv more enjoyable. One cool thing they mention at the end of the article is that laser surgery may soon develop to the point where you could go in and get eyesight between 20/10 and 20/8. [Answer] Assuming perfect optics and perfectly high receptor density on the retina, and taking the wavelength range as a given (visible light), what determines the achievable resolution is just one quantity: The size of the eye (more exactly, the size of the pupil). Ever wondered why astronomers build ever-bigger telescopes? That is the answer. The resolution of an instrument (and the eye is nothing but a biological instrument) is [given by](https://en.wikipedia.org/wiki/Angular_resolution) $$\theta = 1.220\frac{\lambda}{D}$$ where $\theta$ is the angular resolution (for the small values relevant in optics, you can approximate it as distance between two points over distance to the points), $\lambda$ is the wavelength (for visible light, between $400\,\rm nm$ and $750\,\rm nm$) and $D$ is the diameter of the pupil (for the human eye, the [largest occurring size](https://en.wikipedia.org/wiki/Pupil#Optic_effects) is $9\,\rm mm$), so assuming normal-sized eyes, the angular resolution is at best $10^{-4}$ for blue light, that is, you would be able to distinguish two points one meter apart at ten kilometers distance. For red light, the optimal resolution would be half as large. A typical dot mask size for computer screens is 0.025mm; Someone with "limit vision" would therefore see the individual pixels of a computer screen from 2.5 meters distance, at least for the blue pixels (for the red pixels, he'd have to go to about half that distance). Of course that's assuming that the pupil size is not enlarged. Hypothetical humans who grew twice as large eyes (or just twice-as-large pupils) would of course also see twice as well. Also note that the main limitation in our actual eyes is generally not the optics, but the receptor density in our eyes. For example, while the theoretical resolution is best for blue light, the actual eye has lowest resolution there, since the blue receptor density is lowest. That's also why many early home computers used blue backgrounds: The pixels — which were much larger than today — could simply not be that well resolved for blue, so the background looked smoother. According to [this Wikipedia article](https://en.wikipedia.org/wiki/Eye#Visual_acuity) the perfect human eye has an angular resolution of 50 CPD, which if I understand the definition of CPD correctly, corresponds to an angular resolution of $3.5\cdot 10^{-4}$. So the human eye is about a factor 3.5 from the theoretical optimum. ]
[Question] [ We have [Venus flytraps](http://en.wikipedia.org/wiki/Venus_flytrap) which move by closing their 'mouth' to trap prey. There are currently few identified plants with a 'quick' reflex like this. Blooms of course open and close through the course of a day and evening but that is pretty slow. We've all seen things like 'The Wamping Willow' in Harry Potter and the man-eater in [Little shop of Horrors](http://www.imdb.com/title/tt0091419/) or the Crawling vines in [Jumanji](http://www.imdb.com/title/tt0113497/). I was wondering what kind of movement and reaction time would a plant be able to accomplish (while still remaining mostly a plant) whether to trap, entice or ward off animals. Could a tree have say vines on the ground that could be triggered by walking and they would just roll up like a carpet fast enough to trap an animal kill it like a boa constrictor (or add poison spines)? EDT: "While still remaining mostly a plant", I mean I'd like to keep it as close to known plant biology as possible, but since no known plant can do these things, then some fiddling will have to be done. [Answer] The problem I always have with the fictional examples you gave is that those aren't actually plants any more. They're animals, with muscles, nervous systems, etc to be doing that. That said, it seems quite reasonable to imagine a tree like you suggest. If a venus fly trap can move at that kind of speed, why not other plants? We can't really have muscles and call them plants, but we can have hydralic/pressure driven systems. So: Imagine a "vine" of some highly stretchy plant matter. There's a lot of spring energy in it, and the natural configuration is all coiled up. The plant then fills this up with liquid, which makes it straighten out and hang down. When an organism disturbs it, they knock off some weak covering over holes in the vine. The fluid escapes and the vine coils up again. (Bonus option - the fluid is also some kind of nerve agent). Not at all sure if it would actually work, but it's something. The bigger problem you've got here is *why* a plant would do such a thing. It's not going to work as defence against being eaten (most traps are going to be single use, and there's going to be aways around the traps, poision or thorns work better for cheaper). If you're struggling for minerals etc for growth, how do you get to be a big tree full of nerve agents in the first place. Maybe it's part of a symbiotic relationship like [the Bullhorn Acacia](http://en.wikipedia.org/wiki/Vachellia_cornigera). It captures organisms to then be devoured by it's residents, who in turn protect it from anything that tries to eat the plant. [Answer] You've various things like sensitive plants that react quite quickly. This one, for example: <https://www.youtube.com/watch?v=BLTcVNyOhUc> And if you watch a timelapse of a bramble growing: <https://www.youtube.com/watch?v=aNjR4rVA8to> It'll wrap around something and 'strangle' it. But you don't have much strength in a plant - it can fold up, but not push anything out the way particularly. However enter [urtica diocia](http://en.wikipedia.org/wiki/Urtica_dioica) - the common nettle - it 'stings' via brittle hairs, rather than thorns. They're almost like glass, in that they snap off and deliver a poison. But they'll sting if you just brush against them. <http://www.bbc.co.uk/programmes/p00gj39c> And then, you look for something more toxic. Like this: <http://en.wikipedia.org/wiki/Dendrocnide_moroides> So I'd envisage a combination of the 4. A bramble like 'tendril' that curls up around something when it's touched, brushing against it to sting. And 'prickles' it with neurotoxin filled nettle-like hairs. ]
[Question] [ A good friend of mine, who's a doctor, is very well traveled, and he told me he's seen skies of different worlds take all the colors of the rainbow (and the grayscale to boot). I suspect that he might be pulling my leg, since he does tend to exaggerate on occasion. ![The refreshing green sky of home](https://i.stack.imgur.com/DEwmB.jpg) *The welcome green glare of the homeworld's sky* So, is my friend lying or can the sky really be of any color (besides octarine)? If the whole spectrum is too hard, I'm specifically (and in this order) interested in: * Green * Gray * Purple * Orange * Vermillion (I don't actually know what color that is, I just like the name) To clarify: I don't mean briefly for a minute, I want it that color a significant portion of the day. And no, it need not be Earth, and the system planet and star can vary to be whatever is best for maximizing your color-purposes. And no, you don't need to address all the colors, (I mostly care about green) but extra brownie points if you do. [Answer] Most colors would be possible. The two items that determine what color the sky is is the color of the sun and what is in the atmosphere. Having a red star will be the easiest in making the the sky shades of red, since that is the primary wavelengths coming from the star. The rest, it depends on what is in the air to both absorb certain light frequencies and scatter others. Water vapor scatters most frequencies (on a day with even thin clouds, the light is still painful) and when thicker, absorbs most frequencies. I'm not up enough on my chemistry to point out which will do what. [Answer] # Most skies will be blue-ish First off, most gasses are colorless. Taking our solar system as an example, the possible gasses are CO$\_2$, N$\_2$, SO$\_2$, Ar, CO, O$\_2$, H$\_2$, He, and CH$\_4$. That covers Venus, Earth, Mars, Titan and all four gas giants. All those gasses are colorless. Water vapor (trace on Earth and the gas giants) and Neon (trace on Venus and Earth) are also colorless. Second off, Raleigh Scattering, the blue-shifting of reflected light, [happens with all gasses](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770012747.pdf). If one of the dominant atmospheric gas is carbon dioxide or methane (as in Venus and Titan), then the scattering effect will be more prominent than on Earth, since those gasses scatter blue light more efficiently than oxygen or nitrogen. If hydrogen is a dominant gas, as in the gas giants, then the effect will be less. So basically, all reasonable atmospheric gasses are colorless in and of themselves, and all of them will scatter blue light causing a greater or lesser blue tint in the sky. Finally, it is relevant the wavelengths of light that stars up out. [![enter image description here](https://i.stack.imgur.com/pB0JI.jpg)](https://i.stack.imgur.com/pB0JI.jpg) Due to various absorption effects, only the brightest and dimmest stars won't have a spectral maximum in the blue-purple range. O-type stars, extremely hot and short lived, will produce a very purple light; M-type red dwarfs will produce a reddish light. All other stars will peak in the 400-450 nm range, just as our sun does, which is sort of blue-purple. Overall, most skies will be blue-ish. I suspect that given that the peaks of the red dwarf's spectra shown above are on the very edge of the human visible range, even a red dwarf's skies might be more green or yellow than red. [Answer] Magenta might be trickier than pretty much anyting else, because there is no magenta wavelength, it only exist as a combination of red and blue (which don't overlap in the light spectrum). Figure you could fix that by having a binary star system of primarily red and blue light respectively. ]
[Question] [ This question is a bit of an outgrowth of [Can you simply scale up animals?](https://worldbuilding.stackexchange.com/q/316/29), but it does approach it from a different angle. "All else equal" (which it of course never is, but we're good at pretending here, so let's pretend), heavier animals tend to be less agile than their smaller counterparts. This to some extent follows from the fact that their larger mass represents a larger inertia, but it would seem like it would be counteracted by the greater force which can be exerted by the (larger) muscles. I'm basically looking for a way to, within a single species, have a "baseline" size (in terms of weight and possibly height) and a formula where one can plug in the size of the specific individual and the result is some sort of index or factor describing how agile that individual is compared to its peers, to model their relative agility. For the purposes of this question, let's say agility translates directly to how quickly an individual is capable of moving a certain distance from standstill to standstill. (In other words, I have $\Delta{}T = f(d, \dots{})$ where $\Delta{}T$ is time required to move a given distance $d$, and I'm looking for what goes into $f()$.) I have a feeling that the old workhorse $F=ma$ is going to be at the center of such an equation, but that there is more to it than that. I also recognize that it can't be exact, but for my purposes it doesn't need to be exact; I'm looking more for a rule of thumb than exact mathematics. If it makes it easier, the question can be limited to quadrupedal animals; it would be better if an answer applies at least to both bipedal and quadrupedal animals, but that is not a requirement for a good answer (only a great one). * Ideally, there is such a formula established in the scientific fields of study. If so, what is it? (I doubt this is the case, but who knows?) * Alternatively, what factors would go into such a formula for it to be at least semi-accurate? What might it look like? Note that an answer does not necessarily need to state an explicit formula. A description of the factors that goes into answering this and how they interact can be equally valid. [Answer] The factors for an animal are the same as for vehicles in many ways. Agility is essentially a measure of acceleration, and your ability to apply that acceleration in different directions rapidly. The limiting factors for acceleration as animals grow larger are: * Muscle Power * Traction * Mass * G Force But there are also advantages with elements like: * Stride length * Leverage * Energy Storage * Air resistance Unfortunately there is no one simple formula you can apply here, each factor can vary greatly. For example a house cat on a carpet where they can dig their claws in is incredibly agile, the same cat trying to make a sharp turn on polished wooden flooring could well slide into the wall. We can discuss each factor though. **Muscle Power** Larger animals have more power available, the raw strength increases with the square of size (as it's the cross section of the muscle) but total power does increase with the cube of size (as it's the volume of the muscle) so larger animals can end up with plenty of power to work with so long as their tendons and bones can take the strain. **Traction** Claws and hooves are common adaptions to increase traction but you are still limited by the surface area of your feet. Larger animals become increasingly susceptible to problems getting traction and are able to slip and fall more easily unless they can grip something with their claws. **Mass** Mass increases with the cube of size. That mass takes power to accelerate. The positioning and layout of mass should also be considered. Keeping the mass central and being able to adjust it dynamically for example by twisting your body gives you a big boost in maneuverability. **G-Force** Rapid acceleration and deceleration can cause serious injuries, that are easier to handle for smaller animals. Additionally the terminal velocity of smaller animals tends to be lower due to their higher surface area to mass ratio. As a result longer falls are survivable for smaller animals than for larger ones. **Stride length** Larger animals need to take fewer steps to travel the same distance or the same speed than a smaller one. This allows them to grip once and then apply the power smoothly over time rather than constantly re-applying it. **Leverage** Longer limbs give more mechanical advantage to muscles - so long as the muscles can have enough strength to take advantage of it. **Energy Storage** Fleas wind up springs in their legs in order to release it in a single bound - jumping far further than they could without that. Similarly Kangaroos bounce very efficiently due to springs in their legs that store energy when landing then use it to propel the next upwards leap. **Air resistance** Air resistance effects larger creatures less as it is proportional to the square of size whereas mass has increased by the cube of size. A large creature can jump further if it starts the jump at speed X than a smaller creature starting at the same speed just because it is not slowed down by the atmosphere as much. ***Conclusion*** In general larger creatures do not have to be less agile than smaller ones. Their muscle power is proportional to their mass, they have advantages in terms of leverage and stride length, and they are less restricted by air resistance. However they are also limited by the strength of their bones and how much traction they can develop. An elephant's muscles and skeleton could be tuned to allow it to run like a Cheetah, however it would snap every tendon and bone in its body and when it tried to accelerate it would throw more dirt backwards than it would go forwards. Rhinos though have been measured running at 55km/h with a surprising ability to turn and maneuver while doing so. So for a certain range of sizes there is roughly constant speed and turning radius no matter how larger a creature grows. Once the limits in strength of materials and the limits of traction from the ground starts to be reached then the available maneuverability starts to decrease. As maneuverability decreases then increased speeds become more dangerous and less useful so top speeds also tend to decrease as other methods of defense take priority. ]
[Question] [ > > ...no, I mean, supposedly, I believe there is more about it than mere kans on our part. Installations like this one are found all along the spoorwegs, and yes, around some you should tread lightly. Yet most are *safe*, and held, maybe still hold, functional warmers! What was th- > > > Ade, 2nd Class Engineer of *Brug Gibraltar* before getting shot --- Welcome to *a* future. Mankind has brought doom upon themselves, their cities have been flattened by war and weather, and most of the northern hemisphere is radioactive badlands. They put their differences aside to ~~fix~~ keep the planet, reaching an unprecedented scale of globalization, making major breakthroughs as a unified people - just to bomb themselves to smithereens once that immediate fear was off the table. In fact, the fragile peace lasted [less than a decade](http://tvtropes.org/pmwiki/pmwiki.php/Main/InYourNatureToDestroyYourselves) without the external pressure of an extinction event providing something to be worked on. Once that fate became clear, governments hastily began restoring and expanding abandoned and repurposed cold war era bunkers. To little avail. Only a fraction of the populace managed to find shelter when the bombs started falling. Months to years, and in some cases decades, later survivors start emerging again. They are quick to start establishing new communities. Unfortunately, the electro-magnetic-fallout from the bombs fried a majority of the world's power- and communication-grids, preventing these places from easily connecting with each other. Yet, sturdier tech survived relatively unscathed. Most places are still connected by rails and a fair number of [pre-war train-engines](https://worldbuilding.stackexchange.com/questions/101288/train-world-feasibility-of-radioisotope-steam-electric-engines) are found in [rail-depots](https://en.wikipedia.org/wiki/Motive_power_depot) in various states of disrepair - ready for their new job as the lifeline humanity 2.0. The trains are powered by huge [Radioisotope Heater Units](https://en.wikipedia.org/wiki/Radioisotope_heater_unit) (RHU), using [Radium](https://education.jlab.org/itselemental/ele088.html), as described in [this question on the feasibility of such engines](https://worldbuilding.stackexchange.com/questions/101288/train-world-feasibility-of-radioisotope-steam-electric-engines). --- For the purposes of my story I am aiming to have *RHU storage facilities* in rail-depots and/or other secure locations (e.g. tunnels), where RHUs are stored in pits in the floors and hoisted up by [overhead cranes](https://en.wikipedia.org/wiki/Overhead_crane) to be transported or installed into engines. I was originally thinking about having them submerged in a heat-conducting liquid and using the heat to drive turbines to power workshops and machinery around the facility. But to my understanding there are at least 2 major issues with this approach considering I need these facilities to last while there are no people to maintain them for up to multiple decades: 1. *Breakdown of moving parts*: when (not if) the heat exchangers or secondary cycles start breaking down the heat will accumulate in the main 'pit' and eventually ignite things. 2. *Decay of the submerging fluid*: Water would amass algae and other biomatter, [oil would degrade over time](http://www.fluidmetrics.com/degradation.html), [car coolants seem to last about 5 years tops](https://mechanics.stackexchange.com/a/11979) - that is nowhere near long enough... --- **Q**: How can these RHUs be securely stored for decades to even centuries? Solutions will be judged by the following criteria weighted from top to bottom: * **engineering complexity**: The **fewer** moving parts the **better** * **recoverability of RHUs**: The **less work** is necessary to get an RHU back into working condition before it can be reinstalled the **better** * **deterioration in storage**: The **less** RHUs deteriorate in storage in regards to time spent in storage the **better** * **footprint of installations**: The **less space** is necessary per stored unit the **better** * **Availability of used materials**: The **easier to come by** the materials are all around the world the **better** --- This question **is about**: * finding a working storage solution for the RHUs over the time of decades to optimally centuries This question **is not about**: * what element the RHUs are made of. Please refer to [this question](https://worldbuilding.stackexchange.com/questions/101288/train-world-feasibility-of-radioisotope-steam-electric-engines) if you want to propose alternatives to the described radium RHUs * finding processes to generate power from the RHUs, unless it is part of a storage-solution [Answer] # Your primary problem is cooling You will need a constantly cycling cooling system ideally with the ability to automatically top up lost coolant or holding such redundant levels of coolant that moderate losses are not catastrophic. I would advise using water as your primary coolant. Your concerns about buildup of biological matter can be resolved by the simple consideration of the temperature the system is going to run at. Anything short of extremophiles are going to be cooked off in short order. Since this is a nuclear facility a consideration for a cooling system that will **survive unpowered, unmaintained, and unattended**, for example in case of meltdown or earthquake making the building unsafe, could be a part of local regulation for building the yards in that country/state. Based on a scaled up [thermosyphon\*](https://en.wikipedia.org/wiki/Thermosiphon) for example. While this approach is not entirely bullet proof in the very long run, its largely passive nature and lack of moving parts means that facilities that survive the war should survive a considerable period afterwards. Facilities will be lost, some will suffer leaks and be unable to recover sufficient water, or suffer earthquake or other damage and suffer catastrophic failure. The nature of a rail network means that while some depots will be lost, others will survive. --- ### Other considerations **Recoverability**: This is how they were designed to be stored, this should not be a problem if the facility remained intact. **Deterioration**: As for recoverability, hopefully a unit designed to be stored in water will not corrode when stored in water. **Footprint**: Well within standard warehouse sizes, as big or small as you like really. I advise making reference to earthquake proofing. **Availability of used materials**: Nothing special going on here. Concrete, water, steel. --- # \*Thermosyphon > > Thermosiphon (or thermosyphon) is a method of passive heat exchange, based on natural convection, which circulates a fluid without the necessity of a mechanical pump. Thermosiphoning is used for circulation of liquids and volatile gases in heating and cooling applications such as heat pumps, water heaters, boilers and furnaces. Thermosiphoning also occurs across air temperature gradients such as those utilized in a wood fire chimney or solar chimney. > > > This circulation can either be open-loop, as when the substance in a holding tank is passed in one direction via a heated transfer tube mounted at the bottom of the tank to a distribution point—even one mounted above the originating tank—or it can be a vertical closed-loop circuit with return to the original container. Its purpose is to simplify the transfer of liquid or gas while avoiding the cost and complexity of a conventional pump. > > > [Answer] **The key to successful RHU storage** is the ability to safely separate the Hot Slug (heat source) from the mechanical Power Converter assembly. Each component is likely to have a different design lifetime anyway. Separating the RHU into the two components makes maintenance of the overall system easier. **Hot Slugs should be stored** in secure, remote location that can dissipate their heat safely and passively with low rate of physical deterioration, like either under a mountain or open-air in a desert. This should include the facility to re-glassify (re-mold) Hot Slugs shattered by wrecks or flaws. This could also perhaps be (part of) an original Hot Slug production facility. A railway branch may be needed to connect the remote storage facility to the network for work trains. **Power Converter assemblies require** common manufacturing/maintenance skills and equipment. This is where all the moving parts are maintained and replaced. Since the assemblies are likely contaminated after long exposure to the Hot Slugs, this shop seems more likely to be located near an industrial town served by the railway network than in a major city. This is probably also the facility where the Hot Slugs and Power Converters are married and separated. The ideal location for such a heavy repair shop is near (but not too near) the yards serving a major terminal or junction that ISN'T a major city. Access to the supply chains of repair parts and heavy equipment, and to the disposal and recycling chains of used and contaminated parts are also vital, so don't stick this shop in a secret mountain bunker - it's a busy place and needs highway access. The **route for work trains** between the Hot Slug storage range and the Power Converter Shop should avoid population centers and critical infrastructure. A circuitous-and-slow but safe route. Note that having large radioactive power sources for locomotives means most populations won't want trains running through their town/city anymore - **railway alignments may become circumferential** with suburban terminals and yards. Shops and sidings may be spaced a bit farther from the mainline (and from each other) than historical practice for safety. [Answer] To do what you want, the first question is what radioactive material to use (probably not radium). The criteria are how efficiently it supplies heat, how much shielding it requires, and how long is its half-life. There is a very good discussion of possible fuels in the Wikipedia entry on radioisotope thermoelectric generators (RTGs). For your application, the best material is Americium 241. It requires only modest shielding and has a half-life of 432 years (so could meet your desire for RHUs that last centuries). Besides a longer half-life compared to Plutonium 238 (the standard fuel for RTGs), it decays emitting alpha and beta particles plus relatively low energy gamma rays and no neutrons. An RTG's power diminishes over time partly due to the half-life of the Pu 238 (87.7 years), but also because of the degradation of the thermopile material by the neutrons emitted from the Pu 238. To generate mechanical power from the RHUs, you could use a Sterling cycle or other mechanical heat engine. They are reasonably efficient, but do have moving parts. For maximum longevity, you could use a thermopile (an array of thermocouples). At present, the best are only about 8% efficient, but there are no moving parts and, in the absence of neutron bombardment, should last many decades or possibly centuries. As with any heat engine, the cold sink is just as important as the heat source. In a low tech, recovering world, sticking the cold end into a fast running stream might be a practical solution. Information on potential fuels for RTGs or RHUs: <https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator> (see Section 3) Data on Americium 241: <https://semspub.epa.gov/work/HQ/176296.pdf> ]
[Question] [ I've been building a world that has a thicker atmosphere than that of Earth, about half the gravity, and twice the amount of oxygen. My reasoning behind these features is mainly to support the growth of large trees and megafauna, and to make it easier for my races of intelligent bats to fly. Now, one thing I haven't been able to figure out about this world it how these changes, particularly the dense atmosphere, would affect the planet's weather. For example, I've been thinking that because the atmosphere is thicker, the wind on this planet would put more force on anything it's hitting. The thick atmosphere could trap more heat and make more violent storms, if it doesn't just homogenize the planet's temperature. Basically, I think this planet would either have extreme weather, or very little weather. But I don't know which. Therefor, my question: **Given the above parameters, what could air circulation and wind speed be like compared to Earth?** [Answer] In general, a **thick atmosphere** relates to a normal atmosphere, the same way that **syrup** relates to water. Keep that in mind, as it's generally applicable for all basic cases I can think of. > > For example, I've been thinking that because the atmosphere is thicker, the wind on this planet would put more force on anything it's hitting. > > > Purely considering the kinetic forces, you'd expect the opposite to happen: slower winds. A thicker atmosphere means a heavier gas, which means more mass. Assuming the same force is applied, an object with **twice** the mass will move at **half** the speed. Do note that if for some different reason the amount of exerted force dramatically increases, then you will indeed be hit with a harder force. But that has nothing to do with the mass of the gas, but rather the force that propels it. *A falling jar with a liter of syrup will hit you harder than that same falling jar containing a liter of water, but when stirring either liquid with a spoon using the **same** amount of force, the spoon will move slower in the syrup than in the water.* Do also consider that this works both ways. While the wind (at the same speed) hits you harder, you will also receive more support (to help you stay upright) by the wind on the other side of you. If we're standing in a pool (feet on the ground, not floating), and I push you, the water will dampen your movement and you won't get pushed as far as you would if the pool were empty. The same is true of the thicker atmosphere, to a lesser extent than the water. *A spoon stays upright easier in a jar of syrup, than in a jar of water. However, a spoon that is forcefully pulled out of syrup will endure more force than when it gets pulled out of water.* In other words, your body receives more stress/pressure (stronger push, stronger push back), but any difference in end result (your actual movement) will likely cancel each other out (or at least scale accordingly). > > The thick atmosphere could trap more heat and make more violent storms, if it doesn't just homogenize the planet's temperature. > > > This sounds realistic. A thicker gas is likely going to be a beter insulator, thus will indeed be slower at homogenizing the temperature. As temperature and pressure are related (volume is constant for the planet, so irrelevant), a higher temperature leads to more pressure, which leads to stronger winds, as wind is primarily created by pressure differences. > > Given the above parameters, what could air circulation and wind speed be like compared to Earth? > > > Any wind created from **heat**-based sources will likely blow more forcefully (assuming the thicker gas is a better insulator). However, the increased mass inversely correlates to the speed of the wind. Slower and thicker wind, while exerting the same force, has more time to **disperse** around you and will therefore not hit you as hard, comparatively. This may or may not completely negate any added wind force due to heat-based sources. Since the thicker atmosphere dampens the movement of the wind, it also dampens your body's movement (when hit by the wind or any other force), so you won't be blown away easily, but your body will endure more pressure when a strong wind hits you. Last but not least: a thicker atmosphere makes you more **buoyant**. Your mass doesn't change, but your *perceived* weight does, just like how you feel lighter in water (and would feel even lighter when submerged in syrup). You'll feel lighter on your legs, and will e.g. be able to jump higher (again, assuming a jump of equal force). If the atmosphere is sufficiently thick, you could even "swim" in it (even though you'd slowly "sink" to the planet's surface). [Answer] Regardless of chemical composition, an atmosphere twice as dense that is still subject to the heat ranges of those on Earth will create winds with much stronger forces. That said, to answer your direct question; such a planet would have extreme weather, because the only way it could exist in that format is to be suffering extreme greenhouse activity, not on the scale of Venus but certainly more than Earth. Such a planet would be in the inner fringes of the goldilocks zone of its home star and between the heat and the fire risk, really wouldn't last in this state of life bearing for long would be my guess. I haven't come across a lot of sci-fi stories about planets without any life on them, so the rest of this answer assumes that the spirit of the question revolves around how such an atmospheric makeup would impact life. This planet would be on the fringe of those where complex life may be possible. Complex life is far more fragile than we generally give it credit for and this planet presents it with some significant challenges, but first a word on how to consider atmosphere in terms of biology. When discussing atmosphere for life, it's best to focus on the concept of partial pressure. In other words, organisms can generally be quite tolerant of changing pressure overall (we wouldn't be able to scuba dive if that wasn't the case) but we still use a set volume of a specific gas, like oxygen and are *less* tolerant of changes to those levels in gases we need or need to avoid. Generally speaking, the average human can survive if he or she is breathing between 0.16 and 0.30 ATM of Oxygen, less than 0.02 ATM of Carbon Dioxide and other poisonous gases, and whatever mix of inert (or low reaction gases like Nitrogen) is needed to make the balance. An example of this is the Apollo missions, where the astronauts could survive for an extended period in a pure O2 environment because the Apollo spaceships were only pressurised to around 0.3 ATM. As for evolution being able to cater to the conditions described above; evolution is not a magic wand, and complex life still has limits in terms of the environments in which it can form. Most extremophile forms of life of which I'm aware are very simple, often single celled organisms. Increasing O2 and CO2 and saying 'let evolution take care of it' may work (may), but would put limits on the type of life possible and how long its life expectancy can be. But to the question at hand... Firstly a higher oxygen count would actually be detrimental to plant life, for which O2 is essentially a waste product; not because they don't use it in their own organic chemical reactions like all life, but because they (like us) find it toxic in high quantities. This is why they release their excess in the first place. Also your chances of fires would be MUCH higher and catastrophic when they happened. Megafauna would not occur as a result of higher O2 levels, except for maybe insect life because the higher concentrations would allow their bodies to absorb O2 deeper in (they have no lungs). All other animals would have shorter life spans because the higher oxygen count would actually age their bodies through free radicals (especially in the case of lungs). Humans in particular would have long term problems if constantly exposed to O2 levels above 0.3 ATM. With a thicker atmosphere, the O2 levels you describe would probably be toxic. Also there is an issue with a thicker atmosphere on a lighter planet; the only way that occurs is if a massive amount of energy is being dumped into the system, think runaway greenhouse effects. In such instances, the O2 levels might be possible through plant photosynthesis, but only because the CO2 levels would be off the chart for animal survive-ability. Think Venus for the best analog. It's that increase in CO2 that presents the single biggest challenge to life on such a planet because of both the toxicity of the gas itself and the increase in heat and pressure involved in a high greenhouse effect. Combining all these things, it becomes clear that your planet will be hot, have high pressure winds and generally be inhospitable to life, but could be livable if the greenhouse effect is nowhere near as pronounced as that on Venus. [Answer] You would have really strong winds even with low wind speeds, and there is a real-life solid example to support this: **Venus**. Although the wind speed on the surface are really slow, Venus's atmosphere is so dense, that you can simply push a human with a gentle breeze. At extremely high pressures, it doesn't really matter whether the atmosphere travels slowly or quickly. They exert a lot of force. ]
[Question] [ I've had a great idea to leap over the giant boundary of respiration when making giant insects.The largest problem is that insects rely on diffusion through exterior holes (spiracles) to breathe, and the amount of diffusion relies on surface area, so a large insect wouldn't be able to move enough oxygen around its body because the volume of its interior mass would be much larger than surface area, and oxygen would need to travel further into the insect.(This is why the largest insects like meganeura had long, thin, tube-like bodies) My idea is that since lungs (internal respiration) evolved from the gills of fish (external), perhaps the gills of aquatic nymphs like dragonfly larvae could evolve in much the same way. As I've tagged, I'm looking for a reality check, as my knowledge of the movement from gills to lungs is not very sound. My question comes in two parts: * first, of course, is this idea plausible? * and secondly, how would the new internal structures affect the shape of the insect's body? Edit: To clarify, I know that a new circulatory system would be needed along with the lungs, but that's a topic for a different question. Also, I had another idea for the development of lungs or equivalent from the book-lungs of arachnids, so if you like you can touch on that in your answer. [![Nymph gills](https://i.stack.imgur.com/ArY2v.jpg)](https://i.stack.imgur.com/ArY2v.jpg) [Answer] Diffusion of O into the hemolymph it's only part of the issue. They would also need a heart or equivalent, our they'd need ingress into their tissues, or both. That said, there are options: Various plates around the insect could have gaps a flex to act as pumps. This could increase exchange with the atmosphere, but could also account for some circulation to tissues. They could have exchanges at reasonable intervals along their bodies. These would tend towards vulnerability. (Clogging, infection, and gaps in armor.) They could have actual hearts and lungs. The environment could be a better exchange medium than our air. --- Bucal breathing is simpler than what we have, and far niftier than insects'. It might be a good topic to check out to get a feel for the spectrum in reality. ]
[Question] [ In my short story, there are underwater people who are now up to WWII technology-ish (major differences, but that level and population of society). These mermen can hold their breath for as long as we can. There are no out-of-water humans, but different rival societies are vying for the precious resources on land. As early as 100 years ago, they've learned how to extract just like we've learned to extract from under the sea. For control of resources out-of-water (flora, fauna: "fishing for deer," more mineral extraction), how would they dominate the lands? Slightly related: [Weapons for Mer-people](https://worldbuilding.stackexchange.com/questions/17580/weapons-for-mer-people). [Answer] To answer this question, it is important to note that while humans *can* operate underwater, they *prefer* to do most things on land. We've been built by evolution to do best on land, and thus trying to work underwater usually turns out to put us at a disadvantage. This is probably going to be similar for merfolk; they're built for water, so doing anything on land is going to be hard for them. They may be able to invent things that help them survive on land, but at the end of the day they'll be glad to jump back into the oceans. That said, the merfolk may find that there are some perks to working in the fresh air. For one thing, there isn't much resistance; this is bad for swimming, but good for things like weapons. Swords will swing faster, and arrows will fly further. I don't imagine the merfolk will have invented guns by this time, as guns tend not to work too well underwater, but to make up for this I'm sure they'll have many highly advanced underwater weapons that should work pretty well on land (and if they don't, like I said, bows are going to seem incredibly powerful to them without water resistance slowing down the projectiles). Something that tends to not be as dangerous on land is explosives. If you're underwater and a grenade goes off next to you, even if you don't get hit by the schrapnel it's the shockwaves that'll do you in. On land, on the other hand, shockwaves in air don't do a whole lot. Based on this, it's plausible that merfolk won't deal too often with explosives on land. They just won't have the technology for it. If they discover fire, though, that's going to catch on like, well, wildfire. It's something that they can't use underwater, but is greatly effective on land (especially if they're deep-sea merfolk who aren't used to light). From this, we have merfolk fighting with fire and simple projectile weapons (let's say crossbows). Now, as for where they'll fight and with what tactics, I'd say they will mainly be focused on getting back into water. As I said earlier, they aren't going to like being on land. But more than that, they probably can't even survive on land for too long. Humans breathe oxygen, and oxygen can be compressed to offer us a lot of air to breathe underwater; merfolk, on the other hand, breathe water, a mostly uncompressible liquid. Thus, their maximum water supply will be a fraction of our maximum air supply, especially since without water resistance anything the merfolk carry is going to feel a lot heavier than usual. So I can see land combat revolving around bodies of water, with suited-up soldiers floundering on land from pond to pond, trading bolts and molotovs. Something similar to trench warfare may develop, as both sides build irrigation trenches through which they can swim. The no-man's-land will become the land, and anyone who tries to cross it will find themselves an easy target. [Answer] The same way we dominate the oceans. Think about a submarine: From the outside, it's a vehicle made for going through water, while in the inside it's a container for air, and has everything humans need to survive for a while. Similarly those merfolk people would build vehicles filled with salt water. I don't think they would build airplanes because those would simply be too heavy when filled with water (and WWII technology isn't yet ready for drones). Civil vehicles would have arms similar to the arms of research submarines. Military vehicles might be water-filled tanks. The main problem would be that those vehicles have to be heavy, first because of the water, and second because they need to be tight enough to keep the water inside (and plastics is not yet available at WWII technological level). Therefore even the civil vehicles would likely resemble tanks, just that instead of weapons they have manipulator arms. This restriction will likely also restrict the uses of such vehicles (just like our use of submarines is limited). I think the most common civil vehicle would be a transport vehicle, allowing to transport things over land where the sea route would be much longer or even doesn't exist (if oceans are completely separated by land masses, similar to how our continents are separated by oceans). They would basically have the same function as our ships. Note also that they may use rivers as way to get far into the land before they have to leave the water (assuming they can survive non-salty water, that is; but even if not, for them making a salt water-filled underwater vehicle would probably be easier than to make a land vehicle, not to mention that those river vehicles would have less issues with weight). ]
[Question] [ Often in science fiction, we see that there are swords that deflects bullets, almost every single renditions has the sword wielder having hyper reflexes. The undeniably most famous example of this trope is the *Star Wars* light saber. Forget about the reflexes a user of this sword would need, assume that I have found Superman or a really cool cyborg. Using modern or near future technology, could I build a sword that stops bullets? What about one that deflects them? [Answer] ## Wielder's Strength So your sword wielder has superhuman reflexes, but he'll also need some degree of superhuman strength to hold a bulletproof sword while it deflects a bullet. With that being said, there are a number of materials capable of withstanding bullets: ## ALON Transparent Aluminum Known commercially as [ALON, transparent aluminum armor](http://science.howstuffworks.com/transparent-aluminum-armor3.htm) is made of aluminum oxynitride, a combination of aluminum, oxygen and nitrogen. Before it can end up as a hard transparent armor plate, it begins as a powder. This powder is then molded, subjected to high heat and baked, just as any other ceramic is baked. Once baked, the powder liquefies and then quickly cools into a solid, which leaves the molecules loosely arranged, as if still in liquid form. The resulting rigid crystalline structure of the molecules provides a level of strength and scratch resistance that's comparable to rugged sapphire. Additional polishing strengthens the aluminum alloy and also makes it extremely clear. Now, just as bullet-resistant glass is made of three layers (two panes of glass and a middle pane of polycarbonate), so too is transparent aluminum armor. The three layers, consist of the following: * An outer layer that's exposed to gunfire and made of baked aluminum oxynitride * A middle layer of glass * A rear layer of polymer backing Not only can the aluminum armor deflect rounds from small-caliber weapons and still be more clearly transparent than bullet-resistant glass that's been shot, it also passes a much more important test -- [a 1.6" thick pane resists .50-caliber armor-piercing bullets](https://m.youtube.com/watch?v=RnUszxx2pYc) and anti-aircraft weapons that typically use .30-caliber rounds. This is an impressive feat, especially since it's half the weight and thickness of traditional transparent armor. So, a 1.6" thick sword is thick, but relatively lightweight, and can stop a direct hit from armor piercing rounds. A thinner version could probably easily stop .22 rounds. So that's one possibility. ## Composite Metal Foam [Composite metal foam (CMF)](http://newatlas.com/metal-foam-bullets/42731/) is made by bubbling gas through molten metal to form a frothy mixture which then sets as a lightweight matrix. This leaves a material that offers a lighter alternative to conventional metals, while still maintaining a comparable strength. CMFs have been used to create high-strength armor comprised of boron carbide ceramics as the strike face, with CMF as the bullet kinetic energy absorber layer and Kevlar panels as backplates. To test its durability, such [armor was tested against a 7.62 x 63 mm M2 armor-piercing projectile](https://m.youtube.com/watch?v=lWmFu-_54fI), which was fired in line with the standard testing procedures established by the National Institute of Justice (NIJ). This armor could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 mm. In fact, not only did the armor stop the bullet, it turned it into dust. To put that in context, the NIJ standard allows up to 44 mm (1.73 in) indentation in the back of an armor. So, this type of material could be incorportated into a sword to make sure it was strong enough to deflect or stop bullets. You might need to have a significantly wide sword, depending on how thick the materials are, but a wider sword could still be useable. [Answer] The Jedi may have fast reflexes, but their ability to block lasers is because they have an intuitive feeling of what will happen in the future a few seconds, so they actually predict where the laser will be. It would be totally impossible to 'react' to a laser shot. The laser travels at the speed of light, therefore by the time you have seen the laser it has already reached you. If you could see the person firing, you could see them point the weapon and start tightening their finger on the trigger, but once the laser has fired it's too late. For anything slower than a laser, you would still basically need to be a robot (electrical signals to control) to react in time. It takes time for signals to travel from a human brain to their muscles. Or from eyes to brain. I guess if you were hitting bullets to the side that should work fine- striking them directly and bouncing them back would, as mentioned, transfer force to the defender, but just pushing them off-course wouldn't transfer much of their energy. [Answer] Yes with today's technology and even tech from the early 1900s if not later, you could build a sword able to withstand bullets, depending on the bullet and construction of the sword. Your main issues are going to be what caliber the bullet is, and how much the sword is going to be damaged. [Answer] Jedis (and Sith) don't really have superhuman reflexes, at least in a regards to intercepting blaster fire. > > "The average for these things is just 34.9 m/s (78 mph). This is in > the ballpark of a baseball pitch." > > > <https://www.wired.com/2012/05/star-wars-blaster-speed/> [Answer] If we were to create a sword for the sole purpose of deflecting bullets, I would argue for a differently designed sword rather than a special material. A sword with wider blade Machete-style, would give an increased surface area for better being able to hit your bullets. Bullets already easily ricochet off surfaces that are angled. All you need to do is get this wider weapon to angle correctly and Bingo! [Answer] A giant manga sword is as thick as battleship plating and easily big enough to hide behind in a gun fight. [![enter image description here](https://i.stack.imgur.com/Qycqo.jpg)](https://i.stack.imgur.com/Qycqo.jpg) Carrying it could be a problem let alone using it in a fight...... [Answer] ## Probably not There are definitely materials which can withstand bullets. There are several answers which go over this aspect of the question, and there are definitely materials which can withstand impact from a bullet. There is still a problem, though: ## Bullet strength Assuming these are normal bullets, if the material is rigid, the bullet will either deform or shatter. Deflecting a bullet would involve slowing it down to speeds such that the bullet is not destroyed, and then re-accelerating it in the other direction, something simple rigid materials cannot accomplish. [Answer] Sword can be easily made to be resistant enough, at least for small calibre rounds. The problem is, when it's hit, your arm will have hit force applied to it too, and at best! you will lose your grip on the sword. At worst, your fingers might end up broken. Modern bullets carry really high forces that translate to the target. [Answer] In short, yes - why not? Swords are very hard and very strong - and if you're trying to *deflect* a bullet rather than stopping it, a strong piece of metal held at an angle should do the trick quite nicely! If the sword is likely to be used for deflecting many bullets then you might want to look into specialised materials and clever metallurgy. ]
[Question] [ Chlorophyll-a (the primary one), chlorophyll-b, and(?) beta-carotene *(plus other accessory pigments / carotenoids)* dictate which portions of the EM spectrum are used as energy by plants. [![Absorption](https://i.stack.imgur.com/I7zGH.gif)](http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/chlab.gif) [![Actual production](https://i.stack.imgur.com/84mhd.gif)](http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/phorate.gif) [![Some additions](https://i.stack.imgur.com/7gtbT.gif)](http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/pigabs.gif) Plants only use part of the available spectrum, because of these limitations. The Sun's output is: [![Sun](https://i.stack.imgur.com/5tSAm.gif)](http://hyperphysics.phy-astr.gsu.edu/hbase/vision/imgvis/solarirrad.gif) Obviously, plants are evolved to work in our environment, ie: with stuff the Sun puts out. **Are there any other hypothetical chemical compounds which can transform energy from other portions of the spectrum?** Bonus points if they're made from common atoms, instead of rarer, higher elements. ie: If you had a different star with different output levels (but *are there?*, I *think* that the sun is a blackbody radiator, and all of those curves look generally the same??), what types of chemical compounds might you encounter in their ecosystems? [Answer] **Edit2** Finally getting the artificial/hypothetical part is what you actually asked for I dug deeper into this. ## Artificial Photosynthesis ### Current research There is research on **[Artificial Photosynthesis](http://en.wikipedia.org/wiki/Artificial_photosynthesis#Photosensitizers)** dealing with what potential substances could be used to create a photosystem. The *photosensitizers* commonly used in artificial photosynthesis are mainly **metal-containing complexes** including *platinum*, *rhodium*, *iridium* and most often *ruthenium* as ruthenium polypyridine complexes. **Organic complexes** successfully used as photosensitizers are *eosin Y* and *rose bengal*. ### Hypothetical Photosystems The part of the photosystem determining what wavelengths can be used for photosynthesis is the [Light-harvesting complex](http://en.wikipedia.org/wiki/Light-harvesting_complex#The_function_of_a_light-harvesting_complex). And now **to answer your original question** > > Are there any other hypothetical chemical compounds which can transform energy from other portions of the spectrum? > > > Yes there are. A **lot**. > > Absorption of a photon by a molecule can lead to electronic excitation when the energy of the captured photon matches that of an electronic transition. > > > So basically, **any** molecule capable of absorbing photons / electromagnetic radiation – be it visible light or something else – could be used to harvest light / radiation. ## Natural Photosynthesis in plants > > plus other accessory pigments / carotenoids > > > Just to add some accessory pigments for reference: Name | absorption maximum * Chlorophyll c | 500-600nm * Chlorophyll d | 710nm * Chlorophyll f | 720nm ## Natural Photosynthesis in other organisms ### Purple bacteria As has been mentioned in the comments there is also [bacteriochlorophyll](https://en.wikipedia.org/wiki/Bacteriochlorophyll) which is found in purple bacteria. Name | absorption maxima * Bacteriochlorophyll a | 805, 830-890 * Bacteriochlorophyll b | 835-850, 1020-1040 * Bacteriochlorophyll c | 745-755 * Bacteriochlorophyll cs| 740 * Bacteriochlorophyll d | 705-740 * Bacteriochlorophyll e | 719-726 * Bacteriochlorophyll f | 700-710 * Bacteriochlorophyll g | 670, 788 ### Cyanobacteria, red algae and glaucophytes The [phycobilisomes](http://en.wikipedia.org/wiki/Phycobilisome) found in these organisms can harvest light **between 500 and 650nm** depending on their structure. --- And to give you an idea of what scientist think is possible in terms of naturally occurring photosynthesis / photosynthetic pigments on earth checkout <http://sydney.edu.au/news/84.html?newsstoryid=5463>. Quote from the article: > > "Discovering this new chlorophyll has completely overturned the traditional notion that photosynthesis needs high energy light," Dr Chen said. > > > "It is amazing that this new molecule, with a simple change to its chemical structure, can absorb extremely low energy light. This means that photosynthetic organisms can utilize a much larger portion of the solar spectrum than we previously thought and that the efficiency of photosynthesis is much greater than we ever imagined. > > > [Answer] Already exists, During autumn, temperate plants sacrifice chlorophyll to produce different pigments. These pigments take advantage of the inferior intensity autumn/winter sun. ]
[Question] [ **Assumptions:** * Jupiter's moon [Europa](https://solarsystem.nasa.gov/moons/jupiter-moons/europa/in-depth/) has a [salty](https://www.scientificamerican.com/article/water-on-europa-with-a-pinch-of-salt/) subsurface ocean [in contact](https://europa.nasa.gov/resources/113/interior-of-europa/) with a rocky mantle. * The ocean is populated by [hydrothermal vents](https://en.wikipedia.org/wiki/Hydrothermal_vent) produced by [tidal heating](https://en.wikipedia.org/wiki/Tidal_heating). Global heat flow is [similar to that of Earth (0.089 W/m^2)](https://www.crcpress.com/Astrobiology-An-Introduction/Longstaff/p/book/9781439875766). Lower gravity means lower buoyancy which means less heat transport - so vents are more numerous than on Earth, but less hot. * Europa’s vents release roughly the same nutrients as those on Earth. * The ocean is enriched in oxygen due to [radiolysis](https://phys.org/news/2009-10-jupiter-moon-europa-oxygen-life.html) and crustal ice circulation. * [Chemotrophic](https://en.wikipedia.org/wiki/Chemotroph) bacteria analogous to Earth’s chemotrophs managed to form around the vents around 4 billion years ago. * An ecosystem has developed through billions of years of evolution, in which bacteria are the primary producers. Given the available energy and rough estimates for the chemistry of Europa’s ocean, **how big can Europan “fish” get?** Are “space squid” a realistic part of the Europan ecosystem, or is there only enough energy and food for, say, tiny krill? I’m looking for a science-based answer **based on the structure of ecosystems**. Is there enough energy and food to allow for Earth-analogous trophic levels and thus big fish? If so, just how big can these fish get? If not, what’s the size limit in such an ecosystem? --- **Related but non-duplicate questions:** * [This question](https://worldbuilding.stackexchange.com/questions/30480/how-big-can-the-leviathan-and-kraken-really-be) asks about the size limit for sea creatures in general * [This question](https://worldbuilding.stackexchange.com/questions/141025/what-would-define-ecosystems-in-a-frozen-moon-with-ocean-world) asks if a climate stable enough to support an ecosystem could exist on an icy moon; does not ask about the life within it * [This question](https://worldbuilding.stackexchange.com/questions/37097/would-an-aquatic-civilisation-be-able-to-exist-under-europas-ice-sheet?noredirect=1&lq=1) asks about a possible Europan civilization; does not address evolution or ecosystem development * [This question](https://worldbuilding.stackexchange.com/questions/161180/whats-in-the-outer-system) asks broadly what Europan life would look like; does not factor in energy or resources * [This question](https://worldbuilding.stackexchange.com/questions/17662/what-would-life-around-a-hydrothermal-vent-on-europa-be-like) also asks broadly what Europan life would look like; it focuses on "what features would evolve" as opposed to "is there enough energy for big fish" [Answer] One factor to consider is what kind of life we are talking about. If one considers a colony organism to be one creature instead of myriad smaller creatures, this could allow a rather large form. Without that, the larger creatures seem likely to be apex predators. Further, a largely immobile lifestyle would tend to support a larger size. I could believe a large creature that sits near a vent and eats lots of smaller things, possibly moving from time to time to a different vent. It might be considered to "farm" the vents. The questions at this point might become: how many can be supported by the environment/planet/moon? [Answer] Great Question! I’m going to say relatively small The ultimate issue is that vents provide exponentially less energy than the sun, which means that the food chain can’t get as big due to this inherent constraint. This doesn’t mean you can’t have fish at all, just that you should expect it to be small, like the actual fish that live amongst black smokers, as they have to contend with very small amounts of food. Eelpouts are one of the most numerous species around deep sea vents, and the biggest get about a meter long, and likely get a lot of their food from marine snow, which is ultimately photosynthetic in origin. <https://en.m.wikipedia.org/wiki/Eelpout> ]
[Question] [ On Earth life has six fundamental building blocks for life with them being Hydrogen, Carbon, Nitrogen, Oxygen, Phosphorus, and Sulfur. [(1)](https://en.wikibooks.org/wiki/AP_Biology/The_Chemical_Building_Blocks_of_Life) Those elements of help make up more complex life through amino acids, proteins, nucleic acids / DNA, along with a lot of other things. [(2)](https://www.britannica.com/science/amino-acid) [(3)](https://www.livescience.com/37247-dna.html) Though when it comes to the possibility of extraterrestrial life and xenobiology some individuals like to explore the idea that not all life has to use the exact same forms of life found on Earth. Most popular of which seems to be finding alternatives for Carbon and solvents. [(4)](http://speculativeevolution.wikia.com/wiki/Alternative_biochemistry) [(5)](https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry) [(6)](http://www.xenology.info/Xeno/8.2.htm) Now when I looked through this all it seemed like the possible forms of alternate life had little bounds for having something in common. Carbon based could be replaced with Silicon or Boron-Nitrogen, Phosphorus replaced by Arsenic, water replaced with ammonia, and so on with varying degrees of possibility. The only thing that cannot be replaced it seems is the need for Nitrogen. At first I foolishly thought that like Carbon being replaced with Silicon or Phosphorus being replaced with Arsenic one could just use the same idea with Nitrogen. The problem is below Nitrogen is Phosphorus, already being used for the building blocks of life. I tried to think of a way that Phosphorus could just replace Nitrogen completely somehow and do the almost same job, though learning from the objections to Silicon based life just because elements share the same family does not mean they can replace each other. So that left me rather stuck, as we understand how life works right now, is all life in the universe bound to have to use Nitrogen in some way or another? Or have I completely messed up, missed something, and dealing with a case of Nitrogen chauvinism? [Answer] First, There are no known organisms whose DNA are composed with silicon or boron-Nitrogen or arsenic. **These are theoretical** possibilities based on the **assumption** that these elements/compounds can be substituted for their equivalent in the **DNA Model**. We don't know for sure that these substitutions can even work, because as you mentioned, just because two elements share the same family and ionic charge does not mean that resulting compounds will share the same properties. Currently, Arsenic can end up in our DNA, when this happens it actually causes damage. This is how arsenic kills. **What the previous approaches all have in common is they all try to modify the current DNA Model.** All DNA is, is a means to store information that governs the construction and operation of a cell. **So to start answering your question:** Create an alternative DNA model that has 4 non-nitrogen compounds (in place of the amino acids), that can be used to organically synthesize proteins(or compounds similar to). Obviously, this is a much greater effort than picking similar ions to swap out in the current DNA Model but its more realistic as you avoid the unproven property deficit. **Further rationality:** All life as we know it uses DNA, but all life as we know it exists on Earth. If we found extraterrestrial life on an extra-solar planet that used DNA that would lend credibility to [Panspermia](https://en.wikipedia.org/wiki/Panspermia). Conversely, if we didn't that would mean life as we know it potentially did evolve independently on Earth. This is why it is foolish to assume that extra-terrestrial life will conform to the same genetic model we do. [Answer] The honest answer is we don’t know because we have only one example biosphere to go on, that being Earth's. But we can make some educated guesses. Firstly a few points should be noted. Nitrogen is one of the lighter elements, its more easily formed in stars than the heavier elements and it’s believed to be a relatively common element. So it’s unlikely that a world would exist without any. Although it’s true that chemicals within the same column of the periodic table show many similarities, as you have already pointed out one element is not replaceable by another as increasing atomic weight (among other things) has a very profound effect on properties. Silicon does form many complex compounds showing properties in some ways similar to carbon, but its abilities are a pale shadow of the enormous multitude of compounds possible with carbon. Also compare the relatively benign ammonia with its nightmarish brother borane (or more strictly diborane as borane molecules unlike ammonia have a tendency to dimerise to form B2H6) which is spontaneously flammable on contact with air and contains unusual B-H-B triple atom bonds. So to answer your question I would suggest yes other life in the universe probably does use Nitrogen because it is so abundant. However if nitrogen was not present for any reason I would think that there is sufficient reactivity and complexity to be had with the other elements to create an alternative biosphere without it. In this case the many different nitrogen compounds in nature would be replaced by an array of different chemicals, not necessarily by those of a single element. ]
[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/20435/edit). Closed 8 years ago. [Improve this question](/posts/20435/edit) There are many gods. They are all immortal and cannot harm each other directly. They rarely interact with each other except for occasional chat. A god's purpose is to get as many powers and "god-badges" as possible. Humans can choose freely which god to worship and vote on their miracles etc. There is an important difference from SE however. All gods' ultimate ambition is to become the One-and-Only deity. They must amass as many worshippers as possible with the idea of attracting the *entire* population of the world whilst maximising their reputation and powers. Unpopular gods can only perform small miracles. Popular gods get increasing powers according to rules similar to those of Stack Exchange. To stop things getting out of hand there are impartial Goderators. Their purpose is to make the rules for god behaviour and enforce them. **Questions** Given that the Goderators are utterly fair and don't want humanity to suffer too much as a result of the gods fighting amongst themselves, what rules should they draw up to keep the gods in order? What is the best strategy for a god to become the one and only god? What strategy would a god with zero followers (and therefore very limited powers) need to employ in order to attract a following. **Additional facts and differences from Stack Exchange** Goderators draw up a list of rules for the gods. They cannot stop them from acting but anyone who breaks the rules can have some of their powers or god badges taken away. A god cannot be banned - the worst that can be done is to remove all their reputation and badges so they must start again. Goderators can observe the human world but not affect it at all. Gods are aware of each other but cannot prevent anyone else's miracles or actions. They can form alliances but ultimately they will have to betray these if they are to become the One-and-Only. Humanity know about the gods and who did which miracle or act of destruction. They vote them up or down in their local temple. The vote is done anonymously in a god-proof cubicle so the gods cannot punish or reward for votes. Humanity does not know about the goderators. ]
[Question] [ TLDR: What can modern governments do to force criminal gangs to use melee weapons instead of guns. So I am writing a novel where the main character is pushed out of society, and is forced to join a criminal gang in order to survive. The story is set on modern day earth and guns are obviously dominant in the battlefield. The problem is that I need to keep guns out of the hands of gangs because it will be too violent and nearly impossible for the main character to rise in hierarchy without a lot of luck. I want the gangs to fight using melee weapons (baseball bats, knives etc..). I thought about having strict laws for buying firearms; however, that would not stop gangs from making homemade guns. Edit: I would like to clarify that the purpose of trying to remove gun is to prevent the likelihood of mass murders. While bats and knives may cause injuries; I believe they are less likely to cause deaths. I simply do not want luck to be the only reason why the main character has a successful criminal career. I feel like guns would take the hard work out of success for a criminal. [Answer] My home country (China) has very strict gun control laws. Basically, normal citizen will not be allowed to buy, sell guns, or make it themselves. If guns are involved in a crime case (say, robbery), the consequence will be much more severe. Surely you'll never stop people from making guns themselves, but they won't necessary use guns in conflicts - 6 months in jail for street fight v.s. 10 years if you use guns, what would you choose? Gangs still exists in China, and they fight using knives, bats, metal bars, etc. It seems that strict gun control laws can help prevent people using guns in street fights. [Answer] **Real life solution - make guns scarce in your society** In a country like US, where there are plenty of guns among the citizens, it's a no-brainer for criminals to use guns too. If they choose melee weapons, they would quickly find themselves bringing a knife to a gunfight. In a country like UK, where guns are harder to find, criminals largely resort to simpler weapons like knives. This does not necessarily makes UK safer than US, but dynamics of the crime is clearly different. Also note that "serious" criminals would try hard finding the guns anyways. In addition, you may make gun detection systems ubiquitous (like in "[Total Recall](https://en.wikipedia.org/wiki/Total_Recall_(1990_film))" movie), whereas melee weapons would be typically overlooked by automated systems. [Answer] **Make bullets hard to get** A length of gal pipe, a nail and some fittings, a person can make a basic [zip gun](https://en.wikipedia.org/wiki/Improvised_firearm) in fifteen minutes with basic tools A [plastic gun](https://en.wikipedia.org/wiki/Liberator_(gun)) can be printed on a home 3d printer. There is no way of stopping people from making a gun Bullets on the other hand are a lot harder. Sure people can reload bullets but they still need the powder and the primers. Guns are useless without bullets and firearms would revert back to virtually black powder flintlocks or variant of for the DIY home gunsmith. Easier for criminals to make crossbows. [Answer] Guns bring the heat. To my memory, there have been two firearms crimes in singapore i can remember One was a gangland hitman with a colourful nickname, he escaped but was hunted down [across the border](https://www.straitstimes.com/singapore/courts-crime/guilty-as-charged-one-eyed-dragon-tan-chor-jin-shot-nightclub-owner) The other was 3 robbers in a boat that sank, with one rusty gun and not much ammo. They landed on an island where military training was conducted and well... they basically got hunted down by a regiment of infantry and one of police. I suppose it was good training. (The version of the story I remember involved a regiments of guards and the *gurkas*. One does not mess with the gurkas) Bunch of folks with swords and baseball bats is affray. Its a pain, police will get involved but its not a big deal. Where I live, any use of firearms in a crime carries the potential of a death sentence. If the use of firearms basically has cops decending on your turf, with body armour, big guns, armoured vehicles and such... guns don't make sense. You basically just called down the wraith of the authorities on you and *they will not stop*. Guns themselves can be simple to build and even possess. But if the 'cost' outweighs the benefit, maybe that crappy sword or baseball bat makes more sense. [Answer] I'm going to suggest that you don't need the gang not to have guns, you need them to not *use* them. To that end: It's a gang, gangs have traditions and codes of behaviour like any organisation; more so than many other modern organisations in fact. The gang *chooses* to settle its internal disputes with feats and competitions of strength and skill, guns don't fit in well with that tradition. Minor disagreements are settled in the ring, with or without gloves, serious infractions will be dealt to with bats and personal disagreements involving direct insults that cannot be forgiven will result in the knives quite literally coming out. The gang has guns but only for combating outsiders that aren't seen as having the same honour. They only use them on members as a statement when someone has done something truly unforgivable and they want to show them to be outside the honour of the gang family. [Answer] **Street gangs are a disposable, deniable part of organized crime.** Sure, criminals can buy illegal guns. From other criminals. As Alexander suggests in his answer, there are not *many* illegal guns on the market. The illegal guns get [used and traded](https://www.bbc.com/news/resources/idt-sh/gun_no_6_untold_story_britains_deadliest_illegal_firearm), and with each step in the chain the gun gets more history. The criminal caught holding the gun last might have to answer circumstancial cases for all prior users unless he or she can explain where where the gun came from. That puts the *seller* at risk if the customer knows the seller, yet selling to an unknown criminal is even more risky -- the fool might do something to get caught. In one German [mass shooting](https://en.wikipedia.org/wiki/2016_Munich_shooting#Investigation), the perpetrator paid approximately five times the list price for a handgun that was "deactivated," turned into a stage prop, and then "reactivated." Gangs in your setting might have access to guns like that -- dubious quality, murky history, much too expensive to use it on petty crime. So access to a firearm is a sign of a serious, well-connected [OC](https://en.wikipedia.org/wiki/Organized_crime) figure. OC uses guns to settle their internal disputes, or for selected, high-profile crimes, but they won't hold up a liquor store with a firearm. That's what gangs do with knives and baseball bats. [Answer] Your question is essentially "how do I stop criminals from being criminals?" This is tautologically impossible. The only way to resolve your problem is going to be to make it an "honor among thieves" thing that guns are never to be used. You could make it so that guns are not *impossible* to get a hold of for a criminal, but that it is generally frowned upon to do so. Make it so the use of a gun is considered cowardly, and thus your character won't gain the respect he needs rise to the top. It could be an unspoken rule among all the gangs that any ranged weapon is considered cowardly, and disputes are to be solved "face to face in the ring," so to speak. Any member of a gang using a gun promptly loses the protection of his peers, lest all other gangs unite against his gang to neutralize the threat of a gun user in their midst. As an aside, saying guns will be "too violent" but baseball bats and knives won't is not a plausible scenario. A weapon is only as deadly as the person using it. A baseball bat is quite deadly, and a knife can be more deadly than a gun in a close up melee fight. Just for an example, you can grab a gun, you can't grab a knife, and knives often make worse wounds than bullets. There are also plenty of ways to be plenty violent without using a gun. Recent events show a can of gasoline and a lighter can be plenty violent, and so can a car. The chemistry of many nerve agents is also quite simple. So you have to limit the ruthlessness of the gang in the first place to avoid all of these scenarios being used. The only way to do that is to make it less of a "gang" and more of a "tribe" with laws and customs. This has the added benefit of keeping the government off your back. In this case, the government is willing to turn a blind eye to most of your gang activities since your gangs aren't a threat to their monopoly on guns. So long as no member of a gang uses a gun, the gang itself enjoys less scrutiny from the government and can avoid a crackdown. [Answer] ## Honor only gets you so far If gangs have an honor-code about using not using guns, that will last as long as it takes for someone to 'cheat', eliminate their competition and gain a lot of standing/power/influence. Honor based systems only really work in small one-on-one conflicts where there is social standing to be gained. In larger conflicts where social standing isn't a concern, the most effective weapon for eliminating your enemy will be used, namely guns. This assumes an environment where guns are common and easily accessible. If guns are made sufficiently scarce then gangs will have no choice but to fall back to non-firearm weapons. However, I don't think you can force a group to forgo ranged weapons entirely. Crossbows and bows provide that much needed damage-at-a-distance capability. Aggressive policing to reduce the number of overall guns in society would help a lot. (This assumes that your country doesn't have a super strong gun culture like the one found in the USA.) If guns are sufficiently scarce then home workshops to create guns would pop up to meet demand. Any gang member should have a strong preference for damage-at-range since distance from the enemy decreases the change of getting hurt. Any gang that can make guns will have an advantage over those that don't. However, the equipment to work metal is heavy and difficult to move. Finding gun underground gun manufacturers should be easier than finding individual guns. 3D printing of guns is even harder to track down. Good luck with that one. [Answer] > > "nearly impossible for the main character to rise in hierarchy without a lot of luck." > > > I think that this does not follow. Recent movies (e.g. John Wick) and video games (e.g. GTA) have really made it seem as though one needs superhuman powers in order to succeed in this sort of context. However, both [real life](https://en.wikipedia.org/wiki/Joaqu%C3%ADn_%22El_Chapo%22_Guzm%C3%A1n) and [fiction](https://en.wikipedia.org/wiki/Scarface_(1983_film)) teach us that this is not the case. The best solution, IMHO, to overwhelming odds (in the form of guns, or otherwise) is for your character to rely upon neither luck nor superhuman abilities, but to rely upon their *wits* and *will* to get them through. Gain the upper hand through strategy and charisma. [Words](https://www.youtube.com/watch?v=I_keWS1i3RA) can be more powerful than the sword, at times. [Strategy](https://en.wikipedia.org/wiki/List_of_military_strategies_and_concepts) and [Tactics](https://en.wikipedia.org/wiki/List_of_military_tactics) can turn an opponent's advantage to weakness. Use your [powerful presence](https://www.youtube.com/watch?v=PgYdVNHNz4Y) to intimidate and bend others to your will. Greatness does not follow from simply being able to efficiently batter your enemies. A compelling hobo-to-honcho story has its share of [bravery](https://en.wikipedia.org/wiki/Braveheart) in the face of adversity, but requires equal doses of [sheer will](https://en.wikipedia.org/wiki/Rocky) and [brains](https://en.wikipedia.org/wiki/Joker_(The_Dark_Knight)). Challenge yourself to neither dispose of guns nor to rely on extreme luck for the main character. A little luck is fine, but the character needs to spin those lucky breaks to their advantage in the story ("I totally meant to do that"). Other characters in the story will then interpret that luck as *power*, and once you have peons to fight your battles for you, personal luck becomes a much less necessary ingredient for future success. After all, you want your character to rise in the hierarchy. If they are a higher-up, then they are delegating all of the really dangerous stuff, and get to spend their time telling the grunts that they need to go raise heck [on a Saturday](https://www.youtube.com/watch?v=dDseexwqm5U). [Answer] You're going to have to have some pretty tight controls on the machine tools that could be used to make a gun. However, I think there's a simpler way: Forget about guns, focus on ammunition. While people do reload ammunition they are using commercially manufactured primers and powder to do so. While a simple gun could be produced in any decent metalworking shop and sophisticated stuff could be produced with a CNC machine (which are becoming more and more affordable) the primers and powder can't be made with workshop level equipment. Both must be done with considerable care to avoid blowing yourself up and if you want reliable ammunition it must be high quality also. [Answer] # Culture + restrictions Anything to make the change staring *now* would take a while to catch up. However, with enough time and persistence you can achieve no or very reduced gun ownership. Assuming you achieved it, then the biggest factors are: ## Culture The people just don't *want* guns. This has to be rooted into history somehow but you can't really achieve less-gun owning population without a buy-in from the population. So, the people themselves should shun guns. It doesn't need to be outright revulsion but it would be abnormal to have a firearm. This will help reinforcing itself - even if *some* people have guns, that would still stand out. You can have, say, military who are trained and use firearms but the general population still wouldn't need or want them. ## Restrictions Owning a gun should also be regulated heavily. This is easier to do if it's hard to get more guns inside the country - for example, an island nation can monitor all or most guns in use more easily than one with a large land border where you can smuggle weapons. Still, the *less* guns you have the easier would be to spot if any illegal ones are brought in. And if you impose very heavy punishments for illegal gun ownership and even heavier for *using* said illegal guns, then people, even criminals, would be even less likely to want a gun. For a criminal, it should actually make their "job" *harder* - a gun might be reduced to essentially a one-use occasion. Even if a criminal uses one and escapes, then the police would be on the lookout for the criminal *and* the weapon. People might be frisked on the streets and at travel hubs (bus stations, airports, train stations, etc) thus further inconveniencing the criminal carrying the gun. In an isolated nation (e.g., island) leaving with the gun would be very hard. Due to the culture shunning firearms, the population will also be on the lookout and thus further pressure the criminal not to carry or use the gun again in the near future. Perhaps they next time they get to shoot somebody is when the heat dies down which could take months. That's probably not worth the fuss in the majority of cases. [Answer] Set your society as in a slightly dystopian future, one that emphasizes certain negative aspects of the USA's culture. In US pop culture, homicides committed against the poor are often take the back burner compared to middle class/upper class homicides (there is only so much budget, wall of silence, its just a bunch of bad guys killing each other, etc...). Exaggerate this problem, make your police ignore crimes, including murder: as long as it happens in the slums, and obeys certain unspoken rules. Make one of these unspoken rules be no guns. (As guns have a tendency to travel far when they miss, in densely populated areas this can be very dangerous). Have the police crack down with iron boots whenever a gun is used. Stamping all of the gangs in the area (an any innocent bystanders) into a bloody pulp. This will make the gangs self police the use of guns. As any gang that uses guns will bring the hammer of justice down (hard) on everyone. Which makes using a gun a stupid idea, because your fellow gang members will be first in line to slit your throat and present your body to the local station with roses and an apology, so that the break of the code is ignored. You can add in references to the purge that happened in '29 or some other fictitious event, that explains why your criminals don't use guns. [Answer] The single most effective country at keeping guns from the hands of criminals and gangs is Japan. They do so through the following: 1. Guns are banned. Carrying a gun is, in and of itself, illegal. 2. Ammunition is banned. Carrying ammunition is, in and of itself, illegal. 3. Any search that finds contraband, like guns or ammunition, is a valid search. This is why Japan has a lower incidence of gun use than even someplace like the United Kingdom, where guns are heavily regulated. The exceptions to these are quite [narrow](https://thetokyotourist.com/do-japanese-police-carry-guns/#Do_the_Japanese_Police_Carry_Any_Other_Weapons). Movies filming in Japan typically have to film their gun scenes in other countries as a result. Also realize that you need all three parts. Guns are frequently banned to criminals in the United States, but criminals still get guns. Further, if they use guns and the police are in hot pursuit, they may still get away. Because if they are out of the police's sight for a moment, they can pass the gun off to someone else. The police can't search that someone else, because that would be considered an invalid search in the US (the [exclusionary rule](https://en.wikipedia.org/wiki/Exclusionary_rule)). In a similar situation in Japan, the police would search everyone and finding the gun would justify the search of that particular person. So the gun can always be used in evidence. This increases the deterrent value of gun laws, as people who carry guns are more likely to get caught. So there is little value to smuggling a gun into the country when using it will often get the offender caught. [Answer] You setting could be the deterrent. Place it on a space station surrounded by hard vacuum. Or under a dome on Venus. You have a lot of variety in where to place your society. A firearm in some place where a stray round could quite literally kill millions is one hell of a deterrent for anything that relies on high velocity projectiles. Creating hull breaches, especially close to where the fight is, is just a bad idea. Firearms will likely be strictly controlled if catastrophic damage to the structure is a likely outcome of pitched gun battles. So your guy will grow and learn in a place where firearms and ammo are not readily available, and their use is an extremely bad idea, but other methods of killing are available settle up with rivals. You are also going to want to include some of the other great ideas here and set it in a tight organized crime scenario to reduce the likelihood of sprays of machine gun fire. Mass murder is bad for business. Make it known that the higher up criminals will make you die slowly and in pain if you violate that. Sadly, Mass Murder is not a function of the tools at hand but of the insanity of humans. You aren't going to be able to get rid of that. You only have to look at history for that. Entire cites were killed down to the last individual by Ghengiz Kahn. That was done with human powered weapons. In Oklahoma city, 160 people were killed by a madman with a truckload of fertilizer. In London a guy with a rental truck and a knife killed and wounded dozens. NYC, 3000 killed by madmen with boxcutters aboard a couple of commercial flights. Evil people will find a way. Guns may be convenient, but not necessary for evil. [Answer] **You get manufacturing equipment makers to cooperate with you** As of right now, in real life, most printers have software that detect the presence of the [EURion constellation](https://en.wikipedia.org/wiki/EURion_constellation) on banknotes (a pattern of symbols incorporated into a number of banknote designs worldwide since about 1996) and make it unable to scan/photocopy currencies. You could do the same with gun parts. Most of the core pieces of a modern rifle/handgun are machined using Computer Numerical Control (CNC) equipment nowadays. Assuming your fictional world has similar technology they will likely be manufactured the same way, just restrict some items from being manufactured by usign a similar trick as the EURion constellation. This step could be taken at the CAM ([computer-aided manufacturing](https://en.wikipedia.org/wiki/Computer-aided_manufacturing)) software level, which is the point at which the computer takes the design and converts it into a series of instructions ([G-code](https://en.wikipedia.org/wiki/G-code)) that the machine will follow to make it. Incorporate some form of shape recognition functionality to and restrain the the software from generating G-code for core components (lower/upper receivers for example). [Answer] Everyone on here seems to be going the way of how to remove guns so I am going to go the opposite way. Make it mandatory that all heads of household own a gun and allow concealed/open carry everywhere, like they did in Kennesaw Georgia. Doing so would make it dangerous for criminals to use or even brandish guns without getting shot from the side or behind. In that situation it is better to use a melee weapon so if someone behind you has a gun then you can just surrender with your less threatening weapon. Most people do not want to shoot and kill someone and that can be taken advantage of. In this situation you cannot run and gun or be crazy. You have to carefully pick your target and blend in. Perhaps catch them when they are not looking and no one is around. Knife to the throat and take away their gun if they have one. Prevent any noise and do not get too greedy where you might get your face plastered everywhere then shot from behind. One wrong move or getting impatient and you can get shot by any of the random packing civilians everywhere. Effectively your writing a stealth novel and your guy is patient and careful. Silent in, silent out, nothing seen, nothing left. No need for homemade guns because they could get them if they really wanted to but it is extremely dangerous for them to use them. <http://sharedmedia.grahamdigital.com/photo/2018/03/06/Kennesaw+Georgia+requires+gun+ownership.jpg.jpg_11755124_ver1.0_1280_720.jpg> <http://www.city-data.com/crime/crime-Kennesaw-Georgia.html> [Answer] Sense quick expansions of gases to curb gun crime. Make the sensing very accurate and automatic. To get away with violence, can't release compressed gas at a high enough rate to get away with it...so use a club/knife/sword. This would make crossbows/bows also viable...or manipulation of the sensors : ) I know of no current tech that could do this so its a little hand-wav-ie. [Answer] **Government buybacks work.** New Zealand, to pick one example, bought back [more than 10,000 firearms](https://www.theguardian.com/world/2019/aug/12/new-zealand-gun-buyback-10000-firearms-returned-after-christchurch-attack) in less than a month. If that's not good enough for you, keep raising the price. What sort of criminal is going to be packing a gun if the government will pay ten million dollars for it? [Answer] You could have the government televise how arrested gang members, previous owners of illegal weapons, are tortured until death using medieval torture instruments and methods. For example, you could slowly skin someone alive on national television. This, with the warning that anyone caught with guns illegally will suffer the same painful, long, drawn-out death, would be most effective. ]
[Question] [ Runes are used to enhance the human body's capabilities. They are inscribed onto the skin through a ritual and work by the individual accessing the rune when needed, creating the effect. These incantations vary and focus on attack and defense spells. Effects range from throwing fireballs to summoning sheilds to shooting lightning bolts from fingertips. The strength of runes are linked to the amount of testosterone in an individual. Males are the prime candidates for becoming battle mages, as they produce hundreds of times of testosterone more than women and produce the strongest magic. Females are capable of using these runes, but at a far weaker level. This empire has a cadre of all-female battle mages separate from the men. However, there are a few problems with this scenario. This would be that the process of making runes is expensive and time consuming, and are therefore generally limited to specialist groups within the army. There is also the issue asking an empire to depend upon and maintain a group of battle mages that are far weaker than traditional candidates. These problems seem to make this idea economically unviable for an empire. What would make an empire invest time and effort to create this kind of force? [Answer] A spear has a lot more force than a needle, but that doesn't make it more useful. If you want to skewer an enemy, the choice is obvious; but try knitting with the larger instrument. Runes may be more powerful, the more testosterone the wielder has flowing through their bloodstream, but sometimes you do not want power; you want delicate and concentrated application of force in just the right spots. Raw, unfocused power, could yield a decapitation spell, but power concentrated in just the right places can squeeze the right brain artery and kill with instant aneurysms. It could even be the preferable method, if you really want to sell the otherworldliness of your witch army and scare the opponent shitless. For a non-combative example, try to produce a lock-picking spell when everything you do has the force of a cannonball behind it. You would blast the mechanism to bits, rather than preserve it for future use. Healing is also a possibility; it doesn't have to be total, "wave your fingers and the body repairs itself" healing magic, but just the perfectly sterile scalpel that is precise application of magical force will be tremendously useful for any operation. Less powerful displays of magic are also likely to be less of a display altogether; they could be less noisy, or less radiant; meaning the user goes unnoticed. And how do you distinguish someone assassinated with an instant aneurysm in his sleep, from someone who died of natural causes? Plus, depending on the culture and prevalence of female magicians, women are less likely to be suspected of these acts and could more easily slip away from the crime scene. The top spies and covert agents would basically *have* to be either ladies or eunuchs. So by really tying magic to testosterone, you can not just justify the existence of female magicians, but make them all but required for any monarch with a well-rounded military. [Answer] As an alternative solution I would like to add that you have written yourself in a corner by making testosterone so valuable. But that doesn't mean you can't solve this issue. For example: Testosterone is all about power. The more you have, the more accurate that power is. But that doesn't mean other hormones can't be valuable. For example imagine if estrogen allowed you greater control over your magic? It's great when your mages can throw big fireballs, but if they have trouble firing those fireballs correctly at their target it becomes much less useful. Or imagine if they have less control over the amount of power put in. They can't throw smaller fireballs as they risk throwing a dud with barely any power, but throwing larger fireballs means exhausting yourself quicker especially when you accidentally throw much larger one's than you intended. But a woman on the other hand would have a lot more control with less power. She has the accuracy, she can pump in the right amount of power, but she will exhaust herself quickly with her lower testosterone. Now you have perfect trade-offs with a convergent conclusion to that of KeizerHarm: Men are brute artillery and women are scalpels. Women would be ideal to hunt down male battle-mages, officers and crucial supplies as they have the accuracy to actually hit them. Men are ideal at taking on large battlegroups as their accuracy is less important and with any luck they can last longer in a battle. And if Men use close-quarters spells that accuracy is a lot less important. This means that men focus on CQC more often and women at ranged effects. [Answer] What if they're not a good investment, and that's the point? Maybe they're a show of power, an intimidation tactic. "Look at us, our people have such strong magic that even our *women* can beat your men!" Or as a way of getting enemies to underestimate them. I don't know if you play or know anything about the MOBA *League of Legends*, but one LoL gamer, Tilterella, is known for winning with deliberately bad strategies. His [video on Yuumi top](https://www.youtube.com/watch?v=mVrU-nfWOx8) is a prime example. Top lane is typically solo, while Yuumi is designed to be nearly-useless unless she's accompanying a teammate. But that's actually why he wins - his choice of champion for his role is so obviously bad that his opponents get overconfident and take unnecessary risks, and he has the necessary skill to punish them for their mistakes. He also benefits from enemy players getting irrationally angry when he is succeeding at something that *shouldn't work*, and making mistakes out of sheer rage. [Answer] ## **The problem is finding people who can accept runes.** Put runes (or perhaps too many runes) on someone who can't take them and they go mad, or die, or both. Paying for the rules is easy, it's too expensive for a person but the empire can easily afford this, especially for a war. You go to war with what you have and not what you would like to have. Ideally you'd have 10x as many mages and they'd all be men but you'll take anyone and be glad for them. That female mages are weaker just means you'll make different tactics and uses for them. Spies. Assassins. Healers. **Teams have lots of roles, not all of them require brute force.** ## **Also Skill Matters.** How big an energy bolt you can throw matters, but whether you can hit the other guy with it matters more. That issue comes up a LOT. [Answer] I think the first big question is: What is the goal of this empire's all-female mage unit? ### Male Incompatability How about a slightly different approach to the matter: There are some runic arrays that are incompatible with males, but function just fine with women. The runic arrays are needed for the army because they fulfill a useful role to the empire for whatever reason. A possibility to explain that is that there is a class of runic spells that are actually hampered by a male's higher testosterone levels and/or are more beneficial with a female's higher estrogen levels or anything else that a female has in a higher quantity. The gist is that some arrays are more powerful when applied to a female in defiance to the normal. ### Traditional Obligations Another possibility is that the unit was started when a number of old nobles only had daughters to contribute to the empire's war efforts. The Empire could not refuse the offerings as they know the nobles did not have sons and to refuse risked insulting those that supported the empire, yet at the same time the women offered weren't as powerful and all parties knew it. Thus the idea was born to group these female mages together into their own unit. This fulfilled the empire's obligations to take them and train them and the noble's obligations to send them and allow the empire to train them. Over time with training, research, and a bit of gumption by some of the more disgruntled women of the unit did they claw themselves up from what was basically a squad of low-powered casters into a force that can be reckoned with. ### Unit thoughts If a woman's weaker spells can be cast faster, then it might be plausible that their unit has evolved into a hybrid of magical and martial combat. Quick bursts of power with her runic arrays make for a dangerous opponent -- one can't assume that she is down and out when a quick word might enhance her enough to turn the tide of a battle. This does not go into the idea of many women working together to create something that is greater than the sum of their individual parts. [Answer] ## In warfare, you take any advantage you can Women historically were vitally important to all wars. You could say actually that all wars required them, even if they formed mostly a support role. This is because warfare is: * **multifaceted** - it requires not just 'fighting', but logistics, intelligence, command, food, transport, clothing, scouts, support, training and medical care. * **life-and-death** - those that do not bring all resources to bear will be up against those that do, and will not survive. Therefore you use 'all you can get' including your women (which, in statistical likelihood would be 50% of your force). Your female magic users would definitely be a major asset and any force that does not use them will be up against one that does, and will suffer significant disadvantage. If your society is sexist, like in previous 'real life' societies, their role could be simply making clothes/uniforms, making food, transport/logistics and nursing care - however your magic using women would be much better at these tasks regardless. [Answer] It might be a good idea to consider if you really *need* to explain this using hormones. Instead just handwave the effect in a way that's going to be intuitive for your readers. > > Young guys have power to burn, but tend to prefer loud flashy magic, rather than something quieter and more effective. > > > This could be testosterone making their power uncontrollable, or it could simply be another way nature provides young men an avenue of showing off their fitness. > > As they age and calm down a bit, and certainly after they've become dads, their magic settles down as they settled down. > > > This could be testosterone dropping with age and the arrival of fatherhood, or it could be nature favoring control over power now that flashy displays aren't as needed and reducing the chance an errant fireball will cook the next generation. Now you've got a system which is tied to something most readers intuitively understand, while allowing for the same sort of outliers that we're familiar with in real life: the tomboy witch who goes for flashy spells like her bros, the calmer guy who's always preferred to go the subtle route, and the older teacher who's unflappable control lets them take apart the hotheaded rookie. What's particularly nice about this is that, if you want to have these more complex magic users as a villain, it'll be easier to avoid inadvertently coding them as gay if how they choose to use their magic isn't so explicitly tied to gender. [Answer] **Collaborative work**. As noted by others, you got your power horses through the men and the women could be precision spellslingers. But there is also another role that is important : leading the horses. By combining high power casters and precise casters in group ritual, you get the best of both worlds. You want to be able to shatter only the gate of your ennemy town. You need an energy spear to break through the powerfull mana shield around your ennemy commander. Both need a lot of power and a lot of precision. So your spellcaster conduct ritual, with power lend by the male and directed by the female. You can even get a system somewhat matriarchal : dumb brutes are providing a lot of power with an all-female cadre. Some rare brilliant men might get selected as specialists. (It can lead to treason, it can lead to reverse oppressive scenarios,...) [Answer] # Rage One of the side-effects of high testosterone is rage (think: "roid rage"). That's great for fighting wildly, but not so great if precision is required. This is true even if major force is also required. Your team of battle mages may have enough power to break down the reinforced portcullis of the enemy's castle, but they need to make precision shots, because they *don't* have enough force to level an entire wall from a safe distance. If focus and concentration are required components of successful spellcasting, then there is an inherent trade-off between raw power and control. # Distraction It could be the case that female mages serve a multi-dimensional purpose in battle. One of them could simply be to incite rage, as Ettina Kitten proposes: "How dare they send mage maidens to confront us! Aaaaarrrrggghhh!!!" And now your mages have trouble hitting the broadside of a barn. And/or, they could serve to lower the focus and attention of the enemy mages, especially if their attire matches the typical outfits seen in video games marketed to horny teenage boys (perhaps the only legitimate justification for such outfits). "Whoa...check her out!" "What's she doing out here? Doesn't she know we're fighting a war?" "No, no, don't zap her yet. Let's find out what she wants." **[Fireball to the face]** # Bodyguards Because the male mages are so powerful, they are considered offensive weapons only. They are reserved for the most difficult and challenging field missions. The females, however, are still more capable than non-magical soldiers, and are preferred for guarding high value targets. A female mage guard may, in fact, be a display of extreme wealth and prestige, in addition to the ultimate defense against assassination or coup. They may even be deployed to guard non-human assets, like treasure vaults or armories. [Answer] So most answers in here focus in how a battlemage with less testosterone might also have advantages; the problem is that this doesn't help you bring women to the actual *battlefield*, but restricts them to support roles. So here's a few alternative ideas: ## 1. Cheating the system Could magic be used to just increase the testosterone level? If so, that might be your answer (unless you want tropey sexy battlemages, in which case it's a very suboptimal choice). Even if this doesn't completely even the field, getting them into the same order of magnitude could make them effective enough to throw them at the enemy regardless and hope that they will close the gap with stragegy and manpower. ## 2. Expanding the rules So you explain in your post that "Runes are used to enhance the human body's capabilities". So it makes sense that they'd be more effective at enhancing anything related to testosterone in males, but what about abilities that aren't linked to testosterone? Women can compete with men in long-distance running, and after a certain point even outrun them. To me it seems believable that certain attributes could be enhanced just as effectively in women than in men, given how you described it. And of course, most armies would still prefer men, as raw strength is just easier to use in battle than other skills. ## 3. Some different type of magic This depends on whether your world has other types of magic and whether they are known to the cultures you're talking about. If so, you could just have the women use those different types of macig instead. Maybe making a man a lot stronger with runes is just cheaper than throwing a proper fireball, just as equipping lots of men with rifles is cheaper than just shelling everything with artillery in real life. But that doesn't mean artillery doesn't have its place on a modern battlefield, and in the same way, some more expensive types of magic could still be present in your world in the form of a few specialized groups within each army, and this one nation just happens to make use of the females who can't use runes effectively but still don't want to be limited to support roles. [Answer] If testosterone enhances capabilities, why not make estrogen do the same? Testosterone enhances strength and speed but it’s not like female hormones do nothing. Estrogen in real life enhances survival and memory. Perhaps an estrogen rune can use this? Maybe your empire trains women for specialty missions that don’t require brute force but are still incredibly dangerous. Women, in real life, tend to survive famine, disease, injury, and radiation better than men. Estrogen makes women generally more metabolically efficient\* and they tend to outlast men in harsh conditions. Women have stronger immune systems\*\* (see: coronovirus, tuberculosis, ebola, etc), their wounds heal faster, they are at 40% less risk of dying from cancer, and females tend to live longer even taking into account lifestyle differences. If testosterone enhances offensive abilities in your world, maybe estrogen could enhance defensive capabilities or endurance? \*because of fat distribution, less muscle mass, and smaller size \*\*admittedly only partially due to hormone differences, the extra DNA from the X chromosome plays a bigger role here [Answer] I notice a lot of people either ascribing extra to women like more control or putting them in a spy or healer role. You can already have a group of combat ready women without changing what you have you. A man could crush you with a heavy bolder. A woman instead could fire a small pebble into your head or neck. Both are just as effective as each other when it comes to killing somebody. People are squishy and have a lot of weak points which don't need a lot pressure applied to do massive damage to somebody. Rather than go for a display of testosterone with lightning bolts from fingertips, instead a metal crossbow bolt tethered with a wire could easily shock someone to death without much power. [Answer] # Generalists v. specialists Testosterone increases magic power, but estrogen increase magic control. Thus men are able to channel great power into their spells, but they can only have one or two different runes inscribed. That makes them very valuable as specialists with lots of raw power, and in a diverse group they can overcome any obstacle, though a single man rarely has the whole solution to a complex problem. Women on the other hand, have less power, but much more control. They can accept and use 10 to 15 different runes on their bodies, making them incredibly versatile. While groups of women lack the raw power men-squads have, individually they can overcome most obstacles. Think big cleaver v. Swiss army knife [Answer] # You Can't (right now) The system you have devised is unfair to any kind of low-T individual, in terms of shear output. It has to, since all systems are inherently unfair. However, I attribute this to the idea being relatively young, rather than some kind of bias, one because I have a few remaining specks of good faith to give out today, and two because everyone has things they are inherently good at even down to a genetic level (see: China doing screenings for Olympic athletes at ridiculously young ages). With a few additions to the system, and maybe your world, you can create a much more fleshed out (hard) system, and thus write much more interesting encounters. # Brush up on Endocrinology You have established that you want power to be tied to testosterone levels. Great, you have one aspect of your power system. But there are many more hormones than testosterone that contribute to somebody's functionality. According to [this](https://www.hgha.com/blog/hrt/types-of-hormones-in-the-body/) source, there are around 50 hormones in the human body. That means that you have 50 different aspects to play around with, before you even start looking at other physical attributes. For example, maybe a high level of [epinephrine](https://en.wikipedia.org/wiki/Epinephrine) allows a support mage to have better control, because the higher levels of other hormones won't get to them. Perhaps [galanin](https://en.wikipedia.org/wiki/Galanin)allows for faster casting times. Perhaps a mage with high levels of [osteocalcin](https://en.wikipedia.org/wiki/Osteocalcin) would suffer fewer negative effects from sequential casting. If you come up with maybe around 10-20 different effect son the output of magic based on the different hormones, then you can allow your military to have specialized soldiers suited for the right task, which brings us to... # Your Magic Military Academy Your system is based on runes. Since "runes" implies that they are written in characters besides common script, that means that your cadets have to learn them. Thus, I propose the existence (whether your characters are students or not is up to you) of a magic academy, that teaches to these specializations of course, not everyone can get in, and most certainly not everyone can get into the program they want - instead, a hormone test determines if they can even join as a mage, as well as what programs they can get into in what priority. This allows students to become specialized in their fields, and thus low-T individuals and high-T individuals no longer compete only in terms of testosterone. [Answer] For starters, I agree with the principles raised in other answers: using testosterone might write you into a corner, forcing the use of sexist tropes. If it absolutely must be testosterone, then giving women advantages such as finesse and precision instead of raw power can be a good solution (though even that smells of sexist tropes to some extent). But it's also worth remembering something: testosterone doesn't give ordinary people any magical powers. So it's no wonder etching those runes is "expensive and time consuming": the runes need to make significant bio-magestric changes to the host's body. And given how much testosterone men have, those changes are sudden and dramatic. No wonder the etching death rate is so high! Thankfully women have much lower testosterone levels. Sure, they therefore can't open a volcano beneath an enemy's capital, and maybe this gives them the precision to cause silent aneurisms. But it also means the bio-magestric changes are smaller and slower, leading to much higher etching survival rates for women, too. So while the etching for women is still expensive and time-consuming, the cost/benefit analysis for them is far more beneficial. With men you might get a nuclear bomb, but you're more likely to simply have a disfigured corpse at the end of the process. With women you'll have a super-scalpel (or simply a conventional warhead, if you don't want to use the "finesse" approach), almost guaranteed. [Answer] # Fighter vs. Rogue Male (strong) mages burn bright. Any other mage can sense them from miles away. Sneaking is not an option. Female (weak) mages do not. They can sneak up on an unsuspecting enemy and kill them before they know what is going on. In this special force of female mages, everybody knows invisibility and noise cancellation. In addition they specialize in various spells useful for assassination and sabotage. [Answer] For an example of this from fantasy literature, you could read the Witch World books by Andre Norton. They're set in a world where the some women of a particular nation have magic/psionic powers, and men do not. These powers can overcome physical strength (women can be physically overpowered by men, but only if they men can get close or make a surprise attack). The powers are a huge power multiplier for the women, who are clairvoyant (they can scry on enemies and spy on them). They also have mind-control and other powers that can wreck enemies from a distance. If you're a battlemage who gets attacked by a guy in armor, his size and strength don't matter if you can shoot him, blast him with artillery, order him to commit suicide, or just fly away... Your female rune-mages could employ magical protections, strength enhancers, or field war-golems which they control remotely (maybe they could pilot the things like magical gundams?) A little more about witchworld: To make things interesting, women in this world only keep their powers if they eschew physical relations with men, so it's a major life decision. Women to "settle down" to bear children, transition from being in the leader social class, to a protected mother/child-rearing social class. This does mean that some of their most vile enemies will use sexual assault as a war tactic to nullify the witches' magical powers (these are mature adventure stories with game of thrones-style power struggles, masquerading as pulp fiction, written by woman). Men still do the heavy lifting as soldiers/builders etc. The men serve as front-line troops in their army, pinning enemy armies in place, while the women serve as clairvoyant leaders and magical artillery. There's plenty of war and intrigue in the books, and you'd be missing out if you didn't read at least the first couple of them. To make things even more interesting, they feature a male hero who travels there from earth. He can also use the psionic powers, and because of this, women who have romantic relations with him do not lose their powers. The books deal with how his appearance in the world affects their society. [Answer] What would make an empire invest time and effort to create this kind of force? ### It wouldn't, because you've stacked the deck. You've picked a characteristic to hang magic on which is specifically discriminatory against women. That doesn't make you a bad person. :) But it does mean the worldbuilding you come up with can never have women involved in front-line warfare as a matter of course. Women cannot compete on physical strength, and they cannot succeed through magic. In a swords-and-sorcery environment, this very much relegates women to the position of stuff being done *to* them, not having agency of their own. Our world does have a few examples of women who could fight alongside men on equal terms. Caster Semenya famously has relatively high testosterone levels, for example. These women are extremely rare though, and whilst they outclass other women and most men, they still cannot compete at the same level as elite men. Tennis is a relatively good comparison here, because it requires significant strength as well as skill and endurance, and we do have some straight match-ups for comparison. [Billie Jean King beat Bobby Riggs](https://en.wikipedia.org/wiki/Battle_of_the_Sexes_(tennis)) in a straight contest, but that was pitching the best woman in the world against a 55-year-old. Against any seeded male player, King would have been comfortably beaten, and she was perfectly well aware of this; the point was to take down the arrogant Riggs, not to prove she could be competitive against a top-ranked male player such as McEnroe or Borg. In 1998, Karsten Braasch (ranked 203) beat both the Williams sisters (then ranked 5 and 20) in straight sets, back to back. Women can compete at the same level or even beat men in ultra-endurance events - but this is because they do *not* have quite the same blood chemistry and body composition as men, and the lack of testosterone is a positive advantage. We also have plenty of examples of women historically who were notable military commanders and strategists, but this is not the same as fighting on the front line. Of course this all assumes that the empire invests the time and effort. Historically it was certainly common for rich people to have high-quality, highly-ornamented armour made, in spite of them not being particularly skilled fighters. You could certainly make a case for this being a fashion statement adopted by trend-setting aristocratic women, in the same way as women wear military-inspired outfits today. They would not actually be fighting, but they would have the money to buy the best equipment. You could also make a case for aristocratic men setting up their own group of all-female bodyguards for their own reasons, [as Muammar Gaddafi did](https://en.wikipedia.org/wiki/Amazonian_Guard). The common male fantasy of being surrounded by powerful women willing to die for him could well be a reason! It's not a fantasy of mine personally, I should add, but it's definitely a thing which some men like. Bodyguarding also is more about deterring attacks by regular citizens, and often spotting trouble before it starts, so raw power is less important than intelligence and situational awareness, and women are equally capable here. What you can't make these women though is a practical front-line fighting force. [Answer] # Raw power may kill the wielder While *men* may be much more successful once they complete their training most of them die when they try the limits of their powers, sometimes inadvertently causing harm to others. There is only some much your vessel of a body can take. Even after training not many male power wielders can live to an old age, one mistake is all it takes after all. What makes them particularly bad from a strategic perspective is that they tend to drop dead at times of need by trying too hard. *Women* on the other hand have a lower mortality through training, they can safely develop their skills to greater intricacies. Most don't die even when they are pushing it to the limits. They establish witch schools where seasoned witches can pass on their knowledge. They do not take male students as they are mostly a waste of resources and could accidentally kill their instructors. [Answer] Others have pointed out that the testosterone or estrogen could be sources for different kinds of magic. A specific kind of magic very well could be Anti Magic. As in, women are, with their lower magical strength, much more uniquely suited for combating battlemages. [Answer] **OP's Premise: Testosterone Grants Magic Power** If I were writing this in a magical world, I wouldn't use testosterone by name, but let the reader figure it out by showing him that the powerful magic is created by younger men. And to answer his question: why would there be female battle mages? Estrogen gives the mage control over their magic. Both sexes have both hormones, but men tend to have more testosterone, while women tend to have more estrogen. I still wouldn't use the names of these hormones. To me, they'd break the mood of a fantasy. But it would still be easy to let the user understand men have more raw power, women have more control. Could men, especially the younger men, have enough power to destroy themselves and everybody around them? Huge explosion, not enough control to put the explosion at a far enough distance. Women, on the other hand, might not be able to create such an explosion, but perhaps they could make a small explosion inside the enemy commander's chest? It's not very exciting seeing the enemy commander just drop dead, but it is safer than having a mage who *might* just kill everybody around him by accident. [Answer] By turning runes into a balancing factor. These runes would be formed of someone else's man and transfer some of their chosen attribute to the recipient. For example: strength, speed, vitality, precision, or power. The giver can restore losses in anything but vitality through training. Vitality would be restored over time (or by a healing spell), the amount determined by how much was given. Something else (like durability) would have to be restored through magic. Here's the real genius of this. Most answers assume male battlemages will be high in power but low in precision, but if a female battlemage "engraves" one with a rune containing some of her precision, they would have both power *and* precision. For a powerful female battlemage, simply do the reverse. These runes would add the given attribute to what the recipient *already possesses*, and would potentially become gamebreaking. Why? Because if the female battlemage convinces two male battlemages sweet on her to give her some of their remarkable strength to her through two separate runes, she can simply start working out in the gym to increase both her own strength and *the strength she's already gained!* This works because technically the transferred strength is her own, so it would increase as much as her regular strength does when she works out regularly. This allows battlemages to become much more balanced (and therefore useful) at the cost of making it easy for battlemages to gain a *lot* of power relatively quickly. How you deal with this is up to you..... [Answer] Take example from real-life, the body-builders? I am sure there are some, especially maybe of the less honestly competitive sort, who were born as ladies but had so much training and diet and "supplements" or outright doping, that you wouldn't be so sure what gender these hulky mountains of muscle are today. Especially if coupled with other replies above, like handwaving that in this universe women are intrinsically more capable to precision work vs. raw power, and then getting women who are still precise AND have a lot of raw power, this can be a reason to have such army divisions. It can also explain why getting them is a long and expensive process (you raise and train and feed them for this all their life) and so they are a scarce resource, maybe not available to all sides of conflict depending on what the "food supplements" are sourced from. ]
[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/139738/edit). Closed 4 years ago. [Improve this question](/posts/139738/edit) I'm developing a story about a few hundred modern day US Marines who are transported to a fantasy world and must do battle with an army of Orcs and dragons. I know they will be extremely effective at this (see: literally thousands of other questions). However, to keep things from being too easy on them I'm gonna use magic to even the odds a bit. In the world they are taken to, wizards play an important role in combat, but are NOT so over powered that it becomes pointless to raise huge armies of knights and peasants. Therefore, I need to come up with spells and types of magic that would be useful against my few-hundred marines, but would NOT utterly destroy a standard fantasy army of knights, spearmen, orcs, dragons, and eagle-riding elves. A few I've come up with: * **Stun/Disable all troops in an area**: stunning or disabling a few dozen spearmen would be powerful in a fantasy battle, but not necessarily decisive. However, with the marines relying on a small number of elite troops with massive firepower, disabling most of them for a short time could be quite powerful. * **Interfere with visibility**: Clouding the battlefield such that visibility is vastly reduced would be useful in a medieval-style battle, but would not prevent a melee army from being effective. However, by preventing the Marines from aiming it could completely disable their primary advantage. * **Controlling/Possessing**: Being able to possess a single knight or dragon is good, but not all that OP. Being able to possess the gunner of an M1 Abrams tank could prove far more disastrous. Can people think of any other spells that might prove effective here? [Answer] ## Lead into gold The good news is that the change *made the lead parts of the bullets half their volume* (20% smaller in every dimension), so nothing shoots right anymore and the guns love to jam. (Lead is 11.34 g/cc or 18.25 cc/[mole](https://en.m.wikipedia.org/wiki/Mole_(unit)), and gold is denser at 19.3 g/cc or 10.21 cc/mole). The bad news, is the Marines have a fortune and can simply hire local mercenaries :) [Answer] An easy one would be an area of effect spell that negates combustion within the zone of effect. This would cause firearms to stop working and almost all vehicles would be unable to run. They would be virtually defenceless. Another good one is a creating a localized EMP (electromagnetic pulse) to knock out enemy electronics and equipment. With those two spells alone you could decimate a modern armies land,naval and air superiority,cut off the majority of communications instantly,likely cripple morale and leave them unable to defend themselves adequately. If you wanted you could also use animate object spells on vehicles. Then suddenly your vehicles are all essentially enemy drone units that need to be destroyed by your own forces. In a medieval era such a spell is dubiously useful in warfare,but the era of mechanized warfare would change that. Hope you found these suggestions helpful. [Answer] Rangar Lalazar was a third rate sorcerer from a rural backwater in the early first century. He is mainly mentioned in your first year magic textbooks for his invention of the "water to oil" transmutation spell. It is a good first level transmutation spell that is easy to learn, is emminently useful (for replenishing lamps during late night study sessions) and has very few ways to go wrong. The most notable of which merely causes nearby surfaces to become slippery. However few now remember that he also contributed this spell's opposite to our magical lexicon. So when our scouts reported that the strange metal beasts of our enemies appear to consume oil I directed our wizards to ambush them in the mountains with the "oil to water" transmutation and as they say, the rest is history. [Answer] Your question has multiple angles that have to been considered. We not only need a magical way of dealing with our modern tech, but we need a reason for this spell to exist **before** the modern tech existed, and we need this method to **not** be overly effective against typical medieval combat. One idea would for there to be magic for dealing with specific large threats: I'm talking about dragons. Dragons use fire as a primary weapon. Marines use explosives, which utilize fire, as a primary weapon. A spell to nullify fire in an area would be very useful against a dragon, but nigh-useless against even a peasant with a pitchfork. This spell would also have the side effect of rendering gunfire, rockets, and other similar modern weapons useless. Dragons fly. Marines might have helicopters or other aircraft. A spell to ground flying targets would be very useful against dragons and helicopters alike. It would be useless against a ground army. Dragons move very fast. Bullets, missiles, mortars, ATVs, Humvees, Tanks, etc also move very fast. A spell to impose a speed limit on an area would be highly effective against a dragon. It would be devastating to marines. It would have little to no effect on pike-men marching across a field. It might help, to a limited extent, against archers (although the higher mass of arrows would maintain effectiveness even at lower speeds... and arrows go much slower than bullets and missiles anyway). For the sake of your story, I'd let these kinds of spells be somewhat esoteric. They're not useful on a day to day basis, or for most common threats of the world. A given wizard might know ONE of these spells, and that's all they'd need to aid their local knights in taking down the rare draconic threat. This would mean that your marines will have to adapt their tactics and methods based on which anti-dragon spell your local wizard is familiar with at the time. [Answer] **Animate Dead** Bullets are not as effective on the dead as swords or axes. If someone falls in the fantasy army, they get back up and keep going. If someone falls in the modern army, they attack the soldiers around then causing fear and dread. [Answer] ## Enormous fireballs "But wait!" I hear you cry. "Fireballs work just as well on medieval armies as they do on modern ones!" Ah, but you see, magic becomes much more difficult to control at a distance. And fireballs are generally best utilized some ways away from yourself. But when cast from a sufficiently safe distance, even the most powerful fireball is trivial to disrupt for even the most junior of apprentices. Mages are a critical part of any war effort. But big flashy spells are generally too easy to disrupt to be worth the effort. Unless for some reason you found yourself face to face with an opponent who did not *possess* any mages... Then it might be time to dust off the more dramatic part of your repertoire. ## And don't forget the subtle stuff either. Knowing is half the battle, and an unshielded foe is easily scried upon. Magical mist can conceal sleep spells and enemy attacks if there are no wind mages to blow it away. Familiars can get into all sorts of trouble against foes who don't know to kill them on sight. ## And there are other threats, too Gremlins are easy to discourage with salt and rowan smoke. It would be a shame if this foreign army didn't know to protect their highly complicated and breakable machinery with such measures. Dragons generally refuse to get involved with human wars. But these giant metal beasts that throw fire are an insult, and these flying metal machines are even worse. No dragon could ever let that stand. And *I* know not to get on the back of that nice horse by the river, and *you* know not to get on the back of that horse, but do these strange invaders know to be wary of this poor, innocent horse (who is totally not a kelpie, why would you even say such a thing)? [Answer] "Return to Sender" - a simple magic spell that reverses the velocity of incoming projectiles in the vicinity while it is being cast. For the fantasy army: * Swords, spears, clubs, et cetera are all unaffected * Archers move after firing, so that returned arrows do not hit them * Siege weapons such as trebuchets rely on drag to slow the projectiles as they arc through the air, meaning they "fall short" on the return * Eagle-riding elves drop bundles of darts from a lower altitude than they fly at. Even if these are returned, just they go straight up and then fall back towards their original targets For the modern army: * Bullets fly straight back at the gun * So do tank shells * Grenades are 'fun' for the whole squad, unless you "cook it" to explode before it can be returned Get your KA-Bars out [Answer] Definitely the EMP is a good idea. Would have zero effect on a medieval army but would decimate a modern one. Depending on how primitive your army is, a magnetic spell could also be effective. Metal guns, bullets, tanks and electronics would be affected, but an army with stone spears and wooden shields would be fine. Depending on the how advanced the modern army is there are some technologies that could render them useless. If the modern army uses purely combat drones then a spell could act like a jammer and block signals to the drones so they couldn't receive instructions or communicate. If there are drones or projectiles that rely purely on thermal imaging, a spell could disguise the thermal signatures of the warriors making them invisible and untargetable. Could also go with a sort of bioweapon. If the advanced army is from a futuristic, sterile environment, the primitive army could have a savage virus that they've grown immunity to but the advanced army would be vulnerable to. Things like summoning a flock of birds to fly into the engines of a fighter jet would work well too! [Answer] Instead of only considering the magic, consider the abilities of a fantasy army. They exist in that world, so they would be accustomed and trained to resist magic. For example a fantasy army knows that when a confusion type spell is cast, they only need to counter it by thinking about someone they love (or some such mental control). Modern army? They all start shooting each other and foaming at the mouth. Likewise, a fantasy army is likely to be issued gear with magical protections. Runes, trinkets, charms. These would make magic slide off of them, making them hard to deal with. Modern army? Sitting ducks. [Answer] When you have a modern army and remove the personnel, what you are left is a mile of intricate mechanics. So let us attack that. Firearms have quite a few parts that need to move along. And move along freely. It would be such a shame if a sandstorm of finest sand would happen. Effect on humans ? Itching. On guns? You now have a few weirdly shaped clubs. Or why not attack the movement a little bit more? If you can turn the oils and grease in the weapons into glue or something much less slippery, give it a few rounds and you are back at the weird maces. Another fun thing about iron is that it's characteristic changes with temperature. And also it's thermal capacity is a tenth of that of water. So if you can just remove, lets say 16000J from each kg of material, humans will be chilly, at round 33 deg. Not comfortable, but alive. Iron on the other hand just lunged good 40 deg down. So maybe -20 deg? At that temperature iron is quite brittle. Swords are fine. It's a bulk of metal so it will not shatter. Easily. But the cute little things like springs ? And all the fine mechanics of engines and aircraft? Oh and also the rifle tubing ? It is unprobable that it would explode into your face, but possible and the chance that such a radical change of temperature would wreak havoc is really high. [Answer] How about an illusion or visual distortion spell which makes everything appear to be 1 degree away from its actual location? Against melee attacks and ranged attacks at short range (say less than say 10 meters) it has little effect. But it would make most longer range shots miss. Your marines wouldn't be helpless, but their effectiveness would be greatly reduced. In the same vein, some sort of "heat" illusion might make night vision equipment useless, but wouldn't impede people with dark-adjusted unaided eyes. [Answer] **Magnetic ball** Usually considered as more of a nuisance than real threat, as knocking out of hands a few dozen weapons usually does not cause much harm... except that such messing up with magnetic field should also cause EMP. **Raise dead: skeletons** Lowly vulnerable to piercing weapons, highly vulnerable to bludgeoning weapons. (Negates most of modern weapons advantages, except maybe ramming them with armoured vehicle) **Anti-arrow shield** The faster the object, the more effective it gets. Bow, crossbow - 30-100m/s M16 - 990m/s [Answer] Heat metal: Does wonders to modern weaponry and ammunition. Same with lightning bolts and fireballs: Simple, but very effective and educative. You could even have a wizard zap a tank with a lightning and learn Faraday's cage effect! Other options include invisibility, plain attrition (letting marines run out of supplies such as ammunition), horror type spells and mind control. Also, things that would hinder medieval army would certainly hinder marines as well. If you can turn battlefield into a swamp or rations to rot, you're already halfway to victory. [Answer] I'm surprised no one has mentioned Divination and/or scrying. These schools of magic would be extremely useful to know what opposing armies are doing on the battle field. Enemy supply lines, troop movement, and even things like morale are all laid bare to you through a bowl of water. On the command side it would be like having a spy in their command center with out all the hassle of actually getting a spy in there. Access codes and other juicy secrets are just exposed for the taking. Usually in fantasy scrying requires a piece of material from whoever you're going to scry upon. But this is war, if the rules of scrying are a bit lax, every bullet fired at you is a potential scrying reference. Push back the enemies? I'm sure there are plenty of small personal effects where they had been; playing cards, cleaning tools, ripped clothing, etc. Fantasy armies would likely be less affected by these spells simply by virtue of understanding magic or having their own mages to counter the effect. Scrying and Divination are all about knowing what your enemy is doing; and as GI-Joe taught us "Knowing is half the battle" (the other half is violence, and there are plenty of spells that already to that very well). [Answer] Summoning massive amounts of... controlable bats, crows or anything similar. * Perfect for blocking vision - a solid, flying heat source, can crawl into places like tank visors, IR based nightvision etc. would also be ineffective. * Can attack people who only have light uniforms on them - ineffective against armored knights or thick-skinned orcs or dragons. * Can cause a lot of chaos. Imagine a thousand bats flying around. * Make them echolocate using radar frequencies. * Small and fast - guns would be rather ineffective. Flamethrower? Thousands of BURNING bats flying around - even worse if you don't have fire protection on yourself like a plate armor. [Answer] ## Anti-Explosion Field A spell which creates a field where any kind of explosion or combustion simply doesn't work. Normal wizards use this spell to counter Fireballs from enemy wizards but they found it surprisingly useful to combat marines. Bullets are propelled from the gun cannon by the reaction of a tiny explosion inside the chamber, usually with gunpowder. An anti-explosion field would turn weapons useless. ## Protection from Tiny Objects This spell was made with the intention to defend wizards from enemy arrows, but the arrows were too big and so the spell couldn't stop them. Bullets, on the other hand, are very tiny but fast things. ## Turbulence A spell used to move arrows and change their direction by creating a powerful turbulent wind around the caster. Swords are too heavy to be moved by the wind, but bullets no. The wind has enough strength to just deviate the bullets in a harmless way. [Answer] The animate dead answer had some good points, but why not go all the way and do a [Follow The Bouncing Ball](http://www.giantitp.com/comics/oots0448.html)? Rules cheesing aside, even a single marine suddenly completely losing it and hosing down his own people is bad enough, but even worse than the friendly fire casualties would be the morale loss -- especially if you're positing that the modern army has no effective anti-magical countermeasures. Meanwhile, a peasant army would have a few dozen people affected (assuming they have lower will saves per average than your highly trained and disciplined marines) but peasants with melee weapons can't inflict anywhere near that kind of friendly casualties in short order -- plus, if wizards are a known factor, then this would be something they know might happen, so the morale shock is less. **THAT SAID**, if there's one thing marines are good at, it's adapting *fast* when it turns out that Intel dropped the ball and Charlie's about to dance the Foxtrot, so even if they don't manage to obtain any magical assets themselves (hiring, kidnapping or stealing some if necessary) they should figure out the basics reasonably quickly, so don't expect a given trick to work on them more than, oh, twice... [Answer] **Drain batteries** Render all lasers, radios, vehicles, and computers useless [Answer] **A very large slow zone** This kind of spell would reduce the speed of a medieval army. Strong, but no big deal. However, all modern systems are based on reactions happening at extremely precise moments, through precise speeds ; so even a minor disturbance of the physics speed would break most modern systems. [Answer] Since the modern army equipment works on some kind of redox reaction, what you need is probably a spell capable of triggering that reaction and dissipating energy (maybe against the enemy army as heat). This should work with * Thermal combustion engines * Black powder * Fuel-Cells * Common batteries A medioeval army, being equipped with swords, spears and elastic-energy weapons (crossbows and bows) will not be affected by this "Dispel Redox" spell. [Answer] A complex and very hard to cast spell, that makes all gunpowder in an area suddenly combust. A marine scout spots mages doing this complicated spell and start yelling for his troops to throw their guns away. In a couple moments, bullets start ricocheting all around, rifles break in half and grenades cause a massive explosion in the middle of the battle scene. ]
[Question] [ Despite advancement in air filtration and recycling technology, many spaceships still keep the practice of manually venting air from unoccupied enclosure within the ship. Such practices had been condemned worldwide due to rising in accidents and fatality reports, heavy fines and lengthy jail terms doesn't seems to be effective in curbing such dangerous practice. I am wondering why would someone attempt to illegally mod a spaceship with air vent? [Answer] The same reason why some ships keep illegally washing their tanks in the open sea instead that in the certified facilities: because it's cheaper. Keeping a working filtering and recycling system for air in space is expensive. Dumping polluted air in space is cheap. And in space there will be nobody complaining about some tar patches killing endangered birds or staining some tourist's foot. [Answer] **You might be carrying something other than air.** It can be handy to fill a cabin space with chlorine. Cleans and sterilizes well, chlorine does. But you don't want it in your air filter. Or you might fill a space with water, or nickel carbonyl, or helium-4. And you might want to get rid of that stuff later when you could sell it, or you needed an opaque blob in space that sort of looks like a ship, or you needed the room to smuggle a princess. The air filter / recycler is a temperamental diva with your life in its hands. You want it on a pure air diet. Spaces you sometimes use for moving other gases need a separate mechanism to handle those gases. [Answer] ## Air is heavy. You don't want to move it if you have a choice. You only want as much as you need to breathe. Unless the fines for venting are less than the cost of moving it, it's a simple calculation, complicated only by the factor that you might not even have to pay the fines. ## Air contains evidence Trace molecules of whatever you were smuggling remain in the air. Venting it removes that, and vacuums up much of what was on the surface. Indeed, some spaceships use it as the cheapest regular cleaning technique, which means that venting is itself merely evidence toward, not proof of, smuggling. ## Air sustains fire and corrosion. You don't want air around combustibles or things that can be corroded. To be sure, you have to limit it to things not harmed by vacuum, but all safety measures are trade-offs. [Answer] One of the most dangerous things in space is fire. You have an enclosed space, likely an oxygen-rich atmosphere, and since there is no gravity, there are no convection currents either so fires will burn hotter. Uncontrolled fire is pretty much the worst possible thing to happen in a spacecraft. So maybe every pressurized compartment comes with a vent that can be used to quickly smother any fire before it becomes an inferno. [Answer] The moisture in the vented air condenses into a beautiful crystal cloud. Before reclaiming air from air locks became commonplace, this cloud always coincided with important events of space flight, such as arriving at the destination spaceport. Watching it from the windows was a very common way to celebrate a successful flight. Just like [shooting into air](https://en.wikipedia.org/wiki/Celebratory_gunfire) on Earth, old habits die hard. Government spaceports now monitor for ships puffing clouds, but outer space is still a wild place. Some passengers just won't feel like the trip is complete without the crystal cloud, and the ship owners want their passengers to be happy. [Answer] If you are left-wing, then EvilCorp has somehow secured a *perpetual* (or practically perpetual) patent on air recycling systems. If you are right-wing, then the Air Recycling Technicians' Union has an absolute monopoly on all servicing and repair of ships' systems. If you're just cynical, then it's both and they are working together. Via their initial control of such a necessary resource at a crucial moment in the past, this monopolist has exerted significant political power to ensure that patent-busting or union-busting legislation cannot affect their stranglehold (in fact the reverse: over time they have strengthened property/labour laws to suit themselves). Furthermore, they have leveraged their position in ship maintenance/supply to become an organised crime syndicate / de facto local government in space facilities. All that guff about the so-called danger of venting air into space is vastly exaggerated. Very few people are aware, but many of the "accidental fatalities" were in fact the mob disposing of their opponents and blaming it on illegal venting. Nobody has run the stats, but it's astonishing the proportion of victims of those accidents who happened to be technicians capable of building and maintaining an unsanctioned scrubber. But somehow it seems to be the non-fatal ventings where the law comes down like a tonne of pre-fabricated construction material units. The real reason it is so illegal, is that loading your ship up on bottled air and venting as you go would allow people to avoid their exorbitant monopoly. The reason people do it anyway, despite the absurd inefficiency of venting an otherwise perfectly-good atmosphere when it hits 0.2% CO2 (0.5% if you don't mind feeling physically ill much of the time), is that fixing a broken recycling system doesn't just run up a massive bill, it exposes you to contact with the mob that you'd rather avoid. *Especially* if the problem hits when you're away from your home port, where at least you'd personally know the mobster you're dealing with. OK, a political situation this abusive is probably unstable long-term. So, enter the plot. [Answer] It's the best way to get rid of pests (until you get something like vacuum proof cockroaches) and certainly cheeper than hiring someone to get rid of them [Answer] # Energy Savings In your spacecraft, the *energy* cost might be a major factor... it certainly is on real spacecraft. This is closely related to [L.Dutch - Reinstate Monica's answer](https://worldbuilding.stackexchange.com/a/179993), but where "cheap" refers to energy costs, rather than monetary. I would imagine that the most likely culprits to illegally vent air are also those that are under the most compelling financial incentive to do so. In other words: those without much money and looking to save it through any means. How do you save money in a pinch? Strip the fully-rated power system out of your ship, sell the parts, and jury-rig a minimal power system in its place. That power system might only have *just* enough power to get your ship from point A to point B without drawing too much attention. The ship's air circulation systems and filtration systems put additional strain on those power systems. If you don't need to preserve all the air for your trip, it would take much less energy to simply let the air passively settle under artificial gravity (like in a rotating ring), then vent the heavier gasses (like carbon dioxide). Now you have \*almost free air filtration! Of course, this isn't perfect or precise, so you'll still lose some oxygen and nitrogen along with the waste gas, but you have plenty to spare, right? And it's pretty unlikely that the valve would get stuck open... nothing could go wrong. Moreover, using less energy also means using less fuel to produce said energy. Less fuel is less money, so you've just compounded your savings! Now that you're using passive filtration, you can downgrade your ship's filtration system too, and recoup even more money! --- \* Note that you'll still need to expend *some* energy to recover the loss due to conservation of angular momentum, but that's pretty minimal. [Answer] If you need to reduce the air pressure in the spacecraft it costs less energy to vent than to use a condenser and oxygen concentrator to try and stuff oxygen into a pressurized tank. Assuming you have a low cost or free way of generating oxygen which you probably would (given advances in generating oxygen that we already know of) [Answer] Maybe it's a reclaimed junk ship that they only use for short hauls. Air filtration and recycling system sound delicate and expensive to repair/replace and maintain. In a reclaimed junk ship that's already ratty, that you only meant to use for short trips those systems might not be strictly necessary. [Answer] **Security** You are in a profession where occasionally people get on to your ship with bad intentions. Maybe they are boarders after your trade goods or tax inspectors asking too many questions while you are smuggling. What easier way to get rid of them than to use a central computer control system or door control to eject them into space? Since it will be difficult to trick unwanted visitors into stepping into an airlock you will usually lose a roomful of air whenever you use this last ditch strategy. ]
[Question] [ We know traveling in the vastness of space is very boring, as all galaxies and stars appear as dots against the black emptiness of space. It has been established that portholes play an important role for crews to visually inspect and report on the exterior of the spaceship for any abnormality as a standard safety protocol. However, all the portholes on generation ships are rectangular in shape instead of circular. I was wondering why a state of the art generation ship has such an Achilles heel? Aren't round windows better suited for pressured chambers? [Answer] ## They are screens, not windows ![window](https://intl.startrek.com/sites/default/files/images/2019-01/28d437661d95291767e7402dfe969962.jpg) They are rectangular monitors connected to cameras on the outside. That has advantages to structural integrity, but it also allows the users to cycle through different zoom levels, light sources (infrared, ultraviolet, cosmic background radiation) and also just display passenger information and movies and the like. These would be way more useful than actual windows. [Answer] **The passengers installed these windows.** This, among many other modifications to the ship en route. The windows were made by removing a panel and replacing it with a clear plastic sheet. The panels were generally rectangular elements between hull struts and so the windows are the same shape. The removed panels were supposed to be kept next to the window where they were, so they can be replaced. In fact nearly all of these panels have been pressed into service in other ways over the decades since they were removed. [Answer] ## Actually - we do have angular windows in space. Round windows on aircraft are more the result of reducing metal fatigue. The curvature of the window is more for the corners to not be sharp and form weak points when the metal flexes / expands and contracts to suit differing temperature and pressure during multiple flights. Round windows in shipping are for both practical and aesthetic reasons. Although, if you may notice, most windows on ships are actually rectangular - pressure resistance is more accomplished by the thickness of glass, and the strength of the frame it sits, than it is the shape of the window. In space, pressure is not too much of an issue. Note the windows on the Apollo Lunar Modules are actually triangular to save space and allow for other instruments which had a higher priority: [![enter image description here](https://i.stack.imgur.com/91cFT.jpg)](https://i.stack.imgur.com/91cFT.jpg) In your case, it is possible to have windows of any configuration on a space ship. It is simply an equation of economics, practicality and usability - the glass would likely be designed thick enough anyway to withstand the air pressure difference (only 101 kPa plus live loads), and the frames would simply be designed to suit such a required load. [Answer] # There are no portholes The entire hull is made of, instead of metallic matter, some sort of transparent crystalline substance, that seems supernaturally tough compared to other materials. Due to this construction, the hull is entirely solid, without any perforations or portholes The windows, instead, are simply unpainted sections of the hull. As these windows are a matter of paint, they can be whatever shape the designers want [Answer] A true generation ship would likely be so technologically advanced that pressure issues would be negligible; and geometric issues would be based on artistic and culture preferences, throughout the ship. Pretty much as it is on Earth. Small round portholes here would stand up better to high winds, would be less likely to be broken by debris, easier to clean, etc. But I've seen seaside houses with 8' tall and 30' wide rectangular windows facing square to the sea to take the wind head on. They are just overbuilt to handle a hurricane, in order to create a visually pleasing aesthetic experience. We do the same thing with houses. Mathematically speaking, a circle encloses the most area with the least material, it is the most efficient shape, and the lack of flat surfaces and corners make it more resilient to wind. That's important for huts and stone where material may be in short supply. But it isn't easy to arrange space inside a circular dwelling. We could go triangular, but that has similar problems, so square gives us the most usable square feet of floor space. Yet for aesthetic reasons, nearly all our buildings and houses are built as connected rectangles, not a big square space. (some skyscrapers have a pretty square footprint though.) I would imagine any culture capable of building a generation ship would have the technology to make it look like whatever they wanted, and their aesthetics would override any differences in cost or efficiency. They are building something they intend for people to spend their entire lives in, birth to death in old age. Wouldn't they make it as pleasing and comfortable as possible? [Answer] **It is cheaper** The generation ships production has become such a competitive market, that every cent counts. When building a ship with tens of thousands of windows, you want those windows be as cheap as possible because because a 20% discount on a 10 000 USD, window gives you a saving of around 20M$ per 10000 windows. Due to material inefficiency (the slab of glass can be cut into rectangles with no waste material), the transportation volume (You can store more windows in the same space) and overall streamlining of windows production process (cutting a circle is just more complex/expensive/fault prone), it soon came down to Hexagonal and Rectangular windows, and finally the rectangular won because it was able to cut the production costs by extra 2% on the cutting process while the hexagonal could not match this. [Answer] Generation ships are generally used when transporting a population to colonize a far-off world. Since they'll be building a civilization from scratch, your ship was designed so that it could be almost completely disassembled and the components re-used for building homes, farm equipment, light industry, etc. The window is square because it's destined to become part of someone's living room. All of your colonists will essentially be unskilled laborers upon arrival, so the ship's various parts and sub-assemblies tend to be simple, easy-to-work-with shapes like rectangles. [Answer] ## The body of the ship is made from mangalloy The body of the ship needs to last a long time. In general, alloys that are made tougher by fatigue will survive the constant vibration of your ships engines over the course of centuries of abuse compared to work softened alloys like most aluminum and titanium alloys which would literally shake themselves apart over the long journey. It also resists the brittling effects of cold much better than many other alloys [Mangalloy](https://en.wikipedia.org/wiki/Mangalloy) is a form of steel that contains enough manganese to turn it into a work hardened alloy. This stuff is several times tougher than other kinds of steel and only becomes tougher the more you abuse it. This makes it a very popular choice for things like mining equipment, but it comes with special caveats that make it unpopular in other respects. The biggest thing that makes it unpopular is that it is untoolable. Once you cast it, it is practically impossible to mill or bend into other shapes making it an extremely complicated to create anything other than basic geometric shapes with. However, its toughness also means you can use a lot less steel than you would otherwise allowing you to make vibration proof structures that achieve the same lightness per toughness as aluminum/titanium alloys. Being mostly made out of iron, mangalloy is also significantly cheaper than many other alloys you could choose. When produced in bulk it only costs ~\$375 per ton as opposed to aluminum which is ~\$2500 per ton or titanium which is ~\$4800 per ton. Since generation ships have to be so big, this is a very important factor to consider. So the windows, and everything else about the ship is based on straight lines as opposed to curved ones because the advantages of using this one particular alloy (or something similar to it) far outweighed the disadvantages of square portholes. To get an idea of what making a spaceship out of mangalloy would look like, consider the Tesla Cybertruck. It owes its unique shape to this special steel variant being using it its construction. [![enter image description here](https://i.stack.imgur.com/qF3Y7.png)](https://i.stack.imgur.com/qF3Y7.png) [Answer] Aircraft windscreens are rectangular or more complex shapes as well. Older, 737: [![737 windscreen](https://i.stack.imgur.com/4U1un.jpg)](https://i.stack.imgur.com/4U1un.jpg) Recent, 787: [![787 windscreen](https://i.stack.imgur.com/NCLv3.jpg)](https://i.stack.imgur.com/NCLv3.jpg) Combat, Su-25: [![Su-25 canopy](https://i.stack.imgur.com/1lF5A.jpg)](https://i.stack.imgur.com/1lF5A.jpg) It's very possible to make non-circular pressurized windows. Circular or oval ones are simply lighter. At very high pressures, or against severe cyclic loads, circular windows win. Watertight ship portholes are generally made round or oval. However, atmospheric pressure within a ship is small enough that a non-circular window is a very tolerable weight penalty. If you want an explanation, it's because the designers valued crew comfort above weight savings. [Answer] Airplanes originally had square windows. It's cheaper and easier to build. Unfortunately, square windows turn out to be a horrible idea on something that undergoes repeated major temperature fluctuations. The corners become the origin point of cracks due to metal fatigue and your plane comes apart in flight. Pilots need big windows--but when you look closely you'll find the corners are rounded off. Your generation ship will experience only two temperature fluctuations, one in departing the original star system and one in arriving at the destination system. Thus the reasons against square windows go away and simple engineering says you have square windows if you're going to have windows at all. (As for the radiation problem--you can't hope to put enough shielding in a window. Your window is therefore outside the radiation shield. The dose you would get is low, and it could be made very low by adding an electromagnetic shield. Build a big electron gun/accelerator on your ship. Let's say you boost the electrons to 1GeV and eject them behind your ship. Your ship becomes positively charged to the tune of 1GV. Any particle that wanders around reacts to this field--a negatively charged particle falls in, gaining 1GeV in the process, a positively charged particle loses 1GeV. This means electrons slam into your ship very hard indeed--but they're easy to stop. Any positively charged particle with less than 1GeV of energy is deflected, the ones coming in hotter lose that much energy. The dose from positive particles goes way down, the dose from neutral ones is unchanged--but in interstellar space that was pretty close to zero anyway.) [Answer] ## Because it's better A round porthole is a compromise of structure vs utility. Round windows are structurally stronger and can withstand more pressure than the same material in a rectangle. A civilisation which can build a generation ship has no real reason not to build big windows where they can. The material-science obviously isn't an obstacle! More width means more people can enjoy the view, but a round window is as tall as it is wide, which limits things somewhat if you want a big observation-deck. But really that's not a compromise a generation-ship needs to make. So beef up the thickness, brace the window-frame better and have your wide rectangular plate-glass and enjoy it. [Answer] ## Rapid installation of bulkheads It's not the window that's square. It's the bulkhead that goes over it. The windows are for comfort in low risk cruise conditions. But when the ship has taken damage, or is at risk for taking damage, a bulkhead is fitted and locked down over the window opening from the inside. In fact, the bulkhead is sitting right there, behind a concealment. To install the bulkhead, the gravity is greatly reduced and the bulkhead is simply man-handled into place. This is part of bringing the ship into "general quarters" or other high material condition of readiness. There are also hoist points where the bulkhead could be hoisted into place in full gravity, though that is not generally done. ]
[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/247945/edit). Closed 6 months ago. [Improve this question](/posts/247945/edit) The fantasy setting has (the typical) medieval-level ordinary technology with magic use being a rare craft (although few are completely insensitive to magic — theoretically able to use it — most have limited aptitude and far fewer have any training) of significant but not enormous power (no equivalent of nuclear weapons but teleporting "gates" are not rare and magic fertilization exists). Adamant is a stone-like material that is literally unbreakable (under normal conditions). Its native form is a sphere, typically about a millimeter in diameter. Under very high temperatures (achieved somewhat readily by skilled magicians) it becomes malleable and can be merged into larger units merely by contact. Under extremely high temperatures (achievable only by one group of magicians according to aptitude and skill) a larger unit can be separated by high tension across an already thinned (under very high temperature) section, but this technique is rarely used (with native pieces being small). Adamant is rarer than gold (at least on the continent on which the story is primarily set) and processing is relatively labor-intensive and skill-constrained, so common items would not be made from adamant. Being extremely difficult to adulterate (it is effectively immiscible and making a sphere with an interior of base material would be expensive) and easy to test (besides being unbreakable, adamant has an extraordinarily smooth surface and obsidian-like color and luster). This implies that it could be used as money (store of value, medium of exchange), though small fixed weight units would be impractical (and large chunks are less valuable by weight because separation is so difficult). Its rarity and luster would also admit use as a native (spherical) gemstone or artificially flattened form (both increasing the investment/value and allowing a larger visible surface). Adamant's density will probably be around that of quartz; certainly much less dense than iron and much more dense than water. However, I want adamant to be put to other uses, despite its rarity. It is used for weapons, both because of its durability (forming a very sharp edge or point is difficult — adamant has something like extreme surface tension and adamant 'foil' is practically impossible to make — but once cooled adamant is solid and an edge would retain sharpness) and interaction with magic — is it almost entirely "magically neutral" but increases magical affinity of nearby and touching materials (especially for types of magic harmonious with adamant). Its influence on magical affinity also makes it useful in enchanted items more generally, but the enhancing effect is mainly worthwhile at the higher end of enchanting effort where a more-or-less fixed proportion augmentation has greater value. Outside of money, decoration, (rare) weapons and armor-parts, and magical items, what would adamant be used for? [Answer] Natural adamant comes in tiny, smooth spheres that do not lose their spherocity under wear and tear. Therefore, your unworked adamant is an excellent candidate for ball bearings. There are many useful applications for ball bearings, but none is more radical than the skateboard. Only the noble class can afford skateboards (since adamant is so rare). They invest heavily in crude asphalt walkways so that they can shred the pavement throughout the town. Emulating the nobles, the polite gestures of the entire populace soon take the form of skating moves. Pretending to do an ollie is akin to a bow. Gentlemen should always feign a kickflip when greeting a lady, who is to respond with a suitable compliment, such as "nice" or "most tubular, m'lord". [Answer] ## Construction manufacture very thin rods of adamantium to support almost any construction you could think of. Long bridge without supports? No Problem. Two long thin rods of adamantium layed across the gap and then you can build anything on top. even a small building in the middle of the bridge would be no problem. A big tower? No Problem! Just stick four long rods of adamantium deep in a solid foundation and it will never topple over. Note: these rods would be manufactured in some fixed and easy to transport sizes (for example 50cm, 1m, 2m, 5m) and then connected on-site by some construction mages. ## Tools Wrenches gain more "power" with more leverage. Real world wrenches are mostly limited by real life materials not being able to absorb the tensions you reach with a long lever. A wrench with an adamatium rod as its core wont break or bend even if it is 10 meters long and at that point the strength you can deliver through leverage gets ridiculus. ## Siege weapons Also on the line of leverage lay siege weapons. Imagine what size of trebuchet would be constructable using a adamantium base construction and throwing arm. ## Always just in small amounts Due to its rarity and price most applications wouldn't be full-adamatium-anythings (weapons, tools, constructions,...) but mostly adamatium-plated-xxx, adamatium-cored-xxx and so on. Basically any weakpoint in any system would be a candidate to be replaced by an adamatium version of it. ## And for pure adamantium stuff: Machinery In machinery with gears and axles you like to have two properties. Structural strength and low friction, both are sported by your adamantium making insane mechanical devices possible. Normally high rate transmissions suffer from the immense stress on axels and gears and high friction to overcome. With adamantium axels, gears and a drill head you could make an insane drill that is able to make away with anything. ## pure adamantium stuff part 2: reference items (Credits to DKNguyen) due to its nature of not being able to be bend, formed or erroded at normal temperature levels, adamantium can be perfectly used for reference items like gauge blocks and gauging rods. [Answer] One suggestion I would make would be using it in tooling. An adamantine anvil or hammer wouldn't wear and should be relatively easy to make, tongs or other tools could be used in higher heat environments without risk of being annealed. While being very difficult to make to the required level of precision, it could lend itself well to the beginnings of machining. [Answer] # Security, secrets, and sequestration One requires wealth to step up to the levers of power, but to shape the world around you requires those immaterial possessions that can control populations and move armies. Secrets, artifacts, documents, and the occasional political prisoner must all be kept safe, and for those in power, only the most secure locks, safes, and chests will do the job. Adamant codexes are uncrackable by the world's master thieves and are light enough to carry on horseback, yet as secure as a bank vault. These slim cases ensure that special orders and edicts can be delivered safely, their provenance and chain of trust guaranteed intact; a thousand times better than a wax seal. Adamant deadbolts and hinges are featured on massive stone doors used by paranoid noblemen. These doors are so perfectly balanced they open with the push of a finger, yet when the latch is thrown, thirty stout men taking turns swinging sledgehammers are required to spend days cracking the stone panels by force. These doors are used to buy time for soft targets to escape through secret corridors, but they function just as well for preventing certain problematic rivals from ever seeing daylight again. *In regards to imprisonment, I have a modicum of evidence to suggest that an expensive, difficult-to-use material might be used to detain prisoners: A long time ago, I was a part of the Civcraft Minecraft community. One feature of this political-intrigue-focused custom server was the ability to imprison players in chests. Notorious criminals or embattled leaders would be locked in chests packed deep within layers of modded, enchanted obsidian that took hours to dig through. Setting up these expensive prisons would cost an exorbitant amount of diamonds, but players could dig all night to save their comrades.* [Answer] Maybe it’s too obvious to have been mentioned but the primary use of adamantium is going to be twofold. 1. Firstly, being valuable, as jewellery - portable wealth. 2. Secondly, as picks and drills for adamantium mining - and for tools for adamantium working. In general, it’s sounds like a form of metallic diamond. However - it cannot break. Wow. So make an adamantium wire puller (out of adamantium) and you get adamantium wire. Turn that wire into thinner wire. Repeat until it’s is mono-molecular. A few hundred km of the stuff could be used to create a skyhook - and you have cheap space transportation. Unbreakable monomolecular wire is a holy grail for so many things. How about just using it to slice rocks out of quarries, like a cheese wire? An invisible defence against invaders, slicing anything that walks or wanders into it. [Answer] Ammunition. I know you said outside of weapons, but this is more a component of a weapon rather than a weapon itself. We have magic in this environment, I see no reason we couldnt have some kind of early propellent for use in early firearms like gunpowder, which was used in china in the 10th century. These unbreakable, low weight materials could be used as projectiles that i can imagine would be very good at piercing armor. Load a bunch of these projectiles into a blunderbuss and you have a weapon fit for a king, one that can kill anyone up close, even through plate armor. We have magic too, if telekinesis or any magic that can move stuff exists, we can ditch the gun entirely. Why not just accelerate at incredible speeds through peoples heads? You would only need one pellet of this material as long as you can keep track of it. [Answer] **Free and easy Orbital Launch (and projectile weapons)** A sphere of adamant, as described, must be perfectly elastic. Otherwise, hitting it sufficiently hard would heat it; and heating it makes it malleable, and therefore breakable; and it is described as "unbreakable" under normal conditions; and if being hit isn't a normal condition for evaluating breakability, what is? This means that a sphere of adamant is a perfect energy storage device. This energy storage can be exploited in many different ways, and is probably a much more interesting property of adamant than any merely mechanical properties; there are plenty of sufficiently-strong and sufficiently-tough materials out there, but no society has ever satisfied its need for energy storage. Perhaps the most trivial way to abuse this property is in a stacked ball drop. The traditional stacked ball drop demonstration takes the accumulated potential energy of a stack of spheres (and, conveniently we already have spheres) and transfers all of that energy to the top most (traditionally smallest) sphere, giving it quite significant kinetic energy. In practice, the velocities achievable are limited by the elasticity of the balls and the surface off which the bottom ball is bouncing; but we've just *completely* lifted one of those limitations, and an investment in making a single adamant plate can significantly lift the other (or, depending on the speed of sound in adamant, lift it completely if the bottom ball bounce completes before the sound wave can propagate through the plate). Pointed upwards, a relatively small stack of balls will put a new crater on the moon. With a slight misalignment of the top ball(s), hypersonic projectiles are trivial. Orbit can't be achieved without an additional impulse at or near apogee, but you can get darn close. Other ways to store and extract infinite energy from adamant is left as an exercise for the reader. [Answer] **The mother of all trebuchets** Ladies and gentlemen, step right up, step right up! Behold the wondrous and fantastical adamant trebuchet, a marvel beyond your wildest imagination! Prepare to be amazed! In this grand spectacle, we present to you the one-of-a-kind trebuchet constructed with the legendary adamant, a metal so unbreakable it'll leave your jaws dropped and your eyes agape. This trebuchet, my friends, is in a league of its own. Witness its awe-inspiring strength! With adamant's unmatched resilience, this trebuchet can handle payloads that'll make your ordinary contraptions quiver with envy. Tensile forces? Bah! This baby laughs in the face of pressure. Its spindly frame, arm, and chain sling are forged from adamant, ensuring that destruction shall remain a stranger to its magnificent structure. But that's not all, folks! This trebuchet defies the laws of physics with its unyielding nature. Launch after launch, it withstands the most mind-boggling forces. Without any deformations. And what does that mean for you, my friends? It means you can fling projectiles of titanic weight over huge distances with pinpoint precision. But hold onto your hats, for there's more to this spectacle! The fact that the rods can be so thin and lightweight means that this baby can move! Hitch it up to a couple of horses and you’ve got yourself a rapidly deployable heavy artillery. Just make sure you anchor it before firing or it may take you (and your horses) on a ride. So gather 'round, good people, and witness this mesmerizing display of power and precision. The adamant trebuchet will leave you spellbound, as it catapults objects towards (and over) the horizon with unfathomable accuracy. Step right up, step right up, and embrace the extraordinary, for this is a sight you'll remember for a lifetime! [Answer] Sorry for the lack of imagination, but to melt adamant rather than magic I would see fit a furnace in a cave in a volcano with flowing lava. LOTR style. Since it is not too dense it would be easy to work if you can approach the hot lava, dump it into the lava and wait for the molten adamant to float on it. What could you do with it? In an unstable realm, where conspiracies happen often, a sceptre that can double down as a mace in dangerous situations would be quite useful. A safe or a hollow statue to safeguard something special could be another use. A city on the side of a mountain. A square which has on a side a big rock face on which all the laws are carved. A dedicated adamant chisel would allow to write or erase quickly the laws as they are promulgated. The great chain in front of Costantinople. A long cast iron chain deployed across the strait in front of the city has been for a while a powerful defence that blocked many enemy ships. But lowering and raising it was a tough job. That's when adamant could come in handy. Apart from blocking ships there can be many uses for a chain. [Answer] ## If it is unbreakable the primary use is scientific and industrial. There are thousands of industrial and scientific endeavors that are limited by the tool's ability to stay sharp or resist bending. NIST and similar agencies would likely own most of the worlds stockpile, a material that does not change mass over time would be a godsend to them. nanotechnology, molecular engineering, high precision surgery, the space industry, the possible uses boggles the mind. It is simply too valuable to use for anything else. ]
[Question] [ In my world's magic system there is the otherworld. It is a many layered realm that is made from the memories of the land, the animals and the people. Some spirit worlds fade away if their people have gone or the land has changed too much. These spirit worlds can be accessed by mages, who can form their power to do low magic. Think mind tricks, animal manipulation, scrying, minor environmental manipulation (telekinesis, sparks), alchemy,... Spirit worlds are however inhabited by demons. They can be bound and drained to produce magical artefacts, or called into a body (either the mage's own one for a while, or into a permanent host). While the demon does decay in the real world, it allows one to use high magic. Teleportation, fireballs, shields, liquifying humans, you name it. Demons usually represent aspects of their spirit world (this means emotions for humans, the lands elementals are an entirely different breed). They tend to seek freedom and will live out their desires to the fullest to gain more power in the otherworld. To gain freedom they try to possess the mages or break their bonds. However, while magic abilities manifest from birth on, demons don't care for mages until they are older. Why? [Answer] It's hard enough to fit yourself into the limited psyche of an adult human, now you want us to squeeze into *children*? A demon's gotta breathe, I tell ya! You will note that demons also decline to possess the mentally feeble. But we love nothing better than a nice deranged, depraved adult mind. All those phobias, ambitions, lusts and greed make for such nice cuddly, cozy nooks to camp out in. It's all a question of housing quality and space. [Answer] Demons can't possess refrigerators. Or rotting peaches. The list of things they can't possess is long, it's much easier to list those things which can be possessed. The list is just one item long: human beings. Why? Because some deity or another created humanity to be a vehicle *for* spirits. It's not clear why or how that works, but it does. Otherwise spirits can only have the most limited of interactions with the physical universe. Chimps might have 99% of their DNA in common with us (and be much stronger, more agile meat-suits), but they just don't work. But whatever the mechanism is in the human body that allows that soul to drive around in it, whatever the details are for how it works... there's this one other gotcha. No children. Perhaps the deity made it that way deliberately, or it's a side effect of some other function. Your story need not explain it unless you've decided that it's critical there be an explanation. Details can be included without explaining them... perhaps the exact age varies from child to child, or is exactly on their thirteenth birthday (for a legalistic sort of magic). The change may manifest with a perfect correlation to puberty, or it could be imperfect (short of doing large-scale demon possession experiments, how would you know that 1 in 1000 prepubescent children can be possessed, or that 1 in 400 post-pubescent remain unpossessable for years afterward?). [Answer] The onset of puberty and the consequent sexual drive greatly increase the quality of the juice which can be extracted by the subjects. Think of the difference between unfermented grape juice and wine. [Answer] Growth is inhibited by the presence of the demon. If you possess the children, people will notice that they do not grow and that they never hit puberty. (This is owing to the demon's unusual attachment to time.) It is growth, not aging, though. Adults age normally. [Answer] **As children enter puberty, lascivious desires weaken their resistance to possession.** It's something succubi and incubi have known for a long time: you can't possess those whose greatest temptations and darkest desires are so innocent as to almost be considered wholesome. When someone grows older and begins to see the world in new eyes, the inrush of temptations and internal emotional turmoil makes it significantly easier for demons to possess the body. [Answer] **The spirit is housed in the brain** If you ask if someone has a benevolent spirit, they talk about your actions and thoughts. However, these come from the mind, which is housed in the brain. So it follows that spirit is housed in the brain. Children are still developing. Language, object permanence, sight depth, raw understanding or body movement. That and a lot more is all still being created and modified to have a fully functioning person. After puberty the most important development has been done. This allows for the demon to most effectively move into the brain. Of course some demonic powers allow for more knowledge, power and understanding that the demon already had, but it is still very much linked to the body and brain. So a good basis of a person after puberty makes a demon able to really fulfill it's own desires and gain more power. [Answer] Your setting may not be conducive to this but: It’s a diplomacy thing. There are other entities living in the Spirit Worlds which, by common agreement, are not in an active state of war with your demons. Some are neutral, some are hostile to demons, others are like demons but want any excuse to thin the competition. Humans too, will hunt demons when they find them but they haven’t yet reached the state of ‘holy crusade’ either. Nobody wants a war, but there can’t really be peace. So they exist in a state of compromise (for the time being). One of these compromises is that demons can’t unleash their full capabilities against a child. To do so risks breaking the fragile peace and causing chaotic war not seen since *insert reference to suitable apocalyptic event here*. Any demon that breaks this rule will be hunted and destroyed not only by their enemies but also by other demons in an attempt to maintain some facade of inter-species peace. Only when a child reaches some value of maturity (could be age, puberty or some other mystical event) is a demon allowed to possess a human. Of course, the rules are a lot fuzzier on *helping* the little humans. And they tend to be much easier to possess if you’ve already been riding along in their head for a decade and a half, so demons skirt the inter-species rules by providing magical assistance to child mages, befriending them, helping them, until the right age is reached and the demon can step into a pre-prepared (and in some cases willing) vessel. Technically they followed all the rules, so nobody can spark the magical equivalent of an international incident, and the demon still gets a nice powerful human host. Of course, it might backfire in the demon’s faces, but what is life without a little risk? [Answer] Demons are like vampires: they have to be invited in. Adults can do that. They may be smarter than children, but adults are still pretty easy to swindle, and merely being a mage doesn't make you any less susceptible to accepting bad deals or being taken in by cons. Children, on the other hand, while even easier to trick, are fundamentally incapable of giving consent. Not merely legally, but neurologically--it's not merely a matter of *not understanding* what they are about to do when giving a demon permission to enter, it's a matter of not even being *capable* of understanding. Any appearance of consent is thus invalid, and the demon cannot enter. [Answer] # A demon's ability to affect the world is proportional to the ability of the host to affect the world. It's not so much puberty itself, as the various restrictions humans put on human children that make it harder for a demon who possessed a child to be able to do things. If a demon possess a host, they likely want to be incognito for a bit until they fully check their powers are working as intended, and able to do so away from unpossessed humans who might call for authorities to investigate the possession, or to attempt an exorcism themselves. What's that? This one's host has to be back home by 7:00 p.m.? Given education during the day, that's basically an hour at most to work if they bolt after a 5:30 dinner, which might stand out. Well, maybe I'll get a drink to help calm my host's nerves and get more power usage out of that - wait, my host can't get a drink at the local bar? This is very annoying - clearly something must be done about these parental units, but I can't confirm my host is powerful enough to take on these parental units. And it's likely the authorities would investigate us taking them down, so I'd need to get my host to leave and live in a forest, I guess, and potentially buy things with the leftover funds the parental units had. Wait, my host would get caught trying to use a car and likely pulled over by the authorities? Well, okay, I'll leave as a result, and live sort of out of town - people won't be suspicious if I keep a low profile, and just eat a lot of forest mushrooms. ## Solo children also stand out, and would likely be interrupted by authorities or parental units of other children for being alone and away from others. Much like these above restrictions, a solo child host can't usually walk around disaster scenes unnoticed, and would likely be picked out by parents or authorities trying to help, even if they're trying to do mischief at a carnival or a major transport location. [At best, this starts to get suspicious](https://knowyourmeme.com/memes/disaster-girl/photos/page/1), and makes it harder to get away with actual mischief. You might want to adjust some of these specific rules based on the society in question, but in general - the demons in question have a lot more leeway with what they can do that's demonic if they're older and given more privileges, especially when their host isn't part of a demonic conspiracy through a whole family all in on the possession. And even then, you have societal concerns to worry about Better to wait for them to have more curfews lifted and more permissions provided and expected, and just work from there. [Answer] **Because let's face it, not even demons want to go put up with humans undergoing puberty** See, the thing with demons is that their goal is to extend their power within their realm, which is why they want to make use of potent mages. The problem is that possessing them works best when the mage's and demon's objectives (i.e. hunger for power etc.) are roughly aligned. That just doesn't work so well with children up to and throughout puberty because whatever they are going for is so much more erratic. Only after completion of puberty do humans get a proper grasp on longer-term thinking and planning. Before that, demons can't really effectively advance their own schemes because their hosts just can't be relied on to pursue a single goal for a reasonably long period of time. As a result, with demons being pragmatic, they prefer not to put up with all that flightyness of childrens' minds and rather go for targets that offer better chances to effectively be manipulated into aligning with a demon's agenda. [Answer] > > [Demons] tend to seek freedom and will live out their desires to the fullest to gain more power in the otherworld. > > > Children, as a rule, don't have a lot of freedom. They have parents, teachers, chaperones, babysitters. They don't tend to have money, property, equipment, or resources. They don't have the benefit of years to work on their skills, build their reputation, or acquire temporal power. Other people tend to be dismissive of them, if not hostile to them. Demons inhabit people to increase their scope to act on the world. Why would they inhabit people who don't have that scope? [Answer] **Children are "innocent"** We've all heard people say that. "Children are little angels, innocent of wrong doing! Their souls go straight to heaven!" *In your universe, its literally true!* Childrens souls are repositories of everything that is goodness. Its only as time goes on that the harshness of life makes them darker and more morally complex. Puberty is the cut off point for pure untainted innocence. Perfect place for it to happen too as sex and rebellion come into play. It's a spiritual human flaw that humans cant have sex and still be innocent. Oh well. [Answer] The society in which mages exists has societal controls on children + demon combinations. For example, there wouldn't be too many communities where children would be allowed to arbitrarily acquire and use flamethrowers, just because they can, doesn't mean society would allow it. With this in mind, scenario 1: Perhaps the community/society doesn't teach / enable / license children to effectively bind, control and maximise the connection with demons. scenario 2: As mages mature, their real world influence / access is greater. Demonic society is familiar with this concept so demons prefer hosts that have distinguished themselves in some way - maybe a coming-of-age initiation ceremony. [Answer] **Because demons hate having to buy new clothes** (This is obviously a not too serious answer) If demons possessed still growing human beings, they would also need to buy new clothes to adapt to the varying size. This would force the demons to set apart their fulfilling evil activities for more mundane and boring activities, like visiting shops to buy new dresses and try clothes/shoes in order to buy the right size. In order to avoid such scenario, all demons prefer possessing full grown human beings, which allows them to have an already established wardrobe and, when the dresses become too old, they at least already know the right size of their body, so they can buy online the clothing they need. Of course they still could lose/gain weight, but this could be avoided (even with some magic), while the growth because of age could not be avoided. [Answer] They can't possess the innocent. Trying to do so can do irreparable damage to the demon. So to be safe the demons avoid possessing kids who may not be mature enough to understand the nature of their actions. [Answer] Contrary to what some have mentioned here, I do insist on *it has only to do with sexuality*\*. In fact, being sexually immoral (well, one may argue about *morality* here and there, but *demons* are *chiefly* a religious thing, and religion often has - or should have - ideas about sexuality that are contrary to progressive openness and whatnot) is said to be the *key event* in losing the supreme being's protection as their creature (confer B'reshit / Genesis, as in "the fall of mankind"), which is essential for the so-called demons (evil spirits, or whatnot) to be *allowed* to possess someone. In accordance with this, it is also important to consider that *there is nothing physical* in children not being possessed - this limitation is *purely dogmatical*, i.e. a question of what is *permitted* for demons and what is not. \* To be more precise, it has to be with *sin* - it is just that *moral offenses related to sexuality* are way more common *vices* than it would be for a non-possessed kid to e.g. kill their parents intentionally (even for "culpable" reasons). Should such thing happen, though, it would almost definitely predispose them to the *possibility* of becoming possessed. [Answer] The *Harry Potter*-inspired version: children are magically protected by the love of their parents, this protection disappears at ~~17 yo~~ puberty. [Answer] ## Demons are powered by gametes The demons in your setting require the host's gametes, or reproductive cells, in order to sustain themselves for any length of time. Since children do not start producing these until after puberty starts, demons cannot sustain themselves for long inside a human child. Of course, this also means that any adult hosting a demon will also be infertile. [Answer] Transactions and contracts. The demons expend something and gain something in return. When interacting in this capacity with humans, the child is still in an incomplete form and therefore they have a harder time sticking to them. So the demon would need to expend additional resources to accomplish their goals and so the transaction ends up in their loss. So over time they have learned that if they want to have a good chance of getting a good return on their investment they should only deal with adults. Exceptions will arise and never forget that rituals and the like can be used to prepare proper vessels of any age. Summons can be considered much like phone calls, the other side has to answer before anything can happen and the demons have very good Caller ID. [Answer] They could - sometimes they do - but they cannot do magic in a childs body. Not even low magic - none at all. So even if they are stuck in a child, they can not "act out" until after puberty. Call it brain chemistry, call it hormones, blame it on godly protection - whatever - it simply does not work. And what sane demon want's to be buried in a 14y old craving ice cream, fearing to get fat, having to deal with unclean skin and emotional outbreaks because the classmates obviously ignored the new haircut and all that while being forced to study basic writing and being scolded from parents that saw the growing blush because *this other juvenil person* may have beamed a tiny look towards your host's bodies direction... Plot-Twist: the demons themself do not want this knowledge to get out because it would be a valid (although cruel for the child) way to lock a demon aways for a decade. If drugs get invented that stay off puberty, you could have a demon prison for a longer time. [Answer] # They can possess children, however, there are better targets Even while magical abilities manifest from birth, you have to train and study hard to grow into a remarkable mage. The strongest mages were usually taken into academies while they were infants to undergo very strict training till they reached their current power - or even better, *were born into these academies* so their training essentially starts at day 1. The process is very time consuming a gradual process of perfecting skills and training so their mind/bodies/meridians can handle/channel/generate more Energy/Mana/Qi - even the most talented individuals take a many years to hold their own against the strongest mages out there. Let alone actually confront and defeat them. Demons have their power limited by their hosts - if they try to use too much, the hosts explodes and the demon is at least severely injured. Most of the time they would try to possess at least get an adult - preferably a hosts with more affinity so they can use more power. Nothing stops them from possessing children, however, given that this is not advantageous, they usually only do that if they are desperate and have to hide somewhere - perhaps to recover. Puberty is just the "barely acceptable" threshold - this allows them to use some power - at least enough to search for someone better. Demons would like to possess strong mages, not random muggles and certainly not children, unless they have to. [Answer] We all know how children are so much better at things like learning language. Whatever languages you encounter enough as a child you'll grow up speaking effortlessly. Languages learned later are much harder and few people will ever be truly fluent. This is an actual change in the brain. Demonic possession has nothing to do with puberty, it's that demons can't possess a brain that is still in the rapid learning phase. [Answer] **Priests are too vigilant with children** When people are possessed by demons, the treatment given is to take them to a priest and have them exorcised. This is "game over" for the demon. Demons try to hide the fact that they've possessed someone for most of the time, and they do a good job of it. In order to detect that someone's been possessed, it both helps to be closely familiar with the individual to notice that they've changed, and it helps to be a priest, because they're the experts on demons. In this world, children go to schools run by the Church, until they hit puberty at which stage they're old enough to work full-time. Going to school means that priests spend several hours a day with them, when they're in relatively small groups. If a demon possesses them, the priest would notice immediately. By contrast, a priest would only see an adult once a week, and even then in a large gathering of hundreds of people. So it's not that they can't possess a pre-pubescent child, it's just that it wouldn't make sense to do so. [Answer] Every human has magic. Some learn to use it in complex and deliberate ways and so become mages. Others only do what comes naturally. Natural magic, like everything in nature, is a product of evolution and is devoted to survival and reproduction. Children's natural magic is entirely focused on survival. This manifests as rapid healing, general luck, and immunity to possession. At puberty, some of that magic is redirected to reproduction. Creating a soul is a big deal, and the body needs to be ready. The resources needed for that get pulled away from survival, leaving the 'adult' vulnerable to possession. (Optionally, the trigger might not be puberty per se but first sex, in which case virgins would have other interesting magical properties.) (This does suggest that a prepubescent *trained mage* might be vulerable, having hacked their own body to redirect magic from safety to deliberate action. That's probably too rare to worry about, though.) [Answer] ## Because children's feelings and minds are way too instable Prepubescent and pubescent children experience highly swaying emotions, and are mainly led by emotions (as opposed to rationality) This creates an highly unstable environment that demons have trouble controlling. One misstep, and the demon could get swallowed by the intense emotions. Compared to that, adults that mainly run on rationality / have the ability to control their emotions, are way more stable and less dangerous hosts ]
[Question] [ I was reading about non monetary economies and it says that it is a kind of economy that do not have any money in the economy and all goods and services are free to everyone according to Wikipedia. I see some advantages in such a system which are: * People would not need to worry about bills and housing to pay because otherwise the companies will cut the service; * Their basic needs are met without fear of losing their jobs and their incomes having the risk of becoming a homeless or a criminal; * The crime levels in this world would be much lower since most crimes are committed out of greed and the need to make money for a living; * The technological, scientific and artistic characteristics of this world could be much richer and more advanced than in our own since money would not be necessary to make such developments; * There would be no concept of poor and rich since everyone could have the same standards of living with relatively ease. So people would be only in poverty if they wanted to. Everyone would be equal. * Without money people would not depend financially from their families as they are today. People could abandon their parents houses and go have their own lives in a much earlier age. However there would be many drawbacks of a economy without any money or any means of exchange: * Cities could be much more polluted since in theory everyone over 18 could afford a car. And the numbers of trucks and planes would much higher. However laws could be created in order to determinate who could acquire a car based on certain civil and demographic features; * People would probably be much lazier than they are. I read on Reddit about why money exist and someone said that humans are also animals and will do the least they can to survive and need some sort of "pressure" to be stimulated to do things. So he said that without money people would realize that they could have a good standard of living without doing anything to anyone. I did not agree with him but it was just his opinion. * Since food would be free health problems associated with overeating like severe obesity, high cholesterol and diabetes could soar and become far more common than it is in our world. I am not talking about post scarcity and resource based economies like in Star Trek which they eliminated scarcity and the need to work using high technology and Artificial Intelligence. I mean a world with the same technological level as real life but without any money and without barter as well. People would work and consume without the need of any means of exchange. Would everyone accept to work for free? [Answer] There are two possibilities, really: * A [post-scarcity economy](https://en.wikipedia.org/wiki/Post-scarcity_economy) Goods are produced by automated factories, by robots clever enough to require little supervision but not smart enough to demand civil rights and their salaries. (There might be other robots who get those, but not on the factory floor or goods distribution centers.) Read e.g. the Culture series by Iain M. Banks for an example. * Powerful social constraints *In theory*, people are free to take what they need and only to contribute what they feel like. *In practice*, taking too much or working too little makes the neighbours upset, and one has no *right* to be invited to their parties. We're a site for building fictional worlds, so the latter option is much nicer because it offers more adventure potential. An adventure is someone else in trouble, preferrably long ago or far away ... [Answer] The eternal problem of communism is that *"[from each according to his ability, to each according to his needs](https://en.wikipedia.org/wiki/From_each_according_to_his_ability,_to_each_according_to_his_needs)"* doesn't work unless: 1. The concept of needs is severely curtailed in order to avoid people expressing decadent bourgeois false needs, such as being warm, eating tasty food and not walking barefoot. 2. The concept of ability needs to be supported by a ruthless repression apparatus, otherwise nobody will agree that their level of ability is to clean the sewers. In other words, a nightmarish world where everybody is dirt poor and lives in continuous fear. From a conceptual point of view there are four unsolvable problems with a purely communist society: 1. The problem of local knowledge, or, why central planning cannot possibly work. In a normal economy, the interaction between supply and demand works as a distributed information system which by and large makes sure that producers allocate resources to what consumers actually need. But in a communist society there is no money. Since there is no money, there are no prices. Since there are no prices, there is no way for production to be informed of what's needed to be produced. Since there is no way for production to be informed of what's needed to be produced, you will always have overproduction of some things and underproduction of other things. In principle, a communist society is supposed to overcome this problem by employing an all-powerful central planning organization, which uses pervasive (and invasive) sources of information to learn how many size A bras are to be produced in the next quarter, how many size B, how many size C and so on. Unfortunately, this doesn't work, from both practical and theoretical reasons. Long story short, in the absence of prices the central planning organization cannot possibly know what is the utility to be associated with each and every item that *could* be produced. What they will have to do is make arbitrary choices, with zero hope of ever getting it right... 2. The problem of inherently scarce goods and services. Some goods and services are inherently scarce. There is only so much space available on the sea shore for houses with an ocean view; there is no way to give such a desirable house to everybody. There are only so many seats available at a concert. There are only so many tables in good restaurants. The point being that in a normal economy highly desirable and scarce goods and services will command higher prices, and people will have to prioritize their resources if they really want them. In a communist society there is no money, hence there are no prices, and allocating those desirable goods and services can only be done by decree. 3. The problem of unavoidable collapse. Since there is no money, production needs to be commanded from a central authority. In a normal economy, each and every producer is independent of any central authority, and they thrive or fail on their own, with little risk of bringing the entire economy down. In a command economy, when the central authority fails, and it *will* eventually fail, the entire thing goes to pieces. The sad truth is that the State Committe for Planning is a single point of failure, and it is guaranteed that sooner or later it will fail, because humans make mistakes and unexpected events happen. And then you have a revolution... 4. The problem of incentives. In a society without money it is really really hard to motivate people to do anything more than the bare minimum they can get away with. Quality goes down, progress slows to a crawl, maintenance becomes perfunctory, and eventually a point is reached where the entire economy is a heap of disfunctional rubble. And then you have a revolution... ## And about that barter... Funny thing is, in all known societies, when there is no official money, people will pick one or more commodities and use them as money. Packs of cigarettes, half kilo packages of ground coffee, something. But you *will* have some sort of unofficial currency, because see point 2 above: some goods and services are inherently scarce, and you must have something with which to bribe the bureacrat who allocates them. And of course, trading favors will become pervasive. You won't believe how good people are at remembering and balancing favors. [Answer] These societies exist, but scaling them beyond [Dunbar's Number](https://en.wikipedia.org/wiki/Dunbar%27s_number) is difficult. Within a small group, social bonds are sufficient to have everyone contribute in some way, and groups will expel members that refuse. In such a setting, micro-accounting with money is overhead that brings no real benefit, as it requires assigning prices, a tax-like system for redistribution towards communal projects, an insurance-like system for redistribution if someone becomes unable to work, and several other institutions to manage the system. There is no point in status symbols in such a society, these would be looked down upon by the group as a waste of communal resources. Trade with other groups can be organized similar to exchange within the group, as basically a gifting economy where individual transactions aren't accounted, but people have a general sense of whether the relationship is fair (which can still be unbalanced, e.g. if one group has a bad harvest). [Answer] The Queen was in a mood again. Drone 751-b-5 could feel the slow-down pheromones on his feelers. While b-5 knew perfectly well that the food supply was perilously low, he couldn't stop from slacking off a little in cultivating the mold gardens. And even if the Queen ended up starving them all with her (mis)guidance, there were other colony-cities. 851 was doing quite well, or so he had heard. And, besides the other '51' communities, there were also the '48' and '52' groups. And, he supposed, some surviving '49' colonies. As much as b-5 didn't like to think about the 49's. The slow-down pheromones were great for making sure the community did not overwork itself, but what sort of Queen kept sending it out in the middle of a famine? When everyone was aching so much to work harder? **Daily life in a civilization without money or barter may be possible, but only if your civilization is not composed of humans** [Answer] # No *Please note that I came within an inch of voting to close this question as opinion-based. I'm only answering it because your specific question, "would everyone accept to work for free?" has, IMO, only one plausible answer.* **There has never been a civilization on Earth — at any time in history — where someone walking down the street wouldn't see something they want... and want it.** And therein ends the discussion of "would everyone accept to work for free?" So long as anyone has something someone else doesn't have, there will come a time when that someone else will want it — and while it's nice to believe that an economy can exist that can provide every need, every luxury, every whim to anyone and everyone at any time, the truth is (and it's a truth far too many people won't accept) is that it's *impossible to do that.* > > "We shall execute our king instead, sir, and exalt our tailors," said Chauvelin in Baroness Orczy's *The Scarlet Pimpernel.* To which Sir Percy replies, "More's the pity. Then your tailors will rule the land, and no one will make the clothes. So much for French fashion, and French politics." > > > The only way for such a society to exist is for nothing to be available to anyone that isn't a subsistence need. Except that isn't possible, either. As soon as someone's job allows them to use a pickup truck, someone whose job doesn't allow it will want a pickup truck. As soon as someone is given a new car, someone with an older car (no matter how new) will want a new car. And you can't have red cars and blue cars because someone with a red car will see someone with a blue car and want it. You can't have people with curly hair and people with straight hair because... *Is this making sense yet?* Training humanity to accept the lowest-common-denominator when it comes to living would require training them to accept the drudgery of effort without finding the joy of life. As soon as someone tells a friend across the country that they saw a beautiful butterfly, that friend will want to change locations because (true or not) they will believe there are no beautiful butterflies where they live. > > Publius Ovidius Naso wrote "Fertilior seges est alenis semper in agris" (the harvest is always more fruitful in another man's fields). Which is where the modern proverb, "the grass is always greener on the other side of the fence" is believed to have come from. What both mean is that it's human nature to believe their life would be better if they have something they don't currently have. > > > In other words, the very concept is *inhuman.* Worse, it depends on the removal of innovation, curiosity, the drive for improvement... (it makes Orwell's *1984* and Huxley's *Brave New World* look like paradise). In fact, it would require whoever is in charge (yup, something someone who isn't in charge is going to want...) to give up the very technological basis that allowed them to have the society they have. Keep in mind, such a society would require a ruling class that enforced the condition of equity — not equality, that's impossible in such a society, but equity. Which means no one can fix the machines when they start breaking down... because that depends on the innovation your society cannot have that would permit even the possibility that everyone could work for free. *And anyone who doesn't believe this should read Kurt Vonnegut's* [Harrison Bergeron](https://en.wikipedia.org/wiki/Harrison_Bergeron). So... no. *While getting my dinner this evening I was reminded of the comments of a friend about a month ago. He's a plumbing contractor — and the people who work for him... won't. When he asked one why he wouldn't come to work, the response was, "why should I crawl in attics and crawlspaces when I can stay home on unemployment for the same amount?"* *My thanks to @CodesWithHammer for helping me expand that example. At the time I posted this answer, the U.S. government had created an artificial condition where a skilled laborer refuses to work because all his/her needs are met without labor. Whether or not the employer could, should, or would pay more to overcome the "economic inertia" created by that artificial condition isn't relevant to the question. What is relevant is that the workers could have easily returned to work "for free," contributing their skills for the greater good of society as there were (and there were) people in need of those skills. Given the choice to work "for free," they chose to stay home - thus making my point.* *So... no.* [Answer] There is only one way to make this work on a large scale, and that is extensive slavery. Otherwise there are always many very important jobs that no one would do without getting a significant reward. Sewage work and waste treatment are gross for everyone, woodcutting or such are too dangerous to do them without immediate need. If slaves produce all the required goods, the non-slave population can live in wealth and splendor, free of the worries of money. They just do the prestigious stuff, research, art, architecture and such, whatever they feel like on the day. The slave caste needs to be so suppressed that they don't even think about revolting, either through the incentive of becoming free if they work hard so that they can be on the other end of the master-slave relation, or through so much terror over centuries that their will to be free is essentially non-existent. They just do whatever they are ordered to without question. Since slaves in such a society are essentially dehumanized, they don't count into "everyone". Everyone (who isn't a slave) has everything they need. It's similar to a society where robots/machines produce everything, except that there are already many goods that modern machines can't fully produce without human work and slaves would fill that gap. If someone wants to create a new product, he goes to the slave slums, grabs a few of them and has them do it. If he wants to provide more of those products, he grabs more slaves. There might be specialist slaves which live in slightly cleaner slums, which can build machines to aid large scale production. In essence, it would be a utopia for the ruling class and a dystopia for the slave caste. Similar things could be observed in "communist" societies like the USSR, where many "apparatchiks" lived without need for anything while most of the population lived to essentially serve the whims of their superiors. [Answer] **Money is very useful** Bartering or paying in kind (like I'll give you a dozen eggs for working on my farm) are really only used in smaller community settings, or less developed societies. The problem on a larger scale is that it is very hard to quantify just how many eggs a house is worth. Money is so great because it isn't some product or service that is produced, but a means of assigning arbitrary values to very different things. It makes things more organized and efficient. Further, lack of money does not reduce greed or crime. In a world without money, someone will just steal valuable items instead. If there is a reason for lack of crime in non-monetary societies, it is because of extraneous factors, whether it be a smaller community, strict cultural beliefs about theft, etc. [Answer] > > Would everyone accept to work for free? > > > **If 'work for free' means 'without being paid money', then the answer is yes.** I did not find even one research paper that would suggest that money is the only motivation to make people work. [Most research suggests that correlations between salary and job satisfaction and between salary and work engagement are almost negligible](https://hbr.org/2013/04/does-money-really-affect-motiv). Internal motivations (like curiosity, interest in a specific topic, self-improvement, self-challenge, and so on) are much better predictors not only of job satisfaction and engagement but also productivity. It is also worth considering that for the most part of human history, people worked without being paid any money. Salaried jobs (with salaries paid in money) became common only after the Industrial Revolution. And even with salaried jobs being the norm today, a significant amount of work1 is done without being paid: Domestic labour, child and elderly care, volunteer work, hobbies, and so on. A lot of work is done not because it is rewarded monetarily, but because it needs to be done. For example, I clean my toilet not because I am paid to do it and definitely not because I enjoy it. I do it because it needs to be done to avoid future problems (and because I hate dirt more than I hate cleaning toilets). Some other work is done because it relates to social or personal responsibilities. In modern societies, social responsibilities are often fulfilled by public agencies (e.g. maintenance of public property). In traditional societies, either some members do this work of their own volition or the community will achieve some sort of agreement on who and when does this work. Caring for children and the elderly is often a personal responsibility (although, some traditional societies consider it a communal responsibility) and all work done to fulfil this responsibility is done without pay. And, of course, there will be a lot of work done because people enjoy it, receive social approval and respect, achieve self-fulfilment through it, and similar reasons. There is a caveat. If we suddenly remove money from today's world and ask people to work without being paid, there will be a lot of people who will refuse to work, at least, initially. The number of those people will be most likely higher in cultures that assign high value to money and tend to see money as an indicator of personal success and fulfilment. I am talking here about cultural views and stereotypes, in other words, the perceived role of money in human lives. Whether this view is correct or not is a different topic. **If 'work for free' means 'without being rewarded in any way at all', then the answer is no.** What I mean by 'without being rewarded in any way at all' is that a worker does not receive any benefits, tangible or intangible. There still be some people with a strong sense of responsibility who will work because they believe that it is something they ought to do. There will be some people who work because it is the lesser of the two evils (I hate dirt more than cleaning toilets). And, of course, all those people who work because they enjoy it, find it personally gratifying, fulfilling, etc. will continue working. However, there will be quite a few people who do not work at all because they are not being rewarded. To be frank, I cannot imagine a situation where workers are not rewarded at all. Even housewives whose work is often undervalued, unrecognised, and looked down upon, receive at least some reward from friends and families complimenting their cooking, smart arrangements in the house, the aesthetics, and so on. Although, I do admit that this kind of reward can be insufficient motivation for many people. --- **Some additional notes** ***1. Culture and society*** Even Marx, whose work *[Critique of the Gotha Programme](https://www.marxists.org/archive/marx/works/1875/gotha/index.htm)* made the slogan 'from each according to his ability, to each according to his needs' popular, was admitting that a direct transition from a capitalist to communist society is not possible. In the same work, he suggests that this transition will happen in two stages. At the lower stage, labour contribution to society will determine how much workers receive from this society. The transition to the higher stage (i.e. communism how it should be) becomes possible only when society and its members are completely free from the values and traditions of capitalism: > > In a higher phase of communist society, after the enslaving subordination of the individual to the division of labor, and therewith also the antithesis between mental and physical labor, has vanished; after labor has become not only a means of life but life's prime want; after the productive forces have also increased with the all-around development of the individual, and all the springs of co-operative wealth flow more abundantly – only then can the narrow horizon of bourgeois right be crossed in its entirety and society inscribe on its banners: From each according to his ability, to each according to his needs! ([*Critique of the Gotha Programme*. Part I](https://www.marxists.org/archive/marx/works/1875/gotha/ch01.htm)) > > > Whether you agree with Marx or not, he makes a very good point: Moneyless economies require different cultural values and behaviours compared to money-based economies. I think that a moneyless society will put great emphasis on: * collectivist values Collectivist cultures are more concerned with society's needs and goals. For example, [collectivism was one of the best predictors of mask usage during the COVID-19 pandemic](https://www.pnas.org/content/118/23/e2021793118). Individualistic cultures tend to prioritise personal autonomy and may lead to the politicisation of questions, actions, and activities related to the public good (which could also be seen in the US where mask usage during the pandemic became a political issue and at the same time resulted in a higher number of super-spreaders compared to more collectivist cultures). * civic duties and social responsibilities Civic duties refer to the responsibilities of citizens, e.g. voting and jury participation in democratic countries. Social responsibilities are responsibilities as a member of a group. There are a lot of things that people do not want to do for one reason or another. However, these things still need to be done. A person with a strong sense of duty and responsibility will be much more likely to do unlikeable but necessary things. I also want to note that money is one of many reward mechanisms. Fame, recognition, respect, special treatment, and so on are examples of other reward mechanisms. In addition to rewards, societies employ coercion mechanisms to make their members perform necessary work. The social stigma attached to those who refuse to work can be used as coercion. So, while a moneyless society may not have one of the rewards mechanisms it will still have all other reward and coercion mechanisms. And even if people are not willing to accept working for free they might be forced to do so. The specific use of coercion and reward systems determines whether your moneyless society is a utopia or a dystopia. The absence of money does not automatically lead to any of these two outcomes. **2. Innovation** It is a popular saying that capitalism stimulates innovation. I also read and heard many times that any non-capitalistic country will always and inevitably lag behind in innovation. I am not sure that this is entirely correct. The USSR achieved remarkable success when it comes to space exploration or weapons despite being a socialist country with no free market. In all countries, capitalistic or not, most basic research is done using public funding (the state pays for expensive long-term research). Public funding is also essential for research in the fields that do not yield quick profit or will never be profitable. Private business frequently focuses their research on consumer products that can bring profits and increase the company's value. They are not concerned with the public good and even if they are a responsible company and they have some considerations it is not their top priority or primary goal. It is even possible to argue that while capitalism indeed led to the increase in the quality of life short-term it is also responsible for the massive decrease in the quality of life in the future due to the harm caused to the environment. A moneyless society can potentially be even more innovative than a capitalist society because theoretically people can freely choose their jobs and can unleash their full potential. At the same time, they can be more responsible when it comes to the public good and long-term effects of innovations because they are not concerned with profits. I would be sceptical of anyone who makes any definite statements when it comes to innovation because we do not have any points of reference and/or data to support our conjectures. As a result, most predictions are based on ideology and assumptions about human nature2. --- 1 While some people equate work with paid labour only, this is not accurate. For example, [according to OECD research](https://www.oecd.org/dev/development-gender/Unpaid_care_work.pdf), unpaid care work is one of the important factors explaining gender gaps in labour outcomes (participation, wages, and job quality). Across all regions of the world, women spend on average between three and six hours per day on unpaid care activities, while men spend between half an hour and two hours. Even if we disregard the gender implications and focus on unpaid labour only, we will see that on average families spend between five and seven hours per day on unpaid care activities, which is only slightly shorter than a typical 8-hour workday. Unpaid care work is defined in the cited document as '*Unpaid care work refers to all unpaid services provided within a household for its members, including care of persons, housework and voluntary community work (Elson, 2000). These activities are considered work, because theoretically one could pay a third person to perform them.*' 2 If you visit discussion sites for US conservatives and US socialists/progressivists/communists this point will become very obvious. They use the same facts (or lack of facts) to come to completely opposite conclusions. [Answer] # Would everyone accept to work for free? Yes! There are much more incentives to work than just personal material gain. Despite popular claims, people are not rational beings - we do not make decisions based on cold-blooded rationality, and othen choose actions which are not the most profitable ones, at least materially. Without any kind of money or property, the majority of creative jobs would remain unaffected. The incentive of the artists, scientists and thinkers is not money, but the need of progress, self expression, social respect or self devepolement. Rich people hardly ever decide to fully give up on any work. Even if they do not need money to survive or improve their situation, they still run up a fundations or govern the companies - had the material gain be the only reason for any activity they would remain idle after obtaining certain level of wealth. Also, a lot of non-creative, but essential, workers are also not driven by the greed and desire of money - in many countries teachers and nurses are amongst the worst earning professions and yet people are willing to take these jobs despite the requirements for higher education, long working hours or a lot of work to be done in home after the working hours. In many cases these people would earn much more by working as a shop assistant than by remaining in their profession, but are still unwilling to change their job. Even in cases of the jobs like physical workers or other blue collars, the money is hardly ever the main incentive. Majority of people prefer to have a hard and poorly paid work, than to be unemployed even if some social security is guaranteed by the state. In the situation of forced unemployment when money is not needed to survive, like in prisons, the possibility to work, even for very poor wage, is highly desired. Additionally, one has to notice, that a lot of the most needed work is currently done for free - volunteers, housewifes or activists are performing huge amount of free work, often in the most crucial areas. They care for poor and sick, they fight to counter the actions of corporate lobbyists, they push the society toward the future - in term of human rights, climate or equality. There are enormously important, they may be the most important tasks in the modern society, yet are done mainly for free. Multiple [experiments with a basic income](https://www.vox.com/future-perfect/2020/2/19/21112570/universal-basic-income-ubi-map) showed that alleviating the material incentive to work do not make people less likely to seek for employment. One could argue, that the material incentive to work in fact discourage people to work efficiently. Karl Marx said, that the [alienation](https://en.wikipedia.org/wiki/Marx%27s_theory_of_alienation) caused by the need to perform work which one do not enjoy, leads to the dicrease of one's possibilities and thus hinders the progress of the society. One who perfom his job only to satisfy his most basic needs will never be an efficient worker. Clearly, one could be afraid that if we remove the finiancial incentive and move toward removal of workers' alienation, some jobs would be vulnerable to extinction. But currently a lot of working positions are the so-called [bullshit jobs](https://en.wikipedia.org/wiki/Bullshit_Jobs) which are in fact pointless, or even damaging to both the workers and the society. It is hard to make a claim, that disappearence of such jobs would be a bad thing. **But there is much more to discuss in your question!** The disadvantages of society without money which you mentioned are only valid in the society with money. Would anyone desire to have a car, had he work just in a walking distance from his home or had there be free, comfortable and fast public transport? Would anyone desire to be stuck in the traffic instead of using well designed underground train? In the society without property (or with everything being a public property) the public services would be of much higher priority and quality. Occasional use of car for entertaiment (like holiday travel or just enjoyment of driving) would not cause much pollution. Would anyone desire to eat unhealthy garbage food had he have an access to high quality, tasty and healthy dishes with enough free time to prepare them and enjoy them in the stressless life? I don't think so. One could say, that people just like garbage food - like fast food or kebab. But even a kebab or burger can be made from high quality meet, on fresh oil and with healthy ingredients. It is lack of money, not its abundance, that cause people to eat unhealthy food and pollute the enviroment. **But is it even possible?** The society which you described in your question is basically a communist one - a society in which not only money is removed, but a property as a whole do not exist. If we allow property to remain and remove only money the barter will emerge as a substitute. To remove the barter, the property as a whole has to be removed and everything has to be public. I will not discuss here whether this is achievable in the real life or whether it is a good goal to struggle for. But let me draw attention to some aspects of such society. The greatest advocate of the communist society, Karl Marx, himself emphasised that such society is possible only is some kind of post-scarcity world. He claimed that social structure is a result of material conditions and posession-free society could not emerge in the medieval times when even the food was scarce. He claimed that capitalism is a necessary step toward the communism because it creates the means of production necessary to enter the communist stage. But with time, the capitalist regime becomes obsolote, as it is no longer suitable to control these forces of production - in the same way as medieval nobility was not able to control the industrial forces of early capitalism. One could say, that we in fact already observe this situation, as competition between small capitalists (what is a definition of the capitalism) is currently replaced by monopoly of huge corporations. Marks believed that is will be replaced by property-free comunist society. The most importat aspect here is the fact, that Marks was seeing the capitalism as a force which creates this post-scarcity society which will be able to satisfy the needs of the people without the rule of the capitalist bourgeoisie. So whenever you speak about society without money, you have to speak about (at least in some sense) post-scarcity society. One could argue whether we are already in this stage - current food production is enough to end the world hunger and the wealth created is enough to eliminate the global poverty. Another notion is that creation of society without a property would require enormous change in the way we see the world. Change in such society would not be only cosmetic, but it would require the modification of the basic principles of the society. The goods would not be distributed in any way between the people, there would not be any central commitee which gives food to everyone. It would just be **free**. One could just walk out of the work in the middle of week, enter a plane on the airport, travel to the other side of the world and ride a bike standing on the road and noone would consider it strange or wrong. The change would be fundamental. [Answer] Most armies of the world operate exactly like your economic system, where the nutritional, clothing, health care, and other needs are provided by the 'organization' and the soldier provides 24/7 as-demanded service in return. A central commissary dispenses as available and as needed, according to regulations. Supply and demand are governed by central stores. An economic system whereby the entire society is structured hierarchically like an army, with no outside economy, would be equivalent to your concept. I suspect bartering would still occur, but it would not be a 'barter economy'. I have even seen domesticated dogs cats 'barter' between themselves. The ISS operates by the same principles. The astronauts do not 'buy' their food while on board the station. [Answer] Given a technological level roughly equivalent to today’s, no such society can exist with humans. In order for there to be no money and no barter, there has to be no scarcity. Which means vastly higher or lower technology. Money exist to solve the problem of barter, which is that to a drowning man water is useless and to someone dying of thirst nearly infinite in its value, and both of them would sorta like to have eggs tomorrow morning. Money is just barter on a humongous scale (also why you want your money to be as nearly worthless as possible). You need a species that is motivated by something other than personal wants, one with a shared desire/goal that is so powerful that it overrides anything else and doesn’t tolerate competing desires — someone that expresses a desire for a personal benefit that interferes with that goal isn’t a leper but leprosy itself, killed without thought. I’m not sure how such a species would rise to our level of technology, doing things more efficiently has to an acceptable part of their goal, while allowing for inefficiency in the inevitable mistakes. Perhaps they only became that way after achieving a given level of technology and it has gone up or down since the goal was established. I guess there could be another species on the planet from which they acquire all their technology. [Answer] My previous response did not take into consideration that the OP explicitly states our technology level and available resources would be what they are today in their fictional scenario. That restriction severely limits the possibility for such a society, but I do still believe it would be possible so long as it was done sustainably. The basic premise would be that each person living within the society would need their own plot of land, they would be limited in how many children they could have and it would require that the entire multi-generational family would remain on their given plot with the exception of spouses moving to other established plots. Each family would grow their own food, manufacture their own clothing, and in all ways be self-sufficient. In short, the society could be as large as available land allows, but there would be absolutely no need for exchange or trade. Whatever you grow, harvest, sheer, etc. is what you have to work with. No governments, no laws, just honest farm life basically like what the USA had during the great western migration. [Answer] The themes explored in the descriptive text associated with your question reminded me of a description of communism in Russia, during the earlier days of the Soviet system, that [Ayn Rand](https://en.wikipedia.org/wiki/Ayn_Rand) described in her book *[Atlas Shrugged](https://en.wikipedia.org/wiki/Atlas_Shrugged)*: *Each receives according to their needs, each gives according to their abilities.* It's why she wrote *Atlas Shrugged*, to explain egoism and objectivism and to counter communism. Communism failed, as will the society you are describing. If society gives everyone everything they need, where is the incentive to do anything? If someone gets enraged one night and smashes their television set as a result. Does society immediately replace it? What if the same person repeatedly smashes their replacement television sets on successive nights because they repeatedly become enraged over other issues. Are they entitled to continually receive replacement television sets? Is there no responsibility on people to care for items and not smash them because they become enraged? Would a system of [rationing](https://en.wikipedia.org/wiki/Rationing) be required to prevent this and also to prevent people from eating excessively and becoming obese? If so, how is a fair ration determined? [Answer] My interpretation of your question: "How would life look like, if it's even possible, in a society where people aren't paid anything that serves as a medium of exchange?' IMHO, such society is possible even now and the people will be willing to work without becoming hardcore altruists (it's a different question if such society will be viable in the long run). I imagine following scenario: The whole economy is organized as a planned economy, with no money. Instead of paying people with money for their labor, the government pays with sets of personal, specialized, one-use coupons. These coupons are personal because each coupon has personal ID number of a person to whom it was given, you can't use a coupon that has ID that is different from your ID (unless you a spouse/caretaker/child of the person with given ID). They are one-use in sense, that once you spend given coupon, the other party that received it is prohibited from giving it back to you under any circumstances, these coupons will be destroyed. They are specialized in sense, that each coupon allows you to get specific amount of something specific. Like you can be given a coupon to get 1.5 kgs of beef (no more, no less, and specifically beef). You get a set of many different coupons, like 1 coupon for X kgs of beef(central planners think, that you have a need to eat meat of cows), another coupon for Y number of condoms (central planners think, that people like you have at the least somewhat active sexual life), yet another coupon allows you to visit a theatre for Z times. Basically central planners decide what needs/wants of people like you are, and compensate your labor accordingly. If it's something big (like a car), then you will need to receive and collect (it will likely take several years) certain amount coupons to get this things (like maybe you need to collect 100 coupons to receive a car). These coupons wouldn't be money, as money serve as a medium of exchange, and these coupons don't serve as medium of exchange. It's often said that money serve as a medium of exchange, but the whole concept of "medium of exchange" was invented in context of solving "double coincidence of wants" of a barter system. Like if I have a bag of rice, but I want to have some beef, then I need to find a person who wants to get rice and give some beef in return. If I have some kind of medium of exchange (like dollars), then I can just exchange my bag of rice for said medium of exchange, and then exchange said medium of exchange for some beef, which give me much more flexibility. But this flexibility is gone if I have, say, food coupons for X loaves of bread, that only I can use. Thus this version of coupons can't be considered to be a medium of exchange, at the least if rules are properly enforced. Now let's think about things, that will be different in this society. 1.People will be still somewhat motivated to do their work, but to lesser degree, as central planners have less nuanced understanding of their needs/wants. Like maybe I'm a vegetarian, an asexual, neither meat nor sex interest me. And I don't like visiting a theatre. Thus coupons for beef (and other kinds of meat), condoms (and other kinds of sex-related things) and theatre are just wasted on me. 2.Such system works worse if people are diverse and complicated in their needs and wants. Which will encourage the authorities to try to make people more standard in their needs/wants. The easiest way would be for the Government to get rid of non-standard people, to bully/brainwash them into behaving like the general population, or just left their needs/wants unfulfilled. Like chronically ill and disabled people will have needs/wants that are different from needs/wants of an average Joe, so the government can decide to heal them once and for all, ignore their problems, or even to kill them. Such society will see being different as deeply problematic, people will feel ashamed/depressed for being different. 3.More cumbersome personal finances. You don't get money, instead you need to keep track of many different kinds of coupons. 4.Heavy use of censorship and primitivization of culture. The government will likely to actively shape culture, and it will shape it in a way, that will make people less diverse and complicated in their wants/needs. 5.Stealing/robbing/scamming people out of their money will become a thing of the past, as there are no money and you can't use a coupon that belongs to other person anyway. But stealing/robbing/scamming people out of their things will be increased. 6.No fines, no money compensations, as there are no money. 7.No taxes as we know them, as no money needed to pay for wages. Not a problem at all, since the State is the sole employer and owns all resources and enterprises. ]
[Question] [ After asking this question ([Why would a compass not work in my world?](https://worldbuilding.stackexchange.com/questions/189547/why-would-a-compass-not-work-in-my-world)), I've been spending too much time thinking about navigation and direction - specifically, what *innate sense of direction might my human character be capable of?* My character flies dragons, so navigation is a handy skill to have, especially when flying over places with few landmarks, or having no visible sun or stars to work with. My ideal scenario is that she has a navigating ability that has passed down through generations - perhaps all of her family have it too, perhaps none of them seem to present it, but it's something that her ancestors had and were known for, so she's inherited it from them. I'd also like it to be a very unusual trait. Maybe a few families have a certain predisposition for it, but it's seen as quite a rare, special thing. For example, I've read of [languages that refer to cardinal directions](http://nautil.us/blog/5-languages-that-could-change-the-way-you-see-the-world) rather than 'left' and 'right' and so on, but I'd prefer this heightened sense of direction to be limited to only a few people, rather than being widespread through all speakers of a certain language. She lives in a world where steampunk-level technology is developing (it's more advanced and more prevalent in bigger towns and cities), but I'd really like to avoid using tech to solve this problem if at all possible. I've heard of experiments where people had to wear [tactile compass belts](https://thenextweb.com/eu/2015/12/17/feelspace-helps-blind-feel-right-direction-vibrating-motors/#gref) that vibrate in order to help with wearers' sense of direction, which is super cool, but I'd prefer it to be an innate characteristic rather than an item that helps with her navigation. The other thing to contend with is the world she lives in. She lives in the world described [in my previous question](https://worldbuilding.stackexchange.com/questions/189547/why-would-a-compass-not-work-in-my-world), which, thanks to *L.Dutch - Reinstate Monica*'s answer, is now populated with large magnetic ore deposits, making a magnetised compass basically unusable. I'm guessing then that human magnetoreception wouldn't work? (Aside from the fact that human magnetoreception is kind of a contested topic...) There is magic in the world, but it's more for the existence of the occasional mythological creature than for reality-bending stuff, so I'd *prefer* not to rely on that. So, with all of that, **why does my character have such a good sense of direction?** I'd prefer things to be based mainly on reality if at all possible - I'm fine with stretching things a bit though, like the magnetoreception idea, but would like not to get *too* wild if I've got an option. If not, handwaving it is. [Answer] ## The Same Way Sea Turtles Do Your character has an innate feel for the planet's magnetism called [magnetoreception](https://www.sciencemag.org/news/2016/06/maverick-scientist-thinks-he-has-discovered-magnetic-sixth-sense-humans) just like many real world animals do. But, instead of using the world's magnetism like a compass the way migratory birds do, she uses it like a GPS system the way sea turtles do. Large deposits of magnetic ore would be like familiar beacons that your person could subconsciously feel out. So, not only would your character know their direction at all times, they would know their exact position in their environment too. Even if you were far from home and did not know the landmarks you would you could still feel yourself between several unknown landmarks, and by feeling how they approach/recede as you move will tell you if you are going in a straight line kind of like how keeping eyes on distant mountains makes it easier to go straight than trying to stay oriented in a dense forest where you can only see what is right in front of you. There is strong evidence that the human body already has a natural compass built into it: a ferrous tissue somewhere in the head (probably behind the nose) that tells us which way we are oriented. In your world, this biological structure would still evolve, but how our brains interpret the information would be different. The structure would have to be more sensitive to be able to feel not just the direction of magnetic pull, but the shape of the magnetic attractor too. This way one could feel out distant magnetic landmarks to map out where they are in their heads. As a side note: if your people are strictly human, this would not be a very likely adaptation for a female hero to have. In humans, this ability appears to be more sensitive in men; so, it would be comparatively unlikely for a human woman to have. On the other hand, this could be her "heroic attribute". If this sense of direction is already something that is only ever seen in a handful of men, for her to have it would be completely unheard of and remarkable to those who witness it. ...or it could be that the dragon has turtle like magnetoreception and that dragon riders rely on the dragon to know where it is going more than her own senses. [Answer] **This is a bit of a cop-out answer...** I'm one of those people who tend to know which way they're pointing - but it's not perfect. If walking through a cave tour, I can properly identify "North" most of the time. Why can I do it? I haven't the foggiest idea. Compare this to my wife, bless her heart, who has trouble recognizing "North" in a new area until she can commit landmarks to memory. Just to add magic to the mayhem, I can also "witch" pipes (not water, pipes, and it doesn't matter what they're made out of). I can generally determine how deep they are but am very precise with where they are. Do I know how I can do that? Nope, not the foggiest. I bring this up because, sometimes, you don't need to actually explain anything. Unless the explanation for the ability is critical to plot development (e.g., the bad guy figures out how your heroine's ability works and uses that knowledge against her), detailed explanations often get in the way of a good story more than they enrich it simply because it gives people something "not quite right" to latch onto. **Why is this important?** After Larry Niven wrote his first *Ringworld* novel, students at MIT ran the math and discovered it was unstable. > > A measure of how seriously people take the science of the Ringworld – and how daft it has driven them – comes in a story from the 1971 World Science Fiction Convention, when excited students from MIT apparently crowded out the venue chanting: "The Ringworld is unstable!" ([Source](https://www.theguardian.com/books/booksblog/2010/jul/02/larry-niven-ringworld)) > > > Niven solved the problem by writing a sequel that addressed the instability. But my point remains: if you give someone something that can be determined to be wrong without a good reason, they'll figure out it's wrong and can be charmingly (in hindsight only) brutal. **Conclusion** So, while this is a bit of a cop-out answer, everything in your world doesn't need to be explained. Unless you absolutely must — don't explain it. > > Sometimes I think about Petracola Fularatormus, the angel wing clam.*Beautiful.*This river is the only place on the earth they are found. Underwater they glow in the dark. Now the amazing thing is that modern science cannot explain why.*There must be a reason.*My theory is that they do because they can. (Dirk Pitt and Eva Rohas in the movie *Sahara*) > > > > > > > > > > > [Answer] **She can see polarized light. And so she can always see the stars.** Light scattered from the daytime sky is polarized. Starlight is not. If you can distinguish the two types of light (as can some insects and birds) you can pick out stars against the bright sky. <https://calgary.rasc.ca/daystars/index.htm> On cloudy days her ability serves a built in sunstone, which (I like to think!) helped Vikings navigate on very overcast days. <https://en.wikipedia.org/wiki/Sunstone_(medieval)> If there is a serious storm and thick clouds she still might get lost at night. If she had to navigate on such a night she would try to get above the clouds. [Answer] ### Practice, study, and hard work With practice, humans can learn to be exceptional navigators. Eg A [London cab driver needs to know](https://www.nytimes.com/2014/11/10/t-magazine/london-taxi-test-knowledge.html): > > The six-mile radius from Charing Cross, the putative center-point of London marked by an equestrian statue of King Charles I, takes in some 25,000 streets. London cabbies need to know all of those streets, and how to drive them — the direction they run, which are one-way, which are dead ends, where to enter and exit traffic circles, and so on. But cabbies also need to know everything on the streets. Examiners may ask a would-be cabbie to identify the location of any restaurant in London. Any pub, any shop, any landmark, no matter how small or obscure — all are fair game. Test-takers have been asked to name the whereabouts of flower stands, of laundromats, of commemorative plaques. One taxi driver told me that he was asked the location of a statue, just a foot tall, depicting two mice sharing a piece of cheese. It’s on the facade of a building in Philpot Lane, on the corner of Eastcheap, not far from London Bridge. > > > Your character has a backstory of getting lost. Of spending nights in the freezing wind and rain near death because they took a wrong turn. They've learnt subtle landmarks, star patterns, cloud and wind patterns. They've learnt the subtle sounds that can tell them how far to the nearest coast. When the sun hits them they can use that orientation instinctively to give exact orientation and time of day. [Answer] [Humans already are capable of innate direction](https://www.mentalfloss.com/article/54572/your-sense-direction-innate), and those people who speak a language which encodes it — most famously Guugu Yimithirr, though there are others — seem to always know which way is north. The assumption is that the language forces people to pay attention to this, so they unconsciously hone the skill. See *Through the Language Glass*, by Guy Deutscher, for what this tells us about linguistics, but for your purposes, you just need to know that this is something we already can do, so long as we get practice from early childhood. [Answer] Willing to have this idea shot down, but: * within the parameters of the world, magnetic-based navigation isn't a thing, because of all the magnetic ore deposits, * and she flies a dragon, which isn't your typical mode of transport, and allows her to get quite some distance away from ground level. Could she feasibly have some sort of magnetoreception but only be able to use it when she's flying at some altitude, away from all the magnetic ore? This might explain why compasses don't exist in her world, because there's no point in using them at ground level, and people don't really fly in the sky all that much so haven't needed them there. Might also be a cute thing for character development, if she gets lost all the time at ground level, but suddenly has epic directional ability in the sky. I have no idea about whether magnetoreception could actually be of much use in a human, or be an inherited trait, or even work in a human without serious side effects (especially with all that ore around), so all of this speculation might be kind of pointless. Very much up for discussion if anyone has any ideas! [Answer] **She has been trained to do so since childhood, by the other dragon riders.** The Polynesians got very good at navigating on the open sea, because they live on the part of the globe that only has a few specks of land between the huge ocean. They did (and still do) this by watching the stars, birds, ocean currents, and even by dead reckoning, which is a technique where you know where you are just by mentally 'counting' the amount of time you spent going in different directions. They never even used compasses. As for why not everyone can do this, it takes a lot of time and specialized training to do it, so nobody would learn it or even be able to get a tutor, unless they were really going to use the skill. Also, dragon riders might want to keep these techniques secret, as part of internal rivalries or maybe just to keep the common people from using dragons. I'd also imagine that the time spent flying a dragon for training would be very expensive, and you need real-world experience to learn this. Some sources: * [Polynesian Navigation](https://en.wikipedia.org/wiki/Polynesian_navigation#Navigational_techniques) * [Wayfinding, or non-instrument navigation](http://archive.hokulea.com/navigate/navigate.html) [Answer] # Good memory, sharp senses and spatial skills Robert Downey Jr. played the role of Sherlock Holmes in a movie. There is a scene in which he is kidnapped and taken to an undisclosed location. Upon arrival he knew not only where he was but also the path they had taken. He considered smells, sounds and counted the turns. If your protagonist has been around, she can fell the most subtle details of places with all her senses. In flight, she can tell where she is going by the intensity and direction of the wind - the atmosphere has its own currents, much like the ocean and specially when far away from the ground. Underground, she can do some inertial navigation by counting steps and taking into account the angle of each turn. [Answer] Humans have [built-in accelerometers](https://en.wikipedia.org/wiki/Semicircular_canals). All that is needed in order to be able to tell direction and position is to have a built-in integrator in their brains. Whether we do or we don't have such a [built-in integrator](https://en.wikipedia.org/wiki/Sense_of_direction) is a matter of dispute; but we do know that some people are much better than others are navigating through densely wooded terrain, for example. (As an unrelated but equally surprising ability, it was only in recent times that humans were [shown to be able to echolocate](https://en.wikipedia.org/wiki/Human_echolocation). Maybe we are also able to compete with homing pigeons and we don't know it yet.) [Answer] ## Human Magnetoreception Perception of where you are often relies on multiple datapoints. Having magnetic ore deposits be super prevalent makes a compass useless since it points towards the closest/strongest reading. If however your heroine can sense them she isn't limited to a "seeing" a single one at a time but rather will be able to tell that she just passed a strong one on the starboard and there's a smaller deposit they'll be coming up upon soon. Much like knowing the location of trees, buildings and landmarks allows one to navigate, she would be able to get a sense of where she was just from the quantity/strength/location of deposits near her. This could lead to interesting plots points as desired as many things could interfere with this from weather, solar flares, or mad scientist experiments or even deliberate action from the antagonists if they know she has this ability. Heck, maybe they don't even know, they have some device that historically was effective at confusing her family's spacial perception due to improper shielding and when they "fix" it to work better it doesn't stop it anymore. [Answer] When you mentioned that there was magic in the land, I immediately thought, "ley lines". If there are strong ley lines in this world, e.g. concentrated channels or streams of magic or magical energy, then your character could just be highly sensitive to them. Different lines would have a different "feel" to them, like being able to discern small differences in acoustic tones or flavours or scents. Once she was familiar with the ley lines in her normal flying range, she would be able to sense them and immediately orient herself with a subconscious "map" based on her memories of those lines. That same talent would allow her to immediately and unconsciously start to become familiar with new regions as soon as she starts visiting them. This would be especially functional if the ley lines had predictable qualities to them that would allow her to infer their nature or orientation even on first exposure to them, e.g. lines that flow north/south "feel" similar to each other, but noticeably different from lines running "east/west", and lines that run north-east/south-west would feel like a combination of both. Other possibly qualities could be lines that flow over or through mountains, or large bodies of water, or desert-like environments, large forests or grasslands, etc. Essentially, she ends up with a "feel" for the world and her place in it, where the indicators are only sensible to her with her special sense of ley lines (and a brain capable of instinctively processing the data from that ley sense). In fact, there could easily be others who sense ley lines, but only at a much less refined level, e.g. they can feel it when they are standing in the path of one, but not much else. What would make your character extra-special is her savant-level ability to interpret what her ley sense is telling her, combined with, perhaps, a much-better-than-average ley sensing capacity (akin to being a "supertaster"). [Answer] You dismiss the idea that this is based on her language using cardinal and not relative direction because you want this ability to be limited to only a few rather than widespread This does not follow If the language in question is dying, your heroine could easily be one of the last remaining native speakers, and so one of only a very limited number of people (the rest of whom may be too old or frail for adventuring) with this skill She obviously would need to speak at least one other language (that of her neighbours), but this is not unusual; the average human of our world is multilingual, and was even more common in the past [Answer] You've got flying Dragons and potentially advanced steampunk, so we're already happily sitting in fantasy land. The ability to know where things are could simply be an innate characteristic that the character themselves neither understands or can explain, but they just trust it. Such an ability can be seen in Tristran Thorn in both the Stardust film and novel. Tristran knows where everything is in the land beyond the wall, because he's the rightful king. But how the ability works is never explained, it's just used to let Tristran know his way around a country he's never been to before. [Answer] ## She can sense the matrix Many scientists are confident that we are [living in a simulation](https://en.wikipedia.org/wiki/Simulation_hypothesis). You claim that there is magic in the world, in fact she is living in a simulation and magic is nothing more than the ability to manipulate the simulation in ways that are outside the realm of normal activity. Her sense of location is nothing more than awareness of the matrix. She need not understand nor be aware of this awareness herself. It could just work for her - just as others have claimed in their comments. Spooky. [Answer] You ruled out the planet's magnetism field but why not use any of the other cosmological fields? Consider for instance <https://www.youtube.com/watch?v=zNVQfWC_evg&feature=youtu.be&app=desktop> ]
[Question] [ I want to portray a culture with a significantly different method of perceiving their own mathematical concepts, yet not so as to say something like just "they used a kind of number very often, that is almost never used by [insert name of relevant other culture(s)]." I could bore the audience to death by going over random abstract nonsense from set theory or category theory or whatever, and probably will at least injure my audience by this means, but my question here is: **are there systems of numerals (not numbers) where the difference is not in the symbols but the colors of the symbols?** E.g., let 0 = ***X***, then 1 = the same shape but in red, 2 = that in blue, etc. Let's say then that 8 = the same symbol but in light gray, so there are nine numerals. I'm not sure if this is feasible, but I'm guessing we might then have ***XX***, in dark gray/black, for 9, then the double-*X* in red for 10, etc. So, are there real-world languages that have this feature? Or, are there conlangs, maybe, that involve this construction? In Conway and Guy's *Book of Numbers*, for example, they introduce some quirky things called "nimbers" (for the game of Nim or something) and mark them out by Arabic numerals except colored red specifically, and I don't know if that was purely for the sake of convenience or if it was meant to signal a kind of difference between nimbers and non-nimbers that, even if not color-based *in abstracto*, is obscurely similar enough to a difference of coloration so as to explain the coloration decision in the text. I guess my question more specifically is: have color-coordinated numeral systems been designed, and then shown to be either workable or unworkable? I'm not sure why the related culture would have even come up with this system; a placeholder idea could be that they associated darkness with nothingness = zero, though this suggests that they would have chosen white for infinity instead of 8. I mean, I did say they'd have 8 as light gray, not white, at least because it'd be impossible to read white text against a white backdrop. Maybe clear white would be for infinity *because* it's impossible to read (against the expected backdrop). At any rate, if this idea has already been explored IRL and shown to be relatively impossible as an effective form of numerical communication, I would have to scrap the idea of some culture emphasizing such a notation system (presumably, if some culture tried the system out, they would have either failed more broadly because of their use of this system, or they would have abandoned it). [Answer] # If the colour distinction of the species is large enough Communication works or fails by distinction clarity. We use speach and writing, because we can produce sounds and visuals that can be understood with clarity if learned. Colours should be no different, as long as the distinction is clear and we can reproduce it. It might already be possible with our eyes. Many artists or designers have a great range of colour distinction. This is gained mostly from experience. Most people will be able to learn that a certain shade or shade range is a certain number. You might think that some variables will make it impossible. Light can change the colour drastically. Morning-, day- or evening light all produce different colours. Not to mention that candles or light bulbs have a wide range as well. However, with experience this can be overcome. Just like you can understand someone talking to you in several circumstances. Crowded room, with a vacuum cleaner on or a silent room all influence the sound quality. It isn't foolproof, but it is certainly workable. [Answer] In fact, we do use color-coded numbers a lot. The [electronic color code](https://en.wikipedia.org/wiki/Electronic_color_code) is a well-known (but by no means exhaustive) example, widely used for indicating the values of resistors and capacitors. All electronicists know how to read it: [![resistor color code](https://i.stack.imgur.com/KmQUq.png)](https://i.stack.imgur.com/KmQUq.png) ([image credit](https://eepower.com/resistor-guide/resistor-standards-and-codes/resistor-color-code/#)) [Answer] Usage adapts to the allowances of the writing system, not the other way around. That is, if we have a conflict between the "right way" that we want to write things, and the practical way that we can write things, practical wins. That's how we get shorthand and abbreviations. That's how Þ became the Y in "Ye Olde Shoppe" (because Belgian printers didn't have typeset Þs) and how German oe became oͤ became ö (because they were successively easier to write) and then back to oe (because it was easier to print on English-language computers). Unfortunately, as others have pointed out, colored symbols are really annoying to write in ink, because in pre-industrial civilizations, inks and dyes are really expensive (especially blues and purples; reds and browns are usually easier to get ahold of) and tend to fade relatively quickly, and it's hard to get consistent lighting when you're largely at the mercy of the sun and firelight. So in situations where precision is important - like your tax records, for instance, or your census - scribes will be tempted to add little annotations. Not numerals, of course, the numerals are still there in living color, but *reminders*. Say, reminding you that a particular number is written in red, and not orange. Even if it starts to go a bit orange in the sun. Or apologizing to the reader for saying "green + yellow" everywhere instead of "purple" but, have you priced purple ink these days? Things like that. The problem is - because this shorthand is far more convenient to read and write than the colored numerals, and because it's capable of expressing all the ideas that colored numerals can - it will generally tend to displace them over time. People will get so used to reading and writing the annotations instead that the numerals themselves become vestigial and are eventually forgotten. [Answer] The main problem with this is that it's more complex for no reason. Sound writing systems can distinguish between different components easily. On paper, colors are easily distinguishable enough, but... **What do they do if they don't have the ink to write down number X? What about individual perception of colors, period? Colorblindness would make reading said system impossible, and some people perceive shades of red differently!** That isn't to say the system doesn't have its merits, as by using colors could achieve a much higher information density. Essentially you'd be going from base 10, like we have, to base 16 million (roughly the amount of colors in the RGB color space). Impractical, but could have merit in some edge cases once your civilization goes digital. [Answer] There are some Terran natural languages (or better, cultures) that use some rudimentary colo(u)r coding of numerals. One is the use of [counting rods](https://zh.wikipedia.org/wiki/%E7%AE%97%E7%AD%B9) in (ancient) China, where the positive numbers were marked by red, and the negative numbers by black. The other is the "modern" accounting practice in the "western" world, where the negative numbers ("debt") are sometimes written in red, and the positive numbers in black or blue. IMHO this is historically more limited by the colo(u)rs of available ink - dark blue or black is the default, and you can get red one cheaply (by pissing on lead plates - yes, really), but having any other bright, outstanding colo(u)r is rather difficult. [Answer] Human numeral systems are all quite old, and pre-date the availability of a full range of coloured inks at low cost. That's a fairly recent development, starting with the rise of chemical synthesis in the late nineteenth century. So no widely-used human system of numerals uses colours. I recall an educational toy that was used in the UK in the late 1960s and early 1970s, which had wooden blocks of different lengths, in colours related to their length. The idea was to give children something less abstract than numbers to count and do basic arithmetic with. It was not a success, and did not continue. [Answer] Any culture that values (or thrives from) precise numeric/mathematics will always have multiple way to express their numbers. For example in English, we have: * 0123456789 (often called Arabic numeral) * one-two-three-...- eleven-twelve-thirteen-... twenty one - twenty two - ... (spelled number) * distance three-zero-five mikes (radio/aviation speech) * XII (roman numerals) * tally marks <https://en.wikipedia.org/wiki/Tally_marks> * charts <https://en.wikipedia.org/wiki/Chart> (image taken from wikipedia) [![charts](https://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Composition_of_38th_Parliament.png/440px-Composition_of_38th_Parliament.png)](https://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Composition_of_38th_Parliament.png/440px-Composition_of_38th_Parliament.png) * heatmap chart <https://en.wikipedia.org/wiki/Heat_map> (image taken from wikipedia) [![heatmap-charts](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Heat_map_-_Normalized_Linkage_Disequilibrium_of_Genomic_Windows.png/440px-Heat_map_-_Normalized_Linkage_Disequilibrium_of_Genomic_Windows.png)](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Heat_map_-_Normalized_Linkage_Disequilibrium_of_Genomic_Windows.png/440px-Heat_map_-_Normalized_Linkage_Disequilibrium_of_Genomic_Windows.png) * colored cartographic maps <https://en.wikipedia.org/wiki/Wikipedia:Coloring_cartographic_maps> (image taken from wikipedia) [![map-charts](https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/2017_UN_Human_Development_Report_Quartiles.svg/520px-2017_UN_Human_Development_Report_Quartiles.svg.png)](https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/2017_UN_Human_Development_Report_Quartiles.svg/520px-2017_UN_Human_Development_Report_Quartiles.svg.png) And in non-English language, they may have their own numeral system which may be used interchangeably with Arabic numeral like Chinese or Japanese; which if the number is small enough they use 一 二 三 四 五 六 七 八 九 十 ..., and if it's very long, 1234567890 is used instead (e.g.: representing money). So, regarding your question if there can be culture that represent their number in color instead of in symbol. Then the answer is yes, our culture already done it, not exclusively though. As I claim in the opening (reworded): any culture that values (or thrives from) precise numeric/mathematics will NOT USE ONLY ONE WAY to express their numbers. Our own culture does not represent number EXCLUSIVELY in symbols, but in multiple form. Quoting your question: > > > > > > are there systems of numerals (not numbers) where the difference is not in the symbols but the colors of the symbols? > > > > > > > > > Yes there are: it's called charts [Answer] ## ... in a way ... When we talk about numbers, mostly we mean [natural numbers](https://en.wikipedia.org/wiki/Natural_number) ($\mathbb{N}$) or [integers](https://en.wikipedia.org/wiki/Integer) ($\mathbb{Z}$). Those are 1, 2, 3, ... and ... -1, 0, 1, 2, ..., respectively. Sometimes, we mean decimals or [fractions](https://en.wikipedia.org/wiki/Rational_number) ($\mathbb{Q}$). Those have been known since antiquity, in some societies with decimal notation and zero and in some without it (complicating arithmetic). It takes some pretty sophisticated reasoning to come up with numbers in between the fractions, which leads to [real numbers](https://en.wikipedia.org/wiki/Real_number) ($\mathbb{R}$). The writing symbols for one ("1", "I", and others) and two ("2", "II", and others) can be easily told apart. You can write them in the sand with a stick, on a wax tablet with a stylus, or on a stone with a chisel. If you want to write 1.5, you do not usually write one-and-a-half "I", you use a special notation like $1\frac{1}{2}$. Now imagine a society which rejects the concept of integers as an illusion, and insists that any actual numbers are non-fraction real numbers to start with ($\mathbb{R/Q}$). If one thinks to have two distinct appearances of the same number, that merely means one did not look finely enough, there will be a tiny difference between them. Too small to measure, but it is there because the mortal world is imperfect or some moral reasoning like that. Say you and I are merchants and strike a deal. "Light blue" handfuls of hack silver for "orange" wagonloads of olive oil. I send my teamster to your warehouse foreman, and in the torchlight they exchange "violet" handfuls of hack silver for "brown" wagonloads of olive oil. We go to the magistrate to complain, and the magistrate says "you swapped somewhat blue silver for somewhat red olive oil, the contract was fulfilled, how can you expect divine perfection from your hirelings?" Doing that will of course cripple their science and economy. If a ledger or money order fades in the sun, does that change the amount? How much of a difference is too much of a difference when it comes to selling grain by the pound? [Answer] Not sure if its the answer you are looking for but here is a rabbit hole: Not just a numerical system, but even a Turing-complete [esoteric programming language](https://en.wikipedia.org/wiki/Esoteric_programming_language) that is really colorful: [piet](https://esolangs.org/wiki/Piet) Piet program that prints 'Piet': [![enter image description here](https://i.stack.imgur.com/85HPq.gif)](https://i.stack.imgur.com/85HPq.gif) Based on that, and with some poetic liberties, we can assume a set of nice abstract paintings that would in fact be "programs" with various "functions" including creating fractal numbers, pseudo-random number series etc... In reality, there is such a think as information density and [Shannon's theorem](https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem), which limits the size of a program to the complexity, size, and number/hue of colors of a painting, but the number of colors can be rather large... [More piet samples](https://www.dangermouse.net/esoteric/piet/samples.html) [Answer] I think depending on the biology of your alien species it could work. There are many animals that can change the colour of their skin so completely that they become near invisible. Think the octopus or cuttlefish, as @Kristen Berry mentioned, but there are many others on land and in the sea. To me, this indicates that they can sense colour to a finer detail than humans can. For centuries their lives have depended on their ability to hide. There has also been research on the hogfish from [Duke University](https://today.duke.edu/2018/03/how-color-changing-hogfish-%E2%80%98sees%E2%80%99-its-skin) that indicates they have some ability to sense light through their skin. Perhaps your species could use an ability like the ones in the animals above to sense wavelengths of light (different colours) through their skin. Dealing with numbers could be a hybrid of vision and touch. I envision them doing math kind of like reading in braille while also using their eyes. They could have evolved from a species that had these colour-changing/sensing properties in their distant ancestry. As to the ink problem, perhaps they have used technology to synthesize ink that can respond to signals from their bodies much like an octopus uses a variety of signals to change its colour and texture. That way they could subconsciously direct the colour of their numbers as they work. A system like this seems feasible if you're able to step waaaaaay back from how humans evolved and sense the world. This is a world I would be keen to read about or experience if you are working on something to publish. [Answer] ## Colored tokens as an abstraction layer for counting Colored tokens are extremely useful counting tools specifically because they are not married to a specific numeric system. I could take a set of poker chips and play a game with my kids where white = 1 point, red = 2 points, and blue = 3 points just to keep it simple, and then take the same set up chips to a high stakes poker game and call them \$100, \$500, and \$2500 respectively. The countable chips work the same way no matter how I use them; so, I can use a pocket full of colored tokens to work out all sorts of different kinds of problems. Now imagine you have a highly multi-cultural civilization where you have some people running around using base-6, some base-10, some base-12, etc. Numeric math is largely married to your numeric base and involves a lot of tricks that stop working if using a different numeral system... so the only way to do complex base-16 math for the average person is to count, and tokens make counting super easy. In this way, colored tokens could function a lot like an abacus, but without a fixed number of numerals per row. All I have to do when talking to a person from another background is establish what base system to use, and then we could easily work together using the same base system. [![source : https://www.wallpaperflare.com/poker-chips-on-white-paper-casino-map-play-cube-ace-gambling-chip-wallpaper-wpdzv](https://i.stack.imgur.com/MJgs6.png)](https://i.stack.imgur.com/MJgs6.png) [Answer] No human examples, as color blindness is relatively common in humans. Red Green in men is apparently 14%. So they'd be innumerate and forced to work at Starbox or deliver processed carbohydrates to morons for money. [Answer] Have you read [Can Fish Count](https://link.springer.com/article/10.1007/s00283-022-10221-x), by [Brian Butterworth](https://en.wikipedia.org/wiki/Brian_Butterworth)? There is an interesting discussion of counting practices, including the Yupno counting system from New Guinea: the names of the numbers are names of body parts, starting with left little finger is one; after the fingers the toes are used for counting; after that the sequence goes [21 left ear, 22 right ear, 23 left eye, 24 right eye, 25 nose, 26 left nostril, 27 right nostril, 28 left breast, 29 right breast, 30 navel, 31 left testicle, 32 right testicle, 33 penis](https://hal.science/hal-03598841/document). The Yupno speakers have a gift exchange culture; when it is my turn to give gifts, I need to be able to remember how many pigs you have me last time, so I can reciprocate (Presumably nobody ever gives more than "penis" pigs). This bears on an interesting point: every number system is a solution to a problem; the Yupno system solves the problem of making their gift exchange culture work. Maybe you could consider the problem that your culture is trying to solve. ]
[Question] [ First let's discuss what the heck is quantum tunneling? We know the story of Einstein the Great, his award winning paper on light as particle had received universal acclaims and was plagiarized too many times over the centuries. But it is the wave like nature that allows matter particle to overcome physical barriers, physical barriers here could be anything like electric field you name it. Now suppose something weird is happening right now, every ongoing experiments showed no sign of tunneling regardless the size of barriers... OMG quantum tunneling is broken! What the worst that can go wrong beside having to reprint all the physic textbook? P.S. magic tag is to handwave why quantum tunneling don't work anymore... not that we know why it work in the first place but it's kind of an insurance policy ;D [Answer] We wouldn't notice anything because we would be dead. And with us all life forms. Oh, yeah, that count as "the worst which could happen", I guess. Why? [Quantum tunneling plays a role in cellular respiration](https://en.wikipedia.org/wiki/Quantum_tunnelling#Quantum_biology) > > Quantum tunneling is among the central non-trivial quantum effects in quantum biology. Here it is important both as electron tunneling and proton tunneling. Electron tunneling is a key factor in many biochemical redox reactions (photosynthesis, cellular respiration) as well as enzymatic catalysis. Proton tunneling is a key factor in spontaneous DNA mutation. > > > [Answer] **What the heck is quantum tunneling?** This is key to a coherent discussion of the question. Unlike the name suggests, the phenomenon does not necessitate a repeated interaction, nor does it involve the weakening of the potential barrier. Quantum tunneling is a phenomenon well accounted for in modern quantum theory, in which the phenomenon is built-in mathematically. > > But it is the wave like nature that allows matter particle to overcome physical barriers, physical barriers here could be anything like electric field you name it. > > > The issue with this view is that it incorrectly assumes how modern physics views the quantum world. Particles, as described in quantum mechanics, do not have a "wave-like" nature in the physical sense. The Wavefunction describes the probability of each of the possible "states" the particle may be in. The wave aspect here refers to the built-in limitations on our knowledge of how the particle is going to interact, which is described in probabilistic terms that have the same mathematical form as are those used to describe physical waves (note this does not mean that they are waves, analogous mathematical constructs are common in physics and are never understood to imply a physical connection). Physics does not describe the electrical potential as forming a "physical" barrier. Instead, the "electrical field" is a *mathematical* description of the electrical interaction. Now the above distinction may appear pedantic, however, as we shall see it is critical to a proper answering of the question. > > Now suppose something weird is happening right now, every ongoing experiments showed no sign of tunneling regardless the size of barriers... OMG quantum tunneling is broken! What the worst that can go wrong beside having to reprint all the physic textbook? > > > Since the mathematical theory of quantum mechanics necessitates quantum tunneling, if this phenomenon were to suddenly "turn off", either the theory would change, or math would break. If the theory were to break, the probabilities would change and this would have consequences well beyond the phenomenon of quantum tunneling, instead the entire theory would fall apart. From our theories therefore, it is impossible to say exactly how things would be affected since we would have to reformulate the mathematical theory because the old one becomes broken. In other words...*unless you have a very good understanding of physics (and even then), it is almost never a good idea to modify a physical theory (or even just an equation) and work forwards to the consequences...they will certainly be too numerous and consequential to coherently discuss*. Of course one way to approach the question is to look up all the phenomena that include the phenomenon of quantum tunneling and assume these phenomena wouldn't happen anymore. That is, however, naive from a physical perspective, to understand why it is necessary to look a little at the mathematics of quantum mechanics vs. classical mechanics. Classical mechanics views all interactions through forces (which can be characterized mathematically by energy potentials, this will become important in a minute) upon "particles", which at the simplest level would be would be described by non-deformable masses which fill a definite volume of space. The most pertinent restriction on how forces and particles interact in classical mechanics is described by the conservation of energy: $E = T + V$. For a single particle the total energy is the kinetic energy possessed by the particle added to the potential energy imposed by the forces acting on each particle through each force's energy potential. Quantum mechanics, on the other hand, does not view interactions like this. A "particle" is a mathematical description which describes localized "states" (or collections of information), the best we can do is describe this localized collection of states through guessing information. Our guesses are not random however, we educate our guesses through probability and statistics, which has been found to follow the following equation: $E \Psi = (T+V) \Psi$. The difference is apparent, for a single particle we describe the probability of, say, energy. We first specify a given state. For a given state we can compute a particular energy. The states a particle may have are determined by through the wavefunction. Of course this doesn't mean that a particle can have any energy value, or be anywhere. Take for example the (relatively) simple case of the hydrogen atom which is a classic (pun intended) problem in an undergraduate course on quantum mechanics. The electron's wavefunction (and corresponding probability densities shown as spatial distribution across space) is shown [here](https://upload.wikimedia.org/wikipedia/commons/e/e7/Hydrogen_Density_Plots.png). To understand this idea of multiple states, think of a ball in a normal sized bedroom. Suppose that you had to try to figure out where the ball was. Now the ball could be anywhere, right? Well, if suppose you knew the owner of this room and they were quite tidy, you could guess that the ball is more likely going to be in the closet and not lying in the middle of the room. Quantum tunneling is no different. We cannot know definite things about a particle, for instance, its momentum. When an interaction occurs, we can compute the likely energy of the particle. In our analogy, we might find that the ball is in the closet 99/100 times randomly checking throughout the day, or a particle in a nucleus has an energy of -8 MeV, 99.999% in a given second. However, this is not definite. The ball might end up in the middle of the room during the time the owner takes it out of the closet to juggle for fun, or the particle might have 0.8 MeV of energy and fly out of the nucleus. Thus, since quantum tunneling is an inherent part of quantum mechanics, if this phenomenon were to suddenly disappear, quantum mechanics would falls apart and anything goes. [Answer] **All nuclear fusion would instantly stop - with catastrophic results** Quantum tunnelling is responsible for all fusion processes, including those within our sun. As this is then responsible for the constant release of energy and 'outward pressure' to keep in balance the forces within the sun, this outward release of energy suddenly stopping will enable the gravitational forces of the sun to compress without any outwards pressure, and the sun would go dark and suddenly compress to a very small size. From the earth the sun will blink out after 8 minutes after the phenomenon suddenly occurs, plunging the earth into cold darkness and killing almost all life on Earth. Not to mention all stars in the universe too. [Answer] End of the physical matter, as we know it. Including, but not limited to, the matter our bodies are made of. The nuclear force (the residual strong force, the force holding protons and neutrons in the atomic nuclei together) pretty much requires quantum tunnelling in order to work. No more atoms. Only hydrogen and free neutrons, unable to decay as they usually do. Quantum tunnelling is not a separate phenomenon. It is just an unexpected (from our macro-world viewpoint) manifestation of how the wave-particles in the quantum world behave. That said, it is not really easy to predict what else will break in order to get the tunnelling killed. But I think the above is enough. [Answer] # Most likely nothing will happen. Quantum tunneling is just a theory. It is the way ***we think*** the universe works. **But time and time again the universe has its way to prove us wrong.** So if somebody finds in an experiment that quantum tunneling is **"not working"** anymore, then somebody else will come up with yet another theory explaining why. The OP question could have been asked two centuries ago as **"would anything bad happen if gravity stopped working overnight?"** Einstein figured out gravity (as explained at the time) didn't work sometimes and everything was just fine. [Answer] Given that you want to change physics anyways, there is always the possibility to go back in the history of physics to the point where quantum tunneling was not known. Most of everyday physics was explained so you don't really have a problem. You just need to find plausible explanations for the few unsolved puzzles scientists where thinking about back then. If they matter to you at all. ]
[Question] [ Ancient Man feasted on megafauna. From mammoths to every variety of deer and flightless bird humans have made the most of large wildlife, to the point of tragic excess. So what happens when the animal provides no good meat, no fine furs, and is unsuited for domestication? How would pre-industrial humans exploit a large population of megafauna that they are simply unable to consume? Preconditions: * These animals are toxic for human consumption due to bioaccumulation. * They are the dominant herbivores and are found in abundance. So why would people want to hunt animals that they can’t use for food, and don’t have pretty furs or ivory? [Answer] Bones, Sinews, leather and Glue. No matter what the creature, if it's large, you can make use of it. Megafauna means big. There is a lot of material there, even if you aren't gonna eat it. So the bones. Long bones will provide a building material of various uses, be it a tent support, a handle for a club or axe, or you could use the ribs to make armor. A large animal is going to have plenty of useful bones. Sinews. A big animal is going to have long sinews that will be useful for creating good, heavy duty cordage. It could also be used for bowstrings. Anything that requires cordage that doesn't stretch much. Leather. Even if the pelt is not pretty, it is probably fairly tough. Leather was used for practical stuff long before it was a fashion accessory. Since this is Megafauna, a good skin could be used for a tent. The fewer seams in a tent, the better it can retain heat, so a very large skin is great. In addition, Boiled Leather makes a very good armor. Lets not forget about using the skin for boats. Glue. Animal glues have been in use for thousands of years. Extended boiling of connective tissues renders it down into something strong, light, and even waterproof. Others have talked about territory, competition for resources, and so on. The usefulness of the carcass, even without the meat, gives plenty of reasons to Hunt the beastie down. [Answer] > > So why would people want to hunt animals that they can’t use for food, and don’t have pretty furs or ivory? > > > As long as an animal is seen as a menace, it will be hunted down. And, well, all animals defend their territory if needed. You don't eat a bear, but if you wander around its cubs be sure it will pat you in the face hard with his cute "little" paws. And that pat is a menace for us, so us humans will hunt down bears. That holds for any large animal. And lacking the menace there is always the mindless fun. I have seen hunters shooting down harmless bats just for the sake of testing the freshly cleaned rifle. [Answer] With any animal, there's more than just meat and furs, here is a list of uses of general animals 1. Food 2. Clothing 3. Work/Transport 4. Science 5. Medicine 6. Hunting 7. Pets 8. Sport 9. Art Many of these are removed by your conditions, Furs can still be used even if they do not look very nice Medicine - Not 100% sure how this applies, guess it depends on the type of animal. Even if they are toxic that might still have a use in waging war Science - They could be studied in many applications Sport - Hunting for sport pretty self explanatory Art - Bones can be used as quills? the blood can sort of be used to dye clothing In addition to those you stated that they are in abundance. Due to this they may want to hunt them just to lower their population to make space for farms or other town expansions see [source](https://en.wikipedia.org/wiki/Human_uses_of_animals) for more [Answer] **Reputation**. If the creature is dangerous, killing it might accomplish something valuable to an individual in the community, for example marking the moment a child becomes an adult, or to be considered a fully fledged hunter. [Answer] **Ecological succession.** The Herd rules this world. Where the herd has passed, nothing remains. Thorns and toxins which dissuade lesser herbivores are eaten with disregard. Trees are uprooted and bark stripped. Roots are pulled from the ground. The earth is torn and trampled. The Herd is like a fire, travelling a destructive and voracious circuit around this planet that takes a decade to complete. But the Herd is not a fire. Much of the biomass that was in a place remains in the place - passed in dung and urine, or in the carcasses of Herd members when old or sick ones die. In the wake of the Herd, the churned earth springs to new life. Humans follow in the wake of The Herd. The brambles and shady woods that lie before the Herd are of little use to humans but after the earth has been plowed and fertilized, seeds spring to life and tender shoots and greens grow. Lesser herbivores follow the Herd as well to take advantage of the surge of growth, and these animals make good prey for the humans. The ecosystem of this world is governed by the Herd, which turns over the old and makes way for the new. In this role, the Herd is vital to humans and everything else. [Answer] Anthropologically speaking, when humans have come across an animal that had no useful purpose to us, and that was a threat to us in some way, directly or indirectly, we have hunted that animal to extinction if at all possible. It's what we do. One has only to look at the British Isles for proof of that; bears, wolves and large cats were all extinct on the islands as of the 16th Century, with bears being one of the top priorities of medieval Celts. Bears are only barely trainable if you raise them from cubs, you definitely wouldn't call them domesticated in that state any more than you'd say the same for a cougar or tiger in a zoo, and the meat of most predators went out of fashion as a foodstuff in Western culture centuries ago (though it remains a delicacy among native American nations and in East Asia). And the Eurasian brown bear, close cousin to American subspecies like the Grizzly and Kodiak, is more than a match for even the strongest humans in close combat. So, the Celtic Britons made it a point to kill every one they found, which resulted in the Eurasian brown bear's extinction throughout the British Isles by the 10th Century. Wolves and lynx were lower priorities, more a threat to cattle and sheep than humans themselves, but that threat was still sufficient to cause those species' extermination on the Isles by the Tudor dynasty. The Brits and Irish had subsequently made good headway on the next lower tier of predators, the fox, badger and wildcat, before conservation mentalities gained steam in the late 1800s. Exterminating similar species on the European mainland and in North America was a much bigger ask, and quite thankfully, we didn't manage it entirely before the concept of environmental conservation and the continued dependence of man on the wild food web became mainstream about the turn of the 20th Century with the development of groups like the SPCA and Sierra Club. The UN CITES treaty and member nations' implementations of it such as the US Endangered Species Act have stemmed the tide on systematic hunting, but there's still more of it than we want there to be, and prior to these efforts we made quite a go of it. --- So, back in your world, a large herbivore that is poisonous to eat by a mechanism not destroyed by cooking (at least not without destroying the meat itself), that is not domesticable in any meaningful way as a working or fur-bearing animal, and that is in any way threatening to humans even on an "I'm standing my ground to protect my family group" basis, is going to find itself on a shortlist for extermination in any time period prior to about the early 20th Century of the real world. Anything that can tolerate these herbivores' toxin and so preys on them for food is probably a threat to us and our domestic livestock as well, so depriving them of a primary food source and putting pressure on the predators' numbers is just another benefit to having the toxic herbivores gone. Even in more enlightened times, anyone saying the toxin could be the cure for cancer is likely to be shouted down; if the species is preserved at all it would be purely for the sake of conserving a diversity of wildlife. [Answer] **Competition** If the megafauna eats plants that (much more tasty) domesticated herbivores eat, then it's a safe bet that the megafauna will be either driven off the land or killed. [Answer] **TL;DR: The materials in their bodies are great for uses other than consumption.** Here are their uses: 1. **Furniture.** Due to their size, they will by necessity have large bones. The size of the bones would make them useful for making furniture. 2. **Weaponry.** The abundance of useful bones will also make it really easy to make bone clubs and hammers. These will probably be abandoned once your culture reaches gets firearms, but they will be very useful early on. 3. **Leather.** Here's a useful Fact of Life: The bigger your creature, the more tough its hide has to be. As a result, even if leather made from the pelt isn't pretty, it will still be incredibly useful for things like tents and armor. 4. **Glue.** Depending on the physiology of your hypothetical megafauna, its tendons could be useful for making glue. As a result, you're human society would not need to send [horses to the glue factory.](https://www.straightdope.com/columns/read/1860/are-horses-really-made-into-glue/) This would jibe well with animal lovers. 5. **Bug repellent.** Chances are, if your creature is poisonous to humans, it will also be poisonous to other things. As a result, I would not be surprised if your hypothetical society uses your megafauna's blood instead of DEET. Of course, this would be really messy, but there have been [some pretty nasty bug repellents](https://en.wikipedia.org/wiki/Castor_oil) over the years. [Answer] # Competition The animals tend to eat whatever humans are growing in their fields. It's not fun to lose the year's harvest and have your family starve because of some quadrupede bugger, so you off them on sight. Fences would normally do to keep animals away from the crops, but this is megafauna we're talking about. So hunting is the next most viable option. [Answer] **Food for a domesticated species which assists humanity with hunting.** Dogs can safely eat food which would kill humans. They can also be used as hunting aids. We don't want the dogs to eat the good animals, and the herbivores in question are too large for dogs to kill, so humans kill your megafauna to provide sustenance to their hunting companions. [Answer] Somebody sed using the fat as fuel; don't forget whales - fat used for lamps, and it used to be a component in WD-40. There's one more: If I park a bear in my front yard, I expect the number of robberies to markedly plummet. Foo you say, but Guard dogs... Drug sniffing dogs. Hunting should include hawking; not really mega? I don't know if any hawkers have ever tried to train a condor... it would make an awesome plot element in a fantasy novel anyway OH, and in the Island of the Blue Dolphins the girl used whale ribs as a fence. And in Star Wars: The Empire Strikes Back, they got inside the carcass of a big animal to keep from freezing to death [Answer] I like the other answers. Buffalo were shot by the thousands from trains that were just passing through, just to see if you could bring down a buffalo in one shot. Many buffalo hunters only took the tongues. The herds went from millions to thousands in just a few years. So why do it: fun, sport, excitement, practice with a gun, etc. The majority of large predators were killed in Utah as it was rapidly settled and the predators were a threat to people's herds. Brigham Young sent Porter Rockwell and a large group of hunters out to get rid of the pests. The populations of cougars, bears, wolves, etc. were seriously depleted within half a year. -Porter Rockwell, a biography So, why do it: to protect your flocks and way of life. [Answer] **Secondary Products** Agriculture took a quantum leap when adult humans adapted to be lactose-tolerant. Analogously, the secondary products of megafauna--those that can be sustainably harvested--could prove to be more valuable than meat or motive power. Megafauna may be sheared for natural fibers, or milked, bled, sweated, devenomed, or sampled for valuable genes, enzymes, hormones, etc. [Answer] **Transportation and Construction** A rule of thumb is humans mostly domesticate animals to do things we can't. Horses run much faster than we can. Cows turn grass into edible food (either as milk or meat). Dogs can smell and hear things we can't. Cats catch small rodents. The tricky thing about megafauna is it's difficult to domesticate them because they need so much food. It's honestly a miracle that aurochsen were even domesticated because of their size they are hard to contain, eat a lot, and very aggressive. Supposedly the early European domestic cow population just barely avoided dying out due to inbreeding because of how hard it was to keep aurochsen (I have no idea if the same happened in India with the zebu). The big advantage that domesticates megafauna would bring is as living heavy machinery. Transporting heavy loads, helping to construct things, living war machines. A lot like what elephants did throughout history. Humans woule have loved to domesticate elephants but they couldn't since elephants breed slowly, don't reproduce well in captivity, mature slowly, and the males have a tendency to flip out and attack people around them during mating season. But the only real deal breakers there are "hard to breed in captivity" and "aren't reliably non-aggressive". So they could only tame them sporadically. Indeed having domesticated megafauna around might cause a civilization to advance in unexpected ways because they are no longer dependent on human labor, teams of horses, or the post-industrial inventions of backhoes and cranes to perform large engineering projects. There actually are cases of humans making use of an otherwise toxic organism. Tomatoes and potatoes are delicious but every other part of them is toxic due to them being close relatives of nightshade. Edit:Didn't see the "can't be domesticated part". If that's the case they might just die. It's true they might be useful as building materials, but humans have had a tendency to overexploit wild species used for building materials (i.e., bison, beaver hats) simply because of the tragedy of the commons. If you have a post-industrial society they might be allowed to survive for conservation purposes, or because they are a keystone species whose actions (opening up forests, fertilizing the land with their poop) benefit other species that humans use directly, and so it benefits humans to keep them around. [Answer] Why not use it as weapon? They may not be domesticated but they sure can be herded (using fire/spears/words that hurt their feelings) towards your enemies. And then set them into stampede mode. For instance, set a few on fire and force them to run towards the other side's lines/towns. [Answer] Rare medicinal/therapeutic compounds, real or imagined, are good excuses to hunt any animal with abandon. The white rhinos in Africa just went extinct because their horn is believed to contain a strong aphrodisiac. [Answer] Circuses, rodeos, zoos, conservation tourism. A remarkable creature that seems to serve no other purpose can be used as an attraction. People love to question what they don't understand. Or for science--limitless possibilities there. ]
[Question] [ In a galaxy far far away... M6760 (I made it up) is an unusually massive neutron star billions of light years away and it is surrounded by a spherical Dyson sphere painted in new improved formula vantablack called Perfect Blackbody 2.0 (trademarked & copy rights) using alien tech of course (actually it is depleted carbon nanotube). So from Earth perspective, how can we tell that is it not a blackhole using modern day technology? [Answer] When we “see” a black hole or neutron star, we don’t see the actual body itself — they’re much too small, as well as black holes being black. So there’s no point messing around with Dyson spheres and black paint, because none of that will change what we see. We detect both black holes and neutron stars from their effects on the nearby matter and light, and none of those will change because of what you’re planning. [Answer] I'm surprised no one has mentioned this. Your ultra-black Dyson sphere is easily distinguishable from a quiescent black hole or unnaturally cold neutron star by one major thing, if you're close enough to tell those two objects apart: It blocks out too many background stars. That is, your Dyson sphere, to avoid having surface gravity too great to support itself, will be many times larger than the neutron star, never mind the event horizon of a black hole. Whatever means you use to spot it (IR blackbody radiation, reflection at wavelengths your upgraded Vantablack doesn't absorb), by the time you can detect anything but gravity to know there's something odd, you'll easily be able to tell that, black as it is, it’s FAR larger than anything that should be that black. [Answer] Vantablack doesn't reflect light, but it'll still have black body radiation based on temperature. It may be far into the infrared, but the black body curve is a signature we can recognize from a distance. [Answer] Fair chance this Dyson Sphere is larger than the Golden Gate Bridge. Once you're at that size, painting it is not an *event* so much as an *ongoing activity*. You start at the Presidio, and by the time you reach the Marin Headlands, the paint where you started is at End Of Life, and you must start over. I don't know how big Dyson Spheres are, but probably big enough to probably warrant *at least 5 or 6* paint gangs. So it won't look like a black hole, it'll look more like a black melon. [Answer] We mostly identify black holes by the effects of their gravity on surrounding bodies, and the behavior of accreted matter. We have an idea of where the limit is for the mass of a Neutron Star. If we assume the obscured Neutron Star is mostly isolated from enough dust and gas for the accretion to be noticeable[1], we'd suspect based on the apparent mass. I suspect we'd find it very interesting, even if it is the maximum mass allowable for a Neutron Star, and would search for it to be sure we don't need to change our models. At which point, the question becomes exactly how faint the enclosure can make any radiation that tries to escape, because it is highly unlikely it could be perfectly opaque to all wavelengths. [1] What happens to the enclosure if an accretion disk does form? It depends on the size and other properties of the enclosure, but my guess is that it would eventually get hot enough to have a detectable infrared presence, so I have to assume it's *relatively* "clean" space, and we "only" have to worry about radiation from inside heating it to a detectable glow. The main thing to worry about is that there will be heat, and it must go somewhere. Either your enclosure will radiate it, or it will be destroyed by it. There are also other things, like polar jets etc that Black Holes give off, which it *might* be able to fake, but in the end, you need a way to hide the heat, and obfuscate the mass. Given the above, you need a very massive, very cool Neutron Star, without a lot of accretable matter in the vacinity, and to design your enclosure so as to make any remaining heat difficult to detect, and to deal with any other radio signatures that would distinguish Neutron Stars from Black Holes. Deviate from any of those, and astronomers can probably tell what's up. Infrared and weird behavior of accreted matter, combined with apparently having too low a mass for a Black Hole, will get speculation going. It'd be very difficult to get just the right mass, *and* hide the heat, *and* get any necessary radio shenanigans just right, *and* deal with accretion realistically. The more realistic you want the disguise, the more complex your enclosure becomes, and then you have the risk of someone seeing it from just the right angle to notice that something's off when it passes in front of a star. [Answer] # Curvature Mass bends space. A large dyson sphere encircling a neutron star at the high end of the mass spectrum will bend light differently to a black hole. The dyson sphere would have to be constructed in such a way that its mass was uniform in all directions done the planck length. Otherwise one side of the sphere will curve light more than any other part of the circle seen from earth. # Jets Black holes, and Neutron stars produce jets of accelerated matter at their poles. The energy imparted into the jet informs us of the strength of the thing accelerating the mater. Needless to say Neutron stars accelerate mater to very different energies compared to blackholes. [Answer] The gravitational lensing creates a ring of light around the [photon sphere](https://en.wikipedia.org/wiki/Photon_sphere) of a black hole. A neutron star wrapped in a Dyson Sphere has less mass in larger volume, so it causes much less gravitational lensing and therefore won't create this effect. The distortion of background around it will also be much weaker. [Answer] Vantablack absorbs visible light by trapping said light in its carbon nanotubes, and that light eventually dissipates into heat, so as @dspeyer said, infrared sensors could be used to detect this change in heat/temperature whereas a black hole would not be detected by this method/observation. [Answer] If you cover the black hole with a Dyson sphere you can't tell them apart. The Dyson sphere would have to be large enough to have the accretion disk inside. You are just left with the gravitational effects. At any reasonable distance, you only see the total mass because the stuff inside the sphere will be roughly spherically symmetric. You could tell that it is not a neutron star if the mass were too large for it to be one. ]
[Question] [ **Closed.** This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- You are asking questions about a story set in a world instead of about building a world. For more information, see [Why is my question "Too Story Based" and how do I get it opened?](https://worldbuilding.meta.stackexchange.com/q/3300/49). Closed 7 years ago. [Improve this question](/posts/66708/edit) Let's say we have a simple Telepath (mind control and reading). This Telepath is not interested in being a superhero. He doesn't want to mess around with stopping criminals and stuff because he has a moral code that would prevent him from using his powers on them. Instead, he wants to help homeless people by giving them large sums of money. However, he needs to get said large sums first. Our Telepath is too impatient to get money the honest way, but his moral code prevents him from just ordering people to give him cash. How can the Telepath steal money morally? **Moral Code:** 1. Don't hurt people unnecessarily 2. Help people as much as you can 3. Don't reveal that you're a telepath 4. Never use your powers on **anyone** without their permission Edit: To clarify, Rule #3 refers to revealing your abilities to the world as a whole. It's okay to reveal it to people individually, because no one would believe them if they blabbed since 'telepathy is not real'. [Answer] The only possible way to get money while respecting this ridiculous moral code would be to **become a magician.** Not only would you be able to easily get permission from the audience to "read their minds" (that is why they came to see your amazing magic show) and you wouldn't have to reveal that you were a true telepath (*because magic isn't real, silly! It's just a magic trick!*) but you would also be able to make many millions of dollars (David Copperfield makes about 64 million dollars per year) totally legally, without stealing it from anyone. You might say that it is rare for magicians to make so much money and it's unlikely you would be able to succeed. However, unlike all these magicians you actually can read minds. The shows would literally be **amazing and awesome**. If some tricksters can be successful, so can your actual telepath. Oh, and entertainment can be very helpful for people. You would thus be able to firstly entertain (and thus help) your audience, the people who'd watch you virtually and then also financially help all the homeless people you could give money to. [Answer] Drop the stealing and go for an honest way of earning money. ANY theft would breach this guy's code as it would have a negative ripple effect. For example: Steal $1000 from a store owner. To make his loss back he will have to inflate his prices, drop his workers' pay or sell inferior products. This gets worse when you steal from criminals. So lets look at ways that actually help people: Under the guise of hypnosis your guy could use his powers without breaking rules 3 and 4 (Real life hypnosis is voluntary so the person would have to agree to the procedure anyway) you could do the following: 1. **Human lie detector** - The person being interrogated could even sign a waver allowing all humane lie detection techniques to be used (this fine print allows Telepathy) 2. **Trauma Councillor/Psychologist/ Spiritual healer** - If you can order people to give you cash, you can order them to forget their pain - this would be in massive demand. 3. **Criminal Rehabilitation** - Overwriting convicts' minds to make them good people again (With their permission in exchange for reduced sentences). Government saves on prison costs, convicts get a fresh chance at life. 4. **High Profile Addiction Counselor** - As pointed out by **Mark Ripley**'s comment, the telepath could make 1 percenters' and celebrities' addictions disappear instantly and charge crazy amounts for it. [Answer] Become a Psychologist that specializes in corporate officers; you can ask if it is okay to read their mind; charge them for it, help them, and then make insider trades based on what they know. [Answer] Step 1. Build a web site. One with the standard "By continuing to use this web site, you agree to the terms and conditions" banners. Make sure your T&Cs contain a clause about allowing users to have their minds read. Make the clause humorous, like "I give permission to have my mind read unless I'm wearing my tin foil hat." Nobody would suspect actual telepathy from that. Put on some entertaining but harmless content. Step 2. Plant a telepathic suggestion that makes visitors come back and point others to your site. Step 3. Once your visitor base is massive, plant two more suggestions: An inability to lie *if the lie is purely for personal gain*, and a compulsion to donate all money made by *knowingly using unethical means* to charity. Step 4. Sit back and watch what happens to politicians and their minions in particular. [Answer] Gambling would be one way, there are plenty of games like poker where the ability read the dealer or other player's minds would be a huge advantage. The character might also find taking money from casinos one of the easier things to square with his moral code. The problem with using telepathy to make money directly is that for practical uses you first need to convince people that it is real and effective and that they information you give out is honest and reliable. While this might work in the long term it would take a lot of time and effort to establish that level of reputation. Even with magic, even if you really can read minds a lot relies on showmanship and having the reputation and resources to put on big shows and the marketing to capitalise on it. Ironically being able to do 'real' magic might not guarantee a successful career as a magician, especially if you want to keep the ability secret since you can't do anything *too* impossible. Point 4 make the t ask very difficult and indeed if you need *permission* to read peoples minds that isn't very different from just getting the to tell you what you want to know. You can't even use it to prove whether people are telling the truth or lying and you can't prove that what you claim to have read in their minds is true. Also as mentioned in one of the comments rules 3 and 4 are mutually exclusive, how can you ask permission to do something while keeping it secret ? [Answer] **Start a cult** Model it after the present-day cults that make their followers spend huge amounts of money in order to improve themselves, and make "Share your thoughts with me!" a motto of your cult. Your mind reading skills will help you to empathize with your followers, your mind control will allow you to influence them to create a positive feedback loop - your followers find that they follow your advice, and get better. **Hide your actual powers in plain sight** Be very open about your powers. Describe them as a gift given by a higher being. This will attract sceptics who'd like to disprove your powers - so you openly invite them to a session (or discover that they're sceptics if they don't announce themselves)... and then you deliberately fail to impress them. [Answer] Become an interpreter and specialize in people with speech impediments or complete inability to form audible words. Yes it's 'honest money' but it could be *really really good money* since you could do what few others could. [Answer] A potential work-around for rule #3: if the main character is just painfully unaware of how they present themselves in public and/or is a stupid person, then they can do anything and just not realize it. [Answer] I think working as a "life coach" or something like that would work. The telepath could bypass people's fears with his mind control powers and the people he helps know about his abilities. For example, if someone isn't able to speak to woman he could control him and help him do so. Same for fear of heights, dogs,... [Answer] Maybe hang out with drug dealers. Use mind reading to find the ones who don't like what they do and want out. Offer to help them, and keep all the drug money that's left over. This initial part doesn't violate rule 4 as the money they leave behind will be available for claiming. Riffing off the councilor thing, I also bet that rich folks with troubled kids (or even who are troubled themselves) would pay a boatload of money for somebody who can council or (potentially, if they consent) brainwash them. Now if you can be a bit squishy on Rule 4 for the greater good: I would argue that robbing drug dealers and using mind control to rehabilitate them WOULD be a moral thing to do because it helps them AND everyone else their actions hurt (also, say, robbing terrorists). You'd basically make the argument that it's saving lives and is for their own good. Still, if Rule 4 is hard then this paragraph wouldn't work. [Answer] Have people pay for you to take control of their body and do something they don't want to do, i.e. exercise, public speaking, work. [Answer] Become a con artist. Consider the show **[Leverage](http://www.imdb.com/title/tt1103987/)**, for example. If you inserted a telepath on their team, this person could easily grift without ever breaking the code. > > Don't hurt people unnecessarily > > > This part is easy. The team specifically targets people who kind of "need" to be hurt. Some corrupt CEO wants to allow thousands of people to be killed to protect his bottom line? Using your powers to his detriment helps the greater good. What you deem as "hurt" and what you deem as "necessary" are both subjective, and mind control allows you to perform a lot of useful manipulation without doing any harm at all. > > Help people as much as you can > > > Again, easy. The team saves thousands of lives, recuperates devastating financial loss, etc. > > Don't reveal that you're a telepath > > > It would be tricky to hide this ability from the team itself, but hiding it from the mark wouldn't be excessively difficult. The key would be to keep manipulations subtle, just giving people a tiny push so you hook them when they're on the fence, or using it to read people like no one else can. The mark would be an open book. > > Never use your powers on **anyone** without their permission > > > This rule is obviously the trickiest, for any solution. But as a grifter/con artist, it's a confidence game. That's your job is to get them to trust you. It all depends on how explicit the permission needs to be. If you literally need them to say "Yes, you can read my thoughts", or "Yes, you can take control of my mind", then very few solutions will work. But if you can ask something like "Show me the real you" and use a positive response as permission to read their thoughts, that will take you far. You could also get yourself into position as their advisor and then ask them to "Let me guide you." I'm sure a grifter could come up with clever ways to get the mark to give permission. [Answer] Since the very nature of business IS theft (for example hire an employee at $\$10/hr$ while he generates $\$30/hr$ for you - standard practice, by the way), AND business is "legal" use the councillor of business idea simply to learn how to do business, and then go forth and Steal, steal, steal! ( just like they do) havagooday ]
[Question] [ In my world, trains are the most prevalent form of transportation. Immense subway systems are used to transport people, livestock, and other goods throughout the world. Street level, trams, bicycles, and moving sidewalks are the most common methods of getting around. Besides law enforcement, taxis, and transportation for very important people (politicians and such), cars are not common at all and are heavily regulated. Most people do not know how to drive and those that do need to take extensive courses in order to be licensed. There are illegally produced cars, but they are more common in rural areas. Getting caught with one can land you in jail for a few months/years. Here's the issue: how could criminals move around in such a world? For example, say members of an organized crime group commit a bank robbery, how would they escape with a large sum of cash? If they try to ride a train or tram, they would be very obvious to any law enforcement agent who happens to see them. If a gun fight erupts between two opposing factions, how could they make a quick getaway? The technology level in this world is futuristic. Nuclear, solar, wind, and hydropower are the prevailing forms of energy. Railguns are common. Genetic alterations are not common but do exist. Air transport does not (more an aesthetic choice). [Answer] The key in such circumstances is disguise rather than some different form of transportation. Convince the ID system that you are someone else (or better yet, convince it that you are actually somewhere else) and just go about quietly rather than draw attention. [Answer] * **Impersonate/subvert legal transportation** Presumably there are fire engines, ambulances, garbage trucks, delivery vans, moving companies, and even a few licensed cabs. Get one, alter the license plates or transponder or whatever, and prepare for a shell game to get lost. The getaway planning would have to be extensive, but the expected haul of the heist might be worth it. For a high-profile case, take the vehicle to the entrance of a big subway station and burn it there, perhaps repeating several cycles to shake of CCTV trails. * [Parkour](https://en.wikipedia.org/wiki/Parkour) Possibly connected with the one above, serious criminals train how to cross and exploit urban obstacles. Obviously the police train for pursuit on foot. Who munched more donuts lately? * On a small scale, **skater gangs** Small-time muggers or pickpockets use something like a skateboard. It might be *illegal* to use it on a sidewalk, but it might also be *common* enough as a misdemeanor by rebellious teenagers that mere possession of a skateboard is not effectively prosecuted. [Answer] /law enforcement, taxis, and transportation for very important people/ **Use one of these.** If you don't want your criminals to melt into the crowd or drop into the sewers, have someone come pick them up. You already said who it will be. One gang is in cahoots with the law. Another gang has a sponsor who is a princess. You are not allowed in her car if you have recently been in the sewer. Lone wolf has a cousin who is a cabbie and who chews him out each time she has to come get him, but she always comes and gets him. Until she gets hurt and his aunt comes instead, which all involved hope does not happen ever again. [Answer] You don't mention ubiquitous surveillance cameras, which would presumably be able to track suspects (whether in a car or not) during their getaway, until they enter a non-public space. It's not clear what you see as the big difference between cars and the other forms of transport you do allow. Raw speed doesn't seem that important -- in fact, you allow bicycles, which can be as fast as cars on today's congested city streets. Your scenario seems to be that criminals aren't being chased or tracked immediately from the crime scene, but could be spotted by someone who thinks they look suspicious. > > For example, say members of an organized crime group commit a bank robbery, how would they escape with a large sum of cash? If they try to ride a train or tram, they would be very obvious to any law enforcement agent who happens to see them. > > > Consider thinking further about what would make suspects "obvious". Their stolen cash could be in backpacks or duffel bags that are not inherently suspicious. Are you picturing that all public transit would "scan" everyone's bags like we do at airports today? To understand what criminal activity looks like without cars, you can look at: * Fiction and nonfiction portrayals of urban crime up through the early 20th century (before cars were common) * Modern life in places like New York City where most people don't drive (only [25%](https://archive.seattletimes.com/archive/?date=20030820&slug=drive20) of people have a driver's license). [Banks do get robbed there and suspects sometimes take the subway like everyone else.](https://abc7ny.com/bank-robber-fall-subway-platform-astoria/5728202/) [Answer] In such a society, the robbery would occur via "futuristic" means, not by walking into a branch and getting cash. In fact, cash might not even be used. You are ignoring the most common form of bank robbery today - electronic cyber crime. The biggest worry that bank security people have today is the worry that the international interbank transfer network has been hacked. (No you won't find any discussion of that in the media because it is such a scary proposition. The real worry is that it has already happened.) There have been a couple of multi-million dollar false transfers on that network because of one node being not as secure as the rest of the network. There have been a lot of ransomware attacks recently. The gangs have gotten millions that way. Have you heard about any banks being attacked? No. Because the banks keep that very secret, not that the attacks haven't happened. A few years back, there was a coordinated attack on a major bank ATM network. All around the world, people walked up to ATM's and entered a specific code at the same time which allowed them to start pulling money out fast. It took the bank 20 minutes to identify that it was happening and shut it down. But in that time, the gang got millions. In short, only small time criminals try to rob cash out of a bank today and in the society you design. That is a problem for the local police and the explosive dye packet in the cash will help identify the criminals. The real criminals use the networks that replace cash in your society, never walk into a bank, never have to make a get away, and may be in another country where the police of your society can't touch them. (The banks may hire a group of ex special forces to deal with them.) [Answer] **Never underestimate the value of a good distraction** One of the more clever aspects of the first *Mission Impossible* movie was the theft of data from the CIA in Langley, VA. Yes, most of the screen time was given to Tom Cruise hanging from a wire while ripping off the identical scene from the 1964 film *[Topkapi](https://en.wikipedia.org/wiki/Topkapi_(film))*1 (he should be ashamed of himself for doing that... or at least the writers should have been...). But my point is, the theft would not have been successful had it not been for a great distraction: they set the building up to look like it was on fire, then walked out dressed as firemen. Get everyone looking *over there* and they won't be looking for you *over here.* It doesn't matter what your getaway method is. You could walk away with suitcases stuffed with money, so long as no one is looking in your direction. --- 1 *The creator of the original Mission Impossible series, Bruce Geller, has been cited as saying that* Topkapi *was some of the inspiration for the series. If true, then possibly, maybe, the entire scene could have been construed as "honoring" that association. It was still a rip-off and proof that Hollywood is very rarely imaginative, relying on books to do all the imaginative thinking for them. Which is why we're all here, am I right?* [Answer] I'd say it depends on what your gang of criminals is stealing. In a futuristic world, I'm not sure if cash is going to be that important. In fact, cash may be much more easily traceable than other modes of finance because people don't use it that much.Bank robberies won't make sense, at least not the way they do today. So, let's assume they are stealing something else, something that needs to be physically moved from one place to another, but is still valuable. My best bet would be that they'll conduct a heist, involving deception. So rather than an outright bank robbery involving guns and hostages, they'll be more likely to assume alternate identities, walk into this place, impersonate someone important and carry the valuable item away with them. The mode of public transport won't matter, because the surveillance systems will register them as other people, with identities that can be discarded easily. [Answer] This is already fairly common in the real world for shoplifters. When someone flees a crime in public transit, there's no license plate to track. Buses come and go quickly and often look the same. It's much easier for authorities to pull over a car. [Answer] **Rubbish** in your city is constantly collected. When a sensor signals that the weight of a container passed a threshold the container is lowered automatically in a dedicated underground network and carried away by robots. Obviously an AI checks that there is nothing strange in the container, but your characters might have found a way to fool the AI, so they can jump in few containers and travel through a network where nobody expects them to be. [Answer] Big infrastructure means big maintenance: Your city must be riddled with access tunnels, maintenance shafts, delivery entrances. There will be dumb robots everywhere, whizzing around in the dark. Your criminal can use an illicit key to enter the system. Maybe only the booty needs to be hidden or dispatched somewhere. The criminal can get in a crate and dispatch himself. A suborned robot can help. [Answer] **Misdirection** The robbers flee into a crowded area and hand off the loot to others who are not likely to be stopped. Male robbers handing off to female couriers. The robbers ditch the masks, weapons and coats and step back into the crowd. If a robber is stopped, they have no evidence on them and are likely to be let pass. [Answer] ### Use the goods distribution system, not the people transport system Not just people need transport, goods (consumables, in the most general sense) also need to be distributed. Or collected, after being used up. Food might be distributed through a pneumatic pipe mail system. Air might get distributed through ventilation shafts and air ducts. Water comes through water pipes, but these are usually pressurized and not that easy to enter (unlike you have viaducts, like the Romans). "Used food/water" dis collected via sewage systems, often easily accessible and sometimes large enough for persons, traversing them on foot (or crawling, possibly in a scuba suit) or by boat. Huge objects (like prefab building parts) might be distributed through sky cranes (blimps, zeppelins). These devices have the issue that they require ballast (like water) when not carrying stuff, or some way to compress their buoyant gas so it generates less lift. Maybe a building near the bank gets renovated, old dwelling units (flats) are removed are carried off for recycling, while new ones arrive. Maybe that's the way how people move in that future, you have your dwelling unit oved to another town. Maybe the bank director is currently in the process of moving, and his dwelling unit is an unsuspicious getaway "vehicle"; requiring the crew not only to break into the bank's (highly secured) vault, but also into the bank director's (highly secured) home. Okay, loading a ton of precious metals into this home unit might raise some eyebrows from the transport operators; after all, they need to drop more ballast to lift it. I am aware that you decided against air transport for aesthetic reasons, but using sky crane for the purpose of "construction work" might be okay, since it happens more rarely and requires no traditional cranes and construction machines travelling on roads. The robbers might "transport" their loot separately, fooling the law enforcement who are looking for someone moving a ton of precious metals. Easy: drop the gold into the trash, where it goes into the recycling system. The recycling system has, of course, been hacked (or it has a stupid bug where it doesn't recognize precious metals as such) and produces new goods from that precious material. Which are then bought, or stolen again, by the robbers. In our world, that might be a car made out of gold, which obviously doesn't work your world. Maybe "iron" park benches? Stealing park benches from a public park is, quite possibly, less likely to be noticed, especially if the park so large that CCTV is not present. Or it's some product which is installed in a very private space: "iron" toilet bowls. [Answer] ### Method 1: The crime is not discovered until much later. The best way to do this is to not have the crime detected in time for the criminals to be present. E.g you rob a bank, but at the time of the discovery, they don't know if the robbery was 2 days ago or two months ago. ### Method 2: Crooks aren't physically present. They extort money from the victim, and have it transferred to an offshore account. There it's split 47 ways, and sent to 47 other banks. There it is split again and goes off to a third tier, where some are combined, then forwarded again. ### Method 3: The goods are cached near the crime. E.g. you take a megabuck from a bank. It becomes part of a building near the bank that is under construction. ### Method 4. Send it by bus. You put it in a magnetic box, and clap it on the bottom side of a bus. ### Method 5. You use a politician. Or someone who has a car as part of your team, either knowingly or unknowingly. ### Method 6. Use a fast and/or stealthly drone. Drone is preprogrammed with a destination using onboard GPS. ### Method 7: Your theft enters the infrastructure. Your system has some form of infra-structure goods movement. Someone has to deliver all those Amazon boxes. Wholesale supplies move around somehow. Trash gets collected. This is going to be true until you have widespread and very good replicatator technology. ### Method 8: Send it through the sewers. Goes into a water proof box and dropped into the storm sewer. Fish it out when it reaches the lake, or you have a minion who fishes it out at another point in the system. [Answer] There are many way to get away with it. what trully matter regardless is only the few minute of the heist as once the police lost your track you will have much more time to moove around. 1. bike: as you said bike are a common thing in your word and it would make sens for your crew to use them to navigate trough the city, especially as you can take most pathway that would normaly be accessible only by pedestrian with ease. 2.ebike: i put them in a different point as bike as even modern day ebike or more and more akin to motorcicle in term of speed. So it's up to you if they are readily acessible in your world, but if they are, not only do they leave you the same liberty as the bike in narrow/difficult to squeeze trough space, they let you go at insane speed, comparable with ease with small motorbike, going at 50/70 km/h depending on the model and that's without even tweeting the motor to go faster. but without even going as far as high end ebike, even just a small electrique assistance that cant help you past 20km/h would still be a very nice boost in hilly city. [Answer] Since you don't mention anything particularly dystopian, I shall not go there, not the places that leads. As to "routine" considerations for what you envision, if you've ever played GTA or seen YouTube clips of it, the word "jacking" is probably in your vocabulary. All those vehicles mentioned can be jacked, if one wants to go past the "just use them creatively" approach. Jack a bus and it goes where you want, when you want. Barring obstruction by law enforcement. Hence the likelihood of having to switch along the way. Even trains and subways can be taken, especially with help on the inside clearing routes for you. But parked subway trains can be left and another entered, normally, and abnormally, through simple leaving through rear doors directly to another or through windows that are side-by-side. Even moving, especially if moving the same direction and near the same speeds. A train might be left for its roof, then to exit it via pre-positioned or confederate provided ways up to overpassing roadways/people movers/etc. As mentioned by `Thorne`, loot can be handed off to confederates. One of our stores got robbed by several young men. They handed the money off to a car of confederates and the police had nothing when they stopped them. Fools robbed us on a Sunday, not a Saturday. "Fools" because the ninth individual was an employee of ours who knew there was 10 times the money on a Saturday night. Very clever of them otherwise. Not completely otherwise as they did exactly the same thing again the next week and got caught during the handoff. So things might not work with the smoothness of MI, but... As to actual loot, there could always be inside men at the bank or what-have-you. I remember a John Travolta/Olivia Newton-John movie in which he got nothing, she, the teller, got thousands, and was wrong that he'd figure that out. But with an insider, perhaps one could score quite a few bucks, more than the usual a simple robber gets. It could even be a beard for an electronic robbery. At some point, before too much mayhem or harm to bystanders occurs for the po-po to drop the chase, the fact that they actually took nothing, or that they dropped it ("lost" it)(the physical loot), might lead to the cops downgrading the chase. If they had some cleverness planned for not long afterward, the confusion as cops are called off and the cleverness might get them away. They could also be throwaways. A mastermind plans for them to be caught and they acquiesce. It would have to be for a LOT of money, not really what robbers usually get because they'd be going to jail, but even crooks have relatives, children, parents, folks who get expensive to cure cancers or need some other operation. National Health fixed the burns medically, but the hideous appearance costs cash to fix. Scum trying to score to open a business or buy their first 10 kilos of cocaine. That kind of thing. The loot is passed to confederates, then the chase continues for some length of time, the coppers gradually win, and a DB Cooper-like search commences for the lost loot. But it ain't lost. Those throwaways get their share so others will do it again for the mastermind, or at least, their nominees get their shares that is. To enter a bit of shadow, as opposed to going dark, like I do below, anyone could turn out to be in on it. A politician just happens to drive by at the right time and his car is jacked. Po-po's in on it, some of them, especially folks who can fuzz (pun intended) the electronic stuff. The perps flee through a gang area and the gang rises up to say "Oh no po-po, you ain't passing through our territory." They only need to stick to it long enough to let the robbers get their break from immediate pursuit, then bow to overwhelming police presence. Of course, a plot direction change could occur as they take money for the work before the robbery but disappear the robbers as they come through, maybe even have similar people to continue the run from the cops, and they take the loot. They might have time to disappear it too if the runners give the cops a good run and they have the resources. Back to the nicer thoughts, they could create mayhem several places along the way, mayhem that breaches usually inviolate facilities. That could be the point. They'll get caught, or won't, but the real robbery might commence in one of the mayhem sites. Or several of them. Perhaps some electronic insertion, done by someone who now has access with the blown out hole in the wall and evacuated building. Or an insider there who is waiting to use the "distraction" to overcome physical limits preventing his taking over a system. One perhaps that has millions available for looting, or perhaps a longer game, using the insertion to crack something much larger. Smash the window of a storefront dentist office and you might steal 2-3-4,000 records before the cops get there, and mine them slowly by hand for useful data to sell or use. Break in electronically and you steal 10,000 records in a minute or two, then mine them swiftly for information. Credit card info for instance, that won't be more and more useless as people get new cards, since you use in in hours, not weeks. (Oh, all the posing aside, everyone, EVERYONE, holds credit card info even though they're not allowed to, just because customers want that in many cases, and because of bogus disputes and other reasons. I know VISA will be just shocked, shocked that there's record holding going on. Ah, *Capablanca*, the gift that keeps on giving.) Hate to go DARK, as you don't seem to be aimed there so won't likely have use for it, but when you take away the easy-to-hope-on getaway methods, there are others. The loot is gathered. The bad guys (and they are BAD) are ready to get away from there. The cops are ringed about. Hostage time. Well, no. One goes out. Slides a phone along the ground. A cop views the video on it. It's a truck's trailer, somewhere, maybe this city, maybe a thousand miles away. Coupla guys in it with submachine guns, clearly another who is filming, and there's a family on its knees, momma, 2-3 kids, that kind of thing. Maybe lying facedown, naked to add shock and wretchedness, and a text overlay that says let the boyos go and don't follow, don't track. Or these people all die. Then it fades off and one of the submachine gun boys puts his gun down and lights up a homemade flamethrower. Up to the cops. Frankly, I'm surprised no one's done it yet in our time. Talk about a Hobson's choice. Keeping it light, PLANNING is really the key. And not crackhead planning, not "I need $4,000 by Thursday" planning, but real, master thief planning. In the '30's it was thought the mob and others had a stable of such who'd make plans for any given heist, bank, jeweler's, home invasion, payrolls, whatever. They were not participants, just made plans. And that there were freelancers who did the same and found men (and women) to do the work, taking a split, or a buy-out and walking away, leaving the thieves to it. I wrote some stories and got mostly done on a novel on that idea, set near the Mexican border (Texas), but it seems I'm not a... compelling... writer. (Well, to be honest, not a good one, I guess.) It morphed into the movie standard of con gangs running deep games, even nice guy ones like in *Leverage* but I bet people nowadays would buy back into the masterminds writing up robberies and other heists though. Not necessarily the organized crime aspect, but perhaps high-ranking cops and politicians, being run perhaps by rich men. So maybe think of what there is in your world to give that kind of a twist to their getaway. There's always the not escaping into a crowd, but when the crowd is tasked by the cops, it goes the **"No, I am Spartacus"** route. But that requires a slightly shadowed nuance to things as well. There'd have to be a lot of class hate and anger present in what sounds like an otherwise happy world. [Answer] The key in most criminal escapes is to quickly put distance between oneself and the crime and then disappear: blend into a crowd, duck into a building, hop onto a crowded subway... The first place police will go is the crime scene, and then it will take a few minutes for them to organize a pursuit; you want to be blocks away and calmly unobtrusive before that pursuit gets underway. Bicycles are a good choice; electric scooters might be better. They are quiet and fast, and can get you to a pre-planned rally point where you can change clothes, pack up your stolen goods, and saunter away in different directions. If you want something more futuristic, try disposable jet-packs or powered flying suits. Going up, around, or over buildings will make you difficult to follow and avoid most surveillance (which would mainly be at street level). You'd probably want a power burst to a glide, so you avoid leaving a heat trail all the way to your rally point. ]
[Question] [ ### Situation: Someone (let's call him Bob) is playing games with someone else (let's call her Alice). Bob used his shrink ray to reduce Alice in size by about 40% (for the purpose of this question, don't worry about how this was accomplished, or any of the potential physics issues). He did this while Alice was sleeping, and then moved her. So... Alice wakes up one morning in an unfamiliar bedroom, 60% of her former size (BTW, that's 60% *height*, not 60% *mass*). She is unaware of Bob's shrinking technology, but *is* predisposed to believe that Bob is pranking her by putting her in a room where everything is larger than normal. (Assume she believes that Bob has the means to accomplish this.) Eventually, Bob is going to walk in and the jig will be up, but until then... ### Caveats: * Alice's body metabolism seems to be functioning normally. * Alice's senses (sight, hearing, etc.) are not noticeably affected. * Alice either doesn't speak, or her voice is not noticeably different. * Alice doesn't figure it out from looking at *herself*. * Alice doesn't get up off the bed before Bob arrives. * The bedroom is clean and uncluttered (think 'magazine photo'). * There are no personal effects in evidence. * There are no mirrors in the bedroom. * There are light fixtures, but no visible bulbs, and no other electronics. * There are several pieces of wood furniture (including the bed) and a chair or two. * There are no visible clothes except what Alice is wearing. ...so Alice won't figure it out due to e.g. looking closely at something like a power plug (or smart phone) that would be difficult to fake, or noticing that *the entire world* (not just an immediate space that Bob might "fake") or just too many 'things' are "scaled up". ### Question: Will Alice figure out what has *really* happened before she sees Bob? Is it plausible that she doesn't? If she does figure it out, what gives it away? (Would the change in mass be blatantly obvious, if her muscles are also weaker?) ### Details: Alice is of sound body and mostly sound mind (above average naïvete), but for story reasons is not going to be poking around the room before Bob shows up... but this might not be for an hour (i.e. she has more than a few seconds). She will likely sit up, maybe stand, roll over, or curl up, but is not going to start doing calisthenics. She's also not going to take her clothes off. There is a window, but the view is not familiar, nor is there anything near enough to the window to make the shrinking obvious¹. She can closely inspect her clothes and the bed, and can look at other things in the room, but is inclined to believe the clothing could be a trick (coarser fabric, larger than normal thread and such). (¹ At least, I don't *think* it would be obvious if all you can see is natural terrain, and that not very close by?) ### Parting Thoughts: Thank you everyone that answered! There are some good gems in here that I will use, however, I have ultimately decided to go with my original plan that she won't immediately figure it out (and have therefore accepted [Halfthawed's answer](/a/171649/43697). For *my purposes*, there are several reasons, including that the story circumstances are such that Alice will be less likely to notice the changes to her own body. I was looking more for some *external* (probably visual) hint that would give the game away, and no one (myself included) has been able to come up with one. (I'm also going to throw in something that *looks* "normal size" but isn't as an additional means of distracting Alice from the truth.) Again, thank you all! This question went over *much* better than I was honestly expecting and the responses are of very high quality. Y'all deserve your upvotes! [Answer] **No** Standard Bayesian analysis of the situation will suggest that Bob, rather than somehow violently breaking the vast majority of the laws of physics, has instead decide to play a practical joke by moving Alice while sleeping to a ludicrously accurate scaled-up room. There are objects which don't function well at larger sizes than they do at smaller sizes, so if Alice interacts with them they may cause questions, but since she's not getting out of bed to interact with it, she will assume the mundane explanation. In other words, when you hear hoofbeats, it's probably a horse and not a zebra, [Answer] **Alice is an avid user of World-Builder. While the average person might not notice ...** The bed materials would be courser and stiffer than usual. She will feel colder, especially in her extremities. Her body mass will be distributed differently, e.g., her breasts would exhibit less sag, etc. Her hair will be finer thus less stiff, and it will not fall as low as usual. Breathing will be easier, even though her air passages are smaller, as she has to move a smaller volume of air. She will feel both stronger and be more nimble. All movements will be noticeably fast. Though most of these are not terribly noticeable on an individual basis, you brain is tuned for pattern recognition. You would likely get the feel that something is not right pretty quickly even though you may not be able to put your finger on it quickly. Her world-building prowess will enable her to put the pieces together and realize this is no simple prank. --- Muscle strength various proportional to cross-sectional area, so less arm-weight probably does not correspond to whipping her arms around with super speed and strength. i.e, proportionally faster/stronger but only at the 40% level. However, this reminds me of another subtle square/cube issue. Muscle cells are ultimately limited by the strength of their cell wells - in fact I've read before the limit is actually fairly close to the tear point. The wall cross-sectional area will follow the square law, but I wonder about the motive force within a muscle cell. I am an engineer, not a biologist - my guess is that the motive force within a muscle cell follows the cube law. But, if it actually depends upon internal fibers, etc. it may follow the square law. In this case muscle strength may not vary as I and others previously assumed. BTW, animals have cell membranes, not cell wells (like plants). [Answer] > > Will Alice figure out what has really happened before she sees Bob? > > > **Gravity says she could, but she still won't work it out.** Stuff takes time to fall. We are adjusted by the experience of our entire lives (what age Alice might be I'm too much a gentleman to ask), so we have a very strong instinctive feel for the time it should take for things to e.g. fall from my hands to the floor when I'm standing. If Alice holds something say one meter up and drops it to the floor she will expect it to take about 0.45 seconds (say half a second). If Alice is shrunk by 40% then it will actually take about 0.28 seconds to fall. So she's going to instinctively know that's not right - it's too big to dismiss easily. > > Is it plausible that she doesn't ? > > > If she ignores this effect for a while she might become more adapted to it, but it's a big ask. I think she'll notice. > > If she does figure it out, what gives it away ? > > > Timings of anything depending on gravity will be way off. Throw a ball up, takes too short a time to fall back. Drop something it seems to *race* at the floor faster than it should. Steam rising from a pot - it's going to seem like it's shooting out faster. Things like that. But can she figure out she's smaller ? > > She is unaware of Bob's shrinking technology, but is predisposed to believe that Bob is pranking her by putting her in a room where everything is larger than normal. > > > And the answer here is *maybe*. Humans tend to let go of the initial idea they had slowly even when real evidence has long before demonstrated they're wrong. Alice starts out believing the room may be larger - well that's a darn sight more reasonable than a shrink-ray, so she'll take a heck of a long time to reach "shrink-ray", maybe never. If Alice had a physics background, this might be easier, but a physicist would still balk at the shrink-ray option as it's, well, physically not plausible (impossible as far as we know). [Answer] Yes. Alice will feel lighter, or stronger, depending on how you look at it. Perceived weight (that is, difficulty lifting something) corresponds to strength. Presuming Bob's shrinking technology doesn't change the fundamental laws of physics, mini-Alice's atoms have to be the same size and mass as before, meaning she has fewer of them. Mass scales with volume; that is, as the **cube** of the linear scale. $$0.6\*0.6\*0.6=0.216$$ The strength of muscles scales with their cross-sectional area; that is, as the **square** of the linear scale. $$0.6\*0.6 = 0.36$$ If mini-Alice continued under the assumption that she hadn't been shrunk, she would find she could lift things that looked $0.36/0.216= 1.6666...$ times as heavy as before. If she could lift a 30 kg weight before being shrunk, she could lift a weight that looked like it was 50 kg (but really weighed just 10.8 kg) just as easily. If she could jump 1m in the air, she could jump a distance that looked like 167 cm to her (but was actually the same 1m as before). This is the same reason that insects and spiders can lift heavier weights in proportion to their own sizes. [Answer] The snarky answer is that no she does not notice because Alice wakes up, realizes that this is not her room, then proceeds to roll over and get another hour of sleep. This is certainly Bob's doing and he'll explain himself later when he decides to crawl out of bed and draws upon his life-giving coffee. And now for something less snarky: When Alice wakes up, she is at 60% of her previous height. If I understand the fun-killing Square-Cube Law correctly, this should mean that she has about 21.6% of her previous mass. Given the lack of power outlets and visible light bulbs in combination with Bob's nature, it would not be a stretch to Alice to assume that Bob has done *something*. In fact, the fact that it is not her room at all is the first clue that something is amiss. As Alice wakes, the blankets are going to feel courser due to her smaller size. However, this also depends on what Bob is using for linens. Bedding with a higher thread count than normal may feel like a regular sheet to her smaller form. As her night clothes have (hopefully) shrunk with her, there is nothing there that gives the game away outright either. The next clue is the different fit in the bed that Alice has, or the bed itself depending on what kind of bed it is. For a start, she now only has a bit over 1/5 of her previous weight. This means that the bed she is lying in will most likely not feel quite the same as her bed does. This bed will likely seem a lot firmer than she would recall given that her lack of mass would cause less distortion in the mattress. Now the blankets are light, and maybe with the proportional change in strength, she might notice that the blanket seem lighter, but that will only be really noticeable with a heavier quilt-like blanket. But if Bob has used stock pillows, that is something interesting to note. Standard bed-type pillows only get wider as the bed size increases. Alice will no longer be in proportion to the pillows unless they were custom made for this prank. The pillows will need to be scaled down and recreated to hide this part. As Alice will not really undertake physical exertion during this period, there is no immediate cause for her to find out that she may have gotten proportionately stronger at her modified height. Even then, she might just put it down to a good night's sleep unless she accidentally breaks something. Wood grains could be a potential way to tell that something strange is going on. With 40% less height, the rings and grain of the wood around her would seem about 40% bigger. Depending on the composition of the nightstand beside the bed, the grain of its wood might look off, but not necessarily wrong. Wooden floors would fall under this vein as well. The real question is how well Alice knows Bob in this case. While she is unaware of his Shrink-o-Mat, is she aware of any of his more fantastical inventions otherwise? She does know that he can be a bit of an elaborate prankster, so a scaled-up room is not out of the question and is a logical explanation. But so long as she knows nothing of his paranormal tech, then she would have no reason to suspect being shrunk if a simpler explanation works. I would think that without considering the shrinking hypothesis in the first place, she would not really look for the cues that would point to it as opposed to dismissing them as Bob being a prankster and messing with her. [Answer] Sound and light will be very different. I would not like to say exactly how the differences will impact, but the optics in Alice's eyes will function differently; her smaller eyes will not gather as much light, and as wavelengths have not changed there may be some chromatic effects. (Edit: there is a difference between a child's eye and a scaled-down adult-s eye -- children have much larger eyes in proportion to their size) Similarly her ears are now scaled wrongly for the frequencies she is used to hearing. What was a high-pitched note will be deeper, and she can now probably hear dog whistles but at the expense of loss of sensitivity in the normal human range. Also, as noted by another, square-cube means she is radiating heat much faster and her face will feel very cold. With luck she will not freeze to death, as that would spoil the prank. (And yes, kids do freeze to death where adults don't -- which is why babies must be bundled up warmly). [Answer] **Yes, through Deduction and Analysis of the Meta-Game** I will make a key assumption, as to how gifted Alice's reasoning abilities are. Can she deduce from root causes why she is in such a situation? I believe that the answer is yes, because **Alice is only pretending to be naive on the surface, and is actually a genius in disguise**. From this knowledge, we have three possible conclusions to this question. We can come to this conclusion by following the subsequent train of logic below: 1. Let's assume that although nothing physical seems to be out of place, Alice immediately notices that her surroundings have gotten larger. 2. The first conclusion that she can come to is that Bob has put her in a larger than life sized room. 3. We know this from the question explanation: > > [Bob] is playing games with [Alice] > > > and > > She is unaware of Bob's shrinking technology, but is predisposed to believe that Bob is pranking her by putting her in a room where everything is larger than normal. > > > 4. We must, however, analyze, the reason as to why Bob and Alice are playing the game? Is there a reason as to why *Bob must go so far as to make a physics-breaking shrink ray, rather than, as you said, making a room that is just ~66.66% larger than normal*? **This is because Bob KNOWS that Alice is faking her Naivety, and must go through extraordinary lengths to trick Alice.** --- Now that the situation has been clarified, we proceed to our final two (and one hypothetical) situations, a and b: 5.a) This is the most divergent step. It depends on whether Alice knows that Bob knows about her naivety ruse. It may be that the naivety was a ruse meant to be exposed, so that Bob will go to greater lengths to trick her. If Alice knows that Bob has seen through her naivety ruse, then she also knows that Bob knows using a larger-than-life room would naturally not trick her. She would thus know that Bob would not simply use a larger-than-life room. 6.a) If the room is not the problem, then there can only be one issue: herself. Thus, Alice can come to the conclusion that Bob has shrunk her, rather than made a room larger than herself. 5.b) Of course there exists the possibility that Bob knows that Alice's naivety is just a ruse, and he knows that she knows that he knows that she is acting naive. In that case, Bob can do it either way. 6.b) Bob presents himself in 'enlarged form' through some sort of holograph, convincing Alice of his 'Shrink Ray', although in fact, **there was no shrink ray all along, the room is just large!**, or alternatively, he can use the shrink ray. Both are possibilities, and Alice cannot know which he will do. --- 5.c) Note that 5.a and 5.b all depend on mind games, and which will happen depends on who has outsmarted who. This state, 5.c, is a moot state, where Alice knows that Bob knows that her Naivety Ruse was all planned, as in that case both sides have a clear idea that both sides have all the information. In that case, they would not be playing this game, as both sides are clear that neither is naive enough to fall for simple tricks. They can just have a mind game in dialogue rather than going through the trouble of making shrink rays or larger-than-life rooms. Thus, we can rule out 5.c) and any subsequent 5.d), 5.e), ad infinitum, because they would simply not play the shrink ray or large room game. --- **TL;DR:** Alice is actually a smart cookie in disguise. Whether Alice can figure out that she has been shrunk depends on if she knows one piece of information: whether Bob knows that she knows he has seen through her ruse. If she knows Bob has seen through only her naivety, but not that she expected him to see through it, then she can deduce that he would not pull a low-level prank like increasing the size of the room, and instead has shrunk her. If she knows that Bob knows that she intended for her ruse to be blown, Bob wins, as the odds are against her, and she is lacking information. [Answer] Halfthawed's answer is right (I upvoted that; don't upvote this) - Alice will not work out she's been shrunk - but only because the question is so unreasonable. "Alice's body seems to be functioning normally" rules out any clues like mass/strength oddities and defeats the otherwise clueful points of Gary Walker; and not getting out of bed takes care of the rest. The room isn't likely big enough for the speed of sound of echoes to come into play; her sense of smell and taste might be affected (molecules are the wrong size) but she's not eating or interacting with much and the environment is unfamiliar anyway. If she's wearing perfume, she might find it odd now. Ambient sound might be the wrong pitch and if there is wind outside that might be a solid clue, but I think that's her best shot. I can't convince myself that light would be all that processed differently by her eyes because any effect I can think of involves her rods and cones, but they are "functioning normally." If she can observe ripples in water, they would definitely look a bit odd at her scale, but there isn't any here. I suppose it depends on her relationship with Bob; but her first thought would probably be nightmare or delusion. I think she'd be frightened and start to doubt her sanity. By the same token, any normal person would immediately get of bed and start testing their perceptions against each other to see if they were sane or not. But the question rules that out. Now, why she thinks Bob has the resources to build a scaled-up room and why she thinks it's plausible that he would I don't know, but yes that's her next mental stop. Of course if she knows Bob is a god (which, after all, he is) or trickster, she has other avenues to explore, but again, they don't involving staying in bed, unless she's panicking from fear, which she might well be. Her actions are so constrained by the OP that I don't think we can comment on her state of mind. I personally would start screaming "Bob, WTF!" and then fashion some sort of weapon because Bob's clearly a deranged god, and worse, a cad. She needs better friends. [Answer] The period of a pendulum varies with the square root of length. Her arms and legs are pendula and her head is an inverted pendulum. These pendula now have periods $\sqrt{0.6} = 0.77$-times as long as was previously the case. Steps are faster, arm swinging is faster, head lolling is faster. Her hair swings and bobs faster. That her usual learned control loops are mistimed for the new physics will be almost instantly noticed. ]
[Question] [ So, lately I have been developing a tabletop board-game, the subject of which is space battles. My intention for it is to be somewhat similar to *Armada*, but more realistic (e.g. tyranny of rocket equation, ships drift in the direction they were already going, etc.) However, although I want it to be realistic, I don't want it to happen at the extreme ranges that most people say are probable with space combat. After all, I need this to fit on a table-top. I also really *don't* want to handwave it, as I'm trying for semi-hard science. **Given the following parameters, how do I justify short-range engagements?** * Energy shields exist, but they aren't Star Trek-level perfect. They work by absorbing all the energy of anything that hits them from the outside, storing it in capacitors. Once the capacitors are full, the shield goes down until the capacitors can be emptied. While the shields aren't infinitely powerful, they do have decent durability. After all, they have to protect the ship against interstellar gas and micrometeorites while the ships are moving. * Anti-missile countermeasures are effective, but not 100% effective. For purposes of this question, let's set the optimum effectiveness at 98%, with a small decrease in effectiveness as the amount of incoming missiles increases. * Power supply isn't a problem. For purposes of this question, they have something along the lines of a ZPM. * Most ships have some ablative armor and anti-rad measures. As a result, hits that get through the shields work kind of like in Armada; very damaging, but not an insta-kill most of the time. [Answer] ### Don't segment your battlefield into Cartesian space - then you can use a more "plot-friendly" scaling. Deep Space is 3D, and 3D doesn't transform into table top well (How would you hold the pieces up in the air?). Because of this you're are **already** going to have to project your space 3D to 2D. You're already simplifying space combat significantly. However, deep space projection is not the same as the space within a solar system or galaxy. 2 ships in different orbits around a body, currently a long way apart from each other will shortly be in closer contact with each other with zero movement. Moving between two positions specified by XYZ coordinates has a non-trivial cost to calculate, and more importantly is basically meaningless - your ships position isn't defined in XYZ - it's an orbital height and a parent body. Your ship is "In orbit 1000km above Earth" or "In orbit 5AU from the sun". Not "X: 200, Y:150" At a high level, your ships will be manoeuvring a few squares between systems, and then to a few key strategic orbit types within the systems, so use that as your game board. Divide it up at a high level: "outer solar system orbit"->"inner system orbit"->"high earth orbit"->"low earth orbit"->"on the planet". Two ships in the same orbital region can fight with each other. Your board game map is something like this: Detail view: [![enter image description here](https://i.stack.imgur.com/bGGLh.png)](https://i.stack.imgur.com/bGGLh.png) Trip between systems: [![enter image description here](https://i.stack.imgur.com/8ShNE.png)](https://i.stack.imgur.com/8ShNE.png) As much as I love a nice physically accurate board game - I don't want to break out the cosine table every round to calculate how my ships have advanced in their ecliptical orbits. [Answer] Combat can be short-range if you change the goals of the fight: instead of it being about destroying the enemy ships, it's always about capture. Simply make it so that 99% of battles (missiles, lasers, shields, etc) are just fancy prelude into boarding the enemy ship. This way, battles focus on disabling the other ships while moving in closer and closer to eventually board. One way to do this would be to limit a resource, for example ZPE reactors. Say there are only a fixed amount of ZPE reactors in existence, and more can't be made for some reason. This makes anyone who blows up one a criminal of the highest sort. This way, battles and wars would be fought around possession of this limited yet extremely powerful resource. [Answer] I'd go with powerful engines, heat management issues, and realistic plasma-based weapons. **Powerful engines** Your ability to hit something on the vast distances of space is your targeting capability divided by the agility of your target. Guided projectiles are expensive, unguided projectiles will easily miss if you shoot them from far enough and the enemy ship can change its velocity vector fast enough. Obviously the closer you are to them - the easier it is to score a hit. Ramp up your maneuvrability to reduce the distances at which your hit\miss chances tip in favor of hitting. This leaves lasers as long-range weapon which would suffer only from the diffraction and lightspeed lag, but their inefficiency ties in my next point. **Heat issues** The hardest thing to do in space is to stay cool. Ship produces a crapton of heat thanks to the laws of thermodynamic forbidding 100% efficiency, and this especially true for any kind of large guns like lasers and railguns. The least heat-producing weaponry, like various slug-throwers and autocannons is also coincidentally working best only at very close ranges (Sans missiles, sadly, but as I have said earlier - you can make them expensive). **Realistic plasma weaponry** Doesn't really work with the heat issues, but a realistic plasma gun would be a very short-ranged weapon due to the tendency of the plasma to expand and cool off rapidly. They'd be more like flamethrowers. But they'd be extremely powerful flamethrowers capable of vaporising your opponent, which will urge you to get close and personal with them. As an alternative, your engines can already perform this exact role if you'll point them in the direction of the enemy. Depending on their stats they can be lethal at distances up to kilometers. [Answer] One possible way to make space combat mostly happen at shorter ranges is to have all ships equipped with some sort of FTL-sensor. Let me give an example: Ships are equipped with "Q-DAR" which is like radar, except it accesses quantum reality and can thus gather information about particles in local physical space (or similar technobabble). Practically speaking, a high-end Q-DAR system can map out all matter (including photons) in a spherical, 5-light-minute diameter bubble around the sensor instantly, ignoring usual lightspeed limitations that traditional radar has. This means that as long as the ship with the Q-DAR can move, they can't be hit by lightspeed weaponry like lasers and they can dodge kinetic rounds with ease. Even missiles would be seen from hundreds of millions of kilometers away giving plenty of time to prepare countermeasures. Q-DAR means that ships have to get close enough so that they physical can't dodge so typical ship combat has two ships closing in on each other, wildly dodging, until they are so close that energy weapons and eventual kinetic weapons can't be dodged anymore. If you want to get fancy and include stealth mechanics, maybe introduce an expensive "quantum fuzzer" which makes an area invisible to Q-DAR but also unable to use Q-DAR while "fuzzed". [Answer] 1. Anti-missile countermeasures are advanced to the stage that once a missile / torpedo is in space for any length of time it can be easily avoided / neutralised - the longer it spends in space, the more time the target has to counter it. Therefore the attacker must close to "Whites-of-their-eyes" distance so their shot spends a short enough time in space to stand any chance of defeating the countermeasures. (or longer but still relatively close) 2. Targeting computers require that the target be within a close enough distance that the speed of light is not a factor, i.e. when it's firing the missile, the target is still in the same place that the attacker detects it at, and it hasn't moved in the time it takes light to get from there to here. (or) 3. Armour is so advanced that single-shots are useless, only a continuous burst of projectiles (or a continuous burn from a laser beam or something) has any chance of breaking through. But to do this you need to get close to keep your weapon trained on the target as it fires. [Answer] **Take a cue from history** > > I don't want it to happen at the extreme ranges that most people say > are probable with space combat. > > > Do some research on the development of the F4 during the Vietnam War. At the time, the F4 was not even equipped with guns as all the top-thinkers thought combat would be at a distance at hypersonic speeds only requiring missiles. That proved to be catastrophic. That's the short version. Dig a little deeper and you'll have a historical model as to why your space combat isn't as distant as the experts predicted. You could even add this as part of the backstory. [Answer] # Nanite Scanning Cloud Each ship (or fleet) disperses a cloud of nanites at the start of the battle. Maybe earlier. Maybe constantly if feasible in terms of cost and materials. The nanites scan for attacks and transmit data back to the fleet. This isn't much help against most energy weapons; unless you allow instant data transmission via something like quantum pairing the nanites information is going to travel at the speed of light just like the attack. But against missiles or really any attack that moves slower than *c*, this gives the ships time to react. Redirect shields, launch counter-measures, or even dodge. And the further away the attacks started, the more time and more data the defenders have to deal with them. Of course, since both sides use this (presumably with different encryption and frequencies), just disabling the nanites leaves you just as blind. So while it is a possibility, it is not used as frequently. You could also say that the nanites transmit a constant ping, so neutralizing them (or destroying them with an energy weapon) alerts the other side to your position and intent. The end result is that the closer you are when you attack, the less chance the opponents have to defend and the more effective your attacks. [Answer] To get combat at short ranges you need the technology to favor the defense. Guns: The projectiles can be detected in flight. Shoot from long range and the target simply evades. While you can use a scattershot approach to ensure hits this means only a tiny percentage of your shots hit and the shields/armor are good enough that that isn't going to cut it. Plasma: It's charged, it repels itself, it's a short range weapon by it's very nature. Missiles: Easy pickings for countermissiles--a countermissile is smaller and more nimble. (It just doesn't have the range or the boom.) This means either very large volleys (impractical in most cases) or close range shots with sprint birds. Lasers: You already mentioned ablative armor. At long range a laser can't deliver enough power to burn through the ablative layer because the inherent inaccuracy in the weapon mounts causes the aiming point to move a bit. (Try going outside at night and aim a laser pointer at a precise target 100' away and have somebody near that target observe how it wiggles around. Sci-Fi generally assumes weapon mounts with insane accuracy. Aiming systems which can hold a point at great ranges are slow moving.) [Answer] Anti-gravity wells. All your (capital?) ships are equipped with a kind of "anti-gravity well" generator, that pushes all inbound matter slowly away from their course, kind of like opposite gravity. Like gravity, this force would be only weak, so that attacks from long distances will almost always be deflected successfully, while attacks from closer distances would hit. [Answer] ### Pirates vs Merchant Ships. Make your game about pirates fighting against merchant ships, possibly in a cyberpunk dystopia where everyone (including the pirates) are working for megacorporations. Why are things happening at a close range? Because the pirates pretended to be normal merchant ships and snuck up close to their prey before revealing their true colors. That way, they can more easily board their targets and make off with loot, as well as making it more difficult for their prey to just fire their engines and run away. [Answer] I believe you already have the answer in your guidelines: Long ranged attacks take a long time to arrive, they are predictable. The shield has plenty of time to adjust to maximize absorption at the point of impact and negate any attack from far away. Likewise, anti-missile countermeasures are only 98% effective at short range, but at long range you have a far longer amount of time to build shrapnel fields in the direction of the missile, and since missiles have limited fuel and thus limited maneuverability it's pointless to even try because it's guaranteed the missile will run out of fuel and be checkmated by the CWS. Worst comes to worst, if the ship has to rely on its physical armor it can always orientate itself to reduce damage. The ship can be rotated and offset automatically so long as there is enough time. If an attack comes from far away the ship simply rotates so that the projectile does not penetrate, it deflects, or misses altogether. You could also take ques from real world politics. The US and Russia both had ICBMs with nukes, yet they decided to slug it out in proxy wars in SEA and the middle east. Why? Because you need to use appropriate force, and as soon as you start lobbing nukes so does the other side. In space everyone can target everyone at any time. You always have lines of fire, and it's incredibly easy to throw thousands or millions of superweapons at your foes. But, you can't do that because they would do the same right back at you. [Answer] Space is big and predictable. If you make your missiles pretty dumb so they move in roughly a straight line and at limited speed then they can always be avoided at long ranges. Alternatively you should provide a way to disarm guided missiles you see coming from far away (maybe lasers, maybe decoy flares). In either case the long range missiles/projectiles will require some response, but the response should be an easy action to completely nullify the attack. The only time you can't nullify them completely is when you're busy defending from other ships in close range because now you need to defend from 2 enemies at once. Bit of a selfish plug, but I was designing [Space Chess](https://github.com/csiz/Space-Chess) which has these gunships that shoot projectiles in a straight line. In my play tests, the projectiles haven't ever hit any ship because you can simply move out of the way... Worse, because my map is a sphere and projectiles can orbit around, the shooting ship has to eventually spend an action point to move out of the way too. [Answer] A worldbuilding shift could amplify the weaknesses of long-range missile and laser weapons: ## This area of space is blanketed in a thick nebula, composed of charged antimatter particles. There may be too many scientific liberties needed to create a backstory for how this came to be, but if it can form, we could (perhaps) see the following effects: Starships are generally safe from the effects of the nebula due to their energy shields. Planetary atmospheres tend to protect those planets from stray nebula particles, but over very long time scales the effects of atmospheric annihilation could accumulate. Nebula particles interacting with planetary atmospheres (or any other matter in the solar system) will emit a lot of radiation, interfering with unshielded electronics, including automated guidance systems. It also makes long-range detection of ships difficult. Long-range missiles and torpedos are too small to carry an energy shield generator, so they cannot survive for long before sustaining excessive damage from stray nebula particles. Laser beams cannot maintain coherence over long distances due to the charged particles interfering with them. [Answer] The simple answer seems to be that hitting targets is *hard* when they are a long way away. For non-guided weapons this is sufficient. At hundreds of miles distance the target will appear as a dot to your firing systems and you'll need extreme accuracy from the weapon tracking systems to hit that dot with any sort of beam or projectile. This relates to the angular diameter formula: α = 2arctan(radius/Distance) The angular diameter is the range of angles through which a fired shot will impact at some point on the target circle. Half of that angle is the required tolerance for your aiming mechanism in order to hit the target reliably. Let's plug in some numbers. Assume we're firing on a vessel about the size of a naval cruiser - around 160m length - at 100 km distance. To hit reliably at that distance we our fire control systems to have an accuracy in the range of `arctan(0.08 / 100) = 0.046` degrees - about 2.75 arc minutes. Not too bad for a stationary, spherical target and assuming you don't mind where you hit. Now try to make that shot while both of you are moving, you're both trying to dodge incoming fire and so on. Now not only do you need very accurate weapon mounts, they need to track fast without losing that accuracy. Or you could have *realistic* weapon mounts that work just fine hitting targets with a margin of error measured in degrees. Missiles will suffer for a different but equivalent reason. Tracking a moving target takes fuel, and you can't carry a crazy amount of delta-V along with you. In order to hit the target you'll need to make a lot of precise vector changes over the flight time of the missile and the target is going to be doing everything it can to throw your guidance system off, including shining broad-beam ECM across all of your sensors. It's hard to hit what you can't see... unless you're coming from close enough that they don't have time to saturate your sensor array, or would have to put out massive ECM fans that would blind their own guided munitions at the same time. So close up is the only way to play the game that has any chance of success. Load the port cannons and prepare to come about! [Answer] ## Lasers (and other beam-based weapons) Laser beams cause damage by heating a single point of the ship's hull, so their efficiency can be lowered a lot by simply moving or rotating a bit so the hotspot never stays in one place. When the attacker is close, they can adjust their beam with the target's movement to keep it on point. But when the distance is so large that light-lag becomes a problem, they won't be able to react fast enough. ## Kinetic weapons (dumb, solid projectiles) Can be detected and dodged on long distances, as long as they aren't fired with near-relativistic speed. When they are, then accuracy might be a problem. ## Guided projectiles (torpedoes) Can be detected even more easily, because they generate emission. They can be shot down with point-defense weapons. The further away they get detected, the more time your point-defense weapons will have to lock on to them and destroy them. So the efficiency of point-defense increases a lot in long-range engagements. ## Plasma weapons Dissipate on long ranges, so they are a short-range weapon in any case. ## Bottom line A long-range space engagement is a long and tedious battle of attrition decided by who first runs out of fuel and ammo. If you want to decide a battle quickly, you have to get up close and personal. Your lasers can cut through the hull even when the enemy tries to get away. Your gauss cannons actually hit. Your torpedoes hit before their point-defense guns can lock on to them. Your plasma projectiles do maximum damage. But so do theirs. [Answer] * You could have energy weapons with a fast decreasing efficiency, i.e. their damage could be reduced by the square of the distance, making them very good at short range but pretty useless at medium-long range * For missiles, you may make the efficiency of your anti-missile countermeasure dependant of how long it takes the missile to reach the target (i.e, if you fire at 2km from target, a missile could reach it in 3.6 seconds, if you fire from 1000km away it would take 30 minutes). You can use square or cube of this time in your equations to make the countermeasure efficiency increase rapidly with distance Alternatively, you may introduce a second type of shields using a very different technology (lets call it "super-shield", with specific features: * This super-shield is nearly indestructible and can last a very long time (making any attempt to attack the ship impossible) * This technology however can easily be jammed at short range, making possible to attack a ship only if you come close enough to jam its super-shield (which will by side effect jam your own super-shield, forcing both the ships to use the "capacitor energy shields" you describe in your question Or your ships could have some cloaking devices making it almost impossible to target them unless you're very close. [Answer] For short range space battles, check out "The Lost Fleet" book series by Jack Campbell. That series depicts space battles almost like cavalry charges. A short space of time while 2 ships are moving past each other within 100km at very high speed. This makes manouvers and strategy more important than raw firepower. Alternatively, the use of common countermeasures accessible to everyone would be a thematic option to make long range combat less effective. See Countermeasure drones or other ECM could acheive this. This would make long range combat more of a quick formality prior to an actual combat phase. See Peter F Hamiltons Nights Dawn Triligy. The use of radiation and nuclear drone countermeasures make long range combat pretty much a formality of who has more drones. Hope this helps ]
[Question] [ I am trying to increase the diversity of beings in this sci-if futuristic project, and am considering the use of pantropy to do so. Pantropy means genetically altering humans to inhabit unfamiliar planetary environments, rather than terraforming, which involves changing the planets to suit the humans. However, I have put a lot of work into imaging methods of terraforming other planets, many of which I have already integrated into this project. If I keep them, then this means that people will be terraforming some planets and adapting colonists for others. But why would we do this? Why would terraforming and pantropy coexist in the same setting? (A note on answering: please don’t give a list of reasons why terraforming is costly or pantropy unethical to explain why the other is a better idea; I am looking for ideas as to why *both* should be used, not one over the other. [Answer] # Different goals ## Pantropy Pantropy requires much less resources. You just modify a set of people who are going to live on that one colony, and they will procreate and thus generate new people to work there. But it's also rather limited. Since you are editing genes, that means it would be really hard to modify an already-born person. In vitro gene modification is much easier, cheaper and way more effective. So if you modify some people to live in really hot climates, they probably won't work well in temperate climates. A pantrope is more or less limited to their world. ## Terraforming Terraforming is a really expensive process. You literally have to transform a whole planet for it to be worthwhile. But the outcome means that the unmodified "standard" humans can live there. ## Conclusion Pantropy is for the low-class workers on low-importance colonies. These will be your farmers, miners, ..., who do dangerous resource extraction on otherwise unimportant planets. These planets might feature smaller biospheres for the standard humans who are managing the colonies. Terraforming is for the upper-class planets with regional or super regional importance. This is where your upper-class standard humans live and rule the galaxy from. When I say "standard humans", that doesn't necessarily mean they are unmodified. But they are made for living in the galactic standard living circumstances: moderate temperature, moderate humidity, 1G gravity, non-toxic food with normal nutritional values and such. The pantropes on the other hand are specialized for a specific habitat. Depending on the topics you want to touch on, this also gives you the foundation for some discrimination/class conflict/race conflict themes in your story. For comparison look at the belters in The Expanse. They are pretty much that, though not created on purpose. [Answer] * **Pantropy during the early stages of terraforming, then it just sticks.** Say you have a world that should be shirtsleeve-habitable for unmodified humans in just, oh, three or four centuries. So the colonists alter their offspring to meet the terraforming project halfway. A modified colonist will be able to survive outside in a century or so. Much better for their mental health that they *could* go out, in case a seal breaks. And by the time a baseline human could survive outside, will the colonists change back? That's assuming the pantropic mods can survive in earthlike environments. *(Various writers have expounded on how supposedly the first generation builds things, the second maintains them, and the third lets maintenance slide. So it is a bad idea to rely on domed cities for centuries.)* * **Terraformed worlds can be visited by everybody.** That's assuming space travel is reasonably easy. Once you go through the effort and time of terraforming, you can attract visitors and immigrants without multi-generation schemes to alter their offspring. An artist could come for a tour, a scientist could come for a conference, and so on. That means you can attract top talent to your world. [Answer] # History is a hodgepodge of historical events World 'A' was terraformed by a rich organisation who valued their default human bodies and had the resources to terraform it. In addition this particular world was well suited to terraforming, which is why they chose it. World 'B', a waterworld, is inhabited by fish people, all descended from a group of refugees from a war, who were desperate for somewhere to live and had the technology to transform their genetics. The rich 'default human' inhabitants of world 'A' would quite like to terraform world 'B', but they can't, because the fish people live there. World 'C' wasn't always a waterworld, but it is now, having been terraformed by the inhabitants of world 'B', who having lived as fish people for thousands of years have come to rather like it. And so it goes on. As worldbuilder you get to choose the history of each world individually, and the choice of terraforming versus pantropy could easily be different for each world. Presumably terraforming will usually only be used on uninhabited worlds, and presumably some worlds will be better suited for terraforming than others, so there is a lot of scope for the decision to go different ways in different cases. [Answer] ## Alleviate the effects of law of diminishing returns, speed up the process If you need one of them, as the question implies, it can be better if you do both. You aim at a (so-far unknown) sweet spot where the terraformed environment and engineered humans are as compatible as possible because it optimizes the process. Terraforming is an enormous project, and the further you want to take it, the more it eats up resources. Due to the law of diminishing returns, the last 20 % might consume resources as much as the first 80 %, for example. See <https://en.wikipedia.org/wiki/Diminishing_returns> Engineering humans to adapt to a non-terraformed environment, on the other hand, is error-prone due the sheer complexity of any biological organism. You don't want to take it too far because you don't really know if the engineered humans function as intended: need for genetic engineering at this time strongly implies that the required genetic solution is not yet known. Therefore, you do small adaptations at a time; they are safer and easier. Law of diminishing returns also apply here. So, it could be more reasonable to start terraforming and genetic engineering at the same time, and work up iteratively until desired level of compatibility has been achieved. That is the sweet spot where investment in time and resources is more or less as small as possible. [Answer] ## Comparative Advantage of the Methods For some parts of adapting a human to a new environment it is just cheaper to alter the human or the environment respectively. Thus, simple economics creates an adaptive mish mash. For example, it is hard to supply a human brain with energy. That is why you build an oxygen atmosphere and bioreactors to produce food. But that the same time you tweak the digestive system. On another note, adjusting gravity is hard. But adopting humans for zero or low gravity is rather trivial. ## Because People Want It In settings like The Culture or Orion's Arm Automation is so advanced that economic limitations are rather inconsequential. In this case groups might just prefer one way or the other. Different groups might consider either adaptation style artistically valuable. [Answer] ## Life only works in a narrow band Is your planet's ambient temperature above the boiling point of water? No amount of genetic engineering is likely to make a creature (beyond some extremophile bacteria) that can live in that. Is there no oxygen? Nothing resembling a human could survive until you fix that. Most planets will require terraforming. (With the exception of Earth, every celestial body we've had a good look at would not support anything even vaguely like humans.) ## Humans are optimized for conditions we may not be able to exactly duplicate. If your planet receives half the light that Earth does, it might be easier to engineer more sensitive eyes (and less sensitivity to light-based mood disorders?) than to make the local star brighter, or to drag the planet closer to the star, or to set up orbital mirrors to make things brighter... **Terraforming and pantropy are not mutually exclusive ways to address colonizing other worlds.** [Answer] **Scary Sensitive Aliens** The baddy alien empire is out to get us! The aliens like the same atmosphere and gravity as baseline humans do. And they cannot or will not do genetic engineering to their people. That is why we engineer ourselves to live where the aliens cannot. Invading our home worlds is difficult when every invader needs a space suit not to suffocate, melt, and collapse all at once. [Answer] **Competiton.** One interest conducts colonization using pantropy. Another terraforms worlds and drops in unmodified humans. These interests are competitive and collect returns on their investments in planets and humans. Within these two general camps are subgroups: terraformers using brute force to wipe a world clean and more delicate terraformers making precise alterations. Pantropists who tweak the human genome and pantropists who are making frank human - nonhuman hybrids. There are other schools of thought as regards colonization. Tech centered colonization uses basic humans (or modified humans; whatever is available) and unmodified worlds and leverages technology to allow human existence on these alien worlds. There are a few worlds colonized by wholly artificial / synthetic beings. Once you have invested in an successful approach it makes more sense to improve your methods than to jettison them and start fresh. [Answer] ### It's considered illegal/unethical to terraform a world with native life Suppose an interstellar colony ship reaches a planet which is not a "shirtsleeves" habitable environment to humans, but has its own native life. The planet is close enough to Earth that it could be terraformed relatively easily, but changing the environment from one that's lethal to Terran lifeforms to one that's hospitable to them would do the reverse for the native life, leading to an extinction level event, and unique life forms being lost forever. Having seen enough native Terran species wiped out in the 20th and 21st century, humans are all too aware of the damage they can do to existing ecosystems. There's also the potential that any world with *any* native life at all could one day evolve a new sentient species, and wiping out any existing species could prevent that happening. For that reason, settling humans on a planet with native life is, while not illegal, a minefield of issues the settlers must be aware of. One of those is to refrain from certain avoidable changes to the environment, the most pronounced of which is an absolute ban on any form of terraforming. Some limited form of paraterraforming *might* be permissible if the location being paraterraformed is somewhere isolated with no native life to displace (eg a mountain top), but otherwise settlers must either remain inside the colony, or adapt themselves to fit the environment. A standardised audit for native life, conducted by an independent observer, is an absolute requirement for any world that could potentially host life before the first colonist even lands, and that establishes what measures must be taken in that case. Any colony that broke these rules would find themselves in **very** serious legal trouble, with potential punishments including: * The colony being broken up and the colonists evacuated * The personnel directly responsible facing charges of crimes against humanity in a court of law * The organization sponsoring the colony facing an extremely substantial fine, in addition to the complete loss of all investment in the new colony, in addition to damage to their reputation, making it unlikely partners and colonists will be willing to take part in future projects On less-habitable worlds where no native life exists to displace, no such restrictions apply. A shorter, simpler audit to establish that the world doesn't host life is generally sufficient. Colonists are free to crash comets into the surface to thicken the atmosphere, introduce algae to convert CO2 to oxygen, and so on, safe in the knowledge that no native life exists to displace. [Answer] ## Politics Political party T supports Terraforming while political party P supports Pantropy. Humans are a naturally divisive species and the media loves framing things as an us vs them. As such some people go around terraforming planets while some people are investing in pantropy. They are each convinced their approach is the superior approach regardless of what the other group says. Businesses heavily invested in genetics would be incline to support Party P while businesses heavily invested in terraforming would be incline to support Party T. This would result in lots of money being funneled through various channels into each party propping up legislation that is pro terraforming or pro pantropy. This could get rather ugly and nasty, and much like how there used to be Protestant vs Catholic countries in Europe similar could arise in this future setting but instead it is Pantropy vs Terraforming countries. The end result is some planets are terraformed while other people are adapted to survive in them. There can be also be moderates who try to compromise and do a bit of both. [Answer] On a single world? People want to take their dogs and cats: those animals need terraforming if they’re going to be the same dogs and cats we love. People who can redesign their kids’ genetics will have all sorts of fashion, supply-chain, and cultural pressures that push both for diversity and purification at different times. Gills may be in fashion, especially on a water-common world. Multiple arms could be useful. Bring back the prehensile tail! Lots of useful body-mods for functionality and fashion exist even within Earth-normal parameters. Across many worlds, this should obvious: the galaxy is big, cultural homogeneity is unlikely. Some worlds will push toward standard humans and some will push away, with all the usual reasons for humans to do anything. [Answer] 1. Even on an ideally terraformed planet, as-is humans cannot fill all niches, for example on Earth humans are basically absent at the poles and barely present in the oceans. If your planet has some good resources in those areas then it makes sense to put people there. 2. Excessive and/or fast terraforming will destroy the resource you're trying to get. Say you find a planet that has some plant/animal which produces the most wonderful perfume or foodstuff or other luxury item. If you alter the planet then you'll kill off your resource. Even if you try to modify the resource to grow in other environments that's going to be slow to figure out this new plant/animal and you want it now. You already know about adapting humans so do that instead. [Answer] ### Why do footwear (mechanically modified humans) and sidewalks both exist? Modified humans would be used in places where that process is too expensive (replacing an entire atmosphere), or where the modification is actually desirable (we can fly!). Terraforming would be used for places that don't need much effort to improve, that could be used for high population densities, that are desirable destinations. If the shoe fits, they wear it. [Answer] **There are some very good answers here already, I would just like to add some more.** *Here are some examples why I think they could co-exist:* ### Reasons for Pantropy to exist: 1. Planet core is already solid and therefore no magnetic protection from radiation. 2. Sun / Starlight that reaches the planet is of a specific colour / wavelength that is not ideal for original species. 3. gravity of said planet is too high / too low to sustain the current size of species. ### Reasons for Teraforming: 1. not wanting to make too many differences in the species which can eventally lead to a different enough species which then would become their own species and in case of central government, want to be sovreign and self governing. 2. use of already established ways (legacy technology) of doing the following for example: * Generating energy (i.e. rivers, wind geo etc. (assuming that they are not using fusion yet) * Agriculture * Animal husbandry (I am assuming they are still being used as food source which sounds weird when you consider that this race is advanced enough to terraform and geneticly modify itself) [Answer] ## Contingency Planning for the Known & Unknown Octavia Butler's [Xenogenesis series](https://www.goodreads.com/series/41747-xenogenesis) (Dawn, Adulthood Rites, Imago) offers a deep-dive into this debate, casting both terraforming and pantropy as contingency solutions for long-term survival - of the species, not necessarily any subgroup. The story focuses a lot on balancing survivability, agency, and adaptability, with the humans and their alien rescuers/invaders differing [sometimes violently!] on the relative priorities of each. At any encounter with a new world, three groups are formed: * Planet-side terraformers, with the goal of reshaping the new world to better meet existing, known needs **(max survivability)** * Space-based explorers, who will remain unchanged on their ships, and continue traveling after major resupply **(max agency)** * Evolutionary cohort, modified to not only thrive in their terraformed "homeworld", but also ultimately leave for worlds unknown **(max adaptability)** Essentially having both tools (plus the "neither" stay-in-space option) covers multiple contingencies, and avoids putting all the species' eggs in one easily-destroyed basket. [Answer] # Your worldbuilding is more serious than George Lucas's Don't get me wrong, I like Star Wars as much as the next nerd. But it's got a lot of horrible scifi in it, to the point that sometimes I don't want to watch it, nor even show it to my kid. One of the things that I hate about it is how every planet has a single biome. Every place in that universe is either a planetary snowball, desert ball, jungle ball etc. but without any good reason. If you are being serious about your work, then a planet that has been terraformed for humans will have multiple biomes, because it will have different latitudes (unless you're building something that would not qualify as a planet). It will necessarily have water bodies that are separate from land masses, and different wind and water current patterns in different places. With a range of different biomes in a single planet, humanity may be able to colonize the whole of it by using technology - but some people will adapt to some environment more easily due to their genetic modifications. For example, people with whale-derived physiology will be much more comfortable at the bottom of the ocean than [people who need a giant suppository just to not die there](https://www.youtube.com/watch?v=AqfLxCFdXaE&t=14). People with hands at the end of every limb and a prehensile tail could move more nimbly among both trees and skyscrapers. People who can see infrared would do better in very dark areas, etc. You can be as creative as you want there. You can even take it up a notch and terraform the planet for the modified humans, and see how a non-modified human deals with it. There is this book I love, *The Left Hand of Darkness*, and while the planet in it is not terraformed, it is home to a variety of humans who have adapted to its cold environment. It practically never goes above freezing temperature, even at the lower latitudes. The protagonist is a regular human who is an alien in that world, and the poor guy has a very hard time dealing with the constant cold while the people of that planet are just fine. In one scene, the protagonist and the deuteragonist have to share a small tent, and the heating becomes a problem - whatever is comfortable for one of them, is terribly bad for the other. I can imagine many similar situations between modified and non-modified humans in places that have been artificially adapted to one but not the other. [Answer] ## Pantropy during the early stages of terraforming, then it just sticks. ["As of 1 December 2022, there are 5,284 confirmed exoplanets in 3,899 planetary systems, with 847 systems having more than one planet."](http://en.wikipedia.org/wiki/exoplanet) Presumably humans would start colonizing "first-generation" worlds that are both relatively nearby (relatively easy to travel to) and easy to transform (and not already filled with alien species). Once those are occupied (by Earthlings or alien species), humans would start colonizing worlds that are more distant or more difficult to transform or both. As o.m. suggested, > > Say you have a world that should be shirtsleeve-habitable for > unmodified humans in just, oh, three or four centuries. So the > colonists alter their offspring to meet the terraforming project > halfway. A modified colonist will be able to survive outside in a > century or so. Much better for their mental health that they could go > out, in case a seal breaks. And by the time a baseline human could > survive outside, will the colonists change back? (Various writers have > expounded on how supposedly the first generation builds things, the > second maintains them, and the third lets maintenance slide. So it is > a bad idea to rely on domed cities for centuries.) > > > Let us assume that most [planetary-mass objects](http://en.wikipedia.org/wiki/planetary-mass_object) under consideration for terraforming are on a linear spectrum of high-gravity world, therefore dense atmosphere, therefore high oxygen on one end, vs. low-gravity, therefore low oxygen at the other end, with Earth at 21% oxygen somewhere in the middle. (I feel this is plausible enough and useful for plot reasons, although there are likely many other variables that can't be condensed down into a single linear spectrum). Assuming space travel is reasonably easy (especially if the more extremely modified colonists *can't* survive in conditions that are shirtsleeve-habitable for unmodified humans), after the first "generation" of worlds are completely terraformed (or perhaps 50% terraformed), and colonists begin to be selected to send to the second "generation" of worlds to be terraformed, it seems likely that second-generation low-oxygen worlds will have more volunteers *from* low-oxygen first-generation worlds, and second-generation high-oxygen worlds will have more volunteers *from* high-oxygen first-generation worlds. Even if space travel is difficult, the genetic engineering will probably be easier / more successful starting from the descendants of already-modified colonists and making smaller tweaks, rather than starting from scratch from baseline humans every time. If space travel is *very* easy, some colonists modified to thrive in, say, 15% oxygen levels may decide to travel for the first half of their lifespan, helping terraform even lower-oxygen planets (where they only need the equivalent of scuba gear to work outside, rather than the bulky spacesuits required by baseline humans or colonists modified to thrive at 50% oxygen), then later "retire" on some currently-near-15% oxygen world that is shirtsleeve-habitable to them (or *will* reach 15% oxygen / shirtsleeve-habitable in a few years). After a few "terraforming generations" (likely each one several human generations), there will be a spectrum of modified humans. Also, at any one time there will be a spectrum of worlds inhabited by human descendents: * worlds slightly past the ends of the spectrum of "shirtsleeve-habitable" by any human descendent that are being actively terraformed to bring into the modified-colonist range; * worlds that are technically inside that spectrum, but are still being actively terraformed because it is still "relatively easy" and would allow a greater variety of plants and animals to grow; * worlds that for a variety of reasons are not currently actively being terraformed, but are currently inside that spectrum (possibly because of terraforming activity in the past that was halted before it became habitable by baseline humans). (this builds on o.m.'s answer). ]
[Question] [ I am in a timeline which would be tens of thousands of years advanced from yours, and humans have colonized a significant portion of the stellar neighborhood, multiple thousand light-years across (Last I checked - a century maybe?). Sadly, the laws of physics you devised, on the grand scale, seem to mostly (with a few exceptions) have held up (importantly - relativity). Many of you can probably extrapolate our technology (Ignore the timeline communicator - It was given to me by the Great God of Plot and will be taken away by Him after I have received my answer). Probably the greatest invention is fusion energy and torchships - capable of supporting constant 1g (or more upto Plot) acceleration for an extended period of time, without being a weapon of mass destruction from the heat (due to Plot. One of the few deviations from your world physics. Thermodynamics turned out to be somewhat forgiving! It is still destructive due to its kinetic energy.) I have reached my destination, System X. I was sent here to build a semi-colony semi-military-base, and am the grand authority here. This system is particularly close to routes fleets of opposing factions would need to take to into allied space. I have a few million colonists, and a drone fleet that was sent at greater accelerations and arrived a few years before. It has mined up a lot of the resources we would need to begin colonization in luxury. They even have a Dyson swarm set up that can extract as much energy as I will need. This system is ours for all intents and purposes. The test target is an enemy fleet that will - at its closest point - pass within a few light-years of this system. This will happen in a bit more than a century. We know the ship design and know they have accelerated to maximum velocity - They don't have enough fuel for significant deviations from this course. Thus, I have a few decades to build my weapon. What I have in mind is a huge battery of railguns - as many as Plot demands! They will be capable of accelerating a projectile of mass Plot to around 0.2c max (if that is insufficient, it will be accelerated to Plot). Using my massive fleet of drones, and some calculations about the rate of material gathering, I believe this can be done in the required timespan. But is it viable? Can using thousands of railguns to attack this fleet at interstellar distances work? I must send a report of my plans to my superiors in a few hours (technically, years), so I must be certain my plan will work. It will be ***really*** bad for me if they calculate it will not - and will thus have wasted more then a decade by the time their new orders get here. So I want to be sure this will be able to significantly damage any fleet which passes within a reasonable distance of this star system. Additionally, will they or a nearby star system be able to tell exactly what I am constructing? Not that they could do much about it - this fleet is doomed either way (even if it changes course, it won't have the fuel to stop). But having the element of surprise for the century or so before this fleet is destroyed and their information reaches the enemies would be very useful, especially if our enemies decide to launch other fleets during that time. As a bonus, there is a rather pesky system a few parsecs away whose continuous existence and defiance is a thorn in the Empire's side. Can I use these railguns to attack them? Perhaps I will be able to destroy their off planet installations. Maybe I'll even be able to bombard their planets. [Answer] > > They even have a Dyson swarm set up that can extract as much energy as I will need > > > You should be building a Nicoll-Dyson beam. If you weren't aware of these engineering marvels, it involves constructing a phased laser array on the outside of each element of your Dyson swarm. In the limit, this results in a laser weapon that can turn the output of your star into a beam of destruction that can reach out to stupendous distances with astonishing power... a full swarm with a 1AU diameter with a diffraction limited phased array emitting 500nm light can render planets uninhabitable 100s of lightyears away, and should be able to project a huge zone of deadly power at something mere lightyears away. This isn't to say that building your railguns is pointless as such, but their power and effectiveness is unlikely to match that of even a partial star-sized laser array. If you've got stuff to spare that isn't useful for expanding the Dyson swarm, knock yourself out. Really though, the laser can reach further in the same period of time, striking the fleet further away, inflicting early damage and casualties. It can also apply damage for a longer duration, maximising the chances of you destroying everything flying towards you. As the beam propagates at lightspeed, there's no practical way for the fleet to realise they're under attack until things start exploding, unlike railgun projectiles which might be detectable by various means that I won't go into here (but feel free to ask a separate question on that). The biggest problem you may face is if the fleet is a) watching you and b) has larger fuel and propellant reserves than you thought, and is able to tweak their course slightly. It'll take years for you to notice and respond, but as they have to keep playing this game for at least a century they'll eventually run out of juice and you can waste them at your leisure. They might even send you a surrender message, and dealing with *that* is definitely a job for a separate question. You could, of course, construct vast [zone plates](https://en.wikipedia.org/wiki/Zone_plate) and blow them towards the enemy fleet like solar sails, and put enough intelligence in them to appropriately direct and focus your death beams if you happen to be a bit off. So many different possibilities! Once you've reduced your foes to a thin cloud of expanding ionised gas, you can still use your ND beams for peaceful purposes including terraforming, transportation (both local and interstellar) and reminding your neighbours that if they like the planets they live on or the stars they live around that they'd better not try any funny business. [Answer] The problem with an unguided projectile at interstellar scale isn't accelerating it, it's hitting anything at the other end. Here's the scale of the problem. Assume that your railgun has *perfect* bench accuracy: that is, if you fire it twice at the same point, it will hit the *exact same point in space*, every time. Assume that it's 1km long, but despite that length, its muzzle end can be oriented with nanometer precision (and its back end will remain perfectly stationary as you orient it). Even with this ludicrously well-calibrated gun, when you're aiming at a target 1 LY away, the effect of *each nanometer* of traverse on the end of the barrel is to move the potential point of impact about 10km. If your opponent's ships are significantly smaller than this, your gun still isn't accurate enough to address them. And this is assuming that pointing the gun is the only aspect of accuracy, which it isn't. If there's anything at all even slightly off about the gun - mass concentrations in the projectile, imbalances in the magnetic field caused by minor variations in conductivity along the barrel - or targeting parameters - minute gravitational pull from other planets in your system, the impact of solar radiation - anything that could throw its trajectory off by so much as a nanometer as it leaves the barrel, you're doing no better than shooting blind. (This is assuming your projectile's width is negligible, which it probably would be if it's a railgun, unless someone has plans for a hyper-accurate railgun with kilometer-wide slugs. A gas cloud, plasma, or beam of light would expand as it goes, making hits more likely... but spreading its force of impact across the whole area. It would still need to be extremely accurate to stand a chance of hitting, though.) [Answer] # Railguns *have to be* useless if there is relativistic travel Unfortunately, absolutely base table-stakes for being to travel at any significant fraction of C is some kind of detection, deflection, or shielding technology that can shrug off incoming projectiles, because by traveling at that speed, you have turned *everything you run into* into a projectile traveling at a similar fraction of C. As per the very-well-worth-reading paper, [The interaction of relativistic spacecrafts with the interstellar medium](https://arxiv.org/abs/1608.05284), *mono-atomic* collisions can cause non-negligible wear and tear over time. A single 10-micron speck of dust can crater the surface of the ship. And while collision with something larger is *unlikely*, over large interstellar distances, with sufficient ships, it becomes a real problem that needs to be confronted. “How do we not die if we collide with a fist-sized meteorite” is a question that will have to have been long-since resolved for the setup of your universe. Therefore, we have to presume that if ships *are* traveling at that speed, they have technology that makes those collisions pain-free. As a result, tossing projectiles at them will have no effect, even if you could hit an elephant at that range. [Answer] **Fast moving space ships will be watching for incoming impactors.** This fleet is moving fast and can't dodge. Space junk and rocks are a threat to them. They will be watching for such and they will have countermeasures as have frequently been bandied about on this stack. Space is not hazy and you can see a long way using various EMR frequencies. 0.2c is fast but radar and lasers are faster. As regards the fastest of those two they argue but races always wind up a tie. In any case these ships will have countermeasures to divert or disable incoming trash which includes your railgun rounds. [Answer] You could never hit, at that range, with a rail gun - but not for the reasons listed. You're firing projectiles with mass on fight paths that last years. Every single object in area will interact with them, in terms of gravity. They'll be attracted in very slightly different directions, depending on the flight path. Unless you have *perfect* knowledge of all mass concentrations in a volume measuring cubic light years and the capability to predict the motions and interactions of all these objects... you're projectiles are going to drift this way and that... Pulled by that rogue planet, slowly moving off course... [Answer] Railguns are unlikely to produce velocities higher than a few km/s. The physics involved in electromagnetically propelling the projectile by an electrical current passed through the rails and projectile mean they will be slow in comparison to a simple chemical rocket. I will assume some translation error and take "rail gun" as referring to some other mass driver/beam launch technology capable of reaching the desired velocity. Apart from that, any mechanism for accelerating a projectile to 0.2c is likely to be somewhat *noisy*. Even a tiny fraction of the total power being emitted as electromagnetic radiation will be noticeable from a great distance. If they have the slightest reason to be on guard, they are likely to notice you shooting decades before your projectiles arrive. However limited their propulsive abilities might be, they're probably sufficient to dodge given this much warning. Your projectiles likely need some tracking ability just to enable them to hit their targets at such extreme range, but this can be countered by firing projectiles to intercept them, damaging or destroying their tracking and propulsion systems. The advantage is on the side of the defenders: they can launch smaller projectiles at slower speeds to cripple your projectiles. It comes down to an arms race between weapons, countermeasures, and counter-countermeasures. [Answer] While it has been mentioned in passing in a couple of the answers, I don't feel like the gravity problem hasn't been given enough airtime here. Even if you solve all of the aiming problems (pointing it in the right direction, getting *exactly* the right energy output, etc.) and even if you have total knowledge of the distribution of gasses, radiation, and so on in the path, you still need to solve the N-body problem to accurately predict the path of the projectile. Not only do you have to solve a problem we can't even consider an answer to (except in certain *very* limited example cases), you have to solve it for every gravitational source in the vicinity, *for the entire flight time of the projectile.* Which is another way of saying: nope, not going to happen. For the sake of argument, let's assume that you have solved the N-body problem. You have a Matrioska Brain capable of the calculation, and some way of actually measuring all of the mass in the system with sufficient accuracy to get the input data the calculation needs. You calculate the trajectory and make the shot. Once the shot is made any disturbance that wasn't already part of the calculation introduces errors. A ship changes course unexpectedly, an asteroid collision breaks up a couple of rocks in an unexpected way, a slight change in solar emission alters the net force by a tiny amount... and the projectile misses it's appointment. Railguns are fantastic because of their kinetic potential, not their accuracy. Getting hit with a mass travelling at an appreciable fraction of light speed is going to ruin your day. But over long distances? Either it's going to miss or you'll have enough warning to get out of the way. Even if you don't have detectors sensitive enough to see them coming in all you need to do is make tiny adjustments to your engine output at random and you're effectively impossible to hit at relativistic ranges, even with SOL weapons like lasers. If you really want to hit them that far out, send some AI-controlled torpedoes with exciting sub-munitions like nuclear pumped lasers, or drones with railguns that will do the damage but from close in instead of impossibly far away. [Answer] Relativistic shotgun (only works on approaching ships). You don't need to get anything up to speed, the incoming ships are already moving plenty fast. What you need is to overwhelm their automatic impact defense systems and also keep them from avoiding your weapon. Bring in the shotgun approach... Figure out how good their defense systems are, how accurate your guess is as to where they'll be, and how much maneuvering they can do to avoid you. This gives you the mass you need and the volume you need to put it in. Then find at least enough mass to equal that. Something that's not very solid works well: one of the [asteroids that's basically a pile of rubble](https://astronomy.stackexchange.com/questions/41233/how-do-comets-nuclei-stick-together/41235#41235) would be a good bet (note that you'll need some way to contain it during transportation). Drag it out to the area you anticipate them passing through. Then shake it. Pieces everywhere, big huge cloud of crud filling up enough volume that they won't be able to avoid it with enough density that it will overwhelm their defenses. Sit back and await results. [Answer] If there have been Questions more loose, someone might be able to point them out. In building weapons targeting any great distance, the viability of railguns seems like a reasonable consideration… until you spoil it with all that other stuff. To stay on topic, a weapon targeting interstellar distances has three basic requirements: Launch power; accuracy; warhead power… who sees another, please chip in. May we ignore the warhead? It gets there, or it doesn’t… As posed, your Question seems to ignore accuracy, leaving the launch power of rail-guns. Are you asking whether a rail-gun could do the job at all or how efficient it might be, as compared to other technologies? If this Worldbuilding technology, why not simply state that your railguns have that capability? If this is about real-world technology, can you explain how SE Worldbuilding permits that? “Ordinary” guns have put shells 111 miles high and whether at that height they came close to escape velocity, you might like to research. Apparently, explosive-powered guns can’t readily give their projectiles a muzzle velocity of more than ≈2 km/s, while railguns might exceed 3 km/s. If you’re in a timeline tens of thousands of years advanced from ours, why are you asking about such trivia? How could it matter that humans have colonized a significant portion of the stellar neighborhood, umpty light-years across? Why is it “sadly” that the laws of physics seem to mostly have held up? More usefully, how have those laws failed? Can you explain, or would you rather drop that? How could even you, let alone any ordinary person, “extrapolate” technology tens of thousands of years advanced? What is the timeline communicator you’d like readers to ignore? What shows that your Great God of Plot is more than a dream you had? How in thousands of years is the greatest invention fusion energy and torch-ships? Is that limitation your own, or what? When your ships are capable of supporting a constant 1g or more “upto Plot” what does that mean? 3G? 15G? 315G? If you’re dealing with a mere 1G, how could any period of time matter? What kind of interstellar object could not also be a weapon of mass destruction due to its mass and velocity or as you yourself said, kinetic energy? Did anyone else retain the will to live even up to this point? ]
[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/137281/edit). Closed 4 years ago. [Improve this question](/posts/137281/edit) I'm writing a story about the aftermath and consequences of a runic magic system being mysteriously introduced to the human race by an unknown entity. Every week a new rune is given to everyone on Earth over the age of 13, and everyone can keep any six of their choosing before having to give one up to make room for the next week's rune. Each rune represents a supernatural power the bearer is capable of using. Initially society manages to adapt and cope with this radical change in the status quo, but by the end of year one, various factors, both from the rune system and from malicious third parties, combine to cause total societal collapse, resulting in a very long period of time where civilization is struggling to re-assert itself, and the superpowered survivors of the initial collapse and dieoff fight to survive in the ruins of the modern world. This brings results in a certain issue I need to address. You see, during that first year when things seem like they're going to be okay, several one-week-only runes grant humanity the opportunity to take part in transhumanism. Occasionally a new fantasy race is introduced to the world, and everyone on earth will be given a totally genetically randomized body as a member of that fantasy race that they can switch between freely for that first week, and keep forever (in exchange for giving up their old body permanently) if they so choose by staying in that body when the rune disappears. One of these races is a fairy-like creature called a lightwing. They're one foot tall, can fly, and while they're significantly weaker and more fragile than humans, it's not nearly to the degree that their size would suggest. You see, I want lightwings to be strong and tough enough that while they are weaker and more fragile than humans, their strengths and weaknesses with the other races balance out, and a fight between a lightwing and a human of equal skill and equipment would be a fair fight. But here's the issue I'm having: If an individual lightwing is a match for any other creature, then when the apocalypse hits and resources become scarce, the fact that lightwings are tiny (and thus require way less food, water and space to survive) would give them an insane advantage over the other survivors during the initial decades after society collapses. People would be fighting over scarce resources that would go a lot further for lightwings than for anyone else. I can't see any reason why they wouldn't utterly dominate the post-apocalyptic environment. The supplies that would keep a small band of five human survivors alive would be enough to feed a veritable swarm of lightwings that those five survivors couldn't possibly hope to compete against. And then when people start re-establishing communities and growing crops, the lightwing population would explode (relatively speaking) from the small minority they were before the apocalypse to much larger populations than any post-apocalyptic human community would be able to feed. When it reached the point of open warfare between these communities, the lightwings communities would rip the competition to shreds through sheer force of numbers. Now, I obviously don't want this, but I still don't want to make individual lightwings inferior to individual humans to balance out their superior numbers, because that would somewhat dehumanize them and make them way less interesting as individual characters, especially since I want the story to revolve around smaller groups rather than large-scale warfare, at least at first. My initial planned solution to this was to make lightwings require just as much food as any other humanoid despite their tiny size, but the problem with this is that the concept of a tiny humanoid consuming, digesting, and excreting several times its own body weight in food per day sounds like it's going to need some very careful magical handwaving to not seem utterly bizarre (and gross). I'm prepared to try and handle that if I have to, but it occurred to me that I might not have to. There might be some other option I have to make the lightwing "zerg rush" strategy less viable. **What else, besides not having enough supplies to feed them, would keep my small fairy creatures from assembling in larger numbers than humans with the same resources and attacking in swarms?** [Answer] They reproduce like cicadas. Some small creatures take their time about reproducing. Some cicadas take 17 years to reach sexual maturity. That's more time than larger creatures such as dogs and cats. Your fairies may reach sexual maturity only after they are 40 or 50 years old. And then, like cicadas and so many other insects, they mate, lay eggs and die, all within just a few days. That would make the loss of fairy life more dangerous to them as a species than the loss of a human life is to us. They will want to play cool with other races. [Answer] Flying creatures have a much higher metabolism for their size, especially non-gliding kinds like fairies. If you assume they have a metabolism similar to a hummingbird, then a 10 pound fairy will need just as much food as a full grown man; so, scarcity would be just as meaningful if not more so to them because not only do they need just as much food, but they will need to stop to eat more often because of their smaller stomachs and lesser body fat. Aside from this fact, (since you asked for an answer that does not involve eating a lot for their size), what constitutes as a fair fight may be relative. Their speed and agility may give them the opportunity to out maneuver a giant warhammer for a quick slash to the neck, but their advantages may have well-known counters such as using nets, flails, water hoses, specialized armor, or other weapons & techniques that make it an uneven fight. Basically, other races can adapt their methods to kill lightwings much more easily than the inverse; so, while they may do well in the opening days of a conflict, an enemy that is prepared to fight them will typically win, even if outnumbered. [Answer] ## 1. Transhumanism runes are no longer available. If you and your family were hungry, and had the opportunity to change yourself such that you all would not be so hungry, probably you would do it. You are right that after the Fall lots of people would want to be Lightwings. But after the Fall (or at some point before) the Transhuman runes are no longer available. The Lightwings that already exist will not increase in number - there is no way to do it. Except possibly by breeding... ## 2. Lightwings have no inherent affiliation with other Lightwings. If I am Latvian in the US, and somehow Latvians have a survival edge after the Fall, I will find other Latvians. For one, I go to church with a bunch of them. I have been to their houses. For two they speak and read Latvian. I can put up signs. Also there is a restaurant we all used to go to and so I would recognize them if I saw them. They think like me, we have a shared background, we can talk and we get along. We can definitely team up. Your Lightwings are raised human. Their families are human and their background is their human background. The only thing I as a Lightwing have in common with other Lightwings is that at the time Lightwing bodies were on offer, I thought they looked cool and I thought I would try it out. I chose Lightwings because I have always been hot for Tinkerbell but maybe it turns out that a vast majority of people who chose to be Lightwings chose that because they were old and aching and very heavy and were tired of it. These old folks qua Lightwings like to complain and argue, and voice their suspicions about what kind of people the other Lightwings were before they were Lightwings. They are not much for the teaming up. My buddies, on the other hand, are a bunch of other things besides Lightwings. In once sense that is a shame because there is no Tinkerbell equivalent, but otherwise it works well. It is easier hanging with them because they are not fussy old jerks and actually our strengths complement each other. [Answer] Lightwings taste really good. Like, really really good. Finger-licking, marrow-sucking good. While they hold their own one-on-one against the general population, there is a rare subspecies that specializes in hunting/trapping lightwings (after all, what lightwing can resist delicious bluebell pollen). Lightwings need to stay hidden to avoid capture. Large population centers of lightwings are like a smorgasbord for trolls. Some brave lightwings use a glamour to hide their identity while wandering in plain sight. Tales of their gruesome demise when revealed are well-known. [Answer] # [Kleiber's law](https://en.wikipedia.org/wiki/Kleiber%27s_law) and [Square-Cube Law](https://en.wikipedia.org/wiki/Square%E2%80%93cube_law) You say they eat less than a human, but... The Kleiber's law states that the metabolic rate of organism scales at 3/4 power of their mass. The Square-Cube law states that each time you x2 the radius of an object, you x4 the surface, and x8 the volume. A human weight 110 lb and has 5 ft of height. A fairy has 1 ft. That is five times the size, or $5^2 = 25$ the volume, which is linearly related to mass. A fairy would weight $110 / 25 = 4,4 \text{ lb}$. If the metabolic rate of an human is 2,000 calories, the metabolic rate of a fairy would be $(2,000 / 110^\frac{3}{4}) \times 4.4^\frac{3}{4} = 178 \text{ kcal}$. A human needs $\frac{2,000 \text{ kcal}}{110 \text{ lb}} = 18 \text{ kcal/lb}$ while a fairy needs $\frac{178 \text{ kcal}}{4.4 \text{ lb}} = 40 \text{ kcal/lb}$, they need more calories per the same abount of body mass. **What means all that?** It means that the relation of food mass / body mass is higher on fairies, so they are much more vulnerable to dehydration, malnourishment and starvation. They are able to survive much fewer days without food or water, due they has a higher metabolic rate in proportion to their size, and so they can carry less fat in their own body. # Little Offspring Fairies grow and develop much slower compared to a human. Despite their size, they need much more years to mature, and when they do, they breed less often than humans does (less fertile or actives?). # Fragile Fairies are much fragile than humans. They are much more fragile towards sickness, cold, hot, hunger, wounds, diseases, etc. By the way, fairy medicine isn't so advanced as human medicine, they are a quite new race. Even more, maybe fairies need a much stricter diet due to their fragile bodies. [Answer] **Predation** We need to qualify your statement, `a fight between a lightwing and a human of equal skill and equipment would be a fair fight.` The problem is this: what kept the lightwings from overwhelming humanity before the apocalypse? It had to be something. So, let's talk about *why* they're an equal match. Let's talk about *flies.* Flies suck. They buzz around your head. You swat them with your hand and it it doesn't phase them. You grab a fly swatter and you can only kill them (unless you're lucky) when they land somewhere and wait for death. It's a good thing flies are dumb as rocks or they would have overwhelmed humanity a long, long time ago. Except that humans discovered aerosol poison. And ultraviolet light (but this isn't as important). Now, ignoring the fact that aerosol poisons would work against lightwings as well as flies, the point I'm making is that the lightwing's advantage is small-mass and high-speed. The human's advantage is strength. Since they're both intelligent, one would hope that's a wash (although the gas fields of WWI proved that intelligence on both sides doesn't always avoid death. Aerosol poison is a real problem for you). But this doesn't mean there aren't predators. Making the lightwings godlike is bad for your story. Another statement you made is this: `an individual lightwing is a match for any other creature.` The reality is: they absolutely cannot be (or they would have overrun the humans a long, long time ago). You know what lightwings have problems with? *Hawks* and other birds of prey. Sure, they're smart enough to use swords. They might even have magic. Hey, maybe they have mini AK-47s. But when swift and mighty death is approaching you at a bazillion miles an hour from the heights of heaven and you don't know it.... **Predation** [Answer] They eat things that humans do not, and that is as scarce as human food. You could make them reliant on some shared resource but have others be completely separate if you want to give them a reason to fight (they both drink water, but eat totally incompatible foods, for example). This doesn't solve the living space issues - lightwings could fit in smaller spaces, but fighting over their scarce food means they isolate themselves into smaller groups. They may also need some special environment to be comfortable and happy. Humans like to be out of the weather and somewhere around 70 degrees. Maybe lightwings need very high humidity, or they can't handle extreme temperatures. Those examples might limit their range too much for your story, but some other acceptable requirement could limit their ability to congregate in large numbers but still allow them to live in various locations/environments. [Answer] Having just watched the scene in *The Matrix*, where Agent Smith describes how humanity is the only 'mammal' seemingly incapable of establishing an equilibrium with its surroundings, the only answer so far is that, ***that is just not their way***. Otherwise this answer will quickly dissolve into reasons against the statement that humans have *not* established an equilibrium (*oh, no... we're running out of oil. Again*). On the face of it your question seems story based, but it's actually one of logistics; as all good questions are. **Native Americans had respect for their land**, because they had respect for the generations that would come after them. It's simple sound logic. But what compels a culture to comply is a question for the ages ... or a damn history book. You should watch *[Wizards](https://en.wikipedia.org/wiki/Wizards_(film))* [Answer] Nosajimiki's answer is definitely the most significant. Maybe they don't need as much food - but they need to spend a massive proportion of their time eating in order to maintain that lightweight metabolism. Nosajimiki has missed a lot of the other consequences though. Unless they have some supplemental magic to help, a 5oz fairy cannot carry a 1lb coconut. Not even if they grip it by the husk... Basically, anything involving moving, lifting or pushing stuff is going to be beyond them. They can't drive. They can't operate most machinery. They certainly can't carry any weapon larger than a poisoned needle, and they can't wear any armour, protective clothing, gas masks, or anything else heavier than gauze. Operating computers should be OK, with a suitable keyboard and mouse - but they may need help to push it into a USB socket against the connector retention spring. They would have a huge advantage for some assembly work such as fine-pitch soldering, but they would never be able to use a screwdriver or spanner, or to move the circuit board themselves. So lightwings can certainly find a role in society, but there's an awful lot they can't do. For an example of small and large fairy creatures coexisting in a semi-modern environment, read Tad Williams' *War of the Flowers*. It's a pretty good book anyway. [Answer] Being big (like us) helps when the winter comes, the mass grows faster then the radiating surfaces. Your tinkerbells are too small, they mass-surface relation will kill them when the temperature falls. Also, they have wings and wings are basically radiators. They will spend most of their time eating sugary foods and drinking water to keep their body hot enough for them to live, like hummingbirds. Also, being so small they won't be able to access some of our sources of sugar - they won't grind cereals, nor milk cows. Fires will be dangerous for them. Flames that would just hurt our fingers with 2nd degree burns will burn their internal organs because they don't have enough mass protecting their liver and heart and brains from fire's heat, they are too small. They would have to live like sentient hummingbirds: will have to domesticate new plants and animals to get their sugary diet and will be restricted to the tropics. Domestication takes time and until they can somehow create on their own plantations of flowers full of sugary nectar and domesticate those ants that have a sugar reservoir on their abdomen, like some brazillian ants (I belive China has a similar ant species) they will live a miserable life. Also, predation and competition. If you are 1 foot tall, cats, dogs, birds, rats, some insects and snakes change from pets to predators. And in the niche of eating sugar, bees will compete with you. A full-sized human can stand a lot of bee stings because we are too big and our skin too hard. Your tinkerbells won't. A bee sting in their abdomen will get right into the liver and the bee's venom will kill them. So, they won't rule the world, they will live a miserable existence hunting for sugar, attacking bee's nests in deadly battles and hiding from one of the most lethal predators the earth has ever seen - the cats, both feral and domestic. I hope they chose well the other five runes. [Answer] Because lightwings are solitary creatures. To the point of being unable to exist with other lightwings unless it's mating season. They explode. You move one lightwing to another one and closer they get they start to magically vibrate and when they touch they resonate with each other channelling their inner magic on the same oscilloscopy level of recipient and it make them explode. Also ancient curse. Modern curse. that one rune that make them die. and that spell that make more than three lightwings on square meter turn into hotdogs. [Answer] The answer to that one is pretty simple - fairies are stupid. Look - they are 1 foot tall. So on average (assuming human proportions), compared to a 6 foot tall, 200 pound person, they weigh something like 1 pound. That, in turn, suggests a brain weight on the order of 1/4 ounce. How smart can such a being be? Even if you assume a brain which is 10 times larger than human (proportionate to body mass) you're only up to about 2 1/2 ounces. Furthermore, fairies will need significant investment in brain tissue to control their wings, which will reduce the "spare" brain capacity required to do abstract thinking. [Answer] ## It doesn't matter It doesn't matter why faeries can't form super swarms, because if 1 faerie can come anywhere close to handling a single human in combat, then a troop of faeries is going to utterly destroy an equally sized group of humans if they put their mind to it. How? Guerrilla warfare. There just aren't any practical ways to defend a camp from a group of small, intelligent, flying intruders. There will be faeries in the food. Faeries in the sleeping bags. Your shoes will go missing, your nets will have holes, and all the buttons will mysteriously vanish. Unless the humans have an underground bunker with an airlock, they're utterly screwed if the faeries decide they want the humans dead. Even with an airlock, I wouldn't put it past a determined faerie to be able to sneak inside. [Answer] **They are less fertile than humans** Like in they have a really hard time having little fairies. This resource is used in Eragon's elves: they live very long (immortal unless killed) and they are way stronger (in everything) than humans. How to balance the species? Make it difficult to them to have kids. Like in extremely difficult: in their visit to the biggest elf city it's said they only have 2 infants iirc (read this a long time ago). You probably don't need to make it **that** difficult, but it's an easy resource to balance species. Also you can make it so they take longer to mature, meaning they are *child fairies* a longer time, slowing the rate at which they can create a big army. **EDIT**: you can use the same resource the other way around to balance other species that are dumber/weaker/more prone to war/whatever.. just make them extremely fertile. [Answer] If your fairies retain their intelligence then there aren't many options actually **Arrogance** Simple enough. Because of how easy it is for them to survive and flourish(as compared to non-fairies), they begin to believe the world belongs to them, all the more so when you consider their numbers. In other words, they develop a sense of manifest destiny. They don't go around in large swarms mainly because they see no need/can't be bothered to organize themselves sufficiently. Hostile encounters between fairies and non-fairies tend to be in small groups or even one on one because of a twisted sense of honour, which is probably just a veneer for sadism. [Answer] You say they require less resources because they are tiny yet still are equal in a fight with a human. But why wouldnt you just say "they might be tiny but still use similar amount of food and water as humans"? Give them an ability for eating a lot in a short amount of time to shut people up about "tiny mouths=needs to eat most of the day" and you are done. [Answer] They need less food and water, but they are more sensitive to pollution of various kinds. Which is why they abandoned the neighbourhood of human beings and dwelled by preference in glades deep in the forests. So, there are lots of areas where humans may thrive, but fairies can't abide. [Answer] ## Calcium deficiency Lightwings' zippy flight patterns are fine for soft tissues, but the high G-forces wreak havoc on their bones. Thus, these creatures require relatively **very high levels of calcium intake**. In fact, they reward other species younglings which leave calcium-rich teeth out for the fairies to collect. It turns out that this need for calcium is the fairies' [biological limiting factor](https://en.wikipedia.org/wiki/Limiting_factor). There can only be so many fairies as their are younglings to leave calcium deposits for them. [Answer] ## Dating is hard in the apocalypse Sure they don't require as many resources to survive, but I'm assuming there's no more Tinder/OKCupid/etc in your apocalypse world, nor will there be fertility clinics/sperm banks/etc... Finding a life mate is hard enough even w/ all of the modern day resources available to us. After the fall populations are naturally going to be lower, and spread out more. And probably not a ton of people switched (assuming the option to do so was pre-apoc). If anything, any fantasy-race aside from humans is going to have a hard time maintaining a viable population increase unless their breeding cycle is much quicker. ## Intraspecies bonding Having once been human, there's a good chance your lightwings will still fall in love with humans, and vice versa. Especially if small groups have better survival odds in the wilderness cross-species teams will likely develop, including non-platonic relations (nevermind they won't be able to produce offspring). ## The End of the world is no place to raise a baby Many people (regardless of body form) will choose to forego children just because surviving the apocalypse requires so much resources that could be spent surviving. Add to this that since Lightwings are new, figuring out how everything works might not be an easy task. Even if they've got access to books, there's not likely to be any literature on their reproductive situation, nor on child rearing and there are probably vast differences in how a lightwing baby is raised from how a human one is. In fact some "expected" handling of lightwing babies may end up being lethal or injurious. [Answer] They're fascinated by bright lights, hence the name. If your humans can survive the night, they'll find the entire Lightwing army staring stupidly at the sun, which is when most predators hunt for them. [Answer] They are way less social than humans, large lightwing villages have around 20-30 individuals, whereas the smallest human communities typically, bands, range from 20-50 individuals. The typical human community in your setting are tribes with ~150 individuals. An individual human and an individual lightwing are evenly matched, but a human community and a lightwing community are not, in most cases lightwings are at serious disadvantage. This is not hard to achieve, if lightwings are less trusting, and only tend to congregate as immediate family they can't form the large groups humans can. Alternatively if you still want to be somewhat social, their magic start to interfere with each other. If you get to many living to close their magic stops working, or at least becomes more and more unpredictable and problematic. So a lightwing family may be fine IN a large human community, but a large community of lightwings turns into a huge fight, or more likely it is so disruptive they immediately split into smaller communities. [Answer] The easiest way is to limit their diet. Maybe they can only eat fruit (which goes bad rapidly and is more scarce in winter), or any one particular type of food. Maybe they can only eat raw meat, for instance, forcing them to hunt and making food storage essentially useless (but making a large sized rat a veritable feast). Even with lower-than-a-hummingbird metabolisms, restricted food sources could make being one less attractive. Or you could limit them other ways. Such as, they don't eat at all but subsist off dew and sunlight (legends of fairies have suggested they once did). If that's the case then periods of dryness or dark could be very weakening to them. That would be a major factor in choosing to stay a lightwing, especially with only 7 days to become used to it. If night times forced a person to seek cover and hide because the longer the night went on the weaker they'd get, well, a lot of people wouldn't be happy with that sort of trade-off, no matter what power they had by day. To someone used to always being strong, suddenly feeling great weakness would be a disorienting and frightening feeling, especially especially for someone who's sole focus is survival. Seven days isn't really enough time to get used to or adapt to such a thing either, so quite a number of people might Nope right out of their trial period and never look back. Another limiting factor could be language--maybe lightwings speak only their own language and must relearn the dominant language, and even then may never speak it very well. This would mean families and friends may not be able to speak to one another, and that could be heavy factor in deciding. Also, never underestimate "peer pressure." Choosing a form also means choosing other things. If a husband wants to be a lightwing but the wife wants to be an elf, they have a decision to make--separate as a couple or choose another form (unless they don't like sex). Or say the couple is fine with it but their child is stubbornly set on being an orc--how does a lightwing raise an orc? Or if all a child's friends are orcs, will they want to remain a lightwing? In this form they may rule at hide and seek, but they'll certainly never be part of a baseball game. Those sorts of peer group and familial pressures may drive a lot of people from the choice. [Answer] The desire to breed may be more of a social construct and less determined by environmental factors. A study living in a mouse utopia where the population was observed to collapse despite an abundance of food and space, even after the population had returned to previous numbers of successful growth, eventually continuing to fall until they all died out. <https://www.youtube.com/watch?v=5m7X-1V9nOs> One argument may be that due to the long-life and societal age of the fae races has led to a breakdown in the social behavior needed to grow a population. A real-life parallel (although with entirely different factors) can be seen in Japan where the annual birthrate has fallen to the lowest in history and is continuing to decline, despite an abundance of wealth, food, prosperity, and relative safety from invaders as they have no immediate neighbors due to being an island nation. It's interesting to try and speculate based on the obvious factors but both research and observation has shown that this is only a partial factor of population growth. Take the mcguffin of your choice and run with it. Sometimes the mundane can prove more interesting to the reader than a definitive reason. For example, you can take a failed study of your choice where certain unknown factors exist that lead to a collapse, providing similar parallels in your story, only to be understood by those familiar with such studies on societal collapse. [Answer] Lightwings get cancer really easily. Much more easily than humans. (Kind of the opposite of elephants who [only rarely get cancer](https://www.nbcnews.com/health/cancer/why-elephants-don-t-get-cancer-n441141).) Since the apocalypse involved lots of radioactive things being splashed around, your Lightwings can only visit and live in very constrained areas. They can't even eat [bananas](https://www.independent.co.uk/life-style/food-and-drink/features/let-me-ask-you-this-are-bananas-radioactive-and-is-it-true-that-eating-too-many-can-kill-you-9610080.html). So you get little clusters of Lightwings living in the really nice, pristine areas, surrounded by species who are less vulnerable, but the outside species can't push in because the Lightwings out-breed them, and the Lightwings can't push out because of the radiation...and you get conflict on the borders. ]
[Question] [ In my story, a French soldier from WW1 died in a horrible way, and became a ghost. As such, he's still wearing the same military uniform as he died, the same equipment, etc. He can react to his environment, and talk to people, but he doesn't realise that he's dead, and that he's not between 1914 and 1918 any more. Now, in late November 1944, he has joined the American army heading to Germany to end the war. Beside the fact that he cannot die or get wounded, how could one guess that he isn't a soldier from this period? Or at least, what could make someone suspicious about his true identity? Edit : Thank you for your numerous and interesting answers. First, I'm a beginner writer, and this is my first question on this site. Also, I'm French, and as we've established, French people are very bad at English, and I'm sadly no exception. My story follows the American army, and not the strange French soldier. The point is to fool the reader about the ghost's true identity. Then, is there a way to make the misunderstanding the longest ? What are the hints that just make the character appear weird, and what constitute a blatant proof of his weird state ? Also, I said that the soldier joined the American army, but let's say he just met them, and is trying very hard to join them. Is it too much of a stretch for the G.I. to accept him, whatever he says ? [Answer] ### They Think He’s in *La Résistance* I’m going to do a bit of a frame challenge, after seeing your comments. The problem here isn’t why they’d get suspicious, it’s how to make it believable that he could possibly fit in at all. So, The American squad is expecting to meet a local guide who wouldn‘t have any kind of standard-issue uniform or rifle. They've never seen him before and don't know what he looks like. Maybe the person who was supposed to recognize their contact and translate got killed, so they just have to make do. He, for his part, has heard that America is joining the war, but has never seen G.I.s. The fact that he’s in what looks like his father’s old kit, and they have strange foreign gear, is a surprise, but none of them knew what to expect. Maybe he wasn't in uniform when he died. The one American who speaks French isn’t perfectly fluent, and has a lot more important things to worry about right then, so any odd nuances that might give the ghost away fly over his head. And the ghost just makes allowances for bizarre questions like whether he’s “resisting” the Germans and tries to answer what the American meant. Until the end? [Answer] # Everything ### Language First and foremost, if he was a French soldier in WWI, I can't imagine he'd speak English, which would make blending in as an American soldier difficult. ### Clothing The French army in WWI wore a blue greatcoat and (depending on the stage of the war) red trousers, along with a domed helmet. This flamboyance would not blend in even a little bit. ### Weapon French infantry in WWI were armed with the 1886-designed [Lebel bolt-action rifle](https://en.wikipedia.org/wiki/Lebel_Model_1886_rifle). This would be entirely unlike the weapons issued to the American soldiers, and though the Lebel stuck around even 'til WWII, it was shortened into a carbine, so it wouldn't even match French weapons of the period. ### Tactics The trench warfare of WWI taught all the nations involved a lot about why you didn't establish trenches. Any "over the top" attitudes from the weirdly dressed, French-speaking, archaically armed new soldier would be confusing to his American colleagues, assuming anyone could understand him. [Answer] He would be in a military prison as soon as he tried to mingle with the US army, if not killed. Wrong uniform, wrong language, wrong weapons. Your whole story would be about his conversations with psychiatrists if they decided to allocate any to his case. And it would probably be no stranger than other stories they would have heard. [Answer] > > but he can't realise that he's dead, and that he's not between 1914 and 1918 anymore. Now, in late november 1944, he has joined the american army > > > There are a number of inconsistencies: * How does he register without anyone noticing that he's 20 years old but on his papers he's closer to 50 (born in 1895 or so) * How does he register without noticing the year on the papers or by chatting with others * Difference between 1914 and 1945 is significant: technology, transporation, clothing, etc. How does he not realize that everything has changed around him? * If he was in WWI he was necessarily European. And now he's in America (how?) to register for the WWI war? Doesn't make sense, he must know it's another war. And he's already registered for WWI anyway, in the German or French camp. [Answer] He won't be able to become a member of the US Army. He's clearly French, and they won't accept him. As he doesn't seem to be a Resistance member, they would send him to the Free French forces engaged in the campaign. In Normandy, the [2e Division Blindée](https://en.wikipedia.org/wiki/2nd_Armored_Division_(France)) and the [1er Bataillon de Fusiliers Marins Commandos](https://en.wikipedia.org/wiki/Commandos_Marine) landed on D-Day, so there would be French units accessible. A French unit is far more likely to realise there's something very odd about the fellow. Becoming an informal guide to a small unit is far more plausible. However, if he has gaps in his knowledge concerning things that have changed since his death, the soldiers may jump to the conclusion that he's a German agent, or working against them in some way. ]
[Question] [ One of the annoying problems with most urban fantasy series I've read is that they seem to mostly try to avoid discussing the fact that most of their fearsome magical foes could be felled with a simple gun. Many works just ignore guns entirely and never explain why we should fear the guy that can toss around fireballs when I can toss around just as viable metal death simply by visiting my local gun store. I'm toying with trying to justify the lack of guns by making it relatively easy to create a magic that prevents gunpowder, or any other form of similar explosive concoctions, from easily igniting within a certain radius of the mage. So guns aren't brought to a magical showdown since it's presumed they simply won't work during one. Of course humans are tool makers, and if guns failed to be an option we would come up with alternative tools to serve the same purpose. My question is what those tools would be, and how limited they might be compared to magical alternatives. Lets say there is a small, but functional, urban magic community within the larger non-magical society. Within that community there will be people who do not have access to useful offensive magic who wish to defend themselves, but cannot depend on a gun for that use. What would the logical alternative weapon for someone expecting to face a mage to carry? I'd accept both modern items that can be purchased and easily modified for combat in our current society, and also potentially specially crafted weapons that don't have much of a niche outside of the magical community. However given the small size of the magical community and economy of scales a specialty weapon can't be too hard to make before it becomes too cost inefficient to be a staple weapon for most in the community. Presume enchanting of magical weapon is limited and not a viable option for a non mage. I have toyed with allowing limited alchemy combined with basically a paint-ball gun firing alchemical potion-balls but haven't decided if I want that to be a viable option, I'm looking for alternative options. I'm mostly looking for option to defend against otherwise normal magic wielding humans. Though bonus points if there are options that may work against things with superhuman reflexes or durability as well. [Answer] Lots of frame challenges are possible. But I'll answer straight instead. I'll also assume that the magic stops any combustive propellants, not just gunpowder, so you can't just use rockets like the [Gyrojet](https://en.wikipedia.org/wiki/Gyrojet). ## Electrothermal weapons This is not to be confused with [electro-thermal-chemical](https://en.wikipedia.org/wiki/Electrothermal-chemical_technology), which combine ET with high-power propellant. [Electrothermal weapons](https://power-labs.com/electrothermal/) store energy in a supercapacitor and discharge it to quickly vaporize a neutral, non-combusting propellant. This is a modern high-tech option that will be most similar to existing guns in performance. You do need to charge it, like a phone, but the solid for heating can be packaged inside a cartridge, like in a modern handgun. Supercapacitors store up to 100 Wh/kg and release energy at 15 kW/kg. To overcome the second limitation, you'd either add a charge capacitor or a membrane in each cartridge, which breaks at firing pressure. 15 kW gives you 10 shots per second at 750 joules/shot and 50% efficiency, so even an automatic is doable, with a 1 kg capacitor good for 30-50 shots. Both options bring the drawback that the gun will take a bit of time to fire. For a pistol-sized weapon with a smaller capacitor, it will take about 0.2-0.3 seconds from trigger pull to a full power shot, if a bursting membrane is used. If a charge capacitor is used, the gun can fire instantly, but it will leak energy while charged. Still, even with these limitations, it's practical, powerful, and possible with modern technology. Electrothermal tech is being considered for next-generation tank guns, as it can pack more energy into a shot than gun propellants. Supercapacitors and high-power electronics are expensive, though. I've done some research a few years back, and a reliable personal weapon would cost high four figures. It's still not an unseen price for high-end firearms. Plus, in a world where they're actually necessary, your electric car will probably have a charging rack for your e-guns. ### TASER Already covered in other answers, this is the go to gun for less-lethal self-defense. Unlike mace, it doesn't rely solely on pain. Unless you need to pierce armor or match the magic's range, in which case you go to... ### Pneumatic crossbows Citizens who can't afford electro-thermal guns, will have to settle for pneumatic or spring-powered weapons. Spring power is limited and difficult to reload. Compressed air is much bulkier than gunpowder, but you can fire off multiple shots even in an emergency. The most lethal and reasonably long-range option, if we exclude guns, is crossbow bolts. [This is one such airbow](https://www.benjaminairguns.com/kit-benjamin-airbow). It does look like a gun... it does work like a gun. They are used for hunting. A standard bolt at 450 fps has similar 250-300J energy to a small handgun, but can be considerably deadlier with the right tip. Or can pierce armor if needed. You can guess who fields a [subsonic armor-piercing rifle](https://en.wikipedia.org/wiki/SR-3_Vikhr). It's automatic and a crossbow isn't, however. [![The picture depicts a Crosman Airbow. It is a PCP (pre-charged pneumatic) crossbow, which means the bows are propelled with air, much like airguns which fire pellets and BBs. Overall, it looks like a regular pellet PCP, with a visible air gauge tube at the front to check how much pressure is remaining. The airgun is also outfitted with a top rail to attach a aiming scope like depicted on the picture. An arrow container is also visible at the top, which allows the shooter to grab them for a faster reloading.](https://i.stack.imgur.com/0IEQL.png)](https://i.stack.imgur.com/0IEQL.png) ### Pneumatic guns Let's not forget high-tech airguns. A [.457 hunting airgun](https://www.benjaminairguns.com/air-guns/big-bore/bulldog-457) delivers 600 joules of energy - more than a .45 ACP pistol bullet. In comparison, common BB guns and airsoft guns produce 1-2 joules. Anything above 100 joules is firmly in the lethal category, and a 600 J weapon can be used for big game. The secret to these airguns is pre-charged high-pressure air, storing almost firearm-like pressure in a steel or carbon fiber tank. These figures are obtained at 3,000 psi. Fill tanks are loaded to 4,500 psi and storage tanks to 6,000 psi. This allows for easy top-down filling through pressure regulators. If someone is willing to use a boost compressor rather than a regulator to refill their gun, or just get a factory-filled 6 ksi (ksi=1,000 psi) tank, they can double their power, reaching rifle levels. Or, better, apply that to pneumatic crossbows - I find them cooler for a magic-enabled setting. One reason airguns don't go to 6,000 psi ([or even 16,000](https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2478.1980.tb01255.x) that's been used industrially) is noise. Noise depends on muzzle pressure, and a 3,000 psi airgun doesn't scare prey as far away as a 10,000 psi shotgun. Similar pressure will mean similar noise. But if guns don't always work, you'll see a competition for power and pressure in airguns, and it won't stop at 6 ksi. ### So... volts or bars? The common limitation of air-powered weapons is that they remain subsonic. Some can reach Mach 0.9, but that's it; air only expands at the speed of sound, and it gets cold in an airgun. Bolts can still penetrate armor at subsonic velocity, due to their high sectional density. Modern tank rounds are basically supersized uranium bolts. Electrothermal guns have no such limitations. They heat up the gas, and hot gas has a higher speed of sound, so they can fire supersonic, rifle-like bullets. Even out of a short barrel. Air also has a limited capacity. Hunting airguns only store enough air for 4-8 shots, with slow reloading as you have to open and close the valves. Electrics are going to start at 30, and battery swaps are as easy as a magazine. ### Why not both? It's also possible to combine the technologies - superheating the compressed gas with an electric discharge, to push the round to high supersonic velocities not possible for pneumatics. A pure electric will be simpler, but with a hybrid, you can have the reliability of pneumatics and the power of electrics if charged. The cost and regular maintenance required for electrics will be worth the capacity and firepower for combat professionals, since they carry a Christmas tree's worth of battery-powered gadgets as it is. An air cylinder, on the other hand, can store its pressure for decades without decay. You will probably see electrothermal weapons in police and military service, and high-pressure pneumatics plus the good old TASER used by civilians. Hybrid weapons are likely to be available as high-end civilian/sporting options. [Answer] **This is a [Frame Challenge](https://worldbuilding.meta.stackexchange.com/q/7097/40609)** > > I'm toying with trying to justify the lack of guns by making it relatively easy to create a magic that prevents gunpowder, or any other form of similar explosive concoctions, from easily igniting within a certain radius of the mage. > > > Allow me to introduce you to the Law of Unintended Consequences: > > The Law of Unintended Consequences reflects the natural results of using a simple system to regulate a complex system. Those results are often unwanted if not down right invasive. > > > **Your magical solution to prohibiting firearms is impractical** 1. Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat. ([Source](https://www.grc.nasa.gov/www/k-12/airplane/combst1.html)) We usually think in terms of an explosion, but combustion includes animal (yup, including human) metabolism. So, if your magic prohibits gunpowder from igniting in any way that can be explained with the word "chemistry," you just killed everyone and everything within the area of effect. 2. But let's assume your magic is more magical than that. No scientific term can explain *why* the gunpowder or "any other form of similar explosive concoctions" (how the magic knows this is, well... magical...) doesn't work. It just doesn't work. But you just stopped every combustion engine within the area of effect. You just stopped the guy who's trying to nail down the frame for his house with a [Ramset](https://www.ramset.com/). Heck, you just extinguished little Timmy's campfire... and the marshmallow wasn't done cooking yet. You might have even stopped factories from operating. You certainly shut off everyone's gas/oil/wood burning furnaces in the winter. But that can be solved by limiting the area of effect, right? 3. Enter a good sniper like Staff Sgt. Hunter Bernius, who [hit a training target more than 7,500 feet (1.4 miles) away](https://www.businessinsider.com/how-a-marine-hit-a-target-nearly-8000-feet-away-2019-8). Who cares if your magic can subdue explosive force if that force occurs *outside the area of effect* and the consequence of that force (bullets, building debris from an explosion, radiation from a nuke...) impacted the mage instead? Oh, complimentary photo of the problem via the link above: [![The picture depicts some kind of soldier laying on the ground, looking through the scope of what seems to be a designated marksman rifle or a sniper rifle, facing towards us. His face is painted in green camouflage, and his outfit looks like military green. His body is partly covered in some kind of ghillie suit for better camouflage; although his camouflage is questionable, because the background is white and his entire body appears to be mostly green.](https://i.stack.imgur.com/OsYjB.png)](https://i.stack.imgur.com/OsYjB.png) **Prohibiting a specific branch of technology (inevitably firearms) is a popular question on this Stack** And it doesn't often work. Especially when it's so easily replaced with spring-loaded air guns with the power of .22 to .38 caliber rifles or modern bows/crossbows or even a [wrist rocket](https://en.wikipedia.org/wiki/Slingshot) like the following bad boy. [![The picture depicts a very sophisticated black slingshot. Instead of looking like a traditional child toy, this one looks closer to a crossbow.](https://i.stack.imgur.com/DxaaK.png)](https://i.stack.imgur.com/DxaaK.png) or even spring-loaded projectile weaponry or the use of poisons. In short, there's an innumerable number of weapons that have already been created throughout human history that are, frankly, quite effective *against just one person.* But, in the end, what you really need to do is not prohibit firearms, but come up with creative ways for mages to protect themselves against firearms. That tends to avoid the Law of Unintended Consequences most efficiently. [Answer] ### Something of a frame challenge Your mages don't have to stop gunpowder from igniting if they can just do this ![A still frame from the movie _The Matrix Reloaded (2003), from the scene where Neo stops all the gunshots from The Merovingian's henchmen by merely raising his hand in a "stop" sign. The picture seems pixelated, and there seems to be a curve to it, which suggests this picture was taken with a smartphone camera while the movie was playing on the TV.](https://live.staticflickr.com/2835/33509570903_0efdd60780_b.jpg) Some kind of force-field like 'magic shield' is a common trope - perhaps in your world it can stop bullets or even explosions and the like. The side effect of this is it make your mages too powerful, but perhaps your magic shield has a weakness against something else. [Answer] apart from the already stated impossibility within any reasonably consistent universe, it's quite possible to create high power projectile weapons that don't rely on chemical explosives. * electromagnetic rail guns * (cross)bows * compressed gas canister driven weapons * high speed pistons in general (hard to do mechanically) And then of course there is always the option of going for directed energy weapons. * plasma guns * lasers * particle beam weapons Or there's another class of mages that creates amulets that let the wearer use those chemical explosives anyway by nullifying the nullifying field projected by your mages. This is a magical fantasy world after all, no reason there can't be counter-magic magic. [Answer] ## Everyday Carry Weapons > > Lets say there is a small, but functional, urban magic community within the larger non-magical society. Within that community there will be people who do not have access to useful offensive magic who wish to defend themselves, but cannot depend on a gun for that use. What would the logical alternative weapon for someone expecting to face a mage to carry? > > > What you are asking about is colloquially called an Everyday Carry Weapon. ECWs are often NOT weapons of war. They are designed around being cheap, small, and convenient enough to carry every day as opposed to maximizing your killing power. While militaries will likely pivot to using high energy lasers, railguns, or air riffles, these are all much to cumbersome and expensive to consider as ECWs. In general, there are 6 classes of ECWs used today. I would rank them worst to best as follows: 1. **Firearms**: Opps, darn magic... make that 5 classes of ECWs. 2. **Blades**: The most common of these is a pocket knife which doubles as a helpful tool. Larger blades like machetes are often carried in more crime torn countries, but would be out of place in a "civilized" urban settings. The usefulness of these as ECW weapons goes way down in a magic filled community though. Because you'd probably just make yourself a bigger target trying to bring a knife to a fireball fight. So people will likely still carry knives as tools, but rarely consider using one as a weapon unless they know they are facing a muggle. 3. **Bludgeons**: Walking sticks, batons, nun chucks, brass knuckles, etc. These are very simple and cheap self defense weapons generally meant to protect yourself against an unarmed opponent. These weapons are typically capable of lethal force, but much harder to accidently kill a person with than a gun or a knife. The key here is that they are mostly meant for fending off an unarmed attacker. If you want to arm yourself against a mage, these are not a good option. That said, I'd still rank these above blades because a bludgeon hurts much more acutely than getting stabbed; so, if magic requires a lot of focus, the pain of a stick to the arm may make casting much harder than a knife to the arm which can take several seconds for your brain to even register. Also, a good blow to the head can instantly incapacitate a person. 4. **Disguised Items**: These are any variety of weapon that does not look like a weapon such as kubotans, tactical flash lights, etc. Some disguised items also overlap with other classes of ECW like a cane sword. This category of ECW weapons is so wide, it's hard to say how good they will perform against a mage, but by in large, you make your ability to defend yourself more surprising to an attacker. This could play to your advantage if it makes closing the range to cut off a mage's casting finger easier, but it can also disadvantage you since a person who is not visibly armed is a more inviting victim to begin with. 5. **Sprays**: Weapons that use a chemical irritant to blind or distract an opponent. Depending on the nature of magic, these could either be a really good idea or a really bad one. If magic requires considerable focus, the pain may break the focus and prevent casting. But if it's more emotion driven, then the pain may amplify the mage's fear/anger causing him to caste giant walls of flame or lighting in every direction not only killing you, but burning down the better part of a city block. If it is the latter, I would expect ECW sprays to be outright banned. 6. **Stun Guns and Tasers**: Weapons that use electricity to incapacity an opponent. These would probably be the most effective against a mage since they interrupt the whole nervous system instantaneously making casting impossible regardless of if you have an emotion or focus based system. While the Stun Gun will likely become the undisputed best ECW , expect people to carry all 5. Why? Because that's what people do in the real world. Every person who carries an ECW has different personal values and physical capabilities; so, while one person may prefer a stun gun, another person may want something smaller like a keychain spray, or harder to hurt yourself with like a baton, or they don't want the fo paux of "being armed"; so, they pick a kubotan... or they want something more versatile that they might already have a daily use for like a knife, tactical flashlight, or walking cane. ## But With Magic, Everyday Carry Defenses May be Better Here in the real world, when a person pulls a gun on you, you've already lost. It does not matter what is in your back pocket if they draw first. In a world of magic, this problem is heavily amplified. Unless a mage needs a wand or some familer looking focus to cast a spell, then by the time a mage points his finger at you, you are already dead-to-rights. This makes the value of any ECW go WAY down when the mage can always win before you even know you are being threatened... but what about Everyday Carry Defenses? The only way to defend against being ambushed by a stranger with a gun in our world is to armor yourself head to toe with 30+ kg of body armor... this is not every day suitable which is the whole reason people choose ECWs instead of ECDs. But in a world of magic, a good defense may be better than a good offense. A basic 30\$ amulet of protection may not do squat against a veteran battlemage using a mil-spec wand of rip you apart at the molecular level... but against some punk mage off the street, throwing a "level-1" magic missile at your face, it could be the difference between getting 2nd degree burns and a mild tan. Unlike mil-spec defensive charms that involve wearing rings on every finger, 3 amulets, and robes covered head to toe in elaborate runes all designed to work together to cancel out everything from boiling blood spells, to being turned to stone, to being banished to demonic worlds... a simple but versatile protection charm would be all you need to turn your average a magical mugging into a simple fist fight. [Answer] Speaking of compressed air weapons, if I were expecting a mage to ambush me, I'd probably carry a... ### [Taser](https://en.wikipedia.org/wiki/Taser) Assuming they're not walking around in plate armour, it'll work just as well on them as anyone, and no gunpowder required. The same is true of a lot of less-lethal weapons, for that matter. I'd bet a blast of bear spray to the face would do a lot to disrupt spellcasting. [Answer] **It's been done kinda** [![The picture depicts six books written by Brian McCellan. The three at the top row are: Promise of Blood, The Crimson Campaign, The Autumn Republic. The three at the bottom row are: Wrath of Empire, Sins of Empire, Blood of Empire. On the first row, the books mostly depict a man in what seems to be a Napoleonesque military outfit, carrying a musket outfitted with a bayonet fixed at the front. The second row books mostly depict the environment, with silhouettes from the character seen from afar.](https://i.stack.imgur.com/371YL.png)](https://i.stack.imgur.com/371YL.png) In the Powder Mage series, there are a bunch of different types of mages of which powder mages are one who have the ability to control gun powder. They can snort it to make themselves faster, stronger, more alert, better senses etc but they can also make gunpowder inert or detonate it at will. Enemies invent air rifles to hunt powder mages. They don't bring anything with gunpowder as the mages can sense all gunpowder around them and can detonate it at will which happens many many times in the series. [Answer] Probably either crossbows/bows or an airsoft gun that is very powerful. Edit, an airgun, not an airsoft. [Answer] *Yet Another Frame Challenge* Do nothing. [Reality is unrealistic](https://tvtropes.org/pmwiki/pmwiki.php/Main/RealityIsUnrealistic), you know. You think powerful wizards would be harmless in a modern setting because anybody with a gun could take them down. That's because you are thinking of gunfights like [this](https://www.youtube.com/watch?v=Y-EhncCgbaw&t=3m40s), but gunfights are really like [this](https://www.youtube.com/watch?v=evgpWTm_-rE). It's very easy to think about aiming carefully and shooting while you are behind your keyboard, but reality is another thing. Yes, a single bullet could kill the most powerful mage, but so could do an arrow or a knife. The problem is hitting. When you are against someone who can deliver area-efect fireballs directed by the mind, you don't trust your accuracy that much. [Answer] These days we are seeing a lot of advancement in technology that allows railguns and coilguns to be more viable. These types of weapons don't require gunpowder and instead use electromagnetism to send a metal slug at the target. A company called [Arcflash labs](https://arcflashlabs.com/_accelerators/fully-assembled-guns/#) has demonstrated 3 different handheld coilguns that they have sold publicly, and while yes they are not very powerful, they are making a lot of progress. There are also many cases of people making homemade coil/railguns which could add in an interesting DIY element. I don't think it would be too much of a stretch to imagine your world having further developed weapons like this, especially if regular guns are unviable, as the gap in capabilities could get people to invest more in these kinds of alternatives to level the playing field between mages and non-mages. [Answer] I think perhaps you are missing the point. Why does it matter that a normal human may turn up with a gun? They have to carry a specific weapon, with limited ammo. As a mage you have concealed weapons with near limitless power, accuracy, and fire rate. The range of options for a single mage can be from pea shooter (just to distract someone), taser for stunning, through riffles, to bazookas, and beyond, all in 1 person. The mage may even be able to shoot round corners, through obstacles, unmissable targeting, etc. The human might be able to get a lucky shot in if the mage is careless, but in general if a mage and a human are in the same area in a shoot out, then the mage is a one man army vs the human with their one pistol. Also if the mage has even a minimal advantage in speed, shield, predictive abilities, etc, then attempting to hit them with a projectile of any type is even more likely to fail. > > One of the annoying problems with most urban fantasy series I've read is that they seem to mostly try to avoid discussing the fact that most of their fearsome magical foes could be felled with a simple gun. > > > Doesn't every scene in every DC/Marvel comic or movie when the police/army turn up to stop the bad guy, answer the question why fearsome magical foes **can't be** felled with a simple gun? [Answer] A world in which a wizard can be killed with a gun is an interesting premise. A world in which a wizard cannot be killed with a gun is an interesting premise. A world in which wizards can stop combustion of gunpowder but there is a 1:1 replacement for a gun that can kill mages and that replacement is widely available - well, at this point the only difference between our world and the imaginary world is that mages control ignition of gunpowder. Mind you, not "mages control ignition of gunpowder and all the consequence that would have on functioning of our world", it's just about gunpowder. If you want to remove guns from your world, then why are you trying to invent weapons to replace a role of the gun in a story? Making conventional, most powerful weapons available to us mortals have no effect on wizards is a narrative device, one that shows how powerful people with magic are. If any other person can kill a wizard just as easily with a gun-but-for-mages, then what was the reason for removing guns in the first place? What is the point of offensive magic, if mages with no offensive capabilities can use an offensive gun? I can only see that working in just a single context and that would be a story about mages with offensive powers becoming obsolete. You need to decide - are mages so weak, that they can be killed by a bullet, or are they a more powerful class of humans that forces us to revert to pre-combustion weapons to fight them? If it's the first, then why not address the problem by mixing firearms and magic with each other? If it's the second, then mages without offensive abilities and non-magical people might as well carry daggers with them - not because they are effective, but because it gives them a fighting chance. If there is a special witch-hunting that fights mages, they might use crossbows as the second best replacement for a gun and work in squads of dozens, camped on the rooftops. Defeating powerful mages or defending from them is a creative puzzle for the writer that can be solved with wit, overwhelming numbers, ancient artifact, protective magic or otherwise. It engages creativity far more than a single-fit solution can. [Answer] Well, there are a few options; If the mages aren't immune to projectiles, regular humans could use weapons like crossbows or [cheiroballistrae](https://en.wikipedia.org/wiki/Cheiroballistra) to attack them from a distance. If the mages have some protection against projectiles, then regular humans might have to resort to polearm weapons like [halberds](https://en.wikipedia.org/wiki/Halberd) or [glaives](https://en.wikipedia.org/wiki/Glaive), which might give them a chance of being able to injure a mage before the mage can attack them. [Answer] Instead of focusing on preventing explosion, make it so that mages have spells that can block high speed projectiles, make it easy to cast, and long lasting and maybe invisible, something like mage armour. If you set a limit on what speed the projectiles has to be below to bypass the shielding spell. This may force non mage troops to use crossbows, bows or melee weapons instead. [Answer] This has been done, more or less, based on the velocity of the projectile, in Patrick Rothfuss "The Wise Man's Fear". Kvothe builds a magical device that detects a crossbow bolts and cancels its velocity with runes. There are various safeguards (extremely high velocity only, doesn't go off on organic material so it doesn't get triggered by birds or wildlife, will detect metal / stone / horn arrowheads, etc). [Answer] Since it's a fantasy novel I don't think we need hard science here. Some ideas: 1. A mad mage experimenting in the 90's somehow unleashed reality splitting spell that unintentionally altered physics, specifically making gunpowder non-combustible. He died in the process and his lab was destroyed. You don't need to go into details on unintended consequences etc. 2. Not your gunpowder idea but: The spell to stop high velocity projectiles just short of your skin is relatively easy, but the power required scales based on the mass of the object. A bullet? Simple. A car? Damn that's tough. The ground coming at you as you fall from a building? Well that's technically the whole earth so nah. This will prevent stuff like air compression rifles and crossbows nullifying the intended scenario you want. Either way soldiers deal with mages using modern swords of your own imaginations design. Or flamethrowers ;0 [Answer] Magic of predicted outcome to stop that which would do someone harm by a slight glimpse a few microseconds into future that stops the intent of the weapon without regard to the speed it is traveling, how it is propelled, or even how or what it is constructed from. A magic glimpse at the future to prevent, or a magical regression to redo and counter. Covers just about everything conceivable from the intentional to the accidental. Just call it a spell of protection, loosely explain the concept if need be, reconcile the rest with hew fact we have already conceded to the existence of magic ;) One can hardly argue the viability of magic and believe in its existence at the same time. Unless of course you are quoting A.C. Clarke and the magic is meerly perception, not true magic (if there is such a thing). But even still, sufficiently advanced tech may be able to pull this off with temporal mechanics, and thus appear magic in context. Still a win/win IMO. [Answer] The offensive weapon brought to bear will entirely depend on the defensive abilities of the average mage in this urban fantasy world Previous answers have given a wide variety of ideas and I will give them the credit where they are due. I would observe that for an urban fantasy setting, there are going to be two main drivers for what weapons will be most effective in evening the battlefield between the mundane and magical. ### Magical Defences We know from the question that there is a primary defensive field that somehow prevents gunpowder from being utilized for firearms. Beyond that, there are whatever other defensive enchantments the average mage will use to ensure their safety. If their standard defences are against bullet-like projectiles, then most likely people will have some manner of melee weapon. If their defences are geared towards fists and blades, then people will use something small enough to not trip those defences. If the anti-gunpowder spell/aura is their only real defence, then expect a lot of assorted things based on personal choice and preference. On the reverse, if they have a near impenetrable defence in personal range, then expect combat to be about getting out of range of the anti-gun aura and shooting them. In the end, it's about what will be the most useful weapon to break through the most common defences. ### The Masquerade Unmentioned is the mostly traditional Masquerade -- that veil that separates the normal mortal world from the supernatural world. Given the premise of "*small, but functional, urban magic community within the larger non-magical society*" in the question, I will be making the presumption that your weapon would not only have to be useful, but be legal under mundane laws. Possibly altered from what we know due to the knowledge of magic. Depending on the part of the world that this community is in, what weapons that are readily available could be very different. If mundane laws evolved with the knowledge of the supernatural, then expect evolved laws to aid (or hurt) the available choices ### The Weapons Cache Personally unless explicitly defended against, I would suspect that some manner of light melee weapon would be the item of choice like a serviceable knife or a baton. So long as the knife isn't too big, it would be the type of thing one could carry around to handle stubborn boxes and tie straps, or any other odd thing that one needs to cut. It likely wouldn't raise eyebrows if seen unless it was blatantly magical. A baton would be a bit of an odder choice, but it isn't as inherently lethal and can be hidden in other ways. Also if it isn't metal in origin, then it can likely travel on aircraft easily as it isn't blatantly a weapon. Both of these should be relatively legal to possess, even if not in an ideal form. Likewise, both would be easier to acquire than other more exotic items such as crossbows or tasers. Not that they are bad weapons -- just that there might be more issues possessing them legally. In a place where guns are more commonplace or less forbidden, an enchanted airgun might be useful for mages to help defend against their fellows. As a bonus, it wouldn't be hard to make these things out of special materials to handle specific threats. Or have them blessed for extra effectiveness against the undead. Tiny runes carved into the weapons could further enhance the power of the weapon. Of course, all this is predicated on the need to have a weapon to defend themselves against threats from mages. ]