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[Question] [ I'm not quite sure if this question fits in with worldbuilding but I have honestly no idea where else I would ask it. I've recently stumbled upon a ['ship designer' tool](http://spaceengine.org/shipeditor/) that allows you to build and design rather neat looking starships by selecting various parts and placing them, then eventually exporting the model. I've been using this in a multiplayer roleplaying game in Aurora4x to bring some life to my ship designs. I'm wondering if there are any more tools like this out there? I haven't been able to find any with some google searches. 2D or 3D, doesn't really matter. I'm sorry if this question doesn't fit in this stackexchange. [Answer] <http://aero.go.usu.edu/mu5/> a program with many premade parts to choose from and assemble them as you wish. <https://freecadweb.org/> a 3D design software that allows you to build from scratch, there are several, far better programs for this but this is the best free one i can find. other than inventor pro which you could look into here: <https://www.autodesk.com/education/free-software/inventor-professional> <http://ship.shapewright.com/> a simple, online, random ship generator <https://github.com/a1studmuffin/SpaceshipGenerator/> a complex, downloadable random ship generator some of these are harder to use than others and some are way simple, in my opinion the last one is the best option so try it first [Answer] I'm a 3D Generalist, and I'll give my quick thoughts: Any decent **3D DCC** (**D**igital **C**ontent **C**reation) tool will handle this task well, whether it's [**Modo**](https://www.foundry.com/products/modo), [**Blender**](https://www.blender.org/), [**Maya**](https://www.autodesk.com/products/maya/overview), [**3DS**](https://www.autodesk.com/products/3ds-max/overview), [**Lightwave**](https://www.lightwave3d.com/) or [**Cinema 4D**](https://www.maxon.net/en/products/cinema-4d/overview/): Blender's free, Modo is super-artist friendly, Maya & 3DS are the 800-lb gorillas as they're Autodesk. All of 'em would work - for me, *I'd* choose to do this in Modo - but that's just my personal preference based on workflow and skillset. Made by me, with Modo: <https://cdnb.artstation.com/p/assets/images/images/012/093/365/large/gerard-falla-experiment-01.jpg?1533004330> <https://cdna.artstation.com/p/assets/images/images/016/080/830/large/gerard-falla-toy-05.jpg?1550810955> [Answer] Kerbal Space Program with the Realism Overhaul and Procedural Everything mods. There are also thousands of free mods for various parts. [Answer] ## [Blender](https://www.blender.org/) Blender is a free, open source 3D application. If you're not looking to model a spaceship from scratch, you could find some models online and arrange them to create your ship. [Answer] Not a tool-software, but a game: [Space Engineers](https://www.spaceengineersgame.com) It is sadly not open source or free2play, but you can build starships to your liking, and the attached Steam workshop features thousands of different designs. [Answer] **Fractal generator.** If you want Apollo-looking or Battlestar Galactica type ships, other answers have those covered. If you want semi-organic looking things that might have been discovered in a nebula and turned into a spaceship, or grown from crystals in the atmosphere of a gas giant, you could start with fractals. <http://usefuljs.net/fractals/> [![nova fractal](https://i.stack.imgur.com/Lo6HA.jpg)](https://i.stack.imgur.com/Lo6HA.jpg) This is the Nova fractal. You can imagine its magnetic meteor shield there on the right. I am hanging out in the bar, back on that tail part. [Answer] **Lego** If you happen to have lego (or similar) pieces lying about, just playing around can give you some nice spaceship-y forms. It's probably easier to build really small (think microfighter) models than ones that fit the minifigs to scale. I find aiming for a certain aesthtic (like star wars) but letting the pieces most close at hand guide you can give nice but unexpected results. Either use the piece directly as a game piece or take a top-view foto and cut the background, giving you a 2D-image. **Pencil & Paper** forces you more to think before you draw, or use the eraser a lot, but is a time tested method to develop ideas. **Hot glue and cardboard** is also a quick way to build huge models, though it's hard to make them look neat. It's also harder to undo things you don't like and advisable to work from plans, though you certainly can just glue stuff to your model until it looks right - this too could be a way to arrive at something a bit unplanned. ]
[Question] [ We are the only sentient civilization currently known to man, and sight is an integral part of both our everyday lives as well as most major technological advances throughout human history. Without the ability to see long distances, we may have never yearned to reach the horizon in ancient history, so there may have been no desire to explore beyond our immediate surroundings. At the very least, the printing press, which really jumped civilization forward a bit through mass production of books and media for spreading knowledge, would have been implemented differently, where instead of adding ink to pages it adds some form of texture (similar to Braille), which seems to me like it would be less effective than print at a massive scale. And finally, computers as we know them are heavily reliant on sight. Most of the way we interact with them is through visual means, either through displays for PCs/tablets/phones, or even with visual indicators such as LEDs on the wide range of other computer-powered devices we interact with each day such as cars, microwaves, etc. Now, imagine a world where the dominant species is one without sight, as defined as the ability to take electromagnetic radiation and convert it into an image. How could such a species overcome this huge disadvantage to eventually become a space-faring civilization? Some thoughts I've had: * Echolocation (or something analogous to it) could provide the means to navigate the immediate environment. However, this likely would not allow for "sight" over longer distances. * Perhaps this echolocation analogue could tell the difference between different textures on an item, and up close was able to provide spatial resolution that approaches that of our eyes. * There is always a potential for some sort of neural interface, but then you would have to explain how they developed such advanced technology. Feel free to come up with any (biological, physical, mental, emotional) traits for this race to help explain how they could accomplish this. [Answer] # Electromagnetic radiation is awesome For two main reasons: * it's abundant * it goes in straight lines through the atmosphere Why is that important? because this makes the information (for the sake of discussion a photon is a bit of information) very reliable. If the information you have is slightly less reliable (e.g. photons go in a curvy fashion) this dramatically hinders your ability to sense things that are far away or sense close things with a high resolution. If the information is reliable but not abundant, I guess you could get by if you have the time to collect enough information to make any decision. ## Replacements? As far as I'm aware, there's nothing else that has these qualities except radiation. Sound doesn't go in a straight line and therefor it's very hard to locate it. All forms of echolocation rely on waves in the air (or whatever intermediate material) and are therefor inaccurate. You may say that dark matter is a viable solution, but since it goes through *everything* it provides no information at all. Consider the way we use light: our eyes have millions of sensors (rods and cones) that operate side by side. This only makes sense because each sensor receives slightly different input, because of the location of it in the eye and the focus of the retina. This enables us to do extraordinary parallel computing of the data, something that we don't come close to doing in any other sense. ## Possible solutions If the species doesn't rely on any kind of radiation for information, perhaps a solution would be to invent a new type of atmosphere and a type of material that can go through it in a straight line. In our universe, unfortunately, I don't know of any other solution. **Edit:** It was pointed out to me that I didn't actually answer the question :) # Technological solution Could technology help the species succeed without eyes? *Yes.* [This lab](http://brain.huji.ac.il/) and others work on a "sensory substitution device" (SSD) that converts light to sound and help blind people see. The theory behind it is that the brain is plastic. The brain areas that are meant to handle vision can learn to handle sound as if it was vision. Now, a blind species wouldn't have these areas, but imagine you connect this kind of device to every child for millennia - eventually something will happen. Is it feasible? absolutely not. Not only would creating any kind of device would be virtually impossible for a blind species, not to mention the amount of global cooperation that's put in place for any kind of manufacturing, also the theory, the knowledge that there's such a thing as radiation and that they could work hard for millennia and unleash it's power is utterly unattainable. The only real solution is a different species that gives them the technology to translate radiation into something they can understand, perhaps even to brain stimulation. [Answer] Echolocation can be very accurate if well developed however it doesn't work in space, what they could "see" would stop at the walls of their space ship. they might have to develop technology that sees light and converts it into a sound. It will also really slow down their research into space since they would not know anything was out there in the first place. Without extreme technological substitution or outside intervention a species that relies on echolocation might stay earthbound. Echolocation has advantages, it can possibly see in 360 degrees, but it is also slow the faster you are going the more distance you loose. in a plane that breaks the sound barrier they become effectively blind. It can see through solid matter, they could see all the parts in a device without taking it apart. I imagine they would make amazing mechanics for this reason. They might be able to see flaws in material making them excellent engineers since they would not have to rely on technology and surface features, everything would be partially transparent to them. They might have very little concept of privacy since it is very rare for them. They would be excellent geologists since they would grasp seismology much more easily. This species would have little problem developing other technology but high speed flight and space travel would be drastically delayed if they develop at all. As for printing they might print with lead on paper using drastically different densities instead of color. As for computers they might actually have an easier time than us, since they might be able to make sound systems that project a 3D "image" for them. You would have to worry about bleed over from other people's computers. Imagine a computer with a simple speaker could achieve for them the same effect as a 3d hologram has for us. [Answer] ## Cave-Dwelling Radio "Telepaths" Maybe they don't see visible light, but what if these organisms developed biological radio for communication? While radio *is* electromagnetic in nature, its wavelength is too large to properly resolve images in everyday life, so radio detection would probably not fall under the category of "sight". However, it has other uses: it can be used to transmit information a great distance away, allowing your creatures to communicate "telepathically". Low frequency radio can even penetrate dirt and rock, which would be useful for a social cave-dwelling species. They wouldn't see the stars the way we do, but the ones who left their underground home might "hear" their radiation by pointing their biological radio dishes skywards. This could lead to curiosity, which could lead them to develop space travel. What would make this even more interesting is if they started picking up radio signals from other civilizations... they could actually *hear* it directly, without the use of equipment. (They wouldn't hear *sound* of course, but they might recognize its complex pattern and realize it was being produced by something intelligent.) A more mundane, but similar answer: they just develop radio technology for communication and detect radio waves coming from the sky. After analyzing them they would realize that stars existed even if they couldn't see them. [Answer] Though a true answer lies after, I will start by answering your question with a question to put my answer into perspective: *Mock question* > > Hello fellow dolphins who live under the waves of Dearth with me. I have come to > worldbuilding.stackexchange.dearthnet to ask a question about aliens. > As you know, our leading scientists believe that we might actually be > descended from non-intelligent dolphins from another planet, and the > religious folks too point to their bibles which state that > dolphin-kind came from the third planet out from a yellow dwarf star; > even though I find those verses hilarious, since they also state that > those dumb ancestors had something called "eyes" that allowed them to > sense EM radiation, and furthermore that there were creatures with > eyes but no echolocation, it does make me wonder since such creatures could not possibly get a good 3D view of the world around them and would likely be their own doom as they swam into objects because of their lack of depth-perception as we are accustomed... > > > Now, imagine a world where the dominant species is one without > ~~sight~~ echolocation, as defined as the ability to take > ~~electromagnetic radiation~~ sound waves and convert it into an > image. How could such a species overcome this huge disadvantage to > eventually become a space-faring civilization? Some thoughts I've > had... > > > Now to get to the real answer, and let's think of it from the perspective of the Dearth dolphins. As demonstrated above, humans themse-, I mean ourselves, have a similar problem already. There are numerous energies and forces which we cannot directly sense with our organs, and most of the EM energy itself is included in that. In the case of EM though, we have a leg up since we can at least sense part of it, [seeing wavelengths from about 400-700nm](https://www.google.com/search?q=what%20portion%20of%20em%20can%20humans%20see&hl=en&site=imghp&source=lnms&sa=X&ved=0ahUKEwj5uYTGwoHTAhUK3mMKHfDNA3sQ_AUIBygA&biw=1164&bih=860&dpr=1.1#spf=189 "Human-visible EM wavelength"). Some of the things that humans cannot sense are things that other animals can sense. Take magnetism for example. There are many animals which have a sense that we unfortunately cannot tap into: [magnetoreception](https://en.wikipedia.org/wiki/Magnetoreception "Magnetoreception"). It does wonders in helping animals get around. I wonder if the birds looking at our airplanes think "How can those humans possibly have figured out how to fly a plane, and to reach such distant locations accurately nonetheless, when they cannot sense the earth's magnetic field like we can?" I also wonder if the birds can pick up at all on the magnetic fields of the sun or of other celestial bodies; probably not, despite the fact that you can [tune in to hear Jupiter's static on a good radio](https://science.nasa.gov/science-news/science-at-nasa/2004/20feb_radiostorms "Jupiter Radio"). ## How did *we* do it? So, how have humans accomplished the feat of "seeing" energies and forces which we cannot directly see? We hypothesize the existence of something, figure out a way to test it, verify, create devices to detect it, then finally we convert the data into a different format which we can see. Take an EEG graph for example, generated by an [electroencephalograph](https://en.wikipedia.org/wiki/Electroencephalography "Wikipedia EEG"). It is something that we cannot detect without the EEG, but we then turn it into a visual graph as on the linked page. We do the same with devices that create graphs of electrical current and with seismography and many other things. We can view the data in a meaningful way that allows us to act on it almost as if we had sensed it personally. Now, this gets more interesting when we generate full pictures of things we cannot see. A great example of this is with an [MRI (Magnetic Resonance Imaging)](https://en.wikipedia.org/wiki/Magnetic_resonance_imaging "Wikipedia MRI"). Better than the bird's magnetoreception, an MRI allows us to look inside of a person, generally for medical reasons. The below image uses magnets to show us a picture via the EM that our eyes see, but it also has the added benefit that the picture is an fMRI showing an added layer of information (the colored spots) which we can do because we use technology to combine all the data into an image in the format we desire. If you look at the picture below, you will be doing the same thing we are talking about. By observing the picture below, you are looking inside someone's brain by "seeing" magnetism even though you have no biological way to do. [![Brain fMRI including activation areas](https://i.stack.imgur.com/vPAvK.jpg)](https://i.stack.imgur.com/vPAvK.jpg) Image public domain courtesy Wikipedia at same link as above There are other cool images we could dig up that do similar things. I wanted to include some of x-ray visuals, microwave/radio-wave visuals, and the like because there are cool instances of those, but those are technically EM radiation, just not the wavelengths our eyes detect, so I'll forego that here. You can use Google images to turn up plenty of them, [especially for astronomy](https://www.google.com/search?hl=en&site=imghp&tbm=isch&source=hp&biw=1164&bih=835&q=astronomy%20xray%20radiowave%20microwave%20images&oq=astronomy%20xray%20radiowave%20microwave%20images&gs_l=img.3...1279.13992.0.14091.41.8.0.29.29.0.409.649.2-1j0j1.2.0....0...1ac.1.64.img..10.2.647...0j0i24k1.A3cNgY6M0z8#hl=en&tbm=isch&q=astronomy%20xray%20images&*&spf=191 "XRay Astronomy Google Images"). ## Now here's how *they* do it Now let's bring this all back around to our dolphins of Dearth example case. **Information Distribution** As you pointed out, the printing press may have developed differently. Yes, that is likely. As you suggest, something more like braille is likely. For creatures primarily dependent on audio, audio recordings would also be likely. A [phonograph cylinder](https://en.wikipedia.org/wiki/Phonograph_cylinder "Phonograph Cylinder") is a device which can be used to record and playback audio, and it does not require any electrical components; it can also be made using very basic mechanical components. There are simple designs which are easy to create; [here is a link to one you can buy which records to and plays from a wax candle](https://www.adafruit.com/product/1843 "Wax Cylinder Recorder"). I once saw a TV show where a small team (3-5 people, if I recall) was left on an island with limited resources and were given objectives they needed to accomplish, including documenting wildlife; one of the guys used wood and wax to create a recording cylinder - they recorded bird songs with it. It was dumb simple. Your creatures can do similar, and you can use a playback to record another cylinder, though the quality will degrade quickly. Every time you want to re-boost your quality, you would need to recite the recording again, preferably in the presence of a room full of recorders, then distribute those to remote re-recording centers. Also note that sound travels much easier through water, so in my specific example of dolphins sound will travel easily and far. Phonographs are their printing presses; slightly less efficient but they will get the job done. **Electricity** After discovering electricity (Doesn't require light or modern technologies), they realize that something keeps interfering with it. While experimenting with their electronics, they discover that electric signals in some conductors produces interference with other conductors. This can take many forms but they all amount to the same thing; we get this phenomenon in devices as simple as a wire carrying the signal from a microphone to a speaker (our dolphins likely figured out microphones and speakers much sooner than we did; it's their primary sense after all), and in that case you will literally hear the interference. A bit more on electricity further below. And this interference leads to... **And finally, EM detection (aka "seeing light")** Some bright dolphin comes along and decides to deliberately cause an electrical "interference" to be detected remotely for the express purpose of wireless transmission, and thus the blind dolphins' radio technology is born. They do not even understand light yet, nor do they have any idea why this works since they do not understand EM. They will, however, continue to experiment and progress until they have figured it out, much the same way we have for energies and forces that we can only measure with devices. As soon as the blind, intelligent dolphins realize they can use their radios as radar, they build the biggest ones they can and point them where they cannot go: up. They find an empty expanse in the sky. Disappointing. "What if we keep building bigger?" some ask, "We might find something way far out, like millions of miles out!" "That's absurd," some will say, but eventually it will be done and other planets will be detected. So begins radio astronomy for our blind, intelligent dolphins, and they are surveying space. Obviously the general populace wants in on this action, so their scientists invent helmets which fit them and include a surround-sound echolocation system to transform the EM data into audio data so that they can all see it in their natural sensory format. There is another point you may have thought by now: What about detecting the energy put out by the other planets, and stars etc. for that matter? They will undoubtedly, and soon, realize that they can "see" even without the radar using passive radio detection, which might come before the radar detection of other planets mentioned above, or it might come after, depending on the frequencies they are using. Either way, they will soon see *everything*. We have come full circle and seen the steps they would go through. **Disclaimer (Handwavium and more on electricity)** The only hand-waving I did was "and they discover electricity," but that's not even a stretch since [humans started using electricity thousands of years ago](https://www.google.com/#q=ancient+human+electroplating&*&spf=387 "Ancient Human Electroplating") for electroplating; maybe some people understood what was going on, maybe not, but we know early humans stumbled into electricity at the very least and knew how to make a battery and use it. I don't know how they discovered it either; I just know they did, so this might not actually be hand-waving after all. As pointed out in the comment by @Mormacil, dolphins are likely to have a better up-close-and-personal demonstration of electricity than other creatures because there are marine creatures capable of generating and using electricity such as electric eels. Perhaps these dolphins even farm electric eels to use as their generators. **Computers!** As you said yourself, computers *as we know them* are reliant on sight. The original computers and their output did not utilize monitors as we know them. Their input was not with keyboards, and their output was not by light. So this issue kind of resolves itself. I imagine early [vacuum tube computers](https://en.wikipedia.org/wiki/List_of_vacuum_tube_computers "Vacuum Tube Computers") could have been attached to the audio recording devices mentioned above to provide output even easier than the paper printing that some of our early computers used, so the output device is already covered and likely invented before computers and can interface easily with our original human computers. Input might be more of a concern; my example of dolphins for example, hopefully they have better graspers, or maybe they can use audio for input as well (that could indeed be translated the other way from mechanical audio playback into the mechanical early computers). Also note that there were technically ancient computers too, even more advanced than the abacus, and some early computers even controlled devices [such as this computer-controlled artificial lion from the 1400s](http://dangerousminds.net/comments/leonardo_da_vincis_incredible_mechanical_lion "Computer-controlled Artificial Lion") and [there were humanoid robots too](https://en.wikipedia.org/wiki/Leonardo%27s_robot "Medieval Robot"). Computer technology, even computer science theory, is actually older than the electronic computer as we know it. Now DASA (Dolphin Aeronautic and Space Administration) uses the telescopes from above, possibly in conjunction with computers (whether electronic or mechanical), and have made a major discovery; DASA has released a publication about the third planet from Sol possibly having large oceans of water. These dolphins are looking at Sol wondering if there really could be intelligent life there, or anywhere else in the universe for that matter, and we have come to the point at which our young dolphin of planet Dearth asks their worldbuilding.stackexchange.dearthnet question that I led with at the beginning. [Answer] Our skin makes an excellent visual sensory organ. It absorbs EM spectrum and reacts to it. And we can reprogram it in humans to be usable for sight. See this article in the section about "BrainPort" and tongue sensors: <http://blogs.discovermagazine.com/crux/2014/04/28/blind-sight-the-next-generation-of-sensory-substitution-technology/#.WExH7rVOLYU> You trivially know which way the sun is from your skin. It's a short hop to more discrimination of that incoming information. It is thus my contention that any species that is exposed to useful EM fields is going to develop sight, so your species is going to have to be cave dwellers initially to pass my believability test. If they are so deep to avoid all light, then their first hurdle will be even seeing the stars to know there's a reason to go up to space. Maybe they heard about it from other animals. They could develop the equivalent of seeing-eye dogs, animals or lesser sentiments that see for them. That could cover a wide range of activities, and maybe lay the groundwork for how they interact with other alien species they meet -- already used to multispecies conglomerates. [Answer] ### Questions Although you define perception of the electromagnetic spectrum as sight, I think your echo-location provides you with an easy analogy to sight, in that both of them provide some form of spatial image, albeit echo-location has no colour. Some animals' perceptions are dominated by an enhanced sense of smell - so the world within which they live is very different to those who use either sight or echo-location - everything is dynamic, fading, all the time. The difficulty I have though, is finding a reason to explore space if you cannot see; without perception of the electromagnetic spectrum the sky offers nothing more than a great absence. As you get higher in altitude, sound diminishes - as do smells, and vibrations - everything other than vision is weakened by the lack of an atmosphere. The deep - oceanic depths, I would have thought, would be far more interesting to the unsighted - for the same reasons - increased density could be seen as an enhancement of one's senses. ### Answers So, putting aside all physical senses, I guess one could start with some form of telepathic empathy - maybe the beings can sense great loss and suffering from above and strive to do something to assist. There are real risks - not being aware of the electromagnetic spectrum, these beings would be prone to all sorts of radiation exposure. It may lead them to develop artificial eyes - sensors, and so on - but then they would still need to interpret the results in a meaningful sense, which would not necessarily tap into their existing sensorium. I don't see any particular reason why they couldn't develop technology - and even manage to escape the gravity well. But their understanding of the huge distances would be very difficult to comprehend without being able to measure distances; let's say that their empathic ability allows them to measure distance very well - so then they can guess at the distances they need to travel. Then they are faced with all the problems that we have today when it comes to interstellar travel. I have suggested elsewhere that the best way to travel between stars is to wait until the stars get very very close. Every now and then a star comes maybe only 70k AU away from the sun, so this would be an opportune time to travel (unless you want FTL also). Star-hopping is far more unexplored as an idea in SciFi - maybe because we are so impatient - but what if these beings are not so short-sighted - and are willing to wait hundreds of millenia to travel between stars - as they would have ample time to populate each solar system, the overall expansion of their sphere of influence would exponentially speed up, so although it would be a slow start, they could (in stellar time) populate much of the galaxy quite rapidly. [Answer] Without sight, I don't think a race would explore space without being uplifted by another race. The reason is the same reason that a race from a perpetually overcast world wouldn't get into space. They don't know it is there. You have to know enough to ask the question before you can start answering the question. If they can't hear, feel, or smell/taste it, does it exist for them? I would imagine that on that planet, nothing can see. Otherwise, anything that can see will have an overwhelming survival advantage. Therefore, they likely don't have anything that flies. They may be able to leap (and pray for a good landing spot) or throw toward a noise but everything in their experience is that since nothing stays up, there must not be anything up there. I would imagine that if you encountered such a race (and somehow learned its language), that explaining where you came from would be difficult. A long way away would make sense to them but they would get the wrong idea. Saying "up there" would make them think you came down from a mountain or something like that. [Answer] **I think blind people are severely underestimated here.** It's true that being blind is a huge disadvantage in our society, but that's only because everything we build is made with the target audience of two-eyed humans. Which of course, we did because we use our eyes all the time, even for things where they are not the best tool. Among other things, eyes are slow and suffer from tunnel vision. A very simple example: traffic lights. You have to stare at them, and keep staring at them. In some cases for minutes. And they expect you to react right away when they turn green. (Some countries have fixed the latter by lighting up orange before switching to green though) The traffic signals for blind people are not as widespread, but when they are available, you'll notice that they are much more user friendly than their visible counterparts, even for people that aren't blind. I think the assumption that blind people could not create advanced technologically is false. Blind people tend to take a backseat in our society, but when everyone is blind, we are not collectively going to sit on hour hands. We are certainly not going to wait for a predator to pick us off one by one. It's our ears that will safe our skin. Compared to those, lack of eyesight is a minor disadvantage. We create tools that offset our weaknesses. We make spears, because we have no natural weapons. I'm sure we can come up with something that prevents us from running into trees. It's true that no amount of tools will help someone from present day society if he has just lost his eyes, but if a species never had eyes to begin with, they wouldn't be nearly as helpless. As for **computers**, I don't think it is much of a stretch either that we would have invented it by now. They wouldn't have evolved into machines with displays for output, sure, but thats hardly the only way we can interact with them. These days, even computers with displays have support for blind people. See screen readers and the Web Accessibility Initiative (a standard for websites to enable the use of voice interaction, etc). Remember that while those are crutches, *they are only necessary because we didn't design computers for blind people right from the start.* Besides, why would eyesight be required to create a machine that does calculations for you? Because of the details involved? Considering how huge the first computers were, I sincerely doubt that we couldn't take the same approach of starting big and miniaturize when we get more comfortable in the field. **Books** would probably be produced earlier if we had been blind. Putting ink on paper in seemingly arbitrary patterns, is rather complicated compared to punching holes in a rectangular grid. As for **space travel**. There's as much incentive for blind people to explore as there is for people with eyesight. Blind people, too, will wonder what's above their heads and beyond the water. In fact, they might have been even more curious than we are. Without eyesight, a vast, empty ocean is more of a mystery. The majority of space is not observed with human eyes, by the way. Many of the pictures you see from space agencies like NASA are not even 'just close-up views'. The colors used are simply made up, because the observed phenomenon usually have nothing to do with visible (colored) light. We made tools for observering the stars, *because our eyes are inadequate to make any meaningful observations*. Well, we can take note of the location of stars, and how the moon is lit at this time of the month, but that's about it. We cannot even look straight at the sun! If we're making tools for stellar observation anyway, and we build computers that interact with us in a non-visual way, then we'd make the same progress as we do now. **So, how would a blind species reach the stars? The same way we did, with passion and the occasional flash of brilliance.** [Answer] * They find hot rocks and craters appearing on their planet through history. * They figure out it came from the sky. * They try to send their own species higher and higher seeing if they hit anything. * They realize that communication between ground and sky become harder and harder the higher they go. * They eventually invent something that can send information (let’s say sound in this case) long distances and later something that works in space too. * They keep sending millions of probes, until they eventually hit something and there we go! Basically, a huge waste on resources, time, and very reliant on luck. In short: **Throwing balls everywhere that tell you what they hit through radio signals.** I'm no expert. [Answer] It's important to note the role of sight in current humanity in forming the view of the world we hold. There's quite a few 'mind trick' games online that can show you a few pieces of how your mind processes what it sees and how it can be tricked...there are several things that our mind just draws in for us. As much as we like to think our sight is an end all, it's actually a picture in our minds that we derive from multiple sources and our minds will actively make assumptions in your perception of the world around you. All senses play their role, along with past experience, in forming our view of the external world. I bring up this just to point out not one sense can be employed to replace sight, but a combination of many. Electroreception through ampullae of Lorenzini. You may recognize this as the sharks ability to detect the electric stimuli. It can also be extended to recognize the earths magnetic field which bird, insects, fish, and sharks all seem to use. This could actually have really interesting implications for computer use...monitors would draw images with magnets. Echolocation. From the electroreception above...these creatures now have a 'magnetic' map of the world around them drawn in their heads. Layer on the physical location of things using echolocation and you now have a decent picture in their head of what the world around them is. Layer in the other 4 senses to various degrees and I think these creatures can have what they need to get to space faring. [Answer] There is an interesting "rock" species introduced in a game : [Litheor](http://galaxylegion.com/wiki/index.php/Races#Litheor) While there is no description on the senses they use, I believe the most suitable sense they have developed, and alternative answer on your question is a sense of [gravitational waves](https://en.wikipedia.org/wiki/Gravitational_wave). I imagine this species would have such refined sense that they can detect even minor gravity differences on their high-gravity home planet. Like echolocation, they have evolved to use this to navigate through their planet, and eventually they detect gravitational shockwaves from supernovas, and they learned about the space - just like our ancestor look up to the stars. I can't imagine the details from this point onward, but they can figure out how to use this to observe the space, and eventually become a space faring species. Most likely they won't realize about electromagnetic radiation until later, because they lack the sense to detect it. ]
[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/63674/edit). Closed 3 years ago. [Improve this question](/posts/63674/edit) In my high fantasy medieval world, the ocean is populated by underwater fish people and land dominated by your good old human. Different type of fish people (shark, whale, turtle, shellfish, etc.) live at different depths, and forming their own kingdoms. Several kings would sometimes band together, forming a massive alliance that spanned across the ocean. What I'm curious about is how would trading look like, both the trade with other underwater kingdoms, and trading with humans. How would the age of sail different now that there are multiple powerful kingdoms under the ocean? Note that neither human nor fish people are capable of fully engage each other, as there is currently no means for human to push their forces deep enough underwater, and the fish people are unable to leave water for too long. Piracy, however, is very much possible, and I envision fish people are going to be doing most of the raiding. The trade routes between underwater kingdoms are too deep undersea for human to raid. The fish people could leave the water, but only for a short period of time through the use of magic. So I imagine there'd be trading ports that are partly submerged, sort of kind of like Venice, and trading between human and fish people can be conducted there. Now I know there are a lot of stuff people want from under the ocean, pearls and what not. But what would the fish people need from people up above? What kind of quality goods would they be looking for? And how would trade looks like between human kingdoms oversea? Would they stay pretty much the same, with the only difference that now there are fish pirates? I imagine the underwater currents might serve as the trade routes between underwater kingdoms, as a mean of quickly getting goods from one place to another. They'd probably be using muscle beasts, sort of like the counterpart of human trade caravan. How would their ships look like? --- To sum up my question: 1. How would trade look like (methods, trade-route locations, ships, etc.) between: * humans and other humans oversea * humans and fish people * fish people and other fish people undersea 2. What would the fish people seek to gain from trading with humans? 3. Other interactions you can think of that related somewhat to trade? Piracy, mercenary, slave-trade, fish people eating humans and humans eating them back as a delicacy, etc. [Answer] In order to figure it all out, let's go back to First Contact between humans and fish people and play it forward to see how it would work. If you don't mind, I'll name the fish people 'pisces' to make it easier. They first meet, and they're both unknowns to each other. Humanity has a history of not dealing with unknown Others too well, so things would probably be tense at first, until everyone realizes that neither poses an existential threat to the other - the humans can't destroy the pisces, and the pisces can't destroy the humans. A peace is drawn up and trade is able to begin. Interspecies trade begins primarily in the major coastal human cities - the pisces are able to surface for a short time there, while humans can't descend to the depths of the pisces cities - and stays there. The humans will have to get pisces trade goods to interior cities on their own. Intraspecies trade is a bit more difficult, but not drastically. Your idea of the pisces utilizing oceanic currents is a great one. Add in the idea that they've, say, semi-domesticated whales and are able to utilize their migration patterns to move wares and you've got yourself a pretty good system. (Off topic, but I'm actually kinda reminded of interplanetary trade within a star system - you'd have a base on Earth, a base on the moon, on Mars, on various asteroids, and you'd have essentially set paths between them based on orbital mechanics. This system is the same idea, just using oceanic currents instead of orbits.) The issue becomes human-human trade. Trade within one 'country' or even continent isn't a huge problem, you can just do it overland. We've been doing that for millennia. But how do we get ships across the oceans safely? Basic economic sense says that it's better to trade with wealthy nations than with poor nations. A wealthy nation is able to produce more, so you can have more options to trade for, and they're able to buy more of your items as well. As such, it is in the interest of the pisces for the human nations to become as wealthy as they can. I can easily imagine that there would be agreements made permitting trading ships to traverse the oceans (relatively) free from harm. There will quite obviously be bandits, pirates, etc, but a simple agreement that there won't be any governmental action taken to prevent human-human trade will make it much more feasible. As far as what the humans trade with the pisces, I can imagine that metal would be a big part of it, especially tempered metal. It's rather tricky to get fire underwater, so the pisces would likely have little to no concept of metalworking. Knives, buckles/clasps, sturdy fishhooks (okay, that may be too insensitive).... All sorts of things that are drastically improved by being solid metal. The only major interaction I can think of is shipwrecks. Humans and pisces can make all the agreements they want, but ships will occasionally get caught in storms and sink. What happens to the cargo? The humans can't get at it, so (in our world) they could just call it a loss... But the pisces could get to it, recover some of the cargo.... Does that mean they get these trade goods for free? Are they obligated to return what they can to the humans? Would they skim some off the top before they did return it? I could almost imagine groups of pisces going around the coral reefs, the shoals, the Bermuda Triangles of the world where shipwrecks are common, and scavenging whatever they can get their hands (fins?) on before anyone reports the loss. Get several of those groups going around the world and you could easily have a black market of human trade goods. But this is starting to get into idea generation. TLDR, it would honestly look a lot like international trade in our world today. Trade what you have, that the other party doesn't, and make sure that you're both able to prosper as a result. [Answer] lets start with the basics **What would an aquatic race want**: remember it needs to survive underwater or they won't want it. They won't have much use for clothing water is not an insulator like air so clothing does not help much in maintaining warmth and there is no rain to keep off. **Glass** especially mirrors, bottles, and lenses no way to make glass under water. glass floats will also be popular. **Brass, copper, and steel**: steel is actually alright underwater as long as it stays underwater, it will rust faster than on land but will stay usable for decades. . tools and weapons will be especially popular, even brass nails will be valuable. **Lumber** especially poles: very little wood underwater and again as long as it stays underwater it will not rot any faster than on land. **Gold**: again no way to smelt metal underwater, they can work gold but have no way to smelt it. silver will become quite ugly very quickly however. **Pottery** plates are useless but jars are easier to make on by shaping and firing than carving as aquatic races would have to do. **Surface foods** food has always been a popular part of trade, this will run both ways and will be most common where both civilizations are close to each other. Cooked food will be popular, every animal ever tested shows a preference for cooked food sue to the higher nutrient availability. Now for the aquatic races **What can they offer**. **Sponges** sponges have always been valuable enough for trade and they are far easier for them to collect than fishermen. **Ore** there are ore deposits underwater just as on land. Many are actually easier to collect. **Fish**both as direct trade and as indirect by selling information about movements **Pearls** this one should be self explanatory **Maps** seafloor navigation maps take a lot of time to make, an aquatic race can make them much faster and cheaper, they will need a human agent to copy them to air friendly materials. **sunken ships** the location and recovery of sunken ships and their cargo will be profitable and fairly easy. This of course could create pirates. **Art** coral carvings, shells, and similar art will always have a market. **Ship maintenance** certain aspects of ship, bridge, and dock maintenance will be much easier for an aquatic race this could easily be worth trading for. **Travel rights and guards** through territories/kingdoms will be a big deal, for those aquatic races that are amphibious this will run both ways. Remember they can sink ship with ease if they want to. I could easily see a negotiation for guards for ships. who better to stop merfolk pirate than other merfolk. There will be other things they can offer all depending on how they live and what their technology is like. maybe they make a seaweed extract that is really savory or collect a snail venom that is useful for treating cholera. I can picture trade houses built out of stone that have a waist/chest high wall with water on one side and dry land on the other. trade partnership between merchants should be common. Math and standardized measurements will be important, a pound of iron on land is not a pound underwater. writing will probably be exchanged each way just for the novelty value. I imagine their written language will be runic relying on carving rather than ink, I could also see a knot based language like Quipu. Both can be read like braille which will be useful for fishfolk that live in deeper waters. Although I could easily see them farming bioluminescence coral or sponges for light. Pencils work just fine underwater provided you write one slate and not paper, ceramic slates may be popular since they can be made for a much cheaper cost. [Answer] *What would the fish folk want?* Anything you make with fire. Anything that you can't easily craft in water. **Textiles** There's a [question on here about writing and an underwater civilization](https://worldbuilding.stackexchange.com/questions/59791/what-could-an-aquatic-civilization-use-to-write-on-with/59805#59805). In the answers you'll see that textiles are difficult to make in water--the process of drying and weaving, and because land-based things, like wool, cotton, silk, etcetera are just better materials to make clothing. Your fish people would want textiles specifically made to hold up underwater, but you can bet that some merchant will find a way to market them. **Books/Writing** Not the standard kind. But printing underwater is problematic. Out of the water, it's easier to make "books" that hold up underwater. They might be made of fabric and the letters sewn, they might be made of thin pieces of bone or ceramic, the words painted on and preserved with a sealant. Ink and paint doesn't do well underwater, and it's difficult to make fabrics underwater, so this is likely something that would be produced topside. **Leather** Degrades quickly underwater and it definitely needs land and fire to dry and cure it. However, during Medieval times there were a great many fabrics used that didn't last in regular air for long--these were used by the nobles and were seen as luxe items that would be replaced regularly. (Not everything they wore was like this--there was a lot that would hold up to use, but there were wearable items crafted NOT to last). A crafty merchant might treat this leather differently so that it would last a little longer under water, but I see this as something that high-status fish folk might wear. **Ceramics** They can carve things but don't have a kiln. This would be a luxury-type item. They eventually degrade under water, but I can guess that if there's a trade, land folk will be willing to make things that last longer **Tools and Weaponry** Crafting and tempering metal underwater is not an easy task, and the hardness of tempered metal is better than most materials you could find underwater. **Glass** This is amongst the things you can make with fire. It would be a luxury item, of course. *What would land lubbers want?* Pearls, coral, food, recovery of lost ships (as John Robinson said in his answer), farmed seaweeds, fish, and whales. And, since this is rare, [Byssal (Byssus) Threads](http://marinelife.about.com/od/glossary/g/byssalthread.htm) *Slave Trade?* I am not sure how this can work, at least, BETWEEN the two, because they exist in completely different environs. And getting slaves to work when you can't spend much time topside (or "downside") is problematic. *Piracy* The fish people have the advantage here. It absolutely will happen. In and out, fading back into the ocean. Or, just sink the ship. Everyone will drown and you can take it all. I would think that if they want merchants to continue USING a route, that they would just take some. *Eating Each other* If it's culturally acceptable, sure. But do keep in mind that most things living in the sea find land creatures, well--yucky. We probably just don't taste right. That's why, unless there's a gathering of sharks and they get their blood-lust on, they mainly spit us back out. That's my theory anyway. But, your world your rules. [Answer] 1. "Humans and other humans oversea" 50/50 chance the merpeople leave sailing ships alone ("Oh look, another cargo ship. Better leave it alone, or the humans might restrict their trade with us or raise their tariffs") or attack them ("Oh look, a cargo ship! Let's sink it and claim its treasures!") "Humans and fish people" I agree it'll be in coastal areas, mostly because it'll be easiest for the two to interact there. If merchants tried to negotiate from their boat, they'd have to drop anchor and probably have to shout to overcome the distance between them, unless some sort of platform is lowered down. Humans would want: seafood, coral, pearls, shells, treasure from shipwrecks Merpeople would want (credit to Erin, who realized these first, thought the last is my addition): Glass, ceramics, metal, textiles, jewelry "Fish people and other fish people" They'd have merchants with extensive delivery networks, much like freight companies back in the day. Mounted sharks, whales, or just well-trained dolphins could carry goods from here to there quite effectively. As for what they trade: Anything from the humans is fair game, I assume they'd trade things like shells or walrus ivory between themselves as well 2. What would the merpeople seek to gain? As stated above by me and others, anything that can't be made effectively underwater (metal, ceramics, textiles, glass). Mermaids would probably love mirrors and human jewelry, whereas mermen would be more into weapons. Also, trade relations are a pretty effective conflict buffer; you don't try to tick off your trading partners, do you? 3. Piracy and mercenaries? Absolutely. Piracy for obvious reasons, mercenaries less so: the two sides (human and Mer) will want to influence each other, the Mer by sinking ships, either to support their allies or as acts of vengeance for CAM (Crimes Against Merpeople); the humans by hiring mer-mercenaries to escort their ships, to attack those responsible for their sunk ships, and to attack those mer-kingdoms who won't negotiate as they desire. As for the slave trade, there are actually some options for humans here. Number one, seeing mermaids perform or hearing a siren sing could be an exotic form of entertainment. *Eating* each other, though, seems poorly thought out. Why on Earth would they do that to each other? Curiosity? Something is clearly wrong if this is actually a thing, as this would *severely* curb friendly relations. ]
[Question] [ I need someone to fact-check me and tell me if there's anything immediately bogus or physically impossible with the scenario I'm about to propose. Billions of years ago, under the ice of Europa, the first single-celled organism developed. Over time, members of this single species began to differentiate and eventually an ecosystem of multicellular organisms evolved from all the different strains, just like what likely happened here on Earth (albeit grossly simplified). However, unlike on Earth, this single progenitor organism never died out or was outcompeted by its offspring, and eventually it even began to group together with other cells of its kind to form simple logic gates (kind of like what we've been doing in the lab). One thing led to another and this ancestral species eventually developed into a bacterial supercomputer, from which emerged crude sentience. As the first and as far as it knew only intelligence underneath the icy surface of Europa, it inevitably came to the conclusion that all these other more complex organisms that it birthed so long ago lacked its collective hive intelligence, or indeed any intelligence, and were there merely to serve as extensions of itself. Relying on their distant evolutionary connection, it began to infiltrate other organisms in its ecosystem and turn them into biological fingerpuppets, as they were to it little more than large colonies of cells marginally differentiated from its own that existed only to serve a specific purpose, like a new limb. At the end of the process, what we have is a single massive colony of this primordial microorganism that has gained intelligence and has differentiated its cells into many different types which each form their own colonies (read: organisms/animals) that are controlled by the central hive intelligence. Thinking as this organism does, the entire ecosystem is then nothing more than one gigantic organism. Is this plausible/realistic and could it pass as the plot for a hard sci-fi story about exploring the oceans of Europa? Or is it complete garbage psuedoscience that only reveals my admittedly shaky grasp on a bunch of different interconnected fields? [Answer] ## This is a creative idea, and I would love to see how it turns out. Let's play with it until it works. --- ## Scientific problems and solutions to them > > under the ice of Europa > > > I would caution you with this one. Europa is incredibly cold, so any organisms developing will want to make use of thermal energy below the surface - such as geysers. Consider less of an "all encompassing" creature and more of a web across all geologically active faults and spanning all geysers. Somewhat hard to do, but possible. > > However, unlike on Earth, this single progenitor organism never died out or was outcompeted by its offspring > > > Not necessary to provide the circumstances you desire, and it adds a layer of unlikeliness. Consider killing it anyways, I'm sure its offspring will suffice. > > eventually it even began to group together with other cells of its kind to form simple logic gates (kind of like what we've been doing in the lab). One thing led to another and this ancestral species eventually developed into a bacterial supercomputer, from which emerged crude sentience. > > > This isn't impossible, but as other answers have pointed out, it's also not very likely. Consider something like that [described in the second best answer on the recent question you asked](https://worldbuilding.stackexchange.com/questions/63538/could-a-microorganism-possess-intelligence), which involves "smart" colonies of algae. While I'm not sure exactly how this evolves, Earth examples prove it's completely possible. As other answers noted, crude sentience must exist for a purpose - if this organism survives by reaching heat and processing minerals, which can be done through plantlike reflexes, there is no need to evolve higher thinking. Consider evolving a couple predators to refine those reflexes over time. > > As the first and as far as it knew only intelligence underneath the icy surface of Europa > > > See the above - there must be other intelligences to co-evolve if you want a crude sense of consciousness to develop. Also note that reproduction happens - while this may be one big clump of "algae", with individual cells that reproduce asexually, some are bound to split off and attempt to colonize. You must explain why there are not more of this organism. You could solve this problem by making your colony analogous to [Pando](https://en.wikipedia.org/wiki/Pando_(tree)), the largest single tree on Earth. It's beneficial for cells to remain with the main "mind" because it provides nourishment; if they split off, they will be devoured by the newly evolving plankton and other microorganisms. > > it inevitably came to the conclusion that all these other more complex organisms that it birthed so long ago lacked its collective hive intelligence, or indeed any intelligence, and were there merely to serve as extensions of itself > > > I disagree with "inevitable" and I have discussed why there must be other intelligent (though not necessarily self-aware) organisms above. However, the "extensions of itself" idea is somewhat like the original "animals are here to serve humans" as opposed to "they evolved too" mindset, so it is credible. > > Relying on their distant evolutionary connection, it began to infiltrate other organisms in its ecosystem and turn them into biological fingerpuppets, as they were to it little more than large colonies of cells marginally differentiated from its own that existed only to serve a specific purpose, like a new limb. > > > The evolutionary connection part isn't credible - we are connected to primates, but does that mean we can control their minds with ours? I suggest leaving that out. You could, however, combine some qualities of angler fish - in which the males fuse with the females to reproduce - and of a certain nasty fungus *Ophiocordyceps unilateralis* - which has evolved to control the brains of ants at a fundamental level. Perhaps the motivation for this is that new bodies provide nutrients and processing power - but "mind pry" thing will take time to *evolve*, something which an asexual colony will not be able to do for a very, very long time. The marginal differentiation part may be important, but would involve creating more mouths to feed with little productivity; dead weight will become a problem. I suggest absorbing much different intelligent species with brains that are of some use - or just absorbing to digest - rather than to add mass. > > At the end of the process, what we have is a single massive colony of this primordial microorganism that has gained intelligence and has differentiated its cells into many different types which each form their own colonies (read: organisms/animals) > > > I've addressed most of what can allow this to happen by now - the "different types" would come from capturing different organisms to use, etc. Sounds good. > > central hive intelligence > > > As TessellatingHeckler pointed out, brains are not fast when considering the size of this thing - so a creature spanning the planet will have some delays. Combining slow metabolism (most of Europa is cold) and long latency issues, expect a fairly slow mind. Regional intelligences with some overlap might work better - they can all do the same things, but memories may not be consistent, and there will be a delay in spreading any new. --- ## Plot potential **As a character** If the mind is a character instead of an obstacle, it will be extremely complex, and you could create an infinite number of plots around it. The ever-present **dementia**, **confusion**, and **isolation** may be aspects of its personality, a cause for potential suffering, and a reason to sympathize/empathize with it. **As a monster** On the flip side, if it's "evil" or "heartless" and functions just for its own survival, your characters may take advantage of latency and confusion to escape it or destroy it. **As a philosophical discussion driver** *I urge you* to take advantage of the potential discussions this creature offers you. To list a few: * Who defines good and evil? + Perhaps this hive mind, growing up alone, isolated, and hungry, will have different morals. Who are we to decide that it's morals are "wrong"? * What are the differences between *living* and *being alive*? + Similar to the above. Sure, its "living" in the biological sense, but can this creature really feel "alive", in constant solitude, cold, and hunger? * What happens when you die? + A scared, isolated mind may witness the death around it and come up with a religious viewpoint. + If it has consistent views with ours, perhaps it proves there *is* a creator. + If it has completely different (but not disprovable) ideas, are they any less valid than ours? * Do we have a soul; are we special? + Is there a fundamental difference between human consciousness and others out there? + Is "soul" just an idea, or do we believe after meeting this that we're special? --- ## Other notes and discussion > > hard sci-fi > > > Hopefully I've brought you close to hard sci-fi, but I can't guarantee anything. Speculative evolution is difficult to call "hard" but I think you're close(ish) now > > is it complete garbage psuedoscience > > > Even if this ends up being pseudoscientific, there's no reason to stick to hardness! The facts and figures explaining a creature can be boring - imagine if *Godzilla* explained how the creature dealt with crushing gravity! Furthermore, I'm sure your story will be great regardless of how realistic it is. **Closing thoughts** This is an awesome idea, can be justified with a few tweaks, and would make an excellent, complex story that reaches deeper levels of thought. Go for it, dude. [Answer] @Durandal has already touched on plausibility of that evolution. I question the plausibility of a single intelligence because of signal travelling time - Europa is ~10,000 Km in circumference, at the speed of light a signal going halfway round and coming back would take 33mS. And that's assuming a direct route, no encoding/decoding costs and no route-switching costs. [Human nerve signals max out at 200 miles per hour](http://hypertextbook.com/facts/2002/DavidParizh.shtml) which means biological return signal would take 31 hours to get to the other side of the brain and back, if it encompassed the whole planet, so a thought might take days or weeks - difficult to have a single mental state, and I guess regions of the planet would become isolated and split off from the larger whole due to (quakes, ice sheets shifting, etc). > > could it pass as the plot for a hard sci-fi story > > > A sci-fi story yes, planet-sized or wide-area intelligences with movable parts have been written before (*Ender's Game, Pandora's Star, I Robot, Dark Side of the Sun*) but with a definition of "*Hard science fiction is a category of science fiction characterized by an emphasis on scientific accuracy, technical detail, or both.*" - I think it needs details to be fleshed out. You have a lot of chains of connections all building to a very very specific outcome, but without (so far) explaining reasons why the chains might connect in that way, to lead to that outcome. e.g. * Billions of years ago. one thing led to another. eventually. inevitably + (Invoking a long period of time to gloss over details) * began to group together. form simple logic gates. from which emerged crude sentience. + (Why would those coincidental and useful things happen, instead of much easier and more boring things happening - like clumping together to form gooey blobs?) * came to the conclusion that [they] were there merely to serve as extensions of itself. + (Would it need extensions of itself? It doesn't need to fight, or move, or forage for food. And How come it can control cells in a way that we cant control our body cells?). [Answer] They main plot hole I see is the development of intelligence. There is no reason for it in the first place, no predation to escape, no prey to hunt. No quickly changing environment to react to (other than maybe chemical, and the answer to that is usually adaption, not intelligence). Take the biological supercomputer away and you have basically what we *expect* to see in a development stage where single cell life has just evolved, but not yet taken the step to multicellular organisms. The next part that seems completely implausible is the progenitor organism *not* being outcompeted by its offspring. The only way this could happen would be in a stable environment and the organsim being the best adaption to the environment evolution could produce *ever*. And again, no need for intelligence in such a setting. A hive-mind would need to go trough development stages that evolve the basic concepts, long distance signal transmission (to keep it a single mind) and development of things like sensory organs and memory. And there is basically no need for anything having a brain-like function if there is no information to process, so sensory comes before brain. This contradicts the progenitor being the one that evolves intelligence. Its much more likely that the latest offspring will have aquired all this over the course of its evolution than the progenitor having all of it from the start. I fail to see any pressure that leads to the development of intelligence in such a setting. [Answer] The trouble with your scenario is that cells just *do* out-compete each other, even when they aren't supposed to. I don't claim any expertise in biology (human or otherwise), but my understanding is that the human body has multiple systems in place to kill off cells that multiply when they shouldn't. *Multiple* systems, and cancer is still a common occurrence for us, even when it's in our cell's best interests to look out for each other. The organisms in your scenario don't have even half of the the advantages that cells in a human body do. In your scenario, each new organism has every reason to try to out-compete all of the others (including your microscopic "Adam", of course), because it hasn't had time to evolve into something that would treat its relatives differently to strangers. Give them that time to evolve, and - as I understand you - you kill off organisms that were supposed to be part of your network. I wonder if an alternative approach you could take (also bearing in mind Durandal's concerns about the evolution of intelligence) is to start with a fully developed ecosystem, with an intelligent, predatory organism that can expand to absorb other life forms, then have some big event cause it to become the sole inhabitant of the planet. Let's say such a creature evolved in such a way that it eats a whole load and grows very big (procreating somewhere along the way), then at some point gets too slow and can't move very fast, whereupon it normally gets eaten by other stuff or starves to death (all of which is fine from an evolutionary point of view, of course, since it has already reproduced). But one day a big event like a natural disaster wipes out the creatures that eat it, along with the rest of its species. It just got lucky. Shouldn't be alive, but it is. Since plenty of other (less dangerous) stuff also survived, it has plenty to eat (note: it probably doesn't; I'm handwaving like a madman, here). It keeps growing, getting bigger and slower until it doesn't matter how slow it is. It just expands until it consumes everything, and eventually the whole world. Of course, there are various holes in this setup too, but they might - *might* - be easier to handwave away, if you're set on this idea. I would also say, as a final point, that ultimately, if you're creating a fictional world, you're *creating a fictional world*. Things **can** be a certain way "just because", and I think if the story or game or whatever else it is that your world is used for is good, most people will forgive you for a few inaccuracies. [Answer] I really like the idea, however one thing bothers me : "This single progenitor organism never died out " Anything is subject to decay, how can it not die out? If its cells continuously replace themselves then yes it didn't die but technically it s not the same entity as in the beginning after a few million years. [Answer] You have a detailed and interesting scenario developed, with ideas definitely worth exploring, but I object to the implied assertion that Earth *isn't* one giant organism. As far as I can tell there is one and only one reason we don't consider it a single organism today: the conclusion is insulting to us. ]
[Question] [ An assortment of alien adolescents accompanying adult aliens on an alcubierre-drive ship just happen to have been passing near the Sol system. Having noticed that there is lots of EM radiation coming from the third planet, their ship was stopped so that its scientists could gather data. Firing up their quantum computers, some of the digital transmissions were decrypted. The aforementioned alien adolescents saw one of the decrypted transmissions, which happen to be a broadcast compilation of alien/monster and modern warfare movies, in particular, but not limited to, movies like Godzilla, Super-8 and Cloverfield. Having entirely missed the point (since they neither read nor speak English) that the movies were intended to be entertainment, the alien adolescents have misinterpreted them as documentaries recording what they see as humanity's barbarity, celebrating warfare, the destruction of hapless lifeforms and the unjust capture and escape of an alien pilot and its ship. The alien adolescents have resolved to show those arrogant humans what a *real* giant monster attack is, and to that end, they have designed a giant robot, a snakebot with a circular cross-section 1 Zode-la in diameter (1.19 km), and 2xPi Zode-la in length (7.48km), plus a 1.5 Zode-la (1.79 km) tapering tail (9.27 km long in total) that can mate with the snakebot's similarly-shaped mouth, forming a 4 Zode-la (4.76 km) high torus that can move in a rolling fashion, as well as being able to move in other serpentine methods when not hooped and rolling. The robot has a [maraging steel](https://en.wikipedia.org/wiki/Maraging_steel) core and mechanism, with six equally-spaced hydrogen-fusion power-plants along its length for redundancy, any one of which could power the entire bot. The outer 1 Zode-gu (1/8 Zode-la, or 224 metres) is armour, made from overlapping, flexible arrangements of depleted Uranium-Tungsten alloy plates coated with Boron-Carbide. To build all this, the alien adolescents simply program a 1 Rel-ek (3.84 liter) capacity atmospheric-descent-container full of versatile programmable construction nanites, which will self-replicate until there are enough to build, operate *and maintain* the snakebot. Fortunately for the humans, these *aren't* military nanites, which are chock-full with weapons designs, strategies and [rod-logic brains](https://worldbuilding.stackexchange.com/a/22048/75), just *one* of which could be expected to render Earth ripe for conquest (for whatever value of "conquest" is chosen) all by its lonesome. No, these are just engineering nanites, individually only about as smart as a human, and only with fairly basic programming. Unless given about the same time as a human committee, these nanites won't be coming up with too many innovations. Hearing their seniors approaching near the end of their design conference, they jettison the incriminating nanite pod. The container lands on Antarctica, and the nanites immediately start building the snakebot. The better part of a decade later, we have 8.3 or so cubic kilometres of snakebot, weighing at least sixty billion metric tons advancing on the cities of the world, with the objective to destroy all human infrastructure. **Question:** The alien adolescents' goal is for their snakebot to flatten all human infrastructure more substantial than a tent, and to generally knock humans back to something approximating the stone-age. Since the alien adolescents intend to be slightly more sporting than the humans in the "documentaries" seemed to be, the engineering nanites are programmed to build only one snake-bot, and to self-destruct, individually if separated or captured, or collectively, along with the snake-bot if possible if the bot is mission-killed or achieves its objective. On the other hand, they want to protect their snake bot until it completes its mission. Given the likely capabilities of a species capable of building an alcubierre warp-ship and rod-logic nanites, what offensive and defensive weapons might the alien adolescents (who can be considered to be about as intelligent and well-educated as the users of WB SE) build into the outer armour of their snake-bot designs, considering their goal and that they have seen fairly recent movies containing images of modern human weapons - including atomic weapons - in use, and can speculate on their probable design and function. What use would each of these weapon systems be expected to fulfil? Since the alien adolescents know nothing about human biochemistry, toxins are off the table, save as an accidental side-effect of a physical weapon system. Any weapon deployed on board the snakebot must address the matter of resupply in the field, though remember that there will be quite a few nanites hanging around in the bot to act as its brains and self-repair mechanism, that could be repurposed to making ammunition if necessary. Since this is [science-based], we aren't having any hand-wavium weapons here. If you couldn't say, or find out, how it works if asked, you don't get to include it in your answer, since the alien adolescents' schooling won't have covered it yet. That includes any futuristic technology required to make an alcubierre ship work. **EDIT** In response to a comment by Gianluca, I recalculated the mass of this thing. My original calculation was that it weighed around 600 million tons. This has proved to be wrong, it actually weighs in at around 60.2 *billion* tons, assuming that it has 50% internal voids and that 5% of its armour is Boron-Carbide plating on top of Tungsten-Uranium plates/scales. [Answer] This question is a bit weird. Although the aliens are clearly inspired by Earth monster movies, it seems to me that they would be more likely to base their monster on some pre existing creature from their own biome. They already understand the Ravenous Bugblatter Beast of Traal and its various modes of destruction from watching National Xenographic specials as children, but where will they learn about snakes? For that matter, if they were big fans of National Xenographic and did catch the Planet Earth Christmas Special (widely considered to be the worst show ever, and never rebroadcast), the segment on the snake would either show a constrictor, so they would believe the appropriate measure for their snake would be to swallow and digest cities (that hinged jaw on a 9km long snake is a masterpiece of engineering), or that the snake should inject venom into its prey. Since the fangs on a beast that size would be as big as office towers, it is a bit unclear as to what, exactly, they would be injecting venom into (or what would need venom glands the size of city reservoirs to poison). Given their research seems to be a bit hasty and incomplete, I will give them a pass here and say they logged onto Galactopedia and learned about the spitting cobra. [![enter image description here](https://i.stack.imgur.com/8Mmcg.jpg)](https://i.stack.imgur.com/8Mmcg.jpg) Their huge mechanical snake can rear up and strike, and eject either a cloud or a stream of some powerful acid (Galactopedia was not clear on the nature of cobra venom, so they made the next best guess). Given the size of the creature it can certainly have venom glands that would put a water tower to shame, and a fusion powered internal ecology could synthesize common acids relatively quickly, so the huge cobra would not run out of "venom" to spew. With the size and power available, the acidic "venom" could be shot out to several kilometres, taking out incoming bombs and missiles. The launching aircraft, unlike the movies, would be relatively safe. Some glide bombs can be launched from over 100km from the target, and missiles have similar ranges (remember that the next time the intrepid movie hero goes to "eyeball range" to release a weapon). The major weakness is the snake will have a lot of inertia, so swinging the head rapidly around to engage multiple targets coming from different angles will be difficult. This suggests the best strategy is to simply overwhelm the creature with a squadron of "Strike Eagles" or SU-34 "Fullback" bombers coming at all angles and releasing dozens of bombs or other armour penetrating ordinance at the same time. [![Strike Eagle](https://i.stack.imgur.com/2qXAY.jpg)](https://i.stack.imgur.com/2qXAY.jpg) Otherwise nuke it from orbit. Its the only way to be sure. [Answer] The first thing the military in the various films do is shoot at the creature with small arms fire. Your monster is quite obviously immune to that kind of damage, and will ignore it, just like the monsters in the films. The next step is larger weapons - tanks, small air-to-ground missiles, and ground-based explosives. Those are unlikely to do much more than mar the finish of your monster, but at least it will notice. The response is the usual mounted weapons: * Teeth. Nothing screams monster movie like a tank getting bit in half then thrown into an airplane. The national guard dealt with, the monster next goes up against the full forces of the army, taking long-range missiles to the face (always to the face). These are bigger than the previous missiles, and may cause it to at least halt its attack; the response is, usually, widespread destruction that causes the government to halt its actions, even though they seemed to be working, and instead retreat. This weapons has to be flashy, over-powered, and useless outside a minimum range. Fire breath, laser-beam-eyes, and sonic shockwaves are all possible; however, I suggest: * Heatwaves. The creature heats internally, turning red-hot and melting and/or burning any nearby objects. I can imagine a lead scientist working with the military explaining (in dubbed English) how hot skin makes the monster invincible, and to stop shooting at it. Finally, we come to the last chapter of the monster movie: the military's deus ex machina weapon. This is a nuke, another monster, a really big sword, the common cold - something that could easily destroy the monster, but hasn't been used before for... reasons. Of course, the teenage aliens don't want their monster destroyed, so they pack as many real weapons into as possible to combat this weapon. I would suggest: * an [anti-missile gun](https://en.wikipedia.org/wiki/Phalanx_CIWS), to bring down any large-scale nukes before they go off. * a high-powered rail gun, for long-range base-destroying. * defensive skin-shedding (the nanites can make another layer), to repair damage. * body-slam enhancing rockets, also useful for a quick retreat. * legs and/or wings (surprise! It's actually a mecha-lizard/wyvern/dragon!). * a large victory sign that reads "Hi mom!" (or, alternately, something slightly rude). Of course, the aliens may have overestimated the size of their snake. This snake-monster is ***huge***. It's big enough to level most cities *by sliding straight through*, and its skin is tough enough to withstand anything but a direct nuke - even then, that would only make a hole, not destroy it utterly. Earth military wouldn't even bother to send tanks at it; as soon as it shows up and starts smashing stuff, they'll try to nuke it to a cinder. Not those little nukes, either; anti-missile guns will wipe out anything that comes near enough. They'll use the big ones, the well-that's-it-for-this-planet ones. It won't be pretty. We can only hope the parents catch on and stop it before it actually destroys the world... [Answer] building off of the previous replies: how about a grid of point-defense laser batteries covering the entire outer skin, with support from advanced targeting systems? They would have to be able to retract inside when the portion they cover rolls to touch the ground or something, but otherwise would make the snake (even more) indestructible, as it is already immune to bullets and light explosives and is now able to shoot down any number of missiles or bombs that come its way. This assumes that the fusion reactors are each able to cope with the demand of thousands of fairly powerful energy weapons individually, as specified, but solves the problems of ammo by not needing any. Although really, if they wanted to follow kaiju tropes, the only additions would be some kind of breath weapon (plasma, acid, etc) and a natural meelee weapon. [Answer] If they've watched the sort of films you're talking about then the only possible answer is that they make it breathe fire. It would probably glow and make a strange sound first (cos that's what happens in films) then open its mouth and fire would spew out. Beyond that if they want it to complete its mission then small arms are no threat. It would need radiation detectors to detect nuclear land mines and some sort of medium range interceptor missiles that can be used both to take out the land mines and any incoming nukes. Beyond that it's fine. It will rampage around as a virtually unstoppable self-repairing killing machine. P.S. Note that something like this forming would most likely get noticed, even in Antarctica. That thing is big. [Answer] None of your material can withstand a direct hit with a nuclear weapon. Uranium has a melting point about 1100° Celsius Tungsten is about 3400° Celsius Boron-Carbide is about 5000° Celsius (the highest you use) A nuke develop temperatures in the million degrees scale, so a direct hit will vaporize them. The problem here is that the snake is really big... or not ? A nuke with a 2 megaton yield produce a fireball with a radius of about 1.27 Km The biggest nuke (as reported) the USA deployed is the W53 (Titan II) with a 9 Megaton yield, which produce a fireball with a radius of about 2.33 Km Given that your snake has a diameter of about 1.2 Km, a somewhat direct hit with a 2 megaton nuke can cut it in half and probably is sufficient to disable it. A W53 nuke that hit the snake in the middle probably destroy it, taking into consideration the direct and indirect damages. **Update** I seems that I have misinterpreted the question and interpreted it as how it is possible to destroy the snake. But given the limitations of the question, (science-based tag and explicit exclusion of futuristic technology) I think there is nothing that the snake can have that can save it from a direct hit from a nuclear weapon since we have no idea how to build something that withstand such conditions. But to answer the question, the best defense that the snake can have is to intercept all the things (by air, land and, eventually, sea) that come closer than few kilometers from it. I would tend to exclude lasers, since once you enter a city they are useless, and opt for a electric railgun with a high rate of fire. [Answer] For the most part, a giant metal snake is a pretty formidable weapon i itself. If one came rolling through the average residential area, the effects would at the very least be comparable to a violent tornado. However, considering that Earth has land 149 million km^2 of land, and even if only half of it is inhabited with major human structures, that is still a lot of ground for a 9km snake to cover. Basically, people will notice quickly. Even though the snake might fair well (depleted Uranium-Tungsten sounds *pretty* indestructible, especially if the snake moves fast), no doubt extra defenses would be put up to protect from this snake. Therefore, for the most part, it will need offensive weapons. One such weapon could be fire. It doesn't necessarily have to breathe fire, but rather just make some sparks, perhaps with live wires powered by its power plants. This will have the added bonus of having some defensive use, as well as wrecking essential buildings without necessarily setting them on fire. A large enough voltage applied to, say, a human power plant, or some center of communications (internet, phone) will definitely shut it down at least long enough for the snake to destroy the rest of the surrounding area. Additionally, it could take advantage of its environment. If it happens to be by a coastal city, for example, it could go into the water (presumably it can swim- how else would it get off Antarctica?), and cause enough tidal waves (perhaps with the help of extensible fins pressed against its body) just by smacking the water hard enough. Even if this might not *exactly* cause what people would expect from tidal waves, enough buildings would be devastated to allow the snake to burn the rest, and roll around on what's left. This could last maybe a few hours, allowing it to hit maybe 7, 8 modern cities daily (assuming it doesn't "sleep"). Suburban and rural areas, being made of mainly plaster, wood, and the occasional grassy field, would not stand against the snakebot even if it didn't have any weapons. This leaves non-coastal cities, where, again, even if the snake had no weapons, it would still likely destroy everything quickly. Your snake is BIG. The tallest building in the world, at 828m, is not as tall as the diameter of its cross section. The average skyscraper is not even half its *radius*. Honestly, more of a problem is what can humans possibly do to avoid the giant snakebot of doom, because at the moment I can't think of anything. Sending out the snake unarmed is probably enough to destroy mankind in a matter of years, as the only thing that could conceivably harm it is nuclear bombs, for which fleeing and a strong exterior (you got that) are the only defense. Congratulations. You've doomed all of mankind to inevitable destruction by giant alien snake robot. [Answer] Many comments are concerned with the snakebot's vulnerability to nuclear attack, but I believe the concern is overblown. The snakebot would protect itself from nukes the same way the world's major powers do: airspace sovereignty and a missile defense system. Except the snakebot has a major engineering advantage, as I'll explain shortly. The snake's most important weapons system is that described by @Duncan Urquhart: > > a grid of point-defense laser batteries covering the entire outer > skin, with support from advanced targeting systems > > > This grid could effectively enforce a no-fly-zone of at least 100km radius. Google "horizon calculator" for details. The bot is a great platform for multiple heavy lasers (have you seen how big those things are?). I would also add hypersonic rail guns for use in bad weather, and high-power long-distance radar. **The Engineering Advantage** The alien designers don't have to concern themselves with collateral damage. Designing a system that can literally shoot at anything that moves, whether it's on the ground, in the sky, or in space orbit overhead, is much easier than designing a typical human weapons system that has energy, space, and cooling constraints and has to fit on a ship, be stocked with ammo, and have a certain level of safety features. The targeting subsystem may not even require special coding for nuclear ICBMs: a generic "vaporize anything coming in my direction" module probably would do the job. The system naturally would shoot out any orbiting satellites as soon as they come over the horizon. Humans will have only a few hours to react before most low-orbiting satellites and all geostationary satellites on the same side of the planet are taken out. This is not nearly enough time for any kind of massive coordinated attack. And without satellites, the world's military are essentially stuck to WW2 tactics. Pre-GPS ICBMs are not precise enough for a direct hit on a skinny target like the snakebot, even if it was stationary. Even if you shoot a barrage of ICBMs, the bot's targeting system can prioritize the ones flying directly at it, and still avoid a direct hit. Humans will run out of ICBMs fairly quickly. Cruise missiles are slow, easy targets. ]
[Question] [ I'd like to travel really really fast, and I've got some scientists proposing a novel new way of doing so. They've developed the technology to generate extremely powerful controlled gravitational waves. Based on my knowledge of these things, I understand that they propagate at the speed of light as a ripple in the time-space continuum. My scientists tell me that I can ride in a patch of distorted space in which I don't actually need to exceed $c$ locally in order to effectively travel faster than the speed of light relative to a destination. Of course, a single gravitational wave travels the speed of light, so I know I can't go any faster by riding one of those, but my scientists are proposing that I ride the moving interference pattern between two sets of waves, since a local maxima caused by wave interference can effectively move significantly faster than $c$, based on the angle of the intersecting wave patterns. [![enter image description here](https://i.stack.imgur.com/Mz2YG.gif)](https://i.stack.imgur.com/Mz2YG.gif) If we image the blue sections of this image to be peaks in which the fabric of space is streched, we can travel in one of the blue bubbles, which should "move" faster than *c*, since they don't represent an actual moving wave, but rather the intersection point between two waves. The effective propagation speed of one of the intersection points is based on the angle at which the two waves intersect. Specifically, propagation speed *s* can be given by the equation $s=u/\sin{\theta}$, where $u$ is the speed of the wave front and $\theta$ is the half-angle between two otherwise symmetric waves. My scientists tell me that, if we line a potential space lane with gravitational wave emitters, we can create a route that can be traveled at what are effectively superluminal velocities. However, they're asking me for a very large sum of money to do this. Should I fund their project or rescind their grant money and feed them to my pet sharks? [Answer] **No can do.** I was able to find the answer [here](http://gizmodo.com/your-questions-about-gravitational-waves-answered-1758269933), written by LIGO scientist Dr. Amber Stuver: > > **How valid is the wave-like-in-water analogy? Can we “surf” these waves? Are there gravity “peaks” like there are “wells”?** > > > Stuver: Because gravitational waves can travel through matter unchanged, there isn’t a way to surf them or use them for another kind of propulsion. So no gravitational-wave surfing. > > > The “peaks” and “wells” is an excellent point. Gravity is always attractive because there is no negative mass. We don’t know why but it has never been observed in a lab or any evidence found elsewhere in the universe. So gravity is usually represented on spacetime graphics as being a downward curvature, or your “well.” A mass traveling by the “well” will tend to bend inward toward it; this is gravitational attraction. If you had negative mass, you would have repulsion, which would be represented by a “peak.” A mass moving by a “peak” would tend to bend away from it. So there are“wells” but no “peaks.” > > > The water analogy is very good at talking about how the strength of the wave decreases as it travels away from its source. A water wave will get smaller and smaller just like a gravitational wave will get weaker and weaker. > > > Slightly simplified, this means that you can't use gravitational waves for propulsion because they don't transfer energy quite in the same way that water waves do. The analogy breaks down further because gravitational waves are [plane waves](https://en.wikipedia.org/wiki/Plane_wave), not sinusoidal waves - so you shouldn't try to visualize them as being anything like water waves. [Answer] No, you can't "surf" it because you're not attracted or repelled by the boundary. Feed them to the sharks. This is pseudoscience and building such emitters would require more energy than the sun uses, and transfer very little of it to any other objects. [Answer] It might be possible to distort spacetime along your path with *massive* gravity spikes, not just a few waves. However, even if you did, you would have to wait a period of time proportional to the time it takes light to travel for the gravity wave/spikes to decrease the path length between you and your destination. Of course, the effect of trying to do so would likely disrupt the entire fabric of the universe as the equivalent of a gravity EMP propagates outward from their emitters. I think the idea may be similar to that of [The Speed of Darkness](https://www.youtube.com/watch?v=JTvcpdfGUtQ), and similar limits apply, other than the unique ability to distort spacetime. Of course, you are talking less about a nice calm ripple of gravity and more of a "Hulk is angry that the can of spam doesn't open" kind of gravity wave. Sure, the can is going to get opened, but it is less clear if any of the soft squishy meat on the inside will survive the encounter. [Answer] The answer is to produce the same but opposite direction wave to produce thrust. The thrust will be produced due to compression of the fabric of space-time. Gravity waves can come in different forms. One from binary, and one from a rapid expansion or contraction of matter. The only waves I conceive will provide thrust are the explosive type, because of it's contraction in 2d shell contraction expansion configuration. Imagine a bomb goes off, then imagine the compression wave just passes a second bomb when the second one goes off. The second bomb is forced toward the first explosion. Now change them from bombs, to gravity pulse devices. The second one isn't forced away only warped until it activates, and that opposing force generated propels the two attached pulse devices, or array of... [Answer] I suggest you keep your money and wait for the publication of [NASA research that has already been funded, performed, passed peer review and is due to be published at the end of this year.](http://www.ibtimes.co.uk/emdrive-aiaa-confirms-release-date-controversial-nasa-eagleworks-space-propulsion-paper-1579443#) For if you're not familiar with the terms, what you're describing sounds a hell of lot like the [Alcubierre drive](https://en.wikipedia.org/wiki/Alcubierre_drive). The research to be published is about verifying a suspected warp bubble generated by the EmDrive as [explained here](https://en.wikipedia.org/wiki/White%E2%80%93Juday_warp-field_interferometer#Interferometer_experiment_with_an_EmDrive). [Answer] You don't need to be riding it...you just need to be in the force field of the wave/distorted SPACE. This force field will do the work opposite to the motion itself. ]
[Question] [ The movie Back to Future revealed that Mr. Fusion (MF) produced by Fusion Industries (FI) was in widespread use in 2015. What the movie did not reveal was the FI was privately funded by Bill Gates. FI used 10,000,000,000 dollars and the entire first year of production at a cost of 2500 dollars for each unit and selling them at 5000 each. So on the first day to take orders (tomorrow - Sep 11 2015) there are 4,000,000 units available and they sell out completely very quickly once people realize that MF is legitimate. MF is thus widely deployed before the end of 2015. A single MF unit can output 1 MW continuously as long as it receives a steady supply of fusion materials notably banana peels, Miller beer and of course the can itself. A a beer can is almost entirely aluminum or tin-coated steel, it is essentially useless for fusion as MF can only fuse hydrogen. Doc Brown tossed in the beer can as comedic element. The only real fuel was the hydrogen in the water, hydrocarbons, etc. Fortunately hydrogen is very common in banana peels and beer. Note: to get the wattage required for time travel requires storing the energy over time and releasing it in a burst of energy -- this technology comes from a more distant future and is thus not available. An MF unit lasts 20 years without maintenance when used continuously at full power, at the lowest power usage (10 kW) an MF unit can last up to 50 years without maintenance. FI has an absolute monopoly on the product by including the best tech ever designed to prevent reverse engineering as well as an iron-clad license agreement. For example, China remains ineligible for importing MF units until they totally revamp their IP laws. The end result is that you cannot maintain a MF unit, it has to be returned to FI for a 1000 dollar trade in credit on a new unit. What this really means is that electricity now costs about 0.001 cents per kWh or about 10,000 times cheaper then before MF. Not surprisingly, power usage grows dramatically at first, but eventually levels off to a 5% increase annually. Due to widespread use of MF, global carbon dioxide emissions plummet over the following years. But earth faces a new danger. Waste heat from the operation of MF units. MF can only convert 20% of the fusion energy into electric power. Part of the loss is in the generation of magnetic fields, etc. the rest is lost in converting the nuclear energy into electricity itself. At current energy usage levels, the heat contribution to the Earth's energy balance is negligible, but at the new 5% rate of increase annually, we are going to overheat the earth soon. Of course, once the electricity is used, it ultimately converts to waste heat too unless it leaves the Earth in the form of light, etc. You have been appointed to chair the presidential commission to fix the heat problem that is expected to be serious within 40 years if no corrective action is taken. How do you fix this for 40 years from now? How you fix the heat problem on an ongoing basis assuming that at least 10% of the population wants to continue living on the Earth. --- Yes, I read Midas World quite a few years ago. The solution to the problem in that book depended upon moving the population into space, which is part of the reason why I mentioned the 10% Earth based population requirement. I would also like to clarify what I mean by a significant heating problem in 40 years. At that point, the global warming due to fusion will reach 2 degrees Celsius above baseline. Currently Earth receives 173,000 TW of solar radiation. A 2 degree rise means that mankind is generating about 4,660 TW of fusion heat which means mankind has 932TW of electric energy coming from about 932,000,000 MF units and Bill Gates is now the first trillionaire. This is a huge increase from current power levels of about 18TW globally from all sources. With a 5% growth, the temperature rise will far exceed that before long as the doubling period is only 14.2 years. [Answer] My answer is to apply monetary economics. I shall assume that technological or bio-technological solutions to increase the ability of the planet to dispose of significantly more waste heat than it does today are not feasible or desirable. Secondly, with all that MF power, lets get people making use of it to develop a spacefaring civilisation! So my recommendation to the commission is roughly as follows: 1. The (world) government shall establish a currency for which one unit can be redeemed against the rights to operate a MF that produces one unit of waste heat. This is similar to todays money which is redeemable against future consumption - now we explicitly tie money to entropy production. This currency replaces the current fiat system. Money based on energy usage has been quite widely discussed in the context of peak oil. This situation is essentially the same. 2. The quantity of currency is fixed according to the capacity of the earth to dispose safely of the waste heat, so its different to todays money in which the economy is not energy constrained is is more constrained by supply and demand of finished goods. 3. The government mandates that FI with their fantasticly secure technology that cannot be reverse engineered add a 'waste meter' to each MF that is loaded with the credits/money and will refuse to produce power when the credits run out. 4. These constraints do not apply for MFs used off-world, and this stimulates movement of power hungry manufacturing processes, and in time, residential establishments to move off world. Asteroids and comets are fetched to power the off world MFs. Since the off-world economy is not energy constrained, it uses its own forms of private currency similar to modern bank created money/credit. These currencies float against the terrestrial currency. 5. Because the rights to production of waste heat on earth cannot increase, those trying to save money in terrestrial heat-currency may be subject to a negative interest rate or inflation in the terrestrial currency if he actual quantity of waste heat that can be safely disposed of by the planet declines due to government decree. When the global heat production limit is increased the terrestrial currency appreciates versus the off world ones, and vice versa when the terrestrial limit decreases. 6. The 10% remaining on earth must spend their terrestrial currency on power production to maintain their standard of living, but also on importing finished goods from off world manufacturies (the data centres may also be off world). The off-worlders selling goods to earth get in return terrestrial currency that they can only redeem by either coming to earth an living for a while (many off world workers probably don't live off world all the time), and by importing stuff which cannot easily be manufactured in space - mainly stuff like quality food and drink, works of art, things like that. Ultimately to work, there has to be an equilibrium in which neither the off world nor terrestrial economies run a persistent trade surplus. [Answer] **Short Term Solution.** We have a big problem, and need to combine a number of changes to really make enough diference. Raising the price of MF by a large amount will crash the economy and save lots of energy, but the pain of such an approach makes it political suicide as well as being very likely to result in major wars. Fortunately widespread use of MF has greatly accelerated the economy and the rich Earth can afford needed mitigation steps. An energy tax should be part of these incentives. Encourage energy conservation. In the 1950's oil was cheap and people did wasteful things like building houses where the walls were not insulated, drove cars that got 10 miles per gallon, etc. The incredibly cheap energy of MF has encouraged similar behaviors and eliminating the waste will save considerable energy. Economic and regulatory incentives will be needed to make this happen quickly. Processes that are particulaly energy intensive and wasteful may need special treatment. Work with the FI company to increase the efficiency of MF itself. Since this technology is tightly controlled, it may be necessary to take measures against FI that will be politically damaging since most people are fond of the cheap energy. Assuming significant gains are archieved, economic incentives may be needed to push out the most efficient units more quickly. If FI data shows that most MF units are swapped out within 30 years, no incentives will be needed. Implement some of the [climate engineering](https://en.wikipedia.org/wiki/Climate_engineering) solutions to reduce global temperatures that are being considered today. E.g., Change rooftops, roads, parking lots, etc. by using white paint or other diffuse reflectors. Note that non-compliance is easily detected making it easy to penalize if needed. Note that geoenginering projects that focus on CO2 reduction will not be effective since CO2 production has been largely eliminated by use of MF. The tight control of MF turns out to be useful as the government can embargo MF shipments to countries that do not take similar measures. **Long Term Solution** Develop space technogies that will help move industry and people to space. The [space fountain](https://en.wikipedia.org/wiki/Space_fountain) and similar technologies must be included as it could be used as a basis in the future for increasing heat transfer away from earth and moving the earth as well as solar shades. Note that getting rid of waste heat in space is not as easy as radiation is the only way to shed excess heat however you really have no choice but to move some heat off planet as usage increases. Move industrial, agricultural, commercial and residential processes to space. [O'Neill cylinders](https://en.wikipedia.org/wiki/O%27Neill_cylinder) may become very common in Earth and lunar orbits, solar orbits, etc. Some satellites use reflective foil on our surfaces to reflect nearly all of the sunlight away - a similar strategy would be used on O-Neill cylinders. Automated facilities could run hotter than Earth. Require near Earth facilities to direct their heat radiation away from Earth. Move the earth's orbit outward. Done slowly, the moon orbit will be stable. Solar radiation is proportional to the square of the orbital radius so moving the earth outward by 1 percent will reduce radiation by about 2 percent. A space fountain that uses the sun's gravity to return the stream will change the orbit. We need to get very good at space fountains. Use space fountains to increase Earth's heat loss. It is easy for the mass stream to spend a few hours in space for each round trip, plenty of time to radiate nearly all of the heat to space. The mass stream will also need to spend enough time on earth to pick up significant waste heat so a design modification to a space fountain where the stream loops repeatedly before returning to space allows the mass stream to absorb more waste heat. High temperature superconductors will make space fountains very efficient. **Final Solution** Stop increasing energy use without bound. Slowing the rate of growth helps only in the sense that it delays the negative outcomes. Bitcoin mining is an example of basically unproductive use of energy, i.e., no physical goods or services are created, but if you can make more money than you spend on energy and computers it will occur. With the incredibly cheap energy of MF there will be a number of low-value activities that suddenly become economically viable. An energy tax would reduce or eliminate low-value activity. Ultimately, though there is no further energy consumption possible. Note that some of the short term solutions are mostly intended to reduce the growth rate. At 5% growth it is only 107 years from a 2 degree temperature rise until the MF energy use matches the energy coming from the sun and 441 years after than the Earth mankind is proucing more heat than the entire output of the sun. One gram of hydrogen converted to helium releases 3.39E11 joules. Alternatively, 1 MF at full load consumes 46.5 grams of hydrogen per year. It really does not make any sense for MF to have to deal with banana peals, beer cans, etc. as feeding with pure hydrogen it entirely practical given the small quantity of fuel needed. Pure water would be an excellent feed stock. So how much water? Water is 11.2% hydrogen by weight so a single MF will consume 0.415 kg/year of water, giving off 0.369 kg of oxygen and 0.043 kg of helium and 3 grams are converted into energy (E=MC^2). At the 2 degree global warming level, we are consuming 387 metric tonnes of water per year. A cubic km of water is a gigaton so that is 2580 years worth and the earth has 1.335E09 cubic km of water. Unfortunately the 5% growth rate means that 592 years after that, we consume the entire contents of the oceans in a single year (150 years after we exceed the energy output of the sun) Einstein allegedly said that compound interest/growth was the powerful force in the universe. Although he likely never said this, he would have been right. Having a economy that must continuously grow in order to prevent collapse (as is true in most if not all modern economies) is indeed foolish. --- Why did I answer my own answer? To be honest, none of the other answers dealt with the harsh reality that 5% growth in perpetuity is completely impossible. I did not notice that @rumguff referred to this problem in a comment when I wrote this answer. Since he also has a decent answer re: changing economic incentives I will be accepting his answer. I would also like to observe that population growth once mankind expands to space would continue and even hosting 10% of the total population on Earth might be a problem eventually. Though growth rates have been observed to decline in modern economies I strongly suspect that the changes of incredibly cheap energy and space expansion would cause a renewed population boom. --- @rumguff has apparently abandoned WorldBuilding, so I am accepting my own answer. [Answer] Using the thermal energy pumped into the Earth's atmosphere to power a series of lasers. Pointing the lasers offworld (potentially at colonies or ships) can be used to power human expansion across the globe. [OTEC](https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversion) is a reasonable way of stealing heat and converting it back into power at a global level, coupled with large offshore windfarms to pull back energy as warm air from developed landmasses causes climate change. You can build the laser arrays on the roof of the OTEC buildings (as they don't require any cooling towers or aboveground exhausts) and as long as the arrays are built to fire [window wavelength](https://en.wikipedia.org/wiki/Optical_window) lasers you can ship quite a lot of heat offworld. Sadly: This approach is exorbitantly expensive, both in development costs, construction costs and maintenance costs. The maximal thermal-electrical conversion efficiency for a tropic-based OTEC plant is 7%, so you're going to have to produce an awful lot of OTEC plants to balance this out. Another (slightly barmy) plan is to scoop up large amounts of water, heat it, load it into rockets (or your very own hovertrain), and fly in a straight line away from the earth, spraying water as you go. The water would cool due to blackbody radiative effects, and thanks to gravity would fall back to earth with less energy than it left with. If your launch mechanism is efficient enough you could theoretically create a lot of these 'heat spikes', increasing the effective radiative surface of the earth and thus cooling it down. Of course, if you have enough tech and control ability to do that efficiently, you might as well just put up a giant, overengineered parasol at the L1 Lagrangian point and turn down the sun by 5%. Or you could limit the number of MF modules available on-world such that the heat equation eventually balances out at a temperature you're comfortable with. The lower C02 should compensate for the warming effect by allowing enough of the excess heat to radiate away, at which point you're laughing. [Answer] Let's take this a step further than we already have. Let's take this where it was going - everyone has cheap power for their homes and industries, and no one anywhere on the planet has had any need for the grid in any form. In the worst case scenario, absolutely everyone on the planet has totally decommissioned their distribution grids. EVERYTHING runs on a locally installed MF - despite the wild temperatures. The whole planet literally depends on it. The solution becomes to take a step back. The basic theory of economics is the accounting for costs. There is, until this point, no one paying for the cost of the heat generation, so no one is doing anything about it. Step one is going to involve regulation and taxation. Heat is the new global warming demon. Money will change hands. Now what we need to do is rebuild the grid, but probably not the WHOLE grid. This thing is perfect for what we in the power industry call islanding - smaller chunks of the grid that can be operated separately without problems. If we rebuild the local distribution, it turns out a Megawatt of electrical power goes a long way. Lots of units would get mothballed or recycled, and Fusion Industries bails out with its golden parachute after the designs are appropriated by pretty much every government in the world, at gunpoint if necessary. Now we need to modify the way we USE that power. Here we have box that makes heat and electricity in response to being fed water. The winning design will lock this thing *inside* of a boiler and just let it run. 80% of this thing's output is pure, high quality heat, and it produces four times more heat than it does electricity. I can safely say recovering and delivering 40% of that is doable. I have then turned a 1 MW unit into, potentially, a 2.6 MW system, with an overall efficiency of around 52%. Limiting this to smaller scale systems and piping steam to local heating loads can further increase system efficiency, and regardless of price, would get very popular as people get absolutely disgusted every time they walk into their backyards past the little box that emits no less than 40 kilowatts into free air whenever it runs. Demonstrably, the planet has an absolutely insane cooling capacity as-is. Once we get this heat output under control, things will pretty reliably return to normal. [Answer] Besides encouraging people to go into space or building fantastical radiator schemes, the best way to control the heat is to look at reducing the *other* source of heat energy; the Sun. With the amazingly cheap energy of Mr Fusion, mega engineering projects will be quite simple and low cost in today's terms, so building a "sunshade" at the Earth Sun L1 point will be affordable in terms of what resources we need. Putting a sunshade up and reducing the incoming insolation will cool the Earth, and the design of the sunshade could be adjusted to vary the amount of insolation depending on the cooling scenario you desire. Note this isn't a total blockage of the Sun like a solar eclipse, but a reduction of incoming solar energy by 1 or 2%. A translucent shade will work well in this scenario. As a bonus, the engineering work and resource development will encourage people to move off the Earth to join the Lunar or asteroidal mines or the building crews at L1, bringing people and their Mr Fusion's away from the planet and reducing the heat burden on the Earth. [Answer] 1) If you're talking about the Mr. Fusion from Back to the Future I toss the report in the closest trash can. There's no way something that size can dissipate 4MW of heat. It's actual efficiency has to be upwards of 99% 2) If the report is accurate I laugh at radiators. We don't need any fancy schemes to get rid of heat, we just need to turn down the fire a bit. Solar incident radiation is about 1kw/m^2. (Yes, the raw number is higher but some is reflected away. I'm looking at what gets through to warm the planet.) Since the MF is producing 5MW (the amount it produces as power almost all ends up in the environment eventually.) that translates to 5,000 m^2 of solar energy. I impose a tax on all new MF units sufficient to pay for the launch of 5,000 m^2 of sunshade. This sunshade is in the form of a large solar sail craft (or likely multiple craft) that is hovering somewhere to the sunward of the L1 point. It keep station on Earth but is **not** actually in orbit, it's using the energy being reflected off the sail to hold position. (If it were in orbit the radiation pressure would push it off position. Thus you set it up so the radiation pressure pushes it into position instead.) You might need to increase this tax somewhat to make up for the decreased agricultural production. Expect yields to drop by something more than the % of the sun that's blocked. [Answer] To begin with, a very fast and affordable solution is not to use coal and concentrate on submarine volcanoes, to move the turbines into the ocean. It's a simple solution available with today's technology levels. Free heat and cooling in one. ]
[Question] [ I am writing a SF story, in this story, a life-form(You can just call them alien) from another universe comes to earth. They used "imaginary velocity" to make their time elapse faster than all beings on the earth. When the alien is using "imaginary velocity", they eat humans. From SR, the formula for time dilation is: $$t^{'} = \frac{t}{\sqrt{1-\frac{v^{2}}{c^{2}}}}=\gamma t$$ if I plug in a imaginary number for $v$, for example $2ic$($i$ is the imaginary unit), then I get: $$t^{'} = \frac{t}{\sqrt{5}}$$ $\gamma$ is less than 1. this means the time for the objects with imaginary velocity elapse faster than the objects in inertial frame. In the story i will make it $10^{16}$ faster than inertial frame.(human's $10^{-16} s$ = alien's $1 s$, when the alien spent one day in their reference frame, only $86400\*10^{-16} = 8.64\*10^{-12} s$ passed from human's reference frame) So no people can see what's happening, also no machine can detect the actions of aliens.(in the latter part of the story, the situation will change) Is their any contradiction with the theory of relativity or other physics? ps. There is a known problem that all observable must be real numbers. However, I decided to ignore it. Since tachyons have imaginary mass and some SF story also used this in their story. --recently added $v=2ic$ means the object move $2ic$ m in 1 s, the distance is also imaginary. So, it is not moving in the real spacetime. You will see that object as "not moving" even if it has $2ic$ speed. [Answer] It is difficult to answer this question without you telling us what a velocity of $2ic$ means. However my 5c is that this will not work. Examine an alien moving from Human A to Human B, with a distance of $d$, at a constant speed of $2ic$. Lets ignore for now the fact that this statement is meaningless. From the perspective of the humans the alien will spend time $t=\frac{d}{2ic}$ to cross this distance. Also, from the perspective of the human the alien will age $t'=\frac{d}{2\sqrt{5}ic}$. From the perspective of the alien the humans are moving at a velocity of $2ic$. He will need to cross a distance $d'=d\sqrt{5}$ and will do so in time $\frac{d\sqrt{5}}{2ic}$. Meaning the formulae does not provide consistent results in the presence of imaginary velocities. TLDR: If the alien is moving at $2ic$ with respect to the humans the humans are moving at $2ic$ with respect to the alien [Answer] 1. Instead of making time a complex dimension, you could have another (real) time dimension. That allows the state to evolve without moving forward in *our* time. 2. Are the aliens made of matter? Unless it's made of stuff other than our familiar protons and electrons, it could not operate differently than the normal rules of the universe. 3. If they are made of *stuff from another brane* or somesuch, how could they eat meat made from normal matter? Perhaps the *time freeze* is a technological ability, using an enveloping field to allow time to (in effect) pass faster inside. That is a staple of SF, but generally unexplained: #1 above could be used . [Answer] How can we get imaginary velocity? This is pretty obscure Physics I'm afraid. Now lets first go to basics. What is velocity? $v = x / t$ Now as you already noted. If v is imaginary, then either x is imaginary or t is imaginary. Let's assume we are in a 3,1 spacetime shall we? I know its pretty hard to imagine, but lets pretend ;). If my understanding of the Wick rotation of 3, 1 spacetime over the time axis is correct, it would imply our friends with imaginary velocity inhabit a 4, 0 spacetime or 4 euclidean space. Things get weird really quickly. I can't seem to figure out how to type out my workings wrt to TDSE, but the jist of it is that, when you plug in imaginary time into TDSE, you get a particle that is confined to a single point in real time (or at least drops of exponentially from a single point in time), but is periodic on real space, covering the whole of space... [Answer] This is pretty way over my head as far as the maths goes, but I do just want to point out the difficulties of moving extremely fast. Namely, wind resistance, relative force and all sorts of other nasty physics effects explored in various forms of fiction to date. An excellent example of this is in *The Thief of Time* by Terry Pratchett. In the book there are history monks, who can bend time as they wish. Various examples of the difficulties and advantages of this can be found in the book, including the simple difficulty of walking, talking and breathing in an athmosphere which does not want to behave at your speed. Another good example is in the recent film *Xmen Days of Future Past*. Quicksilver has speed as his "mutation" and as you may remember, can cause people to summersault over by simply *touching* their face. You'd therefore have to make your aliens superhumanly strong, able to operate in near vacuum, and incredibly resilient so they can simply survive in the high speed environments of imaginary velocity. [Answer] Complex arithmetic is not a geometric construct, as much as it is a 'cheater' logic used to provide snobby academic types with means to impress and daze laypersons with negative answers to squared functions. All instances of complex arithmetic are trivial (in the philosophical sense, not the mathematical), and as such I find your attempt to actualize it in a work of SF refreshingly humorous! I'm going to go ahead and assume we're using complex arithmetic to describe pan-dimensional motion. Let's insist the 'observable universe' exists in three dimensions and we give locations as vectors (v = [x,y,z]) and velocity as velocity over time (v/t). I want to make this an exercise in 3-manifolds rather than familiar euclidean space, but that makes me dizzy. It shouldn't matter over a small enough portion of space. Anyway, a human could be the classic example of Sagonian flatlander when viewed by our aliens. Or the aliens could be just as flat a we, yet able to project itself where our dimensions intersect. Many principles of flatland relativity might not 'scale' along the other dimensions, or 'proportions' of objects and energies change with respect to motion perpendicular to familiar references. Objects of this 'imaginary' universe might therefore react differently to gravitation, dilation, etc. many questions arise, such as: if we accept motion with an 'imaginary' element to also satisfy complex arithmetic, doesn't that mean a force could decelerate what it might otherwise accelerate? also: do we allow imaginary components to other aspects of reality, such as 'imaginary' mass, 'imaginary' charge, 'imaginary' gravity? Or are such imaginary components already provided by imaginary space? Are our aliens pandi or transi? that is, are they Pan-dimensional bodies/intelligences, built of materials from both the real and 'imaginary' dimensions; or are they Trans-dimensional, able to, through some exploit, transition between our dimension and their home dimension. The former allow aliens to "eat" puny humans from every direction simultaneously, or even from within! Yikes! Before we attempt to validate any sort of equation we must consider: TIME is a perception of and an attempt to measure and count the CHANGE in state of a three dimensional, mechanical device (clock, brain, planetary motion, etc). As a strictly human invention it might not have meaning to the aliens at all. SPEED is a distance traversed across three dimensional space by such a given time. It's hard to consider an alien as an being with capable intelligence while operating without time. For this reason, assume we cannot allow an 'imaginary' time component. There is another reason I think we should disallow (t+it) from our equations. If we are measuring time by 'seconds' than are assumed to have a clock. If we move trans dimensionally, are we carrying this clock with us? or are we leaving this clock to return to it later? This also affects the way in which we're comparing the motion and the metabolic rates of the extra-planers. This is similar in principle to the reason time appears to dilate near the speed of light. Remember, the speed of light is invariant at any reference. The motion of mechanics within the clock are not changing, rather the energy of a system increases as it accelerates, thus the underlying reference for motion is changing. We are implying a sort of 'imaginary' time my simply allowing an imaginary component for each each spacial dimension. We describe velocity thusly: v = [(x+ix), (y+iy), (z+iz)] / t this is 'time invariant'; the alien motion is trans-dimensional, yet occurs within the same reference of time as any human observer. For example, a human could move a mile in the 'real' universe in a minute. Or an alien could move at the same speed, over the same amount of time, along the 'imaginary' universe and appear to NOT MOVE AT ALL. Also, it is possible for aliens to exist as 'purely imaginary' constructs, meaning they can phase in and out of human perceptive existence. They do this as a function over topography, rather than an increase/decrease of relative time scales. [x,y,z]/(t+it) is a 'positionally invariant' case, meaning aliens occupy the same space as us, and are at all times fully accessible, yet can modulate the rate and scale of physical forces acting upon them. The later case is more restrictive, in that a change upon t affects x,y,z uniformly. The former, I like because thinking about moving along the -ix and the +iy at the same time makes me want to stand on my head! This concept is illustratable by considering the 3-sphere model of the universe: In the case where our 'observable' universe is a 3-fold we allow 4 dimensions and say the universe is the group where any point is given by |∀p| = SQRT(w^2 + x^2 + y^2 + z^2) = 1. 'imaginary' motion would not simply be a scalar, otherwise it might be possible our aliens are able to attain the 'Singularity'; where |∀p| = 0 although I don't know why they'd bother to go there or how they'd return. Or are they already and always there? In either case, adding complex geometry is not simply scaling the existing dimensions (thus increasing and decreasing speed). it is the proposition of doubling the number of dimensions. If you observe, moving from one, two, to three dimensions, the origin, or singularity, doesn't change. It is always 0; 0,0; 0,0,0; respectively. It follows more dimensions would share our singularity at the same point. For every dimension element of our frame, we add an imaginary element. Alien 'imaginary' dimensions confer the same constraint in that |∀p+ip| = 1. Velocity in any direction is given as a Magnitude. |v|. Because we're in a complex plane, we are essentially allowing velocity to be negative. If so, motion along a supposed 'imaginary' dimension is different from motion along the traditional plane, in that the classical Newtonian 'equal and opposite force' becomes 'equal and potentially perpendicular force' This could mean the aliens, when they exert themselves upon the 'real' universe, would appear in a vastly decelerated frame as a static, immutable thing, such as a tree or rock, while absorb incoming energy (by projecting it along the perpendicular reference of it's 'imaginary' aspect), or it might be super fast like a plasma and amplify every inbound energy (causing air to heat, voltage to multiply, etc). 'imaginary' motion could be interpreted as a change in SCALE. Increased/decreased gravitation: Our aliens would become LIGHTER in the presence of a GREATER gravity, and crushed by the empty expanse between distant galaxies. They might even phase from our detection altogether. Your provided equation is okay, but I don't like the (c^2) bit because the speed of light is SUPPOSE to be a constant and invariant. I think what you're attempting to do is give velocity as a fraction of the speed of light. Don't do that! let c = 1 and you simplify that part of your equation to 1-v^2. Even a human where moving at 0.999c faster than an alien, it would still be 1c less than the speed of light! I'd argue that the point at which our aliens intersect with with an earthling, IE, when they eat one, speed is not an issue, rather, the alien's path of motion is equivocally perpendicular to the human. His intersection upon our plane would take the form of an expanding/contracting sphere which would, as it became more distant along the imaginary plane, simply become insubstantial to the point of phasing out completely. It would be like a blackhole emerging from nowhere, to suck you in. Don't even bother to ask Alice what is happening to that entangled-particle friendship bracelet you're share/wearing, but I assume the effect would be similar to ripping her arm out of her socket in a direction perpendicular to everywhere. [Answer] Even if there was nothing wrong with the imaginary numbers, there is another issue: moving $10^{16}$ times faster would cause very nasty side-effects as the air molecules cannot get out of the way. There is an interesting explanation of this problem on xkcd: <http://what-if.xkcd.com/1/> ]
[Question] [ As I'm sure you're all aware, human beings at some point in their lives -- generally post-puberty or so -- stop growing. As a result, there's some easily-predictable measures, such as the average height of a human, and some pretty consistent standards in our society, such as the height of a typical door or a ceiling. This, however, relies on some sort of bizarre internal biological mechanism that basically, at some arbitrary point in our development, says "Okay, we're done growing." And while there are a few examples of genetic abnormalities where that mechanism fails, by and large that's a constant across virtually all life on our planet. But what if it weren't? What if this biological mechanism simply had never existed? Clearly there are some upper-bounds on physical size due to the infamous Square-Cube Law -- such as reaching the point where our bones fail under our own weight, or where our heart simply can't keep up with the vastness of our circulatory system -- which would likely take the place of generic "old age" as putting in place the upper limit on how old we could get. But what would be the more subtle impacts on our biology? And how would this change the face of our society? [Answer] The square cube law is the biggest impact already. Humans are already nearly as big as we can be before we get to suffer, already the tallest humans have major health issues. If we continued to grow at the rate we did through puberty we would reach a point of pain and easy injury in only a few additional years, and death not long after that. It's not old age if it happens shortly after adulthood even begins! You would have to either have us grow much slower or have the rate of growth cut back drastically after puberty to have anything remotely like a normal life span. Similarly by the time that anyone is significantly large enough to have any impact beyond needing slightly taller doors we would have reached the point where our size is causing pain and easy injury, at the very least. The square cube law comes into play so rapidly that, unless it is hand waved away, you can't do anything interesting with humans that continue growing before they are too weak to be interesting. [Answer] You've already mentioned door and ceiling heights - these would have to be higher than the oldest (and therefore tallest) people. Depending on how tall we could actually grow before the same fate as that that overtook Robert Waldow overtakes us all you might have buildings that are two or even three times taller per floor than current buildings. This would mean that there'd have to be more skyscrapers per city to house the same number of people as we have now as the overall heights of buildings wouldn't be higher than it is for our buildings. There'd be impacts on other technology like cars and aeroplanes. These would have to be larger. With aeroplanes it could be that people over a certain age can't fly as they simply can't fit inside the craft. This could have had a serious impact on the development of flight. Engineers with the skills necessary to invent aircraft could be too large to build a craft capable of lifting them off the ground. This could have delayed or even stopped us flying. [Answer] Several points come to mind: * Food - you would need an ever increasing amount of food to sustain and fuel growth of the body. A bigger stress on food production worldwide. * Buildings - not just doors and ceilings, but think about accommodating a drastically wider range of different sized people. If a big family were to live together, the room and furniture sizes would also have to pertain to each member. It is hard to imagine everybody sitting at the same dinner table. Rooms and furniture for grandparents would have to be enormous compared to the childrens' room. * Similar for transport and everyday items. You would not only grow-out of your clothes, but also your car, bicycle, sports gear... Creating even bigger stress on economy and increasing recycling * Public venues - imagine building a cinema that can comfortably seat everybody - with a chair not too big and not too small... Also taking into account that you wouldn't want a huge grandpa sitting in front of you... * All in all - the world would be drastically different - the society, economy and politics would be more segmented according to age (size)... [Answer] As the Wadlow case shows fast continuous growth equals faster death. Unless... PHASE I The average human lifespan would shrink, a lot. Doctors would probably find a way to create artificially the puberty gland thing. (I can't find it but it basically regulates body growth.) But before they're done our population has shrunk a lot. By the time the Growth Regulation Device (GRD) is cheap enough for the masses most of us will be people who have less need for it. (People who are genetically predisposition to be shorter. Like myself...) PHASE II Alright. Now it gets interesting. Using the GRD humans allow themselves to grow for a year or to when they turn (40?). At 40 your cells stop regenerating. However because you grow your body heals up a bit. In the end this could help extends human lifespan dramatically. ]
[Question] [ My society has a typical line of succession (like the UK monarchy before a female child was given equal status). The eldest son has priority, followed by other sons, and then followed by his daughters. Unfortunately, the king has died young. He's spent too much time visiting other ladies and has left two children. An illegitimate daughter (who is unaware she's his daughter) and an unborn illegitimate son. According to most western constitutions would the unborn son be next in line (presumably with an interim ruler) or would the daughter? [Answer] A male child would always take precedence over a female one. From [wikipedia](http://en.wikipedia.org/wiki/Primogeniture#Male-preference_cognatic_primogeniture): > > Male-preference cognatic primogeniture allows a female member of a dynasty to succeed if she has no living brothers and no deceased brothers who left surviving legitimate descendants. A dynast's sons and their lines all come before that dynast's daughters and their lines. Older sons and their lines come before younger sons and their lines. Older daughters and their lines come before younger daughters and their lines. > > > This was the most common primogeniture practiced in Western European feudalism > > > If the girl child does not know, does that mean that other people do know? In practice in this sort of case the selection of the child is pretty much a technicality and may well owe a lot to politics. A Regent would be appointed to run the kingdom in the child's name and would become King in all but name. The politics behind selection of the Regent and which child that Regent controls would likely have a larger impact on the results of the succession than the status of two illegitimate children. [Answer] In a typical European monarchy, both illegitimate children would be out of the line of succession. Instead, you'd be working your way back up the king's ancestors, trying to find one with a living legitimate male descendant (eg. the king's third cousin or somesuch). If someone wants to use the son as a figurehead for their regency, you might get a civil war between the son's supporters and the legitimate king; if finding a legitimate king is too hard (or the person in question is too unpopular), the nobles might be willing to ignore the son's illegitimate birth. [Answer] Some other questions: are illegitimate children considered heirs in the culture? As far as I know, this wasn't the case in Middle Ages. That the father was expected to help his illegitimate children earn their living somehow is another question, the father is dead now. According to the law, closest male relative of the former king should become a new king. [Tim B's](https://worldbuilding.stackexchange.com/a/2619/95) already cited the rules for determining the heir legally, but in practice the question is who is the closest relative among neighboring kings willing to use their army to get their heritage (I assume that most of the kings are relatives to each other, as in medieval Europe). Also, when a dynasty dies out, the nobility usually has some right to influence who will be the next king, and if most of them agree on a candidate, they might get to the throne even if some other potential heir tries to get it by force. Anyway, hard times begin for the country. ]
[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/171287/edit). Closed 3 years ago. [Improve this question](/posts/171287/edit) I want to rough out the crew needed for a large FTL spaceship which is on a survey mission. My basic scenario is my civ is recovering from a dark age and is exploring its surroundings using (ex military) "carriers". The spaceship has: * autonomous FTL equipped message drones; * autonomous [in-system] drones; some equipped for entering & leaving a planetary atmosphere; * 10 manned unarmed in-system ships [that are able to land on a planet or moon]; * 2 manned armed FTL capable ships, with minimal survey equipment; their primary purpose is to defend the carrier. My question is, how many crew will it require!? At present, I have the following [shifts x people]: * [3x10] operational [bridge] crew [who handle the ship] * [3x10] power crew [engine room, power plants etc] * [3x10] IT crew [maintain computing services; provide analysis of data gathered] * [1x100] marines [a 100 person unit able to provide military support] * [1x5] squadron crew [oversee the drones & parasite ships and their crews] * [1x60] the 12 parasite ship's crews * [3x5] science team [help analyse survey data] * [3x10] parasite ships maintenance staff * [3x10] drone maintenance staff * [3x10] environmental crew [maintain / recycle: air, water, food, sewage, rubbish] * [3x20] farm crew ["grow" {fresh} food for the crew] * [3x25] support crew [people who run the various spaces: eg cooks, waitresses, cleaners] * [3x5] medical staff [doctors, nurses, lab-techs] * [3x25] hotel staff [run the accommodation, do the laundry etc] * [3x10] security team - internal "police" ~615 people Also, what "departments" have I missed? If the mission is multi-year (which I think it would be), should I include childcare & schools? cheers Steve --- [edit] Firstly, my thanks to everyone who read the question and especially to those who gave answers! My updated crew is as follows: * [12] command staff * [12] power crew [engine room, power plants etc] * [12] IT crew [maintain computing services; provide analysis of data gathered] * [5] squadron crew [oversee the drones & parasite ships and their crews] * [84] the 12 parasite ship's crews [including 5 scientists per ship] * [12] science team [help analyse survey data] * [30] maintenance staff [parasite ships + drones] * [30] environmental & farm crew * [25] support crew / labourers * [15] medical staff [doctors, nurses, lab-techs] * [10] hotel staff [run the accommodation, do the laundry etc] * [12] security team - internal "police" 259 people, down from my original 615. I agree that multiple shifts are not necessary, so where before my basic unit was 3x10 I've changed that to 12 (8+2+2). I *still* have some "support" crew, which will amuse some of you. I have also sacked my marines. I was always assuming that there would be lots of automation, robots & AI; but the lower [human] numbers reflect me increasing their workload. :) [Answer] Whether or not you end up with more or less crew, there are some fundamental failings in this list in terms of how the labour is distributed. I'll go through the basics to give you an idea of how to better distribute crew across the functions. **Every Marine is a Rifleman** This is becoming a controversial saying in the modern world as focus shifts to other forms of combat techniques than the old school trench warfare, but for the purposes of your carrier, I'd recommend you take it to heart. Having 100x marines on board your ship doing nothing until you get to a planet on which you want them to land is a terrible waste of resources. I'd argue that they are your cooks, environmental staff, cleaners and launderers (and for Pete's sake, you really don't need waitresses) until they're needed for combat. They spend a part of their week remaining combat ready, and for the rest of it you put them to work. Air, food, and space on board any space ship is going to be precious, and you're not going to bring people who have a single function. Everyone on board your ship will have a secondary skill and will be able to back someone else up. That is just the way of it. In the case of combat specialists, they won't just be sitting idle on your ship until they're needed, and when they are, other people can fill the gaps while they're away. After all, less to clean, launder, fix, feed, etc. **Night Shifts** While bringing redundant skill sets for critical functions like the engine room is laudable, you won't bring enough for three full shifts. You'll have a primary shift that will operate during the ship's 'day' hours, and then a small skeleton crew for the other two shifts that monitor things, fix the really simple problems, and have at their core the most important function of all; wake up the day crew if something goes really wrong. The same will be true of your maintenance teams - the night shifts will be there to sort out the easy stuff and make sure no-one pinches the CPU out of a damaged drone to start up an in-ship Quake server. The real problems will be sorted out by a primary shift, and everyone else is going to be caretakers, pure and simple. **Smaller Bridge** I can't help but notice you put the same number of people on the bridge as you have maintaining the engines, the IT systems and the boats and drones on board the carrier. That (IMHO) is way too many. I'd argue that you may need that size for an officer corps, acting as department heads for the other functions on board your ship, but certainly not all directly on the bridge. Let's face it; the bridge isn't where it's happening in any event. Effectively, the bridge is there to point the ship in the right direction and get out of the way of things that won't move because you're bearing down on them. Most of that (given how many IT people you have) should be automated after the initial programming by a much smaller bridge crew. But, I'm going to assume that you didn't mean bridge explicitly and that you were referring to the command staff. If so, then that makes sense but you're (again) not going to need 3x shifts worth. You might have more than 10, but a small complement of them are going to have the sole function of waking up the primaries in case of trouble. **Military Police** If you have around 600 crew on board your ship, all intent on serving a specific mission, and you need 30 cops with you to keep the peace and the law on board your ship, then I deeply suspect your captain isn't a good judge of character. You already have some marines assigned to day jobs on the ship in flight, put a couple on to investigating stuff when it arises, and your captain is judge and jury which I think you'll find is close to the truth on a modern military vessel in any event. **Science Team** You call this a survey mission, but you bring 100 soldiers, 90 ship crew and maintenance, and only 15 scientists? That's not a survey mission, it's a reconnaissance mission. If you're serious about this being a survey mission, you'll have a lot more scientists on board, or a lot less of everyone else. In essence if you need 600 people to carry about 15 scientists and it's a scientific mission, you're doing it wrong. Very wrong. The main reason I don't think you're wrong about the IT staff count is that they'll be split across two priorities. Keeping the ship running, and keeping the scientists running. As such, you'll find that members of the science team will accompany every away mission or landing, and you'll have specialists in xenobiology, geology, chemistry, physics, etc. on board your ship ready to analyse whatever findings they come across. Arguably, they would also make good cleaners, cooks, etc. when you are travelling between worlds, although knowing academics as I do, good luck keeping them as organised or as focused as the marines, especially if they haven't had anything published for a bit. But, I digress. **Double Ups** I'd make the point that the farming work is likely hydroponic, and that it does as much to maintain the atmosphere aboard the ship as any dedicated crew, so I'd argue that both functions would be tied into one set of jobs, not separate departments. Same with the engineers and the drone and ship maintenance teams, especially if space is at a premium on the ship already. **To Summarise** The less people you have on your ship, the better. Space is risky, and expensive. People are fragile and hard to keep alive out there, so the fewer you have on your ship the better for that reason. To that end, everyone has to have multiple reasons for being there and this is why the current list is so long - it doesn't take into account that many of the functions are part time and therefore could be done by people who do other things when not needed for that function. Also, we have to remember that automation is now a thing and the fact that we have drones entering military use at a far greater rate than new fighters and combat aircraft should tell you that the ideal crew for your ship (if it has good internal repair drones and brilliant programming) may well be zero. In any event, segregating people so rigidly by function may not be the best idea because if you are trying to keep a crew to its minimum in space (which is something you should always do) then you really want generalists wherever possible, not specialists. [Answer] **Lift details from history.** At first I was thinking of the voyages of Captain Cook. 2 large ocean going ships. <https://www.sl.nsw.gov.au/stories/captain-cooks-voyages-discovery> > > Cook's second Pacific voyage, (1772-1775), aimed to establish whether > there was an inhabited southern continent, and make astronomical > observations. > > > The two ships Resolution and Adventure were fitted out for the > expedition. In 1772, before he set out, Cook created a map which > showed the discoveries made in the Southern Ocean up until 1770 and > sketched out his proposed route for the upcoming voyage. In 1773, > accompanied by naturalists, astronomers and an artist, Cook made his > first crossing of the Antarctic Circle, claiming that he had been > further south than any person. > > > His 49 crew members are listed here. <https://www.captaincooksociety.com/home/detail/a-table-of-the-crew-of-cook-s-three-voyages-1768-1779> I am sure the sailors on Cooks voyages would have been delighted to have hotel staff aboard to turn down their sheets! --- But I think more clever would be to model your explorations on a smaller voyage of discovery. [![lewis and clark](https://i.stack.imgur.com/1UfX1.jpg)](https://i.stack.imgur.com/1UfX1.jpg) **The Lewis and Clark expedition** is a great model for you. They had about 40 people along. <https://en.wikipedia.org/wiki/Corps_of_Discovery> This included officers, soldiers, contract boatmen, Sacajawea and her husband (and her baby!) to translate, Clark's slave York, and a dog. Good variety. Instead of interacting with the Amerinds your party would be interacting with the far flung vestiges of the fallen civilization. All sort of exciting things happened on this voyage. Lewis and Clark did not find some of the things that they were looking for and I can imagine that for your story too - your people hope to find another refuge of the Unfallen like themselves. They keep hoping. You have to have core characters to move a story otherwise people get confused. The core characters of the Lewis and Clark expedition are distinctive enough to tell apart in a narrative. I get the impression that the working men were too - soldiers from the East coast and French-descended boatmen from St Louis. [Answer] I'm going to go ahead and add my comments. Most of them were already stated by Tim (he's very thorough), so I'll credit him as needed. At the end I'll put a running tally for you. First up, as Tim said your 100 marines can handle other jobs when not on the ground doing marine things. As such, it would not be unfeasible to replace a number of pre-existing "specialists" with lay marines. Think of it this way: If a job requires dumb labor, it only requires 2 or so overseers and a number of added folks to move things around. Namely, your environmental, farm, support, and hospitality crews can be cut down significantly and replaced with off-duty marines. This also gives a lot of flexibility for where human resources are applied. If a farm just needs to be checked for decay or disease midway through the growing cycle, most of the marines whose job that is can be sent to do something else. Also, Tim pointed out that the presence of MP called your captain's character judgement into question. I have to both agree and disagree with that. I may be wrong, but a captain doesn't go through and hand-pick each of the 600+ people who get to be on his ship. The crew may be a combination of recommended specialists, groups of people subcontracted from companies, people the captain has worked with in the past, and whomever's handy. As such, some of the people may be used to working with each other, while others may not work well with others. While I agree a dedicated MP force isn't wholly necessary, I don't think the idea should just be vented out the airlock. Instead of Military Police, replace them with a handful of people well-versed in interpersonal relationships; diplomats, mediators or, in some cases, bouncers. This way, they have a job off-ship as well as on it (This concept alone should be employed everywhere. While I expect specialists to, well, specialize I expect everyone else to be able to do more than one thing, even if it seems lame). The shortage of scientists on a survey mission (again, mentioned by Tim) is concerning. Those numbers are more indicative of "a scouting mission that we're claiming is a survey mission so the enemy doesn't think we're looking at their defenses". At the same time, you don't need as many scientists as marines because, again, marines can help with things requiring less finesse. Tim mentioned night shifts. Yes, the night shift doesn't need as many people awake as the morning and evening shifts, but it still needs *some* people awake. I'd lay out the shifts like this: * **Morning:** 1 overseer/specialist, 4 adept people * **Evening:** 1 overseer/specialist, 4 adept people * **Night:** 3 adept people This assumes a 5-person shift according to your tally. The percentages would remain roughly the same as you scale it up, or the job requires more expertise (like medical staff) you can increase the number of overseers/specialists. You should only think about childcare and schooling if the mission would span decades, not years. The most you'd need to employ is a nursery worker per shift, plus a couple of extra eyes. If you have children of educable age on board you're wasting space and resources. However, if a child is *conceived and born* on the ship and *grows* to an educable age then you'll need educators. One educator per 15 children. A tech-savvy person could probably commandeer a drone to educate instead, but that may not go over well with rowdy children. Finally, I would tweak a few numbers here and there, but nothing major. Round numbers are great, but sometimes you don't need *quite* as many people as you've listed (again, spread the marines around). The final tally will assume a night shift with 20% less crew members, but I won't go changing anything in the tally proper. **[Post-tally note]** So I added 45 laborers because the tally came to 305.8 crew members and I realized that I was relying pretty heavily on having marines to bolster numbers, but not thinking about what would happen if the marines *actually had to do marine things*... * [3x10] operational [bridge] crew [who handle the ship] * [3x10] power crew [engine room, power plants etc] * [3x10] IT crew [maintain computing services; provide analysis of data gathered] * [1x100] marines [a 100 person unit able to provide military support] * [1x45] laborers [like the marines, these guys get spread around. Unlike the marines, they don't do fighting.] * [1x5] squadron crew [oversee the drones & parasite ships and their crews] * [1x60] the 12 parasite ship's crews * [3x15] science team [help analyze survey data] * [3x6] parasite ships' maintenance staff * [3x10] drone maintenance staff * [3x2 + off-duty marines] environmental crew [maintain / recycle: air, water, food, sewage, rubbish] * [3x6 + off-duty marines] farm crew ["grow" {fresh} food for the crew] * [3x2 per occupation + off-duty marines] support crew [people who run the various spaces: eg cooks, waitresses, cleaners] * [3x5] medical staff [doctors, nurses, lab-techs] * [3x5 + off-duty marines] hotel staff [run the accommodation, do the laundry etc] * [3x5 + off-duty marines] mediators [diplomats for ground missions, interpersonal issues, and the like] * [3x1] nursery workers, plus 1 educator per 15 expected educable children. This puts the crew at a nice round 350 people, not including educators. ]
[Question] [ In building an sentient alien that is unique among the sea of humanoids, I aspire to explore quadrupeds. For a quick visual reference, this is what I have: [![The quadrupedal race that uses two "tail tentacles" as graspers](https://i.stack.imgur.com/iYA5C.png)](https://i.stack.imgur.com/iYA5C.png) *proportions are definitely off, but in reality they'd probably be more bear or cat-shaped, or some mixture of the two* Key features: * Split prehensile tail * Size of a polar bear * Adapted to cold climates The main thing I'm having issues with is the prehensile tail. For this species, it's the key to their tool use and advancement to a sentient race. However, aside from a best-case-scenario arboreal evolution history, I'm having difficulties justifying a possible evolutionary path that leads to a split in the tail, resulting in two dexterous "tentacles". So, the first set of questions is thus: is a prehensile tail even a plausible way to use tools and advance? If so, could a prehensile tail "split" as shown? Even if it's possible to split the tail, is this even necessary to allow the species to effectively use tools? As a side thought, I'm also taking into account the rest of the creature's physiology. Humans do not have fur or a thick layer of blubber to keep us warm; that costs energy. Energy that could be better used to enhance the brain. So, even with a thick layer of fur, could this race still have enough energy to attain sentience? To be on the same page, I use sentience in this fashion: intelligent enough to form complex social networks that turn herds or packs into tribes, and then into towns, cities, and nations. [Answer] # Used to be cute and little Just because now they are huge doesn't mean they were always. At one point they used to jump from tree to tree using it to grab branches. Given a few evolutions they now live on the ground and use their tail to create nests. Given a few evolutions and an ice age: They grew to be much bigger and able to put on the pounds of fat and fur needed to survive long cold nights. They're tail was now used to find and dig out food from the snow and ice. Evolution happens again (does it ever stop???): It now knows to throw things. Fast forward: They throw rocks at walls and collect the sharp pieces. Hunting/Foraging is now much easier. Brains gets bigger. Blink: Fire can now be created at whim. Blink: Farms now start. [Answer] **There is not much issue with your creature. Most of the issues are explanatory more than anything else.** The split tail is not an issue split tails have evolved more than once in earth life (costly in marine animals), and if you look at an elephants trunk it is easy to see why such a structure might be useful, they basically function as fingers. You could even have it be a common feature in a whole group of organisms on their planet, maybe the split serves some important developmental function so it is never completely lost in the clade. That gives as strong jumping off point. Your creature will likely use its mouth as well as it really needs another limb for generating counter forces, the opposing "limb" does not need fine manipulators but it does need some strength and gripping ability. Precisions angled impact using opposing forces is necessary to master flint knapping which is the beginning of really all advanced tools. You can do alot with one hand as long as you have grippy anchor to oppose it. Unless I am reading its anatomy wrong the neck is fairly long and stout so it should work fine. The full size of the brain was probably not achieved until after the advent of fire and cooking as it was in humans (the hominid brain rapidly doubled in size after the discovery of fire) cooking food drastically increases its available caloric value. Your real problem is why it has the tail in the first place, anatomically the animal is not that different than a ground sloth or a chalicotherium. The only real use of a prehensile tail is in climbers so it likely evolved from a small climber, as it evolved larger size is altered the feet into something more elephant like, losing any use as grippers. It will need to be far more social of course and may even end up more social or at least more cooperative than humans, with the reduced grasper count. **But you need a reason it kept the prehensile nature of the tail**, It is a lot of tissue and neural support it will need a strong selective pressure to keep it around. The exact reason is going to be up to you, I suggest some kind of very strong sexual selection or something similar or perhaps some unique feeding mechanism. Because it is an alien organisms perhaps it serves a purpose not seen in earth vertebrates, like as a mating organs or some vital use in child rearing. **You will need a more fertile/productive cold climate region than earth**, you need to support social groups of these organisms year round prior to any technology, but it does not need to be that much more fertile. Just more efficient photosynthesis should be enough. That's not too hard photosynthesis is not so efficient that more efficient means evolving elsewhere is unbelievable. [Answer] > > is a prehensile tail even a plausible way to use tools and advance? > > > This might be the limiting factor for your sentient, tool-using species. I can think of two problems with this design: # 1) The tail is at the back but the head is at the front If your creature relies on it's eyesight (which I assume it does) it will have difficulties knowing if what it tries to do actually works or not. Try solving a rubiks cube. Pretty hard, right? Now try solving a Rubiks cube behind your back... **Solution: long neck or scorpion tail** I think your creature would either evolve a long neck so it can turn around and look at it's tail or evolve a long scorpion-like tail so the end of it can dangle in front of it's head. If you go for the scorpion tail, instead of going above the creature, it could also go **below**. Think of it like a dog tucking it's tail between it's legs. I think this would be more fitting for a cold environment since it would minimize heat-loss. # 2) Having only one tail is like having only one arm If you carve a spear you hold the stick in one hand and use the other to carve. Having only one arm makes this a lot harder. You have to use the environment to fixate the wood so you can use your arm to carve. It might not be impossible, but your species will have a very hard time building anything if they **only** use their tail. An easy solution would be to not only use the tail, but also the "hands" and/or mouth. Gorillas for example walk on four "legs" but still use the front two for grabbing stuff. You seem to have thought about this problem as well and came up with the split tail as a solution. I think this could work quite well, the proportions are a bit off however (as you said). The "tentacles" should be a lot longer to serve the function of a "left arm" and a "right arm". By that I mean that both the left tentacle as well as the right one should be able to **independently** grab an item. Do they need "fingers" for that? You could split the tentacles again, which probably makes grabbing things easier, but it's not necessary. One tentacle can also just wrap around an item to grab it. # So how would a species like that evolve? Figure out a plausible reason for an animal to evolve a tail that can grab stuff and the rest is easy. Evolution itself will try to move your tail in your field of sight and will also favor a split tail as this means you can grab two items which makes tool building just that much easier. [Answer] I agree with Murinus about being able to see what it is controlling. I had written out much of that myself (scorpion tail), before they posted first. I'd also point out good peripheral vision could be useful. Perhaps this creature is a prey animal. Remember also that long skinny appendages don't especially do well in the cold. The more surface area, the more heat you lose. **Reasons to use a tail** As for whether or not a tail could evolve in such a way, if the tail was not originally like this, perhaps it used to suit some other purpose. Perhaps this species dragged food, young, or shelter materials (fallen trees) long distances over snow or ice with it. Over time, this became their primary use, and they got better at gripping and manipulating such things. Perhaps what is now a tail (or two), used to be another pair of legs, that, over time, stopped being used as legs (because it was too busy dragging things back to its shelter/clan, or while migrating), and grew more and more tail like. This form of tail could explain the split, but would more likely have some form of fingers, or claws, than it would tentacles. [Answer] **It is a mammoth.** Elephants are intelligent, social and long lived. Mammoths almost certainly were, and were floofy to boot. The intelligence of elephants is clearest when they must survive in arid lands with low / intermittent food density and hard to find water. They remember the tricks they figured out and the old ones teach the young ones. That is true for Siberia as much as Africa. That hard triangular head is a tusk equivalent. Your creature uses the head like an elephant uses the tusk. Probably it can be more vigorous about it. It could break ice. It can break up frozen carcasses. These things can't afford to be picky in the frozen wastes. The tail is a trunk. It is for all the elephant like things the trunk does. Elephants get a lot of mileage from their lips too, and for this lipless wedgehead, the tail does lip duty as well. [Answer] Your creature could eat using it's ass an poop with their mouth. The tail would be really useful in that case, and I'm pretty sure it'd enable some laughs. [Answer] These aliens could have evolved from simple segmented worms that crawled on the sea-floor and ate the microbial mat. It might have evolved extra segments on its sides to increase their surface area for breathing. To increase area further, the extra segments may become more leaf-like. They might also gain light sensors in order to find brighter spots which would likely hold more food. They might evolve to sense and eat smaller creatures. To do this they might use their gills to push themselves forward to swallow the prey. This would start this world's version of the Cambrian Explosion. The front end of the worm would gain image-forming eyes and a brain. This front end would also gain tentacles derived from the lateral segments, in order to grab onto prey. They would also become larger and more efficient, gaining a complex arterial system that eventually formed a closed circulatory system, as well as dedicated gills covered by an operculum. They might also start to move by undulations, and gain a long tail with flukes at the end, reducing the body to only having 4 flippers. Some structure near the end of the tail might join the digestive tract and become the anus, freeing up space in the tail for pure muscles. They might also gain hard rings in the segments, to protect themselves from other predators. These rings might evolve to articulate, and become a skeletal system. The ring part would be reduced in the limbs and tail to make space for muscles, but would stay in the body, to protect the innards. Their tails and limbs might increase the number of segments, in order to have more bones and so more flexibility. The bone-rings of the head might fuse into a skull. The head-tentacles would also become bony jaws, and would gain sharp serrated blades for slicing up larger prey. The jaws would likely fuse into a single set of jaws to prevent prey from slipping through the centre. They may also use the jaw-moving muscles to bite with, which would likely cause the upper jaw to become fixed to the skull. In order to obtain more oxygen, they might start to gulp down air. This would lead to the oesophagus gaining a lung-like structure, which would likely form into a true lung. Some individuals might end up in a swampy region. Due to the large amount of obstacles, they would likely move around using their flippers rather than their tail. Their flippers might become sturdier and stronger for moving around, and their tail would likely shrink. They might become fossorial. This would lead to the front flippers gaining spikes at the end to remove dirt from burrows. They might also gain a hard, scaly layer over the skull, in order to be able to put their head into a burrow and remove anything sharp. Other predators might move into the swamp, and so the burrower might start to run from the water when threatened. They might become more suited for land, with the skin gaining a hard water-proof layer, the legs thickening out of the hydrodynamic flipper-shape, and the gills reducing to rudiments. They might also retain their eggs in their body, and become viviparous. These tetrapods would diversify into many forms, some of which would be predators. These predators might become cursorial hunter, and would likely become endothermic in order to stay warm throughout their hunting. They might also evolve a layer of air-trapping filaments to keep the heat in. Some of these creatures might move into colder regions, and gain thicker fur and a rounder body. It is possible that there might be many species of psychrophilic plants. These plants would support communities of the furry creatures that have moved into the cold. Some may evolve to build nests using their tails. Their tails would likely become longer, and the vestigial flukes might be used as fingers. Eventually, they might learn to make tools, which may lead to an arms race which would end in a sapient species much like the one in the question ]
[Question] [ In the world I am designing, instead of mammals, birds are the dominant species. In this world, replacing the niche of deer gazelle and cattle are a group of animals known as Quadrabirds. These are similar to flightless birds but with the their wings turning into a type of walking limb, hence their namesake. What I am wondering is how such an animal would evolve? My current thoughts are related to the fingered bird, The Hoatzin. A list of all Planet of the Aves questions can be found [here](https://worldbuilding.meta.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940) [Answer] I think the Hoatzin is a good starting point. The young have claws on their wings that allow for climbing. These claws are lost in adulthood, so the first evolutionary step is for a Hoatzin to evolve neoteny, retaining the claws and becoming secondarily flightless. It does this to save on developing wings and flight muscles, and to exploit the niche taken by monkeys. Larger Hoatzinids become primarily land based. They climb trees as needed but rely on their claws for defence. They eat leaves and fruit. However climate change results in a shrinkage in forests and so some evolve to live on the new grasslands that are taking their place. Here there are predators like eagles, so extra bulk is an advantage. The obvious food source is the grasses so that is what they eat. Their feathers are reduced to a thin covering (except for tufts that the males sport during the rut) and their claws are mostly used for digging for roots and the annual rut. They swallow stones to help break down grasses in their stomachs. [Answer] Your quadrabirds don't have to loose flight to have a walking fore-limb. Another answer already mentions that some groups of pterosaurs folded their wings when on the ground and used them for walking. There is an excellent article about this [terrestrial locomotion at pterosaur.net](https://pterosaur.net/terrestrial_locomotion.php), which includes some nice sketches. (I've said it before on wb.se. Are you folks not getting this yet? *Modern literature needs more quetzalcoatlus*.) There is also a living species showing an example of convergent adaptation, the New Zealand Lesser Short Tailed Bat, ([Mystacina tuberculata](https://en.wikipedia.org/wiki/New_Zealand_lesser_short-tailed_bat)). In this case, it is not hard to find [videos](https://www.youtube.com/watch?v=P2wjXRTd1vU) of their walking pattern, so you can actually study the mechanics of it while designing the quadrabird. [Answer] Well the short answer is that they probably wouldn't, bird forelimbs aren't designed to support a load in that way. Not to mention that, for all intents and purposes, simply flying away from your predators is better than running from them in most circumstances. But given that this is fiction, we don't need rules; check out the [Azhdarchids](https://en.wikipedia.org/wiki/Azhdarchidae). There's a lot of evidence to suggest the sort of quadrupedal stance your Quadrabirds would have. [Answer] # Theropods Take a look at the Theropods. They are the precursors to modern birds. Some of them were plant eaters which puts them near enough in the same niche as deer. With a little imagination, no mass extinction events, and maybe a much heavier animal, its easy to see how they could slowly adapt to walking on four legs. [Answer] In a previous answer I suggested ways to evolve avian wings back into useful limbs for another purpose. One idea I like is that the wings evolve into legs. If you don’t need the manipulation of hands, getting 4 walking limbs with hooves in front should not be a problem. ]
[Question] [ From the movie Tremors, behold the graboid: [![It followed me home mommy, can I keep it?](https://i.stack.imgur.com/lMEBP.jpg)](https://i.stack.imgur.com/lMEBP.jpg) These are vicious, SUV to bus sized sandworms that have acquired a taste for human flesh. They are known to "swim" through the earth really fast too. I know some characteristics the graboids have in the movies are unrealistic (their speed comes to mind). What I am interested in knowing is: how would a realistic graboid species look like? And how could such a species (the realistic, not the movie one) have evolved? This question is part of the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/). [Answer] ## We do not see the Graboid, the graboid does not see us The graboid is a highly evolved megafauna. Similar to the giant sloth and the cave bear, the Graboid does indeed have a miniature equivalent; The star nosed mole. The star nosed mole is the [fastest eating mammal](https://www.newscientist.com/article/dn6961-speediest-feeding-mammal-revealed-as-a-mole/) on earth, able to find, identify, eat, chew and swallow down its food in an average of just 227 milliseconds – less than quarter of a second. By comparison, it takes people 650 milliseconds to brake after seeing a traffic light turn red. Evolving to hunt down other megafauna the mole grows to extreme sizes and since it is now hunting more dangerous animals with better weapons, its [super nose](https://neurophilosophy.wordpress.com/2009/08/26/the_star_nosed_moles_amazing_appendages/) evolves harder, claw-like weapons. Finally, the speed. Most moles clock in at an impressive speed of 5 mph for short distances through their pre-dug tunnels. But since we fail to see graboids digging, it may be safe to assume that they just travel through their tunnels. Since the full size of Graboids is never truly revealed- we only see their super specialized noses- we cannot guess just how fast the star nosed graboid would be, but we can assume that it would be much faster than humans. [Answer] They are descended from [placoderms](https://en.wikipedia.org/wiki/Placodermi). Having an animal that size burrowing requires handwaving no matter what so let's focus on the anatomy. Hard bony plates on the head, check Bony plates instead of teeth, check. Smooth skin or superficial scales on the rest of the body, allowing for the evolution of spines, check. The potential for a single pair of limbs in certain life stages, check Internal postcranial skeleton to support body, check The potential for huge sizes, the largest is 8 meters long, check Bonus several freshwater species are or are nearly blind and are bottom dwelling. So you have a burrowing placoderm that evolved for terrestrial soil. [![enter image description here](https://i.stack.imgur.com/fqy3p.jpg)](https://i.stack.imgur.com/fqy3p.jpg) [![enter image description here](https://i.stack.imgur.com/Tppok.jpg)](https://i.stack.imgur.com/Tppok.jpg) [Answer] Well there are creatures which [swim through loose, dry sand](http://www.ncbi.nlm.nih.gov/pubmed/25524983) so maybe the graboid can do that. However, the real world ones are all small. Here's a [video explaining how the sand swimmer snake does it](https://www.youtube.com/watch?v=Lqw2YrPNB9U) by being long, skinny and smooth. ]
[Question] [ Our planet has a surface full of silicates and a core made of iron. It's due to this that Earth is the way it mostly is - most rocks and many minerals contain some form of silica. But what about a planet with an iron surface and a core of, let's say, mercury (to have an element denser than iron)? This isn't to say that this planet is purely iron and mercury, but it has the ratios of what we have of silica and iron, respectively. (This would mean that ~90% of this planet's crust would be iron.) Is such a planet feasible? And if so, how would that affect plate tectonics and development of life, if life is even possible on this kind of world? [Answer] A very close variation to such a planet already exists in our own solar system. It's the first planet Mercury (not the chemical element mercury, but the planet). Wikipedia states: > > Although Earth's high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not as compressed. Therefore, for it to have such a high density, its core must be large and rich in iron. > > > Mercury's core is 42% of its entire volume. In contrast, Earth's core is a paltry 17% of its entire volume. I cannot say anything about the presence of element mercury on this planet however. Iron appears to be far more common in our solar system than mercury. The supernova that created the debris from which our solar system was formed, had much larger amounts of iron as compared to mercury. Iron has atomic number 26 and it is far far more likely to be formed in the core of a red giant than mercury that is more than twice heavier (with an atomic number of 80). Basically you expect high-iron planets close to their parent stars. The simplest reason being that solar wind sweeps the planet's atmosphere and some lighter elements away, leaving only the heavy ones behind. In our own solar system, the inner belt contains 4 terrestrial planets while the outer belt contains the gas giants. It is very likely that a sizable portion of the inner planets was swept away by solar winds and was later captured by the outer planets, making them truly monstrous planets. So all in all, yes, planets containing very high ratios of iron are possible. However planets containing an equally high ratio of mercury (element) are very unlikely. This being said, the question of life on such planets is purely opinion bases. I would not expect any *earth-like* life on those planets. We, being carbon based organisms and being used to seeing life of only one type, have no idea what really defines *life* and how can it form. For us, life is impossible without water (and lots of it). And then you need nutrients and a long array of essential chemicals to kickstart the evolutionary history *the way it happened on earth*. We cannot say how life can evolve on other planets and under what conditions. We also don't know what *type* of life it would be. [Answer] Start from a stellar remnant, it is theoretically possible that a planet composed largely of iron and heavier elements could be formed as the result of the destruction of a star. A fragment of the core of a Sol-like star near the end of it's life would be mostly Iron from stellar fusion mixed with the heavy elements that were pulled into the star from the original [Molecular Cloud](https://en.wikipedia.org/wiki/Molecular_cloud). Such a world would be extremely radioactive and would start out white hot but the surface would eventually cool and solidify. I would expect that the [Crust](https://en.wikipedia.org/wiki/Crust_(geology)) of such a world would be largely Iron, the way the Earth's crust is largely [Basalt](https://en.wikipedia.org/wiki/Basalt) with the equivalent of [Continental Crust](https://en.wikipedia.org/wiki/Continental_crust) being composed of the lighter [Transition Metals](https://en.wikipedia.org/wiki/Transition_metal) like Titanium and Chromium, and some lower density compounds formed by heavier elements. The mantle would indeed have a good percentage of Mercury but would almost certainly contain a lot more Lead than any other single component formed by the decay of many heavier radioactive elements that were originally in the stellar core and will also have a lot of still radioactive isotopes that haven't yet decayed. I would expect this world to be extremely geologically active, the mantle is going to be much hotter than Earth's and the world as a whole will have far greater heat reserves for far longer. It will be hotter because it's composed of denser minerals with higher [heat capacities](https://en.wikipedia.org/wiki/Heat_capacity#Specific_heat_capacity_2) and because more heat is constantly being pumped in by far more radioactive decay than in the Earth. The world will have more heat reserves because of three mechanisms; higher energy crystallisation reactions, repeated crystallisation and dissolution due to radioactive decay destabilising crystal structures, and, because of the relatively high levels of radioactive isotopes (as a percentage of the whole), more radiogenic heating, including more long half-life isotopes. The mantle is probably going to have a similar viscosity to that of the Earth, if not being even more fluid due to the high percentage of Lead and other low melting point heavy metals. If those assumptions hold then tectonics will be almost identical to the Earth but with higher temperatures and different "rock" forming minerals/alloys. Life as we know it, i.e. carbon-based and water soluble, wouldn't stand a chance on such a world, at least not initially. There's too much ionising radiation, too many heavy metals in the crust, and too little of the elements we need to function, Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, and Phosphorus account for 99% of the mass of the Human body ([Source](https://www.thoughtco.com/chemical-composition-of-the-human-body-603995)) and all of them, with the possible exception of Hydrogen, will be vanishingly rare on this remnant world. Now it is possible that such a world *might* be able to accumulate large volumes of lighter elements later in it's evolution through collision with debris from the planetary system, if any, of the star system that centred on the star it was part of. This material would initially coat the world forming a, [geologically](https://en.wikipedia.org/wiki/Geologic_time_scale), short lived "life layer" that could support Carbon-based life for a time before tectonic activity mixed this material into the mantle. Let me know if you want me to go in depth on any of this stuff, I've gone pretty lightly over a lot of bits. [Answer] **Life isn't possible according to any model we have but the planet is fascinating.** Since this planet (IronForge) has such a high concentration of very heavy metals it probably formed in the remnants of a very heavy supernova or series of supernovas. Earth has only trace amounts of mercury compared with the terrestrial ratio of silica to iron. > > The mass of the Earth is composed mostly of iron (32.1%), oxygen (30.1%), silicon(15.1%), magnesium (13.9%), sulfur (2.9%), nickel(1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. > > > So if we take all those elements and multiply their atomic mass by three, while keeping the ratios the same, we get the following list: * Mercury * Chromium * Technetium * Krypton * Indium * Radon * Promethium * Zirconium Any free oxygen has been consumed a long time ago. Carbon based life and silicon based life will have a very hard time finding resources to form cell structures. Is life possible? Extremely unlikely and if there is life it won't look anything like life on Earth, obviously. By shifting the weight of IronForge so much higher compared to the silicon-iron ratio of earth, the amount of industrial heavy metals in the crust and general environment will be far far higher than on Earth. With a radon-krypton atmosphere, any life will need to fight very strongly against the radiation coming from radon and radon decay products. This is in no way a pleasant place to visit for humans. The air itself is radioactive and there's heavy metals everywhere. Estimating which elements will be in the crust or in the core is beyond my ability to estimate. Having a mercury core would be interesting because it's conductivity is so high. [Answer] [16 Psyche](https://en.wikipedia.org/wiki/16_Psyche) has a *surface* that's estimated to be 90% metallic (iron), as it has an extremely high radar albedo. It's presumed that it's the former core of a protoplanet wherein gravity started to separate metals from minerals but then the rocky exterior was blasted apart, leaving just the metallic core. However, despite being described as a "metal world", the density is lower than Earth's, so I'm not sure what the discrepancy is from. [An orbiter](https://en.wikipedia.org/wiki/Psyche_(spacecraft)) is planned to launch in 2023. [![Psyche orbiter logo with tagline: "Journey to a metal world"](https://i.stack.imgur.com/ydQdL.png)](https://i.stack.imgur.com/ydQdL.png) The atmosphere of the rocky planets largely came from volcanic mantle outgassing. That was Earth's "second atmosphere", the first one after the hydrogen/helium nebulous atmosphere. If the planet was impacted violently enough to rip off large portions of the mantle, the source of much of that outgassing would be gone, so the atmosphere around it would be thinner than normal. [Answer] Iron is the last element that forms in large quantities before a star collapses into either a neutron star or a black hole. **All heavier elements have much less abundance in the universe** as they are mostly produced only in Neutron star mergers. These are extremely violent astronomical events which are also extremely rare, limiting the abundance of heavy elements that can end up in planets. So, a close to full iron planet is about the heaviest you can get. I wouldn't think that anything like a mercury planet would be possible. ]
[Question] [ Well, Luminescence really but I liked the alliteration. Would there be any reason or mechanic why plants may develop that glow in the dark? Ideally they would do so in response to stimulus such as touch, but continual or periodic glowing would also be acceptable. Is there a plausible mechanism through which they both could develop the ability and have an evolutionary reason to do so. Most of the reasons why animals do it (such as distracting predators, luring in food, or attracting a mate) do not apply to plants. I know we've genetically engineered plants to glow through bioluminescence, but I'm not aware of any cases where they have naturally developed the idea. Really I'm looking for a scenario where a "glowing forest" (or at least some glowing plants within a forest) could evolve naturally and be relatively widespread on a world. [Answer] First off, there are lots of different ways organisms can glow, luminescence, fluorescence, and phosphorescence are all subtly different ways for organisms to produce light. I'm going to assume you just care about having glowing plants of any sort and so will focus on evolutionary reasons for "why" they might glow instead of "how". (Although the "how" is pretty easy, they just make the appropriate proteins). Light is primarily used as a signal by living things. The most likely reason for plants to make light is to try to communicate a message to other organisms. But what would a plant want to say? Lots of things! I'll give a few examples that came to mind below. **Attracting symbionts**: Many plants already produce flowers with bright colors in order to attract insect pollinators. It's not a far stretch to suggest they might emit light at night in order to attract nocturnal insects. **Warning predators**: Aposematism is a fancy term for the use of warning colors. Lots of animals utilize bright coloration to advertise the fact that they are poisonous, or foul-tasting, or otherwise unpleasant to potential predators. Some plants use their coloration in this way already. Plants could step up their warning game by emitting light as well if they felt so inclined. While the two above suggestions would work, they are simply extrapolating from existing visual cues that plants use. The following are some more... creative suggestions. **Self-defense**: Plants suffer from all sorts of small parasitic insects like aphids and caterpillars. Imagine if in response to injury plants glowed in the affected area. The glow would serve to attract predators that would eat the insects eating the plant. The dark insects would be highlighted against the glowing plant leaf or stalk. **Synchronizing something**: Another suggestion is for plants to communicate with each other. Perhaps they want to synchronize their flowering times, or pollen release. Plants are known to be sensitive to light in many ways already, from phototropism to knowing what time of year it is. A glowing forest could help synchronize them all. [Answer] Evolving light generation is not that difficult an issue, it seems fairly common. The reason is more difficult. Maybe a tree that is pollinated exclusively by something similar to hummingbirds? A light generating tree would allow the birds to feed during night, this would be of great value to the birds as hummingbirds have fast metabolisms and low energy reserves. Thus the birds would end up spending nights at the tree. Hummingbirds are generally assumed to be worthwhile to trees as they provide pollination and eat insects to get proteins. A touch response version might make sense if that attracted predators eating herbivores the plant wants to get rid of. Alternately the leaves could explode, creating a brief flash. The plant could use nitrocellulose or other nitrated compounds for this for this. The benefit would be that a herbivore trying to eat such plants would simply fail and given how jumpy most herbivores are probably be scared enough to avoid such plant in the future. Nitrocellulose (or other explosive) would also act as energy and nitrogen storage. Usually high energy compounds attract herbivores, but not if they explode on contact. [Answer] They would do it for the same reason plants flower: **to attract pollinators**. Imagine there is a place where fireflies are ubiquitous. If a plant develops the ability to be bioluminescent, it can attract fireflies looking for a mate, similar to the mimicry [seen with existing plants](https://en.wikipedia.org/wiki/Mimicry_in_plants). Flashing, touch sensitivity, or continual glowing could all evolve depending on the pollinator that is co-evolving with the plant. ![enter image description here](https://i.stack.imgur.com/I3Gtw.jpg) > > [Bee orchid](https://en.wikipedia.org/wiki/Ophrys_apifera) flower resembles a female bee closely enough to attract males in search of a mate > > > [Answer] If a planet had a slow rotation and so a long day and a long night, it might make sense that a plant might need to harvest as much light as possible during the day. One possible mechanism to harvest and store extra energy during the long days would be to charge [glow-in-the-dark](https://en.wikipedia.org/wiki/Phosphorescence) pigments within those plant. During the long days, the pigments not only could function as a sun-screen, but also convert harmful ultraviolet into useful (for photosynthesis) visible light. During the night, the glow gives a small amount of light for the plant to harvest for photosynthesis. Photosynthesis tends to be optimized for certain frequencies of light. Some [articles suggest](https://en.wikipedia.org/wiki/Grow_light#LEDs_.28Light_Emitting_Diodes.29) that red and blue light have the best efficiencies for photosynthesis. Although we think of glow in the dark as just the green-white glow, but there are pigments that produce a variety of colors, including red and blue, which is what our plant might do to further boost the efficiency of this process. The plant would glow, then, as a bi-product of this energy storage, and so it wouldn't take energy away from a plant's metabolism. ]
[Question] [ Sort of like a meta-question, but here it goes: I'm trying to write a story, which there'll be a land where the worldbuilders gather and live together, and use their worldbuilding power together. It's a fantasy world, so presumably whatever they've come to mind and designed would come to life. And exactly only that, so for example, if they've decided on the overview of the city but not on the inhibitants yet, there'll be a magnificant city without interior and people sitting in there. In order to capture their characteristics, I'd need to know how worldbuilders think and act, what's their approach to worldbuilding, and such. They may be different from people to people, but I think there might be some common traits among them? [Answer] I like this idea, but I suspect the majority of people drawn to your community would be more likely to be visual artists, architects, interior decorators, urban planners, and (especially) politicians/political philosophers rather than traditional worldbuilding hobbyists. The idea of getting to decide everything about a city and see it magically appear is very different from the experience of sitting around drawing a map and figuring out linguistic drift for the fun of it. Just being able to make a city be whatever you want without rules whatsoever has a way broader appeal than what writers and worldbuilding hobbyists do. If you've seen *Inception*, think of the scene where the architecture student wanders around making her own personal city in a dream, breaking all the laws of physics in the process. Almost anyone with any sort of interest in the visual arts would enjoy that kind of canvas without limitations. Worldbuilding hobbists, though, are often the opposite of that. We like playing within restrictions just as much as we like crazy flights of fantasy. We like the intellectual game of making things plausible using real-world sciences. We enjoy the element of it that's like solving a puzzle, love it when our own creations surprise us, and live for that moment where we think logically about something we made up and discover something new about it ("Aha! *Of course* they'd have an economy based around glass!"). If you are imagining a world where there are absolutely no limited resources required to engage in these magical worldbuilding activities -- where land and magic are unlimited, so your average hobbist can give this new occupation a try -- I could imagine old-fashioned worldbuilders inventing games where they designed, say, physics systems and then tried to guess their outcome of those systems or worldbuild within those sets of rules. It could also imagine some people wanting to get together and enjoy the social experience of collaborating on a city or world, but that's not exactly the same thing, and I think many people in the former group wouldn't be automatically interested in the collaborative element. Both are in a sense forms of constrained writing, but the collaborative part would presumably be more likely to draw, say, people who like improv, or people who play story-heavy roleplaying games. On the other hand, if there are resource limitations, I wouldn't expect the attitudes of worldbuilding hobbists to be heavilly represented in the worldbuilding field, because then in would be more a matter of money and politics, especially if real people are going to live in these invented places. At that point it stops being unlike the real world, which is already full of people building stuff with others. Last but not least: consider the fact that a lot of worldbuilders are less interested in inventing landmasses and decorating palaces than inventing (and rationalizing) entire cultures, including things like religions and traditional table settings and the outcomes of wars. For those people, you would need for it to be possible for this magic to create something like AI citizens for this activity to be really satisfying. Otherwise I think you'd find a lot of worldbuilders right whether they are now: writing works of fiction on paper, where they can control everything except the things they prefer not to control. [Answer] I can't speak to world builders in particular, but I do know of a particular fictional universe of world builders: Myst. And I'm highly disappointed that this question has been here a year and nobody else brought it up yet. I think the universe described in Myst (particularly the novels) points out important elements that would arise in a society of world builders. After all, we're not talking about a group of people who can only *imagine* worlds; they can actually go there. That changes things. A lot. If you dig through the Myst lore (ie: if you're willing to suffer through the sometime mediocre writing in the novels), you find out all kinds of interesting things about the D'ni, the people from whom Atrus is 1/4th descended. The people who invented the Art, and the people who built a culture around it. They lived in a cavern 3 miles beneath the Earth's surface. Why? Well, if you have the ability to go to anywhere more or less at will... does it matter all that much if your home is a cave? You don't do your farming in a cave; you have bountiful harvest worlds for that. You don't strip-mine your cave; you have mining worlds for that. And so forth. If you are always just a few steps away from any world, the one you live on starts being less important. There were public recreational ages, acting much like parks and so forth. Many D'ni nobles had their own private ages, analogous to owning a ranch and lots of land. But more than this is the relationship between the D'ni and the peoples of the worlds they "create". Indeed, the quotes there are very important, because it is the ultimate D'ni heresy to claim that using the Art of Writing actually creates anything. They say that it simply links to an already-existing world. That important, because everyone, *everyone* who starts thinking that they're creating worlds rather than discovering them immediately wants to lord their power over the native populations of that world. So my interpretation of the D'ni's views here is that it's a conscious effort to *not* start seeing other worlds as subjects waiting to be enslaved. And I think that is probably where real world-building starts running afoul of human nature. Because if you really can build a world... what happens if you build life? How do you treat that life? Is it OK to create people who exist solely to serve you? Well, what if you create them such that it is their nature to serve you? Do these world builders have that level of control (notably, the D'ni do not)? What if the life you create starts doing things you don't like? Is it OK to destroy what you've created? If you're going to create a world where world building is a legitimate thing people can do, this is a question that absolutely must be answered. Do they treat them as casually as a novelist, who creates people that go through horrific torments in some cases, even casually discarding a character who has served their purpose? Or do they treat them with the respect befitting a world? Or is it some of both? How much of both is it? [Answer] One common trait would be a balance of imagination. A world builder, by their trade, must be able to imagine a world that others have not imagined. However, they must also share this world. They should be used to tempering their imagination with the stark reality that it has to fit within the imagination of others, or be lost. If there is a society of worldbuilders, they would also likely subscribe to the first rule of improv: you never oppose something that has already been stated. I don't think I can claim that all world-builders follow this philosophy, but if a large number of them banded together, they would almost certainly accept such a philosophy as at least as important as the Golden Rule. [Answer] There are two ways to approach worldbuilding: outside-in and inside-out. These approaches would have distinct signatures to outsiders who observe these worlds. Outside-in starts with a planet and then postulates creatures to fill it. As the question states, such a world might appear barren before it is filled. The [inside-out approach](http://j-bush.com/world-building-from-the-inside-out.html) begins with those details with which the protagonist of a story interacts. The "troping" (armchair literary analysis) community calls this a [world limited to the plot](https://allthetropes.orain.org/wiki/World_Limited_to_the_Plot). In a universe where fictional creations come into existence, such a world might appear to outsiders like various forms of [small secluded world](https://allthetropes.orain.org/wiki/Small_Secluded_World), where the only part that exists is the part of which the protagonist is aware. It might look like the Other Mother's world from *Coraline*, where the edges fade into patchy pieces surrounded by a plain white void. Or it might look like the block-transfer-computation-powered city of Castrovalva from season 19 of *Doctor Who* or the titular town from the film *PleasanTVille*, which incorporate toroidal wraparound. And if the inhabitants' physical appearance hasn't been explained in detail, the inhabitants might look similarly without detail, like characters in animated cartoons for preschoolers. ]
[Question] [ Other than photosynthesis being an issue, if the Earth's surface became inhospitable and humans were forced to live underground, what biological changes would they be expected to go through to adapt to the new environment? For example, let's say the makeup of the atmosphere changes and the environment aboveground becomes too harsh to exist on, forcing the population to live underground. How would generations of no sunlight effect skin colour? Or the ability to absorb needed vitamins? Would eyes develop to adjust for less light or would new senses replace the less useful ones? [Answer] You've touched on the major points already: vitamins and skin colour. They are linked to an extent. **Vitamin D** is the major vitamin we get from sunlight. It's partly a "happy vitamin" in that it provokes serotonin neurotic responses, which makes you happier (have a look over at [Biology.SE](http://biology.stackexchange.com) for more details on this response). So, one big problem you'd have is higher depression rates (and at risk of being a bit more morbid, higher suicide rates). You would, however, find that light-skinned people suffer less: they are capable of producing vitamin D through UV-B exposure faster. On that note, bring the tanning beds underground with you. **Melanin** is a pigment found in hair and skin. It is the chemical that determines your skin colour. It appears to be an adaptation to sunlight. This is why, generally, people who live by the equator have darker skin. When underground, this chemical would be needed far far less, so you would find that over time and several tens of cycles of macroevolution, most people are fair-skinned. Depending on the conditions underground, you may also find people's senses altering. Moles, for example, live their entire life underground and have almost no sense of vision, despite having binocular eyes. If the underground homes that humans now live in are dark, you will find that through both adaptation and evolution, they de-evolve having such good vision. You can find better definitions for micro and macro evolution on [Biology.SE](http://biology.stackexchange.com), but in general terms: * **Adaptation** is small changes that can take place over an individual's lifetime. For example, you might find that the colour-sensitive cones in a human retina degrade in favour of the light-sensitive rods. * **Evolution** is the Darwinian theory: individuals with characteristics that make them more likely to survive are more likely to reproduce and pass these characteristics on (natural selection). This means over time, cones may be eliminated completely. [Answer] Keep in mind that essentially *all* energy in the world comes, directly or indirectly, from sunlight. While caves may have some life most of it either regularly travels above ground for nourishment or hunts those that do. If the earth above was rendered inhospitable to all creatures the real issues would be starvation due to an inability to get food/energy. The only two sources of energy, and thus food, that would be viable are geothermic, which is very limited, and sunlight. This means figuring out a way to grow/capture/use food from above ground to sustain the below population. Perhaps plants still grow reliably above ground and those living below can manage limited trips to fetch it? Still, if they are not farming that means far less food available, and thus a much smaller population, in any given area. This is a follow up to the below comment, but is a point I feel deserves better stressed then my comment could, as I think it's the most important detail. Humanity's evolution, regardless of environment, is first and foremost driven by our technology! We no longer adapt to our environment, we adapt it to us. This doesn't mean we are not evolving, but it's a very different evolution then the type you're used to. We are evolving to be more intelligent, to better work in a *complicated* social enviroment where working with others is the only way to achieve anything, and evolving to work with our technology. We are not, however, evolving to be better suited to living in the cold, or heat, or any enviroment really because we simply build technology to work around our limitations. For instance, our leading cause of death in America is heart disease. We would be evolving to not die from the fatty foods we eat. Our next most common cause of death is Cancer, which likely means slowly evolving means to detect and destroy cancerous cells (which our body already does a pretty good job of, only a very very tiny fraction of cancerous cells become cancer). Of course, those are today's causes of death, with as fast as our technology evolves, our leading cause of death in 2 generations may be completely different; which means we won't really have time to evolve to adapt to those particular threats. Instead the long term adaptions will likely all be about working in social groups, use of technology, and general fertility. This makes questions of human evolution in the underground hard to answer, since first I have to ask what technological approach we would use to adapt the underground. For instance our eyes are a great example. Plenty of cave-dwelling species have either lost their eyes or had then degrade to a fraction of what they were, since being able to detect light is useless in an enviroment where there is no light and eyes are a vulnerable spot we need to protect. Does that mean our eyes would degrade, probably not! Humans would instead set up lights to allow them to see like the did above ground, because that's how we work *now* and it's allot easier to adapt our enviroment to support our need for light then it is to adapt our eyes to work without light. Over a few generations we may get better about seeing in darker areas perhaps, but our eyesight would not be significantly changed unless we were unable to create lights. The same principle exists everywhere, we will adapt our enviroment to our current needs long before we would evolve to better suit our enviroment! Some changes may still occur in terms of physical evolution over a short time period, However, these will be simply favoring certain existing genomes over others. Certain types of humans may become more common rapidly, for instance perhaps one skin tone is less prone to vitamin deficency from lack of light then others, or maybe short people may quickly become dominant as it becomes hard to survive in tunnels if you're too tall. These changes could start to have a measurable, though still not overwhelming, effect in a small number of generations if a substantial enough number of humans die out (the more deaths, the more evolutionary pressure) However, this isn't creating *new* phenotypes, simply prioritizing certain existing ones. Humans would still look human, just with certain types of humans being a bit more/less common. It would take a huge number of generations to have any significant change to phenotype, for humans to start looking different than humans of today. By that time, our technology and culture should have adapted to the difficulties of living underground and we would have long since adapted our enviroment to support us. In short, I don't anticipate any huge change in human structure or format, at most, certain current physical traits become more common. Which become more common, depends on what evolutionary pressures we were unable to address with our technology. *IF* I knew exactly what enviroment humans would create for themselves below ground, I could anticipate what the most common things to kill us below ground were and anticipate what evolutionary pressures they would give us. However, I would first need to project our technological and cultural adaptations before I could begin to infer our evolutionary ones. The end result is that I see this question as being one about how our technology and culture will evolve and adapt. The real question is what cool technology will we use to work around whatever problems forced us underground. That technology drives everything else, and is a very interesting question in it's own right. However, it's also a very difficult question to answer without knowing very exact details as the cause of our moving underground, thus the reason I have to ask follow up questions to give any useful advice. Since sunlight is such a huge source of energy for...everything humanity would therefore do everything they could to find a way to harness that energy. Thus exactly *how* off-limits the above world is would be a huge question, because we will find a way to use technology to harness the energy and light above ground if at all possible, and that ability impacts everything about later technological, cultural, and physical evolution. The question of how much warning humanity has before being forced below ground is also critical. How much technology we have to help us adapt depends on how much time we had to develop and build technology before moving below ground, which in turn affects everything about eventual development. Finally how many humans died during the first 1-2 generations is a huge factor on whether we would notice any phenotype difference due to moving underground. If only 10-20% of humanity died out, then I wouldn't expect a huge difference in phenotype, beyond skin coloration, to occur because we clearly adapted our enviroment fast enough to avoid facing significant evolutionary pressures. if 50% of the population died out, then we would expect to see those with *existing* phenotypes that are better adapted to life below ground to be the norm. Again this is more about how common or perhaps exaggerated existing traits are, they would still likely look mostly human. [Answer] To change and adapt human biology **natural way would take many thousands of years,** especially if changes are drastic, like substantial changes in our senses or metabolism. Even natural selection does not make too strong darwinian pressure because our society does not allow to people die because they are less optimally adapted - because if we as society have resources, we help such people survive (i.e. diabetes). Much will depend **how much resources the underground society has** (which is not obvious from your question). * How do you power and feed such civilization? Would all food have to be grown in hydroponics powered by nuclear power? Where oxygen comes from? * Do you have enough people surviving to be able to repair malfunctions and train replacement as people die out? For all complicated technologies? Repair mining machinery? * Is it possible to go out for pillage party to bring some resources, metals, oil, books, equipment, maybe harvest food? Or is surface too deadly even for short trips? We had few questions in recent few weeks about how small remnants of society after disaster can survive, do your research. **Well-functioning underground civilization with enough resources can focus research on developing (bio-engineering) adaptations necessary for such conditions.** If you don't have resources, then well, it will take much longer and your civilization might not make it. Most likely possibility is that even if surface is uninhabitable for few decades, life was not completely wiped out, and after few decades people can start returning to surface, at least for short time (farming, harvesting). So you don't need to adapt to underground life forever, and civilization will survive even if substantially weakened in number and knowledge. There is way too many moving parts to provide answer better than "it depends", because - it depends. [Answer] Well considering many animals that live with lack of sunlight, humans could possible become like moles or bats. That is if we didn't add man made light. We would have less melanin which would cause lighter skin since the lack of sunlight. But many plants will die if all of Earth lost sunlight, so we would be extinct before we could adapt unless edible plants adapted before us. But this is all off the top of my head so :/ [Answer] I want to take a different approach to answering this question. The person asking has gotten great factual answers, but no fun ones. Just for fun let's remove some variables and do a thought experiment. Let's suppose that right at the time homo sapiens appeared, some of them departed the group and began living underground. At that point there technology was limited to sharp rocks and fire. Now fast forward to the present. Assuming a very high level of evolutionary pressure, What would the descendants of those people look like. Here is my guess. > > Average height: 4'5'' > Skin tone: Extremely pale white, bordering on translucent. > Face: No visible eyes at all, vestigial eyes would be shrunken and hidden behind the skin of the face and the skull which now covers the vestigial sockets. > Build: Powerful, well muscled, very little bodyfat > Hands: Oversized by 1/3, Nail thickened into blunt wide claws for digging. > Proportions: Arms are elongated and hang by the knees > Movement: lopes on all fours when running, fully bipedal otherwise. > Optional adaptations: > -Echolocation, which might com with larger possibly pointed ears. Short sensitive tentacle like appendages hanging like a long moustache from the face, prehensile and loaded with touch receptors. > -Bioluminescence, can be controlled with will but naturally reacts to the emotions of the individual, comes with functioning eyes that are very large, similar in shape and size to grey alien but with human like whites, iris and pupil. > > Lifestyle: Hunts other underground creatures and farms algae or fungus that can survive in underground climates. > > > This answer produces a fun sci-fi like subterranean hominid. I have no idea if that is helpful, but I enjoyed writing it. [Answer] I haven't read a single reference to mating. Females (and males for that matter) natural instinct is to seek out the strongest to mate with. In our current societies, that person is extemely intelligent but it's the 'athletic intellegint and not the 'nerd intelligent' as always. In the future, will the most athletic alpha be the person of a height that makes the best of low level tunnels and/or larger than average eyes sockets to enhance available light (and cones and rods). I'm talking of course about the studly males commonly featured in Anime. Evolution depends on natural selection for the most part and natural selection is dependent on mate selection. In totalality, my post is an oversimplification but aren't they all? [Answer] Vitamin D already covered. Your people would have serious problems with **Alcoholism** and probably with **SAD**. It is not known why people living in Northerly parts, and especially North of the Arctic circle, have high rates of alcohol-related problems. It seems to be universal, in that the problem is shared by Europeans, Orientals, and Native Americans. The only answer known so far is banning alcoholic beverages, or for individuals to abstain. Absence of sunlight is the probable cause. Also linked to absence of sunlight is SAD (seasonally affected depression). Some find staring at a bright light for some minutes each morning helps. It is very hard to get artificial light at sunlight intensity and even harder to match it's spectrum. It may be that solar UV on skin is the key, not bright visible light in eyes. We know about vitamin D but is there something else made in our skin? For some, only the certainty that Spring will arrive keeps them going. For some, even that promise is not enough. Suicide rates are anomalously high, along with alcoholism. And your people are *never* going to experience sunlit summer days. Finally there is "cabin fever" or "Yukon fever". After months cooped up indoors with extreme cold and darkness outside, people go.mad. Not sure if this is recognised as a medical Northern winter syndrome or not. ]
[Question] [ Your average Invading Alien Species shows up and plans to invade Earth. They are Default Dumb Movie Aliens and don't have nanotech, AI, space habitats, diplomatic abilities, self-replicating factories, slaughter bots, or anything else one expects a Real Interstellar Empire might bring to the table. Their plan is to invade the earth using infantry (because The Author can't be bothered to learn about combined arms tactics), to enslave humanity, and to turn Earth into a colony. This is known to us because The Plot requires us to know it. You know how this usually goes. The Plucky Hero wins because the Aliens never heard of cyber security. But what if the World Governments decide that there is no hope and **Subvert The Expectations of the aliens by committing collective suicide while Trashing The Place?** Think of this as a final, species level f-you salute. **How hard is it to do this?** My current best idea is to use salted nukes/cobalt bombs, deliberately releasing toxic chemicals and mass producing hydroflourocarbons\*. Is this the best strategy? Assuming we commit 30 percent of the world economy to this for a year, how bad would the damage be? **The ideal outcome would be toxic, irradiated waste lands under a Venus like atmosphere.** Edit 1: The Aliens want to take Earth intact. They need our environment because The Plot requires them to require it. We know that ruining the Earth in the manner described above will deny them all their objectives. Don't think to deeply about how the aliens work or think, The Author doesn't do that and neither should you. \*I meant sulfurhexafluoride. [Answer] ## If we can't have it, you can't have it either! This is exactly the level of petty that the human race is, and if faced with an unwinnable war and insurmountable opposition, this is exactly what I would expect them to do as their "Last hurrah". For your handwavium to work, all the aliens need within the premise of your question is this: (near) **infinite reinforcements**. Sure, humanity could fight back, take a battle or two, make machineguns go brrrr. But there's just an infinite amount of the buggers. It becomes increasingly obvious that even if we go down fighting, we cannot "win" against the aliens Zapp Brannigan-style of combat. So we want to go down the pettiest way possible of course. As per your question: *"My current best idea is to use salted nukes/cobalt bombs"* Sure, we could pop all our nukes and nuclear power plants, but that's boring. The aliens recognise a lost cause when they see one, so they leave and go conquer another civilisation instead. Instead of destroying the earth instantly, it would be infinitely more middle-finger-ish of us to poison the earth slowly. This would make the aliens think they have won, and waste copious amounts of their time trying to harvest a dying planet while being powerless to save it. This would of course delay them from moving on to another conquerable world and set back their race as a whole. Or at least get one overworked alien overseer fired for not meeting their quota. Your other ideas would hold more merit for a slower, yet equally irreversible death. Which is, of course, a better way of sticking it to the alien menace. I quote *"deliberately releasing toxic chemicals and mass producing hydrofluorocarbons. Is this the best strategy?"* Most likely, yes. We spend all our money on supersizing and automating our production of Chlorofluorocarbons, and release them into the atmosphere. ([Note that Hydrofluorocarbons were invented to replace the much more dangerous Chlorofluorocarbons](https://www.greenamerica.org/faq/what-are-hfcs-and-how-are-they-different-cfcs-0), so we'd have to go back to basics for this one). At the same time we unearth and burn as many of our fossil fuels as possible. Within moments our ozone layer and atmosphere will be irreparably ruined, and [UV-radiation form the sun will take care of the rest for us.](https://www.greenmatters.com/p/what-happens-ozone-layer-gone) Of course humans have extensive experience with this already, and getting humanity behind this approach wouldn't even be too hard. All you'd need is a [copious amount of misinformation and lies](https://en.wikipedia.org/wiki/Don%27t_Look_Up), and we'll get right on destroying ourselves. I doubt you'd even need to tell them why. And with humanities current approach, I might even doubt the aliens make it here before all of this happens regardless. [Answer] ## We only tried to kill the aliens. Since the aliens have been foolish enough to send wave after of wave of infantry against us, they have provided us with an endless supply of genetic samples to study. Even though these alien lifeforms may have the same basic requirements as human, there is inevitably some difference between human and alien biology to exploit. If we can make herbicides that distinguish between crabgrass and wheat, then creating a xenocide that can distinguish between Earth biology and alien biology is not that hard. Last year, a pharmaceutical company had an AI invent 40,000 chemical compounds that are suspected to be hazardous to human life in just 6 hours. Do the same sort of test on some alien genetic samples, and all you have to do is weed out all the chemicals that might also be toxic to Earth life and anything left can be quickly tested on the many platoons of aliens for actual lethality. Whatever chemical gives you the best bang for your buck, is the one you use. Thanks to recent creepy advancements in AI, your humans could go from theory to selective bioweapons in a matter of days. ## But we didn't have time for clinical trials... So we've made a bioweapon the kills aliens: CHECK! ... but the OP requested suicide: Not Check? You see, the problem with the OP's presumption is that we can and will trash the place on purpose all while devoting massive resources to fighting an actual war. We might unleash a nuclear holocaust or something of that nature, but even detonating the entire world's nuclear arsenal is going to at most make the world on average, unpleasant, and any toxin we try to manufacture might kill us all long before it reaches sustainably toxic levels world wide, again cutting our trashing off at mildly unpleasant levels before we can do any truly serious damage, but if the toxin is a thing we have a very high relative resistance too, then we can win the war first (putting us on less of a restrictive timeframe), and continue to make a hell-of-a-lot of the stuff before we realize that we've poisoned ourselves into annihilation. The toxin kills humans too, but only by a very slow and unexpected vector so by the time we realize there is a problem, we've already dumped billions of tons of the stuff into the air making Earth so inhospitable to alien life that they will wish they were landing on Venus if they ever come back. The toxin of course kills us all off eventually, but what was just enough to be our undoing is millions of times what the aliens can sustainably take, so even if the chemical slowly breaks down or settles into various sequesters over time, it will have to go through many many half-lives before the Earth becomes non-toxic enough for the aliens to return. And since this chemical is fictious instead of a real chemical with properties your readers can just look up, you can say it will last as long as you need it too. Need Earth to still be a death world to these aliens 50,000 years later? No problem, because it is if you say it is. [Answer] First, we don't have any of these: * ***Planet DeorbiterTM 3.0 - Planet smasher version*** * ***Supernova gunTM - Free your hydrogen energy ©*** * ***Super-duper ultra matter-antimatter planet converterTM*** * ***Pocket black hole creatorTM - Release your darkest dreams ©*** We need to work with what we have as today. And here are our weapons, and we can produce a lot of them: * Fire! Fire! Fiiiiire! * Atomic bombs * Cobalt bombs * Hydrogen bombs * CFC * Coal * Oil * Mercury * Arsenic * Lead * Microplastics * Herbicides * Junk So, here goes the script. 1. Aggressively mine all the coal and oil as possible and burn it all! 2. Orange agent and other aggressive defoliants should be produced in mass and spread out over everything that is green. 3. Mine and purify the most mercury, lead and arsenic as possible, and release it all over the soil, specially in forested areas. 4. Burn down all the forests! 5. Release as much as CFC as possible. We will need large-scale CFC factories happily throwing all that CFC in the atmosphere. 6. Release as much sulphur dioxide, lead and methane smoke as possible in the atmosphere. 7. Aggressively get the most salt as possible from the oceans and drop it over fertile land. 8. Build a canal draining lake Victoria and lake Tanganyika right into the Indian Ocean. 9. Build a canal diverting the Nile from Khartoum right into the Gulf of Aden. 10. Close the Gibraltar strait with tons and tons of concrete and stones until a wall several dozens of meters high blocks the Mediterranean Sea. 11. Close with concrete the Suez canal. 12. Close with concrete the Bhosphorus and/or the Dardanelles strait. 13. Dig a deep canal from the Black Sea to the Caspian Sea. 14. Dig a lot of deep and large canals to drain the Great Lakes as quickly as possible and also avoiding them from refilling (including even lake Winnipeg). 15. Nuke ice caps in order to force calving, avalanches and ice meltdown. 16. Dig deep into tectonic faults and nuke them. 17. Remove undersea soil and sand from atolls and corals and drop that sand in freshwater lakes. 18. Burn oil and coal in open pits on ice caps. 19. Concrete Denmark to Sweden closing down the Baltic Sea. 20. Fill the sea around Indonesia with sand and rocks took from elsewhere and concrete everything until there are land bridges connecting Sumatra, Singapore and West Malaysia to New Guinea, Philippines and Australia, making all of them a very weird and long peninsula of Asia instead of an archipelago. So, the waters from the Indian Ocean will need to travel all around Australia in order to reach the China Sea. But we can go further and also connect China to Taiwan and Taiwan to Philippines, making all the sea there isolated seas that would start to dry up and shrink making that a very new large peninsula of Asia. 21. Close the Bering strait too. 22. Create a land bridge from Djibouti to Yemen and another from Dubai to Iran. 23. Create a deep canal draining lake Baikal into the Okhotsk Sea. 24. Get the excess sand from Sahara, Arabian and Australian desert and dump them in places that used to be green, mostly into the Amazon forest, Congo forest, US midwest, Europe and China. 25. Dig a deep canal to divert the Mississippi river from the Spring lake into the lake Michigan. 26. Any remained land places that are still more or less habitable to vegetation should be nuked and "chernobylized". 27. Produce microplastics in a scale as never seen before and dump everything into the oceans. 28. Mine dangerous green-house natural gases like methane and let them leak in mass into the atmosphere. 29. Unbury all the junk that we ever produced and buried, let all the gases escape, burn all the biodegradable stuff and drop the non-biodegradable part into the seas. 30. Connect with land bridges Busan in South Korea to Tsushima Island, Iki Island, Kyushu, Honshu, Hokkaido, Sakhalin and mainland far-east Russia. This will make the Japan Sea an isolated sea that will shrink like the Aral Sea did. 31. Connect with land bridges Hokkaido to the Kuril islands until Yamchatka, so the Okhotsk Sea will also become isolated and eventually shrink. This will trigger a disaster comparable to some known mass extinctions. But even with all of that, in a few million of years, nature would likely be able to recover and go on, with or without us and the aliens. Also, the land bridges serve an interesting purpose: To kill archipelagos and make lakes and interior seas shrink (even the Mediterranean Sea). This will make the continents more arid and more similar to Pangea. Europe-Asia-Africa will become much more a single continent than what it is today. The Americas and much of Oceania including Australia would also be connected to Europe-Asia-Africa. Only Greenland, Antarctica, Iceland, New Zealand, Madagascar, England, Ireland and a few small archipelagos would remain detached from the NeoPangea. Finally, if you want to: 32. When the isolated seas already have shrank down significantly and the aliens are already landing, nuke some land bridges and let a deluge happen. [Answer] It really depends on your (the Aliens') definition of permanent, because honestly very little apart from cracking the planet into bits will truly permanently (ie *forever*) ruin a biosphere. The cobalt deposited in the environment by a salted cobalt bomb has a halflife of only ~5 years, so while it would make the planet uninhabitable, permanently wreck the biosphere it would not. CFCs break down over time (fairly quickly actually, as shown by the ozone hole repairing itself after only a few decades) so are only effective at tanking an ozone layer if continuously released. The ozone layer also has much less of a job to do protecting sea life, so even if you could get rid of it permanently if the aliens like it under water they might not even notice. Even the longest lasting "forever chemicals" break down over time, they are only "forever" on human timescales. And they (PFAS) are also not very toxic, so they wouldnt permanently ruin the biosphere either. Most chemical weapons that would give the aliens trouble (not reliant on earth biochemistry specifically, so things like chlorine gas rather than say, a nerve agent) are pretty reactive to have their effects, so they also wouldnt be very long lasting. To truly wreck a biosphere you essentially need to sterilize it, down to the bottom of the deepest parts of the ocean. Bacteria have even been found pretty deep into the earth, just chillin in fractures in the bedrock doing chemosynthesis. All of that life would need to die for there to be no chance of recovery, because otherwise life, uhhh, finds a way. We could weaponize life though, if we relax the constraints a bit then a very aggressive organics digesting microbe could essentially grey-goo the planet while being just as dangerous to the aliens as it would be to earth life. Or the traditional grey-goo (nano machines that eat everything and make more of themselves) could also apply, though they would be subject to potentially being "turned off" somehow by the aliens (an EMP maybe, for a fictional setting anyway). There's also the route of not ruining the biosphere, just making it so difficult to use the land that the aliens dont want it anymore. There are places in the world today that are so full of land-mines and unexploded ordinance that no one goes there. If we had a bit of warning to prepare we could scatter all the nukes and beyond metric f---tons of conventional ordinance as land and sea-based mines everywhere. We couldnt actually get *everywhere* but the aliens would have no idea where was mined and where was not (assuming no scanning equipment, anyway), so would have to assume everything was. And removing those is expensive, time consuming, and dangerous. This way makes a lot of assumptions about the aliens not having the tech to easily remove the mines though, which a more realistic spacefaring empire would probably have (whether its just good enough AI/drones that the removal can be automated, or whatever else). [Answer] *Permanently* ruining the earth would be pretty hard. I believe pollution, nuclear weapons, etc, will at best get you a few thousand years of ruining. My proposal is **deorbit the planet**. You can find [a number of topics that dealt with this](https://worldbuilding.stackexchange.com/search?q=earth+move+orbit) to get some hints, though I couldn't find one that directly answered your question -- most assume far future tech, take thousands of years to accomplish, or are trying not to ruin the planet. In your case, we have modern tech, a short timeline, and we don't care if we ruin the planet because that's kind of the goal anyway. I propose space missions to move asteroids that will slam into Earth. Moving the Earth itself is hard, but moving big asteroids and then relying on gravity to give them real momentum should be easier. If we can get the asteroids to slam into the earth at an angle that reduces our orbital speed, then we deorbit. The asteroids pretty well ruined the planet, but the orbital change will make it permanent. I'm kind of relying on your statement that the aliens are pretty dumb. They basically just throw ground troops at a planet until they win. Space combat is not their thing (and maybe that's why they picked us to take -- they regarded us a non-threat in space combat). They can shoot down missiles coming right for them but it's not hard to slip past them with rocketships that are "not a threat". What are we doing with those rockets? Where are they going? The dumb aliens don't even care. Maybe we're fleeing. Great! Send more troops down! Maybe we can get the moon in on it, too, or as an alternative. Smash something into the moon such that the moon gets deorbited into the earth. I believe that would ruin things permanently. Other options could include ["gray goo"](https://en.wikipedia.org/wiki/Gray_goo). Self-replicating nanotechnology that just consumes everything. That's a bit fantastical at the moment. So is deorbiting the planet, really, but I think moving asteroids is within our ability, and intentionally throwing them at the planet with specific impact angles seems feasible if we really apply ourselves. [Answer] The only brute force way to 100% ruin a planet is to deorbit it. This would require nearly as much mass as the planet and would require a type 2 civilization, which probably has better plans than suicide. However our goal is to ruin it for the purposes of the aliens. So why would aliens want Earth? The question mentions turning earth into a colony. A colony is useful when it can supply a resource. What does earth have that's worth fighting for? Not the common rocks, or the common gases, or water. All of those can be found in massive quantities around the galaxy. If you're taking over planets, it's because you need something rare enough to require multiple planets to get what you need. **Heavy elements**. Every supernova only creates so much of it, and it tends to be very useful. If aliens needed a cosmic amount of any heavy element, it would explain needing to set up colonies in far away star systems. And luckily for us, this would be far more feasible than de-orbiting the planet. Mine as much of every heavy element from the crust that aliens could possibly want. Launch into the sun or destroy. This would still be a massive operation, but could be done by a type 1 civilization. [Answer] De orbiting the planet sounds like a good idea. But How about deorbiting the moon? Many planetary functions rely on the moon and if the moon crashed into earth its game over anyway. (we already have impact craft technology but its time to refine it to be sure one could do a meteorite bombardment of the moon) Regardless, the nuke idea is probably pretty good, but as Chernobyl has shown, wildlife can adapt and survive. Either that or creating a perfect Von Neumann machine. (self replicating robots that eat anything to reproduce.) [Answer] **The question needs additional clarification/information.** If the aliens concerned have actually arrived in the solar system and are in the process of trying to conquer the planet there are ZERO options available to humanity for ending all life on Earth. There aren't enough nuclear weapons to do so (doped or not), there are no biological weapons that would do so and no other actions we could take like trying to induce a runaway green house effect that would end all life/destroy the ecosystem in anything baring multi generational time scales. There is in fact only one sure way of achieving this end and it requires the ability of Earth to access and operate in deep space. If the aliens are actually here that should by default be impossible simply because they control the 'high ground'. Nothing we launch would be capable of escaping the attention of a species with interstellar travel capable technology levels. If instead the Aliens just sent a radio message saying something along the lines of '*We are coming to invade, resistance is futile, we will arrive in 25/50/100 years.*" Then perhaps we have time to initiate a space program designed to de-orbit a rock big enough to destroy all life aka the movie Deep Impact. Other than that we simply don't have the technical capabilities to end all life on Earth. Life is tough. [Answer] Not hard at all. I think that in order to ruin earth, we just have to keep doing what we are doing. All we have to do is destroy the ozone layer and fill the earth with greenhouse gases in order for our big blue planet to turn into a second Venus. If you want to take the short way out, start a Nuclear World War. With just 100 nukes, you can basically destroy humanity one way or another. The nukes may make a huge cloud of dust and gas covering the earth for months, maybe even *years*. The cloud covering would impede the sun from coming down into earth so the world would freeze. Basically a new ice age. ]
[Question] [ It has been suggested that lava tubes at Hadriacus Mons could provide a location for a human habitat that would screen out harmful radiation. <https://en.wikipedia.org/wiki/Hadriacus_Mons> My idea for a colony is that it was initially built inside the lava tube (which I gather is huge - 190m wide, 160m tall (100m below surface). This could hold say a 50-story structure of some kind. Once in place, you could extend structures through the surface with radiation protection so you could have windows and a view outside. Space isn't a problem, but I'm thinking materials are. Assume this is in the future and we have advanced ships and a presence on Mars for many decades - beyond exploration and into settling. **Question: What's the best method to build a city colony structure in the lava tube?** Would it make the most sense to build a "skyscraper" inside with access to the surface? Or would there be some better way to build in this huge open space? Alternately you could begin tunneling in to the rock itself within the tube and build inside the Mars rock itself. Apparently you might be able to make "mooncrete" (<https://en.wikipedia.org/wiki/Lunarcrete>) - could you make a sort of "marscrete?" NOTE: Think long term, big city, permanent settlement - we are past the exploration stage. **EDIT: People are still thinking of the exploration/astronaut stage -- think more about this as a full fledged functioning colony 100 years later. As I said in my note - big city. We are beyond worrying about potatoes for food and oxygen. We have the technology to reliably put oxygen safely in the whole structure. We can ship food and materials in from Earth or other colonies. That's the background. Now we want the best structure with that in mind inside the lava tube.** [Answer] 3D printing…. Building on the experience learned from building moon habitats that used 3D printing a lot has been learned that can be transferred to Mars. Of course neither the moon or mars have a lot of free water, so 3D printing of concrete like materials was more difficult than on Earth. On the moon the scaling up of [solar sintering](https://www.google.com/amp/s/www.3dprintingmedia.network/regolight-project-uses-sunlight-sintering-3d-print-simulated-lunar-regolith/amp/) turned out to be important. On Mars since less sunlight was available, fusion furnaces were used to sinter the crushed and processed mars rock instead but many of the control systems and robotics and software to plan out the city were based on what was learned on the moon. Edit: Here is is a link showing some 3D printed concrete structures presently being done (on earth). [3D concrete printing](https://all3dp.com/1/3d-concrete-printing-guide/) These types of techniques could be automated and used to smooth out the lava tubes, help provide more smooth sealable air tight surfaces, as well as build structures in the tubes. [Answer] Start building in the middle of the tube. That means you can transport materials from both directions rather than just one. Build the heavy structures here in the middle. Like nuclear reactors and water purifiers and oxygen makers. Build the potato farms on either side of the tube. They need sunlight after all. People also require sunlight to not go bonkers insane. So build homes on either end of the tube near the farms. (**Edit:** That means the yummy potato oxygen can be pumped into the homes) Make sure to leave a long throughfare between the two sides of the tube. You will need to expand the homes deeper into the tube as population increases. Don't burrow into the tube wall. There is no need for this. The tube is already burrowed into the mountainside. Why burrow further. It needs the same amount of materials, since you still need to build walls inside the walls to run electrical wires and heating tubes behind. A single large building is a bad idea. You want each home to have a separate oxygen supply. That means even if one home starts to leak space air you can just run next door. [Answer] **Gonflable!** [![inflatable house](https://i.stack.imgur.com/l9nNj.jpg)](https://i.stack.imgur.com/l9nNj.jpg) AKA inflatable building. You need to blow pressurized atmosphere anyway because we like that. Let the atmosphere you blow in there serve a structural role too. Down in the tube all you need is to keep the atmosphere from blowing away and a strong inflatable shell will do fine. It is cheap. It will conform to the tube walls. It is easy to make it modular for expansion or rearrangements. It is easy to patch from the inside. [Answer] My idea is a rotating donut-shaped base living area that would constantly be spinning to passively give astronauts their share of exercise while working. The donut would be on thick steel poles that extend to the sky about 10m. The donut will also be made out of steel. Although Mars dust can be a big problem for it can be detrimental to the lungs and is electrostatic, in order to enter, their will be a series of airlocks. The first is where they will 'dock' their spacesuit after work outside, which will most likely be covered in dust. After docking, they will slide out into a room, and then go into the main hub. Food will be a problem to, so an area for aquaponics would be set up to provide astronauts with a nutritious variety of foods. [Answer] I assume that since you want to build a city the first phase of the colonisation is already advanced. Thousand of small living modules sent from Earth where used as bases to build many glasshouses to grow food, now Mars is dotted by many villages. Those villages used Martian perchlorates as a source of oxygen and energy, but now to build a city they need a lot more energy, from Earth they'll send a mini nuclear reactor. It will be used to process Mars ores and build some more. Once you have abundant energy you have a lot of different choices. Since aluminium and magnesium are abundant on Mars surface, the easiest way is to use them in alloy to make prefabricated building parts. It will be easy to transport them to the building site thanks to the low gravity. So the prefab parts will be big chunks. The building inside will have thick layer of a silicone type that is denser than the one used now. Over it instead of plaster there will be a layer of tiles. On the outside they are not necessary until they will have enough resources to seal the tubes and change the atmosphere inside. Bare metal will rot very slowly in Mars atmosphere. The city will be a single huge lattice structure, with sealed pipes used for walkways, service tunnels and shuttle tracks. BTW The prefabricated parts will be bolted not welded together. Building a city with a scarce workforce in a difficult environment is expensive. If a marsquake cracked the tunnel, creating the risk of a landslide and forcing people to abandon the area, rebuilding everything from scratch would be difficult. A city on Mars must be a structure that could be dismantled and reassembled somewhere else. [Answer] This concept is covered in the [Mars Trilogy](https://en.wikipedia.org/wiki/Mars_trilogy) by Kim Stanley Robinson. In the novel, the lava tubes are sealed off in 1km sections, pumped up to a breathable atmosphere and 'terraformed' with soil (very hard to make) and water. As you correctly surmise, this produces a very large amount of living space (the lava tubes are 100's of km long) which is shielded from cosmic rays and (not incidentally) well hidden. ]
[Question] [ Well, after asking [Would mermaids be affected by tongue-eating lice evolving alongside them?](https://worldbuilding.stackexchange.com/questions/212920/would-mermaids-be-affected-by-tongue-eating-lice-evolving-alongside-them), I realized they would be a worthy addition to a more monstrous subspecies of mermaid. There's only one problem: why? As in, why would mermaids allow these parasites to replace their tongue? What possible benefits would make this worth it? In the linked question above, Mel suggested the lice could supply antitoxins or a greater vocal range, while Michael suggested the parasite could supply teeth and a tongue to infected mermaids, but I'm not sure how viable either of those are, and I don't know how to find out, ergo I am asking this. In other words, my question is **What Benefits Could Tongue-eating Lice Have For Mermaids?** **Specifications:** 1. Yes, I am aware that these parasites could be given a place in a mermaid's body simply because of societal/cultural/traditional reasons, but that just doesn't seem to cut it for me. As far as I am aware, humans (and therefore mermaids) need *justification* to do something as drastic as allow a parasite to kill, eat, and replace a useful (if not vital) organ. **TL;DR: The best answer will account for the pros and cons of this unusual organism and explain what benefits it could logically have that would enable symbiosis with its host, therefore rendering it *not* a parasite but a symbiotic organism.** 2. There is magic in my world, so one can use magical abilities as benefits in one's answer, as long as those magical abilities have a **logical basis** that is **aptly explained.** If this sounds like science-based magic, which is frowned upon, so be it. I prefer magic that makes sense (ie. that has a logical foundation) over the chaotic nonsense usually found in fantasy. **Final Note:** If you need to vote-down or VTC, please explain *why* so I can improve the question. Thank you! [Answer] This looks can be a [mutualistic relationship of the service-resource type](https://en.wikipedia.org/wiki/Mutualism_(biology)), facultative for mermaids (i.e. they don't need the parasite to survive) * The parasite can't hunt or feed itself, so it depends on the mermaid to get food (the resource) * After the tongue is replaced, the parasite gives the mermaid her hypnotic voice (the service) The consequences * Regular mermaids don't have their signature voice, and they tend to not venture in the open wide world * A monster mermaid (with the parasite) has hypnotic voice and possibly needs to eat more to compensate for the parasite or have different dietary requirements than a regular mermaid, so those are the ones your explorers / adventurers are more likely to see * Up to you: the relationship between the "regular" mermaids and "monster" mermaids - do the regular mermaids consider the monster mermaids uncivilized degenerates that allowed themselves to be degraded by a parasite? A form of exile? Or is acquiring the parasite a rite of passage, making the "monster" mermaid an adult? [Answer] ## They enable Parthenogenesis. Monstrous mermaids have a hard time finding sexy sailors to mate with - either because of how they look, or their fame as men-eating monsters. Maybe its their size, or even their biology - even if male humans could mate with them for the fun of the couple, that pairing by itself doesn't produce viable offspring. Enter the tongue-eating lice. The lice itself doesn't bring that many mechanical benefits for the monster-mermaid. It replaces their tongue and make them a little bit more monstrous, even. But the lice pumps them with special substances that, when introduced to their bloodstream, enables them to get pregnant and give birth without needing a male - [as it happens in some parts of nature already with different pairs of host-parasite.](https://onlinelibrary.wiley.com/doi/full/10.1046/j.1420-9101.1999.00082.x). Thus, the lice-enabled mermaids are able to survive without needing mates. They can still bring sailors to their lairs and do evil things with them, mind you, but they don't *need* their man-juices to continue their species. They probably just want to eat them, since their babies will come no matter what. This creates a terrifying setup for your world, with the opportunity for exciting reveals - a sailor going for a kiss and finding out not the inviting tongue of a mermaid that wants to get frisky, but the parasitic lice of the fish-woman that is about to eat him alive can make for an awesome campfire tale inside your world, for example. So, the lice. A mermaid that gets the lice gets the ability to reproduce without any external help. This enables them to shun their sailor-loving cousins, retreat deeper into the seas and, over time, become more and more like a monstrous sect of murdering-sea-witches. The lice, for them, isn't only a cultural marker of their tribe, but also a tool for survival. It's how they "free themselves" of the two-legged dryskins, keeping their race "pure", without external "interference" or "contamination". Give them some extra magical abilities to booth, caused not by their lice but by the focus they give to magical learning, and you can get a truly terrifying foe for your heroes. [Answer] They're instruments of torture for a despotic regime. The equivalent of cutting out tongues above the surface... the sort of thing you do when you're unhappy with what the victim is saying. But it's so much more than that too. A man who was victim to this (supposing he survives) might still give his kids a peck on the cheek for affection (hopefully a long distance away from where the mutilation took place). But who would allow that if there's a monster in the guy's mouth? You can feel it moving around on its own. It doesn't obey you. When it's hungry, it clamps down, and the nerves are always raw. And it's always hungry. You can't eat in the presence of others, lest they glimpse it. You're mute. You're forever outcast. Most, I think, would soon become insane. Those who don't suicidally depressed. Can it even be removed safely without modern medical intervention? Now, this isn't a benefit to those who would suffer from the thing. But it is to the benefit of those who wish to be cruel, to punish, and to torture. Presumably other merfolk. ]
[Question] [ Most of us are well aware that chocolate is already a bit addictive to human beings... maybe it's the caffeine or the sugar? But what if there were a species to which chocolate was as addictive as heroin? Not only is it the best smelling/tasting and enticing thing they've ever encountered, but the first time they try it, they are instantly hooked. Attempting to forgo chocolate results in severe withdrawal symptoms. However, other human sweets/foods do not cause this, unless there is chocolate in them. Only chocolate, specifically. Other than the cravings, withdrawals, and a surge of "happiness" upon consuming chocolate (endorphins, probably), chocolate doesn't have any other typically associated drug-like effects such as hallucinations or motor function impairment. What could be causing this phenomenon? Assuming the species functions under the same basic physiological systems we generally understand in life as we know it, as opposed to being a weird fifth-dimensional crystalline-based goo being or some other fantasy dodge. Is there any way to explain or justify this extreme addictive effect? [Answer] # Theobromine > > Theobromine...is a bitter alkaloid of the cacao plant...It is > classified as a xanthine alkaloid, others of which include > theophylline and caffeine. The compounds differ in that caffeine has > an extra methyl group. ([ref](https://en.wikipedia.org/wiki/Theobromine)) > > > While smaller amounts of theobromine can be found in other foods (like tea) and caffeine can break down into theobromine, the largest source is from chocolate. Theobromine is not considered addictive in humans, but it certainly does have some effects. > > The contributions of theobromine are less clear and its psychoactive > effects appear subtle...Although two early > studies failed to detect psychopharmacological activity...[one] found that 5 of 7 > participants were able to discriminate 560 mg theobromine from placebo > or caffeine, suggesting that theobromine might be about one tenth as > potent as caffeine. While theobromine did not significantly increase > any subjective or behavioral measures...when all subjects were combined, the compound increased > alertness, headache, and irritability in some individuals, suggesting > the possibility of individual differences in sensitivity. Using a > higher dose, [one study] found that 700 mg theobromine > lowered blood pressure, decreased self-report calmness and increased > subjects' ratings of how interesting they found performance of study > tasks. ([ref](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3672386/)) > > > Your aliens may have biochemistry where theobromine leads to dopamine staying active for longer than normal. Like cocaine does in humans. > > The brain’s mesolimbic dopamine system, its reward pathway, is > stimulated by all types of reinforcing stimuli, such as food, sex, and > many drugs of abuse, including cocaine... > Besides reward, this circuit also regulates emotions and motivation. > > > In the normal communication process, dopamine is released by a neuron > into the synapse (the small gap between two neurons), where it binds > to specialized proteins called dopamine receptors on the neighboring > neuron. By this process, dopamine acts as a chemical messenger, > carrying a signal from neuron to neuron. Another specialized protein > called a transporter removes dopamine from the synapse to be recycled > for further use. > > > Drugs of abuse can interfere with this normal communication process. > For example, cocaine acts by binding to the dopamine transporter, > blocking the removal of dopamine from the synapse. Dopamine then > accumulates in the synapse to produce an amplified signal to the > receiving neurons. This is what causes the euphoria commonly > experienced immediately after taking the drug. ([ref](https://www.drugabuse.gov/publications/research-reports/cocaine/how-does-cocaine-produce-its-effects)) > > > In fact, all additive drugs work in similar ways. > > All drugs of abuse, from nicotine to heroin, cause a particularly > powerful surge of dopamine in the nucleus accumbens. The likelihood > that the use of a drug or participation in a rewarding activity will > lead to addiction is directly linked to the speed with which it > promotes dopamine release, the intensity of that release, and the > reliability of that release. Even taking the same drug through > different methods of administration can influence how likely it is to > lead to addiction. Smoking a drug or injecting it intravenously, as > opposed to swallowing it as a pill, for example, generally produces a > faster, stronger dopamine signal and is more likely to lead to drug > misuse. ([ref](https://www.health.harvard.edu/newsletter_article/how-addiction-hijacks-the-brain)) > > > I see a future of cacao crack and mainline milky ways. In seriousness though, different species react in different ways to the same substances. The same amount (adjusted by weight) of chocolate that leads to pleasure for humans will kill a dog or a cat. > > Theobromine is toxic to a dog when it ingests between 100 and 150 > milligrams per kilogram of body weight...It would take 20 ounces of > milk chocolate to kill a 20-pound dog, but only 2 ounces of baker's > chocolate or 6 ounces of semisweet chocolate. ([ref](https://animals.howstuffworks.com/pets/question348.htm)) > > > So, for your aliens, theobromine has an addictive effect. Chocolate being the easiest and tastiest way to get it. [Answer] @Cyn has a great answer, and I would add that Theobromine is also being used in toothpastes and other products because of it's unique properties. Aside from Theobromine, and looking at the manufacturing side of chocolate, I might recommend also: # Ammonium Phosphatide [Ammonium Phosphatide](https://en.wiktionary.org/wiki/ammonium_phosphatide) is a type of salt [approved for use in the USA](https://www.foodprocessing-technology.com/contractors/ingredients/palsgaard/pressreleases/press14-2/) as well [as the EU](http://www.ukfoodguide.net/e442.htm). It operates like lecithin (that is, as an emulsifier), and is usually manufactured from rapeseed oil. You can read a detailed description of this [in this paper](https://www.palsgaard.com/media/232839/emulsifier%20yn%20-%20the%20unique%20ingredient%20in%20chocolate%20production.pdf), which focuses on it's use in chocolate production. Like many types of salts, it's [addictive "just like cigarrettes and hard drugs"](https://www.dailymail.co.uk/health/article-2013703/Why-salt-addictive-It-stimulates-brain-cells-just-like-cigarettes-hard-drugs.html) because of how it interacts with the brain. As such, it is not unfathomable to consider an organism with a brain that interacts with this specific type of salt in a way similar to heroin. ]
[Question] [ Imagine we took earth and slowed it down so that a day lasted 100 years, could humans (or any life) survive? Let's assume that there are no ill effects of slowing it down, no massive tidal waves, no continents melting as they slide across the surface, and the atmosphere stays in its relative location. In short, every particle just decides to take a break from spinning. Would life be able to survive? I have this image in my mind of people living on the band between the hot and cold hemispheres and gradually moving their settlements along with the rotation of the earth. In one regard, energy would seem to be relatively easy to harvest - just put a boiler in the sun-facing region and a condenser in the dark region and you could have a nice steam engine. Would people be able to use this easy energy to overcome the challenges presented by the scorched and frozen earth that surrounds them? [Answer] The big problem I see for survival is not energy, it is growing plants for food and feed. The dark side is going to turn into a desert, no grass or crops or trees or any photo-synthetic life is going to survive even a year of night, and there is no time for them to adapt. Which means all the wild animals and insects that depend upon plants are dead, and all the predators that eat those are dead. You have a similar problem with the oceans; the photosynthesis that creates the basis of the food chain stops. Most of our oxygen comes from that activity, When the Pacific is on the dark side, you just created a low-oxygen planet, and that is going to kill trillions of fish. Some plants will do fine with 24/7 daylight, and may adapt to it, but every year, 1% of these high-light plants move into night and will die there. Coming out of night into the day, there is no guarantee that what has become desert is going to suddenly sprout with life. Just as the Sahara was once green, but rain doesn't help it grow again. Or, the constant sunlight may turn the bright side into a desert, too. When the big agricultural regions in the US and Asia go dark, there goes the food supply for the world, and here come the food wars to figure out which 20% of the population gets to live on 20% of the former supply. As for the energy, solar energy is not usable for all daylight hours, the sun is only high enough for about 10 hours a day. You will still have the dawn and sunset bands where insolation (that is the technical term) is strong enough to extract useful energy from sunlight. So similarly, only 37% to 42% of the slow earth, at any given time, has sufficient insolation to use for either photovoltaic power or solar concentration (thermal) power. I don't think "wild" humans survive this. A high tech civilization could, the power generation could be mobile, crops grown indoors and given artificial night by simple shading mechanisms, oxygen generated the same way. But there is no huge advantage to having 24 hours of sunlight versus 9 or 10 hours, in terms of energy this is just a linear relationship. The bright side isn't going to boil, the atmosphere is a fluid and will act as a heat conductor, the flow will circulate hot air to the dark side, where it will cool, and that will inevitably push cool air to the bright side. But the lack of photosynthesis: That's going to kill us all, we will be starving for both food and oxygen pretty quick, and there is going to be mass extinctions of wild life that may well destroy the ecosystem on Earth. [Answer] In addition to what @ChristmasSnow said, 7.7 billion people "*gradually moving their settlements along with the rotation of the earth*", when 70% of the Earth is ocean, and a big chunk of that is the Pacific is -- at best -- impossible. I'm dubious as to whether **anyone** could do it, since the ocean storms caused by those winds will be stupendous. [![enter image description here](https://i.stack.imgur.com/A8nFR.jpg)](https://i.stack.imgur.com/A8nFR.jpg) [Answer] Edit: clarifications in **bold** Over these long distances (dark side DS and bright side BS) trapping heat and conveying it from BS to DS is impractical because of heat losses along the **steam pipes** You would rather harvest **electric** energy on BS and export it to DS. **solar stations converting heat to electricity would do better, but the length of power lines cannot stretch to infinity** Put it another way: **a thermosolar power plant concentrates heat by mirrors to a solar tower. This tower is now hotter than its surroundings** . This heat difference relative to the environment is sufficient to generate electricity and conduct it to DS. **resistance losses through power lines is small at urban scale but too large if we stretch lines across the globe so producing power locally is better** Second way: this slow rotation creates an almost eyeball Earth where strong winds rise up and move from BS to DS, cool and descend and move back to BS. So, wind energy will be more available in DS and will not require moving any energy source from BS to DS. **it also encourages local production** [Answer] What you're essentially doing here is tidally locking the planet: making one half almost permanently day and one half almost permanently night. For the first week or so, the effects would not be that noticeable, but plants on the night side would start to die from inability to perform photosynthesis. After the first week or so, things start to get weird. The temperature on the night side will gradually drop until the night side freezes over completely and basically becomes Antarctica during the winter. The temperatures on the day side will gradually rise until the oceans, lakes, and rivers all dry and that side of the planet becomes a desert. To survive, humanity would have to live on the boundaries between these two zones, which would be a temperate area permanently in sunrise/sunset. All farming would have to take place here, and people would only be able to grow dark-tolerant plants that could survive in reduced sunlight. As these would probably not provide enough biomass by themselves to feed the human population and their livestock, fungus farming would take off, with various types of mushroom replacing most of our food crops. The only use I could think of for the night side of the planet would be for penguin or seal farming if the population decided to invest the necessary resources to protect themselves from the cold to do that. However, the day side would probably be used as a mining venue, since all plant and soil cover would be gone, leaving the sand and minerals exposed. In short, your civilization would be nomadic fungus farmers, chasing the sunsets around the planet over its long rotation period. [Answer] While you've already selected an answer, I thought I'd respond. As has been pointed out, your power idea doesn't work. The relatively large separation required means you get unacceptable losses in the connecting pipes. By the time hot material gets to the cold sink it's no longer hot. Plus (not mentioned) this enormous (hundreds of miles) pipeline network has to be moved every few years. I suppose you could propose burying the pipes, but every 100 years you're going to get a glacier advancing over the terminals and grinding them away. Possible, I suppose, but very expensive. Furthermore, water is going to be a big problem. The dark side will essentially be a big ice cap (and if you're not lucky an atmosphere cap) with cold winds at ground level constantly blowing from the dark side and returning at higher altitude. This will tend to lock up all water in the cold regions, with only a small amount of water vapor available from the sunrise zone. This will restrict the habitable zones significantly. While animals and people can move faster than the terminus, this is not true for plants. At the equator sunrise will move at about 250 miles per year with lower speeds at higher altitudes. There simply aren't many plants whose propagation mechanisms will cope with that. Add to that the narrow habitable zones implied by the water problem, it's just not clear that the habitable zones will be able to support any significant amount of plant life - and hence no animals or people, either. ]
[Question] [ The development of microgravity cuisine is an interesting topic, especially when it comes to transferring simple processes like the successful thermochemical processing of muscle tissues (e.g. barbecuing of meat). A man, who is a butcher and owns a small restaurant, and his friend, an astronaut qualified as an aerospace engineer, decide to do something nobody has done before: to *host a barbecue for the crew of the International Space Station*. Knowing that most of the food is provided in dehydrated or toothpaste form and a grill party would greatly improve the morale of the ISS crew, which is worried about their jobs due to yet another NASA budget cutback, mission control agrees and tasks the butcher-engineer duo with the design of the **MEAT** (Microgravity Edible Animal biomass Transformer) module. The following clarifications are made: * A *barbecue* is a session of meat preparation, whereas the meat (mostly animal muscle and fat tissue) is altered in its consistency, taste and digestibility by means of prolonged contact with a strongly heated surface. * The meat, which is that of freshly slaugtered pigs, cows, sheep and chickens, may be transported to the ISS in refrigerated form but is otherwise unaltered. There are some sausages included in the package (a total mass of 50 kilograms). The meat is brought to the station ready for preparation, e.g. correctly cut up by trained butchers. * The MEAT module should be brought to the ISS by a small spaceplane along with the meat and assembled by means of EVA and Canadarm. * The module should be reusable. * It is up to you to decide how much meat is prepared in a "batch". Generally, the preparation time for a normal meal should not exceed 3 hours (from freezer to plate). * An astronaut with technical knowledge (and a passion for cooking) should be able to operate and program the module without extensive mission control input. The preparation time for a spontaneous BBQ should not exceed 24 hours. * The taste of the products of the MEAT module should be at least extensively similar to that of meat prepared under normal conditions. * The by-products (smoke, coal) should be dealt with properly. * Speculative technology expected to be avaliable in the aerospace sector by 2025 may be used. Your task is to **draft a design concept of the MEAT module and describe its function, under observation of above clarifications.** [Answer] A good BBQ has a few key attributes (aside from starting with quality raw meat, which has already been arranged): * High and/or long-lasting heating. High heat for searing steaks and for cooking up burgers. Lower but longer-lasting heat for roasting a whole chicken, ribs and other large (especially thicker) items. * Smoke. Bad for you, but adds flavor. This can be from charcoal but with a has BBQ it is from meat fat/drippings that burn up. * Intense flavors - e.g., BBQ sauce. Sauce can always be added after cooking, but a good sauce on the meat while it is being BBQed can really make things great. What you don't actually need is fire. Which is a good thing, because fire and space stations don't mix well. A space station with an uncontrolled fire - and any fire can **become** uncontrolled very quickly - is deadly. In addition to the possibility of burning up the station, the oxygen required would be a major drain on station resources. But BBQ and broiling aren't so different. So we skip the traditional fire and figure out how to broil large (relatively) quantities in a space station that has limited power. That's where the arm, airlock, etc. come in. The MEAT Module consists of a large sealed metal box. The inner section contains a series of adjustable metal grill racks. Unlike on Earth where the meat is simply placed on the rack and possibly covered (but with the cover several inches from the meat), in order to BBQ in microgravity every piece of meat is placed between two grills. That keeps everything in place while conveniently providing the all important "grill marks" on both sides of the meat without human intervention. Which is a good thing because... The MEAT Module is loaded with meat on the racks. The racks are installed on a motorized rotisserie for even heating. The MEAT Module is sealed, pressure-tested and then sent out through an airlock for the Canadarm to grab it and place it in sunlight. However, while the MEAT Module has a large glass window on one side to admit sunlight for heating, the key is the second part of the system - the **MEAT Amplified Glass Natural Integrated Furnace, Yaw-stabilized** or **MAGNIFY** (OK, that's a mouthful, not easy to come up with a good Y word) which is a large glass lens that focuses sunlight into the MEAT window in order to produce heat levels necessary to BBQ meat. Fat/drippings from the meat will contact the inside of the MEAT Module and smoke pretty much instantly, providing the unhealthy but oh-so-yummy smoky flavor of BBQ. The MEAT Module window will include an automated windshield wiper of sorts to scrape drippings off the window during cooking to prevent blockage that would impair the effectiveness of MAGNIFY. After the meat is fully cooked, the astronauts use Canadarm to disconnect MEAT from MAGNIFY and retrieve the MEAT module and enjoy their dinner. Prep time is minimal. Figure one hour to prepare all the meat, including plenty of sauce (note that the sauce has to be on the thick side due to microgravity, but it can be spicy), another hour to load the MEAT Module and get it into the airlock. 30 minutes to deploy. Another hour or so to cook, more for ribs, less for burgers (after all this trouble, I'd go for the good stuff) and 30 minutes to disconnect, retrieve and open. [Answer] The simplest device would be a version of a [solar cooker](https://infogalactic.com/info/Solar_cooker). Since we want to cook meat, the meat needs to be prepared and sealed inside a cooking vessel, as exposure to vacuum would rapidly dehydrate the meat and result in something resembling a piece of leathery jerky. While some people might even enjoy that, we are talking about a BBQ party. [![enter image description here](https://i.stack.imgur.com/leT9o.jpg)](https://i.stack.imgur.com/leT9o.jpg) *Earth based solar cooker* [![enter image description here](https://i.stack.imgur.com/cTicE.jpg)](https://i.stack.imgur.com/cTicE.jpg) *A Scheffler cooker. This reflector has an area of 16 m2 (170 sq ft), and concentrates 3 kW of heat* Placing the cooking vessel at the focus of a parabolic mirror will rapidly heat the meat inside. The vessel will likely need to be rotated so the heat energy is evenly applied through the meat, which is sandwiched between racks to hold it in microgravity (as described in another answer by manassehkatz). A few refinements might include a means of adjusting the position of the cooking vessel relative to the focus point, as a means of controlling the temperature of the meat. Bringing the cooking vessel close to the focus will result in elevated temperatures to sear the meat, while moving it farther away will allow for slower, more prolonged cooking. A ventilation system will be needed to circulate the air and more importantly draw the liquified fat and oils out of the meat. If there is no provision for this, the fluids coming from the cooking meat may simply remain as sizzling blobs on the meat, making cooking more difficult. As well, the ventilator can be programmed to release "smoke" into the cooking chamber, to provide desired additional flavours to the meat. I will assume the meat has been marinated and sauces applied prior to being loaded into the cooking racks. A final refinement may be to have a digital camera inside the cooking chamber, so the astronaut/chef can judge the progress of the cooking, and apply any extra touches like extra "smoke" injections or delivering shots of sauce to the cooking meat as required. Like any real BBQ, other astronauts, NASA mission control, the ESA (as well as SpaceX in Hawthorn, CA) can also look in and provide commentary and advice to the cook during the process. The Russian cosmonauts are likely to look on in horror, but since they have an ample supply of vodka, bread and borscht to bring, they are more than welcome to join the party. [![enter image description here](https://i.stack.imgur.com/rjC1B.jpg)](https://i.stack.imgur.com/rjC1B.jpg) *Houston, we have a problem.....* [Answer] This... Is actually the easiest question in the whole site. The MEAT module composed of two parts: * A knob at some place in the ISS that is as far away from docking stations and solar panels as possible. The knob must be able to rotate continuously on its axis. * A sphere or cilinder, attached to the knob by a steel tether. This is the housing part of the module, and should require an airlock, as well as a cooling station (for beer) and cooking station (for the meat itself). It should preferably have a very large bathtub and a very powerful sound system, as well as the capacity to vent smoke (from coal and weed) to the vacuum outside. All you have to do is spin the housing part of the meat module around fast enough that the people inside will feel at home in 1g. With one gravity, air, alcohol, coal and proper equipment (even 50's or 60's technilogy within the module will do), it is up to the people involved how they will prepare the food. Wanna take a pig to the module and slaughter him there? You are a monster, but that can be done. Wanna receive your ham by whatever bastard child of Uber and SpaceX is hatched in the next decade? That works too. P.s.: at some point people will be drunk enough to try and exit the module while it is spinning, on a dare. The airlock should be in the direction of the spin to reduce the chances of someone being thrown into space. Expect some Darwin honorable mentions and awards anyway. [Answer] The Meat module has several types of tasty products to deal with, It can be broken out into a handfull of modules that will give our lonely astronauts a lot of flexibility while keeping things safe from both a food handling and a space station not catching fire standpoint. First: [Induction Cooking Plates.](https://en.wikipedia.org/wiki/Induction_cooking) Cast iron plates that can be adjusted to grab flat cuts of meat like steaks or even spatchcocked chicken. Current is passed through the induction plates that causes the cast iron part in contact with the meat to heat up to a specified temperature. This will be essential for getting the proper grill marks. If used in a small rotating chamber, fats and liquids will gently move away from the meat and element to be collected, possibly for later use. Next: [*Sous Vide*](https://en.wikipedia.org/wiki/Sous-vide) Use this method to bring the internal temperature of the meat up to a a safe point. Sous Vide uses a small heating element and an impeler (to keep the water moving) to create a very precisely controlled water (or other liquid) bath. Foods are vacuum sealed in plastic pouches or jars and submerged in the bath until the food and water temp are the same. The beauty of this method is that it can hold that temperature almost indefinitely with out loss of meat quality. Like Medium rare? Set the sous vide bath to 54 degrees c. Well Done? kick it up to 69 degrees c. I have seen pros and cons of searing the meat before and after a sous vide bath. I leave that to our culinarily minded astronauts. All that said, Sous vide can be time consuming, but it is also very forgiving. If you have to walk away from your cooking to tend with something else for a few hours, you don't ruin anything. Sous Vide can also be used to cook all of those wonderful irregularly shaped meats. Finally: An Oven. refer to manassehkatz brilliant answer for this one (MAGNIFY still has me laughing), though it doesn't need to be very large. Why an Oven. Some of the wonderful parts of well Barbequed meat is the crispness of the outside of the dish. This can only be achieved by a hot, dry method. A small chamber that can reach adequate temperature to finish off dishes in a matter of minutes after internal temp has been reached via sous vide. Sauces and marinades can be applied to the meat then sealed in the vacuum pouches prior to cooking. Or, if thick enough, applied just before popping into the MAGNIFY unit. You now have not only given your lonely ISS folks a way to BBQ, but they also now have some means to cook all sorts of things. Maybe someone can send them some fresh curries next [Answer] **No Futuristic High Tech Needed** The unique flavor of BBQ is due to the assorted delicious carcinogens and carbon compounds transferred to the meat by the smoke from the coals. We most likely find meat prepared in this way delicious because for a few million years our earliest hominid ancestors used fire to cook meat. We quite literally evolved a pleasure response to the falvor to goad us into seeking the experience as often as possible thus motivating hunting behaviors and better propagating the species. Our hominid Ancestors were terribly dull and never bothered to try looking for meat in space, so the challenges or orbital meat cooking never crossed their primitive minds. Today we have propane burning BBq grills that utilize a bed of lava rock to spread wood-chips across to generate that evolutionary sought after flavor of wood-fire cooked meat without having to burn a bunch of primitive disgusting charcoal like filthy cave-dwellers. Problem is, even glorious clean burning propane fired anything in space is a **horribly dangerous** idea. That's why our steaks are going to be cooked electrically. The device looks like a large VCR, it has a slot into which meat cartridges are inserted. (just a steak, fillet, or burger inside a metal grill-mesh box about the size of a VHS tape. Once the Meat cartridge is inserted the device's front door closes and seals to prevent anything flammable from combusting within the device. The electric heating elements heat up and begin grilling the steak to pre-programmed settings (rare-well done, medium well, etc etc). During the cooking a tiny amount of charcoal and a wood-matter of suitable smoking variety is burned inside of a small re-loadable canister within the cooking chamber by it's own smaller electrical heating element, the resulting smoke is circulated within the cooking chamber to enhance flavor. **Saftey Features! LOTS OF THEM!!!** The interior of this cooking chamber is monitored by a few cameras as well as several heat monitors that ensure the wood and charcoal are smoldering, not fully combusting. If at any point full-blown combustion occurs the first line of defense is that the entire device is completely sealed and insulated heavily as well as being tucked into another sealable flame-retardant pouch. Any fire ought to burn itself out fairly quickly with no oxygen to feed it. Next, the device contains within it several cylenders of CO2 and Halon, which can be either manually or automatically discharged should a fire occur further smothering and extinguishing flames. Tragically, this will ruin your steak, but it will also prevent you from turning into a piece of human BBQ by exploding into flames in a hyper-oxygenated environment so you will have to deal with it. This entire device shall only be operated within the disposable resupply module, should a fire somehow bypass all of these safety features the resupply module can be sealed off and it's atmosphere vented. Finally, if all else fails in some cosmically unfortunate explosion of Murphy's law the entire resupply module can be jettisoned from the station. You will be forced into the unenviable position of having to watch your thick juicy steak be horribly over-cooked and dried out as it burns up during reentry. It could all utilize off the shelf level tech to accomplish your space BBQ and still be fairly safe and tasty. ]
[Question] [ I have a series of astronauts landing on an asteroid. I'd like to know the threshold of mass for them to not fly off into space. Specifications: * Assumption is all astronauts are under 180cm, 80kg. * Assumption is an astronaut may jump lightly and not fly off into space. * Request is **a comfortable radius of said asteroid**, which has an average density of 2 g/cm³ (pretty dense), with a mostly spheroid shape. * Weight and height includes equipment (this is far future); astronauts are fit. In my story I'd like to see my astronauts be able to jump up into the 'sky,' but able to come back down without flying out forever. If there are other factors I should include, please let me know. Also, I will accept a magnitude-of-order rather than an impossibly precise answer (thus not hard-science). EDIT: AND I KNOW THIS AFFECTS THE ANSWER - 80kg, not 30kg. I will still accept the best answer if it used 30kg due to my error, but showed the math. [Answer] # How to calculate surface gravity See [here.](https://worldbuilding.stackexchange.com/questions/64823/do-the-moons-of-mars-have-enough-gravity-to-colonize/64829#64829) # How much gravity do you want? Lets say I can jump 1 meter on Earth (I can't). Then using kinematics equations, my initial velocity upwards was $$v\_f^2 = v\_i^2 + 2gd \rightarrow\sqrt{2gd}=4.4 \text{ m}/\text{s}.$$ I want my escape velocity to be comfortably above that, so lets say escape velocity is 10 m/s. You shouldn't be able to jump off that. Escape velocity can be calculated as $$\Delta v = \sqrt{2gr}$$ where $r$ is the asteroid's radius and $g$ is surface gravity, which itself can be calculated from $$g = \frac{4}{3}\pi G\rho r$$ as shown in the above link. Setting escape velocity equal to 10 and plugging in we get $$10 = \sqrt{\frac{8}{3}\pi \left(6.67\times10^{-11}\right) (2000) r^2} \rightarrow r = 9459.$$ **You cannot jump off a 10km radius asteroid.** Probably. --- \*\*Edit\*: Thanks to Mithrandir24601, I should have calculated mass as well. As he does in the comments: $$M = \frac{4}{3}\pi\rho r^3 = \frac{4}{3}(3.14)(2000)(9459)^3 \approx 7.1\times10^{15} \text{kg}$$ [Answer] The maximum height that a man can jump is [a bit over 70cm](https://en.wikipedia.org/wiki/Vertical_jump#Standing_vertical_jump_norms) for the very best athletes. This is because the only thing that matters is how high your centre of gravity rises. I will assume 80cm. Work is force times distance. Weight is the force $W = gm\_0 $ and when you jump a height $h$ under Earth gravity of 9.8m/s with a weight $m\_0$, $E = hgm\_0$ is the work that gravity did to bring you to a stop at your maximum height (all of the kinetic energy being converted to potential energy). The work you performed to initiate the jump is also force times distance. It equals the gravitational potential energy at the top of the jump exactly. When jumping on an asteroid, the length of your legs and your strength we will assume don't change (a fabric-based space suit has a springiness in the legs, so this is an approximation). You perform an equal amount of work to what you did on Earth, namely $E = 0.8m \times 9.8 m/s^2 \times m\_0$. Escape velocity is given by (see Space Mission Engineering: The New SMAD edited by Wertz, Everett & Puschell, 2011, p. 201) $V\_e = \sqrt{2GM/R}$ where $G = 6.674 \times 10^{-11}m^3 kg^{-1}s^{-2}$ is the gravitational constant, M the mass of the central body and R your distance from its centre (I assume for simplicity it is circular). Density $\rho$ is in the region of $1000kg/m^3$ for icy bodies and $3000kg/m^3$ for rocky ones. In the case of a nickel-iron body we will approximate the overall density as $8000kg/m^3$. We want to calculate the diameter R of a body where your kinetic energy at escape velocity equals $E$ above. $$0.8m \times 9.8m/s \times m\_0 = E = KE = 0.5m\_0 \times V\_e^2$$ $$0.8m \times 9.8m/s^2 = 0.5 \times V\_e^2 $$ $$ 15.68 m^2/s^2 = V\_e^2 = 2GM/R $$ still assuming a sphere $$ M = \rho \times V = \rho \times 4/3 \pi R^3 $$ $$15.68 m^2/s^2 = 8/3 G \rho \pi R^2 $$ $$ \sqrt{(2.8 \times 10^{10} / \rho) m^{-1} kg } = R$$ Substituting the densities from above, we get roughly $R\_{icy} \approx 5300m$, $R\_{rocky} \approx 3100m$, $R\_{iron} \approx 1900m$. Now let's see what happens with your numbers. The astronaut can still do an equal amount of work to jump but their mass will be $m\_1 = m\_0 + m\_{suit}$ on the asteroid, $\rho = 2000kg/m^3$. A NASA study from 1996 (see The Origins and Technology of the Advanced Extravehicular Space Suit by G.L. Harris, American Astronautical Society History Series Volume 24, 2001, p. 455) specified a maximum pressure suit assembly mass of 27kg for missions to Mars. This excludes the life support systems, for comparison Apollo had (see p. 440) 63.2kg of life support on a suit of 100kg total. We'll assume the future suit is a form-fitting elastic suit with almost all mass in life support, giving no springiness in the legs and massing just $m\_{suit} = 30kg$ total. Note: You gave the astronaut weight as 30kg. This is a small child so I assume 70kg is intended instead. $$ 0.8m \times 9.8m/s^2 \times m\_0 = E = KE = 0.5 m\_1 \times V\_e^2 $$ $$ 0.8m \times 9.8m/s^2 \times 70kg = 0.5 \times 100kg \times V\_e^2 $$ $$ 10.976 m^2/s^2 = V\_e^2 = 2GM/R = 8/3 G \rho \pi R^2 = 8/3 \times 6.674 \times 10^{-11} m^3 kg^{-1} s^{-2} \times 2000 kg/m^3 \times \pi \times R^2$$ $$R^2 = 9.815 \times 10^6 m^2 $$ $$R \approx 3100 m $$ It only happens to be close to the rocky body approximation above because the increase in mass was made up by the decrease in gravity. Edit: Finally, since you want mass: $$ M = 4/3 \pi R^3 \times \rho = 4/3 \times 2000kg/m^3 \times \pi \times (3100m)^3 = 2.50 \times 10^{14} kg $$ Really finally this time: Since you updated the mass to 80kg and we may assume a suit mass of 10kg included in that, here's how the answer would change from my 100kg with 30kg suit mass answer: $$V\_e^2 = 10.976m^s/s^2 \times 100kg/80kg = 13.720m^2/s^2$$ $$R \approx 3100m \times \sqrt{100kg/80kg} \approx 3500m$$ $$M = 2.50 \times 10^{14}kg \times (\sqrt{100/80})^3 = 3.6 \times 10^{14}kg$$ ]
[Question] [ Im sure some are familiar with Bioshock's "Rapture City," a (somewhat) successful underwater city that was able to maintain stability and house an entire population. But, using current technology and engineering, could we (and how) construct a city off the west coast of the United States that: 1. Is located on the side of an underwater ravine. 2. Has a max depth of 400 meters 3. Can inhabit max of 30,000 people 4. Has a source of food and water (preferably not imported from the mainland) 5. Adequate defense systems 6. Standard city departments (Education, law enforcement, public works, etc.) Keep in mind, however unrealistic, that budget is practically unlimited, but stay reasonable. NOTE: If any further clarification is needed, let me know. The more critique,the better [Answer] Yes, this is completely possible today. In fact we already have large elements of it. We have submarines and submersibles, we have diving gear. There are [underwater hotels](https://www.google.co.uk/search?q=underwater%20hotel&espv=2&biw=1334&bih=764&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjahN7GzvfMAhVCDMAKHdHtC0kQsAQIJg). You have two basic choices for the buildings: 1. You can be linked to the surface air and have routes to the surface. This has the advantage of letting you enter and leave while being dry and cheaper air circulation. Your buildings need to be strong enough to withstand the water pressure though. 2. You can pressurize the buildings to the same level as the water and just have open pools for access in and out. This has the advantage of letting you access the water around you from the buildings without needing airlocks but you need to pump down and pressurize all of your air. Anyone heading to the surface would spend a LOT of time in decompression. In practice there would most likely be a combination of these, with buildings at the top linked to the surface and others deeper open to the water. Transition between these buildings could be done using air locks to equalize the pressure. Note that the depth you mention (400m) is **just** inside the range of human survival. [The records for deep diving](https://en.wikipedia.org/wiki/Deep_diving#Depth_ranges_in_underwater_diving) at external pressure are around 432m. In practice you would most likely need most of your city higher (and at less pressure) than that as we just have no idea what the long term effects of living in those conditions would be. The problems here aren't technical. They're practical and financial. Would you want to live in a steel can underwater breathing recirculating and pressurized air? Especially when doing so would be substantially more expensive than living on land. We have the technology today to build this. What we don't have is the reason to do so. [Answer] It's technically possible but not financially feasible but I see your budget is practically unlimited. And it would always need power to generate oxygen from some type of water source. The hydrogen might be used as fuel also. Power would also be needed to make freshwater from sea water. Any metal parts exposed to seawater would need constant upkeep as salt water is very hard on even the best metal parts we have today. Any moving parts and water intakes and output tubes would need constant upkeep to keep barnacles and other creatures off them. Barnacles, algae, and seaweed are HUGE problems for water intake tubes today, especially near areas where nitrogen-rich runoff goes right into the ocean. Algae is less of a problem in deeper areas where there isn't much sunlight but barnacles and other "fixed" creatures like coral tend to be a problem at many depths. ]
[Question] [ Everybody, even those who are complete beginners in the field of Astronomy, know Io, the cryovolcanic moon of Jupiter that looks like a burned pizza with skin cancer. Volcanoes constantly spit out sulphur in various forms and compounds, which gives Io its characteric coloring that consists mainly of yellow, red and orange fields with occasional black or green patches. The pattern can change completely within 2 weeks! [![](https://i.stack.imgur.com/HmBrw.jpg)](https://i.stack.imgur.com/HmBrw.jpg) Now, for my SF novel, I want to create a similar celestial body, with one condition: the planet is going to be **blue**. Light or dark blue with occasional white, black or green patches, with severe cryovolcanism just like Io has. [![](https://i.stack.imgur.com/aez1V.jpg)](https://i.stack.imgur.com/aez1V.jpg) My questions are: * What chemical elements or compounds could lead to such a coloring of the planet or moon? * How could they be created naturally and occur as a part of a cryovolcanic system like Io's? EDIT: The compounds which color the moon blue should be solid at a temperature of -200 degrees. [Answer] As anyone who's studied inorganic chemistry knows, many [salts of copper](https://en.wikipedia.org/wiki/Copper#Compounds) in the +2 oxidization state have colors ranging from green to a nearly black dark blue, including some remarkably intense shades of sky blue like those of [copper(II) sulfate](https://en.wikipedia.org/wiki/Copper%28II%29_sulfate) and [copper(II) nitrate](https://en.wikipedia.org/wiki/Copper%28II%29_nitrate): [![](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Copper_sulfate.jpg/234px-Copper_sulfate.jpg)](https://commons.wikimedia.org/wiki/File:Copper_sulfate.jpg) [![](https://upload.wikimedia.org/wikipedia/commons/thumb/6/6b/Copper%28II%29-nitrate-trihydrate-sample.jpg/320px-Copper%28II%29-nitrate-trihydrate-sample.jpg)](https://commons.wikimedia.org/wiki/File:Copper%28II%29-nitrate-trihydrate-sample.jpg) Images from Wikimedia Commons. Left image by user [Stephanb](https://de.wikipedia.org/wiki/Benutzer:Stephanb) at the German Wikipedia, used under the [CC-By-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0/deed.en) license; right image created and released into the public domain by user [Benjah-bmm27](https://commons.wikimedia.org/wiki/User:Benjah-bmm27) at Wikimedia Commons. One important detail to note is that the colored forms of most of these salts are hydrated, i.e. they include some water molecules as part of the crystal lattice. Removing this [water of crystallization](https://en.wikipedia.org/wiki/Water_of_crystallization) will typically destroy the [coordination complex](https://en.wikipedia.org/wiki/Coordination_complex), and hence the color. Thus, in addition to copper, your blue planet also needs to retain at least some water (although it need not be present in liquid form). In a pinch, other small polar ligands like ammonia may also serve the same role (either alone or mixed with water, as in e.g. [tetraamminecopper(II) sulfate](https://en.wikipedia.org/wiki/Tetraamminecopper%28II%29_sulfate)), although the exact hues will be different. Ps. Some [iron salts](https://en.wikipedia.org/wiki/Iron#Chemistry_and_compounds) in the +2 oxidation state, such as [iron(II) sulfate](https://en.wikipedia.org/wiki/Iron%28II%29_sulfate), also have a blue-green color, but iron compounds can take on many other colors as well, depending on the oxidation state and on the other compounds present. Unless you tweak the surrounding chemistry just right, an abundance of iron is far more likely to give your planet the rust-red hue of [iron(III) oxide](https://en.wikipedia.org/wiki/Iron%28III%29_oxide), just like on Mars, than the deep blue shade of [iron(II,III) hexacyanoferrate](https://en.wikipedia.org/wiki/Prussian_blue) (a.k.a. Prussian blue). [Answer] TL;DR: Add methane, remove organonitrogens and other yellow substances. Both Neptune and Uranus get their blue hue from methane in their atmospheres. So you can start out with a moon like Enceladus, which is white but has cryovulcanos and then add methane. Or you start out with Titan, which has cryovulcanos belching methane, and remove the organonitrogen haze. [Answer] It's not easy being blue. You only have to look around to see how little blue there is in nature. Oxygen is blue, and freezes at -218\*C, but pure oxygen is rather too reactive to consider existing in in substantial amounts. It would react with almost anything it found. Many of the "ices" would either be white, due to dispersion, or tinted with red, due to the formation of thorins. Methane would look red. On the other hand, most rocks are grey. If you are willing to imagine rather far-fetched geology then there are a few pigments that could occur: Ultramarine does form naturally as a metamorphic rock. If you could imagine the right conditions existing in your volcanoes you could dye your methane snow with ultramarine. The elements for Prussian blue (iron, carbon, nitrogen) are also available in the universe. However Earth's geology seems not to allow its synthesis naturally. Oceans look blue, and a nitrogen ocean could cover the planet to give a blue colour to much of the planet, with the continents being some other colour. [Answer] Vulcanism shows nice on the picture, but this *blue hue* you see has little to do with vulcanism.. **Because how the moon was formed..** Moon formation is a very violent process. Multiple collisions, giant pressures, blasting planet crust material in orbit. Now suppose your blue moon was *torn off* a planet with [Corundum](https://en.wikipedia.org/wiki/Corundum) that is aluminium oxide (α-Al2O3) in its crust.. in conditions of high pressure during impacts, blue Sapphires will form. While the planet-moon system stabilized, these sapphire rocks and pebbles rained down on the moon's surface, making it look blue, when the sunlight reflects on it. [![enter image description here](https://i.stack.imgur.com/XKVGF.jpg)](https://i.stack.imgur.com/XKVGF.jpg) (CNN) <https://edition.cnn.com/style/article/sri-lanka-sapphire-horana/index.html> ]
[Question] [ I once heard someone claim that if we had four digits on each hand our mathematics would be well in advance of what it is. Presumably this is because 4 is a power of 2 and those clever computers calculate in powers of two. Personally, I think that they do so for electrical reasons, but am not enough of a mathematician to tell if math based on powers of 2 is easier, more intuitive, or in any way superior. So, if we had four digits on each hand, would we be be mathematically more advanced? Would there be any other major impacts? (and would cartoon characters only have three digits? ;-) --- [Update] I doubt it makes any difference at all to mathematics, where symbols are involved. But to arithmetic? If multiplication & division were simpler, what then of pyramids? Or even just bridges, etc? Would earlier perfection of the arithmetic of engineering have had major impacts elsewhere? --- [Upperdate] I am reminded of [this 2,000+ year old computational device](https://en.wikipedia.org/wiki/Antikythera_mechanism) (complete with complex gearing). Could power of two based calculation have led to even greater devices? [Answer] Not really. There's a similar argument that [cultures with different languages are better at math](http://www.wsj.com/articles/the-best-language-for-math-1410304008) due to how their number-words are constructed. For example, in English, the number of 11 is called "eleven" and the number 15 is "fifteen", but in Chinese, Japanese, Korean and Turkish that number is basically called "10 & 1" or "10 & 5". That doesn't sound difficult but for early language learners, adding the extra baggage takes up time. Fifteen plus twelve has to be translated to 15 + 12 then 10+5 + 10+2 and then you get the answer, 27, which is then 20+7 or twenty seven. It's actually worse in other languages... for example, 99 is ninety nine in English, in Korean it's "9 10's & 9", but in French it's quatre-vingt-dix-neuf... which is literally "4 20s & 10 & 9". Because there's less 'lag' in Chinese, Japanese, Korean and Turkish, they've found that children in those cultures as a whole understand math faster, which propagated the original stereotype that the entire culture is just seemingly better at math than Western cultures. However, once those students get into more advanced mathematics including numbers in the abstract, all of that edge vanishes, so all cultures *should* be on the same level... however, there is a lingering psychological impact. Those who basically learned to hate math starting at those very early ages do even worse once math becomes abstract. Having a base 8, or octal, math isn't going to be structured all that differently in the grand scheme of things. Anything that goes down to base 2 will be effectively the same for any large computations. Now if we had 4 fingers on one hand and three or five fingers on the other... THAT would most likely have an impact. [Answer] On the one hand (pun intented), we might get a little bit better at the maths necessary for computer science, but on the other hand, we'd probably be worse at music, and maybe many other forms of art. Without the added precision that comes from our five-fingered hands, we may never have achieved some of the masterpieces we hold in such high esteem today. That said, everyone's standards would probably be lower, so I imagine this would not have been much of a problem, but there is a definite possibility that with fewer fingers, humans would be limited just enough to not invent certain things, and end up over a long time to not be nearly as advanced as we are today. Plus, think about typing. You can always learn to think in octal, but it's another problem entirely to learn to type as quickly as someone with two extra fingers. It might only be a loss of a few seconds per person per day, but with millions of people typing for years this is going to add up. It may also become a bit more of a hassle to type out larger numbers, as they will require more characters. This could end up costing a lot of money for extra ink and paper. Add to all this the fact that computers have only recently been developed, and that technological advancement is exponential, and I think it's far more important to make early advancements than late ones. Things like extra-precise building techniques and more complex art may have had more of an impact on early human development than maths, so I'd put my money on having less fingers actually being more of a hindrance to humanity in the long term. [Answer] At first I was going to say I doubt it, all bases have good and bad things about them. Not only that other bases have existed in human history, such as base 12. However, with 4 digits our base counting system would likely be [Octal](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=octal). which everyone would be using by default. Computers use binary, and programmers used octal and still often use [Hexidecimal](https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=hexadecimal) to help make reading binary easier. So by having Octal be the base standard that everyone understands vs. having to learn it like learning a second language, many more people could have a better understanding of how to interact with computers with a closer number system. By volume alone this could have an impact on our technology. It also would have likely spawned earlier and more lasting work into computing machines. Better machines earlier would of course imply more advanced mathematics as well. [Answer] Switching the base does not give you any advantage. Mathematics has developed independently in many places and the most common numeric bases have been 5, 10 & 20 which is related to the number of digits one has (1 hand, vs 2 hands, vs hands & feet), but the Sumerians and later the Babylonians used base 60 and their understanding of math was excellent. It's all a matter of habit. If you use octal everyday for a year you'll find it's no different than base 10. I work as a software engineer and can assure you that binary, octal & hex are rarely used in modern programming. The only use I can think of is when you are manipulating bits directly, which back in the day people did often, but nowadays is mostly taken care by the programming language / libraries. ]
[Question] [ I'm not sure if this question belongs here or over on Physics Stack Exchange. The Earth and Moon are unique in the Solar System in that the Moon is a significant size compared to the Earth, at 1/4 the diameter and 1/80 the mass. In the Solar System planets are distributed in an exponential fashion with each being roughly twice the distance from the Sun. (See the [Titus-Bode law](https://en.wikipedia.org/wiki/Titius%E2%80%93Bode_law).) In each case, the attraction of the Sun is by far stronger compared to the attraction of other planets. A favorite theme of science fiction illustrators is several large moons hanging in the sky. (Sometimes they even get the phases right.) Is this possible? Can a planet have a stable configuration of multiple moons, each one large enough to provide a visible disk and signficant ground illumination? For the sake of discussion, let's call the minimum angle one degree (twice the apparent size of the moon. So we could use a moon twice the diameter of our Moon. This would be eight times as massive. Our average 6-foot tides would be 50-foot tides. Yikes. We'll call moon #2 Selene. Make it much smaller but much closer. If it was 1/8 the diameter and 1/4 of the distance it would appear half as large and have 1/500 the mass, but tides go as the third power of distance, so it would have a net effect of 1/8 the tide of our Moon. The orbital period would be about 1/4 the length of our Moon's - about a week. Now, I'm guessing that if were exactly 1/4 of our Moon's period there would be resonance, and everything would come crashing down around my ears. But now I'm stuck. What determines a stable configuration? [Answer] I am a senior physics major, and have access to some pretty cool software. I have been running some simulations on this, and I think that I am getting pretty close to a 3 body stable orbit, but it is very fragile. The small moon the middle seems to keep falling into one of the other bodies eventually. The only way that I can conceive it being stable would be to have the moons orthogonal to each other, but even that should collapse eventually. One interesting option I found that works is to have two moons of similar size tidally locked with each other in orbit around the planet. It's pretty stable, and would make a neat view. However, if you want to keep your moons the way they are, that's fine. If I can get it to be stable, I'll send you some numbers. As a bonus, Some interesting effects of our moon: -Tides (obviously) -keeping earth's axial tilt stable -slowed the earth down Tides: You seem to have the right idea here Axis Stability: Earth is at a fairly constant 23.5 degree axis tilt (varies between 23 and 26 degrees) and that stability is due to our moon. For example, Mars, without any massive moons, has an axis tilt that varies between 15 and 35 degrees. Your first moon will have twice the gravitational potential energy as the moon, and the next moon will have about 1/125 of the PE. This is negligible compared to the first moon, so your planet would have much more consistent weather and seasonal patterns than earth, so everything is fine here. Slowdown: The Earth used to have days that lasted about 6 hours, but the moon changed that. It slowed the Earth down considerably, to about 25% of its original rotational velocity. Your first moon would initially slow down your planet twice as much as the moon, meaning that if that moon was captured on earth instead of our moon, days would be 48 hours. (As long as the capture process was the same.) [Answer] You have to deal with the 3 body problem, specifically the small moon being pulled toward the much larger moon, and then moving away, and how this would destabilize the small moons orbit. The distances you set up could support this, but calculating the effects of that extra mass is interesting. Larger planets can support more moons because they have much greater gravity wells, and the moons orbits can be far enough apart to not bother each other. Mars has two moons, but they are not much more than captured asteroids, and not much gravity. To answer the second part, The small moon would have its own little tide. When the tides caused by the second moon synced with the first, they would be bigger than the already massive tides as you already thought. ]
[Question] [ **Background** Water is a very mysterious figure. He doesn't say much, he doesn't do much, but he is also at the forefront of an elite group of like-minded magic users. Water knows *trust magic*. With his magic, Water could, for instance, raise a person's trust in himself when faced with nervous or critical circumstances. He could also render a man utterly devoid of self-trust, leading to episodes of hopelessness and depression, not to mention being useless in day-to-day activities and combat. He could lead a whole population and form a religion whose sole purpose is devoted to worshipping the almighty non-existent giant spaghetti monster. But Water is a good guy in our story. There are believers, then there are haters. Water was thought to be a fraud by many, for could he not merely lift his finger, figuratively speaking, to gain himself loyal followers? At least that's one reason that failed to escape the sceptics' clench. Those who knew Water, however, understand that it was good enough of him not to extend his power to convert those who do not trust him. **Question** 1. Is the background psychologically sound? 2. How can it be used in combat? For the second question, I am looking at a scale of combat typically seen in mainstream battle manga where the fight is mostly one-on-one, and occasionally involving small (<1k, say) groups of people. However, having Water acting as a strategist behind a full-fledge war is also an interesting possibility that I have considered. For example, a mastermind that wreak havoc the enemy lines by coordinating betrayals or planting spies that never have to worry about being exposed. I am rather happy with Water's potential on this scale (unless you also have something more to add! :) ), so I would like to hear some input regarding a smaller combat where Water is directly involved in the fight himself. Best answer will be given to the use of trust in combat that are * **creative** - The fight wouldn't be too interesting if all Water does is tricking his opponent to not fight him. * **subtle** - What if Water actually does nothing but merely tells his opponent the nature of his ability? Simply by knowing that what you are trusting right now may be false can throw chaos to one's decisions. [Answer] The answer to your first answer is yes, of course. If you look in the many disciplines of martial arts, *many* will refuse to force their friends to agree with them, so you have many examples to draw upon for exploring how this can occur. One powerful approach you can use to limit Water's abilities is to make its trust increasing abilities symmetric. He cannot increase someone's trust in him without increasing his trust in them. He also cannot decrease anyone's trust *except* for the ability to decrease trust in himself (yes, this is an ability... trust me ;-) ). Why those strange rules? Because I have a soft spot for the systems that evolve from that point outwards, and because it builds a lot of the behaviors your describe in your post from building blocks that are simple enough to be turned into hard magic or soft magic as you please. Symmetric trust is an interesting concept because it makes it very hard to see where the boundary of your "self" ends and the other's "self" begins. Take a physical example. You are rock climbing, and you thrust your hand out to a handold. It curls around the hold, tensing to support your weight. You trust your hand to hold fast, and not decide to wave to the cute girl on the ground. Likewise, the hand trusts you to not, say, put it palm down onto a hot stove (yikes!). This seems intuitive, because you consider your hand to be part of your "self." Now consider the person you would trust with anything. You know that if you asked them to hide a body, they'd go do it. Likewise, they trust that you wont throw them away carelessly, letting the cops pick them up when they discover the hidden body unless there was a good reason for it. What do you call this person? Your right hand man. Coincidence? I don't think so. Thus, its reasonable to model Water's ability as one which allows water to *blend* with his foes or his friends. Once he does this, his merest thought can become a hallucination in the other fighter's mind, making him think there's an opening to attack when there is not. But now there's a catch: Water has to believe there is an opening there too. If he overuses this ability, he may find himself reduced to a quivvering pile of goo, incapable of doing anything because he believes he has weaknesses everywhere. It is Water's best interests to do *just enough* with his abilities to finish the fight off with his actual combat skills. Water's second ability is just as important as his first: he has to be able to break free. Otherwise he will carry with him remnants of every fighter he ever fought as everything they believed circles around in him. He needs to be able to doubt himself, but how does that interact with symmetry? It implies that he doesn't necessarily get to choose what part of him gets doubted, he just has to accept whatever that doubt is, and maneuver it to split his personality in half. Visualize this: Water could be treated as a cell, perhaps a white blood cell. Water reaches out and finds a bacteria. First, he brings it into himself, letting his cell wall engluph the bacteria. It is now a part of him, as empowered as any other organelle in his body. He then instigates doubt, cleaving his cell wall, doubting the value of himself so long as he has the bacteria. The cell wall is pulled inward to surround the bacteria with a lipid barrier, still inside the cell. As far as the bacteria is concerned, it is still part of Water's white blood cell. Finally, surrounded in what is called a lysome, the "suicide bag" of the cellular system. It immediately begins receiving a transfusion of very non-trust based attacks such as acids and enzymes, and is killed. The remains of the bacteria are either then disposed of, or carried along as inert examples to the lymphatic system for analysis. Its very hard for bacteria to prepare for this lysing effect, because they don't get to see the enzymes and acids that get injected into a lysome. They're never present outside of the cell wall. Those hateful vengeful compounds are only let loose on a part of the cell that the cell truly hates and wishes to destroy. Meanwhile, you have Influenza, the flu virus. This is the human cell's worst foe... the yin to its yang. Influenza knows that, as a virus, it can't do anything until it is permitted the privileged of being part of a cell, so it simply attaches to one, and waits to be drawn in. Once inside the cell, it *still* doesn't do anything, because it knows its being invited in on a temporary basis. The cell quickly builds a lysome around the flu virus and begins pumping it full of hate. That's where Influenza gets weird. It has a protien on it which is rather uniquely suited for this event. When the pH goes low enough (acidic enough), the protien denatures, losing its form. In the center of this protien, hidden from everything else including the cell that captured it, is a non-polar segment. A non-polar section of protien really wants to find non-polar stuff to embed itself in (the water-based suicide mixture it is bathing in is decided polar), so it flies out like a grappling hook and embeds itself in the lipid wall of the lysome. Once there, it undergoes yet another denaturing act, basically hauling in the line of the grappling hook, pulling the virus right up through the wall of the lysome. Now the virus is where it wants to be. The cell thinks it's fully encased in the lysome, and so the cell is trusting itself to continue manufacturing protiens. But influenza is still within the cell's "trust" region, the cytoplasm. It begins slyly leaking instructions into the machinery, and... well... you've almost certainly felt the result of this at least once in your life unless you get the vaccine every year! This also creates a wide array of rationales for why Water doesn't just use his trust magic on all of his friends. Its hard to make a large system that is trustworthy unless it is segmented into parts. Consider, the mind uses neural impulses to tell the muscles to contract, but never once does it decide "you know, you muscle fibers really should all just be part of the nearest neuron." They allow for specialization. For more fun, consider a more complicated example. In the cellular metaphor, trust is binary: you're on the inside, or you're on the outside. Consider a system which has shades of trust, and how that would affect his abilities to reach out and touch others. The sky's the limit here! [Answer] Ok. Lets assume for a second that Water has complete trust (no pun intended) in his ability to both completely manipulate peoples trust and understand it. Water can both completely understand where his opponents trust lies, and tweak it however he likes. (On a side note, you could also make this power something he grows to learn over time, rather than what he starts with, but that's beside the point right now). For one on one fights, because you don't want him to simply trick his opponent into not fighting him you need to do two things. 1. There needs to be some sort of *expensive* or *difficult* way to defend against or reduce his mind magic. Otherwise, everytime he gets into a fight with the next bad ass enemy, he could simply raise their trust in him to the max, effectively forcing them to listen to him and stop fighting. Even if he does have morals preventing himself from doing that to someone, when he gets into an extremely dire situation, those morals are going to fly out the window, and that might begin to annoy your readers. 2. He needs to know how to fight. He doesn't need to be the very best, in fact he shouldn't be the best at swordplay or whatever weapon you decide to give him. Water should be able to, with a small amount of difficulty, be able to take out the lowest grunts without his trust magic. Otherwise he simply wont even be able to begin having any sort of fight with others. Now that we have that out of the way, lets focus on ways he could do combat. ## One vs. One * Manipulate the trust they have to make them believe that they are going to be hit in a moment, making them defend immediately * Make them disbelieve their skills or judgement. Once they start believing that they cant preform that particularly difficult maneuver, every time they attempt it, they will falter and will not be able to complete it. * Make them trust that he is weak and useless, or all full of talk and rumors, so they let their guard down and allow him to attack when they are off guard. * And for the subtle part, if it's difficult for him to change so many things, simply make them believe totally in his ability to completely manipulate them. Our minds automatically alter what we see based on experience, and our trust in it. So if Water makes them believe completely that they cannot actually trust what they see, or that they should completely believe what they should see, suddenly the world becomes a very strange place that they cannot trust. Their own subconscious goes out of wack, and they will quickly realize that the world they are fighting you in is very different from the one they have been living in till now. (See this video for where I got the inspiration for this one : <https://www.youtube.com/watch?v=Y2gTSjoEExc> ) ## Larger Groups * For larger groups it seemed like you had it figured out, but you could also tweak his power a bit so that when he has a large number of people that trust him in close proximity, his power gets *much* stronger. Upwards of several hundreds or thousands maybe? Once that begins happening he could be able to alter large numbers of people, giving him the power to completely change the course of a battle in progress. ## Final Thoughts Overall I would say that you have a very powerful guy here. Don't be afraid to nerf him in some way so that he's not so over powered but it's up to you. I would say when you do use this character, *explain* what he is doing while he is doing it. For example, if Water's opponent suddenly drops his whip, explain that Water could interpret his mind to know that he was beaten by his Fathers belt when he was young, and that Water exploited those memories to make him trust that he was becoming his Father. Good luck with your world! Hope this helped! [Answer] About the psychology, Water can make select people see him as a fraud, or no one really important, thus escaping deeper scrutiny (no trust, or neutral trust). Now, for the combat. I will assume that Water is telepathic, can find and alter where lies the trust of the enemy. In a one-to-one fight, make the enemy paranoid. Now he trusts no one and nothing; his support could fail; his guns could be rigged; his equipment could be sabotaged; etc. The enemy will at least pause, if not retreat, creating an opportunity for attack. In a one-to-many fight, and assuming that trust magic has no distance limitations, make the leader have a [face-heel turn](http://tvtropes.org/pmwiki/pmwiki.php/Main/FaceHeelTurn): distrusting allies and trusting enemies and rivals. This will put the troops in disarray. And, for flavor, make some quiet soldiers paranoid to the point of executing his comrades or superiors; no one will expect such an attitude from them. Bonus if the above soldier manages the armory, and he suddenly thinks that the [BFG](https://en.wikipedia.org/wiki/BFG_%28weapon%29)s are somehow faulty (because the producer isn't reliable - no trusting it), and tries one by one to check... [Answer] The obvious, but boring, answer is to have him walk up to enemy generals and assassinate them. Everyone trusts him in their camp, the general sees no need to defend himself etc. I'll assume that either Walter is not this powerful, or is too moral to do that because...yeah boring story that way lol. In fact if he can make people trust him when he says "I mean no harm" he can pretty much shoot and kill anyone without issue. Again this seems boring if you want complex 1 v 1 battles, so lets assume he isn't that powerful. You mentioned making people distrust themselves. This alone is an absurdly powerful ability. Moral is a major affect on combat effectiveness. if you can make someone have enough self doubt they will run from you without issue, or suck in a fight. However, it to can be a bit bland as a go-to fighting technique, particularly for one V one fights. So lets look at what you want and see what rules we can create that allow interesting and complex battles, not just easy anticlimactic kills. A few rules come to mind. 1. Trust magic is limited, the more someone distrusts him the harder it is to get them to trust him and vice versa. He is not so powerful to get nearly-mind control level powers where he can get someone to do anything he wants because they trust him when he says it's a good idea. 2. If someone knows he is working his magic they can better resist. The degree of power he has depends on how long he has to work, rather they know to expect something, and how strongly someone is resisting; plus how strong their own heroic will power is. This is to give a few options. On epic 1 v 1 battles his powers are not game breaking because people know to expect them and can resist to a good degree. However, when he is working subtle outside of battle his powers are still quite useful because people aren't actively resisting. Power level is suited for the type of activity he is doing. It also prevents him from ever being too gamebreaking. So lets look at the types of uses. **One V One battles** It sounds like your thinking anime and manga style battles here, I'm going to work with that for the sort of feel I'm trying to create, so hopefully that's a correct presumption. The obvious first step is to imply someone with strong will power can better resist him. That way he can walk through mooks (you have to have your heroes beat mooks to show how awesome they are) but the strong characters can better resist because they have stronger will power. Besides shonon series always seem to build up the whole heroic willpower trope to sometimes unreasonable degrees, it may be interesting to *justify* the trope they all tend to use as an actual mechanic of the world. I'm also going to assume that Water has some ability to fight outside of his trust magic, so that fight scenes can include the more traditional dodging of attacks and throwing of punches, again trying to keep up with shonan series, and because trust magic is otherwise too boring in a one v one fight (either it works and he wins, or doesn't and he looses, not much middle ground). In terms of his battles I could see a few techniques he could use. 1. Mind games. Get under your enemy skin, mess with their head and freak them out. If his power is dependent on how inclined someone is to believe him then knowing the psychology of his enemy, to know what they are likely to believe, or want to believe, allows him to make better suggestions. In addition giving them a verbal smack down to destroy their confidence, which you can use your trust magic to reinforce, can work to great degrees to destroy moral. It can also justify long verbal banter and soliloquies and all the sort of talk that often happens in these style of shonan stories. The down side to this approach is that it's sort of a 'bad guy' thing. While intentionally messing with ones confidence like this would presumably work well, and could be made interesting to watch, it definitely feels a bit evil. However, I think you could manage a good guy version if you added a bit of a [Warrior Therapist](http://tvtropes.org/pmwiki/pmwiki.php/Main/WarriorTherapist) feel to these conversations. Yes he gets into your head and messes with it to undermine your effectiveness, but he does it in a way that ultimately is meant to build you back up. For example imagine the enemy has someone child raised to be a super soldier [TykeBomb](http://tvtropes.org/pmwiki/pmwiki.php/Main/Tykebomb), who the badguy manipulated to feel that he was the only one she could trust so she would fight for him. Water may dig into that trust she has for the badguy and point out how much the bad guy doesn't deserve it, which may devastate her and ruin her edge in combat, but would also be the first step to [helping her realize she doesn't have to fight for him](http://tvtropes.org/pmwiki/pmwiki.php/Main/DefusingTheTykeBomb), which ultimately would help her to heal and go to leading a normal life. He got in her head, messed with her, but in doing so he helped her realize her own delusions (that the person who raised her as a weapon loved her) which helped her to ultimately heal. He could potentially do this a good bit, destroying their confidence in battle, but only so he can help rebuild them to be better people later. It's much harder to write, but it could make an interesting character, and explain both why he is a good guy and why he has so many followers. Perhaps those he fight often [join his side later](http://tvtropes.org/pmwiki/pmwiki.php/Main/DefeatMeansFriendship), and people presume it's because he is mind controlling them but really it's just because they appreciate the way he helped them heal their own mental wounds and made them a better person, they actually [want to join him](http://tvtropes.org/pmwiki/pmwiki.php/Main/MagneticHero). 2. Illusions and deception. The whole [look behind you](http://tvtropes.org/pmwiki/pmwiki.php/Main/LookBehindYou) trick may actually work if you can say it in a way that sounds so believable someone actually expects a trap! Perhaps he can do similar, messing with people's beliefs so much that they aren't sure who they are fighting against. In effect he says something so believable that their minds make it real. Imagine he tells someone he is too fast for them to hit, only he says it so believable they actual accept it. For a few seconds he never seems to be where he should, he almost seems to teleport elsewhere with his speed. Only he isn't any faster, they just believe it so much that for a split second it *is* true for them. This gets close to the game breaking territory I mentioned before, but there is an easy way to keep it from being to strong, people can shake off their belief once they have time to think about it for a second, but for a split second they do believe him, and for that split second he has an advantage. It won't last, but it's an opening. Imagine he is in a fight with a badguy who uses a gun as his preferred weapon. After a volley of fighting, him dodging to try not to be hit while badguy shoots enough bullets to kick up dust the camera freezes on the dustcloud, we watch the dust to clear and find the badguy has his gun pointed at water from only 5 paces away, too close to dodge, and gloats that he has won. Water smiles and says that he would be in trouble, except that the he was counting and the gun should be out of bullets. The badguy gets a scared look on his face and for a split second looks down at the amount counter on the back of the gun, to see he still has plenty of bullets; but during that second Water runs in to close the space between them and lands a punch while the badguy is distracted. To keep it interesting Water will have to come up with new tricks. He needs lies that have at least a little plausibility so the badguy will trust it for a second, and he only gets a brief advantage before they realize it's a trick. Of course the more he gets into the badguys head the longer it will take for them to realize the trick. And some badguys may simply [say they aren't falling for it](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwi__ZDg9rHJAhWJwiYKHa4pAcEQFgghMAA&url=http%3A%2F%2Ftvtropes.org%2Fpmwiki%2Fpmwiki.php%2FMain%2FNoSell&usg=AFQjCNGsl0yKAAQZWkHj52pVVly--90NUg) when he tries a trick, to keep things interesting. 3. subtler gambits The above may be his main weapons, but he would have others to use on a case by case basis. The ability to resist his trust magic is based off of your seeing something that could be manipulation, so if he can work in things you don't notice as manipulation ploys they could stick work. Another scenario. Water tries a trick like above on a badguy and the bad guy simply says he knows about Water's tricks and [won't fall for them,](http://tvtropes.org/pmwiki/pmwiki.php/Main/NoSell) before throwing a surprise attack and Water complains that he hurt his foot/leg avoiding the blow, but he should be fine. Later the badguy barely dodges an attack and Water says he would have landed that attack if he didn't have to be careful about putting weight on his injured leg. Later as the badguy is pressing an advantage Walter accusing the badguy of cheap tactics and points out that if he hadn't been wounded in the first surprise attack he wouldn't be loosing now... Finally, as the badguy is moving in for the kill on the apparently beaten foe Water leaps forward, using his supposedly wounded leg to propel himself, to move in past the badguys guard and land a nasty blow which ends the fight. It's later revealed that Water's leg was never hurt, but by constantly complaining about his wounded leg he convinced the badguy that it was too badly wounded for Walter to keep fighting (even though he *was* using the unwounded leg through the fight, the bad guy didn't notice it). Thus the badguy got sloppy and wasn't ready to defend against an attack that used waters supposedly wounded leg. Water points out that the badguy may have been ready to resist his more overt tricks, but was too willing to accept Waters complaints about being wounded as true, he wasn't on guard to defend against those. **Small group battles** Much the same as above, but with some added tricks. Making an enemy distrust something another enemy unit says could be useful. Making them second guess a command by their captain rather then following through can result in a vulnerability to exploit. In addition he can encourage his allies. Moral has a huge bonus in a fight, so just telling everyone that they are going to win this fight, and making them believe it, can really boost moral and thus effectiveness. Sort of like the way bardic music works in an RPG, it's a free buff to those he fights with :) **non-battle strategies** One of the things your notice is that many of the tricks above were short term tricks, people saw through them well. I like that angle, overt trust attacks only work as long as Water is actively using his magic, subtle long-tern effects must be more believable and carefully crafted. The big thing here is, once again, to get into the psyche of his opponents, but in subtler ways. I think playing mind games by making people *think* he is manipulating them when he isn't would be a very effective ploy here. Briar patch something by telling someone they totally shouldn't travel through that mountain pass were snipers could easily get you. The enemy is so afraid that your manipulating them that they would go out of their way to do the opposite of what you say and fall right into the trap. Eventually have him always contact people and tell them things just to mess with them. Have him make up obviously blatant lies, and tell people random things, just to force his opponents to have to wonder what trick he has and second guess what ploy he may have going. One of the limits of his trust power in large scale battles is that it only works on those he actively manipulated, and he likely can't get to the important people. However, he likely knows quite a bit about how trust and the human psyche works. He may know how to sow disinformation and mistrust without using his powers at all, just by knowing what information to send when and where. I could see plenty of mind games that require no powers at all this way. Another good trick is to mess with information lies. If he can convince spies or enemies he faced of something that isn't true it will mess with enemy intelligence. He could use this to set up ambushes or bait people by trying to confuse reports of what he is doing and where. I would suggest giving him an ability to bestow to others some limited ability to use his trust magic, for instance perhaps he makes some sort of dust that you can blow on someone face to make them trust you more. He probably can't make many of these items, but let him do something with it. The reason why is because he can't use his abilities too well for large scale operations because everyone will recognize him and attack on sight, before he has a time to manipulate them. So his picking a select few to do his subtler work for him, and gifting them with some bonus that will help them manipulate others, will allow him to extend his reach beyond where he can physically go, and allow for more mistrust in enemy lines that can be exploited. However, I would make sure you set clear limits on what he can do here, make it clear that one or two individuals he can aid, but he can't give everyone on his side insta-trust goggles or anything like that; no mass producing these tricks. ]
[Question] [ Today's dinosaurs--the birds--have a uniquely avian piece of anatomy called the syrinx, located at the base of the trachea. Because it is located at a point where the trachea branches to the lungs, the syrinx makes birdsong a possibility. The syrinx is an anatomy unique to birds--the non-avian dinosaurs, apparently, didn't have it--which makes it a competitor against that other vocal organ, the larynx. Is it possible for one animal to have the syrinx AND the larynx in one body? If no, then why not? If yes, then what would the advantages of having both vocal organs be? [Answer] I would say it is very unlikely for an animal to have both of them. I say this because the primary reason for both of them is to produce sound. Having either one satisfies this need. Animals learn to deal with the noise makers they have to make the sounds they need. If they can't make a sound then they really don't need it to survive. This is not to say some strange occurrence might not allow it, but if so it would be for a true need to be able to differentiate different kinds of sound. An amphibian life form might have a need to make sounds differently underwater and above water... [Answer] Actually, birds *do* have both: a larynx high in the throat and the syrinx (often called the inferior larynx) down near the bronchial tubes. Bird larynxes are not used to produce sound, and may be vestigial; I couldn't find much information on them at all. I think it's safe to assume that syrinxes evolved fairly late — possibly as a side effect of the respiratory adaptations birds made to optimize the exertions of flight — so it's likely that there was some ancestral proto-bird species that had both a functional larynx and a functional syrinx. But it's a duplicate function, and the syrinx is a superior organ for producing sound: it produces a greater range of sounds than a larynx, and incorporates many of the 'sound shaping' features that in mammals require the involvement of lips, tongue, palates, throat, etc. Since the larynx adds nothing unique to the combination, there's no advantage in maintaining its function. If a species did have both as functional organs, it might allow for more complicated vocalizations: e.g., tri-tonal sounds (some birds can already produce two sounds at once by differential use of each side of the syrinx), or odd sound effects (think Peter Frampton singing through his guitar). But since most of the sound would be formed *before* the air hit the larynx, the larynx would be a post-processing instrument, not a primary generator. [Answer] **possible it is, but not for long** You see, it is already believed that the syrinx came to be by two possibilities: mute dinosaurs which developed it (most unlikely) or dinosaurs,which, like every other animal, had a larynx, but developed a syrinx and then lost its larynx. The reason for that is simple: you don't need 2 structures that do the same thing especially when one seem to be better than the other. This theory of Dinos with both structures is the most accepted, and a good example why it's unlikely, there's simply no point. Lastly, the advantages: maybe a larger array of possible sounds, but clearly not significant enough to justify its permanence in the organism, especially since we have birds that can mimic from other birds to chainsaws, cameras and guns with their syrinx alone, showing how effective it is. [Answer] I would say no. Because excluding humans, other mammals have their larynx much deeper down the throat, somewhere close to the syrinx you mention. Having them both together in a close vicinity would be a waste of body resources as both would tend to create very similar sounds. So no, unless there is destined major creature redesign or a very very precise mutation (the chances of which are 0.000000000000000000001%), there is no chance of finding a creature which *naturally* has both the organs. [Answer] **We honestly don't know.** Birds actually do have a larynx, and it *does* participate in vocalization, but not through the vibration of vocal folds (see reference below). But we have no idea as to whether a syrinx or larynx with vocal folds are mutually exclusive, how the syrinx first evolved, or what the two organs would function like together. Aside from a handful of extinct birds that have preserved syringes, sound-making anatomy is virtually unknown in extinct animals, and all extant species are either predominantly syrinx or predominantly larynx-with-vocal-folds vocalizers. Non-avian dinosaurs, for all we know, could have had both. A lot of people, especially on the Internet, have been going around saying that dinosaurs “couldn’t” vocalize because of how the two traits are distributed in living animals, but that’s not how phylogenetic bracketing works. If an unknown taxon is bracketed by a living group with state B (crocodilians and turtles with vocal folds) and another group with state C (birds with a syrinx), the answer to the most parsimonious state for the unknown taxon isn’t state A (neither), it’s “uncertain”. The broader problem is that vocal organs (e.g., a larynx with vocal folds) and the anatomy of the throat don't preserve in most fossils. An ossified syrinx occasionally preserves in the fossil record, but only rarely and it seems to be limited to Neornithes. However in order to evolve an *ossified* syrinx, you have to evolve an *unossified* one first, and we have no idea when that happened. Most of the Liaoning non-avian dinosaurs appear to lack an ossified trachea but *Scipionyx* apparently has cartilagenous tracheal rings. Pterosaurs and megaraptorid theropods have features (a pneumatized furcula) that today are correlated with features related to a syrinx (i.e., a clavicular air sac) in birds. So for all we know they did have an unossified syrinx. There is also evidence that hadrosaur crests modulated sound production, which means there had to be some precursor sound-making ability in order for selection to act on the sound-making function of the crests. So the distribution of sound producing elements in Archosauria outside extant taxa is pretty much unknown. Maybe most dinosaurs had a larynx? Maybe most dinosaurs had an ossified syrinx? Maybe some had one, some had another, and some had no ability to vocalize at all? [Maybe the reduction of the larynx as a functional element is due to the miniaturization trend in maniraptorans in general](https://science.sciencemag.org/content/345/6196/562?casa_token=os630j_GoycAAAAA:hBww9vYp4tKKnAwB1UyostqS7APrrIYRrUcn3NOBiH2vHwA1xBwB0o6m3_uuGQW5pvs2H8D984hC5zY)? We don't know. Similar transformations of traits that seem "mutually exclusive" with animals having both features at once have been seen in evolutionary history. Synapsids went from a quadrate-articular jaw joint with the condyle on the cranium and the socket on the mandible to a squamosal-dentary jaw joint with the condyle on the mandible and the socket on the cranium, and went through a phase where both joints were functional at the same time (e.g., [the cynodont **Diarthrognathus**](https://en.wikipedia.org/wiki/Diarthrognathus)) before the original joint gradually lost its original function and became part of the mammalian inner ear. If we didn't have these transitional fossils people might surmise that mammals evolved their jaws independently from all other tetrapods because these two jaw joints come off as mutually exclusive in function. Another example can be seen in dinosaurs. Many dinosaurs and most crocodilians have only teeth, all birds today have toothless beaks. But many dinosaurs also have beaks, and some species have both beaks and teeth (e.g., most ornithischians, many maniraptorans). The problem is unlike teeth, vocal parts don’t fossilize. [This reference](https://zhejiangopterus.wordpress.com/2020/01/25/the-evolution-of-stem-bird-vocalization/) and associated references cited within does a pretty good job at summarizing the whole syrinx versus larynx debate, including references about birds having both. ]
[Question] [ We are on the verge of the age of self-driving cars. This is a fact, with Google, Uber and other companies rushing to develop safe, self-driving road vehicles. What is less clear to me is the social impact of it. To keep the question short and sweet, think of the vast world of American Suburbia, where possibly a majority of Americans are currently brought up, with parents often reduced to the role of being their kids drivers for various afterschool activities and even play-dates. Or conversely, the kids as prisoners of their parent's willingess to drive them anywhere. Now in a few short years, our roads will be awash in self-driving cars. How does this change US society in respect to children? **Do parents let teens and tweens self-drive away, unleashing a new era of freedom for parents and teens alike? Or do they keep an even tighter leash on them, by constantly monitoring all their comings and goings, 'helicoptering' in at the most embarrassing times? Something else altogether?** [Answer] First, I want to point out that in many cities (for instance, New York), most people simply don't drive, and many never learned how. In these places, things might not change too much, as most people who don't have a car aren't going to buy a self-driving one. Public transportation will probably be self-driving, but this probably won't change much; letting your kid take the bus or a taxi to school isn't going to feel any more safe to a concerned parent with or without a driver. The case it sounds like you're considering is more of a suburban scenario, where kids get a car some time around high school, and can start driving themselves around. In a self-driving world, these kids might end up getting cars *even sooner*; imagine a spoiled twelve-year-old cruising around in a Mercedes. Even families who can't afford an extra car for each kid might just get one to drive all the kids to school, or program their own car to return home after driving them to work, so anyone in the family can use it. The result of this is that more people will be able to get where they're going, faster. Parking lots should be a lot emptier, while highways will be busier (unless they open up some super-efficient self-driving lanes). One possible result of this is that families will grow further apart. Compare a parent who drives their kid to and from school to one who doesn't; the former has a lot more time with their kid, and gets to see them in close temporal proximity to what might be the most important part of their day. This trend will continue, as kids no longer need their parents to drive them to friends' houses, or school functions, or sports, or anything that they do outside of the house. The family home may end up being the *only* place families see each other, unless they make a point of going places together. On the bright side, this means that parents should be much less worried when their kids start branching out in their teenage years. There just won't be much of a perceived difference, except that the kids won't be home as often. Thus, the kids should have a much higher level of freedom than they do today. Parents are already having a problem keeping up with their kids on the Internet, this is just a further level of that. Now, after saying all of this, I will suggest that parents are going to fight very hard to keep these changes from happening. People like us who are alive now are going to expect the levels of interaction we have today; the next generation may expect less, though, and the next generation even less. The more we automate our lives, the less we need to see of each other; just look at how social media allows people to *feel* like they have 'friends', even though they don't have any meaningful conversations. Families may 'feel' like they are just as close as before, but if they take full advantage of self-driving cars, I think it's inevitable that everyone will grow further and further apart. [Answer] A few of the answers touch on this, but I feel it deservers more focus. You do not **own** a self-driving car, you **subscribe** to one, or rent one as needed. The self driving car doesn't compete with the family car. It progressively replaces the family car, with a different type of service. Like NetFliks doesn't compete with broadcast TV, it replaces it with a different service (as compared to Channel 10 competing with Channel 9). **The self driving car service is much more like a Taxi.** There is no need to have a car sitting in the carport at night, when that car could be driving club goers into town. There is no need to have to have a large carport full of workers cars when they could be going to take people shopping. The cost of a Taxi is mainly in man power. Thus self-driving taxis would be cheaper than Taxis. Self driving taxi's are also cheaper than personally owned cars too. Because they save on: the opportunity cost of not being used all the time (as they are), and on the parking costs at paid parking, and on the land costs in inner city household parking. They will also have the advantage of never being out of fuel, since a self driving taxi (like any taxi) would not be sent to your location if it needed fuel or repairs. And it would always be properly serviced (unlike personal vehicles (I know my car is a year over due for a service, just cos I put it off)). The do have some increased costs over personal cars, like the owner taking profits. So it depends on competition and supply/demand, the exact price point. Thus **Self driving Taxis will replace personal cars, and taxis.** The trick is waiting for legislation to catch-up. While today's cars need supervision, the future ones will not. We have been making progress in this, one of my professors worked on self driving cars decades ago, and apparently they were pretty good, but they were not allowed on the road at all. Todays are better, and are allowed on road with supervision. **Tomorrows will be better still, and will be allowed on road without supervision**. **Until then we can basically treat self-driving cars as just another convience/safety feature, like Electronic Breaking, and Cruise control -- nothing really changes.** Once legisliation catches up, then we have the real question. **The key difference between a self-driving car service, and a taxi is just the price.** In Australia, the UK and the US today, a **Taxi might cost you about \$2.50/km**. (I was surprised to find it so consistent.) Lets say the price got down to **\$0.80/km** (My math suggests the Running/Replacement cost is about \$0.26/km, assuming 96,300miles/year,` \$0.16/mile for fuel, \$50,000 purchase cost, and replacing it after just 2 years). There is another difference, in that before there is a person involved, where as now there is a machine. I suggest that on the whole it is irrelevant. In both cases any fear of the driver is statistically irrational. Some people are going to be scared of trusting a machine. Other people today are scared of leaving the kid with a stranger at all. Now we can compare how people would interact with cheap taxis (ie self driving cars) to how the interact with taxis today. If you google for "Send kids to school in Taxi" you will find a lot of result. People do do it, it is quiet common. I imagine it would be come more common with a self-driving car. Googling "Sending kid on playdate in taxi" returns far fewer relevant results. This [forum discussion](http://www.dcurbanmom.com/jforum/posts/list/386168.page) has people very unhappy with the idea of using Uber for such a thing. Though a lot of that comes down to the very unchecked nature of uber drivers.(The stranger concern is aggravated, compaired to for taxi's where the driver is going to lose their job if the suggestion of something untoward going on). I suggest that with younger children, where the parents normally will sit and have coffee while the children play, there would be no change. When we get to older children and tweens, I expect the cheep taxi service would come in to play. After all we already see children going to a friend's house via the bus or the other kids parent after school. So if the friend came to school via self-driving car then that would be the way they would go over after school. In short, minor changes for younger children For teenagers, today on a weekend job, they can't really afford to take a normal taxi. And for teens to young for work, on the pocket money they can squeeze out of their parents, similarly can not afford. What they can afford is public trainsport. Now even the cheap-self driving taxis are still significantly more expensive than today's public transport. I thus suggest that a lot of teens would be fairly unchanged, with regard to their travel. Change may be that instead of walking to the trainstation, they get a pick-up. But it is still out of their reach to do things like take a self-driving car for a day trip to another city etc. On the other hand, in places that have no public transport system (like where I grew up), there may well be more significant changes. Parents may be more willing to pay for a self-driven taxi, than to drive them themselves. Particularly since the parent may not own a car. In short the additional freedom doesn't amount to much. It is still too expensive, though it is close. [Answer] Well for one, self driving cars will reduce traffic and accidents by a large margin. The cars will also put a lot of cops out of work, increase productivity and allow for new innovations, such as the self driving conference room. **A self driving car still would require an actual licensed driver for situations the car couldn't handle, so you can't simply toss them in the car an say "Nissan, take them to daycare" and watch it drive away.** As for your questions: > > Do parents let teens and tweens self-drive away? > > > **Probably, since it's safer than letting them drive on their own.** This depends greatly on how good the self driving system is of course. > > Something else altogether? > > > This all is related to how self driving cars are implemented. There might be a system of buses that is used in this way, with drivers there in case something happens. Automation is great provided the environment works for it. A fleet of vehicles that rotates around, either responding to messages for pickup or following a set pattern makes sense. I don't imagine that remote access would be implemented since it allows for nefarious deeds. [Answer] One of the great hassles of having middle to upper class suburban teenage and tween children is the driving around to soccer, ballet, piano, and other extracurricular activities. Lower class parents who can't afford such extras will see no change with self driving cars. However, lower class parents who can afford extras but don't have the spare transportation capacity to get their children there will benefit. Some families do very well at together time and others don't. Decreased driving load on the parents may emphasize or demphasize family togetherness. Certainly, the power to get a child to an activity without parental involvement is incredibly powerful. Determining the best practices for pickup and drop off will need to be figured out, as will security practices to mitigate kidnapping concerns. Self driving cars won't be deployed everywhere at once so there's a decade or so to experiment. For the more paranoid parent, the ability to know where a child is at any time will offer peace of mind. Further, the knowledge that a car can be dispatched effortlessly for a teen in a compromised situation will also be helpful. Sure, there will be the horror stories of overbearing helicopter parents who misuse the information provided by a self driving car but as now, these kinds of parents are the exception rather than the rule. *Security Concerns* In 2015, the trend known as "Internet of Things" is pushing ever greater amounts of automation and intelligence into every day objects. Lightbulbs, thermostats, cars, everything...which is great for convenience but as of yet security doesn't appear to be big concern. Unless security is addressed then self-driving cars are going to be susceptible to hijacking or snooping. *Ownership Models* My guess is that in the suburbs, small communal car businesses will pop up, kind of like apartment management companies. A normal human owns the car but puts it under management of the management company. The management company handles scheduling and maintenance for a fee or cut of the renter fees. In larger cities, I think Uber or Uber-like models will prevail. What I'd love to see but doubt will happen is if instead of Uber buying a giant fleet of self-driving cars, they continue to utilize the self-driving cars owned by former drivers. Thus, "ownership of the means of production" remains in the hands of non-traditional capitalists instead of the already crazy rich. Then a driver can buy other self-driving cars and increase their income without selling their time. [Answer] I might point out that this would be more of a return to historical norms than a new phenomenon. Before driver's licenses were invented, young people were just about as mobile as their parents, not particularly more or less. A young person was just as capable of walking or riding an animal somewhere as his parents were. Parents might tell a young person that he's not allowed to go somewhere alone, but the only limit was really what was imposed by parents, and not things like an inability to drive or legally get a license. I don't know what the cultural norms were back then. I don't suppose that parents let a 5 year old wander around without supervision. But how about a 15 year old? When I was a boy, people who were not old enough to drive routinely rode bicycles everywhere. My parents only drove me if I was going somewhere that was impractical to reach on a bicycle, which was rare. I regularly rode a bike to school, to the library, to stores, to friends' houses, etc. I haven't been following the development of self-driving cars that closely, but from casual news stories I've read, there appears to have been remarkable progress in the last few years. I think it's a pretty safe prediction that they'll be practical for routine use within as little as a few years, though probably not as soon as the more optimistic predictions. People are always saying that some new technology will be everywhere in just 3 or 4 or 5 years, when it's really still decades away. But we'll see. I'd guess it will take longer for them to be legal throughout the U.S. and Europe than proponents assume. People with something to lose economically, like taxi drivers and cities with mass transit systems, will fight them tooth and nail. There will be studies proving they're dangerous, protests, and court cases. Some cities or states will ban them. Like California refused to allow plastic plumbing pipe until 2002, decades after the rest of the country was using it routinely, citing "safety concerns" but everyone knew the real reason was that plumbers fought it because it made plumbing work too cheap and easy. Or see the present opposition to Uber. Etc. You also have to consider the cost of a self-driving car. I just found a study that estimates it will add $7,000 to $10,000 to the cost of a car. And of course it will be a while before there are a significant number of used self-driving car available for the cost conscious. So initially, self-driving cars will be limited to upper-income folks. To an extent a family could share a self-driving car, of course. I presume there would be some mechanism that mom or dad could drive the car to work, than have it drive itself home to take the kids somewhere. But there are limits to that. It can't be in two places at once. And plenty of parents would say no, the car has to stay with me in case I need it in an emergency. Some families could afford to buy one or more additional cars for their kids, but many could not. Presumably there will be self-driving taxi services. As you don't have to pay a driver, these would ultimately be cheaper than human-driven taxi services. But the cost of the service would still have to recoup depreciation on the car, operating expenses, insurance, and all the other costs that go into running a business. Very few families are willing to routinely pay for taxis to shuttle their kids around today. Perhaps with self-driving cars the cost would go down and thus the numbers would go up, but it doesn't follow that this would become common practice. Consider how many parents today won't let their kids walk or take a bike somewhere. Would they be more willing to let the child make the trip alone in a self-driving car? Maybe it would be perceived as safer. Maybe not. I've seen news stories about parents getting into trouble with children's services agencies for letting their kids walk to a park by themselves. It's quite possible that social pressure or actual laws would make it illegal or otherwise unacceptable to send children under some age anywhere by self-driving car. Personally, I couldn't imagine putting a 5 year old in a self-driving car and sending him off on a 100 mile trip by himself. I'd be terrified of all sorts of real and imagined dangers. ]
[Question] [ Assuming only plausible advancements in science, a Martian colony is established before the end of the century. (Sooner if possible). What materials would be needed in regular shipments from Earth? How often would those shipments have to come? (Based on plausibly-sized transport space craft) **What sort of time frame would be possible before the Martian colony was truly self-sufficient enough to declare independence from their Earthling overlords?** No FTL. Ships use an energy - > thrust drive such that matter is not expended in generating thrust. Solar or nuclear power is enough to move ships around. Earth has a moon base and orbital stations and shipyards. Most ships belong to the Earth Space Navy, but there are a few rogue ships that may prey an an undefended transport. Mars has a valuable resource that Earth wants and therefor it funds the colonization effort. Mars wants trade as equals rather than being a colony that must pay tribute to the motherland. [Answer] This is one of those "it depends" kind of questions. But it's really a pretty good one. > > "Mars has a valuable resource that Earth wants and therefor it funds the colonization effort. Mars wants trade as equals rather than being a colony that must pay tribute to the motherland." > > > This puts us squarely into Imperial territory: the concept of the "wealth pump". An empire exerts control over a foreign territory in order to extract wealth in some form. In this instance, it's defined as a single resource. It's kind of simplistic, but probably useful for present purposes, to say that there are are four main methods of imperial control: * **Force: direct military action.** This is pretty obvious. Historical examples abound. Given the difficulties of interplanetary combat, it might not enter into the picture here. * **Force: withholding necessities.** This one is much less common in Earth's history, but clearly a factor here, when Earth can simply stop sending basic supplies that are necessary for the Mars Colony's wellbeing. * **Financial compulsion.** This is the primary technique that the present-day American empire uses: legal and monetary systems of unequal exchange, enforced via such instruments as transnational banking systems and the International Monetary Fund. I mention it because I'm sure that the Earth - Mars conflict you are seeing would involve legal and financial arrangements of this sort. * **Religious or ideological control.** You don't mention this one, and it probably wouldn't make too much sense in the context. However, the longer the timespan we're looking at, the more likely systems of ideology are to grow up around the situation. To answer your question: *How long would it take for the Mars Colony to become able to defy the authority of Imperial Earth?*, you need to first answer the corollary: *How do the Martians get it done?* This is in turn worked out by analyzing Earth's control over Mars. The Martian goal is "trade as equals, rather than being a colony that must pay tribute". This means that Mars has the initiative: until the Martians do something, Earth will be likely to remain satisfied with the situation it has already set up. To dig a little more into the Martian goal, here are some characteristics that would be necessary: * The four means of imperial governance noted above must be collectively more expensive than they are worth. To take the military example: the cost of interplanetary military expeditions would be very high, even with the reactionless space drive you posit. When does someone in charge on Earth stand up and say, "Why do we keep blowing money out of the airlocks? Can we get the stuff some other way?" * None of the four means of imperial governance can be overwhelmingly decisive. For example, if Mars depends on shipments of water all the way from Earth, Mars isn't going to be in much of a position to do anything about the situation. So you need to work out how the Martians will be able to sustain an independent existence. * Earth's desire for the Martian resource must be high enough to provide a strong incentive to come to terms with Mars; but not *so* high that Earth is willing to pay enormous prices in order to get as much as desired. So, there is the Martians' desired strategic end state. How long will it take the Martians to get it done? In my opinion, you have enough flexibility built into your world here that you can pretty much make it take as long, or as short, a time as you please. Between your ability to modify social, economic, and political conditions on Earth; your ability to tweak the characteristics of your space drive and your precious Martian resource; and your array of Mars Colony scenarios of population and industrial capacity; you could easily set this up to run long or short. Decades? Centuries? Up to you. Your world will support these outcomes. Honestly, now you get the fun part: playing with different parameters to set up a piece of invented future history that is intellectually absorbing, and satisfyingly dramatic. :-) [Answer] A very large part is how valuable does Earth think Mars and it's resources are? The more important, the longer it will take, less then less. If we get a small colony there say 5-10,000 people and all it does is cost to keep them around and there is a small tourist economy, They might become independent much faster, because it would be less of a hassle to let them buy what they need and not have the administrative overhead. In as little as a couple dozen. However, if they had an incredible mining opportunity, say something we need for space travel, cheaper to get it off the surface and abundant. Then it will be a colony will have to be very large and feel disenfranchised and that decisions being made don't reflect the good of those living on Mars, then it could take a 1-2 hundred years. [Answer] if I were you, I would use as a example how long did it take to America (the continent) to gain independence from European powers, I would say it took about 200 -300 years between Columbus reach America and most of American countries being independent. I would not expect Mars to form a single country/nation. Maybe colonies from USA would gain independence before colonies from China, or even company colonies. Do the math on how long took to travel by sea from Europe to America and how long would take to travel between Earth and Mars and you can get some ideas. I would match Columbus "discover" of America to an state of Martian soil terraformed or autosufficient, as you cannot fight your imperial master if you depend on it for food. However you can fight your current imperial power with help of another imperial power (British helped South America colonies to gain independence from Spain) ]
[Question] [ How much TNT do you need to blow up Mount Everest? Is this even possible and can mankind survive a huge explosion like this? Or would the whole world be covered with dust? And if you can survive this huge explosion then from how many kilometers away would you still able to hear the explosion? [Answer] The most valuable data probably comes from [Operation plowshare](http://en.wikipedia.org/wiki/Operation_Plowshare). In one test, a 104 kt explosion, displaced 11 million tons of soil, about 100 ton of soil for a ton of TNT. Let's say for the sake of getting a lower bound, that Mount Everest is made of soil. Mt. Everest has a volume of about 1.5 million million cubic meters, and a cubic meter of soil weighs about 1.5 tonnes, so a soil Everest should weigh a little over 2 million million tonnes. So we should need at least 20 000 million tonnes of TNT for the job. If instead we used thermonuclear bombs of [the highest yield](http://en.wikipedia.org/wiki/Tsar_Bomba), we'd only need 344 of them. In 1960 the combined yield of the US nuclear stockpile was just about 20 000 Mt, so that would be in the ballpark of what is required. Of course, Mount Everest isn't made of soil, but on the other hand, you may be able to use the weight of the mountain to crush most of the rock, by starting at the base. [Answer] It depends a lot on the geology of the mountain, of which I know nothing. Is the rock sedimentary? Does it have horizontal strata or do they slope steeply downwards? Is one of the strata weak? It might be that all you have to do is shake it hard enough and gravity will do the rest. One really big hydrogen bomb? A medium or small one? Look up Cumbre Vieja (Canary islands) for a case of serious instability, and if you live on the USA Eastern seaboard, worry. Somewhere on my travels, I forget exactly where, I passed a roadside memorial to the people who had once been camping in the valley below. There was no valley below, just a field of boulders. One summer day, after heavy rain which lubricated a fault, a mountain had collapsed downslope under its own weight. That's an extreme case but not a unique one. It's said that the Swiss have permanent explosive mines in carefully selected locations in their mountain passes. If someone ever tries to invade, a large chunk of mountain will fall on them. [Answer] I estimate that if you were to attempt such a thing ( which I would not recommend ), the necessary force would be at minimum 3.332\times 10^{10} tonnes of TNT to level Mt Everest. ]
[Question] [ In the book 2010: Odyssey Two by Arthur C. Clarke, Jupiter is turned into a star. Presumably this is done by making it more dense, so if Jupiter were to reach that density and become a star, what would be the impacts on the Solar System? [Answer] The impact would vary greatly depending on where you are in the Solar system. Firstly, assuming the actual mass of Jupiter has not changed then it will still hold its current place in orbit, although there may be some odd effects while it is first collapsing. As the calculations [here](https://astronomy.stackexchange.com/questions/6052/what-would-the-effects-be-on-earth-if-jupiter-was-turned-into-a-star/6097) show the actual impact on earth would be minor, some nights would be a little brighter. There would be a tiny bit more heat. The effect on the other planets would also be small, they would get more heat and light a they passed Jupiter in their orbital paths but then that effect would fade as they moved further apart. The place where you are going to see a change is the moons of Jupiter. Assuming they survived the process that ignited the gas giant they would immediately have a large sun immediately above them in the sky. This sun could easily be so bright it turned them all to cinders, however if the brightness was tuned appropriately it could actually move some or all of the moons into the habitable zone. You can expect to see the frozen surface of Europa melting, potentially even forming an atmosphere. The other moons too would greatly increase in temperature, and the possibility of them getting to the correct temperature for life as we know it cannot be ignored. Io, Europa, Ganymede and Callisto are all sizable moons. Ganymede as the largest has twice the mass of our own moon and would be a promising place for life to develop if it was able to hold onto an atmosphere. One interesting point though is that all of these moons are tidally locked, if Jupiter turned into a star they would all always have one side pointed towards the new star. That would make for some very odd weather patterns on the surface as discussed in some other questions on this site. [Answer] ## Physical properties If Jupiter turns into a star, it would likely turn into the least massive star possible. This would make it a [red dwarf](https://en.wikipedia.org/wiki/Red_dwarf) - in particular, a red dwarf of spectral type M9V. We can infer a few key properties from this: * Mass: $0.79M\_{\odot}$ ($82.8M\_J$) * Luminosity: $2.69\times10^{-4}L\_{\odot}$ * Surface temperature: $2400\text{ K}$ * Radius: $0.095R\_{\odot}$ ($0.924R\_J$) In other words, Jupiter would get much more massive but a little bit smaller. It would be fairly dim in comparison to the Sun. ## Jupiter's moons What would be affected first? I'd put its moons on the table. By Kepler's third law, the period of an orbiting body is $$P=\sqrt{\frac{a^3}{M}}$$ where $a$ is its semi-major axis and $M$ is the mass of the body it orbits. Since Jupiter has increased dramatically in mass, the periods of it satellites will drastically decrease, and they'll speed up quite a lot - both by a factor of about 9. So the moons would probably be orbiting at a much quicker rate. But what else? Well, there's always the [Roche limit](https://en.wikipedia.org/wiki/Roche_limit) to contend with. Inside the Roche limit, a satellite will be torn apart. Now, $R\propto M^{1/3}$, where $R$ is the Roche limit and $M$ is the mass of Jupiter. Therefore, the Roche limit would increase by a factor of 4.36. This would tear apart many of Jupiter's inner moons, likely forming a more dramatic ring system (Jupiter already has a ring, but it's not very massive). ## The other planets Let's go even further out. Would the other planets be affected? Technically, yes. I'd worry the most about [Saturn](https://en.wikipedia.org/wiki/Saturn). At its closest, it's $4.4 \text { AU}$ away from Jupiter. Is that an issue? I'd say yes; if Jupiter became a star when it was this close to Saturn, there's a chance Saturn could be gravitationally captured. On the other hand, if it became a star when the two were furthest apart ($15 \text { AU}$), there wouldn't be any trouble - at first. But once Saturn caught up to Jupiter in its orbit, it could get caught. The other planets, too could be affected. I don't know just how many (if any) others would get captured by Jupiter; it depends on how close (or far) they are from the Sun. But the solar system would certainly be an interesting place. At least, more interesting than it already is. ## Habitability This new Jupiter would not change the Sun's habitable zone much, nor would it create a substantially large habitable zone of its own. Keep in mind that M-dwarfs are really dim, and this particular dwarf would give off a fraction of a percent of the energy that the Sun does. To give an example of just how drastic this is, here's a model ([code here](https://github.com/HDE226868/Binary-habitability)) of a binary system of a Sun-like star and an M5V red dwarf (slightly hotter than our new stellar Jupiter): [![enter image description here](https://i.stack.imgur.com/MgEOG.png)](https://i.stack.imgur.com/MgEOG.png) The separation is 5 AU, and the small dot in the upper half is the habitable zone around the dim star. The stellar Jupiter's habitable zone will be even smaller, and won't affect the rest of the Solar System, although some of its moons may be habitable - at least, the ones that haven't been torn apart by tidal forces. ]
[Question] [ I was thinking about a different possibilities for habitable planets. And I was wondering what actually causes a planet to be tidally locked? I am assuming it more than chance that the bodies rotation and period are the same. I started thinking what it would be like to be on a planet that circles a huge star, one that would take earth decades or even centuries for one year. Seasons would be the same for most of ones life etc. I can think of a lot of cool questions for that, but I then thought that maybe the planet would be tidally locked if the star was very large. So what are the things that go into a body being tidally locked? What causes it? [Answer] There is quite simple [formula](https://en.wikipedia.org/wiki/Tidal_locking#Timescale) that will give you the tidal-locking half-time $$T = 6 × 10^{12}\, \frac{a^6 R \mu}{ (M\_s M\_p^2)}\; \mathrm{years}$$ * $a$ - semi-major axis, or simply the radius of circular orbital trajectory in meters * $R$ - satellite radius in meters * $M\_s$ - satellite mass in kg * $M\_p$ - parent planet/star mass in kg * $\mu$ - rigidity, approximately $3×10^{10}$ for rocky objects and $4×10^9$ for icy ones. Please note that the prefactor $6 × 10^{10}$ currently used on Wikipedia is very probably wrong, so I provided a more realistic one. ([See the discussion](https://en.wikipedia.org/wiki/Talk:Tidal_locking#Contradicting_formulae_in_.22Timescale.22).) The tidal locking is approximately exponential process, so it is very quick at the beginning and gradually slows down. Typical situation is, that planets in the habitable zone are tidally locked for red dwarf stars. Moons are very often tidally locked, unless they are very far from their planet. [Answer] [Tidal forces primarily](http://en.wikipedia.org/wiki/Tidal_locking#Mechanism). When two bodies are orbiting each other, they're both pulling on each other. However, this pull is not uniform across the entire mass of each planet. On each body, the surface nearest to the other body has more pull than the surface farthest from the other body. This changes the shape of both bodies. Making them a little more oblong. Other factors would be when the internal mass of a body is not evenly distributed. Making one side heavier. You're correct that it's not chance that the rotation and period are the same. The 1:1 ratio of rotation:period is what results after long iterations of orbits and tidal forces. It's actually a stabilization of a orbital system. For example, the Moon and Earth are still stabilizing. Ever so slowly the rotation of the Earth is slowing due to tidal forces. Eventually making a day on Earth as long a Lunar month (don't worry though, that process is so slow, the Earth and moon will be consumed by the Sun's expansion by then). [Answer] There are many questions and nice answers about this over on physics.SE. One example is [this one](https://physics.stackexchange.com/questions/112356/synchronized-rotation-of-the-moon/112361#112361). Which also points towards Wikipedia [here](http://en.wikipedia.org/wiki/Tidal_locking#Mechanism). See them for the long answer. The short answer is this. You have a planet, you have a moon. They each have their own gravitational fields that "pull" at the other. This pull is not evenly spread through the planet or the moon so there is some flexing in the planet and the moon as they rotate under the other one. This produces enough friction to slowly decrease the rate at which the other body appears to rotate until the system is tidally locked. This drag means that the net forces in a pair of orbiting bodies is towards a tidally locked pair so it is a stable configuration that can endure other millions of years if not longer. There are a huge amount of details I am glossing over here but that is what the other references are for. Since the Earth/Moon system is tidally locked you can see what this flexing looks like by going to the beach and watching the tides. I know scientists sometimes have very unimaginative names for things. ]
[Question] [ Airships went out of fashion for a variety of reasons including: * Materials science level made constructing gas bags difficult. Cow-intestine were used to make the bags * Filling the airships with gas was expensive and eventually airplane fuel became cheaper * Lack of accurate weather forecasting and primitive IFR capabilities led to crashes * Materials science level made constructing a light-but-rigid airframe difficult and expensive * High profile accidents tainted public perception (R101, Hindenburg) and military perception (Arkon) Today though, it seems that many of these challenges can be overcome with modern technology: * We can construct gas-bags using light materials (near future materials can construct even better bags) * We have accurate global weather forecasting and a mature air traffic control system * We can manufacture ultra strong lightweight composites like carbon fiber to build structures * Even disregarding electrical propulsion and solar panels, our propulsion technology is far more efficient today Unfortunately, Helium has only gotten more and more expensive (we're due to "run out" eventually) and the only other viable lifting gas is hydrogen, which has a very bad rep. Still though, for decades, hydrogen airships were operated just fine and saw successful, extensive use in warfare and more limited deployment in the civilian sector. Furthermore, the people who built and operated these airships weren't idiots, and apparently deemed the risk of using hydrogen as "worth it" which leads me to believe that hydrogen airships aren't quite as idiotic as the high-profile accidents would lead us to believe. So, my question: **With modern (and near future) technology, could we build a safe hydrogen airship?** By "safe" I mean an airship that's roughly as safe as a modern commercial aircraft. [Answer] Yes, but it would take time and money. If you do that they could easily be the safest form of air transport in the world. When talking about Airships people assume they are soft, flammable/explosive, slow, can't handle any wind and crash if you look at them funny. You can see this in any question about airships on this site for example. It goes so far that people will actively seek disadvantages to make their arguments work, like saying they were loud (they weren't). Jet engine aircraft have actually been in the same spot at one point. The first high-altitude jet engine aircraft were involved in several high profile crashes with the loss of everyone on board. This caused public opinion to think that aircraft broke apart for no reason, would explode and were generally unsafe. Without computer simulations to properly test what could have happened the only method of testing was using a physical plane and simulating the conditions of a flight several hundred to a thousand times to see what happened. At the time a ludicrously expensive and time intensive method. Yet the aircraft company did the test anyway, they found out that the shape of their windows caused stress fractures which caused all the crashes. The entire air industry learned from it and now we fly with rounded window edges and the public opinion isn't that aircraft crash randomly or explode anymore. If that test never happened it would have taken decades longer before anyone would have build a working jet airliner. Airships were in the same position, only they never got tested (because they didn't know how). However with modern materials, simulations and capabilities we can make safe airships, just like we've made our aircraft orders of magnitudes more safe than our early aircraft designs. Airliners can take off and land with a burning engine that falls off halfway through flight nowadays! The gas: Hydrogen is one of the most flammable substances on earth, but only when it has enough oxygen. The interest in hydrogen cars and hydrogen fuel cells let to research into how safe it was to have them onboard cars and large fuel tanks compared to regular gasoline. They found out that due to how hydrogen burns it's actually safer compared to most types of fuel we use today. With the addition of more partitions between gas cells, more individual gas cells and other safety measures you can make it very safe. Let's compare it to the Hindenburg for example. The Hindenburg was a lighter-than-air craft, so to land it needed to vent it's hydrogen (or pump it into the same gas cell and fill the empty gass cell with air, the Hindenburg seems to have mostly vented it though). This hydrogen could have stuck around the craft when sparks for a flame occurred. Modern engines would be less likely to cause a spark and with the introduction of hybrid airships that problem goes away entirely. Hybrid airships get most of their lift from gas, but the remaining lift is generated by regular old wings and vectored thrust. This instantly also removes the need for mooring masts and allows these hybrid airships to land in rural area's where regular transportation cannot reach. Another problem with the Hindenburg was that it's skin was made from flammable materials. As the flames kept burning across the airship's skin the hydrogencould mix with more oxygen and ignite, keeping the process going until it was so big it engulfed the Hindenburg. As for that mix with oxygen, hydrogen is stored at atmospheric pressure. If you puncture the gasbag there won't be hydrogen spilling out as there's no pressure behind the gas to push it into the atmosphere around the ship. In WWI biplanes with incendiary ammo needed to first fire a couple of hundred shots into the airship, then wait a few minutes for diffusion to cause enough hydrogen to mix with the air before returning and actually setting that hydrogen outside of the airship on fire. If the airship's skin then also catches fire more hydrogen is quickly released to mix with the air and keeps the process burning. During WWII there was even a ship that got caught by Axis flak weapons twice, lost about 50% of it's lifting gas and made it home without going up in flames or crashing. Compare that to say an modern (or old) aircraft that would lose 50% of it's lifting surfaces in combat, very few aircraft are able to take that punishment and make it home. It's speed: Airships are seen as slow, lumbering beasts. Yet even the WWII airships could reach 130km/h. You could say "but compared to other aircraft that is slow", but that's an unfair comparison. It's like saying "ah but my racecar is faster than your truck". Yes it is! But your racecar cannot haul half as much cargo as my truck and my truck can do so for a lot less fuel per cargoweight carried. It's safety measures: A crash like the Hindenburg could have happened by venting hydrogen, which hybrid airships wouldn't have to deal with, or leaking. Leaking can be reduced by having more gasbags and redundant safety measures. Non-flammable envelopes and gas bags can increase safety measures, as can the application of self-sealing materials, buffers and compartimentalized gasbags. If one gasbag gets punctured or even burns up completely, the other gasbags can be insulated enough not to catch fire. Similarly you can reduce fire hazards by adding a helium mix to the hydrogen (if necessary by putting the hydrogen gasbag into a gasbag with helium). This means that the hydrogen will have a harder time mixing with enough oxygen to become flammable and stay flammable while not going for the full cost of a helium airship. Another good safety measures is modern sensors. The Hindenburg couldn't measure it's leakage very easily and many airships crashed in storms or due to human error because sensors and modern weather control wasn't available. Just like ye oldy aircraft frequently crashed due to storms and human error because we didn't have the sensors and weather control data to keep them flying but those same measures have made them incredibly tough to crash (unless once again human error causes a lack of maintenance or design flaw). Tl,DR: Modern materials, sensors, knowledge, design, use of hybrid airships, safety measures and all the good stuff we've been using for modern aircraft would make a modern airship extremely safe. Their ability to get quite literally shot at and still make a safe landing several hours later makes them the safest, most resilliant aircraft available to mankind. The biggest hurdle is public opinion and the time+money to design good airships. Aircraft have been build for decades now, and when you look at the Airbus we see that even today a large aircraft design can be hard to pull off. Modern airships in the last decade or so have been build, but due to public opinion it is hard to find people willing to invest and use airships which is the main reason for airships to fail, not their actual safety. Airships are safe, it just takes time and money. [Answer] Short answer: no, you can't make a safe hydrogen airship. There are basic physical and chemical reasons for this. First, hydrogen is the most flammable element, ignitable in mixtures with air from about 4% to 94% hydrogen. That means the smallest leak, in either direction, produces a hazard of (explosive) ignition, and a hydrogen fire is effectively impossible to extinguish (flooding with inert gas is the only practical method, and that carries an immense weight penalty due to the amount needed to flood an entire airship envelope). Second, airships, by their nature, *must be* fragile. This is a machine that has to float like a soap bubble; the entire rigid structure and payload must have an overall density the same as that of air (at operating altitude, which is typically less than ground density). Any attempt to strengthen the airframe must generally be applied to making the same soap-bubble construction lighter, so the total hydrogen required to float is reduced -- because making the whole ship smaller is better than making it more rigid or stronger, both in terms of cost and safety. Third, as noted in comments, airships must be moored by their nose, which means each ship needs a circular space with a radius slightly larger than the length of the envelope. Where airliners can be parked with their wings interlaced, so passenger capacity of thousands will fit on a football field (either kind), a single airship that can carry a couple hundred won't quite fit in the same space. Plus, the airship (when moored outside) must be allowed to swivel around the mooring tower, like a ship turning at anchor with the tide or current -- because the wind shifts. There was an incident in which a complete wind reversal (180 degree shift without blowing in the intervening directions) flipped an airship vertically over the mooring mast -- and since the ship was intentionally heavy while moored, the weight of the ship collapsed the nose cone of the envelope frame. Related to this, they can't be loaded and unloaded with passengers sheltered, the way modern jets are -- rather, the passengers would, at best, be carried to the ship by what amounts to a tall bus, and the ship would be subject to movement while attempting to load passengers and cargo (since it can't be rigidly tied down, due to its fragility). There have been airship hangars built, which do a very good job of protecting the airship -- but they still take up a huge amount of (expensive) real estate compared to aircraft hangars (they're big enough to have *their own weather* inside), and it's a long, slow production to move the dirigible into and out of the hangar, with the slightest turbulence or crosswind being a recipe for disaster. Another concern is "hydrogen embrittlement". Most if not all metals in contact with hydrogen will absorb the gas into the metal's crystal matrix. The hydrogen then causes defects to form in the lattice, resulting in the metal becoming brittle. If the hydrogen never gets into contact with the metal structure, well and good -- but hydrogen also diffuses through almost anything else (not quite as badly as helium, the molecule is bigger, but it still does it). This also means you can't prevent hydrogen leakage. Finally, airships are *slow*. The *Hindenburg* -- arguably the most advanced airship ever in commercial service -- had a top speed of around 100 mph and cruised at about 80 mph (160 and 130 km/h respectively). It took *days* to cross the Atlantic from Germany to New York City. This was comparable to airplanes of the day, except that the *Hindenburg* could make the trip non-stop, where airplanes of the early to mid-1930s could not. However, since then, airplanes have increased speed by a factor of four or so (for commercial transports), and airships likely can't be made to do so, simply because of the amount of power required to punch that immense gas bag through the atmosphere. The highest cruise I've seen for a proposed modern airship was around 200 mph (320 km/h) [Answer] ## Yes, to some extent at least. All the progress we have atm is helpful, all the new materials, and approaches - we definitely can do better than it was done 90+ years ago. And [LZ 127](https://en.wikipedia.org/wiki/LZ_127_Graf_Zeppelin) had 590 flights, 17,177 hours, and 1.7 million km under its belt. And it had hydrogen as its lifting gas, so as hydrogen as part of its fuel, that [Blau gas](https://en.wikipedia.org/wiki/Blau_gas). And that isn't bad, even by modern standards. with modern material and technologies, we sure can improve it, and expect more safety and miles on it. However it does not mean we can do that immediately, this is interrupted technology, even if there are some modern versions of airships. But if we would like to have it to be used more, we will need to go through interations of development, testing, operation, improvements and maturing. Hydrogen is **not** the only lifting gas, another one is methane - yes, it has half of the lifting power, but if we consider Blau gas as well the LZ average lifting 100k m3 hydrogen and 30k m3 of Blau gas average lifting density of available gas volumes was 0.370kg per cubic meter, and methane is 0.657kg - so the difference in lifting capacities is 70% of its hydrogen analog. They used Blau gas for keeping the same buoyancy during the flight, but we, as carbon neutral party, can easily compress some percentage of co2 from engine exhaust for the same purpose, it does not require that much effort. ## what difference it makes permeability of hydrogen is notorious, and it is one of the challenges, to make things safer, and methane is better for our purposes by that aspect. So as it is available in great quantities off the shelf. Methane also is a product and good portion of natural gas which is carried over long distances by [LNG carriers](https://en.wikipedia.org/wiki/LNG_carrier) and [CNG carrier](https://en.wikipedia.org/wiki/CNG_carrier). They carry that gas in liquified form or in compressed one(at 250 bar), so as that gas is transported by pipes in huge volumes, where the pipes are available. Meaning there is a demand to haul it in big volumes. All three approaches have their cons and pros, liquifying isn't free, pressure 250 bar is quite demanding for big volumes, pipes have to be built and they have no flexibility in where they deliver stuff, etc. Airships could be another means to deliver natural gas - which could propel the development and mature of that technology. Advantages are no need to liquefy the gas which dumps big installations dedicated for that, and basically, refueling may happen out of the well. Neutral buoyancy is achievable with pressures less than 2 bars which put less demands on the materials, less than 250, so as it within the capacities of materials we may use to build that airship. So one LNG tanker is from 18'000 up to 266'000 m3 of liquified gas, 422 tonne per 1000m3 of liquid gas. For a potential airship if half of the lifting capacity is the mass of construction of that ship then per each 400t of lifting gas it can carry 200t of cargo(oil as an example). or 1.25 bar with no cargo. ## what other advantages it may have Airships are not bound by land or sea - so one can have shortened, more direct routes aren't limited by restrictions of canals, delivery can happen when it needs to be, no need for pipes to shore/port. with that "400t of lifting gas, it can carry 200t of cargo" there clearly is a problem, u can't unload more than 50% of that gas(can't is a bit too strong, but other approaches require more doings, not necessarily worth it), but there is also a thing other means will have a hard time to have - energy-free delivery using [Jet stream](https://en.wikipedia.org/wiki/Jet_stream)'s which are high altitude wind/air flows. (solar powered is also an option) Those are proposed as a potential energy source because "*Winds at higher altitudes become steadier, more persistent, and of higher velocity.*"[[6](https://en.wikipedia.org/wiki/Airborne_wind_energy#High-altitude_wind_for_power_purposes)], so as they were one of the factors behind [Loon](https://en.wikipedia.org/wiki/Loon_LLC) (internet access, worldwide through high altitude balloons, atmospheric [Starlink](https://en.wikipedia.org/wiki/Starlink) equivalent) All those winds also need some technologies and have their challenges and bring some difficulties, but wind power tries to comeback even on an oil tanker's so ... ## what we are better at, than in old days Variety of materials which are available to us today, and means to shape them and strengthen them with different kinds of fibers(basalt fibre is suffice no need for carbon) - that one is clear and obvious, so as helpful to make airship to come back. Less obvious, for this application, ofter overlooked one - we are way much better at detecting things, in this case, gases leakages, etc. if we combine that - in old days they had no other ways than have a single layer gas cell, but we can have a multilayer structure, a typical double-hull strategy used in the oil tanker industry. There are 2 aspects to the design - detect leakages, and recuperate the loss of gases due to permeability or internal shell damage, and preventing mixing of it with air. we can easily detect different gases at ppm concentrations (parts per million) or better which way less than any combustible mixture ratios(parts per hundreds). Thus we can be aware of what and why happens inside out lifting volumes, and offset some naturally happening processes(gas permeating) and small leakages due to wear and tear. And thus we can say when and what needs a service and most likely where it needs it and how much. * by double layers I do not mean something drastic, it can be the same gas cell, just two layers of the same(or not) material with some spacer in between in which we can have neutral gas flowing, carbon dioxide as an example(Dichlorofluoromethane, Propane, etc), a flow of which carries away any leakage and is collected in some membrane separator, to recuperate lifting gas, and place it back. Those two factors are the main factors for my yes answer. uncertainties are mostly because advancement in other areas does not make us automatically good at designing and building airships. plenty of research and development needs to be made, and it needs to build some expertise at using them and ironing kinks we may oversee at the beginning. practice makes perfect, and there are commercial use cases for the technology, beyond current use, to help development and usage. And in general, airships do make sense, not worse than current cruise sea ships. And that can allow visiting paces which not possible to reach by sea alone. They do make sense as cargo delivery means, for medium and long distances. if no free energy of wind then they can't beat sea transporting, but at slow speeds(20-40kmh), they are not much worse than railroads efficiencies, which potentially places them at 3rd place in terms of energy-efficient means for cargo transporting. So maybe one thing we are waiting for is another Elon Tusk, who has the money and a will/a taste for them At least as it looks on a napkin, if we dive into details it may or may not look better or worse, but some development with modern approaches do happen so it not a totally dry field. [Answer] ### Current tech no. Near future.... maybe safe? **Safe? Maybe. Practical? Doubt it.** To make a hydrogen airship safe, you need to design it such that a leak and flame does not lead to the destruction of the air frame. If a modern Hindenburg was to catch fire while airborne, it should be able to recover after jettisoning some ballast. If it catches fire multiple times such that its losing lift and cant recover, it must be able to navigate towards an open area, set down in the field, evacuate all passengers and crew within 90 seconds of coming to a stop (airline standard).... **without burning anyone or dropping them to their deaths!** Hydrogen in air burns at 2045 degrees C. So you need to find a substance that's: * is extremely light. * is extremely strong * is airtight * doesnt combust or melt at 2000 degrees C And build your airship out of that. Few layers of Graphene sheets for the gas cells, and carbon nanotubes for the structure. (Or carbon nanotubes for the whole structure if graphene seeps hydrogen). With melting temperatures of 3500-4000 degrees, these wonder materials will stand the heat. Graphene will loose strength after at a while at 900, but with a bit of experimentation a design could be found such that one gas bag leaking to air and igniting just burns out - it doesn't rupture its neighbours and cause a chain reaction. Graphene is also light enough that you could double hull your hydrogen gas bags adding further safety, such that a puncture only leaks the tiny margin of hydrogen on the edge, rather then the entire bag. No it wont make airships practical again - especially with aircraft manufactures actually looking at hydrogen powered aircraft. But they could be made safe from a fiery death. [Answer] **Hydrogen-filled aerogel** An [aerogel](https://en.wikipedia.org/wiki/Aerogel) is a synthetic solid material with very low density - most of it is gas. [Graphene aerogel](https://www.extremetech.com/extreme/153063-graphene-aerogel-is-seven-times-lighter-than-air-can-balance-on-a-blade-of-grass), sans air, is seven times lighter than air. If it is filled with hydrogen rather than atmospheric air (mostly nitrogen), such an aerogel will be far lighter than air. Since hydrogen can't burn unless exposed to oxygen, you just have to seal the blocks of aerogel with a thin, airtight layer. If exposed to a lot of fire, I imagine that the material will be quite flammable, but it would not be explosive. It would probably be safer than tanks of jet fuel, which can be quite explosive. Compartmentalization between fireproof walls combined with [gaseous fire suppression systems](https://en.wikipedia.org/wiki/Gaseous_fire_suppression) would likely making it very safe. ]
[Question] [ This is the second question in a series about my ongoing worldbuilding project, which seeks to explain the evolution and biology of various fantasy creatures. The first one was: [Is petrifying vision plausible?](https://worldbuilding.stackexchange.com/questions/113648/is-petrifying-vision-plausible-in-an-animal) Now, I ask you to review a concept I developed myself and inform me of its plausibility. The hydra is a well-known beast featured in Greek and Roman mythology - a serpentine, many-headed beast that lives in swamps. In my project, hydras are portrayed as amphibians that mate like Ceratiid anglerfish - males fuse themselves to the larger female's body and mate with her throughout her lifetime. Eventually, the circulatory systems fuse, and the hydra becomes a chimera. The reason that Ceratiids to do this (It is thought) is because encounters between individuals are very rare, and mating opportunities must be exploited to the max. Similarly, my hydras are also naturally rare. To give you an idea of the exact life cycle of a hydra, here's a rough summary: 1. All the hydras in an area will be born at the same time due to the short period of the hydra's life where it is mature. This is for predator satiation - the predators of young hydras (Namely giants) are overwhelmed by a relative feast of prey, thus letting the majority go. 2. The male is born and immediately moves to find a female, which may take weeks or months. During this time, he grows from the size of a salamander to that of a man. 3. When he finds the female, he attaches himself to her body and begins to mate. 4. Every time fertilization occurs, the female lays an egg. However, hydras are constantly moving, so eggs are often far between. 5. Eventually, the female will have between 6 and 15 males attached to her. Hydras live only to mate, and she - and all her mates - will soon die. How plausible is this premise? Is it possible that such a phenomenon would evolve in a creature of said anatomy, and are there any problems that it would cause if it did come about? If you require any further details on these creatures, think it is unclear or too broad, or have spotted an error, please say so in the comments and I shall amend the question promptly. Also, if you do give it a VTC, *please* say why, as closing a question without giving criticism is wholly unhelpful. [Answer] /Hydras live only to mate/ Life stages that live only to mate (e.g. adult cicadas or mayflies) do not grow, because they do not eat. So your hydras would stay the size they were when they became adults / reproductively mature. If your hydras are rare and males immediately start looking for a mate, they will find their sisters. You need to have them less rare, or some sort of group egg laying site (like salamanders) or some dispersal phase or your hydras will suffer from consanguinity. Other organisms with parasitic / multiple males have a big size discrepancy. The females are much bigger because they contribute body mass / energy to eggs. The males contribute only sperm. If you have a parasitic male that attaches for the long term that implies the female has a long term survival - like a female anglerfish. If your female does not eat she does not have a long term (unless perhaps she were truly immense - but still she will use up her reserves quickly). I do not see any selective advantage to the male, the female or the offspring from having two shortlived parents irrevocably joined for their short lifespan. --- If you have a cicada like life stage that lives only to mate, you need a larval stage where the hydras accumulate energy and body mass. This could also be your solution for dispersal. The larval hydras could be aquatic, highly mobile and disperse widely. It is not until they metamorphose into the adult stage that they carry out the behaviors you describe. Some fish assume gender according to bodily resources - the big ones become female because they are big enough to do it, and the little ones are male because they do not have bodily resources to make eggs. So too your larval hydras - the rare lucky ones grow big and then become female. [Answer] **Temperature dependent sex determination.** [This](https://en.wikipedia.org/wiki/Temperature-dependent_sex_determination) how you get one long-lived large monster with several heads. Mummy Hydra lays eggs throughout the year. The Summer eggs hatches all females that feed and grow much like crocodiles. Most of them are picked off by predators early in life. Those that survive reach mating size in about five years at which point they emit pheremones to attract males. The Winter eggs hatches all males. Males immediately begin searching for a nearby female to attach to. Most of them fail or are picked off by predators. Those that find a mate are ensured safety by the size and strength of their motherwife. This way the adult symbiote monster can live a long time and grow to monstrous size through its lifetime. You also prevent siblings attaching to each other which is bad for genetic diversity. **Edit:** Rather than laying throughout the year I suggest two large clutches in Summer and Winter respectively to 'overwhelm' predators as you suggested. [Answer] If they only live to mate, wouldn't it make more sense for them to protect and look after their eggs? And how can Giants feast on them if the eggs are spread wide and far apart. It feels like you want a creature with a turtle like egg laying pattern, rather than an Angler although you could just borrow the fertilization part. It would make more sense, that after the hydra accumulates 5-15 males, she rests and lays eggs until she dies. Her corpse becoming food for the new generation and the sudden boon of 1000's of baby hydras confusing any giants who are nearby. ]
[Question] [ Let us imagine a human-sized mantis (1.7m tall, 70kg / 5'8", 154 lbs.), but with the forelegs modified to have a shape closer to human arms. So each arm would have two main segments, and end up in a multi-segmented, multi-fingered, grasping-capable hand. In order to make this creature feasible without violating the square-cube law, let us imagine that it evolved a closed circulatory system and a pair of huge, highly vascularized and alveolated lungs, capable of expanding and contracting just like ours. Add a diaphragm, just because. The mantisman would have tracheas only in the abdomen, and those tracheas would lead into those lungs. **Its metabolism and phisiology would be on par with ours.** The point where such a creature differs from us is the skeleton. This creature's skeleton is its external chitin layer. The muscles are inside and attach to their skeleton in a different way, compared to us. [![I wonder is besides grasshoppers there are also lawnhoppers and woodshoppers](https://i.stack.imgur.com/A46d8.png)](https://i.stack.imgur.com/A46d8.png) I know, not a mantis, but it's the best image showing insect muscles that I could find. What I would like to know is how this creature's musculature would compare to ours regarding strength, more specifically lifting and carrying weight. Other aspects of strength, such as arm-wrestling or doing pull ups would be appreciated, but are not needed for this question. **Edit:** I know that some insects and arachnids are capable of feats of strength, such as ants and spiders being able to lift many times their own weight. What I don't know is if that would scale up with size, nor if the reason they are able to do so is directly related to their muscle arrangement. [Answer] Very general answer, because you do not seem to care about scaling a mantis, but rather seem interested in something human-sized that looks like a mantis and has an exoskeleton (man-tis): * The **peak** force of muscles scales with their cross-sectional (c-s) area. Things like holding force, lockability, fatigue, they are all dependent on the concrete physiological implementation. So a man-tis with human-size, human-style muscles is human in that department. * The **breaking** force of muscles and tendons also scale with c-s area, which is good news, because with an exoskeleton, there is more area to attach the tendons to - no more pulled tendons for man-tis! * **Joints will be a major headache** - humans often use the ball-in-pan system or one of the variations, which has the nice property of keeping the area involved in taking the strain somewhat constant with angle and, more importantly, keeping the area involved as big or bigger than the c-s of the bones forming the joint. Man-tis will not have that. Joints will be more like flexible rings of the exoskeleton, stabilized by fibre-direction (in those leathery membranes) and hydrostatic pressure. They will hold up fine, but quick movement might go out the window because those pressures need to be coordinated. Furthermore, limb-angles may exist that penalize force applied over long time. * **Tubes are much more stiff**, compared to rods of the same weight, so that bodes well for the exoskeleton, but making a tube with the outer diameter of a muscular arm from just the material contained in an arm-bone will result in a terribly **buckle-prone** (because thin walls) tube. You can offset that with internal pressure (which will need some structures containing and producing it) or additional material - both solution take away c-s area that could otherwise be used for muscle (and is, in a human) * this point is very important, from the point of view of your question: Armwrestling. As you know, if you have armwrestled, angles, lengths, ratios, geometry of the contesting arms and attached wrestlers - all need to be considered. **With everything else being equal**, the slightest advantageous twist of the hand will produce a superior angle of attack, leading to the inexorable defeat of the other. In our scenario not all is equal - general mass, yes, muscle physiology, yes, but everything else is different, and not better/worse different in a clear-cut way. **One could just as easily construct a man-tis winner or looser** - it all depends on the specific angles of attack and muscle c-s coming to bear, in a prolonged contest maybe even the circulatory performance to muscles under strain. * In a (wo)man-tis/(wo)man olympiad, with its different contests ranging from fatigue over speed, acceleration, strength to repeatability of movement, i'd see the humans on top, primarily because an olympiad was conceived by humans, and is therefore tailored to their abilities (a man-tis has two (three?) sets of arms, which one is allowed in weight-lifting? or may man-tis use them all?) * To resumé: Contests will be tailored so the contestants are comparable, which is why most sports have categories for children, elderly, men, women... a human/man-tis olympiad will be boring, because there will be no contest. Some categories will be won by man-tisses all the time, some by humans. Boring. 'Lifting force': I struggled with lifting my printer the other day, although i routinely lift cement sacks five times its weight, simply because the box it came in was designed in such a way as to make every way of holding it incredibly disadvantageous. Man-tis may be able to lift ten times more weight than humans, but only five inches up, and a tenth of the capability of humans over its head - does that make it stronger or weaker than humans? **Man-tis can exist, with the alterations you already proposed to its respiratory system, but the exact strengths and weaknesses are completely up to you.** [Answer] An explanation of the body stresses that a scaled up insect would have to deal with is here under Session 5 Giant Ants Attack! - <http://fathom.lib.uchicago.edu/2/21701757/> It talks about the mechanical stresses on the exoskeleton to support the weight of the larger insect, and the joint structure of insects. A key paragraph about the joints from the above article - > > One estimate suggests that mammalian joints are called on to withstand forces as much as 100 times the animal's body weight during normal locomotion. (In humans, the peak forces on the knee during running can be 15 times body weight.) Arthropods, even though they have more legs than mammals, have it even worse; their joints may see forces as great as 3,000 times body weight, 30 times higher than mammals. Because joint contact areas are much lower in arthropods than vertebrates, the difference in stresses must be much greater. Now we come to the heart of the matter. As you scale up an ant, body mass must increase faster than joint surface area--indeed, the stress on the joint should increase in direct proportion to size. > > > The preceding paragraphs explain why the arthropod joint is required to withstand the higher forces. [Answer] > > I know that some insects and arachnids are capable of feats of strength, such as ants and spiders being able to lift many times their own weight. What I don't know is if that would scale up with size, nor if the reason they are able to do so is directly related to their muscle arrangement. > > > What reliably scales with size is **power** output of the muscles. Power is produced chemically and is subject to several hard constraints. ATP and Pcr stores in the muscle limit peak power; the cardiovascular system's oxygen throughput limits sustained power. Based on the power constraint alone, a creature of a given size can carry 1000 times its weight at 1 cm/second, or 1 times its weight at 10 m/s (force\*distance/time=const). How this power is distributed between force and speed will depend on the creature's exact physiology. I've seen feats of nature impressive enough to lose belief in evolutionary impossibility. The outward effects of adaptation for high strength/low speed would be thick short limbs and vice versa. The mammalian endoskeleton is generally more favorable for high speed and high instantaneous force than an exoskeleton. The joints are compact, the muscle is well-cooled and has a lot of room to change shape. In comparison, an exoskeleton is like an aircraft fuselage, it's good at distributed static loads, but not at strong shocks and high acceleration. Force on the skeleton is determined largely by acceleration, so running fast would be riskier for the mantis than a mammal. Carrying weight, however, would be a lot more efficient, with most loads going through the exoskeleton. So the human-sized mantis would likely have good strength and excellent ability to carry loads, but not be as good as a mammal at jumping and running. Its sustained strength would be determined by its cardiovascular system. To make good use of its muscle, the mantis will need to circulate at least twice more blood, as both a coolant and an energy source. In the gym, it's going to be very good at most weight exercises, doing dozens of reps (given good circulation). But not as good at complex full-body exercises, because of the system's limited instantaneous capacity. They won't be good at throwing punches, as that takes explosive strength and speed, but will be good at holding force. Carrying as much as 5x own weight over long distances, but not very fast, should be quite doable. Perhaps 10x if someone else puts it on their back. It takes a lot less muscle effort to keep their exoskeleton straight than it does for a flexible bipedal human. Arm-wrestling between one another will be viable, but more like how non-wrestlers imagine it - arm vs arm, slowly forcing the opponent down. A human athlete puts their body's force on the opponent's arm in one strong move; it's forceful and would be dangerous. Due to exoskeleton limitations, the mantis population will likely be a lot more uniform between athletes and non-athletes than humans. So they could be able to arm-wrestle amateurs, but at risk of permanent injury if they come against an athlete. [Answer] > > What I would like to know is how this creature's musculature *would compare to ours regarding strength,* more specifically lifting and carrying weight. > > > **Yes, it would be comparable.** So, let's look at the square-cube law another way: *the larger something is, the slower it is in all areas **relative to its size.*** It's metabolism and reaction times slow down, its top speed slows down, etc. It also lifts less mass relative to its own body weight. So scaling a mantis up to human size would result in a mantis with human strength, human speed, human reflexes, and so on. Keep in mind that the average human weighs 45 - 50 kg, and most cannot lift more than half their bodyweight without specifically training in a gym to do so. Even lifting 20 kg (50 lbs for us Americans) **repeatedly** would be a struggle for some. You might be interested in these videos. They'll point out some of the problems with increasing the size of an insect without allowing for how scale determines the way an organism interacts with its environment and changes its metabolism, respectively. <https://www.youtube.com/watch?v=f7KSfjv4Oq0> <https://www.youtube.com/watch?v=MUWUHf-rzks> --- > > Edit: I know that some insects and arachnids are capable of feats of > strength, such as ants and spiders being able to lift many times their > own weight. What I don't know is if that would scale up with size, nor > if the reason they are able to do so is directly related to their > muscle arrangement. > > > No, this does not scale up, particularly if the mantisman has the same metabolism as a human. In a certain sense, metabolism is a way of talking about how much energy an organism is capable of producing. Because smaller organisms have faster metabolisms, they produce the energy necessary to lift many times their own mass. They also have a higher surface area to mass ratio, providing more surface area for interior muscles to connect to and generate force from. In contrast, a mantisman with human metabolism is going to have much less energy to lift with, and a lower surface area to mass ratio that reduces the amount of area the muscles can use. [Answer] The issue with human-sized insects, or the [Attack of the 50ft Whatever](http://tvtropes.org/pmwiki/pmwiki.php/Main/AttackOfThe50FootWhatever), is as mentioned in the comments, the Square/Cube law. Specifically, if you double the dimensions of an object, it's mass increases by eight times, however muscle strength only increases by the cross-dimension surface area, which will increase by 4 times. Thus, a higher proportion of the creature's strength must be dedicated to moving itself, leaving less available for other tasks, like lifting food to your mouth. The reason why muscles only increase by a factor of two, is because we care about muscle strands. It doesn't matter how long the strand is, what matters is how many there are. Thus making your arm twice as long just makes each strand double in length. It's only when you also increase it in the other two dimensions does you muscle gain power, as there is now four times as many muscle strands. The other issue with giant insects is that they don't have lungs, but instead use [Spiracles](https://en.wikipedia.org/wiki/Spiracle), but that's not the focus of your question. ]
[Question] [ I'm aware that 'tatooine' worlds don't make good habits for planets, normally. From what I've read, either a planet has to orbit one star really closely, or orbit both stars from a really long distance away. I envisioned a kind of double solar system, where there are two stars that are close enough to orbit one another, but far enough away where they can each have planets of their own. In such a situation, its possible to have habitable worlds orbiting both stars, but they would be conceivably close enough where intelligent life from these worlds could potentially have some awareness of each other, and possible communication, even with our own current level of technology. Of course, orbital calculations are beyond me, and from my understanding would require a supercomputer to work out. I don't believe I've ever heard of an actual 'double solar-system' like this, which would lead me to believe that such a thing is not possible. If it matters, I wasn't thinking of either of these stars as having that many planets. The stars are close enough where outer-planets like in our system simply can't exist. And one only has one planet: a gas giant, with multiple habitable moons. The other is more like our solar system (well, inner solar system anyway, there's only 3 or 4 planets). [Answer] ## Yes, and the planets can orbit in the habitable zones. [This page](http://exoplanetes.esep.pro/index.php/en/maps-en/2-uncategorised/584-planets-in-binary-systems) gives a long list of planets in these S-type orbits, and states > > For a few systems (2 so far), there are planets orbiting each member of the binary. In this case, the system is divided into two "binaries", one where the first star is the "central star" and the other star is the perturbing companion, and another one where the roles are reversed. > > > It's important to note that many of the planets in S-type orbits are quite close to the main star they orbit, meaning that the influence from the other star is small, and the orbit is stable over reasonably timescales. This shouldn't preclude a planet from orbiting the other star in the system. One thing that's worth noting is that binaries where S-type orbits are possible usually have a large separation - that is, the stars are pretty far apart. This makes it possible for the planets to be in a larger range of orbits, meaning they aren't restricted to orbiting close to one star. Therefore, in wide binaries, it's more likely that a planet could orbit in the habitable zone of one of the stars. ## Examples I've been able to find (to be updated): * [WASP-94](https://arxiv.org/abs/1409.7566), a pair of F-type main sequence stars, each with a close hot Jupiter orbiting it. * [HD 20781](https://en.wikipedia.org/wiki/HD_20781)/[HD 20782](https://en.wikipedia.org/wiki/HD_20782), two G-type stars, each with 1-2 planets (one at 1.3 AU orbiting HD 20782, two at <1 AU orbiting HD 20781). * Kepler-132, a pair of G-type main sequence stars, although the structure of the system has been disputed. * [XO-2](https://en.wikipedia.org/wiki/XO-2_(star)), two cool K-type stars, with a confirmed hot Jupiter around one star and two possible planets around the other. I've found these by perusing [a list of exoplanets in binary systems](http://www.univie.ac.at/adg/schwarz/binary.html) and doing some cross-checking. Doing [some simulations of the HD 20781/HD 20782 system](https://worldbuilding.stackexchange.com/a/120364/627) indicates that it should certainly be habitable. The two stars are separated by ~9000 AU, both are G-type stars like the Sun, and stable orbits exist around 1 AU, in the habitable zones of the star. The same goes for the other systems, which also have extremely large binary separations. To make a long story short, yes, this will work. [Answer] ## Here is how you do it: <https://www.youtube.com/watch?v=mVh84wBCP_s&t=0s&list=PLduA6tsl3gyi72fEb-_zWk_yh8XkEWfjT&index=5> Edgar has a really great series on how to calculate everything you need to know about solar systems, as well as how plausible different types of systems are: <https://www.youtube.com/watch?v=IE805Vdm0sk&t=34s&list=PLduA6tsl3gyi72fEb-_zWk_yh8XkEWfjT&index=6> Edgar's series is great, and it seems a shame I don't see him cited here more often. I'd also check out barycenters. <https://en.wikipedia.org/wiki/Barycenter> You might notice that this particular orbit: <https://en.wikipedia.org/wiki/Barycenter#/media/File:Orbit5.gif> is the one most commonly associated with S-type systems, but that *doesn't* mean that the stars in such systems always have the same mass, as the gif suggests. Have fun! [Answer] It seems strange to me that someone would even ask that question. I think I read that as a general rule, if Planet A orbits star B at distance C, another star D in that system will not destabilize the orbit of planet A if star D never gets any nearer to star B than a distance of about 5 times distance C. The nearest star system to Earth, Alpha Centauri, is a double star. And it has often been calculated that planets orbiting in the habitable ones of either Alpha Centauri A or Alpha Centauri B would have long lasting stable orbits. Earth orbits the Sun at a distance of 1 astronomical unit, or AU. The equivalent distance around Alpha Centauri A would be a little larger, and that around Alha cCentauri B would be a little smaller. Since the two stars never get any closer to each other than 11 AU, any planets that might be in their habitable zones should have orbits stable for a long time. And there are many other binary star systems in which calculations indicate that any planets in the habitable zone of one of the stars should have stable obits. Of course there are many binary star systems where the two stars are too close for planets orbiting one of the stars in the habitable zone to have stable orbits. There are even stars so close together that a planet could orbit in the habitable zone around both of those stars and have a stable orbit. ]
[Question] [ **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. [In Lyman Stone's fantastic blog post about George R. R. Martin's A Song of Ice and Fire series,](https://medium.com/migration-issues/its-okay-that-westeros-is-poorly-designed-f11e473b13ac#.qu8gmynyl) Stone mentions that the seasonal cycle of Westeros is very unrealistic. > > Here’s the truth: Medieval societies probably could not survive 6 winters in a row. Even modern societies would be hard-pressed to survive that. It’s not clear that any large-scale civilized life with organized polities could withstand a decade without a growing season. > > > Yet Westeros does it a lot. We don’t know how. We don’t see any of the things we would expect to see in such a society. Cities and castles should have incredibly vast storage facilities, on a scale unthought-of in Medieval Europe. But that’s not what happens. Cross-Sea trade connections should be spectacularly robust. They don’t seem to be. I mean to ship the cereals needed to feed the winter-hit areas for decades on end would require almost a post-modern level of globalized trade flows. > > > Is he right? Let's do an experiment. Let's take **medieval England** (or a similar region) and change one thing -- we'll make the winters last for two years and the summers last for three years. Would humans be able to survive? What technological and societal changes would be needed? There's a lot of factors to consider, but to make things simple, let's just focus on food (i.e. how much additional food would need to be stored during the winter, etc.). Let's ignore questions like whether houses need to be constructed differently do keep people warm, etc. --- NOTE: This question is tagged as [hard-science](/questions/tagged/hard-science "show questions tagged 'hard-science'"). This means that answers should be based on evidence, not conjecture. At a minimum, answers should contain the following: 1. It should cite reputable sources that explain how medieval England (or a similar region) obtained food during the winter. 2. It should perform some sort of calculation to determine how much additional food would needed to survive the extended two-year winter. 3. It should then propose realistic solutions to the challenge of storing food during the winter. The answer should use some sort of calculation to determine how much food each solution would contribute (e.g. increased trade could supply x tons of grain). --- An additional note. Although I begin this question by talking about Westeros, I am only interested in answers that focus on medieval England (or a similar region). I'm not interested in answers that talk about Westerosi technology. This is a hard science question, and therefore I'm interested in how *the real world* would be effected by extended winters. [Answer] Yes, I think it can be done. First, let me direct you to [this question](https://scifi.stackexchange.com/questions/132901/what-do-people-in-westeros-eat-during-winter) and its answers. One point that's well made in Ram's answer is - you are assuming everyone will survive. Or even most people will survive. Your world, with three year summers and two year winters, is milder than the assumptions in that question (which mentioned six years)... but a lot of people are still going to die, especially the ill or sickly, oldest and youngest, the poor (including beggars, the crippled, those without sufficient safety nets), and some percentage of serfs or peasants, with the expectations that these people will, over time, breed enough to cover the loss. It would be rarer to lose the richer, the better connected, those with valuable training, nobles and royalty (and their favorites). Their deaths would still occur, but the danger to them would be somewhat offset by *money*, that enabler which could let them afford the very best in preservatives, techniques, and an abundance of many rare things that would increase their chances of life - like honey, which by itself lasts decades and preserves beautifully ([Crystallized fruit](http://www.histoiresucree.com/fruits_confits_history.html) might contain nutrients for years). Or the best in whatever foods do keep nutrients, cheeses, meats, dried fruits, and fresh whatever can be foraged or hunted or force-grown in the winter. This happened in *real* medival times, it can happen in yours, too - and with the continuation of the upper/controlling levels of society, the society itself will continue despite the loss of those considered expendable. With a scale of three-to-two for summers and winters, - um, wait, how does fall/spring fit into this? A few extra years for the full four-season's cycle, or carving out time between the two extremes? Nevermind, with the season cycle weighted to have more growing season than dead season, it's likely that the amount of food produced during the whole 5-year-year is sufficient for a 5-year-year... if they produced in each month of summer, as much food as our medieval society produced in each month of summer, and stored for the winter the same percentage of food our medieval folk did, and lost the same percentage to spoilage, they would find they had relatively more food (by three-to-two) as our medieval folk had for the winter. Of course, they would probably eat the extra in summer instead of saving it and either be stronger to survive the winters or feed more people in the summers and lose more people in the winter, but the point remains, enough food can be produced. The problem is preserving it for a scenario where the growing doesn't happen in smaller regular intervals, but instead the results of a single much longer growing season must last for a much longer timeframe during the winter season. They would need a lot more storage space, minimum 5-8 times as much (8x for going from 3 months to 24 months of stored provisions, or 5x for storing for a five-year-year). At that amount of space, they may prefer to build stone or [earth](https://en.wikipedia.org/wiki/Earth_structure) warehouses, thickly insulated with [sod](https://en.wikipedia.org/wiki/Sod_house), instead of the more usual dug cellars which might destabilize houses at 8x. This would be less efficient during the summer, since it would be less insulated and therefore less temperature-stable, but the cold weather during the winter would help keep everything preserved. So, lets look at foods and their preservation. First, there are foods that are already preserved for two years or longer, that in fact are considered better for longer aging - cheeses, meads and wines, long fermented or cured foods (which today are gourmet or luxuries), could be preserved for the two years required. Of course, these will also be expensive - but the upper class could afford them, which is kind of the point. Then, there are more common foods that can be made to keep a long time. The [methods of the time](http://www.ling.helsinki.fi/~vaasjoki/exlibris/medfood.html) include [drying, liberal use of salt to brine or cure, smoking, and pickling with vinegar, verjuice, or lemon](http://historymedren.about.com/od/foodandfamine/a/food_preservation.htm). The use of nitrates, used in preserving meats, was also known to extend shelf life - in medieval times, this would most likely be [saltpeter](https://umeshmadan.wordpress.com/tag/saltpeter-history/), which formed naturally in stables and caves and could also be produced with some effort anywhere manure could be gathered and aged. Saltpeter was most famously known for its use in black powder, which was sometimes used to [preserve meats](http://indianapublicmedia.org/amomentofscience/gunpowder-preserve-food/). One common example is salt cured meat - barrels of salted pork or beef could [easily last a year](http://www.survivalistboards.com/showthread.php?t=147203) and possibly be good for multiple years (one reason it was so common on [medieval ships](http://www.sca.noaharney.com/a-meal-onboard-ship-in-the-16th-century/)), and [salted cod lasts for years](http://ochef.com/714.htm), [salt cured and smoked hams](http://www.countryhams.com/ediblememphis.htm) or procuitto [would take a year to cure](http://www.go2gbo.com/forums/survival-skills-discussion/cured-meat-storage-life/), and [could last months after that without refrigeration](http://ochef.com/714.htm), and some very dry jerkies, fish, or sausages [will keep almost indefinitely](http://ochef.com/714.htm). Then we get to drying. Dried beans [will keep almost indefinitely](http://www.eatbydate.com/proteins/beans-peas/beans-shelf-life-expiration-date/), although after a year or two they will lose their stored moisture, and need longer to soak and cook - though they do not lose their nutrition. Dried grains will vary, some sources suggest [6 months to a year](http://wholegrainscouncil.org/recipes/storing-whole-grains) for grains(although that is *stay fresh for*, not *go bad after*), others suggest [8-10 years for soft grains and 20-25 for hard grains](http://www.heart4home.net/2013/08/grain-shelf-life/) if kept dry, cool, and out of sunlight. Probably the truth lies somewhere in between - grains that are not dried spoil quicker, and grains may lose nutrition and flavor after that six months to a year (but still be edible and have nutrition, just past its "best-by" date), and those dried and kept in favorable conditions may [last much longer than expected](https://www.usaemergencysupply.com/information-center/self-reliance/storage-life-of-dry-foods). And, after a grain has been ground into flour, it could be further preserved by making hardtack - dry, twice baked crackers (also known as ships' biscuits) which lasted at [least a year](http://www.christopher-columbus.eu/food.htm) in the [very poor conditions](http://sarahs-history-place.blogspot.com/2011/10/food-of-nelsons-navy.html) found on ships, but which might last and be eaten [fifty or a hundred years](http://www.askaprepper.com/hardtack-biscuits-100-year-shelf-life/) later if kept in better conditions (without killing or starving the eaters). Fruits can be stored by drying, either in the sun or an oven. Such will last at [minimum 3-6 months](http://www.eatbydate.com/fruits/dried-fruit-shelf-life-expiration-date/) at peak condition (at room temperature), and will still be edible possibly for years afterwards with less flavor and nutrition, and can have its shelf life extended by storing at colder temperatures. The same is true of dried vegetables (sun-dried or oven dried), [6-12 months](http://foodstorage.pbworks.com/w/page/12969810/Dried-Vegetables) for best flavor and nutrition. Of course, storing at colder temperatures, as would occur during the winter time, will extend shelf life considerably - at least doubling the time it can be stored without additional loss of nutrition. [Pemmican](https://en.wikipedia.org/wiki/Pemmican) was made from meat that was shaved thin and dried thoroughly, and mixed with rendered tallow for storage. [Confits](http://historymedren.about.com/od/foodandfamine/a/food_preservation_2.htm), or potted meat was salted, cooked and stored in its own fats. Rendered tallow or suet was shelf-stable, could last for years, and could be used to block air or water from reaching already preserved food (which spoiled them faster). Pickling vegetables or meats often done with a brine of water and salt, and vinegar or verjuice for better preservation, and herbs and spices added for flavor - such pickles would last for months, and the [nutritive value was as high or better](http://www.answers.com/Q/How_did_people_store_food_in_the_medieval_times) in fermented pickles as it was in fresh vegetables, although often lacking in vitamin C. Additionally, it was known foods lasted longer in cold storage - medieval folk without access to refrigerators could still use this knowledge by utilizing mountain caves or [packing food in cellars with snow and ice during the winter](http://historymedren.about.com/od/foodandfamine/a/food_preservation_2.htm) - which would use the cool temperatures of the underground rooms and the packed mass of snow and ice to keep the foods cold long after the snows melted... [or even mining snow and ice from high altitudes to keep these foods cold even longer](http://www.answers.com/Q/How_did_people_store_food_in_the_medieval_times). In your two-year winter world, that means much of the food stored during the winter would essentially be frozen for much of the time, which can double the shelf life of many dried or otherwise preserved foods. And, finally, not all food production would halt in the winter. Some animals would be kept long into the winter season, fed on stored grass or hay, acorns, or perhaps supplemented with stale or ruined grain, and slaughtered periodically (except for breeding animals) to reduce demands on winter feed. [Pigs were a choice animal to keep](http://www.ling.helsinki.fi/~vaasjoki/exlibris/medfood.html) for the poor, since they are not fussy and could supplement scraps with forage even in the winter. Hunting was also an option, with game animals reserved for nobility and hares and rabbits and such the prey of commoners. A certain amount of [fishing](http://www.regia.org/research/life/fishing.htm) should also be possible in the winter, ocean fishing [fleets](http://www.cliffordawright.com/caw/food/entries/display.php/topic_id/13/id/96/) or individual fishing in rivers or ponds as the temperature allowed. There *may* have been some winter foraging, ([pine tea](http://www.ramblingtart.com/2013/06/12/viking-tea-hungarian-beads-and-a-medieval-breakfast/) was used by iron age vikings, it was a winter source of vitamin C). There may have been some gardening, using [glass gardens](https://en.wikipedia.org/wiki/Greenhouse) or heat produced from [decomposing manure](http://www.buildingconservation.com/articles/pineapples/pineapples.htm) (I admit the time is wrong, but the idea is there), the products of which would be mostly for the rich, but there would be sources of fresh nutrition to balance out the loss of nutrients and flavor from the longer-preserved foods. So how would the society have to change? A *lot*, a *lot* more planning. People would have to regularly store food during the long summers, and have the discipline to store even when there would be plenty of food after the stored food needs to be eaten (using the stored food from earlier harvests throughout the summer, so all of the later harvests can be fresh-stored for the winter). And they might produce more in the longer growing season than simply the summers back-to-back could account for, since they could stagger harvests (and share the labor of plowing and harvesting when it doesn't have to happen at the same time), and have time to forage, and have fewer crops vulnerable to, or growing seasons shortened by late or early frosts. Possibly the planning might take the form of a heavier tithe for the lords, who also might distribute some extra back during the winter, at least to keep enough people for summer farming, when it's harder for people to manage that extra planning for themselves. There would also probably be more time in winter to pick up artisan skills and handicrafts (needed to afford fresher nutritious foods), to tell stories, to figure out ways to survive and improve their lives - things which did happen in winter, but like the growing season of summer, magnified by the stretch of time it covers. Also, preserved food will be losing nutrition and flavor as the winter drags on, and so many people will suffer malnutrition and starvation by the time winter's over even if they have enough unspoiled food to survive - they will have to recover during spring and summer. Better preservation methods or winter foraging or growing methods would be a priority - although it is possible that many foods would be more durable, since seeds (grains and nuts) would have to survive the winters in good enough condition to sprout, and the animals would adapt to surviving the longer season cycle as well, making the whole world relatively the same as ours since it had adapted to all the season lengths. [Answer] Let's start with the types of food which could last that long. Starting with [Long-Term Storage of Special Survival Foods](http://www.thenewsurvivalist.com/long_term_storage_of_special_survival_foods.html#mbp_toc_B): > > The following foods if stored properly have an indefinite shelf-life: > > > * Whole Wheat Berries > * White Sugar > * Salt > * Pure Sorghum Molasses > * Pure Honey > > > Certain other foods, if stored properly, can keep for 5 to 10 years or even longer. All stored foods should be dated so they can be rotated out when the time comes to replace them. > > > * Other cereals, such as oats > * Dried Beans > * Dried Corn > * Rice > * Couscous > * Whole Spices > > > Now, the way in which you have to store them is: get rid of **moisture** and **oxygen**. That's the hard part. Didn't someone find seeds stored in a pot from ancient Egypt or something, and didn't some still germinate? I think you *can* store these foods for this length of time using GoT technology, but at the moment I'm not sure what that method of preservation would be. I would also like to point out that you might be able to store animal feed as well (not sure how long it will keep) and then you can feed that to animals and they'll produce milk, eggs, and meat. Chickens love insects too. [Answer] Well, to be fair, with the foods I have considered (seen) it's not possible. And that is considering modern technology, let alone medieval. <https://www.foodsafety.gov/keep/charts/storagetimes.html> <http://wholegrainscouncil.org/recipes/storing-whole-grains> Both show that, even frozen, shelf life is up to a year in ideal conditions. The only option would be to find a way to grow it in winter, which I'll admit I didn't bother reading up on. The only other option I've considered is the research done by NASA to have food that lasts for years, but that is advanced tech even by today's standards (and I've not read up on the hard science behind it, so I'll stay well clear of debating that). Just to clarify things, this answer is based on 'the greater good'. In other words, because all options other than 'freezing' is off the table for the masses (salt, cheese, wine, dried fruits... all too expensive for the majority), I see no options where there won't be consistent casualties of this world. So, unless the lords of the land make those preservation techniques available to the masses (which likely won't happen), you face a realm where death is the norm. I understand this is the case in George R. R. Martin's work, but that is the exact reason I avoid it in the first place -- as this showcases cruelty for the sake of cruelty. ]
[Question] [ [This answer](https://worldbuilding.stackexchange.com/a/40806/6799) states that "guided evolution" would help babies develop under constant 3-4g's. This answer has inspired me to ask , **what sort of genetic tinkering would help humans adapt to life on a planet with 3-4 G's?** Basic background information: Humans have mastered star travel. FTL travel and FTL communications have been mastered. It is the late 2300's. Humans have decided to found their first interstellar colony. They have chosen a relatively nearby world with 4G's and otherwise hospitable conditions. Human satellites and drones have been surveying this world and mapping it's continents for decades. It orbits a sun-like star, and has no known indigenous intelligent races. Five thousand colonists have set out to establish a settlement. Human technology allows massive biological changes. Humans can not only modify their physiology, but also their genes. Essentially, humans can do anything they want to their bodies at a good price. Assuming infinite ability to change their bodies, **how can my humans modify their bodies to better adapt to the environment of this world?** For the sake of argument, most of the planetary surface is covered in "grasslands" and is dotted with lakes and small seas connected by rivers. There are some mountains, but very few. # EDIT I want humans to be able to survive on the surface of the world on the great plains. They must be able to stand upright and must still be recognizeable as humans. We will assume that food is in abundance and all we need to account for is the plains and gravity. If you want to, you can take other considerations into account, such as adaptations suited for the plains, but for the purposes of this question answers should include anything that helps remain identifyable as a human while providing as much advantage to humans over native life as possible. Some ideas for points to cover might be; * How would we change our inner biology? Would organs be better placed in different places? * Would bone structure require modifications? * How would we modify our bodies to help them bear children? * What about reducing mass reducing weight and muscle strain? It must obviously be biologically possible for the human to survive. [Answer] Make them shorter. There are a number of option to consider, however making your people shorter is probably the easiest thing you can do. If you cut people's average weight by just 10 Kg that turns to 30 or 40 on your planet. You have to reduce mass as much as possible so no fat people on fat earth. Copy the birds. Birds need to be light to fly and need a lot of power to move. Give them strong hollow bones, and powerful muscles. Consider replacing the components of the extracellular matrix that form bones with lighter and stronger materials. Engineer better actin molecules for stronger and more efficient muscles. Your people will also need a very active metabolism since now moving around and everything is 3 or 4 times more energy expensive. The best way would be to have them walk on all four but you probably won't like this solution. EDIT: After some consideration this seems like an impossible task. Let's forget about the 4g and let's stick with 3 that is already more than what we can handle anyway. to survive on Fat Earth you need to: **be short** a 155 cm tall guy is already 150 Kg. Cut the sexual dimorhpism; women will have to do with men as tall as them **be skinny** as I said no fat people allowed **have hollow, rocket grade bones** maybe you can replace the Calcium in hydroxylapatite with the lighter and stronger Beryllium which is in the same group and therefore should be chemically similar **have stronger but not massive muscles** As I said engineer better molecular mechanics for muscle contraction. Bodybuilders are also not welcome since we need to cut mass as much as possible. **eat almost constantly** or at least eat very very caloric food since now everything is extremely energy consuming and you cannnot afford to store energy as fat. Your masochists will probably enjoy swimming in the sea since there the buoyancy would give them some relief. [Answer] I invite you to take a look at the [bone structure of the hero shrew](https://en.wikipedia.org/wiki/Hero_shrew#Adaptive_significance). This little creature can survive being stepped on by a grown man, but from the outside it looks like any other shrew. Similar modifications of the human backbone are probably necessary to live in high g environments for any extended period of time. Also, shrews are generally pretty awesome. I'm just saying echolocation, venom, eating scorpions, monster metabolism … well, maybe don't splice it all in. [Answer] The gravitational impact isn't on the body, but on every molecule that makes up that body. That is to say that any bodily process that relied upon "heat rises" or any other such basic concept needs to be revisited. But generalities.. A lighter body wouldn't work out too well: with higher gravity comes higher pressure, with higher pressure comes increased load bearing requirements for any and all parts of the body...not just as regards your own weight, but atmospheric pressure, the ability to move and influence external masses etc. You wouldn't want to be short and stumpy: leverage is king, the great muscle multiplier. Massively more powerful circulatory system: It's not enough to recognize that blood weighs 4\* as much, the muscles are also doing on avg.. 4\* as much work so they need a commensurate increase in delivered payload. You'd have to redesign the circulatory system almost entirely, because with that 16\*(?) increase in load on the heart you're also creating immensely more heat. Atmospheric density would require reworking the lungs somewhat, you'd have a much higher oxygen content (assuming the average chemical levels are the same across the entire atmosphere) it being significantly heavier than nitrogen. [with increased gravity the separation between chemicals in atmospheric levels becomes more pronounced/the greater the energy demands are the greater the stratification] This is a boon for our metabolism, but still not nearly enough to make our lungs sufficient to the task of delivering sufficient oxygen. The best solution...well, hard to say, but I'll tie to: The energy required for both internal process & external effect will be multiplied, requiring greater resources, but I think it's a mistake to go for "eat more." See, when we consume (eat, drink and breathe) we don't destroy anything, rather the body transforms one compound to another, creating heat and etc and what the body doesn't manage to use is [largely] dumped out. This is massively inefficient, as the system, when dumping out compounds, could rather use subsidiary processes to reformulate the 'waste' products back into usable forms, separating and re-separating essentially ad infinitum in a closed system. The whole "tree converts x to y so we can convert y to x" thing can all be performed internal to a single organism, and not just for oxygen and carbon, but for every element and compound required in the operation of the organism. On the one hand this might provide also a method for using thermal energy rather than extruding it as waste also, on the other this would be even more complex a task than doing the transmutations in the first place, so we might end up with a creature that can't exist at temperatures above -20C or else it would fry itself. So heat management becomes a greater concern than [other] resource management. The body might be provided with buoyancy devices, not sure how effective such a concept could possibly be, but say.. fluid (as per joints) or hydrogen sacs might help to spread the load or decrease the overall load on the organism's skeleton. I'd imagine that such attempts would require such a volume as to be less than useful, but it's not like I've done the math here. Really though it seems to me the body would have to be reworked from the ground-up, every membrane has been taken up into the evolved collective because of it's operating characteristics at 1g, quadrupling the energy (not one-shot but permanently) of every particle the membrane is supposed to restrain or redirect is going to have significant impacts. Specifically childbearing? Assuming normal human babies: They would: Die as soon as they were forced to rely upon their own hearts. Muscle density in babies being what it is, a baby wouldn't even be capable of screaming. Bones would snap even more frequently than adult unmodified humans. Assuming a child survived birth and magically had a heart and lungs that could operate at 4g, its growth would be immensely retarded. It would be blind due to suspension deformation in the eye. Its skull would crush its brain, being too soft and solidifying too slowly to resist gravity's downward stresses. Liquid where it shouldn't be (lungs) would take that much more effort for the lungs to expel. Let's talk about weeing and pooping? Your sphincters are designed to hold materials up to a certain pressure, gravity multiplies downward force, ergo..higher gravity makes you incontinent. Not entirely sure if sphincters would give up 4 times earlier, but certainly they would be under more strain earlier. Disclaimer: The Above Is All Guessery I just read some of the answers in "related to" questions and have to reiterate the point that gravity does not act upon the whole of a body, but every constituent particle. It is *not* like having to carry extra weight on your back..and not like being a 600lb person. The materials, fluids and molecules in a fat person at 1g behave the same as they do in a regular weight person. Answers like "wear an exoskeleton" don't help hardly a bit, as instead of being 'crushed' to the floor, you're being 'crushed' into the exoskeleton. If 'live under water' would help, wouldn't we suppose NASA would of built a huge tunnel up into space filled with water so shuttles could sedately swim to the surface? Gravity doesn't stop exerting its influence just because you're in a suspension. If we put a put a person in a centrifuge pod full of water and turn it on, for instance, the difference we get is that before the person is crushed to the rear of the centrifuge...the water must be force out of the way. Which takes..no more time or effort than it takes a person to move through water under any other conditions. Can water be compressed? Does it matter? I don't see how it can matter. Pick up a bath full of water. Pick up a bath full of water under 4G. Submerge yourself under water in 4G conditions and you're dead even quicker than in atmosphere. Every one of those water molecules weighs 4\* as much as on earth...you are not water. Perhaps..turn people into jellyfish. Babies could be grown in vats in space and engineered to the desired specs before being dropped. I mean, it seems to me that 24th century man could do it [hell, if people put their minds to it and discarded any misgivings now we could probably find a way and make it happen inside 40 years [that is, apart from actually getting to this planet], but the result couldn't be human by any but the most generous definition.[not that this is a problem, just pointing out my view of the scale of changes required.] [Answer] First of all: your bones would have to be able to carry 4x the load they carry at present, so they'd have to double in radius. Then your muscles would have to be able to do the active work, so they'd have to increase in volume too, thus adding to the load they'd have to carry. Then your heart would have to pump blood to these bones and muscles, so it would have to increase in size. It would also have to supply the brain at against this increased gravity. The vessels in the brain and everywhere else would have to accommodate the increased pressure, and that in turn would change the way the capillaries work. All the organs would have to work harder to support the increased metabolic requirements. Your lungs would have to be able to resist a pressure 4x as great as they are currently designed for. Pick another, smaller planet - there must be hundreds of billions in the galaxy, and I am sure your advanced technology has gazetted them all by now. But on second thoughts, with a slight modification of the conditions, it may be doable. The modification is this: the new breed of humans must be recognizably human - *but not all the time*. This allows us to use an approach that has already been successfully applied in terrestrial biology for hundreds of millions of years. We simply add a second phase to the modified human's life. During the first phase, he lives as a human, in an environment such as we're accustomed to - maybe on a nearby planet, or in a special nursery environment on Planet 4G. Then he pupates, and is transported to the harsh 4G environment, where he emerges in this new phase, inhabiting a body designed from scratch to fit the planetary conditions. At the end of this phase, he dies and is buried on Planet 4G. There are minor operational points to consider - for example, in which phase does he breed? But these are not important. This solution came to mind as I watched some butterflies in my garden. Thank them for it. [Answer] The major weak points will be tendons and blood flow. Yes, stronger bones will be good and should be part of the mix. Stronger muscles are necessary but they can be trained. However, the tendons tend to be the weak point as they can tear away from the bones or just snap. They must be strengthened and more strongly anchored to the bone. None of that is important if you can't get the blood in the feet back up to the heart so it can be sent back around. We should take a page from elephants. The tegument/skin of their feet and lower legs is much stronger than ours. It acts as compression socks so the movement of the muscles of the foot and leg can more efficiently pump the blood back up to the heart. ]
[Question] [ The flight-mechanisms and exoskeletons of insects are only practical at their current scale -- the wings interact with the air as more of a 'fluid' medium at their scale, than gas as birds experience it (I may be wrong on this). Second, their exoskeletons are less cumbersome (and indeed helpful) at the micro level they exist at -- whereas on a larger scale the dynamic would be very different in both how their muscles work and the efficiency / weight of their construct. So to really create a believable creature that is a genuine insect (or better said, arthropod, sea or land) what changes would be necessary to create a creature that is strong, robust, and threatening? [Answer] One of the biggest limitations is actually breathing and circulation. See here: <https://www.quora.com/Entomology/Do-any-insects-have-hearts-and-lungs-or-do-they-have-a-completely-different-system-of-breathing> > > Hearts: Sort of. Insects have an open circulatory system, meaning their organs just float in blood. It's similar to how human organs float in lymph, so we call insect blood "hemolymph." However, insects do usually have a tube on their back that has holes to take in blood and pumps it up to the front of the insect. This sets up a current of hemolymph flow in the body. So, yes, insects have a "heart" and maybe an aorta... but no other blood vessels. Also, large insects have smaller, muscular "hearts" by the starts of their limbs or wings to help pump blood in those body parts as well. > > > Lungs: Nope! Insects have a completely different system of breathing. They have a system of tubes called trachea leading from holes along the sides of their bodies called spiracles to their organs. Air flows in the trachea as it does in our lungs. You can think of the trachea as being blood vessels for air only, carrying oxygen and taking CO2 from every tissue directly. Insect hemolymph, likewise, does not carry oxygen the way our blood does. Small insects just have trachea, while large insects can pump air through them using their muscles or even air sacs. > > > This design does not seem to scale well and is one of the main reasons that prehistoric insects could grow considerably larger than our insects today. The higher oxygen concentrations in the air then allowed it. [Answer] Tim B had an excellent answer (take a second to up vote that now). There's also the mechanical limitation of the exoskeletal structure. Using chitin as the structural material and exoskeletan as the structural technique, Terrestrial insects are limited to about a 3 ft diameter size. Any larger and they couldn't move because they'd weigh too much for their structure. The largest size an insect could be is the smallest of all the limiting factors. So it's important to know that even insects breathing pure oxygen could never grow to a size much larger than the stated 3 feet. [Answer] The main limitation to insect size is gas exchange. An insect does not possess any lungs or gills; instead it possesses various holes (spiracles) on the outside of its body, which lead into tracheae that branch out all over the body and supply oxygen *directly* to the animal's tissues. Insects don't have blood in the traditional sense, because they don't need it, thanks to the fact that gasses just diffuse right into their cells instead of having to be diffused into the blood first. Now here's the kicker: in places where the exoskeleton pinches and becomes narrow (i.e: joints on the extremities), the trachea still needs to pass through. In smaller insects, this is not so much of a problem, since their tracheae don't take up much space and can be very slim; able to pass through their tiny joints. As an insect gets larger, however, the trachea needs to grow disproportionately large to accommodate gas exchange into the extremity. Once the trachea takes up 90% of the space within the joint, the insect cannot physically grow any bigger, because it still needs to fit in things like tendons and ligaments. For an insect to grow to human-size or larger in our type of atmosphere (low oxygen density), it would need to change its entire respiratory and circulatory system. Doing so would render the question moot, since if it were to alter its biology at such a fundamental level, it wouldn't really be an insect any more. ]
[Question] [ I am sure most of you have seen Star Wars. In Episode IV: The Empire Strikes Back our heroes travel to Bespin, a gas planet with a habitable zone to refuel at the floating cloud city. Well of course "mild peril" ensues and one of the heroes ends up almost falling off the bottom of the city into the endless skies. [![enter image description here](https://i.stack.imgur.com/Un2vE.jpg)](https://i.stack.imgur.com/Un2vE.jpg) I have always wondered, how far could he fall and still be in a breathable atmosphere? So this brings me to an actual place in a film I have designed: Where a character pulls that stunt Luke Skywalker almost did and falls from a cloud city-esque spot in a breathable atmosphere down as far as possible before he is rescued. So here we go. **How deep can an Earth like atmosphere go before it causes serious ill effects?** Requirements: **Both the one falling and the rescuer must survive the trek with no major ill effects.** **The atmosphere must remain breathable, no passing out or delirium allowed.** [Answer] **Some assumptions and thoughts** * Air mix is same as Earth for oxygen and nitrogen. It is the partial pressures of these gases causing toxic reactions which would be fatal, not the physical force exerted by the pressure. This is *provided* the faller does not have any unreachable air cavities inside their body which would cause physical harm when slowly squashed to a smaller size. Most of the human body is relatively incompressible, being made of water, and the purely physical resistance to high pressures of the human body goes well beyond where a normal air mix would be highly toxic. * Gravity is somehow around 1g, and does not change significantly over the distance of a fall (as you will see below in general the falling distance is small compared to planet radius, so it's not too bad an assumption). Some gas and ice giants do appear to have this gravity in their outer layers, but Jupiter has for example 2.4g, where the numbers would be quite different (and make it quite hard to achieve anything) * We start the fall from a typical sky-diving height, and then add on smaller "layers" that are roughly equivalent to one earth atmosphere. Each layer is thinner than the last, because it is denser. The extra density also reduces the terminal velocity. * I quickly researched the pressure at which normal air becomes toxic to humans, and found [recommended safety limits for diving with normal air](https://en.wikipedia.org/wiki/Breathing_gas) at 66 metres of water, which is 7 bars (1 bar == 1 normal atmosphere). This is considered safe for long-term operating. For the duration of a temporary drop we can probably double that and still have plenty of room before short-term toxic effects become a problem. * I am ignoring possible effects of temperature changes with depth. I have absolutely no idea how significant they would be, or even sure in what direction. My gut feel is that temperature would increase with pressure, and could become a serious threat in addition to the toxicity. A higher temperature would also reduce the density required for a specific pressure, making each layer thicker, increasing time possible for the drop, provided it didn't get too hot. For comparison, on Earth, a height difference of 1000 metres in the densest part of the atmosphere corresponds to a temperature difference between 5 and 10 degrees Celsius. At that rate it could get *seriously* hot on a relatively shallow drop. The density of air is proportional to the pressure. At sea level, 1 millibar of pressure change is roughly equivalent to 9 metres distance. But you do need to now include the fact that the pressure is higher, so the next one millibar going down might be in 8.99 metres. When you ignore temperature, then the relationship between pressure and volume is covered by [Boyle's Law.](https://en.wikipedia.org/wiki/Boyle%27s_law) - which means the same weight of gas (that applies yet more pressure further down) is in a smaller volume. However, to calculate pressure you effectively take a fixed-unit width "column" of air to calculate the weight. Which means air at twice the pressure is twice a dense and creates the same amount of pressure in half the height. **Rough guesstimate** I cannot be bothered with the maths for a smooth curve*\**, seeing as we're also ignoring some other physics. So we can approximate the fall as follows: * Starting at 1 atmosphere, the unlucky person falls 9000 metres with a terminal velocity of $60 ms^{-1}$, taking 150 seconds. * The next section is at 2 atmosphere. It is only 4500 metres deep, but terminal velocity $v$ is proportional to density $\rho$ as $v \propto \frac{1}{\sqrt \rho}$, so speed is $42 ms^{-1}$, taking 106 seconds. * Next section is 3 atmospheres. 3000 metres deep, velocity $35 ms^{-1}$, taking 87 seconds. We can see a pattern here, each deeper part of the atmosphere takes a little less time to cross. It will take quite a while to reach what is considered safe diving distance pressure in air at 1g. But once at that depth, problems with toxicity will start happening faster and faster. Doing the sums up to completing layer 7, I get roughly 600 seconds, or 10 minutes of sky-diving, over a distance of about 23 kilometres. This is not much distance at all, compared to the depth of our "full" atmosphere. That's because there are very large distances spanned by ever more tenuous gases. Once you get into breathable sections of air, it is not very deep at all. Interestingly the character would be travelling at 80 km/h (or 50 mph), which is below the top speed of an experienced cliff diver, and roughly equal to speed reached from a fall from 30 metres in our normal atmosphere. Our faller could survive impact with a little luck or skill, and should be able to cope long term with the need to breathe at least. Going as far as the "risky" layer 15, I get 960 seconds, or 16 minutes, and a distance of almost 30 km. At this pressure, the character will have been breathing in increasingly dangerous partial pressures of nitrogen and oxygen for the last 6 minutes. I think [nitrogen narcosis](https://en.wikipedia.org/wiki/Nitrogen_narcosis) would strike earlier out of the two, but I have not been able to find accurate timescales on which it would occur. Our intrepid falling character could go further perhaps. But every minute they would be breathing a highly toxic mix of gases. They would likely already be suffering ill effects, confusion, hallucinations. They would quickly black out and die. I cannot give you a time for those effects to occur, or a point of no return. **Including temperature effects** Looking at [a fact sheet for Jupiter](http://astronomy.nmsu.edu/tharriso/ast105/Jupiter.html) there is a temperature profile of that planet which shows a 2 degrees Celsius warming per kilometre in the gas giant's atmosphere, at the cloud-tops level and below. So assuming you start close to zero Celsius at the top, a person could drop maybe 20km before heat stress started being a bigger problem than poisoning. But you could also maybe handwave in a gentler gradient to allow a longer drop. You have the choice of two nasty ways to threaten your character. --- *\** You can get better accuracy on this estimate, and still avoid getting into calculus, by making each layer smaller. I have done so, using several thousand layers with much smaller changes between them. I have also checked the calculations against an [online pressure calculation tool](http://www.csgnetwork.com/pressurealtcalc.html) and got agreement within a few tens of metres for depths at pressures of 2000, 3000 and 4000 bars. The difference is on the order of 10% shorter times and distances, probably less than the effect of ignoring temperature, and within range of changing other variables such as composition of the atmosphere, strength of gravity etc. So I have left the original numbers in from the crude estimate, because it is easier to explain. ]
[Question] [ Humanity is in a late medieval stage, prior to the discovery of steam and combustion but quite knowledgable about metalwork . A country decides to build a large-ish city and 7 long chains leading to mountains, in the hope they may lift the city, a testament to their riches and people – and inevitable hubris, of course, as someone inevitably takes it down. A few details: * There is a mountain range surrounding the valley the city is built in. The city has poured funding into huge half-kilometer chains reaching this distance. * The chains are not attached to the mountain-side; long holes (with spaces for housing and material transport) have been dug into the mountain side, with structural supports to ensure the chain isn't just attached to one place. * This design is replicated, albeit to a smaller extent, in the city, with about 50m between the hole the chain enters and where it's attached, again for redundancy. * The chains are literal chain-links, and can be of any thickness and material available to late-medieval society – neither cost nor scarcity are problems. * The chain-points in the mountains are of any height above 300m. Structural supports can be made in the mountains, but nothing can prop the city up from below. Will it be possible to erect such a city on the valley floor and ultimately lift it, or is it an impossibility to lift something that large? How large, if at all, could such a city be before it is structurally unsafe? [Answer] **No.** As the old adage goes, a chain is only as strong as its weakest link. It's clear that any single link in the chain must be able to support the entire force imparted from its portion of the city. It'll be best to go with a studless chain, which reduces the weight per link at the cost of making the chain more difficult to handle. This is the [largest one manufactured](https://books.google.com/books?id=dnsTFT9UYA8C&pg=PA688&lpg=PA688&dq=6.25%22%20studless%20mooring%20chain&source=bl&ots=Aals82Mb3x&sig=9gt6pUpFSDpYalBtz1VADv886sM&hl=en&sa=X&ved=0CCUQ6AEwAWoVChMI0uPa_vyFxwIVyBeSCh237Q1Q#v=onepage&q=6.25%22%20studless%20mooring%20chain&f=false) to date: [![enter image description here](https://i.stack.imgur.com/2HmaF.jpg)](https://i.stack.imgur.com/2HmaF.jpg) It was made to anchor the [Schiehallion oil platform](http://www.offshore-technology.com/projects/schiehallion/). It uses 14 of them to hold it in position. Note that this platform floats, it's not being held up by the chains, they just keep it from drifting. That chain is [rated for around 24,000 kN before breaking](http://www.sci-chain.com/?page_id=13) (for earth gravity that's about 2,447,318 kilograms. It has a mass of about 504 kilograms per meter. So the half a kilometer of chain alone would weigh 250,000 kg. If you hung the chain by the top link, that top link would experience 2,452 kN of force. It can support itself, so that's good. You have seven of them, so you have about 154,000 kN of force to divide among them if they are also supporting themselves. The weight of the city would be hard to guess at, but looking at what we have left it's not going to be a very big one. 154,000 kN will be about 15 million kilograms in earth gravity. That might seem like a lot, but if you're using limestone or granite to build your city, you can only use about two olympic swimming pools worth, about 5300 cubic meters. Not a very impressive city. Not even a very impressive castle, of course, aside from the chains. [Answer] You would need chains quite a bit longer than half a km, or else you'd have to build in a valley even narrower than Yosemite (1.6 km wide on average, per Wikipedia). Slightly better would be to use wire ropes: <https://physics.stackexchange.com/questions/121233/which-is-stronger-wire-rope-or-chain> as with suspension bridges - because that is effectivetly what you're proposing, a suspension bridge with buildings on it. Early 20th century technology can get you a bit over 1 km wide (e.g. Golden Gate Bridge at 1280 m), while some recent efforts span almost 2 km: <https://en.wikipedia.org/wiki/List_of_longest_suspension_bridge_spans> [Answer] The scale for chains stretching half a kilometer while holding up a city would be a true wonder of even the modern world. Medieval metallurgy would not even be capable making chains on that scale - probably looking at well into the 19th century for that kind of capability. Even with that kind of capacity, it is doubtful that wrought-iron would have the tensile strength to even hold its own weight suspended across half a kilometer. [Answer] Looking at the geologic side of it, even with the strongest materials available today there would not be a chance of drilling such large and long tunnels into the mountain without self-collapsing due to the pressure of water and the weight of the sole rock. Furthermore the surface rocks simply couldn't stand so much tension of an anchorage by many orders of magnitude. Also, even a small earthquake would amplify much more on a suspended structure and the anchorage points would produce such a huge increase in tension that even a stable structure in normal conditions couldn't stand the sudden increase of stress. [Answer] Even if you could build it, living there might not be a good idea. The [Tacoma Narrows Bridge collapse](https://www.youtube.com/watch?v=lXyG68_caV4&t=1m5s) shows what happens when the wind gets under a suspended structure built before people understood that sort of thing. At best, it'd be like living on top of a jelly. At worst, the jelly would be living on top of you. ]
[Question] [ Okay, following my [previous core question](https://worldbuilding.stackexchange.com/questions/14473/sci-fantasy-terraforming-the-earth-and-magic-nanomachines/), after the apocalypse, one of my sets of survivors in this setting, the Usnay, managed to live in a fleet of ships for over a thousand years. This is probably less of a direct question, and rather me making sure I have all my ducks in row here on the thoughts behind their survival, to ensure I'm not missing anything critical, and to have a bit of a reality check, I suppose. **Here are the facts:** * They are living as a fleet of ships that are relics of the mid 21st century (2060). There are probably around sixty to eighty vessels total. * This includes their escort: three prototype navy destroyers that protect the civilian fleet from threats. These destroyers were state of the art at the time, with onboard cold fusion reactors, some form of magnetised armour plating, probably a deck mounted railgun or two, flak point defence, and stores of missiles and [supercavitating](http://en.wikipedia.org/wiki/Supercavitation) (hypervelocity) torpedoes. In other words, enough to murder the crap out of anything looking at you funny. * The oldest of these destroyers is effectively the government centre and the flagship since it combines defence, order and early warning. Navigation orders come from the flagship as it analyses its records of the seas and uses its instruments to determine the best routes that avoid the roughest seas and disasters waiting to happen. * We can assume the first captain of this fleet was a pretty awesome person. After all, as the world broke down from nuclear war, they went around rescuing ships and coastal populations, and they planned for living on the sea for quite a while from the start. * They have converted a couple of Oil Tankers into Hydroponic or Aeroponic Farms (probably converting various tanks into rotary hydroponic facilities). I'm a little concerned about the engineering required in this conversion but hopefully its feasible. Given the kind of [crops that grow best hydroponically](http://modularhydro.com/ArticleLibrary/WhatCanYouGrowHydroponically.html), their main diet will be beans, tomatoes, cucumbers, strawberries, and leaf lettuces. Sounds like a decent salad! This is supplemented by fishing (at least some of the fleet will be fishing trawlers). Going by [the figures in this question](https://worldbuilding.stackexchange.com/questions/9582/how-many-people-can-you-feed-per-square-kilometer-of-farmland/) and assuming the absolute worst case scenarios, we can assume our two hydroponics tankers can support a fleet population of at least 10,000 people or so. * Many places actively catch rainwater with various devices and filter implements, but a couple of vessels may also be specialised in waste treatement and desalination. The fleet tends to stick to rainy climes where possible. Some processing of waste occurs where possible to save fresh water, but it is otherwise dumped into the sea. * Some vessels may bolt and tether to one another where this is convienient and appropriate; unbolting again if a storm is approaching. There are also freight barges that ship stuff and people between the various other vessels. * A converted Aircraft Carrier has effectively become a huge apartment block. Parts of planes were probably cannibalised to make structural components for homes here. This wasn't likely straight away, but rather after the long quiet set in and population density began to rise a bit. The aircraft carrier can also be assumed to be relatively new, probably also with its own fusion reactor. Its possible that its planes were actually drones if airforce development went/continued that way; though I doubt the successor to the F22/F35 was phased out instantly. Its also possible that a cruise ship or two are part of the fleet as alternate accomodations. * They have 'magic' for maintainence. This is, as noted in previous topics, the ability to interface with ambient nanomachines. We can assume that most generic rust and wear to the hulls can be fixed by nanomachines assuming they have access to some new materials occasionally. * Some trips to land are possible during this time; but are dangerous due to the demons that now inhabit the land. Since the demons have unpredictable abilities, engagement with them is on a purely last-resort basis for a ground crew (those few demons that might attempt to swim/fly out to the fleet would be annihilated by the destroyers, but coastal support for landers may be more difficult). Nevertheless, obtaining metal scrap and rare earths (and in earlier trips for the first century; canned foods), is possibily worthwhile enough to warrant it. **I guess my main questions here are:** **A)** How long would this conversion take? I'm assuming a couple of generations? This [question has some good ideas about design](https://worldbuilding.stackexchange.com/questions/7181/is-building-giant-ship-cities-in-a-water-world-a-good-idea) (semi-submersibles, rafted components) but my plan assumes that is not possible to access any large manufacturing facilities for any significant length of time, and the skilled labour to use such facilities may be rare as well. **B)** Given the available nano-maintainence, I assume the ships will be fine for this period (if rusty in all non-essential sections to preserve resources). Alot of the central crux of this plan assumes that most of the tech will last and last for a very long time. This [topic's main answer says that the hulls will last many generations](https://worldbuilding.stackexchange.com/questions/14893/how-long-would-a-carrier-group-survive-unattended-anchored-just-off-shore). But how long will modern ordnance stay live and usable? What about the computers? I'm also assuming that our Fusion reactors are [Deuterium => Tritium](http://en.wikipedia.org/wiki/Fusion_power#Deuterium.2C_tritium) and that we can indefinately sustain them using some process to extract it (2H) from seawater. **C)** How would people evolve during this time (both physically and socially)? I know a couple thousand years isn't enough for drastic changes, but I'm assuming that people will become favoured towards being darker skinned. They will also steadily lose the concept of personal space. I have them currently on a loose pseudo-military hierarchy/meritocracy with the Sea-Marshal as the leader. **D)** And of course, anything else I might have missed! *Other possible reference topics looked at include: [Would it be possible for a city floating on water to exist?](https://worldbuilding.stackexchange.com/questions/13774/would-it-be-possible-for-a-city-floating-on-water-to-exist/) and [What would be the ramifications of someone who has lived their entire life at sea?](https://worldbuilding.stackexchange.com/questions/13780/what-would-be-the-ramifications-of-someone-who-has-lived-their-entire-life-at-se)* [Answer] Very well thought out. **A)** I'm sure the conversion from armored battle fleet to floating colony would take a while, but that would be ok because you wouldn't need it to be done in a hurry. It would just happen naturally in a lot of small steps as more people came on board and more structure was needed. Each step would be as fast as resources allowed, as people worked together to do it, but the steps might be spaced out a bit until need dictated. For instance, in the early years raiding the shore for canned food and dry goods would be the major focus, with people starting farm prototypes in some of the carrier hangers. When the tankers are salvaged the farms would be moved over and expanded whenever parts were available to do it. The warships would have machine shops aboard, and additional tools would be salvaged whenever possible. Scrap could be obtained without going ashore by scavenging boats from marinas, as well as ones that drifted out to sea. Oil drilling platforms would be a wealth of scrap, parts, and tools. They would be stripped of tools and their positions would be mapped out, and the metal harvested one by one as the need arose. You haven't said much about the demons (where they come from for instance), but I can see some small Caribbean islands being purged and turned into havens to store excess resources and possibly dry dock (to bring newly salvaged boats up to speed). **B)** Not really sure, but it kind of depends on what a computer looks like in 2060. Same for other electronics. I propose that the nanomachines would be able to repair them as well. Explosives are potentially a little more difficult, but with things like rail guns you need a lot fewer explosives. Military ordinance should be [pretty stable](http://www.rifleshootermag.com/uncategorized/how-to-determine-gunpowder-shelf-life/), so probably a long time. Hopefully someone else can add to this :) **C)** I don't think there would be much physical evolution over only a couple hundred years. Mutations from leftover radiation would not be beneficial and mostly fatal. If you had any changes, like skin darkening, it would because of mixed marriages, which there would likely be a lot of. Any kind of racism would be poison in that tight of a community and would have to be dealt with severely and swiftly. Plus the constant contact with other children would quickly teach them that there aren't any differences except skin color. Socially you're probably pretty spot on. People might lose a lot of modesty and personal space, but most likely it would change into a mental personal space, where you just wouldn't see/pay attention to things that didn't concern you. (I remember reading a book set in medieval Japan where rooms had paper walls, so basically no real privacy, so people just put up mental walls, not paying attention to stuff happening in other rooms.) People who still needed space would live/work on the smaller boats where there would be less crowding, or in the farm where you would have the impression of privacy. Extreme cases would be the scouts, leaving the fleet to look for supplies, and returning to the convoy when they needed to. [Answer] **But how long will modern ordnance stay live and usable?** I’m an old Ammo Sgt/Ordnance solider here so my answer is based off that experience. The shelf life of the ordinance depends upon the type. Rail Gun: Indefinite. There is no explosive here to deteriorate. Keep the rust off and you're good. Flak Point Defence (assuming this is to stop incoming missiles?) Laser Type: Indefinite if you keep it running. (The U.S. Navy is currently experimenting with lasers) Explosive Rounds: 50-100 years. Depending on which plant it was produced in after the 60 year point a growing % will start going bad. You can often still shoot them, but 1 out of 1,000,000 will explode on you and 1 out of 100,000 won't fire at all. In another 10-20 years it might be 1 out of 100,000 will explode, and 1 out of 10,000 won't fire. Trained ordinance specialists can track which batches from which plants are going bad first and avoid them. Missiles and Torpedo’s (Highly variable depending upon type) Dumb design: 40-60 years. Few missiles are dumb in the U.S. army ordinance (but there might be dumb torpedoes). However most cheap designs have a shelf life of 40-60 years. When these begin to fail they become less stable. They might explode in storage, or fail to explode. More expensive dumb designs have failsafes that keep them from exploding when they get old. Smart Design: 10 years unless you can upkeep guidance components. These have a very short life span. However it’s due to their guidance components. Once they go they can no longer target accurately. They won’t accidentally explode on you for a few more years though. We had to do monthly checks on our smart missiles optical components. Bombs and missiles from the air craft carrier supply would fall under the same smart/dumb category. These numbers are for general storage conditions. These would be sealed buildings that are not climate controlled or temperature controlled. For example, if you left your spare ordnance in shipping containers on one of the cargo ships. If you can keep the ordnance in a climate controlled environment their life spans will be longer, maybe even doubled. The air craft carrier would be the only vessel that could do this in bulk. Then there is always the question of how old the ordinance was before it got to your fleet, and what kind of environment it was stored in. I served approximately from 2000-2010. During this time I helped destroy a large amount of WWII ordnance and some WWI. It was around and still usable. Just remember, the longer it sits the more likely something will go wrong. [Answer] > > **C)** How would people evolve during this time (both physically and socially)? > > > They would become excellent swimmers, foragers of the ocean, highly skilled at do it yourself jobs, navigation and reading the sea. I'd recommend reading up on the Bajau ethnic group as to how a people might evolve over time. Some of these people never set foot on land and live their entire life as nomads on small boats. They come together to form societies on the ocean. I've heard some of them can free dive for great lengths underwater on one breath of air. Living like this would be a lot freer and more independent than being stuck on big overcrowded vessels. [Guardian article on the Bajau ethnic group](https://www.theguardian.com/environment/2010/sep/18/last-sea-nomads) [Answer] I can only take time to deal with A. at the moment. My background is engineer, blacksmith and metal worker. and a bit of hydroponics. Q A) How long would this conversion take? .. my plan assumes that is not possible to access any large manufacturing facilities .. the skilled labour .. be rare as well. Without skilled machinists, welders, and the really heavy equipment they would need to make proper, safe modifications on tankers, military vessels, and a carrier your people would only be able to jerry-rig .. flimsy construction that will get wiped away in the first heavy storm, even when inside the ship. If I was in urgent need of living quarters for 10k plus people i would rather have a container ship than an aircraft carrier. With a plasma cutter, a few heavy duty stick welding machines it would take amateurs only weeks to create a floating apartment block. an important question - the bigger the ship the more bunker fuel you need to run its engines. Maybe you get a nuclear carrier, but all the rest need a huge supply of fuel. Smaller ships need less but carry fewer people .. you need a detailed numeric analysis to find the sweet spot between fuel usage and capacity versus size of ship. Tugboats might modify the equation a bit, but in all cases you need a lot of bunker fuel. ## Food Supply They will not be able to clean the storage tanks of an oil tanker well enough to be safe to use for hydroponics. You would do much better with a bulk carrier with wall to wall retractable hatches to allow sunlight in during the day but protect the crops at night and in bad weather. I did research into commercial hydroponics years back. Your folks are going to find it from hard to impossible to obtain the minerals/chemicals needed to create balanced nutrients for the different sorts of plants you want to grow. And you need a chemist with the specialist knowledge of plat nutrition to kill from burning the roots off the plants. Good news - nearly any plant will grow in gravel-sand mediums as long as its roots stay damp enough to be able to absorb nutrients. And the water needs to be aerated to supply oxygen and filtered to keep it clean. Even root veg like carrots, potatoes, and beets do well if the medium is soft and sandy. Even corn can grow if you can feed it enough nitrogen. Special needs items like willow trees would be good to have a source of ASA, rubber trees .. if they can obtain roots, seeds and cuttings of useful plants they can grown them. The problem with food crops is that you need to be thinking in tones per hectare. You need to have enough coming to harvest each month for all the mouths you need to feed. So if you need a hectare per month then you need 12 hectares total. You can reduce floor area needed using vertical farm techniques, but you still need enough chemicals to provide 12 hectares with nutrient laden water, and you need a lot of water. Lets say you need water 10 cm deep ( .1 metre) in each hectare, which is 10k sq metres, so you need 1000 sq metres of water, 100 litre, or, in total 12000 litres of water, and hundreds of kilos of chemicals to make the nutrient solutions .. and you need a diff solution for each type of plant you have some challenges to overcome to make your story work .. but only if you need a high level of realism. Water World was an extravagant movie totally divorced from reality, except for the part about thugs being willing to follow the orders of the most vicious bully. I hope you do better with your floating survivors [Answer] # "Magic" was the end of them They rely on "magic" for maintenance. It doesn't seem to allow them to make new ships suited for their purposes. The result is that their own creative efforts are very crude and limited, while the all-powerful all-knowing machines around them retain a continual stasis. We've [read this story before](https://www.barnesandnoble.com/w/n-space-larry-niven/1000418096), after a fashion. [More than once](https://en.wikipedia.org/wiki/Gal%C3%A1pagos_%28novel%29), I'd say. In the static environment, dominated by outside forces, the humans degenerate into a form just barely capable of invoking the "magic" to fill their needs. ]
[Question] [ In my reading of sci-fi I came across a fascinating concept: an alien race called the Chromatics that had a partially photonic nervous system. They were described as having very fast reflexes. Now I am planning on introducing a plant-like race of aliens. (They are actually planimals) Because I find the idea fascinating and it seems that real plants might have a [photonic nervous system](http://www.bbc.com/news/10598926), albeit a very primitive one, I'd like my aliens to share the trait. What I need to know is if a photonic nervous system would grant this race faster reaction times than a human and if so by how much. [Answer] There are a number of issues with fast nerve conduction. Whether this is achieved by photons travelling down organic fibre optic cables, or electrons travelling down organically deposited wires, we get a situation that, over any typical distance found in an organism, a signal takes effectively zero time to be transmitted. This differs from many animals' sodium-channel depolarisation-wave axons, where transmission speeds are in the order of 3-120 metres per second, depending upon myelination. However, this is not the only part of the problem. In most animals, communication between nerve cells occurs by neurotransmitter/receptor coupling. This, too, is relatively slow, as neurotransmitter released by a neuron takes time to diffuse across the transmitter/receiver gap. However, in a system where axons do not rely on myelination for impulse acceleration, but instead use a wire or optical fibre which results in a much greater conduction speed, faster intra-neuron transmission would be more beneficial. This could be achieved by implementing some sort of mechanical connection rather than a chemical one. If, on the transmitter neuron firing, a mechanical gate was operated that connected to a mechanical gate in the receiver neuron, the neurotransmitter delay could be significantly reduced. This leaves only the neuron body's sodium-channel gates as the slowest link in a neuron's reception/firing process. However, this is difficult to overcome, as the voltage threshold of the sodium-channel gates is how a neuron acts as an integrator. Still, removing the axonal delay and the neurotransmitter delay would significantly speed up motor control, sensation and processing. An alien species will not have the same structures, but the arguments in favour of mechanical connections between neurons and photonic/electrical conduction are the same. The consequence of greater speeds in neurotransmission and communication would result in significantly faster reaction times. Human visual-motor reaction times (eye-hand) are on the order of 280ms (typically 190ms-410ms). A significant part of this would be axonal pulse propagation and neurotransmitter delays, though some of it is also depolarisation integration that cannot be so simply overcome. I would speculate that if a human was enhanced in this manner, a reaction time on the order of ten times faster should be achievable, i.e. 28ms (typically 19ms-41ms). This also presupposes that muscular interaction is involved. Just because nerves operate faster does not necessarily mean that muscles do so too, though with faster neurons there would be selection pressure toward more responsive muscles too. With thought processes, which do not involve muscular activity, we could expect more like a twenty-fold increase in processing speed. So, we have our hypothetical neutrally-boosted creature. If we pitted such a being against a human in hand-to-[whatever] combat, provided that its muscles operated at a similar speed, there would be no contest. It would be able to see the human begin an action, would be able to analyse and predict the probable intention of the action, and before the human's action could be completed, it would be initiating a counter-action. Should it decide to attack, it could see the human's attempt at defence and would be able to think and react fast enough to circumvent that defence. In missile combat, such a being would be likely to be able to *see* bullets, though avoiding them entirely would still be very difficult. However, dodging or catching arrows would be as easy as dodging or catching a thrown ball would be for us. If we were able to experience *being* such a creature, we would notice that our thoughts flowed much more rapidly compared with our bodies. We would be able to see things moving about us in slow-motion, however our own bodies would seem similarly slow. We'd have more time to think about our actions before having to perform them. It is likely that to a human observer, such a creature could seem abrupt and jerky, but also incredibly precise in its movements. In order to save energy, it would move as little as possible until movement became necessary, at which point it would move as quickly as required. In a combat situation against a slower opponent, that would likely look like a series of almost static poses with very quick attacking movements in between. Defensive manoeuvres might look almost leisurely, as the creature would not need to take as much time to think about the appropriate defensive action, which would as a consequence not need to be executed as quickly. ]
[Question] [ Y'all should know by now that [I want to build a Death Star](https://worldbuilding.stackexchange.com/q/3458/2072) ;-) Let's assume that we did that already -- and against the odds, we've built *two* of them, and they're currently in orbit around a planet; let's say planet Earth. What would happen to our planet if two extra [metal] moons joined our orbit? * Tides would probably be affected; how? * Would sunlight patterns be affected? * Would there be differences if these gargantuan constructs stayed in place over one spot, or if they had a moon-like orbit? * Anything other major effects that I'm missing? [Answer] What would happen? Not much. [Canonically](http://starwars.wikia.com/wiki/Death_Star), the Death Star is about 150 km in diameter. I can't find an official number for the mass, so I'll assume an average density about 10% that of steel, for an overall mass of 1.0×1018 kg. I'll also assume that the Death Star cannot orbit closer than its [Roche limit](https://en.wikipedia.org/wiki/Roche_limit), which, if I haven't botched the calculations, is about 9,000,000 m above the surface. Feed the mass and distance into [Newton's law of gravitation](https://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitation), and this gives a force on a 1 kg object on the Earth's surface of 8×10-7 N, or about 1/100,000,000th the force of Earth's gravity. Simple geometric calculations give an angular size of about 1 degree, twice that of the Moon. **Edit:** Even in a much closer orbit (175 km, putting the lower edge just above the [Karman line](https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line)) will have little physical effect, producing a force of only 0.02% of Earth's gravity. The *psychological* effect of something with an angular diameter of 45 degrees passing overhead, trailing a plasma cloud from its lower edge, is a different matter. ]
[Question] [ Let's say I have a binary star system. The planet is orbiting the smallest star similar to the Sun at 1 AU, the same Earth-Sun distance. The other star is located at around 50-100 AU from the Sun star. This second star is 2-3 times more massive. It will run out of combustible before the smaller star. It might take less than 500 million years but I don't know exactly how long it is supposed to take. When that does happen, a mid sized star is supposed to become a red giant and then a planetary nebula. I've read that the temperature inside the nebula could get quite high (several thousand degrees) and would encompass all the stellar system. I know life could not survive that event, but I don't know what would happen to the planet at that distance. **Some questions:** 1. **Would the planet get destroyed in the process?** 2. **Could the planet lose her satellites?** 3. **Could this change the orbit of the planet?** 4. **Does it have an impact on the other star ?** [Answer] This is more informed guesses (I've not done all the math), but... 1. **Will the planet be destroyed?** Likely not. With nebulae having densities ranging from [100 to 10,000 particles per cubic centimeter](http://en.wikipedia.org/wiki/Planetary_nebula#Physical_characteristics), it won't be massive enough to simply disintegrate the planet. This is despite the fact that they're blazing at a few [kilometers per second](http://en.wikipedia.org/wiki/Planetary_nebula#Lifetime), and the planet will be molten. 2. **Will the planet lose its satellites?** It depends on their size, but likely no. The density of a nebula is a few thousand time thinner than earth's atmosphere, so it's likely not going to blow things off course too much. 3. **Could this change affect the orbit of the planet?** Yes, but it's unsure how much. It depends on how massive the stars/planets are, how they're configured, etc. 4. **Does it impact the other star?** Yes. There's now a lot of matter running around that it can om nom nom and gain more mass. Depending on what materials are ejected and the makeup of the star, the nebula can change the star's color or extend its life. [Answer] # TL;DR To make a long story short, the planet will lose its atmosphere and some of its crust, but most of it will remain intact, even in the worst-case scenario. That should be the major effect you'd have to deal with. ## Nebula properties Let's review [some key characteristics of planetary nebulae](http://www.scholarpedia.org/article/Planetary_nebulae#Physical_and_spectral_properties_of_planetary_nebulae): * Density: $\sim10^2$ to $\sim10^6$ particles/cm$^3$ * Expansion rate: $\sim10$ km/s * Temperature: $\sim10000$ K The central stars are extremely hot (20,000 to 200,000 K) and luminous; their peak emission is likely at ultraviolet wavelengths - too short for the human eye to see. This also means that each photon is more energetic than a photon emitted by the Sun, on average. That's not fantastic for an ozone layer. I suspect that there would be atmospheric loss on the planet orbiting the companion star, although at a distance of 100 AU, this could be minimal. ## Ablation Stellar winds and outflows tend to have negative effects on planets in the nearby vicinity. For example, some Hot Jupiters may have their atmospheres stripped away and become [chthonian planets](https://en.wikipedia.org/wiki/Chthonian_planet), thanks to intense radiation from their parent stars. The same thing should happen here - and keep in mind that the wind of the central star is likely much greater than the nebula's expansion rate. For planets close enough to the central star, [they will gradually be ablated, and have their atmospheres stripped away](http://adsabs.harvard.edu/abs/1999MNRAS.306..806S). This is one place where I disagree with PipperChip's otherwise awesome answer. It's thought that planets with small enough orbits may even form large tails, thanks again to the ionizing radiation. In short, yes, for the relatively brief duration of the planetary nebula (tens of thousands of years, perhaps), the planet could be stripped away, depending on how close it is. It depends on the binary separation. The planetary mass-loss rate is $$\dot{M}=1.05\times10^{-11}\left(\frac{L\_\*}{5000L\_{\odot}}\right)^{1/2}\left(\frac{R\_p}{3\times10^4\text{ km}}\right)^{3/2}\left(\frac{a}{20\text{ AU}}\right)^{-1}M\_J\text{ yr}^{-1}$$ where $L\_\*$ is the luminosity of the star, $R\_p$ is the radius of the planet, and $a$ is its semi-major axis. Here, for an Earth-like planet, $R\_p=6371\text{ km}$ and $a\approx50\text{ AU}$, in the worst-case setup. Perhaps we can assume that $L\_\*\approx10000\text{ K}$. Therefore, we see that $\dot{M}\sim1.13\times10^{-12}M\_J\text{ yr}^{-1}$, or $\dot{M}\sim3.61\times10^{-10}M\_{\oplus}\text{ yr}^{-1}$. Assuming the planetary nebula disperses after about 10,000 years, an Earth-like planet will lose 0.00000361% of its mass - enough to rob it of its atmosphere and some of its crust. Now, the planet will already have been bombarded by stellar winds during the red giant and asymptotic giant branch (AGB) phases of the companion star's life, meaning that it will have *gained* mass - and possibly already had its atmosphere stripped by the AGB star's strong wind. Depending on the outcome of that particular evolutionary stage, the planet will have accreted $$M\_{\text{acc}}=2.62\times10^{-9}\left(\frac{R\_p}{3\times10^4\text{ km}}\right)^{2}\left(\frac{a}{20\text{ AU}}\right)^{-2}\left(\frac{M\_n}{M\_{\odot}}\right)M\_J$$ where $M\_n$ is the nebula's mass. For the same $R\_p$ and $a$, and assuming $M\_n=M\_{\odot}$ (typical for a higher-mass star), we get $M\_{\text{acc}}=6.00\times10^9M\_{\oplus}$ - much less, it turns out, than will be lost. Therefore, most of the mass lost will indeed involve normal matter present on the planet from before the AGB phase. ## Nebula morphology Planetary nebulae are not always uniform, [but come in a variety of shapes](http://www.scholarpedia.org/article/Planetary_nebulae#Morphology_of_planetary_nebulae), including spheres ([Abell 39](https://en.wikipedia.org/wiki/Abell_39)), distorted spheroids ([Helix Nebula](https://en.wikipedia.org/wiki/Helix_Nebula)), and [bipolar lobes](https://en.wikipedia.org/wiki/Bipolar_nebula) ([M2-9](https://en.wikipedia.org/wiki/M2-9)). Spherical symmetry, as in the case of Abell 39, might not be great, but a bipolar nebula could be a lot better for the planet. If the axis was pointed perpendicular to the orbital plane of the other star, there is a chance the companion star (and by extension the planet) would be spared the brunt of the nebula's side effects. One problem, of course, is that bipolar nebulae exhibit strong stellar winds, which energize the particles, but those would be then directed away from the orbital plane of the planet. I was hoping to get some actual data on this, but even in the years since this question was asked, we don't have any examples of planets in planetary nebulae, and only a small number of binary systems. [A few dozen planetary nebulae have been shown to harbor binary stars](https://arxiv.org/abs/1105.5731) as of 2011, and that figure likely hasn't risen by much since then. However, there have been plenty of efforts to model how a binary companion would affect the morphology of a planetary nebula, and it's slowly being understood. In particular, [a binary star system inside a planetary nebula may lead to ionized filaments of gas](https://arxiv.org/abs/1105.5731), smaller-scale structures pointing away from the central star. I don't know to what extent these could be beneficial for the planet - there isn't a drastic change in the shape of the planetary nebulae. Hopefully, more examples in the future can give us a better understanding of what you nebula would look like. ]
[Question] [ The year is 1933 in Europe. The Germans have developed the Flak 18, one of the first true antiaircraft artillery. Previous attempts during WW1 were clumsy and generally unsuitable for the task of shooting down flying things. The new Flak 18 is purpose built to put the hurting on airplanes. During a training exercise in the Black Forest, German scouts discover a great cave filled with treasure, the bones of many many animals and an overwhelming smell of sulphur...a dragon's lair! The main German force is still 30 km away and the dragon is not yet home. The scouts have been gone, taking a small treasure sample with them. They leave the smell of fear and excitement behind them, a dinner invitation to the dragon. You, oh answerer of questions, are the dragon. Your horde has been violated and the tasty treats left a trail back to their camp. Your first snatch-and-grab was a resounding success with many tiny morsels consumed in a single night. Your stomach bubbles in happy contentment. But there are many more to be had and you soon grow hungry. Your next attack however, is not as successful. As you fly to the camp, black puffs of smoke appear in the air around you accompanied by angry buzzing hornet noises that bounce of your beautiful scales. Suddenly, you take a glancing blow to the chest that nearly knocks you from the sky, so you retreat. How will you get more tasty morsels? --- You are a: * Smaug sized dragon with the ability to breath fire to a distance of 50m. You have the usual horns, claws and thick scales. * Operational ceiling without load is 10,000m for an indefinite period. * Operational ceiling with a 1000kg load is 5,000m. * able to hover for very short periods * able to get airborne without any kind of running start. * top speed in level flight is 200km/h. * top speed in a dive is 400km/h. * able to appreciate the subtle nuances of charcoal meat but prefer rare or medium rare at the most. The German camp of 1000 men is in a large clearing running along the valley floor surrounded by tall forests. A paved road runs the length of the valley. The surrounding ridges are inaccessible by truck because of the dense trees. They have [no tanks or armored vehicles](https://en.wikipedia.org/wiki/Tanks_in_the_German_Army#Interwar_period). If you are so inclined, please write your answers from the perspective of the Dragon instead of the more typical third person view. You are up against a German army of strict 1933 capabilities. The only magic in the world is that somehow a giant dragon has somehow found its way into 1933 without prior discovery. [Answer] First, since approach by air wasn't successful the last time, I'd be cautious and approach by ground. A lot of people think of a dragon flying high above, and forget that we can walk, or hold our legs in close and slither like a snake. On my first foray into the camp I got a pretty good look at the layout. Now, I land a distance away and make my way through the trees as quietly as I can. My night vision is excellent, and I'm approaching from down wind, so I have a good idea of what is coming up ahead. I run in to two of the creatures walking through the forest, but come up behind them, and so am able to catch them unaware. It was a good snack and much appreciated, as this silent sneaking is much harder than my normal majestic flight. When I get to edge of the clearing I can see the prey in their small wood dwellings. From my first attack I know they have things that throw hard lumps of metal at me, but they aren't strong enough to pierce my beautiful scales. From my second, failed attack I know that they are adaptable, and learn from their mistakes. They have some level of intelligence, as they are tool users. Unfortunately for them, they are also tasty. There is a thin barrier around the camp, and once I go through it the whole camp will be on the alert. I will have to move quickly, but what strategy should I use? If I strike them and run they'll learn from it and may make it harder next time. I should hit them hard, destroy as much of their camp as I can, and try to scatter them into the forest, where I can hunt them at my leisure. I see their game trail heading out of the valley, and decide to drive them away from that. There are many of them, and I will lose some meat to fire, but since most animals are scared of fire I'm hopeful that they will leave the clearing instead of burning. It's dark, the camp is quiet, and there is no moon. I smell many of the creatures here, but few of them are out in the open. I burst from the forest by the road with a roar that shakes the very stars, and follow it with a stream of fire that sets several of the larger buildings near the gate on fire. Flame spreads, and several metal tanks near one of them explode in giant fireballs. I wasn't expecting that, and flinch back, but it's over quickly. I roar again, and pause to admire my work. Utter, beautiful, chaos. Creatures are emerging from their dwellings and looking around, lit by the fire. Some use their metal throwers, but again they don't have much effect. Many more begin to run, as I hoped, when I see a flaw in my plan. The barrier that surrounds their camp will keep them from getting into the forest as I planned. Easy enough to fix, if I move quickly. I jump into the air, my wings spread for a quick flight just above the roof tops, and I breath fire below me to sow more panic and confusion. When I reach the barrier on the far side of the camp, I land, tearing down a large section of it. Then I leap again, back toward the entrance. I dip my head down as I glide, snapping up a running figure. Mmmm, nice. Then I smash some more buildings with my long tail. I see some different structures from elsewhere in the camp, and this was the area where the light flashes came from, before the buzzing hurting things attacked me. I loose my flame, and make short work of the hurtful things. When I over look the camp again, I see many of them have fled, and only a few remain, looking discouraged that I've mostly ignored their feeble attack. Cheer up little ones, I will ignore you no more! I move quickly among them, grabbing with jaw and claw, eating as many as I can. Then as the others scatter I unleash my rage, smashing and burning the remaining buildings, giving them nothing to return to. Once the task is done, it is now time to play. I turn toward the forest. It's time to hunt! Later, when my belly is full, I begin to ponder... Where does that game trail lead? [Answer] A valley clearing with tall forest all around and one paved road in/out? Sounds like a recipe for dinner. **Step 1:** I rip up a bunch of trees and block the paths, and set fire to the forest in a circle around the camp. I clear a "ring" of area around the outside of the fire, so I don't burn down the entire forest, and so that the fire only spreads towards the camp. This is also to prevent anyone from trying to run away. **Step 2:** Staying as low as possible, while above the treeline, I start lobbing trees into the camp. Ideally the scenario should be somewhat like this ``` \ / Front view \ ME / where the = are stacked trees blocking the path \ |||||=||||| / where the ||| are burning forest \|||||=|||||/ and the \/ represent valley walls <--- Throw trees this way <------ ME |||| V ||||| Side view where __ is clearing, || is burning trees ||||________V__________||||| ``` Note that in the sideview we can see that by staying away low and close to the treeline, the enemy can't actually see me because there are burning trees in the way. Once I think enough trees have been thrown in to cause a decent amount of casualties, and to disable their main flak cannons and what not, we proceed to step 3. **Step 3:** Fly up high and see if they start shooting at me. If yes, go back to step 2. If not, continue to step 4. **Step 4:** Since they've stopped shooting, I'm safe to swoop in and pick out my din din~ Since they were in a clearing, they won't be charred at all! Rare humans, pre-tenderized by the falling of giant trees! [Answer] While I waited for the scratches on my armor to mend themselves, I pondered the arrogance of these fleshlings. To strike at me, ME! The knights of old and I had an understanding: they run when I appeared on the horizon and I let them flee. Perhaps I slept too long. Whatever world this is, it should be reminded who is *really* in charge. But doing so will require more tact than this morning. These fleshlings have tricks I've not seen before. I'll need to investigate these smoke balls, see where they come from. I stand and spread my wings. With a strong shove, I leap into the air. The setting sun gives me a last farewell before dipping below the horizon. Not that I care. The world is my playground, by day or night. I can hear the fleshlings beyond the ridge, but I won't just rush in. I land on the cliff overlooking the fleshlings. I stretch out and settle in, surveying the area. I can see them. All of them. They almost glow in the dark to my eyes. Some small groups are standing off from the rest. Six groups, four fleshlings each. They are near strange iron monsters with gaping mouths pointed at the sky. The monsters are silent, but subservient to the fleshlings. I've not seen their kind before. It is a good enough place to start. I pull back from the edge and rise to my feet. Once more, I leap into the night sky. A few flaps put me in the perfect position. I fold my wings and tilt forward. In seconds I descend silently out of the night onto these arrogant fleshlings. I see the monsters on the edges of the camp. I inhale deep; feel the fires sparking in my chest; and, with aim born of long practice, unleash my fury upon the flesh below. Fires bloom beneath me, igniting the flimsy armor of the fleshlings and reducing the subservient beasts to slag. I turn, spreading my breath in a ring around the fleshlings, passing from one monster to the next. When my fires have set a ring of trees on a course for ash and the monsters are destroyed, I plummet to the center and land with a thud. Pebbles strike at my sides and wings, a few at the corner of my jaw, but these are less irritating than the sands of the far south. Hemmed in by the instrument of my wrath, these fleshlings are now set to realize they are inferior to my glory. With a gleeful roar I set to the task of recovering my hoard and enjoying a feast the like of which I haven't known in many long years. [Answer] George the Dragon here, stepping out of the time machine into 1933. I would start by making sure I was as light as possible for the outbound trip. Needless to say, a pre-sortie bathroom break would be most certainly in order! Next, given the presence of the guns, I would study whatever maps I had, looking for likely ammunition stockpile sites. Given that the 8.8cm FlaK 18 was only good up to 25,600' due to limitations on shell fuzing and accurate target heightfinding, and I can get up to 32,000', I can outmaneuver the gun's ability to accurately deliver shells my way by maneuvering in the vertical plane, in a not-fully-predictable sinuous fashion as they need to accurately determine how high up I am to set the shell to go off next to me, instead of going off prematurely or bouncing off me without detonating. As a bonus, they might send a convoy out to deliver ammunition to a gun-site, which would allow me to follow that convoy back to the dump. Once the ammunition stockpile is sighted, I would strike swiftly, using a maximum-speed dive to get within striking distance of the target. Since they are using time or altimeter fuzes on their shells, getting an effective hit on me during the pass would be a matter of sheer luck or swift changes in shell settings, not aiming alone. Now that the ammunition dump is burning brightly, I simply use the speed to enter a zoom climb initially before transitioning into a maximum sustained rate climb back to cruise altitude, and can cruise home, performing a penetration descent on arrival to again minimize my time in the 'hot zone'. No food yet tonight, but boy, they'll be in a pinch for a while! Serves 'em right for shooting at me, morons...and maybe I'll be able to hunt in peace for a few days or weeks while they bug HQ for replacement 88 ammo. ]
[Question] [ Shortly after the [Washington Naval Treaty](https://en.wikipedia.org/wiki/Washington_Naval_Treaty), the British designed and built two [Nelson-Class Battleships](https://en.wikipedia.org/wiki/Nelson-class_battleship), and a decade later these designs inspired the French [Richelieu-Class Battleships](https://en.wikipedia.org/wiki/Richelieu-class_battleship). Both of these designs have a very significant quirk, in relation to this question: All the guns in their primary batteries are capable of firing forward. Now, there were a few issues (Especially with the Nelson class) of firing all the guns directly forward - But this question assumes these issues have been or can be solved. The question is simple: **Would a line of battleships with Nelson-style configurations have the advantage when their [T is crossed?](https://en.wikipedia.org/wiki/Crossing_the_T)** In most T-crossing scenarios, the ships being crossed are at a disadvantage because their rear weapons cannot fire. In earlier warfare with fixed guns, it was even more devastating because almost all of their guns could not fire. Nelson-style configurations, however, do not suffer from this and can fire all of their weapons on the targets in front of them. All of those targets which are presenting wide fronts, while each of the Nelson-style ships are presenting narrow fronts. To be completely fair, I don't envision this as an ideal position for the Nelson-style ships to be in. Their enemy can still fire every one of their guns. However, the Nelson-Style ships don't have the disadvantage that normally comes with having their T crossed, so perhaps the playing field is going to be a little more level. I am curious as to what sort of things I may be missing out. I'm not a military or naval strategist - My interests lie significantly more on the engineering and technical end of things, so those are the details that stick out to me. Relevant information: This is targeted at the world I'm building, 50s ish tech where shipbuilding is advanced but [aircraft never gained dominance](https://worldbuilding.stackexchange.com/questions/81301/delaying-the-development-of-aircraft). Battleships tend to be [bigger and have bigger guns](https://worldbuilding.stackexchange.com/questions/75754/advantages-disadvantages-with-large-naval-guns), but realistically speaking treat the ships as being largely equivalent except for gun placement. [Answer] # Think Squadrons, not Ships * A battleship is a couple hundred metres long. With a reasonable safety distance for maneuvers, two ships will be roughly a kilometre apart. A squadron in line will be several kilometres long. * Effective gunnery range will be a few tens of kilometres. * Speed is 30 to 50 kph. A squadron in line might take ten minutes to steam past a stationary observer. A battle fleet takes longer. Draw it up on graph paper and measure or calculate the ranges. Assuming that both sides have the same gunnery range, the crossing force will be able to concentrate the fire of **all** their ships against the **lead** ship of the enemy for several minutes while the rest of the enemy is still out of range. [Answer] By the time of your scenario crossing the T is a less useful tactic. The nail in its coffin is radar, which allowed ships to get a very accurate picture of the enemy's position and bearing, even over the horizon, which combined with mechanical gun computers, meant that guns could be laid very accurately. If you could get into a position where you could cross your opponents T it still meant that you could get more guns on target but given kilometres of maneuver room and forewarning it was considerably harder. The most recent example of crossing the T Battle of Surigao Strait (1944), but in that battle by the time the T was crossed the Japanese had already been crippled by the US who outranged them and they were trapped in a strait that meant they were not free to turn to broadside. What this boils down to is the ability to fire all of your guns when bow on is of limited utility. It would mean that in the event that your T was crossed you could reply with all your guns, so you'd be equivalent going up against a ship with equal weight of fire, range, and positioning data. However T crossing is going to be rather rare, potentially a ship might go it's entire service without ever using this feature. [Answer] A force of *Nelson*-style battleships would be at a great disadvantage if their T was crossed to their rear, which was a valid tactic, although a bit harder than crossing the T to their front. This tends to suggest that T-crossing wasn't a major factor in their design. The actual reason for the design was to save weight. They were designed in the immediate aftermath of the [Washington Naval Treaty](https://en.wikipedia.org/wiki/Washington_Naval_Treaty) which had placed limits on the weight of battleships. Putting all the turrets close together reduced the total weight of armour needed to protect their magazines. The British were very keen on protecting magazines after several of their ships exploded at the Battle of Jutland. [Answer] I'm by no means a military history buff, so take this with a grain of salt... I'm thinking that it would largely depend on range and given the blockade formation (several ships side by side) that this would probably be a longer range engagement to start off. Long range shots tend to be parabolic, aim high on your target and expect an arch in the shot. This may sound obvious, but determining distance tends to be more difficult than direction... More or less it's much easier to adjust left and right than it is to recalculate the distance (pitching the barrel up or down) With that out of the way... You'll present a smaller target approaching head on, from a left right perspective, but a slightly larger target on the other axis. See: <https://en.m.wikipedia.org/wiki/Projectile_motion> for the math. I think I get the source of the question... In earlier naval combat "broadsiding" was more of an issue. Canons were shorter range and shots tended to require less of an arc and you could place a lot more cannons down the length of a ship in fixed placement, but by the 1920-30's artillery had progressed enough to allow for much longer shots. These larger artillery pieces also tended to have larger calibers and longer barrels, so a forward facing placement was a bit more practical. Kind of the difference between a volley of fire approach and a more targeted approach. [Answer]   Nelson-class could not fire all of their guns facing forward. As you can see from the picture, third turret is below second turret. When guns from third turret face forward, they aim directly into second turret. <http://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/The_Royal_Navy_in_the_Interwar_Period_Q70606.jpg/790px-The_Royal_Navy_in_the_Interwar_Period_Q70606.jpg>   Richelieu-class could theoretically fire all of the guns facing forward (guns from second turret over first turret). But problem remains, if such ships steam in battle line, could guns from second ship fire over first ship without hitting him ? And could gun laying equipment on second ship even detect targets (and shell splashes) when first ship in line blocks their view ? <http://upload.wikimedia.org/wikipedia/commons/3/34/Richelieu_1943.jpg>     **Therefore, crossing the T remained relevant tactics until the end of era classic gun-armed battleships.** [Answer] As others have mentioned by this time period crossing the T did not offer much of an advantage. Older ship designs had primarily fixed broadside armament that could on fire to the side of the ship. They few if any guns that could fire forward or rearward. Many battles were two lines of ships sailing side by side. If you could arrange your line of ships to cross in front of or behind the enemy, all of your broadside guns could fire down the length of your opponents ships doing tremendous damage. More modern ships had their guns in turrets that could be rotated to fire in different directions. The guns were far more accurate and had a much longer distance virtually eliminating the lines of ships sailing side by side in battle. Add to this weapons like torpedoes and aircraft and the line of battle were no longer effective and crossing the T effectively no longer existed. [Answer] I would think that by the 1950's in your scenario, "crossing the T" would be considered archaic. Firstly, even early in WWII, capital ships had radar, and by the end of the war radar had been well developed. Secondly, scouting ahead is still possible, even without airplanes or zeppelins. Destroyers or Frigates with radar, powerful optical systems and radios would be ahead of the capital ships, both to warn them of the enemy approach, but also to spot for the big guns. Finally, and perhaps a bit of a stretch, artillery weapons might have reached well beyond the few tens of miles of traditional Battleship guns. The Germans pioneered this with the "Peenemünde Arrow Shells", highly aerodynamic shells fired from a modified version of the Krupp K-5. Ranges of well over 100km are claimed, and apparently this is why "Anzio Annie" could not be bombed - the allies were looking in the wrong place and had no idea the range of the cannon was so great. A Battleship with such weapons would need to operate in a much different fashion than a more conventional ship. Assuming some form of airplane is possible, then an observation plane flying well ahead of the ship is needed, otherwise, very fast scouting ships would need to sail in a ring formation around the Battleship far enough out to identify targets and radio in corrections (even a radar set on the Battleship itself would not be able to detect targets that far over the horizon. Even when wisely dispersed, with proper radio procedures Battleships would also be able to concentrate fire, even a fairly long column formation would still see the rear ships able to fire over the column and add their firepower to the battle. So, no, advances in radar, communications and artillery would render the idea of "crossing the T" archaic. ]
[Question] [ A message arrives from several light years away. It is a complete prepared document, not a two-way communication. The document can contain line-drawings and diagrams, both 2D and 3D, plus movies (a time dimension) and overlays. Now it’s straightforward to teach the syntax and encoding through careful examples. It can talk *about* polygons and such that it illustrates, and recognisable depictions of things we know about like our solar system and immediate stellar neighborhood. So we can understand the names for specific objects, properties of those objects, etc. From mathematical examples we know about category containment, and using our own solar system as a Rosetta Stone we learn words for various properties and how they are expressed. So, we can then understand when they mention, for example, a planet named `label` with a particular mass and radius, that we didn’t know about before. To recap: categories and properties are learned from known examples, and can then be applied to other things. But how can they communicate an idea like “like” or “desire”? How can they teach the words needed to convey a polite invitation? It’s easy to describe a navigational course. But how to say “the ship you make should follow this course”? And given that it’s possible, how do they say they would “like” us to visit? That is, a polite invitation rather than a demand? --- By “polite” I don’t mean usage of diplomatic protocols and rituals, which they cannot know. I mean that it is a request (not a demand) and they would be *happy* for a visit, but we are free to decline. --- Although the sender is a powerful KⅡ or higher civilization, they are just [passing through](https://worldbuilding.stackexchange.com/questions/52675/how-to-set-the-lightsail) at 10% *c*, and don’t know us in detail — only what they can see from 10’s of light years with [enormous synthetic apertures](https://worldbuilding.stackexchange.com/questions/45756/how-big-can-we-make-a-telescope) on the order of half a light year. [Answer] I don't think they actually need to communicate this explicitly; the invitation will be implicit in the message. The message must be aimed directly at earth for us to be able to receive it, so the navigational informational will also be specific to us - a depiction of a ship traveling from earth to their planet, for example. If they have sent us specifically this course, we can reasonably assume that it must be either because they desire us to follow it or desire to tell us to never follow it. Since we would not even know about their existence if they hadn't sent the message, we can reasonably assume that they are not telling us to keep away, and so implicitly a message that outlines a navigational course from earth to their planet must be an invitation to travel that course and visit. So long as the aliens can assume we will interpret the message as showing a ship traveling from earth to their planet, they can reasonably assume we will understand it as an invitation to visit. **Edit:** If you actually need them to teach us their language and make the difference between a polite request and a demand explicit (for story reasons, perhaps), then I'm not sure it's possible. If it were a human language, the only way I can imagine this could work would be showing video/cartoons of situations of language use where it is obvious from context (facial expressions, other people's reactions etc) which are polite and which are impolite ways to say something. But without a common cultural or even biological frame of reference I don't see how it could work with an alien species. I think interaction would be the only way to do this. --- **Response to question edit:** > > By “polite” I don’t mean usage of diplomatic protocols and rituals, which they cannot know. I mean that it is a request (not a demand) and they would be happy for a visit, but we are free to decline. > > > Again, I think this is implicit in the message itself - is there any way that it *could* be a demand? To demand there has to be some way for non-compliance to be enforced, which would presumably require them to visit us. If they are unable or unwilling to do so then a demand would be empty. Communicating that it is a demand would probability be easier than that it is optional - a tree-diagram of possible future sequences of events 1: "receive message, humans travel to them" 2: "receive message, humans do not travel to them, they travel to earth." Perhaps they could communicate that it was optional by adding a third option 3: "receive message, humans do not come to them (then nothing happens)" and by showing option 2 as being crossed out in someway? [Answer] ## Informational maze Imagine it is mosaic mosaic mosaic .... n times ... mosaic of datasets and that tree of those mosaic/datasets it is just one of the possible interpretations of the main dataset send by the aliens. The same way as you may have an encrypted message, which is compiled in the way that there exists set of m keys with decodes the encrypted message in m meaningful texts. Each time you decode one layer of the alien message it gives you x new keys to dive deeper in the message. The data sets are any data sets - images, texts, schemes, math, models, whatever it might be. Let say in the data set there is $n$ layers and $m\_n$ possible keys in each layer. So potentially the message can be interpreted in $(m\_n)^n$ meaningful ways. [![enter image description here](https://i.stack.imgur.com/Xvh9Ds.jpg)](https://i.stack.imgur.com/Xvh9D.jpg) [source](http://www.designerstalk.com/forums/discussion/76804/photo-mosaic-software) On the picture, especially when it is small we see something which for us looks like something similar to eye picture, the human eye. So for a human, it can be a meaningful information, but for someone else is just mosaic from smaller pictures(data sets) which in the particular case are different eye images but it can be any images(data sets). So, not a human will not get a human key in the layer and the layer will be kinda transparent for another alien(not human), most likely for an alien the piece of information will be just a data set with no layers in it(they will not see that it is the picture of the pictures). But a human will see the eye and it might be a key to interpreting the data set in a human way and as result get next human oriented layer of the information. Alien sees nothing here, except - yeah there is some kind of information, we understand that but we have no clue how to interpret it, and for them, the particular piece of information will be the dead end in decrypting the whole set. Which keys get those who decrypt the main data set will depend on who they are. And the whole dataset with all those layers will form an n-dimension maze, and the path trough the maze will be different for different species, humans, rocks whatever - those who decrypts the information. And that allows the aliens to encrypt different information for different aliens, in one message. ## Beauty is in the eye of the beholder Which information opens depend on the interpretation, the particular combination of keys, and probably the sequence in which they were obtained - all that will determine the result, the "message". But what if one sees let's say 2 keys. [![enter image description here](https://i.stack.imgur.com/UN9n5s.jpg)](https://i.stack.imgur.com/UN9n5.jpg) On the picture, it is the matter of your own preference what to see. You can interpret it in any way (there is a lot of such pictures on the internet I just took first from the list). There 3 sets of stories about the picture, one set perfectly fit one interpretation, one set fit another interpretation, one set which fits both or neither. Same is with ideas interpretations, the story [Shakespeare in the Bush](http://www.naturalhistorymag.com/picks-from-the-past/12476/shakespeare-in-the-bush) - true or not, but the difference in interpretations of an idea may lead to different actions. Same story in any dataset. One can see the things he likes to see in the data set. And may prefer one interpretation over another interpretation, by working with the information which he likes more. The choose can be conscious or unconscious it is not important, but the choice itself defines the preference of the decoder. By !preference we define not preferred stuff and do it the same way trough the moving on the path of preferences maze. The aliens can create the message for different types of aliens, even without knowing them, possible with the use of the modeling system from another alien related answer [Aliens are on their way. What can cause them to not understand us?](https://worldbuilding.stackexchange.com/a/41975/20315) So yes, if aliens have emotions, we can transfer them the message which will have the proper translation of emotions, including our translation of politeness into their emotions and concepts. So yes it is possible to send emotions, and do it even in the way they will not think that you smile but have a knife in another hand. But mostly I agree with @Tharaib's [answer](https://worldbuilding.stackexchange.com/a/70647/20315), it is complicated and not very much needed. Send them information about presence - polite invitation Send them schemes of a magical power device, working in the way they will discover later, after they will have critical mass of those devices, that it will explode in 100 years all at once - it will be kinda demand - you have 50 years to fly to us, and try to get proper information how to stop collapse of your civilisation, your move. ## Note It is possible that after decryption, there will be a hologramme of George Washington in his national costume on pure english(better than my) will polite invite the human civilisation to the aliens. [Answer] Aim at the basics of life and hope that life is somewhat universal. If I show you a video of a creature eating and then excreting, I can probably get across to you the biological need that the creature has for that food -- especially if consumption of food is common across life forms. Then I can work from there. a) Fear. Show another creature eating the carcass of the original creature. Show it excreting. Then show it stalking one of the original creatures, and show that creature running away. Do this with several pairs of species. b) Desire. Show the original species, trying desperately to reach a just-out-of-reach piece of food. c) Animosity. Two animals fighting over the same piece of food. And so on. If you do this with enough different creatures, we would hope that they would see the analogy and focus on the commonality across the videos instead of the aspects of any single video. By recognizing the value of food, they can probably extract the sentiments around it. It may be less successful if they're a bunch of sentient plants who never compete for resources sentiently, but even there, we could reasonably hope that they have animals on their planet and can compare the behaviors. [Answer] A commonly understood way to share a concept or idea is by extending an example of it first. To show politeness to a civilization they do not know much about, they can first share information about themselves in the message, choosing images and concepts about themselves that they value highly and that they interpret to be welcoming and polite by their own standards. This can be followed by the directions to their location. Although very simple, the message would be clear: This is who we are. This is where we are. Having the communication end there is universally understood by the recipient of the message that the next step in communication is up to them to initiate, just as it would be understood during in-person communication. It would be unusual to interpret a message extended this way as a demand to come visit. They also do not need to worry about if their customs and values will be offensive to a civilization that would interpret them that way, because if so interpreted, then the recipients of the message simply choose not to go visit. If, on the other hand, the message recipient finds connection with the alien culture and can understand and correctly interpret what was extended as polite and welcoming, then those message recipients might choose to visit. [Answer] Ways to communicate "come here" - Human - Earth Bobites - Bobia Human - Bobia --- Human - Earth Human - Mars Human - Travel - Earth - Mars Human - Travel - Bobia --- This would work and is a good assumption that the translation is "Humans travel to Bobia". You will have also had True/False, numbers and atoms already translated in this as well as some logic functions so there are things that you would use from logic like... = = IS + = AND TRUE = YES/DO/PLEASE/WE WANT FALSE = NO/Negation So message might read: FALSE BOBITES [travel/move] (to) EARTH TRUE HUMAN [travel/move] (to) BOBIA A question might be phrased more like: HUMAN [travel/move] (to) BOBIA TRUE FALSE The True at the beginning only means "We want" because we are assuming that normally the statement would not have True at the begging. And we'd also assume that if they wanted to tell us something is true they'd make the statement "blah blah blah = true" or reverse for "true = blah blah blah". The = making it clear we're saying IS rather than a preference statement But really you could get a lot more sophisticated than this because I'm doing it off the top of my head, but you have pictograms for things like "over" "under" "to" "away". You likely would have a symbol for star which would double as "light" too. Basically to do this you would have to deconstruct language and then build it back up. This isn't too hard. You just have to use pictures for actions with a symbolic name for that action then write what you want using logic symbols and these verbs. It would likely be crude, but you could do it with a little effort. You would have to be careful with "give/take" and some others because it is easy to consider the whole of the action rather than separating them into give and take. But over all the only issue is the risk of misinterpretting, but thats a risk with all translations and lanuages, even perfect ones. [Answer] In my story, I plan to do this by using *parables*. Starting from a base of diagrams, geometry, math and logic, and phyeical size, mass, motion etc. from labeled drawings of the recipient’s solar system, it will start out describing the purely physical characteristics and behavior of several groups of animals. The animals are simplified cartoon characters, having just the needed features for their respecive niches. A sketch shows that it has digestive system, circulatory system, central nervous system, limbs for manipulating the environment, etc. Then various scenareos are given where the animals do their thing. It will be clear that they need to engage in survival activity, with certain conditions being manditory for survival and broader conditions being desirable. As a prerequisite, the idea of a computational device is explained. Examples include clockwork, electomechanical devices, photonics, fluedics, semiconductors, etc. all shown as being described by logic gates or mathmatical rules with equivilent algorithm descriptions. So, it can note that the animal’s brain has a state, with storage of memory and evaluation of inputs and decision making. A set of descriptions is ascribed to the brain. These will be understood by the reader as being moods or emotions or however they think of such things, even if that’s different from what we can imagine. The cartoon animals are seen to have goal directed behavior to promote success of the species, with long term survival goals and short term immediate goals. We (for example) would label these descriptive symbols with words like “want”, “fear”, “pain”, “happiness”, etc. So, simple animals “desire” food, shelter, mates, etc. and are “happy” when such a goal is acheived. Then advanced social animals are “happy” when cooperating and communicating. Then technological beings are “happy” when crafting a new tool or creating art. By starting with pure goal-directed behavior, the same terms can then be applied by analogy to successivly more advanced species and abstract reasons. So when they code “we desire…”, the reader can trace the meaning of that from analogy with situations that are more optimal without being matters of immediate survival, like access to rich food sources for exploting over the coming season, for a preferred mate, for a meeting of representatives of two tribes when they are each doing just fine and not in direct competition with each other. [Answer] If they know about our (humans on Earth) existence and want us to visit them, they must also know our biology and customs in details. You do not send an invite letter on millions of drones, randomly in the galaxy. A map of route from Earth to their planet, with a smiley face and heart sign would convey the message particularly well. A video of a welcoming party, waiting for guests would also help. If a civilization is advanced enough to interpret their message (as in, to interpret where the planet is and what is the route to them) they would also have an excellent chance of understanding the feeling of anticipation in the video. ]
[Question] [ So I went and saw Rogue One recently. Wonderful movie... **If you want absolutely no spoilers STOP READING NOW.** The Death Star shoots up a couple planets in the movie. (Not much of a spoiler but still.) They don't poof like Alderaan in episode 4. (They aren't completely destroyed.) In Rogue One the laser hits the planet causing a massive explosion (Looks very similar to an atomic blast.) followed by an eruption of dirt flowing like a tsunami outward destroying everything is sight. Now I think that this is not a very accurate depiction of a planet destroying laser [This article seems to confirm my suspicion.](http://www.forbes.com/sites/ethansiegel/2015/08/15/the-science-of-the-death-star-the-physics-of-destroying-an-earth-sized-planet/#374d47fa6921) And I was curious how an actual planet destroying laser would destroy a planet. My question is: Assuming we have a laser that has enough energy to destroy a planet (Greater than or equal to 2.24 × 10^32 Joules.) what effects would it have on the planet? What exactly would happen to the planet? Would the laser just super heat the planet liquefy the surface or would the planet actually explode and turn into an small asteroid field? Here are some things that might narrow down the situation just in case this question is too broad. * The planet we are shooting is Earth. * The laser is just an extremely, extremely powerful laser there is nothing special or unique about it. (No Kyber crystal fuel.) It doesn't matter how it works it just does. * The definition of destroyed is very vague. However if you have seen the death star in action you should have an understanding of what destroyed means. The planet should no longer be considered a planet after the laser has done it's job. [Answer] The sheer physical energy of the laser will rapidly turn matter into plasma (certain efficiency and coupling effects will be enhanced or degraded depending on the wavelength of the beam, but I suspect that at these energy levels the amount of difference it will make will be overshadowed by the scale and scope of the beam itself). In the first microsecond, the atmosphere under the beam will immediately be turned into a superheated ionized plasma, expanding rapidly outwards from the strike. The idea anyone within a few hundred kilometres will survive being lashed by supersonic waves of plasma is questionable, at best. Striking the surface will result in substantially the same thing, rock, soil, plants etc will be converted into a star hot plasma. Interestingly, the plasma will try to "run up the beam". but the extreme heat and electrostatic repulsion of the ionized plasma will tend to drive it apart, resulting in a massive inverted cone of plasma leaping out of the ground and into the vacuum the beam has created. For areas outside the immediate strike zone, a supersonic shockwave will blasting away from the area, continuing to excavate a larger and shallower crater entered on the strike zone. Something very similar will happen if the beam lands in the ocean or body of water, the main difference being the plasma will be largely hydrogen and oxygen, rather than an unholy mess of silicates, metals and organics. Burrowing through the crust will take a bit of time, although the massive pressures developed by the plasma will clear out the laser channel and prevent the hole from collapsing due to static pressure. The oceans might actually allow the planet to survive for a time, since water will continually try to flow into the plasma "hole" and the boiling sea water will carry a great deal of energy into the atmosphere, meaning the beam might have to dwell for a while to evaporate enough ocean to strike the seabed. Assuming you haven't targeted the edge of a crustal plate or the magma chamber of a super volcano, the beam will continue to the point where static pressure is finally able to overcome the pressure of the expanding plasma. You will already be feeling earthquakes, but now the beam is "pushing" on inflowing rock (at the scale of planets, matter should be treated as a liquid). Depending on the depth of the hole, magma or even plastic rock from the mantle might be flowing into the hole to be immediately vapourized. An observer in orbit will see the huge inverted cone of star hot plasma exiting the atmosphere and accelerating into space. Some of this may "condense" around the edges of the cone, and shower down around the planet, igniting a global firestorm. Much of the remaining atmosphere may well already be poisoned by various oxides as the hot plasma reacts with atmospheric oxygen. If at this point the laser is stopped, there will be a sudden inflow of rock, water and gasses into the huge vacuum that was created by the laser and expanding clouds of plasma, generating more violent storms, earthquakes and tsunamis. The surface of the planet will have been scoured by supersonic waves of plasma streaming outwards from the strike zone, and as the plasma cools, the surface may well be covered with a thin glassy layer of rock vapour that condenses on the cooler surfaces. If the laser continues for a prolonged period of time (I don't have the math to figure this out, but intuition tells me this will take several hours), the pressure waves of the plasma will be moving through the mantle and around the core, creating violent earthquakes on the opposite side of the planet. As an aside, the planet will also be getting some severe earthquakes due to the plasma plume acting as a rocket engine and pushing against the Earth as well. In terms of planetary destruction, the laser will fairly rapidly strip off the planetary atmosphere, by heating the gasses to well beyond the escape energy required to leave the gravity well. The water will be eliminated by a similar process, but lasting for a considerable period of time, given the massive amounts of water on the Earth. Carving a hole in the crust will trigger violent earthquakes, but shattering the crust or lifting massive chunks of the Earth bodily into space is likely not going to happen for a while yet. The increasing amounts of energy in the mantle will stir the plastic rocks there violently, triggering massive earthquakes and probably shattering continental plates along the edges, but until the mass of rock reaches the point where it is essentially turning into "steam", you won't see the crust blow off into space. Once the crust is blasting into space because the mantle is turned into vapour, we should consider the core. The violent pressures in the mantle will actually increase the pressure on the core, but asymmetrically. As the amount of matter over the core is suddenly reduced, the core will violently be disrupted, and the huge amount of energy from the heat and pressure will be dumped into the remaining mantle, "splashing" it violently into space. So I do hope someone can do the math to get some real times, but my sense of the matter is the laser will strip life off the surface in a short period of time, but will need more than a day to impart enough energy throughout the mass of the planet to actually blow it up. [Answer] It's highly likely your laser of doom will actually start generating antimatter. See, when you focus a powerful enough laser into a small enough spot, you start generating electron-positron pairs (this is what the Extreme Light Infrastructure laser is supposed to accomplish when finished - and it's only a petawatt class laser, focused so that the beam has a radiance of >10^23 W/cm2). So the death star likely generates quite hazardous quantities of positrons and electrons which will almost certainly annihilate each other to produce lots of gamma rays, whether this has much of an effect on the overall level of destruction is open to debate. Needless to say, when the thing's running there'll be supersonic shockwaves full of molten rock bullets, plasma that makes the sun look like an ice cube, xrays, gamma rays and antimatter. Just something to be aware of (you know, so you can attach the correct safety labels to it) ]
[Question] [ Many mythologies across the world independently devised monsters with similar appearances and/or modus operandi. Many modern encyclopedias of mythological monsters often include cross references between similar monsters from different mythologies (e.g. compare lilith and lamia, hippogriff and simurgh, etc). A modern subgenre of fantasy known facetiously as "kitchen sink" fantasy (from the expression "everything but the kitchen sink") includes elements from all world mythologies and usually makes no attempt to reconcile them. If one wanted to avoid this and write a kitchen sink fantasy where similar mythological monsters are different manifestations of the same archetype, what would be good resources? [Answer] You might want to check this page out: [List of legendary creatures by type](https://en.wikipedia.org/wiki/List_of_legendary_creatures_by_type) It gets kind of fuzzy when you're trying to define exactly what counts as a "legendary creature" though. Do creatures unique to modern sci-fi/fantasy literature, TV, or RPGs count? What about those invented by writers from the 1800s? How about the "fearsome critters" of North American folklore? Medieval literature also had plenty of books with more types of weird demons than you can shake a stick at. For the older creatures, though, you can definitely discern clear archetypes which are often mixed together in various ways. Blood-drinkers, animal shapeshifters, literal sexual predators, and child-eating bogeys are pretty much universal. These may be mixed together in almost any combination. Lilith and her ilk get extra points for having all four. Let's not forget water-dwelling predators, which can be found in almost any non-desert culture and typically have one or more of the above qualities. It is telling that the "associated with water" section is by far the largest on the Wikipedia page. Giant humanoids, restless dead, witches with vaguely-defined magical powers, creatures that are an omen of death, creatures that can kill you by looking at you, and mischievous spirits that may be either helpful or harmful depending on how they are treated are extremely common as well. Cultures that valued either wisdom or piousness (both East and West) often had monsters that represented a more subtle threat than the ones who would simply eat you, like tengu or demons. The idea of automatons made by magic or technology is also more common in ancient stories than a modern reader might expect. Then you have the weird ones, like the dream eating Baku, the mind-reading Satori, the Rokurokubi, a woman with a floating head... actually 90% of Japanese monsters can probably be thought of as 'weird' to Western audiences, though no weirder than the aforementioned medieval demons from the west (like wheels covered in legs...seriously). And of course, creatures that are just mash-ups of other creatures are fairly typical, especially among Mediterranean cultures. We might be accustomed to Greek creatures like the Chimera and the Hydra, but from a standpoint of common mythological archetypes they are no less mold-breaking than the wackiest of Japanese yokai. Some archetypes may be more common in certain cultures than others - for instance, Celtic culture tended to have a lot of unpredictable but sometimes-benevolent fae, while most Greek monsters are Always Chaotic Evil. Certain concepts are also culture-specific and may spawn many unique monsters; for instance the idea of mundane creatures or inanimate objects 'advancing' into magical creatures or animated spirits (kitsune, carp -> dragons, tsukumogami) when they get old enough is a common idea in Japan, while Western monsters are typically born monstrous (except when they are ghosts). Keep in mind that many archetypes may be blended unpredictably, even within the same "creature". For example, while modern culture tends to separate vampires and werewolves, many cultures view bloodsucking and animal shapeshifting typical habits of the same creature. There are also some weaknesses shared by many different monsters - sunlight, silver, an inability to cross running water, obsessive-compulsive counting, and occasionally salt are shared by several members of the nebulous werewolf/vampire/witch family and their relatives, depending on the particular legend. Iron is a common weakness among various fae. A lot of spirits and demons are susceptible to certain incantations, and wherever Christianity touched you'll find stories of monsters that are repelled by faith or holy symbols. Yokai can sometimes be outsmarted by separating them from the source of their power (the kitsune's ball, the kappa's water). In fact, the very idea of a mythical 'bestiary' might not be the best way of going about classifying monsters in a "fantasy kitchen sink" setting, given their tendency to blur together. Classifying the *archetypes* themselves and making each individual creature an unpredictable blend of said archetypes might be a better idea. But that's just my two cents. [Answer] Dungeons & Dragons's Monster Manual. For anyone who doesn't know D&D: it's a tabletop RPG, which has regained some popularity thanks to Stranger Things. Think MMORPG but with one person (the Dungeon Master) serving as the server, and you use your imagination, and a lot of pen, paper and dice to play - overall the best fun a geek can ever know in a life. The Monster Manual is the source for data on monsters, which the Dungeon Master uses for reference on the creatures they wish to bring into play. Such data is not limited to combat statistics - the entries will usually contain historical, political, economical and psychological data on the monster species therein. There are, from my last count, at least five editions of D&D. Each one is a whole different beast (no pun intended). My favorite is the second edition (Advanced Dungeons & Dragons, or AD&D for short). I suggest you look its Monster Manual index up on Wikipedia - you will find a wealth of data there for your research, with lots of cross references to make your job easier. But do look for the books proper, so you can see drawings of each monster. Every mythical being from the most popular folklores and some obscure ones has already made its way into D&D at some point. I will give you the classical example: most dragons in the D&D universe(s) are variations on the dragons of european legends and myths, but the "Lung Dragons" and the Mist Dragons species are based on dragons from the far east. Yet they all have a common origin and a common deity (Tiamat, which in D&D is a multi headed dragon, but which ultimately originates from sumerian and babylonian myth). D&D also does a lot of kitchen sink fantasy mixing when it comes to the undead, giants, demi-humans, lycanthropes, shapeshifters, celestial beings and demons. As long as you have a keen eye for folklore, you can often spot the origins of each creature, and also see what they have borrowed from other cultures. One word of advice, though. For geeks in general and worldbuilders in particular, D&D books (specially the monster manual) have the potential to be more adictive than meth. Be careful or you will spend the rest of your life reading and re-reading those books. I know firsthand how hard it is to detox from that! [Answer] I always liked the idea of having the monsters appear and interact within particular areas more than another, because the monsters that appear in an area are actually created by the fears, and thus beliefs, of the people living there. That's playing off the old D&D Planescape setting, of course. Wherein getting enough people to believe in, or fear, a thing hard enough could actually Tulpa-ing the thing into existence, or changing it to suite the vision. Even the planes themselves. Thus the separation and differences between them are caused by the same reason as real life. Different cultures creating different monsters. But once they're there. Once they're real? They can still butcher your community just fine and, of course, once something starts killing you, even if you didn't believe in this other culture's monster originally? Well you sure as shoot believe in it now. It has a life of its own. It can reproduce, and spread. Which actually has some interesting implications on trade and boarder guards in a fantasy setting using that outlook. ]
[Question] [ I've got a near future setting where humanity has colonised the solar system. The setting is relatively hard science fiction, with realistic spacecraft and space flight. However, it is also a setting featuring mecha of both the mini and humongous variety, and I'd like to include other things only seen in soft science fiction. The way something like *Mass Effect* did this was by the introduction of **element zero**, an impossible material that raises or reduces mass in a field around it. I want to justify the more outlandish things in this setting using a number of impossible but otherwise consistent materials, and have been considering something along the lines of a periodic table of magical elements, with a suitably scientific name. What would be the most believable way to introduce materials that violate the laws of physics in an otherwise fairly realistic setting. Some example materials are listed below, though answers do not need to account for all or even any of the specific materials listed. * A light but strong metal that can be used to build 80 metre tall mechs. Must be able to avert the issues caused by the square cube law. Either by averting the law itself or ideally by just being strong enough that the law doesn't render the mechs impossible to build. * A substance capable of rapid healing of physical trauma for use in combat medicine. Substance can be implemented in non combat medical treatment but should not result in the complete elimination of any and all injury or illness. (Good luck with this one, the only thing I can think of is time manipulation or some other effect where it only works within a short time after the injury is sustained.) * A fuel able to render getting into orbit relatively trivial for both the short and long term. Assuming a universe in which cold fusion has been developed if that helps. [Answer] ## As much as possible, hide the fact that your materials are impossible. When you're creating technology that's impossible by modern technological standards, your audience will have the easiest time ignoring that fact if you do as little as possible to draw attention to it. The moment you focus too much on what your impossible material does or how it works, your audience will start thinking about it and realize that "wait a minute, that's impossible!" One way to do this is to stick as close as possible to modern cutting edge science and engineering with only a little bit of a hand-waved jump at the end. For example, when making an 80-meter tall mech, you can say that your engineers use an actively fusion-supported metamaterial layer to support most of the load, without really describing how that works or what it does. Most people know that metamaterials can do cool things, and that fusion provides a lot of energy, so if you combine those two things, your audience can imagine that some how your metamaterial is propped up by all of that fusion energy. Is that a scientifically sound material? Of course not, but it's not so *obviously* impossible as to break suspension of disbelief. Alternately, you can make up a material with some cryptic non-description of how exactly it works, and call it good. Starship Troopers did this with the Cherenkov drive, which sounds like it's somehow related to Cherenkov radiation, but somehow through unexplained means achieves FTL transportation. So long as you don't dwell on it, a reader probably won't focus on the fact that your mechs are made of metasteel, which doesn't exist. Say that your mech is made of metasteel, then talk about it punching things and leave the science and description of that material as a mystery for your audience to ponder. [Answer] In order to answer the first question, you could go with something along the lines of the matter compiler devices from [The Diamond Age](https://en.wikipedia.org/wiki/The_Diamond_Age). Using advanced nanotechnology, they are able to make materials vastly stronger than we can today, using all of the elements currently known. An example of this is dirigible airships that instead of using any lighter-than-air gas, they simply use a vacuum chamber at infinitesimally low pressures to maintain the density contrast needed for buoyancy. No material available today would be able to resist the pressure differences without being so heavy that they wouldn't float. Pure carbon that was perfectly arranged into repeating rings at the atomic level would be able to resist as much pressure as required, without the excess weight we would associate with conventional materials. The second question is the most technically challenging of the three, as you've observed. You may need to handwave this a little bit using the base of [Human Factor VII](https://en.wikipedia.org/wiki/Factor_VII) as a starting point and then explain that it only works on trauma such as bullet wounds or when injected into blunt-force injuries, and doesn't do anything to chronic conditions or diseases. If you made it prohibitively expensive, with no way to reduce the price (extremely technical development cycle, very rare materials required) then disease and injury would still be a problem for the world even if it was able to cure things other than immediately-threatening trauma. The third question would possibly be suited to a similar answer as the first. Using a nanotechnologically engineered fuel you could get the highest possible reaction mass into a small area and then use an on-board fusion drive to ignite it, without the necessity for additional oxidiser material or potential for dangerous ignition runaways, otherwise known as explosions. [Answer] **Points 1 & partially 3** You don't need an imaginary material, most materials have a theoretical strength which is ORDERS OF magnitude greater than their real strength, that's because an Iron Cable in reality has much more defects than we think, and such defects weakens the material (In fact thin cables are slightly more strong because have less defects compared to thick cables). So you just need micro-molded cables in order to have them 100 times more resistant to traction in example. Also you could exploit particles accelerators in order to make impossible alloys (in example by changing atoms at predetermined locations inside space-lattices to another element by adding/removing by brute force protons) by injecting atoms directly into solid matter without having to mold it (certain materials just don't mix when in liquid state, or some materials may have fusion point higher than evaporation point of other materials and that make mixing them very difficult if not impossible). You have very realistic ways to introduce materials that are 100-1000 times more resistant than strongest known materials. Generally an advanced technology may allow to build an object almost atom-by atom in an orderly and predetermined way allowing to make it perfect and without defects, that allows very light vehicle hulls, making a breeze going to space using a minimal amount of fuel in example. Of course that all about mechanical properties of materials, other physical properties are likely to remain the same (melting point, specific weight etc.) EDIT: **Point 2** A fungus that rapidly grow but still relies on human blood (so it does not grow far from wounds) the fungus rapidly stop any bloolet and it try to adapt to external forces (so it effectively can be used to link cutted muscles by allowing the force to propagate), it also has some any-pain properties. The fungus is then digested by body normally through natural healing and also cause the wounds to heal a little bit faster than normal and to leave no scars after healing is done. (damages to organs, nerves are likely to require later surgic intervention) **Point 3** I can hardly think out of a cold fusion engine, probably it should be like any modern Ion engine, but instead of being propelled by batteries or a nuclear reactor it is propelled by cold fusion. So: * Cold fusion reactor (high electric energy throughput) * A reserve of Helium or Hydrogen A strong magnetic field powered by Cold fusion reactor just ionizes gas particles, wich are outputted in small number but at speeds near C, that generates a very effective propulsion. **Summary:** Strong alloys and metals will allow very Big Mechs, and cold fusion reactors are able to power them. Strong materials also allow very strong and light armors for infantry wich have the armors filled with fungus spores effectively allowing healing and by providing a "soft" surface to amortize shocks. Of course infantry will have respirators to avoid growing of fungus in breath-ways and and a special substance inside helmets that prevents fungal growth inside brain (if damaged) and also prevents blood from spreading if brain veins are damaged. For economics resons only helmets may be "atom injected alloys" while the rest of armor may just be micro-molded. [Answer] I always like gravity manipulation as a science fiction device (which is kind of what *Mass Effect* did). If you have your super material as controllable dark matter decay you can have gravity effect fields that solve points 1 and 3. Mechs are built including gravity manipulators that negate their own crushing weight. Space ships use gravity induction engines rather than conventional engines to fly. Point 2 is solved with either nanotechnology or femtotechnology. Have the nanites as quite 'dumb' however, and only able to repair a wound just after it happens (otherwise they might decided to heal a tattoo or necessary amputation, for example). [Answer] What you're looking for isn't so much a material as it is a construct: nanotechnology. While Ben MS has already given you the best answer for part 1, parts 2 and 3 in the question can be answered even more simply by using nanotechnology. For the medicine, you could use medikits that contain millions of nanites, as well as reserves of organic molecules. The nanites would be programmed to spread throughout the body, identify the injury, and rapidly heal it either by stimulating cell growth at a molecular level, constructing new cells directly, or simply filling the wound and forming a lattice that stops bleeding and allows for near-total functionality as it heals at a normal pace. As for part 3, the fuel you're looking for is, in fact, plain old electricity. In order to truly *trivialize* the act of achieving orbit, the best short- and long-term solution would be a [Space Elevator.](https://en.m.wikipedia.org/wiki/Space_elevator) Forget using costly fuel-based engines to achieve orbit! Instead of blasting your way to the heavens, ride in style up a shimmering cable of [Carbon Nanotubes](https://en.m.wikipedia.org/wiki/Carbon_nanotube) (or [Diamond Nanothreads](https://en.m.wikipedia.org/wiki/Carbon_nanothread)), costing only 1/1000 the price of a traditional rocket launch! Plus, thanks to the incredible tensile strength of the materials used (and with some bit of armoring against space junk), the elevator could remain up and running for as long as you're willing to maintain it! First-time build cost only $20-40 billion! [Answer] Although it's not a specific answer, you might want to read Myke Cole's "Shadow Ops: Control Point" series, which embeds magic in the everyday world in an extremely effective way, which to me sounds like you're describing and may give ideas how to simply hand wave it away and still keep the sciencey feel you describe? ]
[Question] [ Some autistic genius mathematician just published a solution to the long-standing problem of P-hard problems being equivalent to NP-hard. The solution just hit Reddit, Slashdot, math.stackexchange.com and several hang-outs of the world's best mathematicians. You don't need a quantum computer. You just need a pencil, a notepad and enough mathematics knowledge to understand the proof (say, graduate maths/physics/CS level) and your specific variant of a given NP-hard problem, and you're able to transform it into a P-hard problem and have your PC crack given hash or re-create a private key from a public key in less than a minute after you finish transforming your mathematical solution into a Matlab script. It's matter of hours until all of SSL, including SSH is broken. By tomorrow TOR will be insecure, and zero-day exploits spoofing website certificates will be available for sale. Probably somebody is already writing a hacked Bitcoin 'miner', not realizing the cryptocurrency just lost all value. And that's just the beginning... What would be the global impact? While the general term "global security crisis" has a nice ring to it, and I can picture the direct impact on the IT domain, I can't quite imagine just *how* would it look like in practice, from a Joe Average's viewpoint. Would armies get involved? Would there be riots? How would the governments deal with it? What kind of impact on the life of common people would this kind of crisis have? [Answer] Charles Stross did a short story about this: <http://www.antipope.org/charlie/blog-static/fiction/toast/toast.html#antibodies> P=NP with low-order difficulty adds a fast track for developing advanced AI - "gods", as the author implies. > > To this picture, add artificial intelligence. Despite all our propaganda attempts to convince you otherwise, AI is alarmingly easy to produce; the human brain isn’t unique, it isn’t well-tuned, and you don’t need eighty billion neurons joined in an asynchronous network in order to generate consciousness. And although it looks like a good idea to a naive observer, in practice it’s absolutely deadly. Nurturing an automation-based society is a bit like building civil nuclear power plants in every city and not expecting any bright engineers to come up with the idea of an atom bomb. Only it’s worse than that. It’s as if there was a quick and dirty technique for making plutonium in your bathtub, and you couldn’t rely on people not being curious enough to wonder what they could do with it.[...] > > > Once you get an outbreak of AI, it tends to amplify in the original host, much like a virulent hemorrhagic virus. Weakly functional AI rapidly optimizes itself for speed, then hunts for a loophole in the first-order laws of algorithmics — like the one the late Professor Durant had fingered. Then it tries to bootstrap itself up to higher orders of intelligence and spread, burning through the networks in a bid for more power and more storage and more redundancy. You get an unscheduled consciousness excursion: an intelligent meltdown. And it’s nearly impossible to stop. > > > Penultimately—days to weeks after it escapes—it fills every artificial computing device on the planet. Shortly thereafter it learns how to infect the natural ones as well. Game over: you lose. There will be human bodies walking around, but they won’t be human any more. And once it figures out how to directly manipulate the physical universe, there won’t even be memories left behind. Just a noosphere, expanding at close to the speed of light, eating everything in its path—and one universe just isn’t enough. > > > [Answer] **It depends** There's a longstanding question of, even if P = NP, whether it actually affects crypto. If you can crack any NP problem in O(n^4) with a reasonable coefficient, it would be earthshattering, driving business over the internet to a sudden halt. However, if the best solution turns out to be O(n^42), then we're probably reasonably safe for now. What does change is how we go about trying to crack algorithms. If a problem is NP, that means it takes O(2^n) computations. Polynomial decreases in complexity like something which cuts n^20 operations out of the loop don't change that O(2^n) complexity, due to the rules of how complexity is calculated. If suddenly everything is O(n^42), that n^20 change is a big deal. Now the algorithm is O(n^22). In the past, finding a pair of ways to reduce complexity by n^20 each wasn't all that important, so nobody bothered cataloguing them. However, if its O(n^42), suddenly that pair of hacks brings it down to O(n^2) *and nobody knew it because nobody cared when it was NP.* [Answer] **Massive Global Economic Crash** Short term, almost everything else can be ignored compared to impacts on global banking. Since SSH is no longer secure, banks will probably immediately shut down their websites and transfers until an [OTP](http://en.wikipedia.org/wiki/One-time_pad) solution can be developed and distributed. That will take *at least* a week, assuming it's government backed and given the absolute highest priority. (A week is a really short estimate, in reality it will take longer). Beyond the stock exchange stopping and credit cards not working, banks can't even reliably identify you to give you money. All of that is distributed systems that are no longer secure, so a local branch can't even protect itself from a malicious user faking authentication details. So while the banks aren't technically crashed, no one can get their money if it's in accounts. Credit doesn't work, ATMs don't work. You're limited to barter and your cash on hand. Full response highly depends on how the government reacts. Best case - they create temporary physical [scrip](http://en.wikipedia.org/wiki/Scrip) and declare martial law. They then ban civilian travel until a security solution is implemented, using the army and national guard to make sure that food is still grown, delivered, and paid for. This would be a temporary measure to get us through the hump. Worst case - incompetent government response means that our [Just In Time](http://en.wikipedia.org/wiki/Just_in_time_%28business%29) food delivery fails. In the first world this means rioting, followed by mass starvation and government and societal collapse. [Answer] If $ P=NP $ with a coefficient that was at all useful, or more generally if a problem considered NP and known to be equivilent to a class of the hardest problems *had* an easier solution of the ease you mention, we would have noticed. I think that $ P=NP $ but with a overhead that's so high that the curves don't cross until an input length that's an unbelievably enormous number and beyond anything that's physically realizable in the universe. In order to have the scenareo you describe, it would take some breakthrough in computing and I don't mean just quantum computers. Maybe oracle chips based on time-travel, that work off a particular formulation of a NP Complete problem. To make it useful you need to figure out how to map your desired problem onto the standard problem. Hmm, that can be automated too... Consider a technobabble discovery in quantum field theory and "accellarator on a chip" technology, that allows a chip to implement a closed timelike curve in a microscopic trap. The self-consistancy principle allows you to use that to reverse any easy computation in one step. In the time it takes to check the magically provided solution, you have it. The easy vs hard direction is the actual basis of public key cryptography, and could be applied to decrypting something like AES if the message protocol has some kind of consistancy check. For example, asking for a message plaintext that gave a specific 256-bit SHA will start spitting out copious numbers of gibberish messages that have that property, but the true plaintext is lost in the volume of possibilities. ]
[Question] [ I realize that many factors affect this answer so assume the following: 1. Star type: [G2 star](http://en.wikipedia.org/wiki/G-type_main-sequence_star) (like our Sun) 2. Composition: O2, N2, CO2, H2O atmosphere 3. Magnetic field: Two different magnetic field strengths (none or minimal & Earth strength) 4. Distance: two different mean orbital radius (Earth distance & Mars distance & if you feel ambitious do Venus too :) ) 5. Duration: I'm looking for geologic times scales $\to$ 1-2 billion years or more) I believe that planetary mass is a better parameter to use than surface gravity. Earth's mass with a magnetic field is sufficient at our global temperature. Mars' mass (about 10% of Earth's) without a magnetic field is insufficient at its colder temperature. Would the Earth without a magnetic field work? Would Mars with a magnetic field work? [Answer] First, kudos to you for realizing that planetary mass is *not* the only thing influencing how a planet (or even *if*!) a planet holds on to its atmosphere. Distance is also an important factor. Thanks for not putting it too close to the central star. I know that this is a terrestrial planet, so it wouldn't be a [hot Jupiter](https://en.wikipedia.org/wiki/Hot_Jupiter), but conditions there would be just as brutal. In fact, we can calculate just how brutal they would be by calculating the [planetary equilibrium temperature](https://en.wikipedia.org/wiki/Planetary_equilibrium_temperature): $$T = \left(\frac{L\_{\odot}(1-a)}{16 \sigma \pi D^2} \right)^{\frac{1}{4}}$$ We can approximation that [$L\_{\odot} \approx L\_{\text{Sun}}=3.846 \times 10^{26}$](https://en.wikipedia.org/wiki/Solar_luminosity). As another approximation, [$a=0.3$](https://en.wikipedia.org/wiki/Albedo). We also know that [$\sigma=5.670 \times 10^{-8}$](https://en.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_constant). Plugging this all in, $$T = \left(\frac{3.846 \times 10^{26}(1-0.3)}{16 \times 5.670 \times 10^{-8}\pi D^2} \right)^{\frac{1}{4}}=9.85856 \times 10^7 \times D^{-\frac{1}{2}}$$ At [$D\_V$](https://en.wikipedia.org/wiki/Venus_(astronomy)), [$D\_E$](https://en.wikipedia.org/wiki/Earth), and [$D\_M$](https://en.wikipedia.org/wiki/Mars), this comes out to $$T\_V=299.986 \text{ K}$$ $$T\_E=254.547 \text{ K}$$ $$T\_M=207.515 \text{ K}$$ As far as approximations go, those are pretty similar to what we see, give or take a few dozen Kelvin (with the exception of Venus, which got screwed over by greenhouse gases). Mars' approximation is actually accurate to within a few Kelvin. Earth is the only one which is off, and that's only by about 30 Kelvin. That's pretty good. Tempted though I am to add in a fudge factor, I grudgingly admit that the model works for Mars, and there are a whole bunch of things on Earth (*cough cough water, land and humans*) which influence its results. Using kinetic energy, we can relate the [root mean square speed](https://en.wikipedia.org/wiki/Root-mean-square_speed) of a particle to its temperature via $$v=\sqrt{\frac{3kT}{m}}$$ At each of the radii, we have a different relation: $$v\_V=1.11 \times 10^{-10}\left(\frac{m}{\text{kg}}\right)^{-1/2}\text{ m/s}$$ $$v\_E=1.03 \times 10^{-10}\left(\frac{m}{\text{kg}}\right)^{-1/2}\text{ m/s}$$ $$v\_M=9.27 \times 10^{-11}\left(\frac{m}{\text{kg}}\right)^{-1/2}\text{ m/s}$$ If the root mean square speed is greater than [escape velocity](https://en.wikipedia.org/wiki/Escape_velocity), then some of the atmosphere will escape. $$v\_{\text{escape}}=\sqrt{\frac{2GM}{r}}$$ I ran the numbers for each planet and gas. I assumed that $m\_{\text{O}\_2}=5.3\times10^{-26}\text{ kg}$, $m\_{\text{N}\_2}=4.7\times10^{-26}\text{ kg}$, $m\_{\text{CO}\_2}=7.3\times10^{-26}\text{ kg}$, and $m\_{\text{H}\_2\text{O}}=3\times10^{-26}\text{ kg}$. I then have a grid of values for the minimum mass, $M\_{\text{min}}$, found by setting $v\_{\text{escape}}$ equal to each of the speeds calculated above. The results are given relative to Earth masses (in $10^{-3}M\_{\oplus}$): $$ \begin{array}{|c|c|c|c|}\hline \text{} & \text{Venus} & \text{Earth} & \text{Mars}\\\hline \text{O}\_2 & 1.86 & 1.60 & 1.30\\\hline \text{N}\_2 & 2.10 & 1.80 & 1.46\\\hline \text{CO}\_2 & 1.35 & 1.16 & 0.941\\\hline \text{H}\_2\text{O} & 3.28 & 2.83 & 2.29\\\hline \end{array} $$ As you can see, these are all a few orders of magnitude below the mass of Earth, and are roughly the mass of the Moon - maybe less by a factor of several. As an order-of-magnitude estimate, this makes sense, given that the Moon only has an extremely tenuous atmosphere. [Answer] For people who are real gluttons for punishment, here is all you would care to know about [Atmospheric Escape Mechanics](http://en.wikipedia.org/wiki/Atmospheric_escape). The article discusses many different mechanisms of gas losses. The easiest to model is the Thermal Escape mechanism (described in detail below). However, two other processes may contribute substantially to atmosphere loss in the absence of a magnetic field; *Pickup* and *electric field acceleration*. I've found no mathematical treatment of these last two but will describe them. **Pick-up** Pick-up is the process whereby hydrogen ions from the solar wind directly impinge upon the gas molecules of the atmosphere of planets with no or weak magnetic fields. When the ions impact molecules or atoms in the atmosphere, they impart momentum allowing them to escape. This is the dominant non-thermal loss mechanism for Mars' atmosphere and bodies with thin atmospheres. **Electric Field Acceleration** > > The dominant loss process for Venus' atmosphere is through electric > force field acceleration. As electrons are less massive than other > particles, they are more likely to escape from the top of Venus's > ionosphere.[3] As a result, a minor net positive charge develops. That > net positive charge, in turn, creates an electric field that can > accelerate other positive charges out of the atmosphere. As a result, > H+ ions are accelerated beyond escape velocity. > > > from the wikipedia article on [Atmospheric Loss Mechanisms](http://en.wikipedia.org/wiki/Atmospheric_escape#Comparison_of_non-thermal_loss_processes_based_on_planet_and_particle_mass) This loss mechanism is the dominant non-thermal loss mechanism on bodies with thick atmospheres. **Thermal escape** In most cases, thermal escape is the dominant atmospheric loss mechanism. As @HDE226868 posted, calculate surface temperature of the planet using solar luminosity, albedo, and distance from the sun. Then calculate the Vrms of the gases. Then compare to the body's escape velocity. ``` | Meas Calc ---------------------- Tmercury | 700 K 438 K Tvenus | 735 K 185 K Tearth | 313 K 254 K Tmoon | 390 K 268 K Tmars | 293 K 210 K Tio | 130 K 95 K Teuropa | 125 K 92 K Tcallisto| 165 K 115 K Ttitan | 93 K 85 K Ttriton | 38 K 35 K Tpluto | 55 K 36 K ``` NOTE1: the problem with this is it calculates the average surface temperature, whereas thermal escape mechanics rely most heavily on the highest / day side temperature. The shown measured temps are the "high temperatures". NOTE2: I've got the albedo of these bodies but they tend to make the temperatures diverge further from the measured values than using HDE's approximation of 0.3 for an average albedo. I use a ratio of 300 as the cut-off for gases. Values above this number indicate the planet can retain the gas for billions of years. Next calculate the escape velocity of the body. These are the values that I get: ``` Escape Body Velocity Mercury = 4,250 m/s Venus = 10,361 m/s Earth = 11,178 m/s Moon = 2,375 m/s Mars = 5,021 m/s Io = 2,560 m/s Europa = 2,035 m/s Callisto = 2,444 m/s Titan = 2,641 m/s Triton = 1,456 m/s Pluto = 1,246 m/s ``` The formula to find lightest weight gas the planet can hold onto is as follows: Vesc must be larger than some calculated multiple of Vrms (I based the form of this calculated multiple off the half-life formula) $$ ln\left (1 \times 10^{9} \div 9 \right )^2 = \frac{Vesc}{Vrms} $$ $$ ln\left (1 \times 10^{9} \div 9 \right ) = \left ( \frac{2GM \times m}{r \times 3RT} \right ) $$ $$ \large m = \frac{ln\left (1 \times 10^{9} \div 9 \right ) 3RTr}{2GM} $$ The 1e9 value is the number of years you want the gas to stick around, this represents 1 billion years. I believe the natural log portion of the equation to be my own empirical fit to the problem. $ \large m $ - Molar mass of compound $ R $ - Universal gas constant $ 8.3144621 \frac{J}{mol K} $ $ T $ - Temperature (K) $ r $ - Planet's radius in meters (my statements above are wrong, it does play a factor) $ G $ - Gravitational constant $ (6.67 \times 10^{-11} {N} \left (\frac{m}{kg} \right ) ^2 ) $ $ M $ - Planet's mass in kg The gases each body can retain over geologic periods are: ``` Molar Body Mass Gases Mercury = 114 ~ Br2 + I2 only; all other gases escape; No ices Venus = 20 ~ N2 and heavier Earth = 9 ~ CH4 and heavier Moon = 203 ~ I2 only; all other gases escape; No ices Mars = 36 ~ F2 and heavier Io = 58 ~ Kr + Cl2 only; all other gases escape; Ices of NH3, H2O, CO2, Br2, etc. Europa = 89 ~ Kr + Cl2 only; all other gases escape; Ices of NH3, H2O, CO2, Br2, etc. Callisto = 81 ~ Kr + Cl2 only; all other gases escape; Ices of NH3, H2O, CO2, Br2, etc. Titan = 39 ~ N2 and heavier; Ices of CH4, NH3, H2O, CO2, O2, etc. Triton = 53 ~ None; all gases escape; Ices of NH3, H2O, CO2, N2, O2, etc. Pluto = 104 ~ None; all gases escape; Ices of NH3, H2O, CO2, N2, O2, etc. ``` Another twist to this is the fact that various molecules achieve much longer longevity when it is colder than their "snow line". Our solar system's snow line for water (the point at which it remains solid and doesn't evaporate/sublimate) occurs at the distance of our asteroid belt. Beyond this distance, solar system bodies can retain their ices. **Hypothetical Planets** It's been a long road but I think I finally have my answer. A simple swap between $ \large m $ and $ M $ generates the equation which determines what mass is required to retain a given gas if you use the assumptions below. First the equation: $$ M = \frac{ln\left (1 \times 10^{9} \div 9 \right ) 3RTr}{2G \large m} $$ Now the assumptions 1. Replacement planets use the same density as Earth. 2. Replacement planets use the same albedo as Earth. 3. Planets need a Vesc/Vrms ratio of 400 to hold onto a gas for 4.5 billion years. 4. Planets need to retain gaseous water to maintain human habitability. 5. The daytime "hot" temp is 1.15x the temperature average. 6. Planets have a strong magnetic field so only thermal loss is important. Which simplifies the equation to: $$ M = \frac{1,200 \times 8.3144621 \frac{J}{mol K}Tr}{36 \times (6.67 \times 10^{-11} {N} \left (\frac{m}{kg} \right ) ^2)} $$ Then what I find is: ``` Orbit of Min Mass Vesc Surface G Venus 0.55e 9,159 0.82 Earth 0.43e 8,437 0.75 Mars 0.32e 7,647 0.68 ``` Remember the mass is the important thing, so the planet could possess a much lower density and, therefore, a much lower surface gravity should the world builder so desire. Interestingly, if Mars were just about 3x its current mass, it *might* have held onto a substantial atmosphere and been a pleasant place to live. [Answer] Around 0.5 Earth masses, or 40 Lunar masses. ]
[Question] [ In another question, [Are flying plants possible?](https://worldbuilding.stackexchange.com/q/11208/147), a point was raised that because of the square-cube law, a large, hollow, spherical plant could fly by having the air inside be a little bit hotter than the air outside. I'm wondering how a plant could heat the air inside of it up. Any ideas? [Answer] **Compost** A symbiotic relationship between bacteria and the plant could produce a significant amount of heat. If the plant, as it grew, shed plant material into an inner cavity then it could be providing its own biomass for [composting](https://en.wikipedia.org/wiki/Compost). By controlling the airflow in through [stomata](https://en.wikipedia.org/wiki/Stoma), the plant could control the amount of oxygen and therefore the speed at which the composting takes place. As the biomass is composted, heat would be produced inside the plant's expanding gasbag. **Sunlight** The large gasbag would naturally absorb sunlight as well, providing additional lift during the day. In the night the plant could allow more oxygen in to increase the composting action and provide more lift without the sun. **Thermogenesis** Of course, some plants have the ability to [produce their own heat](https://en.wikipedia.org/wiki/Thermogenic_plants). This is an expensive (in terms of energy) process, so it's possible a plant could use this sparingly to take flight, but not stay aloft all the time. The most successful plant would likely use a little of all three methods. [Answer] The obvious answer would be by trapping sunlight, in the same way that greenhouses tend to be hotter than the air around them. Biological processes could also be used, but that would cost the plant energy so would most likely be avoided. [Answer] While I agree with Tim in that the most likely would be warmth from the sun as a green house, an alternate would be bacteria that produce heat, maybe a bacteria that breaks down the water into Hydrogen and Oxygen so the plant can float with it. It would also help the plant from crashing into the ground at night, (though that might be a 'special harvest' for those living on the ground) The plants would also need some kind of 'steering', to follow (drift with) the sun north and south as the seasons change. [Answer] Well, there are a number of ways that a plant can raise its temperature. The obvious are: * Absorbing sunlight * Energy released from respiration burning fuel However, to get the fuel, you need to photosynthesise. Again, capturing sunlight. Luckily, photosynthesis isn't endothermic (it just uses sunlight energy), so it won't steal your thermal energy out of the system. As mentioned in a comment [@iAdjunct] you'll need an enclosed space with elastic properties (read: a balloon) that can be expanded as the air heats up so that density reduces inside. Energy needs to be effectively transmitted directly into this inner space to heat the air. Best bet would be some high-respiration specialist plant growth inside a rubber-balloon releasing energy into your trapped inside air, with the green photo-synthesising cells on the outside creating fuel. Luckily enough, as the plant rises its sunlight exposure will increase allowing for greater fuel creation. You'd have a nice little feedback cycle. Your plant would still need contact with the ground at some point, or else have very good absorbency from its environment. Water is essential, and there will be a need for nutrients and such for repair and growth. [Answer] **Perhaps you don't need the plant to heat up the air at all?** (bear with me here) The plant in question (perhaps in winter, with the deluge of water to help build the bubble) begins forming the walls around the "bubble-to-be", sort of like a U shape. This could be grown as a new, vertically-growing attachment in the middle of the plant, while the light-gathering leaves spread out from the base. For the bubble-to-be, everything's ready, except the top hasn't closed up yet due to a small hole right at the top, and small holes at the bottom for rain to escape. In the lead up to summer, the plant gets its seeds ready (attached to the bubble-to-be). In summer, during a *particularly* hot day, the plant finishes closing up the hole at the top of the U (as well as the bottom holes) so that it's now an O, i.e. a fully enclosed bubble, which traps the hot summer air inside. Summer passes. As the weather cools down, heading into autumn, the plant's connection to this bubble dies, and eventually breaks off (once in winter, the mother-plant can begin working on a new bubble-to-be). The bubble still contains the summer air, which has since cooled down but is otherwise less dense than the cool wintery air, and as such, begins to slowly float away. Slowly and over time, the seeds break off from the bubble, falling to the ground in an attempt to start more of these plants. At the same time, this helps the bubble stay afloat as its weight slowly diminishes with the release of the seeds. Come next summer, the bubble has *very* possibly degraded away and fallen back to earth. Even if it hasn't, the hot air of the coming season is now as thin as the air inside the bubble, so gravity takes over. Either way, by the end of the cool season, the bubble will come back down. --- Depending on what you want, I get that this may not be an ideal solution for you if you want these bubble-plants floating around year-long. Also, it's highly likely that these bubbles would die shortly after being released from the mother-plant, their purpose solely to float around and drop seeds. The fact that they're dead would help the bubble float, as the dead plant tissue can have a reduced weight from not needing to contain water to sustain a living organism. All of this would counter an idea that these plants are floating around while alive, though you *may* be able to come up with a way to explain that these bubbles (should) remain alive. Feel free to correct me on anything scientific I've missed, or otherwise play with this idea. Furthermore, while this provides a great way for the plant to spread its seed around (theoretically at least), the evolutionary steps required for a plant to get to this point elude me. [Answer] Use **methane** instead of heated air. Methane is readily produced by all sorts of bacteria, and it's significantly lighter than air at room temperature (0.716 g/L vs. 1.2 g/L). You would need to heat the air to 200°C (390°F) to get the same density. You can of course use heat to add to the buoyancy, but with methane, you don't need to maintain the temperature to keep the plant in air if it can float in the first place. ]
[Question] [ Setting: Large city full of tall buildings, plus zombies The survivors have taken to the higher floors of the buildings. The streets are very dangerous, so going down there is only for emergencies. 1. What would be the supplies needed to survive indefinitely? I guess I'm assuming that they would farm on the roof (and collect rain water), but what would they need to collect? 2. How many people could feasibly survive together in this scenario? 3. How would you connect buildings? Could you attempt to build rope bridges across? [Answer] ## The Food Let's see how much energy a person needs, so we can see how many people we can feed with our food, assuming we can grow food. Daily needs for an adult are about `3500 kcal` according to [this calculator](https://www.bcm.edu/research/centers/childrens-nutrition-research-center/caloriesneed.cfm) (it uses [large calories](http://en.wikipedia.org/wiki/Calorie#Nutrition)) for a male (because there's higher needs), `32` years old, `1.80 m` tall and `70 kg` in weight - [this other calculator](http://dailyintake.net/di_calculator.php) confirms this, giving `15.62e3 kJ` which is the equivalent of `3731 kcal`. Let's average those and round to get our daily needs, per individual are `15e3 kJ` or `15 MJ`. Assuming they live off roof-top crops, they'd be essentially living on a [vegan diet](http://en.wikipedia.org/wiki/Veganism#Vegan_diet) and possibly on a [raw vegan diet](http://www.thehealthyhomeeconomist.com/170-scientific-reasons-to-lose-the-soy-in-your-diet/) as well. Now, I'm going to assume they eat and grow *only soy* for simplicity - I'm handwaving the dangers of eating only one kind of food, especially if it's soy[[5](http://www.thehealthyhomeeconomist.com/170-scientific-reasons-to-lose-the-soy-in-your-diet/)] - variety is necessary. The outlook is pretty bleak though: going by existing rooftop cultivation examples such as [this guy's](http://www.eatingwell.com/food_news_origins/green_sustainable/how_one_mans_foodscape_on_his_rooftop_garden%20%20?page=3), it seems you need at least 3 months before you get food out of this - you also need enriched soil, many kinds of plants to make sure you've got food all year round and there's that looming nutritional variety problem. Even those that *have* done this kind of thing, don't replace *all* their intake needs from these gardens[[7](http://www.motherearthnews.com/organic-gardening/growing-soybeans-zmaz80mazraw.aspx#axzz3FwZT6Yx3)][[8](http://books.google.gr/books?id=0nfmTHu4P2oC&pg=PA99&lpg=PA99&dq=home+garden+dietary+needs&source=bl&ots=yqIN-4oRzJ&sig=-Sq4uuNl-n-XJv8LNpaoY2zh5Tg&hl=en&sa=X&ei=3po6VJD0ENHcarCtgqAL&redir_esc=y#v=onepage&q=home%20garden%20dietary%20needs&f=false)]. But those problems can be handled narratively - lets see if we can force enough food out of soy for the time being. According to [this chart](http://apjcn.nhri.org.tw/server/info/books-phds/books/foodfacts/html/data/data2a.html) (it's badly made, the lists are images so you can't search >:( ) `100 g` of soy beans contain `545 kJ` boiled. That means we need about `2.75 kg` of soy beans, per person, per day. The wikipedia article on [soybeans](http://en.wikipedia.org/wiki/Soybean) gives us an average yield for soy bean crops of `2.5 tonnes per hectare` in 2010. I'm assuming that's the total over a year, but I'm no farmer so I can't be sure. Since that's for a professional, well-tended crop with modern technology, lets cut that yield to 1/3, giving us about `0.8 tonnes per hectare`. Converted to `kg/m^2`, that's `0.08 kg/m^2`. For a single person, we need `979 kg` of soy beans per year, which requires an area of `12.24e3 m^2`, or a square `110 m` on each side. Going by [this paper](http://www.greenroofs.org/grtok/economic_browse.php?id=39&what=view), the total flat roof area in NYC is `21,249 acres` divided over `144,832 roofs`. That's about `342 m^2` per roof, which means one person, over the course of a year, needs almost `36 roofs` to feed themselves, just by roof yield, so that doesn't work. It can still be a good supplement, but you'd probably want to find some way to grow food within the buildings themselves, like this: ![vertical garden](https://media-cache-ak0.pinimg.com/236x/c8/07/19/c8071912b6fb46a866144a15779081f9.jpg) which is known as [vertical farming](http://en.wikipedia.org/wiki/Vertical_farming). If, however, you can find other sources of food, such as scavenged food or make a [cat farm](http://dwarffortresswiki.org/index.php/v0.34:Catsplosion), you'd need about `0.62 kg` of food per adult, per day (if you're an [astronaut at least](http://en.wikipedia.org/wiki/Life_support_system)). That amounts to `220 kg` for an adult over the course of a year, excluding water. You should be able to get this much if dietary intake is varied, especially if it contains meats and dairy products (since there is dried meat, jerky etc. left over in supermarkets, we can assume they get some of this, even while scavenging in the city). The less varied the food is, the more you need. ## The people How many people can survive this way would vary largely. It depends on what food you have available, how many buildings are close-by, how much food is scavengable and in what area. It's hard to make an estimate, but I think the biggest factor by far would be scavengable food by area. As far as I can tell, there just isn't enough yield on these crops and too small an area to get enough to feed an entire group of 4-6 people. It would take tons of work for even one person to manage alone, with just their crops - not to mention farming is a huge amount of work, even on a rooftop. ## Bridges Rope bridges are fairly straightforward, but you'd want someone on the other side, or it can be very tricky to get one to work. I don't know much about how to make them and I can't find much information on it, but as far as I understand, you'd need enough rope to cross the gap one time (with a noose), then add 2 gap lengths if you want to be balancing on a single rope, with 2 side-ropes for handling. You'd probably need 4+ gap-length's of rope to get the simplest of board bridges, possibly double that length. The distance between buildings can be estimated based on street distance.Going by [this NYC street design guide](http://dwarffortresswiki.org/index.php/v0.34:Catsplosion), it seems we'd probably have a minimum of `20 ft` and probably a maximum over `72 ft` for large streets. If you want to connect buildings close by, with just a side path in between, we're probably talking about as little as `16 ft` of distance. Of course, some buildings may be so close you don't need anything besides your legs to cross over. If we want to create a suspension rope bridge, we'd probably need at least `64 ft` of rope and some boards. That's `19.5 m`. You would also need some powerful anchors, but that might be easy to find if there's pipes, chimneys etc. - it would depend on what's available. [Answer] **Disclaimer:** You're going to see a *lot* of [Fermi estimation](https://en.wikipedia.org/wiki/Fermi_problem) here. A *lot*. So don't use my numbers in a scientific study - I certainly wouldn't. **Food** [Rooftop farming](https://en.wikipedia.org/wiki/Roof_garden)/[urban agriculture](https://en.wikipedia.org/wiki/Urban_agriculture) is the only way these people are going to survive. Fortunately for the vegans, there's no way animals can be raised here. Open fields, spacious pens - all things animals need, and all things New York City lacks (I'm assuming the zombies have commandeered [Central Park](https://en.wikipedia.org/wiki/Central_Park)). So the inhabitants of what remains of the city will be forced to turn to fruits, vegetables, tubers, and anything else they can grow. Urban agriculture relies on the premise of growing a lot of food in a small, crowded, artificial, and generally unpleasant space. The best places to put "farms" would be on the tops of buildings (and yes, the zombies have taken over the [High Line](https://en.wikipedia.org/wiki/High_Line_(New_York_City)). Darn.). So How much space do we have? I'll stick to Manhattan for now. It has an area of about 59.5 square kilometers. Taking away Central Park's 3.41 square kilometers, we have roughly 56.09 square kilometers. I'll estimate that a good 33% of that is roads, so we have about 37.39 square kilometers available. But not all of the roofs are flat! However, those that have slanted ones could be used as [hanging gardens](https://en.wikipedia.org/wiki/Hanging_garden_(cultivation)) (which I'll get to later), so it all sorts itself out in the end. With supplies scarce, the top crops will be those that don't need a lot of resources - food, water, etc. Desert-loving plants are always a good bet. Sunlight will be scarce on some of the other floors (and there won't be enough power to illuminate the plants), so any darkness-loving plants (well, there really *aren't* any) would be welcome. You also want plants that can grow vertically. To add to the criteria, the plants have to be easy to care for - you simply don't have the time to teach everyone how to harvest rutabagas. There are a lot of options - really because there *aren't* any crops that fit these criteria - so it all comes down to whatever seeds you have lying around. And in a city, there probably aren't a lot. --- **People** How many will survive the apocalypse? Well, how many can the farms support? We can also use other floors of the buildings to make makeshift [vertical farms](https://en.wikipedia.org/wiki/Vertical_farming). So we'll say that an average of 15 floors per building can be used throughout the city. Now we have 560.9 square kilometers of "land" available for farming. I honestly cannot find good statistics for how much land one person needs to support themselves for a year that would apply here, so I'll say that perhaps one-third of an acre, efficiently designed, could sustain a person. This is about 0.001348952 square kilometers per person. With 560.9 square kilometers available, Manhattan can support 415,804 people - if we push it. So the other 74.4% of Manhattan's once [1.6 million+](https://en.wikipedia.org/wiki/Manhattan) strong population are gone. As [the Soup Nazi](https://en.wikipedia.org/wiki/The_Soup_Nazi) might say to one, "No food for you!" The city simply can't support them. But the other 416,804 are fine - for the time being. --- **Getting between buildings** The whole no-ground-level restriction is a problem, because the ground is generally the easiest way to get from point A to point B. The aerial element means you will have to make bridges of some sort. I'm not sure rope bridges would be a good idea. Who has that much rope lying around? The alternative material would be telephone wires, but there aren't a lot of above-ground ones in New York City! I would just go with more static bridges - really just glorified planks. If you can nail together a bunch of 2-by-4s and cross Broadway, you're set. But a) Don't fall and b) There isn't a lot of material to make bridges, is there? Sure, you could cannibalize some construction sites, but you're going to run out eventually. You could try to play a giant modified game of Jenga - taking out walls in buildings and, in this case, using them to make bridges - but you'll still run out eventually. Besides, most skyscrapers are made of steel and other metals. You can't break them apart as easily as wooden buildings. But for the sake of this question, let's make some assumptions. Say you can knock down two of the four outer walls of each floor of each building. NYC apparently has [5,937 high-rise buildings](https://en.wikipedia.org/wiki/New_York_City#Architecture), which I'll take to mean buildings ten stories or above. Let's say 75% are in Manhattan. Maybe they have an average of 50 stories apiece, and they are, on average, 50 feet wide and 10 feet per story. So now we have .75 times 5,937 buildings times 50 stories/building times 2 walls/story times 500 square feet/wall = . . . 222637500 square feet of material. Some of it may be glass, but glass is strong enough. For all intents and purposes. Let's make another guess, and say that the average distance between buildings in Manhattan is 50 feet, and each bridge should be about 10 feet wide (Don't trip!). You can therefore have about 445275 bridges in Manhattan. They'll all have to be at about the second or third floor, in order to avoid high-level wind gusts and low-level zombies, so you can forget about great views, but they'll suffice. [Answer] Some things to consider: * **Water:** You have 21,249 acres of roof area (as reported by @ivy\_lynx), which is ~86 million square meters. New York annually has 700-1500 mm of rain, which gives you ~86 million cubic meters of water *annually*. That means, assuming people use on average 2 liters per day, rainfall can sustain ~120000 people. And that's assuming you use *all* the roof are for collecting rain (on the other hand it should be quite easy to expand that with some glass, etc.). * **Bridges:** More than just bridges, you need an effective communication (i.e. cargo transport). I think that pairs of directional ziplines might become common. I believe that there should be some accessible supply of ropes that people use for construction work. * **Light:** either electricity (i.e. fuel for generators) or fire (e.g. wood). There are number of tasks that require light at night, and that might become some really important resource. * **Entertainment:** Books (easiest), story tellers, musicians, etc. That won't be necessary at first, but depending on the length of the stay, it might become an issue (people with too much time on their hands often become troublesome). * **Child care:** There are just so many ways a child could hurt itself in such a setting, so perhaps special child care areas would emerge. I hope this helps ;-) [Answer] There are a lot of good answers here already, but I'd still like to add my 5 cents. 1. Organise well. Ensure security against both zombies and renegades and manage your resources efficiently for maximum survival. Cooperation is they keyword, lacking any police conflict will kill you faster that anything else. 2. In most big cities there are already several rooftop gardens present today. Best start there. Learn and extend. Without elevators only a limited set of floors can be utilized anyway. Acquire books on the subject of (rooftop) cultivation and nutrition. 3. Cultivate beans, potatoes, unions and veggies. In separate plots so pests will not eat all in one go. The yield per year divided by yearly consumption will determine the number of people you can feed. Anything else is conjecture. Any number problem is easily solved: Scavenge to make up the deficit. The population level will naturally go to the sustainable level. Life as it has become. Life as it has been for almost all of human history. 4. Keep bees. They will fertilize your crops. 5. Keep rabbits or rats or even goats as long as you can. High calorie food at high investment, definitely good for morale. Goats can provide milk and cheese. 6. Produce methane gas from waste to have fuel to cook with. 7. Dry and store your surplus for winter and sure to come bad times. 8. BEWARE OF FIRE as there is nowhere to run to and no one to call. Best cook outside, prohibit lights inside. Sundown == bedtime. 9. Keep your buildings whole. They WILL degrade. 10. There is no way to safely build bridges without going down. So go in fast and use what is on hand. Steal buses, park in street to connect buildings and possibly create a semi safe zone. 11. Implement a plan to pacify the environment, then expand. Possibly by luring groups of zombies somewhere, and then drop heavy stuff on their heads as a friendly competition or free time hobby? One day the city will be a zombie-infested death trap of collapsing buildings. One day you will need to move to the countryside. Develop a plan for that. ]
[Question] [ Dragonfolk have skin that looks like rock, but sometimes, some of them turn colorful with very bright horns for the same reason salmon turn from grey to red, while others are always bright and colored. In the image there are 4 examples, but the dragonfolk can span any color range, and their pigmentation can change based on what they eat, how much they eat and other factors like age or lifestyle. I know that frogs and other squishy things can have very bright, almost luminescent colors because their skin produces pigments, but what about horns? Horns are not made of skin, and the dragonfolk's horn are basically part of their skull, it's basically the shape of their frontal bone and it's covered in bone related stuff, not soft and mushy or scaly skin. If the horns break, they work like any other bone, if gone missing it stays so, but if re-attached and held it place, then it fuses back and all nerves regrow back. So what kind of materials could result in such colorful bony horns? Does the stuff that colors bird's feathers also work for horns and can it be influenced by diet, like a dragon that eats too much of one food turns from green to purple and so on? Consider those are actual bony horns as they are part of the dragon's nasal structure as they are an internal musical instrument filled with fibers, sacks of air and hollow tubes giving them the ability to mimic any sound they hear, kind of like lyre birds in real life but more complex. Also the surface of the bone, the colored part doesn't have to be literal bone but it has to be hard, as bone possibly. [![enter image description here](https://i.stack.imgur.com/x7kaM.png)](https://i.stack.imgur.com/x7kaM.png) [Answer] The most vibrant colors you see in nature, like peacock feathers and butterfly wings, do not rely on special materials. They are not pigmented colors, but [structural colors](https://en.wikipedia.org/wiki/Structural_coloration). Any material can have vibrant colors if it has the right microscopic structure. (Even [chocolate](https://www.npr.org/sections/thesalt/2014/06/14/321816570/holographic-chocolates-look-as-beautiful-as-they-taste).) ![Peacock feathers](https://upload.wikimedia.org/wikipedia/commons/9/93/Peacock_feathers_closeup.jpg) These microscopic structures are very thin. The downside is that they are fragile. Your dragonfolk might have to shed and regrow the coloring once a year at the start of mating season. [Answer] 1. Many horns on Earth's animals are keratin, which is the same material that makes hair. So you could use the same mechanisms that control color for human hair and animal fur (which is also keratin). In humans, that's melanin. In animals, among other things, it's a gene called [Agouti](https://www.hudsonalpha.org/genetic-elements-controlling-fur-color-reveal-a-connection-between-dogs-wolves-and-an-extinct-species/). 2. You could also use mineralization. This would require you to set rules about what dragons eat (for example, in the movie *Reign of Fire,* they eat ash). It's not necessary that they simply eat rocks, but they may do so for digestive purposes like birds eat grit. If a dragon favors gold-rich rock for digestion, the result would believably be golden horns. [Answer] ## Can you have colorful diet influenced hollow horns, yes, but not the way you describe. We need to break this down into several parts. 1. Horn is made of keratin, the same stuff in scales, nails, hair, feathers, and claws. Horn is basically a super-specialized type of skin. It can contain many different pigments in fact flamingo are pink because of beta-carotene a pigment in their diet that builds up in the keratin of their feather and skin. Basically every color is possible through keratin born pigments (although no blue pigments exist in animals there are blue pigments that could evolve on an alien world). You can even have colors not visible to human eyes just like birds have. 2. Can the horn be made of nothing but bone, No. Horns can have a bone core or not but horn is made of keratin. Rhino horn has no bone core while a rams horn does for instance. If there is no horn over the bone it is antler not horn, and you have basically no color options, and more importantly probably can't be permanent. Below is a cross section of a bone cored horn. [![enter image description here](https://i.stack.imgur.com/Fbh7v.png)](https://i.stack.imgur.com/Fbh7v.png) 3. Can the bone in the horn be hollow, yes. In fact many ungulates and reptiles already have hollow bone cores in their horns. in ungulates it is often a direct connection to the frontal sinus. one issue with de-horning cattle is it can actually expose the sinus and may not heal properly. You can even see part of the sinus in the antelope horn above. 4. Can horn be as hard as bone, surprisingly yes. Antler is actually very soft bone and horn can match it in hardness. horn will never be as hard as the hardest bone but soft bone like antler is fine. Of course there is not much reason to want horns as hard as the hardest bone, bone that hard is very brittle and a horn that hard would break easily. [![enter image description here](https://i.stack.imgur.com/V3x7Q.png)](https://i.stack.imgur.com/V3x7Q.png) [Answer] Chameleons have fluorescent compounds in their bones that glow under UV Light, So perhaps your Dragon's horns glow colorful colors at night only.[![Glowy colorful lizards](https://i.stack.imgur.com/QoAEd.png)](https://i.stack.imgur.com/QoAEd.png) Or we take this a step further........ Your species of humanoid dragons could have naturally phosphorescent (when a material can absorb ultraviolet radiation and emit it as visible light that lasts between seconds to hours) compounds in their bones, possibly Calcium sulfide. They absorb UV rays in the day and emit visible light at night, slowly fading until the next day. Different colors could be produced by different impurities, like the different kinds of Quartz and Aluminum Oxide gems found all over the world (also off-topic fun fact: Rubies and Sapphires are both gem-quality forms of AL3O2, colors varying due to different impurities) The horns could also just be full of some sort of biomineral or other compounds that produces different colors [Answer] You ask: > > what kind of materials could result in such colorful bony horns > > > Where colorful is defined as: > > very bright almost luminescent colors > > > The problem I see here is that no known natural pigment could make horns "very bright." Colorful, perhaps, if by "colorful" you mean taupe, brown, dark brown, or very dark brown. While antlers might be made of bone, horns (as @JBH points out) are made of keratin, which means that they could easily be colored with melanin, the substance that colors hair. Your options, however, would pretty much be limited to a monochromatic spectrum, where: * lots of eumelanin = black horns * some eumelanin = brown horns * not much eumelanin = blondish horns * pheomelanin = red horns??!! None of these colors would be "very bright" or would even come close to luminescence. Mineral sources might be the closest you could get, but even then, there is no existing science to show how eating minerals might affect horn pigmentation. The best you'd get is conjecture. So I present my alternate solution: ## They are dyed as a fashion statement Your dragon people don't have naturally colorful horns. In fact, even the nutrition sources that cause their skin to turn colorful *have no effect on horns.* But colorful horns are pretty. And having a colorful, bright, luminescent body with... brown horns? Boring. So your dragon people start a trend where it is popular to get their horns dyed. **There are two ways to dye horns:** **1. Painting** - there is a trend where people paint the horns of their livestock. In India, especially, where cows are considered sacred, people [paint the horns of their cows](https://www.superstock.com/asset/india-rajasthan-udaipur-region-diwali-festival-farmers-painting-horns-holy/1566-11159687) in honor of the Diwali festival. So lower-class dragon people that can't afford expensive treatments paint their horns. It becomes an art thing. They might even match their horns to their skin. It's no different than painting your keratin-based nails. Want to change the color? Just use some acetone to wash it off and start again ;) **2. Injection** - there is a concept of artificially infusing rhino horns and elephant tusks with dye in order to devalue the horns and prevent poaching. These procedures, like that undertaken by the [Rhino Rescue Project](https://rhinorescueproject.org/infusion-in-action/), involve drilling holes in the horn and filling them with pigment. Upper-class dragon people might take advantage of some expensive variation of this treatment to dye their horns. They might even return for the treatment every few months or so, as the horns grow out or the dye fades. Just like getting a hair color treatment. Granted, there are some challenges with this procedure. First, the horns are [not actually bright pink](https://www.reuters.com/article/uk-factcheck-rhino-elephant-pink-dye-poa/fact-checkrhinohorns-and-elephant-tusks-are-not-being-dyed-bright-pink-to-deter-poaching-idUSKBN25V1Y1) as some sources suggested, but rather a pale color that fades with time. They also grow out as the rhino's horns grow. However, the procedure does exist and it's possible it could be modified to cause bright, colorful horns. Realize that the goal of the animal rights activists is to make the dye as *invisible as possible* so that the animals are not targets, but with some science this could be modified. Not sure this fully satisfies your question, but the way I understand it, your primary question is "what kind of material could result in such colorful bony horns," while "can it be influenced by diet" is a secondary question. So in response to the first: injection or paint could result in colorful horns. In response to the second: no, it can't be influenced by diet. [Answer] ## Paint (frame challenge) As part of their traditions, dragonfolk *paint* their bones according to age, rank, and lifestyle. They use natural pigments (e.g. ochres and other earths, ash, chalk, oxides, carbonates, flower and plant extracts, cochineal, &c.) mixed with water, resins, beeswax, egg whites, oils, or other substances, depending on the desired longevity and a recipe's adherence to keratin. It is still related to the dragonfolk individual's diet (but only indirectly, similar to how traditional human fashion and body decoration usually was indicative of an individual's diet). Of course, this frame challenge can be used in conjunction with naturally occurring colours. ]
[Question] [ **Could you have advanced mechanical engineering without, say, advanced electrical engineering accompanying it?** Thick clockwork, clickety clackety stuff, does it need steam/electricity by default? **How would you explain armatures, automatons, wood or metal prosthetics that somehow trump even modern medicine/tech irl in a mostly medieval setting, where this exists in one exclusive location/society**? Magic exists in this world, and it's mostly medieval tech, with this one civ having that narrow focus on mechanical *somehow*. Let me elaborate. I'm mostly writing worldbuilding/lore, no real plot as of now. I try to find holes in the lore because it really bothers me when that happens, it has to be cohesive or it just crumbles for me. So if you can assist me with that, I'd hugely appreciate it. I have one civilization particularly that is unlike all the other ones that all use magic in all the more traditional fantasy ways, channeling it and using it offensively; each civ having their own spin on it. Except one civ, which seemingly uses no magic straight up. However, they actually do have access to it in their own way, they don't really channel it and use it offensively directly like other civs, they just have special ores, special resources, and other such things that have, somehow, allowed them to develop advanced mechanical technology in a mostly medieval world. And other civs can't really replicate it, because it's not a globalised world so speed of information is slow anyway, but also, simply because they won't have access to these resources. It's not really advanced mechanical tech we have now, it's more like steampunk, if that makes any sense, you know how in steampunk there's plenty of tech that is honestly indistinguishable from magic? but it's still cohesive in-universe. That's sort of what I want. The thing is, I don't want gunpowder in this world, I want it to be the typical western medieval fantasy, where magic mostly explains the thousands of years of stagnation. However, is what I've laid out enough explanation for this one particular civ's tech prowess? it wouldn't be hugely overpowered, but it'd still be impressive you see and sort of be able to take on the other civs who do use magic directly. I'll illustrate in a second. It's hard to conciliate advanced tech where it doesn't belong, so to speak. I guess my question is, can it belong? :p As I said previously, imagine things like armatures, automatons, wood or metal prosthetics that somehow trump even modern medicine/tech irl. Think of Shingeki no Kyojin/Attack on Titan's 3DMG (I believe special ore is the only explanation for the insane air pressure they produce in such a small device?), Dishonored (tallboys, clockwork robots), Bloodborne's trick weapons, Violet Evergarden's arms, Sekiro's arm prosthetic, the Dwemer in Skyrim/TES (not sure how they did it, maybe I should look into it), I'm sure you're seeing a pattern here of crazy mechanical devices. I'm trying to think of other stuff like it, but can't think of anything atm. **Can you have all that without... steam or electricity?** Assuming magic could explain it (**how would you explain it? I want an in-universe explanation**, not just "well, it's magic lol"). Steam tech would be fine and really cool actually, but I have a hard time imagining steam tech existing without gunpowder or electricity, or low level electronics coming right after. If you guys can somehow explain that being feasible, I would love that, I could even start thinking of low tier trains if steam tech is available. But mainly, **I'm preocuppied with mechanical tech that is seemingly magical in a medieval world**, and it's also "stable", in the sense it won't kickstart a tech revolution elsewhere. It's just this rly unique particularity of this one culture/civilization (this exclusivity I was trying to explain with those native resources). [![enter image description here](https://i.stack.imgur.com/0ehyr.gif)](https://i.stack.imgur.com/0ehyr.gif) [![enter image description here](https://i.stack.imgur.com/icYws.gif)](https://i.stack.imgur.com/icYws.gif) [![enter image description here](https://i.stack.imgur.com/zJEZl.jpg)](https://i.stack.imgur.com/zJEZl.jpg) [![enter image description here](https://i.stack.imgur.com/puYf2.jpg)](https://i.stack.imgur.com/puYf2.jpg) [![enter image description here](https://i.stack.imgur.com/RUQq9.gif)](https://i.stack.imgur.com/RUQq9.gif) So, to reiterate and summarize, the idea would be that this land in particular would have relics or so that can't really be reverse engineered, but humans are crafty and would still find a use for it nevertheless, they'd use them as they are. Maybe an ore that produces that much pressurized air for something akin do the 3DMG, or whatever. Or some relic that can power clockwork robots. This could have a similar effect to magic stagnating tech, in fact, because it would impede "normal" tech progress. TL;DR How do I have steampunk tier prosthetics working without electricity? Magic exists, but the answer can't be just a hand wave. [Answer] What you might be looking for is Earth Mages! Ok, this may get a little strange and we have to kind of work backwards, but lets start with mechanical engineering stuff. A substantial part of fine and delicate machines all the way up to the modern day (and I'm not including electronics) has to do with material sciences. Fine mechanisms are limited by the strength of the material you are working with. Will a brass gear hold under the strain put on it without deforming? It probably won't be a problem for a larger mechanism but it becomes significant when you are talking about, say, a watch. The tiny gears there aren't strong enough to hold up under much more than a light spring. Also, imperfections become a problem the smaller you mechanism is. A tiny burr on the tooth of a gear means nothing on a larger machine, but gets exponentially more significant the smaller you go. Here is where material sciences matters. figuring out how to make tiny mechanisms that are strong enough and precise enough. Enter your Earth Mage. Forget the parts about chucking huge rocks around. That's not practical and it takes far too much energy. Put the brakes on the magic system with a very simple "You can only move as much earth or minerals or whatever as you could with your body" type limitation. This keeps your mages from being massively OP in other areas, but it works perfectly when in conjunction with things like material science. Imagine a very precise kind of lens to allow you to see those very tiny flaws. The glass you use could be much clearer much earlier in your history if an earth mage can remove bubbles and imperfections from the glass. Those very tiny flaws in the mechanism could be removed by the tiniest of tools, that could only be manipulated by magic. That would allow for a degree of fine workmanship that is nearly impossible even today. Add to the precision aspect by being able to magically strengthen an alloy Imagine brass that is strong enough to withstand some of the energy generated from a steam power source without deforming, yet is thousandths of a millimetre thick! Earth mages and engineers working together could build working, almost portable Babbage type mechanical thinking engines! Just Imagine what a Leonardo DaVinci could have done with the ability to create mechanisms that strong and fine. Your key limiting factor would be power sources. Fine mechanisms would be vastly more efficient, but sooner or later you run in to TANSTAAFL (There ain't no such thing as a free lunch) You can't get more energy out than you put in. You will have to give some thought to the mass of your energy sources. With Purely Steam power, you have to consider the weight of the water as well as the heat source. Flywheels might do well for some applications. Compressed air or other gasses could work too. Electrical power is always an option if you want to delay the advent of the transistor or microprocessor. You could also limit supplies of lithium on your world. That is what makes light weight electrically powered machines attractive in our world. Keep battery tech limited and a lot of applications become inefficient and unattractive. Make crude oils hard to come by and you might not get around to internal combustion engines as fast. I know the Diesel engine was designed to run on vegetable oils, but if droughts are a common enough thing, then the thought of using food as fuel might put a stop to that line of thinking. To limit other nations gaining access to your technologies, Keep a very sharp eye on anyone who has the magical talents, as well as anyone who can tinker with mechanisms. You need both to create the wonderful machines. If another culture picks up one of those machines, they can't recreate it if they don't have an earth mage. If they do have an earth mage, they can't recreate the tech without a mechanical engineer who understands the mechanism.Establish that artificers of a certain caliber and earth mages have to come up through their respective guilds in an approved fasion, and have those guilds jealously guard secrets, and you can put of replication for a very long time As to your no gunpowder. All you would need to do there is to make one of the three traditional components rare or hard to get to. You need Saltpeter, Sulfur, and Charcoal. Charcoal and Saltpeter are just too common and available almost anywhere. Sulfur, in the form of Flowers of sulfur could be your rarity. It can only be found (in your world) near active volcanos, is dangerous to get to and so is correspondingly precious. Someone might work out the formula, but with Sulfur being too expensive, it would never grow to the levels of use we see in our own history. [Answer] You can surely get some [clockwork](https://en.wikipedia.org/wiki/Clockwork) > > By the 11th century, clockwork was used for both timepieces and to track astronomical events, in Europe. The clocks did not keep time very accurately by modern standards, but the astronomical devices were carefully used to predict the positions of planets and other movement. The same timeline seems to apply in Europe, where mechanical escapements were used in clocks by that time. > > > However the main problem with those mechanical devices will be how to power them: if you want something carriable by a single person you have not much more than spring loading, which is rather inefficient. You won't achieve anything like in the references you mention. [Answer] The other nations use magic directly, this nation, indirectly. They have a cave that uses magic to fulfil the needs of the supplicant. Got an arm missing - do a little dance and sing a little song and before you can blink a new mechanical arm has filled its place. The arm is coated in some unknown dense material and so accessing its innards to ascertain how it works can't be done. This prevents copy cat designs by other nations and solves the power problem... we don't know because we can't know. Maybe it ticks, maybe every now and then it vents steam but who can explain the wonders of magical mechanical arms. You can put in all sorts of limitations - only works for people of a certain genetic disposition, can only be in the form of hard goods, must meet a need rather than a want etc. [Answer] The **ancient Greeks** had the means to produce the [Antikythera mechanism](https://en.wikipedia.org/wiki/Antikythera_mechanism). It was discovered in 1901 when and ancient ship wreck was discovered. Until then, it was thought the ancient Greeks didn't have the technology to make precision gears and gear mechanisms. The Ankytheria mechanism has more recently been described as the first mechanical computer as it is believed to have been used to show the position of specific celestial objects. The ancient Greeks even devised and form of [steam engine](https://en.wikipedia.org/wiki/Aeolipile), even though it was most likely didn't have practical uses at the time. [Useful steam engines](https://en.wikipedia.org/wiki/Steam_engine) were being made in the 1600s. European science and technology ***might*** have developed much earlier had not [secular teaching been banned in favor of "Christian scholarship"](https://history.stackexchange.com/questions/30726/what-happened-to-all-the-scholars-and-scientists-of-western-rome-during-the-barb) after the spread of Christianity in Europe. The ancient world had it share of very intelligent people who development many scientific principles and developed potentially interesting mechanical devices, only to have the ideas and devices forgotten about when people with other ideas attained power. [Answer] **You need metallurgy and precision tools, but not electricity** Many of the most important metallurgical discoveries (e.g. the Bessemer process for steelmaking) came out in the 19th century before electricity was a widespread thing. The real revolution in mechanical engineering had to do with interchangeable parts, which also date to the early 19th century. Basically "blacksmithing" began to be replaced by "machining" and we developed lots of machine tools to make increasingly precise, increasingly repeatable, cutting and shaping of metal parts. You would certainly need power to operate your machine tools/factories, but there's no reason it couldn't be water power or steam power. Now, the expense for most "steampunk" technology is a little ridiculous, which is why it's fictional. You could hire 50 peasant mercenaries with crossbows for the cost of one shiny brass automaton, and you wouldn't have to have a mobile mechanic's shop and crates of every possible replacement part to keep them going. Given that this is a fantasy universe though, I see no reason why it couldn't happen. You don't really *need* electricity until you want telegraph, radio, electric lighting, or to give your machines a "brain". Although modern manufacturing uses computer-controlled machine tools (CNC machines), manual machining is quite capable of very sophisticated operations. It just took a lot more skill in the day; you couldn't pull some kid off the street and make him a "machinist" overnight. [Answer] In our history, the craftsmanship to make these machines has been around for millennia. Just look at jewelry or armor from antiquity. It is often amazingly precise. Someone else pointed out the Antikythera as another example. What you need is a portable energy source. That is why electricity. That is why gunpowder or steam, waterwheels, windmills, or livestock turning a crank. Sure you might invent a spring that can propel your hook like a gun once, but you have to put a gun worth of energy into winding it up before you can do it again. If this one civilization is the only one with access to this energy source, say a refined ore like you mention, their technology/magic would be uniquely theirs, or at least very rare in the wider world. Just dream a way to convert that energy into a piston or rotational motion and you are set. Now, if you really just don't want electricity or gunpowder, you understand that the pre-dreadnoughts operated without electricity. I'm sure we could find ways to build weapons without gunpowder. Mechanical calculators, mechanical weaving looms and sewing machines, really almost anything built before about 1880 would be on the table. ]
[Question] [ It's tempting to think that anything with the outer shape of a human would simply collapse in a heap if its skeleton were not there. That is surely true if the internal structure was the same as ours but with the bones simply non-existent. However the human tongue, the elephant's trunk and the octopus's whole body work perfectly well without bones to support them. An octopus can squeeze through remarkably small spaces <https://en.wikipedia.org/wiki/Octopus> I'd like my land-living approximately human-shaped aliens to be able to walk upright on land and disguise themselves as humans but also have the ability to get where humans can't by squeezing themselves through small apertures. The question is - could a creature without a skeleton actually hold and balance itself upright on land for any appreciable length of time? What difficulties might it experience? --- Video of octopus walking on land <https://youtu.be/TFzpC_e44Tg?t=43> EDIT A hydrostatic skeleton, or hydroskeleton, is a flexible skeleton supported by fluid pressure. <https://en.wikipedia.org/wiki/Hydrostatic_skeleton> A muscular hydrostat is a biological structure found in animals. It is used to manipulate items (including food) or to move its host about and consists mainly of **muscles with no skeletal support**. <https://en.wikipedia.org/wiki/Muscular_hydrostat> [Answer] As you can see in the video, the squid isn't really "walking", it's dragging its body across the ground and can't keep it's shape up. The human skeleton is incredibly important. It attaches the muscles we have, and if you look at the trunk of an elephant or your tongue you can see it's attached to bone at its beginning and only really needs to support its own weight, and can "rest" by being limp most of the time. Simply removing them and replacing them with flesh would be a bad option. Replacing bones with more muscle could work. Up to a point. Muscle is pretty heavy, and a solid tense muscle is very strong and applied well could partially replace bone. In fact your muscles right now are well capable of pulling itself out of its attachments with your bone, but smart design in your brain prevents your muscles from doing this unless in extreme situations, where you might actually damage yourself in order to survive imminent death. This is also where the stories about parents who single-handedly lift a car from their child come from. The big problem here is that it would make you heavier than you already were and cost more energy just to stand upright. And energy requires oxygen for most animals, and your human impersonator would be panting as if he was jogging when just idly standing by. [Answer] If you wish you can go to a different direction and form your "alien" on a "swarm" cell system, if the cells comunicate to each other and can specialize themselves very fast, they would not build a skeleton by the actual definition of the word, more like a temporal skeleton I guess. This would make sense if they travel from planet to planet and have to adapt themselves in order to survive. They could also gain interesting abilities like fast evolving, claws, etc. These would be great feats for a horror book alien, if this is what you are building. [Answer] In short: No. I think you misunderstand what a skeleton is, though. A skeleton isn't a structure of bones exclusively. That's what we typically think of because that's what OUR skeleton is, but there are two main types of skeletons: endoskeletons and exoskeletons. An endoskeleton is like ours where its skeleton is on the inside. An exoskeleton is like an insect's where the skeleton is on the outside. A skeleton is merely a support framework. In the case of most larger creatures, it's bones. In insects, it's an external protective shell. The skeleton doesn't have to be composed of the same rigid materials as ours are. You can substitute our calcium-based skeletal system for something more malleable like a naturally developed rubber of sorts (think something like Monkey D. Luffy) or a skeleton that is a series of non-Newtonian fluid-filled sacs that are activated and deactivated at will or by certain stimuli allowing them to shift between stiff and "fluid". [Answer] Would it evolve naturally? Most likely no. Is it possible? 100% yes. There is no need for a land based creature to have a skeleton. Muscular hydrostats can work well. Biology is just a unit of self replicating chemistry. Chemistry obeys the laws of physics. A muscular hydrostat can be strong enough and efficient enough with the proper geometry to walk or run bipedally. Without a skeleton, such a creature could not lift as much as a person of the same size, but they most certainly could support their own weight. I came across an article the other day trying to claim the maximum size of an exoskeleton. They kept insisting that exoskeletons are more limiting then endo skeletons by comparing the theoretical creature to arthropods. If an exoskeleton creature had lungs, then the argument against higher oxygen concentration or air pressure is void. If the animal didnt have to molt the exoskeleton but continuously grew it, then the argument about dying during a molt is void. If the exoskeleton was made of something other then chitin, with a higher strength to weight ratio similar to what we have, then the high weight is void. The arguments that the above people made are also void. They claim that it cannot work because they havnt seen it, yet it doesnt break the laws of physics or biological chemistry so it is possible. ]
[Question] [ Imagine that, through some cosmic phenomena not yet understood, the Sun 'burps' and ejects a vast amount of its mass into the cosmic void. A huge coronal discharge, perhaps. A pressure bubble inside that bursts. A mega internal explosion. The loss of mass is sudden and dramatic, but in a trajectory that does not traverse the planetary plane, and thus does not destroy any planets. Perhaps it occurs along the axis of the planetary plane. That is, the Sun does not 'burn out', go nova, or any other destructive end-of-life process, it just loses a substantial amount of mass. No other destructive radiation or other event that would immediately destroy the planets. This loss of mass would result in a dramatic decrease in the gravitational pull of the Sun. This would affect all of the planetary orbits, as their escape velocity from the Solar System would decrease. If they kept their current velocity, I presume they would move further from the Sun. **A. How much mass would the Sun have to lose, in order for Saturn's current velocity to become its escape velocity from the Solar System?** This is a tricky calculation and equation, as it has to account for the diminishing gravity of the Sun, not an increased velocity of Saturn. That is, it does not ask for the new velocity of Saturn sufficient to reach the escape velocity of Saturn from the existing Sun, but asks for the the maximum reduced mass of the Sun such that the current velocity of Saturn becomes its escape velocity. The following are ancillary, but not essential, questions that might arise from answering **A.** **B. Is there any absolute principle of physics that would make this absolutely impossible?** **C. Is it feasible that Saturn, along with its moons, could become an intragalaxy or even intergalaxy wanderer using this technique?** The ultimate goal is to put a sentient self-sustaining colony on one or more of its moons, and then have it wander the Universe. How to give it the ability to sustain life on a moon for millions of years is another question not within the scope of this question. **D. Does it make more sense from the escape velocity perspective for my ultimate objective to consider another planet, such as Neptune or Jupiter?** I need a planet with sufficient composition for it to become a source of power for the moons. Jupiter, for instance, naturally emits a very high level of radiation that could provide a source of energy for its moons as a substitute for the Sun, but again this is beyond the scope of this question. What happens to the Sun because of the loss of this mass AFTER Saturn becomes a wanderer is not within the scope of this question. How the Sun actually loses the mass is beyond the scope of this question. That it can somehow lose this mass is to be taken as a given assumption. [Answer] # A naive first calculation The formulas for orbital velocity and escape velocity are $$v\_o=\sqrt{\frac{GM}{r}},\quad v\_e=\sqrt{\frac{2GM}{r}}$$ I get $v\_o=9.6\text{ km/s}$ for Saturn. For this to equal $v\_e$, the Sun's new mass would have to be $0.5M\_{\odot}$, if we neglect the mass of the ejected gas. By doing the algebra, you can see that this number is the same for any mass and any orbital radius. In short, if Saturn achieves escape velocity because of solar mass loss, so should the other planets (assuming circular orbits). # A more realistic model Here's why it's actually important that we establish how the Sun loses mass. As others have said, the ejected matter will then influence the gravitational potential, and by extension the escape velocity at Saturn's orbit. To start, we need to model the solar mass loss. I'm imagining that in a dramatic but compressed asymptotic giant branch phase, the Sun is losing mass at a rate of $\sim10^{-4}M\_{\odot}\text{ yr}^{-1}$; its wind is isotropic, sending material streaming away from the star in all directions. I'll ignore the fact that [strong winds from evolved Sun-like stars can ablate planets](https://worldbuilding.stackexchange.com/a/1394/627). We can model the density of the wind by $$\rho(r)=\frac{\dot{M}}{4\pi r^2v(r)}$$ 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. For massive stars, we normally assume that $\beta\approx1$. We can then find the gravitational potential by solving Poisson's equation. From this, [we can determine the escape velocity](http://www.astro.wisc.edu/%7Emab/education/astro330/lectures/lecture_9.f10.pdf): $$v\_e(r)=\sqrt{2|\Phi(r)|}$$ where $\Phi(r)$ is the gravitational potential of both the Sun and the gas. You should be able to work backwards from here to determine the mass-loss rate and wind terminal velocity, given a desired escape velocity (Saturn's current orbital velocity, $9.6\text{ km/s}$). Calculating the potential for other mass-loss scenarios is beyond me, because I don't know the proper density distribution; I can only talk about modeling stellar winds. I suspect that bipolar jets would contribute very little, as they are away from the orbital plane and would presumably be moving very quickly (even compared to $v\_{\infty}$, which can be $\sim2000\text{ km/s}$ for massive stars, though perhaps a mere $\sim300\text{ km/s}$ for a Sun-like star). Similarly, a massive coronal mass ejection or super-super-superflare wold be hard to model. [Answer] Interesting. Not that I want to answer my own question, but I would like to sum up the math from both HDE 226868 and kingledion (to whom I acknowledge and thank very much for their input). As a general rule of thumb, it looks like the mass of an orbited body has to be reduced by about 50%, or half, in order for an existing orbital velocity of a satellite to become the escape velocity of the satellite to the reduced orbited mass. **EDIT** That is, when the Sun's mass decreases by 50%, EVERY planet's orbital velocity will become its escape velocity, at pretty much the same time. Strange, but apparently true. **End Edit** This could be a useful rule of thumb in so many different situations. How it gets reduced by 50%, of course, is another question. [Answer] Even though @AlexP is right about the mass still existing, it's believable enough that -- unless you're writing Hard SF -- you can just *assert* that the Sun -- for example -- burped out 20% of it's mass and off zoomed Saturn. For more realism, have the mass get burped in the opposite direction of where Saturn is. Saturn (and all the other planets...) gets pulled towards the new epicenter and then flies out into interstellar space. [Answer] The math already presented by HDE 226868 and kingledion is bang on so I won't repeat it, but I feel they have neglected one possibility. The mass of a star can theoretically be reduced artificially through the process of [star lifting](https://www.youtube.com/watch?v=pzuHxL5FD5U) so it may be possible for an arbitrarily advanced civilisation to pull enough material out of the sun, and displace it from the solar system, that Saturn would exceed escape velocity. ]
[Question] [ I'm trying to figure out how fast my tiny critters from a previous question, [Mistraille](https://worldbuilding.stackexchange.com/questions/47891/why-is-this-creature-afraid-of-water-but-not-of-body-or-plant-fluids), can travel. Why? It's not that I'm detail orientated and want to know the exact decimal point of speed they can reach but rather I want to know how much time my victims with open wounds have to prevent the carnivorous Mistraille from infecting them. **Critter Details** * My critter is very very tiny, about the size of plankton and zooplankton (think microns). * They always travel in a group/swarm and are named after their appearance, a low lying mist or fog back. * They travel by crawling on the ground, hopping or jumping (on top of each other if necessary) and gliding on proto-wings. (see generic sediment transport image below). * They normally travel with the direction of the prevailing wind, but can travel against it if necessary. * They travel with more 'determination' (speed and cohesion) when prey has been smelled. **(for the purposes of this question, wind and 'determination' can be ignored as I only need to figure out their basic speed. Wind and 'determination' dynamics are more story orientated).** [![sediment transport image](https://i.stack.imgur.com/w2LCY.jpg)](https://i.stack.imgur.com/w2LCY.jpg) **Victim Details** plants or animals with open sores or cuts can be infected by Mistraille and then be eaten from the inside. If given enough time; * plants could produce a resin or gummy substance to seal the 'wound' * plants could send out a signal and the surround plants could uproot themselves to 'run away' with the wind. * animals and humans could cause the wound to be covered with a seal (gummy plants) to prevent the Mistraille from infecting them. * animals and humans could 'run away'. **But all of this takes time.** How much time do they have? seconds, minutes, hours? --- **QUESTION** In a lab-based situation with no outside forces helping, How fast could a microscopic critter realistically travel metres to tens of metres? **BONUS** What body characteristics would make them slower/faster? [Answer] # Microscopic Cellular Motility There are many factors affecting motility of organisms at the microscopic level, but viscosity of the medium and concentration/density of the organism (swarm) seems often to be the greatest factors. Temperature certainly affects microbial motility, and the fastest moving bacteria are found living as thermophiles at high temperature where the rate of everything is higher and in organisms who depend on speed to make their living (eg predators) as opposed to simply moving up a chemotactic gradient looking for food. As suggested, the best method for determining motility rates for microbial life is the "body length per second" measurement. This normalizes the distance to the organisms relative size and you can begin to see how microbial motility really differs from macroscopic motility. To put it into perspective, Michael Phelps, olympic swimmer, swims 100 meters in about 50 seconds, which is about one body length per second. A sailfish can travel about 30 m/s which equals about 15 body lengths per second. At the microbial level, for example, when *E. coli* undergoes a chemotactic walk it moves with a speed of roughly 30 um/s, which translates to around 15 of its body lengths every second and an *Ovobacter sp.* moves at a mind-boggling 1mm/sec (remember it's only ~ 4um) 200 times its body length per second by utilizing almost 400 flagella. Here's a table showing several bacteria and archaea motility measurements. [![enter image description here](https://i.stack.imgur.com/NWaSY.png)](https://i.stack.imgur.com/NWaSY.png) ## Speed Limits Your microbial organisms will undoubtedly move fastest when gliding or swimming as opposed to crawling or jumping. The molecular basis is that crawling and jumping requires the polymerization of the actin molecule or mobilization of microtubules for movement. This also goes for virulent strains like *Listeria* that move around inside the victim's cells by taking over the host cell's cytoskeleton. Swimming and gliding, on the other hand, often employ a flagellar rotating mechanism which is happening orders of magnitude faster than polymerization required for running/jumping. Recent microbial research has provided evidence that suggests that motility may play an emerging, important role where dense communities of microbial life exist where their survival and growth is predicated upon more sophisticated communication (like Quorum Sensing), relative location, and level of cooperation, all of which are subject to motility. ## Size Limits Another question you might ask is how large can your organisms grow and be able to move through a viscous environment at x um/sec with the amount of force yielded from most bacterial motors? The relation $F=6\pi\eta RV$, known as [Stoke's Law](https://en.wikipedia.org/wiki/Stokes%27_law), governs the relation of force (F) to velocity (V) in a fluid viscosity η, where R is the radius of the organism moving through the medium. Using the viscosity of air (assuming your world's air is like Earth's), $1.81×10^{−5} Pa.s$, a motor force exerting ~ 5 pN at 50% efficiency, and the average Mistraille size of micrometer-scale plankton, you can play with the size of the organism to get a feel of their relative velocities. Since these microbes prey on other organisms (animals/plants you mention), you might find changing the viscosity to match air, water (inside target's cells), or blood of the victim. [![enter image description here](https://i.stack.imgur.com/8PyAD.jpg)](https://i.stack.imgur.com/8PyAD.jpg) [Answer] It seems that the fastest recorded insect (the Australian Tiger Beetle) was clocked at 2.5 m/s running on its hind legs. These beasties also have vestigial wings, similar to your Mistraille, but cannot fly. But it seems that the smaller the creature the slower the absolute speed. To compare speeds more accurately one should look at the bodylengths per second. When this raw metrics is taken a Californian mite is the fastest creature at 322 bl/s. Much better than the beetle's 120 bl/s, but only 0.225 m/s is actual speed. This mite is a much closer likeness to your Mistraille, but I would go even further. The mite is 0.7 mm in length whereas plankton, as you mention, can be as small as 0.002 mm. This would inevitably lead to a further decrease in actual speed, even if their speed relative to their bodylength was impressive. As another reference, fleas which are roughly 2 mm in length travel at about 1.5 m/s when jumping using their explosivly strong hind legs. I would approximate something generous in the region of 0.2 m/s for the Mistraille, under their own propulsion that is. Other things to take into account: * The proto-wings may increase this speed * Being so small and moving in air rather than in water, the Mistraille have an incredible advantage when it comes to accelerating. This includes changing direction and stopping, which would all be performed very rapidly due to their low mass * The same problem/advantage as a falling flea. During the descent of a "hop" whilst falling and unpowered your small creatures will be subject to a very harsh terminal velocity I would say that the Mistraille are going to move fastest with the aid of wind, maybe in some combination of running, hopping to catch the with, gliding/falling whilst resting, followed by further running. This might also give them the tumultuous, jerky, mist-like movement you're describing. The only thing I can think to make them faster is real wings (you could still limit how much they can fly), or large hind legs giving more of a cockroach-like upright run or a bigger flea-like hop. This is a great article covering several points relevant to your questions on speed/anatomy: <http://www.bbc.com/earth/story/20141021-the-fastest-insect-in-the-world> As for how long their prey have, that very much depends on how soon they can detect the presence of a Mistraille cloud. However, assuming a moderately large swarm visible at 100 m, moving at a wind-boosted 2.5 m/s, that gives them 40s. Not long enough to do much other than run really! Something else you might want to account for when they are wind-aided is their unpredictable course due to gusts and the shifting breeze. ]
[Question] [ Not sure if this is too broad, but I am currently in the process of making a few flying alien species and, of course, didn't want to use the old insect or bat-like wings. Of the types of wings (or flying surfaces) I can think of present on earth, there are the limb-bound wings using finger bones for support with skin membrane in between (bats and pterasaurs), small limbs with growths to provide more surface area e.g. feathers (birds), vein-ridden insect wings and the simple gliding surfaces of some mammals (skin flaps of some possums and squirrels) and lizards (outward facing sails on draco lizards). While this is quite the list, to achieve a more 'alien' powered flight I need a different structure. So basically, is there another possible structure for wings used in powered flight? (not looking for biological jets, sky-rays or whale-blimps). *Edit: I have developed two different groups of creatures to fill the large animal niches of my planet, which are the mammal-like quadrupeds (four limbs) and the reptilian-like hexopeds (six limbs), the latter of which I favor as a candidate for the flyers. They have the typical spine, defined head and a rib-cage-like lattice with vital organs encased. Their environment is much like earths, but with a slightly denser atmosphere, so I'm guessing their size could vary from quite small (bee hummingbird) to larger than Quetzalcoatlus. I do want powered flight, so flapping is most likely essential.* [Answer] Take a page out of *Charlotes Web*. Many spider types do actually use their web making ability to float away. Other spires can steer while falling, another type of flight. Weird thought. Squid like creature. Many many tentacles. Each has some sort of feather or micro fiber covering it. They use these as modular wings. [Answer] I'm not sure whether there's another wholly different structure that could be used, but if you're willing to fudge the physics, you could take inspiration from more unfamiliar aquatic creatures. Perhaps the six-legged species has membranes between the three legs on either side and flies by whipping its whole body. Perhaps instead, the membranes connect all the legs and also the tail(?), and they fly by "doing the wave." [Answer] You might want to take a look at mantas. Maybe you could adapt their style of propulsion? They also have the advantage of having a massively different skeleton from birds and bats. Apart from the skeleton, the primary difference is that the movement of their fins is a wave pattern, where part of the fin goes down while a different part goes up, as opposed to the movement of bats and birds. I have no means of telling wether this is feasible in air, but the dynamics should be similar to water, so it might just work. ]
[Question] [ A general question here, relevant to many world-building scenarios. Language drifts, to the point that I likely could never understand old English, but I'm not sure how much. I want to know how long it would take for a language to deviate form it's origin that two people, speaking extensible the same language, could not understand each other. In addition, what factors could one use to justify limited language drift, to expand the range of time between two speakers in which one could understand the other. I've tagged this as time-travel, so for now assume you have a traveler from the past/future speaking to someone from the same region dealing with language drift for answering this question. However, any feedback on what language drift would be like if you had two cultures starting with the same base language before becoming isolated I would appreciate that two. Would two cultures drifting from the same starting language become indistinguishable from each other twice as fast as a language becomes indistinguishable from it's past/future version; or are there more complex factors in play? [Answer] *"what factors could one use to justify limited language drift"* There's no one answer to the question of how long it takes for language to drift. There is no predictable rate of so much language change per century - indeed it is difficult to know how the amount of language change can be measured. It depends on the culture and physical situation of the people concerned. **Physical isolation**, such as being spoken on an island, tends to prevent a language from changing by the obvious means of preventing other, potentially "corrupting", languages from ever being heard. Icelandic is an example. The medieval Icelandic sagas can be understood by modern speakers of Icelandic. **Literacy** tends to preserve language, but the tendency is not absolute. For instance Classical Chinese is perhaps the language that has been able to be read by most generations (although Tamil may be a competitor). However because written Chinese gives scant guidance on pronunciation, that has probably changed a good deal even though the grammar and form of the characters remained relatively stable. On the other hand **lack of literacy** can *also* preserve language, if the culture concerned has a strong tradition of storytellers, griots or bards memorising poetry or oral history. It seems that the coming of literacy has often meant the decline of the great feats of memory that people can accomplish when they have to. **Political continuity** also tends to limit language drift. English lost most of its inflections after the Norman conquest. This was probably a combination of the effect of the reduction of the amount being written in English (scholars continued to write in Latin, but the language of law and administration changed from Anglo-Saxon to Norman French) and the effect of loss of status; English was seen as the language of peasants so nobody fussed about it being used "improperly". Another political factor is simply the use of laws to repress dialects seen as damaging to national unity. **Use as a language of religion or scripture** certainly preserves a language. For example Latin, Sanskrit and Hebrew. On the other hand this only really works if the scriptural language ceases to be the language spoken in the streets. Classical Arabic is preserved in the Koran but spoken Arabic has diverged into very different forms across the Arab world. (Update: After further research I replaced the original mention of Thai with Tamil. Greek and Aramaic are also examples of classical languages that can be read "naturally" by modern speakers. Hebrew is another example, but it was not continuously a living language. It is difficult to pinpoint when enough drift has occurred in a language to make it a "new" language, so there is controversy over which of these languages is oldest.) ]
[Question] [ Plants can have very different pollinators: The wind, insects, and even birds. However, is there a conceivable scenario where a plant could naturally have evolved to depend on humans as pollinators, where the humans (at least in the early stages of development) wouldn't know that they are pollinating the plants? Note that I'm not after the scenario where a modern developed humanity killed the natural pollinator and thereforehumans now have to provide the pollination themselves; rather I'm after a scenario where a pre-civilized human tribe would though their usual behaviour, without knowing it, pollinate the plant in question, and the plant would actually be adapted to make the humans pollinate it. [Answer] **Yes, the plant only has to be appealing to humans in some way.** Some of the most successful plants alive today are so bountiful because humans have found them to be beautiful or beneficial in some way (food, medicine, mind altering, etc.). In many cases this is because we've intentionally planted more of them. However, this could easily start out as a process that's not intentional or unknown to the humans. The humans could then use this plant for its beneficial properties and through that use, spread the pollen. For example, if the plant were visually appealing, humans would pick the plant to wear or display. Transporting the plant to be displayed or wearing this plant while walking through a field of the same plant would act as a pollinator. [Answer] I don't see any reason this could not happen. Humans work just as well as pollinators as any other motile creature. Some things I would consider in this scenario: * The idea makes a lot more sense if the humans you are referring to are a nomadic people that make a regular annual trip, meaning they make stops at regular prime locations on a fairly regular basis. * The plant would have to have something that humans want/need. Normally this means fruit...unfortunately fruit is the result of pollination. This means you would either need a plant that can fruit and flower simultaneously (which I do not believe happens for any plants) or the plant needs to provide something else in the first place. There are a host of potential things a plant could provide to get us to pollinate * Material for camouflage or decoration * Material for making rope or clothing * A drug of some sort...could be medicinal or...you know...recreational I am sure there are more possibilities, hopefully these get some ideas flowing for you. An additional note...if we are talking prehistoric/nomadic humans it is likely that even adults wouldn't know they are pollinating, I don't know when we figured out how pollination works but I am guessing it was only in the last couple centuries...(I could be wrong on that, complete guess) [Answer] Many people raise [Orchids](http://en.wikipedia.org/wiki/Orchidaceae) many who raise them cross-breed them intentionally, creating a unique sub-species. These species would not exist without man's guiding hand. [Answer] Are you sure you don't mean propagators, instead of just helping with the pollination? Pollinators get rewarded, mostly with nectar - which isn't very efficient for humans. ## Corn Corn only exists because humans plant it, its seeds are unable to break free of its husk and self-propagate. "This is not only due to the tight husks, but also because the kernels adhere strongly to the ear and do not easily disarticulate." However, it can self-pollinate, or cross-pollinate. Farmers don't like it to, because that doesn't lead to the best seed. The best seed for production is created by double hybridization (4 inbred lines). But that veers away from the question. Many other plants are the same. ## Humans are better Humans also make [better pollinators](http://www.npr.org/blogs/krulwich/2013/12/04/248795791/how-important-is-a-bee) than insects. We're just too expensive to be used as pollinators in most cases. Hmm, that link doesn't have the follow-up to the follow-up, which said eventually the labor costs got too high to employ humans. But, if you want humans doing it without knowing it, you're going to have issues. Now, some things (pig prohibitions) are done via religious reasons, which are ecologically sound (great Saharan forest elimination) - because some people realized there was a problem, but most humans did not. ## Scarification You might want to move off of pollination, and rely on scarification of the seed (needs to pass through a digestive tract in order to grow) and make it a fruit which is human-specific. [Answer] I say stick with the insects. They better organize the way they pollinate and they are a lot faster. If it were a human the plants would die off faster than if it were an insect (preferably bees). This is the main thing people don't think - the way it will affect the economy. [Answer] Some plants have developed seeds which adhere to animals and humans (think of burrs) so they can propagate, but this is the end result after pollination. What would be needed is a plant which can detach its stamen and adhere to passing creatures in the manner of a burr, allowing it to shed pollen over a wider area. This has some issues, since the pollen is going to become very widely distributed and thus very diffuse. In most creatures (including plants) with sexual reproduction, the "wining" strategy is to deposit *more* of your reproductive material in the female receptor, hence the very intimate nature of sex. Plants have domesticated bees and other insects to carry large quantities of pollen to the receptive pistils (O.K., coevolutionary pressure caused this development). If a plant broadcasts pollen, then an almighty amount will be needed (which explains those spring allergies), but a detachable stamen that serves the same purpose would have to be rather large in order to carry enough pollen for this strategy to work "better" than simply broadcasting pollen to the winds like more conventional plants. So a detachable stamen with barbs or other attachments to hook onto fur, skin or human clothing is needed, and one which can carry sufficient pollen to outcompete plants which simply broadcast their pollen, or have evolved to co-opt insects to do the job. ]
[Question] [ *Based off of this deleted question: [Why and how would a completely urbanized city-planet exist?](https://worldbuilding.stackexchange.com/questions/808/why-and-how-would-a-completely-urbanized-city-planet-exist)* *Related:* * *[How would a completely urbanized city-planet support its population?](https://worldbuilding.stackexchange.com/questions/810/how-would-a-completely-urbanized-city-planet-support-its-population)* * *[How would the global environment of a completely urbanized city-planet be affected?](https://worldbuilding.stackexchange.com/questions/811/how-would-the-global-environment-of-a-completely-urbanized-city-planet-be-affect)* * *[Why would a completely urbanized city-planet exist?](https://worldbuilding.stackexchange.com/questions/812/why-would-a-complete-urbanized-city-planet-exist)* A strong government would naturally be required, as the cost, in resources, time, and intelligence, to maintain such an enormous construction would be astronomical. This is even more paramount if the city extends greatly both above the natural surface and into the ground, as they would be expected to do so once all horizontal space is occupied. Could the city-planet ever be privately owned, or would it have to be controlled by a centralized body? Could crime even exist if such an extremely strong local government is required? How would terrorism be prevented from taking out sections of possibly kilometers-high load-bearing populated structures? [Answer] In general, I would advise not to assume that centralized systems will be prominent in the future. The trend toward centralization in the late 1800s through the mid-1900s was largely a result of the network effect in analog communication technology giving an advantages to vertical hierarchal organization. It pretty much reached its limits by the 1970s at the latest and died utterly with the digital age. It keeps on in government largely by inertia and governments ability to force people to support it no matter how dysfunctional it becomes. All the action in systems theory today is in decentralized systems like swarms. I wouldn't look to centralized systems of the past century as models for the future. That would be like someone in 1775 assuming that the America of 2014 would be some form of Monarchy because almost all government up to then had been monarchies. > > A strong government would naturally be required, as the cost, in > resources, time, and intelligence, to maintain such an enormous > construction would be astronomical. > > > Even if you look at modern cities with notionally strong centralized governments, like modern day New York, you will see that the vast majority of operational decisions remain private e.g. who buys and sells what property, who pays for most construction, how the businesses who directly or indirectly pay all the taxes operate. Government remains a relatively thin gloss on top of the private sector. The private sector exist a priori to and without government but government cannot exist before and without the private sector. A strong centralized government would only be absolutely necessary if the city planet had no actual economic rationale and the government had to forcefully direct the allocation of resources to and within the city to prevent the spontaneous flow of resource away from the planet city. > > This is even more paramount if the city extends greatly both above the > natural surface and into the ground, as they would be expected to do > so once all horizontal space is occupied. > > > I don't see why. Skyscrapers are and have historically been completely private constructions. Even within single buildings, you can have internal private property. This is the concept behind condos and coops. > > Could the city-planet ever be privately owned, or would it have to be > controlled by a centralized body? > > > If the entire planet was owned by a single entity, it would function internally as if run by a non-representative government. Corporations operate internally much like governments (more accurately modern government administration is are modeled on corporate operations) which is why corporation often stop functioning and go out of business. A more interesting question is if such a city could operate primarily with billions of private owners using just decentralized, voluntary, private decision making and exchanges. Clearly it could. As long as the planet city had a functional/economic reason to exist, it could operate by decentralized spontaneous cooperation. The great cities of the English speaking world e.g. London and New York, grew to the largest cities of their day in a decentralized manner and only became centralized as they declined in relative dynamism. Just because people are crowded together and very interdependent doesn't mean they can't exist without Hobb's Leviathan threatening them constantly. Property systems work very well to allocation resources on a voluntary basis. Ownership means the ability to make decisions about the allocation of a resource. Property system manage the allocation and transfer of that decision making authority. Property system can allocate any resource, not just land area. For example, in a giant planet city arcology, a valuable "resource" would be load bearing structures. Anybody wanting to build a new structure would have to build over an existing structure. To build over, you would need to put load on an existing structure. The ability of the existing structure to handle the load or be adapted to do so would be very valuable and so could be made a property. People could sell the load bearing capacity of their property just like we sell off water or mineral rights while we continue to live and farm on the land surface itself. Water, air, power can all be managed by property systems without centralized coercive government. It's even quite possible that a centralized government can't scale beyond managing systems of a certain size and complexity. Centralized government by definition means fewer decision nodes which means fewer people making more of the decisions. Since individuals can only process so much information per unit of time, as the system managed gets larger, the decision making process gets slower and slower. In a vast planet city, the decision making process might get so slow as to cause the system to be effectively paralyzed. (Corporations stared decentralizing in the 1970s and many argue that large modern cities have already reached the point were they must decentralize of implode.) By contrast, decentralized system have a huge number of nodes and make decisions in parallel. They can scale massively and get faster the larger they become. Biological systems work this way and they are far more complex than a city. > > Could crime even exist if such an extremely strong local government is required? > > > Strong centralized governments tend to foster crime, not suppress it. When governments have no competition, they have little incentive to be either efficient or effective. Centralized governments are more prone to corruption both from within and from external criminals. Centralized government tend to evolve to see the world as divided between not the lawful and unlawful but those within the government and those outside the government. Those inside the government don't care if those outside get mugged. The Soviet Union had shockingly high levels of even common street crime dating back to time of Lenin and they never managed to control it even though they were a police state. Their police states focused on political threats, usually from their fellow ideologues, and ignored prosaic crime. Likewise, the Russian mob didn't just spring into existence when Communism fell it was around for a long, long time. It survived by fostering corruption within the Communist regime itself. Similar patterns existed in all totalitarian states. You can see the same effect in the complex of big city political machines, unions and mobs that highjacked many US cities in the 1920-1970s. Organized crime was massive and eventually, unorganized crime grew out of control as well even as the local governments got proportionally larger but more effective at the same time. > > How would terrorism be prevented from taking out sections of possibly > kilometers-high load-bearing populated structures? > > > The bigger the system, the more robust and hard to disrupt it will be. It's been said that you couldn't might not be able to destroy Hoover Dam even with a nuke and couldn't even dent it with any plausible amount of conventional explosives. The support structure for a kilometers high structure would be similarly massive and hard to destroy. A more likely target would be the informational systems that would control power, water and air. A planet city would have no natural buffer left and would function more like a spaceship. The easiest way to kill a lot of people would be turn off their ventilation. Again, a decentralized system would be more robust. In the early days of electricity before it was socialized, there were often lots of redundant cables strung all over because many different companies each supplied power on their own cables. Sounds chaotic and wasteful and was to some degree but on the other hand, such a system made a city and region wide blackout impossible while they occur fairly often with the "efficient" centralized system. In a planet city where interruptions in power and air could be lethal in mere hours, it would be suicide to have a single, centrally controlled system. One clever terrorist could bring down the entire system for billions. A tangled chaotic system of private suppliers of power and ventilation would be far safer. As much as we twitch about our high technology systems, they are arguable more robust than their precursor technologies. For example, it inconceivable that a major modern city would simply burn to the ground but massive fire routinely destroyed major cities up until the late 1800s when concrete and steel replaced wood. The great Chicago fire is just the best know of several major fire that destroyed big swaths of several major US cities. Fears that enemy agents and anarchist would burn down entire cities where quite common and it was in fact tried. Had they known more about how to set fires, they might have succeeded. Imagine people a 150 years ago contemplating a modern skyscraper. They would assume that assume it that, even if it stood, it would likely soon burn to ground. After all, it would be filled with wood, open flames would provide heat and light, fire suppression systems were a bucket of water and fire resistant materials except asbestos unknown. We're probably in the same situation when we try to imagine a future system like a planet city. [Answer] Trantor, the capital world of the Galactic Empire in the novels from Isaac Asimov, is completely urbanized and (citing Wikipedia) > > To support the needs and whims of the population, food from twenty > agricultural worlds brought by ships in the tens of thousands, fleets > greater than any navy ever constructed by the Empire. > > > So the answer to the question is that it is supported by external food. Other kinds of support like Police and Military are just like any other place: if the Govern has the monopoly of violence, as it should be, it simply needs to continue being that way. [Answer] > > How would a completely urbanized city-planet be maintained? > > > In general, I think that an urbanized city-planet tends not to be a practical idea, except perhaps in certain circumstances which would also determine specific answers to the question. You seem concerned with crime and terrorism, and certainly those could seem like issues, though I would think they would be less difficult than the physical and environmental issues. But I think it's very difficult to answer generally without knowing many more specifics. > > Could the city-planet ever be privately owned, or would it have to be > controlled by a centralized body? > > > Since ownership is an invented concept, I would say there is no real obstacle to this. It just requires people to agree on an ownership system that accepts it. I'm not sure what problems you are anticipating, or even whether you mean one person or entity owning the whole planet, or the planet having much of it owned by many different people. If you mean the latter, I would expect that real estate ownership, as on earth today, often doesn't involve great freedom from the law nor from government control. > > Could crime even exist if such an extremely strong local government is required? > > > Yes. Keeping the planet and life on it working are immense problems, but not the same problems, though some solutions to the practical problems would perhaps also help a lot with crime control problems. For example, the lower your population, the less work and material required to maintain life support, and also the fewer people to keep in line. Alternatively, the solutions might not lend themselves to crime control: If the reason the planet works and makes sense has a lot to do with having a large population which contributes to the maintenance of the planet somehow, it might not be compatible to try to track and control them all - some solutions might even require an abundance of lawlessness, or at least a wide range of jurisdictions with different laws, in order to work. In any case, I would expect that there would still be a range of regions with different levels of law enforcement. > > How would terrorism be prevented from taking out sections of possibly > kilometers-high load-bearing populated structures? > > > There are so many possible answers to how a city-planet might exist and what it might be like in the first place, that no one answer could address this. I would say that realistically, long long before any society would even begin to really consider the strange prospect of having a city-planet, that they would probably need massive advances in mental health beyond where we are now, that would tend to detect and defuse people who would do something like that. In Sci Fi examples such as Asimov's Trantor, or Lucas' Coruscant, they had very capable police and security, and perhaps very strong construction and good scanners for devices capable of such attacks. It wasn't enough in either case to prevent catastrophes (see even Anakin and Obi Wan crashing a warship onto Coruscant). [Answer] There's at least two completely different scenarios which would drastically affected how it was managed. * The urban environment develops over time like a megacity. This probably leads to: + privately owned land + taxes and large public sector + crime and police + probably pollution + supplies of everything comes in by the local equivalent of road and rail (perhaps space elevators?) and certain things are very expensive, probably including bulk consumables such as food and fuel. + if the supply chains prove inadequate then you end up with either a ghost town or people starving (similar to cities under siege such as WW2 Leningrad). + if certain things can't or won't be allowed in then you get black markets and smuggling (perhaps even odd situations like cars being smuggled through tunnels into Gaza) + It needs a powerful local economy to provide employment for massive numbers of tertiary sector workers, and/or a short travel distance from other planets. + generally everywhere looking a look like middle of New York, London, Tokyo, Beijing etc. * An urban environment designed to meet a specific need. + Single employer (similar to military bases, oil rigs, scientific research bases, the Death Star etc) + Or not designed as a society, could be like a giant cruise ship/holiday camp or even something like a hospital or prison + Whatever it produces/consumes has to moved on and off the planet, so massive focus around spaceports/space elevators etc (unless the planet controls a space-based industry such as mining or spaceship construction). + Crime is dealt with by eviction, termination of contract, court martial etc + Resources are centrally allocated. No markets or competition. + Company rules replace laws or social norms. + Generally everywhere looking like a factory or military base. No personalisation or individuality. + Maybe a temporary installation, or the workers/soldiers/inmates might be temporary [Answer] You could probably look to the Hive Cities and Hive Planets from Warhammer 40K lore to get a good idea of how to administer and support such an immense city-state. **Food supply** If your city isn't surrounded by vast agricultural lands, or have internal 'agri-towers' (think vertical farmland built up like skyscrapers) then you're going to need a strong external food supply, like a nearby agri-world to support the population. This can lead to two situations: 1) food supply is local in towers or farming plots just outside the city, and many people receive it from many sources. Smuggling and food theft become serious issues as people look after themselves over the collective. One group may sabotage food supply to hurt others and fights for scraps are commonplace 2) food supply is external and a strong governmental body (or corporation) rations the food coming into space-ports to ensure everyone is fed. Of course, inevitably, the rich get more, the poor less and bribery and corruption run rampant in the rationing centers (which I imagine as vast militarised fortresses protecting the resources from the starving mobs) **Maintenance of infrastructure** Maintenance issues would also be a serious problem, when your cities are a kilometre or two high, and packed solid like say, beijing, a lot of traffic is moving at all times. Any modern material would quickly crumble under its own weight or under the constant stresses of its inhabitants. before you even start building this city a big leap in construction techniques or materials are needed. Depending on tech levels you'll either have a city-wide construction site constantly repairing, replacing and shoring up buildings as they fail, or some self repair function could be build into the infrastructure itself (piping full or repair nanites, automated robotic construction crews, etc). You could also have a third route, just keep building atop the crumbling ruins beneath in endless layers of city-scape **Law and Order** Let's take a small scale (compared to this at least) city like Medellin. There are already large sections of the city the police will not go into without military backup. And that's a simple 2d (ish) city spread out over a large area. Now if that were to be transformed into a towering mass of skyscrapers, and population density increased even further, the criminal underworld could effectively gain control of large portion of the mega-city if living condition were low. And lets be honest, the sheer size of such a city would means large sections will be overlooked, or abused by the governing body. Any police force that attempts to control such a place would need to be very heavily armed and armored, and have a brutal set of tactics. That, or you would need to abandon sections to cartel rule and trust they wont bring the whole city down around everyone's heads. **Environmental impact** With such a large portion of the planets surface taken by urban areas, the environment will be severely compromised. Even in our modern level of urbanization there are concerns over sustainable levels of rain-forest to ensure oxygen supply. This would be a serious issue if your source of food is external, as not even the agri-towers could assist with air quality control and oxygen liberation from carbon-dioxide bonds. Take Japan or China as a small scale version. They have very large industrialized cities, and air quality is below acceptable human levels in some sections. Now scale it up, and you have a serious environmental catastrophe. Now of course, you could have some sort of large scale air purification systems (these are already in R&D today) to cut down on airborne contaminants, but there is still industrial runoff in water tables, that poor abused ozone layer, and lack of ecological diversity. If your entire planet (or a large majority portion) were to be city, then it would be a very poor place to live, from an environmental perspective. ]
[Question] [ I'm writing a murder mystery set on an interstellar starship. Context: The victim was found dead in a zero-gee chamber inside the ship. The ship is in interstellar space and traveling at around half the speed of light (the chamber is a therapeutic room artificially kept at zero gee). My question: What would the corpse look like? Are there effects I should be aware of (for example, I assume the blood won't pool down and produce splotches)? Thank you! [Answer] Some phenomena normally occurring on a corpse will be different due to the microgravity environment. * You won't have [livor mortis](https://en.wikipedia.org/wiki/Livor_mortis) as on Earth bound corpses. > > Livor mortis is a settling of the blood in the lower, or dependent, portion of the body postmortem, causing a purplish red discoloration of the skin. When the heart stops functioning and is no longer agitating the blood, heavy red blood cells sink through the serum by action of gravity. The blood travels faster in warmer conditions and slower in colder conditions. > Livor mortis starts in 20–30 minutes, but is usually not observable by the human eye until two hours after death. The size of the patches increases in the next three to six hours, with maximum lividity occurring between eight and twelve hours after death. > > > * Lack of natural convection might make more difficult the diffusion of molecules produces by corpse decomposition. This until enough pressure in built up to push the gases around. If you have forced ventilation around the corpse, the above doesn't apply. * Bodily fluids won't spill from the body, except for blood sprayed as a consequence of a wound inflicted when the person was still alive and the heart was beating. * Corpse cooling down might be slower: again, in lack of natural convection, the corpse will reach thermal equilibrium with the surrounding only be radiative exchange. In case of presence of forced ventilation, the above doesn't apply. Since you don't mention exposure to vacuum of space, I am assuming that the corpse is in an otherwise life supporting room, thus I am excluding effects related to exposure to vacuum. ]
[Question] [ I'm brainstorming for a rocky planet with similar mass to that of Earth's, orbiting a red dwarf star. It is tidally locked with no natural satellites, yet I'm bent on having liquid water on both sun-facing and "nighttime" sides of the planet. 1. For that to be possible, I explored the possibility of a denser atmosphere, perhaps a higher content of CO₂, ocean and winds that diminish the temperature differences between night and day sides, tidal heating, volcanic activity, and strong mantle convection. 2. Since it orbits a red dwarf star, a strong magnetic field must exist to prevent the planet's atmosphere from being stripped away by solar winds. Though it wouldn't be a flare star, as a red dwarf, I think it would still be less stable in terms of luminosity than our sun. Despite having slow rotation, could the planet's powerful magnetic field be justified by strong mantle convection and plate tectonics? 3. It has a year of roughly 15–30 days, and though it doesn't have any natural satellites, I'm considering another rocky planet with an orbit close enough to exert a gravitational pull that would cause strong tides (hopefully making a liquid ocean on both sides of the planet more feasible). 4. I'm also considering an axial tilt that would allow inhabitants to measure time through seasons in the year-long day. I'm having a go at world building for a high school project, and I'm starting with the planet. A reality check from this community seemed necessary as soon as I found you. I'm still very much an amateur at this. I'd appreciate any information. [Answer] ## In a nutshell: Yes, you can keep your water with a thick atmosphere but you've set yourself a difficult scenario with a lot of hoops to jump through to survive. There is a lot in your question, I'm going to take some of the bits separately to discuss them: > > Rocky planet with similar mass to that of Earth's, orbiting a red dwarf star. It is tidally locked with no natural satellites. > > > Given the tidal locking, similar earth mass and orbiting a red dwarf [things are already looking risky](http://www.nbcnews.com/id/30136580/ns/technology_and_science-space/t/can-life-thrive-around-red-dwarf-star/#.WLAJ0n_sTIU), you need a strong magnetic field which in turn requires [rotation](http://lasp.colorado.edu/%7Ebagenal/3750/ClassNotes/Class13/Class13.html) for a magnetic dynamo. The faster the rotation, the stronger your field. We're rotating rather slowly in our several days of orbit. However if you increased the size of the liquid iron core (and probably the size of the planet a little) then we could get a largish magnetic field due to the convective flow of material within the planet. But now we come to the red dwarf, you've got very little chance of your [atmosphere surviving the coronal mass ejections](http://online.liebertpub.com/doi/pdf/10.1089/ast.2006.0127). The red dwarf calms down later in its life though, so perhaps - if we assume your atmosphere survived - we can discuss other methods. > > For that to be possible, I explored the possibility of a denser atmosphere, perhaps a higher content of CO2, ocean and winds that diminish the temperature differences between night and day sides, tidal heating, volcanic activity, and strong mantle convection. > > > Yup, a stronger global warming effect would definitely help (though you need to have kept a thick atmosphere for this). Your strong volcanic activity could help with the production of CO$\_{2}$ and other gasses. > > Since it orbits a red dwarf star, a strong magnetic field must exist to prevent the planet's atmosphere from being stripped away by solar winds. Though it wouldn't be a flare star, as a red dwarf, I think it would still be less stable in terms of luminosity than our sun. Despite having slow rotation, could the planet's powerful magnetic field be justified by strong mantle convection and plate tectonics? > > > As I mentioned above, we can (potentially) hold onto the atmosphere if we have a large liquid iron core and strong convection. You should aim to hold onto the atmosphere until your star calms down and then use volcanic activity to repopulate your atmosphere. > > It has a year of roughly 15-30 days, and though it doesn't have any natural satellites, I'm considering another rocky planet with an orbit close enough to exert a gravitational pull that would cause strong tides (hopefully making a liquid ocean on both sides of the planet more feasible). > > > This wouldn't be a stable system, the two planets would eventually fall in towards one another. In this case, too, your planet would in fact be a dwarf planet since it hasn't sufficiently [cleared the surrounding area](https://en.wikipedia.org/wiki/Clearing_the_neighbourhood). > > I'm also considering an axial tilt that would allow inhabitants to measure time through seasons in the year-long day. > > > You would still get seasons since the rotational axis of the planet is stationary relative to the orbital axis. > > I'm still very much an amateur at this. > > > None of us are "professional", searching the internet for relevant information is a skill but everyone has it to some degree. It just takes practice. **Summary** You need: * **Large liquid iron core** to provide the convection required to support a magnetic field and warm your planet a little. * **Your atmosphere to survive the early years** until the star has calmed a little, you can also use your strong volcanic activity to repopulate the atmosphere. * **A thick atmosphere** this provides the global warming effect and the gasses will mix, providing high winds which keep the temperature comparable on both sides. * **To be slightly further out in the habitable zone** since your atmosphere will keep you warm, you don't want to be *too* warm and evaporate off your water or atmosphere (though a slightly higher mass will help here). [Answer] > > though it doesn't have any natural satellites, I'm considering another rocky planet with an orbit close enough to exert a gravitational pull that would cause strong tides > > > if this rocky planet has enough of a gravitational influence to generate tides and orbits close, it can also influence the orbit of the planet itself, eventually ending up in either an expulsion from the system or a satellite relation. For you reference Jupiter has gravitational influence on the inner solar system, but doesn't generate significant tides in our seas. > > I explored the possibility of a denser atmosphere, perhaps a higher content of CO2, ocean and winds that diminish the temperature differences between night and day sides, tidal heating, volcanic activity, and strong mantle convection > > > for tidal heating to occur, you need to remove tidal locking. Tidal heating happens when the material is stressed by the tidal wave. In a tidally locked configuration the minor body simply assumes a "pear" shape, deformed toward the major body, and this deformation is static. You can rely on strong vulcanism or radioactive decay to keep the dark side warmed up above the temperature of equilibrium with space. This can very well keep water liquid, depending on the atmospheric pressure. > > I'm also considering an axial tilt that would allow inhabitants to measure time through seasons in the year-long day. > > > I think that even if the axis is tilted it will follow the tidal lock and change orientation along the orbit, same as the moon does (reference [here](https://en.wikipedia.org/wiki/Orbit_of_the_Moon#Inclination), as posted in an answer to this other [question](https://worldbuilding.stackexchange.com/questions/72000/if-our-moon-had-an-atmosphere-could-it-have-seasons)). Therefore no seasons. [Answer] # Yes Using Venus as a guide, a planet can be much much warmer than it should be due to a [heavy atmosphere of greenhouse gasses](http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/venus.htm). To make the Venus situation work for your planet, simply dial down the output of the sun (you already said it is a red dwarf, so great) until the [planet should be chilly](https://en.wikipedia.org/wiki/Effective_temperature#Planet) and frozen...like Mars here in our solar system. Then dial up the greenhouse effect and include ['super-rotating' 100 m/s winds](https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Circulation). That should do it. The greenhouse effect warms the planet from its black-body temperature of 200 K to a balmy 300 K; and high atmospheric winds distribute temperatures relatively evenly around the planet. Now, whether your people want to live under a crushing carbon dioxide atmosphere the thickness of water is another matter. [Answer] Also tidally locked planets have around circular atmospheric movements, see the clouds of the Venus: [![enter image description here](https://i.stack.imgur.com/8RKSB.jpg)](https://i.stack.imgur.com/8RKSB.jpg) Note, although the Venus rotates, it does it very slowly. The circular motion has a different, more complex cause as the Coriolis-force in the Earth. Furthermore, it can have an enough thick atmosphere to equalize the temperature (like in the Venus). [Answer] This is a reasonably model of a tidally locked planet that could have liquid water present on its surface. The OP has identified the majority of the features the planet needs to satisfy the situation. There already is an earthlike planet that has many of these features already, with the exception of being tidally locked. That is, the planet Earth itself. The atmosphere, the oceans, and clouds are excellent mechanisms for redistributing heat on Earth. Earth's relatively faster rotation means temperature variations won't be too extreme. The presence of greenhouse gases such water vapour, CO2, and methane in the Earth's atmosphere also help smooth out temperature variations. It is not unreasonable to assume similar mechanisms will smooth temperature variations to allow for the presence of liquid water on the proposed tidally locked planet. However, the more prolonged heating on the dayside of the planet, especially compared to the nightside, will mean there will be a steeper thermal gradient. Effectively strong wind systems will be necessary to carry heat from the hot dayside to what could have been a very frigid nightside. This will keep the nightside from being locked in permanent frozen night. This a planet where extreme weather will be very extreme, but these extremes, by our standards, will be their normal weather. Expect to find a planet of storms. You might consider the possibility of an [orbital resonance](https://en.wikipedia.org/wiki/Orbital_resonance) to allow the planet to be less tidally locked. This will permit both sides of the planet to be exposed to its primary star. The conditions will be less extreme, but the periods of day and night will still be quite long and the weather stormy. This is only a suggestion for the OP to consider to see if it makes a better world for his purposes. [Answer] Let's address this in order: 1. We don't have any examples of a tidally locked world with an atmosphere to work from, but the theory is that a deep thick atmosphere will even out thermal inputs across the world, that *is* somewhat supported by Venus which has a longer day than it's year so the sub-solar point, the place where the noon sun is directly above is always moving but very slowly. It's unknown whether that pattern of atmospheric convection can be supported with no rotation at all. Similarly a world with deep salty oceans that supports a large web of currents redistributing heat from equator to poles and in this case light to dark would likely work for keeping water at liquid temperatures across the globe but the problem again is recycling the cold water back from the darkside where all the energy is going out of the system without it all freezing up on the journey around the night side. Assuming you have a liquid water distribution you should see corresponding atmospheric mixing and heating so in some ways the water system is more important than the overlying atmosphere. 2. Red dwarves can be as active, or even more active, than their yellow counterparts like Sol so you can have it flare if you want, it's variability is entirely up to you. You will still need a strong magnetic field due to stellar proximity just to keep the solar winds from tearing the atmosphere off the planet at an Earth similar thermal input rate. That means that there is strong rotation at depth in the core, Earth's liquid metal outer core is thought to be our primary field driver, that may or may not translate into an active crustal system, that depends on the relative thickness of the crust, the mantle and crustal chemistry and a raft of other issues. Most known red dwarves are very old and metal poor but if you use a fifth generation red dwarf with a similar chemistry to Sol and a planetary system with similar chemistry then you can easily justify an entirely Earthlike world with similar geophysical systems. If you use a sixth or seventh generation star like Sirius (in metal abundance not temperature) an orbiting world should be richer in heavy metals like Iron and also in transuranics meaning the world will be more geologically active and have a smaller hotter core and a larger liquid outer core that would create a massively strong magnetic field. 3. Strong tidal motion would certainly help with thermal distribution, but it would only be really influential if it was sufficient to actually move a reasonable amount of water right around the planet as it goes. If it's moving in a separate orbit at a vastly different rate of motion (which it would have to be to generate that kind of tide if it's not an orbiting satellite) that's not likely to be a stable orbital arrangement in the longer term, in fact it's likely to result in the tide inducing world being ejected from the system after a couple of passes. You could have a reasonably large world that causes some tidal melting of surface ice and small Roche Tides at superior conjunction without it being big enough or close enough to cause orbital instability, or in fact planetary scale tidal mixing. Earth experiences about 5 metres of Roche Tide from the transit of the moon after all. Such a passage is going to cause internal tidal heating from those Roche forces which helps the overall thermal equation for the world as well as mobilising large surface ice deposits due to the same effect. It's also going to cause any amount of geological upheaval. 4. Axial tilt makes no difference whatsoever on a completely tidally locked world because the axis is going to remain in the same relative orientation along with the star facing hemisphere. You need to look at orbital eccentricity to create seasons on a tidally locked world, which may also help with thermal distribution, but I don't think it does. While you're looking at strange worlds you could also look at using a Mercury analogous three-two spin-orbit resonance instead of a tidal lock too. The planet completes three days every two years. This removes a lot of the problems with a single continuous input point in the thermal cycle. It also creates strange phenomena like the fact that the sun appears to travel backwards across the sky for part of the year. ]
[Question] [ Let's take this image as our fireball in question: [![enter image description here](https://i.stack.imgur.com/KpTDX.jpg)](https://i.stack.imgur.com/KpTDX.jpg) And let's further assume that it travels about 30 meters before burning out (twice the range of a WWII flamethrower) and travels at the speed of 20 m/s (which, apparently, [is about how fast a 10-year-old can pitch a baseball](http://www.yougoprobaseball.com/average-pitching-speed-for-8-9-10-11-12-13-14-15-16-17-18-year-old-how-fast-should-i-be-pitching)). The flame's temperature is in the region of 1,300 celsius, [in line with actual flamethrowers](https://books.google.com/books?id=onyXCwAAQBAJ&pg=PA30&lpg=PA30&dq=how%20hot%20do%20flamethrowers%20get%20celsius&source=bl&ots=uM52Hq2PcQ&sig=ik9WAeJNsTXKrWJPStwFWnTdzUs&hl=en&sa=X&ved=0ahUKEwjXyK6DrNXOAhVCJB4KHY6sChMQ6AEITTAI#v=onepage&q=how%20hot%20do%20flamethrowers%20get%20celsius&f=false). What how much energy, measured by kilocalories, would be required to fuel such? [Answer] Like all great physics problems I'm going to make some assumptions. The fireball is going to be approximated as a sphere of superheated air. Nothing is actually burning to provide the energy. The specific heat of air is around 1.0 kJ/kg K and air density is about 1.225 kg/m^3 (at sea level) so to raise a ~1 cubic meter of air to 1300 C from around 20 C is going to take: E = 1 m^3 \* 1.225 kg/m^3 \* 1280 K \* 1.0 kJ/kg K = 1568 kJ = 396.3 kcals This would be a low estimate to just create a "fireball" that instantly dissipates to the environment. A more impressive moving fireball would deal with the air expanding under heating and things around the fireball absorbing heat, things like moving the "fireball" would also raise the calorie requirement. In addition the magic heating process may not be 100% efficient requiring even more energy. ]
[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/34208/edit). Closed 6 years ago. [Improve this question](/posts/34208/edit) There are a lot of religious people who would love it if we could [scientifically prove the existence of God](https://worldbuilding.stackexchange.com/q/10017/6781). What would happen if, while attempting to prove the existence of God, we instead proved the existence of a devil? Assume the proof is scientifically rigorous—it is repeatable, statistically sound, etc. What we don't know: * The proof does not demonstrate anything about the nature of this devil, so we don't know if it is a singular Devil, a horde of devils, or the ghosts of *Homo neanderthalensis* with a vendetta against all *Homo sapiens*. * The proof still doesn't prove or disprove the existence of God. Of course, many people would correlate the existence of a devil with the existence of God, and although ["correlation doesn't imply causation, ... it does waggle its eyebrows suggestively and gesture furtively while mouthing 'look over there'."](https://xkcd.com/552/) In any case, further attempts to prove the existence of God will fail to do so but might solidify the proof of the devil's existence. * This doesn't prove or disprove any existing religions (though if there are any that have the specific doctrine "there is no devil", those have now been proven to not be 100% correct) What we have been able to determine: * There is a real, malevolent psychic force that wishes ill upon humanity * This force doesn't necessarily want us to go extinct (then it wouldn't have anybody to torment) * Its goal is to make as many people as miserable as possible * Its influence is only psychic, and even then it cannot force anyone to do anything. * It is not limited to influencing a single person at a time * It is intelligent enough to not easily give itself away while influencing someone—people will usually mistake the influence as one of their own thoughts. How would society at large react to this development? [Answer] It is hard to answer with precision on all aspects that that observation would bring to the society at large. Nevertheless, I think we can surmise the following points: * it would be a scientific revolution. As was noted in the comments by Cort Ammon, it leads to some implication on the soul-matter relationship, questions would arise about why he was never observed before? what is the nature of the devil? where does he live? or is he actually living? Many new branches of research would be started. Furthermore implications on evolution, history, big bang, etc. would be evaluated. * Many religions would claim that the existence of the devil is a proof of the existence of a God, and that they were right all along. * Some religions would probably appear with a unique God, but malevolent. * Some religions will claim that there isn't only one, but in reality many, so no single God, but several Gods. * The religiosity rate would increase considerably. Not everyone will trust the scientific results, but nevertheless many agnostic and atheists would convert to one or other religion. * Relationships with people and laws would have to go through a hard path: people behaving badly might be under the influence of the devil. Or they possibly might just claim it to get out of trouble. With increasing crime rate. And others might be wary of it by distancing themselves. Laws and law enforcement would have to evolve to include that new possibility. Can one be accused of wrong doing when acting under the influence of the devil? How to find whether they are lying or not? Etc. [Answer] I think the key word here is 'scientifically' I'm going to assume here that the scientific proof does not invalidate or substantially change our current understanding of how the universe works. With that in mind; Given this scope, the impact on our society would be largely the same as if we found out our universe was a giant simulation, or that free will and our sense of consciousness are all illusions; it would be used as an excuse for every wrongdoing ever committed from then on. The real impact would be on our understanding of crime and punishment; right now it's entirely based on the concept that we as individuals have free will and therefore any malfeasance we commit is a result of our choice and therefore our responsibility. If the Devil exists in the form you describe, then every illegal or immoral act - EVERY one of them, could potentially (and probably) be the work of the Devil instead. How do you manage a society in which '*the Devil made me do it*' is a valid legal and moral defence? The trick here may be that if we can scientifically prove the existence of such a creature, we could develop a defensive technology to protect ourselves from it. That (to me at least) would be the first order of priority. It might actually make an interesting scientific experiment; measure criminal and immoral acts for the years preceding the application of this defence, then measure the incident counts for the same acts afterwards. Then we'd get some useful data on just how active he is, how much of an impact he's had on us and what percentage of malfeasance is inherent in our population without his influence. [Answer] One of the first things that comes to mind is to use the (or this) Devil as a scapegoat. Imagine using a possession defense to stay out of jail after murdering someone: since this is the Devil we're talking about, you know *some* people will actually need this defense, it's just now everyone and their kleptomaniac mother is going to try it, and I bet it'll be harder than ever to tell if they're telling the truth. Similarly, imagine you think some country's government is possessed by the devil. Now people may agree with you, and you could go to war over it. Since the Devil wishes us harm, he's going to do whatever he can to turn this newfound knowledge against us. So expect a lot of bad people to go free and get the things they want, and a lot of good people to get punished and hurt/killed. The fact is, learning that the Devil exists doesn't really help; if we knew what he was doing, that might be useful, but just knowing that he's doing *something* is liable to make everyone extra suspicious and jumpy. I actually think this is good reason to believe the Devil does not exist. If he did, he would probably make sure we knew about it, just so we would think we saw him behind every shadow. [Answer] Society would likely react the way they react to current entities whose effect is similar, i.e. they don't want you gone, they just want to make you miserable... by tolerating the nuisance, and looking for ways to avoid contact or interaction. Like, the tax collector. That's one for you, nineteen for me... ]
[Question] [ I want to create an inland forest on the western side of a large continent that features cenotes instead of rivers. Is this possible, and if so, how can I make it work? Any requirements for altitude or soil structure are acceptable, so long as the area can support a fairly dense forest biome. [Answer] This is possible and we actually have an example on Earth (at Yucatan peninsula). <http://www.divecenotesmexico.com/cenotes> "Mexico's Yucatan peninsula is low and relatively flat with no surface rivers or streams. However, below the ground run the three longest underground water systems in the world (Ox Bel Ha 180 km; Sac Aktun 172 km; Dos Ojos 82 km) which have directed the distribution of human settlement on the peninsula for the last 10,000 years...the world of the cenotes and underground rivers. (...) Cenotes were the only source of water in the jungle for the Mayan civilization and are considered sacred by the Mayan people." What you want from geologic point of view is flat land and soluble rocks below soil (for example limestone). For exact details it would be the best to refer to multiple sources available on Yucatan geology. ]
[Question] [ Recently I had an idea for a world setting. A large part of this world focuses around a habitable satellite the size of Earth orbiting a Super-Jupiter. The fact that it's a moon is pretty integral to everything, so if it does't work out I'll probably scrap the idea as a whole. My question is, could a satellite orbiting a Super-Jupiter be habitable? If so, how different would it be from life on a planet? How would days be experienced? Would it be tidally locked? etc..? [Answer] If moons about our gas giants are an indication, the moons would likely be tide locked. This makes for some interesting differences in cartography. On earth's globe there's two non-arbitrary points: The north and south pole. And there's a non arbitrary great circle: the equator. But for a tide-locked world, there are 4 non-arbitary great circles and 8 non-arbitrary points: Non-arbitary points: Near point Far point Leading point Trailing point North pole South pole Great Circles: Equator Circle containing near point, far point, south pole and north pole Circle containing leading point, trailing point, north pole and south pole ![enter image description here](https://i.stack.imgur.com/dyfaE.jpg) (In this image I called the leading and trailing points the Left Ear and Right Ear.) I would expect the tide locking to have a huge impact on evolution of the inhabitant's religion and culture. For example I would expect the near point to become sort of a Mecca. They might build a temple on the the near point. Viewed from this temple, the gas giant would hover motionless at the zenith. Or the moon has some [obliquity](http://en.wikipedia.org/wiki/Axial_tilt), the gas giant might trace an [analemma](http://en.wikipedia.org/wiki/Analemma) with the analemma's center at zenith. If this gas giant is like the giants in our solar system, it will likely have a whole family of moons, many of them near planetary size. It would be like a [mini solar system](http://hopsblog-hop.blogspot.com/2013/01/mini-solar-systems.html). But travel between moons of a gas giant could take place at a much faster pace than travel between planets. Launch windows between destinations would occur on the order of weeks apart vs years apart (for example earth to Mars launch windows occur each 2.14 years). Trip times between moons would be on the order of weeks (Hohmann trip time between earth and Mars is about 8.5 months). An elevator could be built from the moon's far point through the gas giant/moon [L2 point](http://en.wikipedia.org/wiki/Lagrangian_point#L2) and another elevator built from the moon's near point through the gas giant/moon [L1 point](http://en.wikipedia.org/wiki/Lagrangian_point#L1). If such elevators were built on each moon, the civilization could travel between moons using virtually no reaction mass. [Answer] It could definitely be habitable. Beyond that, there's a huge range of possible environments such a planet could have. In general, when we think of a 'moon,' we tend to think of smallish planetoids with hostile environments, but that's mainly because that's what we tend to see in our solar system. In another solar system, the moon orbiting your super-Jupiter could be the size of Earth. The moon may or may not be tidally locked. If it is, it will experience one 'day' every time it revolves around its planet. If it has particularly long days, the day/night temperature swings will be a bit more extreme. If not, it will experience days like those we experience on Earth. The biggest difference will be seasons, which will be based on the orbit of the moon around the planet, rather than the star. There will be seasonal effects both from any inclination of the rotational axis of the moon and from the position of the moon relative to the planet it orbits. If the moon is on the star side of the planet, it will receive more intense light from the star, due to its closer proximity, as well as additional light reflecting off of the planet it orbits. [Answer] As far as being tidally locked, the pieces that go into tidal locking are, the ratio of mass of both bodies, (planet and moon) the distance between them, how fast where they spinning at the beginning and how much time has passed in their little dance. Our moon was not always tidally locked to earth, but there has been a lot of time for it to occur. The Earth used to have about a 6 hour day and it has been slowed by the moons tidal actions to our current ~24 hour day. eventually the Earth would be tidally locked with the moon (meaning that from the earth and the moon would always have the same view of each other. However this is estimated to take about twice as long as the remaining time of our sun's life. So this means that an earth sized planet does not need to be tidally locked with it's super giant, but it would also likely have a much longer rotational period. Might have an orbital period of 60-100 days, farther away would reduce slowing affects of large planet and allow more reasonable seasons to measure. A 'year' of 100 days would give approx 25 days per 'season', 25 facing the sun, 25 behind the super planet, and then of course how long does the planet take to orbit the sun? Is every 4th earth year colder because it's at the planets farthermost reaches, and 2 years later warmest summer? Or is is farther out and a much slower solar year? To far away and the sun will have little affect, just a little more or less light. [Answer] Expanding a bit on HopDavid's answer, if the moon is totally locked, then the ecology also becomes different. The point closest to the Jovian would be the "hot pole", since it receives the heat and reflected sunlight from the primary, while the opposite point would be the "cold pole" (although that is a relative term; a moon with an atmosphere would have lots of ways to conduct heat between the poles.) As well, the "Left Ear" (leading point) would be subjected to more radiation from the primary's radiation belts than the "Right Ear". We can assume that the moon has an active magnetic field of its own due to the molten core (hotter than the Earth's due to the constant "kneading" from the retinue of moons orbiting the primary, much like Io in our own Solar System), so the radiation is not instantly lethal to most life. When plotting ecosystems, the moon will look a bit like a beach ball painted in a checkerboard pattern. One set of rings will run from the hot pole to the cold pole, and be areas of discreet temperature and illumination, while a second set of rings at 90 degrees to the first will run from the Left Ear to the Right Ear, indicating relative exposure to radiation. Because of the active tectonic forces, the moon will have many active volcanos and subduction zones, so the various geological cycles will be quite rapid, with almost constant mountain building and oceans and seas opening and closing in relatively short (million year) timeframes. The carbon cycle and hydrological cycles will also be affected by the rapid "turnover" of the crust, so conditions will be rather different from Earth (although how different might depend on your starting assumptions.) This will be a very interesting world to visit, but if we were able to get to the system, most people would probably prefer to remain in a colony in free space. [Answer] How would life be on a Jupiter moon? **Nasty, brutish and very, very short.** Jupiter has these **[massive radiation belts](http://www.jpl.nasa.gov/releases/2001/belts.html)** generated by its magnetosphere, which are about a million times stronger than Earth's. They were powerful enough to damage or throw into safe mode all of our hardened interplanetary probes. It is estimated that the accelerated plasma is energetic enough to [kill unshielded humans in minutes](http://anstd.ans.org/uncategorized/space-radiation-interplanetary-radiation-belts/). This would scale up supra-linearly with the size of the super-Jupiter. Organic compounds (such as complex organic molecules, people or cats) on an exposed satellite surface [would be destroyed in minutes or hours.](http://www.astrobio.net/news-exclusive/hiding-from-jupiters-radiation/) **So colonies are unlikely**, especially if you want them to live on the surface. ]
[Question] [ I have a region on a 'Eurasia' style continent that is surrounded by large mountains. The reason that I came up with was a very dense and volcanically active microplate that was being compressed on three sides. As such, *three* large mountain ranges, and a abutment into the nearby inland sea. I want this region to be home to an absolutely *insane* amount of silver. Not [argentite](https://en.wikipedia.org/wiki/Argentite), [acanthite](https://en.wikipedia.org/wiki/Acanthite), or copper-ore byproducts, but *massive* quantities of pure silver running like rivers through stone. Instead of *one* lonely mountain, an area of mountains that collectively stretch across a 8,000-ish km arc. If it is pertinent, prograde orbit, earth-esque biome layout, the region in question is an east-facing cup of mountains bordering a large inland sea, with the lowest latitude being 45, and the uppermost reaches into the low 60's. The *civilization* era is [High Medieval](https://en.wikipedia.org/wiki/High_Middle_Ages), but with massively improved healthcare and sanitation. Here is a political / geographic region map I created using the Inkarnate software. [![Angveld Region / Geography](https://i.stack.imgur.com/PqQHC.jpg)](https://i.stack.imgur.com/PqQHC.jpg) The 'Lakelands' are a massive volcanic caldera surrounding a mega-hotspot which erupted some couple of thousand thousand thousand thousand years ago. If my geology is correct (which it likely isn't) Silver is usually upwelled from divergent ocean crust, and upthrust at convergent boundaries, or hydrothermally refined from cooling magma chamber precipitates. I wanted a mix of the two to cover my bases. The weird step-like tiers of the Northolt, Stonerill, Midlands, and lowlands were a vain attempt to use "folding" (like in the great basin of the US), and copious amounts of erosion via river to make some nice landforms. The real mountains, as in formed by tectonic processes, are the Andwynns in the south, the Spires in the North, and the Lakeland rim. --- *The big question* for actually qualified people to surmise. Where, and to what degree, would the *native* silver deposits be, and how would one reasonably maximize this as a worldbuilder? You may: 1. Alter the composition of the *planet* itself. Insomuch as gravity remains similar, magnetosphere remains earthlike, and that life would still be feasible. 2. Introduce traumatic events to the planets surface, i.e. asteroids, planetary collisions, etc... With the consideration of the amount of time required between such events and a humanoid civilization interested in mining strategic metals. Without creating unreasonable effects on biodiversity and/or making life infeasible post-event. 3. Alter the geographic situation of the region. Without altering the landscape to an extreme degree. I.e., mountains can get smaller, hills can be added, rivers diverted, and volcanoes shifted. Mountain ranges may not be subtracted or added, only shortened/heightened. 4. Use magical means. Gods are active forces walking the surface. *I don't want to use the 'a god did it!' reasoning*, especially given the selfish nature of my pantheon (they created the world as a private retreat and got stuck there.) Mortal mages exist, but they are limited by their perspective, knowledge, and understanding. I.e., a Mage could manipulate gravitational vectors if they had a complete understanding of the subject. 5. Use valuable metal alloys, notably [electrum](https://en.wikipedia.org/wiki/Electrum), if all else is unfeasible. I wanted to avoid baser metals, because the smelting process is convoluted for pure forms of silver. Apparently the Egyptians used molten salt and water to refine ore rock, which I like the idea of. --- 1. I wanted to avoid involving the practicality of a state or civilization hoarding a metal, thus making it common, to keep the question straightforward. I will link another question about the viability of a artificially constrained market. Once I can get a general feel of *exactly* how much silver I'm dealing with. [Answer] Native silver never occurs in isolation in vast quantities. It is always associated with sulfides of silver, such as argentite, acanthite and others. It is also associated with [nickel and cobalt arsenides](http://www.minsocam.org/msa/collectors_corner/arc/Krieger_p715-723_35.pdf). It is [rarely found as a native element](https://geology.com/minerals/silver.shtml). This has been observed in a number of geological provinces: * The silver deposits in the [Erzgebirge](https://en.wikipedia.org/wiki/Ore_Mountains) of Europe * The [Cobalt district of Ontario](https://en.wikipedia.org/wiki/Cobalt%2C_Ontario) * Silver deposits near Wickenburg, Arizona * The Great Bear Lake district, Canada * Sarrabus, Sardinia * Sabinal, in Chihuahua, Mexico Many silver deposits are of [hypogene](https://en.wikipedia.org/wiki/Hypogene) origin - they form at great depth where temperatures and pressures are high and water can remain a liquid above temperatures of 100° C. Minerals crystalize from hot aqueous liquids in such environments when temperature and pressure drops. > > Most native silver is found associated with hydrothermal activity. In these areas it often occurs in abundance as vein and cavity fillings. A few of these deposits are large enough and rich enough in native silver to support mining. > > > It is would be possible to have "absolutely INSANE amounts of silver ... [in] massive quantities of pure silver running like rivers through stone", but it would be associated with "absolutely INSANE amounts" of non-native forms such as sulfides of silver in addition to nickel and cobalt arsenide. If such a place did exist it would be a spectacular world class deposit of silver. [Answer] ## Alchemy For a tongue-in-cheek solution, relying on magic and accident: "someone tossed the Philosopher's Stone into a volcano and it's still reacting with the mantle". That "prima materia" sought by alchemists was held to have some very desirable properties. One that isn't so famous is that it could be "compounded" - once you had some, you could use it to make more indefinitely. The rules of alchemy are yours to dictate, and you can justify anything you require - Earth has formed natural nuclear reactors before. You can state that under volcanic conditions, alchemy can turn molten rock into silver. So, suppose that: Someone dropped some into a volcano and a fragment found its way into the mantle. The *prima materia* started "compounding" underground, spreading through the mantle. (Presumably under geological pressures and temperatures, exotic reactions are possible that weren't predicted in an alchemist's lab.) Your upper mantle is doped with alchemical catalyst, and now any volcano will spew incandescent rivers of silver. --- Of course, the common materials are a baseline for any world. What about the rarer metals, like legendarily-strong and hard-to-smelt iron? If the same alchemy is busily converting it to gold, then iron will be rare and prized, while gold and silver will be toys. Don't forget to make the *prima materia* low-density, or it might be Midas to your planet's iron core and destroy the magnetosphere. But perhaps the gods thought of that. [Answer] **Europe used to be below sea level** *I'm no expert*. I did go through a plethora of articles of silver forming and how it is found as you peaked my interest. The added difficulty is the native deposit requirement. Silver is created in relatively cool stars. One article explained that during the formation of the solar system, the inner solar system where the Earth resides was too hot, leaving the Earth "depleted from volatile elements" like silver. However, later in the formation of the Earth silver is found in higher quantities. As the inner solar system cooled off, astroids and the like can deposit silver. This is why in a lot of silver on Earth has traces of extraterrestrial origin, according to the article. Silver seems rare but widespread. The widespread nature isn't a direct problem for the story, as the metal is often in such trace amounts and bound to other elements that it's not minable. Native deposits are very uncommon, so most silver is found combined with some other materials. Silver can be concentrated however. A few articles condensed into a few sentences: native silver from the crust can be "created" most easily via submerged volcanoes. Water filters down into the rock, dissolves many material and can take the now free silver with it. It goes into or close to the magma chamber and thanks to gravity and crystallisation it can be separated, creating concentrated deposits of, among other chemicals and metals, native silver. This is than expelled through the vulcano, leaving it on the ocean floor. **Forming of huge native deposits of silver** From what I read, the best would be a combination of the two. The advantage is timescale. Geological processes take millions of years, so it can all happen a long time before the continent is formed. After the creation of the Earth, it is assumed it didn't have a moon yet. At a certain point a huge celestial body crashed into the Earth, possibly giving it the tilt that gives us the seasons, while the celestial body got trapped in the gravity well and became our moon. The impact could shatter a tectonic plate in multiple pieces, ablate enough that it'll become lower than the water and deposit a lot of silver from the asteroid. (This could have as an addition that your moon shines brighter or is a bit like a mirror, because of a higher silver content on the surface.) Because a whole lot of land is now below water and the crust/tectonic plate crushed, it can get very high vulcanic activity, spilling out lots of native silver among other things. This can mix with the silver deposited by the impact of the now moon. Due to geological activity the silver gets properly trapped in the rock, while tectonic activity pushes the land above water after a time, in addition to creating a lot of mountains and faults because of the increased tectonic plates/activity. You'll likely have a lot of native silver, along with other metals and not native silver. It can explain the vulcanic activity and mountains around a certain area as well. The only thing is that silver will always crop up in other areas around the world, although probably not as abundant, especially in native deposits. But again, this is an answer created by just looking through a boatload of articles. None are terribly specific in quantities of formation for example. [Answer] ## Volcanic domes you already have the right conditions, the rest is luck and since you are writing the story you make the luck. the largest silver deposit on earth is a dacite volcanic dome in Bolivia called Cerro de Potosí, it produces large amounts of native silver and very easy to smelt silver chloride. it has been producing for hundreds of years. It formed from deep magma rising to the surface. As a side note it also produces a great deal of tin. <https://link.springer.com/article/10.1007/BF00189185> [Answer] ## A long time ago, in a system far, far away ... Start with a rocky world that contains the usual mix of elements expected to form a planet. The entire world needs to be hot for a long time, allowing geologic sorting of the elements to occur based on density. Note that separation into layers will certainly be imperfect, but maintaining high temperature for a long time and cooling only very slowly, will allow time for convection currents to die down and maximize separation into layers. This planet is discovered by beings that do large-scale mining of asteroids and planets. The miners do refining in place to improve the purity of the cargo since customers don't care for the associated heavy industry associated with refining and they willingly pay the premium for the refined metals. The miners are in the process of harvesting the enriched silver layer and have started moving the cargo transports when they are suddenly destroyed by a nasty space virus, malicious AI, or something else. Sadly, the miners are wiped out to the last person. The mega-transports containing millions of tons of silver are now on an unintended trajectory that collides with your planet sometime in your distant past. ]
[Question] [ Would a race/species that lives twice as long as humans experience linguistic evolution at half the rate of humans? If not, would it be slowed down at all? Would any cultural characteristics have a noticeable effect (e.g. extreme cultural conservatism slowing it down)? If this wouldn't have a noticeable effect, what other factors might contribute to one culture speaking a much more "archaic" descendant of a proto-language than another culture with whom they have significant contact? [Answer] There are various aspects to linguistic drift to consider. The example that comes to mind is American Southern English, which preserves archaic words like "yonder", but also pushes the vowel shift such that using "drunk" as the past-tense of "drink" is necessary because "drink" and "drank" are pronounced more or less the same[1]. See also: Yorkshire English preserving rimnants of thou and thee long after they fell into disuse in most other dialects. There's also the matter of top-down influences. Using English again, most of our whacky spelling comes from the establishing of standards more or less mid vowel-shift, so everyone kept writing for the old pronunciation, but speaking with the new. There's also the way in which "thou" fell out of use, which is to say, it became seen as rude and low-class[2], which trickled to the rest of the Anglophone world from the well-connected politeness-influencers of the Elizabethan era. Compare to the 20th and 21st centuries, where regional dialects in the US rapidly started to flatten with the spread of mass media, especially movies and national television programs. The English of today is certainly mutually understandable with the English of the earliest audio recordings, but I doubt many would have trouble distinguishing Edwardian English from Millennial English, for most dialects. As for life-span, life expectancy has increased over the past 150 years, but mass media and the overall rate of cultural and technological change has made it such that one could argue that Millennials and GenZ are speaking different dialects from their grandparents, especially if they're from a region with less media influence. Meanwhile, the life-expectancy among American Southerners, and indeed most of their ancestors all the way back to the Scotch Irish[3], have generally had below-average life-expectancies, but have arguably been slower to change. My conclusion, then, is that, if longer life-spans would slow linguistic drift, it must come with the old having a great deal of cultural influence, and perhaps even some stagnation besides. It seems that things like pronunciation are more likely to change randomly, whereas the loss of archaic words and phrases is more likely to come from being connected to the wider cultural influencers. Isolation and rurality seem better predictors of archaicisms than lifespan, but it seems that isolation and rurality negatively correlate with lifespan. So long-lived, insular, gerintocratic rural subcultures seem like the most stable. * [1] There are many dialects under the "American Southern" umbrella. I don't even think "American Southern" is an official term. And there's a lot of local variation as well. Generally speaking for the set of dialects I'm most familiar with, though, the drink/drank merger was pretty prevalent before the internet and affordable cable. * [2] To grossly oversimplify, anyway. It's more like "thou" (or "thu", because I have no idea how to get my phone to type thorn) was the second-person singular, then the French introduced the T-V distinction, and also took over polite society, so using "thou" the old way was a peasantly trait. Then using it at all. Interesting that political correctness managed to wipe out a whole pronoun, but profanity remains exactly the same, and even grew stronger over the past generation or two. * [3] People in the South have always had diverse backgrounds, and those have jointly influenced the resulting dialects. I focus on Scotch-Irish, rather than Cavaliers or the numerous African ethnicities or Indians, because they were saying "yonder" for centuries before coming to America, whereas the others (excepting the Cavaliers) were speaking completely different languages. I should also note that, as of about GenX or so, "yonder" became something of a class marker, such that you can tell a lot about someone under 50 based on whether or not they use it casually. And it rhymes with "under". \* I am not a linguist. On the off chance this answer seems acceptable, please do wait to see if an actual linguist shows up and tears it apart. [Answer] Regardless of how we learn it, language is constantly evolving for a very simple reason; our lives are constantly changing. New social interactions and methods arise and replace old ones as different ways of seeing the world fall in and out of fashion, technology both encroaches upon us and enables us to do things we thought impossible before, and we need new words to describe that over time. Further, anyone who has ever traveled abroad for an extended period often returns with a bit of an accent or an odd turn of phrase picked up while living away, and that is a good thing. Sure, we pick up language from our parents and teachers when we are young, and therefore our adaptability to new phonemes and words and concepts is far more pronounced during that time but it never goes away. If it did, it would literally make it impossible to learn new things as we could only incorporate ideas for which we developed a vocabulary before a certain age and life just doesn't work like that. At least, not for the sufficiently curious. Further, the fact that people learn new languages as adults for work or pleasure proves this point completely. An extended lifespan may reduce our adaptability somewhat but it isn't the material factor in the evolution of language; the rate of external change is. Want proof of this? Well, in England, you have the [Annual Royal Christmas Message](https://en.wikipedia.org/wiki/Royal_Christmas_Message). This is really useful for testing the proposition of change of language because it's been delivered by the same person for an extended period - a person whose contact with the general population is somewhat controlled but still there, and there are recordings of it around the place that you can access. As an exercise, find as many of them as you can, and play them in sequence. Does the Queen's voice change? Does her use of words? Does the prevailing theme change over time? Does she use words in later recordings that were not in general use in the 30's for instance? I think the results might surprise you. In short, the length of a lifespan may have a factor in the rate of change, but that is overwhelmed by the rate of change within society and that is what really drives the need for language to evolve. It's the concepts we discuss among ourselves, the new devices and technology that enable new ways of doing things and new practices, all of which need names, that really changes how we approach language and as such, is the principle driver in the way language changes. As an aside though, if you look at linguistic theories like [Grimm's Law](https://en.wikipedia.org/wiki/Grimm%27s_law) you'll also begin to see that language has to be convenient, and language tends to migrate from complex forms and difficult sounds to make down to simpler forms and more convenient sounds at a rate which is proportional to the commonality of the word that's evolving. That is going to happen regardless of how long someone lives. [Answer] In my opinion, linguistic evolution would be accelerated within a long lived species. A pre-lingual individual, who discovers the fundamentals of language and develops a simple vocabularies of grunts and hand-gestures, would benefit from improved tribe organization and cooperation with her peers. That benefit, experienced within a single long life, would accumulate, inspiring her to expand the original vocabulary and apply the idea of language to more and more aspects of her life. Shorter lived species would have less remaining lifetime left, after first learning language and then realizing its benefits, to achieve such expansion and broadening of use. In the same span of time that a single long lived speaker learns, uses and grows their language, several generations of shorter lived speakers would attempt the same achievement. But each of those shorter lived generations would spend a larger relative percentage of their life learning language, while their longer lived alternative only has to learn once. So in my opinion, longer lived species will develop language quicker and achieve more complex language characteristics than their shorter lived equivalents. [Answer] In English linguistic drift essentially stopped once literacy became common. Shakespeare's English is still mostly understandable now, although there are changes in meaning, some odd constructions. Go back to the Canterbury tales, and it's a lot harder -- a lot mroe than the increase from 400 years to 600 years would seem appropriate. Big difference was that more people could read and write. A written language doesn't change much. ]
[Question] [ Imagine an Earth-like planet orbiting a Sun-like star [in the inner halo of the Milky Way](https://en.wikipedia.org/wiki/Galactic_halo). As a halo star, it will likely be somewhat [metal](https://en.wikipedia.org/wiki/Metallicity)-poor, having formed early in the life of the galaxy, but other than that, we can assume the planet and star to be like our own. The system lies about 4 kpc from the Galactic Center; as such, it completes one orbit of the galaxy in somewhere between 100 million and 200 million years. While in the halo, the star is unlikely to be near other stars, but during each orbit, it passes through the disk of the galaxy twice. If the star is traveling at $\sim$300 km/s, then it should take it about 3.3 million years to travel through the disk, where it will pass by numerous other stars and other objects. I'm trying to determine if these passages will show up in the planet's [geologic record](https://en.wikipedia.org/wiki/Geologic_record) many millions of years in the future. Ideally, alien geologists (with the same tools as human geologists today) would be able to use recurring signs of interactions in the disk to figure out the period of the star's galactic orbit. I only have one vague idea: the planet would be more likely to be near a supernova while in the disk, which would cause changes in isotopic abundances in certain rock layers. However, I have no idea whether or not this is plausible, and if it would be detectable. **Would the trips through the galactic disk be apparent in the planet's geologic record? If so, how would they show up?** [Answer] **Space dust deposition might be different in the disk.** [Cosmic dust](https://en.wikipedia.org/wiki/Cosmic_dust) of extraterrestrial origin rains down on the earth all of the time - thousands of tons of it. In your scenario, as the planet passed through the disk, one would expect a change in the quantity and composition of dust accumulating. The dust might be comprised in part of dense elements unusual to find in the crust, like iridium. Or the dust particles might contain some with microscopic shapes characterizing an extraterrestrial origin. It would be easiest to study this someplace like the moon where dust can pile up undisturbed. Comparable accumulators on the Earth would be the deep ocean and Antarctic ice. I looked to see if anyone has studied cosmic dust accumulation in the ice. I found this. [Interstellar 60 Fe in Antarctica](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.072701) > > Earth is constantly bombarded with extraterrestrial dust containing > invaluable information about extraterrestrial processes, such as > structure formation by stellar explosions or nucleosynthesis, which > could be traced back by long-lived radionuclides. Here, we report the > very first detection of a recent 60 Fe influx onto Earth by > analyzing 500 kg of snow from Antarctica by accelerator mass > spectrometry. By the measurement of the cosmogenically produced > radionuclide 53 Mn , an atomic ratio of 60 Fe / 53 Mn = > 0.017 was found, significantly above cosmogenic production. After elimination of possible terrestrial sources, such as global fallout, > the excess of 60 Fe could only be attributed to interstellar 60 Fe > which might originate from the solar neighborhood. > > > If you had strata from an accumulator dating back a very long time (for example a deep ocean core)you might note a period difference in dust constituents corresponding the passage thru the disk, or maybe just a thicker layer of dust corresponding to the greater amount of material in the disk. No supernovas. Nothing flashy. Just dust, and more dust. [Answer] Assuming an Earthlike planet orbiting a halo star and passing through the galactic disk, let's look at the case for geological evidence of supernovae. Because the planet is Earthlike we can assume the geological evidence will be effectively the same for the Earth. If its passage through the galactic disk takes it close to more supernovae than the Earth has experienced in its past, then that evidence will give a stronger geological signal. > > Past supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata. Subsequently, iron-60 enrichment has been reported in deep-sea rock of the Pacific Ocean by researchers from the Technical University of Munich.[11][12][13] Twenty-three atoms of this iron isotope were found in the top 2 cm of crust (this layer corresponds to times from 13.4 million years ago to the present).[13] It is estimated that the supernova must have occurred in the last 5 million years or else it would have had to happen very close to the solar system to account for so much iron-60 still being here. A supernova occurring so close would have probably caused a mass extinction, which did not happen in that time frame.[14] The quantity of iron seems to indicate that the supernova was less than 30 parsecs away. On the other hand, the authors estimate the frequency of supernovae at a distance less than D (for reasonably small D) as around (D/10 pc)3 per billion years, which gives a probability of only around 5% for a supernova within 30 pc in the last 5 million years. They point out that the probability may be higher because the Solar System is entering the Orion Arm of the Milky Way. In 2019, the group in Munich found interstellar dust in Antarctic surface snow not older than 20 years which they relate to the Local Interstellar Cloud. The detection of interstellar dust in Antarctica was done by the measurement of the radionuclides Fe-60 and Mn-53 by highly sensitive Accelerator mass spectrometry, where Fe-60 is again the clear signature for a recent near-Earth supernova origin. > > > This suggests the amount of Fe-60 present in geological strata may be taken as evidence of close supernovae events. However, there are more extreme possibilities for the impact of supernovae on Earthlike planets. These will occur when the supernovae are a bit too close for comfort. > > Gamma ray bursts from "dangerously close" supernova explosions occur two or more times per billion years, and this has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth. > > > The good thing is dangerous close supernovae will be, in general, rare. Unless, of course, the galactic disk is rich in stars undergoing supernova. Then passage through the galactic disk will be somewhat fraught. In conclusion, the impact of supernovae will appear in geological evidence both in terms of the isotopic abundance of Fe-60 and, possibly, in mass extinction events. Please note: This has confined itself to considering the evidence for supernovae on the hypothetical Earthlike planet orbiting a halo star. REFERENCES: [Near-Earth supernova](https://en.wikipedia.org/wiki/Near-Earth_supernova) [Answer] **Signatures aren't your problem, Uranium is** Most dating is done with Uranium and if you can't get absolute ages on surrounding rocks you might be able to figure out this pattern exists but you need corresponding strata to have minerals like zircons (mostly found in volcanic ash) with uranium imperfections to get an accurate age. They could easily isolate the strata from the pass-throughs as long as there are impacts or such deposits with different isotopic signatures, but I can't come up with a dating method that works on long enough time scales without using heavier elements. (We come up with way more subtle effects all the time). Maybe with a list of element concentrations against a list of radiometric dating techniques? **An alternative** Maybe once the fact a pattern is found to exist geologically astronomical models could work out the likely time frame ]
[Question] [ How would fire honey be useful and manageable to a beehive/bee colony? # Info In this scenario, bees harvest nectar from a particular flower. The nectar is not only spicy from [capsaicin](https://en.wikipedia.org/wiki/Capsaicin), but literally fiery. Tiny embers are magically suspended in the liquid, sparks dance over the surface. The bees should be changed as well. They need to produce this firehoney like normal bees would produce normal honey. Instead of royal jelly, a queen is determined by getting fed ember-rich honey. Only the bees that survive this are queens. The worker bees utilize this honey by absorbing its capsaicin into their venom, making their stings much more painful. The queens have unique stingers because they store an ember in their stinger. They also have no barbs (like those a bumblebee would have) which enables them to sting as many times as they like (in unusual circumstances.) # Question The bees need to be able to slurp up the nectar to process it to make honey (regurgitated, treated, digested nectar). They also need to be able to store it in regular wax. * How can they withstand the heat in their stomachs? That is to say, * What part of their body structures, body plans (levels of organization, cephalization, structures inside germ layers,etc), and anatomical/physiological structures/systems (organs+organ systems) need to be changed to enable this fire-honey to be made? The flowers have evolved alongside them to become these heat-producing flowers, simply because the flower gets pollinated by attracting the bees. While the nectar is no more/less nutritious than that of any other flowers, it *does* radiate a fair amount of heat (probably useful in winter, detrimental in summer.) This nectar is slightly more abundant than any other flower. It is useful because it only grows in a select, highly remote/inaccessible by air place, meaning that the bees have found and filled their niche. There are no other species that use this flower, and indeed no other bees (hence, no competitive exclusion principle as two species compete for a niche). There is an overabundance of flowers (they flower year-round) and they produce plenty of nectar. The colony has settled into a logistic growth curve as the bees rapidly bred to meet the high carrying capacity. The petals of the flower are just as hot as the nectar (and the nectar is the same temperature as the pollen.) Ignore the effects of heat on (1n) haploid gametophytes. The pollen can survive. The question is: how can the bee do it? The nectar is at around 180 degrees Fahrenheit (~82 degrees Celsius). The actual sparks are at around 1200 F (649 C), however, their low thermal energy and unique composition (chemical formula UnObTaNiUm, if you want to know) keeps them from actually boiling the nectar. The heat of the rest of the flower is identical to that of the nectar. After being pollinated, the flower doesn't turn into any fruit. It's a small wildflower. You may use the heat of the flower as an energy or heat source. **And thank you to all in the [Sandbox](https://worldbuilding.meta.stackexchange.com/questions/6168/sandbox-for-proposed-questions), especially @JoeBloggs and @Secespitus, who helped me work on this draft.** [Answer] > > Tiny embers are magically suspended in the liquid, sparks dance over the surface. > > > The 1200F (649C) sparks are a reaction between the embers in the nectar and the atmosphere. Therefore if you remove the atmosphere interaction, you remove the issue with the high heat sparks. Now you just have to deal with the 180F (82C) nectar. Much more manageable. * Once your bees have slurped up the warm nectar, with an embedded ember, it is in an airtight stomach container. The nectar provides a 'safe' lubricating layer between bee and ember. No sparks are produced once imbibed. Seeing as we have the magical UnObTaNiUm element, we can use this or one of it's close Isotopic cousins, to include in a protective mouth, throat and stomach mucus lining. This will have slowly evolved in the bee with exposure to the firenectar over the millennia. This lining will not provide total protection, else your human or other type characters could possibly decide to harvest the bees for the protective mucus instead of the honey. So the mucus lining wears out quickly once exposed to the nectar. This means that the bees harvesting range will be much shorter than normal bees. Typically Bees forage around 3-5km (max up to ~10km) from the hive, your firebees wil have to be closer to the hive in order to deposit the nectar and embers before suffering irreparable internal heat damage. Nectar will be deposited into the honeycomb. Once a honeycomb unit has a single ember in it, it should be capped with wax so that no more embers are added. Embers should be spread out amongst the honeycomb to spread the heat evenly (bees are cabable of this level of decision making). Bee eggs and larvae could only be fed pure honey (no hot embers) while queens could be fed honey formed near or from the ember cell (similar to royal jelly). The wax of the honeycomb may have a similar UnObTaNiUm isotope that the bees stomach lining has, maybe a more stable version. I imagine the wax walls of the honeycomb will be thicker and more spaced out than the dense honeycomb structure we are familar with. Bee hive locations are chosen for variety of reasons, protection from the wind, and size being two of them. When normal bees live in a hive, they typically raise and maintain the temperature inside the cavity to a temp of ~32C to ~35C. With your excess heat coming from the nectar, I would imagine that the bees would select larger cavities to help dissipate some heat as well as changing their wind preference. This would allow the wind to blow through (or at least around) the hive and expel excess heat, cooling the hive down. Good luck to any Honey Badgers in the area. I doubt dropping one of these hives will be good for any nearby vegetation. You may have some very localised weather effects as well! ]
[Question] [ Perhaps one of the most popular flavors of worldbuilding is *steampunk*, which is basically today's technology under Victorian attitude, architecture and materials. The clear inspiration for steampunk's overall style is the Industrial Revolution's heavy emphasis on metals and factories and coal and those sorts of things. The fact that real Victorian society was nowhere near as extravagant--let alone BIG--as the steampunk culture, I had to ask: When would be the best point of departure in our timeline for steampunk to be a reality? What materials and resources would be needed to create this possibility? [Answer] Looking at this the other way, you need to understand why steam technology was eventually outmoded by internal combustion engines and electric engines between @ the 1880's and the 1920's (like most things, supplementing older technologies takes time). The first issue with steam is that the power to weight ratio is generally lower than with competing systems. Since steam is an external combustion system, you need the extra mass of boilers, steam pipes, condensers (if fitted) and so on to extract the chemical energy of the fuel into mechanical energy. Internal combustion engines (Otto, Diesel and Brayton cycle) all dispense with the intermediate step, so engine machinery is much lighter and more compact. This scaling effect works downwards rather than upwards. Large steam powered systems continued to dominate in locomotive engines and ships into the 1920's and even into the Second World War (many ships were powered by "triple expansion engines", for example), and thermal generators are still dominated by steam generation whether coal, oil or even nuclear powered. On a very large scale, steam is still competitive. The second issue with steampunk is flexibility. Since steam is generally competitive when you are looking at large systems, then you are tied to the location of the steam engine, rather than being able to move around as needed. Factories in the steam age use a single large steam engine which drove a series of drive shafts along the ceiling. Pulleys attached to the drive shafts drove belts or chains down to the machines below. You could imagine a computer server room filled with mechanical "Babbage Engines" all running off a locomotive sized engine in the back, but this technology, like others, isn't going to scale into PC's, laptops or tablets (the idea of a person carrying a scoop of coal for their laptop, adjusting the chimney for the correct draft and waiting for the boiler to come up to pressure for a laptop Babbage machine should give you some idea of where this is going. To actually make a steampunk society, you would need to jump-start steam technology by several decades. Very simple steam and atmospheric engines were invented as far back as the 1rst century AD, but Roman society generally thought of these devices as toys. What we understand as steam engines were invented in the early 1700's, so your point of departure will be to commercialize steam technology and improve it before James Watt's condensing engines were introduced in 1781. Perhaps James can be born several decades earlier, or Newcomen's engine introduced in the 1690's and a budding genius develops the condensing engine (which was far more fuel efficient) in the early 1700's. The point is to give Steam engines such an entrenched advantage in terms of sunk costs, developed infrastructure and the huge mass of technicians and other trained workers needed to keep steam power viable that competing technologies will find it harder (although not impossible) to break into the market. The widespread availability of stem power and the costs of conversion would allow for a much longer time-frame for steam to be viable, and for steam engineers to develop cost effective responses to internal combustion and electric power (steam cars and even steam airplanes were developed, so it is possible to have a Steampunk age lasting perhaps from the 1700's to the 1950's in your timeline). [Answer] **It's not about what you need to make a steampunk world but what should be missing.** Let's look at your world and see what isn't steam powered. * cars * trucks * some trains *Wait what? Surely more than that, my phone and computer are electric.* Nope, ultimately they're steam powered. It's just that steam power is more effective on a large scale then transmitted via electricity. *So where did it all go wrong?* Henry Ford is where it went wrong. Until the high production output of his factory any given car was as likely to be steam powered as petrol. Steam trucks lasted even longer. **To make your steampunk world you need to remove Henry Ford and central electricity distribution and it's all up in the air from there.** In spite of increasing regulation relating to the noise, steam and smoke from steam wagons, they lasted until cheap war surplus trucks displaced them in the 1950s. They have power advantages for short haul high load work, e.g. steam engines produce full torque from a standing start. Allowing this technology to mature in a way that was not effectively permitted could well mean that a "steampunk" world of a sort would exist. [Answer] To make a steampunk era more likely, you need to remove easy access to petrol and internal combustion engines. Without a liquid fuel with high chemical energy that is convenient to store and pump, the internal combustion engine would not have made it big. I think i remember reading somewhere (although i cannot find it at the moment) that students tried to rebuild the first Daimler engine, and failed. The story claimed that this engine could only work because of some lack of precision: rebuilt with modern technology, materials and precision it simply would not work. So, assuming that liquid fuel was much more expensive / harder to obtain in large quantities, and maybe Gottlieb Daimler working with higher precision, and thus failing to get his engine to work, a steam/electric hybrid punk era might have been feasible. While it is of course true that small steam engines don't make much sense, other than maybe for "portable" generators, i think you could have an interesting steam / electricity mix. Now all you need is a somewhat more reasonable Austrian monarch, to avoid the first world war, and you could have had a nice, prospering and reasonably rich electric steampunk society. Avoiding the first world war would have helped expanding the turn-of-the-century era that was so much in love with intricate, complicated and richly ornamented designs, that were so brutally replaced by ugly, but easy-to-produce, cheap and reliable means of destruction. [Answer] This is an old thread, but one that still comes up when you search for steampunk. So, for anyone reading this in 2020 or beyond... I think the only two realistic explanations for a world in which steampunk level tech might exist have nothing to do with inventions themselves: 1. A huge global disaster that drastically reduces the earth's population (along with much of the research and/or scientifically literate people) in the 1800s/early 1900s. I'm talking something on the scale of a severe global plague that mutates into a deadly and highly contagious form that absolutely decimates the human population worldwide. Or maybe a supermassive volcanic eruption (i.e. Yellowstone) that wrecks the atmosphere, causes tsunamis, global crop failures (and likely wars over food supplies), and leads to a mini ice age. The society that's left behind after conditions improve would essentially have to start over again with whatever scientific understanding the average layman had. 2. A very powerful, influential religion that infiltrates governments across the globe (or at least in places where scientific progress was being made in the 1800s). Something like the vatican mixed with a radical eco-warrior type movement that shuns certain technology and criminalises anything that goes beyond clear and obvious natural law (basically, a technology version of 'burn the witch'). People like Edison and Tesla are now hunted down and would-be investors are donating to the 'church' instead of backing research. ]
[Question] [ This was inspired by the question [How would tattoos fare on reptilian scales](https://worldbuilding.stackexchange.com/questions/4807/how-would-tattoos-fare-on-reptilian-scales) Let's assume for this question that humans never lost their hairy, hairy bodies and are covered in fur. How would tattooing work? Would they use scarification, or maybe freeze branding? [Answer] **Branding** With thin hair, such as horses have, obviously, branding could be a preferred option. It would depend on your creature's design. **Shaving** As an alternative to tattoos, distinctive patterns can be continually trimmed as identifying symbols in your animal. This works for simple patterns. **Coloration** This can be a temporary alternative to your tattoos, by dying the furs. However, I think the following would be most what you're looking for. **Shaving + Tattoo** Shave the area, apply the tattoo, and then continually keep that part of the area shaved, so the drawing and pattern will show when you want it to. [Answer] One possibility is quite... nasty, and as such it would probably not be used for "stetic only" tattoos but just for cultures that use those tattoos as a way of identification / tribal identity. The word here is [scarification](https://en.wikipedia.org/wiki/Scarification); produce designs out of wounds on the skin. In this case, since you want the affected area to be easily visible, you would look for a part of the body which already has little hair on it (shoulders) and mark it with identifiable shapes. As you would want a relatively big patch of skin to be affected (so it does not get covered easily), you probably will want burning it instead of other methods (like the one with the Euler formula in the article). An example could be similar to the rank insignias used by the military, with more "bars" of cleaned skin marking a braver warrior or a more important chief. Once that is done, it is up to experimentation to see if the affected area can be colored with more traditional tattoos. With time (and a more advanced technology), more cosmetic "tattos" could be accomplished by using depilation. [Answer] Since an injury can make the hair grow back a different color due to the skin trauma, one might use that process to create permanent hair color patterns. Perhaps they would experiment with different sorts of injuries which might create different shades of color. Also, how about hair grafts to create color patterns. They might even have adapted scalping and fused it with grafting. Multicolored individuals would be great warriors... ]
[Question] [ How would society function if people had the ability to easily erase existing memories or imprint false memories? Let's say that this is fairly easy to do, but requires that the person is able to touch the victim. It is common for criminals to do it for scams or for concealing other crimes, and spies try to do it for political reasons, though it is strictly illegal even for government agents. This is a well-known and easily-understood problem. Law enforcement can determine if it is happening or has happened to someone (though they can't tell if a person did it to themself), and people often go to prison for it. This is a world with some magic, but the memory-imprinting itself may be magical or technological (I haven't decided yet). How do governments and law enforcement approach this problem? How do ordinary people deal with it? [Answer] **Unless something is done to make memories reliable, this will result into a complete dystopia** Let's imagine that for a moment, anybody could alter your memories simply by touching you. Shake your friend's hand as a greeting and you suddenly remember you still owe him 100 dollar for that time he bailed you out of jail because you launched a bunny into space and got fined for it. You're still not certain why you ever thought launching a bunny was a good idea, but hey, you clearly remember doing it. *Now this might sound silly*, but you can see where I am going with this. Allowing anybody to touch you would be opening yourself to basically anything they could possibly want. That leaves two possible solutions for dealing with the problem: **Prevent people from touching you** One solution would be to simply prevent anybody from ever touching you. People would go around in hazmat suits to prevent their memories from being tampered with, only coming out with their closest friends and family who they absolutely trust. Society as a whole might have a difficult time advancing quickly when everybody is in bulky outfits that restrict your movement a lot, but the alternative is that anybody could be turned into a terrorist with nothing more than a touch. **Don't use the human memory** If the human memory is that easily manipulated, people are not going to be able to trust their own memory, ever. You have a world with magic, you might also have advanced technology, the obvious solution would be to simply stop storing your memories in your brain and instead use something else. Upload them into the Cloud, store them in a computer chip, a magical repository, whatever. Simply stop using your easily fooled human brain and instead store all memories in something else. [Answer] That’s a great analogy for how human memory isn’t very reliable now, and you might want to focus on the “can’t tell if you did it to yourself” exception, because all of us actually do this to our own memories all the time, on top of our own biases when we tell our stories to others. Yet we accept eyewitness testimony as evidence. Maybe the inspiring story that motivates a character to succeed is a noble lie he forced himself to believe because he couldn’t live with the truth? There’s a gambit where two people agree on a story and then make themselves believe it, so nobody can ever find out what really happened instead? Instead of wiping their victims, people force them to do it to themselves—can this be faked?—so it can’t be detected? If the authorities can tell *who* altered someone’s memories, but not *how*, what happens if some parents say they erased a run-of-the-mill scary memory, but someone else accuses them of covering up abuse? A scheme where someone who realizes they’ve had some memory altered by someone else implants a memory that they know will look as if the other person did something very unethical? The penal rehabilitation system almost certainly makes use of this, and it seems likely to me that many rape victims would choose not to remember the traumatic details instead of prosecuting, for example. That probably leads to a world where there’s less pressure on the system to change. The direction I’d gently suggest developing it is: this isn’t really so different. I mean, what would society be like if humans could kill each other or even themselves through physical contact, maybe by tightly constricting the neck or with a tool such as a knife? That’s a world where everybody would be constantly afraid of each other, avoiding any kind of contact with other human beings all the time, right? To ask important questions, they’d go to websites. Well, you’re asking what would happen in a world where *even sincere recollections can’t be trusted*. At first, it looks as if the reason for that is this memory-altering magic. There’s a way out, though: we can detect that magic, the reason for all our uncertainty, and get the reliable Truth we wished for. But is it ever that simple? [Answer] Well, the obvious solution is to write down as much as possible. I guess everyone without exception would write a diary. Also, people may make photos wherever they are. So, basically people would do everything we already do to help our memories, except that they'd do it in excess. In addition, of course we wouldn't let anyone touch us whom we don't trust. People would probably have a quite conservative treatment of sexuality. Prostitution would be basically non-existent because neither side would know if the other side wouldn't implant false memories concerning the price (if not worse) during the act. This possibility of changing memories would certainly of big interest to intelligence agencies. On one hand, they are interested that the opposing agencies don't mess with their agent's memories, on the other hand they are interested in messing with their opponent agents' memories. Especially the memory about for whom those agents actually work would be a prime target, as if the agent believes he's working for you and is in that other agency undercover, he'll tell you whatever secrets of the opponents you want to hear. Afterwards, they again change the memory so that the agent no longer remembers the incident (and possibly even no longer remembers that he worked for an agency at all). Note however that not every use of that capability needs to be bad. Imagine if the tedious learning of facts could be replaced by the teacher just touching you and implanting those facts into your memory. If it is done by technology, you might even have "tinned knowledge" which you can buy and transfer without a second person being directly involved; such tinned knowledge could be government-checked for false memories, and would provide more safety than a teacher who might have other goals besides knowledge transfer (but then, if you don't trust the government you'll probably not want to use tinned knowledge, as you never know what government manipulation you'll load into your brain that way). [Answer] **Memories can be preserved by sharing it among your friends and family**. "False memories" can also be described as "arbitrary memories" which means that any memory you choose, true or false, can be implanted in someone else and thus preserved. To detect changes to those memories, some kind of [checksum](https://en.wikipedia.org/wiki/Checksum) will need to be introduced. (I have no idea how you would implement such a thing.) Society will work to prevent malicious manipulation, just as it does now. Scammers and con men are found and punished by law enforcement. Advanced techniques will develop for determining when and where a person had their memories altered. A poetic justice would be to have perpetrators of memory crime be subject to memory wiping or memory alteration of cherished memories or... The memories that compel them to crime. Individuals will take measures such as spreading important memories among friends and family (with their permission, of course). Instead of keeping a special memory in just a single person, spread that memory around to other people. In real life, we do this with our memories already by sharing on social media and old school printed photos. There may even be a market for "memory keepers", individuals who make it their job to retain other people's memories for a fee, much like a bank will store a person's money. **Computer Analog** This kind of problem exists for computers and has for a long time. A file (or memory) can be arbitrarily deleted or modified by any number of "attacks" such as normal malicious human attacks, degradation of storage media, errors in writing, errors in reading and so on. Various approaches have been implemented to solve this problem. From a file system perspective, [ZFS](https://en.wikipedia.org/wiki/ZFS) is an example of a memory storage system that rigorously checks for and corrects file corruption errors. For failures across multiple storage devices (or the brains of friends/family as noted elsewhere in this answer) there is the RAID arrays that store data across multiple devices. Thus, if a part of the memory is changed/deleted then it can be detected or recovered from. But these computer analogs depend on the kind of computational rigor that only computers can provide. Human brains and minds do not have such rigor so the comparison can only go so far. [Answer] > > How do ordinary people deal with it? > > > In this society, touching in general is probably prevented as much as possible. Your memories are a major part of what makes you who you are, so it seems likely that you would protect that nearly as much as you'd protect your life in general. > > How do governments and law enforcement approach this problem? > > > Consider a lie detector test which is 100% sure to work and provide truthful (*as the accused remembers it*) information. That is what law enforcement may be able to do with this power if they suspect someone is withholding information. Just plant some memories that the police are completely trustworthy(*or however elaborate it needs to be to get the truth out*) and delete them later. I think its most acceptable that this would require permission from the accused, but it would be incredibly suspect if someone would *not* do it. This would be most important in theft, and robbery. (*You need to remember about the money to make any use of it*) Having no memory of the time over the crime becomes a liability for anyone who is accused because they don't know their own defense very well, but it would still be possible to prove that somebody committed a crime without unreasonable doubt. Essentially, every accused person will be claiming innocence, and possibly even think they are innocent - even the person who actually did it, which is only slightly different from reality. This makes police work a little less about reading people and little more about the cold hard facts. [Answer] I want to stress an important point about your question. **It is actually possible to implant false memory, and it is fairly easy.** Of course it is not as easy as just handshaking, but still... Research have been made and the result are creepy. I advise you [this wikipedia article](https://en.wikipedia.org/wiki/Memory_implantation), particularly the part "Legal case". Basically the idea is that a man was accused of multiple sexual assaults. At first he was denying the whole, arguing he did not recall anything. After a while, he started to remember. A psychologist make the following experiment : he invented a case of sexual assault by the man, and ask him about it. After a while the man could "remember" it very precisely. (note that it does not make him innocent, it just proves that you can not trust a confession) I also advise the lecture of this other article about the [misinformation effect](https://en.wikipedia.org/wiki/Misinformation_effect). The big difference with your scenario are : * Most people are not aware of the possibility * For what I know, it is not a crime (since most of the time it was not done on purpose) However, the most probable reaction of the population is no reaction. If you do a more general parallel with manipulation (by publicity for example), it becomes fairly clear : you can prove that manipulation works, most people are convinced that it works, but still everybody think it will only affect others. Most people will probably just ignore the fact *their* memories could be altered. It could perhaps change if the educational system heavily adapts to it and starts to teach people that the risk is real and have to be taken in account (other answers are good about how to do it). Or the government will just erase the memory of the possibility of doing it in everybody. ]
[Question] [ One of the cities in my world is built on the ground floor beneath and around giant tree. Giant tree cities seem to pop up fairly frequently in science fiction and fantasy, but how would they actually work and how would the city be designed? An obvious question seems that of sunlight. How much would be blocked out by the tree, and what effect would this have on the city? It's also possible that the tree could shed leaves in the fall, but that would depend on the type of tree. Are there any other concerns for a tree based city? (BTW - the world includes magic and is currently at about 1500s technology level) [Answer] The biggest one would be growth. If you build your house between two branches, then in some period of time, your house could easily be in two pieces. Or if you anchored it to one branch, it could be simply swallowed up by the tree's growth, depending on how the house is attached. Sunlight actually I don't think would be too much of a problem, unless the tree is extremely dense (coniferous trees, for example, might make it perpetual night). But with most other trees there's enough space for light to move around between the branches that you should be ok. It might lead to a sort of value system, where houses on the outsides of the tree, which have an actual view of the sun, are worth more than those which are on the inside and only get light that's been bounced around of few times first. People might try to build farther and farther up the tree, and farther and farther out on limbs, to make more expensive houses, but those houses would be quite unstable in any kind of wind, and the branches at either of those places are by definition much less strong than those near the trunk of the tree. Leaf collection would indeed be a big problem, but the nature of the problem would change depending on whether this is a huge normal tree (leaves are normal size, the tree's just really old) vs. if its simply a huge version of a tree (and the leaves are scaled up to match). In the first case, you might be able to simply build a roof over every area, sloped enough to make the leaves slide off, but for the second a single leaf might be able to crush something, and you probably wouldn't want to live in a tree which shed leaves. Maybe an old dead tree would work. Fire, obviously, would not be something you want to break out in this city. Small ones can be controlled, and even a house fire might not be able to break through the tree's bark before it went out, but some magic systems include the ability to make fires which can't be put out - and those would make short work of your tree. Wind storms could be problematic for people and structures built on flexible areas of the tree. The more things get built on a branch, the more it sags, and the more it bends the structures already built on that limb. A slight misstep while walking would hurt (eventually, depending on the height of the tree). Children's games most often require a large open space to run and throw things, and its one thing when your baseball falls in the neighbor's lawn, but a completely different story if the ball falls a couple hundred feet down out of your tree. A large pavilion could theoretically be built to give them an area to play though. If any of the houses are actually cut into the tree, then you run the risk of eventually hurting/killing the tree if you go deep enough. Also again, if the tree doesn't die, then it's gonna keep growing and your house is going to change shape. Traffic (even foot traffic) would require a huge 3D spiderweb of roads bridges and stairs in order to facilitate movement between branches, and that would probably greatly increase the difficulty of people unfamiliar with that section of the tree to navigate around, find a friend, or catch a criminal on the run. I'd suggest the mages look into levitation. Also if it snows there, then you'd have to coordinate the shoveling of each person's house, so the guy at the bottom doesn't end up getting all the snow of the 25 houses above him dumped onto his roof. [Answer] Since I need a higher reputation (50) than I currently have to ask questions in the comments I will have to make the following assumptions: We are talking about average human size inhabitants. While the tree would have to be enormous to hold any size civilization under and around it (per the light being blocked impact) the leaves and or fruit that fall from it would not match in scale. (i.e. not crush a house when a 20 ft apple fell.) With that here is my shot at it: Significant agriculture would need to exist outside of the trees drip line to support the local population. (1500's technology would prevent mass transportation of food stuff to sustain a sizable population.) Waste management of said population. Nutrient management of tree. Impervious area (houses, hard packed ground/stone from roads, etc.) around the tree inhibit water penetration to the roots as well as competition from surrounding agriculture. Canopy cover should provide relief from the heat of the day and also provide shelter from storms. Said underground development does not undermine the integrity of the trees ability to grow and remain standing. [Answer] The closest I could come to in real life is termites infesting a tree. However, knowledge of how water travels up to the leaves through the trunk is very helpful, because you just solved your problem with elevation. Now here comes the tricky part: does it stand up to the inverse-cube law, gravity, and material mass/weight? Brush up on your tree and world's gravity. Light can be handwaved with magic, but it would be cool if you could find the breaking point and set it up so that there could be windows to let in the sun. [Answer] There are a lot of things to think about. Starting with sunlight, yes, it will be pretty dark under the tree. The closer to the trunk the darker it would be. Some trees, like Walnut, have a natural herbicide that kills many plants around them to reduce their competition. The largest living Walnut tree is this one: ![Largest living Walnut tree](https://i.stack.imgur.com/xrLPE.jpg) It looks like a spring picture before it has leafed out. Large trees need food and water, generally from the roots in the soil, and while the trees can find ways to get water and even some nutrients, most will still be provided from the ground. The roots also supply stability to the tree so it doesn't fall over. This means a whole 'highway' system might show up from the roots sticking out of the dirt around the tree. It would certainly affect farming for some distance since the roots would go out at least as far as the branches and I've seen many trees reaching much farther than that. If it is a seasonal tree, when the leaves fall it could bury a city. No matter what, trees lose and drop limbs. On a large tree this could wipe out a whole city block. Is it a fruiting tree? Nuts could be the size of coconuts and be deadly, even apples falling from 300 ft. could kill. A rain of berries (or cherries) could drown the town in food, also likely bringing many animals to the harvest, some wanted (animals for food) others not so much. Either way, the clean up would need to be done. The more I think about living in/around a large tree, it seems best to either live inside of it (hollow out a living space) or live hanging underneath the large branches. ]
[Question] [ DISCLAIMER: This question was closed on Astronomy Stack Exchange as off topic, so I'll try my luck here. I'm trying to understand the climatic effects of the far future scenario of an Earth-like planet with a reduced rotational speed caused by tidal locking with the moon (day-night period of 28 days, one hemisphere always facing the moon, the other never facing the moon). I understand that observations of the moon's surface temperature have shown day temperatures of 120°C and freezing cold nights of -230°C. **How would the day and night temperatures of tidal-locked Earth vary?** I am also interested in climatic effects caused by the reduced tides, coriolis force, increased evaporation, but this may reasonably be outside the scope of this question and it's answers. [Answer] This should be similar to planets that are completely tidally locked to their star, since the day would be very long. There is several articles that study their climate. For example [Joshi 1997](http://crack.seismo.unr.edu/ftp/pub/gillett/joshi.pdf) or [Joshi 2003](http://www.geo.brown.edu/classes/geol1950g/Joshi2003.pdf), or [Yang 2013](http://arxiv.org/pdf/1307.0515v1.pdf). While the Earth has difference in average temperatures between equator and poles around 40 K, these articles predict temperature differences 40-70 K for tidally locked planets with Earth-like atmosphere. Earth, however, would not be completely tidally locked, it would only have very long day. This could be paradoxically more dangerous for its habitability. Earth is very vulnerable to freezing into a snowball state. If completely tidally locked to Sun, the insulated side of the planet would probably never freeze. With very long day, however, the freezing of the night side might trigger the global freezing of the Earth. According to [Linsenmeier 2014](http://arxiv-web3.library.cornell.edu/pdf/1401.5323v1.pdf), planets with high obliquity are less vulnerable to freezing, while planets with low obliquity are quite vulnerable. However, the day length after tidal locking with the Moon would be 46.8 days, not 28 days, since the Moon gets further from Earth as the Earth rotation slows down, which in turn slows its orbital period. At this point, the Moon would be 1.4x further than it is now. [Answer] The wide temperature ranges on the moon are also to a large part caused by the lack of atmosphere. Atmosphere tends to soften such effects. Take a look at polar regions on earth for a better comparison. Midwinter and midsummer there can give very long periods of continuous daylight and continuous darkness. Reduced tides would not have a large climate effect (you would have small tides from the sun and none from the moon but tides don't have a huge effect on weather patterns), reduced coriolis force would result in different weather patterns though and reduce the tendency and strength of storm cells. My recent weather question might help you there: [Creating a realistic world map - Currents, Precipitation and Climate](https://worldbuilding.stackexchange.com/questions/1353/creating-a-realistic-world-map-currents-precipitation-and-climate) ]
[Question] [ My World has Dragoons, these are Dragon Riders and the riders are expert marksmen. They use magic arrows like explosive/fire/wind/homing arrows for offensive (basically magic archers) along with dragon's own offensive weapons like dragon breath. Dragons are somewhat intelligent creatures like Dolphins or Orcas in our world. These Dragoons have no counter apart from other Dragoons, there are some anti-air magic spells but not with long range or damage, a magic archer of similar capacity like Dragoon will be able to do some damage from surface to air but these are rare as most such archers will be Dragoons themselves, thus who ever wins the air fight will dominate everything, all nation invest greatly in raising Dragons and training Dragoons. My confusion is how would naval battles work in such a world. This world's technology is equivalent to renaissance era or early modern era, i.e. 1550s to 1800s, gunpowder does not exist. The ships will be similar to medieval ear ships but without any cannons. They mainly use sails or oars, there is no magical propulsion system. Will an aircraft carrier like ship for Dragoons be possible? I was thinking a large river barge like ship with flat top for ease of Dragoons to take off and land (Dragons need small space to run in order to take off). But how will this ship move? Sails will obstruct take off and landing of Dragoons, oars will take too much space as a ship of this size will need many oarsmen but a huge space will be taken by Dragon sheds. Considering the importance that Dragoons have in my world, the navy is lacking in this aspect. Any suggestions/ideas would be greatly appreciated. [Answer] Would it be possible? Sure! Would it be *useful*? That's quite a different question, and I suspect the answer is "no". See, aircraft carriers are for projecting your air power to places where you don't have a handy airbase. Aircraft tend to be a bit fussy about the places they can land and take off from, and have exacting dietary requirements. If you want to do battle across an ocean the benefit of aircraft carriers becomes very readily apparent (or at least, the people who don't see the benefit tend to get sunk, but that's survivor bias for you). Dragons, on the other hand, don't really need hard runways, and don't need a logistics chain with avgas and spare parts and ammunition. You haven't said what they eat, but I'm guessing you could put a dent in the local livestock population and keep your wing of dragons flying. You could probably operate dragons from tiny, rocky, hostile islands where you'd never lend and aircraft and have a job surviving without being able to fly supplies in and out. [![Soay in St. Kilda](https://i.stack.imgur.com/LP4vQ.png)](https://i.stack.imgur.com/LP4vQ.png) ([Soay](https://commons.wikimedia.org/wiki/File:Inselsoay.JPG)) That just leaves trying to fight wars of conquest across oceans. I'm not gonna say that you *can't* do that with Renaissance-era logistics, but trying to fight a foe who can field the same weapons as you but *doesn't* need to bring supplies across an ocean? The locals will prevail. That's why the US doesn't have a Queen as head of state. > > a magic archer of similar capacity like Dragoon will be able to do some damage from surface to air but these are rare as most such archers will be Dragoons themselves > > > You'll be able to fit quite a few people firing self-guiding exploding arrows onto a warship. You can arm them with quite different weapons from the ones that mobile troops need, and protect them better. You can probably also fit artillery of the sort that's rather harder to carry on a dragon. The ships can be well defended by surface-to-air archery, making attacking with dragons a risky sort of affair... this won't be like a WW1 or WW2 attack at all. > > I was thinking a large river barge like ship with flat top for ease of Dragoons to take off and land > > > Instead of a carrier intended to launch dragons at sea, I'd suggest you'd do better having large transport ships capable of carrying dragons *at all*. There'll be a risk, being stuck on the surface and all, but it'll be so rarely that you'll need to ship dragons at all that it shouldn't be a problem other than when your colonizing a new land. Your barges will be slow and poorly manoevrable compared to a more conventional transport, putting them at greater risk from the weather and from other ships. The dragons they carry have limited effectiveness against a prepared foe. Dragons might work well against undefended merchant ships, but history gives us things like the [East Indiamen](https://en.wikipedia.org/wiki/East_Indiaman) which were merchant ships but were very much able to defend themselves. The ships in your world should be no exception. That leaves you a small window of opportunity for dragon *piracy*, but I don't think your carriers will work out. [Answer] **Trimaran and dragon-power.** The idea would be to make use of a design of ship that would have the dragons crouched on the two outer hulls then migrating to the central-hull for take-off and landing: [![A three hulled ship](https://i.stack.imgur.com/othjw.png)](https://i.stack.imgur.com/othjw.png) Design by Earl Edwards, aeroyacht.com via [web archive](https://web.archive.org/web/20150628060206/http://www.aeroyacht.com:80/2015/05/19/trimaran-rave/), 2022, photographer unknown, fair usage. Whilst on the outer-hulls, their clawed feet grip onto specially formed perches - the wings of the creatures can be used as sails, or when becalmed can either flap for thrust or even be gently dipped in the water to row. At the very rear of the outriggers, there would be rudders for additional trimming of direction. If you really wanted to, you could have a couple of central sails for long trips which can be lowered on pullies to lay horizontally out of the way. [Answer] ## Dragons should see three big uses in naval combat. 1. recon, because of height and range dragon can drastically improve how far a navy can see, if you can see the enemy before they see you you have a huge advantage in naval combat. depending on how far they can fly they can also be used for communication, being able to contact bases and other fleets is also a big advantage. 2. bombers, exploding arrows are not that useful against ships incendiaries are, simply dropping containers of burning liquids would be absolutely devastating against ships, this is the reason fire ships wee so dangerous, ships are surprisingly flammable. with the ability to hit the sails this is even more devastating. as a bonus bombs can be dropped from height so counter attack is hard. this works against land targets too. 3. anti-dragon, dragons are your best defense against other dragons, exploding arrows should be way more effective against dragons than ships. these are the same used we see for early planes in naval combat, learn about naval combat in WW1 and WW2 so wee how aircraft become a game changer to naval combat. **Carriers** Carriers for dragons should not be too difficult, even if they need a runway they should not need much, there are no flying animals that can not get airborne within a few steps. You can easily simply leave off the front few sails of a ship, will it be less maneuverable and slower ,sure, just like real carriers. The solution is the same as well, don't send them by themselves. You can add an enlarged projecting forecastle/bowsprit to make your runway longer, especially since you are leaving off the jibs. Landing should be even easier since they should not need a runway for that. this means dragons can land a lot faster than they can take off. You will need a lot of signaling to coordinate but hand flags and wing movement should work. Worth noting there will be 2-3 ropes that need to be lowered before launch but it will take time to get dragons ready anyway. Also depending on the dragons wingspan there may be ways around this. In the real world no ships are built this way, because there is no reason to leave off these sails, why make your ships slower for no gain, but with dragons you are getting a gain. We know from damaged ships that ships could sail without these sails they are just slower. Your other option for a landing strip is strange but would work, a runway on an outrigger. Make it light enough it barely makes contact with the water until dragons move out onto it, then the ship tips a bit and you have a runway. More awkward, your not getting help with speed or maneuverability, but you get a longer but narrower runway. you also can't use studding sails on that side while using the runway, so it gets even slower in combat. you don't want anything like a river barge on the ocean, it will sink the first time you have bad weather. It also does not solve your propulsion problem, you still need sails, which means your ship will end up shaped like a normal ship anyway. likewise oars are a poor choice ships powered entirely by oars are unheard of, oars are for maneuvering and combat you don't use them all the time, you still have sails. [Answer] Possible? Absolutely. Practical? No. [![A ship of the line, circa 1700s](https://i.stack.imgur.com/cUhDT.png)](https://i.stack.imgur.com/cUhDT.png) Above is a picture of a ship of the line which was more or less a common sight in warships in the 1700s. Those cannons were heavy, ranging from 450 to 1000 pounds. And most ships of the line carried dozens of them. That doesn't include the powder and cannonballs to operate them. So depending on the size and weight of your dragons, that shouldn't pose a problem for the technology level. The runway could pose an interesting issue, mostly because of the lack of sails. But, I'll get to locomotion later. The real issue here, is the material you'll use. If these dragons have claws, wood is a poor material to use for the runway. They'd scratch and claw at it, rendering it useless before long. That means the thing that they need to run on will eventually be little more than wet sawdust. I'd recommend a layer of sand or dirt so their claws can sink into it without requiring expensive repairs. As for the now lack of sails? Oars were still common in the age of sail, for smaller ships and lowering the crew required to travel. Because oars were not quick and certainly were not efficient. However, [galleys](https://en.wikipedia.org/wiki/Galley) were known for being oar-propelled. There's an issue, though. > > The galley is characterized by its long, slender hull, shallow draft, > and low freeboard (clearance between sea and railing). Virtually all > types of galleys had sails that could be used in favorable winds, but > human effort was always the primary method of propulsion. > > > The two concepts--ship of the line with its multiple decks, and the galley with its oar-power--are mutually exclusive, for the most part (some exceptions have been brought to my attention). However, you literally carry your own answer. If you were to combine oars with dragons pulling like a draught animal? You could still achieve a decent speed. How good? Depends on how many oarmen and how many dragons (and how much power either can offer when contrasted with the calories they'll burn). There is a unique advantage to having dragons as well. They can fly in more food to prolong time at sea. Granted, that means it'll be easier to track them, since they'd need regular food runs, depending on how many pounds of meat the dragons will need per day. But it offers the possibility. However, food runs are limited by distance from the shore (or food stocks) to the ship. And there's also the limiting factor of carrying capacity for the dragons. This could be mitigated by fishing, but these are warships--they aren't designed to focus on such things, normally. That being said. Is an aircraft carrier the most practical application? No. They'll be slow and cumbersome ships with incredibly high maintenance cost. The best I can imagine this would be used for is hit and run tactics near the coast, and that's kind of defeating the point of having dragons that can fly and land anywhere there's a stretch of land. Why wouldn't an aircraft carrier for dragons be useful? Average speed of a ship of the line? 12 knots. That's 22 km/h. And that's with the slew of sails meant for propulsion. Average speed of a galley? 3-4 knots (5.5 - 7.5 km/h), but 2 knots (3.7 km/h) in formation. What's the average cruising speed for your dragons? Say a dragon's speed is comparable to a bird of prey? * Bald eagle: 120-160 km/h * Golden eagle: 320 km/h * Red-tailed hawk: 190 km/h "Well, yeah, but isn't that the case for planes on an aircraft carrier now?" Yes, but also no. Average speed of a modern aircraft carrier (Nimitz class): 30+ knots (56+ km/h). With 85-90 aircraft carried and 5,000 crew. The major differences? * Airplanes need maintenance while not being operated, but not fuel. Dragons will need to eat regardless. While it can be argued they'd need less calories if inactive, they still need to eat. * Airplanes don't need to be entertained. No matter how well trained, no animal will cope well with being cooped up for long stretches. * Airplanes don't start fights. No matter how well trained, every animal will have moods, and sometimes being playful or even spiteful could be that mood. Adding to all this, there's a point from Starfish Prime's answer. Carrying the dragoon themselves (without a dragon) would be more effective. And you can fit those archers in far more places than you could ever fit dragons. Granted, a ship's less maneuverable than a dragon, and slower to boot. But unless you feed a dragon a chicken and that holds them for a week (as is the case with crocodiles), then pound-for-pound, the dragoon will consume far less rations daily. And the major limiting factor for travel by ship is food. You might get away with one or two dragons. Ten might be pushing it. So dragon piracy sounds like something that could be a thing. But realistically, getting 80-ish dragons on a ship with that level of technology with all above-mentioned issues, sounds like some serious handwaving needs to take place. However, if there's a logistical reason why this needs to happen? A barge in the middle of a large lake or a vast sea? I can see some merit in that. They would however be much more useful as pit stops, not transportation directly. The speeds are just too slow, and landing and takeoff are just not as much of an issue when compared to airplanes. Let alone keeping them properly stocked to feed that many dragons over long periods. [Answer] Aircraft Carriers are older than people think. The first aircraft carrier by the best definition (Must be able to launch and recover an aircraft while underway) was the *U.S.S. George Washington Parke Custis* which saw active service in the United States Civil war from 1861 to 1865. The Custis launched a single hot air balloon, tethered to her deck, to conduct recon on confederate positions. A telegraph line in one of the tethers allowed the flight crew to telegraph real time troop movements to the ground crew who could then give aerial intel to the commanders on the field. It's a far cry from the capitol ship super carriers of the modern U.S. Navy, but it meets the definition. The earliest Heavier than Air carriers appeared shortly after Heavier than air flight (the development of the latter was really the most critical tech break through). Some concerns you might want to look after are the arrangement of sails and the amount of space a dragon needs to take off and land. In the case of the former, you have to consider the sails interfering with launch and recovery operations. In real life, Carriers carry very medeiocre weapons platforms (or that is to say, mediocre weapons platforms that can't fly away from the ship). The best armed carrier in the world in terms of weapons platforms is on paper the Russian's Navies *Admiral Flota Sovetskogo Soyuza Kuznetsov* (*Kuznetsov* for short) which, for complicated political reasons is classified by the Russians as an "Aviation Cruiser" rather than an "Aircraft Carrier" (get used to this... since the early 20th century, almost every nation has used very insistent terminology for their naval vessels to meet the letter of one treaty or another, while dancing on the corpse of it's spirit.). In effect, *Kuznetsov* is armed like a carrier and a cruiser. On paper sounds amazing. In practice, the *Kuznetsov* is terrible at being both. And the reason is that generally in naval warfare, the direction you need to aim weapons to shoot things is going to be in a general "our planes need to be flying here" direction. One way to get around this is to consider the dragons take off as being more bird like than air plane like... and have them climb the sturdy main sails to the top to launch and land on them to recover. Remember our definition of "aircraft carrier" is "Launch and Recover Aircraft while underway" which this meets the definition. About a quarter if not more of the world's modern aircraft carriers exclusively use helicopters or VTOL air planes to achieve their carrier status. Such as Japan's new *Izumo* class Helicopter Destroyers (again, see my note about insistent terminology to cheat. Carriers are decidedly offensive weapons, and the Japanese Defense Force cannot by law be an offensive military. Despite the name, Destroyers are not offensive weapons in nature. Additionally, Japan's closest military ally, the United States, might have something to say to Japan making carriers again. It's out of politeness that the U.S. doesn't tell Japan they aren't fooling anyone.). Now, since carriers are a huge investment (Most nations can only field one carrier. The U.S. is the only one that fields 11 carriers. And 20 "amphibious assault ships" that are not Super Carriers, but still have carrier capabilities as a primary feature and are fairly large by conventional carrier standards. Presumably they aren't carriers in a rare display of modesty. Nobody is fooled.). They are almost always capitol ships. In modern naval warfare, sending a carrier out by itself is a great way to get yourself a sunken carrier. To prevent this, Carriers travel with several escort ships as a collective unit called a "Carrier Group" (Battle Ships were handled similarly.). The other ships in the group will be dedicated to protecting the carrier. Modern groups typically include at least two cruisers that act to intercept air craft and missiles targeting the carrier and destroyers, which will protect the surface ships and submarines that will protect the fleet from other submarines. Finally, the Carrier will almost always have some of their aircraft compliment in the air to add additional protection against aircraft... to say nothing about supply ships which serve to resupply all the group with various needs. Carriers were game changers in naval warfare in the first two engagements they served in in a shooting war. At Pearl Harbor, the Japanese used carriers to such great effect, that it upended centuries of naval doctrine. Prior to that, all the Navies were built about Battleship doctrine. Today, Battleships as a weapons platform are all but obsolete. At the battle of Midway, the U.S. and Japan rewrote the rules of naval warfare when both were able to sink enemy ships without side laying sight on a single ship of the enemy fleet. Up until those points, carriers were seen as experimental ships and novelties. ]
[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. Suppose that there is an alien spacecraft travelling towards the Sun. This spacecraft is similar in design, size and power output to [Voyager 1](https://en.wikipedia.org/wiki/Voyager_1) and [Voyager 2](https://en.wikipedia.org/wiki/Voyager_2) as they were immediately after launch from Earth, and is coasting in its orbit (no powered maneuvers taking place). Also suppose that a budding scientist on present day Earth just so happens to point their instruments (optical telescope, radio telescope, or something else; ground-based or space-based) in exactly the right direction at exactly the right time. If the spacecraft is communicating at all at this point, it seems unlikely to be transmitting in the direction of Earth. How far from the Sun (or Earth) could the spacecraft be where we'd still have a chance of detecting it, assuming for a moment that all events line up perfectly for detection? Would we be able to determine that it is likely an extraterrestrial spacecraft, as opposed to some natural interstellar object? [Answer] The angular resolution of an optical system is given by $\phi\_0 =1.22 $$\lambda \over D$, where D is the diameter of the optics. The angular size of an object of size d at distance R is given by $\alpha =arctan$$d \over 2R$$=$$d \over 2R$ Equalizing the two angles we get $1.22 $$\lambda \over D$$=$$d \over 2R$ Solving in R we get that $R=$$dD \over2\times 1.22 \times \lambda$ Assuming $\lambda = 500 nm$, and considering a mirror diameter of 10 meters (equal to the mirror of the GTC) and a size of 5 meters for the object, we get $R = 40\times10^6 \ m$, or 40 thousand km. This distance is about the height of the geosynchronous orbit. If we instead are using passive radioastronomy, we have the largest structure on Earth to have a diameter of 500 meter (Chinese FAST) operating at a wavelength of 0.10 meters. This would give a minimum detection distance of about 11000 meters. But I guess in this case we would first see the optical trail of the satellite burning in the atmosphere. [Answer] # IR detection Source: [Ledeboer, 2018](https://ttu-ir.tdl.org/ttu-ir/bitstream/handle/2346/74119/ICES_2018_134.pdf?sequence=1). Instead of using reflected optical wave light from the sun, lets try to detect something that the probe itself is emitting. Any radio emissions are very unlikely to be targeted at Earth, so the most likely emission that we would capture would be black body radiation from the probe itself. Voyager's propellant lines are filled with hydrazine, which must be kept at a minimum of 1.6 C (275 K). These lines are external to the spacecraft, so they set the limits for how cold the spacecraft can get while being 'operational.' The current model in the paper above suggests that Voyager's hull temperatures are in the range 15-20 C. Lets round this to 300 K. The emissions curve at 300 K looks roughly like this: [![enter image description here](https://i.stack.imgur.com/qlVXa.jpg)](https://i.stack.imgur.com/qlVXa.jpg) One possible alternate calculation of detection is to simply use the optical resolution equation that L.Dutch used, except substituting in a wavelength of 10,000 nm for 500 nm. This makes the detection range 800,000 km: greater than the distance to the moon. I tried to calculate difference between Voyager's IR emissions and background IR, but couldn't get enough data; not on background spectra, Voyager's surface area or in many other areas. I did note that cosmic IR background peaks in the 100-1000 $\mu$m range, significantly higher than the peak for Voyager. This suggest that we might be able to get good resolution at the lower wavelengths where Voyager's IR emissions will be maximized. [Answer] Optics are a bad choice, so maybe thing about the [radars used in tracking space debris](http://www.esa.int/Our_Activities/Operations/Space_Debris/Scanning_and_observing2), which have incredible resolution. Of course, that will be reduced the farther out you are looking. Detection of a 2cm object at 1000km is not out of the question, so detecting something 12' large (if you just want to see it, not gain any surface information) would roughly be 180,000 km. By using an active transmission component, it can double the detection range. So around 400,000 km isn't out of the question with current equipment (optimized for a different purpose). It wouldn't be out of the question to use more power, more or larger receivers, different frequencies etc. to increase this range by a considerable amount. You eliminate the largest factor by allowing the 'lucky spotting' scenario. With this in mind, I see very little reason why detecting something at the edge of the solar system with a purpose built system is out of the question. As for knowing if it is alien or not, I doubt this is all too feasible without receiving transmission from it. You would know its path, speed, and approximate size. Other than that, you'd have to wait for optics and the object to be much closer. ]
[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. Could a planet support both large mammalian megafauna and non-avian dinosaurs at the same time? My worry is that bigger mammals have progressively more trouble with dissipating body heat, whereas large dinosaurs were generally cold-blooded, meaning they didn't have as much trouble. (I'm no expert so if megafauna got along fine in very hot temperatures, or vice versa for dinosaurs please feel free to correct me.) Thinking of making a world with slightly less of a tilt than Earth's, about .7g and an atmospheric composition similar to Jurassic times (avg. Temp=300K). [Answer] **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. **Dinos are not cooler than megafauna** Well, to talk about megafauna handling the heat well... please consider the closest thing we have today, the African elephant. The daytime temperature in Kenya, one of the places where elephants live today, can easily reach around 28 C, or 301 K. So saying "megafauna can't handle the heat" looks a little baseless from where I'm standing right now. As for dinosaurs being hot-blooded or cold-blooded, I found a paperabout this topic. The researchers, using dino teeth, were able to determine body temperature. What they found was that the temperature of larger dinos was already below previous estimates. [Here](http://science.sciencemag.org/content/333/6041/443.full?rss=1) is the paper. I'm going to quote from the abstract here: > > This temperature range is 4° to 7°C lower than predicted by a model that showed scaling of dinosaur body temperature with mass, which could indicate that sauropods had mechanisms to prevent excessively high body temperatures being reached because of their gigantic size. > > > Large dinosaurs probably had thermal regulation, and this was irrelevant to whether they were hot- or cold-blooded. The paper authors did not take a stand on the hot-blooded versus cold-blooded debate in the paper. > > An unresolved question is whether such adaptations could have compensated for the high internal heat production associated with endothermy, or whether large adult sauropods must have had both heat-dissipating adaptations and a low basal metabolism to maintain body temperatures in the 36° to 38°C range that we have measured. > > > I looked at a few papers and they all brought up "thermal inertia" or "inertial homeothermy." I even found a paper about such ([link](http://www.angelfire.com/planet/paleo/articles/Seabacher_Pb.pdf)) in which the author argues that thermal inertia alone would have been enough for large dinosaurs. Unless you have cooling elements, like an elephant's ears, you aren't cooling down quickly. Stegosaurus was suggested to have used its plates in a similar fashion ([link](http://science.sciencemag.org/content/192/4244/1123).) [Answer] The answer is "Yes and no." There's no *a priori* reason that large mammals and dinosaurs couldn't coexist. It's not obvious why one would automatically out-compete the other, especially since some dinosaurs were probably warm-blooded. But there are some limitations, the biggest being that *carnivorous* beasts can never be very common and compete with each other for food. See [Why Big Fierce Animals are Rare: an Ecologist's Perspective by Paul Colinvaux](https://rads.stackoverflow.com/amzn/click/0691023646). So, yes, they could co-exist, but no, you can't have all the predatory dinosaurs and all the big predatory mammals at once. You might well be able to sustain populations of many grazing animals of each type. (And then we'd get to see in a fair match -- no cheating with space rocks! -- who out competes who.) [Answer] Mammals have the smallest and most flexible blood cells of all vertebrates, which are made inside the mammals bones. It allows for miniature capillaries, and perhaps different sensory abilities. Dinosaur blood cells could divide, they kept their nucleus, and were larger, and so they could have different bone structures, perhaps stronger and lighter. Mammal bone structure may be limited by the marrow, which doesn't exist in birds and dinosaurs. Most current research suggests that Dinosaurs, the most recent family of giant lizards, were not cold blooded. Scientists use terms like Archosaurs, to describe all large lizards. The older lizards had temperature regulation like crocodiles, and the later ones had feathers and warm blood. They can measure isotopes from teeth and bones to determine ambient temperature at time of growth, which were about 35.7>t'>38.2 in dinosaurs, warmer than crocodiles (30) and colder than birds (38) <https://blog.everythingdinosaur.co.uk/blog/_archives/2011/06/20/4845668.html> You are focusing on only one factor, to say why they couldn't co-exist. Mammals were in a nocturnal ecosystem niche and only small advantages in one group of animals provides enough pressure to prevent the other group from becoming the same size and competing with them. Other advantages can be: Faster growth rate, bipedalism(dino's had either 2 fast legs or armor/size), full body armor protection(elephants are jelly for velociraptors), live-bearing versus egg laying(pregnant and young mammals), neurological(some dino's had secondary brains in the spine), skeletal(bone marrow vs hollow bones), muscular and other factors that tailored dinosaurs to speed strength and efficiency at large sizes. Dinosaurs did live in cold forests, and the best boreal megafauna are like balls of blubber with little legs compared to dinosaurs, feathers are better protection than fat. The reason why birds did could not return into the ocean and become masters of the seas like whales, is because they would have to lay eggs in the sea which even penguins and marine birds haven't evolved. There were warm blooded sea-swimming dinosaurs (mososaurs) that looked like diplodocus which gave birth to live young at sea, so birds like penguins and gannets are fairly close to becoming whales again given time. [Answer] **This question asks for hard science.** All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. hey blue whales are technically Megafauna , and birds are just avian dinosaurs(flying dinosaurs) and the coexist, therefore you senario could is completely plausible even if the tilt of earth was a bit different that today's. ]
[Question] [ I recently read Brandon Sanderson's articles on magic systems and they gave me a lot to think about, especially in the form of costs and weaknesses. I think I came up with a fairly interesting system for those two things. (Questions are forthcoming, I promise.) Essentially, magic at its core is influencing the energy flow of the world. To do this, you have to immerse yourself in it, feel it, then subtly nudge or forcefully redirect it. Doing so, however, causes you to lose your own individuality and draws you further in. You risk becoming disconnected from reality. To avoid this rather nasty consequence, you have to have some kind of emotion or feeling to anchor your sense of self. This anchoring has its own ramifications. When you immerse yourself into the flow of magic and fixate on your anchor emotion, it becomes the only thing that you can distinguish as yourself. You become that emotion, for lack of a better word, in order to keep yourself grounded in reality. That's the basis. Some other details: * The desire to delve deeper into the flow requires self-control to suppress, and without it you will eventually dive too deep and become hopelessly disconnected. Using magic becomes a struggle between your emotion, self-control, and the desire to pull more power. * Obviously, more powerful anchors are required in order to delve deeper into the flow. While past memories can serve as weak to medium strength anchors, the strongest ones are feelings that come about in the moment and are immediate. * Emotions require a drive to be powerful anchors; they can't be just happy or sad. Even love and anger are circumstantial. While love can bring about the desire to protect, by itself it is not a particularly strong anchor, and likewise anger in general will be a weak anchor but can carry the desire to injure or destroy. * Actions that are outside the scope of the anchor emotion wreaks havoc with the delicate balance mentioned in the first bullet point, in addition to creating more stress on the user of the magic. * Very important: the deeper into the flow you are, the stronger the emotional anchor needs to be and the more that emotion becomes you. You have the most conscious control over the magic when you are using very small amounts with a weak anchor; using close to your capacity of magic with an intense anchor leads to little more than instinctual actions aligned with the feeling. So, onto my questions. 1. Are there any obvious flaws with the system I don't see? (Only talking about the costs and weaknesses aspect.) 2. How will using magic with this system affect a person's personality? Will it make them prone to emotional outbursts in the moment, scarily self-composed, or somewhere in between? Thanks for all of your answers ahead of time. This is my first post on the Worldbuilding Stack Exchange, so be gentle and tell me if I can do anything to clean up my post. Also, any ideas not related to my questions are welcome as well. [Answer] > > 1. Are there any obvious flaws with the system I don't see? > > > I don't think so. The magic seems to be quite well balanced: minor feats are easily achievable without much risk. This will make small feats of magic cheap and common place in society, which should be fine for a fantasy setting. However, for every major use of magic you have both stronger restrictions (requirement of a strong emotion that supports that particular magic action) and a generally increased risk of losing yourself in the magic. This means that society as a whole can never completely rely on magic and technology will likely also be developed further. > > 2. How will using magic with this system affect a person's personality? Will it make them prone to emotional outbursts in the moment, scarily self-composed, or somewhere in between? > > > There's two ways to look at this: short term (just one person changing during his lifetime) and long term (basically the effect of magic on the evolution of your people). In principle I would say that in any case the final answer is 'somewhere in the middle'. Obliviously the ability to feel strong emotions in general and about many different things in particular, will give a person access to powerful magic that can be used in a variety of ways. The downside of this emotional range is of course, that it can be quite overwhelming and will significantly increase mental problems, stress and so forth (which could manifest as emotional outburst). Since self control is necessary to use magic safely, a healthy balance seems about right. An individual person can try to go either way: someone with a set goal and strong ambition/drive could fully embrace all their emotions and have strong magic, but suffer through the consequences of increased mental problems (they may well lose the focus of their actual goal during depression like stages) and the risk to overdo it someday. On the other hand a person 'who plays it safe', would focus more on his/her own mental control and would therefore not be able to use strong magic, but could reliably do smaller spells or the like. From an evolutionary view, it would make sense that your people/humans can generally feel stronger emotions without losing their self control (basically increasing the power level of magic that can be used safely). Depending on when humans figured out magic (which in this case might be quit early), they could have significantly stronger emotions than we have at a comparable level of self composure - still, its probably best to have some variation in the population. On a side note you could also have (very rare) persons with overly strong emotions (and therefore magic capacity), but barely any self control (kind of like a reverse Asperger's syndrom). [Answer] > > Are there any obvious flaws with the system I don't see? (Only talking about the costs and weaknesses aspect.) > > > Well, you mentioned that diving deeper is risky, but didn't mention any specifics of what would actually happen if you dive too deep, beyond a vague notion of "becoming disconnected from reality". So I'm going to try and explore that aspect. Assuming I understand the system correctly, the deeper you dive, the more your anchor emotion will consume you. So depending on the emotion you're harnessing, diving too deep could have some interesting effects: * **Happiness:** You sink into euphoria. Using magic feels *so good*. You want more. You dive deeper. The bliss increases. You never want it to end. You'd keep diving until you couldn't be pulled out even if you wanted to. I imagine it like drug addiction: you'd end up strung out on the floor, helpless, overwhelmed by your own high. This would probably eventually kill you. * **Sadness**: I don't know why you'd use sadness as an anchor emotion, but let's say you did. You'd get progressively sadder until eventually you reached the point of a nervous breakdown, at which point you'd stop resisting and be dragged into the flow, lost forever. Again, this would basically kill you. * **Fear**: This could make a pretty good anchor, actually, because it would likely prevent you from diving too deep out of fear of the potential consequences. If you *do* dive too deep, you'll probably get the same result as sadness: hysterical mental breakdown followed by catatonia and death. Or maybe a heart attack. * **Love**: Hoo boy. In most magical settings, love is treated as being directly proportional to power: the stronger your love, the more powerful your magic. But what happens when you love someone too much? *[Bad](http://tvtropes.org/pmwiki/pmwiki.php/Main/LoveMakesYouCrazy) [things](http://tvtropes.org/pmwiki/pmwiki.php/Main/LoveMakesYouEvil). [Bad things happen.](http://tvtropes.org/pmwiki/pmwiki.php/Main/Yandere)* (Bad things also happen if you browse TV Tropes too much, so be warned) * **Anger**: This one's pretty obvious. Using anger in a fight is not a good idea. You're angry. You want the other person to just *die*. You push harder. You want the power to kill them. You grow angrier. You want the power to destroy *all that opposes you*. You push harder. You grow angrier. It's a vicious cycle. Soon you're consumed by your anger and lose all control, all rational thought. I wouldn't want to be in your vicinity when that happens. I imagine quite a few evil magicians have lost themselves in this manner. > > How will using magic with this system affect a person's personality? Will it make them prone to emotional outbursts in the moment, scarily self-composed, or somewhere in between? > > > I imagine people would try to use positive emotions like love and joy as anchors, especially for powerful magic, because being taken over by sadness or anger would *not* feel good. Too much sadness in one go and you might end up needing therapy afterwards, and you'd definitely swear off using sadness as an anchor again. You wouldn't want to feel that way again. You could balance this by making different spells require different anchor emotions (to do fire magic, you need to harness anger, for example). I'd say experienced wizards would be more along the lines of "self-composed", as they'd have plenty of experience at handling their anchor emotions and would be much better at controlling them. Amateur wizards, or those who already have emotional problems, would be more affected by their anchor emotions. I don't know whether they'd be prone to outbursts when they're not using magic, but they might struggle when they are. [Answer] > > Are there any obvious flaws with the system I don't see? (Only talking about the costs and weaknesses aspect.) > > > I don't see any obvious flaws in your concept. This is an interesting way to balance the costs and effects. > > How will using magic with this system affect a person's personality? Will it make them prone to emotional outbursts in the moment, scarily self-composed, or somewhere in between? > > > Now we come to the interesting part. There is a lot of room to explore with this concept. My first idea was pretty much what [F1Krazy](https://worldbuilding.stackexchange.com/a/82500/28789) already mentioned: drug addiction. Magic feels like a drug and should be treated as such. You have to be careful, you shouldn't use it all the time and for everything, but some people won't be able to withstand the feelings and getting lost in your own happiness, becoming addicted to magic. But drugs have another aspect - they might help your wizards. Imagine that your people invent a drug that makes you forget the last hour or so reliably. By taking this drug after using magic you would forget about the feelings of getting lost in the magic. It could help your wizards ease out of their most recent magic high. They could more easily become useful members of society again and this process might be faster than the normal acclimatation. Drugs become very important for wizards. This is just an extreme example. Everything that helps to reinforce their feelings to live in the here and now, in the reality that currently exists, will help them cope with the effects of magic. Another usage of drugs could be to make it easier to use magic, for example in the battlefield. When you are on the battlefield it might not be easy to use destructive magic if you are afraid of dying and can only use magic that would make you invisible or teleport you away. This is because of your restriction: > > Actions that are outside the scope of the anchor emotion wreaks havoc with the delicate balance mentioned in the first bullet point, in addition to creating more stress on the user of the magic. > > > Likewise you wouldn't be able to heal anyone if you are afraid right now. You either need extremely fine-grained control over your emotions, which is neigh impossible for most humans, even if they adapted to magic and therefore emotional control, or you could simply try to invent drugs that help invoke a certain feeling in your soldiers. This is basically trying to create a super-soldier that is not afraid anymore, which people already tried in reality. But as you have access to magic and creating a few pills shouldn't be that hard for wizards you might have the drugs necessary and in a wide variety for every use-case. This is especially important because of your restriction: > > While past memories can serve as weak to medium strength anchors, the strongest ones are feelings that come about in the moment and are immediate. > > > You could even make this dystopian: your wizards are forced to take drugs on a regular basis to perform magic in a way regulated by the government. For example prisoners with an ability to perform magic might be used as magic-slaves to reduce their sentences, which could be used as a means to create more drugs or goods or energy or anything else your society might need. Having control over your emotions would be an incredibly important asset and status symbol in your society and might even be used for marriage reason - hoping that your children will have a knack for magic and good control over your emotions. People who are often angry will have problems fitting in - people would be afraid that they might do something bad when they are in a rage. On the other hand people who are always friendly and happy would be incredibly popular, not only because they are nice people to hang out with, but because they are powerful and they can't hurt you. Instead they would be able to heal you whatever may happen to you. A great safety net. ]
[Question] [ In my current worldbuilding project, I intend to create a region dominated by a civil war between a number of feuding Houses (upwards of 50 originally) that also share familial ties. Since these relations are expected (and intended) to become highly convoluted, I want to use some method of tracking the relations that is clear, maintainable, and can support an arbitrary number of bloodlines. Is there any software that can manage and display the genealogical history of multiple families in a single view? [Answer] A "family tree" (a chart showing all direct ancestors of a single person) is rather simple and easy to follow. A "family group sheet" (a list of parents and siblings, with spouses, of a single family unit) is also fairly simple and easy to follow. Combining these two things for a single family (each node of the family tree needs its own family group sheet) can get rather complex. Setting up a combination of multiple families with all the links between them over a lengthy period of time quickly becomes *very* complex. A "single view" for such an arrangement, with all the crosslinks, would be completely illegible. The best compromise for this would be to develop a chart for each family, with spouses. Each spouse would have their origin family prominently marked on the chart. [Answer] May I suggest the use of [Gramps](https://gramps-project.org/wiki/index.php?title=Features). It is open source freeware and specifically developed for genealogy. It can display really huge and complex charts. I use it for my world building to keep track of family relations. Creating a custom calendar is a bit of a hassle, but possible. Gramps has aso lots of other features, you might find helpful. You can also look through the recommendations of this [site](http://www.techsupportalert.com/best-free-genealogy-family-tree-software.htm). ScionPC for example can easily create a custom calendar, though display options seem to be more limited compared to Gramps. So far I only used Gramps and I am entirely satisfied with it. [Answer] If you have access to a Macintosh there is a great geneology app called [MacFamilyTree](https://www.syniumsoftware.com/macfamilytree) by Synium Software. It can do everything you asked for. A suummary of features is a good idea (from the Synium site) : *Explore your personal family history and discover your origins, your ancestors and how your family has evolved over the course of time. MacFamilyTree 8 offers numerous options for you to capture and visualize your family history. No matter how you want to illustrate your family relationships ... Conduct your research with the help of a free online genealogy archive with billions of records, create websites or do your research on the go with MobileFamilyTree for iPhone, iPad and iPod touch. MacFamilyTree also lets you create family books in a flash - share them as a PDF or print them.* [Answer] Flowchart software would probably be the best thing to use here. As Michael mentioned, however, it would require more than one view per family, as it would indeed get highly complex. Even [FamilySearch.org](https://familysearch.org/), a high-end genealogy service, doesn't really let you see the whole "family network" at once. However, an interesting idea is that it lets you focus on a single person somewhere along the line and see both their ancestors and descendants. So perhaps you could choose an individual and focus some trees around him or her. As for the recommendation of software, a quick [Google search](https://www.google.com/search?q=creately&oq=creately&aqs=chrome..69i57j0l5.2049j0j7&sourceid=chrome&es_sm=93&ie=UTF-8#safe=active&q=flowchart%20software) for flowchart software pulled up many results. A lot of the results are proprietary, but things like [Gliffy](https://www.gliffy.com/) and [SmartDraw](http://www.smartdraw.com/) should work — Gliffy will give you 5 free flowcharts (and it's pretty easy — I was able to make a very simple two-generation chart in less than a minute on my first try), which may or may not be enough depending on how complex you wish to get, and as for SmartDraw, it does have some purchasing options, but also a free download. If you dig deeper, you might find something else that suits your needs better. You might also want to try some [wiki-like software](https://worldbuilding.stackexchange.com/questions/499/what-software-is-available-for-keeping-and-organising-notes-about-your-world) if the flowcharts don't work out for you or if you want some extended note-taking capability. [Answer] Mind mapping software is designed to link unstructured but related information, which sounds like what your families will be like. You might want to look at something like MindMeister. [Answer] Personally, I'm a fan of [FamilyEcho](https://www.familyecho.com/). It's simple, easy to use, and free. It also lets you make multiple family trees, add information about each person, set a person's gender as nonbinary (though it isn't labelled as such), and add gay relationships with children. The only problems that I've found are that it doesn't let you give someone multiple partners at a time (it sets ones you already added as ex-partners) and there are no way to set more than two people as parents. The latter one makes it difficult when trying to map non-nuclear family units or trying to add an adopted person's biological lineage. ]
[Question] [ If the North and South Poles' ice melted instantly, what would be the effect on humans and other animals? Would the sea creatures thrive? Would a lot of land get covered by water? [Answer] Well, the first effect is the temperature on the earth would drop significantly. It takes a lot of energy to melt the ice on the planet, and if it comes from the atmosphere, you get a massive drop in temperatures. (Find that [here](https://worldbuilding.stackexchange.com/questions/1435/what-effect-could-drop-the-freezing-temperature-of-water-globally-to-%E2%88%9240-celcius).) Second effect...yes the water levels would rise. The north pole is mostly sea ice and this would have little effect on ocean water as the ice displaces the same amount the melted water would. The south pole melting would increase sea levels by around 200-300 feet (pending study you want to accept). Most of humanity does in fact live close to the ocean...a country like Bangledesh goes 47% underwater (that's the highest population density country on the planet). This is around 1/4 of the American population under water as well. Sea creatures won't necessarily thrive. Most of them have adapted to the salt water concentrations they are used to and a quick adjustment stands to harm them. Otherwise, unless there is something fundamentally helpful (delicious?) for them to take on land, it wouldn't have much a difference. As a more scary alternative, certain nuclear power generation sites could be submerged, potentially flooding the nearby water with radiation. Your worst case scenario is if this sudden increase in fresh water alters the current (great oceanic conveyor belt if you will). This is the cycle of heat throughout the ocean...certain areas (Europe primarily) remain temperate by warmer tropical currents cycling water to the northern regions. If this cycle was to falter, England would likely freeze over. Most of these points here are answers to much more specific versions of this question on Worldbuilding. [Answer] The ice near the North Pole is floating, so no sea level rise would result from that. The South Pole melt would only have an effect if it reached the ocean. If it was a sea near the South Pole, no effect either. If you melt all the ice caps on Greenland and Antarctica, a significant sea rise would occur. Usually numbers like 200 feet are quoted. [Answer] > > If the North and South Poles' ice melted instantly, what would be the effect on humans and other animals? > > > * Humans would be in a bit of trouble as a significant portion of the worlds arable land would be under water. If this all happened at once with no warning that may not be terribly detrimental as the bulk of the world's population would be dead...*so thats good.* * Land animals would be similarly in trouble as entire habitats and species would be completely wiped out. > > Would the sea creatures thrive? > > > * Maybe in the long run, the rapid changes to temperature and ocean depth would wreak havoc on ocean environments. Reefs would be in water 200-300 *METERS* deeper meaning they would have trouble surviving with their food and light sources no longer being available. Similar to land based animals there would be a great upheaval and mass extinctions most likely. In the long run marine life would bounce back, there would likely be a significant increase in algae and other simple water life with the reduction in the numbers of predators. Ocean animals would definitely be the first to bounce back though. > > Would a lot of land get covered by water? > > > * See the map link Vincent provided, its an excellent resource **Some additional notes** *Geopolitical Stuff* * Every communist nation would be either A. Underwater or B. Decimated * Northern Europe is totally hosed...water joke for you there. * The US East coast is now an island * Russia is essentially gone, only the sparsely populated west would remain * Africa becomes the center of the world as it is the least impacted by the water level rise, its hard to predict how the weather pattern would end up but if you assume the continent gets more moisture in the north it would end up being the population center of the world. * The pacific rim...more of a lip now * Japan survives surprisingly well landmass wise Eventually a new balance would be achieved of course, nature is skilled like that. [Answer] Beyond sea level increase, also weather patters will drastically change. After melting Greenland's glaciers, less dense fresh water would stop Gulf Stream which transfers heat from equatorial Atlantic to Europe. Europe would go colder (decrease of agriculture) and hurricanes would get stronger. Melting permafrost in northern tundra's of Canada, Alaska and Siberia will release huge amounts of methane, which is very potent greenhouse gas (more than CO2) which will increase greenhouse effect. If things go really bad, like it did 55 MY ago in [Paleocene–Eocene Thermal Maximum](http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum) and it was [tropical hell](http://thinkprogress.org/romm/2009/02/08/203664/big-snake-titanoboa-nature-garden-of-eden-lindzen-thermostat-hypothesis/) in Alaska - up to 74F warmer than present. Salinity of water would not change significantly (amount of added fresh water is small). ]
[Question] [ I am looking for a site that will do the following for free: * Allow me to upload a map of a world (either URL or file, I don't mind). * Allow me to tag/label that map, to mark the locations of thing (either plain text, or URL links). * Host the image. Bonus: * Let me change/update the image without wiping the tags (as the map becomes more detailed) * Allow multiple people to edit the tags/labels. Note: I am aware that I could add the information on my own computer and then load the map up to somewhere like imgur. That is my backup plan. Note 2: Please do not post answers to things that you *think* might work. [Answer] Working free map editors as of today include: * [Inkarnate](https://inkarnate.com/) *signup required. Has been in "Beta" for years. Example image from the [Inkarnate main page](https://inkarnate.com/)* [![Inkarnate map example](https://i.stack.imgur.com/rOfi8.jpg)](https://i.stack.imgur.com/rOfi8.jpg) * [Worldspinner](https://worldspinner.com/) *signup required. usability not tested, but free and online. Example images from the [Worldspinner gallery](https://worldspinner.com/gallery/)* [![Worldspinner interior example](https://i.stack.imgur.com/YOynm.jpg)](https://i.stack.imgur.com/YOynm.jpg) [![WOrldspinner exterior example](https://i.stack.imgur.com/2afdg.jpg)](https://i.stack.imgur.com/2afdg.jpg) * [RollForFantasy](http://rollforfantasy.com/tools/map-creator.php#contentContainer) *no labels, added only to give more options in case others go offline. Example image randomly generated.* [![enter image description here](https://i.stack.imgur.com/6J9lL.png)](https://i.stack.imgur.com/6J9lL.png) --- Feel free to alter this list as new options arise or old ones go down. I only looked into online map editors here, there might be suitable ones that need local installation. [Answer] Use Google Drive. When you create a new document, click 'more' and you have the option to create a **Google Drawings** document. You can insert your map as a picture (upload or URL) and then make the labels using text boxes. The labels can be freely edited and changes will show up real-time to viewers. You can control access so that the document is publicly viewable. Click the 'Share' button in the upper-right hand corner and then click 'Get shareable link.' All you have to do is give someone the link and they will be able to see your map! You can then enable editing either for all viewers or just for a few specified accounts. Hope this helps! ]
[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. From time to time I'll see things talking about how thanks to all of our radio communications, we're effectively broadcasting our existence to the entire universe. However, when I did some back-of-the-envelope calculations a while ago I found something interesting - by the time a radio station's broadcast reaches Alpha Centauri (the solar system closest to ours), ignoring any effects of our atmosphere, a 1 m^2 receiver would, on average, receive a single photon every seven hours. Of course that is only a single radio station, but throwing more radio stations into the mix would just make the signal less coherent and indistinguishable from random noise. When you consider the sun as well, it seems like all of the Earth's radio signals would be a drop in the bucket. How much noise would the Earth have to broadcast in order to change that? For this question, the goal is for the noise broadcast from Earth to still be noticeable by the time it reaches a distance of 500 light years (that only covers about 0.01% of the galaxy). You can assume that alien civilizations are looking for signals of intelligent life, but not that they are focused on our solar system. [Answer] First off, this question is just the inverse of [this question](https://worldbuilding.stackexchange.com/questions/39571/how-far-away-would-an-alien-civilization-need-to-be-for-us-to-not-notice-them). So, apologizes to MichaelKjorling, I'm going to crib his answer to get some results. # Assumptions * In order to be noticeable at 500 light years, we need to be able to detect us at that distance. # What is the attenuation over 500 light years? [Free space path loss](https://en.wikipedia.org/wiki/Free-space_path_loss) in decibels (dB) is given by $$20\log\_{10}\frac{4\pi d}{\lambda}$$ where $d$ is the distance between antenna and $\lambda$ is the wavelength of the frequency in question. In the US, the highest energy general transmission (as far as I can tell) are UHF stations in the 512-608 MHz range. This may be an important thing to revisit; emission into space is determined heavily by directional broadcasting characteristics. But we'll just use this assumption for now and say that the wavelength is 0.5 meters. Meanwhile, 500 light years is $4.7\times10^{18}$ meters. Plugging into the equation above, free space path loss is 401 decibels. That is a lot! This means power is $10^{40}$ lower at the receiver than at the emitter. # What is the most sensitive receiver that we have? First, since radio transmission terminology is not generally well known, a brief discussion. In order to receive a signal, you need to be able to pick it out of background noise. That background noise includes both background noises from deep space, and interference from local signals. For example, if our UHF transmissions at 550 MHz happen to line up with the most common radio frequency on a distant planet looking for us, in-atmosphere recievers are going to have a tough time finding us. The unit of measure for the signal here is [dBm](https://en.wikipedia.org/wiki/DBm), or decibel-milliwatts. If $P$ is the power of a signal in milliwatts, then the signal strength is $$10\log\_{10}(P).$$ Thus, a 1 W signal is 1000 mW or 30 dBm. The gain of an antenna is measured in terms of [dBi](https://en.wikipedia.org/wiki/Antenna_gain#Gain_in_decibels). This measure uses the same log scale that the signal strength does, so we can simply add the measures to together to calculate total signal strength. The rating of a receiver is the smallest signal that it can pull out of the noise background. Following [MichaelKjorling's](https://worldbuilding.stackexchange.com/a/39591/23519) answer, assume that an alien civilization specifically searching for us can detect the signal at -200 dBm. In addition, assume a 80 dBi antenna gain from a dish like Arecibo. # How much noise do we have to put out? Free space path loss is -400 dB; antenna gain at a foreign civilization is 80 dB and the signal detection threshold is -200 dB. Therefore, signal emission strength must be 120 dBm at the source to make it detectable. This is equivalent to $10^{12}$ mW or 1 GW of emission power. # Conclusions The Earth is almost certainly not gong to reach this power level. WBCT is the most powerful FM radio station in the US, with effective radiated power of 320kW, or about 85 dB. But this dish is not pointed into space, and so its emissions are further attenuated by the atmosphere before reaching into deep space. There is really no reason to increase the power of such a dish, becase it already has plenty of power to reach the horizon. Any direct signal's line of sight is limited by the horizon; once past the horizon the signal no longer reaches the surface and coverage moves up into the atmosphere, where it isn't really useful. Furthermore, if you start increasing the emission power of lots of different radio communications methods, then they will start interfering with each other. A 120 dB signal emerging from the earth's atmosphere will bounce of the moon and back to Earth at a much higher power than it will reach 500 light years away. So, all in all, the Earth is unlikely to ever emit enough *noise* to reach a planet 500 ly away. Now, a directed signal is another story... ]
[Question] [ At 4:56 in this video essay, Edgar states that at an axial tilt of 60 degrees, the tropic and arctic climate bands will be switched, so that equatorial regions would be cold and polar regions hot. <https://youtu.be/J4K3H9aNLpE?t=4m56s> Is this plausible? It seems to me that it should be more complicated than that - on a solstice, everything from 30- 90 degrees north or south would be dark, including one of the "tropical" poles, and everything on the opposite side of the planet from 30 - 90 degrees would have a full 24 hours of sunlight. [Answer] Note that I am using averages and it is also simplistic to avoid getting to much into details that would not have a big impact on the answer. **During the northern summer:** * At 60 degrees, the planet receives the most energy from the star. It is the warmest at that time of the year. At sea level, I would expect average temperatures in the 30s in humid climates and 40s in dry climates, based on what is observed on Earth. Of course, during daytime the temperature rise far above 40 in dry climates but the temperature gradient is much smaller in tropical climate (between the day and night). * The pole would have a temperature climate similar to the ones we have here on Earth close to 45 degrees. Temperature ranges in the 18 to 22°C and can rise higher especially in the interior of large continent like Asia, given the climate is also dry there. * The tropics too would have a fairly temperate climate at this time of the year. * The equator in the other hand would be at a much greater angle, receiving much less direct sunlight. The quantity of energy received would be comparable to what Earth receives in the 80s degrees of latitude. Svalbard is one example and the climate of the warmest month is barely above 0° C. **During the southern summer:** * At 60° N, it is extremely cold. There would be no sunlight for several months. Actually, anything about 4 or 5° north of the equator would have a least of few days of complete darkness. I would expect something a lot colder than Antarctica or Siberia but I don’t have specific numbers. * The tropics would be about as cold as our poles are in winter. Average temperatures in the range of -40° would be common. * The equator would have “Nordic” climate like Scandinavia if they are near warm water currents or like Canada if it is not the case (Northwest Territories). The vegetation in that part of Canada is made up of taiga and tundra. During the rest of the year, the temperatures are in a large transition from one extreme to the other. **Summary: Are Arctic and tropic climate switched?** Summer: * Arctic: 30-40° C * Tropic: 18-22°C and hotter if it is really dry Winter: * Arctic: -60°C and possibly colder * Tropic: -40°C **Conclusion:** The Arctic region is hotter in summer but colder in winter. It is not exactly a switch. [Answer] # No; the equator is always warmer than the poles Earth has a 23 degree axial tilt. That means that the sun is never more than 23 degrees from the equator. The equation for incident solar energy ($E$) for any given day is $$ E = E\_d\cos{A\_i}$$ where $E\_d$ is the incident energy of the sun overhead at noon and $A\_i$ is the angle of the the sun above the horizon at noon. There are plenty of associated factors like cloud cover and refraction of light from various layers of the atmosphere, but we can ignore them for now. On the Earth, over one year of sunlight, the total incident sunlight can be calculated as the percentage of the maximum possible sunlight ($E\_{max}$); that is, the amount of energy you would receive if the sun was directly overheat at noon every day of the year (i.e. a planet with no axial tilt). We will define a year to be $2\pi$ units long, so $E\_{max} = 2\pi E\_d$. The motion of the sun over the course of the year can be modeled by the sine (or cosine) function as $$A\_i = \max\left[\frac{\pi}{2}, A\_{tilt}\sin{t} + L\right]$$ where $t \in [0, 2\pi]$ are times within one solar year and $A\_{tilt}$ is the axial tilt of the planet and and $L$ is the absolute value of latitude (north and south do not matter). Note that if $L$ is greater than $A\_{tilt}$, then the location is outside of the tropics and the sun can never be overhead. Also note the `max` function is necessary, since if the sun is more than 90 degrees away, it is still giving zero light. Plugging equation 2 into equation 1 and integrating over a year, we get $$ \begin{align} \frac{E}{E\_{max}} &= \frac{1}{2\pi}\int\_{0}^{2\pi}\cos\left(\max\left[\frac{\pi}{2}, A\_{tilt}\sin{t} + L\right]\right)dt\\ \end{align} $$ The closed form solution of this indefinite integral is derived from the [Bessel function](https://math.stackexchange.com/questions/1047067/what-is-the-integral-of-sin-cos-x) with some added complexities due to the `max` function, but we can solve it numerically. For Earth, axial tilt is 23.5 degrees or 0.410 radians, and the solution is roughly 0.958. That is, the equator gets 95.8% as much sunlight as a planet with no axial tilt. A solution for the Tropic of Cancer (or Capricorn) at 23.5 degrees from the equator is 0.878. At 60 degrees (north or south) the value is 0.478, while at the pole it is 0.128. So far, this reflects reality pretty well. Now, let us change the axial tilt of your planet to 60 degrees. The corresponding number for the equator is 0.743; and for the poles 0.294. You have succeeded in making the entire planet into a temperate or cooler climate; but you have not succeeded in making the poles *warmer* than the equator. A general proof of this for any axial tilt can be seen by observing that the derivative of the integrated function is just the function itself. That function in turn is maximized by $L = 0$ for $A\_{tilt} \in \left[0,\frac{\pi}{2}\right]$, so for any non-tidally locked planet orbiting the sun, the equator will receive the most solar radiation. [Answer] Indeed, topics by their solstice definition would move to 60 degree latitude (which is Northern Canada and Norway). But tropical ecosystems won't move there. In fact, there might be no tropics as we know them at all in the new Earth. Today, Earth year-around average temperature is 14.6 degrees Celsius. Let's keep in mind that this average is not likely to change much. Every summer, high latitudes will be awash in sunlight and weather will get quite warm. But every winter they will plunge into polar nights and all species that aren't adapted to it will die. The climate there may be similar to modern day highly continental one, like Kazakhstan or northern China. Equatorial regions will be in a constant twilight, with the sun hanging low to horizon. But good thing is that these regions will get constant sunlight with 12 hour long days throughout the year. The climate there may be comparable to coastal Pacific Northwest. Because there will be no constantly cold places, massive glaciers are unlikely to form, and if we start with modern day Antarctica and Greenland, the ice shields there will likely melt. But the main key that will define the climate zones will be ocean currents. With high seasonal variations, the presence of absence of those current will define whether highly variable swings or smooth temperate stability will dominate. At the moment, it would be very difficult to predict how the current will change. ]
[Question] [ **Could a planet's biosphere be as insanely violent a la *[War Against the Chtorr](https://en.wikipedia.org/wiki/The_War_Against_the_Chtorr)* or *[Fragment](http://www.warrenfahy.com/page_book_fragment.html)*?** Pretty much every organism, even the plants, is omnivorous and voracious. The two biggest obstacles to this than I can think of are: 1. where the energy comes from the power that ecosystem and 2. how anything lives long enough to reproduce. For the first, I imagine that the planet's sun produces more intensive radiation than ours and the ecosystem is largely dormant punctuated by occasional bursts of violent activity where the predators feed and mate. For the second, I imagine that everything is hermaphroditic/parthenogenic and organisms are able live in colonies or symbiosis that defend one another long enough to reproduce. This is explicitly mentioned in both of the books listed. Of course I have probably missed or overlooked something. [Answer] Yes. Though you'll have to give careful thought as to why it came about. With regards to energy: This doesn't actually matter all too much. All more energy means is that things happen faster. If you look at the competition for light in rainforests or for a good spot next to the vent in marine thermal vent environments you'll see competition that is no less vicious just for being slow. Ants end up in wars that would make medieval kings question the existence of god. Microbial colonies use chemical weapons against each other. Even ivy will literally suck the life out of it's host. If you want these creatures to be a threat to humans then they'll need a decent energy source, but don't go thinking that slow means nice. With regards to reproduction: It's all about making sure that you are the one that comes out on top, not anybody else. To that end how vicious you are really doesn't matter, as long as you're only vicious to things that aren't your progeny/going to mate with you. Thank of it this way: In any fight the victor is going to be the one that reproduces. The more vicious creatures get more food and have the chance to reproduce: the less vicious creatures... don't. The biggest issue here is *why*. Why has your biosphere evolved to the point where literally everything has teeth? For the answer to that we need to look at what drives things to be/not be vicious here. 1: Plenty. Plants here aren't vicious: unless you look at ones that grow in resource starved or high-competition environments: then the knives come out. The reason for this is that their foodstuff (light) is comparatively plentiful. They don't have to compete with each other for it. If they are in an environment where there isn't enough to go around then you'll see various survival strategies arriving. In the jungle, for example, where space and sunlight are at a premium this takes the form of trying to block the sunlight from reaching other plants (as that's the resource that's required) or killing for nutrients that other plants may already have leached. In the desert water hoarding is the norm: and some plants and creatures develop stunningly dangerous ways of defending their stash. For your world you'll want to make sure that there are plenty of most resources, but also that every creature is competing for the same scarce resource. 2: co-operation Your animals are much simpler. Why are they vicious? It's the only way to survive. The only issue here is that groups that co-operate with each other outcompete those that don't. In the short term there may be a downside, but in the long run the group (which may be composed of multiple species that don't try to kill each other and instead only kill plants) will come out on top. So you need a way to stop co-operation being advantageous in the long run. 3: Stability This is the big one. If an environment is stable then a species has time to specialise. Omnivores become herbivores/predators. Predators become hunters/scavengers. The scavengers are no longer in conflict with the omnivores, and so they don't try to kill each other. Avoiding stability gives no one species a chance to specialise in any way that doesn't involve ripping resources out of the cold dead mandibles of their competition. If your world is constantly beset by natural disasters (high vulcanism or extreme weather associated with high solar energy input) you create a situation where no stable equilibrium can emerge, there is no long term for co-operation to be advantageous over and resources, though plentiful, are often torn away by Mother Nature. This will turn the brief pools of respite from the chaos into vicious gladiatorial arenas where only the most brutal and adaptable creatures can thrive. Hoarding behaviours are pointless, as your work squirrelling away resources for next year can all be undone with a single tornado, so you may as well live fast, kill as much of the competition as you can and lay your eggs in the corpses, trusting that your young will survive long enough to evade the next apocalyptic event. Oh, and if any of your young do survive and come back to meet you: They'll be trying to kill you before you eat their prey. So kill them first. [Answer] A violent biosphere offers a couple of problems, but when you start to play with growth rates and the general rate of metabolism in a creature much can be done that way without the need for creatures to work together or live in symbiosis. Important to note is that there still is a food chain so you inevitably get layers in the ecosystem. -Micro organisms These are already very virulent on earth as they can rapidly exploding population (Culture). On your planet with a biosphere as violent as the one you're aiming for you could up the rate of mitosis to feed the layers above. -Small/rodent sized predators. These can be predatorial to attack prey its own size, it could also eat plants and micro organisms in order to get energy. (It can live on the micro-organisms and plants, but need the prey for nutrients to grow or reproduce. -Everything else. You could follow the same basic guidelines as the one above. Plants for sustenance, meat for growth and reproduction. Some could be kleptoparasites, stealing kills from others or just straight up scavengers. Especially for smaller species, scavenging might be a viable way to survive since the bigger species will leave a mess and not fully consume their kill. (Some might, but it's likely not all will or leave behind some parts of the carcass). Anyways, the key to having an ecosystem like this functioning is the accellerate the metabolism and reproduction at the bottom of the foodchain in order to justify the violent biosphere which demands a lot of energy. As you have mentioned in your question, having the planet irradiated with more energy is a good way to have autotrophs and micro-organisms reproduce and grow at accelerated rates. Furthermore, it's very likely some creatures might develop very good tactics to avoid being eaten. Camouflage, poison, living subterranean, think of it and it's likely to develop in order to sustain the species in a less ideal environment. [Answer] You may wish to find a copy of "Forbidden Planets" edited by Marvin Kaye. It is 6 short stories, but the key one for you is from Allen Dean Foster, titled "Mid-Death". Everything in that world is out to kill everything else, and four crack commandos try to brave the elements to rescue a science mission. The biological explorations are fairly detailed. <https://smile.amazon.com/gp/aw/d/1582882118/ref=mp_s_a_1_3?ie=UTF8&qid=1482417384&sr=8-3&pi=SY200_QL40&keywords=forbidden+planets+in+books&dpPl=1&dpID=31oo7IMJMIL&ref=plSrch> [Answer] I'm getting ideas about insect type creatures here, like how the birthing mite is eaten by the babies. Maybe just a super evolved (disgusting) insect type world. The energy could come from more amounts of hydrogen and methane (or something) in the air, and or something from it's sun / suns/ nearby exploded star / cloud of forming star / etc... ]
[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. My basic question is could life 'as we know it' (carbon DNA/RNA based, using water as the main solvent in metabolic processes) evolve on a planet where the temperature ranges from 16 degrees Celsius (at the equator in summer), to -120 Deg. C at the poles in Winter. For anyone wanting more elaborate details: **Temperature** The absolute average temperature is approximately -20 Deg C, the prior values representing the record high and low values. **Liquid Water** Liquid water at the surface is primarily available from geothermal vents and snow melted by volcanic activity - both of which are spatially frequent and temporally consistent. Water at the equator also remains liquid at the equator virtually year round, with the annual low of -4 Deg C. **Seasons** The planet has an solar orbital period of 1,050 hours (44 days), and negligible axial precession (IE the 'wobble' that causes Earth's seasons) The planet has a rotational period, however, of 4,800 hours (200 days), and it's rotation counters it's solar orbit. This gives it an effective day of 3750 hours (156 days on Earth). The planet's day/night cycle consequentially defines its 'seasons.' It spends 78 days in the winter/night where the lack of sunlight leads to rapid cooling, then 78 days in the summer/day where the planet again warms. **Chemistry** The planet's chemistry is Earth-like, mostly. The atmosphere is 68% nitrogen, 25% oxygen, 5% xenon, 1% argon, and trace gasses. The planet itself is composed of 77% Silicon and silicates, 13% Iron, 5% carbon, carbides, and organic compounds, 3% Titanium, 2% Lanthanides, .07% ground water and perma-ice, and trace compounds. **The biology of the story** *Or does it make sense?* The evolution I currently have starts with proteins boding into DNA/RNA slop and then single cell organisms in lakes and rivers, where geothermal activity creates temperatures as high 120+ Deg C (in places). It eventually evolves into complex land based organisms. Owing to the relative scarcity of energy (for metabolic purposes) on the planet, biodiversity is significantly lower than earth. Perhaps 100 plant and animal species, plus an additional 1,000 bacteria species compromise the entire biosphere about five billion years after life first emerges. Cold climate adaptions can be assumed. Intense competition for resources causes frequent evolutionary arms races and extensions, leading to most extant species occupying a particular niche very well, and having either innate weaponry or symbiotic properties. Under the circumstances, does that story work an a biological front? [Answer] Well you certainly make life there very hard to thrive. The geothermal vents under the ocean are likely the best places to have life spawn and grow and evolve. Geothermal vents would be the only places with enough consistent energy and random chemicals to encourage metabolic processes. After that it could slowly spread out to the farther reaches of the ocean. [![Geothermal vent](https://i.stack.imgur.com/TPezI.jpg)](https://i.stack.imgur.com/TPezI.jpg) From wikipedia about biodiversity around geothermal vents. > > Life has traditionally been seen as driven by energy from the sun, but deep-sea organisms have no access to sunlight, so they must depend on nutrients found in the dusty chemical deposits and hydrothermal fluids in which they live. Previously, benthic oceanographers assumed that vent organisms were dependent on marine snow, as deep-sea organisms are. This would leave them dependent on plant life and thus the sun. Some hydrothermal vent organisms do consume this "rain", but with only such a system, life forms would be very sparse. Compared to the surrounding sea floor, however, hydro-thermal vent zones have a density of organisms 10,000 to 100,000 times greater. > > > And for biodiversity here is another article [about our vents](http://wwf.panda.org/about_our_earth/blue_planet/deep_sea/vents_seeps/). I'm pretty sure they are talking 300 hundred more advanced mulitcellular species, since I can't imagine that bacteria and algae aren't in the 1,000s if not 10,000s. These also happen to be species that I believe are only found at vents, not others that make their homes in more diverse locations. > > Unique biodiversity > More than 300 species have so far been identified in deep-sea hydrothermal vent ecosystems, of which over 95% are new to science. Many are restricted to a particular vent field, making each ecosystem unique. On average, a new vent species has been discovered every 10 days since vent ecosystems were first discovered in 1977. > > > And ancient too > Amazingly, vent life has changed little over time. A whole new domain of life was discovered in vent ecosystems - Archaea, an ancient form of life most closely related to the first life on Earth. > > > You said nothing about a moon, which causes tides and it is believed that tides had a huge impact on life leaving the oceans. The tidal regions are places that are claimed by both the land and the sea, giving a great biome for intermediary lifeforms. The long winters are going to be hard for animals to survive, at least on land. Oceans don't freeze solid, and the vents produce food and energy year around. The winters would likely cause most things to hibernate over the winter (day night cycle). This would likely mean things living on the land would be plants and lower life forms like insects. With such a small amount of energy available (outside the vents) and long winters and no tidal action I would guess that the planet wouldn't be old enough to have 'vertebrate' level animals on land yet (if ever), maybe even only a few plants, such as lichen or moss and some insects having made it out of the ocean. Also 1000 bacteria wouldn't be able to support the evolution of complex multi-cellular life forms even as simple as a bivalve. So I wouldn't try to put hard numbers on those, unless you just want a planet populated by a few different kinds of goo. Here is [another article](https://coastalpathogens.wordpress.com/2014/05/16/how-many-species-of-bacteria-are-there/) about the diversity of insects and bacteria on the planet earth. It starts with insects and then does some extrapolation for bacteria but the numbers are very impressive. > > The total number of bacterial species can be estimated applying the insect ratio of species to individuals. This gives the staggering estimate of 10,000,000,000,000,000,000 (1019) or a ten quintillion bacterial species. This number is very many orders of magnitude higher than the ‘guesstimates’ of millions or tens of millions of bacterial species used by some microbiologists. > > > [Answer] The way you have the world set up, I would say yes. Bear in mind that I am an 'interested amateur', and haven't taken any biology since high school either, but I love reading about science, so all of this is based on my memory of what I've read, along with some google-foo. Here's what leaped out at me from the details you gave: > > **Liquid Water** > > > Liquid water at the surface is primarily available from geothermal vents... spatially frequent and temporally consistent. > > > I'm assuming at least some of those vents are under water (nothing is going to stay frozen around a hot vent). There's where your life probably started; the combination of heat, and chemicals brough up by the vent, is a great setup for organisms that use chemosynthesis. There is at least one hypothesis making the rounds that life on Earth started at hydrothermal vents. Go take a look at Wikipedia's entry for hydrothermal vents, and be sure to read the sections on biological communities and on biological theories; your setup seems almost ideal for life (assuming that life could, in fact, originate in that type of environment). I might argue about the biological diversity; thermal vents are tremendously diverse not just in terms of the number of different types of life at a particular vent, but in the variety of life at different vents. Where you're likely to have much less diversity is the creatures that no longer live at the vents themselves; the less energy is available the fewer creatures and the fewer kinds of creatures you are likely to find, in my opinion (emphasis on **opinion**). It might also be helpful to hit youtube and look for videos that show hydrothermal vents and the creatures that live there. ]
[Question] [ Say an early human civilization is arising on an earth-like planet (Earth, in fact) with one notable difference to the sky: a small ring of debris orbiting the planet. Assume the ring is clearly visible to the naked eye, formed from a recent (on a cosmological scale) but pre-historic asteroid strike, and positioned so that the sun and moon cross behind it at some points during the year. This ring should not be as large or elaborate as Saturn's rings, but otherwise be creative with the exact specs. How might Earth's ring affect the cultural and scientific development of humanity prior to telescopes? For example, * Astronomy * Climate effects * Navigation * Calendar reckoning * Mythology [Answer] Ron Miller, as reported on the Planetary Society Blog, made [some "photos" of places on earth if earth had saturn's rings](http://www.planetary.org/blogs/jason-davis/20130626-earths-skies-saturns-rings.html?referrer=https://www.google.com/). Mr. Miller is no neophyte to such visualizations; he is good at what he does. In any case, people are going to notice those rings even if they're much, much smaller. This question really has a vast number of good answers, but take this answer as a short list of very major effects. # The Cultural Significance From my brief survey, stars *culturally* affect our lives in many ways; from [nursery rhymes](https://en.wikipedia.org/wiki/Twinkle,_Twinkle,_Little_Star) to [astrology](https://en.wikipedia.org/wiki/Astrology). The [Sun](https://en.wikipedia.org/wiki/Sun#Name_and_etymology) and [Moon](https://en.wikipedia.org/wiki/Moon#In_culture) were often gods in various cultures, and therefore are quite important. We used the sun to [mark time](https://en.wikipedia.org/wiki/Solar_time) before the industrial revolution, and some cultures historically use [lunar calendars](https://en.wikipedia.org/wiki/Lunar_calendar). It ought to be pretty obvious from any amount of research into the cultural history of the Sun, Moon, and stars that they play a ***huge*** role in cultures the world over. Adding in some rings to an earth-like planet could include the following cultural effects: * A New God (in cultures that think heavenly bodies are gods...). Yes, ancient gods play a very diminished role in our current society, but in ancient societies they were quite a big deal. That's like having another major religion or political party today! Obviously such a thing so early on would have huge impacts on culture. * New Religious rites; each religion in the world can react or think of the planetary ring differently. Some religions have holidays or events due to [celestial events or timings](https://en.wikipedia.org/wiki/Computus). The ring could alter people's concept of heaven or other afterlives, too! * A new item by which to tell time. That's more of a science thing, though, but it impacts culture quite a bit! * New Iconography. The rings of a planet could symbolize something, much like how some people think of the moon as representing sleep, peace, etc. and the sun representing truth, light, or power. Maybe the rings could represent consistency or endurance? It's hard to say how people would use this in their poems, songs, art, and religions. What does that ring mean to these people? * Architecture may want to conform or use the rings to increase particular effects. Using the ever-present rings may significantly change how people build their buildings. For instance, the [golden ratio](https://en.wikipedia.org/wiki/Golden_ratio) may not have been as important to the greeks. Perhaps they valued the ratio or shape of the rings from their position; therefore old, authoritative, and/or venerable institutions would try mimic the ring instead of having this ratio! This simple change could affect how streets, cities, and buildings are shaped and laid out. * Faster Exploration of the Globe. If the ring appears to touch the ground, you may want to find where the ring actually touches. Since a ring never touches its planet, but people are looking for where it does this impossible thing, they will travel more and further. Imagine if the [Columbian Exchange](https://en.wikipedia.org/wiki/Columbian_Exchange) happened earlier, or [if the European diseases never killed off such large portions of Native Americans because they had already been exposed to them *before* Columbus](https://youtu.be/JEYh5WACqEk)! (The [colonial age](https://en.wikipedia.org/wiki/Colonialism) could have never happened!) # Scientific Significance It could be useful, for at least this answer, to think of science as figuring out what is going on in the world. Humans appear to have a basic need for some level of understanding for what is going on in their world. This figuring out has lead to astronomy, chemistry, physics, and the world we have today. Introducing a new element, such as the rings, gives people a new thing to examine and ponder. Here are some things to consider: * Navigation may be easier. Since the ring(s) won't change their position much, you can use the rings to guide yourself. Assuming the rings go east-west and are roughly at the equator, they will appear in the southern sky in the northern hemisphere. This makes finding your way much easier! Also, some quick math and measuring the angle of the ring will let you determine your [latitude](https://en.wikipedia.org/wiki/Latitude). * The concept of [heliocentrism](https://en.wikipedia.org/wiki/Heliocentrism) may been harder to accept. After all, if we're not the center of the universe, why *do we have a ring around us?* With such a simple defense, it may be quite a while before people take heliocentric models seriously. It should be noted that heliocentrism (as proposed by [Copernicus](https://en.wikipedia.org/wiki/Copernican_heliocentrism)) was made in 1543, but wasn't proved until [1723 by James Bradley](https://en.wikipedia.org/wiki/Heliocentrism#The_view_of_modern_science). Bradley gained hard proof by using [the parallax method](https://en.wikipedia.org/wiki/Stellar_parallax) to measure star distance. The parallax method relies on the heliocentric model, and its results cannot be reasonably duplicated by a geocentric model. Shadows on the ring only prove that the sun is a major source of light; it says nothing about what is revolving around what! * [The Flat Earth Model](https://en.wikipedia.org/wiki/Flat_Earth) may never really have taken off. Especially once people realize the rings never touch the earth but are so obviously curved! * Another system to tell time. Depending on the regularity of celestial events, the ring could be used to tell time better than the sun or moon. I suspect such time-keeping would likely be just as accurate as solar or lunar calendars, because the ring's behaviors are likely not dependent upon the sun/moon cycles, and may just appear to be a static feature of the sky. * Less dark nights could happen; the ring could reflect more sunlight (more regularly) than the moon, allowing creatures to evolve less powerful night-vision. After all, if there is ample light, what evolutionary pressure is there to see in the dark? Maybe color would become more important to the success of more species! # Final Note You should note that I have highlighted older ideas and focused on things which occurred in the far past. This is simply because the presence of this celestial object would impact so much of human life so early that it would be quite impractical to figure out what an earth-like planet with human-like people would look like beyond a certain limit. It simply can affect *so much* that no answer can include all the effects! ]
[Question] [ Could a community of blind people sustain themselves? What challenges would they face, and how would they overcome them? I'm thinking of a small community of around 100 people in a rural environment, but I would be happy to hear of an extension of the idea to a whole planet. I would be especially happy to hear of historical evidence to support the arguments. [Answer] Yes, at least in some circumstances. What is required for a community to be sustainable? **Food** fishing, grazing, beekeeping, gathering, farming and other methods are all possible. **Clothing** Leather making, sewing, knitting, spinning and other methods are all possible. **Shelter** Advanced construction is likely not possible, but beyond caves, simple structures are possible. Making brick and mortar, harvesting trees, simple carpentry, etc. all are be possible. **Defense** Would be at a serious disadvantage against sighted opponents. But if they were the only society or if other societies were not belligerent, they should be able to defend themselves against many animal attacks by building walls and carrying weapons. Attacks by top-tier animal predators could be very hard on the community though, even enough to cause its collapse. Guard dogs, etc. would be a big help. **Education** Clearly the blind can teach and learn, but the question of discovering mining, chemistry, medicine, etc. is much harder if not impossible if everyone is blind. If everyone is blind, it is much harder to bootstrap the process of making a society. Given the hardships in pre-communal living, a blind world may never develop the basics of society in the first place. E.g., [Braille writing](https://en.wikipedia.org/wiki/Braille) was not created until 1829 by Louis Braille that lost his sight in a childhood accident. Some blind people accomplish a great deal that the sighted would otherwise consider impossible, becoming doctors, lawyers, physicists, mountain-climbers, etc. Though we have technology designed to assist blind people, it is clear that some of them have plenty of talent and determination. There is a general problem in making any small community self sustaining. Where do you get all of the needed skills and resources that depend upon in a complex society. Plumbing depends upon pipes, pipes use metal, plastics or ceramics. Water supplies have multiple dependencies, and so on. Who makes the tools? Any self-sufficient small community is necessarily limited to a basic way of life. --- So why no historical precedents? Why would people join together to form a blind community when it is so much more logical to simply live in the existing communities. Why leave friends and family to live in artificially harsher than necessary conditions? I could learn to grow, harvest and spin cotton (making my own spinning wheel), make a loom, weave cloth and make some low-quality shirt. Dyes are another hard step. Much easier to specialize and participate in a larger society and trade goods and services. --- Blind people often were ostracized and still are to some degree. Congenital blindness in particular was often considered to be a result of some evil. People would take advantage of them, abuse them or simply ignore them. The Chinese even had a guild for the blind a kind of self-help society because of these kinds of problems. But the blind did not leave to form a separate community, they stayed with the rest of society and did the best they could. This is why I said there is no historical precedent (that I am aware of at least). Even if many in society ignore or abuse you, there are still advantages to integrating with the sighted to some degree. In marginal societies, e.g., subsistence farming, that would not support a blind person or hunt them, it is not likely that a blind community could be self-sustaining. Even a separate community is not necessarily self-sustaining and a blind community would be even more likely to be dependent upon trade, etc. to acquire things that would be more difficult to produce by themselves. ]
[Question] [ Some time ago, I did a back-of-the-envelope calculation about magnetism, electricity, and [graphene](http://en.wikipedia.org/wiki/Graphene). I was (and still am) curious about developing a "deflector shield" based in known and viable science. I don't remember the exact numbers I used, but my calculations indicated that passing a unit charge through a certain length of graphene would produce a magnetic field capable of exerting enough force at a 30-foot (9.1-meter) radius to deflect or stop an inbound missile traveling at about Mach 2.5, which [appears to be on the slow end of air-to-air missiles](http://en.wikipedia.org/wiki/Air-to-air_missile#Typical_Air-to-Air_Missiles). I don't have enough of a physics background to be confident in my quick numbers, so my question also involves someone being kind enough to check my math. However, my real question is this: Is such a defense feasible and can it be scaled to satisfy the needs of a single soldier, a battalion in open terrain, and a spacefaring vessel? What impact would such a field have on people and things in or near it? As mentioned [here](https://worldbuilding.stackexchange.com/a/10052/6986), employing magnetism in the extreme can have undesired effects, such as levitation and cellular disassembly. So anyone using a magnetism-based shield would need to have some form of protection against their protection. Since magnetism only repels/attracts things with the same/opposite charge, and most things have a neutral charge (just don't walk across a carpet), anything that needed to be deflected by the field would need to be appropriately charged. Is there a way to manipulate the charge of an arbitrary object at distance, such as by firing electrons at it? (Note: this seems difficult and infeasible.) To sum up, since this seems to be a little haphazard: * Is a magnetism-based deflector shield a possible construct? * If it is possible, what scale is feasible: soldier, battalion, ship, fleet? * What impact would such a shield have on people and things in and around it? * What protection, if any, would be needed by the user to defend against negative effects of the shield? * How could the effective charge of any arbitrary object be manipulated at a distance of about 30 feet (9.1 meters)? [Answer] # Is It Possible? In theory, yes! The methods through which a deflector shield would work is straight magnetism and the [Lorenz force](http://en.wikipedia.org/wiki/Lorentz_force). If it's magnetic, it will be attracted to the shield (since it itself is a magnet, and likely a strong one!). If it has a charge, the Lorenz force will swing it off to one side. The faster it goes, the more the Lorenz force kicks in. What about the non-magnetic and non-charged items? A magnetic field will not protect anyone in that case. Fear any missile made of ceramic, or a weak magnetic field producer! # What Scale is Feasible? **For A Soldier?** Bullets, as far as I can tell, are *sometimes* magnetic materials. (Lead [interacts weakly](http://terpconnect.umd.edu/~wbreslyn/magnets/is-lead-magnetic.html) with STRONG magnetic fields.) Given that many types of bullets are made of lead, I think this makes is unfeasible for your troops. Besides that, bullets seem to [have a charge of 1 pC to 1 nC](http://adsabs.harvard.edu/abs/2012SPIE.8382E..16V). That's *tiny* for such a large projectile. While they are traveling quickly, they would need a *massive* magnetic field to get any appreciable force on them. [Here](http://en.wikipedia.org/wiki/Orders_of_magnitude_(magnetic_field)) is a list of items which produce measured magnetic fields. Unless we start shooting plasma or other highly charged particles, this is not going to work for bullets shot by infantry. **For Tanks or Ships?** It seems that most shells for tanks and other high-powered weapons of war [use steel](http://en.wikipedia.org/wiki/Shell_%28projectile%29#Modern_shell) casings for their weapons. Steel reacts to magnets decently well, so we can not eliminate the shields based off of material alone. We should note, however, that this would result in the deflector shield unit actually \*attracting\*\* the projectile, which presents the possibility that what would be a clean miss would be a hit. I personally prefer avoidance whenever I can, so I would not fund this style of deflector shield against modern arms. Deflector shields could by deployed at the ends of a craft, to attempt to steer projectiles away from the middle. It turns out calculating the force between magnets and magnetized objects [can be tricky](http://en.wikipedia.org/wiki/Force_between_magnets#Force_between_two_magnetic_poles). Assuming that $B=\frac{\mu\_0 I}{2\pi r}$ and $F=\frac{B^{2}A}{2\mu\_0}$ (this is possibly a wrong approximation), the force on the shell is: $$F=\frac{\mu\_0 I^{2}A}{8(\pi r)^{2}}$$ where A is the surface area of the projectile closest to the deflector shield. For a [125 mm BK-14m HEAT round](http://commons.wikimedia.org/wiki/File:125mm_BK-14m_HEAT.JPG), that is about $0.04 m^2$ At 9.1 m away with 1 Amp you get about $7.6\*10^{-12}N$ of force. That is a pathetically small force for an anti-tank weapon. In effect, no, this is not feasible for a ship, a tank, or any atmosphere based item against modern weapons. Modern projectiles simply do not have enough charge, nor can we produce strong enough magnetic fields to deflect massive objects in this way. If you opponents shoot [plasma](http://en.wikipedia.org/wiki/Plasma_(physics)), then deflector shields may come into being, as plasmas are highly charged and the Lorenz force can easily dictate their movements. # Effects of Massive Magnetic Fields Magnetic fields, especially massive ones, can cause problems. Such as: 1. Levitation (first [frogs](http://www.physics.org/facts/frog-really.asp), then other life forms, depending on diamagnetism and intensity of your field.) 2. Pulling electrons off of you (from a massive [Hall Effect](http://en.wikipedia.org/wiki/Hall_effect) gone bad) 3. Wiping out information on hard drives 4. Getting your keys stuck to the deflector shield generator 5. Massive power bills # Where Are Deflector Shields Feasible? In space, against highly charged particles going fast, you may effectively use a deflector shield. Space.com reported that [several scientists were investigating](http://www.space.com/6128-star-trek-deflector-shield-envisioned-mars-mission.html) such a field to protect astronauts against cosmic rays and other high velocity, electrically charged baddies in space. A [more recent article](http://www.cnn.com/2013/06/27/world/europe/star-trek-shield/) from CNN talks about some improvements and more thoughts on this. There are other variations as well, such as the plasma-field, but that is out of the scope of your question. [Answer] Based on what has been said, a magnetism-based deflector shield doesn't sound practical at all. However, in my mind, this does raise two distinct possibilities; 1. A strong enough magnetic field could potentially be used to draw projectiles away from a targetted object, and; 2. ...a magnetic field could also potentially be used as a "projectile trap" a la the alien mech suit in District 9. Wishful thinking, maybe, considering the power requirements needed, but it's given me something to think about. ]
[Question] [ # Info I'm designing a breed of cow that produces acid instead of milk. Part of the reason this is useful for my story is that the cows produce as much acid as a dairy cow would milk (through selective breeding/genetic modification.) Now, the dairy industry in 2013 produced [769 million tonnes](http://www.fao.org/dairy-production-products/production/en/) of milk. Let's assume that the acid marked is half that (384.5 million tonnes). The dairy industry and a market has grown around this for a couple of reasons: [Protonation](https://en.wikipedia.org/wiki/Protonation). Research into the renewed possibility of an "alkahest." And the criminal applications: if the acid was sold/stolen on the open market (or illegally) it would quickly become an agent for breaking through safes, etc (with the risk of damaging the internal components.) This would make the material resistant to the acid (see below) quickly become implemented as a security measure everywhere, which would create more and more ingenious ways of getting around that protection. The acid is equal parts [perchloric acid](https://en.wikipedia.org/wiki/Perchloric_acid), [aqua regia](https://en.wikipedia.org/wiki/Aqua_regia), and [flouroantimonic acid](https://en.wikipedia.org/wiki/Fluoroantimonic_acid). In other words, it's ***nasty*** stuff. A minute amount of unobtanium is used to keep them from neutralizing/oxidizing/destroying/whatever each other. The cow creates these from the special feed it is given. According to [this source](https://www.calpaclab.com/teflon-ptfe-compatibility), flouroantimonic acid, perchloric acid, and aqua regia (which has 2 components) are all held by [PTFE](https://en.wikipedia.org/wiki/Polytetrafluoroethylene) (Which you might know as Teflon). # Question How could a cow protect itself using that material? By which I mean these two points: * What would it need to eat (what would its diet be) to best synthesize the PTFE and * What would the PTFE line; The parenchymal tissue? The udder cavity? Would it wear out over time? Further clarification on what answers must include: * What changes to the diet of a regular cow, plus antimony supplements (for the acid) would need to be made to allow for the synthesis of the PTFE * Would there need to be an additional lining of cells to produce the PTFE * What organs/ducts/etc would the PTFE line EDIT: You may use the acid to help you do whatever you need to do, such as mixing w/water for heat, using it to dissolve things, etc. --- Please do not use magic as an answer. Handwavium is already being used for the nonreactivity of the acid; not for the protection of the udder tissue. That's why I came here to ask it instead of saying "it's magic." I've set a premise; please don't [unbuild it](https://worldbuilding.meta.stackexchange.com/questions/4500/there-are-too-many-world-unbuilding-answers-and-comments). I'm using both the reality-check tag and the science-based tag because I want a reality-check with science. Try to work with the premise I've set instead of saying "it's unreasonable for the calf/cows don't produce acid milk/it's impossible for that to happen and the science-based tag shouldn't be used." I'm using the science-based tag in this setting because I want science-based answers to a problem *set on an already built premise*, which is set in stone. My reality-check is specifically about *how it can protect itself*, not about whether this is a reasonable premise or possible situation. --- Thank you to all in the [Sandbox](https://worldbuilding.meta.stackexchange.com/questions/6168/sandbox-for-proposed-questions) for helping me develop this question, especially @Raditz\_35 for all his expertise and guidance. --- For those interested, there is a slang code built around this substance: "Cheese": When the magic keeping the acids stable degrades and the acids form a useless substance. "Cream": When the acid is separated into its components to selectively harvest only one acid from its components. "Ice Cream": When the acids are cooled and pressurized for transport. "Burnt Milk": When pressurized acid explodes. "Yogurt": When a gel is made out of the acid. "Skim Milk": When water is added to the acid, invariably causing dangerous, explosive reactions. [Answer] Okay, I’ll throw in my two cents to this question. First of all, this is not going to be a happy cow and I really hope that you don’t have a farm in real life. Honestly, there’s a reason that nobody’s even bothered to attempt biological PTFE synthesis, largely because of the amount of wince-inducing enzymes I’m going to have to use for the synthesis pathway. Sadly, this setup certainly fails the ‘reality-check’ tag. ## Pathway Curiously, it’s possible to construct a pathway to PTFE of which the only real diet change would be the addition of [fluorite](https://en.wikipedia.org/wiki/Fluorite). I’ve sketched out this pathway below, which might be good to refer back to as we walk through it. Essentially, to get PTFE we need tetrafluoroethylene (TFE). TFE is made from chloroform and hydrofluoric acid (HF). To get HF, we need fluorite and a strong acid - sulfuric acid is what’s used industrially, but I’m going to argue that hydrochloric acid (HCl) could work alongside a catalyst to simplify the pathway. To get chloroform, we can mix ethanol and bleach. Of course, bleach isn’t a great food for living things so we should also synthesize that from ozone and NaCl. ![Diagram of PTFE synthesis from plausible natural ingredients](https://i.stack.imgur.com/dV7SK.jpg) The majority of the starting ingredients can already be synthesized biologically from normal feed, specifically ethanol, NaCl, and HCl. Ozone *could* be obtained in parts-per-billion quantities from normal air, which means that the only base ingredient we need to add to their normal food is fluorite. Now, we should note that there are a couple immediate problems with this pathway. First of all, many of these reactions don’t occur at room temperature and instead require 500+K to occur. However, if we invoke the mystical power of **enzymes** we can reduce that activation energy to something like internal body temperature. I use “mystical” to describe enzymes here, but they’re not magic or handwavium - just biological catalysts. Catalysts reduce the activation energy of a reaction by organizing, stabilizing, and orienting the molecules in such a way that it’s no longer brute-force random noise (high temperatures) that allow a reaction to go to completion, but instead a [choreographed dance](http://www.xvivo.net/animation/the-inner-life-of-the-cell/). Second of all, most of these ingredients are *awful*. I’ve compiled here a list of the warnings on Wikipedia about various chemicals we’re using: [**Ozone**](https://en.wikipedia.org/wiki/Ozone) is one of the greatest oxidisers we know of, which is why it’s so dangerous. We can smell it at ~1-2 ppb (parts per billion), and it’ll start to [damage us](https://en.m.wikipedia.org/wiki/Ozone#Health_effects) at ~100 ppb, with an LC50 of ~50 ppm (parts per million). Given these restrictions on the concentration of one of our reactants, this may be a very slow reaction even when operating at near-lethal concentrations. [**Bleach**](https://en.wikipedia.org/wiki/Bleach) is used to kill things. Plain and simple. We use it in bio labs to get things really really clean, and after we do so we usually label them “not to be used with sensitive organisms”. Here’s the warnings from Wikipedia: > > “... ingestion of bleaches can cause damage to the esophagus and stomach, possibly leading to death. On contact with the skin or eyes, they may cause irritation, drying, and potentially burns. Inhalation of bleach fumes can damage the lungs.” > > > [**Chloroform**](https://en.wikipedia.org/wiki/Chloroform) is also pretty terrible for humans - that’s why we pass out when we sniff it, and why it can kill us if we consume more than a thimbleful of it. Here’s some Wikipedia warnings: > > ”Prolonged dermal exposure can result in the development of sores as a result of defatting.” “Accidental splashing into the eyes has caused irritation.” “... causes depression of the central nervous system (CNS), ultimately producing deep coma” “use of chloroform [for anesthesia] has been discontinued because it caused deaths due to respiratory failure and cardiac arrhythmias” > > > **Acids** are not great for humans. They won’t melt you (well, most of them) but they can quickly ruin your day. Here, we’re talking about some of the worst. [**Sulfuric acid**](https://en.m.wikipedia.org/wiki/Sulfuric_acid) is pretty terrible stuff and hard to synthesize, so I opted for the tamer [**hydrochloric acid**](https://en.m.wikipedia.org/wiki/Hydrochloric_acid) (**HCl**). It’s possible that you *could* [synthesize sulfuric acid biologically](https://en.m.wikipedia.org/wiki/Sulfuric_acid#Manufacture), but HCl and an enzyme will probably work just as well together. However, it’s worth noting that HCl is still pretty terrible. We humans synthesize this stuff naturally for digestion in the stomach, where it constantly eats away at our mucus linings and causes heartburn and ulcers when it escapes. But neither of those acids compare to [**hydrofluoric acid**](https://en.m.wikipedia.org/wiki/Hydrofluoric_acid) (**HF**). This stuff has been described as [“movie acid”](https://worldbuilding.stackexchange.com/q/82204/28789) because it’ll eat through, like, everything. Metals, organics, whatever. The first video that pops up when you search for HF is “flesh eating acid”. The OP didn’t include HF in his acid cows because even PTFE is permeable to it. *Please sir, may I borrow a little of that unobtanium?* Finally, [**tetrafluoroethylene**](https://en.wikipedia.org/wiki/Tetrafluoroethylene) (**TFE**) is not fun stuff either. I couldn’t find any specific hazards associated with it besides “weak carcinogenic effects” but it’s given 3/4 for health hazard, 4/4 for flammability, and 3/4 for reactivity by the [NFPA](https://en.m.wikipedia.org/wiki/NFPA_704), better known as the “fire diamond”. And *all* of the above assumes that you’ve managed to insert suitable genes for these various, custom-designed enzymes into their genetic code in such a way that they’re properly duplicated, transcribed, and translated. Most enzymes (proteins) aren’t stable under strong acids, instead hydrolyzing into individual amino acids... which *also* aren’t stable under low pH. Also, DNA falls apart under low pH. Fun, right? Your genetic engineers probably hate you and have all quit. You’ve turned your cows into essentially fume hoods for synthetic chemistry, and they’re unlikely to be much more than a pile of chemicals after a while. And they all have cancer. Oh, and while they *were* alive, you fed them rocks. > > Cool question, *murderer*! > >     - a vegan somewhere, probably > > > ## Tissue linings You can pick whatever tissue you want to line with PTFE. I initially thought that the stomach would be a good choice for this because it’s already dealing with acids, but the substances we’re working with are so far beyond “normal” acids that the 5-6 pH unit difference body tissue and stomach tissue is blown out of the water by the ~20 pH unit difference between body/stomach tissue and fluoroantimonic acid. If your genetic engineers have succeeded at all of the above, they’ll have no problem turning the cow’s head or hooves into acid cauldrons. Which really begs the question of why we’re using cows at all. ## Scalability So, the problems listed above arose from the creation of a single cow. You’re interested in making **264 million** of them. I can not express strongly enough how much I would advise against this course of action. Problem #1 being that we’d actually [run out of rocks](https://en.m.wikipedia.org/wiki/List_of_countries_by_fluorite_production) to feed them. We’d also run out of ozone and have to synthesize that artificially, which the environmentalists will *not* be happy about because it’s a major pollutant at ground level. Heck, we’d even put a dent in the world ethanol supply. ## Possible saves Biologically synthesized PTFE fails the ‘reality-check’ really hard. However, there *are* some options if you’re willing to be a little flexible. ### Glass [Biological silica](https://en.m.wikipedia.org/wiki/Biogenic_silica) production is a real thing. Diatoms make their frustules out of glass by secreting silica nanospheres which they then glue together. Glass *is* [vulnerable to erosion](https://www.alfa.com/media/Art_Superacids_2016.pdf) by fluoroantimonic acid, but so is our stomach mucus vulnerable to normal HCl -we just secrete it continuously. I’m also confident your genetic engineers would be happier to insert eukaryotic diatom genes into a eukaryotic cow than archaeal bacterial ones. ### Waxes As pointed out in a comment, waxes might also be a way to store these acids. Again, they’re not immune to the results but constant secretion might also solve that problem. In fact, they’d probably react with the acids themselves and substitute fluorines in place of the hydrogens, which would create a structure very similar to PTFE anyway. Even better, cows already produce fats which would simply need to be elongated/saturated, or you could borrow some honeybee genes (wow, same kingdom even! Maybe you’ll be able to re-hire some of your old engineers now that you’re making such reasonable requests) and do wax production directly. Good luck!! (Shoutout to the [Answer Sandbox](https://worldbuilding.meta.stackexchange.com/questions/656/sandbox-for-proposed-answers) for some help developing this answer!) [Answer] Let's assume a more complex process. The comments are correct that biologic, glandular tissue cannot protect itself against the acid. The problem requires that the acid both be contained, and that it be produced by a cow. Let's suppose a complex chemistry when the mammary glands produce the precursors. To prevent the glandular tissue from being destroyed, there shall be several types of glands which produce a reactant. Let's also suppose some solvent, which from the comments must not be water. The precursors are expressed into the milk ducts, which are muscularly restrained to prevent backflow to the glands. The milk ducts each conduct their particular chemical to mix with the next chemical, which then further reacts until eventually, the ideal gruesome mix reaches the udder. The ducts are lined with materials that are impervious to the precursors and the products. Until the final steps, these may be able to be semi-permeable, so that water may be removed from the mixture, which concentrates the milk. It is also necessary to get all the water (if there was any) out of the milk before it is mixed with the fluoroantimonic acid, which can not exist in water solution. The synthesis methods carried out in the mammary glands are beyond my knowledge of chemistry. At the least, you will need this sequence of synthesis approach, with the milk ducts becoming pure, non-permeable PTFE by the end. The good news is that the cow can reuse the fluorine handling enzymatic systems both to make the PTFE and the fluoroantimonic acid. Heaven help the calves looking for a meal. [Answer] **You need a molecular assembly style process.** Protein synthesis is accomplished by adding the correct nucleotide to the end of the chain and repeating until the protein is complete. A similar molecular assembly process could convert long-chain hydrocarbons into long-chain fluorocarbons. I am not able to design the needed assembler, but I think it as least passes the plausibility test. A somewhat rigid assembler could walk down the chain (able to constrain the current section of the long-chain molecule during construction) , replacing hydrogen with fluorine 1 atom one at a time. The assembler will require a steady source of fluorine, which is common in many foods as well as water sources. Too much fluorine is toxic, but with the right balance of intake and usage, this is also feasible. It will be necessary to coat every organic surface in contact with your nasty acid. This limits the ability of the body to handle cell growth / death / replacement because a PTFE layer must remain in place at all times. The surfaces could be designed so that it sloughs off gradually allowing cell growth on the inner layers, and PTFE coated dead layers actually in contact with the acid to form the safety barrier. You still have a problem, how do you get the PTFE to adhere to the underlying cells. The methods uses commercially are not going to work inside your cow. Might I suggest that the solution for this is constructing the PTFE/cell boundary into something similar to Velcro. This will not be a strong adhesion (especially if the cell material is the lipids layer used in animal cells), but it could be strong enough since it does not have to survive high shear / sliding stress, etc. common to to skin. ]
[Question] [ I have a race of humanoid species, who, like elves, have better senses than humans. They live in mountains and hills. They look like humans but have longer faces, smaller eyes and are most famous for their long noses (like noses between 5-15cm). Then I wondered, if their long noses would have an effect on the sound of their voices? I know this is a far-fetched question, but could anyone help me with this one? BTW: sorry for bad english. Not native speaker. Thanks a lot! [Answer] ## They will definitely sound different Most of human speech is made through changing the shape and spatial relationships between the lips, teeth, tongue, oral cavity and throat. Changes to the shape and materials of any of these structures will have an influence on the sounds that can be made. The [IPA chart](https://www.internationalphoneticassociation.org/sites/default/files/IPA_Kiel_2015.pdf) (pdf) shows many of the sounds that a human being can make, definitely not all sounds. You'll notice for the consonants that the ones to the left are made further forward in your throat while the ones to the right are made further back in the throat. If your creature lacks or alters any of these vocal structures it *will* sound different. For example, if the nose somehow makes the dog people's lips more rigid or so they can't be controlled at all, then they won't be able to pronounce the /p/ or /b/ sounds since those require lips to form. The sounds of their vowels will also change since there's now a much larger resonator cavity in their skulls compared to the nasal cavity in humans. Generally, the tones would be lower because big resonators work best with low frequency sound. A really helpful exercise would be to make lots of the consonants and vowels but pay close attention to how your mouth and throat move when you make different sounds. It will help you a lot with trying to imagine what sounds these creatures can make. Or, you can go to the [Pink Trombone](https://dood.al/pinktrombone/) website (SFW, but creepy) and play around there. Without more specific geometry it's just not possible to figure out what the exact sounds will be. ## General Guidelines 1. Bigger cavities create deeper notes. 2. Removing or altering vocal structure compared to a human will alter the creature's ability to make those sounds. Experiment with the IPA chart to compare what the creature looks like vs human anatomy then adapt from there. [Answer] The effect will be rather small. The sounds of human speech are formed in the oral cavity and their frequency is determined by the tension and length of the vocal chords. Changing the nose length will not affect this system very much. In particular, they will be able to form the usual phonemes of human speech and they'll be understandable by us. Trained singer make use of all possible resonators in their body, and the bigger noses make different resonators from the normal human noses, so one can expect some difference in the "colouring" of the sounds we make, and the difference will be biggest for singers. ]
[Question] [ I'm working on a fantasy setting that's literally a giant tree on a planetary scale. Magic is in effect, so concerns of how a tree that large could survive are irrelevant, but I need to figure out what water sources usable by it's inhabitants could feasibly exist on a tree of that size. I know bogs could exist, because bogs actually occur in the canopies of real life redwoods, but what about other sources? There's a highly diverse epiphyte community, including some plants that are normal-sized trees, as well as both normal-sized and giant equivalents of real life epiphytes, so there might be bodies of water inside the cups of giant bromeliads or something similar, but could lakes form on the surface of the tree itself? What about rivers and streams? I probably don't want anything so large as a sea, let alone an ocean, but, if possible, how big would lakes be able to get? If it matters, the tree in question isn't attached to any true planet, when you reach the base of the tree, you find a field of spongey material that can't be seen through a thick, surrounding mist, and if you travel on that field more than a couple miles from any point of the trunk on this surface, you end up more or less back where you started. On the other hand, there is a fairly regular weather system, with rain and other precipitation falling on localized regions of the tree, and some areas being typically drier or wetter than others. Though a root mass exists, it is, for want of a better way to describe it, "out of phase" with the plane of existence the rest of the tree is on. A few surface roots protrude in the area around the base of the tree, extending about half the distance that can be traveled out from the trunk. The other plane where most of the roots are could in theory be reached via magic, but no one's ever tried due to the sheer *uselessnes*s of the surface around the base of the tree, which inhabitants refer to as "the mist ring". There is no other effective mass of the "planet" other than the tree and the various lifeforms growing on it. From the base of the tree to the top of the canopy is roughly 10,000 miles, with a canopy spread of maybe 12,000 miles. It has definitive "upward" direction rather than growing from a central mass. The main trunk is relatively short and thick before masses of branches start splitting off - about 1,600 miles in diameter and branching off at a height of 2,000 miles. Some one race has a fairly extensive tunnel network inside the trunk and some branches, though not reaching the heartwood. Gravity has a definite downward direction, but there's also a very slight pull toward the trunk. Something that falls off a branch will tend to "drift" towards the center of the tree as it falls. It's also worth note that gravity isn't nearly as strong as Earth's, somewhere between 0.2 and 0.5 Gs. The tree is fully stationary. I'm as of right now undecided as to how weather patterns move, but some clouds can definitely enter the canopy in a way that some precipitation might fall on lower branches but not upper ones. [Answer] *You've already mentioned accumulation in bog material, leaves, and flowers. So I'll ignore all that.* **branch bowls** Where two or more branches exit the trunk and are near to each other, they will create depressions or bowls as the base of the branches grows outward. On a tree this size, those bowls could create sizable lakes (several square miles at least). Such bowls can occur with diminishing size anywhere from the trunk to the tip of the branches wherever two or more branches diverse perpendicular to the rootball. A bowl could also form at the very top of the trunk between branches. Such a bowl would be nearly unique in that it would have the least amount of taint from sap. **Sap** Whether or not sap is consumable is story dependant, but there would be a never-ending supply of it (well... assuming your population doesn't grow too large). This can have a fair number of story elements as a tree this large may have different kinds of sap depending on how deeply you "mine" the bark or tree. Since the sap is a nutrient-carrier for the tree, it can have a variety of healing/healthy properties... not the least of which is coating the biggest honking stack of flapjacks the universe has ever seen. *Note that most of the standing water I describe here is likely to be tainted with the sap(s).* **Decantation** Water falling on or condensing on the upper branches will (often) flow back along branches to the trunk, then down the trunk to the rootball. You could have substantial rivers flowing along the trunk and underside of larger branches after rainfall. Smooth bark would allow the water to spread out and flow shallow. Rough bark would form pools, waterfalls, and channels. **Hollows** Branches die, and when they die they can fall away and leave a gaping hole in the tree. That hole could hold a lot of water... maybe even thousands of square miles of water. Rivers decanting down the side of the tree would decant along the "roof" of the hollow for a ways before falling in a glorious waterfall to the inner sea. Cracks in the wood would allow water to seep in in a manner similar to terrestrial springs. **Man-made hollows** If your people can mine, they can create their own hollows. They wouldn't be large — call them ponds — but they'd be perfectly useful for drinking water. **Bark tears** Areas where the bark has separated from the tree could cause water acculumation. **Barrels** Your people have an awful lot of wood available to them. Barrel-making (if they can find a suitable replacement for the metal straps... leaf fiber, maybe) would be a booming business, and you can let them accumulate water from leaves and other flows. *Flows can be created with tarps made out of leaf material. Your people can divert rivers fairly readily.* ]