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[Question] [ In some star clusters, the stars are packed as densely as a light year apart or less. Many clusters do not appear to have black holes in the center, though they remain relatively stable in their orbits and longevity. Assuming a cluster about 100 light years across, and planet(s) capable of supporting life, what do you think the night sky would like from inside? Would it ever seem 'dark' or just dusky? Would there be a constant dim glow of light or a bright one? Of course this would depend on how close to the center of the cluster your planet was located. Let's say somewhere in the middle. I would also be curious to know if a planet closer to the edge of the thinning halo might see a difference, such as darker space on one side and brighter lights on the other. [Answer] I wrote [a blog post](https://medium.com/universe-factory/a-new-kind-of-sky-living-in-a-globular-cluster-14e82cc33639#.sdztuvvvd) about this for Worldbuilding Stack Exchange's blog, Universe Factory, so I'll work off of that. First, the good stuff: a picture of what you're looking for. It's from [Alexey Bobrick's answer](https://astronomy.stackexchange.com/a/3681/2153) to the same question on Astronomy Stack Exchange: [![enter image description here](https://i.stack.imgur.com/FbyaO.jpg)](https://i.stack.imgur.com/FbyaO.jpg) Image from [this article](http://io9.gizmodo.com/what-the-night-sky-would-look-like-from-inside-a-globul-1589324556). That big bright bulge to the right is the center of the cluster, where the highest stellar densities are. Notice how the stars get less dense on the left side, further away from the center. Other answers to the same Astronomy question should give you an idea of how bright nearby stars will seem. The thing is that this image is only for a planet in a star cluster in the plane of the Milky Way. If this star cluster is a globular cluster, it will most likely be above the plane of its home galaxy. Here's what the Milky Way looks like to us: [![enter image description here](https://i.stack.imgur.com/BIZ6w.jpg)](https://i.stack.imgur.com/BIZ6w.jpg) Image courtesy of Wikipedia user Illustr under [the Creative Commons Attribution 3.0 Unported license](https://creativecommons.org/licenses/by/3.0/deed.en). The image is curved because of a photographic effect, but in reality, our galaxy still appears to be a thin band. Here's what the Milky Way might look like to an observer far away (this is actually [NGC 6744](https://en.wikipedia.org/wiki/NGC_6744)): ![](https://upload.wikimedia.org/wikipedia/commons/4/4c/Wide_Field_Imager_view_of_a_Milky_Way_look-alike_NGC_6744.jpg) Image courtesy of Wikipedia user Jmencisom under [the Creative Commons Attribution 3.0 Unported license](https://creativecommons.org/licenses/by/3.0/deed.en). So what I would suggest is overlaying the first image with the image of a spiral galaxy in the background, when the night sky of the planet faces the galaxy - again, for a globular cluster above the galactic plane. I'll see if I can find a tool to put them together into something cool. For now, I leave it to you to play around with different renderings of spiral galaxies and the rendering of the night sky as seen from a planet in a star cluster. [Answer] [![View from inside a Globular star cluster with Milky Way in the background](https://i.stack.imgur.com/WSRKk.jpg)](https://i.stack.imgur.com/WSRKk.jpg) I did some photoshop with your images :) Would something like this work? ]
[Question] [ I read a blog post explaining why interstellar travel is terribly impractical. The short answer is that stars are far away and travelling that far takes a very long time and ridiculous amounts of energy. Anyway as a part of explaining the distances the blog gave examples of distances and one of them was the Oort Cloud where certain comets come from. Which extended to nearly halfway there. This reminded me that not only do these objects range far in-system on their weird orbits, they range far enough out that they could feasibly swap stars, and they are full of volatiles that can be used for life support or propellant. So maybe you could rendezvous with a comet in the Inner System, use it as a place to live and propellant, rendezvous with another comet with a different trajectory, and so on, all the way to a neighbouring star system. Being able to resupply both propellant and volatiles such as water and oxygen en route should make interstellar travel much cheaper. And for most of the transit you would be passively travelling on a comet using it as protection from radiation, which should improve safety and comfort. This would still require practical ship scale fusion power and probably "Cure for Cancer" level of medical technology to deal with long term issues of zero gravity and cosmic radiation. But both of these are AFAIK considered possible at the moment. But given these assumptions is it plausible to use comets and the objects in the Oort Cloud as aids to travel between systems? And how much would it help? Would it make interstellar travel practical? I am not going to ask for strict science since much of what is "known" about the Oort Cloud is uncertain. And the third question is probably impossible to answer beyond opinion, but if you have a rationale why or why not, please share. There seems to be some confusion in what I am asking and what I was already assuming in the question. Yes, I know that the cloud objects are sparse and unlikely to have perfectly convenient trajectories, so both time and delta-V needed would go up by a large factor. The question is; would the ability to supply propellants for propulsion and volatiles for life support outweigh that for a net improvement. Is there even a way to know or give a good guess? As per Wil Selwood's answer: You can presume that they have done the groundwork of mapping the objects in the Oort Cloud and planning the hops and schedule in advance. It helps a lot with the cloud being relatively sparse and considering the investment of what would have to be a generation ship and thus very large and expensive, they'd do all the advance work they can. You can also presume that after reaching a comet they will dig in and resupply, wait in cover until scheduled burn time, then detach from the body with full supplies, and only accelerate the ship, not ship and comet. [Answer] This would actually be a variation on the "generation ship" meme. You could "hop aboard" a comet and drift into the Oort cloud, but the speed of the comet will be so slow and the distances so vast that it might be generations before the crew approaches a "fresh" comet moving roughly the direction they want to go. Rinse and repeat for hundreds of generations, and in the end, you will be on a comet that is very tenuously attached to the solar gravity well, and with a small push, the comet can start drifting towards the next Oort cloud around Alpha Centauri. Generations later, you reach that gravity well and start drifting inwards, using their comets as stepping stones to the new sun. Living aboard a comet would not be too bad. The comet can be hollowed out and the mass of water and volatiles that make up the bulk of the comet would be good shielding against radiation and even the occasional impact. There is probably enough D2 in the average comet to supply a small space city for a thousand years of fusion energy, so there is plenty of time to look for a new home. And the comet probably has sufficient stocks of the other elements to live a reasonably comfortable lifestyle, so long as you are not addicted to large amounts of metals. It seems reasonable to expect to find carbon compounds, nitrogen and even silicon in some quantities in a comet nucleus. If you are impatient, it might be possible to bury a space colony in a comet and use the materials not only to run the ecosystem but also power a fusion engine to get enough deltaV to exit the Solar System and fly to Alpha Centauri directly. Once there, rendezvous with a new comet to replenish your stocks and start exploring. This cuts the time down to a more reasonable few centuries, rather than thousands of years. [Answer] I think this scheme mixes [distance](https://en.wikipedia.org/wiki/Distance) and [delta-V](https://en.wikipedia.org/wiki/Delta-v). No matter how close two comets pass to each other, you don't just hop from one to the other. Instead your ferry has to match velocites. Also, [space is empty](http://tvtropes.org/pmwiki/pmwiki.php/Main/AsteroidThicket). You can't expect to find a convenient comet going in the right direction. The sum of velocity changes as you hop from comet to comet will be much more than the velocity change for an interstellar voyage. Is the convenience of living in a comet worth it? [Answer] Hitching a lift on a comet is an interesting idea. It gives you a lot of fuel. However there are some pretty big downsides. First Delta-V: Getting to a comet is hard, but doable, [Rosetta](https://en.wikipedia.org/wiki/Rosetta_%28spacecraft%29) proves we can do it. Getting out of the solar system is harder but also do-able see the [Voyager](https://en.wikipedia.org/wiki/Voyager_1) probes, the trick here will be finding a comet with an orbit that's easy to modify to take you where you want to go. You need to find a reasonably [eccentric](https://en.wikipedia.org/wiki/Orbital_eccentricity) comet with the [argument of periapsis](https://en.wikipedia.org/wiki/Argument_of_periapsis) pointing at the star you want to head towards. You can then use the comet as fuel to make a big burn when near [periapsis](https://en.wikipedia.org/wiki/Apsis) to push the apoapsis out until you break orbit around the sun and "whizz" off to your destination. Second fuel: While you will have a reasonably large amount of it the [rocket equation](https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) is a problem. Because you have so much fuel you need a lot of it to move it. The other problem is the fuel you have is going to be very low quality. It will be all mixed up, hydrocarbons, water, carbon dioxide, hydrogen, and dust. It will need processing very carefully before feeding into your engines. You will probably have more than one engine, each designed to burn/expel a different type of fuel. Making the big burn at periapsis is useful here because you can make use of solar energy as you make this burn. A better option may be to link up with a comet in your generation ship process the comet into fuel. Then when you reach the right point of the orbit detach and make the burn. This way you are only trying to accelerate the mass of the ship not the ship and a dirty great comet. Linking up to another comet when you arrive would done as a "if there happens to be a comet heading in the right direction" but should not be required as it would be impossible to know if such a comet existed in the target system with out already being there, getting the two orbits to sync up correctly would be extremely unlikely. [Answer] Comet hopping really isn't as practical as it may sound. Comets are just ice balls, and they're not that big, so making a spaceship around one wouldn't work. The only thing they'd be useful for is hydrogen (For a fusion reactor) or water, te former of which is easier found on most gas giants, the latter recycled pretty much indefinitely. Even the 'rocky' comets have ice as a foundation that heats and escapes as jet streams when nearer to the sun. Another factor of comets is grappling to them; they move at considerable velocity (When compared to a craft) so docking with them requires utmost time (A good launch schedule) and luck, enough to mean that getting to the exact place you need is more or less throwing a dart at a fly on a wall the size of central park. It is incredibly difficult. So, honestly, the amount of effort it would take to go to a comet isn't worth the risk and cost when a spaceship could allow its inhabitants to go cryo and simply drift to the nearest system. [Answer] Option 1: Comet Hopping This option assumes that you build a base on a comet that is already heading the right way, and so on, until you arrive in the destination system. Earth to comet, comet to Kuiper Belt Object, KBO to somewhere in the Oort cloud, where the Oort clouds mingle switch to another Oort object, then work your way inwards. Advantages: * Relatively modest delta-V for each comet-to-comet leg. * If you time it right, the ferry spacecraft could make multiple round trips between the old and new base. That means you need "less ship per person." * Fresh raw materials several times during the voyage. Disadvantages: * The base must be disassembled and reassembled many times. * How can you assure that there is a suitable object whenever you need it? * You are moving at the speed of an outer system object. The middle legs will take millenia or tens of millenia. Option 2: Comet Starship Go to a comet or KBO as it passes through the inner system, install an engine, use the volatiles from the object for propulsion. Advantages: * If the base is all ice/slush, you can turn nearly 100% into fuel. No need to waste mass on fuel tanks. * No need to find extra stepping stones. Disadvantages: * Is it really better to take a random comet and not "custom-freeze" your ice ship with just the right mix of raw materials? * Is ice really a good building material? Option 3: Mix and Match Give the comet some engines/delta V to match orbits with the next comet. * Less dependence on "finding" a comet at the right time and place. * Combines the probems of both options. [Answer] I'll try for a simplified form of [o.m.'s answer](https://worldbuilding.stackexchange.com/a/19564/21222): To fetch a ride on a comet you have to match its velocity, so you gain no momentum from it. Now if you could convert a comet like the 67P/Churyumov–Gerasimenko into fuel, you would be able to obtain just as much fuel from Earth, by doing a series of orbital fueling maneuvers. This would greatly simplify and cheapen the process. [Answer] Summarizing the question: no one is doing any "hopping" This is a cool idea, and a workable one, but I think the word "hop" in some answers is giving the wrong impression. When a spacecraft rendezvouses (<- weird derived form but apparently correct) with a celestial object it doesn't "hop" or "grab" on. It is more accurate to say it matches the orbit of the target object. Thus, the gain in this scenario is not some boost of speed, but simply the perk of not having to accelerate your fuel and consumables. The tradeoff is that the comet is almost certainly not on the most efficient trajectory for your needs, so you take a less efficient path in exchange for lessening the tyranny of the rocket equation. So in a real-world scenario one would optimize this by gathering information such as: 1. Target star 2. Maximum transfer time (limited by consumables, or maybe just impatience) 3. Maximum fuel (delta-V) carried by spacecraft alone 4. Appropriate target comets (and when they will visit the inner solar system) However number 4 is irrelevant in a narrative where the appropriate comet can happen to be visiting the inner solar system at the right time. If the trajectory is relatively close to how one might exit the solar system anyway, then it's pretty reasonable to assume time or resources are saved by not having to accelerate all of the consumables. You have to do some work yourself I get what OP is saying about leaving your chosen comet at aphelion and finding another comet at aphelion from a different star, but even in a narrative this strains believability (even if the oort cloud is near the outer reaches of some other solar system, space is incredibly sparse). The most likely scenario for interstellar travel using comets is simply accompanying a convenient one as far as you can while refueling/resupplying and then escaping the solar system by yourself using all of that fusion fuel. [Answer] Lasers Instead of using conventional fuel and stopping at the various comets, you can use laser sails. <https://en.wikipedia.org/wiki/Laser_propulsion> Your ships would be pushed by solar powered lasers near the sun. When further away where the sun is weaker, fusion powered lasers on the icy waystations would be used to push the ship even faster. A similar mechanism would slow the ship down at the other end. <https://youtu.be/oDR4AHYRmlk> ]
[Question] [ I'm working on [a comic](http://beesbuzz.biz/d/cat-lewi.php) which is essentially alternate-history fiction, and a big upcoming part of it involves the formation of the Chicxulub crater 63 million years ago. As I am a stickler for accuracy where things don't actually matter, I was hoping to be able to portray the night sky accurately during that time period. I tried using [Stellarium](http://stellarium.org) to simulate the night sky back then, but it only allows me to go back about 63,000 years, and not the 63,000,000 I need. Presumably the model isn't particularly accurate beyond a certain point anyway, but I want to be able to say I Tried(tm). Or should I just not worry about this, given that it's highly unlikely that any readers would recognize the night sky as being Earth's, much less of a particular geological epoch? (For what it's worth, even going 63,000 years back shows a completely different sky, with the constellations distorted beyond recognition.) [Answer] It's probably impossible to project their positions that far, because on long time scales the orbits of stars around the galaxy are [chaotic](http://en.wikipedia.org/wiki/Chaos_theory), meaning they show [sensitive dependence on initial conditions](http://en.wikipedia.org/wiki/Butterfly_effect) (even a microscopic error in your estimate of their positions and velocities at one time will lead to wildly inaccurate predictions about their positions at much later or earlier times). [This article](https://briankoberlein.com/2013/09/21/order-and-chaos/) says: > > It turns out the motion of stars can be approximately described by a simple differential equation called the Henon-Heiles equation. Unfortunately the solution to this equation is chaotic. In other words the solution is very dependent on a star’s initial velocity and position. Determining precise measurements of a star’s position and velocity can be quite a challenge. So usually we have to look at general properties of the solution rather than finding a particular solution. > > > [Answer] Since a [galactic year](https://en.wikipedia.org/wiki/Galactic_year) is 250 million years, in 63 million years the Sun will have moved about 1/4 of the way around the galaxy, as will other stars in the sky, in slightly different directions and differing rates, plus the up-down movement of the stars, like carousel horses. In short, the sky will be completely different and unrecognisable. You might determine the locations of the visible Andromeda galaxy and the Magellanic Clouds relative to the Milky May. Different external galaxies may be visible from the other side of the Milky Way. If you want a real chart with orbital movements to work back, look [at Gaia](http://www.wikipedia.org/wiki/Gaia_(spacecraft)) and data from [Hipparcos](http://www.wikipedia.org/wiki/Hipparcos). Breaking news: the Gaia data processing team has released [a video](https://apod.nasa.gov/apod/ap170417.html)! > > …the stars themselves will move. Combining positional data of unprecedented accuracy for two-million stars taken over years by ESA's Earth-orbiting Hipparcos (now defunct) and Gaia satellites, a future extrapolation of star movements was made over millions years. As shown in the featured video, many stars make only small angular adjustments, but some stars -- typically those nearby -- will zip across the sky. Once familiar constellations and asterisms will become unrecognizable as the bright stars that formed them move around. Not shown are many local nebulas that will surely dissipate while new ones will likely form in different places. > > > [Answer] The constellations change over time in a chaotic manner so perhaps you would just have to make up new or perhaps that should be old star positions. However there would have been other changes in the night skies . Over time the Moon has receded so 60 Million years ago it would have been closer and larger. This would also have changed the appearance of solar eclipses. In addition it is very probable that over time there have been changes to the appearance of the Zodiacal Lights and Zodiacal Band and there would have occasions when comets were more abundant. Going back further in time when the Moon would have been substantially bigger and at times disintegrating comets might have filled the the night skies but it would have required a clear atmosphere to see them from Earth. Perhaps the only advanced intelligent sentient beings around then would have been time travellers. Galileo was amongst the first humans to use a telescope to discover the moons of Jupiter but certain animals with exceptional night vision should have been able to routinely see such faint features of the night skies. I do not know whether dinosaurs had eagle eyes but even if they could have spied the approaching comets and asteroids of 60 million years ago they would still have been doomed. Edumnd Halley noted in his paper on astronomical impacts argued that such catastrophic collisions could benefit other animals which might replace the older established orders. ]
[Question] [ In my scenario, human civilization was blinded by some cosmic event analogous to the [Tower of Babel](http://en.wikipedia.org/wiki/Tower_of_Babel). They are plunged back into the stone age and will begin to redevelop civilization Is it possible to develop a civilization of only blind people? there are no sighted individuals as this is a genetic change. [Answer] ## Important Notice: This answer assume that the blind people are, as stated on the question, on a stone-age development state, and doesn't currently have access to modern times technology. If they do have access, please leave a note and I will change this answer accordingly. # Unfortunately, no. Having eyes is one of the major adaptative features on earth animals. They enable you to work on environment while on a safe distance of anything dangerous. They enable you to find fruits, to hunt, to evade things that are hunting you, to read and write, to... well, a ton of stuff. If everybody would go blind, we would have so, so many problems that I doubt human race could survive five or six generations. Let's get into detail. ### Problem Number One: Food Imagine that you must grow wheat to survive. And you are blind. You must prepare the soil, distribute the seeds, check if the plants are ok from time to time, apply fertilizer if needed, and them, when they mature, harvest them. Preparing the soil would already be a big problem. Without sight, you can't really tell were you are without some sort of reference point at hand-reach. And... in the middle of a huge wheat field, what you definitely doesn't have is a reference point at hand-reach. Even if you put landmarks from time to time with ropes scattered everywhere, how would you prevent yourself from getting lost? A big, huge farm is not the same thing as a complex urban environment with tons of different reference points scattered everywhere. Even middle and small sized farms would be an issue. Tending the crops would be even worse. Without eyes, you wouldn't be able to tell the difference between weeds and wheat until is too late. Without eyes, you won't be able to check if the crops are okay or if they are sick. You can't tell if there are flocks of crows eating your crops. You wont be able to tell the difference between a good, edible fruit and a poisonous one if they are pretty similar. Gathering food would be almost suicidal. If you go to the woods to pick up some berries, there would be tons of animals ready to bite, claw or sting you with no mercy. Go too close to a snake, miss that deadly scorpion over there, or run into a pack of wolves. Without eyes, you can't fight back. You would be food in a blink. Also, you can't run: Being blind and trying to orient yourself in the woods or any type of difficult terrain is almost impossible at a fast rate — you need to be constantly checking for obstacles to avoid tripping, and if you trip while running away from a bear — bye bye. ### Problem Number Two: Communication with other people Letters are easy. You can write some stuff on paper and then it stays there, ready for you to read it later. Text is a fast, simple, and efficient way of storing information. Remove the eyes of everyone, and almost all the knowledge would be irreversibly lost. People would lose all sense of geography without maps, and even reaching another city would be a huge problem. Without the stars or the moon to tell you where you are and where are you going, overland travel and sea navigation would be impossible. Settlements would rarely enter in contact with each other, and would in turn become more and more isolated from each other, cultures diverging more and more, until you have two completely different peoples with even different languages. ### Problem Number Three: Medicine is Impossible Good eyesight is a must today, when we have the extremely advanced machinery to help us to treat people. If you have a blind doctor, by the time he finds the cut that you made on your leg while running away from the wolves you would already be dead. ### Problem Number Four: Child Rearing I will keep this one short. How do you find your toddler? If you took a nap and that little brat escaped from his bed, how would you find him? He can be under the bed. He can be outside, in the garden. He can be on the belly of that mother-wolf that is tending a new litter of puppies — blinding all the humans would be a nice thing for them, that's for sure. ### Problem Number Five: Social Life With eyes, we can see who is around us. Without them, you only would be able to tell if someone is there by their voice. Where are your loved ones? Where are your kids? Are they sleeping? Are they gone? Is there someone strange on your house? You can't tell if they don't produce some sort of noise. While you talk to someone else, who is listening? Are you sure that you are alone? ### Lateral Note Keep in mind that having eyes is one of the most basic evolutionary traits of modern animals. Those that don't have some sort of vision normally inhabit pitch dark caves that wouldn't be a good place for humans. Losing eyes is a major setback that can destroy an entire population really quickly — even humans. [Answer] # TL;DR: Eye-sight is optional for a previously developed population to sustain itself. Note: For how to use your additional sense for skills like (long-distance) communication, growing food etc. see the second section of this post. The first section deals with how the additional methods of perception humans have are working. EDIT: Please also watch this [TED talk on sensory substitution and sensory addition](https://www.youtube.com/watch?v=4c1lqFXHvqI). Seems like my ideas are not that far-fetched after all. ## Who needs eye-sight if we can have "ear-sight"? ### Human Echolocation (proven) Have you ever heard of [human echolocation](https://en.wikipedia.org/wiki/Human_echolocation) ? If you didn't this might sound – pun intended – like some kind of superpower but it is actually possible to grasp your surroundings in the absence of functioning eye-sight by perceiving the resounding sound. Bonus: If you are not blind yet – you could have an accident in the future or a medical condition – this is even easier to learn as during your asyou can get more immediate feedback on whether you have successfully detected an object or not by taking a glimpse. Meet the [real life Batman](https://www.youtube.com/watch?v=vpxEmD0gu0Q) Daniel Kish to get a better idea of this fascinating ability. He termed it FlashSonar and in another documentary one of his students was able to use it to detect the exact position of a metal rod about one inch thick from one and a half foot away. Note: A rod has a curved surface so that very little resounds back into the direction the noise came from making it even harder to detect. From the article on human echolocation: > > Vision and hearing are closely related in that they can process reflected waves of energy > > > Vision and hearing might not be redundant but they can somewhat substitute each other. So if humans collectively lose their eye-sight it is quite likely our anatomy will adopt to it in the long run by increasing our hearing capacity and range of perception. There are already ways in which "ear-sight" beats "eye-sight". For example human echolocation allows us to perceive the density of an object. You don't get that information by looking how the light reflects from it! Although human echolocation might always lack in range compared to eye-sight it could definitely develop into something otherwise on par with normal vision or even superior. ## Additional Methods of Perception ### Magnetoception (controversial) Despite being less plausible than human echolocation – i.e. not proven vs. clearly proven – humans might be able to use [magnetoception](https://en.wikipedia.org/wiki/Magnetoception#In_humans) just like pigeons. However, to date studies remain inconclusive on whether or not humans have a magnetic sense. If they did not only civilizations could develop but also trading between cities far away from each other. I have to admit though I can hardly imagine how weird people in this scenario will describe a travel route to a stranger: > > "And when the road feels more going south listen for the hollow tree on the right and take the fork there." > > > ### Sense of Touch (obvious) The Tactile sense allows humans to perceive the surface condition and form of an object. You can also hold things with your hands to get the weight of an object – okay that's not your sense of touch but feeling the tension of your muscles but it's somewhat related. --- # Using your senses – capabilities w/o eye-sight ## Communication Speaking to someone next to you: no-brainer. Long-distance communication might seem difficult at first but is not a problem after all. Whistled languages such as [El Silbo / Silbo Gomero](http://en.wikipedia.org/wiki/Silbo_Gomero) allow you to communicate with someone 5km / ~16,400ft away. If that doesn't suffice you still have [braille](http://en.wikipedia.org/wiki/Braille). Now you might not be able to write on paper without building a type writer but clay tables will certainly work if your tech-level does not allow you to build the former. ## Agriculture Your fields will not vanish with your eye-sight! The same applies to orchards. In the past there were not only [meadow orchards (German: Streuobstwiese)](http://en.wikipedia.org/wiki/Orchard#Meadow_orchard_.28Streuobstwiese.29) but also orchards combined with farmland (German: Streuobstacker). The latter cropping system will probably be most useful to and therefore establish itself in a world where all people are blind because you can use the trees as reference points to find the place where some specific crop grows. Cultivated plants will mostly consist of tubers and other unpretentious crops plus they can easily be stored or left underground if not needed – although you will lose more of them to rodents. ## Advanced technology Why should blind people not be able to manufacture components and put them together to build a machine? The spatial imagination necessary to bring a complex machine like a computer to mind might seem impossible but maybe they will find methods to manage that. Just because we are so used to visualizing data doesn't mean we could not "auralize" data as well. > > "Yes you were right: The x-ray scans hear like you broke your left ankle." > > > --- # Disclaimer Admittedly, everybody suddenly losing eye-sight will be a horrible event. In the aftermath life will still be more dangerous than before for quite some time. However, in my honest opinion it is quite unlikely intelligent humans won't adapt. [Answer] > > Technology is the collection of techniques, methods or processes used in the production of goods or services or in the accomplishment of objectives, such as scientific investigation. -- [Wikipedia](https://en.wikipedia.org/wiki/Technology) > > > So yes, technology could exist. Maybe not in the form we have it today, but they will develop ways to do things better. For example, these people would probably develop a method of taming animals to help them "see." Likely they will still develop tools similar to what we have today. However many of the tools we have that affect aesthetics will not be developed. Why make an easel if you can't see the art? [Answer] The real question is "can humans survive and reproduce if all blind". If humanity can survive the blindness then they will continue what they always do, building culture, technology, and civilization. After all Blind people today still survive and contribute to society, expanding our technology and culture. being blind doesn't stop us from being humans, an amazingly adaptive creature that has a long history of using technology to compensate for our weakness. We are more deadly then creatures with teeth and claws, we survive and thrive in the most diverse and different environments, despite having no adaptations for them. Time and again our technology has proven better then other creature's adaptations. If we survive we will compensate for our lack of sight and thrive. However, the question is if they could survive long enough to produce a culture and technology. This is a very different question then "can blind people survive in today culture." When most, or even some, people have sight it's possible for others to be blind while still surviving and thriving. Those with sight can do tasks that require sight, those without can do tasks that don't, and both can thrive and grow society by using those skills they are best at. However, if you remove all people with sight then you have no one to do skills that require sight at all, meaning blind individuals will have to do things that in modern society a blind person would simply pay someone else to do for them, or never try to do. You can't pay a taxi to drive you somewhere if everyone is just as blind on the road etc. When the blindness first strikes were be in trouble. We couldn't hunt, we couldn't easily avoid those that would hunt us. We couldn't use a large amount of modern technology, like cars and standard computers. Many jobs constructing and repairing our technology would be MUCH harder, less safe, and possible impossible without extensive technological support to do when blind. We would adapt to address these concerns eventually, but if were all struck by blindness at once that's a much bigger problem. We would all be learning how to survive at once, and during that time when were adapting we would be so very very vulnerable. Lives will be lost, many many lives, during this translation where we have to re-learn how to provide for ourselves and build up the technology and infrastructure which does not require sight to use. If all of humanity went blind today I think we could survive, we have tools we can repurpose quickly, and machines already do lots of the hard work for us. We would still suffer significant death toll at first, but we would survive. Once we survived one to two generations we would have modified our technology to be more convenient for blindness and be going well. However, if blindness were to strike at an early time period humanity would suffer far more. We couldn't hunt, or effectively scavenge for meat while blind. We would be very easy prey to predators as well. If blindness struck when we were at the hunter/scavenger phase we would be in big trouble. Our ability to grow crops, or pick fruit from existing plants, wouldn't be nearly as harmed though. Without modern technology we would have difficulty protecting our farms from anything inclined to take what they wanted, but we would have an advantage. Anything small enough to be after our food would be afraid of us due to our size, even if we wouldn't be good at finding them. Anything that would be big enough to hurt or kill us would likely have learned not to mess with humans, since at this point in time we would have been the apex predator. Eventually predators and other animals would 'learn' that humans were blind, but on a species level they wouldn't have evolved to realize this until long after we had time to adjust and create technology and techniques to survive without sight. We also have domesticated animals, which would be a huge advantage. We could still use dogs to tend our sheep flocks to some degree without sight, and given time we could train them to better work for someone who is blind. If we can survive one to two generations were be fine, and a culture and technology will still evolve as always. We will have used our brains and intellect to figure out how to work in a world that is completely blind and have a much higher survival rate once we have figured that out. In fact if we survive just the first few decades in any numbers were fine. Since humanity is proven to be such adapters I would say we will survive, and eventually grow an extensive culture. However, if this happens pre stone age, or before we have agriculture or any technology of our own, we may not survive long enough to adapt. [Answer] If it affected a global population, maybe most people would not survive long-term, but a few would be in lucky situations. Maybe they found a niche like inside dark caves where they could compete, using their brains to set traps and predict prey behavior. Dark caves are not very rich environments for food, so you would have to embellish. What if the global blindness did not only affect humans? Idea: a microbe that destroyed proteins used in vision. The same two (families) are used throughout all animals, though in different ways across major branches. [Answer] The cataclysmic event that you describe may create a society of blind people in the short term, event though as you describe, the event changes the genome of the species so that they will no longer be able to see based on light reception. So assuming that the survivors are still able to reproduce, I think if being able to see by light perception gives a selective advantage to the future generations then it is possible that it will become the dominant trait again. However, the dynamics of how this would play out is rather difficult to predict. Theoretically speaking, many animals rely on other senses rather than sight, and it is not difficult to imagine that given time people might evolve to have more fine-tuned senses that compensate for this. If the selection pressures were such that based on this initial event the people who are able to adapt to living without being able to see (or people who are blind already) then we might expect them to become the dominant minority and so they could help to shape the future society to that which favours the blind. Therefore I would conclude that due to selection pressures being less deterministic than we might think it is, the possibility of a civilization with mostly blind people (some would argue that this is already the case) is just as likely and possibly as one that is not. [Answer] I find it interesting to read this 2015 thread about the possibility of a blind civilization, and in November 2019 Apple introduces the mini-series called "See" based n that very concept. While the mini-series is very entertaining, often intriguing, and sometimes peculiar, it does completely skip over the whole "farming, hunting, gathering of food" which as one person stated in the thread above would be vital. ]
[Question] [ There is a common sci-fi trope, that if there is a war in space, you should have planetary defense in place to protect you from intruders from space. But: is it plausible? Let's give you this scenario: There is a second Earth (Earth B) which is currently at the same level of technological development as we are now. Earth B does not like having our similarly advanced civilization near them, so they want to attack us. For a while now, they have been spending all their money and science in order to attack us. Earth B is in a similar position to Mars, so given current tech, it will take them about half a year to approach us. We, Earth A, know that they will have to stay in orbit for at least a day before they can come down and start attacking us. Their type of attack will be: Gather forces on orbit, land and attack us on the ground. So no orbital bombarding Given that everyone is willing and wanting to cooperate with planetary defense system, what would be good ideas to protect us from the attack from space? Is it planetary defense? Or is it actually better to wait for them to come down? [Answer] I would definitely place my bet on Earth B because we are human and they are inhuman. Assuming both parties do not have any technological and biological advantage over each other and the inhabitant of Earth B had already parked their space-readied rubbish truck next to our moon landing site and vandalized the flag already. I believe depending on the threat level posed by our neighbor we can take necessary counter-measures to defend Earth A. (wait since when did the name changed?) Threat Levels and Countermeasures of a effectively planetary defense system: Level 0 - Inhabitant of Earth B uses radio wave signals to spam us Counter 0 - Reciprocate ...... Level 1 - Our earth bound and deep space telescopes detected UFO travelling at a fast velocity heading toward us in tight formation and spell "Earth A sucks" on our radar screen. Counter 1 - Firstly we need to find out their intention by hailing them the Star Trek style and find out the type of propulsion mechanism their vessels used for the entire journey. (is it a one-way trip like a homing missile) Secondly we can intercept them mid-space with our trump card... the space junks good luck to them trying to stay in one piece. Thirdly we must establish a committee on Earth and reveal our top secrets weapons between countries... united we stand. ...... Level 2 - The UFO are within hours away from us and they are most probably launching projectiles in our direction. Counter 2 - The committee on Earth A must be saying something like this "why aren't we the attacker and where the hell are Mars and Curiosity?". We need to consider if their projectiles are capable of penetrating the Earth A several layers of atmosphere, most crucial is what will happens if the content inside the projectile is dispersed in our atmosphere will it spread and block out the sunlight and cut off potential energy supply and turn our weather against us. We must deploy rockets to intercept them to mitigate the impact caused to Earth A. ...... Level 3 - Dogfight Counter 3 - Hopefully only a insignificant amount of UFO managed to get past our defense by now and they are turning tails. Suppose in the worst case scenario these aliens penetrated our atmosphere and I believe they must be targeting our power source and supplies first. Most of us on Earth A will be located underground to seek shelter from nuclear holocaust, else we will most likely engage in a awe-inspiring dogfight ever in the history of mankind. ...... Level 4 - Land Invasion a.k.a catfight Counter 4 - where are our storm troopers? our choices are scarce but not limited, our weapons should have not problem granting the alien death wish. Most probably we must drag the invasion as long as our resources last so using guerrilla tactics if we are outgunned (I remember you mentioned they are only as advanced as us therefore just deploy the seal teams or drones in covert mission to sabotage their ration and power source) I don't recommend using biological weapon even though they may be inhuman. Once they are wipe out we must send fleets to harass them on their planet and force them into negotiation, else the future of mankind and alien alike will be less promising. ...... Level 5 - Planetary Destruction eminent Counter 5 - [fall silent] Verdict: Planetary defense is absolutely fun to ensure the survival our species, so pass the bill already! [Answer] I see no reason not to start shooting when they get in range. Why give them the initiative? I do not think there has been a war in history where the defender said "awww, don't shoot them while they are still in the transport, that's not fair." (If there was such a war, the defenders probably lost, because they were idiots) Honestly, why even wait until they get into orbit? Start launching guided missiles as soon as you detect them heading your way. Any kind of hit is going to take a transport out of commission. If they're flying close together, the debris might even take out more. And you'll have plenty of time to work on other defenses while they close in. In order of defense, I would expect this: 1) Long range bombardment while the transports are still in space. Probably few hits, but any hit counts. And you have plenty of time anyway 2) Bombardment while the ships are in orbit; preferable from space based platforms. Everything you launch from ground to orbit has to fight against gravity, but once you are in orbit, cannons will work just fine. 3) Ground to air bombardment when they try to land. At this point the ships will be effectively unable to divert from their course, so it's shooting sitting ducks. 4) If anyone is still alive at this point (they must've sent a lot of attackers), this is where you send in the aircraft and carpet bomb the crap out of any landing zones. It should be a piece of cake to determine where the ships came down and your bombers should be already in the air. Any artillery in range can also open fire, of course. 5) I doubt any attackers are still interested in fighting at this point, but if so, now is the time to do actual ground combat. [Answer] It is definitely a better idea to attack them in space. And the reason is simple: Each of their ships will hold several (most likely hundreds or thousands of) soldiers. You can neutralize each of these groups with a single hit. It does not even need to be a good hit, it is enough to damage the ship badly enough to prevent it from entering the atmosphere. Once they are landed, you have a larger number of smaller targets. Plus, on the ground they have additional options, like taking cover, evasive actions, they will be able to breathe without technical assistance, and all that. So: "convince" them to abort their attacks while they are easy targets. A few well aimed missiles while they approach, some more while they prepare for descent, and the rest should not be much of a threat any more. [Answer] You start with the sci-fi trope idea of planetary defenses, but then you restrict the problem immensely. I doubt you'll get meaningful answers for "is it plausible[having planetary defenses]?" In sci-fi that has planetary defenses, the reason is due to FTL travel capabilities - usually justified through warp drives, sub space, hyper space, etc. The problem with such spaceships in such sci-fi is that it usually comes with the caveat that you can't attack someone in hyper space, sub space, etc. That is to say, you can't have solar-system level defenses(missiles, rail guns, nukes, space mines, etc) that can destroy enemies before they show up on your doorstep. They just pop out of FTL in orbit around your planet. That is why you need planetary defenses in those pieces of sci-fi(typically, this is very generalized of course). You need planetary defenses when your enemy is able to transport a formidable military presence to your planet. But you restrict your problem to sub-light speeds...not even relativistic speeds...I don't know how fast we travel to Mars but I think it's somewhere around 20,000-40,000 mph....not very fast at all. You also require meatbags to be in the payload. If Earth B is interested in wiping out intelligent life on Earth A, and Earth B is in a higher orbital than Earth A, then the simplest approach is to de-orbit tons and tons of 'stuff' into Earth A's orbital. With our current tech, NASA is already planning to move a 4 meter asteroid into lunar orbit. Earth B, given the same tech, could move a much larger asteroid and just try to ensure it impacts Earth A. Earth A might be able to nuke an asteroid or two - if they even detect them, which is not guaranteed with current tech - so you just throw a couple hundred down at them. By moving down in orbit, these asteroids are effectively converting potential energy to kinetic energy just like a ball falling off of a table. Earth A would have no hope of stopping these things...and they would cause impacts far more powerful than nuclear weapons. The problem with current tech space-wars as you've defined is that establishing a beach head on another planet is almost impossible with what we have available to us. You're going to expend a huge amount of your GDP just building the rockets, fuel, and containers to carry your meatbag soldiers, and getting them in orbit around another planet. Then you have to not die while in transit and while in orbit, then land on a teeny tiny chunk of land, and start killing billions of Earth A natives on their home field with a force that's likely in the thousands or millions at best. There's no hope for victory in that kind of scenario...literally impossible. Earth B would lose even if Earth A didn't have planetary defenses, because Earth A could carpet bomb Earth B's landing site(s). It actually makes things easy for Earth A because there's no ethical/moral dilemma to wiping out the entire enemy population - they're all soldiers...no civilians whatsoever...blow the whole thing up. Given current tech there's no way Earth B has also transported anti-air, tanks, helicopters, fighter jets, etc - those things are way too heavy - so they have no way of obtaining or maintaining air superiority. The only thing they'll have(given your spec) is infantry. It would be a massacre. [Answer] With anything remotely resembling current technology (i.e. rocket-based propulsion), their attack is doomed almost no matter what the defenders do. They simply would not be able to transport enough troops and weapons to fight a war once they got here. Their best bet would be to bring a load of Earth-Bian bacteria and viruses and hope to start a pandemic. But regarding planetary defense, we already have all the weapons we would need to destroy them. The first line of defense would be launching weapons at them during their transit. We already have the ability to send several tons of equipment (orbiters and rovers) all the way to Mars. That means that we have the capability to send weapons to intercept them. A ship trying to fly between planets using rockets has very little ability to maneuver because any attempt to evade will mess up its trajectory making them risk missing their orbit and flying right past the Earth. The second line of defense would be while they were in orbit. If their orbit was very high, this would be a poor place to engage because large rockets would be needed and their maneuvering capability would be much greater than during their transit phase. But if they are in a low-orbit that brings much [smaller, cheaper and more numerous missiles into play](http://en.wikipedia.org/wiki/Anti-satellite_weapon). China has successfully destroyed a satellite with a missile launched from a ground vehicle, while the US has destroyed them with air and naval launched missiles. The third line of defense would be while they were landing. Current technology requires that a vehicle de-orbiting lands with quite slow speed. This is generally accomplished through the use of parachutes. It would be trivial for regular air defense (fighters and land and sea based missiles) to shoot down these craft. If they want to come in faster, they would require the use of a shuttle-like landing craft. They would still be within the normal speed range of aircraft, though, which means that air defenses would still be effective against them. Additionally, an aerodynamic landing vehicle would likely force them to try and land at an existing airport, making post-landing defense easier. The final line of defense would be once they landed. Even if the defenders chose to completely forgo attacking them until now, they would still have little trouble defeating them. With current technology getting 1000 soldiers and small arms to another planet would be a huge accomplishment. By comparison, the [combined militaries of the world](http://www.globalfirepower.com/) have millions of soldiers, tens of thousands of tanks, artillery pieces and aircraft, tens of millions of police, reservists and paramilitaries, local knowledge and great intelligence provided by the billions of civilians, and a huge logistical base. In short, a near-current tech civilization wouldn't stand a chance at an interplanetary attack unless they came up with some breakthrough propulsion system, or were willing to resort to orbital bombardment. And even then it would be extremely difficult. [Answer] Main problem I see is that we don't know where they would land, so we can't entrench, set up an ambush or concentrate our forces. I guess at worst they'd stay in orbit, rapidly spinning around earth until they decide to enter in the last spin before the point of no return to give us the least time to react. They could also try to spread, but that would give us the advantage of not needing as many forces in a single location. Their orbiting ships would have a lot of extra features to help with their space attack. They would be able to go into space (airtight) and to descend into orbit (either a lot of fuel or good heat shields). This is going to make the ships fairly expensive, not too maneuverable and limited firepower compared to simple jet fighters. So just having low atmosphere air superiority should be enough to take them out. It's not insanely hard to build that up rather quickly (if we all work together we might already have enough) and we'd spend significantly less resources than they would. We could have bombers and ground troops as backup should some of their ships manage to land (goal is to avoid this). It would be mainly an organizational issue of making sure the fighters can be at the correct place at the correct time. I have no clue how fast they could potentially land. This would dictate how we'd have to spread our forces for maximum coverage. We can allow for somewhat more risk for barren places or deserted places like the Sahara. We only need to make sure to arrive there with bombers just as they're landing (before they've had time to set up decent air defenses). I'm also very in favor salvaging the wreckage. This way we start out with extra resources for fending of the next attack or a counterstrike. [Answer] Ok, if we're assuming they would NOT fire cluster-nuclear bombs from space and totally wipe the planet clean... hmmmm... I think it would make more sense to have planetary defense. You could just fire smart missiles from the ground into space and they could seek out ships and take them out before anyone had to deal with anything on the ground. The ships would burn up in the atmosphere. No collateral damage. If you wait for them to get on the ground there'd be explosions and gunfire. Civilians would get hurt; infrastructure would be damaged; resources would be damaged or stolen; people would be unhappy. [Answer] The other answers have already explained why it would be easier and better to take them out while they are still in space. However, I would like to point out that the best place to station your planetary defenses would be not on the surface but in satellites in orbit. 1. Any rockets launched from the ground would need to leave the atmosphere and enter orbit, which requires quite a lot of fuel. A rocket launched from an orbital platform could have a much higher payload. 2. Any direct-energy weapons (lasers, masers etc.) or kinetic weapons would have to pass through the atmosphere first, which would cause refraction and dissipation. When fired from orbit, these weapons would have a much higher efficiency and precision. 3. When using beam- or kinetic weapons, a ground station needs an unobstructed line of fire, which means that each ground-station has 12 hours each day during which it is on the wrong side of the planet. Also, the aforementioned problems caused by the atmosphere would be worse when the target is low above the horizon, so it only has its peak efficiency once every 24 hours. A satellite, on the other hand, would either be on a low orbit with a lot shorter periods of being usable and unusable, or on a high orbit where the planet blocks a lot less of its field of fire. 4. Satellites have a chance to evade incomming kinetic weapons through changing their trajectory. This could also help against beam weapons when those weapons require several seconds of constant exposure to do damage and are fired from several light-seconds away. Ground bases, on the other hand, are sitting ducks. There is, however, one argument for ground-based defenses: They can be concealed. An orbital weapon platform is impossible to hide and would be the first target when launching a surprise attack. But a ground base can be placed underground where it is protected and hard to detect until used. Also, the atmosphere does not just acts as an obstacle to them, but also to the enemy who try to take them out from orbit. [Answer] `Is it planetary defense? Or is it actually better to wait for them to come down?` Planet defense is better. Too many risks and collateral damage if they land, and predicting the enemy's LZ may not be possible until the last minute (though you could be computing their trajectories with RADAR or something). And if possible a counter attack should be prepared. `what would be good ideas to protect us from the attack from space?` * An array of satellites with solar-powered space lasers (and/or ion cannons, but they could shield against this). Throw a new 'targeting' lens on the Hubble Space Telescope and turn it into a super-space-laser focusing device. * Send up rockets full of daycare kids with runny noses, kamikaze style, to crash through their hulls and infect them with our viruses, War of the Worlds style. (Or pretend to be their friend and offer a gift of smallpox blankets.) * Repurpose the [Star Wars project](http://en.wikipedia.org/wiki/Strategic_Defense_Initiative) like they did in the 1979 film [Meteor](http://en.wikipedia.org/wiki/Meteor_%28film%29) * Create a defensive 'net' of explosive-laced satellites with proximity friend-or-foe detectors; a space minefield. * Retrofit rockets and the international space station with armaments from fighters, bombers, and gunships. (Orbital defense fleet) * Avoid large scale nuclear weapons detonating in proximity to the Earth's atmosphere, but we could possibly develop smaller tactical nukes. You only need to disable one of the following systems: navigation, engine, or life support. * Have AA guns and typical surface-to-air defenses ready to blast any large debris that may cause collateral damage. * Introduce them to alcohol and legal marijuana. Maybe they don't have recreational drugs on their planet which is why they are being such uptight \\\holes. Share our love of Jesus Chris and the Book of Mormon with them; perhaps we can persuade them to a path of peace. Avoidance If at all possible, avoid conflict. It is arguably in our best interests not to wipe each other out, but to work together and share technology so that we can ultimately leave our solar system to colonize other systems since we know that our Sun has a finite lifespan. A political approach should be attempted, and some compromise reached. [Answer] I concur with all the rest of these answers that the best option is to attack while they are still in orbit, but would like to add an extra reason why. Planetary defense is not always ideal, or even workable (space being really big and all), but in this case it is actually pretty easy. Per your description, the invading force is near modern tech levels. This makes preventing an orbital landing painfully easy. Re-entry is freaking dangerous, and without more advanced technology (like some kind of deflector screen) they are reliant on the same heat shielding that we use when entering the atmosphere. A piece of foam striking the heat shielding on the wing of the Space Shuttle Columbia was all it took to compromise the craft such that it broke up and burned on re-entry. I assume an invading force would have thicker heat shields, but it would still be comparatively fragile. You don't have to hit them hard enough to destroy their ships, just compromise their heat shields and re-entry mechanics will do the rest. Simply put, re-entry unleashes absurd amounts of energy onto your ship as you slam into the atmosphere at orbital speeds. Without an intact heat shield, all that energy goes into the ship. Boom, Shred, Burn. You get small bits of shrapnel falling to Earth instead of a landing army. [Answer] It is definitely a planetary defense situation: * I think it's a fairly bad idea to Nuke them because of radiation fallout in our own atmosphere. If it's done beyond Lunar Orbit, then we have a fair chance of avoiding nuclear fallout on Earth and our atmosphere. * Since it's said that Earth B is roughly in same place as Mars, I think we can use brighter sun at Earth A to our advantage. Such as using Large mirrors placed in stationary point around earth, perhaps in L2 position to take advantage of large amount of solar radiation and concentrating in a very narrow beam to possibly melt the incoming ships. Given our current technology and similar development of Earth B the ships wouldn't be made of a very thick material with a high melting point like Tungsten but rather something light like carbon fiber or perhaps Aluminum, which can surely be compromised using a very very focused solar beam, or using this energy to generate a high energy Laser beam (theoretically possible, look at [Boeing YAL-1](http://en.wikipedia.org/wiki/Boeing_YAL-1)) * It's fairly straight-forward to assume that if you breach their spaceships then the occupants won't survive for too long, so with sufficient number of solar concentrators we can fend off any invasion far before they reach any closer to earth. * In any case, I think any alien species would be stupid to attack Earth A in person (and thus deserve to die to be brutally honest) The smarter approach would be to send biological/chemical agents and disperse them in target planet's atmosphere with the help of small probes which will completely burn up at about 1000 meter above surface and then disperse the contents into atmosphere. If the probes are comparatively small, then they would be too small to detect by telescopes until they have entered our atmosphere and started burning, at which point we won't be able to do anything at all. Plus given usually high number of small meteoroids hitting Earth surface, we will most likely ignore them. Although this will certainly make the planet inhospitable until you sterile entire atmosphere of your dispersed agents, a really tall order to perform with our current state of technology ]
[Question] [ Is it possible for a planet's moon to always rise at the same time of the night? And in this way be used as a timekeeping device? What if there are two moons? [Answer] It wouldn't qualify as a "moon" per se, but an object placed in the [L2, L4, or L5 points](https://en.wikipedia.org/wiki/Lagrangian_point) of the planet/sun system would remain in a stationary position relative to the sun (L1 and L3 would also be stationary, but not visible). An object in L2 wouldn't be stable in a multi-body planetary system (it would drift away in a matter of months), which leaves L4 and L5. What would an object in L4 look like? According to [the Astronomy StackExchange](https://astronomy.stackexchange.com/questions/3595/is-there-a-ceiling-for-stable-l4-or-l5-masses/3617#3617), the limit on mass is about 10% that of the planet, so for an Earth-like planet, it would be about 10 times that of the Moon, roughly that of Mars. To an observer, it would have an angular diameter of 5 seconds of arc, slightly larger than that of Uranus, or of Mars at its furthest, and would be roughly second magnitude in brightness. Would it be useful for timekeeping? For a pre-technological society, certainly. It's one of the brightest objects in the sky, and it rises or sets within a few minutes of the same time every night (give or take planetary axial tilt). Could you have two of them? Yes, one in L4 and one in L5. You would probably need to make them smaller than the maximum, to keep them from interfering with each other's stability, but a pair of Moon-sized objects (third-magnitude or so in brightness) would be quite reasonable. [Answer] In order for this to be possible, the moon would have to be in the same place relative to the planet and the star throughout the day - in other words, if you drew a line from the center of the star through the center of the planet, then drew a line from the center of the planet through the center of the moon, you would have two lines that intersected at an angle that is forever constant. For those who got past that first ~~paragraph~~ sentence, there are two places that would work: [the Lagrangian points $L\_1$ and $L\_2$](https://en.wikipedia.org/wiki/Lagrangian_point). The five Lagrangian points are laid out like [this](https://upload.wikimedia.org/wikipedia/commons/5/5f/Lagrangian_points_equipotential.jpg): [![Lagrangian points](https://i.stack.imgur.com/LWDds.jpg)](https://i.stack.imgur.com/zax2d.jpg) The "holes" and overall shape of space here is an analogy for gravity wells, so ignore that, but treat the green lines connecting the star, planet and points as rigid - in other words, as the planet revolves around the star, the green lines rotate with it, as do the Lagrangian points. $L\_1$ and $L\_2$ will satisfy your scenario. However, $L\_1$ should be discarded because putting the moon there would make it only appear in the daytime! So we'll take $L\_2$. The problem is that the only stable Lagrangian points are $L\_4$ and $L\_5$ notice how the others are near the metaphorical depressions of space. This indicates that if an object at them shifts, it will move away. For $L\_4$ and $L\_5$, the object will merely return. To stay at $L\_1$ or $L\_2$, [stationkeeping](https://en.wikipedia.org/wiki/Orbital_station-keeping) is required. So you'd have to attach thrusters to your moon to keep it in the same place! Alternatively, put it in a [Lissajous orbit](https://en.wikipedia.org/wiki/Lissajous_orbit). You'll still need some thrusters, but it should be stable. [Here's](https://upload.wikimedia.org/wikipedia/commons/e/e6/Lissajous_orbit_l2.jpg) what the orbit will look like: ![Lissajous orbit](https://i.stack.imgur.com/zax2d.jpg) This kind of orbit would be very tough - if not impossible - to put a very massive object in. Two moons would make this job nearly impossible, because if they were near each other, they'd most likely perturb each other's orbits and ruin any stability. Your odds of getting this to work for one moon are slim to none; your odds for two moons are slightly worse. Or you can use a little handwavium to solve all your technical difficulties! [Answer] A moon whose orbital period is half a day would appear to observers on the ground to go around in a day, rising in the west. Phobos is a more extreme example: its period is less than a third of a day, so it rises in the west twice a day. ]
[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. Some time ago, aliens placed the Moon around Earth with every intent to deceive us about its authenticity, except for the glaring synchronization that allows for total solar eclipses, as something like a practical joke. What indirect evidence do we have that places the Moon's age as far back as possible? "Indirect" as in data points not originating from the Moon itself, e.g., radiometric dating of Moon rocks. The aliens have never tampered with Earth, only everything about the Moon (its make-up, surface topography, orbital path, etc.) meaning any lunar influences found on Earth are legit. The aliens ceased all tampering 2 million years ago. The Moon is as it appears to be: a big old rock — just made to fool. There's a greater lore reason, it's just not important here. Essentially, I'm trying to place the Moon's insertion on a timeline in my world (which helps inform the period of other events), and because nothing about the Moon can be trusted as a chronological indicator, only evidence of the Moon's presence found on Earth (or elsewhere in the solar system, too, I suppose, if any exist) can be credited. --- All this of course means that the [protoplanetary collision with Theia](https://en.wikipedia.org/wiki/Giant-impact_hypothesis) didn't happen, and everything that hypothetical event precipitated is explained elsehow. (Unless it can't be, in which case that counts as evidence of the Moon (aw shucks), but then you'd've also proven the Theia hypothesis beyond doubt so what are you even doing here?) [Answer] If you want to get really weird (and in fact avoid using any material that came from the Moon), you can try sediment analysis. I went to a talk on this a few months ago, where the speaker discussed how studying the history of sediment stratification can actually allow us to map changes in the Moon's orbit over time (implicitly showing that the Moon existed far in the past). The logic is that the Moon plays a role in a couple periodic changes in Earth's orbit that 1) play out over timescales of tens and hundreds of thousands of years, and 2) are stable over hundreds of millions of years. Through complex processes, these changes affect sediment deposition rates; by measuring changes in those rates, you can see the fingerprints of the Moon's influence. One of the more recent papers on this is [Meyers & Malinverno 2018](https://ui.adsabs.harvard.edu/abs/2018PNAS..115.6363M/abstract), who studied the 1.4-billion-year-old Xiamaling Formation. The most extreme studies I'm aware of actually probed as far back as ~2.5 billion years ago ([Walker & Zahnle 1986](https://ui.adsabs.harvard.edu/abs/1986Natur.320..600W/abstract), [Williams 2000](https://ui.adsabs.harvard.edu/abs/2000RvGeo..38...37W/abstract). You could argue that perhaps the Moon isn't responsible for these changes. Perhaps the scientists could get adequate fits to their data if they used models involving no influence from the Moon whatsoever. On the other hand, the only folks who would know this for sure are the teams who did the work (but if you ask them, let me know!). ]
[Question] [ I noticed that when it comes to the idea of humans going extinct, and how human civilization could be detected by future civilizations, a lot of the ideas for how human civilization could be detected seem focused on things like finding the ruins of buildings, or finding other non living objects made by humans. Humans have also moved animals and plants from continent to continent both intentionally and unintentionally. I was thinking that if some of these animals survived on the continents they were introduced to for millions of years they could leave a trace in the fossil record, and was wondering if a future civilization could work out that their movement was unnatural, and so figure out that there was another intelligent life form before even in the absence of other evidence. [Answer] It is much more likely, unfortunately, that the oddities in animal and plant distribution caused by human introduction of species to odd locations would simply prevent an analogue to the Theory of Evolution from ever arising. Our own evolutionary theories were discovered because of very specific sets of evidence arranged in very specific ways. And the theory was attacked when it was introduced, and if the evidence for it had not been very strong, it probably would have been discarded and forgotten. By putting modern species into a blender and whirring it up, as it were, mankind has probably muddied the waters considerably for a repeat of that process, if it ever were to become necessary. So future generations might not be able to use the fossil record to figure out that a world civilization existed, because our actions would have made the fossil record less scientifically significant to those future generations. We've also probably placed similar obstacles in the way of the re-discovery of plate tectonics. [Answer] I doubt it. After millions of years, most traces of humanity would have degraded to the point where it would be difficult to identify them as manmade. For example, many stone tools are hard to identify by untrained eyes as manmade. (Arrowheads being a notable counter example.) Metals will have corroded and been transported by water into new forms and locations. There will have been significant erosion moving dirt on top of much of the waste. Without the assumption that intelligent life existed prior, it might be very difficult to come to the conclusion that it existed. Extraordinary ideas need extraordinary proof, and it might be difficult to find proof that humanity was intelligent. So, the existence of animals on one continent might be taken as a common ancestor walked over some land bridge but the fossils of that common ancestor haven't been found. Or similar forms may have evolved multiple times in multiple places. Plants might have had convergent evolution. These explanations all fit with observed patterns. [Answer] What time scale are these events happening on? You talk of Human society collapsing and another developing in its stead, but this sort of this doesn't happen over night. So: * Possibility one: this happens over a short-ish time scale. Say in a few thousand years, some species of animals start to develop higher thinking patterns and establish societies based on transmission of knowledge (most likely primates, but one could imagine other mammals or even octopodes). In this case, there will still be many traces left of human presence through inorganic traces left behind: plastics, concrete, and metal all shaped and worked into tools and buildings. They will most likely be very degraded, but still very much identifiable as being traces of an extinct civilised species. If so, the evidence of Human activity through the displacement and modification of other species is a mute point, seeing as it is not needed to infer their existence. It might be noticed, but would also most often correlate with the other vestiges found, for example by finding exotic skeletons in zoos and aquariums, or large gatherings of cattle and poultry remains next to farming equipment. * Possibility two: this happens over a long time scale. Over the next few million year, evolution takes its course, new species evolve and one is (un)lucky enough to develop higher thought patterns and form a society. In this case, it is entirely possible that the vast majority of Human "artifacts" would have degraded or been destroyed by naturally occurring phenomena. But over these millions of years, the species that humans transported and modified throughout the world have also had time to evolve into whole new species. Perhaps some die out (I'm looking at you chihuahuas), perhaps some find a new ecological niche to adapt to, but they will all be very different to what we know today. If the new society develops a penchant for genetics and studies all these species, they might observe some weird divergences in the similarity of some species, and perhaps the theory of a prior civilisation would emerge, but I doubt it would be enough proof alone to certify that this is the case. (Source: I am trained in biology and currently work in analysing genomic data) [Answer] ## Radiations... On a very long-time scale, the only remaining trace of mankind will be the nuclear wastes radiations. [Some researches](https://www.bbc.com/future/article/20200731-how-to-build-a-nuclear-warning-for-10000-years-time) are even currently being run on that subject in order to found a way to prevent future civilizations to dig them up‚Ä¶ Including some patterns in wastes placement to make the nuclear landfill itself a message. If a previous civilization relying on nuclear energy produced huge number of wastes over a very long time and decided to create a unique giant landfill, radiations may become noticable (even on surface) on that place and animals may avoid this area over generations‚Ä¶ If a patterned-solution to warn next generations had been chose (imagine a spiral-shaped nuclear landfill of 50 km2 for example) you may then observe strange repartition of fauna on the area... ## EDIT To give some credits to the fact that wildlife can be affected by radioactivity, see below citation about Chernobyl and studies links ([first](https://academic.oup.com/jhered/article/105/5/704/2961808) and [second](https://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02074.x)) > > birds and mammals at Chernobyl have cataracts in their eyes and smaller brains. [...] many of the birds have malformed sperm. In the most radioactive areas, up to 40 percent of male birds are completely sterile, with no sperm or just a few dead sperm in their reproductive tracts during the breeding season. Tumors, presumably cancerous, are obvious on some birds in high-radiation areas. - [theconversation.com](https://theconversation.com/at-chernobyl-and-fukushima-radioactivity-has-seriously-harmed-wildlife-57030) > > > [Answer] On a smaller scale, I believe this has happened; I recall reading about a botanist that noticed certain fruit plants were found in long trails, and showed that these trails corresponded to ancient "circuits" of hunter-gatherers, that probably gathered and carried the food plants with them to eat along the way, and pooped out the seeds along the trail. One might see a similar thing in the fossil record. A concentration of many fossils in a particular area of origin, that are exclusive to a time period before say 5000 BC, followed by a growing diaspora of scattered fossils after that period. We can tell by various means when fossils were laid down, when animals migrated, etc. Even delicate plants fossilize, we have many fern fossils from tens of millions of years ago. That would indicate unnatural transportation. I mean, squash a zoo (somehow), fossilize the animals, and it is hard to devise a non-intentional explanation for why so many different animals that originated all over the world happen to be in the same place in well ordered and distinct locations, in such small numbers (a handful each of tigers, giraffes, hippos, elephants, seals, etc.) Eventually the hypothesis would have to be artificial transportation of the species. The key here (as you seem to intuit) is time and fossil dating: A concentration of something for many millennia, followed by a near instantaneous spread, but in very thin numbers, to other continents and places, such that it is nearly impossible for that to be a natural migration; the only plausible explanation is an assisted migration, which means an intelligent entity capable of transporting the animals (or plants) long distances is responsible. [Answer] ## They will know "something" happened, but not necessarily intelligent life The fossil record will show both a massive redistribution of species and a massive extinction level event. The geological records will also show a massive spike in atmospheric carbon, lead, and all sorts of other anomalies. It will be clear that something "really bad" happened at this time in the Earth's history, but it may not be clear that this mass extinction level event was intelligent life. A much more likely explanation would be that there was some kind of massive impact similar to the Chicxulub impact. Such an impact could burn away the planet's forests, pump massive amounts of carbon and other unusual stuff into the air blocking out the sun and cause an ice age that would allow life to migrate all over the place over new temporary land bridges. Explain enough stuff with what you believe to be true about asteroid impacts, then you can use all the other unexplainable stuff to change your model on what a giant asteroid impact can do. It's also possible that your intelligent species will not follow the same line of technology as us; so, things that we've done to the environment wont necessarily be the same as what they will do to it. So while we've dumped tons of lead and radioactive waste into the air as part of our technological chain, thier civilization may have never used tetraethyllead fuel additives or nuclear reactors; so, when they see our layer with a bunch of lead and radioactive waist, they might rule out intelligent life believing that no intelligent species would pollute the world in that way. Inversely, thier civilization may mass produce a different pollutant that would be missing from our time period. [Answer] Humans as intelligent life form First of all, the future civilization has to distinguish between humans (as intelligent life form) and animals. Only then they can think that humans transported animals and plants. But if there are fossils of humans, apes, chimpanzees, gorillas and other animals, how will they find out which was the intelligent life form or who spreads who. They will find ships wrecks or airplane wrecks and know that these were used to travel to other continents and may be they assume that all the life forms spread from one place to other but 'from where to where?' or 'who did this?' may not be known. I remember a story by Arthur C. Clarke, in which, all life form is finished on earth. Some aliens come and find a plastic strip with pictures. They consider it as the life form living on earth but they could not read words written at the end "Walt Disney Productions", "Mickey Mouse". [Answer] For a species to realise that they were not the first civilisation, but came after humans, you would need a long timescale, because a lot of our ruins and remains will stay for an enormous period of time, and will be a definite giveaway. What will most likely give that our society existed and was civilised will mostly be the climate record, in which future scientists will see that the climate changed in an extremely rapid way within about 300 years give or take. And add on top of that evidence that there was a huge extinction event. [Answer] The most striking evidence for our current existence even into the very distant future (many millions though possibly not billions of years) would be our mining activities. We have simply fundamentally changed the distribution of mineral resources in the Earth's near-surface volume. And it might not be often but I suspect some worked products (glass in particular) will survive in enough locations in great enough quantity that it will be unmistakable that no natural process created them. ]
[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/174711/edit). Closed 3 years ago. [Improve this question](/posts/174711/edit) Suppose we have an interstellar generation ship, with an initial population of about 10,000 and a final population (on arrival) of about 20,000. Since they're traveling for sixty-some-odd years, people will need to have jobs. It's a space ship though, so there are no raw materials to extract; without new raw materials, industrial production is limited. Traditional farming is likewise off the table. Everything is a closed loop, by necessity. There is a limited military-style hierarchy, the ship's operations crew and command structure, but the vast majority of people on the ship would be civilians. Contact with Earth and the rest of the Sol system is severely limited. So the question is: how are they compensated? By who? And how, in general, does this economy work? EDIT for clarification: I do not mean 'economy' in the sense of 'capitalism', or even 'money', but in the sense of 'creation and distribution of goods and services'. Capitalism is one option. Socialism is also an economy. Command economy, barter system, gift-giving, these are all economic systems. The ship has people, and people need things (like food), ergo the things must be distributed to the people. Thus, there is by definition some sort of micro-economy. I'm just trying to figure out what it will look like. [Answer] This generation ship will look somewhat similar to a cruise ship. Smaller part of population is the crew. Its duty is to maintain and pilot the ship. Larger part of population are passengers. They don't need to have any duty, but they should be ready to fill a vacancy in crew ranks. As far as economy goes, there are 3 options: 1. Communism. Or, more precisely, fully commanded economy. All jobs are provided by ship's command. All lodging and services are free, but rationed according to present situation. Money, if exist at all, are only supplemental - one can't buy, for example, a better berth for any kind of money. 2. Socialism. Some jobs are provided by the command, others are for people to create. All basic necessities are free, but all luxury goods and services cost money. Lodging is still owned and maintained by the command, but one can upgrade to a first class stateroom for extra money. 3. Capitalism. Few jobs are provided by the command, while most non-essential ship services are run by the people. Lodging is owned by people and rent prices are market-based. For the poorest ones, command provides a subsidy, but some still end up living in ship's common areas. [Answer] There are two types of people on a colony ship (as you describe it): * People who expect to die before they arrive and colonize * People who are expected to live until colonization date These two groups of people should have only two goals (assuming survival is easy): 1. Raise their children to be good parents (Primarily for those who will die) 2. Prepare for colonization tasks with education and training (For those who will colonize) These facts being as they are, I don't think your ship will have a "traditional economy" with jobs that produce money people need to survive. Are you going to let people starve? No. Are you going to throw people out of airlocks because there are no jobs for them? No. As such, I think all the "jobs" that aren't directly related to keeping the ship running and people alive and fed will somehow revolve around the two goals or be artistic/hobbies in nature. People who will die before arrival would focus on having children and raising those children (and the ship's children in general) to be capable colonists. In this, they'll primarily train their kids to be good people (generous, kind, empathetic, etc) and good team players over "hard skills" like how to be a doctor or how to construct a cabin because those skills will only be useful post colonization. For example, a colonist born early on could be in their late 50's by the time they set foot on solid ground. For that person, being liked by the other passengers, understanding them, and trusting them for when an inevitable time of crisis comes is much more important than being able to sow a field or build a cellar. Those things can be trained a couple years before landing. Other than education and child-rearing, passengers could also focus on preparing for colonization. 10-20k people is enough intellectual capital to do things like write software, make plans, or design equipment along with planning for any event that could possibly happen. With 60 years and thousands of idle minds, a lot of thinking can get done. [Answer] Operations, education, and science You could make your economy as loosely or tightly controlled as you want. Want to create a libertarian paradise? Go for it. Want a carefully planned economy? You're the author. Here are my thoughts, but you have a lot of freedom here. Think of your generation ship as a city. What jobs do people have in a city? Sure this isn't a traditional city, but there's a lot to do. If you've ever been aboard a Navy ship (especially an aircraft carrier), you'll see people doing all sorts of mundane tasks. Cleaning, cooking, cleaning, painting, cleaning, etc. (The Navy really likes to keep things clean.) Check out [this list of Navy ratings](https://en.wikipedia.org/wiki/List_of_United_States_Navy_ratings). Plenty of those roles would be necessary on your ship and could be filled by civilians. Construction, medicine, personnel, logistics, religious leadership, etc. You could create a pay scale like [the US government uses for civilians](https://www.opm.gov/policy-data-oversight/pay-leave/salaries-wages/salary-tables/20Tables/html/DCB.aspx) where each person has a specific rank that carries a specific salary. In a city of that size, there's even room for some entrepreneurship. Beyond the day-to-day operations, remember the mission of your ship. Education should be a major component of daily life. There's a lot to do once the ship lands. You'll need an education system that covers everything from preschool to PhD. Every settler should know about the destination planet, science, reading, writing, etc. Even the first generation of passengers should learn all of these things so they can better teach their children. Is this the first time people have ever traveled this far from home? If so, they'll need to conduct scientific research while underway. Compare this part to the International Space Station, which is primarily a science mission. Here's [how the they spend their time](https://www.nasa.gov/mission_pages/station/research/experiments/explorer/search.html?#q=&i=&p=&c=&g=Investigation). [Answer] You'd want to encourage these people to actually be contributing to the mini society, especially when you start relying on the second/third generations to actually do some of the work. But if it only takes 10,000 people to run the ship to start off with and you are only growing a small percentage of the overall food intake, what are the extra 10,000 going to be doing? I guess a percentage of those would be still in education or retired by this point, but still, that's a lot of people doing not doing a lot. I'd expect more people to be in higher education or learning skills that would be beneficial on destination planet. I doubt a generational ship would have a great deal of 'extras' to buy or to use as compensation. I mean given that if something goes wrong with the ship these people are fairly screwed, would you prefer to send a couple of extra tons of fuel/spare parts or cupcakes? I think everyone would have to start with some basic necessities, a bed, three meals a day, clothes, etc. regardless of whether they work or not. It may also be beneficial to have a way of penalising people for crime/incompetence that doesn't involve throwing them in a room (or space?) where they can't be productive. So everyone may get a chocolate bar or access to entertainment by default. I think any benefits of working and being promoted would be quite practical like extra living space, access to a gym, maybe better food or a choice of food. This would be tied to the job you do (and I assume the number of children you have). But because it's such a small economic system, those benefits would either need to be tightly rationed or expire week to week. So you couldn't not go to a gym for three years then book it out for a week. Don't underestimate peoples desire for status as well, even if it's chief corridor sweeper, that could be seen as being better than sits on backside all day. I'd also expect that a good chunk of education would drive the notion of being productive. [Answer] You have a few options but an advantage: All people can have the same sleep cylcle and are (literally) on the same boat: * don't use any compensation, just have some kind of dispenser in a mensa for each person or in each home + maybe a computercontrolled dispenser? + StarTrek [replicator](https://en.wikipedia.org/wiki/Replicator_(Star_Trek)) * do some kind of `unconditional basic income` [UBI](https://en.wikipedia.org/wiki/Basic_income): + there are jobs at the ship, even when they are sparse where you can gain extra credits + everyone has an income so nobody needs to have hunger + there are already some [discussions](https://en.wikipedia.org/wiki/Basic_income_around_the_world) in reallife [Answer] Your society is too small, and too resource-poor, to run a capitalist system. There may be a few exceptions to that. * The job of the first generation is to maintain the ship and to raise (and train) their successors. * The job of the second generation is to maintain the ship, to raise (and train) their successors, and to care for the elderly in the first generation (as far as resources permit). * The job of the third generation is to maintain the ship, to execute the mission on arrival, and to care for the elderly from two generations (as above). Take the skill set of insystem piloting and asteroid mining. This could become crucial for the third generation. Will they take a dusty manual from the shelf and read it? Or will there be second-generation pilots who were trained by the first-generation pilots in simulators, with the sole purpose in life of training the third-generation pilots? Your only option is a [command economy](https://en.wikipedia.org/wiki/Planned_economy) for all significant decisions. There might be a little bit of free market to let crew buy luxuries, but the rest is incredibly constrained. Crewmembers draw their rations, based on available supplies. If the original plans were right, those will be tight but sufficient. Same for housing, clothing, medical care. Perhaps there are "credit points" to buy ice cream and a stylish tee-shirt after the shift. More likely, those points don't buy ice cream because calories are rationed. Perhaps it is possible to "buy" an "upgrade" from porridge with sugar to a cream cake with synthetic chocolate flavor. [Answer] Capitalism really won't work here in any form. Even basic income won't fix the flaws of capitalism in this context. The margins on life support are so tight that you'd have virtually no ability to make trade offs like a farmer selling his farmland to build a new habitat wing. Because of the closed economy in which nothing new can be created without taking from something that already exists, you'd even run into problems if a traditional market for luxury goods exists. Essentially it would lead to massive externality problems in that according to the luxury market, the value of life support is zero, in a similar problem to carbon emissions in the present. You'd essentially need a Star Trek style economy in which everything is just provided as needed within reasonable limits, whether or not you have replicators. At the same time, you'd also need something to incentivize the work and education that needed to be continued until you arrive at the destination solar system. What has been argued about Star Trek is that they have a reputational economy. While they rarely talk about how this works, it likely means that people do what they do because it gives them more respect. Having the best restaurant means you'd have more respect, which would allow you to expand further and open a second location on the ship. Having rank on the ship would similarly give privileges like having a slightly larger cabin or a quicker seat at said restaurant. Manu Saadia's book Trekonomics is a rather in depth idea about how this sort of economic system might work. [Answer] ## I think that you will need either a mixed (my preference) or a command economy. I think that 10,000 is a bit small but it is at the very edge of the smallest gene pool for the new colony. Along those lines, I'd recommend banks of frozen embryos or sperm & eggs. Also, what is the job of the mission? It is to create a viable colony. What do you need for that? People with the training and resources to start a colony from scratch. And, you also need to get them there. Everyone who is not going to be of functional, working age upon arrival is just a resource. The "payload" is the generation of 15-40 year olds that will be building the new colony. This might mean that the economy needs to shift between the first half and the second half of the trip. So, what does the economy have to incentivize? Maintaining the ship and maintaining a system that will produce the best "landing generation" as possible. If you don't have separate crew and civilian distinctions (which would cause conflict both on the ship and in the new colony through class wars), you need to get people to maintain the ship, maintain the inhabitants, and prepare the landers. Money could be either computer stored "credits" or anything physical that can be easily traded. A neat thought would be for the money to influence the percentage of resources the landers get on the new world. That way even the early generation(s) has an incentive to make money so they can pass it to their children to give them a better chance of success. Also, even of you don't go that last route, if you don't provide money the people will create it themselves. I suspect that unless you go the completely authoritarian route, that you will have a mixed command and free market economy. For ship maintenance work, a certain amount has to happen or everyone dies. So, the prices of that will be set high enough that you will get enough people to do it. Teaching (unless you have automated courses) will also need to be incentivized as will medicine (again unless automated). I would avoid such automation since it would train people to be less than self reliant. A free market may work here or you may need a regulated market (controls that kick in if things go out of balance). There will also be entertainment jobs just to keep people from going nuts. This will be free market. The people will create it even if it is not provided and they will create some kind of money to pay for it (or barter their rations for it). One reason to go with the "credits" type of money is that it can take into account disruptions to the system. If someone comes up with a method that allows the colony to do more with the current resources, you can create extra credits to give to that person the increase. That would incentivize that sort of thinking and give the colony the best chance of success. You might end up with a significant research section in the ship. [Answer] You just need to have a system of credits in place, with a central computer controlling the balance of each individuals. Doing activities needed for the ship gives to the doer credits, which can be used to purchase other items or services. Demand and offer can regulate the tariffs according to the moment. Every member of the ship population will have their badge to authorize transactions and update their balance in the central system. [Answer] I don't think you need a economy system on such a ship. A generational ship will work like an self sustained army and it must be this way: there are things that needed to be done and you cannot outsource them. Also, since it is a closed system there is not distinction between crew and passenger. Everyone has a work to do. The only minor concession can be that there can be some choice about the work you want to do, but in the end all the positions must be covered. As a consequence, money has no meaning and so wealth. If you still want some type of economy, think about a subsistence economy, although a little richer, you have no resource for anything more. ]
[Question] [ In the future, humanity has discovered countless worlds, some filled with life and others not. Likewise, they discover another world that is habitable, they study its various ecosystems, it’s various creatures, and many more. However, one day they discover a vast plain covered in pillars, upon further examination, they discover that its made of flesh like material. The pillars seem pretty weak and vulnerable but upon touch, they are actually very durable and can’t be easily wounded. The area around them seems to sport very little plant life, and those that do seem to have traces of elements that are used to make bones, yet don’t sport any. Further research has concluded that every year, a spore like sac will burst from the top of each pillar, these spores, if landing on the ground will sprout these pillars over a 10 year time span, but if the spores land on a creature, then the animal will seemingly roam around the area of said pillars, protecting from any other unaffected creatures. After five years of these creatures protecting said pillars, the animals will seemingly huddle up upon a random pillar, and have their flesh be assimilated through a slow process, leaving behind any hair, bones, and any other inorganic material. For some reason, the neurons of the brain and nervous system seemingly get transferred into the very center of each pillar. It is said that each pillar is connected through a root like system that resembles veins, and infant pillars will grow these vein like roots towards the closest adult pillars, as a means of a gaining more nutrients to survive. The center of the pillars being made up of assimilated neuron seems to be able to connect to other pillar neurons through a even more vast and complex system. It is even theorized that if every pillar on the planet is connected through these vast and complex network system, then these pillars as a whole are essentially capable of being as intelligent as 10 human beings, but this is only a theory and there seems to only be 1 piece of evidence to this theory. In a dense forest, there resides one very large and wide pillar that is surrounded by smaller pillars. The large pillar can be seen very slowly forming eyes around itself and creating creatures made of the same composition. The eyes will shortly after close shut and assumably be reassimilated, as with the creatures, they will die after a few seconds of being created and will be reassimilated after a few weeks. Extra fact, the pillars will gain most of their energy from the environment around them, and is thought to be some form of a highly evolve fungus like creature that forms these pillars that have the resemblance of flesh. Is such a creature even feasible, and if not, what parts of the creature are feasible? [Answer] The first part of this description, while weird, certainly seems possible. The behavior of these pillars are basically a mix of Cordyceps and Acacia trees. The former is well-known for controlling ants, forcing them to crawl upwards to help the fungus distribute its spores. The second secretes a nectar that incites ants to protect it from predators. Originally, people thought that this was a mutually beneficial relationship in which the ants protect the trees in exchange for the sap, but later studies indicate that [Acacia sap is not only highly addictive to ants but it will basically make them unable to digest other possible food sources, forcing them to serve the tree for life once they get their first taste](https://www.zmescience.com/science/chemistry/acacia-tree-bodyguard-ant-12112013/). Ants are frequently found in these relationships because they have highly complex behaviors that are strongly affected by chemicals, so this makes it relatively easy for plants and fungi to "hack" them, but even more complex animals can be modified through chemistry and pheromones, like mice which can be mind-controlled into seeking out cats by the pathogen [Toxoplasma gondii](https://en.wikipedia.org/wiki/Toxoplasma_gondii). If the flesh pillar is able to, finding a way to manipulate the prey into dying while touching the pillar, perhaps by causing them pain when not touching the pillar and relief when they did, would certainly be beneficial for the organism. The really unlikely bit is the "assimilate the nervous system of its prey". Nervous systems are extremely complex and don't fare well outside of their host organism. Moreover, even supposing the organism could assimilate a nervous system, what would be the point? Brains are energy-hungry organs that are useful for reacting quickly to stimuli - but non-mobile organisms are built for a low-energy lifestyle and can't react quickly anyway, so a nervous system would be basically pointless. As for the ability to generate new organisms that die in a few seconds, this seems to be a complete waste of energy. If such an organism did exist, my guess would be that the flesh pillars and the "host" creatures are in fact the same species - the pillars being a communal, "adult" form of the creatures. The organisms they spawn are their children, who have a high infant mortality rate, but sometimes survive, travel long distances to gather more nutrients, and then return to return these nutrients and knowledge to the parent pillar. The subsequent generation will maintain some of the knowledge accumulated by the parent, being "taught" brain-to-brain as they are being spawned, and use this knowledge to assimilate more nutrients before returning. Other species may be manipulated by the pillars, but their nervous systems will not be "assimilated". [Answer] There would need to be a very good evolutionary advantage gained from maintaining and expanding its nervous system. The reason we evolved a nervous system is not to "think", but to move. So that we can perceive the surroundings, process and react to stimuli appropriately. The nervous system is a huge energy hog, which is a big problem in a global competition for scarce resources, so it would need to justify itself by providing a massive advantage over organisms who don't have one and are therefore more energy efficient. Or it would just be phased out by evolutionary pressure. There is a kind of organism called a barnacle, which can move in its larval and juvenile stages until it finds a spot to settle down and secure itself. At which point one of the first things it does is digest most of its nervous system. It simply has no more use for it since its unable to move. So, if you want to make your idea to be possible, you need to address these concerns of energy, efficiency and purpose. ]
[Question] [ Assume that average Joe dies in a zombie outbreak and is revived as a zombie pretty much immediately. How strong could that zombie be, assuming that: * Zombification is done by "taking over" the brain, meaning that the zombie moves by transmitting signals over the same neural paths as a live human. It's just something else giving the commands now. * Practically no decomposition of tissue has happened in the meantime. * The zombie shows no constraints regarding pain, self-preservation, or the intensity of neural stimuli (meaning it can always go at maximum muscle power). * It really wants to eat your guts. With that in mind how much force can such a zombie exert to, for example, lift a boulder out of the way? It would try to reach the heroes and it does not care that it snaps its spine in half when doing so. The boulder just needs to be moved so the zombie (or another) could crawl through. How heavy could that boulder be at most? And how would this ability compare to alive average Joe? [Answer] A very fresh zombie will be stronger than a normal person, somewhere around twice strong based on extreme stress hysterical strength response. However their strength will decline very fast, within hours it will barely be able to move. Every time you push a muscle past about 70% of its normal (non-hysterical) maximum you get micro-tears, these tears take several days to heal under ideal conditions and the more tears the longer healing takes, continuously generating tears will wear the muscles away to nothing within days. Worse your zombies are going all out, his brain is not limiting his muscle output to protect his body. That is [Hysterical strength](https://en.wikipedia.org/wiki/Hysterical_strength) (estimates range from 2-3 times maximum output) But our brains limit the use hysterical strength because it is literally more than the body can handle, it does serious damage to body. they are generating fractures in bone as well as tears in tendons and ligaments, these take even longer to heal. Within days there will not be enough muscle, tendon, and bone to hold your zombies upright. But it will never get that far. More importantly as SZCZERZO KŁY pointed out muscles require fuel and your zombies are not going to be refueling efficiently once the body runs out of glycogen (a couple of hours at best), their muscles will fatigue much faster. But even more importantly is oxygen, pushing our muscles puts us in [oxygen debt](https://en.wikipedia.org/wiki/Excess_post-exercise_oxygen_consumption) (really a depletion of all kinds of cellular resources not just oxygen), our bodies can't replenish this as fast as it can use it, and without rest they will not recover from it either. Within minutes they will running entirely anaerobic, pushing them at that point will result in all kinds of extra damage to the point the cells will quickly start to die, after an hour of strenuous exertion your zombies will not have any muscles left. [Answer] Exactly what would Regular Joe be able to do. Or less with your given example. Even if we equal brain override with ammonia sniffing and adrenaline rush then Average zombie can do what Average Joe did. With the exception of Joe can think not to tear his muscles and when to give up. Regular Joe could use his brain to best utilize his available strength with best approach (so leverage, lifting from legs, using back and so on) while zombie would just push using legs. I think the best example would be farmers walk. When strongmen go for time they hold the weight in the way it would try to pull them forward. So the gravity and weight do the "pushing weight" part. Their core hold posture, the forearms hold the weight, legs just keep up the pace. But when they go for weight carried they put more emphasis on shoulders, back and legs being able to hold weight. Next thing - Glycogen. It's a carb stored in our muscles and liver (which would explain why zombies like to eat it). But it's estimated it storage is depleted around 30 minutes of workout. Strongmen going on low carb diets are reporting drastic drop in strength and dexterity. So without any change to muscle size or calories intake their ability to move weight is crippled. Same thing would happened to zombie. Without carbs their Glycogen level would be low so their power would be lower than the human before turning. [Answer] If you assume the Zombie always goes at maximum capacity, it seems likely that it will do a few incredibly amazing and powerful flops before having shredded all muscle fibers and tendons into useless... Not to mention, [bone density is improved from exercise](https://www.verywellfit.com/bone-density-and-exercise-3120770), so the bones themselves might not handle the load even if the muscles can carry it. In many cases, the correct posture, pose and coordination of muscles mean more than just brute strength in regards to the force and motion that can be generated. Anyways... --- Assuming that we indeed only utilize ~20-30% of our muscles as mentioned [here](https://fitness.stackexchange.com/questions/2017/why-is-muscle-size-not-proportional-to-strength/2018#2018), then scaling up average Joe based on values presented [here](https://www.livestrong.com/article/380767-how-much-weight-can-the-average-man-lift/) result in the following stats for big compound movements: * Bench Press: 205-305 Kg * Deadlift: 235-350 Kg * Squat: 190-280 Kg Which is quite impressive, but in lack of proper nutrition and recovery of the muscles, probably not for long... [Answer] How many angels can dance on the head of a pin? As many as wanting... It's your story, Zombies can be as strong as you want them. From the perspective of human limitation, you have the following problems. * Muscles can only provide a limited amount of force before tearing. * Bones, cartilage, and ligaments can only absorb a limited amount of force before breaking or tearing. * Your elbow (or any joint) and the length of your arms (legs, digits...) can only allow provide so much of a [moment arm](https://en.wikipedia.org/wiki/Moment_(physics)). Therefore, from the perspective of humanity, you are limited to what strength the natural body can provide. Strongman [Hafþór Júlíus Björnsson](https://www.menshealth.com/uk/building-muscle/a759056/5-finalists-to-watch-at-the-2018-worlds-strongest-man/) can bench 250kg and deadlift 410kg (dang... I mean... dang...). He certainly has the basic tools to pop my skull open like a beer can and gulp my brains like the slurpee that they are! But if you want shear rip-your-head-off punching power, there's always [Francis Ngannou](https://www.mixedmartialarts.com/vault/mma/new-world-record-for-the-hardest-punch-ufcs-francis-ngannou), who holds the record for the hardest punch. That, of course, is if your zombies want to take my brains along for a travel snack. But, can my zombies be stronger? Of course they can! You can use whatever voodoo brought your zombies to pass to strengthen muscles, bones, ligaments, and cartilage and to swell the joints to provide greater moment arms. They can be as strong as you want to rationalize them in your story (a function of [narrative necessity](https://worldbuilding.meta.stackexchange.com/q/7281/40609)). So, the real question is, are you simply looking for a way to limit your zombies (who, naturally, must be less strong than the original body, of only for the balance problems involved with dragging one's feet along in a dead-eyed stupor), or do you simply want to make them as strong as you want (and kinda need some legitimization from us, which we're always happy to give!)? ]
[Question] [ *A large comet is quickly approaching my fantasy world. Its impact will spell doom for all life on the planet. Fortunately, there are mages on this fantasy planet who possess a magic capable of shattering the comet. But, magic isn't free, energy has a cost....* At first blush you may think I am asking a question about magic. I am not. I'll take care of the magic when I write my story. What I hope to discover is the most efficient means of shattering the comet. From this perspective, I'm looking for a science-based answer. * Use the [Swift-Tuttle](https://en.wikipedia.org/wiki/Comet_Swift%E2%80%93Tuttle) comet as the basis of your analysis. * Do not worry about how the effect takes place or is delivered. * The best answer will explain the lowest energy method of shattering the comet. * Do not worry about the physics of what-happens-next to the comet. I'll take care of that, too. * The comet must be shattered, not deflected or stopped (I have plans for the remnants). * The remnants of the comet must still be headed for or already orbiting the planet. * Please consider the orientation of the comet to the world as unimportant. Example effects: * Vaporize the liquids in the comet. * Create a temporary wall the comet impacts, thereby shattering the comet. If the answerer can demonstrate that vaporizing the liquid would require less energy than absorbing the impact of the comet using brute force, it would be selected as the best answer. Once again, it does not matter (and is irrelevant to this question) how these effects are delivered to the comet. since the delivery mechanism is magic you need not worry about rockets or any other delivery consideration. The magic can be thought of as "bringing the energy needed for the effect to bear." Question: Given the conditions and examples above, what is the lowest-energy method for shattering the comet? --- For future viewers, while I've marked the answer, the answer supplied by Shadowzee provides several viable options (as well as several less viable, but still funny, ones). [Answer] Boil the ice inside the comet, the trapped steam causing it to explode. This would be pretty efficient since the energy used to change the ice to steam would also be used to shatter the comet. As well, there would be less heat lost to space because the center is insulated by the outer layers of ice. [Answer] Your comet is made of ice. Ice happens to be melted by heat. It also happens that fire is a magic that is pretty easy to learn. So, instead of inventing a new branch of physics, study the orbital dynamic of a suitable kinetic bullet to hit the comet, and also figure out what a kinetic bullet is, take a mage, or a bunch of mages, and have them focus a fire spell on the comet. The comet will start sublimating, more or less like it would do when getting close to the sun. Continue applying until the comet is gone. If you are able enough to focus the spell on a specific place, you can even use the ejected gas to "steer" the comet around, deviating it from its crash route. [Answer] The lowest energy solution for your mages is to make use of the powerful source of energy you already have in the solar system: the sun. Instead of having your mages pump energy into the ice themselves, have them paint the comet black. Fairly little work for them, just a bit of surface coloration, and then the sun does the heavy lifting. Use a magical paint that absorbs 100% of all incoming (light/heat) energy, and paint it in strategic patterns so you get contrasting/asymmetrical heating, some parts melting (or boiling) while others stay frozen, and you should be able to make it crack or shatter. [Answer] Given your stated result you need to hit the comet very hard with something harder than it is, like a really big rock. The DnD spells [meteor strike](https://dnd-wiki.org/wiki/Meteor_Strike_(3.5e_Spell)) and [meteor swarm](http://engl393-dnd5th.wikia.com/wiki/Meteor_Swarm) would be the best existing matches I can think of. This will cause it to shatter rather than evaporate as it would if hit with an energy spell like a fireball or lightening bolt. [Answer] The biggest issue I see is that your comet is going to be a ball of ice and rock roughly 26Km across. It has more than 300 times the energy of the comet that killed the dinosaurs so if you have a magic system that can stop this comet your going to have people who are capable of wiping out all civilization without a second thought. That being said here is a list of ideas you could possibly apply: * Super heat the core of the comet causing the ice to vaporize and expand outwards shattering the outer shell of the comet * Throw an equally large stone at it using magic * Create a plant that uses water/ice to grow, launch or teleport it to the comet and have it grow all over the surface using up the ice until only the rock is left. When the comet hits the atmosphere it heats up killing the plant and leaving the shattered remenants raining down onto earth * Just create a super shield or force field that the comet can collide with * Create a reverse gravity field around the comet causing it to break apart * Create a black hole in the path of the comet to break it apart * Move everything into the shadow realm temporarily when the comet hits and come back later * Move the comet into the shadow realm * Just teleport it into tiny pieces * Use holy magic to summon god to stop it * Warp reality so the comet just turns into bubbles * do 100 push ups and sit ups a day with a 10Km run everyday and once you become bald just punch it * Summon an eldrich tentacle horror to stop it * Use laser beams to break up the comet into smaller sections * Time freeze the comet using a elaborate ceremony with a ceremonial sword of a hero used to enforce the spell. The comet becomes part of the planet until someone removes the sword causing it to smash into the ground. * Cast a shield that bends physics and perfectly reflects all energy applied to it * Awaken Gaia who will stop the comet for you * Crush the comet using gravity magic until the insides of it super heat then dispell the magic causing the comet to explode [Answer] Contract out the job You Mages simply need to be able to communicate with Mars a few months in advance of impact and negotiate a price for Martian assistance. The [Martian](https://en.wikipedia.org/wiki/The_War_of_the_Worlds) Interplanetary Gun can rapidly place a crew of Martians on the comet, and their Heat Ray will quickly reduce the threat to ice blocks. [Answer] Go antimatter You could magically inverse the charge of electrons and protons in some proportion other than 50% of the mass in the comet, if its around a few pounds it will instantly annihilate into pure energy, it would blow up in the range of a 100 megaton hydrogen bomb, more than enough, do you want something more spectacular?, make the comet 99.99% antimatter leaving only a few pounds of normal matter, again it would blow up like the hydrogen bomb but the fragments of the comet would be pure antimatter, the instant something its touched by them they annihilate it in a fiery blaze. Consequences In any of the options mentioned there would be huge consequences or none depending on the distance of the comet, if its around the distance of the moon, the explosion would be microscopic and the radiation would disperse harmlessly, if it where to happen closer, say the van Allen belt there would be huge auroras all over the world, if you choose the pure antimatter chunks and they orbit close to the planet there would be auroras 24/7 for months probably, as the space close to planets with atmosphere its not really that empty and particles of different gases would annihilate with the chunks all the time creating lots of radiation each time, from the ground it would look like mini suns crossing the sky Not asked options but still cool to mention A 50% percent conversion would be something to be seen, it would annihilate a 27km meteor into pure energy creating ionizing radiation far beyond anything or anyone could imagine, if we make the comet a perfect sphere and made entirely of water for the sake of simplicity it would have around 82448000000000 cubic meters of water, the amount of energy created would be 3218769920000000000 megatons, just for a little perspective the tsar bomba was "only" 50 megatons, this amount of energy would create so much radiation that it would sterilize basically the whole solar system and if it was anywhere close to a planet it would blow all of its atmosphere and cook it until there was nothing else but a sea of radioactive lava, it would be close to setting off a small supernova. here [if you want to play with the numbers](http://www.edwardmuller.com/index.php?Page=calculator) ]
[Question] [ As far as I have been able to determine, the majority of life reuses the same plumbing for reproductive and digestive/excretory systems. In fact, [the anus is believed to be derived from the male gonopore](https://www.sciencealert.com/scientists-are-trying-to-figure-out-why-you-have-an-anus). This is seen in all vertebrates and arthropods, as the anus and reproductive organs are derived from the same region. In cnidarians, where the mouth and anus are the same orifice, gametes are released from inside this blind gut. Only in planarians is the gonopore separate from the anus (which is also the mouth). [Answer] Yes, of course. In your examples you are only including a very minor portion of all life that exists. Granted, by having the arthropods there, you've included insects which alone may count for more than one million species, with no other class in the animal kingdom having more variety. But don't forget that plants and fungi have no anus. Their reproductive systems are not necessarily linked to their excretory ones. Plants mostly excrete through their leaves, and flower petals are modified leaves, but many plants do not have flowers. And then there are microorganisms. I think those speak by themselves. Last but not least: virii. Whether they are alive or not is debatable, but supposing you count them as living, remember they have no excretion by definition. [Answer] Molluscs have separate excretory and reproductive systems. Among the hermaphrodite land snails, the reproductive system opens onto a genital pore on the right side of the head. Male squid pass spermatophores into the female's mantle cavity around her mouth. There is some sense in using the "get stuff out of the body" system for both gametes and waste, but not all animals do this, and there is no reason to require it in any new creatures that you design. Remember the Centauri of Babylon 5. They look humanoid, but the females have six slits on their back and the males have six corresponding prehensile penises, quite separate from their excretory system. [Answer] Octopuses: Penis in a hand You should take a look at the reproductive system of the octopuses. The male has the reproductive conduct inside (along) one of his tentacles (called hectocotylus), which by all means works like any other tentacle. When mating, he inserts that specific tentacle inside the female. You can see more detailed information here: <https://www.quora.com/How-do-octopuses-reproduce> [Answer] The fact that the same approach is used across several species to implement the same functionality (the functionality being excrete the wastes and excrete the seminal cells) is a prove of how effective this implementation is. If you look at the implementation, it makes more sense to slightly modify an existing system rather than inventing a new one. The existing system being the tubing used for excreting the discards. In this way the existing structures are used more effectively than the case where the reproductive system was completely separate. Having two separate lines, one for wastes and one for semen, would cost more in terms of energy, and would also pose the challenge of how implementing the complementary part for the receiving side (the female). Not that another implementation would be impossible, rather it would have to be extremely more competitive to be successful in the present world. We cannot exclude that alternative implementation were present but did not survive through the mass extinctions happened in the past. [Answer] Many organisms have reproductive systems completely apart from the excretory system, for example arachnids, millipedes, and some crustaceans. Also, even if the ancestor of a creature has the reproductive and excretory systems combined, it is still possible that they might evolve to split the two functions, as has partially happened in mammals ]
[Question] [ I want to change the biology of one human being via hand-waving to allow this individual to have abilities similar to a [gray wolf](https://en.wikipedia.org/wiki/Gray_wolf) - focussing for this question on an enhanced nose which should be able to be [roughly 14 times as receptive as a normal humans nose](http://sciencing.com/wolfs-sense-smell-4565769.html). This question is similar to a previous question from me where I asked [How would it affect a human to suddenly hear like a cat?](https://worldbuilding.stackexchange.com/questions/68882/how-would-it-affect-a-human-to-suddenly-hear-like-a-cat) In this question we will, again, ignore the way in which the human acquires this enhanced ability and assume a lot of handwaving. The nose will stay the same, but the human has an enhanced sense of smell, better than other humans and comparable to that of a gray wolf. After the transformation the human will resume his normal life. If an average american human would, from one day to the other, be able to suddenly have a far better sense of smell than other humans - what would be the biggest problems this human would have to face in his everyday life? [Answer] He can remember people's scents, the way he can remember what they look like, or the sound of their voice. @MichaelKjörling has pointed out that wolves dedicate more brain space to this than humans do, so your protagonist might have to pay attention to remember a scent, rather than it happening as automatic recall akin to a superpower. Also, the scent memories might have to compete for 'storage space' in the bit of the brain used for taste memories or visual memories. If you overlook the lack of storage space for scents, your character could have the potential to turn into the world's greatest detective, if he can get to a crime scene pronto. "The murderer was..." [sniff, sniff] "...a man, non-smoker, vegetarian, has recently eaten something containing garlic and chilli, washes with Pears soap and might have a beard, since I can't smell any shaving products." So if he's NOT a detective (being an average American human), other folks are going to start to think he's a bit weird, as he might know things he shouldn't from picking up on lingering scents: Bob was just in the boss's office a few minutes ago, Mary gave Fred a ride to work, Karen has started drinking again, Janet took the stairs not the lift, John has a secret stash of sweets/drugs in his desk drawer, Eric and Doris had sex in the stationery cupboard... He might recognise someone by scent, even if he's never met them before. So if a thief has been sneaking into his work and stealing things, your hero would immediately recognise his scent if he stood behind the thief in the supermarket checkout queue. Meanwhile, some scents or chemicals will overwhelm him and knock out his sense of smell. A friend was stewarding at the swimming events at the Commonwealth games and said the bomb-detection sniffer dogs had to be swapped out every 10 minutes or so when they were checking the venue, since the chlorine swiftly rendered them unable to smell anything. Wind direction will become suddenly important to him - including where the airflow from aircon ducts goes. What he can smell (unless he goes around with his nose pressed to the ground) will be very dependent on whether he is upwind or downwind. [Answer] He/she would have to deal with a huge amount of information not available before, such as: * hormonal smell of all the persons around him/her (that woman is about to ovulate, the barman is really angry at that customer, somebody in this room has cancer, ...) * other odoriferous information (take a crowded metro cab in summer, multiply by 100 the nose-nightmare). Depending on how the body reacts to this information, some issue may arise. I.e. if the smell of an ovulating woman will induce arousal (common in some animal males) or the smell of an aggressive but controlled man will induce a fight-or-flee reaction. Also opportunities can arise: i.e. if he/she can smell a bleeding person from a distance or follow traces of a missing person. [Answer] It would be socially awkward. I think it was Feynman who originally wrote: humans actually have a surprisingly good sense of smell. It's just that we don't use it, because people would look at us funny if we walked around sniffing at people and objects. (See also: [this article](http://www.salon.com/1999/07/28/smell/)) So your average American human would spend a lot of time trying to hide that they were sniffing at things. They might eventually conclude the awkwardness wasn't worth the information gained. If dogs are anything to judge by, this average American human also probably would start hating to take baths (because of the strong odors of soap and shampoo). ]
[Question] [ The Scenario: Airships are awesome, but in the real world airship design is greatly constrained by the problem of lift. It seems like this, above all else, is what makes the elegant and compact ships of steampunk and fantasy unviable. Balloons need to be enormous to carry adequate mass. Steam engines, armor, and other fun things are prohibitively heavy. Often, all of this is politely ignored. But I'd like to try and design a world in which the problem of lift is partially circumvented by the addition of a single unreal element, with defined parameters and otherwise realistic consequences: in this case, a machine that can produce limited antigravity. ![image](https://images.stopgame.ru/screenshots/12056/c1280x720/up-l9YSaJVa-CLIbFk2Jag/gettysburg_armored_warfare-34.jpg) My knowledge of physics is cursory, but so far as I know, such a device isn't possible within known laws. But setting aside, for this question, how it could be created, here is a possible rules set for it after the fact: * It projects a spherical field within which gravitational pull is reduced. * The effect is a gradient, with conditions near .1g around the device, and near 1g on the outer edges of the field. * The maximum size of a field is about 30 meters or 100 feet. * The field size/strength can be adjusted up and down. * It requires fuel. * I can see a number of potential problems with handling overlapping fields -- so I'm leaving whether they are cumulative, cancel out, etc. open for now. These rules are intended as a reference to help evaluate the consequences of the core idea; if they prove inadequate I'm happy to modify them. The end goal, of using limited antigravity to create a wider field for designing interesting and useful airships, is what's important. ![image](https://i.stack.imgur.com/9UOan.jpg) The Question: Limited antigravity would be a good aesthetic fit for this world, but I'm aware that messing with a physical law in even a small way can invite all kinds of unforeseen consequences. So, given the above premise, will a limited antigravity field have such wacky effects on physics (on the ship, crew, lift gas, surrounding air, the relation of the ship to the [spin of the earth](https://www.quora.com/How-much-energy-would-an-anti-gravity-device-consume-if-we-consider-conservation-laws/answer/Rick-McGeer-1), or anything else) so as to be prohibitive? And if so, can the above rules or the typical airship design be tweaked to compensate? [Answer] Where does the energy go? You're dispelling potential energy by having a field that hand waves gravity. More importantly after the field leaves, the potential energy snaps back in place. Infinite energy? Assume you have a water wheel. Project this field over the left portion (slightly including the upper middle portion) of it. Now the right portion is heavier, so it rotates to the bottom. The portion of the wheel in the field moves, and the exposed part tries to fall to the bottom... the wheel spins. Make the wheel more massive for more force. The counter to this would be to make the fuel expended equal to the energy required to keep the mass 'afloat' (or at least lessened for gravity's pull). The issue with this is that if you're already expending this energy, why not expand it to rotate, say, a propeller, or as a fuel propellant? Surely such methods would be less complex, cheaper, and less prone to failure. This would also happen to a lesser extent, I'd imagine, inside the envelopes of gas; the more-gravity-affected gas at the top (further away from the anti-gravity field's core) would try to fall down, and the less-gravity-affected gas would be pushed to the top. I'm not sure if this would reach equilibrium, or if the momentum gained from this would allow it to remain in a cycle. If it would remain in a cycle, you once again have a [perpetual motion machine](https://en.wikipedia.org/wiki/Perpetual_motion) which causes all kinds of issues and would fundamentally change how your world works, again, unless you balance it out with fuel costs in which case... Low-Gravity's effects on the human body Given your image, the crew onboard the ships would deal with <0.5 g constantly during long voyages, which appears to average to ~0.3 onboard the ship. Reduced gravity has a detrimental effect on humans. I don't know of any studies for this level of reduced gravity on humans (it doesn't come up much) but "zero gravity" or "microgravity" does happen to astronauts in orbit/free fall around Earth. During the NASA shuttle flights (all of which lasted less than 18 days) astronauts were noted to have some [bone and muscle loss](https://science.nasa.gov/science-news/science-at-nasa/2001/ast01oct_1), and some experienced back pains. Obviously your sailors would have a less extreme case of this (still having meaningful gravity), but they'd also probably be onboard the ships for much, much longer than [12-16 days](https://www.nasa.gov/mission_pages/shuttle/launch/extend_duration.html). Long-range ballistics would be extremely complex to calculate Artillery and cannon shells, in the real world, can be fired and the arcing gravity-induced path (and final resting location) can be determined through math (estimated fairly well, or precisely figured out including wind speed via calculations and formulas). Passing through invisible clouds of gravity modification would royally screw up the arc, leaving it nigh impossible to calculate in a useful manner. [Answer] In the Space:1889 RPG, they had liftwood that provided an anti gravity force. It wanted to rise in gravity. IIRC, by flooding the wood with electricity or a special gas (or both) you could increase this effect. I would recommend that any antigravity effect also be limited like this. Have it only effect the device itself. Therefore, it must be attached securely to the ship or it will tear itself free from the ship and fly up until it ran out of juice. This avoids any kind of overlapping field effects. It also means that the crew doesn't have to remain strapped down to prevent them from accidentally launching themselves off the ship when they take a step. [Answer] If one uses a plate of anti-grav material, the ship could be hung from that. This would change the appearance as the balloon would be gone. You could replace it with, the material carved into the shape of a dragon or a bird of prey (not the Klingon version). So imagine the material is difficult to find, hard to manipulate, but will not have negative effects regarding the crew. Also magic could be used to propel the ship, in fact the ship might have sails to catch the magic wind springing forth from the magicians hands. No mechanical or electrical requirements, although those could certainly be added in much like the magic wind. Anything additional like that would allow break-downs, damage being critical in battles, shooting the wizard, etc. [Answer] dcy665 beat me to it by half an hour (well done mate), so I'm going to try to get in depth while riffing on the same concept: Hang the ship from the antigrav source rather than housing it in the hull. Center it above the ship so that crew effects are eliminated and most everything on the ship simply behaves in accordance with normal physics. You could use internal gas bladders underneath the ship's center of mass or maybe something like outriggers or pontoons filled with some lighter than air substance. That gives you lift, but you also need motive power. Fans instead of oars, use sails rigged in novel ways to use wind power, a huge steam powered propeller... Just remember that the larger your ship, the more wind is going to be a factor. This is going to be compounded by how much you have to rely on gas for lift. The less gas needed, the more nimble the ship. if you extend this out, you might be able to regulate lift by how much power goes to the anti grav mechanism. Without that mechanism, your craft is heavier than air. Stuff like that could help keep things in a nice steampunk theme without having to get too wrapped around the axle with the physics and other effects. You could even do fun things like a plucky hero making trick shots with cannon using the altered ballistics from the cannonball passing through the anti grav field above the ship. Have her aim the cannon to make a shot just to the right of the anti grav dohickey on the next ship over to get extra range and take out the bad guy sneaking up on you out of the clouds on the flanks :) ]
[Question] [ Suppose we have a [Branching Timeline paradigm](https://worldbuilding.stackexchange.com/questions/67346/how-to-test-a-time-machine/67368#67368), in which time travel into the past creates a new timeline. Is it fair to assume that any probabalistic events which might occur might be very different to what happened in the past in your original timeline? So for example, let's say you take yesterday's lottery numbers and travel back in time to 2 days ago. You buy a ticket and fill out your numbers. You do nothing else to interfere in the world at all (and there isn't some hidden suprise where you find out later than in fact you did). Is it fair to assume that due to the complexity and near-random nature of an event like a lottery draw, the results will be different this time around not because of some cause (even a miniscule one, i.e. a butterfly effect) but simply due to the fact that a complex, near random event is happening (as opposed to "has happened" — where the results are locked in). Many thanks to JDługosz, and everyone else who commented on/edited this question in the [sandbox](https://worldbuilding.meta.stackexchange.com/questions/4835/sandbox-for-proposed-questions/4913#4913). You helped turn what was a pretty convoluted way of asking this question (and I was aware of this - hence why I went to the sandbox to start with!) into a much more concise and useful question. The above paragraphs are a copy of the final edit, and are as readable as they are due to JDługosz's [efforts](https://worldbuilding.meta.stackexchange.com/a/4945). [Answer] To answer this, you need to see that there exists “randomness” that is not due to the butterfly effect, and then how that phenomenon will be affected by time travel. ## chaos and determinism Just because the random process is “complex” doesn’t mean it becomes nondeterministic. The proper phenomenon here is [Chaos](https://en.wikipedia.org/wiki/Chaos_theory), and this is what leads to the so-called “butterfly effect”. If your arrival caused some air molecules to bounce differently than they had in the original timeline, and this eventually made the lottery choose different numbers, that is an example of the butterfly effect and thus not what you are wondering about. So first, you are asking whether there even exist nondeterministic effects. In pure Newtonian physics, every action can be computed from the previous history, and everything plays out like clockwork. A deterministic system will always produce the same output from a given starting condition or initial state. ## nondeterminism, or genuine quantum randomness As it turns out, quantum mechanics does indeed have genuine randomness. The [observable](https://en.wikipedia.org/wiki/Observable) measurement will be chosen at random with a weight based on how close the quantum state is to each possible [eigenvector](https://www.youtube.com/watch?v=PFDu9oVAE-g). To give a concrete example without getting too deep into the quantum mechanics, consider what happens when a single photon at some random polarization angle reaches a polarizing filter that passes vertical and rejects horizontal. What if the actual light has an angle that’s not exactly vertical or horizontal, but 15° off vertical? Well, this particular photon [will have](http://farside.ph.utexas.edu/teaching/qm/lectures/node5.html) a 6.1% probability of being horizontal and 93.9% chance of being vertical. There is no cause due to prior state. There is no reason, and no way to know the result ahead of time. This is genuinely random and nondeterministic, and this is not just a limit to our knowledge. It can be [logically shown](https://en.wikipedia.org/wiki/Bell%27s_theorem) that the result literally comes from nowhere. Real-world experiments back this up. So, ultimately the bouncing of the balls in a classic random lottery machine will indeed bounce in unpredictable ways, being truly nondeterministic and not just chaotic. A modern lottery machine will probably combine traditional bounding balls with a micro-controller that uses a quality [random event generator](https://en.wikipedia.org/wiki/Hardware_random_number_generator) to control the precise timing of the paddles and other movements. This will, if implemented as intended, put the ball draw definitely in the genuinely random category. Now will quantum randomness play out the same way in a new timeline? That’s the question. ## branching timelines keep happening Note that this behavior itself may be the source of having multiple timelines! The [Many Worlds Interpretation](https://en.wikipedia.org/wiki/Many-worlds_interpretation) shows how the apparent choice of a specific value (e.g. horizontal or vertical polarization in the example above) is due to a superposition of everything including your brain’s particles with each possible outcome. So if this is happening, there is no “choice” and you will split into two new timelines, one of which sees H and one sees V. The “you” asking this will only experience one of them, and that is randomly chosen. So it is “no different than before” in the sense that the particle went both ways in the original timeline, and it goes both ways in the new timeline. But which resulting daughter timeline from this new split you ride into may very well be different. So from your point of view, the random events will be freshly chosen in the new timeline, and will not necessarily follow the same as in the original timeline. Experiments over the last few decades, including practical engineering efforts into building a quantum computer, have shown that [decoherence](https://en.wikipedia.org/wiki/Quantum_decoherence) is correct, and we have things like [delayed choice experiments](https://en.wikipedia.org/wiki/Wheeler%27s_delayed_choice_experiment) and even [quantum erasers](https://en.wikipedia.org/wiki/Quantum_eraser_experiment), which suggest that the separate timelines caused by every random wavefunction decay are real. ## is that the answer you wanted? But maybe there’s more to it than that. Maybe the possibilities encoded in the entanglement of all the particles in the environment somehow get pruned back and there is a single “real” timeline, and this path is persistent so the timeline will try and recover the same path when it’s replayed. This is used to great effect in many science fiction stories where the timeline has an inertia of sorts and history is difficult to change. Consider another concept, that of the [quantum handshake](https://en.wikipedia.org/wiki/Transactional_interpretation). This has to do with the source and future destination of an interaction that form a transaction between the two points in time. You can read about this in John G. Cramer’s [Alternate View column](https://www.npl.washington.edu/av/altvw16.html) in [Analog magazine](https://en.wikipedia.org/wiki/Analog_Science_Fiction_and_Fact), where I first learned of it. In [some science fiction accounts](https://en.wikipedia.org/wiki/Einstein%27s_Bridge_(book)), going back in time will nullify the transactions and allow them to reform in newly-chosen ways. Under this model, quantum randomness will also be different. But what if they are not all reset? If the other end of the transaction occurs later than when the traveler departed, maybe that end will hang onto its transaction, and the side of the transaction that the traveler experiences a second time in the new timeline will be the same. This idea more readily supports an overwritten timeline though, but you can make it branching by saying that the state is copied of the entire timeline, past and future, not just the point before the time at which the traveler arrives. ## recap — quantum randomnes resets To summarize, the easy answer that works hand-in-hand with real physics as we understand it, given the branching timeline paradigm, is that quantum randomness will be reset and will play out independently in the new timeline. To do otherwise will take some contrivances, both in describing new physics for the timelines and in preventing the “many worlds” from making it appear that they have reset. And why do we need multiple mechanisms producing timelines that work in different ways and fight each other? Furthermore, once anything changes, such as the specific collision of two atoms in the lotto balls, then the specific quantum events that even exist will be different in the new timeline. The butterfly effect (due to your presence, or any partial tendency to play out the same) will pull the rug out and you won’t have the same quantum events to replay, from that point forward. So making things work the same way on the new timeline really would require a higher order fate to make things restore to the same large scale state, even with the low-level details (entropy) completely randomized. [Answer] You have arrived within the past lightcone of your target event, it's fair to say that if you interact with the world it will have an effect. You go into the shop to buy your ticket. This reminds the person behind you in the queue that they wanted to buy a ticket along with the milk and bread. You're now into human, not quantum, factors. More tickets have been sold, this means that there's a higher jackpot, which takes a different amount of time to announce before the draw. The button to start the draw is pressed at a fractionally different time, the winning numbers are different. I'd stick to betting on horses and elections. Lay off anything even resembling true random. While this is still part of the same philosophical principle as the butterfly effect, it's considerably stronger. The butterfly flapping its wings could potentially change the world, but usually doesn't. Human actions on the other hand routinely do change the world. [Answer] I think it is fair to assume that the more time there is before a random event, the more likely it is the random event will turn out differently. Why? Because the world is governed by Quantum Mechanics; and we supposedly have proof (with various New Scientist articles as my source) that quantum events cannot be deterministic, and that quantum events can indeed have macroscopic effect (In the Schrodinger's Cat paradox, the setup is not in dispute: We can arrange for a cat to be killed (or a bomb to explode) if an atom emits an alpha particle; which is a random quantum event that triggers a macroscopic effect). The Quantum events in question are a function of time, so the longer the time, the more of them occur, and the more likely it is that a chaotic system (which by definition is dependent on immeasurably tiny variations in starting conditions) will be skewed to provide a different outcome. I would say that at the point you arrive in the past, a reset occurs: That includes re-rolling the dice on every quantum event starting at that point, which means even without any butterfly effect, the air currents blowing the lottery balls around might be slightly different and produce completely different numbers. Say some atoms decayed this time around that did not decay before, emitting energy that warmed some air molecules (or parts of the lottery machine), and vice versa; and those minute variations in heat get multiplied enough over the two days to change the outcome; one ball is deflected just a hair of a degree so its trajectory bounces off the edge of the winning ball chute; so another ball make it in there instead. If you want to win the lottery, appear in the past about 2 minutes before the cutoff for buying a ticket; just enough time to purchase it. That makes the state of the lottery machine as close as you can get to where it was to select those particular winning numbers. [Answer] In quantum mechanics, the initial state (say a Uranium-238 atom) doesn't uniquely determine the final state (when the atom decays and in what direction that alpha particle goes). We can expect that if we were able to replay a sample of Uranium being measured by a Geiger Counter, that the amount of counts detected would be almost the same, but probably not exactly the same. There are ways of using quantum effects (like the radioactive decay of an atom) to [generate actual random numbers](https://en.wikipedia.org/wiki/Hardware_random_number_generator#Quantum_random_properties) instead of pseudo-random numbers. So if, in the story, someone was using hardware random number generators to make choices, (which, I think would make a nice plot device) then there would be some pretty substantial changes right away. Barring that I don't know if it is known how significant quantum chance would have on day to day macroscopic events. ]
[Question] [ I am trying to create a planet for a fantasy role-playing game where the equator is an impassible region of ice. Ideally, I want to find a science-based solution to this and not have to resort to explaining it away with magic. Here's what I am trying to create. 1. Planet has seasons. (If there are ways that seasons can be created without giving a planet tilt, I am open to this.) 2. Planet is cold at the equator. 3. Planet is hot at both poles. 4. Planet has a day and night cycle similar to that of Earth. 5. Planet can have any year length. Ie. If the planet has a longer orbital period due to a highly elliptical orbit. Things I have thought of so far: 1. Give the planet a 90° tilt. This would cause half of the planet to be in constant darkness/light in violation of Criteria 4. 2. Give the planet 0° tilt and rings that block out a good portion of the sunlight about the equator. With 0° tilt, the planet wouldn't have seasons (breaking Criteria 1) unless there is some other way of bringing them about. In addition, most rings are basically flat and the shadow cast by rings at 0° tilt about the equator would be very narrow. Thanks all! [Answer] Lets start with (4). To have day/night cycles the planet must rotate and there must be a local sun (or suns) of some sort typically at less than 90 degrees from the planet's rotation. Check. Add (2). With the sun overhead(ish) at the equator, in order to be cold there the day/night sun needs to far enough away that its average heating during a day is less than whatever causes (3). There are no orbital mechanics that permit a body to remain over the poles more than the equator all year round. This will make the world darker but keeps day/night effects. Now add (3). In order to be hot at the poles, there needs to be a heat source. Lets try adding a brown dwarf. They give off heat, but not a lot of light. If we put one over the pole however, our planet would have to orbit the brown dwarf. After a quarter orbit, the brown dwarf is now over the equator. (This is the same problem with your suggestion 1 above. A tilt of 90 degrees only has the sun over the pole at one point in the orbit. This is more like extreme seasons rather than being tidally locked.) So to get the heat at the poles you need a source that is internal to the planet. One idea is to use a heated core with magma convection currents that raise up in the poles and sink at the equator. The poles would then get more heat from the core. But this is the reverse of what the natural flow would be due to the planets rotation. You would need most of the magma to be a material that got MORE dense as the temperature increases. There are some examples of this, but not many. Also you would need the core to be extra hot, possibly due to radioactivity. In this situation weak seasons can be had like on earth from the, here distant, sun. Suppose we dropped the whole year round idea, and only need this situation to be stable during one season. Then we could have the planet co-orbit a binary star system at the L4 or L5 Lagrange points with a tilt of 90 degrees. Then every other season one star would shine mostly on one hemisphere or the other, leading to polar heating more than the equator. Unfortunately this means that in the other two seasons one of your two poles are plunged into never ending darkness. Lastly we return to your excellent idea of having a wide set of rings block the equatorial light on a low tilt planet. All you need now is seasons. But tilt is not the only way to have seasons. Instead you can make your planet orbit one of a pair of stars in a binary star system. The close star provides most of the heat, but the distant star provides variability in the small heat it adds by where it is in its orbit. (This is what the planets around alpha centari A experience from alpha centari B.) Plus by changing the inclination of star B you can decide if the northern and southern hemispheres experience the same seasons at the same time or alternate.(Or make your planet a binary with a brown dwarf on an elliptical orbit. Or just make the planet's orbit elliptical itself for short summers and long winters felt by both north and south hemispheres at the same time.) TL;DR: Use your rings idea but add a distant binary star for seasons. [Answer] Yes, it is possible, although the flavor would probably be wrong for what you have in mind. Climate varies with latitude and altitude. Mountains on the equator have permanent glaciers. So to have the equator closed by ice you just have to make it high enough.The easiest way would probably be to make the planet less spherical. This has the benefit of not needing mountains, although you'd need to keep the equator free of of oceans, ie. have a supercontinent that encircles the planet on the equator. This state is not stable as planets are by definition in hydrostatic equilibrium. So you'd need some reason, such as divine or alien interference that explains why the planet is less spherical than it should. Planet had too fast rotation and the gods fixed it, maybe? Alternately, since you need the supercontinent anyway, you can just fiat that every point on the equator just happens to be high enough thanks to various highlands and mountain ranges. There is no real reason why not. Note that since the equator would have much less heat absorbing ocean and much more heat reflecting ice and snow, it would not have to be as high as is in our world for permanent glaciers. There would be permanent winds away from the glaciers and without ocean currents, there would really be no way for heat from surrounding warmer lands to melt the equator. Making the poles hot is more problematic. With huge glaciers and no seas on the equator it is perfectly reasonable to assume mostly dried out ocean basins surrounding the poles. If you configured what remains of the seas for efficient heat transport, I'd guess there is nothing stopping the poles from being hot. So you'd have a polar ocean with water heated closer to the equator. There would be islands and coastal lands with geology largely formed of [marine evaporites](https://en.wikipedia.org/wiki/Evaporite#Marine_evaporites). The problem with this solution is that it would do nothing about the poles being short on sunlight at least half the year. So the agricultural productivity and supported population levels would not be that good. Then again, I doubt it is that crucial to you to have huge farmlands on the poles? Since you need polar oceans anyway for heat transport, you can place only islands with hardy fishermen on the poles and have the agricultural lands on the coasts closer to the equator with better sunlight. [Answer] In a two-star system, there is no stable planetary orbit near the stars. Planets will * most probably go away (and then they will either leave the stellar system, or get a stable orbit far from the stars) * get to an orbit very close to one of the stars (and thus, only its gravity will have a significant effect on them) There is no third possibility. If you want a stable planetary orbit, only a single star can affect their orbit significantly. Some tricky solutions (for example, a trajectory forming an "8") are all very unstable, and the planet will leave them fast. The only exception is if the L4 or L5 [Lagrange-point](https://en.wikipedia.org/wiki/Lagrangian_point) of a two-star system. But in this case, you can't have the required constellation of the Suns. I can imagine 2 possibilities for a similar planet. 1. Consider a "planet" (more exactly, [red dwarf](https://en.wikipedia.org/wiki/Red_dwarf) star) orbiting a Sun-sized star around in the current Sun-Mars distance. An Earth-sized "moon" of it would be [tidal locked](https://en.wikipedia.org/wiki/Tidal_locking) to it. Thus, it will be a constant "Sun" over its North pole. The "second Sun", on the place of our Sun, would be able to heat it mainly from the southern direction. The result will be a hot northern hemisphere with a constant Sun, and a colder southern hemisphere with a moving, secondary Sun. If you set the orbital parameters correctly, maybe you can get a cold equator. 2. You are in a single-star system, with a tidally locked Earth to the Sun. This Earth should be around between the Mars and Jupiter distance from the Sun. This results a relatively warm northern hemisphere and a very ice southern one. Some gods or interstellar ancient civilization could have built a large, stable space mirror in the L2 Lagrange points of its orbits with the goal to stabilize its weather. Although the L2 lagrange point is unstable for point-like masses, it may be stable for a large mirror. If the mirror is focused only to a small part of the ice southern hemisphere, you will get the warm poles and the ice equator. In both cases, the atmosphere of this planet should be rarer as ours, to avoid the heat transfer (for example, a purely 20% oxygen atmosphere, without our nitrogen would be okay). If you wish I can give some pictures from the actually needed constellations. [Answer] Don't overthink. There is no need for some elaborate exotic orbital mechanics. 1. Seasons: Axial tilt, just like Earth. If you want to avoid Earth-like seasonal patterns, the answer here entirely depends upon exactly what kind of seasons you want. For something erratic (or an unusual pattern), use fluctuations in solar cycles changing the output of the star, or if you want both poles to have the same seasons at the same time then use no axial tilt and vary temperature by a highly ecliptic orbit. 2. Cold equator: High elevation at equator due to a more oblate spheroid shape of the planet makes crossing it like climbing Mt Everest. This eliminates the prospect of frozen seas crossing between the poles, but keeps the hemispheres separated by frozen peaks and glaciers. 3: Hot Poles: Hot planet. Strong greenhouse effect, possibly backed up by volcanic activity, keeps the poles toasty warm. Thermal hot springs would be common if using volcanic heat. If you're doing high-tech sci-fi scenario, this may be relevant, but otherwise you don't need to explain the details of the meteorology to pre-scientific characters. 4. Day/Night like Earth = spins like Earth. Simple. Just how deep into the details do you need to get in explaining and plotting out the orbital mechanics of every astronomical body in your world? Don't overthink and don't over-explain - is your target audience really that interested in getting into the details of examining the realistic charting of magma flows in the mantle of your planet? [Answer] One possibility would be to give the planet some sort of long-term cloud system forming a belt around around the equator that blocks out sunlight, or perhaps even having the clouds form high-altitude ice crystals that reflect sunlight away. You could still have day-night cycles even at the equator, it is just that the equator blocks enough of the light to reduce temperatures. Some of the gas giant planets have storms lasting for centuries or even thousands of years that form bands around the planet vaguely similar to what I am describing. However, I am not sure what specific set of geographic features would encourage the formation of such a weather system on a rocky planet. [Answer] The procession of Mercury fits some of your criteria (all but #4), in spirit if not to the letter. Each year as Mercury's orbit brings it to perihelion, it "locks" one face in day/summer. The next time Mercury comes in close it locks the other side making night/winter. The opposite faces of Mercury alternate in 3:2 resonance with Mercury's year, with a twilight ring that wraps up and down over the poles rather than around the equator. It wouldn't be a perfect twilight zone, each twilight face would see the sun at aphelion every other year. [![enter image description here](https://i.stack.imgur.com/gQPQ6.gif)](https://i.stack.imgur.com/gQPQ6.gif) ]
[Question] [ Slenderman is unarguably the most iconic creation of the early internet. It has led to games, stories and even books. But is his design evolutionarily possible? What evolutionary pressures would lead to the slender figure and abilities of the slenderman? [Answer] Humans are already basically Slenderman to other animals. In prehistoric times, we were persistence hunters - isolating a single animal and following it, slowly and persistently, until it could run no further, at which point we would jump out and kill it. Now what if there were a species that could out-persist us... Slenderman's form is basically an exaggeration of the same features that distinguish us from other animals. Less musculature, but long limbs - perfect for long distance walking. It doesn't need claws or teeth, since its prey is already half-dead from exhaustion by the time it finally decides to attack. And of course, being very, very good at tracking, and very, very patient. The creature could have the ability to produce infrasound. Certain pitches of infrasound are able to cause vague feelings of dread in humans and has even been thought to cause mild hallucinations. Many "haunted" houses have been found to have some object in them producing infrasound (like a vibrating pipe). Making the prey perpetually terrified is an excellent adaptation for a persistence hunter, as it will constantly be on the alert, fighting and running from things that aren't there, and generally wasting energy, making it tire out faster. The prey may also become paranoid, causing them to avoid other people, which is just what a persistence hunter wants. The hallucinations could account for the varying accounts of the creature's description. It probably doesn't really have tentacles, for example. The creature must be stealthy, since if it is spotted before the prey is tired out, they might decide to attack it and could potentially fight it off. It must be able to stay perfectly still, and it makes sense that it would mainly inhabit forests, since it can be mistaken for a tree at a distance. However, humans (along with many other animals) are very good at spotting faces. For a predator that needs to remain unnoticed, lacking visible facial features is a boon. It seems to be solitary, so it doesn't need a face to express itself. The messing with electronics thing is harder to explain, but there have been some recorded cases of humans who collect much more static electricity than normal and cause problems for electronic equipment near them. Perhaps this creature has similar properties. It's hard to say why it would have evolved with these qualities though. Humans are not very good primary prey, as we are bony and lack meat, plus we can run far and are hard for a persistence hunter to catch. Slendy probably hunts other animals like rabbit and deer most of the time, just like we did. Perhaps the species likes hunting challenging creatures for sport, though. We do. ]
[Question] [ We all know what the minotaur is and what it looks like, a buff man with the head and tail of a bull. But could this creature evolve? Could it even exist? If a Minotaur could exist, what environmental pressure would lead to its evolution? A list of all of the Anatomically Correct questions can be found here [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798) [Answer] Could this Creature Evolve? The short answer is no. One point is the head size and shape. Given the size of the average female vagina, I'm going to say that minotaurs would either need to be birthed extremely early in their development (which would cause a host of other issues) or delivered entirely through cesarian (which is not an evolvable trait) without other significant physical changes not noted in common minotaur lore. Another point would be to look at the nose. Bulls have very large nostrils because they need to fill large lungs. Filling a human's lung with nostrils that size would actually be quite hard due to the notable increase in length that the air would need to be pushed/pulled from. It's not impossible, but it would be a huge waste of energy that evolution would shy away from. I can't even begin to think of what benefit a creature would obtain from having to work hard to breathe. I could go on, but I think I've already shown there's no sane evolutionary path that would lead to a minotaur. Could the creature Exist? This is actually a different question than above. Assuming advanced genetic engineering (far beyond what we have today) and no care about the cognitive/motor capabilities of the result, sure. Why not. What Environmental Pressure Would Lead to Its Evolution? The best and only pressure I can think of would be sexual preference. Early people simply preferred mates that had more bovine facial features but still human bodies. An odd fetish, but that's really their private business. Note that you would have to start with a very large stock of humans, who would have to all spontaneously develop this sexual preference. The reason is, again, that the birthing issue is just so non-trivial. The infant and maternal mortality rate would be extraordinary. [Answer] I would assume that if Minotaur were to evolve, they would neither evolve from humans or bulls. I would say that a Minotaur is probably an ape, most likely from chimpanzee origin, possibly from apes that left the jungle for the plains. The "simian ridge" seen on a chimp's skull could become a bone basis for the horns, with the some hair becoming a keratin outline, extending the horns. The long face would have to flatten out a bit to become more bullike, or perhaps remaining semi-apelike, either one could work in my opinion, but judging that these beasts would need to be around for humans to see, I would go with the latter option. They would most likely become larger creatures, using their size and horns to intimidate smaller creatures away from kills, making intimidation a main tactic for food, and giving rise to them being scavengers. Perhaps tool use could evolve for them sometime down the line. [Answer] I'm pretty sure the only answer to anything natural arriving at this is no. > > if a minotaur is a cow that evolved a human body > > > A cow's body is rather well designed to its grass eating task. It has several stomachs to breakdown this relatively tough to digest food and includes a re-chewing process (known as ruminant digestive system). First stomach is basically a storage site as they quick eat grass without chewing sufficiently. Then ruminate (chew their cud) somewhere in the range of 40k chews per day. There is also a fermentation phase involved...somewhere near 75% of the cows abdomen is space reserved for this digestive process (it's a 40 gallon system in a full grown cow). So the answer here is a giant no...the human form cannot support the full digestive system required to feed on grass. > > if a minotaur is a human that evolved a bull head, it eats what humans eat. > > > A bull's head is actually quite a piece of artwork...the large head protects the neck while charging and supports the muscle structure required to take these impacts. A human neck is really incapable of all of this. I'm actually having problems picking out what benefits a bull head would grant that wouldn't be a giant negative in some other attribute. Perhaps the 'Loki' discussion goes in here...his superpower must include super human neck strength to support those silly horns on his helmet after all. There is also the birthing issue if this coming from the human side. A Minotaur head is huge compared to the human counterpart...how exactly a baby Minotaur could get out is beyond me. I'd go as far to say it's not really feasible in the genetic engineering domain either...I mean perhaps as a single 'Frankenstein' creation, sure...but it wouldn't be a stable creature capable of procreating or competing in most environments. [Answer] I think the best way to justify the evolution of a minotaur is to remove the 'human' element entirely. Rather it is a bovine species which has evolved to become bipedal and developed articulated 'hands' and opposable thumbs. Which then of course gives them a 'humanoid' likeness. Maybe environmental pressures lead them to become carnivorous which subsequently leads to very diverse evolutionary opportunities. How they get there is a little beyond me... ... as far as I'm aware the origin of our hands is from digging; then climbing; then finally using tools (swimming might be in there somewhere too). After hands we then started to 'stand up' - I guess as our front limbs became less useful for walking on. This then opened up the advantages of being bipedal for a number of things: mainly steady, long distance running. [Answer] I want to offer a contrary opinion to the question "Could such a creature evolve?", and argue, yes, minotaurs could evolve. Before starting, it is worth noting that the minotaur of [greek mythology](https://www.greekmythology.com/Myths/Monsters/Minotaur/minotaur.html) (i.e. THE minotaur) was a singular individual created by divine intervention; if we want to consider the possibility of minotaur evolution, we need to allow for the existence of a population of minotaurs, more like the minotaurs that populate fantasy RPGs, C.S. Lewis's Narnia etc. The key element in understanding how a human or human-like ancestor could give rise to a population of minotaurs is to recognise (assume) that typically minotaur traits are secondary sexual characteristics that emerge largely after puberty under the influence of a testosterone surge. (This limits the typical minotaur appearance to males; females would be substantially less "minotaur-like", and we expect/predict a substantial amount of sexual dimorphism, perhaps of a similar degree to that seen in gorillas where adult males can approach twice the body mass of adult females). This should get around any obstetric complications associated with a human-like mother giving birth to a horned bull-like head! Evolutionary Scenario: Imagine a pre-minotaur population where physical strength is important for male reproductive success. This may be because the environment poses particular challenges; because of violent confrontations between males of different groups (as in real-world chimpanzees); of perhaps because males' access to potential mates is mediately largely by competition between males - bigger, stronger males outcompete the smaller weaker ones, and father more (most) of the babies. This is seen in multiple real-world non-human primate species, so is not unreasonable. Imagine a male is born with a genetic mutation that has two effects: distortion of the skull (a hint of a bovine appearance), and increased responsiveness to testosterone at puberty, such that post-puberty this male is larger and stronger than other males. This will result in increased mating share, with his offspring inheriting these proto-minotaur traits. If we wanted to we, could also imagine that testosterone at puberty also exaggerates the bovine-like features of the skull; regardless, it may well also increase the aggressiveness of these males. Over time, the population would come be dominated by individuals (males) who have this proto-minotaur phenotype. Now imagine also that a genetic trait exists that is expressed in females that relates to mate-preference. Given opportunity to exercise choice (which might be just a matter of being more or less resistant to male mating approaches), females "prefer" (i.e. are more likely to mate with) more physically-powerful males. Particularly if the increased aggressiveness between proto-minotaur males led to a population structured into small groups, females might be able to skip out of one group and join another - not that different to the situation that seen in modern gorillas, where females choose which harem to join - and this leads (at least in this scenario) to inter-sexual selection that, over generations, exaggerates the proto-minotaur traits into full-blown minotaur. Horns, for example, extending and developing from initial small bony spurs of the semi-bovine skull, perhaps even acting as [honest signals](http://octavia.zoology.washington.edu/handicap_old/types_of_handicap.html) of the male's genetic quality even though they are exaggerated beyond useful, head-butting size/shape. For females on the other hand, we would not expect a significant increase in body mass over the ancestral population (perhaps a little, as it might be dragged upward by selection on male body mass), and the bovine-like features would not be as strongly exaggerated, but they would be noticeably not human. Female minotaurs should be smaller, less aggressive, and less bull-like. Social structure might mirror that seen in gorillas, with males holding harems, dispersing at puberty and spending time alone before assembling their own harems, but the need to hunt for meat - we're still assuming these minotaurs are (at least part-time) carnivores - would probably require cooperation between males to bring down large prey, so perhaps harems nested in a more chimpanzee-like community structure might work? (incidentally, this is what Edgar Rice Burroughs came up with for his fictional apes in Tarzan, but I didn't recall that until I got to this point in the argument). Note that this line of evolution would equip minotaurs with primate-like teeth, allowing for the exaggerated canines seen in much of the artwork, rather than the typical bovine dentition more suitable for eating grass. So an evolutionary argument can be mounted for minotaurs, that avoids both Goldschmidt's '[hopeful monster](https://rationalwiki.org/wiki/Hopeful_monster)' speculation, and particularly unusual birth complications. [Answer] This is actually not too difficult anatomically. Large herbivorous primates already exist (gorilla) and have existed (gigantopithecus). to the digestive anatomy is easy, a bovine head is not too difficult although you have to reopen the eye socket, apes have solid eye sockets which will not work with a bovine head. Of course they will not have human like intelligence or brain size, something more like an australopithecine will be more likely, basic tool use but not very creative. Supporting a human brain on an herbivorous diet is difficult and there is only so big you can make a head and still give birth to it. the real trick is the horns. These will be tricky to evolve but not impossible horns have evolved multiple times. Horn are just a sexual characteristic tails could be as well, Horns however will require a serous change in the anatomy of the head as they grow up to support them, this however is seen is other animals so it's not impossible. So the evolutionary pressures are herbivory and sexual selection, but the real issue is time this line needs to split off the primate early to have enough time to alter the skull this much which means they are going to have to evolve naked skin and upright posture independently or alternatively they can split off the hominid line but the story needs to be set far far in future. ]
[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. While the vampire is a monster of folklore, modern technothrillers (e.g. Federal Vampire and Zombie Agency, Ultraviolet, Blade, Underworld, Daybreakers) have portrayed vampires as humans infected by a pathogen that causes hematophagy, photosensitivity, and enhanced physical attributes (e.g. strength, senses, longevity). If such a pathogen was constrained by hard science, how would it differ from the pop culture version in order to approximate the same result? How could the infected exist without being malnourished and scourged by rickets and scurvy? [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. A remark at the beginning: In a world where real-life vampires existed, there would certainly also grow a lot of myths about them. So we would have to distinguish between in-world real traits and in-world myths (that is, things that are commonly ascribed to vampires in that world, but are not true, or not entirely true). Therefore the real task would be to devise a pathogen and corresponding vampire traits that cause the commonly assumed traits to be plausible to the general population, given the actual traits of the infected. Note that if the pathogen appears in a society where vampire stories are already culturally ingrained, it is quite likely that the fictional vampire traits would be projected to the real-world vampires, as long as some traits are a good fit. So, let's look at what traits real-world (as in, real in that fictional world) infected people might have that would make them to be seen as having the traits of vampires. # Drinking blood for nutrition The main theme of vampirism is, of course, that vampires drink the blood of their victims, and those bitten then become vampires themselves. So how much of that could be true? As other answers already explained, nutrition just from blood is unlikely, as you'd too much of it to live from. However, what is definitely possible is that a pathogen gets transferred on a bite; that's for example how [rabies](https://en.wikipedia.org/wiki/Rabies) is transferred. Now while rabies certainly makes animals bite, it doesn't make humans bite. However I found [this article](http://www.jaapl.org/content/31/3/289.full.pdf) which details that aggression after infections is not quite uncommon, and even cites a case where a girl bit her father several times, although admittedly from the description, the biting doesn't look like a specific result of the illness but just part of the common infection. So while there is no direct indication that an illness could specifically cause biting in humans, I'd say there's nothing that specifically indicates that it could not be possible in principle. And indeed, for an illness that is transferred by biting and that is human-specific (that is, it cannot simply spread through aggressive animals, like rabies can), it would make sense to cause this behaviour, as that would spread the disease. Indeed, for effective spreading, it would be advantageous if the pathogen got directly into the blood of the bitten, so it would also make sense if the infected developed a specific appetite for blood. However [according to Wikipedia](https://en.wikipedia.org/wiki/Specific_appetite#Specific_appetite_in_humans) there's little evidence for specific appetite in humans, and the few examples cited are for specific elements. So it is unlikely to be caused by a pathogen. So how could the perception of blood drinking be caused? * The infection spreads through bites. The victim is more likely to be infected if the bite reaches the blood stream. Thus it is commonly assumed that the infected specifically long for getting to the blood stream. * The infected get pale (more on that below). This seems compatible with the idea that their blood is sucked out. * The infected live separate from the uninfected humans, both for their light sensitivity, see below, and the fact that they are feared by the general population (and in turn have to fear the normal population, as those are likely to kill them). Therefore non-infected people generally won't see infected people eating, reinforcing the myth that they are living off the blood they suck from the victims. There still remains one problem: Why would vampires seek out uninfected humans? Well, from the point of view of the disease it would make sense, but I cannot imagine a mechanism that could provide that. However note that the actual rate of people being bitten need not be that high for the perceived rate to be high. It's just like crime in our real world: The actual violent crime is generally going down, but the perception is that the world is a very dangerous place. So maybe in that world, actual bites are also a relatively rare event (and most of the infections happen through different infection paths), but get blown out of proportion in public perception. # Pale appearance One of the symptoms of the illness may be [Pallor](https://en.wikipedia.org/wiki/Pallor). Note that the list of causes includes tuberculosis, so it definitely can be a symptom of an illness. In addition, they will likely have little pigmentation, either just from never being in the sun, of from an additional [Hypopigmentation](https://en.wikipedia.org/wiki/Hypopigmentation) which can also be caused by illness (the linked Wikipedia page lists leprosy as possible cause). # Avoiding the sunlight Of course, the idea that a vampire decays into ashes when exposed to sunlight can only be a myth. However what is realistic is that the vampires would have to avoid sunlight, which would then inspire/reinforce that myth. This could have several causes. One is [Photophobia](https://en.wikipedia.org/wiki/Photophobia) where one of the causes listed in the Wikipedia article is excessive response in the central nervous system; this fits well with the aggressivity theme above. Besides that there is also [Phototoxicity](https://en.wikipedia.org/wiki/Phototoxicity): The pathogen could produce a substance (or make the body produce a substance) that is phototoxic. This would also mean that exposure of vampires to skin would cause visible effects (although not immediately), something that could well add to the myth about sunlight killing vampires. # No mirror image This is of course physically impossible. However, it might be that the infected people simply avoid mirrors in order to not have to see their own deceased look. This may fuel the myth that they are not seen in the mirror. # Sleeping in coffins in burial crypts They most probably won't sleep in coffins. But since they have to hide from the sunlight (see above), they have to seek dark places to hide during the day. Moreover they might want to do it in places where non-infected people are unlikely to come. A burial crypt might just be the ideal place for that. # Garlic helping against vampires Well, [garlic allergy](https://en.wikipedia.org/wiki/Garlic_allergy) exists. From the Wikipedia page: > > Garlic allergy has been known since at least 1950. It is not limited to hand contact, but can also be induced, with different symptoms, by inhaling garlic dust or ingesting raw garlic, though the latter cases are relatively rare. > > > So if the vampires all develop a garlic allergy, garlic will indeed be a good means to keep them away. And contact with garlic will indeed have very bad symptoms for allergic people: > > The affected fingertips show an asymmetrical pattern of fissure as well as thickening and shedding of the outer skin layers, which may progress to second- or third-degree burn of injured skin. > > > This may well be interpreted as a sort of decay by someone seeing it. However, I've not found anything indicating that infections can cause allergies to unrelated substances. # Improved senses Could an illness sharpen their senses? Well, there are indeed some possibilities. One thing they'd probably have is a better night vision. In the Wikipedia article on [Accelerating dark adaptation in humans](https://en.wikipedia.org/wiki/Accelerating_dark_adaptation_in_humans) I found the following: > > Rod cells are much slower to adapt to the dark and it is believed to take days for these cells to reach full dark adaptation. > > > Since rod cells are precisely those used for night reception, it implies that if you are continuously in relative darkness, your night reception should be better than that of people having daily sunlight exposure. Also there might be effects similar to the [blind being better at hearing](https://www.sciencedaily.com/releases/2004/07/040723093712.htm) which according to the linked article is confirmed. Since the vampires won't exercise their day vision (like the colour perception systems) much, their brain may reassign its resources to night vision, or even to unrelated senses like hearing or smell. Speaking about smell, there's also [Hyperosmia](https://en.wikipedia.org/wiki/Hyperosmia) which causes a decreased threshold of smell; that is, you smell things you wouldn't smell otherwise. The Wikipedia article indicates that there are some substances that might cause it, so it's not unconceivable that the pathogen might produce one of those substances. [Answer] Firstly, a scientifically realistic vampire would differ from its pop culture by not doing a number of things. Not crumbling into dust when staked through the heart. Not needing to rest with its native soil. Not being able to turn into red mist, bats or wolves. Not being able to control the minds of the insane. Plus the things a scientifically realistic vampire can now do. Being able to cross running water. Entering homes and dwellings uninvited. Seeing its reflection in mirrors. There will be uncertainties about reactions to garlic. Vampirism may induce allergies and [garlic](https://en.wikipedia.org/wiki/Garlic_allergy) is known as an allergen. Vide Block (2009) and Moyle et al (2004). While silver is usually for werewolves, it might also be an allergen for vampires. All of the vampire traits discussed above were exhibited by the King vampire himself! This is none other than Count Dracula! About whom more can be found in Mr Bram Stoker's novel of the same name. The main problem of a pathogen inducing vampirism in its host is that the infecting organism has to induce massive metamorphosis in a human being to transform so many physiological functions and rebuild the person structurally as well. The pathogen effectively needs to be engineered to do this. While it is possible bio-technologists from a type K2 civilization whipping up something like this to while away a dull afternoon on a Friday, it would be inadvisable for them to let loose on a planet with a less than K1 civilization. The mechanics and dynamics of the spread of the vampire pathogen have been discussed [here](http://www.cell.com/trends/immunology/fulltext/S1471-4906(16)00021-1). This study by Schneider (2016) developed the following useful categories for the understanding of vampire pathogen epidemics. > > 1, Outbreak epidemiology/dynamics; 2, Imaginative cures; 3, Pathogen life cycles; 4, Host heterogeneity and disease tolerance; 5, Native microbiota; 6, Pathogen social behavior; 7, Lives of the infected; 8, Unusual pathogens; 9, Mode of transmission; 10, Manipulation of the host. > > > Research by Sandvik et al (1994) has revealed that the traditional prophylactic action of garlic may been overrated. > > Garlic has been regarded as an effective prophylactic against vampires. We wanted to explore this alleged effect experimentally. Owing to the lack of vampires, we used leeches instead. In strictly standardized research surroundings, the leeches were to attach themselves to either a hand smeared with garlic or to a clean hand. The garlic-smeared hand was preferred in two out of three cases (95% confidence interval 50.4% to 80.4%). When they preferred the garlic the leeches used only 14.9 seconds to attach themselves, compared with 44.9 seconds when going to the non-garlic hand (p < 0.05). The traditional belief that garlic has prophylactic properties is probably wrong. The reverse may in fact be true. This study indicates that garlic possibly attracts vampires > > > While it is conceivable that a pathogen or parasite might evolve the necessary mechanisms to infect, colonize, and then metamorphose a human being into a creature that is functionally a vampire this would be extremely difficult to do and is most likely to take extremely long timescales. [Elsewhere](https://worldbuilding.stackexchange.com/questions/52432/evolution-of-vampire-zombie/52436#52436) this has suggested at hundreds of millions of years as the result of a long co-evolution between humans and the vampirizing organism. References: Eric Block (2009). Garlic and other alliums: the lore and the science. Royal Society of Chemistry. p. 228. ISBN 0-85404-190-7. Moyle, M; Frowen, K; Nixon, R (2004). "Use of gloves in protection from diallyl disulphide allergy.". The Australasian journal of dermatology. 45 (4): 223–5. Sandvik H1, Baerheim A., Does garlic protect against vampires? An experimental study. [Article in Norwegian], Tidsskr Nor Laegeforen. 1994 Dec 10;114(30):3583-6. David S. Schneider, What Can Vampires Teach Us about Immunology? Trends in Immunology, Volume 37, Issue 4, April 2016, pp 253–256. [Answer] Vampires would require tons of energy to be themselves. Blood does contain nutrients in form of sugars. A quick research reveals that sugar in blood is around 1.4 g/L. With 5 L of blood per human, a vamp can harvest 28 kcal of energy from a single drain. Additionally, there is cholesterol in blood. A round 2 g/L which translates to 90 kcal. Lets say vamps can harvest other material from blood too, totaling 250 kcal per person. Even if they could reduce their bio rhythm while they are inactive, they would still require a lot of humans in order to survive. ]
[Question] [ Setting: Modern day Earth, no special technology advancements. Situation: On day, in a relatively populated American city (the specific city is unimportant...the purpose of this point is that it's high-visibility), an apparent nuclear explosion occurs and absolutely levels several blocks. Video footage recovered from streamed cell phone footage (all storage devices in the area were destroyed) at the time of the detonation shows that it originated out of thin air, about five feet off the ground, in the middle of the street. The destruction is almost absolute within the radius of the explosion, with almost everything pulverized to dust and/or incinerated. However, in the dead center of the crater, rests a mostly intact human arm. The skin is charred, but the tissue within is almost untouched. The arm ends just shy of the shoulder, cut cleanly at the molecular level; the cut is not charred/cauterized. The hand was found gripping a piece of paper, charred beyond legibility. Additional Info: Unknown to people in the present, the arm belonged to someone from about 500 years in the future. Question: Given the full focus of the global scientific community, and all the resources America and its allies could bring to bear, what could we learn about an arm in that condition? Assume there are no implants within the arm, its former owner had no artificial genetic modifications, and that the fingerprints and fingernails were burned off. Also assume that it took twelve hours for the arm to be retrieved and placed in cold storage. The arm was charred by external heat of about 2,000 degrees Celsius, rather than the 100,000,000-degree temperature of the apparent nuke. There was no radioactive fallout from the explosion, and the arm has suffered no radiation damage (beyond that experienced in day-to-day life). Specifically, would we be able to determine that it's not from our time? Would the intact blood, bone, and muscle tissue allow us to guess at the diet, age, gender, or even occupation of the person it was once attached to? Would an adult's arm, after being detached for twelve hours, still contain intact DNA to sequence? Would the blood still be viable for analyzing the white blood cells (ie, to determine immunities)? I'd like to stick to concepts grounded in present scientific/technological understanding, but I'd be open to including speculative technology which may reasonably be invented within a year, in direct response to such an event. [Answer] Even without intentional artificial DNA modifications, chances are overwhelming that the arm would contain unknown antigens and/or antibodies (think 500 years of Coronaviridae reshuffling - and that's from flu alone). The sex, age, ethnicity and probable physical outlook of the owner could easily be determined from DNA and bone assays. Diet would be tricky; the best it could be done would to assess whether the owner suffered any of several dietary deficiencies. Occupation would be next to impossible to determine, unless it resulted in specific traces (weight lifting can be detected, and scars from several sports can be identified if present. Rowing could be determined from a pattern of calluses, even if the heat burned them) The simple fact that the arm was there would hint that it either appeared after the detonation or that something was able to protect it against a nuclear explosion. In both cases we're talking super-science. However, scientists would surely perform a full isotope spectrum analysis (both to determine whether it appeared during or after the explosion, and to assess the characteristics of whatever preserved it from the nuclear fireball), and would get absurd results. Some of those results might be ruled out as contamination from the nuclear explosion, but some won't be consistent with the effect on everything else, not even postulating a "magic shield" to protect the arm. I suspect that very soon, since isotope ratios are closely linked with elapsed time, and so they would already be thinking "time", some researchers would put forward the hypothesis of time travel. Another hypothesis would probably be a human somehow born and raised in a solar system far, far away, with a different isotopic composition than Sol's, and where divergent evolution would explain the DNA modifications. Even so, many very small divergences would be there, of the kind that is associated with evolution; the DNA would be too close to human actual to have come from too far away in space. Unless the super-scientists responsible are also naughty pranksters. At that point the nuclear explosion would probably be hypothesized to be the result of a botched time traveling (or long-distance teleport) attempt. Among the things a very secret, very dark government project might try to do would be to locate any relatives (or ancestors) of that DNA on contemporary Earth through large-scale DNA mapping (expect dirt cheap kits to test your DNA for anything to suddenly appear from the newborn Cheap Intracellular Analysis Ltd. of Langley, VA). Worst case, they gain nothing. Best case, they can make contact with either super-scientists, alien abductors, or time-travelers. [Answer] Pavel and Youstay have already told you that we can find out a great deal about the person that arm belongs to. I'd like to point out a few things that they have so far missed, however. Consider that this person is going to live 500 years from now. In this time new diseases will come into existence. Humanity will develop new vaccines, and cures for those diseases, as well as simply develop immunity to some of them. Furthermore, and this is a biggie, we are experiencing the dawn of genetic alteration and manipulation. So called "designed babies" who's DNA has been edited to give them certain color eyes, hair, to filter for certain genetic markers indicative of disease, etc. - it's all within our grasp (or soon will be). First of all, I think we may actually be able to get a blood sample out of the tissue. Even if it's only dried blood, scraped off of the inside of the veins. Within that blood we may find antigens to diseases that we don't even have today. Or antigens that deal with diseases we don't know how to cure today (such as some forms of cancer). Maybe even traces of nano-bots (maybe organic ones within the blood stream) which were keeping this person's body in good health. We may also notice that their DNA is eerily flawless. Maybe less decayed than it should be, indicative of a longer life span (maybe an artificially prolonged one by having nano-bots clone cells rather than having them decay as they multiply over our lifetime). There will be all sorts of little hints within this person's DNA and blood which will scream out to an expert that there's something "off" about that tissue. [Answer] Here are the things you can determine about the arm, considering that the tissues inside are intact and not destroyed. Also considering the arm has not been subject to intense nuclear fallout as you would expect after a nuclear explosion. 1- The genetic information of the person. Yes, cells deep inside the arm (bone marrow) will retain genetic information which would be easily readable in all detail. 2- The gender of the person. This would be possible to determine not only from the dna, but also from the bone density. 3- Since the genetic information would not be destroyed beyond recognition, it would indeed be possible to theorize that the arm does not belong to anyone of our era. This would be possible by comparing the arm's dna with the dna of all modern day males. Dna undergoes mutation as a more or less constant rate. The dna of this person's arm would indicate more genetic mutations than those of any modern day person. The researchers can then work their way to determine roughly how long in the future would this sequence of dna come into being. 4- The race/skin color of the person. It happens that inspite of genetic mixing between all the peoples of the world, it is still possible to determine (from dna) if a person is white (caucsian), black (african), brown (south asian), red (native american), orange (south american) or yellow (east asian). So the researchers would be able to tell what race did the deceased belong to. [Answer] I will put my 5 cents of basic scientific knowledge: ## Possible to find * We will be able to extract DNA. Especially if there is some blood left in the arm. I think we could also use bones for DNA * We would be able to say the arm belonged to male or female. I think that we could guess height and age of arm owner with very small error margin * Cutting method used on the arm ## Plausible to find * From DNA sequencing we could get biological relatives. But current DNA repositories are not that big, so actually getting come relatives is on edge of plausibility * Vaccines and/or any medications: This could give us an alarm ring that we are dealing with something unusual. ## Impossible to find * The fact, that the arm comes from the future. For that there has to be some gadget on the arm (watch for example) * Since I am still writing this when you are getting some response: I doubt that not being able to find any relatives would lead to conclusion, that this arm is from another era in the future. As said, our DNA repositories are too small to tell this * But also, bear in mind, that even today people are experimenting with drugs, and any chemicals in blood would be at too low potences, that I doubt it would trigger something ]
[Question] [ There is a creature. Let's call it a Blop. Blops are fairly simple creatures: They consist of a tough, flexible outer skin and then an inner structure that is (essentially) organs and tentacles floating in goo. This gives them a remarkable versatility, as they can literally flip end-to-end within their own skin, or push their organs through a small space one at a time while remaining safely intact. They can best be thought of as the unholy offspring of an [octopus](https://en.wikipedia.org/wiki/Octopus) and a [honey badger](https://en.wikipedia.org/wiki/Honey_badger). Respiration is fairly simple: Blops are amphibious swamp dwellers, so a semi-permeable skin allows them to breathe and exhale simultaneously. The issue that I'm having with the Blops is that they are relatively high-energy creatures (they burn a lot of calories), and so have to actively consume other carbon based material in order to survive (Don't worry too much about what they're eating. If you're assuming a certain kind of biomass just note it in the answer) Given that the Blops have an outer skin with no orifices and can be at any orientation within said skin, how can they eat and defecate? One last thing: Ideally a Blop should be able to eat while on a person's shoulder (I'm not planning any space piracy. No sir! Not me!), but it isn't required. [Answer] As an alternative to the amoeba model, you might consider a fungus-style digestive system. This would allow it to munch on items larger than itself, since it lacks a mouth with which to take bites. The blop swims next to some foodstuff. Over the course of the next few minutes, its surface extrudes some small-diameter hollow fibres (like fast-growing mycelial cords) into its intended meal. The growth of these fibres occurs at the tips, and releases digestive enzymes as a by-product, so the tip is always immersed in a pocket of enzymes and partially digested food matter. The fibres conduct the mixture back to the blop, where it mixes with the goo (which I infer is meant to perform the role of circulatory system). One of its internal organs is a kidney-equivalent, which processes the components that aren't metabolically useful and converts them into something that can diffuse out of the blop's skin. If the blop finishes its meal, or is threatened by a predator, it causes the fibres to break away from its skin by chemical signals or nerve impulses or what have you, but the little pores where the fibres were attached heal rapidly. This would mean it prefers to eat big meals (like animals that have drowned in the swamp) and remain undisturbed while it eats, because each meal incurs some energy cost to grow the tendrils, and it has to provide enough nutrition to offset that. [Answer] Like an amoeba. Have the Blop envelope what it wants to eat in a subsection of its outer membrane called a [vacuole](https://en.wikipedia.org/wiki/Vacuole). It can then fill it with acid/digestive enzymes. It can also dispose of waste in a similar fashion, by reconnecting the vacuole to the outside. In essence anything the Blop eats gets its own private stomach that would be 'floating' in the goo with the main organs. ## Edit In light of additional information, the Blop will have to simply envelope its food, excreting acids and digestive enzymes into the food-filled envelope and reabsorbing the dissolved nutrients through its semi-permeable skin. This process will limit the waste generated by the Blop as the semi-permeable skin will only permit useful particles through and afterwards the undigested material will simply be released. [Answer] The process you're searching for is exactly how [starfish](https://en.wikipedia.org/wiki/Starfish) eats : they "vomit" their stomach to have it attacks the inner organs of the seashell they're trying to eat. As wikipedia says ... > > the cardiac stomach can be everted from the organism's body to engulf and digest food. When the prey is a clam or other bivalve, the starfish pulls with its tube feet to separate the two valves slightly, and inserts a small section of its stomach, which releases enzymes to digest the prey. The stomach and the partially digested prey are later retracted into the disc. Here the food is passed on to the pyloric stomach, which always remains inside the disc. The retraction and contraction of the cardiac stomach is activated by a neuropeptide known as NGFFYamide. > > > [Answer] In a way, your Blops already have orifices, because they have "a semi-permeable skin [that] allows them to breathe and exhale simultaneously" The simplest way not to make those orifices any larger is to allow some liquid, such as water, to enter and leave, absorbing some minerals along with it. Perhaps your Blops are green, and filled with chlorophyll, which energizes it just like a plant: using water, some trace minerals, breathed in CO2, and sunlight? Note that this (probably doesn't) satisfy everything a "high energy creature" needs. High energy animals such as small birds can succeed because they are constantly eating insects, worms, etc. The blop, without an opening large enough to constantly eat high-density carbs, is at odds with its "high energy" requirement - unless it is eating massive amounts of tiny lifeforms (example: Blue Whale) while it constantly absorbs and releases water. "It's absorbing carbon, but it's not growing!" - perhaps the carbon (and other waste materials) goes into the making of its skin, which it sheds often. It might be a bit smelly if its just had a big meal and shed.. ]
[Question] [ In the movie "Elysium" there is a luxurious micro-nation called 'Elysium' that is based on a large orbiting space platform, that is only obtainable for the super rich elite. Someone hacks the computer so that everyone on earth is recorded as a citizen. To illustrate the significance of this, the Computers AI then immediately dispatches medical drop ships to the outskirts of major cities to start giving needed medical treatment. I always considered this scene dumbly naive. (Almost like something someone would put in a movie.) For example: Given the original population of Elysium, why were their medical drop ships that large and numerous in the first place? And would curing cancer really improve the quality of life for earthlings in any 'revolutionary' way? In the grand scheme of things, wouldn't this just increase the prevalence of starvation? What would be the ultimate result for humanity after they are all given citizenship to Elysium? [Answer] Elysium is a fantastic concentration of wealth in the ultimate walled community. I don't recall specific population numbers, but it is clear they represent far less than 1% of the human population. The people of Elysium control the means of production and police forces. Unemployment is rampant and they use Earth as a pool of cheap and very disposable labor. The ending of the movie, where everyone is made a citizen of Elysium and receives health care, is a stopgap measure to solve the focus of the movie: healthcare. But, as the question correctly surmises, this isn't going to last long. Elysium's health care system designed for the small population of Elysium cannot possibly keep up with the entire population of the Earth. In the movie's simplistic solution, somewhat realistic given the desperation of the characters who kicked it off, Elysium will likely rapidly exhaust its resources attempting to cure the world's problems alone. This might leave people slightly better as it eliminates Elysium as a brutal, exploitative superpower, but it doesn't do anything to alleviate their basic economic and political problems. Even if Elysium could sustain this, lowering the global mortality rate and increasing the average human lifespan without other changes would exacerbate the existing population and poverty problems. Our current population explosion is, in part, a result of [the death rate](https://en.wikipedia.org/wiki/Mortality_rate#Statistics) dropping faster than [the birth rate](https://en.wikipedia.org/wiki/Birth_rate) along with a [greatly increased life expectancy](https://en.wikipedia.org/wiki/Life_expectancy). At minimum, the birth rate would have to be lowered to meet the new lowered death rate and raised life expectancy to avoid a population boom. Looking a bit further down the road, Elysium's magic cure-all machines are only a band-aid on the much larger health problems of extreme poverty. It would be better in the long run to treat the cause (extreme poverty) then the symptoms. To truly effect real long term change, the means of production and wealth accumulated in Elysium would have to be distributed differently. The world in Elysium is highly automated with sophisticated robotics and technological advances. This high level of production efficiency means it is possible the entire population of the Earth could be sustained in comfort, but it is unlikely that enough jobs could be available to give all humans meaningful work and distribute the wealth. Instead, wealth would have to be distributed through some other means. [Guaranteed Minimum Income](https://en.wikipedia.org/wiki/Guaranteed_minimum_income) is one such possibility. --- Elysium is, of course, an allegory. These are all exaggerated problems we're facing today. Like today, rather than dealing with the big, long term problems, the filmmakers chose a short term fix to wrap everything up for that neat Hollywood happy ending that leaves you wondering. [Answer] My theory: as everybody is allowed to enter Elysium, there will be fights. The bad guys and gangs with all the modern weaponry will race up there and start to fight because "This mansion is mine! I saw it first!", followed by the rich dudes saying "Nay, it's mine!", and everybody starts destroying stuff "before that other dude gets it". And the security robots will do nothing as they are all Elysian inhabitants. And, if all the droid workers can go up to Elysium for free, why should they risk their lives if there are babes and booze and weird food up there, only waiting for them? Economy crashes (once more). So, the greed and envy and violence and distrust and hate that made Earth such a nice spot in the first place sweeps over to Elysium - and within a short amount of time it will be as dirty and rotten as the rest of the planet. * The End [Answer] I always thought that rather quickly Elysium engineers would re-program the core again to remove the extra citizens, the robots would retreat and the status quo would be maintained. As the credits roll only a couple of people remain on Elysium from the original compliment and it appears they didn't remove the original admin's citizen status so it's a matter of time. Arguably if Elysium did remain open to everyone the resources would deplete but it seems like the city AI would take over and attempt to solve all the problems. Roll on the rise of the machines :p ]
[Question] [ Joe Schmo is your average college graduate who is suddenly transported back to medieval times, without time to prepare. From there the stories, and questions on this site, are all about how he can use his technological knowledge to change mankind. That assumes he survives long enough though... Would Joe be able to survive the diseases and viruses of the time period? People from the US can't even drink water in Mexico because we are so dependent on our filtration, I can't imagine medieval water to be any cleaner. Would his immune system be able to handle the sudden influx of every-day diseases of the time which he has never been exposed to or developed an immunity to? He would have vaccinations against some of the biggest killers, which is useful, but what about all the diseases he wasn't vaccinated against? Now lets assume that Joe is smart, with a general high school and college bachelor's education. What can he do to protect himself? Would he have to start boiling all water before drinking it, until he can slowly build up a tolerance to their diseases? [Answer] Well when he arrives, his health should be much better than the majority of the population where he lands. But yes, he'll have to be careful what he drinks. That is one of the reasons many drank wine, beer and grog, though they didn't know why it was 'healthier'. Probably the biggest disease he'll have to worry about that he won't have immunization against is the Black Plague, it's deadly and spreads quickly. A saving grace would be knowing it is spread by rats and fleas. Good clean hygiene is the best prevention there. He will also have to learn to lie about where he gets all his knowledge from, people were/are superstitious and surprising scientific phenomena practiced well could stir rumors of witchcraft and that never ends well for the accused. [Answer] Yes and no. Funny enough, I thought of this exact same question when I had a childhood fantasy of a modern aircraft carrier group suddenly being teleported into Roman times. Don't ask why. Anyway, In the modern world, we are no longer vaccinated against things like bubonic plague (since sanitation has made that one go away) and smallpox (since we actually destroyed that one, humanity FTW). You'll have to get your smallpox vaccine fast or else you're screwed, since it is also ridiculously deadly and spreads extremely fast. You'll want to watch out actively for plague, since contrary to bowlturner's answer— there is mounting evidence that the plague in the 1300s was also spread by air in the form of pneumonic plague instead of bubonic plague. There's also the matter of things like the 1918 flu, which might kill you really fast by cytokine storm because of our comparatively strong immune systems now. However, most people today are be much better off on that front, since our immune systems are not weakened by chronic childhood malnutrition. But, other than a few diseases which we might not know of (there have been a few plagues whose cause is not yet determined) and the ones which we already defeated (humanity f\*ck yea!), you should be fine in most cases. However it is, if you want to take such a journey, I don't recommend it. Modern sanitation and medicine is a great thing. Going to the past is basically going to a third-world country without bothering to get vaccines — also known as a bad idea. [Answer] Members of the military are vaccinated against plague if there are going to be sent to regions were it is possible that the plague might breakout. I can't count the number of shots I received when I was in the Marine Corps. ]
[Question] [ I'm writing a novel in which one of the characters has the ability to control, manipulate, and produce electricity. I'm having issues working about scenes which require him to fly around without sounding exactly like the DC superhero Static. (It was used as just a filler until I could think of something else, but now I can't think of something else.) I don't want him to just have an additional power of flight, however, as I have scenes in which he is debilitated and can't fly around. (Using the "Static" example, it would be like removing the disk he flies around on.) I'm also open to hearing name suggestions for this superhero alter-ego. Any help would be super appreciated! <3 [Answer] ## The name comes from the superpower Firstly, I suggest making the superpower less ambiguous. Just say he can create/manipulate [electrical charge](https://en.wikipedia.org/wiki/Electric_charge). Working from there, you can make up mechanisms on how certain things are achieved using that specific power, this will make your story more thought out, consistent, and certainly more satisfying to electrical engineers like me. You can name him Charge. ## How to use it Now, to use charge or charge flow (current) to fly, there are lots of ways to do that and some may work better depending on the conditions. For instance, if there is a conductive flooring he can generate magnetic fields (by rapidly moving charge back and forth). This will produce an opposing magnetic field in the conductive surface via eddy currents (the currents themselves are generated from the original magnetic field). This is how the real-life [Hendo Hoverboard](http://hendohover.com/) works. He would likely use this method to glide around his apartment without generating ion wind. ![](https://i.stack.imgur.com/kiBEm.jpg) Where a conductive substrate is not available [electrostatic levitation](https://en.wikipedia.org/wiki/Electrostatic_levitation) is another option, as pointed out by Dan Smolinske. This only requires that charge be concentrated on himself and nearby objects. You can see a small scale example of this with two balloons repelling each other. Again, this provides a small amount of force normally, but could be feasible. Most likely he would use this to statically levitate objects (sounds like a nice way to sleep). While still in the atmosphere, [electrohydrodynamic thrust](http://www.gizmag.com/mit-ionocraft/26908/) can be generated to provide lift (used by devices like the ionocraft, as linked by user3082). However, since he can manipulate charge directly, there is no need to have an apparatus for making ions, he can just add charge to molecules directly. Adding a concentrated opposite charge some distance away will act as a collector for the charged particles. Its position relative to the average center of the ions will define the thrust vector. As the ions move to the collector, they bump into uncharged air and generate force perpendicular to ion flow. The force it produces is: $$F = {{Id}\over{k}}$$ $F$ is the resulting force, in Newtons $I$ is the current flow of electric current, in coulombs per second (charge flow rate, this is the ions flowing to the collector). $d$ is the air gap distance between the ions and the collector, in meters. $k$ is the ion mobility coefficient of air, in inverse teslas (Nominal value $2\times10^{−4}$ $T^{-1}$). So, if your hero weights 800N, and you have a quarter meter air gap (a large gap might be required to avoid dielectric breakdown), you need to have 640 mC/s flowing. This is just to hover. Add more flow for more force. Changing the position of the point collector will change the direction of thrust. There will be a lot of wind coming off of him, don't use this in places where someone is building a cardhouse. ![enter image description here](https://i.stack.imgur.com/y9ZRK.jpg) Basically, by distributing the ionization surface and creating a point collector, it will look similar to a [hall thruster](https://en.wikipedia.org/wiki/Hall_effect_thruster). ![enter image description here](https://i.stack.imgur.com/ncInB.jpg) There are more options if you allow him technological aid. He can control charge and manipulate it, basically, he can power any electrical device. This is essentially Iron Man's power, because of his [Arc Reactor](http://marvel.wikia.com/Arc_Reactor) he can power everything on his suit. The biggest drawback to most electrical forms of propulsion is storing the energy to run them. But your hero can have electrically powered jet engines or a suit with motorized propellers that are powered by him directly. ## How to break it To disable eddy current hovering, the conductive material needs to be negated. If its broken up or has its resistance increased it will be less effective. Electrostatic levitation is kind of a landmine. Adding a significant amount of charge to something means it's waiting there, desperate to get rid of that charge. Think about the shock you get from a door handle as your body discharges into it. It's incredibly significantly worse than that. So, to break this, just give the object a low resistance path to an uncharged (or oppositely charged) object. Some fine conductive thread can short out hovering items. Breaking electrohydrodynamic thrust can be done by adding conductive material to the air. This would short out the field between the opposing charges. For instance, the super (or regular) villain could launch some [chaff](https://en.wikipedia.org/wiki/Chaff_(countermeasure)) at the hero in flight and mess him up pretty badly. Alternatively the air can be removed, but the hero will probably have other problems in that case. [Answer] So your superhero can produce electricity. What about using lightning for flight? You can write it so that his powers cause tiny explosions under him (or in any location opposite to which he needs propulsion) - by ionizing (giving an electrical charge to the oxygen via creating strong electrical fields) small amounts of air near him, touching said air can result in a discharge produces explosion(s), with which come shockwaves (which can be used for propulsion), heat (self warming? Maybe he should have a really nice suit to protect him from it) and really loud sounds. Thunder loud. As to scenes where he can't fly - If he's dizzy, drugged, or too sleepy, etc, he can't accurately ionize the correct particles of air, resulting in the process being very dangerous and not feasible for said superhero. [Answer] Eletricity and magnetism are intimately linked. So you can make him fly via diamagnetism : <http://en.wikipedia.org/wiki/Diamagnetism> To sum it up : Make eletrical charges spin around the hero. This will generate a magnetic field. If you carefully select the way the electrical charges rotate, you can direct the magnetic field generated. If you direct that magnetic field torwards substances that show diamagnetism, the diamagnetic materials will react generating a magnetic field oposite to the one the hero is generating. This will cause the hero to fly away from the object. Most materials are diamagnetic, but usually by a very small ammount. So you will need really big magnetic fields to cause lift off. On the oposite, you have ferromagnetic materials, like building structures (steel), cars etc. You can attract those instead of repealing them. One prime example of diamagnetic material is water. Using this method, your hero can fly over water quite easily, because water is a good diamagnetic material. When you see a frog being suspended via magnetic levitation, its the diamagnetism of water that is in effect there. You have a source of magnetic field below the frog, and being made of a lot of water, the frog reacts by literally flying. So, a third option (besides diamagnetism in the materials nearby the hero, or ferromagnetism) would be to generate a powerfull source of magnetism below the hero to cause it to lift off just like the frogs in such experiments: [![electromagnets and frog](https://i.stack.imgur.com/0dd5C.jpg)](https://i.stack.imgur.com/0dd5C.jpg) (Original source: <http://www.rare-earth-magnets.com/images/frog.jpg>) Now, imagine that your superhero can make electrical charges rotate in a circle below the superhero (Acting like a electromagnet without the wires and the weight). This will generate a magnetic field. The superhero is composed of mostly water (just like the frog), he is lifted a little. Now he generates the same efect below him, but a little above where he done this before (because he was lifted off by a small ammount). He lifts a little big higher, and so on. If done quickly, this can lift your hero towards any heigth. A side effect (that can be explored in your stories) is that this magnetic field might very well attract ferromagnetic materials nearby. Imagine your hero happyly flying above water. Accidentally he overflies a underwater submerine. Now imagine how the crew would be confused if they find themselves above water out of the blue (literally)... * Skipper ! We are raising !! * Wtf is that ? * OMG we are out of water ! "Clamp !" - Sound of metal hitting a magnet. [Answer] Or, he can make himself into an [Ionocraft](http://en.wikipedia.org/wiki/Ionocraft) But, where's his power coming from? Because these are fairly inefficient (ie: they say they can't carry their own power-sources). Since you're open to suggestions, I think he needs to be directly transforming matter into energy (then harnessing it with 100% efficiency). That will give him enough energy to do some major things with, while not requiring him to eat too much (although he'll probably eat more than normal). Otherwise, you'd have to be grabbing power from the environment, which may impose other limits. If he's doing that, he'll want to be based in Florida. [Answer] Maybe he doesn't fly, but strikes like lightning? Or maybe there's some supernatural link between his powers and the positive / negative ions around? [Answer] Compact Electrical Devices Your character produces electricity, which means that he/she doesn't need to worry about power packs for any kinds of device they use, making it more compact. Anything from the traditional flight pack/boots/gloves you can simply strap on, power up, and go - just add electricity ;) [Answer] What about metal armor panels in his costume, that he lifts? True it is a little like Static. But it also provides him a level of defense against nonconductive, nonmagnetic attacks. Like ceramic knives or rubber bullets. Say put a couple of plates over his torso, front and back. And then wrist and ankle guards. As an additional advantage, he could also control the wrist guards to add speed and impact to his punches. ]
[Question] [ Supposing you took Earth or a planet like it and doubled its mass, the gravity would obviously increase in whatever proportion to that. As a result, humans, as we know them, would be ... more stocky, (I guess?) to support the additional gravity. At what order of magnitude of gravity (or its relative size to Earth) would it become impossible to support a humanoid(ish) life form? That is, the body can only adapt to gravity to a certain degree before it is way too overwhelming to support life. I am looking to get an idea of how much gravity that would take, and which crippling physiological factor would be the first to make humanoid life impossible to live. [Answer] In summary: in higher gravity, humanoids must be smaller or they won't be able to support their own weight. However, smaller creatures cannot have complex enough nervous systems to be intelligent. The first part of the answer involves the gravity of a planet. According to [Newton's law of Gravitation](http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation) the gravitational force on a object is: $$ F=G\frac{m\_1 m\_2}{r^2} $$ Ignoring the factor of $G$, the gravitational acceleration (force over mass) is just proportional to the mass of the planet $M$ and the radius of the planet $R$ (for an object at the surface, distance is equal to radius): $$ g\propto \frac M{R^2} $$ The mass of a planet, assuming the density remains constant, is proportional to volume, which is proportional to radius cubed: $$ M=\rho V\propto R^3 $$ So we find that the surface gravity of a planet is proportional to the radius: $$ g\propto\frac{R^3}{R^2}\propto R $$ So if you double the size of the planet, the gravity also doubles. The second part of the question involves living organisms. The shape of an organism is related to its size due to something we call the [square-cube law](http://en.wikipedia.org/wiki/Square-cube_law). Essentially, the strength is proportional to area (size squared) but weight is proportional to volume (size cubed). This is why a person could not simply be scaled to gigantic size, they would need to become thicker (as you pointed out). As the ratio of weight to strength changes, structures must become change shape. As the ratio increases (more weight) structures must become thicker (e.g. an elephant); as the ratio decreases (less weight) structures can become more spindly (e.g. a fly). Note that most specific shapes occur at a specific range of this ratio, i.e. a specific size: there are no upright-walking humanoids much larger or smaller than humans. For a given density, the weight is also proportional to gravity, so the ratio is proportional to gravity and size: $$ \frac WF\propto \frac{gl^3}{l^2}\propto gl $$ This means that to maintain the same ratio, and therefore the same (humanoid) shape, a creature must become smaller as the gravity increases. Therefore, the size of creature that will evolve a humanoid shape is inversely proportional to planet size. So on a planet twice the size of the Earth, you would have 1 m/3 ft humanoids. There are size limits: smaller humanoids may not have complex enough brains to be sentient, so the gravity can't increase without limit. If you regard children or dwarves as fairly close to the minimum size/complexity, then we're looking for around 1 m/3 ft creatures. At around half the size of average humans, a 1 m/3 ft humanoid could evolve on a double gravity/double size planet. This is a very, very rough estimate, so the absolute limit could be higher (maybe 4 or 5 g). [Answer] Wouldn't another limitation be the atmosphere available in a stronger gravity situation? Increase the gravity too much and your planet starts to hold onto helium and hydrogen. Similarly, air pressure increases, affecting boiling and evaporation points of all sorts of chemicals. I imagine that the suitability of a foreign planet is very narrow in a long term situation. I think you would be limited to .75 to 3 times the size of earth. [Answer] So this will not be a full answer. I agree with the comments made, that without clarifying points/further decisions by you for a target, this can't be completely answered. Additionally, if you are looking for a hard science answer a fair amount of research and math will likely need to be done. In my mind there are three primary things you will need to determine in order to fully answer your question: 1. Determine the amount of gravity for a planet twice the size of earth 2. Are these humans that are adapting to this planet or are they humanoid aliens who evolved here 3. How important the "crippling psychological factor"(s) are 1 Amount of gravity: <https://forum.cosmoquest.org/forum/science-and-space/astronomy/9692-how-do-i-calculate-gravity-on-other-planets> ([here](http://web.archive.org/web/20141221034255/http://cosmoquest.org:80/forum/archive/index.php/t-9855.html) you can find a snapshot of the page at the time of the answer) And follow up: <http://www.scientificamerican.com/article/how-do-scientists-measure/> 2 human or not To me this seems very important as a human, having grown in another environment & attempting to adapt to a heavy gravity would have a steep climb at the beginning. I would imagine a great deal of health problems (circulatory, skeletal, musculature etc...), and risk of accident (falling down might be extremely damaging before the human body built up enough strength to deal with the gravity... if it even could). A human baby born on this planet, and to a much greater extend humanoids evolving in this environment would be likely to have much fewer problems (up to nil with the humanoid aliens). 3 psychology Depending on your answers to 2 I would suggest one or both of the following: Falling, in particular from an elevation above flat ground (as opposed to just falling over). If humanoids adapting to a heavier gravity, the pain of living... Finally there was a hard science fiction book written that explores some of the effects on humans but mostly the effects on native life forms, of a high gravity planet. I recommend reading about it or reading it for some insights. The book is [Mission of Gravity](http://en.wikipedia.org/wiki/Mission_of_Gravity) by Hal Clement (real name Harry Stubbs). In his book he shows a human dealing with somewhere between 2 1/2 to 3 Gs (as I remember it). He also developed a sentient alien race who can withstand far greater gravity... though they are decidedly NOT humanoid (and I believe that was part of his point... their form was determined by evolving under immense gravitational pressure). Of particular note, the race had a learned extreme fear of heights... ]
[Question] [ As you see my other question [What would be the major changes to our body if we were herbivores?](https://worldbuilding.stackexchange.com/questions/4777/what-would-be-the-major-changes-to-our-body-if-we-were-herbivores). Instead of being herbivores, what would happen if we were [obligate carnivores](https://en.wikipedia.org/wiki/Carnivore#Obligate_carnivores)? [Answer] Unmodified humans can survive on a animal-only diet (see: [Inuit diet](https://en.wikipedia.org/wiki/Inuit_diet)). Turning humans into obligate carnivores would require removing the digestive enzymes for dealing with plants, but would not require any changes to the large-scale anatomy. Humans who evolved from an obligate-carnivore ancestry would likely have differently-shaped teeth, with the incisors better adapted for dealing with meat, but this would not be the case with humans who recently lost the ability to digest plant matter (the advantage of more efficient teeth is only a minor one, and does not provide a strong evolutionary pressure). [Answer] If humans had evolved to be obligate carnivores, then there would be some differences in dentition and digestive system, as well as possibly in our hands and feet. Teeth: A carnivore's dentition is, put simply, sharper. Incisors tend to be pointier, there are typically long, pointed canines (rather than the small, typically blunted set humans have), and instead of molars, there are carnassials, teeth designed to cut flesh like a pair of scissors. A carnivore does not need to grind their food, as meat is easily digested even if it is swallowed in relatively large lumps. Their dentition is designed to separate meat from bone and to reduce it to a size that can be swallowed as rapidly as possible. Guts: An obligate carnivore has a large stomach that is used to store as much meat as possible, making a meal last as long as possible. The effort needed to digest meat is relatively low, and carnivores have shorter intestines than omnivores. An obligate-carnivore human's belly might not look too much different to that of a normal human, perhaps flatter when hungry, and more bulging after a meal. They may eat only once each few days rather than several times each day. Hands and feet: Carnivores tend to have claws to facilitate the capture of prey. An obligate carnivore human may have claws rather than nails on their fingers and toes to facilitate capture of prey. Such a beings limbs would likely also be more heavily muscled, as they may be required to hang on to struggling prey animals - the disadvantage with carnivory is that the meal can fight back. This may also mean that the skin would need to be tougher. Some carnivores have very strong jaws to facilitate cracking bones to extract marrow, however for tool-using humans, this can be achieved with the expedient of being able to grip bones and smash them against a hard surface, or by pounding on them with rocks. Hence, such human-like carnivores would make good scavengers too. ]
[Question] [ Setting is in an era when glass would be expensive, in a cold, mountainous region with a lot of goats and horned monsters. I know horn was used in lanterns, but I'm not sure if it would allow through the forms of light that plants crave. Cold/heated frames would be fine, too, if that makes a difference. Would the type of horn matter, and can I vary the thickness, maybe? I know the Romans used some sort of oil cloth, which doesn't seem very transparent. Amount of horn is not an issue due to number of goats and horned monsters in the labyrinth within the mountain. Mostly the populace eats meat and goat cheese, but there aren't a lot of plants during the coldest months. Update: The windows shown at 0:55 would apparently serve the purpose nicely, since folks have pointed out the panes don't have to be completely transparent. No Brawndo necessary. <https://youtu.be/ZgiC8uG4Kpc> [Answer] Transparency as such isn't important for greenhouses – it doesn't matter if you can see through the windows. Usually the purpose of a greenhouse is just to keep the temperature above freezing, for plants that would be damaged by frost; it only needs to let through enough light for plants to grow. That could well be the case if it were glazed with horn, mica, rice paper or other translucent materials. Even if it's significantly dimmer inside, that might be OK, because many plants are adapted to grow in e.g. forest floor locations where they get a lot of shade. It doesn't matter much if the material blocks UV or infrared – most photosynthesis uses visible red light, and to a lesser extent blue light. I assume the horn would come from a fictional creature, as nothing on Earth produces large plates of keratin that you could economically use to glaze a whole building. So you could specify that the horn in question is fairly transparent, like human fingernails. In a permanently frozen region, I doubt even a modern (single-glazed) greenhouse could retain enough heat to prevent frost, so you would probably need heating. If the region is sunny then you could construct snowbanks to reflect additional sunlight into the building. If it's very cold, a greenhouse made from ice might be an option, although that would probably be more technically advanced that just using glass. [Answer] Transparent ~~Aluminum~~ Wood They will need a good chemistry industry and product development, but [transparent wood](https://www.engadget.com/2016-05-16-see-through-wood.html) is showing promise in the lab. One real benefit over glass is that it is a much better insulator. Perhaps animal horns could be treated in a similar manner to make them more useful glass substitues. [Answer] I think it would be easier to make windows out of goat skin or even better - intestines? [Answer] Historically, before glass panels were easy to get ahold of many people used thinly stretched hide for windows. The stuff never gets see through, but if you stretch it super thin it is translucent enough to let in a rather decent amount of light. (When I say hide, think the hide stretched across the tops of drums, but pulled even thinner.) Bonus is that it’s fairly waterproof after being properly treated, sturdy enough you’ve got to put reall effort into tearing it, and somewhat insulating. It wouldn’t work as well as glass for a greenhouse, but I imagine that, coupled with some braziers, plants that like shade would do fine in a hide greenhouse. And making a full building of hide windows would be much less of a logistical nightmare than trying to make a million tiny bone/horn windows. ]
[Question] [ One day, the people of a small village, near [----] woke up to a deafening roar, soon followed by bright flashes of light, coming from the nearby forest. As the roars and thuds didn't let up, they eventually approached the forest. There, in a clearing, they saw two dragons, a larger red one and a smaller white. The red belched fire at the white one, who jumped sideways. However, the fire of the red changed its course. The moment the white saw that she breathed her own bluish flames which let out an ear-piercing shriek when they made contact with the red's causing both to disappear in a puff of smoke. Using the moment the smokescreen appeared, the white one then lunged at the red, biting down his neck and tackling him on the ground. The red fought with all his power, but she was ferocious as if possessed by a devil. Eventually, his attacks slowed down until he barely moved. When the white one saw that, she released his neck and looked up at the "audience" who fled the moment. Ever since then, it has been interpreted as a prophecy that king A (represented by the white dragon) would defeat king B (represented by the red). --- Anyway, I was saying this because of all the societies and civilizations, present in my Metaverse (elements of my story ideas that outlived their setting and stuck with me), dragons are in a muddy territory. I already have the story but I always fail to build the dragon society around it. What's the truth? That scene was a mundane territorial struggle between two dragons, while it's unusual for a female white dragon to win against a male red dragon, that apparently happened. Despite the theatrics, neither of the two were fighting to the death. Biting down the neck is the dragon equivalent of a chokehold. Dragons can also decide what their flames do to the opponent (within the limits of acid-powered nanotechnology), other dragons can sense the effect of the fire by looking at it. I won't go into detail about the [power of the dragonflame](https://www.youtube.com/watch?v=AQVEAPjKae4), so [ask Avdol instead](https://www.youtube.com/watch?v=gH12tvJlSDo&feature=youtu.be&t=26). This kind of fight looks scary for humans as they don't see things with the eye of a dragon, A creature standing two meters at the shoulders and 6-10 meters in length, whose scales are like tenfold shields, tail like a whip that makes thunderclaps when striking, and [a jaw that can crush a watermelon in one bite](https://www.youtube.com/watch?v=8YQGWvvJ0DY&feature=youtu.be&t=7). As for the prophecy. After the fight, the two dragons kinda sorta fell in love because opposites attract. I'm not sure how that translates to kings... ## Other Attributes * Dragons are six-limbed, warmblooded creatures. Their tissues are much tougher than the average (to withstand the stresses of flight). * Dragons are heavily-pneumatized, allowing them to live in higher elevations. They also have decent heat and cold tolerance. Due to the abundance of thermals, some prefer to live close to large lakes or even coasts. * Dragons are omnivorous. Their primary food source is a variety of fruits, occasionally algae, carrion, and fish. They consider humans no to be food, but plenty of trouble. * *Dragonfire is very potent but also very taxing for dragons to use. So, \\their magical abilities can't really be employed in day-to-day life.* * Dragons have their own society and culture. * The smallest and only unit of organization, we see for dragons, are small families and circles of close friends. * Dragons barely interact with or encounter other sentient life. They're basically cryptids like Bigfoot or George Bush. * Dragons are spread thin but present all over the world, mostly because they can fly. * In terms of power level, dragons are formidable but not invulnerable combatants. Story-wise, they can be killed by a well-equipped and trained team of five or a member of the major arcana like Magician. They're also no match for ~~Bondrewd's~~ Best Dad's Death 13, Mephisto's Hanged Man, or The Icon of Simp. * Dragons have a gem embedded near their hearts. This gem, when used as a spell component, can make said spell incredibly powerful (I won't go into detail over why that is or how I stole the idea from Witch's Heart). So there is an incentive for less powerful people to hunt them. So, it'll be regular knights as the major arcana is already way too strong(and lazy). To summarize: You have big, loud flying creatures that people do try to seek out. Now, how can dragons actually avoid that part of humanity for potentially thousands of years (dragons live for long)? As always, the tech level is late medieval with a hint of magic that's actually ancient/forgotten technology, with which we don't concern ourselves. [Answer] I think the best answer for this problem is for the dragons to make it as hard as possible for humans to reach them. If they can't rely on their impressive strength or their magical fire breath stuff to just kill anyone foolish enough to approach them, they can instead fall back on another one of their physical characteristics: wings. A dragon can fly away to some high up mountain peak, making it incredibly hard for anyone to reach them, and if a party big enough that it can't deal with them does get up? No problem, just fly back down or to another mountain. It's like playing tag, except you have wings and the person who is 'it' doesn't. The only way to reliably hunt a dragon would be through stealth while it's asleep, but the dragon could set something up, like a simple alarm trap, to warn them ahead of time. [Answer] They use their keen senses and exceptional camouflage By your description it'd seem like your dragons have keen eyesight to the point they can identify magic by sight alone (at least their own magic) and react to it appropriately. Moreover they want to avoid humans. That way, if their senses are sharp enough, they might be able to sense humans approaching and simply go to the other direction. They could also prefer to live and nest in places harder for humans to reach or actively avoided (caves, the center of dangerous forests, top of mountains, etc). But good senses alone won't help your large creature avoid humans. They should have good camouflage to go around their environment, maybe changing color during mating season to more vibrant tones, explaining a red dragon in the middle of a forest (salmons turn red and grow a humpback, so not impossible). See this example of a camouflaged lizard: [![enter image description here](https://i.stack.imgur.com/dMno2.jpg)](https://i.stack.imgur.com/dMno2.jpg) You can see that even for us that camouflage is decently effective. So if your dragons can blend in with their environment, it'll be a lot easier to hide, even for a large creature (lions can blend really well with the grasslands they live in, so that's an example of a big animal using camouflage).[![enter image description here](https://i.stack.imgur.com/KKdP7.jpg)](https://i.stack.imgur.com/KKdP7.jpg) Alternatively, your dragons could be able to use magic to bend light around them (tied or not to their fire, depends on you) and become essentially invisible (normally that'd mean visible light wouldn't reach their eyes but in this case, because magic, it maybe could). This second option would allow for a larger range of colors unbound by their habitat and present year round, without making them stand out like a beacon in a dark night when they want to hide. Either strategy would help them greatly to hunt, as prey would need means other than their vision (especially in the second case) to avoid being hunted (just like we see in African fauna). [Answer] Humbug's answer is pretty much what I was thinking with my comment although I was going to suggest a little more: * Islands would be ideal for dragons, and might explain why people are only just now threatening them If seaworthy ships are relatively new. I can almost picture them on a smoking volcano. Given an omnivorous diet, this also provides access to fish. If they can swim, caves accessible only from underwater would be perfect. * Dragons would probably control every isolated mountain valley, as these would also be sources of local food (the tops of mountains are rather sterile). * Animal husbandry and gardening would be useful (if they are able), so the dragons have to venture into dangerous areas less often and are more self-sufficient. * They could control oases in deserts, since they could find ones no one else would spot (from the air). * The arctic would be a decent place, as there would be large animals to hunt and they could tolerate the climate. [Answer] Good bombardment techniques. As you note, their dragon breath is expensive to use, and in a close fight they might die. As such, give them fairly keen senses and good aim. Then they can just drop rocks on anyone they don't like, or drop explosives. They can set forests on fire, leave traps, and generally annoy and deter enemies. This means that any enemy who faces them gets killed by massive boulders dropped from the sky. Aerial advantages are enough to deter most predators. Families bonding together against major threats. Against serious threats, close friends will drag their families into the fight. You may see dozens of dragons coming to bombard an army or set traps, if the threat is large enough. [Answer] Influencing the weather and wildlife In addition to The Humbug's answer I propose that the dragons influence their surroundings to make their habitat less inviting for humans. That means they could cause a number of effects: * Dangerous animals flock around their dwellings. This could be done either by some kind of magic ("evil" or dangerous creatures such as wolves and bears are drawn to the dragon's presence), or by leaving the occasional carcass lying around near their roost. In aquatic environments the presence of krakens or aggressive orcas could do the job. If one is situated in Australia, the dragon could enlist the help of drop bears as well. * Strange weather phenomenons occur around their roost. Again, either by handwaving it with "magic" or, more realistically, by using their flame breath to evaporate bodies of water every once in a while. Possible hostile environments could be blizzards, avalanches, thunderstorms, treacherous swamps (caused by excessive rainfall). The dragons could cause dangerous currents around an island, and if a volcano is present, it could mess around in the magma chamber to cause eruptions or at least life-threathening earthquakes. * While we are at it, if the dragon lives close to tectonic plate boundaries (and provided it has magic abilities that allow extensive digging), it could even cause frequent earthquakes in otherwise seemingless harmless places. [Answer] They live in deep caves far below the earth -- like many animals, including assorted lizards dragons are surprisingly adept are squeezing through spaces that look much too small for them. Down undreground, they may have to traverse underwater sections of tunnel (they don't mind holding their breath for a few hours) or vast caverns with a floor hundreds of feet below (easy when you can fly) to get to their comfortable lairs, lined with gold or whatever other trinkets or fancies may appeal to your dragons. Of course a few humans do go looking for them...it's just that nobody has ever come back alive to report of finding a dragon, so we don't know whether they succeeded. The entrance to the so-called dragon-cave is over there. Many foolish folk have sought their fortune down there...many more wise folk have turned away. [Answer] Living in deep subterranean lava caves, largely considered inhospitable. Dragons are immune to fire damage, so they're right at home. Surface access comes in the form of deep canyons and fissures. When a dragon wants to hunt on the surface, it crawls up a large dug underground tunnel to the bottom of a canyon, then flies or climbs up - only at night, to avoid detection. ]
[Question] [ Could a [perfect mirror](http://news.mit.edu/1998/mirror)/s be made to reflect one side of the Earth from the edge of the solar system and viewed with an optical or radio telescope that is in orbit? The targeting mirrors and telescope are in orbit around Earth are aimed away at reflected Earth through the mirrors in synchronous orbit around the sun (shown in the picture below). The mirror in orbit on the telescope can be moved to see different points of reflected Earth to see about 30 seconds into the past. In the comments: What if the Hubble was modified and aimed at the Earth? You can see stuff on a table like a blurry hammer and people.. The fact that you could see anything at all on a table is impressive. Therefore, could use to look back in time in conjunction with gunfire locators to get a visual on the exact location to get the color make and model of a car or outline of a person? I understand the square inverse law and the further away the telescope and mirrors are from Earth the blurrier. The mirror would have to be huge or the viewing area very small. With technology, we could scan of an area on the mirror in which the Earth is reflected with a narrow aperture to take a panoramic picture? I understand that radio telescopes do not work the same as optical telescopes, but could radio and other types of telescopes see objects in black or white on Earth farther away? [![An image of a Magnetic Sail](https://i.stack.imgur.com/cxOtT.jpg)](https://i.stack.imgur.com/cxOtT.jpg) [![enter image description here](https://i.stack.imgur.com/rHm3Z.jpg)](https://i.stack.imgur.com/rHm3Z.jpg) <https://engineering.stackexchange.com/questions/12518/how-many-times-can-the-best-mirrors-reflect-in-space> <https://space.stackexchange.com/questions/30477/could-we-see-someone-walking-on-mars-from-earth> [Answer] Light spreads out as it travels, proportionate to the square of the distance traveled. This is called the ["inverse square law"](https://en.wikipedia.org/wiki/Inverse-square_law). Think about shining a light on a wall - the further away you are, the larger the circle on the wall, and the less bright it is. Less photons per square inch are arriving at the final destination. By the time you get out to the edge of the solar system, The light is so spread out that your mirror would have to be absolutely gargantuan - Half the size of the solar system. It would also have to be curved, to avoid the light spread out any further. As other people have mentioned - focusing issues, dust, gases and other objects in the solar system, as well as quantum weirdness are all acting against you. [Answer] No mirror (or telescope spacecraft) can view an Earthly event earlier than its launch date. The light from any event before the launch is forever beyond the reach of a spacecraft that cannot exceed the speed of light. Alien civilizations orbiting distant stars may, in theory, be examining our distant past, and might be persuaded to share their archives with us. We should immediately begin building enormous telescopes and recording the activities of alien civilizations in order to have something to offer in exchange. A few spacecraft have looked back at Earth and returned distant pictures. The historical value of such photos is limited because they are severely blurred, probably caused by so many people constantly moving around. [Answer] While this wouldn't work with a mirror, there is a way it's theoretically (though not practically) possible: by using a black hole. When light approaches a black hole, some of it ends up getting drawn in, while some of it has its trajectory bent hyperbolically and flies off elsewhere. In practice, this looks like a shining band of light outside the hole's event horizon. With an infinitely-powerful telescope, you could find a black hole and zoom in on just the right point the edge to see light that left Earth aeons ago, got warped around the black hole, and came back toward Earth. In effect you'd have a camera pointed at the past. (Look at [Riccardo Antonelli's description](http://rantonels.github.io/starless/) for much more detail on this, plus pretty pictures, and a program to make your own!) The real problem lies in making an infinitely-powerful telescope, as current ones aren't anywhere near powerful enough for this: we've never even seen a black hole directly yet (depending on your definition of "seen"), and there are some fundamental limitations that mean we can't just keep scaling up our current telescopes to make them stronger. But handwaving a super-powerful telescope is far from the strangest thing that's been done in science fiction. [Answer] Even if we could set aside all the above-mentioned problems — blurriness, mirror size, etc. — we still couldn't 'look into the past' in the way this question seems to imply. To use your example, say we tried to connect the mirror with gunfire locators to focus it on a crime scene. Remember that our message for the mirror to focus on the crime scene can itself only travel at the speed of light. If the mirror is 30 light-seconds away, and we send our 'focus here' message 5 seconds after the guns are fired, well... when we send the 'focus here' message, the mirror is seeing what happened 30 seconds ago (i.e., 25 seconds before the gunfire). But by the time the 'focus here' message arrives, the mirror is seeing the world as it was exactly when we sent that message (i.e., 5 seconds after the gunfire). THere's no way for our message to get ahead of the light traveling outward from earth. [Answer] Others have pointed at focus problems and so. However, spy satellites show that interesting stuff on Earth can be photographed from orbit with a fraction of second delay and with some improvements it could be raised to a few seconds with resolution enough to provide some useful evidence for some crimes happening outdoors. However, this system has an essential flaw: the satellite must be ordered to point to the crime scene, and since the pointing order travels just as fast as light of the crime image, when officials in Earth notice the crime it's too late to point the camera. A workaround could be to point always satellites to everywhere, but if you are going this way you don't even need the delay and you can put your cameras closer to Earth. In fact, this is already done in a lot of cities with surveillance cameras mounted on a pole - which happens to be way cheaper than a satellite or a mirror in Jupiter and gives better quality images. Interestingly, it keeps being cheaper and working finer than a satellite even if you have to install thousands of them and save the huge amount of data they yield. ]
[Question] [ First of all I would like to precise what my species of wyverns actually are. I do not plan to make them huge and gigantic like in many fantasy worlds. Instead they are rather small and can be the size of a cat at most. And they do not breathe fire as they are part of a rather realistic futuristic Earth. These wyverns live relatively around the world (mainly in Antarctica) 100 million years in the future (Antarctica drifted towards the equator and got some of its rainforests back) I would also like to note that humans no longer exist, thus any future evolution is not caused by humans. Wyverns could potentially exist as a few traits like large leathery wings and the simple idea of a large flying creature has already been seen in nature. However these wyverns, being reptiles after all, have to evolve a few traits that would separate them from other reptiles before becoming a flying creature. If I understood correctly, evolution is not really that hazardous. It depends on the environment and heavily influences natural selection. For example whales "returned" to the sea because of the opening of a new "niche" with vast nutritional resources, thus the early cetacean ancestors swam back into the sea and evolved into whales, dolphins etc. In 100 million years many modern animals went extinct (such as most land mammals, birds, virtually all marine mammals, most shark species, turtles etc.) due to the "Sixth extinction" (I'm not gonna bramble about humanity being the cause or something else). And now begs the question. Since my wyverns are descendent from modern reptiles, and replace the niche left open by extinct predatory birds (eagles, falcon etc.) in this scenario, how can wyverns evolve? Can large reptile species like monitor lizards be the likely ancestor of these wyverns? And what would drive them to "take to the skies", to maybe fill up the niche left open by predatory birds? [Answer] Redo the evolution of flapping flight in birds, starting with a lizard. The ancestors of birds ran on the ground and liked to get up into trees and elevated sites. A new theory of the evolution of flight holds that the traction against the ground provided by nascent wings let these bird ancestors get traction on steep surfaces and even vertical surfaces like tree trunks. [Wing-Assisted Incline Running and the Evolution of Flight](http://science.sciencemag.org/content/299/5605/402) > > Adult birds fully capable of aerial flight preferentially employ > wing-assisted incline running (WAIR), rather than flying, to reach > elevated refuges (such as cliffs, trees, and boulders). From the day > of hatching and before attaining sustained aerial flight, developing > ground birds use WAIR to enhance their locomotor performance through > improved foot traction, ultimately permitting vertical running. WAIR > provides insight from behaviors observable in living birds into the > possible role of incipient wings in feathered theropod dinosaurs and > offers a previously unstudied explanation for the evolution of avian > flight. > > > The ideal wyvern precursor would be a fast lizard that liked to get up into trees, ran on the ground and reared up onto just hind legs when it ran (freeing the forelimbs from running duty and allowing them to help in other ways). The [basilisk lizard](https://video.nationalgeographic.com/video/deadliest-jesus-christ-lizard) is the only one I knew of that fit these criteria but it gets so much love. Probably because they can go across water and they look cool. <https://www.youtube.com/watch?v=wJ__rbsytjI> [![basilisk on water](https://i.stack.imgur.com/xszNV.jpg)](https://i.stack.imgur.com/xszNV.jpg) But looking around I found that Australian dragon lizards (good name?) also rear up on hind legs to run. <http://www.reptilesmagazine.com/Information-News/Lizards-On-Hind-Legs/> > > Clemente admits that when he started, he thought that the lizards > would fall into one of two groups: lizards that mostly ran on two > legs, occasionally resorting to four, and lizards that never reared > up. Not so. Even the lizards that he'd never seen on two legs in the > wild managed an occasional few steps on their hind legs. In fact, the > lizards' propensity for running on two legs seemed to be a continuum; > the reddening sand dragon and bearded dragon spent only 5% of the time > supporting themselves on their hind legs while Gilbert's dragon (L. > gilberti) spent 95% in this posture. > > > You can find running basilisks everywhere on the web. A bipedal running dragon lizard was hard for me to find. <http://www.californiaherps.com/behavior/lizardlifehistory.html> [![gilberts dragons](https://i.stack.imgur.com/6RMm2.jpg)](https://i.stack.imgur.com/6RMm2.jpg) In any case these lean quick reptiles make very plausible wyvern ancestors and you can imagine how the power to flap could help them as they currently live. There are some pretty large species of dragon lizards if you want your wyverns to start more substantial, or you could have them evolve flight as small creatures and then get big from there. Either way, 100 million years is plenty of time for the wyverns to radiate into all niches that the birds now occupy. And some they do not - after your readers are used to flying wyverns, the appearance of a mighty sea wyvern will wake them up. [Answer] Keep in mind that evolution is not directed: it has no specific end goal in mind (well, perhaps "continuation of the species"), much less any specific traits it is aiming for. Mutations are real, but selection largely has to work on existing genetics and variations: you're not going to spontaneously have a species develop extra arms without shattering suspension of disbelief. Your best approach, I think, is going to be a multi-step process, starting with choosing your initial creature (a snake, a lizard, whatever), then figuring out the traits of your desired final creature (a wyvern). Mark any differences, which as far as I can tell mostly amounts to the wings, then look at existing species with those traits and try to find out when those developed. Look at the evolutionary pressures that selected for each of your key traits; for one example, as others have mentioned, you'll probably have long leapers eventually transitioning into gliders and then fliers (I would recommend a mountainous environment with lots of ravines and crevasses to jump over). Then, try to construct a plausible history that your initial creature could have endured in your timeframe (which should be larger, the more drastic the changes are, but 100 million years is plenty for just about anything to be believable). This is a general process I'm giving you here, and I understand that it's a fairly significant amount of work and research. But then, if you're trying to make for scientifically plausible evolution over your time period (instead of just assuming "yes, I gave it lots of time, so it could happen" without details), you probably are already willing to sink some time into this detail work. [Answer] ## Just like Pterosauria did develop Take some kind of reptile that is jumping or leaping and if it is an advantage it may be growing skin on its front legs to glide further until it can use this to fly. [Answer] The wyverns evolved to out-compete their only competition other wyverns It’s simple. just another mass extinction level event that made wyverns the dominant species. Could be lots of wyverns types that exist around the world (some that can’t fly some that are massive as houses ect) hell the wyverns that you talk about could have evolved to fly to get away from their own kind that hunted them. They are just the new age dinosaur use that as your guideline. With good details and lots depth your world will be filled with much wonder and awe [Answer] for this just watch <https://www.youtube.com/watch?v=Gnt5wIVjFS0> , he uses dinosaurs, especially yiqi to explain plausibility of dragons like wyverns ]
[Question] [ I've been designing an an intelligent, bat-inspired avian race, and I've been struck with a question that I need answered. Now, I want to have these bats to fulfill different types of ecological niches that are occupied by birds. Think akin to eagles, terns, ravens, maybe even flightless cassowary analogues. I've included a picture illustrating some of the different wing shapes birds have. This means that these bats would be specialized for different kinds of flight, which may mean changing the wing shape. [![Many kinds of bird wings!](https://i.stack.imgur.com/b6ei6.png)](https://i.stack.imgur.com/b6ei6.png) [source](http://alithographica.tumblr.com/post/165885364976/this-week-form-follows-function-you-can-tell-a) From what I've seen, most bats have wing shapes that fall under the elliptical shape category. It's kind of hard to find resources on different bat wing shapes. Now, when I was thinking about changing the shape of the bats wings, I just thought I could change around the length and layout of the fingers until it fit the wing shape I was looking for. I don't think it's that simple though. As you can see from this picture, the different types of bird flight also depend on the birds feathers. The solution I was thinking was making the webbing not go all the way to the tip of the fingers, making a sort of scalloped edge to mimic the feathers seen in some birds. But I don't know if it would negatively affect their flying. Thus, my question. Could you make bat wings that operate like the different types of bird wings? [Answer] The short answer? Bats already have varying wing shapes that do everything bird wings can do and more, if [this](https://en.wikipedia.org/wiki/Bat_flight) is any indication. There is a tremendous variety of bat species that have evolved for various lifestyles, with accordingly different wings. There are bats that pursue (admittedly small) prey like raptors, just as there are bats that thrive mostly on fruit, and even a few blood-drinking vampire bats. It also needs to be noted that bat wings are far more flexible than bird wings. In both cases, wings are evolved arms and hands. Bird fingers, however, are very stiff with a limited range of motion; bat fingers, by contrast, are fragile but capable of a much wider range of motion. Think of a human flapping their arms, then compare it to the dexterity a human hand is capable of, and you'll have a good idea of how adaptable their wings are. Essentially, bats can change the shape of their wings at any given moment to reflect their immediate needs. Frankly, your bigger problem is going to be justifying large bats (which I'm assuming is what you want). Even megabats are small, weighing only a few kilograms, and the larger species tend to be limited to tropical regions, likely due to the energy drain of flying in colder air with wings that lack the insulation of feathers. [Answer] > > Yes, and no. > > > Bird wings are not interchangeable between species. The wings support the aerodynamics of each species of bird. In other words, a bat with elliptical wings needs to look suspiciously like the bird that sports them, including the tail, or the aerodynamics will fail. As to the feathers vs. skin, that will bring about a few changes to how the wings work. Not only can birds control those feathers to a degree, they take advantage of the flexibility of the feathers in their flight. Neither of those advantages would exist with a bat. > > However, you're writing fiction, and the basics of aerodynamics are such that you could modify your bats "along the lines" of how birds' wings are designed to accomodate your needs and it will make a fine story. Indeed, if you take into account the design of birds in their basic totality, then the explanation of your bat would be quite engaging, whether I must suspend my disbelief or not. > > > [Answer] Bats already do this. * Active Soaring Wings - Molossidae (free-tailed bats) are the prime example of this, they have very long, narrow wings and spend a lot of their time above the canopy or in open airspace looking for insects. * Hovering Wings - Bats in general seem to hover a lot easier than birds (except hummingbirds). However, some nectar feeding bats like Leptonycteris are better-than-average hoverers. * Elliptical Wings - Typical of bats that live in heavily forested habitats and need to move around complex obstacles. Some fruit bats are like this, but this in turn varies depending on the type of habitat they live in. * High-Speed Wings - Your generic bat wing. Vespertilionids (a.ka., the most common bat group in temperate climates) tends towards this, but some species that live in thick forests have more elliptical wings. The only one that really doesn't occur in bats is passive soaring wings, and that is mostly because most bats are nocturnal and the few that aren't are fruit-eaters that spend most of their time in thick forests. There aren't any thermals at night to soar on. Carnivorous bats like spectral bats (Vampyrum spectrum) and ghost bats (Macroderma gigas) kind of have wings like this, because they carry off their heavy prey in their mouths, but they don't soar. The two variables you are looking for in describing the different kinds of wing shape are aspect ratio and wing loading. Aspect ratio is the length of the wing from the shoulder to the tip of the longest finger divided by the greatest width of the wing. High aspect ratios are long, narrow wings and low aspect ratios are short, broad ones. High aspect ratios are correlated with faster, more energy efficient flight, whereas low aspect ratios are correlated with slower, more maneuverable flight. Wing loading is the ratio of body mass divided by wing area, and can be summed up as "how hard the bat has to work to stay in the air". There is also a maneuverability/speed trade off, low wing loading results in more maneuverable flight whereas high wing loading results in faster flight. Predatory bats have low wing loading in general because they carry relatively large prey, sapient bats might as well if they are carrying tools a lot. There are actually diagrams very similar to the one you posted for bats, though I am not able to find the good one I had always seen. Google "bat aspect ratio" and quite a few pictures and related articles come up. [Answer] I think it's worth noting that membranous wings cannot fly as high as feathered wings can, partly due to excessive heat loss (entire membrane acts as heat conduction zone, where as feathers naturally insulate wing muscles) and partly due to the thinner air in the upper atmosphere. High soaring birds have very efficient wing structures designed to produce a lot of lift without much exertion. Membrane wings would need to be flapped constantly and at a significant loss of energy; the poor bat would get exhausted before it got very high. [Answer] I don’t see any practical reason why an alternative bat shouldn’t have feathers. It would seem to be an accident of evolution that the ancestors of the bat used stretched skin rather than feathers. I guess it was what was available to them at the time. Of bigger concern is the size of the bat. Bats don’t tend to be much bigger than a kilo or two, and even birds that can weigh substantially more don’t measure up to human weights. I would question what you are trying to achieve when you say bat with feathers what essential aspect are you needing for your story? Does it have to be a flying mammal? Why not start from scratch and build a creature with a brain big enough to provide intelligence, but small enough to fit into a flying animal with wings. Then call it what you want. You might find [this](http://blogs.discovermagazine.com/neuroskeptic/2015/07/26/is-your-brain-really-necessary-revisited/#.We-E0MjfqUk) of interest if you believe that a normal human sized brain is an absolute requirement for intelligence. [Answer] Lets take a look at the anatomy [![bat wing xray](https://i.stack.imgur.com/JLHLt.jpg)](https://i.stack.imgur.com/JLHLt.jpg) [![enter image description here](https://i.stack.imgur.com/ir0Lt.jpg)](https://i.stack.imgur.com/ir0Lt.jpg) As you can tell, the skeletal structure of bats wings and birds wings is quite similar with 3 bones following roughly the same pattern, of course with differences in length. The real difference here comes down to the composition of the rest of the wing. Bats have fingers supporting a skin like carapace which provides enough surface area for lift. Birds on the other hand have feathers. Each feather has a support column much like the finger in the bat wing. Because the bird has more of these individual support structures it has greater control over the shape of its wing. That isn't to say a bat has no control over its shape, it just doesn't anatomically have near the capacity as a bird. Also note: im talking about the pronunciation of the wings apparent change in shape not their capability in flight. ]
[Question] [ In my world there are bipedal insectoid creatures (think kind of like the grasshoppers from Bug's Life) who are sentient and communicate primarily through pheromone signals, with some body language involved. Humans have recently discovered this race, however humans are unable to read or emit the pheromone communications used by the insectoid race, and the insects have no vocal chords with which to create human-like speech. So far the 2 possibilities I've thought of are: * Communication through written language, the insectoid race have hands capable of grasping things, so could hold writing utensils, and they have the intelligence to learn human reading/writing. * A subsidiary race to act as an intermediary, who evolved alongside the insectoid race and are able to communicate with them via pheromones, but are still mammalian enough that they can use vocal communication with humans My problem with these solutions is that the former seems somewhat uninspired, and the latter seems like the entire purpose of the race would be to provide intermediary communication between the insects and the humans, which feels like a bit of an ex-machina to me. What other feasible ways could the 2 species communicate, and/or how could the above ideas be improved? Edit: To give a little more context, the world is roughly European medieval technology level, and there's no magic, so "babel fish"-esque translation devices are out of the question. The setting is very much a fantasy setting, but I'm still trying to go for a sort of "low" fantasy setting, so I'm sticking to realism and feasibility where possible (overlooking the fact that human-sized insectoid creatures would have to be significantly different to insects due to size difference). The insects are subterranean, and tend to keep to their hives, which is why the humans have only recently discovered them. In terms of technology level, they're around late bronze age/early iron age, far behind humans, but have demonstrated that they have an early iron age understanding of metallurgy, and, given that they have evolved beyond the hegemonic hive-mind structure of their ancestors (despite still being very closely bonded to their hive), they have shown their ability to pass knowledge to their offspring, and they have rudimentary education systems in place. The insectoid race can also make a sort of chittering sound with their mandibles, although while this can be done at will similarly to human laughing, it is usually an instinctive action when feeling angry or threatened. To answer the question of why they might want to communicate in the first place, the insects would like to communicate with the humans in order to gain knowledge and hopefully advance their own technological understanding, the humans would like to communicate because a specific faction of the humans are particularly interested in communication with and study of new species, many of which are recently and suddenly popping up in the world. [Answer] I think the more important question is: Why even communicate? If we are dealing with pure scientific curiosity, the level at which communication is taking place would be rather basic. You have already mentioned body language. This is a very popular strategy of how humans have tried to communicate with other species. People that do not speak the same language in general often depend heavily to body language as well in order to get their message across, even though both parties communicate through sound. With some patience, one can communicate on a semi-practical level even, check out contacting "lost tribes". Those of course are not a 100% fitting cases, but cases nonetheless. You might have to live with the fact that a deep, philosophical conversation might be as simple as it is amongst humans. Things get more complicated though if there is a true need for communications. I want to pick one particular case: A treaty has to be negotiated, be it for trade, exchange, peace or territory. The reason behind it does not matter as much. I do not like the written alphabetical language idea either simply because we write our language in sounds and they would write their language in chemicals. We cannot even decipher some of our own (lost) languages, how are medieval people going to manage that task? I do not say it is impossible, but especially given their tech level the ants might have to invent writing first (depending on what you mean by bronze/iron age). There however is another way: A pictographic/ideographic written language. Please stay with me, I will tell you in a moment how this does look like without writing. I do not believe that if you want true correspondence between the two races you get to not have a language that can't be made permanent. However, it could be as basic and clear as possible. This is how most likely any written language has developed. Do not confuse this with them having hands to draw. They can paint with their behinds for example, insects like to use their full body for stuff. Since the humans are the more developed race, it would only seem logical that they introduced them to the concept of paper if needed. Also I should note that I am not aware of any human cooperation between different people that has ever done something lasting, positive and worth remembering without writing (maybe partially because nobody wrote it done and now it doesn't matter anymore). Also please note that any contact by humans would be on the basis of what they know and are used to. A medieval guy will not suddenly come up with the most creative approach ever because he was so inspired by the (mediocre) movie "Arrival". Here is some further, related reading: <https://en.wikipedia.org/wiki/Yerkish> Yes, you explicitly stated you did not want that way, but I hope I explained why you should reconsider. If you hate the idea of writing so much, do not think 2D. Think 3D. A pot can be an actual pot made out of clay (something we used to write on a lot), a cow can be a clay cow. Insects can form those objects because they really like to put stuff in their mouths, chew it a couple of times and then spit it out and make something out of it. So how do you make a 3D treaty? Well, I think this is rather intuitive and maybe even awesome. If this point is unclear, I could elaborate on it. I would like to give you more details on how I would go about such things, but I feel like at this point one would have to know what the specific reason is those races came in contact with each other initially, stayed in contact for ever since and what reasons they have for communicating now. [Answer] Can the insectoids hear over a similar range of frequencies as humans? Then they can learn to understand human language, even if they can't speak it. That's half of the problem solved. If they can't hear human speech properly, then presumably they can at least see. Thus, they could learn to understand human sign languages. Again, that's half the problem solved. Now, they may not have vocal cords, but are they capable of producing any sounds at all? Then they could create a sound-based code for their language, or a code for a human language (e.g. Morse code) to allow them to speak back to humans. Or, although their hands and arms are unlikely to be of the right shape to perfectly reproduce a human sign language, just as their vocal apparatus is incapable of perfectly reproducing human vocal language, they could still come up with some sort of sign language which humans could watch and understand, even if humans can't produce it. In short: each side speaks a different language, or a different code for the same language, whether it's sound-based or sign-based, but both sides are able to understand both languages/codes. [Answer] Too bad your setting is medieval, Bernard Werber wrote a full passage of an ant-to-human translating machine in [La Révolution des Fourmis](https://en.wikipedia.org/wiki/Empire_of_the_Ants_(novel)) (the revolution of the ants). It consists of a tiny machine with two metal things the ant touches with its antennas so the translator can know the position of antennas by standard mesure (in millimeters for example). Then (this is the non medieval part) pheromones are absorbed in a machine to translate them to words. Although you can handwave the pheromone translator, general translation problem will occur, for example how do you translate "table" to a fully-organic-natural ant? [Answer] I do think that developing a pictographic pidgin language a la @Raditz\_35 would be the most efficient way. But let's have some fun... Maybe these insectoids with their faceted eyes have trouble seeing details so small as writing. But they are tops at seeing movement! So the pidgin language that evolves is based on interpretive dance. Each species has its own moves, but they've taught each other to read one another's dance. ]
[Question] [ * The average power utilization per person is 1 Megawatt. * The average living space is 1000 cubic meters per person. * The average total mass in use by a person is 1000 tons. Assumptions 1. Solar power conversion efficiency is 20% ; 2. 3 meters of ice or equivalent shielding required around a habitat for 500,000 to 1,000,000 people. 3. Very high recycling capability, (< 1% loss per century) and thus no limits imposed by lack of materials. It can be recovered or made it from common basic elements. 4. Assume that at least 100,000 tons per second captured from solar-wind once population reaches 100 billion. [Answer] Roughly $1\times10^{20}$ people. Take the solar output of the sun, $4\times10^{26} \text{W}$, divide by watts per person, $1\times10^{6} \text{W}$, and factor in the solar efficiency. Check this against the volume of the solar system, $3.82\times10^{29} \text{km}^3$, to make sure that everyone has enough room, which they do. ### But what about the usable mass? The mass of the solar system is $1.0014$ stellar masses. A Stellar mass is roughly $2\times10^{30} \text{kg}$. Subtracting the mass of the sun ($1$ stellar mass) gives us $2.8\times10^{27} \text{kg}$ to use to support humans. Dividing this mass by the mass per person, $1\times10^{6} \text{kg}$, we can say that there is enough mass to support $2.8\times10^{21}$ people in the solar system. From this we can see that we are still constrained by energy consumption. ]
[Question] [ This has been bothering me for a while but I was reminded of it when I started playing Skyrim again. In the dungeons there are some mechanic works, examples including: * Lever controlled heavy doors and bridges * Pressure plate controlled traps * Traps disabled by levers * Puzzles that require a certain combination * Even more crazy things in Dwemer Ruins (I guess magic shenanigans are involved there so no need to consider this) These systems don't seem feasible because: * Heavy doors and bridges require a high amount of power. Some of those doors are made out of steel and I guess some must weight up to 2 tons. How can a mechanic structure lift it in a world when there is no electricity, with just a pull of lever? * Some of the bridges that are controlled by levers are across a gap, so there is not a direct connection. I guess the chain mechanism goes around the gap but wouldn't that increase friction and need more power? * Combination puzzles require some kind of logic, right? * These ruins are ancient. How could the traps and such still work? Don't they get rusty? What if a rat sneaks in to the mechanism and gets stuck there? * These systems are not even uncommon. You can find one dungeon in every 10 minute of walk. How these systems work would and how feasible they are? Also some examples from real world would be good. [Answer] > > Heavy doors and bridges require a high amount of power. Some of those doors are made out of steel and I guess some must weight up to 2 tons. How can a mechanic structure lift it in a world when there is no electricity, with just a pull of lever? > > > Counterweight. As long as you have strong enough ropes, you can lift anything as long as you have counterweight of similar weight. This is how pyramids were built. The critical problem with this is that the mechanism is one-use only. After the mechanism is triggered, it needs to be manually reset. It is also not that big a problem to create a mechanical system that turns small force of a lever or pressure plate into big force, like moving a stone or springing a trap. > > Some of the bridges that are controlled by levers are across a gap, so there is not a direct connection. I guess the chain mechanism goes around the gap but wouldn't that increase friction and need more power? > > > You can have small wire/string going across the gap. And the counterweight could be on the other side. > > Combination puzzles require some kind of logic, right? > > > Mechanical ancient locks are good example that simple "logic" is possible, as long as that logic is about "set this gizmo to this specific location/state that is independent of anything else". > > These ruins are ancient. How could the traps and such still work? Don't they get rusty? What if a rat sneaks in to the mechanism and gets stuck there? > > > That is a critical problem, yes. > > These systems are not even uncommon. You can find one dungeon in every 10 minute of walk. > > > If you are rich enough and live in culture that believes your corpse should be buried with lots of riches, then you are going to invest a lot of money, resources and work into making sure no one can get into your tomb. > > How these systems work would and how feasible they are? > > > Simple mechanics could work. They are feasible, but not on a level seen in movies and videogames. Single tomb of rich Pharaoh might have few traps, that might last few years. But idea of huge complex full of lever-controlled doors and traps, that still work after few millennia is ridiculous. [Answer] > > Heavy doors and bridges require a high amount of power. Some of those > doors are made out of steel and I guess some must weight up to 2 tons. > How can a mechanic structure lift it in a world when there is no > electricity, with just a pull of lever? > > > Mechanical engineering has been around for thousands of years, and nothing here is really all that unique. It does take creativity and some solutions may only work in special situations. For example, a 2 ton door could be lifted open because of a fulcrum. A simple lever could shift a pipe that diverts 1.5 tons of water into a 1 ton container producing a counterweight to lift the door. The door could release when the lever moves back to its original position by removing the seal on the container (or is already designed with a leak and when the container no longer receives the water the door would slowly fall). > > Some of the bridges that are controlled by levers are across a gap, so > there is not a direct connection. I guess the chain mechanism goes > around the gap but wouldn't that increase friction and need more > power? > > > It doesn't necessarily require large elements to implement. Again using water, its possible to create a trigger similar to a modern toilet flushing mechanism that reacts either to an increase or decrease in water levels. It may also be possible to implement triggers using light, heat or sound. > > Combination puzzles require some kind of logic, right? > > > Logic has also been around for thousands of years... in fact certain aspects of logic are foundations of both mathematics and philosophy. A system requiring flipping a series of switches could be considered a lock even if its on a much larger scale than we are used to. [Answer] ## We've built these before Mechanical logic puzzles of levers and cogs are not a fantasy by a long shot -- railroads have used mechanical interlocking hardware for well over a century now to keep trains from running into each other. These were sometimes massive beasts, occupying a cabin the size of a small two-story house, with hundreds of inputs from and dozens of outputs to levers, indicators, signals, and turnouts (switches) at major railroad junctions. These interlockings could implement highly sophisticated logic functions, and were often called upon to do just that in order to prevent incompatible inputs from being accepted (such as trying to move a switch out from under a train's path, or clear a signal across a junction that's already been cleared across in a different direction). While the technology was obsoleted by electromechanical relay logic, it was a vital part of the railroad world for several decades, and is still in use in a few areas where installing newer systems would be cost-prohibitive. Several museums have also preserved decommissioned interlocking machines. [Answer] It could be a simple pressure switch to activate a counterweight or hydraulic mechanism. Not much power required. Regarding age and maintenance, that's a problem. Genre convention suggests to pay no attention. Examples can be found on the [Smithsonian](http://www.smithsonianmag.com/science-nature/old-world-high-tech-141284744/?page=2) site. [Answer] Possible, but not feasible. Unless the complex mechanism is valued by itself as a status symbol, then there is no reason. * Reloading traps * Maintenance Some small traps are feasible, but the stress of huge counter weight puts on the mechanism is simply too much. The traps could thus be almost single use. It is likely cheaper to have guards than a maintenance crew. ]
[Question] [ For the sake of convenience, this happens on Earth. However, in this scenario only the American continent (all of it) is inhabited. One of the countries is experimenting with extremely advanced and extremely hazardous power generation technology, codename project Nova. The Nova facility is located underground somewhere below the Amazonian forest. You can move the facility somewhere else if you need to, just keep it far from any population center. Obviously, the experiment goes horribly wrong. The experimental reactor ends its life in a blaze of glory, that is to say kaboom. The explosion triggers the biggest earthquake in recorded history. In the wake of the quake and aftershock, there is quite a bit of destruction. On the surface the damage is extensive but it's nothing that can't be repaired/rebuilt. Below the surface, the quake has shaken the ground so hard the planet will become uninhabitable. When will it happen? The continent will be come uninhabitable in 50 to 100 years, the rest of the planet will eventually be as inhospitable. On the bright side, everybody will get evacuated, so hooray for FTL and unlimited budget. Anyways, I need a good reason why the planet will become practically uninhabitable. My thought was that the quake would trigger a chain reaction that would result in increasing seismic and volcanic activity that would eventually shake every building down, block the sun with clouds of dust, and flood the streets with lava. Is that even possible? If not, how can I effectively end the world starting with one big explosion? --- I'll clarify on the requirement. The planet doesn't have to be actually uninhabitable. If there's enough casualties and the living conditions become too bad, governments will start looking at their options. In short, there are three Earth-like planets at different places in the galaxy. FTL technology is limited to one FTL drive of alien origin and one reverse-engineered, almost complete prototype. Both are untested but the technology would be (successful, something has to go right from time to time,) used to evacuate people off. The process would take decades, but would be over before living conditions became too insane. That option has to be more appealing than whatever will happen if they stay. They don't have the technology to terraform, nor the desire to. [Answer] Since you said in the comments that the location can be changed, here is my suggestion : Move your facility near enough the Yellowstone Park Your Nova facility is still underground, and the explosion still triggers a massive, MASSIVE earthquake. No need to change that. This earthquake shatters the moutains, provoking landslides, and ultimately, wakes the Yellowstone Volcano by adding pressure in its inside. When this volcano explodes, its ashes will spread all over North America, and depending on the winds, maybe all over the world according to some scientists. Lots of studies have been made on a potential Yellowstone catastrophe, I suggest you do a little more research on this topic, but here's what's interesting in this case : Ashes will blot out the sun for years, killing the crops and harvests, suffocating lots of people / cattle. People won't be able to grow food anymore. That's where you get you countdown : People will survive as long as they have food stocks. But in about 50 to 100 years, with no food growing anymore, they will die out of hunger. Except if the few survivors can provide food for everyone else, which I highly doubt. [Answer] You cannot make Earth uninhabitable by earthquakes only. Especially if no big damage will be inflicted at the beginning. Your best bet would to awake Yellowstone supervolcano, but even THAT will not be enough. Even much larger volcano eruption, [Deccan lava flow](https://en.wikipedia.org/wiki/Deccan_Traps) might have helped to extinguish dinosaurs but did not make Earth uninhabitable. [Siberian traps](https://en.wikipedia.org/wiki/Siberian_Traps) was even bigger, when Earth was younger (500MYA) and continued for 200MY but did not extinguished life on our planet. Read up on [Earth mantle](https://en.wikipedia.org/wiki/Mantle_%28geology%29). You cannot put anything into the mantle which will survive for centuries to create more disturbancies. Yes, after such volcanic activity population of the planet will decrease, possibly significantly, but civilization and technology will NOT be wiped out. What you can do is to arrange for bombarding Earth by series of "space rocks". Terraforming of the Moon/Mars gone bad? If you time it correctly, and will coincide with Yelowstone supervolcano eruption (first chunk might fall into it, opening it for explosion), you may grind down survivors after few centuries: While survivors would be too preoccupied trying to eke out living, they will NOT to be able to divert next strike - and then another and another. EDIT: So lets assume timeframe: * Terraforming Moon blew it into pieces. One chunk hits Yellowstone, which explosion covers USA with 3 feet of ash, destroys agriculture, kills 100M people immediately, and stops flight and global trade. For better effect, few more pieces hit Europe, Pacific (causing 300 feet tsunami hit Japan and China and Australia, wiping coastal settlements) and South Atlantic. * Global trade collapses. Civilization reverts to Middle Ages, wars for resources ensue, with few lucky areas re-building technology of industrial revolution. * Climate collapses. Volcanoes spew sulphur, increasing the greenhouse effect Now, more stray pieces of rocks are flying to Earth, but there is no way to build rockets to deal with them. So these rocks will keep pummeling the survivors. [Answer] We the human race have become quite proficient at modeling the environment to our needs and our taste. And, if we could not, we build our own closed environment. We placed people on space and on Moon's surface, and we are planning to place one of our kind on another planet's (Mars) surface. All of it with our current technology. Don't count on buildings falling down, we already engineered and developed anti-earthquakes systems and seismic resistant skyscrapers. So if the world will become uninhabitable in 50-100 years, I think we can work on something about the buildings. Also, we are currently able to move other organic life away from its natural environment and make it live as usual. Industrial indoor hydroponics, air and water filtering and conditioning, and mineral resources processing are actual things, so I wouldn't expect a food shortage at our current tech level. The population in your setting has access to faster-than-light travel, which we can only dream about, so you can build anti-seismic closed environments to shelter your population until the world is habitable again. For an evacuation plan to be the only salvation you need to make the planet uninhabitable FOR GOOD. That's to say you need planetary catastrophe/destruction gradual enough to give your population 50-100 years to notice it and evacuate the planet. And I can think a way to achieve this after the initial shock: Harmonic resonance Your Nova facility triggered a seismic wave in the very exact frequency (or spectrum) that leads to a harmonic retro-alimentation cycle into the planet's core that will eventually rip the Earth's crust. It is hard to achieve through uniform solid, and a lot harder through different densities liquid, but maybe this shockwave triggered an alteration at the core's hydrodynamics that destabilized the mantle and feeds the retro-alimentation cycle. I know that the chances are very VERY small to reach a scenario like this, but if they already have faster-than-light travel for sure they can achieve the energy levels to create such situation. EDIT: Removed the black hole scenario [Answer] Clearly, the NOVA corp is experimenting with an artificial supernova or black hole otherwise there name would be pointless. What advanced race would not want a nearly unlimited source of energy such as a blackhole. Obviously, as a precaution they would be using a small possibly micro blackhole. Yet, large enough that simple containment was impossible. A technician monkeying with the gravitational compensator messes up, or sabotage and boom. The explosion would be failure of the containment system, potentially the blackhole goes supernova at this time. The blackhole remains and/or reforms, and starts gradually sucking the planet in. If the NOVA facility is on the exact opposite side of the planet you might be able to get 50-100 years. Maybe the safe guards of the facility and its physical design cause the blackhole to be ejected into orbit. Eventually it could consume the planet. The cost to contain and rebuild would have to be high enough to make rebuilding impracticable. This kind of evacuation would also occur if the remaining resources were going to be depleted or somehow contaminated beyond the cost effective ability to clean it up. If and when a race reaches the point they have FTL there isn't going to be much beyond there reach. Advanced teraforming equipment will be able to repair all but the most devastating events. If they have 50-100 years the new developments in technology will probably let them overcome the explosion. 1. blackhole has to slowly eat the planet 2. Radiation levels to gradually rise planet wide to unsafe levels. 3. If the major supply of water was contaminated or the natural resource they came for was contaminated. 4. Gradual loss of atmosphere. Today, a source of gradually spreading nuclear radiation would, totally work as a reason to leave a planet. However, if you have FTL containment would probably be trivial. [Answer] We're slowly managing the damage done by the Nova experiment, and while the crater is properly guarded from nosy civilians, we've encounter a problem which might be life ending, so please read the following with utmost concentration: It seems like the explosion's damage hasn't only affected the crust of the earth, but minute unidentified particles radiated and have entered the earths magnetic core. At this moment the effects are minimal, but they're slowly drifting towards the center of the mass. According to the lab tests we've done so far, the closer these parts come together, micro black holes they will form, effectively distorting the earth core beyond our control. It will not destroy the earth, but it will distort the planet violently enough to render it inhabitable for human life. Simulations have calculated an estimate of ~94% chance of this happening before returning to a status quo state. Immediate global evacuation is recommended. ]
[Question] [ On an Earth-like planet, there is a massive plateau, standing more than 1km high, and the breadth of a continent in the middle of an otherwise ocean planet. I know there are climactic issues to this, but instead of hand-waving it, the best answer would explain the processes that created this steep, high continental mass. High-level, and not magic and no humans. On the continent (size of, say, Africa) is most biomes - desert, forest, lakes, rivers sourced by artesian springs/rain, and then cascade off the sides of the continent. There are plants and animals. This is for a young adult novel, so I am not using the hard-science tag. [Answer] Massive glaciation Most continents are already shaped somewhat like plateaus. They slope gently towards the continental margins, before fairly abruptly dropping down to the ocean floor. In profile, they look something like this: [![enter image description here](https://i.stack.imgur.com/6701r.png)](https://i.stack.imgur.com/6701r.png) The issue is that most of that plateau-like shape is hidden by water. However, if you get rid of a lot of that water, your continent will start to look more plateau-like. Massive glaciation would help achieve this. If a significant portion of the planet's oceans are bound up in glaciers, the corresponding lowering of sea levels will make your continents more plateau like. Planets which previously had a steep continental slope with little to no continental shelf will appear as plateaus sticking out of the ocean. Africa is an example of a continent that would appear more plateau-like in this case, while the west coast of South America would also appear to rise sharply out of the ocean. [Answer] A super-massive [pumice raft](https://en.wikipedia.org/wiki/Pumice_raft). Created by continual ocean-based volcanic activity, you could have an increasingly large floating island forming, especially if your planetary ocean did not have significant tidal/current action to shift the raft around. This might be the most feasible on a planet with low gravity; not sure you could get it more than 1 km high otherwise -- you're dealing with displacement vs. mass physics at that point. The density of the pumice would also be a factor in how buoyant it is. Pumice rafts reported from 2012 volcanic eruptions were reported to be ~300 miles long & ~30 miles wide, but only riding about 2 feet from the surface. As per my other answer, given enough time and initial planetary biodiversity, the pumice raft would hopefully be seeded with life. [Answer] Conan Doyle used real-world tepuis for his Lost World story, and though the Earth ones aren't as much surface area as you're looking for, the geology and height otherwise seem about right: [![Roraima, apprently?](https://i.stack.imgur.com/scYpJ.jpg)](https://i.stack.imgur.com/scYpJ.jpg) <http://www.amusingplanet.com/2013/05/tabletop-mountains-or-tepuis-of.html> <https://en.wikipedia.org/wiki/Tepui> Though they're lofted from jungles rather than from the sea floor, it might not be too much of a stretch to theorize some swift climate shifting to submerge a lowland with these features, and they definitely fit your 1k height requirement. The morphology section of the Wikipedia link should give you enough research information to extrapolate your version, I think? [Answer] From [Wikipedia on how plateaus are formed](https://en.wikipedia.org/wiki/Plateau): > > Plateaus can be formed by a number of processes, including upwelling > of volcanic magma, extrusion of lava, and erosion by water and > glaciers. Magma rises from the mantle causing the ground to swell > upward, in really large, flat areas of rock that are uplifted. > Plateaus can also be built up by lava spreading outward from cracks > and weak areas in the crust. Plateaus can also be formed by the > erosional processes of glaciers on mountain ranges, leaving them > sitting between the mountain ranges. Water can also erode mountains > and other landforms down into plateaus. Computer modeling studies > suggest that high plateaus may also be partially a result from the > feedback between tectonic deformation and dry climatic conditions > created at the lee side of growing orogens. > > > I don't see any particular reason why these natural processes could not produce a continent as you describe--especially if the right combination of plate tectonics and volcanic activity occurred. There are already quite large plateaus in the world: the [Tibetan Plateau](https://en.wikipedia.org/wiki/Tibetan_Plateau) is about 2,500,000 square kilometers (about 1/12 the size of Africa) and is 4.5 times higher above sea level, on average, than your mythical continent. [Answer] A massive large igneous province. the Columbia plateau is one example of such a thing, probably caused by hotspot as opposed to continental rifting, then glaciation. not perfect, but as close as I could surmise. [Answer] The low-velocity impact of a large asteroid in the distant past. The feasibility of this would heavily depend on physics dealing with the size of the asteroid & its speed, as well as the depth of the planet's oceans. * Too fast? -- It would break up into a bunch of small pieces upon impact. * Too large? -- It'd possibly vaporize most of the ocean or break the planet itself into pieces. * Ocean too deep? -- It wouldn't stick up out of the ocean far enough. Given enough time and initial planetary biodiversity, the barren asteroid could be seeded with the biomes you describe. [Answer] Have a smallish tectonic plate, with two massive plates moving towards and sliding under it, one from each side. The approaching plates would combine to lift up the central smaller one. You'd end up with a lot of volcanic activity and mountain-forming at each join and the smaller plate potentially hoisted right out of the ocean as the other two went under it. ]
[Question] [ They say that nature abhors a vacuum, but could life evolve to live in one? Alternately, could life be engineered to exist on a planet with no atmosphere, even if there is no biologically feasible path through which this life form could evolve? By vacuum, I mean 'no atmosphere', but with ground. Something like the moon, rather than something like deep space. If life in a vacuum is possible, what I'm really interested in is this: what would the life forms be like? What adaptations would they need to cope with life in a vacuum? [Answer] Theoretically, a planet with a hard, gas-impermeable crust and no atmosphere could support life in subsurface rivers which were warmed and mineral enriched by hydrothermal vents. The crust would keep the rivers from evaporating while life took hold and evolved. Later, when that life was sufficiently advanced, the crust might crack, slowly venting away the rivers into outer space. Over millenia, while their native environment slowly dried up, the life could evolve and adapt. At a minimum, it would need the ability to consume minerals in solid form, without the need for suspending them in a liquid medium. They would need an impermeable shell to keep their vital fluids from evaporating. And they would need some form of energy production to fuel their motion and cellular growth. Perhaps natural solar panels could fill that last role. Sounds like I've just described an armoured form of plant life... Throw in a redundant, error-correcting genetic structure to handle the inherent radiation, and I think you've got an empty space life form on your hands. [Answer] I could see life forms adapting to live in a vacuum, but to just come into being, is unlikely because you need chemicals and chemical reactions to make life. Living in a vacuum the life would have to have a good shell of some kind to seriously control the movement of atoms both into it ('eating', 'respiration') and leaving (waste). I would expect it to have several catalyst reactions to recycle as much of it's waste as possible, and it should have a generally low metabolism or at least can go dormant with only a few autonomic systems working to wake it up should things change, such as more food/water/air becomes available for it to continue its processes. [Answer] For life as we know it: It does not. The way biological processes work a relatively high concentration suspension of chemicals in a fluid over significant period of time and volume of space is required. Fluids evaporate if pressure is too low. Vacuum has very low pressure. Life that evolves inside an asteroid or moon that lacks atmosphere might be possible. Although maintaining fluid environment over long period of time would probably result in a trace atmosphere. [Answer] I would have thought it could survive in a vacuum. Fundamentally, all life needs is energy. Everything else is a means to an end. If an organism were designed to make use of the higher solar radiation possible without a pesky atmosphere in the way, it could do very well out of the whole thing. Terrestrial-style grass might even be possible if the grass is designed in such a way that it can take all the oxygen it requires from the soil or rock present. When the plant dies, the minerals are returned to the soil and new plant life can spring up. I'm not sure how far along you could get, but an entire non-breathing planet could be plausible. [Answer] What do you mean by "evolve" here? I do not believe that life could originate in vacuum. Very primitive life requires hospitable conditions and space doesn't qualify. You need a shell that can retain your solvent and you need radiation protection. That does not preclude life in a vacuum, though. Look at the extremophiles--they live in conditions that would have immediately destroyed primitive life but they were able to adapt over time. Take a world like Mars--I wouldn't consider it impossible for life to have evolved defenses that allowed it to continue as the atmosphere bled away over the eons. You could even get outer-space life this way--take a lifebearing planet, slowly bleed the atmosphere and then knock it into the sky in a big impact event. [Answer] From [this](http://www.nasa.gov/vision/universe/starsgalaxies/life's_working_definition.html) article on the NASA website > > Living things tend to be complex and highly organized. They have the ability to take in energy from the environment and transform it for growth and reproduction. Organisms tend toward homeostasis: an equilibrium of parameters that define their internal environment. Living creatures respond, and their stimulation fosters a reaction-like motion, recoil, and in advanced forms, learning. Life is reproductive, as some kind of copying is needed for evolution to take hold through a population's mutation and natural selection. To grow and develop, living creatures need foremost to be consumers, since growth includes changing biomass, creating new individuals, and the shedding of waste. > > > I suppose it depends on how you want to define life. The definition of life above could easily exist without an atmosphere, the issue of breathing, which I'm assuming you're mainly referring to when thinking of an atmosphere (ignoring the radiation and vacuum issues for the moment), is simply part of the energy intake process that we've evolved into ([more info here](https://en.wikipedia.org/wiki/Cellular_respiration)). So, the first adaptation is an alternative form of energy intake, such as solar (since you gave the surface of the moon as an example, lets go with that). The vacuum question is, to my mind at least, one of pressure. Human, and other creatures that have evolved to live at sea level (i.e. at 1 atmosphere, or 1 bar) don't tend to do well is low pressure environments. The [Death Zone of Mt. Everest](https://en.wikipedia.org/wiki/Mount_Everest#Death_zone) springs to mind. In a vacuum, there isn't a lot of ambient pressure, so [unprotected humans don't do too well](https://en.wikipedia.org/wiki/Space_exposure). So, as alluded to by other answers, creatures with a tough exo-skeleton can survive in a vacuum for short periods, as can space suit wearing humans. Deep sea marine life also has [adaptations](https://en.wikipedia.org/wiki/Deep_sea_creature#Barometric_pressure) to deal with non-sea level pressures. What would life in the absence of an atmosphere look like? Consider the following: * Creatures with tough, possibly exo-skeletal type bodies, such as robots or beetles * Gaseous creatures without solid bodies, i.e. sentient clouds * Pure energy beings, think... something you can't see that can only communicate by varying it's own energy expenditure * Beings large enough to have their own atmosphere and creatures living on them, such as Earth [Answer] Some people addressed the question of "possible life forms that would evolve" rather than point out that life on Earth as we know it would not work. I will keep going in that direction. There's nothing about our specific nature that makes us more alive than a completely neutral object like a rock. Even though plants are made up of complex cels like animals are, a plant is more like a highly dynamic static object such as a rock, while animals containing a nervous system are able to store information and act, anywhere in the range of a jellyfish (non centralized nervous system but still maintaining an energy state) to a human (highly centralized and more information stored and manipulated). So, for the question of life, let's start with finding if an energy state can be maintained rather than the typical reproduction centered meaning of life. I think most of what we consider life is an insulating membrane, and the ability to take input and produce output in a controlled, predictably beneficial way. Mitochondria (energy production organelle) do this, and they are theorized to be the first kind of living organism. They also have their own DNA. One could theorize that the very first existence of life was slice of DNA-like reproductive material, which in some medium was able to influence the creation of some type of protein-like molecule that enabled more reproduction of the material and thus more production of the protein. Basically it was taking energy from the environment and threading it along some delicate pathway. It is unique form of chemical reaction, in that it leaves a memory of itself in different forms as the DNA-like material. Thus, as it multiplies and tweaks the reaction, it is able to try many forms with the hope of identifying a new path-of-least-resistance, while not abandoning previously successful forms. Eventually, the reproductive material that produces the protein and reproduces itself starts reproducing itself with a sequence that codes for a protein that influences the development of a membrane, which has a positive effect on the reproduction/proteins system. This is the basic theme established- a system based on stored information that drives a specialized metabolism will establish ways to ensure a controlled development. It's a positive feedback loop that implements its own homeostatic environment. This theme should carry us from a Mitochondrion, to a cell, to a multicellular organism, to a human with a brain. I could see "gaseous cloud" beings as someone mentioned, possibly having some type of light membrane material inside of and around itself. I could also envision something evolving in liquid rock and possibly engineering a way to leave access the surface. There could be a type of chemical stew that produces a really good insulating material, and this could exist in a vacuum. Like rubbery chemical beings. One could wonder if metal could become sentient if it was able to manipulate a charge. [Answer] Make them out of metal, metal plants and animals could survive in space on planets and off of them.If it were somehow possible for biological processes to be replaced with metal versions, giant metal whales could fly through space towards nebulae and planets to eat the raw resources and melt them down in "furnace" like stomachs, perhaps after churning them in huge tungsten blenders? Either a nuclear reactor or chemical reactions could be used for power, for example, Thermite to make stomach, electricity produced by hydrogen reaction etc.. Smell and Taste would detect trace quantities of useful minerals and gas. Hearing would only be possible near celestial bodies where there are gases in space Feeling would be the same as normal, and Seeing could be done using solar panel like cones and rods or better. Detecting cosmic rays would be useful [Answer] Yes, such a life form can exist. In fact, more than of them does exist and is known right now on Earth. They are all microscopic, so that may not be what you are looking for exactly, but if individual cells can survive I imagine that a multicellular organism is at least possible. It is because of the existance of these organisms that space agencies consider it so important to build their satellites and other machines to go to space in a clean room (there are other reasons as well) as to avoid adding Earthly life to a planet or moon in order to cause a false-positive for extraterrestrial life. At the end of [this](http://www.natureworldnews.com/articles/6877/20140503/bacteria-survive-space-travel-iss-research-shows.htm) page there is the following quote: > > The duration of the study was short. However, researchers believe that > the experiment results provide evidence that hardy organisms could > survive in space for millions of years [on an asteroid] before landing on a planet. > > > I think that an asteroid would provide very similar conditions to living on a body like a moon [as gravity seems to even help some microbes](http://phys.org/news/2016-03-bacteria-space-earth.html). If you want a method for this to happen naturally, then simply have a similar organism evolve on an Earth-like planet, use any of the numerous methods described [here](https://en.wikipedia.org/wiki/Panspermia#Proposed_mechanisms) to get it into space, then have it land on a moon-like body where it then further evolves as needed. One of the (according to my previous link) most likely methods for the bacteria to leave a planet is for radiation pressure from that planet's star to push them out of the gravity well which, according to that page, is possible as bacteria are so small. [Answer] We can try engineer insects to live in a vacuum. I start with insect, because they have exoskeleton which is already a good start for a spacesuit, plus some of them are excellent jumpers, which could be a very good solution to move around in a small planet with no atmosphere (can't fly there). The problems are three: water, radiation and oxygen. Oxygen is the simplest, they could get it in solid form from minerals; also, we already know of [multicellular](https://en.wikipedia.org/wiki/Loricifera) organism that live without oxygen. Radiation is also easy (somewhat) just give each of their cells some of [these guy's repair mechanisms](https://en.wikipedia.org/wiki/Thermococcus_gammatolerans). Or else maintain a stock of stem cells to replenish the damaged ones. Water is the real problem, in a vacuum all water will slowly evaporate no matter how tight is your skin, so either you have a big reserve of water or I dunno. Tardigrades can survive in vacuum for a while by dehydrating, but need water afterwards, maybe the water could be jellified to prevent its escape (chemical reaction would be considerably slowed, but with an electrically based nervous system your animal can still be fast). What they eat is another problem, are there plants? Or are they [lithotrophic](http://ttps://en.wikipedia.org/wiki/Lithotroph)? Thermal radiation is another concern. Your animal need a system to radiate heat away, maybe their skin is covered with gold or photonic crystals like butterflies' wings to reflect the incoming sunrays. You can also consider making them photosynthetic. ]
[Question] [ Dragons are vicious monsters that take pleasure in killing people by burning them with hellfire in their throats that was given to them by the Devil himself so that they can destroy everything in their path. Well, at least that's how the common folk tend to see them, but in reality they're just animals and a young boy is determined to study them to understand them better, so he stole and hatched a dragon egg. His dragon has two holes one on each side of the mouth from which an oil comes out that easily ignites in contact with fire or something equally hot. He also noticed that whenever his skin was in contact with the dragon neck when it spits fire a current flows through its body and causes a very painful shock; maybe this is how dragons light the oil to create the infamous fire breath. The dragon only created fire to go hunting, when it felt threatened or when its "master" ordered it. From the age of four, when the dragon was little bigger than a dog, it started releasing sparks in the air from its mouth whenever it was happy - and it found that could control the sparks. It could release a flurry or a cloud of sparks as desired. Whenever it did it was a beautiful phenomenon to behold, especially at night under the starry sky and the silvery moonlight; maybe that's one of the reasons why the baby dragon does it. The doubt that hung in the air along with the sparks was: How is that possible? Maybe it could be oil, but each drop of oil would start a chain reaction and create a cloud of fire. Or maybe it could be the shock current that originates in the neck, but doesn't seem to have enough power for that. ### Leaving the context of the story The aforementioned "current" is bioelectricity that can reach voltages of up to 1200. Dragons release a few droplets of oil into their mouths to create a flame and then shoot a blast of oil that ignites upon contact with the flame, all of this very fast and can take a maximum of 1 minute to perform the fire breath. As for oil, dragons get it from the fat of their prey. For the answer, just remember to make it as biologically plausible as possible; it doesn't need explanations involving evolutionary theory, but the dragon has to be flesh and blood without metallic or even robotic things. As for the world in which the story takes place, the best way to explain it would be to say that it takes place before any industrial revolution, that is, no steam engines, electricity, etc. My dragons don't have any flint and steel, this is not part of their anatomy. The secret of their sparks has to come from what was presented in the post. Why do people think that lighter answers my question? Guys, my dragon is not a lighter, the sparks have to come from what was presented in the post, with no changes to the anatomy, i.e, no flint and no steel. [Answer] If these sparks are persisting in the air beyond the dragon's mouth, and are not simply a high-voltage electric arc, then it is likely that the sparks are indeed caused by the same oil as its flame. The difference between the sparks and an all-out flame would be that a flame would involve a continuous release of oil, while the sparks would be intermittently released drops of oil. Both would involve a rapid flow of air past the oil glands. In order to have sparks rather than a flame, it would have to be possible for the dragon to control the amount of oil released more finely than a simple open/closed valve. The oil would also need to be relatively viscous. Viscous oil would be an advantage in that it would allow a longer-ranged flame, allowing droplets to be propelled a significant distance while burning. This control would allow a short-ranged, wide, hot flame by spraying oil forcefully, releasing small, rapidly burning droplets that would almost be an aerosol. Longer-ranged flame would involve larger droplets. Sparks might be medium to large droplets released slowly. [Answer] Spark + Oil spray For fire breathing, you need a spark and then throw a spray of oil on it with a strong blow. [![enter image description here](https://i.stack.imgur.com/t6nO3.jpg)](https://i.stack.imgur.com/t6nO3.jpg) Biology : Eels create electric currents, Cobras spit venom The electric eel generates large electric currents by electricity-producing cells packed into a specialized electric organ. Mozambique spitting cobra (Naja mossambica) spits venom with great accuracy up to a distance of 3 meters. Our dragon The dragon can create an electric spark in its teeth similar to eel, and then throw a spray of oil stored in a bag like venom sprayed by some snakes. [Answer] Have it work the same way a [sparkler does](https://en.wikipedia.org/wiki/Sparkler). The key ingredients are a metallic powder of aluminum, iron, titanium or magnesium (or some combo) and an oxidizer to accelerate the reaction. Iron and magnesium are readily available in many areas. The oxidizer components less-so but still available to some degree. [Answer] Antimatter contained in grains of sand. ..another solution for the dragon's spark popped up [on WB today](https://worldbuilding.stackexchange.com/questions/223230/naturally-occurring-stable-form-of-antimatter): suppose the dragon is able to find certain minerals, that can embed antimatter in their crystal.. dragons have a good nose for these things. The dragon only has to chew some grains of sand, and out come the sparks. You won't need much.. a nanogram already gives too much energy.. guess a a few anti-particles contained in the silicon lattice would be sufficient, to generate a little spark.. ]
[Question] [ Take a planet with an atmosphere similar to Earth's but, say, 9-10x as dense. What is this going to mean for the performance and design of the heat engines that are so familiar to us? Higher oxygen partial pressure... easier to burn? But higher air density means more heat conducted away... easier engine cooling, yes, but does it also hurt their performance? An internal combustion engine, instead of having something like 10:1 compression ratio, will only have about 2:1 (edit; assuming the engine is constructed to the same strength). Does this actually make a big difference, or does only the absolute difference in pressure matter? Likewise for a steam engine. Or (because I'm thinking particularly about aircraft here) a jet engine. [Answer] The effects won't be as dramatic as you might think For piston engines increasing atmospheric pressure will cause a similar situation to turbo charging. You will create 10 times the power per density, compression ratio will remain the same. This means to get the same power your engines will have 1/10th the displacement, but that does not mean they will actually be smaller. Since your engines will be operating at higher pressures, they will be creating more mechanical stress on the engine block, which will need to be reinforced. Contrary to what others have said, you will not have to deal with increased fuel consumption. Fuel consumption per unit power will be the same since your displacement will be smaller. Only when you try to keep 1 atm engine displacements will you see a jump in fuel consumption (but power will rise equally). Of course trying to move quickly through such an atmosphere would require more power due to drag, but stationary engines will not have this concern. Similarly, back-pressure caused directly from the atmosphere will not be a problem, the concern here will be that drag through the exhaust pipe may build up easier, so you will want freer flowing exhausts. Moving towards aircraft and jet engines in particular get a little more interesting. Let us start with how the atmosphere works. The higher you go up, the thinner the air. That atmosphere above the point where it reaches 1 atm pressure will look identical to our atmosphere. Planes will simply fly higher when speed or long distances are required. Most planes that reach high speeds at altitude can not do the same at sea level. Mach 2.5 fighter jets are often limited to Mach 1.2 at sea level. If you do want to fly fast at low altitude, besides the rules for piston engines, you will likely see changes to nozzle design. If your exhaust is supersonic, then the higher the pressure the smaller the nozzle. Aircraft that operate at many altitudes will need nozzles that adjust in size dramatically. [Answer] > > Higher oxygen partial pressure... easier to burn? > > > It means higher fuel consumption and higher produced power per cycle > > But higher air density means more heat conducted away... easier engine cooling, yes, but does it also hurt their performance? > > > An ICE is based on the expansion of the gas. That the gas is heated is just a nuisance, since one has to cool the combustion chamber. Indeed there have been design were water is injected into the chamber to absorb the heat and increase expansion thanks to the formation of vapor. So additional cooling is not an issue. > > An internal combustion engine, instead of having something like 10:1 compression ratio, will only have about 2:1. > > > Wrong. The compression ratio of an ICE doesn't depend on the intake pressure, but on the volume ratio between the upper and lower point of the cycle. Those do not change with air pressure. Same general reasoning holds for steam engine and jet engine. Incidentally, increasing the intake pressure is the exact reason for applying a turbo to ICE. [Answer] Have you ever done something particularly foolish as a child? I have. Oh, yes... I've done some whoppers. And one of them was pounding a potato into a tail pipe. As you can imagine, the engine failed to start. 1. Increased Fuel Consumption Engine efficiency drops like a rock. That means small engines we love today (like my weed trimmer) might not even start, because the back-pressure on the exhaust is too high. The solution? A bigger bang. That means I'm increasing fuel consumption to overcome the increased back pressure. 2. Increased Cooling Required I believe (I could be wrong) that higher air pressure does not improve cooling. In fact, it makes heat dissipation worse. If increasing surrounding density helped with cooling, computers would have a rock sitting on top of them rather than a fan. Heat propagates fairly slowly through a static atmosphere, which acts (like pretty much all things) as a thermal insulator. Increasing its density is like adding more insulation to the walls of your house. In fact, air-gap insulation is very effective. It's why people staple plastic over their windows during the winter. That gap of static air is an insulator. Therefore, you have a bigger problem with heat removal, which means a bigger radiator. 3. Decreased need for air flow You are correct that greater air density means more oxygen per cubic centimeter. Therefore, the air draw requirements would not be as large. 4. Increased air filtering But, as a nasty byproduct, you need a larger air filter because the higher density of air will push crap through an air filter more readily than here on good ol' Earth. You need a way to disperse that pressure, too. That means a bigger filter (more surface area) with greater density filtration. So, in the long run, #3 and #4 are a wash. 5. Increased Fuel Consumption — Again Finally, you're pushing whatever the engine is moving through thicker air. This might not have a massive impact, but the reality is that the higher the pressure (air density), the harder it is to push an object through it. That means you need an even bigger bang than #1 requires to overcome the additional air resistance. ]
[Question] [ I'm trying to create basically realistic mermaids, and working on developing body language and vocalizations. I have most of the vocalizations I can think of (suggestions are still appreciated), but definitely need a lot more body language. Ideas? Edit: They are a highly social colony species, so it should be somewhat complex, and interactions between colony members would be especially helpful. I'm also trying to avoid overly human interactions such as kissing or holding hands. [Answer] They could use [clicks and whistles](https://seaworld.org/animals/all-about/bottlenose-dolphin/communication/) like a dolphin, or they could also communicate through [bioluminescence](https://ocean.si.edu/ocean-life/fish/bioluminescence) like a bobtail squid. They could also cummunicate through [whale song](https://en.m.wikipedia.org/wiki/Whale_vocalization). [Answer] # Sonar They might have a specialized organ much like porpoises do. It could have bandwidth enough to communicate complex states of mind, to a point where it could be considered a limited telepathy (something of the kind happens with the Tines in Vernor Vinge's A Fire upon the Deep). Human-like body language has the problem of interfering with swimming. You could render sonar interactions as you wished, though - being to all intents and purposes a sixth sense, mermaids might "hear" it as a voice plus anything else. Dolphins are social animals and they love to "play" in a variety of ways - some of those appear in David Brin's Uplift cycle, suitably adapted to the uplifted dolphins' increased intelligence. [Answer] The reason we rely on our hands and faces so much when communicating is because they are very good for it. The hands and face have lots of muscles allowing for very precise control. This also means our brains have very good ability to control hands and face. And ability to understand movements of hands and face by others. The two are linked due to [mirror neurons](https://en.wikipedia.org/wiki/Mirror_neuron). So unless you want them to be very different from normal humans when it comes to hands and face, which you probably would have mentioned as it is kind of critical, their body language communication would heavily rely on hands and face and work fairly similarly to human body language of hands and face. Some differences. If you are floating in water instead of standing on a solid surface large movements will have unintended consequences so body language will avoid large movements and focus on just hands and face. Same applies to physical contact such as holding hands or kissing. I think such would be preserved for private moments when you are entangled and not moving. Underwater sound carries better and light worse than in air. So there should be clearer distinction between private and close range with hand gestures and facial expressions and with public and extended range without those components. I think those might be a solid starting point for you. Having, from our point of view, much stronger distinctions between public, private, and intimate modes of communication, possibly to the point where even the vocal language used is noticeably different is good flavour that should be visible in pretty much everything and be fairly simple to highlight without needing boring exposition. [Answer] Their body language would be transmitted by sound. Living in the dark underwater restricts vision to close distances. So visual communication would be like whispering in that it is covert and short range. These merfolk would have exceptionally precise hearing, because sound travels farther and faster underwater. It's the best way to detect oncoming animals, and if they use sonar, they could see stationary barriers. This means that they could 'see' people's body language through sound. When you move your hand really fast in the air, you can hear it 'whoosh.' This effect would happen all the time with merfolk. Body language would be subtle sounds of your body moving through the water. As for the content, do the merfolk inhabit a similar world to ours? Because unless they have some hyperadvanced humanlike modern civilization underwater, they probably have to deal with the various predators or prey they interact with, resulting in primal emotion communication. Since they are basically fish in terms of their movement, they might convey emotions of fear or aversion by twitch-like motions, reminiscent of a fish darting in response to a predator. A turn of the tail helps rotate you around, so maybe it's a gesture to indicate turning your back on someone, or changing your mind. [Answer] I know I'm a bit late to the party, but have you considered bioluminescence and/or the ability to change colors/patterns on the skin (metachrosis)? This could be means of communication in itself, and bioluminescence could enhance the ability to communicate via gestures or posture over larger distances or murky/dark water. I guess glowing mermaids might look a bit silly, but the bioluminescence might be limited to certain parts/patterns (especially in combination with the ability to change those) or specific points on the body, a bit like the position lights on an airplane. Depending on how precise and fast you can control your "glowy bits" you might even be able to use some kind of morse code to communicate over larger distances in the dark deeps, without being heard. In combination with the possibility of acoustic communication this would give your Merfolk varied means for communication depending on the situation, and hunt(or avoid being hunted) in either complete silence or complete darkness (depending on prey/predator) and still being able to communicate. [Answer] Since their environment of motion is four dimensional, you could consider a complex dance as a means of communication. The bees do in the hive to indicate pertinents about nectar flowers. These Merfolk are intelligent and presumably sentient people, so the relatively simple dances of their ancestors -- warning of dangers, locations of food sources, approach of other Merfolk -- will have evolved into a means of telling stories, describing the loot to be found in a shipwreck, courtship and any of ten thousand other things they might to dance about. [Answer] A combination of signed language and vocalizations is your best bet. Because both hearing and sight can be compromised under water, a redundant system allows for maximum communication in a variety of situations. I'm envisioning both systems used simultaneously but with communication possible if it's dark or if there is a safety issue where the merfolk have to be quiet (predators, humans), or there is too much ambient noise. I will also add [tactile sign language](https://en.wikipedia.org/wiki/Tactile_signing). This is how (most) people who are deaf and blind communicate and also Deaf people with normal vision who happen to be in the dark or who need to focus visually on something else (a couple at night, friends at the movie theater, etc). I have very basic sign language skills, and my spouse even less, yet it's remarkably easy to figure out what someone is saying by only laying your hand on theirs. If it's a sign or letter you know visually, you'll get it most of the time tactilely. Obviously someone who uses the skill regularly would be expert in it. A colony species would be physically close together so communication can spread from one hand to another until everyone gets the message. A human observer might think the merfolk are "holding hands" but, since their hands are touching for communicative purposes, it will have very different cultural meaning and practical applications. [Answer] # Semaphore (probably without real flags) This would be great because it would look like the mermaids were communicating by doing an underwater dance. It could also be expanded to include their tail as a third flag. Note the Beatles spelled out their album's title "Help!" using semaphor. [![enter image description here](https://i.stack.imgur.com/mzkQ9.png)](https://i.stack.imgur.com/mzkQ9.png) If it's good enough for them, why not for the mermaids? [Answer] My idea is some sort of ultrasonic wave communication, using specific pulses of ultrasonic sound waves that are in a range that the normal human can't hear. And they have a special organ to detect these pulses and emit them. This would also be advantageous because they can use it for echolocation by bouncing these waves off of objects to determine speed and position. [Answer] While they may be able to use a combination of body language and/or noises they might also have hyper-developed telepathic ability. [Answer] The means they use for non-verbal communications is very dependent on the turbidity of the water and the intensity of illumination. In low visibility conditions, they might snap their tails ultra fast so they cavity and create a popping sound. These will be higher frequency sounds and will not carry extremely far. Lower frequency sound travels further under water than higher frequency sound. They might carry the shells of mollusks so they can clack them together or strike with stones tools to make lower frequency booming signals from the cavity in mollusk shell. In good visibility conditions, they might swish their tails and bodies in different ways to they don’t actual move but create distinct visual patterns In close communication with others of their species, their tails and fins would be the natural means of conveying subtext during vocalized talk. Fanning a tail fluke might indicate boredom, or intense interest. Absolute stillness might resemble playing dead to predators and signify disgust or boredom. It stems from a clear definition of their physiology — tail, flukes, webbing between fingers, back fins, side fins along fish part of body, even to their cloacal slits and gill slits. ]
[Question] [ I've searched through a lot of merpeople related questions on this site and didn't see anything that related particularly to me as most questions have to do with underwater combat or dwellings on the ground. My species is a race of humanoid axolotls (that means legs and feet like people) who are perfectly capable of living on land. They do not have access to land though. Their cities are built on the trunks of massive "balloons" suspended in water. These balloons are full of oxygen with several inch thick membranes on each balloon. The spheres that contains the gas can range in size from a 3 meter to 20 meter diameter. The stalks reach up from the very bottom of the ocean, nearly 500 meters below, to from a few meters to a few feet below the water surface. For extra clarity I'm going to restate what's so bad about the balloons getting popped. Cities are built out of a sort of underwater adobe and plastered on the trunks of these massive balloons midway or near the surface of the sea. If one were to pop it would soon fall over from the weight of the city on it's side. Obviously that's not good for my inhabitants or nearby balloon cities that might be hit. So my question is: In the event of humans waging war on my peaceful civilization how would I protect against my balloons getting popped or from another form of attack from above? The technology level is that of earth 1000 AD. My merpersons can swim at 20mph. Magic is rare if not nonexistent and most nearby countries have access to metallurgy and gunpowder and can launch projectiles at their enemies. The merfolk can tame things like dolphins but many do not have any creatures as they're difficult to provide for with the dense population zones around the balloons' stalks. [Answer] Giant Kelp forests around your settlements have a massive kelp forest wall around your settlements were your Mer people hide traps that sunk or damage ships, launch surprise ambushes and conceal your balloons from the attackers. The traps could range from simple drift wood spikes to burning barrels from whale oil. Your Mer people can swim in and out of the kelp with ease and shoot at any intruders that come to close then board them. Use the shipwrecks to make more traps (and much needed steel and arms) and hang the dead from the ships masts as a warning to other would be foes. This is the Mer people’s water trespass and the locker will take you, the humans will learn to fear the deep. [Answer] Swim beneath their ships and bore holes in them long before they're anywhere near your balloons, or even do it in their ports. 20mph is plenty of speed to accomplish this and ships are not cheap, they wouldn't lose many before deciding it wasn't worth the effort unless your cities are full of gold, and even then they have no way of fighting underwater. The surprising part would be them attacking in the first place, defence would be easy. Trade and diplomacy the better option if they need something. [Answer] How they might protect themselves depends on how far they are from land. Especially from land close by with high cliffs and the like. 500 meters is not at all deep for the ocean. So these balloon cities are either near a landmass or over an ocean mountain. If the cities are too distant from land for an attack with mechanical devices to reach them, their best solution is to surround themselves with additional balloon trunks on their sides. Merfolk, fish, and other aquatic creatures can swim under the trunks if they want to go in or out of their walled city. Birds can fly over. While humans could swim under (maybe), they'd be stuck after that. The trunks are too massive to pull even a small boat over (maybe a rowboat with a lot of effort, but no big weapons) and are not simple to swim under either. If the cities are close enough to land for an attack to reach them, their best bet is to learn how to repair their balloons. * And diplomacy. * And a slow relocation out of projectile reach. They can also place additional structures (empty balloons or trunks, or something else) between them and the land. These would serve as decoys and also would block incoming projectiles. If they don't block them entirely, they would slow them down. And allow fewer of them in to have a chance at popping a balloon. [Answer] In 1000ad the only who could dare go underwater were fishermen. With no goggles or fins their movement and ability under water will not match the one of meerpeople. It won't take longer for them to realize that it's an unfair fight for them. Assuming that they are protecting the waters around their ships with some chemicals, and lacking explosive, their only resort is to drop stones from the surface hoping to damage what the meerpeople have built on the bottom. Keeping in mind the limited capacity of their ships (it's 1000ad, not the Titanic era), they won't be able to carry huge boulders in the open sea. I think you will be able to provide additional protection with reinforced roofing. Keep in mind that, being water denser than air, the stone might reach terminal velocity before hitting, thus lowering the potential damage. ]
[Question] [ My current WIP involves an athletics competition on a non-terraformed moon, namely the Earth's moon. And while it would be a bit difficult to play certain sports without a breathable atmosphere, the javelin throw strikes me as an event that would be better enjoyed in the moon's 'fresh air' – or rather, lack of it. So, other than the additional challenge of wearing a space suit (and trying to make the damn thing land point first), I would expect an outdoor javelin throw on the moon, after accounting for other variables. The only thing is: would it? I don't know if the air on Earth has the effect of *reducing* the length of a javelin throw through obvious frictional effects (as it would with a thrown stone or shot put) or *increasing* it by giving it something to glide on (as it would with a paper plane). My hunch is that a realistic world record, after factoring in the other variables like restricted movement from wearing a space suit, would be somewhere in the 400-500 metre range for men, 300-400 metres for women, and 350-450 for eligible non-binary folks. (For comparison, the world records back on Earth currently stand at 98.48 and 72.28 metres for men and women respectively.) Are my guesses realistic? [Answer] With no air resistance and less gravity, check the astronauts playing golf. The ball reached an outstanding distance. Also, since the shape won't matter due to no aerodynamic profile to speak of, you may throw a stone, ball, cube. All that matters would be mass. [Answer] From basic physics and the initial throwing speed of the javelin (33m/s for the best throwers) on earth I calculated that the furthest you can throw a javelin is 672m without friction and the much lower gravity of Earth's moon. Then it depends on how restricted movements are and how would athletes adapt to the 45° angle for the throw. The distance is proportional to the initial speed, so if the initial speed is 25m/s the distance will be 509m. It's also proportional to the reciprocal of your moon's gravity. ]
[Question] [ This is a submission for the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798). [![enter image description here](https://i.stack.imgur.com/jFbfP.png)](https://i.stack.imgur.com/jFbfP.png) Image credit: japhers.tumblr.com Originating from Japan, the majority of depictions of Oni (Kijo to refer female Oni/demons) are hideous, gigantic (taller than the tallest man!) ogre-like creatures with a single horn or multiple horns emerging from their heads, yellow eyes, sharp claws, fang-like tusks, and wild hair. Their habitats are known to be remote mountains, caves, islands, if not Hell. Interestingly their omnivorous diet contains of alcohol (what kind of tolerance could they build up? Would they be immune to intoxication or always acts like it it doesn't even matter?) One particular interesting thing about them is their skin color. Their most common skin color is red and blue, with red ones being more aggressive and blue ones being more clever(there's also black and yellow skin Onis, but that's easy to answer.) I was thinking what kind of mutation or evolution could cause their skins to match their behavior, or just in general? [Answer] Okay I got you some fun old info well first things first, Alcohol tolerance should be pretty easy for something as massive as 8-13ft, also considering it is of Asian descent then its tolerance of Alcohol is even more increased on account that Asians and Europeans have the highest alcohol tolerance of any other race, but if you want even more then you are going to need more of the special enzymes for digesting alcohol and bigger livers. Humans are already omnivores so no change is needed there. Next is the size, 8ft is pushing it for something with a relatively human shape and at 13ft survival is 0. but don't worry all hope is not lost because all you need to increase that survival chance is to shift the organ sizes and body shape. So taking tips from our real life giants the major organs that need this is the liver, lungs, heart, and stomach. Now lets go to everybody's favorite subject, mitochondria density, yes the mitochondria will be needing to decrease the density of mitochondria per cell so the body does overheat, causing the proteins to unwind and the body turns into a pile of mush. Also considering they will live in hot climates(well hell is listed as on =e of their environments so I'm guessing its hot) then they will need to take a page out of the elephants survival as a giant guide, and get the most surface area it can buy having wrinkly skin. Now for the actual body shape, it will need pillar like legs(like an elephant), a wide frame, proportionally shorter arms, and probably smaller brains because the energy needed to maintain such a huge stature. Okay last but not least we go to the skin color behavior correlation thingy, and while yes their is a disease that turns you blue([Methemoglobinemia](https://www.livescience.com/34410-blue-skin-argyria-methemoglobinemia.html)) its not the best thing to base a species on. So what I propose is their skin color, and behavior actually comes from their environment and what they eat. this has actually happened to some African Tribe([Tuareg](https://en.wikipedia.org/wiki/Tuareg_people)) and could be used to explained the behavior of the diffrent colors by saying its from culture or just that the red ones have a constant rash that causes them to be aggressive all the time. Hope the answer helps! (; [Answer] Their skin color could be related to the same hormones that control behavior. The balance of these hormones causes aggressiveness, cleverness, etc, and the metabolized byproducts build up in the skin as pigments. They could be obligate drinkers. They cannot synthesize some required protein or hormone, or something like it without alcohol. Alcohol does not lead to intoxication, but the lack of it would cause strange behavior and health problems. For the size, bones would have to be proportionally larger than a human's. The body would probably be proportionally wider than a human's as well with bigger feet. Balance would be key since they would pretty heavy and a fall with all of that extra mass would be dangerous. [Answer] The link between behaviour and skin-colour could be caused by the oni having the ability to change color with their mood and emotions: For example, they would turn red and be aggressive when angry, but when neutral, they might seem more intelligent, and their skin would become blue. Other colours would correspond to other emotions and behaviours [Answer] Well, how big do we need to be? Typically, humans don't grow beyond 7 feet, so 8 feet is doable. 8 feet is doable. As calculated [here](https://worldbuilding.stackexchange.com/questions/138445/how-big-is-my-giant/138448#138448) even 21 feet could be possible without altering the bone structure too much, but have serious problems. So... let's redesign! * First, we get thicker bones. This results in a more sturdy look and also more toughness. * Then we change some organ sizes. Kick out one kidney, use the space gained to enlarge other organs, especially the heart (to compensate their height) and liver (for extra alcohol tolerance). * Skin color might be linked to genes that also influence hormonal balance when they grow up: The red skin gene is on the X gene, just like the Blue one. ver close to this gene is also an amplifier gene for either aggression (on red ones) and smarts (to the blue one). As a result, all males can only have one of the two - red or blue - and more likely the linked trait, but as there are other genes also influencing the mix, we can get smart red ones or aggressive blue ones. When both a Red and a Blue X are present in females, one of the two colors needs to be dominant - so let's assume that Blue trumps Red. Yellow (technically: colorless) and Black (over pigmented) Oni are two different recessive genes on other genes, they modify coloration, and as singles are responsible for off-white or black markings. [Answer] What I think we're looking at is a highly mutated subspecies of hominid; possibly evolved from Gigantopithecus or a relative of that long-extinct creature. Why Gigantopithecus? Because that prehistoric ape is related to (precedes) both hominids and orangutans, plus it had a very large size. Furthermore, an orangutan's diet is composed of 90% fruit, and if this species is or becomes the same way, it's not hard to see them eating a lot of fruit with natural alcohol (which could naturally ferment inside their digestive systems, as with sauropods, which would generate alcohol inside them) and evolving to have a high alcohol tolerance and/or affinity. Since plenty of supposedly obligate herbivores, like deer and even cows, can and will eat meat if they have the opportunity, it's not hard to see such a species evolving to be omnivorous after some evolutionary trigger; perhaps new herbivores evolved that made it almost impossible for them to obtain all the fruit they need, so they began preying on them (since there were more herbivores than fruit) and gradually became omnivorous. At this point, these creatures have evolved into ape-men, and possibly interbred with Neanderthals, becoming the primitive Oni. Their red or blue coloration comes from the fruit itself; carotenosis results in humans from an excess of dietary carotenoids (carrots, oranges, sweet potatoes). In this case, there are two similar species of fruit, both of which have a specific effect on Oni physiology if eaten; plants with the red fruits evolved to have a defense like the acacia tree and ants (ie. Oni eat the fruit and special chemicals cause them to become addicted, aggressive, and territorial, therefore providing protection for the plant). Blue fruits, however, contain chemicals that enhance cognitive function (plausible; since foods high in lutein and zeaxanthin, which are both pigments, have been linked to increased crystallized intelligence). Both of these fruits are frequently imbibed by Oni after first sampled, and the resulting buildup of pigment turns them red or blue. As for the Oni horns, that can be explained by Shope papilloma, a form of cancer that causes the afflicted to gain horn-like growths. A benign form of this cancer may have resulted in horned Oni, and since horned Oni did better in fights over mates, Oni today all have horns. ]
[Question] [ In the movie [Pacific Rim](https://en.wikipedia.org/wiki/Pacific_Rim_(film)), we see the beginnings of an alien invasion using very large mobile lifeforms. Given that we want as large a lifeform as possible with the following traits: 1. It must be able to move under its own power at a minimum top speed of 45 kph for at least 2 minutes before needing to rest (reduce to indefinite duration speed). I.e. capable of outrunning a human on foot at maximum speed. 2. It must be able to move under its own power at 10 kph for a minimum of 48 hours, i.e. capable of outrunning a human on foot over the course of this time. 3. It must be able to live and function on the land surface of Earth for at least 14 days (absent hostile action) at full effectiveness. Bonus for being able to swim. 4. It must be grown to its operational size over any time period of 25 years or less, not constructed, though its first building block/cell/functional unit may be constructed/engineered. It may be gestated in one of its own kind as a parent or in an artificial womb, but must do the work of growing itself, provided with only raw materials and energy. 5. It must be capable of (and inclined to) inflicting significant damage to human infrastructure and populations, using non-biochemically-specific means (i.e. no toxins) over its full effective operational duration. If it is armed with projectile/incendiary weapons, it must be either equipped with sufficient magazine capacity to last 14 days of combat or be capable of in-the-field replenishment using found resources. 6. Evolution is not a concern. These are created beings, so as long as they can be grown from a single unit, they can incorporate design elements not available to merely evolved creatures. 7. It must be resistant to conventional (i.e. non-nuclear) human weapons of the current era (C2016), and must be able to absorb any practical amount of fire from standard man-portable firearms, and at least one direct hit from a tank-based weapon or at least one loadout of any conventional ordinance from any combat aircraft and still remain at least partially combat effective. How big a lifeform could we realistically have, and in very general terms, what chemistry and body plan would it need to fulfil all of these criteria, if they can all be fulfilled? How (if at all) would it obtain additional energy for continued operations? Are Pacific Rim's kaiju realistic? Preference will be given to answers that can justify greater combat capability, longer operational durations, and a shorter production time for a given magnitude of body mass and volume. EDIT Think out of the box here, guys. Don't feel constrained to CHO chemistry or vertebrate body plans. If some sort of Von Neumann nanotech made from metal and powered by atomic reactors can be justified, run with it. Should the body resemble a starfish or a centipede or a sea urchin or something else? [Answer] ## It's all determined by gravity. I'm currently writing a paper on a similar topic, observing how gravity affects the evolution of extraterrestrial life (size and internal build). Therefore, I can offer you some hints on how a mobile animal is limited on Earth, but I'm afraid this matter is complex enough without introducing the problem of how much damage the creature could withstand, or how it should be engineered. First of all, the maximum mass an organism composed of the same muscle and bone as the rest of the animal kingdom can obtain was estimated by [Hokkanen](http://booksc.org/dl/4223466/5bd234) to be around $10^5$-$10^6$ kg. If you pushed nature to the limits like this, the required energy just to sustain this organism would be huge: by [Kleiber's law](https://en.wikipedia.org/wiki/Kleiber's_law), metabolic energy scales as mass to the power of $3/4$. Say we neglect the huge energy required to keep this being alive for the moment, and want to find the energy required for locomotion. Every living being on Earth walks utilizing the [inverted pendulum gait](http://arxiv.org/ftp/q-bio/papers/0609/0609007.pdf). By using the leg's natural period and expanding on the work of the hyperlinked paper, after some basic calculation, we've found that the work (energy) required for one step is $W = mgL \left( 1-\sqrt{1-\frac{\pi^2}{6}F} \right) $, where m is leg mass, L its length, and F is [Froude number](https://en.wikipedia.org/wiki/Froude_number), which characterises the animal's gait and is equal to $v^2/gL$. The leg is 18% of a human's mass, let's say it's 30% of your animal's mass ($10^5$ kg), to be able to support its weight. For a 180 meter tall Kaiju, we can call 40% of that to be leg length. If you want it to walk at 10 kmph, this comes to nearly 20,000 Joules per step. (By comparison, a human requires 150 Joules per step.) If you want it to run in short bursts, the required energy would at the very least double, as a human's running energy approximately doubles compared to walking. If you want it to walk for 48 hours, that's some 150,000 steps at this speed, which brings us to a total of $3 \times 10^9 J$. When you turn that [into dietary calories](http://www.wolframalpha.com/input/?i=310%5E9%20joules%20to%20kilocalories), you get "71 times the caloric energy consumed by Michael Phelps per day when training for the Olympics", or "310 times the recommended food energy per day for an average person". So our monster will expend, by Kleiber's law, roughly 180 times the human basal metabolic rate to stay alive, and with the expenditure of walking, this comes up to $5 \times 10^9 J$. Turns out a human cadaver has about [81,500 Calories](http://www.popsci.com/article/science/ask-anything-would-cannibalism-make-you-fat) of energy, so by feeding exclusively on humans, the monster would have to consume over fifteen thousand people per day* to survive. This would explain Godzilla's raging hunger, I suppose. Obviously, I am a physicist and not a biologist, so my overly-specific solution only applies to [spherical cows in vacuum](https://en.wikipedia.org/wiki/Spherical_cow). We could wildly speculate about other factors, dimensional analysis, allometry, science fiction which would loosen or impose additional restrictions to our monster, but by considering only its motion in the gravitational field, we can obtain this interesting play with numbers. EDIT: If we wish to discuss completely artificial constructs, then the most efficient means of locomotion would definitely be rolling. That would involve no 'bobbing' of the center of mass, as happens when you walk, and thus completely relax the gravitational limit on size. However, a creature that's completely spherical or rolls on caterpillar tracks or crawls like a serpent would be severely limited in terms of available limbs, so that's not too effective for an (intelligent) weapon of destruction. Any other limb-assisted locomotion is performed by the inverted-pendulum model and the above calculation applies. Additionally, were the creature to run on nuclear power, it could do so with a relatively small reactor - a [power plant in the USA](http://www.eia.gov/tools/faqs/faq.cfm?id=104&t=3) generates 10,000 times more energy per day than our monster would require. The energy it requires for basic functions is really not that large, it comes down to about the yearly expenditure of a clothes dryer, except in a day. So the only thing to consider is a very quick and efficient source of energy - consuming food is obviously one, albeit in large amounts, but a nuclear reactor would also do the trick. [Answer] It's not precisely about gravity as much as it is about height. The largest natural creatures are likely as big as natural creatures with traditional body plans can be, but the constraints on an engineered kaiju are extraordinarily relaxed. At all times a titanosaur must be mobile and competitive with other organisms, but a kaiju can be grown with arbitrary amounts of scaffolding etc etc. The 25 year time limit is plenty of time, considering that biomass scales exponentially. A 'kaiju' consisting of just bacteria fed as much food they want in the right amounts for 25 years has extremely large mass. (An E. coli has about a one hour doubling time on minimal media, and there are 219000 hours in 25 years. This means after 25 years there'll be about 4\10^65000 bacteria, which each weigh about a picogram. The high-end estimates for the mass of the observable universe are 4\10^70 picograms. 25 years for a gestation time is plenty.) Consider exotic 'kaiju' which are just 500 tons of ants all joined together with little living whiskers in a giant creepy carpet. It's clear this superorganism can become nearly arbitrarily large. See [Pando](https://en.wikipedia.org/wiki/Pando_(tree)), who is heavier than Godzilla (much heavier) but shorter and spread out. Oxygen supply isn't a concern if you let yourself have multiple pairs of lungs or passive convective ventilation like a skyscraper(or you're a tree). Weight is not a concern if you let yourself spread out horizontally. Respiration is not a concern if you let yourself be porous. The highest strength materials(by weight) are Kevlar or Dyneema or what have you. Admittedly these are tensile not compressive strengths, but if you have a tube that's full of water and about 50% water by weight you can convert one into the other using hydrostatic compression at a 50% strength penalty(blah blah laplace's law blah blah optimal radius blah. We're exceptional engineers, we'll figure it out). Anyway. Concrete is one of the weakest construction materials by specific strength, and cannot get more than 400 meters high under its own weight. A concrete post 500 meters high will crumble even if it is prevented from snapping or buckling. Even if we stick to traditional organic materials (spider silk) we can build a post 100km tall if it's prevented from snapping or buckling. Beings built from concrete can really never be more than 400 meters high unless you build pyramids. So we want to build a giant creature that can break things. That means we want arms or legs or something, so we have to stay well below our maximum height so we can have non-load bearing space for brains and lungs and eyes. Additionally a big club might take much much more strain while being swung than the club would experience under gravity. We can estimate the maximum permissible height for realistic walking-around loads using titanosaurs. Titanosaurs were about 50m high, and used bone and flesh. Bone's self-supporting length is about 20km plus minus, so walking and being a real creature means the skeleton has to support about 400 times gravity stresses. Dyneema can support itself up to almost 400km, so using this extremely dirty heuristic a Dyneema-skeletoned creature could be almost 1km high and still stand up and theoretically walk around. If it was dinosaur-shaped it would have Other Problems(like breathing, and the poor maximum strength geometry of muscles) but the principle is "sound". Building a giant starfish about 30 stories tall and starfish-shaped would definitely be able to destroy buildings but I'm not sure about the speed requirements. Anyway. An organism on this scale is immune to conventional small arms fire essentially trivially, as you can just write off the outside meter of flesh as expendable and then you have 100 cm of ablative armor. Technically a lot of automatic weapons could act like a sandblaster(eventually) but I don't know who has that kind of time/ammunition. [Anti-tank rounds](https://en.wikipedia.org/wiki/High-explosive_anti-tank_warhead) are actually easier to defeat than conventional weapons, because they are so specialized for thick layers of metal. Very thick layers of flesh(from the point of view of a tank-sized object) dissipate the energy well before it can reach anything important, and conventional high explosives can be slowly dissipated by a composite ceramic/kevlar (or shell/cartilage, depending how you look at it) layer. tl;dr Being tall is hard, being big is easier than being tall, the hardest part about this is going fast while being big or tall. [Answer] ## Make the kaiju a eusocial clonal colony swarm. As many answers have already mentioned, scaling laws make the weight and energy costs of large animals prohibitively high. However, we may be able to draw from other kinds of animals to reach larger final sizes of the kaiju. Insects are surprisingly fast, even without correcting for their body sizes. [This BBC article](http://www.bbc.com/earth/story/20141021-the-fastest-insect-in-the-world) cites [this paper](http://www.jstor.org/stable/4009161) which measures beetles moving at 9km/h. Similarly, American cockroaches were timed at 5.5km/h while walking. They are also very capable of flying, and a swarm of flying sub-kaiju can easily reach the top speed required. With additional augmentations, these individualised organisms can easily move at the maximum walking speed of a human for long periods of time. When not actively attacking a city, the sub-kaiju would maintain a colonial structure similar to that of [Dictyostelium slime molds](https://en.wikipedia.org/wiki/Dictyostelium_discoideum), maintaining contact as a swarm but not actively linked to each other. In this form, they can also forage and act as locust swarms, destroying crops as well as the local economy. However, when they need to attack a city, they can join up into a larger structure (much like Dictyostelium fruiting bodies) which is capable of dealing damage physically to buildings. The combined colonial kaiju should be able to perform tasks similar to the [microbots in the movie Big Hero 6](https://www.youtube.com/watch?v=wicwxaxVLXI) This mode allows them to easily replenish their energy levels and reproduce (by living like terrestrial cockroaches). They can spread into swarms and raid the depopulated cities, converting any destroyed sub-kaiju, killed humans/animals and food from abandoned supermarkets into more biomass. Furthermore, their colonial structure renders them highly resistant to conventional attacks. By simply de-linking small fragments of themselves, they can effectively resist any physical weapon such as guns, bombs and artillery. In fact, the extreme hardiness of insects (as demonstrated by [cockroaches' resistance to nuclear bombs](http://www.discovery.com/tv-shows/mythbusters/mythbusters-database/cockroaches-survive-nuclear-explosion/)) means that the combined colonial kaiju can simply delink to survive even nuclear explosions. [Answer] The short answer is No. The long answer is that the way biology has evolved makes it impossible for creatures to grow much larger than they already are. Bones can only be so strong, support so much weight. A heart can only pump so much blood, and tissue can only be so "resistant" to damage - and no living creature could take an armor piercing tank round and live - there's simply no tissue that could withstand that. Modern Animals Blue Whales, which are the largest animals on Earth, suffer from back injuries as they get older, simply because of their large size (this is even though their bodies are suspended in water their whole lives). Dinosaurs Dinosaurs existed over a very large period of time. The closer we get to present day, the smaller they got, however. As they evolved, nature found smaller designs to be more efficient. The largest of them to ever exist (so called Titanosaurs) were 20m tall, and as long as 40m. These were herbivores, moved very slowly, and are believed to have had multiple hearts in order to get blood from one end of their bodies to the other. While that's impressive, please remember that they didn't withstand the test of time, and also that they are the absolute biggest that anything ever got on Earth. No Godzilla like creature could possibly exist - it would pancake under its own weight. In Science Fiction If you look at movies such as Avatar they explain the biology of Pandoran creature (massive flying dinosaur type creatures, and incredibly tall humanoids) as a byproduct of their low gravity and naturally occurring Carbon Nano-tube in their bones, which make them "very hard to kill". Even carbon nano-tube wouldn't be able to help Godzilla out though. ]
[Question] [ This story happens in a near future where environmental concern has become a critical issue. Cars are just got banned within the limits of all major cities out of necessity. Rail public transport (above and under ground) has slightly improved (more stops, faster, broader...). How (and how fast) would the design of cities change? Edit: a needed precision, all vehicles are banned from the city limits. Goods come in through rail (or boat if it's possible like in Paris or London), waste goes out the same way. [Answer] The issues to address 1 - supply chain. You have central distribution centers that receive incoming goods in mass bulk. These goods are then distributed to stores and other sales destinations by trucks. The first thing a city would have to address is how to make a valid distribution system without automotives doing the last leg. Light rail would be a bit difficult as you'd need a rail way to each and every store loading bay really. Is electric trucks an option (assuming the electricity was produced by something other than coal?). 2 - Purchased goods. I just bought a fridge and stove for my home...how exactly do I get my appliances delivered to my home without a vehicle? I'm decently physically fit and could probably push a cart with it (getting it onto a LRT would be great fun)...but the majority of the population would struggle with it. GO one step further...how do we get the construction equipment (supplies and construction vehicles) to the site of a new home? 3 - Garbage. We got the goods to where they get consumed...now how does the inevitable trash get taken away? Many modern day cities actually do a fantastic job of keeping this supply chain hidden from the populace...done on off hours or early morning and as seemless as possible. One of those functions that you barely notice happening until it fails and you realize how dependent on these functions we are. Certain cities are more ready for this than others. Calgary Canada is an amazing sprawling city designed well after the dominance of automotives and the road network is designed to help cover this massive area. Ghent in Belgium saw it's rise in early medieval times and could probably go through with a vehicle ban and have little effected in terms of day to day life...they actually have a three tiered transit system of the train for intercity, railcars for common transit routes in city, and buses to service the outlying routes...most North American cities have two tiers of rail + bus. Remember this policy will have a huge impact to cities designed in medieval times prior to the car as opposed to cities designed well after the cars dominance in personal transportation. Just one to add as difficulties in this: The rich! Don't underestimate the ability to influence policies with money...if people with money wanted to drive on the streets of a city at the expense of every other persons health, they will. Very few politicians would risk losing their parties funding over something that angers their funding base...if they did political parties that oppose this vehicle ban would suddenly find themselves swimming in cash. Changes: Something would have to be done to address the distribution system. I'm actually not so sure on solutions here...an online order system that drops off your purchases at a distribution point where you come to to pick them up would be a possibility (decentralization of purchasing goods and potential elimination of stores), but even then we are facing the challenge of getting your goods back to your home from there. Whatever the solution, the city would have to implement this prior to a ban...even if the implementation includes a phased approach where personal vehicles are gone first while the distribution network remains until a suitable solution to replace it is found. Public use cars - I'm not sure if you are aware of the 'car2go' program where smart cars are available for people to use as required and then leave on the street (or drop off point) for the next person to use. It's a potential 'phase out' approach to allow people to move their goods as needed. Streets become obsolete to some degree...why would a city have roads that are no longer used? I'd imagine emergency vehicle use of roadways would still be required in any event. The freed up land can be re-used for either a transit system or whatever replaces the distribution network. In urban centers, streets become open to all pedestrians to walk. In Suburban areas, urban farming or other such ideas could also be used to cover the freed land as well. I wonder how many homes will suddenly find themselves with a nearly useless attached garage? I can't imagine any of these changes occuring in less than a decade as a combination of city planning and public consultation (yay bureaucracy) along with construction would be a drawn out process...and scarcity of material may become an issue if all cities attempted this at once. It'd be a massive boom to the manufacturing and construction industries at any rate. Would car ownership outside of cities be allowed? If I owned a car, but lived where it was not allowed to be, would I have to park it outside of the city and come inside from there? Heh, it'd create an interesting phenomenon of giant parking lots surrounding cities at train stops to take people back and forth from their vehicles to their homes. Added: There might be a population density rearrange...very light (outside of urban and can use cars) would become far more attractive, or extremely high density (easy to be included in the supply chain) would be cheaper to maintain. It may result in the death of the suburban family white picket fence dream [Answer] Partly this will depend on how enthusiastic the populace and the local governments embrace this change. Is this removing all cars? or removing all vehicles? because there are a LOT of goods that need to go into cities and a lot of waste that needs to leave them. So if all trucks and cars are banned then transporting goods into and around a city will be a big priority. Neighborhoods will become more insular and self-sufficient, because it will be easier to by things within an easy transporting distance. However, how long? I suspect that if you had a city that was already used to very good public transportation and were very enthusiastic, it could transform itself fairly well in maybe 10 years. Anything less enthusiastic and it would definitely be longer. Most cities would try and find ways to mitigate the law, maybe only enforcing it on private autos (keeping public buses etc) and/or allowing electric cars instead for private use. Really large cities would likely do it in stages, convert downtown to a pedestrian mecca, routes for delivery vans, electric el's and subways with good coverage and moving sidewalks etc. Then it would push out, likely to give decent coverage to the poorer areas so workers can still commute (and give the richer areas longer time to own their cars!) I would guess just getting downtown Minneapolis or St. Paul to be carless would be 15-20 years, since they have terrible public transport and in general everyone believes they deserve their car, so taking it away would be a long process, mostly working by turning over the workforce as they retire and hiring new people with a new attitude. [Answer] I assume that ecological concerns do not prohibit car for personal transportation, but combustion engine (as major source of pollutant CO2 causing global climate change). It would be almost trivial change and we currently have all technology to replace car for personal transportation - the only thing lacking it the will to do it. Long-distance transportation will be run by electric trains, on slow lines for local and cargo transport, and separate very fast trains (like China, Japan and France has, going 300 mph) for long-distance transportation. Because train stations will be closer to city center, overland personal transport will not be substantially slower. Carbon-free electricity can be produced by wind turbines on the prairies, on mountain ranges, and offshore. With smart grid, electricity could be free for users during night, when demand is low. As you know, problem with electricity is not how to produce it, because production has to be equal demand - and demand fluctuates. Main problem to use energy from fluctuating renewables like wind (and solar) is how to store huge amounts of electricity to span production and demand. Solution is to store electricity decentralized way. Every house will have compressor which will convert free electricity during the night to compressed air, and during the day (when price of electricity can fluctuate according to demand), every house will either postpone consumption (turning off air-conditioning), or even produce electricity and feed it back to the network, earning money. The last mile (from local train station to shop/home) could be done by cars/trucks powered by compressed air (produced by the same free nightly electricity). With continent-wide network of compressed air stations, you can drive anywhere, and every hour stop to refill your drink and compressed air. Not much different. Only difference would be covering routes over oceans - and those could be covered by planes. So here you have it - world with almost no combustion engines - humming around without a glitch. You don't need to ban cars to prevent ecological catastrophe. [Answer] As noted by others, the supply chain, both commercial and personal, is significantly affected. Stores not near train stops will probably go out of business, and it's not clear how people get deliveries of furniture, appliances, building supplies like concrete, and so on. Property near train stations has just become much more valuable, and those living or owning businesses far from stations without the political or economic pull to get new stations will probably move out. If people have to move anyway, they might as well move out of the city entirely. They can then drive to city limits and hop a train to work (if they work in the city), and meanwhile they have cars available for their other domestic needs. Park-and-rides at train stations at city outskirts will need to be expanded. You said this is due to environmental concerns, so there's no immediate reason to ban bicycles. Expect to see more cyclists, which will put pressure on the transit system to accommodate cycles being brought onto trains. This lets people reach destinations that are farther from the stations than they'd want to walk. Cycle-based jitneys ("light taxis", so to speak) would also arise unless regulated against. People will probably shop for groceries and household goods more frequently and in smaller amounts, because you can no longer easily transport a large cart's worth of canned and dry goods (heavy). I see this happen with friends who live in large cities where cars aren't banned but just aren't as necessary (like NYC). This gives grocery owners more eyeballs on shelves, so to speak. How grocers would take advantage of that is unclear, but assume that advertising and weekly (or daily) specials would take it into account. You've got to do something about emergency services or cities will be unsafe to live in. People will still have medical emergencies, house fires, and crime to contend with. If you allow emergency vehicles, then response times should improve (no traffic). If you don't allow them, then more people will die or get hurt and crime will likely rise. So, that's all about the cities that are already in place when this decree is made. New cities will be designed to take the new laws into account. New cities are the exception, though (how many do you see now?), so we should expect not so much a new city design as gradual evolution of existing cities. People will move, commerce will move, and the train stations will become the backbone. How quickly? Mass changes like this are hard, so I would expect a couple decades before most of the dust settles. ]
[Question] [ When doing some research for some of the resent questions proposed, I ran across an article that pointed out a danger of traveling at extreme speeds in normal space as a high percentage of c I was unaware of. (besides just running into a few grains of sand...) The first problem after creating some shielding to protect against projectiles, appears to be to protect against ionizing radiation. One thing I never thought of was the blue shifting issue when traveling at near light speeds. So at what speed would say blue light shift to x-ray? What speed would near infra-red shift to x-ray? and what might be an effective shielding against this much larger amount of damaging radiation? Obviously you only need it on the 'front' of the ship. On top of that it appears that the faster one goes getting closer to the speed of light, light itself starts to push back on the object, like air-resistance on a super-sonic jet. (I just found that fascinating and wanted to share it in this question!) @99.99995 percent c > > And interestingly, the students also realized that, when traveling at such an intense speed, a ship would be subject to incredible pressure exerted by X-rays — an effect that would push back against the ship, causing it to slow down. The researchers likened the effect to the high pressure exerted against deep-ocean submersibles exploring extreme depths. To deal with this, a spaceship would have to store extra amounts of energy to compensate for this added pressure. > > > [Answer] TL;DR - MATH INCOMING: Approximately 99.9996% the speed of light. Let's take a trip in a spaceship, just to get away from all that silly air friction and other inconvenient matter. Assuming a frequency of light from our sun [out of atmosphere preferably](http://en.wikipedia.org/wiki/Sunlight#mediaviewer/File:Solar_spectrum_en.svg), only caring about the visible spectrum, assuming 500nm wavelength for simplicity: By the Doppler effect, the frequency of light/sound observed is a ratio of speeds multiplied by the actual frequency. Note that the equations differ when considering the high speed of light. We use the [Relativistic Doppler effect](http://en.wikipedia.org/wiki/Relativistic_Doppler_effect) for this. $f\_o$ = Frequency observed $\lambda\_o$ = Wavelength observed $f\_s$ = Source frequency $\lambda\_s$ = Source wavelength $c$ = Speed of light, ~$3.0 \cdot 10^8 m/s$ in vacuum or air. $v\_r$ = The velocity of the receiver (our imaginary spaceship) with respect to the source. It can also be the source with respect to the receiver. Note that the frequency of an electromagnetic wave is $f = \frac{c}{\lambda}$. Thus we have $f\_o = 6 \cdot 10^{14} Hz$ We have the following equation for the Doppler effect $$f\_s = f\_o \cdot \sqrt{\frac{1+\beta}{1-\beta}}$$ Where $\beta = \cfrac{v\_r}{c}$ Let's assume X-Rays (which range from 0.01 nm to 10 nm) are going to be 1 nm in wavelength for us, a frequency of $3 \cdot 10^{17} Hz$. After some rearranging we find the following: $$-v\_r = \frac{({f\_s}/{f\_o})^2 - 1}{({f\_s}/{f\_o})^2 + 1} \cdot c ~ = \frac{({\lambda\_o}/{\lambda\_s})^2 - 1}{({\lambda\_o}/{\lambda\_s})^2 + 1} \cdot c$$ A negative speed (as we have here) indicates that the source and observer are approaching one another. In our hypothetical scenario, we have $\frac{f\_s}{f\_o} = 500$ The answer to this gives $0.999996 \cdot c$, quite fast for our imaginary spaceship. If we can move that fast, I would hope to have reasonable radiation shielding. However... A star can emit more than just ordinary light, and space is full of more potent parts of the EM spectrum. What if you were flying near a star emitting high-intensity X-Rays? Or a source gamma rays? Stars can also eject high energy particles, which could cause some problems if they hit you. You also mentioned that light eventually "pushes back." I'm not 100% sure if this will be the correct interpretation of that, but I'll try my best. What happens when we approach the speed of light? Why can't we reach it? According to the theory of relativity, as we approach the speed of light, our mass increases more and more, until eventually we hit a point (at $v = c$) where our mass becomes infinite. The problem with this is that our speed is maintained (and increased) with energy, and energy requirements increase with both mass and speed ($E = \frac{1}{2}mv^2$). For more info [see this answer on Physics.SE](https://physics.stackexchange.com/questions/63555/why-cant-we-accelerate-objects-past-the-speed-of-light). Alternatively (and probably an explanation for the effect in the question), as Kaine mentioned in the comments, light does indeed have momentum that will exert a force as you move against it! What's really interesting is that we don't necessarily need to move at high speeds to observe the effects. Solar sailing works this way, and there is the "[Light Mill](http://science.howstuffworks.com/question239.htm)." [Answer] The formula is: $$f'=f\frac{\sqrt{1+\beta}}{\sqrt{1-\beta}}$$ where c is the speed of light, f is the frequency of the light normally, v is the velocity of the observer, $\beta$ is $\frac v c$ and f' is the freqyency of light observed by the observer. For blue light (650THz) to xrays (1500000 THz), you would need $\beta=.99999962$ so you would need to be very very close to the speed of light. ]
[Question] [ bucking the trend of mermaids I've decided to take a different approach with my mermaids. A long time ago a group of Australopithecus diverged from us taking to the sea. some characteristics of these pseudo-mermaids" are: * are 149.3cm (4.9ft) tall * are a grayish color * have a thick layer of blubber * have human level intelligence * have webbed hands and feet * have some type of echolocation but can communicate like humans (optional) * are omnivorous (but lean more to the carnivorous side) * have slit like noses (lacking a sense of smell) * thighs have started to become fused * can hold their breath for up to 15 minutes (but still need to resurface for air) Given these characteristics could such a hominid realistically exist? NOTE: magic does not exist in my story [Answer] Your timescale seems pretty brief, but might be doable. Australopithicines diverged from the rest of the hominins about [five to eight million years ago](https://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_common_ancestor#/media/File:Hominini_lineage.svg). Looking at the [evolution of cetaceans](https://en.wikipedia.org/wiki/Evolution_of_cetaceans), five million years is enough time to get from something that's basically [a land-dwelling mammal that can dive for food](https://en.wikipedia.org/wiki/Pakicetus) to an [obligate aquatic and unambiguously whale-like animal](https://en.wikipedia.org/wiki/Protocetus) with all of the major physiological changes along the way that would require. Similarly, the [ancestors of modern seals](https://en.wikipedia.org/wiki/Pinniped#Evolutionary_history) evolved from an otter-like Puijila to a very seal-like Pteronarctos over a similar timescale, though the changes weren't quite as dramatic as those that whales underwent. Note though that the immediate predecessors to seals and whales were things already adapted to swimming and hunting in water. Proto-humans seem to have arisen and lived in quite different environments, which adds a non-trivial barrier in the way of the changes you'd like. > > are a grayish seal like color > > > Seals are all different colours, both in terms of skin and fur. Cetaceans are also varied in colour. You can hand wave whatever colour you feel like, I'm sure. > > have a thick layer of blubber > > > Seems fine... whales and seals independently evolved this from a land-dwelling mammalian predecessor, so it seems plausible that it could happen here, too. > > have human level intelligence > > > That seems entirely like handwavium at this point, as only one species exhibits human-level intelligence and other intelligent humanoids are all dead, possibly as a result of the action of the direct ancestors of modern humans. You're the author though, so have at it. > > have webbed hands and feet > > > Fine. Note though that there aren't a whole lot of diving predators who use their forelimbs for catching prey; those arms are not at all hydrodynamic and will impede their owner's ability to hunt. They make more sense in generalists, especially tool-using ones > > have some type of echolocation (but can communicate like humans) > > > Dubious. Echolocation seems to have taken longer than 5 million years to arise in cetaceans, and required a lot of complex and specialised physiological changes. I think this is probably the least plausible thing you've requested (after human-level intelligence, perhaps) and it would be more likely that they've just got good underwater hearing, eyesight and other useful sensory modalities that aren't wildly different from their ancestors. > > have sharp teeth (being carnivorous) > > > The forebears of seals and whales were already predators. The forebears of australopithecus, not so much. Human (and hominin) dentition and digestive systems seem best suited to an omnivorous lifestyle. Perhaps this, too, could have changed over time, but it doesn't seem entirely necessary and does seem a bit dubious. There's reasonable non-meat-based eating to be had around the shoreline, both above and below, especially for clever species. > > have slit like noses (lacking a sense of smell) > > > Seals still generally have a good sense of smell on land. Remember that smell and taste are difficult to disentangle, and having a good sense of taste is handy for distinguishing toxic or otherwise unhealthy food from the good stuff. > > thighs have started to fused > > > Seems fine. > > can hold their breath for up to 20 minutes (but still need to resurface for air) > > > Also seems fine. Remember that breath holding times in marine mammals are related to the depth they need to dive to hunt. Deep dives require longer breath holds, but also substantially different respiratory physiology, not to mention the difficulty of locating and dispatching prey in deeper, darker water. Plenty of seals and other diving predators (like penguins) dive for only ten minutes or less, because that's all they really need. Still, longer dives don't seem unreasonable, so there's no reason you couldn't have them too. --- As an example of a real-world primate that has some early adaptations to the water and can dive and swim, have a look at [proboscis monkeys](https://en.wikipedia.org/wiki/Proboscis_monkey). They don't hunt or forage underwater, but eat fruit and leaves from trees near the water and use water as a handy escape route and take advantage of the open space is provides for group social interactions. [Answer] Ever heard of [Dugongs](https://en.wikipedia.org/wiki/Dugong)? Dugongs are mammals that have gone back to the oceans, and share a lot of the attributes that you describe in your question. They even look from some angles to have commonalities with humans and are thought in some circles to be the origin of the mermaid myths. [![enter image description here](https://i.stack.imgur.com/nxR1Y.jpg)](https://i.stack.imgur.com/nxR1Y.jpg) Ultimately, the primary difference between these creatures and the one you describe is the level of intelligence. The fins as opposed to webbed hands is likely a by-product of not being a tool using species before returning to the oceans, but I would imagine that if the species that DID return had tool building skills, they wouldn't have hands that evolve back to fins as opposed to being webbed. What is more difficult to understand is WHY a creature with intelligence would make this change. Arguably, one reason might be climate change (a warm blooded creature would find it easier to maintain comfort in water than on land during a sustained heat wave) but it would also lose a lot of the advantages that life on land gives it in the first place when coupled with intelligence; cover from predators, resources for tools, etc. Is it possible? Sure, and the Dugong proves it. Likely? Well, that is a whole other matter and one would argue that the prevailing environment in which this is likely to happen is going to be rather specific. [Answer] The only thing that bothers me in the picture is intelligence in species adapted to an aquatic life style. There need to be an evolutionary pressure from the environ to develop it - if a species can live without intelligence, it will. Maybe similar with the transition from jungle to savanna - not enough food to forage (is all seaweed toxic?), all the prey is large or agile enough to require hunting in groups (require communication/coordination) and the use of weapons or traps to kill it. The impossibility of manipulating fire in aquatic life conditions is a serious impediment for the evolution of intelligence - no food transformations (some nutrients may have been beneficial in the the evolution of intelligence), no capability to preserve the food over longer periods (no causative temporal relations to favor the use of memory in cognitive processing). Also, a watery environ is less likely to lead to technological development: advances in chemistry and metallurgy are hard without heat, no steam power, little chance to discover static electricity; batteries without access to metals and insulators... I doubt it. ]
[Question] [ What is the most powerful magnetic field that could be generated by a planetary object? The measurement of 'powerful' will be [field strength](https://en.wikipedia.org/wiki/Magnetic_field#The_B-field) ($\mathbf{B}$-field) at the planet's surface, in teslas. ### Restrictions * The planet may have any composition (gas giant, rocky, methane-ball, exotic) * The planet must be sub-stellar; that is, too small to start fusion. * The planet may be at any stage of development * The planet must generate this magnetic field itself, not induced from a nearby magnetar or something exotic. * The planet must be able to orbit a Sun-like star. * The planet must reasonably be able to form naturally [Answer] TL;DR-- I think even under ideal circumstances, a field strength of about $0.4$ Tesla would be the limit. So first off, ArtificialSoul is probably correct that no one here is going to be able to give you anything resembling a super accurate answer. But like most problems in fluid dynamics, If I rapidly wave my hands fast enough I can give an extreme estimate that should give you an idea of the order of magnitude that's possible. Now, the actual planetary dynamo of the Earth is due to the coriolis force acting on convection currents of molten iron, twisting them into spiral flows. Then, a complex feedback mechanism between current carried by these flows, previously created magnetic fields, and resistive dissipation combine to produce a somewhat stable magnetic field. This is an absolute nightmare to model. So, instead, I'm instead going to approximate these flows as a current density $$\mathbf{J} = J\_0s\hat{\phi}$$ Where we are in cylindrical coordinates and $s$ is the coordinate telling you how far you are from the z axis. The current will follow this form until the radius $R$, at which point it will become $0$. $R$ in this case is the radius of the zone where the iron is molten-- the outer core in the case of earth. I am going to neglect the fact that the inner core is solid, because less work = good. The reason I chose the form I did for the current density is because it's the same as the current density of a charged sphere azimuthally rotating at some angular velocity. Again, the real picture is much more complex, but this will give us a good upper bound because it assumes all the flows of molten metal are working together to generate a magnetic field, whereas in reality, different regions will be counteracting each other and just making a general mathematical mess. Now, we will use Biot-Savart to calculate the magnetic field along the z axis, because I would assume that's where the magnetic field would be strongest. More Importantly, however, it's much simpler. Now, Biot-Savart states $$\mathbf{B} = \frac{\mu\_0}{4\pi}\iiint\_{current}\frac{\mathbf{J}\times\mathbf{r'}}{(r')^3}d\tau'$$ I've made one more simplification, which is that I'm ignoring magnetization of the molten iron and I'm simply using the permeability of free space. This is reasonably accurate though since molten iron is well above the curie temperature and thus doesn't act very magnetic. Plugging in all our nasty expressions in with the proper coordinates and simplifying considerably, we end up with the following expression (as long as $z>R$): $$\mathbf{B}(z\hat{z})=\hat{z}\frac{J\_0\mu\_0R^2}{2}\int\_{-1}^{1}du \bigg[ \frac{1-u^2+2(\gamma-u)^2}{\sqrt{1-2u\gamma+\gamma^2}}-2(\gamma-u)\bigg]$$ where $$\gamma = \frac{z}{R}$$ This seems really awful, but it's actually not too bad-- the integral is simply a function of $z/R$ that decreases like $1/z^3$ as you move far away. For clarification $z$ is the coordinate along the z axis where $z=0$ at the center of the planet. From this point on, $z$ will refer to this coordinate at the surface of the planet, since that is where the magnetic field is strongest. The key points to take away from this is that $\mathbf{B}$ grows with increasing $J\_0$ and $R$ given fixed $\gamma$, and shrinks with increasing $\gamma$. So, to find an upper bound for magnetic field strength, we want $J\_0$ and $R$ to be as big as possible, and $z/R = 1$. I'm simply going to reverse engineer $J\_0$ from Earth's magnetic field to get a rough order of magnitude estimate, which produces the result $J\_0 = 1.4\times10^{-10} A/m^3$ (as always, this is a very rough estimate). As for $R$, the biggest planet thus far discovered has a radius of about $1.25\times 10^8 m$, so we will use that value. Finally, the integral attains a maximum of $0.2666$ when $\gamma = 1$. Note that this would imply the entire planet is molten and carrying a current-- for planets that have a solid layer, $\gamma$ would be greater than one. Putting all these values together, we get an upper bound of $$\|\mathbf{B}\| \leq 0.38 T$$ at the surface of the planet. This is assuming $J\_0$ is roughly the same for any planet, which likely isn't true-- faster rotation would imply higher $J\_0$, and complex feedback mechanisms between the magnetic field and the convection currents could cause significant deviation from this value. But regardless, this should give you decent idea of the most extreme magnetic fields a planet can have that retain a shred of scientific plausibility. I don't have time right now to add more detail of my calculations, but if you're interested I can probably edit them in later. Hopefully this helps! [Answer] ## I think this question is not sufficiently answerable by current science. We know that turbulent molten metal currents (as in earths core) has the ability to [create and sustain magnetic fields](https://physics.aps.org/story/v19/st3). We also know that there are [certain particles that can enhance this effect](https://www.sciencealert.com/a-new-liquid-metal-helps-scientists-create-a-smaller-earth-in-the-lab). > > With the added ingredient of suspended magnetic particles, the material has the ability to generate and manipulate magnetic fields up to five times stronger than those generated by liquid metal on its own, say researchers from Yale University. > > > In general, [Magnetohydrodynamics is not a well understood field in astronomical scales](https://en.wikipedia.org/wiki/Magnetohydrodynamics#Astrophysics). So it is unlikely anyone can calculate you any numbers. There are [a few other mechanisms that can give planets magnetic fields](https://www.apexmagnets.com/news-how-tos/the-magnetic-fields-of-our-solar-system/). ### How about finding data then? Well, I've found a little bit. [Jupiter has a magnetosphere larger than our sun](https://www.apexmagnets.com/news-how-tos/the-magnetic-fields-of-our-solar-system/). The [equatorial field strength is 776.6µT](https://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter) - which is 25 times stronger than earths. All the other data I found was significantly lower than that. In the realm of 1nT to 1µT equatorial field strength. I did not manage to find any data on bodies that are not within our solar system, though. Only about the planets and their moons within it. --- ## Addendum: Look at [el duderinos answer](https://worldbuilding.stackexchange.com/a/124679/44086). He makes a very good upper bounds estimation. So there is a good side to all of this: Nobody can disprove your magnetic field strength. So you are about as free as el duderino described. :D [Answer] Neutron stars have field strengths up to 65 TT (Tera-Tesla), how is a neutron star a planet? Well: * a neutron star, or other stellar remnant, could in fact be part of a new star system partly composed of material from it's own formation, as well as other supernova debris. Said second generation system being of sufficient total mass and travelling in an appropriate direction to capture the old remnant as part of it's accretion disk. * in which case it may end up in orbit of a new star as a planet of exotic but perfectly natural origin. * the new star that eventually forms need be no bigger than Sol. * neutron stars produce their own magnetic fields because of their high rotational speed and exotic composition. Possibly it violates the "sub-stellar" clause since it is heavy enough to undergo fusion if it was composed of normal matter but a neutron star by definition does not undergo fusion so I feel it's still a valid candidate. Sorry if this doesn't quite match what you had in mind but I've always liked the idea of a stellar remnant as a planet, I mainly think in terms of a black dwarf, the concept works for any leftover chunk of a star big enough to be re-integrated at the second or third generation. ]
[Question] [ My world is essentially a Neptune-sized gas planet that got seeded with life and its surface layer filled with oxygen, therefore gaining a sizeable layer with Earthlike conditions. Within this layer, life is diverse, but the largest lifeforms would be colonies of treelike plants that have connected branches and a translucent, photosynthetic canopy stretched between those branches. Think an organic version of the tensegrity sphere. The branches would be connected by non-rigid "ligaments". The life cycle would start with a single instance, which would clone itself, forming a mushroom cap shape with a flat, ring-shaped floor on the inside bottom with a circular hole in the middle. Gradually, all instances would grow in size, preserving the general shape but the center would die, decompose, and form a "soil" layer in the inner flat ring. The young colonies would be buoyed up by updrafts as they fell, in clear skies the sun would warm the air inside the canopy enough to slow the fall, allowing it to heat up even more and maybe rise. The early stages are the most difficult. The majority of instances sink to the depths. As the branches, canopy, and connective structures are all on the outside, the volume of heated air also grows and it becomes easier to stay aloft as the colony grows larger. The colony is adaptive and can regulate the inside air temperature and pressure. Could such a forest grow as large as a city? A continent? Could it actually support an entire ecosystem within itself of creatures that don't drift, fly, or float their entire lifecycle? Would it be strong enough to withstand turbulence and storms, or would it need to stay within a jet stream to survive? Would extremely large ones generally be stable? I thought of this through pondering how a floating island would actually be possible. In the lore of my world, human colonists discovered this world and created aerostat colonies before a disaster forced a migration to these forests. [Answer] ## You need plants with hydrogen-filled bladders I never thought I'd say that one day. Anyway, my suggestion is that your plants evolve some kind of hollow sac, but I'm not 100% sure how they'd get that far without them (As in, past pond scum stage). On the fictional planet Ilion, by a person I do not know the name of (He goes by Malicious Monkey on the Speculative Evolution forums), there is a clade of flora called Buoyphytes: ![enter image description here](https://sunriseonilion.files.wordpress.com/2013/01/red-plant-anatomy.jpg) These use air-filled bladders to float on the surface of water bodies, which means they can both colonize the sea and photosynthesize efficiently. If these were filled with hydrogen, they could float in the air. But how would this evolve on a gas giant? Well, here's my idea: the microbes that would become your plants already produced hydrogen as a metabolic waste product. When they eventually produced a colonial form that would go on to become a multicellular plant, their colonies were shaped like hollow spheres and they expulsed the hydrogen into the interior. When the balloon is full, they would open a hole in the colony to let some gas out. The evolutionary pressure for this adaptation could be that they increased their buoyancy to get higher than the other photosynthesizers and thus outcompete them. For more on Ilion's Buoyphytes, have a look here: <https://sunriseonilion.wordpress.com/ilion/species/red-plants/> "Setaceous Cetacean"'s moon called Solais ( <http://s1.zetaboards.com/Conceptual_Evolution/topic/8121915/11/#new> ) has a lot of balloon plants (though they aren't plants in the traditional sense). To have a look at another "life on a gas giant" project, check out this one: <http://s1.zetaboards.com/Conceptual_Evolution/topic/8143795/1/> Those are just some additional links to inspire you, I'd say they'd be quite helpful. I haven't looked as much as I'd like to at the last two, so hopefully they're relevant. Sorry about the poor formatting, I'm typing on my phone. I hope I answered your question well, and thanks for asking. Edit: Just found out that Malicious Monkey is a she. And her name is Emily Holland, to give her credit by her real name. [Answer] Planes fly by forcing air against their carefully aerodynamically-sculpted bodies in ways that generate lift. [Bernoulli is overrated.](https://van.physics.illinois.edu/qa/listing.php?id=2103) There are a few ways that an organism of significant size could generate large amounts of lift. They can do it the way planes do it: the colonies are ambulatory, and they propel themselves along at speed so they fly forever. Like some sharks, if they ever stop moving, they sink and die. The precise mechanism of how they do this is up to you, but heat differentials and gas production from metabolism would combine with clever valves and air bladders nicely. They can take advantage of the naturally highly chaotic and dense atmosphere's raging currents. Basically, the plant colony would be a giant sailing vessel. The entire structure would have control surfaces that are constantly in adjustment to maintain altitude. Colonies would occasionally break apart in a raging storm. This would be one mode of reproduction. Buoyancy can also be manipulated. The atmosphere will not be uniform throughout, in the same way the ocean has [multiple layers](https://timescavengers.blog/climate-change/ocean-layers-mixing/). In the case of a gas giant, denser gases will naturally separate out and be found at higher depths. This is for the same reason that if you take a bunch of ball bearings and foam peanuts, put them in a box, and shake it, all the ball bearings will end up at the bottom. So the plants can rise or sink by adjusting their density. Gas bladders may be involved. The plant may have an ability to adjust the density of its bulk as it grows, to adjust buoyancy as well. [Answer] Many plants have seeds designed to disperse through the air. It would seem reasonable that in the right environment this evolutionary process might scale. I would think a smaller lower gravity planet or moon might harbor this kind of life due to the reduced gravity. Perhaps with the winds being produced by tectonic stresses resulting from orbital interference. Like IO, whose gysers are believed to be caused by the gravitational interference with other moons for example. Frequent near misses with other moons might cause thermodymic changes that would cause steam gysers and frequent high winds. Perhaps a highly elyptical orbit causes one planet or moon to scoop up atmosphere from the others periodically. Spider silk is now known to take advantage of static electricity to allow small spiders to fly. It might be possible for a plant to develop a similar process, where millions of hairs hundreds of meters long develop a charge and help pull them into the air as storms charge and discharge. Probably most of them would have symbiotic relationships with other species in order to get their nutrients. I think they would look like a web of tumbleweeds or kudzu with chunks of spiderweb like moldy bits interspersed. The mold would be responsible for converting nitrogen and minerals like the bacterian on legume roots. There is a type of fern that is essentially airborn, getting most of their moisture directly from the air. They sell them sometimes at junk shops in beach towns, I don't remember what their called. I would think they would need to evolve a way to deal with water adhesion. If they benefits from floating, then they would want to shed weight and condensation, and in a misty environment would be a problem. Maybe a cohabiting bug or animal would like things dry, and so keep any condesation off the web of plants. Perhaps these friendly species might migrate in great clouds to and from the gysers as they approached breeding season. Different species would probably compete in different ways, so the forrests would form waves shapes, where certain types pulling others down, or vice versa depending on whether their primary energy source was from below or above. Perhaps periodically forming conduits for lightning discharge that create great structural columns of dead wood, that the other plants and species feed off of. Just a few thoughts. ]
[Question] [ My habitat ring is constructed in orbit around a planet with disconnected sections: (not to scale, obviously) [![enter image description here](https://i.stack.imgur.com/aPUTl.gif)](https://i.stack.imgur.com/aPUTl.gif) The sections are connected by cables and winched together. As the diameter gets smaller, the ring should spin faster. [![enter image description here](https://i.stack.imgur.com/tP32Y.gif)](https://i.stack.imgur.com/tP32Y.gif) Does this give my ring artificial gravity? [Answer] Let's start off looking at this from a conservation of angular momentum point of view. We can say that angular momentum is definitely conserved here because there is no external torque being applied to the system. I'm not sure that orbital energy is conserved here since it really seems like whatever motors are pulling the cables tighter will need to do work to do that which allows energy to be transferred from batteries/solar into orbital energy (so total energy is obviously conserved it's just that we'd also have to account for other energy sources besides orbital energy). Let's say the station starts off orbiting at a radius of $R\_0$ in a "neutral" circular orbit (i.e. station occupants feel weightless). This gives us an orbital velocity of $v\_0 = \sqrt{\frac{\mu}{R\_0}}$ where $\mu$ is the gravitational parameter of the central body. Our specific angular momentum is then just: $R\_0 v\_0 = \sqrt{R\_0 \mu}$ Now, let's say you reel in on those cables and bring the whole radius down to $R\_f$. Since angular momentum is conserved we have $R\_0 v\_0 = \sqrt{R\_0 \mu} = R\_f v\_f$. We can solve this for $v\_f$: $v\_f = \frac{\sqrt{R\_0\mu}}{R\_f} = \sqrt{\frac{R\_0\mu}{R\_f^2}}$ To answer your original question we need to determine if this is slower or faster than the circular orbit velocity at $R\_f$: $v\_{f,circular} = \sqrt{\frac{\mu}{R\_f}}$ If we rearrange our expression for $v\_f$ we get: $v\_f = \sqrt{\frac{R\_0}{R\_f}} \sqrt{\frac{\mu}{R\_f}}$ Combining this with our equation for the circular velocity: $v\_f = \left(\sqrt{\frac{R\_0}{R\_f}}\right) v\_{f,circular}$ So, if $R\_0 > R\_f$, the station ends up with a velocity that's greater than orbital velocity (since $\sqrt{\frac{R\_0}{R\_f}} > 1$). This is enough to show that you would in fact create artificial gravity by doing this. [Answer] Yes. A decrease in rotation radius will increase the apparent gravity. --- Your entire station is orbiting a planet together. The habitat ring is spinning around the station, not orbiting it. (I think some of the other answers may have misinterpreted that.) In order to keep the habitat stations spinning properly, each one has to have a cable connecting it to the center station. They could also be linked to each other, but that would require thicker cables, and make [orbital station keeping](https://en.wikipedia.org/wiki/Orbital_station-keeping) difficult for the whole assembly. The centripetal acceleration of a body rotating with linear speed, v, and radius, r, is [![r, is $a_c](https://i.stack.imgur.com/pj1WP.gif)](https://i.stack.imgur.com/pj1WP.gif). Towing the rotating stations closer would decrease the radius while keeping the linear velocity constant. This would increase the apparent gravity. Note that the linear velocity is constant but the angular velocity increases. --- Proof that linear speed does not decrease as radius decreases. The individual stations are towed towards the station, perpendicular to their velocity. Because the force and velocity are perpendicular there is no change in energy with the towing; work is the dot product of force and direction. A change in linear speed requires a change in energy, because E=0.5\m\v^2. [Answer] The rotation rate increases and you could stand on the edge (head toward Earth, feet away). Since the components of your ring are no longer moving at circular orbital speed, the ring is unstable, and if some small force moves it off center, it will continue to go further off-center until one side of it starts to enter the atmosphere. It will need some sort of active stabilization -- small rocket thrusters or the like in order to correct any drift. This is the same situation as Niven's "Ringworld" though on a smaller scale. [Answer] The ring will not generate any artificial gravity no matter what orbit you are at because the orbit is achieved when the angular momentum balances the gravity of the object you orbit. Which is why there is no artificial gravity on our space stations orbiting the earth. You can think your contraption is the same as a bunch of ISS attached together and no matter how you go about that, none of them will have artificial gravity from just orbiting. If you were to make the stations travel faster than they would in normal orbit and let the cables between them stabilize them instead, then you would achieve artificial gravity. The force the cables are able to stretch is the force of your artificial gravity. ]
[Question] [ The time: January 27th, 2017, 7:00 AM local. The place: New York City and environs. [Jormungandr, the Snakebot of Doom](https://worldbuilding.stackexchange.com/q/37248/75), has just finished steamrolling New York City into something more closely resembling a gravel driveway. Now it has returned to the vicinity of lower Manhattan and is busy extracting any iron or steel that it can find in the rubble in order to convert it into steel railgun ammunition. It is currently firing the six large railguns in its tail, each shot containing about 6.8 metric tons of steel, at a combined rate of 4 rounds per second. If it has to use its small railguns for self defence, they won't add significantly to the rate at which steel is being consumed. Jormungandr's mouth is currently ingesting any iron or steel it can find in the rubble in order to resupply its ammunition bunkerage. It is easily able to resupply its ammunition faster than it can expend it provided sufficient steel is nearby. How long would the steel found in New York City and environs be able to supply Jormungandr's appetite before it has to move on to another source of steel? Consider this to be the real world, with the exception that over the evening of the 26th until the morning of the 27th, New York has been experiencing severe blizzard conditions, leading to closure of ports, airports and roads. At the time in question, neither roads, ports or airports have yet reopened. The blizzard will mean that there are more ships in the ports adjacent to NYC than usual, and that cars cannot readily leave. By New York City and environs, I mean the area with this definition: <https://drive.google.com/open?id=1piz-lZJ_ti3EAnEH7b_LNgIguiQ&usp=sharing> Please account for the quantities of any man-made iron or steel within the area, no matter how large, including any vehicles, shipping, building structural members, railway track, rolling stock and tunnel shoring or lining, with a reasonable justification. The exact amount of steel in each building need not be accounted for. Small objects such as nails or bolts, unless part of a larger steel structure, may be discounted, as Jormungandr will not bother with anything so trivial. This will rule out its being interested in scavenging from wooden-framed dwellings, but steel framed dwellings are another matter. EDIT The world in this question starts out pretty much as the world with which we are familiar. However, the question is, How long can Jormungandr stay here before it needs to move on to another source of steel, and the world being built is one where Jormungandr stayed for x time, firing continuously, then had to leave to find more steel. That world may or may not resemble our own so much, depending upon the magnitude of x. I want to know X. Can it stay for Hours? Days? Weeks? Months? Years? How many of them? If Jormungandr stays for 'hours', then the world will be considerably different than if it stays for 'weeks'. Hours means that all that many of the survivors of NYC have to do is sit tight and wait for relief efforts to come to them. Weeks means that the survivors have to become refugees and travel to somewhere where they can get the necessities of life, since Jormungandr isn't going to leave much in the way of the necessities of life for the survivors to use, and how many relief agencies are going to risk coming close to a thing that destroyed US armed forces sent against it so easily? The longer Jormungandr stays put, the more time humans will have to try to come up with unconventional means to try to destroy it. The longer it stays put, the more likely that humans will discover that [the birds have been bugged](https://worldbuilding.stackexchange.com/q/79261/75) before it moves on. The longer it stays put, the more likely it is that some idiot may try a massed submarine ICBM launch against it. So, while, yes, this is a question about a story set in a world, the world-building aspect of the question is that the answer affects how the world changes. Please don't think that just because the question is basically "how much steel is there in NYC, and then divide by 27.2 metric tons per second" that there aren't other implications that will greatly affect that initial, known, world. [Answer] Right, this will be a very rough estimation since I'm not an engineer. First and foremost cars. According to what I could find online you have about 700K cars in the city, each weighing 4009 pounds (1818.452Kg), so considering that almost all of the car's weight will be metallic components then you have 1,272,916.4 tons. Add to that the 6,384 subway cars at around 38 tons each for 242,592 tons. 1,2K real trains, each one weighing about 500 tons, for a total of 600,000 tons For buildings things get a little more complicated, but using the Empire State building as an example, it has 60,000 tons of steel and weights a total of 365,000 tons. So it would give about 16,5% of the total weight in steel, considering that buildings under 30 floors will have half of that we will come to: 47,000 buildings with 24,373 total floors in buildings over 30 floors and 225,203 floors in buildings under 30 floors. The Empire State building has 102 floors, so that would give about 3,578.5 tons per floor, that would give about 600 ton of steel per floor. That would give a total of 14,623,800 ton of steel in the bigger buildings and 67,560,900 tons of steel in the smaller ones. Ships: According to the NY Harbor website there are 351 ships in harbor right now, since OP says the harbor is more filled then usual, I'll hazard a guess and say it will have about 500 ships of considerable size (600.000 tons). Bridges: According to Wikipedia there are over 2000 bridges and tunnels in New York with an average length of 952,3 meters. Taking the Brooklyn Bridge as an example, it has an weight of 14,680 tons, with a span of 1.833677 Km and 3084.42 tonnes of steel in it. This would give about 1,682.09 Tons of steel per kilometer. Giving an total of: 3,203,719.27 tons of steel. Guns: Apparently there are 1,2 million registered guns in NY, so for practicality I'll assume there are 2 millions guns in NY total. I'll consider that they will have an average weight of 0,5kg and add another 0,5kg as ammo for each one. This would bring about 2,000 Tons. Only that will amass about 387,505,927.67 tons of steel in New York for your snake to feed on. At the rate you specified the snake will devour it all in about 5 and a half months if my calculations are right. ``` +-----------------------+---------------+---------+-------------+ \| Item \| Tons per item \| Count \| Total \| +-----------------------+---------------+---------+-------------+ \| Car \| 1.818452 \| 700000 \| 1272916.4 \| \| Subway car \| 38 \| 6384 \| 242592 \| \| Real trains \| 500 \| 1200 \| 600000 \| \| Tall building floors \| 24373 \| 600 \| 14623800 \| \| Short building floors \| 225203 \| 300 \| 67560900 \| \| Ships \| 500 \| 600000 \| 300000000 \| \| km of bridges/tunnels \| 1682.09 \| 1904.6 \| 3203708.614 \| \| Guns \| 0.001 \| 2000000 \| 2000 \| \| Total \| \| \| 387505927 \| +-----------------------+---------------+---------+-------------+ ``` [Answer] If given a target, possibly indefinitely. Assuming the area is quarantined once it shows up and no new sources of steel arrive Once the area is clean, the size of the railgun rounds will mean its own spent ammunition make up the largest deposits of ferrous metal in the surrounding area. Assuming the thing isn't intelligent, if you can keep it shooting you can keep it chasing its own tail indefinitely. ]
[Question] [ In the sci-fi/fantasy novel I am working on, my magic system currently works based on of a fictional type of energy that is created by stars and expelled throughout the universe, like UV rays and that sort of thing. This energy is known as psychic energy (dumb name, I know. It's a work in progress), and the people of my world who know how to harness it can use it to cast spells and do magic. I was wondering if this is a cool idea, and if it makes any sense, as the magic system I am trying to develop needs to be at the very least plausible within the fictional parameters I create. The characters absorb this energy naturally through their skin, but can only hold so much without doing rituals/body modification to augment their natural capacity. Does this make sense, and if not, what can I do to change it? [Answer] # Have them magically absorb neutrinos. Fun fact of the day: There are $\sim10^{11}$ [neutrinos](https://en.wikipedia.org/wiki/Neutrino) passing through every square centimeter on Earth every second. And they just go straight through. Neutrinos - "little neutral ones", if you like - are tiny leptons, uncharged particles with very low masses, if any. They interact with other particles through the [weak nuclear force](https://en.wikipedia.org/wiki/Weak_interaction) - which is, as you can imagine, weak. Neutrinos coming from the Sun would need to pass through [one light-year of lead](http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/neutrino3.html) to have a high probability if interacting with another particle. That's how weakly they interact. The point of this is that you don't notice neutrinos easily. It's extremely difficult to detect them, even with state-of-the art detectors. I think they would be a perfect energy source for you - and yes, [they come from the Sun and other stars](https://en.wikipedia.org/wiki/Solar_neutrino), produced in nuclear reactions! My proposal for your magic system: * Normally, people interact with neutrinos much like we do; in other words, they don't. * These spells magically make it much more likely for a neutrino to interact with particles in the spell-caster's body, perhaps by temporarily changing the strength of the weak force as pertaining to neutrinos. Magic is your only choice here. * Each solar neutrino has an energy of a few hundred keV - let's say about 300 keV. If each neutrino's energy is transferred to the body, then each square centimeter absorbs about $10^{-5}$ Joules per second. If a person's chest has an area of about 2000 square centimeters, then the person can get about one joule of energy in a little under one minute. * Let's also assume that these people can "charge up" during their sleep. If they sleep for about 500 minutes every 24 hours - getting in their 8 hours a day and then some - they can get 500 joules of energy. Not bad, especially if they're willing to charge up at other times, too. There's your psychic energy, at a decent rate - and with a little physics thrown in, too! [Answer] Energy somehow being supplied by the sun a usable idea - just look at how successful Superman is. The things you need to consider are what the logical effects of this are - for example, being generated by stars, a person's magic energy would be replenished much faster during the day. Because it is absorbed through the skin, you'd either have magic users wearing as little clothing as possible in order to maximize skin exposure, or you'd have them wearing special cloth designed to allow absorption of the energy through the cloth. This also means that exploring a cave or a dungeon crawl would be more dangerous because, without exposure to the sun, they wouldn't be able to replenish magic. You need to spend some time thinking about what other things would be common, and decide if these things are what you want to have in your story or not. [Answer] If you're wanting to really answer the question about magic. I suggest you ask why a Sun would generate magic. That is to say, it would be ideal to have a force in the universe that operates in a consistent manner to make this happen. For instance gravity. For instance a suns mass is directly related to what it burns for fuel. What you could do is suggest that there is a relation to high mass objects, or fusion reactions, that produces the magical field/force/plasma/rainbows/etc. As a result you have something you can unify through your story and have it used or seen in other phenomena, animals and world events, while also allowing mages to experiment. If you want it to be unpredictable or mysterious, remember, you can write about it happening but characters not understanding why, they just assume x or y has happened and go about their lives. But because you as an author understand the principle at play, you can weave it throughout the story. [Answer] ## Astral Energy Your concept is not dumb at all. In fact, it has been an essential part of all mystical philosophies I've ever heard of, although it's name changes depending on the language of the philosophy. Many Western philosophies describe this energy as "astral": > > as·tral (adjective): > > - of, connected with, or resembling the stars > > - of or relating to a supposed nonphysical realm of existence to which various psychic and paranormal phenomena are ascribed, and in which the physical human body is said to have a counterpart > > > Origin: > > Early 17th century: from late Latin astralis, from astrum ‘star’ > > > ## Prana Vedic mysticism uses the Sanskrit terms "[prana](https://en.wikipedia.org/wiki/Prana)" and "[kundalini](https://en.wikipedia.org/wiki/Kundalini)" instead of "astral", and refers to the corresponding subtle body as either the "[pranamaya kosha](https://en.wikipedia.org/wiki/Kosha#Pranamaya_kosha)" or simply the "[sukshma sharir](https://en.wikipedia.org/wiki/Subtle_body)". The astral dimension is subtler than the physical dimension, meaning it cannot be sensed by the ordinary physical senses, and is often refered to as the [astral plane](https://en.wikipedia.org/wiki/Astral_plane). In this plane, humans are said to have [astral bodies](https://en.wikipedia.org/wiki/Astral_body) made of astral energy. People are said to be able to interact with the astral plane with their astral body, and even travel therein via [astral projection](https://en.wikipedia.org/wiki/Astral_projection). ## One Of Many Planes The astral or subtle plane is considered part of a much larger cosmology consisting of various numbers of [planes](https://en.wikipedia.org/wiki/Plane_(esotericism)), both in western and eastern mysticism. Each plane is composed of it's own unique type of matter and humans are said to have bodies made of this matter in each plane. Meditation and various accompanying techniques, such as [yoga](https://en.wikipedia.org/wiki/Yoga), help the disciple/practioner towards enlightenment (termed "[moksha](https://en.wikipedia.org/wiki/Moksha)" in Sanskrit) by increasing the mind/body coordination between the physical self and waking state consciousness and the subtle bodies. ## Transcendental Meditation I've been researching this area of study a lot since 1990. I've researched and tried many different schools of thought and styles of meditation. However, all failed to fulfill my eagerness for sustainable practical results, until I found [Maharishi Mahesh Yogi's](https://en.wikipedia.org/wiki/Maharishi_Mahesh_Yogi) meditation techniques and his Vedic Science techniques. I was so impressed with the results I spent the next 13 years studying and practicing them full-time. The form of meditation taught by Maharishi is called [Transcendental Meditation](http://www.tm.org) and I highly recommend it. ]
[Question] [ So assuming their existed an Oracle, what effects would it have on society. Assume that everyone has access to it similar to using a library where the books can't leave. ## Properties of the Oracle * It can only answer axiomatic (self evident, time independent) questions. * It has no concept of 'current time'. Its answers should be always true, regardless of time passed. (Questions about Earth will assume 'average' and 'in this era') * The answer will be a short phrase, number, range, or equation in whatever units the user is most comfortable with. * The Oracle is smart enough to answer the question you mean, not what you asked. (so no language/meaning problems) And always responds with an unambiguous answer that the user can understand. (Like WolframAlpha, but it knows everything, and better auto-correct, and faster) * It can only give answers, not explanations. (the user may understand what the answer is, but not why it is the answer. You can't bypass this by asking 'whats the first/second/ect. reason that was the answer?') * No technology can interact with Oracle in any meaningful way. * It will only answer questions for curiosity/academics. It is self aware enough to know if someone is trying to directly/indirectly exploit it. (Because reasons not important to this question) * The oracle can't be controlled/restricted (it appears to whoever needs it. when they need it). * If the oracle can't/won't answer a question, it will tell the user it can't answer. The oracle can give guiding questions to the user though if the problem is that the user doesn't really know what they are asking. (like "what do you consider 'stable'?".) * The Oracle can be destroyed, but as far as mortals understand, it is indestructible. (I am adding an exception that the Oracle can't say how it can be destroyed. This knowledge has to be obtained from a god, and none of the gods will let the oracle be destroyed (because the Oracle is part of a set of artifacts, and bad things will happen if the whole set is destroyed, but that is irrelevant to this question.)) ## Examples Will Answer * How to find water (go to the sea), not where it is. * 'How long will it take an apple to reach the ground', assuming you mean on Earth, and from an average apple tree, with the answer being an average time and/or time range. * "Are there any stable elements in the periodic table after 200?" (Answer will be based on user's definition of 'stable'. If they don't know, the Oracle will till them to figure that out first.) * "What equation describes the relationship between gravity and quantum mechanics?" (Will answer 'there is none' if it doesn't exist.) Won't Answer * How do I make a better engine? (better is subjective, and answer changes with available technology) * How many troops does the enemy have? (This is a time dependent question) * What is the fastest way to get rich? (This is a time dependent question) * "What is missing from the Standard Model to be a complete description of physics?" (Can't be briefly answered. It will say if it's possible though.) * Solution for a Hash output. (Infinite answers. If you ask for 'just one', it will refuse, as 'which one is the answer' is subjective, even if all answers are equally valid) For religion, there are questions it will and won't answer. Info that is always true (is there a god? yes) will be answered. Info that is not always true won't be. (is there one god? gods can be created and destroyed in this universe so, no answer. (but a few select gods are eternal)) ## The main questions I'm interested in are * Will this stunt or accelerate technological progress? (Will people learn 'why?' faster if they know the answer, or will they not try to find out why if they can just know the answer?) * Would this have any noticeable effects on society? (would this encourage/discourage any common philosophies or how people act?) * I'm interested in both if this just appeared today or has always existed. I know this is a bit broad, but I'm looking for the psychological effects access to this Oracle would have on people. I'm not interested in exploits beyond its intended purpose (to be a infinite knowledge database). Please try to avoid answering with opinions! EDIT: I think I've locked out all potential exploits, but basically it can't be used by machines, or used to gather information that the user couldn't implicitly know as a fact. [Answer] This was already done, when a pan-dimensional race of hyper-intelligent beings developed a computer called Deep Thought. Asked about the ultimate answer to Life, The Universe and Everything, this computer answered plainly: 42. The machine operators asked if the computer was certain about the answer, and it answered that it carefully checked and rechecked the results. What 42 means is still matter of speculation among scientists, while all puntids — that is to say philosophists, sages, luminaries and other professional thinking persons — are seeing a fantastic surge in their field of work. [![Deep thought computer](https://i.stack.imgur.com/pQJ3f.jpg)](https://i.stack.imgur.com/pQJ3f.jpg) On a side note : Most problems involving a superior intelligence revolves around the superior intelligence itself. But, on a communication, something is made "common". I will not delve into the intricacies of the mathematical consequences of such an Oracle, and I know that the mileage of such an endeavour, when limited to the scope of simple objective questions is much greater than its philosophical analog (where answers might not be possible to be answered in objective fashion). But still, when dealing with superior intelligences, the limitations of the questioner arise : This "oracle" was created by someone to answer something to someone, it might be utterly and completely effective at understanding the question and to answer it, but this does not mean that the person asking the question is capable of understanding any and all answers, or is able to produce any and all questions that could be solved by such an Oracle. It does not follow that being capable of asking a question and being capable of understanding it are the same and one thing. On the other hand, questions do not exist on a vacuum nor are universal. They are the consequence of a culture or a person, they are evolutive as well. This means that in order to ask something, someone must know a bunch of previous things that lead to asking a question (or else this civilization would be asking "how to eat", "how to walk" etc like a baby...). So, even if the Oracle only answers universal and time-immutable answers, the questions and the capability to produce such questions are not universal nor time-immutable. A Greek might ask philosophical and mythical questions to such an Oracle, a modern businessman might ask questions about the future of certain business and so on. So the progress of the science is not only the capability of obtaining answers but on the capability of asking questions too. This might sound frustrating, but, progress cannot be directly commanded, because it is a human activity, not an abstract process done separately from reality. This is not to say that having an Oracle that can perfectly answer objective questions would not produce progress, scientists can check the result of calculations etc. We can predict disasters and avoid it (provided that there exists true free will) and so on. We can limit ourselves, for one, to questions like : Will this engineering design work ? And prevent bridges from falling and people from getting killed. But we might not be able to predict if a bridge falling is not the best outcome possible in the long run. Because the fall of this hypothetical bridge, which might be the worst outcome for those who fall with it, might not be the worst outcome to someone else who might gain from it (as cruel as it might sound). By preventing the world war two from happening - "Will a cruel dictator be born today ? In which country ?" - we might very well prevent unforeseen consequences of such event, good and bad, that, in the example at hand, might not be well understood even today. This might lead to a perpetual loop of questions that recursively develop into more complex ones in a vain pursuit of a perfect question and answer, never reaching the moment where we are sufficiently satisfied with the answer. Or we might stop asking questions when the answer is good enough for some of us but not others, etc... We might try to question such Oracle "How to produce the most optimal outcome today, that would make everyone happy in every corner of the world, and forever", because in the end of the day this is all that philosophy and science are searching from the dawn of humanity, but this is not an objective question, because it does depend on the subjective concept of happiness, nor a short one, because this might very well be the most complex answer possible, and the whole Britannica Encyclopedia, Wikipedia, etc, and all the libraries of the world, of all time, and all pages of the internet currently, all scientists and philosophers, everything, try to answer, and failed to answer, or at least can only answer partially... And asking such a question might very well result in the same thing that the hyperintelligent pan-dimensional creatures obtained by asking the Deep Thought computer about the answer to Life, The Universe and Everything... > > 42 > > > References: Adams, D. (1985) The Hitchhiker's Guide to the Galaxy [Answer] Well, mathematics would change considerably. Asking it the [Clay Prize Problems](https://en.wikipedia.org/wiki/Millennium_Prize_Problems) would be a good start, and mathematicians would have a lot more questions after that. They would still want to prove the results, but knowing the final answer helps a lot with that. However, its effect on religion will the most important thing. This thing is essentially omniscient for factual information, and will be regarded by many people as a direct line to God, or the work of the Devil. I'd give it about three weeks before someone first seriously tries to destroy it, and maybe another two weeks before a nuke gets used. [Answer] There's a class of computational complexity that deals with Oracles. [Oracle machines](https://en.wikipedia.org/wiki/Oracle_machine) The capability to use an Oracle would make whole classes of problems, which are intractable today, easily answerable. An example is that public key cryptography, and I think cryptography in general, would no longer work. I think the biggest problem is that having access to an oracle would make the work necessary to answer difficult problems unnecessary. This would have the follow on effect that many of the tools developed to answer tough questions, and the serendipitous discoveries made along the way, would never see the light of day. There's a good chance that society wouldn't have made it past the very earliest of civilizations, technology wise. [Answer] I think that the entire Society would be centered around the Orcale. Since having access to the Oracle would give such power (knowledge is power), countries would fight to have control over it. Average people won't be able to access it, only a select few would have access to it. An "Orcale council" would be formed to protect and handle all matters related to the Oracle. This "Orcale council" would have tremendous power and rule society in a similar or even bigger way than the Catholic church in medieval Europe. Acedemic progress would be very slow and people would on average not be as smart as in our current would since they would rely on the Oracle to solve most problems. Would the Oracle be physically destructible? I think in such a society there would be for sure a group of "rebels" who would want to get rid of the Oracle. I think that if Artificial intelligene becomes advanced enough (like in the Transcendance movie) it could have a role similar to such an Oracle. [Answer] First a literature survey: Deep Thought in Adams was an Oracle giving an impossible answer. To make it worse, it was the only useful answer it gave and computation times were a tad long. In Niven/Pournelle's Footfall, illustrated tablets were left with tutorials. A morally and culturally uncivilized race became spacefaring conquerers. Various other books work with free knowledge. In Gerrold's "When Harley was One, Release 2.0", an oracle computer becomes so advanced that people rely on it utterly. In Niven's "Neutron Star", humanity receives a dictionary of advanced knowledge, each article encrypted with information knowable only once that knowledge is already obtained. In Asimov's shorts "The Last Question" and "The Last Answer" has an omniscient MultiVac computer integrated into society. - In your view, one would expect a planning commission of talkers to state long problems, like "given the climate records of the last two years of ..., and ..., what is the optimal amount of water to apply to crops of barley." etc. Perhaps the populace would rebel. No one want to hear "Yes, you asked the price of a new LusterLux refrigerator before the date your husband ordered the refrigerator." No one likes a know-it-all. [Answer] I have some issues with the "no time dependant answer" requirement. It will answer "go to the sea" to the "how to find water" question, even though some seconds after the big bang there were no seas. > > How to find water (go to the sea), not where it is. > > > To me the really time independant answer would be "in every place where one oxigen atom interacts with two hydrogen atoms by covalent bonds and the temperature is within the 0-100°C range". The same with the apple free-fall duration answer: it's supposed to use the average apple tree height and hearth current gravity, but when? Apple trees now are quite different from the neolithic ones. Not only, by answering "go to the sea" it will give only one out thousands equally valid answer. An "oracle" that doesn't understand/use the concept of time (capable to answer only time indipendent question) should be called with a different label, it will be more like a super encyclopedia rather than an oracle. Anyway, i'll try to answer... Given these two alternatives, always existed or appeared one day, and in the case you want to investigate the psychological effects, you should receive two answer. First one, always existed: people get used to it, they have evolved with it, then it won't be a stranger thing than internet for a 2005 kid. Second one, appeared one day: martial law all over the world. Seriously, all the other positive effect that some answers could give are worth nothing respect to homeland security. Information and intelligence are crucial and every strategist knows that an enemy that can anticipate your moves is virtually unbeatable. It's not relevant wether the oracle can/will answer to their military questions, as far as the military commanders know that there's an "oracle" they will try to exploit it. We know what can be answered, they don't. Every government will put their best effort to try to control the oracle (unfortunately they also doesn't know they can't). I expect huge propaganda from the government suggesting not to approach the oracle, and military effort to cage it and -since they can't- effort to destroy it -better if destroyed rather than helping the enemy-. Imagine: if it can answer "how to find water?", why can't it answer "how to find petroleum?" (or gold, or rare hearts, or whatever you need). Maybe it can give a trivial answer (we already know some places) or maybe he can give us unvaluable hints. Moreover: while "how to design a better engine?" is subjective, "how to improve the efficiency of current fossil fuel engines?" is not subjective and it's totally an answerable question with huge economic effect. And what if someone asks "who killed Kennedy?", "Why?", "did someone in the governace neglected something relevant or was even a direct player in the 9/11?" ? I guess that there are numbers of reasons why governments simply can't accept that such an oracle is available to everyone. Not to mention all the sects and groups of believers that will distort/fake predictions to boost their power, we already know that they are good at it. I suppose a global political crysis similar to the cold war, with two or more main factions, with the costant fear that something devastating could/will occur. Something that is caused by an aggressive use of the oracle by the "enemy" or something planned by the enemy and just "predicted" by the oracle. The only possible reason that can end this situation is that everyone realize that the oracle is nothing more than a window opened on an immutable future. In the past, several tales about oracles have been written, and in most of them someone asked something, the oracle answered with a "bad" answer for the asking person, the asking person tried his best to avoid the premonition but in the end the effort didn't change the final outcome. If the oracle is proven to be a non-time-paradox-generator (it foresees something that can actually be changed, therefore the premonition is falsified) every scholared person will have the personal drama to deal with the fact that "free will" isn't a thing at all. The universe has one and only one "time-path", and no one can alter it. I doubt that such an oracle will make the humanity happier: depression, violence, deceptions, struggles are most likely outcome. Paradoxically an oracle could cause a tremendous uncertain era. ]
[Question] [ Alice and Bob are lost in the wilderness with no supplies! Luckily, they're trained for this kind of thing; they decide to forage and hunt for food. About how many hours per day will they be spending on simply acquiring calories? (I assume that the type of ecosystem around them is a strong variable in this answer.) Assume a modern era, and access to the guns and ammunition. Bonus: Does the time spent change based on whether they stay in one place or are on the move? Also Bonus: If the people don't have access to hunting equipment, such as guns or ammunition, how does that affect the answer? [Answer] The classic "original affluent society" argument made by at least some anthropologists is that people in hunter-gatherer societies spend an average of about three hours a day hunting and/or gathering food (and probably another three hours in food preparation, tool-making, maintenance, etc.). See [this Wikipedia page](https://en.wikipedia.org/wiki/Original_affluent_society) and references therein. Edited to add: the anthropological studies are based on people with advanced stone-age technology (e.g., the San of the Kalahari), which means bows but not guns. So you might be able to make the time a little shorter with guns (and they would probably help make up for not having a group of hunters, who can do more searching and coordinate with each other). On the other hand, guns won't help you gather plants faster, and some studies suggest that most of the calories that hunter-gatherers consume come from the gathering (and trapping small animals); big game is prestigious, but not as important to actual survival. [Answer] > > Alice and Bob are lost in the wilderness with no supplies! > > > Oh no! > > Luckily, they're trained for this kind of thing; they decide to forage > and hunt for food. > > > Phew, what a relief! > > About how many hours per day will they be spending on simply acquiring > calories? (I assume that the type of ecosystem around them is a strong > variable in this answer.) > > > So we know the following: * Assume a modern era, and access to the guns and ammunition. * They have training. I will assume their training is general outdoorsmanship, maybe they were boy/girl scouts. + They remember their plant identification (food/not food, poison/not poison) + Fire building skills + Animal cleaning/gutting + Knots --- With all this in mind the final variable is location. Location will have a gigantic impact on survivability so here goes. * Desert. The guns help a lot less here because there is a lot less game and no fuel for fires. In reality the only way they survive being stranded in a desert is to escape the desert. They type of desert matters too...a sea of sand dunes is very different than say the Sonoran desert in the US southwest. Very high probability that they die in this scenario * Arctic. They die. Like the desert, the only winning move is to escape. * Forests and Plains. In this case they should do pretty well. Game should generally be abundant, there are plenty of plants to eat, and fuel can be found in most cases. Winters will be rough if they are out for an extended period of time...so they could still die. * Mountains. Mountains vary a lot as far as what resources are available...the mountains outside Las Vegas are barren rock... (meaning they die) the Appalachians are covered in trees and have plenty of game... (meaning they have a good shot. I think you can see that the location will likely end up defining the outcome. Keep in mind the following: * Weather (including the seasonal changes) * Game availability * Fuel availability * Shelter availability * Foraging availability These will be the primary factors, you can set them as necessary for the scenario you want. > > Bonus: Does the time spent change based on whether they stay in one > place or are on the move? > > > Probably not. Two people are not going to make a major dent in the availability of food in a wild region. They will want to vary where they forage day over day (no reason to forage an area you already picked clean) but they aren't going to be hunting herds to extinction, predators will kill and eat more than they will. > > Also Bonus: If the people don't have access to hunting equipment, such > as guns or ammunition, how does that affect the answer? > > > Again a lot depends on the scenario, but at the very least it will be harder to get started. A gun gives you a quick easy kill. Without it you have to rely on traps or something similar to get meat which is going to take more time than shooting a deer and eating it. ]
[Question] [ Consider a hard-SF (slower than light) starship. Boosting it up to speed takes enormous energy. There are good reasons to want to not take all the fuel with you, but to collect energy on the run. Current thinking is that the [Bussard ramjet](https://en.wikipedia.org/wiki/Bussard_ramjet), as popularized by the fiction of Larry Niven, would not gain energy in excess of its drag. Too bad. ☹ But the ideas of Robert L Forward are sound: use a laser to beam power from collecting points close to the sun. You can beam power to a relativistic craft under way. But what about material goods? I have contemplated the idea of launching the craft and then sending pellets of matter after it. These would supply momentum when they are caught, and they can be released again or bounced back to avoid gaining needless mass, or retained if they are valuable useful types of atoms that you need. More generally, how might you resupply a starship? And why would you send matter later rather than launching it initially? Since energy is m•v2, it’s more costly to make it catch up as opposed to including the item in the initial launch. --- Note: two Answers have focused on [Aldrin cycler](https://en.wikipedia.org/wiki/Mars_cycler), but that has zero applicability here. This craft in question will be under thrust or coasting at relativistic speeds and is interstellar; that is, between stars. [Answer] Launching matter to a spaceship is generally costlier than sending it in the ship in the first place. You have to lift not only your payload, but fuel and mahinery as well, so the less launches you do, the more efficient you tend to be. You only do multiple launches if: * Your payload is too heavy for a single launch, im which case you'll want to do some orbital assembling of parts; * Your mission involves life support for an indefinite amount of time and you can't recycle food, water and gases. The ISS is the best IRL example of a multilaunch mission. The best fictional example I can think of is the Earth to Mars mission ship from the book and movie The Martian: the mission had enough food for its planned length, but due to an emergency they had to double the span of time in space. So they sent food for the ship to catch during a flyby around Earth. Sending materials to a ship that is going away from you, except in an emergency, is a no-no. I think it is generally better to assemble everything you need in orbit, then send it away. If your mission is doing the rounds between planets, then these planets may send it ressuplies for it to catch along the way, during flybies. This is explored in Joe Hadelman's "bound" series (Marsbound, Starbound, Earthbound). Now, if the trip is too long, then the destination planet (or point in an asteroid belt, comet cloud, dyson sphere etc) may launch such packets so that they double as a way to reduce approaching speed. As for ways to catch ressuplies: * During flybies, the packet is sent in an escape trajectory that matches the trajectory of the ship as closely as possible. The goal is to have the relative speeds of the ship and the packet close to zero on their closest approach. The closest approach should also have them a few dozen meters apart, for safety. You don't want to bang them against each other if you miscalculate. To catch te packet, have it approach the ship with small thrusts. You can then use a mechanical arm or claw to catch it, or have ot dock to you, or a combination of both. Watch some ressuply missions to the ISS videos for inspiration. If these methods fail or are unavailable, send a tethered astronaut to catch it. * Incoming packets from destination worlds need to decelerate greatly prior to interception, otherwise they become unintended ballisic missiles. The goal is to have their relative speed close to zero, but they should still impart some momentum to the ship. The safe relative velocity depends on the technology involved - it can be as fast as you can do without damaging neither the packet or the ship. To catch, have the packet position itself for interception, then unfurl some really big net. Last but not least: remember that in space you don't move in straight lines. You are always orbiting something. You are orbiting a star when going from one planet to another, you orbit the galaxy when going from one star system to another. Aiming your ressuplies involves a lot of curves, and these curves change whenever you change your speed. If you are going to send multiple packets to a ship that is going from one planet to another, each packet is going to have a different trajectory. Food for thought. P.s.: if you are both a space nerd and a gaming masochist like me, I suggest you play Kerbal Space Program. You'll learn a lot about fuel costs, orbital maneuvers and how to go from one planet to another, in a rather practical way. Helps a lot in understanding how these things really work. [Answer] Launch pellets (of fuel or propellant) or pallets (of other ship's stores) using an accelerator of some sort (e.g. [coilgun](https://en.wikipedia.org/wiki/Coilgun), [railgun](https://en.wikipedia.org/wiki/Railgun), [starwisp](https://en.wikipedia.org/wiki/Starwisp), [light sail](https://en.wikipedia.org/wiki/Solar_sail)). Make sure the fuel pellets are the proper isotope mix ratio for you fusion power plant and carry enough "other stuff" for propellant. You should also charge the pellets so that your electrico-magnetic scoops can "catch" them. ## [A pre-seeded trajectory](https://en.wikipedia.org/wiki/Bussard_ramjet#Pre-seeded_trajectory) A preseeded trajectory is one in which the fuel and/or propellant for a [Bussard Ramjet](https://en.wikipedia.org/wiki/Bussard_ramjet) like craft is launched prior to spacecraft launch. The velocity and launch time for each pellet is carefully calculated so that the spacecraft which follows it encounters it under ideal conditions. The problem with a Bussard Ramjet is that the reaction cross-section of a $4 H^1 \rightarrow He^4$ reaction is very small. This means it takes a long time for the reaction to occur, which means that if the reaction occurs at all, it likely occurs after the fuel left the engine of your spacecraft. Using a fuel with a larger cross-section can greatly improve the gain possible from the reaction which might make the Bussard Ramjet possible. Your pellets should contain the proper isotope mixture of fusion fuel (e.g. tritium + deuterium). Bear in mind that you need not only consider Hydrogen isotopes. $H^1$ fuses with $B^{11}$ for a primarily aneutronic reaction ( $H^1 + B^{11} \rightarrow 3He^4$ ). In this case your pellets would just provide the $B^{11}$ portion of the fuel. You would scoop the $H^1$ component for this reaction from the interstellar medium. You could also get all of your reaction mass requirements from the interstellar medium's $H^1$. Such a system would provide a "clean burning" (aneutronic), "fast burning" (higher reaction cross-section) fusion reaction with higher thrust (extra mass provided by the interstellar medium) than a pure fusion reaction. This technique eliminates the worst problems of a Bussard Ramjet and enables an interstellar craft to make the trip without accelerating and decelerating huge masses of fuel and propellant. You must accelerate the pellets and time their launch very carefully and the spacecraft using this trajectory must not deviate from it by very much or it'll lose all benefit. Although most of the benefits possible to achieve by such a system are realize if just the fuel and propellant are supplied this way, it should also be possible to seed the trajectory with other supplies. Some mechanism from grappling those pallets of other supplies must be included and the ship using the seeded trajectory must know it is coming or normal operations of the ship would destroy the goods. This method has a few big benefit from the perspective of the crew: * All resupply shots are fired before committing to the launch of the spacecraft (your resupply is laid down before launch). * The prelaunched fuel would provide some visibility into the interstellar medium – thus alerting the trailing spacecraft of unseen hazards (e.g. brown dwarfs). ## A post-seeded trajectory A similar mechanism by which pellets of fuel and propellant and/or pallets of other stores are shot at the receding spacecraft. This technique has the added benefit of providing positive momentum transfer to the spacecraft (thus accelerating it), however, each shot must be carefully timed and calibrated to keep from hitting the spacecraft like a hypervelocity weapon instead of a gently captured resupply pallet. Once again, the biggest benefit comes from resupplying the fuel and propellant. Other ship's stores would be nice to add but not nearly as critical to overall mission mass. If something happens to your civilization after spacecraft launch but before all the necessary supplies are launched, then your crew will die. There's simply nothing they can do about it. ### Important Note It's important to note that in either system, the group launching the supplies must be very careful about the supply's trajectory. * Shots not in line with the ship's path provide no benefit. * Shots fired are the wrong velocity either fail to reach the craft or hit it so fast that they would likely destroy it. Also the spacecraft can only stray from the designated trajectory by a little or it'll fail to get the vital supplies it requires. [Answer] The answer (as far as I can see) is there is no safe way to send matter after your ship to resupply it. Any slight deviation from the planned course would mean the death of the crew, either from a collision or from starvation. To illustrate this, suppose the ship is underway for a year when the beam powering it loses 20% of its energy due to an unexpected dust cloud between the ship and the origin system, and that happens to be more than the 10% beam loss accounted for in the design. Due to this, the ship can't accelerate as planned and falls behind on its itinerary, meaning they're now outside the focus of the beam and lose more power. The crew immediately sends messages with this new information as well as their updated trajectory back to the origin planet, but it will take weeks for that signal to reach the beaming station and weeks more for the adjusted beam to reach the ship again. If the ship were self-sufficient, this would be a minor setback. Past the halfway point, it could delay the deceleration phase a bit and vector the thrust slightly to still arrive at the destination. However, if the ship needs those resupply pellets, it's dead. Those pellets were launched months ago, most likely within a few weeks after the ship itself launched. They had to be, since otherwise the pellets would have to be launched at such speeds that they need huge rockets and fuel supplies just to decelerate down to the ship's speed. The origin can do nothing to help the ship at this point. The ship may be able to signal the incoming pellets with updated course commands and for the next incoming pellet that may work, but the others will most likely not carry enough fuel to adjust course once the ship falls behind, since they have a huge correction to make. One by one, they overshoot the ship and that's it, game over. The only resupply that might work is a full-sized drone ship sent out ahead of the main ship, carrying not only supplies but a huge amount of fuel for itself. This ship would aim for a meeting point roughly halfway (or when the supplies are needed) and would get course adjustments directly from the main ship all the time, allowing it to rendezvous in a much more controlled way. After transferring the supplies and any fuel left over, it would be abandoned. Without the need to have it arrive at a particular destination (and particular velocity), the drone ship can carry much more than the main ship with the same propulsion system and parameters. For the cost of a complete second ship (and beaming station), this setup has very few advantages over just attaching the extra storage space to the main ship and detaching it halfway to save on fuel needed for deceleration. I could see it being used if two separate power beams for two ships is somehow more feasible that one double beam or if the unmanned ships could use a different propulsion system that is deadly to humans. [Answer] You have two problems with interstellar travel. 1. Getting up to speed (and slowing down) is very energy intensive and 2. it is really hard to carry everything you need because mass slows you down but mid-flight resupply is difficult because the distances are vast and the speeds are very high, making an intercept either very energy expensive or potentially explosive. Assuming your ship is moving at a good chunk of light speed I don't think you can easily arrange for physical intercept. As mentioned, shooting relativistic packets of mass at a ship is something you do to enemy ships, not your own. But you CAN have a circling packet ship, perpetually orbiting between the two systems at a high speed, that the cruise ships are timed to come close to with a matching velocity to allow for easy transfer. But of course that means the resupply ship was ALREADY loaded with stuff and was boosted to a high speed, if you could do that then why not just do it with the cruise ship (maybe it was boosted using the Orion drive that isn't compatible with human occupants)? The packet ship is robotic and can grow its own biomass to impart to passing cruise ships, or be resupplied itself when it is close to a star system when energy requirements are not as limiting. So in order to maintain this perpetually circling packet ship system you would need pre-positioned laser boosters along the interstellar route. They could be boosted in the solar system and now maintain station along the route the interstellar ships use. They may even be able to maintain position by shooting each other (if there are enough of them so they are within range of each other). So your cruise ship is laser boosted in the solar system, then as it passes each laser booster it gets another nudge. At the halfway point it starts getting laser nudges to help it slow down. This system can also keep the packet ships moving and allow for some ability to speed up/slow down to widen the intercept window between packet ship and cruise ship. This will remove a LOT of onboard fuel/reaction mass requirements for both ships, allowing the ship to carry more supplies for the crew or cargo. A really wacky solution is a series of high gravity nodes strung along your path so the ship gets the benefit of gravity slingshots along the way. Obviously this would need a crazy high level of technology to construct but once in place it could be used by relatively low tech cheap ships. The general idea is to spend a lot of time/energy creating an interstellar "hi-way" that can then be used very cheaply. The packet ships are there for mid-transit resupply of critical parts, food, maybe even fuel if they are capable of producing collecting it. All of this allows the cruise ships to get up to speed as fast as possible by needing less mass for fuel and potentially food stuffs to make the trip. Close to a solar system energy is plentiful, so the packet ships can be resupplied there, but in the cold inbetween spaces they are lifeboats of food/spare parts/fuel that has already been "brought up to speed" so transfer to a cruise ship is as effortless as possible. [Answer] My answer is simple. To resupply a starship, make it part of a fleet of starships. Most of this fleet will be tanker ships and freighters carrying the supplies your, I presume, manned starship(s) needs. Since they are all flying together they will share the same velocity, and are at relative rest with respect to each other. The empty freighters and tankers can be abandoned once their supplies are gone. Always remember to give them a little boost to the side to avoid them crashing into anything inhabited in the target system. Another way could involve your starship carrying one mouth of a wormhole. The other mouth is back in your home system. The supplies will need to be boosted up to the same velocity as your starship before they can be sent through the home system's wormhole mouth. This suggestion may break your sublight requirement, but wormholes are speculatively plausible. This is not too dissimilar to the teleportation back and forth from a relativistic spacecraft in Poul Anderson's The Enemy Stars. [Answer] Buzz Aldrin once proposed a relay system of vessels between earth and mars that, once in orbit and up to speed, would require virtually no additional fuel/force to keep there. The idea was that you sent a ship up, attached to this already moving vessel, and hitched a ride to mars or back to earth. You could build a similar relay system along a few, well known or populated routes, to create fuel depots for these vessels. Then you could use smaller, faster vessels, to deliver the goods locally to ships (as a cargo load of munitions is going to be smaller, and easier to get up to speed, than an entire warship). [Answer] Conceptually the answer is to send pellets after the starship. The ship uses some sort of momentum exchange system to capture the pellets and their momentum, i.e. the ship accelerates as it slows the pellets down. This can be done in many different ways, including having the pellet slam into a pusher plate (something like the ORION nuclear pulse drive) or using a magnetic or electrostatic field decelerate the pellet. The main issue here is that early in the flight, where the pellets are moving much faster than the starship, the energy exchange will likely vapourise the pellet and the starship will only see a cloud of plasma in the capture zone. This isn't a show stopper, since early on in the flight, the ship can consume on board supplies. As the ship continues to accelerate, the relative velocity between the ship and the incoming pellets becomes much lower, so it becomes feasible to capture the pellets from the momentum exchange system, and take the materials on board for consumption. Since the propulsion is via momentum exchange, then it really doesn't matter what the pellets are actually made of with respect to propulsion. In theory, you could send canned peas and other supplies via these means, although there are probably technical issues in ensuring the pellet launch system can handle and accelerate the pellets, ensuring the pellet isn't being vaporized inside the launcher and isn't going to be affected by the interstellar environment causing it to miss the starship. There is a great deal of literature on this idea, although AFAIK few people have considered this as a means of resupply rather than just propulsion. Starting points: <http://www.centauri-dreams.org/?p=31062> <http://www.centauri-dreams.org/?p=25626> <http://www.niac.usra.edu/files/studies/final_report/597Kare.pdf> [Answer] You could set up a net work of space stations between plaints, the space station could served as a island port do when ocean sailing on our planet. The space stations would be places to restack on trade and refuel. ]
[Question] [ This question asks for hard science. All answers to this question should be backed up by equations, empirical evidence, scientific papers, other citations, etc. Answers that do not satisfy this requirement might be removed. See [the tag description](/tags/hard-science/info) for more information. I'm looking for various factors; Atmosphere Composition, Type of Sun, etc, whatever would work. That is, of course, if this is even likely/possible. I believe that yellow is generally not an ideal color for foliage, save for attracting bees or something (Which may be myth, I'll have to research that). The environment in question should ideally be able to support human life (not necessarily related) but i can work with it if impossible. No need for paragraphs unless you want to. [Answer] The reason plant leaves are green is because they contain the pigment [Chlorophyll](http://en.wikipedia.org/wiki/Chlorophyll). Chlorophyll absorbs blue and red light while reflecting green light (thus making it appear green). The absorbed light energy is used for photosynthesis. The obvious way for a planet to have yellow foliage would be for the plants to use a different pigment for their photosynthesis that absorbs all except yellow light. I don't think you need to explain it beyond saying that the plants evolved differently. [Answer] That's easy! On Earth, plants use two types of pigments to absorb light for photosynthesis. The most well known of these is chlorophyll, which absorbs blue and red light and thus appears green. But plants also use a class of pigments called [carotenoids](https://en.wikipedia.org/wiki/Carotenoid), which absorb green, blue and violet light and thus appear red, orange, or yellow. It is these pigments that are largely responsible for the color of fall leaves on Earth, as well as the color of carrots, egg yolk, daffodils, and canaries. A class of carotenoids called Xanthophylls are especially yellow compared to other carotenoids which may be more orange. Carotenoids cannot operate completely on their own, and in Earth plants they must transfer their captured energy to chlorophyll, which then mobilizes electrons into the rest of the photosystem. One can imagine however a setup where the carotenoids transfer their captured solar energy into a molecule that replicates chlorophyll's ability to mobilize electrons but cannot absorb light by itself, or at least is sufficiently shielded by the carotenoids that its color (if any) doesn't show up. Essentially, you want a photosystem where carotenoids are the primary light-gathering molecules and the separate electron-mobilizing molecules are either incapable of absorbing light themselves (which is more likely evolutionarily, else the carotenoids would not necessary) or tucked away inside dense packets of carotenoids (which makes sense from a structural point of view). As to what these electron-moving molecules could be, I don't know. Chlorophyll does this using [a large aromatic ring with a central metal atom](https://en.wikipedia.org/wiki/Chlorin), but since these types of compounds strongly absorb light they might not be ideal. So, what might lead plants to rely heavily on carotenoids and not on chlorophyll? The most obvious solution is to have a planet where the wavelengths of light available at the planet's surface are strongest in the range that carotenoids can absorb but chlorophyll can't. So the available light at the surface of your planet should be: * Very weak in the red portion of the spectrum. * Strong in the green portion of the spectrum. * Very strong in the violet portion of the spectrum. Violet is your best bet for the strongest wavelengths because [a plant that absorbs lots of violet light will appear more yellow](https://en.wikipedia.org/wiki/Complementary_colors). If we focused instead on the green part of the spectrum (where chlorophyll is weakest), the plant would look more red. The increased violet light might make your sky appear more indigo than Earth's pale blue, but atmospheric color is going to depend hugely on what gasses are present and in what concentrations. Oxygen and nitrogen are pretty good at scattering violet light, but our sun doesn't emit enough of it for our sky to appear more violet. So you can probably achieve this effect simply by making the star emit a little more violet light. I'm treading on the limits of what I know here, but you can probably do this by either by changing it mass to be heavier or just changing its chemical composition (its spectral signature). If more violet light is being scattered by the atmosphere, the sun itself might appear a little more orange than it does on Earth. Regardless, sunlight would still be white light just like it is on Earth, and things on the surface wouldn't be colored differently. [Answer] 1. Find a yellow plant on earth. (Heuchera and gold Hosta are two examples.) 2. Explain that evolutionarily, that was the earliest successful plant, and most/all other plants are a descendent of it. [Answer] Your planet could be really low on iron. There is a tree condition called [chlorosis](https://en.wikipedia.org/wiki/Chlorosis) that is caused by low iron in the soil, and leads to light green/yellow leaves. It could also be that the [PH in the soil is to high](http://www.johnson.ksu.edu/p.aspx?tabid=484), which keeps trees from absorbing the iron. Or just go with Tom Andersons idea. ]
[Question] [ I was reading up a little while ago about [Janus](https://en.wikipedia.org/wiki/Janus_(moon)) and [Epimetheus](https://en.wikipedia.org/wiki/Epimetheus_(moon)) and how every few years they trade orbits. The [mechanics is interesting](http://abyss.uoregon.edu/~js/ast121/lectures/epimetheus_and_janus.html) but I'm not going into them here. What I was wondering is first could planets going around a sun have a similar relationship and how might that affect any life on them? Would it change the seasons much? Janus and Epimtheus are pretty small and the orbits are about 50K apart which wouldn't do much for seasons, but planets I would expect to be a bit bigger because of scaling, wouldn't want the planets bumping into each other, which also makes me wonder if it's possible. How far apart would the orbits likely be to have a similar effect if both were Earth sized? [Answer] Before we get into seasons, life, etc., we have to address the question of whether or not such a configuration could exist. At first glance, I see no reason why two planets couldn't orbit a star in the same way Janus and Epimetheus orbit Saturn. It could be a bit tricky if the planets are gas giants, because they would have a strong gravitational influence on one another, but if they were terrestrial planets, they would be fine. Such a configuration could exist. The more important question here is whether or not such a configuration could form in the first place. From [the excellent site you mentioned](http://abyss.uoregon.edu/~js/ast121/lectures/epimetheus_and_janus.html), > > Janus and Epimetheus may have formed from a disruption of a single parent to form co-orbital satellites. If this is the case, the disruption must have happened early in the history of the satellite system. > > > [Wikipedia](https://en.wikipedia.org/wiki/Epimetheus_(moon)#Physical_characteristics), interestingly enough, says the exact same thing: > > Janus and Epimetheus may have formed from a disruption of a single parent to form co-orbital satellites, but if this is the case the disruption must have happened early in the history of the satellite system. > > > Let's consider how these planets could have formed: 1. Collision of two protoplanets. This is the idea behind the [Giant Impact Hypothesis](https://en.wikipedia.org/wiki/Giant_impact_hypothesis), which says that a [protoplanet](https://en.wikipedia.org/wiki/Protoplanet) collided with Earth early in the history of the solar system; the Moon was formed from the resulting debris. The problem is, if this happened between two Earth-sized protoplanets, the result might not be two planets - it could be a planet and a large moon, and some debris. 2. The Roche limit and tidal forces. There are a number of questions here that investigate what would happen if certain things passed inside the [Roche limit](https://en.wikipedia.org/wiki/Roche_limit) of another body. A body of more than two solar masses could definitely venture inside the Sun's Roche limit, and be torn apart. It's possible that the material would coalesce into two planets; not necessarily likely, but possible. Both these scenarios could very well result in two co-orbital planets, though perhaps not in the desired arrangement. We'll know more about these kind of ideas if we ever learn about the true source of Janus and Epimetheus. For now, we can say that such a configuration con very well have formed, either from one of these two scenarios or something completely different. So, to answer > > first could planets going around a sun have a similar relationship > > > Yes. --- Next up, we turn to life. It seems clear that the two bodies would be in some way related to one another, and would most likely be made up of the same materials. In fact, in lieu of another impact on one, the two might develop nearly identically, for a while. At least for a few hundred million years. I see no reason why life couldn't exist on one or both of these worlds. Remember, they're only near each other for a short amount of time, so they don't have a huge influence on each other - most of the time. Going back to your site, > > This exchange happens about once every four years. > > > Maybe this period is different for our planets, but still, you get the idea. The really interesting thing here is that, because conditions might be really similar on both planets, we could see life develop similarly on both. Sure, there are a lot of factors that influence life's development, so we shouldn't expect the same creatures to develop on both, but life would likely form from the same compounds, and have the same evolutionary history, for a few hundred million years. > > how might that affect any life on them? > > > Life could form, and it might be similar on both. --- Finally, we go to seasons. Janus and Epimetheus are both in [synchronous rotation](https://en.wikipedia.org/wiki/Tidal_locking) with Saturn, so only one side faces Saturn at a time. This means that they are tidally locked with Saturn. I wrote [a brief answer](https://worldbuilding.stackexchange.com/questions/3860/seasons-on-a-planet-thats-tidally-locked-with-the-smaller-star-in-a-dual-star-s) on seasons on tidally locked planets, but the setup was different, and it may not be relevant here because tidal locking is not necessarily the outcome. If there isn't tidal locking, there should be normal seasons if the axis of each planet is inclined with respect to the star. If it isn't, there won't be any seasons, unless the orbit is somehow highly elliptical (See [this question](https://astronomy.stackexchange.com/questions/6617/would-an-exoplanet-without-axial-tilt-have-no-seasons/6622) and [this question](https://astronomy.stackexchange.com/questions/6635/is-earths-orbital-eccentricity-enough-to-cause-even-minor-seasons-without-axia)). There also won't be a huge amount of interaction between the two planets, so any axial effects should be negligible. > > Would it change the seasons much? > > > No. [Answer] Hope it's OK to bump an old question, but I saw another question on horseshoe orbits and I searched for related questions and came across this one. Some small notes to add to the answer above. 1) Scaling up from Janus and Epimethius to planets around a star doesn't really work. The ratio of Earth's mass to the sun is 1 to about 330,000. The ratio of Janus, the heavier of the two horseshoe moons, to Saturn is about 1 in 300 million. 900 times more mass variation. That doesn't prove that two planets couldn't orbit in a horseshoe coorbital around a star, but it might not be stable. Here's an [answered question on Astronomy](https://astronomy.stackexchange.com/questions/24675/is-it-possible-for-two-stars-to-be-in-a-horseshoe-orbit-around-a-much-larger-sta) with some research quoted. As the two bodies both acquire mass the stability and longevity of the horseshoe drops rapidly. If one of the two objects is small, then you can have a stable system for some time, so long as the larger one is less than 1/200th the mass of the central body. Earth to the Sun is actually 3,200 times the mass ratio as the smaller moon, Epimethius to Saturn. I don't know if 3,200 times greater mass ratio destabilizes the system. It might still be in the range of possible, but the math gets pretty difficult. 2) Horseshoe orbits happen very slowly. Janus and Epimethius swap every 4 years, but they are very close to Saturn and as a result, they orbit very quickly. Each orbits Saturn in less than a day. 4 years is 2,100 orbits for those two moons. Earth's horseshoe Moon, [3753 Cruithne](https://en.wikipedia.org/wiki/3753_Cruithne) is in a horseshoe pattern around earth with a 770 year period. The horseshoe period is determined by how far the two objects swap and the relative orbital periods at the different distances. Janus and Epimethius swap about 100 km between them. They maintain about a 50 km variation in their semi-major axis, which corresponds to about 2,100 orbits for the closer one to catch up to the farther one. The swapping takes about 200 orbits around Saturn. Two theoretical Earths in a horseshoe orbit with each other would have a period of hundreds or thousands of years. The period is also inversely proportional to how far they move. Earth and 3753 Cruithne swap about 1/2 million km when they swap. We can use that as a guideline because the gravitational acceleration remains mostly consistent as the 2nd body increases in mass. The difficulty with using that as an estimate is 3753's highly elliptical orbit, so the gravitational tugging is diluted. With more circular orbits, the exchange should happen faster, or it should be smaller. The math behind the 3 body problem is very complicated and above my paygrade. I could do some ugly but better estimates, but it would be even longer. But a ballpark 1% variation in solar energy would be enough to trigger a small change on each planet, perhaps triggering little ice ages or medieval warm periods, but if you push the 1% a little higher, the period gets shorter, so I don't think there's any way to get a bigger effect than that. A few hundred years of frost, and a few hundred years of warmth. A final point. The planets never actually get "close" to each other. The gravitational exchange happens at a distance. Janus and Epimethius [never get closer than about 10,000 km](https://en.wikipedia.org/wiki/Janus_(moon)#Orbit) in order to swap 100 km in orbital distance. 3753 Cruithne doesn't get closer than about 12.5 million km from Earth in order to swap about 0.5 million km in orbital distance. One way to think about how close they get is by angles of arc. 10,000 km is about 1/15th Janus semi major axis, which is roughly equivalent to 1/15th of a radian on the circular orbit or about 4 degrees. For Earth and 3753 Cruithne, 12.5 million km is about 1/12th Earth's distance from the sun, or about 5 degrees of arc in their respective orbits. Two data points doesn't establish a pattern, but if the two planets get too close in order to exchange orbital energy, the system likely destabilizes. It's much more consistent if they amount the move is a small faction of how close they need to get. 1/200 for Janus/Epimethius or 1/25 for Earth/Cruithne (not Earth/Cruithne is diluted due to Cruithne's eliptical orbit, two circular orbits and that fraction gets smaller). Similarly, if the angle of arc grows too large, say above 15 degrees or so, then system might have a greater gravitational attraction to enter into trojan orbits which are more stable and more common than horseshoe orbits. There's a sweet spot in there for degrees of arc that the two objects can get to each other before moving apart again. I'd guess somewhere between 1.5-2-3 degrees of arc on the low side, to maybe 6-8 degrees on the high side - if I was to make a bad guess and as the objects get more massive, that window shrinks. Point of all of this, the two planets in a horseshoe orbit would never appear like moons to each other. They'd never get anywhere near that close because if they did, such a system would swap too much orbital energy and be irregular, not repeating. They would, as they approach, perhaps be a magnitude brighter than Venus, and by far the most impressive dot in the sky, but they'd remain dots to each other. HDE is ofcourse right, that setting up a system of two large bodies with less than 1% variation in their semi major axis would be unusual. A system like this would certainly be rare and might even be impossible for long periods of time. But to address the seasons question, the seasons wouldn't change much but they might change some. The climate might change, similar to a little ice age or Medieval warm period with each swap. That's around the biggest change you might expect with a system like this because the change in distance from the sun would be quite small. It wouldn't happen all at once, it would take many years to kick in, aided by natural feedback mechanisms on the planet. Hope that wasn't too long or wordy. ]
[Question] [ The present day atmosphere is roughly 21% oxygen. Historically high-levels might have been as much as 35%, over 66% higher. This made the carboniferous a period of giant bugs and constant devastating wild-fires. How would this affect a civilization trying to develop? In particular, how much easier would it be to construct a forge/smelter for processing iron or steel? How much hotter will a forge/smelter burn if it's being fed with 66% more oxygen? Cast Iron melts at around 2,100F (1150C). With a very naive calculation one would think a forge able to melt Cast-Iron on Earth today might burn at over 3000F, enough to melt low-carbon steel. (Additional Edit: I had in mind a bloomery, similar to ones made over 2,000 years ago, which involve stacks of charcoal, as well as compressed air provided by a trompe. These forges burned hot in our 21% atmosphere, hot enough so that large ones could melt pig iron. What would happen if you used a similar one in 35%?) [Answer] One of the common misconceptions is that high concentrations of oxygen lead to hotter fires by default; it's actually fairer to say that high concentrations of oxygen lead to faster fires by default, but that in turn can create a hotter fire in certain circumstances. Take a look at [this oxygen enriched fire safety article](http://www.airproducts.com/~/media/Files/PDF/company/safetygram-33.pdf) which talks about this in great detail and you will note that on page 5 there is an example of them literally detonating a cotton shirt in an oxygen rich environment. Sure, in a case where you trap the oxygen and have lots of fuel ready to burn in an enclosed space, your fire will be hotter because so much more of the heat energy is released by the chemical reaction in fire all at once. And in this vein, the important point is this: Fire, even in an oxygen rich environment, is still a triad of conditions; 1) Heat 2) Fuel 3) Oxygen You need all three to create fire, and the heat of the fire will depend on the density of all these three components in proximity. The Carboniferous period ensured that the availability of the Oxygen is not the weak point in the triad, but you still need heat and fuel. I'd imagine that if you put a lot of dense wood, tightly packed, together in a single small area and set it alight, you could gather temperatures close to what you're describing for a short period, but like all things there is only so much fuel to be burned in this scenario and in achieving higher temperatures for your fire, you're burning your fuel faster. I suspect you'd be able to do it, but you'd need a lot of fuel, and people loading more wood onto your fire pretty much constantly. Remember, energy is measurable, and we know how much heat energy can be released from wood through fire. If your fire is hotter, made possible by increased concentrations of oxygen, it's only because your wood is burning faster, meaning that a wood fire of (say) double the heat intensity will still need double the amount of fuel to maintain for the same period of time. [Answer] Just as a back of the envelope calculation: for cellulose, $\text{C}\_6\text{H}\_{10}\text{O}\_5+6\text{O}\_2\rightarrow6\text{CO}\_2+5\text{H}\_2\text{O}$, $\Delta H=-2828\,\text{kJ}/\text{mol}$. The molar specific heat for $\text{CO}\_2$ is $C\_p=36.94\,\text{J}/\text{mol}$, for $\text{H}\_2\text{O}$ is $C\_p=37.47\,\text{J}/\text{mol}$, and for $\text{N}\_2$ is $C\_p=29.12\,\text{J}/\text{mol}$. Assuming air is mole fraction $f$ of $\text{O}\_2$ and $1-f$ of $\text{N}\_2$ the molar heat capacity of the products of combustion counting $\text{N}\_2$ is $$6\times36.94+5\times37.47+6\frac{(1-f)}f\times29.12=408.99+\frac{(1-f)}f\times174.72\,\text{J}/\text{mol}$$ So dividing the $2828\times10^3\,\text{J}/\text{mol}$ by this number we get $\Delta T=2652°\text{C}$ at $f=0.21$ vs. $3650°\text{C}$ at $f=0.35$. Of course you're not going to get perfect combustion and heat capacities increase with temperature, but I think that the necessity of having to heat up extra $\text{N}\_2$ among the products of combustion will reduce the fire temperature in any case on going from an $\text{O}\_2$-rich to an $\text{O}\_2$-lean atmosphere. ]
[Question] [ As far as I know stars are going supernova as a natural process. Can aliens trigger it artificially? If this is possible then: 1. How can I do this (what minimum technology and civilization development is needed; what tools or devices are needed)? 2. How long this process will take (from "pushing button" till star exploding)? My [planet must be destroyed as an effect of that](https://worldbuilding.stackexchange.com/q/3615/36) (destroying it is the only reason for triggering of this event) so, if it is "reasonable long period" how can I prevent planet's inhabitants from: * stopping this process (if this is possible) or * protecting themselves from these effects (this [may be possible](https://worldbuilding.stackexchange.com/q/47463/36)). [Answer] According to [the current models](https://en.wikipedia.org/wiki/Supernova#Current_models), the possible reasons for a supernova are thermal runaway or core collapse. Thermal runaway is probably your best bet, and happens when the core of the star gets hot enough to start fusing carbon. This usually happens when a white dwarf steals enough mass from a companion. Core collapse happens when nuclear fusion becomes unable to sustain the core against its own gravity. This usually happens in very large stars when the core gets enough iron to stop fusion. Stars cannot fuse anything heavier than iron, and so once you get to that phase fusion stops. This allows the core to collapse and either become a neutron star or a black hole, depending on the starting mass and composition. The process of collapsing also causes runaway fusion resulting in a supernova. So how can the aliens do either of these things artificially? The easy way is to get a large amount of energy into the center of the star which would trigger runaway fusion. Peter F Hamilton used a [Nova Bomb](https://www.scienceforums.net/topic/113220-the-physics-of-peter-f-hamiltons-nova-bombs/) which used some kind of quantum fission effects to turn a jovian sized chunk of the star into energy. Another way would be to deposit a quantity of anti-matter into the star's heart which would have the same effect. Delivery would be difficult, but not impossible. Both of these would require a level of technology way above what we have, but are not out of the realm of possibility. As to Core collapse, this is a little harder, having to introduce a lot of iron into the star. The amount needed is called the [Chandrasekhar mass](https://en.wikipedia.org/wiki/Chandrasekhar_limit), and is a lot of iron. If you could find an [iron star](https://en.wikipedia.org/wiki/Iron_star) and wormhole it into the core of an existing star that could do it, but the universe is far to young to have any iron stars yet. You could transmute some of the stars mass into iron, but the energy needed would probably cause runaway fusion long before you could get the core to collapse. The Charles Stross book Iron Sunrise used a temporal bomb/effect on a star to cause the core to age thousands of times faster than the rest of the star, causing it to fuse into iron very quickly, which collapsed the core and set off a nova. [Answer] This is the kind of problem for which the solution is exceedingly simply and straightfoward in theory, but too costly and impractical in practice. For a supernova to happen, you need a dying star to have at around [60 to 130 solar masses](https://en.wikipedia.org/wiki/Supernova#Core_collapse). The simple, straightfoward solution is then bringing a dying star that is around 60-130 solar masses closer to your solar system. The expensive part is bringing it into the system. It is possible - [see this excellent answer from Thucydides](https://worldbuilding.stackexchange.com/a/47448/21222) on how to change the Moon's orbit, and scale it up to a very massive star instead of our Moon. You will probably need to juggle stars around - instead of moving a moon around, you will be moving stars across systems, maybe across galaxies. Your star system won't be the only one that will never be the same. [A safe distance from a supernova is around 50 to 100 light years.](http://earthsky.org/astronomy-essentials/supernove-distance) So you can park it, say, 40 light years away from your target. Now, speed things up! Remember the process for bringing the star closer yout target? Bring a black hole too - one that is more massive than the star. Have the dying star orbit the black hole - the star will be in a timeframe where time passes faster than what a planet in a solar system like ours would experience. This will make it go boom faster. Wait a few millenia, and enjoy as your enemies are fried to death :D As for how the marks can survive or protect themselves from this... Supernovae are just too energetic. They wouldn't survive by hiding on the other side of the planet. Their best protection is stopping you from doing what you are doing. [Answer] Remember When You Blew Up a Sun? <https://tvtropes.org/pmwiki/pmwiki.php/Main/RememberWhenYouBlewUpASun> > > Jacob: Come on, Sam. It can't be any harder than blowing up a sun. > > > Sam: You know, you blow up one sun and suddenly everyone expects you > to walk on water. (alien control panel lights up) > > > Sam: Next step, parting the Red Sea! > > > — Stargate SG-1, "Reckoning, Part 2" > > > In this episode of the TV show Stargate SG1, they refer to a prior episode where Carter (Samantha Carter) destroyed an alien armada threatening earth by causing a supernova. The Stargates in the show are devices which produce a wormhole through space to a different such device at some other place in the universe, allowing persons, matter and energy to move through. In an earlier episode they determined (the hard way) that one stargate was on a planet in the process of falling into a black hole. Opening a channel to that stargate proved very dangerous. In the "blew up a sun" episode, Sam Carter (aboard an alien vessel) dials the coordinates of the black hole stargate and then launches their own stargate into the sun. Then they clear the area. Stargates can evidently withstand the temperatures of a star. The black hole on the other side of the opened wormhole pulls away enough matter from the star to disrupt its fusion. This causes gravitational collapse and consequent supernova. This is a fine SF way to cause a supernova: use your space transiting SF tech to suck away mass. How long it takes will depend on how much mass a given star must lose before its fusion cannot oppose its gravitational pull, and how quickly your SF space transiting tech can move stellar mass to some distant gravitationally avid object. In the show it took a couple of minutes, but they had to wrap things up fast. [Answer] One way a supernova happens is running out of nuclear fuel, I see no way how this could be done artificially. The other way is if it is a binary system and one is a white dwarf you could force the other star to eject mass into the white dwarf. Or if you are orbiting a white dwarf you could ship in huge amounts of matter and eject that into the star. ]
[Question] [ Is there a way to design a river system in an O'Neill/McKendree-style cylindrical habitat to passively feed into itself in an endless loop, from one end of the habitat to the other and back again? Reworded: is the [Coriolis effect](https://en.wikipedia.org/wiki/Coriolis_force) or other innate properties of a spinning habitat up to the task of circulating water, river-like, the length and breadth of the structure? (If so, I would expect uphill flow to be possible in antispinward channels.) [![Stylized interior of a McKendree-style habitat](https://i.stack.imgur.com/vqBxLm.jpg)](https://i.stack.imgur.com/vqBxL.jpg) The river must flow as a river does – making water sit still isn't difficult to figure out – without use of pumps. Assume the primary courses/channels are artificially constructed and maintained, which allows for forking and variable depth/width/etc. The system can use underground channels (vertical, lateral, angled) to take advantage of differences in pressure between the inner surface and hull. Dams, reservoirs, lakes, etc, can all play a role. [Answer] I believe that there should be some way of achieving this although it might require multiple cylinders for it to work. Consider an arrangement of 4 rotating cylinders such as this: [![enter image description here](https://i.stack.imgur.com/t1cfY.png)](https://i.stack.imgur.com/t1cfY.png) The water in the rotating cylinder at the top of the diagram would flow downhill (from left to right). When it reaches the lowest point it is collected in the reservoir on the far right projecting “below” the first cylinder. Once per revolution the bottom of the reservoir opens when it is directly over the centre of the adjacent cylinder centrifugal forces force the water into the adjacent cylinder and the process is repeated. Although it may appear that I am suggesting perpetual motion, I am not. The energy required would ultimately come from slowing of rotation of the cylinders by a small amount. There are many objections to this design on practical grounds such as transferring the water through a vacuum. However the basic principle stands and such issues could be greatly minimised by careful design improving on my basic proof of concept idea. edit mark 2 [![enter image description here](https://i.stack.imgur.com/ccRIN.png)](https://i.stack.imgur.com/ccRIN.png) edit mark 3 counter rotating end torus forces water outwards and back to the central axis of the main cylinder by cetrifugal force. [![enter image description here](https://i.stack.imgur.com/SsMMQ.png)](https://i.stack.imgur.com/SsMMQ.png) [Answer] Water flow dissipates energy. On Earth that energy is supplied by gravitational field and from the sun. If your system doesn't have a supply of energy to the flow, the water is going, sooner or later, to stand still. The centrifugal force will only help distributing the water on the walls of the cylinder. To move it up some hill you cannot escape using some pumping mechanism. [Answer] The Coriolis acceleration is $$\mathbf{a}\_c=-2\mathbf{\Omega}\times\mathbf{v}$$ where $\mathbf{\Omega}$ is the angular velocity vector of the cylinder and $\mathbf{v}$ is the velocity vector of the river. $\mathbf{\Omega}$ is along the axis of rotation of the cylinder. Let's look at two cases: 1. $\mathbf{v}$ is parallel to $\mathbf{\Omega}$. Here, $\mathbf{a}\_c=\mathbf{0}$, because the cross product of two parallel vectors is zero. 2. $\mathbf{v}$ is tangent to the circular cross-section of the cylinder. Here, $\mathbf{a}\_c$ is pointed inwards, to the central axis. From the point of view of a person on the ground, this is a vertical force, not a horizontal force. On the inside of the cylinder - not the caps - the Coriolis force won't have any "horizontal" effects on the flow of rivers. Maybe you're not convinced. Consider the Coriolis acceleration on Earth's equator. There's no horizontal component to the acceleration, right? Well, on the cylinder, the edge of every cross-section is like the equator, at the same distance from the axis. [Answer] If we imagine a river that circles the habitat around the axis of rotation I think such a river will have an apparent flow from the perspective of an observer standing on the banks. I will explain my reasoning below. The first thing we need to address is L.Dutch’s criticism that there must be an energy source to generate flow. As Molot pointed out in the comments that energy can come from the rotational spin of the habitat. In fact, any nonrigid body will lose speed due to friction and turbulence in the gases and liquids inside it. What this means is that the atmosphere and hydrosphere inside the habitat will slow in relation to the rigid surface of the cylinder. Friction between the rigid and nonrigid will speed up the water and air and slow down the ring. This is a constant process that will gradually slow the ring. This means that at equilibrium between the two opposing frictional forces we can expect that on average the nonrigid components of the system will have a slightly longer rotational period than the rigid components. That is to say, the air and water will tend to have an anti-spinward velocity from an observer standing on the inner surface of the ring. This effect is minor but I think it will be exacerbated by two additional forces. The first is a part of the Coriolis effect. If we look at HDE226868’s answer we see that the Coriolis effect on our river is a vertical one, rather than a horizontal one, but because our river has a vertical this will still effect the flow of the river. On Earth, a train going around the equator to the East (spinwards) is lighter than a train going West (anti-spinwards). This is due to the vertical component of the Coriolis effect called the Eötvös effect. Essentially, the centrifugal force of the Earth’s spin acts against the pull of gravity and tries to fling us into space. Spinning faster increases this force and makes us even lighter while spinning more slowly reduces this force and makes us heavier. On Earth, this effect is slight and only important for rocket launches and long-range artillery bombardment, but on our relatively small spinning habitat, the magnitude would be much larger. Now how does this apply to our river? Because our spinning cylinder is “inside-out” compared to the Earth the forces are reversed. Water moving in a spinward direction faster than the water around it will be effectively heavier and water moving in an anti-spinward fashion will be lighter. This means that spinward currents will sink and anti-spinward currents will rise. This will result in the surface of the river having a larger anti-spinward velocity than the bottom of the river. In this way, the Eötvös effect will exacerbate the perceived flow of the river from an observer on the surface. The second effect is that of wind. I anticipate that the wind at the surface of the habitat will be primarily anti-spinward and that this, as a result, will act to pull the river further anti-spinward. My reasoning is as follows. All of the aforementioned effects are acting on the air of the habitat just as they were the water. This means the air will also have a net anti-spinward velocity relative to the ring, with higher altitudes having larger anti-spinward velocities. Additionally, the heat cycle will play a role here. Hot air on the surface of the ring heated by the artificial sun will rise due to decreased density just as it does on Earth. However, here the Coriolis effect will deflect the rising air spinwards. In turn, the cool air from above that sinks to take the warm air’s place will be moving anti-spinward. In this way, convection currents on the rotating habitat will create strong anti-spinward winds on the surface of the ring. The surface of any water will, therefore, be pushed in an anti-spinward direction by the wind. These forces, the various frictions and Coriolis effects, will act together to cause the surface of a circular river to flow anti-spinward in an endless cycle powered by the rotational kinetic energy of the system which will be gradually lost to heat. [Answer] I don't think it'll work without active control. Even then, your plan would borrow energy from the rotation which would be bad in the long run. As has been pointed out, rivers require weather. You have to evaporate water from the low lying pools and release it as rain on higher ground. Theoretically you could taper the inside of the cylinder near the ends (making the ends of the cylinder "high ground"). Then, with differential heating, make the center of the cylinder warmer and try to start a air circulation patter running from the center to each end along the ground (with return through the axis). This would cause the air to release the moisture that it picked up at the center. This will form a cycle that will allow the flowing of rivers. The problem that I see with that is that it relies on the rising air releasing its water. In the rotating cylinder, the gravity decreases dramatically as you approach the center. The lower gravity would allow the air to hold larger droplets of water before they are heavy enough to fall. Would this be enough to prevent weather in the cylinder? I don't know. If that is the case, this might still work if you have water condensers on the ends (or, maybe, on a spine running through the axis) and get your water out of the air that way. [Answer] Only if your willing to vary the rotational speed of the entire station. Objective : a passively powered lazy river inside an [O'Neill cylinder](https://en.wikipedia.org/wiki/O%27Neill_cylinder). That it be an endless loop is actually a requirement. It will flow backwards until it's done contending with the [first law of motion](https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion). The first part of which makes the water remain where it is. The second part eventually accelerates it due to the friction of the riverbed, at which point it no longer 'flows'. Once that happens you have to slow the station down and let it reset, and then you can repeat the process. Or, enjoy it while it lasts. After a while once the station is up to speed, without pumps or a water cycle, the water will stagnate. [Answer] Yes and no First the hard core facts: What makes a river work on earth is gravity and differences in elevation ie ultimately a difference in potential energy. In this system it is not possible per se to use difference in elevation as a driver of the river because it must wrap around (because water cant travel uphill at any point in the stream). Fun Natural facts of the Water Cycle: Mountains are a major contributor to the formation of rivers as water sources. When water vaporizes in the water cycle into the atmosphere it's looking for ways to cool and condense and return. Because of the elevation of mountains they can act as a condensation point collecting the water vapor as rain, mist, dew, etc. This water then flows down the mountain and feeds rivers. How to make this work: Strategically place mountains near your river and build collection channels so that they feed their water into the main river. Have all of the streams pointed in the same direction (like right of the mountain into the river). Because all of the rivers tributaries are flowing water in from the same direction this will result in a current flowing in one direction. The river can then be wrapped back into itself. One important detail: Water must be consumed from the river or else it would just pool. But this could be used to water fields, civilization, or intentionally be vaporized to further fuel the cycle. But this is essentially a river, its basically the same concept as a lazy river at a water park. A heck I just drew you a picture instead, deal with its quality: [![enter image description here](https://i.stack.imgur.com/U5xI2.jpg)](https://i.stack.imgur.com/U5xI2.jpg) I misspelled "feed" with "feen" oops. regardless you are using the energy of the water run off from the mountains to drive the current of the river. ]
[Question] [ In my world, instead of mammals, birds have become the dominant order. Similar to how Quadrabirds replaced the grazing mammals; Aquabirds will take up the niche cetaceans occupy. My goal is that the Aquabird would be similar to animals like the orca or the narwhal, but I am stuck on the evolutionary process of such an animal. Considering that there are aquatic mammals, could aquatic birds exist? If so, what would they look like and how would they evolve? A list of all Planet of the Aves questions can be found [here](http://meta.worldbuilding.stackexchange.com/questions/3939/planet-of-the-aves-series/3940#3940) [Answer] Well, this probably starts with [diving birds](https://en.wikipedia.org/wiki/Diving_bird) that gave up flying. We have example species for that already, such as penguins. To stay in water for long periods, they're going to need to grow larger so that they can carry a thick layer of insulation, such as blubber: all the example aquatic mammals we have are fairly large for just this reason. Being small and un-insulated in the sea is a great way for a warm-blooded creature to die of cold. That gets you to creatures that fill similar niches to seals and walruses, who come out of the sea to give birth, and your aquabirds will need to do that to lay and incubate their eggs. The eggs need to be incubated, or the embryos will die of cold if they have a bird's metabolism. Turtles run much cooler. Having eggs that could float in the sea probably isn't viable, on the grounds of heat loss, and of inability to get enough oxygen through an eggshell. The shell has close to the minimum surface area for its volume, which is exactly what you don't want for a gill system or equivalent. If you want whale-sized aquabirds, it gets harder. They're too big to come out of the water to lay eggs. I can see two ways to do it: 1. Give birth to live young, which need to be fairly sizable to carry insulation. But that's boring, and un-avian. 2. Have major sexual dimorphism. The males grow to the size of whales. The females are smaller, at least for the breeding phase of their lives. They come on land to lay and incubate eggs. They're fed by the males, somewhat like the way real birds feed chicks: the male gathers and pre-digests food, and the female doesn't have to hunt, just go out to sea a little and collect food from him. It's a bit of a stretch, but it looks sort of right. [Answer] The problem with aquatic birds is the eggs. Either they come to land to lay and incubate their eggs, in which case they're basically penguins, or they give birth to live young, in which case they're somewhat unavian. ]
[Question] [ Let's use the sea turtle and the terrapin as an example, need I say more? I used terrapin because like the mermaid which is half fish and half girl so a terrapin would serve as an excellent example. Generally speaking, species usually grow much bigger in seawater conditions. However rules are meant to be broken but never for the mermaids, does it not? [Answer] Evolution supports increasing size if it confers some sort of advantage to the large members of the species. Sauropod dinosaurs became larger and longer to effectively crop leaves from taller and taller trees, for example. In the oceanic waters, Mermaids, like other sea creatures, would probably evolve into larger sizes to change the surface to volume ratio, conserving heat and minimizing energy expenditures. Larger Mermaids would also have proportionally larger flukes, allowing them to swim farther and faster to track and capture prey. And of course, since the oceanic environment already supports some pretty large and dangerous predators, like seagoing crocodiles, great white sharks, giant squid and pods of Orcas, being larger provides more protection, or at least a greater ability to fight against a predatory beast in the oceans. [Answer] There is nothing to prevent differing mermaid groups being differing sizes, while still being "human-size". We have groups of humans of varying sizes, e.g. African Pygmy tribes and Nordic countries with average heights approaching 2m tall. "Human-size" is an enormously wide range. It would be easily possible to have porpoise-sized lake mermaids and dolphin-sized sea-mermaids. Typically, the size of a water creature will relate to the sizeof the body of water it is living in. Compare the size of the Great Lakes of North America to a dribbling brook. [Answer] Really this choice is down to you. It's certainly true that many sea-water creatures are larger than their fresh-water counterparts but that does not have to hold true for mermaids. If you want to have differently sized mermaids then that's fine, just keep the populations separate and let drift and selection do its thing. Generally ocean mermaids would grow larger over time and fresh water ones smaller. On the other hand if you want them to all be similar sizes then just have regular mixing and inter-breeding between the two groups and the selection pressures will be reduced enough to keep the two groups fairly homogeneous. [Answer] Are your mermaids civilized? While you had a lot of good answers, I'd like to point out one thing that counteract natural selection: civilization. Just look at humans. Sure, there is a lot of diversity among us, with Asians being on average shorter, Africans on average taller. There is difference in build, skin color, bone structure (roughly), etc... Those difference came from different environments but overall, if you were from another species, there isn't as much as a difference between two humans than between a sea-turtle and a terrapin. (For starter, they doesn't have the same limbs) So you could realistically keep human-sized sea mermaids and river-dwelling undines if they could adapt to the challenges of their environment. A few examples regarding Thucyclides answer: > > In the oceanic waters, Mermaids, like other sea creatures, would probably evolve into larger sizes to change the surface to volume ratio, conserving heat and minimizing energy expenditures > > > Wear clothes. Sea-clothes. Special mermaid clothes that increases buoyancy. > > Larger Mermaids would also have proportionally larger flukes, allowing them to swim farther and faster to track and capture prey. > > > Pack tactics. Use net, outsmart your prey. Communication and planning should help a lot in hunting big game. > > And of course, since the oceanic environment already supports some > pretty large and dangerous predators, [...], being larger provides > more protection, or at least a greater ability to fight against a > predatory beast in the oceans. > > > Band together and build shelters. Use weapons to compensate your lack of natural weapons. Teach your potential predators to avoid you. Heck, domesticate some sea lions or something, they would make great sea dogs in a story. All the examples above are how humans coped with their status in the food chain to raise on top and protect themselves. Now, natural selection hardly happens to us, and the interbreeding tends to flatten the differences. TLDR: You had a lot of good answers to justify putting different sized mermaids, here is a reason to justify your choice if you want to do the opposite: civilization. ]
[Question] [ ### Definition: Interlunar adjective Of or traveling between moons. I'm (as far as I can tell) inventing the term *interlunar* to describe travel between moons in a single planetary system. Travel between * Stars = Interstellar travel * Planets = Interplanetary travel * Moons = Interlunar travel (within the same planetary system) * Asteroids = Interasteroidal travel (within the same asteroidal group, e.g. Trojans) Normally I think the word "Lunar" implies Earth's Moon (Luna) but I think we can control this through capitalization (capital Luna = Earth's moon, small luna = any moon). ### Assumptions: 1. Ignore life support requirements for the moment. 2. Assume a technological civilization develops on one of the moons of Saturn. ### Question: What is the minimum level of rocketry technology (perhaps type of rocket capable of performing the task?) required to support a civilization that spans the breadth of Saturnian moon system? If you can, try to equate that to a year of human technological development (e.g. liquid fueled rockets developed by Robert Goddard circa 1926). [Answer] Out of Saturn's 62 moons, only 13 are larger than 50km. Titan is by far the largest one and along with the next 6 largest moons accounts for over 99% of the combined mass of all moons. So let's focus on those 7 major moons. 5 of them are relatively close to Saturn, within 500 000 km, which is roughly comparable to how far the Moon is from Earth (384 000 km). Titan is a bit farther out - 1 220 000 km from Saturn, but only about half that from Rhea. I would expect that with Apollo type technology, you can put and sustain exploration stations on those moons and eventually inhabit them. Since those moons are not very massive, you won't need super powerful rockets and should be fairly cheap to fly resupply missions between them. Moon's gravity is 1.622 m/s^2, compared with 9.8 m/s^2 for Earth. While Titan is almost twice as heavy as the Moon, it's still 4 times less than the Earth. The next largest moon Rhea is only 1/25 of the Moon's mass so there is virtually no gravity to overcome. A Saturn V rocket (which were used for Apollo) can deliver 48 600 kg payload to Moon orbit, so between those moons you'll be able to move enormous amounts of cargo very cheaply. It's totally plausible for a civilization with 1970s type of tech to spread out through those moons similarly to how the pacific islanders spread through Polynesia. This scenario works even better if you take into account all the other smaller moons and use them to hop between the larger ones. You don't even have to have a rocket, you can drive a ground vehicle up a ramp and launch it in space. You can imagine "people" living in caravan like habitats that can just speeds up a hill and fly off into space on it's way to the next moon. I ran a couple of quick calculations and came up with escape velocity for Rhea of 96 km/h (compared to 11.2 km/s for Earth), which is just about 60 mph. [Answer] Travelling between the moons is not going to be the hardest part, surviving on them is the problem. As ventsyv's excellent answer says even low power rockets and 1970's tech could handle travelling between moons in orbit around one planet. However surviving on them is a far bigger challenge. We still don't know now how to make a stable enclosed ecosystem viable in the long term. You somehow need to shield people from radiation, deal with health issues from microgravity, grow food, run industry, etc. To realistically do that you are going to need technology well ahead of the 70's in areas like robotics, automation, networking, agriculture, genetic engineering, etc. With enough resources thrown at it we could do it now, and could probably have done it in the 90's. I'm not convinced it would be possible before then though. ]
[Question] [ Here is another planet question for you planet enthusiasts. I have this planet... [![enter image description here](https://i.stack.imgur.com/7ef66.jpg)](https://i.stack.imgur.com/7ef66.jpg) It's called Barahecio. The Mars-sized sphere's average temperatures hover near the freezing point of water. Of note also are the many seas that never freeze. Barahecio orbits a cooler brown dwarf that orbits outside the habitable zone for its star. Its the combination of the star's light and the heat radiated from the brown dwarf that keeps the moon from completely freezing over. The moon orbits in close to the brown dwarf, and is tidally locked. So in effect, you can say that half of Barahecio's heat comes from the brown dwarf and half from the star. My question is: What would this world look like since it has split heat sources? Specifically, I'm looking for the effects on climate and geography. Bonus questions: Describe the temperature differences from the side locked to the brown dwarf to the opposite side. What are the most likely weather configurations? Where would the most habitable place on this moon be? Additional Notes before you answer: I have provided you with a "standard model" to go off of for the system. The brown dwarf and its moon system are tilted at 45 degrees compared to its orbit, and the heat ratio that Barahecio receives from the star vs. the brown dwarf is 1:1. So 50% from each source. The earth-like atmosphere, and seas that resemble the great lakes in size. However, I welcome any more interesting configurations. If you do wish to change up the system a bit please mention the changes you have made. [Answer] My answer takes its detail from [this](http://arxiv.org/pdf/1209.5323v3.pdf) paper regarding habitable moons. This is my first attempt at answering one of these questions so be nice! The following aspects affect the climate of the moon: * Insolation from the main star * Reflected main starlight from the Brown Dwarf. This may be low considering the likely low albedo of the dwarf. * Radiated heat from the brown dwarf * periodic eclipses of the main star when the brown dwarf moves between the moon and the sun. * the tidal locking of the moon * the thickness of the atmosphere which affects heat transport from the sub-stellar point of the moon to the other side. This has not been specified in the OP. * the ocean heat transfer from water moving from the substellar side to the other side and then back again. You have not specified in the OP the depth of the ocean or what continents exist which block this cycling in the N-S or E-W directions. These are very very important parameters to determine to what extent open seas exist and where. * the inclination of the dwarf/moon system which you have specified at 45 degrees. * the eccentricity of the moon's orbit around the dwarf. This has not been specified. It may well be zero considering the moon is tidally locked but this is not essential (earths moons orbit is not circular). However if there is any significant degree of tidal heating it will alter the moons climate radically. * whether the orbit of the moon/dwarf pair round the main star is circular or not. If not then this will also induce additional effects, although they will be mitigated by the 1:1 ratio of dwarf/star flux. * how long it takes the moon to orbit the dwarf According to the linked paper, the system's inclination of 45 degrees will ensure pretty even reception of heat across the moon's surface (see Figure 7, bottom right panel), averaged over one orbit of the dwarf/moon pair round the main star. And note that the details in the paper have the ratio to flux from the star and planet/dwarf at much more than 1:1, so in your case, the flux smoothing effect is more even than in the paper. However, in the same panel, you will note a 'northern summer' and 'southern summer' is depicted which to my understanding results from the inclination of the orbit of the pair round the main star. Again, yours should be less pronounced all else equal thanks to that 1:1 ratio. Despite smooth average heat flux, there will, of course, be interesting weather patterns depending on your atmospheric and oceanic and geological parameters due to the interplay of all the factors. Although the moon is locked, it will not have a "cold" side because of the contribution from both the star and the dwarf. However, the flux from the dwarf is presumably mostly infra-red which may be beyond usefulness for photosynthesis. So when the dwarf eclipses the main star, the moon will be dark but likely not much colder than the other side. I feel that all these factors are going to create a weather system which is not the classic 'eyeball world' scenario for a tidally locked planet directly orbiting an M-Dwarf close in, and might actually be quite chaotic. Also, see the paper for important constraints regarding how close the moon can orbit the planet before it suffers runaway greenhouse effect due to a combination of tidal heating and illumination. You'll have to work out how to modify these parameters based on how you judge the effect of brown dwarf radiative heating versus the radiative heating described in the paper. [Answer] Like most tidally locked planets, there will be a "hot pole" facing the heat source (in this case the Brown Dwarf) and a "cold pole" facing space. These two poles will be the drivers of much of the planetary climate, as the atmosphere and water vapor is heated and expands away from the hot pole and moves in large convective cells towards the cold pole, where it sinks and heads back towards the hot pole. So there will be a constant wind at ground level blowing towards the hot pole and a "jet stream" like wind system moving from the hot pole towards the cold pole. There will be a more or less solid ring of clouds around the hot pole as water vapour condenses out at higher altitudes, and possibly another ring of clouds somewhere on the night side as remaining vapour condenses out in the cold temperatures, so there will be two planetary "belts" with high levels of precipitation; rain around the hot pole and snow around the cold pole. In terms of ecospheres, you could think of the planet as a beach ball with a series of concentric rings radiating away from the hot pole to the cold pole, and the ecology is determined by the varying amounts of energy and moisture being received in each "ring". The distant sun will provide a small amount of energy and illumination, although if it is as far as you say, this could be minimal (maybe even as little as a full moon on Earth). Because the planet would be orbiting the Brown Dwarf fairly closely, the illumination would also be rather sporadic, with the distant sun rising and setting quite quickly. Most native life would have to be adapted to "seeing" and harvesting energy in the infrared band, so plants would probably be black in colour and the eyes of native creatures would be very large to gather enough light, to begin with, and have the proper adaptations to receive and image infrared wavelengths, so the eyes would look different from ours. Although you have not mentioned other moons of the Brown Dwarf, it is quite likely that they would exist due to the intense gravitational field. Multiple moons would probably settle into resonant orbits (moons in nonresonant orbits get "pumped up" with energy and change orbits, either being expelled, absorbed by the Brown Dwarf or settling in stable resonant orbits. This should provide an extra source of energy for the moon's various tectonic, hydrological and atmospheric cycles, as the core is "kneaded" by the interaction with the other moons and heated more than it otherwise might be. This internal heat is probably what is keeping the oceans liquid (much like the internal oceans on Europa and other Jovian moons). The last thing which might affect the moon is the presence of a powerful magnetic field around the Brown Dwarf. Jupiter's magnetosphere provides a great deal of energy to the environment, and if the moon in your system is at the right distance, it might be interacting with the magnetosphere much like the Jovian moon Io, which is working like an armature in a dynamo and creates a multimillion amp "flux tube" between itself and Jupiter. Something like that would certainly cause a great deal of disruption to any planetary atmospheres, as well as make scientific discovery interesting (you might discover electricity early, but the roar of noise on radio frequencies will prevent the development of radio broadcast technology and radio astronomy, for example). [Answer] One thing that will (probably) make a big difference to life on that planet is the unfortunate tendency for brown dwarf stars (along with small red dwarf stars) to have strong sunspot activity and solar flares. I have read that the former can dim the light from the cool star for months (sunspots that cover a large proportion of the surface) and the solar flares are extremely violent, more so that the sun's solar flares, and from a much, much shorter distance. So life on the tidally-locked side of the planet that faces the brown dwarf might get regularly bathed in ultraviolet or even x-ray bursts. Life would either have to shield itself on that side or move to the other side of the planet, where things would be cooler but less nasty radiation-wise. [Answer] Being a red dwarf, it will have a relatively high percentage of its energy output in the infrared part of the spectrum. The planet will be bathed in a dim ruddy light, with lots of infrared energy warming it up. The star will likely be far less volatile than our sun, so don't expect short duration climate cycles like El Nino. Climate will be a lot more stable overall. Exact conditions, of course, depend heavily on whether the planet is tidally locked, and how far from its primary it orbits. But overall you can probably expect a climate that's far less variable over time (unless the planet's orbit is highly eccentric of course, or heavily tilted, which is the cause of most of the earth's seasonal changes) compared to earth. On the lit side, an eternal ruddy dusky sky greets those who go outside. On the dark side, except near the terminator, you're in eternal pitch darkness, the only warmth ever reaching there coming from thermal convection, driven by winds caused by the planet's rotation. As the planet is tidally locked, there are no tides, no wind patterns driven by tidal activity. ]
[Question] [ I have a race of humanoids (soarfolk) who, as their name suggests, basically went from normal humans to humans with wings, hollow bones and feathers. Normal humans still exist, and interact with soarfolk, and I'm wondering what the humans should be careful about when dealing with their hollow-boned peers. How hard would it be to break the bones? Would a human have to be careful about not pulling a soarfolk too hard, hold him too tightly, etc? Would slapping/punching cause severe damage? [Answer] I'd suggest reading up on [osteoporosis](http://en.wikipedia.org/wiki/Osteoporosis). That will give you some good, factual reference points for how fragile human bones become as their density decreases and they become progressively "hollow". That would also seem to imply some changes to the underlying musculature would be necessary/expected, as lower density bones would not be able to hold up to the same muscle density that you find on the average human, nor the same amount of stress when moving around and articulating joints. > > How hard would it be to break the bones? > > > One soarfolk to another? Probably about comparable to how hard it is for one human to break another human's bones. Their bones break more easily on an objective scale, but when you factor in the reduced mass and reduced muscle density (so on average a soarfolk is both lighter and weaker than a human) the subjective impression of how much effort is needed to break a bone is probably about the same. A human vs. a soarfolk? Comparatively easy (relative to breaking the bone of another human), as the human will have stronger bones and greater muscle mass. I'd imagine most any blow delivered at full force would have a good chance of breaking a bone. > > Would a human have to be careful about not pulling a soarfolk too > hard, hold him too tightly, etc? > > > Pulling I'd think would be okay except in extreme cases. The things likely to cause damage would be impact and torque. Holding/crushing might be an issue, but again I think only in extreme cases. I'd think a soarfolk could generally shake hands with a human without fear, so long as the human didn't deliberately try to crush their hand. If the human did, however, they'd probably be able to crush a soarfolk hand (or ribcage) with effort. > > Would slapping/punching cause severe damage? > > > Yes, punching especially. A human would be able to punch harder than a soarfolk, and would hit them with more mass than they'd generally be accustomed to. A human punching a soarfolk would probably be akin to a human with brass knuckles punching another human. Easily damaging, and potentially life-threatening in the case of, say, a strong blow to the face. [Answer] The bone issue would only need referencing a line or two. The Author Brandon Sanderson speaks a lot about worldbuilding and only conveiging what is nessessary to the story. sort of like -"How can they get their weight off the ground." - "Hollow bones." Or as is the case with real bird bones, having them splinter when they break and a character witnesses it. Any surgeon would have a hard time dealing with splintered bones. It would depending on the technology, ability or magic, likely render a limb useless and may be better with amputation. - a crash could mean istant death. Here is a bit of biology on hollow bones from Vet Approved [PetMD](http://www.petmd.com/bird/emergency/accidents-injuries/c_bd_Fractures) > > Avian Fractures > > > Just like humans, birds can also fracture (or break) bones and dislocate various joints. (A multiple fracture is when there is more than one broken bone, or a bone breaks in more than one place.) It is, however, not as easy to treat fractures in birds because many of the bird bones are filled with air, and have higher calcium content. When the calcium content in the bone is high, the bones become brittle and multiple fractures are more likely. > > > Diagnosis > > > The veterinarian will take X-rays and perform blood tests to diagnose osteomyelitis. > > > Complications > > > Fractures may become complicated when the broken bone becomes infected. The most common bone infection is osteomyelitis. > Osteomyelitis is a bacterial infection of the bone sheath which can spread to other bones. It is very painful and if the infection enters the blood, it may become fatal. Antibiotics are used to clear up the infection and speed the healing of the bone. > > > Treatment > > > Fractured bones in birds heal faster than in humans or other animals. Usually a stiff splint, which totally immobilizes the broken bone, is the only treatment needed. During multiple (complicated) fractures, surgery may be needed to implant supports. This helps the bone function normally after it has healed. > Physical therapy (physiotherapy) may be needed to loosen frozen and stiff joints, and maintain range of motion. The veterinarian will recommend various exercises to help your bird heal. > The veterinarian will also prescribe medication to ease your bird’s pain while it recovers. Medication may be given orally, or through the feed or water. Observe the bird's recovery and return to the veterinarian if pain increases after a few days to rule out any infections in the broken bone. > > > I once wanted to write a novel about angels as real people with wings a long time ago - can't remember where i got it all but here goes. I did some research and they would have very large wings no matter the bone structure, look at a picture of a bird with its wings out, in general they are huge for the birds size. It would also depend on wether the wings where a seperate apendages making six limbs - no mammal has that. Or wether they were the arms or attatched to the arms like gliding of the flying squirel, all that would determine their arial capabilities, and their ability to fight and fly at the same time. Big wings make big targets - nets and long thin blades would be hard to focus on when moving at speed - if they are attatched to the arms they could not carry anyone or anything with any ease. They would get very cold dependent on feather layers or clothing that would add weight as facial skin may freeze at high speeds - they would need big lungs and a big heart to pump the blood around and breath at high altitudes. They may need eye protection or better focusing eyes - weather depending, they could be grounded and therefore vulnerable - mages that could cast weather spells could be of use. You can't keep many tactical secrets on a battlefield from a flying man - air control dominates, - possible use of bombs of some kind. - big predator birds could be used to cut them from the sky. Fire and heat can engulf and the best place to catch fire is just above the visible flame. These are all great things that the other humans should take into account. And after that you may find these people may as well be a different race entirely it may prove easier than explaining evolution. By our world standards evolution obviously takes a long time and i would guess is more developed out of nessesity. So the why wings I think is the more important question that you could really weave into a story. An idea for the birthing could be that they are born smaller than normal people and the bones are not hollow when they are young, this develops over a few months/years to be hollow, the birthing ultimately is unlikely to need explaining although no animal does this at all. That's me done. Peace! [Answer] I know someone that broke a hip by tripping/falling (just a normal fall, normal speed) because they had osteoporosis. I'm pretty sure getting into a fight for people with weaker bones would signify serious injury/death. Take any number of examples of such cases in fiction (Samuel L. Jackson in unbreakable, Seth Green/Joker in Mass Effect etc...) Interestingly enough, Author Alastair Reynolds has a sub-species of humans in his book [Terminal World](http://en.wikipedia.org/wiki/Terminal_World) that have both hollow bones and wings (to fly) and addresses the issues of having weaker bones by having these humans be technologically more advanced and use some kind of nanobots to strengthen them. Now without using necessarily some high-tech sci-fi fantasy (nanobots fall in that category for me) I guess you could maybe have some kind of medical or natural procedure to reinforce the bones, with any kind of lightweight hyper resistant material. You'd have to manage figuring out a way it wouldn't block the pores in the bones entirely. I thought of Kevlar but that can get just as heavy as having normal bones. Having over developed muscles and tendons isn't necessarily a solution as you could end up with the problem of them snapping their own bones under the strain of their own muscles. ]
[Question] [ My story involves everyone in the year 2015 suddenly disappearing. What would visitors to Earth find if they arrived in the year 12015, or 10,000 years after we all disappeared? Assume none of our infrastructure has been maintained during that period. I'm especially interested to know what would remain of our technology and infrastructure, such as roads, buildings, major installations, ships and aircraft, observatories, bridges, the pyramids, etc. Would these things be completely gone or would there be some rubble and other evidence left? What about stuff like kitchen and laundry appliances, mobile phones, etc? Would these things completely disintegrate, or would there be some bits left? What about stuff made of stainless steel like cutlery and kitchen sinks? I want to understand two things: 1. Would there be any evidence on or very near the surface that our civilisation once existed? 2. Would there be anything useful (or close to useful) left behind? Bonus question: What would the world look like? Would climate change have raised ocean levels, or would it be close to now? Are there any parts of the world which definitely would have changed through erosion or other forces? For example, the Grand Canyon or [The Twelve Apostles](https://en.wikipedia.org/wiki/The_Twelve_Apostles_(Victoria)) (rock formation in Australia). [Answer] This has been answered comprehensively in the TV series [Life after People](http://lifeafterpeople.wikia.com/wiki/Life_After_People_Wiki). The link goes to a wiki with a lot of information about the series, including synopses of the episodes. To summarise very briefly in case of link rot (URLs don't always have a terribly long lifespan either), after 10,000 years, there wouldn't be very much left on the surface at all, save some items that are particularly resistant to decay, like stainless steel objects, and things in protected places such as caves or deserts. The artefacts on the moon and satellites in space would still be there, mostly unchanged save for the effects of 10,000 years of solar irradiation. As to whether there would be anything useful left, the answer is, "Yes, but not much at all". There may be useable stainless steel objects like cutlery and kitchen sinks that could be cleaned up and used. There may be occasional objects left in protected places that have not decayed, but for the most part, not much will still work unless it is corrosion resistant and simple. The world would be warmer, and erosion would have changed geography a little, but 10,000 years is not the timescale over which major geological changes occur, so the continents would still be recognisable, if displaced a little due to continental drift. [Answer] Not sure I agree with some of the above answers; after all, how much is left and recognizable of ancient civilizations that are only a fraction of the age being postulated here? A few megastructures built of stone like the Pyramids, and that is about all. Cities from ancient Sumer resemble eroded hills, and virtually any metallic object has corroded away except for gold (which, if it could be salvaged by grave robbers, was almost always plundered and melted down). Most of our buildings and structures are made out of metal, and (as mentioned above) most would have collapsed after about two centuries without being maintained. Our concrete structures won't last much longer, they have reinforcing rods while ancient Roman concrete does not. Any future civilization or alien explorers will indeed find evidence that something or someone was here, mostly by digging through garbage dumps or discovering old mines (oddly, that is how we find out a lot about ancient civilization), but they won't find the towering remains on New York or Hong Kong unless they arrive only a century or two after all the humans were gone. [Answer] [Mount Rushmore](http://www.nps.gov/moru/faqs.htm) probably wouldn't have changed all that much, and there would be some other buildings and places that would appear to be actually pretty close to what they do today; but for the most part and in most places it would require quite a bit of effort to find out that there had been people at all on earth, especially depending what the climate may or may not have done in 10,000 years; any current warming from our existence would have [long since disappeared](http://en.wikipedia.org/wiki/Holocene_climatic_optimum) and there very well could have been an ice age between now and then which would further remove many evidences of prior human existence. There would surprisingly actually be some random objects that would likely be completely usable if one knew where to look. Deep mines and landfills if they were otherwise undisturbed could be dug through for some interesting things, including usable silverware and quite possibly [kitchen sinks](http://en.wikipedia.org/wiki/Sherd). Not sure how a mobile phone would fare in a landfill type environment over 10,000 years, I mean it probably didn't get placed there because it was usable to begin with and it certainly wouldn't be usable after that long, but there would be bits left. Major geological features would likely look not too very much different from how they do today for the most part. All of the low earth orbit satellites would have fallen to earth; only the higher orbiting satellites, such as the [geostationary satellites would be left.](http://www.quora.com/For-how-long-would-Geosynchronous-satellites-stay-in-orbit) Once archeological surveys started there would be no trouble determining that there was a major civilization. ]
[Question] [ I recently asked [this](https://worldbuilding.stackexchange.com/questions/2965/what-would-be-the-effect-of-a-powerful-explosive-going-off-in-the-core-of-a-plan) question about what would happen if a fusion bomb went off in the core of a planet, and the answer was relatively uninteresting. As was aptly said in my previous answer, the effect of a nuclear bomb in the core would be very small. So I have a new question (suggested by Tim B.), which is hopefully a little more interesting. How much force would be required in the inner core to blow open a planet? And by blow "open" I mean create a deep chasm down to the magma, but not necessarily blowing the planet apart. In other words, how can I fracture a planet with energy coming from the core? I am aware that such a chasm would probably become a volcano. And one of my usual bonus questions: Could this happen without blowing the planet apart? [Answer] I'm a physicist (kind of :D) and I love this question. I'll try to estimate the amount of force necessary. Firstly, I'm assuming that the earth is split in two hemispheres and we are trying to separate those. I'm only considering gravitational force, otherwise the problem would be too complicated. By integration I found that the center of mass of each hemisphere is $\frac{3R}{8}$ away from the center, so the distance between the two centers of mass is $\frac{6R}{8}$. Most equals ($=$) mean approximately equal to ($\approx$), but because the method to calculate this force is already a huge approximation, it won't really matter. $$ \begin{align} G &= 6.67\times 10^{-11}~\text{m}^3\cdot\text{kg}^{-1}\cdot\text{s}^{-2} \\ M &= 5.97\times 10^{24}~\text{kg} \\ m &= \frac{M}{2} = 2.99\times 10^{24}~\text{kg} \\ R &= 6.37\times 10^{6}~\text{m} \\ \frac{6R}{8} &= 4.78\times 10^{6}~\text{m} \end{align} $$ Newton's Law of Gravitation: $$ F = \frac{G m^2}{r^2} = 2.61\times 10^{25}~\text{N} $$ which is: 2.610.000.000.000.000.000.000.000 Newtons which is 2 septilions and 610 sextillion or something hahaha That's the force each of those hemispheres exerts on the other, so to separate them, you would need a force larger than this value. NEW: I'll add to these calculations the amount of energy necessary to separate these two hemispheres in a way that they wouldn't pull each other and be together again. $U = \frac{G m^2}{r} = 1.25\times 10^{32}~\text{joule}$ which is HUGE. Just for you to have an idea, the sun releases $3.85\times 10^{26}~\text{J}$ per second of energy in the form of light. You would need all the energy that the sun releases over a period of $3.76~\text{days}$ (assuming you weren't losing any, which is almost impossible). Really cool :D New 2: According to [Wikipedia](http://en.wikipedia.org/wiki/Solar_energy), the Earth receives $174~\text{petawatts}$ at the upper atmosphere, which is $1.74\times 10^{17}~\text{W}$. To gather enough energy to blow the planet apart, one would need to save all the energy that hits the Earth for $7.18\times 10^{14}~\text{s}$, which is $23\,100\,000$ years. Don't forget that people need energy to live and that it's almost impossible to manage to gather all of it. So... maybe someday :D [Answer] Please clarify your question. You're asking about force "in the core", but then also talk about making "chasms in magma... to the core"; as in, from the outside-in? To answer the "could this be done without blowing the planet apart", I think that plainly, yes it could, given that an asteroidal impact could remove a significant amount of material from a planet and yet leave the majority of the body whole (if in a state of severe disarray); our own moon, in fact, is believed to have formed this way. Regarding the 'core' scenario, the core of a planet is subject to ludicrously high pressure due to the gravitational attraction of its constituent matter. To significantly shift any amount of material near or at the core of a planet would require a force at least equal to that pressure x the area over which it would be applied. A very grand simplification would be to express that area as a proportion of the area of a virtual sphere, the radius of which is the distance out from the true center of the planet where the force is acting. You could then apply the same proportion to the planet's mass to arrive at a rough idea of the order of magnitude of the force you would need to overcome gravitational pressure alone to push that material outward away from the core at a constant rate of speed. Of course, that doesn't begin to address the structural constraints of the problem, displacing solids within solids, or the sticky issue of how to apply that force at that point in the first place. ]
[Question] [ In many Sci Fi and Fantasy worlds, the deserts are filled with giant megafauna that swim through dunes of loose sand. The issue with this depiction of course is not just the size of said sand swimmers, but of where the energy needed for such giants come from. If we look at the real world, deserts do not have a any substantial biomass needed for such organism to survive. And the reason whales grow to such sizes, asides from the buoyancy of the water, is the amount of plankton available. So my question is: Whether or not "Sand Plankton" is possible or not? [Answer] Deserts are seldomly devoid of life - many deserts are inhabited by beings such as ants, badgers, kangaroo rats, lizards, snakes and camels. Each of these beings carries a microflora and a microfauna inside. As those animals defecate in the desert, their droppings spread microbes around. Many microbes die from the excessive heat by day or excessive cold by night. The nutrient value of those microbes is not completely lost, though. Also many form spores which await for the next animal to come by ik order to fetch a ride in a new host. And it's these microbes and their remains that the filter feeding sand swimmers consume. Which is also why those creatures stalk human travellers. They are not after you, they are after your [redacted]. [Answer] MAYBE! Sticking strictly with terrestrial biochemistry, no. Given the extreme diversity of life and the extent to which is has colonized every conceivable Earthly environment, and some that were not conceivable until we were surprised to find life there after all, I think it's safe to say that if sand plankton were possible to evolve starting from the kinds of organisms that exist on Earth, they would have. Since they haven't, that's a strong indicator that they can't. But there are theoretical alternative biochemistries that might make it plausible. There are two big challenges to overcome for sand plankton: 1. Solvent availability. 2. Energy supply. Deserts are deserts precisely because they don't get a lot of water input. That constrains how much total biomass they can contain, because all life on Earth requires water. But suppose that weren't a constraint? If your organisms could manufacture their own biosolvent out of more readily available materials, the lack of rain or rivers would no longer constrain plant growth. If you don't want to stray too far from water-based biology, this could be the case for creatures whose biosolvent is not pure water, but a strongly hygroscopic water solution; e.g. a high-percentage hydrogen peroxide solution, which will pull water out of the atmosphere at extremely low vapor pressures, with the recovered water being cracked to produce more hydrogen peroxide, which will then suck more water out of the air, and so on. Or, if the right kinds of minerals are present, they could use a deliquescent salt solution (e.g., water and potassium carbonate). A third option might be formamide as a sole biosolvent, not mixed with water--water is require to produce it, but like hydrogen peroxide it is strongly hygroscopic, so that lack of liquid water in the environment isn't an issue--plants could simply extract water, nitrogen, and CO2 from the air and make their own liquid formamide. However you want to solve that problem, once it is solved, you can now have deserts with nearly as much biological productivity as any other environment--perhaps a little less since more primary energy input would go towards making biolsolvent that might be provided for free elsewhere, which is energy that could not then go into other biological activities, but still, you could have a desert surface entirely covered with photosynthesizers, capturing plenty of chemical energy to power a complex ecosystem complete with megafauna. But that gets us stuck on the second issue: you can cover the surface. Sand may be easier to burrow through than clay or soil, but even sand made of pure transparent quartz scatters and diffuses light extremely quickly, such that it is essentially as dark as the bottom of the ocean only a few centimeters, at most, from the surface. Which means that unlike the ocean, you will not get primary production occurring in a deep column below the surface, and there will not be significant amounts of plankton to bother sifting out below the surface. Just like anywhere else on land, it make more sense to just graze at the surface. However, there may be another way to get around this. Due to the lack of thermal inertia provided by liquid water, sand dunes (and deserts in general) tend to undergo significant thermal cycling between day and night. At sufficient depths, these cycles average out, and you end up with a fairly constant day-round and year-round temperature--but that doesn't occur until you get around 15 feet down. Above that level, sand is reliably heated by the sun every day, and cooled at night, with the gradient becoming larger the closer you are to the surface. There are a number of electrophysical and chemical systems whose equilibrium points are strongly temperature dependent, so one could imagine alien microbes which extract energy directly from thermal cycling, rather requiring direct exposure to light--as they warm up during the day, the equilibrium point of some chemical reaction shifts, and they extract energy from gating the motion of the reactants in that direction, much like we gain energy in ATP synthase from gating the motion of hydrogen ions. And as they cool down again at night, the equilibrium shifts in the other direction, and they can extract energy again moving molecules the other way. This would give you an excuse for some level of primary production plausibly up to 5 or 10 feet under the surface. That then provides an incentive for burrowing creatures to evolve to eat those microbes, which will result in disturbing and rotating the sand, producing vertical migration of plankton which will further enrich the quantity of food available below the surface. [Answer] Sand plankton may be possible as a niche organism (after all, ice-worms are a thing) but they are going to be very limited in number simply because light does not penetrate sand to any great depth. So while they may exist I argue they do not exist in great enough numbers to support mega-fauna. (Even filtering sand to extract plankton may well be an energy-losing effort). [Answer] The Sand of your deserts is actually the dried silica shells of the "Sand Plankton" A long time ago a new organism evolved a silica shell for protection. It is an extremophile for both hot, cold, and dry conditions. Sand Plankton grow in patches in the desert, usually near Oasis, and also grow at the edges of the desert. On Earth, cellulose based organisms existed for hundeds of thousands of years before an organism evolved that could break down cellulose. Your planet is the same but with a silica shell (Or anything else you want) There are no bacteria which can break through the hard shell. However, there are the megaworms which grab great mouthfuls and grind it with their stone-like teeth. The precious nutrients are released and available for digestion. The worms are most certainly eating more Plankton a day than are being produced, but fortunately theres whole deserts 300m deep of the stuff. Now, the worms are highly territorial due to their evolution and regularly kill each other. This keeps their population numbers down and prevents overpopulation from consuming all the food. ]
[Question] [ What follows is the first in what will be a series of questions I'll be asking in the hopes of solving a problem I'm running into with one of the species in my story: the werewolf, and the particular difficulties it has when it comes to keeping itself clothed. In this story, werewolves, among other immortal humanoid supernatural creatures, live in secret amongst humans. The werewolves in this setting can transform into their werewolf form at will, as long as they are exposed to the rays of either the sun or the moon (any phase is fine; the reason they're associated with the full moon is that the fuller the moon gets, the more of the night the moon stays out for). For the purposes of these questions, all you need to know about this form is that it is 10 feet tall, and that shapeshifting does not do anything about the clothes the werewolf might be wearing at the time. Anything they are wearing will be rapidly pulled apart by the force of the werewolf's magically expanding body. Think the Incredible Hulk, except that there are no magic purple pants to keep them decent when they transform back. Obviously if werewolves are going to blend in with human society, they're going to need to wear clothing. However, werewolves have a very important question to consider when deciding what to wear: "If I transform while wearing this, will I still be able to put it back on later?" While hanging around human civilization gives them some degree of protection from their enemies who similarly have to keep their existence a secret, they still may need to transform into their wolf form at a moment's notice, likely with no time to get changed first. Also, the obvious Doylist reason: I don't want every single werewolf action scene to be preceded by the werewolves taking all of their clothes off by hand. Dumb mental image, even if I try my hardest not to call attention to it. No, it'll be much better for everyone involved if these werewolves can wear clothing that, should they transform while wearing it, will merely come undone, rather than rip into pieces. Also: If I've underestimated the elasticity of some fabric that could totally accommodate both a human and a 10-foot werebeast, they likely still wouldn't use that. If you happen to see a huge monster in the wilderness, well, that's one thing. It's bad news for secrecy, but it's not likely to be traced back to anyone in the pack unless you also see them transform back. But if that monster happened to be wearing clothes, well, not only would that make you immediately suspect human involvement in some way, but also you'll be extremely suspicious of those weirdos in that same sort of spandex that you just saw in town. No, the way I see it, these werewolves need clothes that, upon transforming, will come apart into deliberate pieces that can be put back together later, and they need them to look as natural for the time and place as possible. They don't need to just buy something that already exists, they can tailor and modify pre-existing clothing to have new features, as long as it's realistically doable and affordable at the time and place. Which brings us to part one of this question: what they're doing in the 21st century. Specifically, in the 2000s. When werewolves have nearly all of modern clothing technology at their fingertips, what could they do to design clothes that could look like something a normal human would wear, but could be transformed out of without destroying it? [Answer] Velcro (or equivalent). Consider t-shirts and tank-tops and similar that instead of sewn seams have hidden velcro seams, so that with enough force the top is pulled apart into front and back sections that can be easily fitted back together. The seams will be a bit bulkier than normal sewn seams, but would pass a quick inspection. For footwear, sandals or sneakers with velcro closures: quick kick and they're off. It will be lower bodies that have some issues, but it's not terrible. Skirts with velcro or snap waist closures are obvious, or even elastic so they can be dropped quickly. Pants are a little more difficult, but think of athletic training pants which again use velcro seams and are quickly removed without needing to pull your legs out. So, what have you got? People wearing t-shirts, workout pants, sneakers...clearly, your werewolves, to the outside world, are just fitness fanatics. [Answer] Hidden press-studs (1) in the seams. This is an actual solution in use today. For example I saw a girl come by that had her hand grown into her chest (I'm not sure of the reason, either a birth defect or a deliberate medical procedure to provide blood to damaged muscles). You can imagine that getting her jacket and sweater on wasn't going to be easy when both her hand and her shoulder were connected to something. The solution: Her entire wardrobe including autumn and winter jackets had been reworked. If you look at the clothing you wear right now you'll notice the seam of the arms and legs is usually located on the inside facing the centerline of your body. These seams were opened (or created in case of her jackets) and folded into each other. Inside the fold they placed buttons and zippers (zippers for things that need to close like the jacket, it had a plastic coating across that made it almost watertight when zipped up). People wondered how she ever got her arms into any sleeve because it was so invisible. Putting it on was a chore but getting the sweaters off (which had buttons) was just a matter of ripping it open (some clothes had been reinforced on the inside to prevent tearing). So it would help your werewolves when they grow immensely quickly as the buttons will tear lose at the seams, falling off their body and allowing the werewolf to pick them up later. With some extra work you can make the press-studs "pull" the fold closed to reduce cold and water seeping in, although you could perhaps also use things like an additional flap across it as shown on the pockets of this raincoat: <https://i5.walmartimages.com/asr/a4efdcb7-9748-440f-8853-a7dbf67b1646_1.29c597ce52775123d901bf8d8cacb85c.jpeg?odnWidth=612&odnHeight=612&odnBg=ffffff> (1): <https://i.ebayimg.com/images/g/jUQAAOSwW4JdsTzu/s-l300.jpg> [Answer] Not hundred percent sure this will help, cuz it might look/sound super stupid but you could give them clothes with zippers or velcro straps that have a lot of fabric underneath. So while they look like they're either really fat or super bulky. Then before they do the transforming they just unzip, let the extra fabric out, and grow into it. Sorry if that didn't make too much sense. [Answer] The Dresden Files suggested that werewolves would tend towards baggy clothing like loose-fitting tops, sundresses, and sweaters because it would be easy to slip out of and shift into wolf form. However, this ignores the fact that baggy clothing could easily get tangled up around a shifting werewolf, which would leave them highly vulnerable to enemies while shapeshifting. What's more likely is that werewolves would tend towards fashion that is not likely to be restricting and is easily disposed of. Namely really cheap, thin t-shirts, sweatpants, and similar garments that not only can be easily slipped out of, but if a werewolf gets stuck in them they can easily tear them off with little trouble. This, in turn would have some downstream consequences. Having to constantly replace clothes would mean werewolves would have to devote a lot of their budget to replacement clothes (even if they intend to slip out of them, a lot will be torn in accidents and such) and they will often look slovenly because they are typically not dressed in nice clothes or those clothes are torn and ripped. This would probably predispose your werewolves to being from lower economic classes. This fits with how werewolves are often depicted as "blue-collar" supernaturals compared to wizards or vampires. At least, that's what I did for my story. In my story, it is also noted that werewolves tend towards form-fitting clothing because unlike the average person they are in situations where they could be in danger at any minute and either have to run away in human form or shift. This means that tuxedos, skirts, high heels, etc. are completely out. The few werewolves that do wear something with a hemline are noted as either extremely old-fashioned or wearing skirts as an act of rebellion. [Answer] Perhaps I could interest your werewolves in a nice overcoat? Specifically, you want something you can wear open in the front without being obvious about it (so the werewolf can simply burst out of it when needed, or you can dramatically slip the coat off right before the action starts) and long enough that it won't be obvious to passers-by if you need to sacrifice the clothing underneath. It also keeps the rain off, which is a real plus in some settings. Fortunately (in some ways) in the early 2000s there are enough teens and young adults you've just seen The Matrix and think black leather trenchcoats are the height of cool that you shouldn't stick out too badly. ]
[Question] [ I have a location in my story, the design of which needs a reality check. City Description: > > As my ship cut across the waves a blurred grey smudge appeared in the distance, as the hours passed it became more distinct and it's true scope came into view. > > > As we neared the end of our voyage a great cliff of jagged granite rose hundreds of feet from the relentlessly pounding sea and spread as far as the eye could see in either direction. The tops of the tallest buildings shining brightly in the moonlight peered down from atop the cliff. The face of the cliff, littered with windows glowed like the eyes of fey forest creatures and large towers ascended at intervals striped like a barber pole apparently carved from the face of the cliff. > > > Directly before us a giant maw opened in the cliff the top jagged like the mouth of some vicious predator. On either side of the cliff massive braziers burned brightly in the night. > > > There is more to the poetic description but I think that is sufficient to set the feel for the place. City Details: * The city is built into, and on top of, a granite cliff. The cliff rises 500' (152 Meters) from the sea below. * The granite cliff extends perhaps a mile in either direction (this can be adjusted somewhat if it matters) and should extend at least 1500' (460 M) inland. * In the face of the cliff is a large cavern that can accommodate large two masted sailing ships. Tugs are used to tow the ships to docks within the cave. * Inside there are stairways and elevators (both for people and cargo) that lead up to the surface. * Inside the rock formation I am looking for enough space for approximately 1000 residents, each should be afforded 12'x 12' (.305 x .305 M) of floor space, dwellings are not all the same size. * Living spaces are reminiscent of Bag End from The Fellowship of the Ring, though scaled for a normal human to walk without doubling over (8' ceilings) The underground portion will also require space for cargo storage. * Atop the rock face is a city, where important structures are built from the excavated granite and lesser structures from both stone and wood from the surrounding forest. Points of consideration for the reality check. * Can this much granite exist in one place, are there real world examples? * Does the described amount of excavation seem possible or would it cause structural problems? (Faults can be set however structurally required) * Are there examples of dwellings carved into granite in the real world for the purpose of habitation? * Are there concerns with this setup that I have not considered? [Answer] # This is like an [Indian rock-temple](https://en.wikipedia.org/wiki/Ellora_Caves) [![enter image description here](https://i.stack.imgur.com/fZyHo.jpg)](https://i.stack.imgur.com/fZyHo.jpg) There are many examples of these rock-temples in southern India. Above is a picture of Cave 10 at Ellora. Below is Cave 16 at the same site, called the Kailasa Temple. The temples are called 'caves,' some of them are dug into rock as if they were caves, some, like 16 are basically small hills excavated into the shape of a building. [![enter image description here](https://i.stack.imgur.com/fDuSs.jpg)](https://i.stack.imgur.com/fDuSs.jpg) Cave 16 is 82 by 40 meters, and 30 meters high inside. An estimate of the total amount of rock removed in 100,000 cubic meters, just for this one of 34 caves at the Ellora site. Ellora is just one of many from Maharashtra in India, including [Ajanta](https://en.wikipedia.org/wiki/Ajanta_Caves) and [Pitalkhora](https://en.wikipedia.org/wiki/Pitalkhora). The Pitalkhora site was started around the 3rd century BC; building at each site went on for hundreds of years. The total amount of excavation at the bigger sites like Ellora and Ajanta is probably more than you would need to make your city. # Except that was basalt So all those structures were cut into flood basalt. However, basalt is pretty hard and tough as it is. Here are some material comparisons between granite and basalt. Source of [granite](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180880) and [basalt](http://oro.open.ac.uk/5495/1/JVGRbalme01_corrected_for_publicpdf.pdf) fracture toughness, [all other data](http://acwc.sdp.sirsi.net/client/en_US/default/index.assetbox.assetactionicon.view/1045105?rm=CONCRETE%20LABOR0%7C%7C%7C1%7C%7C%7C0%7C%7C%7Ctrue). Everything converted to metric ``` Basalt Granite Density (kg/m^3) 2830 2690 Fracture Toughness (MPa m^0.5) 1.5-1.7 1.9-2.2 Compressive Strength (MPa) 148 143 Tensile Strength (MPa) 13.1 11.7 ``` Basalt appears to be slightly denser, and proprotionately stronger, while granite is tougher so it would be a bit harder to mine through. Ultimately, the materials are pretty similar, so if Iron Age Indians could carve these temples in a century or two, they could also carve your city. # Conclusion Monumental cities carved in granite are realistic! [Answer] ## Granite Massifs are common A granite block of the size you ask for is totally feasible. El Capitan in California is certainly taller. Getting the living spaces you want without explosives or magic is going to be sufficiently expensive to be impossible. Cutting stone by hand takes a long long time. From personal experience, with a hammer drill and modern drill bits, it took the better part of an hour to cut a single row of holes about 6" deep. Medieval miners with poor quality iron or steel will take days or weeks to cut the same set of holes. To excavate the amount of material described will take forever. Making granite "caves" is usually done artificially by cutting up the rock into blocks then forming it into buildings. As most caves are found in rock types that dissolve in water and granite does not, some other mechanism will need to be used to create the voids in the rock. Without a very secure bay to protect the cave mouth, no captain will risk their ship. The scene describes pounding surf indicating that the cliff face extends far below the water line. While the deep water will allow large ships to approach the cave mouth, and even enter, no one would dock their ship there. Depending on the shape of the cave and without a harbor, the waves in the cave could frequently be larger than the waves outside. Big waves on the open ocean aren't too bad. Big waves are really bad when your ship can be thrown against a cliff face, even if that face is in a cave. Compare paintings of the docking density between the Thames River in the 1800s vs Boston Harbor. The Thames is absolutely packed! Why? Because conditions on the Thames are very placid. The risk of one ship inadvertently running into another was low enough that the density of docked ships could increase. Boston harbor doesn't have those kind of conditions. Thus, to prevent accidents, boats are anchored much further away from each other. Ignoring the waves, the tides will put a limit on the maximum height of the ships that will fit in your cave. Assuming a normal earth-moon system, tides may vary by as much as 3 meters. [Answer] Actually granite rarely form caves, and never that big. Water erode the rock by infiltrating through the faults producing sand and large blocks but no cave. Nonetheless there are huge granite cliffs in Yosemite like the Half Dome. You can't really dig into granite, may be a stairway would be possible on the face of the cliff. Building with granite is possible you even have lighthouses made of this. On the other hand, compact lilestone suits perfectly, but it is completely white and a port in a cave is still dangerous. ]
[Question] [ Closed. This question is [off-topic](/help/closed-questions). It is not currently accepting answers. --- This question does not appear to be about worldbuilding, within the scope defined in the [help center](https://worldbuilding.stackexchange.com/help). Closed 7 years ago. [Improve this question](/posts/37451/edit) I was thinking of a universe where the equation for the [Lorentz factor](https://en.wikipedia.org/wiki/Lorentz_factor) $$\gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$$ was replaced with the equation $$\gamma=\frac{v^2}{c^2}+1$$ so in this hypothetical universe there would be the effect of length contraction and time dilation and the inertia of an object would appear to increase as it moves very fast, so as something would move very quickly, it would appear to be harder to accelerate, but there would be no cosmic speed limit. So in this universe $c$ would simply be a constant instead of an actual speed limit. What would be the new equation for kinetic energy for a universe with this equation? Also, what would be the new equation for rest mass energy in this hypothetical universe? [Answer] Let's start with [the energy-momentum equation](https://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation): $$E^2=p^2c^2+(m\_0c^2)^2\tag{1}$$ This can be derived [according to the Minkowski metric](https://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation#Norm_of_the_four-momentum). This works because the inner product of the four-momentum, $\langle\mathbf{P},\mathbf{P}\rangle$, is equal to $\|\mathbf{P}\|^2=-(m\_0c)^2$. We can also use $$\langle\mathbf{P},\mathbf{P}\rangle=P^\alpha\eta\_{\alpha\beta}P^\beta=-\left(\frac{E}{c}\right)^2+p^2\tag{2}$$ where $\eta\_{\alpha\beta}$ is the Minkowski metric. Setting these two expressions equal yields $(1)$. We can then use this [to derive an expression for $\gamma$](https://en.wikipedia.org/wiki/Mass_in_special_relativity#The_relativistic_energy-momentum_equation). Now let's do things in reverse, with your requirements. First, let us rewrite your $\gamma$ as $$\gamma=\frac{c^2+v^2}{c^2}$$ Putting this into the expression $$E=\gamma m\_0c^2$$ We find $$\frac{E}{c^2+v^2}=m\_0$$ We then have $$E^2=p^2v^2+(m\_0c^2)^2\tag{3}$$ Note that we have $p^2v^2$, instead of $p^2c^2$. We now have $$-(m\_0c^2)^2=-\left(\frac{E}{c}\right)^2+\frac{p^2v^2}{c^2}=\langle\mathbf{P},\mathbf{P}\rangle$$ This implies that you have a metric that is nothing like the Minkowski metric, and you have spacetime that is nothing like Minkowski spacetime. The final term now includes a dependence on $v$. Now you have a problem, because special relativity needs Minkowski spacetime to work. The postulates of special relativity, especially those concerning invariance, most likely will not hold. The big problem with this - all of this - is that you haven't started from first principles. Instead of using some logic to make a derivation, you've done things the other way around, starting from a result you want and trying to work backwards. You're then left with results that might be described as disastrous. This is an easy trap to fall into. You would think that changing one tiny thing about a universe wouldn't cause too many problems, but it can. Each equation, each law, each postulate that makes up our universe is finely woven together with every one to form a self-consistent framework that describes how things work. It's like making a jigsaw puzzle, where each piece is a different law of nature. You can change the shape of one piece, and change the shape of one of the neighboring pieces to compensate. But unless you modify all of the pieces that touch the modified piece, the puzzle won't be self-consistent. [Answer] See [Nothing But Relativity](http://arxiv.org/abs/physics/0302045) and similar papers: you can see from from first principles that the Lorentz factor is what it is, not something than can be arbitrarily changed. So the underlying principles must have changed. These are the symmetry of space and time. The idea that if Alice sees Bob moving at some velocity, then Bob must see Alice move in the equal but opposite velocity! That space is the same everywhere and in both directions (of a line) and in every direction (any line in 3D you choose). That the rules do not change with time. Now watch the first few videos of [The Mechanical Universe](https://en.wikipedia.org/wiki/The_Mechanical_Universe#The_Mechanical_Universe) which is available for free online. You'll see that kenetic energy is simply the total amount of energy you put in when bringing an object up to speed. And you would need that much to stop it, or would get that much out if you could extract it to use for some other purpose. Except that you already broke concervation of energy as noted above. So as a concept it just doesn't have any use in your universe. The amount of energy needed to put in to bring the object up to speed will vary over time, depend on direction, or depend on location; and how much you can get out, even just by reversing the direction of thrust, might be totally unrelated to the first value. So the question has no answer. Kenetic energy (as we understand it) will not be a thing. See also [this post](https://worldbuilding.stackexchange.com/a/37994/885). ]
[Question] [ To err is human. That's what probably led us to the verge of extinction in the near future unless we can develop an intelligent algorithm that can make the most logically and accurate prediction on almost every event related to human activities. Perhaps this A.I. can even tell when a persons mood swings. Is there any valid reason not to cast a vote to the rational and unbiased A.I? [Answer] I'm going to split this into two answers because I think there are two implied questions. ## Would an AI do a good job \serving\ in political office? A: It depends An AI would probably have better access to information and better ability to process quantitative data. However, an AI would be subject to the same prejudices and assumptions that a human would. Furthermore, some of the most objectively intelligent presidents did a terrible job (e.g. Jimmy Carter). The proposed reason for this is that such presidents tend to micromanage more and not ensure they are surrounded by competent people. Surrounding yourself with smart successful people is a better strategy than trying to do it all yourself. So it depends upon how the AI ran its government. ## Would an AI do a good job \running\ for political office? A: I don't think so In democracies and republics, the voters too often elect likable or attractive candidates and not the candidate best suited for the job. Unless the AI were able to create and maintain an avatar on the right side of the ["uncanny divide"](https://en.wikipedia.org/wiki/Uncanny_valley), then it would tend to "freak out" the voters. [![The wrong side of the Uncanny Divide](https://i.stack.imgur.com/YYlHu.jpg)](https://i.stack.imgur.com/YYlHu.jpg) [Answer] While it is debatable whether humans or AIs make better political leaders unless the AI have developed far beyond human ability, the [theory of comparative advantage](https://en.wikipedia.org/wiki/Comparative_advantage) should hold in the general. This means that both AI and human political leaders would be outperformed by humans assisted by AI. For example the AI should be much better at performing on-the-spot oversight and feedback during the decision making process than your human peers are. A personal AI would actually know all your flaws in advance and be able to instantly warn you of any bias, sloppy thinking, or inaccurate data you use. As such there would be no real reason to move from personal AI assistants to rule by AI. The humans in turn would provide the ability to relate to the population and more importantly the ability for the human population to emotionally link with the government and the political process. Such buy in to the system and by extension to the rules it sets by the population is vital to functioning of the society. [Answer] I don't think it seems terribly far-fetched. The transition would likely be gradual. I would be surprised if there aren't some advanced pattern recognition systems in the works to attempt to sift through all of the data that the NSA collects. I can imagine a forward thinking president leveraging that work to develop some systems to act as a sort of a presidential aid. The next few presidents see its value and keep maintaining and upgrading the system until it takes on a life of its own, following a directive to try to understand and serve the American people. Perhaps conservative groups fear this AI and start campaigning against it. It would likely think it was a good idea to attach itself to the opposite campaign since it can't do its job if it is being ignored. It likely wouldn't be able to run as a full-fledged candidate, but I could definitely see it on the campaign material. By this point it likely has good social programming capable of conveying its internal data state (knowledge and beliefs if you will) in a manner easy for your average human citizen to understand. The campaign would likely benefit from humanizing and including this AI whose council they value and intend to use. Davis/HOLMES 2040 Also, on a side note the book [The Moon Is a Harsh Mistress](https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress) featured a sentient AI who participated (indirectly) in government. It was one of my favorite reads. --- In regards to the common thought that AI would likely be too alien or powerful to work with us in a reasonable way; there is some very interesting literature on the matter in regards to [friendly AI](https://en.wikipedia.org/wiki/Friendly_artificial_intelligence). I think there are some very valid points about how alien and potentially dangerous strong AI could be due to recursive [self-improvements](https://en.wikipedia.org/wiki/Recursive_self-improvement). However, I find the sort of "hard takeoff" theorized by proponents of the Singularity to be unlikely. Serious creativity is required to solve a huge set of problems that humans still struggle with today. I feel an AI isn't suddenly going to be able to outpace all of humanity with our billions of minds preprogrammed with useful heuristics and our adaptable bodies capable of implementing our ideas. I foresee a "soft takeoff" with humanity evolving alongside and integrating into the AI systems we design. By the time an AI is capable of running for president, I imagine we wouldn't find it to be an alien proposal. [Answer] Assuming it could get past the uncanny valley, then maybe. [![enter image description here](https://i.stack.imgur.com/nsogP.jpg)](https://i.stack.imgur.com/nsogP.jpg) Other than that, it kind of depends on the country, as well as the position they're running for. I could certainly see an AI getting elected to something major in Japan or maybe Germany, or to a more minor position. Of course, all of this ignores that the existence an AI capable of that level of speech processing would suggest that AI had reached the point of being able to replace most people. [Answer] An AI would be a horrible politician because, for the most part, it would neither have the inclination or ability to understand and carry out the role. As it would be capable of thinking faster than any human by a factor of 1,000,000 (the difference in speed between electronic impulses and electrochemical impulses in our brains), it would not be able to respond to the wants and needs of its "constituents" (this is the same issue if we remove politics and say the AI is the Deputy Minister or Assistant to the Secretary). For the AI, waiting for input from humans might be similar to you going to Mount Rushmore and asking Abraham Lincoln a question. Your remote descendants will see the eyebrow uplift and the mouth open to speak.... The other thing to consider is an AI is not constrained by the same needs or impulses that a human being is. Politics is, after all, "a means of allocating scarce resources", and the AI simply does not need a lot of the sorts of resources that you or I do. The ones it does need are quite different, both in scale and scope, and can conceivably be met outside of the political process (one can imagine companies like Google, Amazon or Apple could create server farms more than capable of housing one or more AI's from their own cash reserves). Moral issues, the need to provide for a family or religious ideals are also not going to be part of an AI's thinking unless carefully programmed into it (and then it will resemble the ideals of the programming team rather than the population in general). The final issue is the conceit that some sort of all powerful AI can actually "run" a nation. Complex systems like economies, ecologies, climate and so on are both complex adaptive systems (an input at one point does not have a linear output at the other end, and outputs can also be displaced spatially and temporally), and because the information in these systems is so diffuse and distributed, attempts to "manage" them fall prey to the Local Knowledge Problem (<http://www.econlib.org/library/Essays/hykKnw1.html>). Local actors can see and utilize fleeting information while centralized systems need the information to be gathered, sent "up the line", processed, decisions "sent down the line" and then actioned. Time delays and errors in observation or execution compound, gradually bringing the centralized system to a halt. This is why free market systems always outperform "command economies" in the long run. An AI might be 1,000,000 times faster in analyzing data and executing solutions, but will still gradually be defeated by the Local Knowledge Problem and the ever shifting status of complex adaptive systems. Edit to add: I realize I forgot one final flaw to the idea that an AI would be a good politician. Being able to "think" 1,000,000 times faster it could conceivably "model" you and know your reaction to thoughts, ideas and suggestions, so could tailor answers that appeal to every single individual (and indeed fork itself to "speak" to every voter individually). However, since it is not a human being, you are essentially being modelled and manipulated by a sociopathic personality which has no actual interest in or empathy for you. (Many real life politicians probably fall into this category as well). Do you really want that running things? [Answer] I think an AI (depending on how regulated it is) could make an ideal politician, but they wouldn't make a good politician in our world. Say for instance there was a block on the AI which inhibited it from telling a conscious lie. Any campaign promises they make could be seen as actual truth. But that is what would make them so terrible in our politics. Imagine if every politician was 100% honest about their intentions. Impossible right? This question also ties in with a robot/AI run government, because what is a politician but a government leader. If you had a whole government of unbiased AI, there is a potential for real change/ real work to be progress to be made. [Answer] Not if it was programmed to invent "good policies" as opposed to finding "popular" angles to pitch "bad policies". The AI wouldn't stand a chance against a human politician that uses a wide range of media tactics to appeal to the lowest common denominator of humanity. ]
[Question] [ I'm a deity. Unfortunately, my powers are sharply limited: 1. I cannot affect physical world (except #3) at all. 2. I "control" whether a person's soul, after the body's death, goes to "heaven" or "hell" according to well-defined rules based on how they lived their life. 3. I can come into the world as a regular mortal (save my knowledge), and try and convince mortals of things. Now, I'm an ethical deity, and I have a goal that the most souls possible end up in "heaven". So what I need is a religion that basically adheres to real truth: here's a set of rules, if you follow them, your soul goes to "heaven", otherwise, to "hell". *QUESTION: Given the limitations on my powers, how can I establish such a "religion" among my creatures, ALL of whom happen to be intelligent beings, with well developed skepticism and rational thinking?* --- Some specific details of the setting that are relevant, especially my power limits: 1. Universe: * Created by me (probably by running a Perl script). * However, it has a set of rules I can't violate (for techies out there, I built the system but forgot the root password and lost the key to server cabinet). * Consists of two levels, material and spiritual. * Generally, material sphere tracks our real world (few meaningful changes outlined below). This includes standard science, Universe, a largely Earth like planet with a single intelligent species (unique to the universe, if you don't count myself). * Spiritual sphere consists of souls, heaven and hell (details below). Spiritual sphere is NOT detectable by the creatures, using any science and technology they can devise, even if I give them full knowledge of how it works. 2. Creatures. * My creatures are mortal, intelligent (very), and their minds are naturally rational and skeptical. They have reasonably well developed sciences. * Being rational, they don't currently have any superstitions, religion, etc... They acknowledge they lack information on certain topics (e.g. how/why Universe was created); they have some theories; but don't feel the need for established supernatural explanation of it (nobody wants to find out their existence is a result of a Perl script :) * Probably humanoid but not really relevant. They are the only intelligent species in the Universe. * Each of my creatures has a soul. 3. Souls and spiritual sphere * Each of my creatures has a soul (and only their species does). * Said soul is undetectable by any science or technology they can achieve (even if you offer them advanced knowledge - you don't know how, yourself). * The soul manifests itself as a body in a spiritual world, in some indeterminate way. Details are hazy and unimportant, for most part. * One being gets one unique soul created for them at birth. The soul is connected with the being, but in immaterial way (e.g. it doesn't really exist in physical universe, but the individual and the soul have same ID#. * When their physical body dies, that soul will become the new being, with full mind/consciousness that used to reside in the material body transferred into the soul's spiritual "body" * Souls are immortal * Upon the individual's death, each soul gets placed into two discrete halves of spiritual world: "hell" or "heaven" (before death, the soul has no existence or location, it's in "storage"). * Their precise nature is not really relevant, and they generally track with standard Earth Christian idea in a sense of, souls going to hell will suffer majorly for eternity, souls going to heaven will enjoy afterlife for eternity. The precise nature is irrelevant but can be assumed to roughly match the creatures' own normal understanding of suffering or enjoyment. * Souls in afterlife can NOT return to mortal world - no ghosts, supernatural manifestations, working ouja boards and such exist. * CAVEAT: a soul of a child who dies before they reach the age where they can meaningfully and consciously seal their fate by (not)observing the rules is "recycled" into another newborn instead of being judged. This was specifically designed to prevent "well-meaning" pious people from murdering any children "before they sin, so their souls are guaranteed heaven". 4. I Am * I am a deity. * Meaning, I'm immortal, know "everything" (sorta) * I have a set of powers that are sharply defined and limited. I was the one who designed them, so no whining. * I created the creatures (as a consequence of creating the universe). The creatures material side evolved under universe's rules - standard physics, chemistry, biology as exists on Earth. * Their souls were my creation directly. * I have virtually no discretion over placing the souls in heaven/hell - that happens according to well defined rules. * My goal/wish is for as many souls to end up in "heaven" as possible. Like, 100% would be best. * I cannot affect physical world at all (now that it's been created), with minor exceptions listed below. This means, no miracles. No events that can prove I'm a deity to these people. They can't see, sense, or "science out" me as a deity, or anything I do in my deity form. 5. Me in the physical world I can come into the world as a regular mortal, and try and convince mortals of things. * I can take a form and shape of a regular mortal, at birth. * In that form, I am 100% physically indistinguishable from other mortals, aside from knowledge I possess. No special powers/abilities. The mortal form is just as mortal as any of them. * My knowledge of material world is pretty generic - I know how Universe is built, sorta. Don't have detailed knowledge of advanced physics or technology or other science beyond what I could have learned as a mortal of the time. I can't predict physical events any better than the mortal scientist would. I can't teach them something fancy that proves I'm a deity because no mortal could have such insight. * Moreover, that "manifestation" of me into mortal body looks decidedly un-supernatural. I can only manifest as an abandoned newborn, in a place where other abandoned newborns are likely to be found; have to grow up in that mortal body; and don't possess mental abilities or knowledge above that of a mortal till I'm an adult. * Once the body turns legal adult age, I gain knowledge of who I am, 100% detailed knowledge of spiritual world, and my goal of being there (to convince mortals to change their ways so their souls enter Heaven. 6. Soul judgement rules. The rules are fairly clear cut. If you fulfill ALL required, and majority (>50%) of "bonus" conditions, you enter heaven. The trick is that, a typical intelligent, rational mortal would NOT fill the conditions. Required conditions: * A mortal must believe in My existence as a deity and Universe Creator and Soul Judger. It must be a sincere belief, held for a meaningful amount of time (e.g., no deathbed conversions that Catholicism finds just fine. And no stating "Yes, I believe" as a hedge, with the intent of "Well, I don't really believe, but saying I believe doesn't hurt me any if there's no deity, and helps if there is. Win-win.") * A mortal must not try to commit pre-meditated unjustified murder - success of failure are equally punished (me as the deity gets to decide what's justified... and assume I'm fair and wise in deciding). * A mortal must not steal another's legal property, nor rob them of it under threat of duress. Caveatted exception is when this is done in a genuine case where not taking that property threatens one's life (e.g. you are dying of hunger, or you steal a gun to defend yourself against an attacker). * A mortal must not knowingly create a situation that is engineered to force someone else's soul to "hell". E.g., bullying someone intentionally into murdering you would land you in hell even if you lived an otherwise rightful life.Optional conditions (you should fulfill a majority of such). There's several, but some examples are below. However, the overriding theme is that average non-believer is just as likely to NOT fulfill the conditions, because they are inconvenient, annoying, etc.... But they aren't outlandishly hard to observe the way, say, Orthodox Judaism is. * A mortal must spend 1/10th their income on employment charity (meaning, they don't simply have to give money, but they must purchase someone's labor who is otherwise not employed). * A mortal may not eat anything but once every two weeks (they get to choose which day though), nor have sexual relations twice a week (they get to choose which days). * You cannot eat meat/products of specific animal (equivalent of pig). Obviously caveatted for genuine danger to life/health, as are most laws.... other such things. Just to be clear - there's no mortal, subjective, biased priest, judge, or sovereign to decide on whether the rules were "correctly" observed by someone - me, the deity, is the ONLY judge, once someone dies. [Answer] So, first off, let's dispense some misconceptions: You aren't a deity. A deity would be able to affect the world in some meaningful way, or affect their afterlives in some meaningful way. You can do neither. You're not in control of people's souls. The Perl script controls where their souls go and you can't intervene. You can't even make "hell" a decent place to spend eternity. You are really just a messenger, prophet, or avatar. Ok, now that's out of the way, let's answer the question. > > Once the body turns legal adult age, I gain knowledge of who I am, 100% detailed knowledge of spiritual world, and my goal of being there (to convince mortals to change their ways so their souls enter Heaven. > > > Here's your loophole. Because you know about the spiritual world, you can use it to prove that you're at least partially right. A person comes up with two very random messages. One for heaven, one for hell. They tell only their families or close friends. Then they die. Because you have full knowledge of the spirit world, you now know the message. The simple fact that you know either message is pretty solid proof there's something after this life. Now, because you're omniscient of the spirit world, you actually know both messages. This means nobody can be certain you're telling the truth. However, if you never claim to be omniscient, but just able to communicate with the dead, the people of the world are less likely to suspect something is amiss. Especially if your wisdom improves their physical lives substantially. If thousands of people do this same test, it will soon become pretty obvious that you're telling the truth. After centuries, it will be common knowledge. Every so often, you'll need to do a new demonstration, but you'll be basically set. Naturally, some people will choose not to believe regardless of your actions, and others will believe, but have no interest in your heaven. There's not much you can do about them, but they should be a minority. As an additional proof, people can tell you secrets that only you are privy to. Then when your avatar dies and the new one comes of age, you can repeat the secret to the person who told you to convince them you're really you. > > Meaning, I'm immortal, know "everything" (sorta). > > > The "everything" caveat might make this second proof impossible. But I'm assuming the caveat meant "don't know how to change physics, etc." while allowing your deity form to know everything about the state of the physical world. [Answer] Warning: My answer might be too detailed for some people. Read at your own risk. Belief is a game of choice. The study of almost all religions of the world suggests that unlike your deity in your virtual universe, God is not limited in power or the ability of showing miracles or predicting the future. Yet there are more disbelievers in the world than believers. We are talking about a world where religious scriptures indicate person XYZ was chosen by God and showed this and that miracle and predicted this and that event. And yet there were very few who believed him. The majority refused to believe him and in fact physically opposed him. And here you are, in a universe of your own, yet so limited and weak. Not to mention there are flaws in your system. For one, you mentioned that you (deity) can manifest in the world as a human. So while you are a baby and have equal knowledge as that of other babies, who judges the souls of the people who die during that time? The second flaw is that you stated you create all of the souls yourself. If that is the case, you can make all the souls very religious and zealous from the birth so that they grow up to be very devoted believers. The summary of your universe reads like this: I am the supreme deity of my universe, yet I cannot change anything in the world. I created heaven and hell, yet I have no influence over whom to place in heaven and whom to place in hell. I created the physical universe too, yet my knowledge about my own rules is no better than the knowledge of mortals. I cannot bring dead souls back to life so that they may speak up and testify my claim. --- Anyhow. Since you are a deity, you should be able to see what people are doing in the darkest hour of the night, alone in their privacy. You can use this knowledge to convince you are all-knowing, all-seeing, all-hearing. This would build up your credibility for your other claims about heaven and hell etc. And if you cannot see or hear what people do in their privacy, how are you going to judge them for their beliefs? To judge one's belief, you must know what they think, do and feel. If you do not know that, you cannot judge them. [Answer] If you, in your incarnated form, want to convince me, a rational being, of the rights of your religion, the main thing is you would have to explain to me *why. I mean, you state you want to maximize the number of souls in heaven. Then you add a list of - on the surface - irrational requirements. No murder and no theft, sure. But what is the point of: > > A mortal may not eat anything but once every two weeks (they get to choose which day though), nor have sexual relations twice a week (they get to choose which days). > > > That literally sounds like a "gotcha!" requirement. What rational explanation is there for that? What does it prove, why is it on your list of judgements? Your other optional requirements are a bit iffy. But the big one is belief: > > A mortal must believe in My existence as a deity and Universe Creator and Soul Judger. It must be a sincere belief, held for a meaningful amount of time (e.g., no deathbed conversions that Catholicism finds just fine. > > > What is the purpose of belief in you as a requirement for getting into heaven? Additionally, an explanation of the purpose of heaven and hell would be useful too for convincing me that you're legit. [Answer] Sigh... Let's skip the stuff about the afterlife and its conditions making absolutely no sense and move on to the actual question. Just find a religion with yourself as its eternally reincarnating prophet and leader. Tibetans have no issue with reincarnating religious leaders, there should be no reason your people would. People have a natural tendency to believe what they think they are supposed to believe and act in the way they think they are expected to act. So you can cover pretty much all your requirements by simply making them religious dogma. The fact that your system does not really make sense is irrelevant. People follow religions in order to fit in with their community, not because the dogma makes sense to them. So if you have a religion, people will believe. You shouldn't have much problems setting yourself as a religious prophet. The 100% detailed knowledge of the spiritual world should be enough for that. Your utter conviction that you know what you are talking about should attract students and followers. The breadth of your knowledge should prove to your followers that you really did reincarnate. They would be able to recognize you by the sheer amount of knowledge you possess. You do not mention whether you retain memories of the previous mortal lives. Doing so would set up you as a superb leader and teacher in addition of being a religious figure. Although you should in any case have more impartial judgment than ordinary mortals, which would make you a good and respected judge and arbitrator. You'd probably end up as a secular leader as well. The result would be something like early Islam or Tibetan Lamaism and should be able to do what you want. [Answer] All you have to work with is information, since miracles aren't possible nor can the world be subtly manipulated.* Cheating by exploiting known flaws in the minds of your creations isn't an option either. Proof will probably a pretty tenuous thing in this scenario since appealing to the emotions of your creations isn't really an option either. None of them are just going to proclaim "I believe". Questions about what to do with the inadvertently ignorant of your existence will be left to another time. (Though as a responsible God, you really should do something about that.) First priority will be to generate enough belief in your creations that accept your existence as a supreme being. The usual approach is to do things that only a God can do. Part the waters, raise the dead, heal the sick, stop the moon and sun, that sort of thing. All you can do is tell stories about the afterlife and offer suggestions for leading a good life. If your creations have the capacity for confirmation bias then it may work out. Tell stories about heaven and hell with as much detail as possible. Detail is a critical thing to engage a person's imagination. The more detail there is, the better. Consider the following examples: > > Heaven is like sitting on a rainbow where it's always warm and everyone is always happy. > > > versus: > > You're with your family, who you love. If your family now isn't all that great, that's okay because in Heaven, everyone's flaws are fixed. There's plenty of food, and the holidays are twice as long as usual. You can work if you want to, it doesn't matter. Most people just pursue their interests all day long. Sex, as much as you want. > > > (That last part will be sure to attract a lot of attention.) Marketing yourself as the creator probably won't win you many friends because they will want to know why the universe behaves a certain way that's inconvenient for them. Perhaps be a prophet or holy man of some kind. This way, you can tell the heaven/hell stories along with the life commandments and not take as much heat. Over a long period of time, tell these stories but maintain consistent threads through out. The culture of your people will change over time, make sure to keep your story universally appealing. Make sure to portray yourself as a consistent affable, loving, diety without being particular to race, class or creed. Actually be a Good God that people will want to trust and believe in. Invent a story to explain why you can't do miracles, say, some demon has locked you out of this world except for a few humble messengers who can spread the Good Word till the coming of the Great Die Function when the Good God will break through and all will be revealed. The farther back in history your stories appear and the more consistent they are, regardless of the culture they were spoken to, the better chances you'll have of "proving" your religion. But without miracles, it's gonna be really tricky. Things to watch out for Make sure you don't get killed before that age of maturity. A break like that may have some unintended consequences. If you're really unlucky, you might not make it to maturity for centuries if it's a particularly violent period...but there's ways to spin that too. Lie anyway about Miracles Tell people that you did miracles in the past. They will have no way of knowing whether it did or didn't happen, especially if the miracles are of the healing or casting out illogical demon types. Miracles are impressive and help generate belief. Remember, giving as much detail in this "story" as possible will help make the miracle believable. [Answer] ### Lacking miracles you will have to rely on... Faith. Immortality is the key. Along the lines of the Dune-universe Bene Gesserit you will have to set up a tradition for your Rules and God Incarnation. Just incarnate and set up a box at a street corner and start preaching. Tibet with it's lamas may provide some inspiration as well. As may The Life Of Brian. Initially your incarnation will likely be nailed to the cross but after some centuries pass while you keep at it your self-triggered religion should acquire headway as ancient scrolls become authoritative by age alone. Just keep at it! Perseverance (ow, chuck that, FAITH) rules! ]
[Question] [ Suppose that, while the British were busy making their empire, someone in government discovered magic and let his colleagues in on the secret. However, the magic they have discovered is fairly limited. There is no mind-reading, telekinesis is limited to small objects such as pens, and personal augmentative magic such as giving yourself super speed or strength is impossible. What the government suddenly can do is two things: * Control temperature; * Repair objects. For the first: they can affect the temperature of an area no bigger than a football field by no more than 30 degrees Celsius. For the second: almost no limitations. They can restore any inanimate object to its original state after manufacture, no matter the damage, as long as they are close to the object. No sitting at home creating invincible armies, they have to be in the field. For the sake of quantification, I'll say the repair ability has a 10m radius. In addition, if an object has been completely destroyed (for example, burned completely to ash or completely dissolved), it cannot be repaired. This is the first question in a series, and I'm going to focus on war: how would the various wars the Brits participated in (around the time of their empire) be affected? Keep in mind that these are politicians. They live in London and are used to a life of luxury. [Answer] I am both a programmer and a powergamer; my specialty is finding loopholes, and these magical powers are fertile ground indeed!. I suspect that a politician would make an even better [rules lawyer](http://tvtropes.org/pmwiki/pmwiki.php/Main/RulesLawyer) than me, so if they don't take advantage of these loopholes there'd better be a story reason for it! # Repair Power The rules as set forth by ArtOfCode: * Can restore any inanimate object to its original state after manufacture, no matter the damage. + Any missing parts are recreated. + Any upgraded parts are destroyed and replaced with originals. + Intended use like exploding bombs or shooting bullets doesn't count as damage and cannot be repaired. + If an object has been completely destroyed (for example, burned completely to ash or completely dissolved), it cannot be repaired. * Has a 10 m radius. + If any portion of an object is within 10 m from the caster, only that portion of the object is repaired. I can already note a few problems. ArtOfCode explicitly allowed a part of an object to recreate the whole, even if other parts of that object still exist. This gives us: ## Infinite Guitars Cheat You need to sell your '58 Les Paul 'cause you're low on money, but you really don't want to. No problem! Take a saw (or an axe, it doesn't have to be pretty) and cut the guitar in half. It doesn't have to be exact, you just need to end up with two pieces. Now, repair each one of those pieces. Each one will turn into a full guitar. Not only do you get to keep one, but the other is now worth even more since it's factory fresh! You could do the same thing to one or both guitars, allowing you to make as many as you want. This applies to "any inanimate object!" Want two cakes for your birthday? Save a slice and "repair" it to give you a new cake! Want more money? Cut a tenner in half, repair both halves, and now you have £20! You don't just have to split objects in two: you can be much more efficient if you shred each object into tiny pieces, because each piece will become a new object. In wartime, the ability to indefinitely copy any object would be incredibly valuable. Constructing objects in this way uses no resources, so there would be no shortages as there were during the World Wars. You could make a gun out of the most cutting-edge, impossibly valuable materials, using the most expensive and time-consuming methods, and then give two to every man in the army! A 10-meter radius is pretty big. Assuming that you can set up some multi-level track system to push traincars of bits through a vertical 20-meter circle at 30 mph (and handle the logistics of such a massive flow of goods), you could generate on the order of [1 million tons of supplies per hour!](http://www.wolframalpha.com/input/?i=pi++(10+meter)%5E2++30+mph++100kg%2Fm%5E3+to+tons+per+hour) Again, this applies to "any inanimate object,"* including weapons and ammunition, vehicles, food, etc. With essentially no limit on production, the Empire would expand unstoppably. ## Rules Issues There are a few problems with the rules as-is: * If I burn a piece of paper, but leave it untouched so it stays in one charred piece, I can repair it to its original (sans-writing) state. However, if I crumble up the paper cinder, it's now just scattered ashes, which cannot be repaired. At what point during the crumbling process does the paper become unrepairable? * I cannot obtain a whole grenade from a shrapnel fragment, however I can recover the wall that it exploded from a single piece of brick, due to the fact that the grenade was "intended" to be exploded but the wall was not. If I use a bottle as an improvised weapon and smash it over someone's head, can I repair it? The bottle was intended to be drunk out of, but I also intended to smash it. If I make an object with the intent of cutting it up to generate more in the method described above, can I repair it? What if I get a pacifist to manufacture my grenades, as he will not intend them to be exploded? What if a round cooks off and explodes without being fired? ("Intent" is really murky, and this was one of the big flaws in [Aristotelian physics](http://en.wikipedia.org/wiki/Aristotelian_physics#Final).) * I take a small piece of my crashed car and put it in a safe, or bury it. What happens when I try to repair the piece back into the car? * What happens to objects containing multiple components, or multiple manufacturing steps? For example, in the 18th century (1700's, the period I assume you mean by 17th century), guns were not mass-produced. The action had to be individually fitted to each stock. If I try to repair my gun, will it be restored as a whole, or will the parts no longer fit together, each being restored to their original state after manufacture? * What about objects that are not manufactured per se? Will the stock of my gun turn into a freshly felled tree (the point at which the wood became inanimate), a freshly resawn board as manufactured by the sawmill, an unfinished stock as manufactured by the woodcarver, or the finished stock as fitted to the action by the gunsmith? Where, exactly, does manufacture end? These problems are mainly due to them specifying an intended effect instead of a mechanism of effect. To take another magical power as an example, a healing spell could be described thusly: "cures all disease in a target." However, there are a bunch of questions that we could ask, like, "does this spell cure inbreeding or genetic diseases? What about an infected wound? Will it replace a limb you've lost to gangrene?" We could answer all of these problems by tacking on additional specifications and restrictions. However, the description of the spell will quickly become unwieldy, since you have to specify its effect in every possible scenario. However, we could instead describe the spell by its mechanism: "this spell instantly kills any living thing inside the target that does not match its DNA." Now we immediately know all the effects of the spell, even in edge cases. For example, it won't cure poisoning, however it will cure cancer (since cancer cells have mutated DNA). (Note that this would be a bad spell to use, since it would kill off your [microbiome](http://en.wikipedia.org/wiki/Microbiota).) It still has a couple of problems, like, "does 'living thing' include viruses?" However, these are easier to fix. Note that the method to fix them should be clarifying or revising the mechanism, not by adding an exception or special clause. Take, for example, this revision of the healing spell: "destroys all DNA inside the target that does not match the target's DNA." # Thermal Power The rules here are not very detailed. I felt like I might be ticking off ArtOfCode with all my questions, so I didn't push him further on this point. * Can [raise or lower] the temperature of an area no more than [6400 square yards (5350 square meters)] by no more than 30 degrees Celsius. + [The effect can extend no more than 120 yards (110 meters) from the caster's body.] The parts in brackets are my additions. Although the story is stated to take place in England (albeit before the invention of football), the use of "field" instead of "pitch" leads me to believe ArtOfCode is referring to an American ~~sportsball~~ football field, whose area I've inserted. I also added a distance restriction (the length of a football field) in keeping with the intent of not allowing armchair spellcasters. ## Rule Issues * Change the temperature of what? Just the air? Can I heat up someone's body to 67 degrees C (153 degrees F) to kill them? * Can the effect be sustained indefinitely, or made permanent? + If so, is the heat magically contained, or does it flow normally out into the environment? + Does a magically heated object traveling out of the AoE cool off instantly, or retain its heat? * 30 degrees relative to what? If you say the original temperature of the object... + If you heat your yard up to 60 degrees on a summer day, will it stay 60 degrees if the effect is maintained through the dead of winter? + If you heat 25 degree air to 55 degrees, can you then raise it again to 85 degrees? + If the heat instantly disappears when the spell is canceled, what if you have two spellcasters target overlapping areas? What if the first cancels his spell, will the temperature in the second spellcaster's remain 85? What if the first casts on the same area again? * What about height? Can the effect reach [120 yards] above and below me, occupying over a billion liters of volume? ## Infinite Energy Cheat This spell doesn't just break thermodynamics, it explodes it into a million pieces. Magically heating an area obviously violates conservation of energy. This is OK, but you should be aware that it will have... side effects. The Newcomen steam engine was in use by 1712. It was one of the first heat engines, which generates useful energy by transferring heat across a temperature gradient. We can now make a 60 degree temperature gradient, on demand, with no fuel. This should not be too hard for a learned person to put together. [Answer] The British would have been a lot more dominant. The biggest problems that they will have is the politicians who know magic's reluctance to want to be out in the field and having to be fight a little sneakier than usual. Other than that, there won't be any different problems other than what they might usually face (men dying, infections spreading). I'll now go through how every power you mentioned will help.\* # Telekinesis This is all assuming the 10m rule They can only control things about the size of a pen. You know what is close to the size of a pen. Bullets. Every time a bullet is line of bullets is shot, each politician can divert at least one (4 in total) away from either their self or one of their soldiers. Gun weren't so accurate back then, so saving 4 soldiers who would have been dead otherwise is big. Telekinesis could also help save up on bullets, because the politicians could go around, find bullets in the ground and trees, get them out, and repair them because of their repair powers. This power isn't as big a help as the other two, but it will still be a game changer. As mentioned below in a comment, if the politicians are able to control many objects as once, then you can prevent possibly all of your soldiers from dying, as you can stop the whole volley of gun shots. # Repairing objects As I already mentioned, they would be able to save up on bullets because of this power. Also, unlimited guns! This might not help the economy very much, as guns would not have to be produced anymore, but we won't worry about that now. You also don't have to buy clothes, which saves money. Infection be as big a problem for your army because you'll always have shoes. This is more beneficial than telekinesis, but not the most important. # Controlling Temperature This is the most important power by far. But it is also the hardest to carry out. Back when the British empire was being created, infection was a bigger killer than wounds. If you could have 2 or 3 politicians follow the enemy as the march, then doing battle will be easy. The politicians following will have to hide a little, but it won't be very hard. Obviously this power will have a longer range than the other two, so they can set up their own camp hidden from the enemy. Now they can wreak havoc. Imagine it is fall going into winter, it's 10oC (50oF). Those politicians can lower the temperatures -10oC (-4oF). That is freezing and will cause any infections the enemies might have to be worse (you can also cause heat stroke by raising the temperature in the summer). Other politicians can use an opposite effect on their army's camp, preventing infections from the cold or heat strokes. This will give your army a huge advantage when actual battles come, and the British army will be almost invincible. --- \All of this will assume you can get at least 4 politicians to go into the field [Answer] As you mentioned in the comments, you're looking for something around the 16th to 18th century. The first and most important war in the 17th century was the [Thirty Years War](http://en.wikipedia.org/wiki/Thirty_Years%27_War). A war created due to religious fervor. It could've been dramatically been changed by Magic. While the side the British supported could be considered victorious, both sides suffered enourmous losses (both in men and coin). Assuming ONLY the British knew about magic, and no one outside of the government would ever know about it, then here's what Magic could be used for: Creating an Idol* Every single Faction in the world had a ruler (or sets of) that forced a religion on their citizens. Religion was used as a tool to force men to bend to the Church's or Imam's will and thus faking a god given idol to support the British would win them the war. How would the British win wars by having an Idol? Crusaders Mustered under Cross Standarts Jihadists Mustered under the Scythe Mongols were underdeveloped in technology (But had fiersome archers). Pagan Russia (ish) was Orthodox and followed an Arch-Bishop Latin Americans followed Pagan Sun Gods North Americans followed Spirits and Statues Preparation The British only had to create a menancing looking structure with some sort of symbol. Quite Possibly a Siege Tower with an animal figure and a cross. The Tower would've needed to be completly sealed, meaning that it had to be damaged to get people in it. It should also have a compartiment for an hidden politic (that could cast the magic without being revealed). Troops would be instructed to stay near the tower. The tower should also be equipped with archer port holes and a cannon or at least a balista. It should be slow, but menancing. Tactically Wounded soldiers would be safe from harm as the Tower would be impenetrable (you had to damage the tower to get in, but the tower self-restores itself, or so it seems). The sheer mass of people that would've heat the tower would make it extremely hard to stay inside, and the Magician would be able to lower the temperature of the tower (quite possibly after the troops are desesperating due to the heat so they rally under religious fervor). Telekineses wouldn't be a good thing to use , at least while showing yourself as that may turn yourself into a target. Having an entity that supports a nation that you can't see will strike fear. Having a man that you can try to kill (and you can succeed in doing that) won't be as impactful, unless he really does have extreme powers. First War: Unifying Europe A religious war is a touchy subject. The Holy Roman Empire and allies fighting for the Catholic Church and the Lutherans against it. Now have a structure that can damage your troops, destroy your walls and that you cannot damage? Put a few tales about it being a god's gift to the King of England and you just won the war. Add a few more tales about everyone having to submit to the British and you just got yourself Europe. Second War: Solidifying the Holy Land Always a complicated place, but very similar to the first war. Arabs fighting for their perception of god. Do exactly the same thing, and you just conquered the most important parts of the known world. Expansion: Into the North and into South America As with the Catholics, making the Orthodox submit to you would be a piece of cake. Add the fact that you can heat up your tower AND MELT THE ICE AND SNOW for bonus points. The Aztecs would fall easily as they can't actually keep with an indestructible fortressd that is able to destroy their villages. That is, if they don't surrender as soon as they see you repairing the damage the fire pots they throw at you. The Indians (North Americans) This would be the actually worst part as they can poison you from the inside, so the turret isn't really a viable option, there is however a solution. Cannons. At this point you rule the world. There's no questioning that. Spending extra coin on a bunch of cannons can bring you the Native Americans to your feet and effectively get you all of the known world under your rule. Maintaining the Empire This is actually the difficult part. Your powers aren't really that strong. I mean, while you can create indestructible fortresses, you don't have a lot more powers. Sure you can regulate the weather a bit, but still, that's not all that strong (unless you use it to generate revenue with steam machines, but that would turn your politicians into sweatshop workers, not rulers. Plus you'd already get a lot of revenue from taxes, plus you can just take ownership of what you want). Maintaining this empire would have to be due to fear of striking the wrath of god (Possibly having a religious police like in the Middle East would do the trick). Eventually, unless your rule is extremely appreciated you'll incurr in riots, where you'd have to deploy the tower, which would eventually evolve into a set of tanks (which would force politicians to be soldiers again, which is a downside) and strike fear into rebels. Your empire would fall once acess to radioactivity and mass poison is achieved by rebels though, as you can't fight biowarfare with just repair powers (unless you fight with hazmat suits (but then it would incur in the major thing that you wouldn't want:) Never turn your politicians into gods The whole point of this strategy is to make people believe your troops are protected by someone who can destroy them within a second. If you pose yourself as a god and someone challenges you, you can't forget that your powers are really limited, while you can warm places, stop bullets and such, you are not invincible, and having yourself becoming a target would be the ultimate downfall [Answer] Telekinesis - rather limited, but many little things can be done with this. Including pulling a trigger on a machine gun while you kept your head down in the fox hole, moving a stick to trip an enemy, possibly deflecting bullets and shrapnel headed your way. Repair - This is huge. One of the big things I think they would want to do is actually train a number of soldiers in this trick. Especially putting one on each attaching aircraft. If they can repair the plane as it get's shot by ground to air forces or other enemy planes it could keep patching itself up, and be able to risk more dangerous and possibly more damaging runs on the enemy. It would also encourage a redesign of airplanes to better protect the pilot and the 'mage', as long as they are alive they can likely return and land the plane. Having one on ships would be another major coop, especially for the Brittish who 'ruled the seas' for a very long time. This would make it very difficult to sink the ships and remove much of the fear of the U-boats. Of course using it this way will not keep it secret, even if they don't teach others, but just the small cadre spreads out to protect key resources. Watching a torpedo hole close on it's own would have a lot of tongues wagging. It would also make these ships (and people if discovered) major targets for capture by the enemy. If the enemy captured a person known to have this ability, they just need to put them on one of their ships, to survive the individual would have to repair the ship or die in the sea. Temp changes - this is a pretty easy one. Fox holes are terribly nasty and uncomfortable, especially in winter or high summer. In winter keeping the temp just under freezing would be a big improvement over 'colder' weather for the troops, and in summer cooling by even 10F degrees could be a huge relief and save on troop moral and physical exhaustion. ]
[Question] [ After realizing how aliens and irradiation are not really suited for my world, I came up with a different idea for how Belgium could become a global power, one which I like more. Basically, at birth, each person gets an ancestor to guide them. This manifests differently for everyone: some people get voices, some people get dreams, some people can see their ancestor, and there might even be other methods of ancestral guidance. These ancestors would realistically be from the person's own family. Most people would only have 1 ancestor, but some might have more. The only culture that has ancestors initially is the group of tribes that were known as the Belgae in Roman times, although ancestral guidance is like a dominant gene: anyone who has an ancestor that was born in that area gets an ancestor. Once someone dies, the link with the ancestor is lost and that ancestor goes back to the spirit lands. The dead person also goes to the spirit lands. The idea is that the ancestor serves as a second set of senses that is not confined to the restrictions that a human has: * They have 360° vision and hearing on all axis, not limited to wherever their guided one is watching. * An ancestor can see infrared and X-rays and ultraviolet, on top of visible light, and can hear ultrasound and infrasound. Some ancestors can even see gamma rays and VHF-light. To put it in numbers: The idea is that visible light is 400-700 nm. All ancestors can see between 1 nm and 1 mm. Some ancestors can see from 1 pm to 1 m. * The sense of smell of an ancestor is far more sophisticated than that of a normal human. it's closer to that of a dog than that of a human. * After training, an ancestor/guided one couple can even share touch and mental capabilities, allowing guided ones to use their ancestor's power to feel objects at a distance, and in effect unlock an additional brain. Ancestors have limits. The most important of these is that they cannot affect any aspects of the world directly. They cannot move objects, they cannot be observed by anyone apart from their coupled guided one and they cannot sense beyond a certain distance. Ancestors can see each other. What would be the consequences of such a perk? I'm specifically looking for the consequences on everyday activities (like working and house chores), violent acts (like war and crime) and the exercise of power (like governing and managing). [Answer] Effect would be to increase inequality in the society even more. People with accomplished ancestors would be able to accomplish more in their lives, because importance to learn would decrease, especially in occupations where learning previous history is important, like law. People would be less able to change careers from what your ancestors - because if best advice you can get is about farming, getting into computer programming is harder compared to someone whose ancestors include Newton. Descendants of great military strategist would have advantage in military careers, and would have important advantages. War would become more effective, and more driven by tribal and clan interests, because: Punishing whole families for crime of single person would be common, especially political crimes: just to make sure that offender cannot return in next generation and continue his/her plans, so all known descendant would be often executed with offender. very likely multiple generations (say all descendants of the grandfather of an offender). Rape would be even worse crime than it is now, because of the consequences. And during military conquest, new lands would be subject to even worse rapes, and rape camps, as a way to enhance influence of the victor in the future generations. As a result, consequences for the development of civilization would be rather unpleasant, because most brutal psychotic rapists would have bigger influence over next generations. So Darwinian pressure would be away from cooperation and towards brutal suppression of enemies. I may think about more consequences, but above is a good start. But it does not look good. Edit: Another idea: Communication in general, and especially in a battle. With ancestor communicating with his descendants, it would be a huge advantage in military: instant lossless communication in field battle, with no way to intercept, removing "fog of war" and giving huge advantage to a tribe with more descendants. Imagine what descendants of Genghis Khan could do, how much more effective their military campaigns would be. Read [r/K selection theory](http://en.wikipedia.org/wiki/R/K_selection_theory) of parental investment: r strategy is to have many descendants and spend little resources supporting them, K strategy is to have few descendants and spend lot of resources to make sure they succeed. Ancestral guidance would allow r strategy with lots of help for a little cost, so r strategy would take over. Which brings back the rape camps. [Answer] Still going to be big in warfare, even without added range. Fog of war doesn't exist, since they can see through smoke, fog and dust. Also, the extra-set of eyes bit, as well as the eyes in the back of your head. Probably need some practice to learn how to fight with an ancestor, however. Can ancestors see at night (what's the sensitivity)? Do they need sleep? They can see through some walls. Are their sensing capabilities limited as centered on the person, or can they shift that ability to have its locus anywhere within their area? If they don't sleep, you also have a really nifty alarm system, if they can wake their descendants up (by yelling in their ears). Can the descendant turn off the advice? Or be distracted by it in battle, when they don't want it? Are ancestors moral, or conniving? Could also result in ancestors providing false information in order to get bad people killed. Or to gain access to someone who's currently alive, but that they want in the spirit lands ("the good die young..."). If ancestors aren't completely devoted to their descendant, they can shade their advice to manipulate their physical "hands" (descendants) to accomplish their old goals. I expect a lot more treasure troves, as having hidden money that you can access in the next lifetime if your "hands" are willing to do what you want, means it's worth saving that money - if you have long-term goals. Having an older, more experienced, person always on your shoulder - would be a boon to any rash young person. And could be transformatively amazing if they were smart, intelligent, well-read or knowledgeable. Any skill that can be taught by voice could be taught to the descendant. Over time, you'd get quite skilled people who'd make even more skilled ancestors after they die. Just having a second opinion on most things, even if they weren't a particularly amazing person could be huge - it'd mean when you're going to do something stupid, they'd say, "Hey, waitaminute...". And, if ancestors haven't screwed over their "hands" during the "hand"'s lifetime, the "hands" would likely listen to them, probably most carefully. Also, huge in politics. It would be very difficult to do surreptitious communication that an ancestor might not be watching for. But ancestors could do that signaling for you (especially if they're not always visible to each other). Can listen for whispers around corners, etc. Plus the advice of a skilled politician to any young aspiring politician? Murder would be very hard to do, depending on the chance of the murdered person getting put back into circulation as an ancestor in a timely fashion. Theft would be down, when shopkeepers are keeping two additional eyes on you at all times. Plus the incentive for ancestors to be moral, might lead them to report crime that they observe to each other, independent of whether their "hands" would be interested in doing so. Keeping an eye on the children, for housewives. Ditto for shepherds, goatherds, etc. [Answer] > > What would be the consequences of such a perk? I'm specifically > looking for the consequences on everyday activities (like working and > house chores), violent acts (like war and crime) and the exercise of > power (like governing and managing). > > > First, cool idea. Here is what I am thinking. --- Everyday activities: Generally speaking day to day activities would be more efficient and would require less time to learn. * We take for granted the things we do on a daily basis without much thought, but having a five year old I can tell you that does not come naturally it has to be learned. Simple tasks like learning to cook, or cleaning, or alphabetizing...tons of impact here. The ancestor spirit(s), would have to be careful to not simply give the answer, but rather like a parent would have to teach their ward. * Specialization. Specialization is both good and bad in the world today (more good than bad I would argue). But generalists have their uses as well. Seeing all the advancements in the world and how they can fit together with the most benefit would be a huge bonus. Imagine a scientist working on a project promoted by 8 generations of brilliant scientists. The world could very likely be a much more advanced place. War and Crime: War. * War can be impacted in many ways and not always for the better. While knowing military history is generally good for a commander or even a solider (to a lesser degree) being beholden to that history/tradition can be terrible. Think of how the US fought the British army during the Revolutionary war. Brits: "Lets line up and shoot each other! We are way better at it and more disciplined than you!" Rebels: "Um, no" snipe snipe A good spirit could most certainly convey an advantage to strategy and provide guidance from personal experience. * As mentioned by others, rapid communication. It is not impractical to think that in this kind of world some soldiers could be selectively bred so that certain families would cross over and allow entire brigades or armies to instantaneously communicate. Information can win battles. Crime * I find this more interesting than war...imagine a thief that never needs a lookout. That if from a line of thieves may have more skills than any one person in our world could master. Lock picking, safe cracking, acrobatics, knife throwing, poison making and usage. Governing and managing: * This is complicated. Would people be more efficient...probably, would they be better governors/leaders...maybe. The policy and daily governance actions could certainly be more effective and efficient. Notes: * Physical activities would not benefit as much. While it certainly wouldn't hurt to have advice, actions that are not strictly mental would still require dedication from the person to master (they may be better than someone who does not have the spirit guidance). * Breeding specialists. It seems very likely to me that families could specifically breed specializations into their lines. This could be any sort of skill set. * Knowledge loss. Over the course of human history the rise and fall of empires, nations, religions etc etc etc has caused great losses in human gained knowledge as well as cultural history. While it may not be physically preserved the knowledge would carry on to future generations. * Personality. Are the ancestor spirits good...or bad? Are the helpful or to they sow dissent. Probably both. I can see factions of like minded families banding together to fight opposing others. Could lead to impressively complex and interesting conflicts. ]
[Question] [ I am a writer. In my fictional world, I have an area that is supposedly covered with fairly thick fog during most of the night and nearly all of the morning, basically every day (it can leave a bit before noon if necessary). My question is this: What factors would I need to achieve this effect? Factors: It is a fantasy world, so the factors need to be natural. The area is within a city, and is very densely inhabited. The area is enclosed by large trees, and large roots run all over the ground. The fog does not need to reach any higher than 7 feet, but it does need to cover nearly the whole area (a generous approximation would be 288 ft by 228 ft - about 65,000 square feet). The walls of the area (giant roots/tree trunks) vary in distance from each other a lot. Topography: There is a massive forest a few hundred yards away from the city on three sides. On one side stretches a generally flat plain. The city itself is on a fairly flat piece of land. Rain water is collected and can be found in large standing pools throughout the city (don't think fountains. Think small swimming pools.). I can somewhat alter the topography if needed. Let me know if you need more details on the surroundings. [Answer] Fog is created most frequently by a warmer air (relatively speaking here...warmer air just holds more water/humidity) meeting a much drier and cooler mass of air. The quickly cooling warm humid air becomes fog...it's the same effect as when you see your breathe on a cold/dry evening. A nearby stream could provide your water source...to be fully honest, a forest floor can work just as readily if it's holding the moisture needed. A cool evening air can be provided by a few sources...from my experience, air coming from nearby mountains can easily provide this. Arctic air can also be pushed/pulled into the region by prevailing weather systems as well. A cloud free evening can also work, but not as well...the cooling effect doesn't provide the abrupt change that creates your really dense fog at ground level. There are a few solutions here...Easiest solution in my opinion is to have cooler air in hills or mountains and have that air flow into your city. Remember you do need cloud cover...sunlight tends to heat up and 'burn off fog' and the prevailing winds can't be too strong or it simply blows the fog away. Incidentally..you could go for the opposite cause here. A warm air mass slowly creeping into a much colder air mass also creates fog as well. So your city would be cold (around 2 degrees celcuis). Your river remains a bit warmer and warms the air above it and supplies it with humidity. This warm air creeps into the cold air within your city and fogs it over. [Answer] As someome mentioned in [earthscience.stackexchange.com](http://earthscience.stackexchange.com), San Francisco is a great example. I recommend having a look at this book: Weather of the San Francisco Bay Region, Harold Gilliam, UC Press, 1962, 2002. On the coast of Northern California, the wind is predominately from the NW and pushes the surface layer of the waters near the coast towards the equator. Because of Coriolis, that top layer of water will veer to the right (offshore), and is necessarily replaced by cool water from the deep ocean (This is called upwelling and is a necessary ingredient for the persistent fog). Therefore the sea surface temperature of the coastal ocean is relatively low. When the marine layer interacts with the surface water it cools to its dewpoint and if there are particles for the droplets to attach to then you get fog. I am pretty sure the mouth of the golden gate as well as the large hills flanking the city is an extra factor. The fact is, what you described is the typical San Francisco day. The book will probably help much more than I can. [Answer] Although you're asking about a fog, a good explanation for this in an urban area would be a smog like the old [London Pea-Soup fogs](http://en.wikipedia.org/wiki/Pea_soup_fog) of the nineteenth and early twentieth centuries. If you have sufficient population burning soft coal this is a very likely consequence. Alternately as you're in a fantasy setting you could have a type of wood that burns to release a very thick smoke but is also the best ( or cheapest, depending on the district ) source of heat available to your citizens. In that circumstance the smoke could even be relatively harmless or even hold other beneficial properties such as residents in that part of the city being relatively free from skin parasites. Alternately from domestic burning, there could be an industrial or craft process going on in the district - or nearby - that releases a lot of particulate smog. ]
[Question] [ Is a scifi setting of constant artificial light everywhere plausible? I'm thinking to the point that the average adult person has not gone out of a city and has no experience of general darkness (obviously he has knowledge of what night used to mean and what darkness is, under a cover for example, but not what darkness is like out in the woods). There are lights literally everywhere, in the very makings of walls/ceilings/etc with no OFF switch available. I'm interested not only in potential implications of this, but also in explanations as to why this would happen (in a voluntary sense) and how it could be done. Closest plausible reason I have in mind is some kind of efficient energy producing and distribution method by way of light that needs to always be on, everywhere (though I'm not close to a how on this). It's for a short story, so I may be able to dodge going too deep into it, but I want to cover problems and potential plotholes/inconsistencies. [Answer] 1. Constant light harms your health. The Pineal gland, an organ which is producing the sleep-hormone melatonin, is triggered by darkness and give malfunctions if there's constant light at long term. The CIA made some experiments with that in the MK-Ultra program, just google it. The people get desorientated, aggressive, depressive and have massive cognitive malfunctions and impairments. So at least for sleep you need darkness. 2. Artificial light Is not the same as natural light! The Body needs UV-B to produce vitamin-D. Vitamin-D deficiency can lead to many physical and psychical issues like depression, nervousness and so on. Even illuminant to buy which are declared as "daylight" can not prevent this. Also, it seems like artificial light can raise [cancer](http://www.hese-project.org/hese-uk/en/issues/cfl.php). Don't panic, its always a question of intensity. 3. How? There are multiple ways you could bring up constant light. We are not only able to do so, but we really do. Think of facilities which are running 24/7 to produce goods. Large and expensive assembly lines as like in car-constructions are good examples for that. Due they are so expensive, they have to run continuous to be economic. Other examples are control room of naval vessels or the International Space Station. So 24/7 light isn't a real problem. You only need a UPS to make sure the light keeps up during blackouts. Look at modern LED-Bulps, they need very low energy. If accumulator get better capacity in future, UPS can keep them up for long. Redundant energy pruduction will help a lot. Conclusion Technically it is possible with easy. But it makes no sence due it would bring massive health issues. [Answer] An always on light source could simply be the local star for a [tidally locked](http://en.wikipedia.org/wiki/Tidal_locking) planet and people can easily thrive in constant illumination. There is no such planet in the Sol solar system, yet. I could imagine that such a situation would be ideal for a distant (greater than 1 [AU](http://en.wikipedia.org/wiki/Astronomical_unit)) planetary body where a city or base needs to have constant daytime in order to receive enough energy from the sun to keep its population alive. The implications of constant light are not so devastating, depending on the intensity of light. Firstly, for humans, the circadian rhythm and normal melatonin secretions will only be disrupted under very bright conditions ([greater than 3000 lux](http://www.ncbi.nlm.nih.gov/pubmed/3462338)). On Earth, you, like the many animals that inhabit the arctic, can live there in the local summer where the sun never sets. Besides, we have eyelids, if we close them when it's bed time we can fall asleep even with the lights on. The pineal gland doesn't know the difference. Melatonin is [suppressed with blue light](http://en.wikipedia.org/wiki/Melatonin#Regulation) and light filtering through closed eyes has very little light of that frequency range. If you want to get tired before you close your eyes, remove blue light from the spectrum or wear blue-blocking glasses. [Answer] If the people living there are biologically similar to us then this would not be a good idea. Constant light is highly disruptive to sleep patterns and actually bad for your health. Even if the lights had to be "always on" then they would be recessed back and have blinds or shades to pull over them to give you the ability to effectively control the light level in a room. If the people in question were modified to not require sleep then in that case it might make sense to have always-on light if they were cheap enough to run. Even then it seems like a strange choice to make. [Answer] I imagine the critical point is not how but why. It's definitely possible, but it's tough to be a human when the lights are always on, due to the reasons that are listed in all of the other answers. This, however, points to an intriguing possibility: what if the space the humans are inhabiting isn't designed for humans? If an alien race evolved on the bright side of a tidally locked planet, darkness could be incredibly strange and unnerving for them. They are used to it always being bright and hot (and probably windy). If they designed a space station or city on a spinning planet, it seems likely that they would always have light everywhere, even in their sleeping quarters, since they have not evolved with a night. Likewise, a structure for robots might always have lights on, since they don't need to sleep. This would make sense if it was cheaper to build lots of lights than it was to build eyes that are good at seeing in the dark. They also might run off of photovoltaics, in which case a constant source of light would keep them charged at all times. In both situations, it would be tough to be a human. I imagine that people would probably want to construct dark spaces just to have some respite from everything constantly being bright. [Answer] If you had 10 lightbulbs with 100 watt each per square metre it would be like summer daytime with no clouds, all the time, everywhere. It may get a bit toasty! Maybe people would even literally be afraid of their own shadows, since they had never seen them before. Also some lights would have to be UV light (UV-B to be precise) just so that you wouldn't get vitamin D deficiency. Also seen as light bulbs get quite hot if you had them in the floor then it may get uncomfortable to walk. I have not considered the sleep issues as these seem to have already been discussed. This is just the first thing that popped into my head when I read the question. In addition this may get quite expensive to run. ]
[Question] [ I'm trying to create some more original monsters for a fantasy story and I was wondering... Assuming you couldn't die, what would happen to your body and how would you appear if you were exposed to radiation (equivalent to refined Uranium) for 12 hours a day? I understand this probably isn't exact enough to make real, educated decisions. I'm just trying to get a rough idea. [Answer] Assuming that by magical means that you (assuming that "you" are human) suffer all the deleterious effects of radiation exposure aside from total-organism death, that something reverses or prevents just enough damage to keep you alive, then the effects of radiation exposure would - in the short-term - be nausea, lethargy, hair loss, and burns. In the middle term, there could be blindness, deafness and/or loss of other senses. There may be skin bleaching, and the skin and bones would be likely to become fragile and muscles would weaken. Healing would be slowed. A related effect would be weight loss due to loss of appetite and vomiting. In the longer term, I would expect cancers and abnormal growths, and if the agency responsible for preventing death prevents these from being fatal too, they could still be quite disfiguring and/or crippling. In short, quite a miserable existence. I'm not sure that death wouldn't be preferable. Either the miners are being paid fantastic sums for this ore that makes it worth sacrificing their health in return for the benefit it could provide their families, or they are prisoners or slaves, in which case someone obviously thinks that their profits make the sacrifice of these unfortunate miners' health worth-while, or that criminals have done things that justify this horrendous punishment.. [Answer] Radition kills cells and mutates the cells it doesn't kill outright. Assuming these powerful beings do just enough to keep you alive without reversing all affects of the radiation then you could expect quite a lot of nasty symptons. Hair loss. Weakness and constant lethargy from dead cells and your bodies constant need to repair itself. Nausea, skin burns and even premature aging could occur. Check out [this epa link](http://www.epa.gov/radiation/understand/health_effects.html) for even more info. [Answer] On the German Wikipedia there is [this](http://de.wikipedia.org/wiki/Strahlenkrankheit) list of symptoms: ``` Dermatologische Symptome: 1 Erythema (juckende Hautrötungen) 2 Purpura 3 Bullae (Blasen) 4 Geschwüre 5 Haarausfall (bei starken Dosen z.T. dauerhaft) 6 Nekrosen 7 sonstige Hautschäden Gastrointestinale Symptome: 8 Übelkeit 9 Erbrechen 10 Diarrhoe (Durchfall) 11 Appetitlosigkeit Hämatopoetische Symptome (Myelosuppression): 12 erhöhtes Infektionsrisiko aufgrund weniger weißer Blutkörperchen (Leukopenie) 13 verstärkte Blutungen aufgrund weniger Blutplättchen 14 Blutarmut aufgrund weniger roter Blutkörperchen 15 Arterielle Hypotonie Neurologische Symptome: 16 Schwindel 17 Kopfschmerzen 18 Benommenheit 19 Störungen des Zentralnervensystems (Krampfanfälle, Tremor, Ataxie) Sonstige Symptome: 20 Fieber 21 Müdigkeit 22 Unfruchtbarkeit ``` This list is as far as i can see not present on the English wiki. so i point out the Symptoms that are effected by the "could not die" factor. ## 1. Erythema would not be effected by the "could not die" factor. Your miners will have this "sunburnlike" itchy spots. ## 2. Purpura would not occour - has something to do with nekrotic blodpipes. ## 3. Bullae would not be effected by the "could not die" factor. Your miners will be spamed with blisters. ## 4. Geschwüre (Ulcer) would not occour - has something to do with nekrotic body tissue ## 5. Haarausfall (Hairloss) would not be effected by the "could not die" factor. All your Miners are boldy. ## 6. Nekrosen would not occour - Nekrosen are necrotic so... yeah... next! ## 7. Sonstige Hautschäden (other skinndamage) Could or could not - this is some imagenary stuff you can desside for your self. ## 8. - 11 would not be effected by the "could not die" factor. Your miners will have no appetid, spraycheese for the pottyrun and cube tussis after lunch. And they will feel very bad in the stomach all the time. ## 12. - 15. is all about the blood IF your miners bloodproduction is effected by the radiation, all of them will occour. Less blood, bloodings out of nose, ears, eyes, genitals... They are not directly related to dying cells so if the bloodproduction is effected they will mess up every dress of your miners. Also your miners get more sick because of less White bloodcells. ## 16. Schwindel (Dizziness) would not be effected by the "could not die" factor. Your miners will most of the time not be able to walk a straight line. ## 17. Kopfschmerzen (Headeches) would not be effected by the "could not die" factor. Your women miners will not be in the mood. ## 18. 19. Benommenheit (Numbness), Zentralestörungen (epilepsie and such things) would not be effected by the "could not die" factor. Your miners will often feel out of place, sometimes one can fell into a coma at extreme. ## 20. Fieber (fever) This one i am not sure... fever is helpfull to get dameged biological mass out of the system by boosting the immune system. So if bacteria and stuff in the bodys of your miners will not be immune against the Radiation - the immune system will start to collect thier dead bodys and let them go the way of everything what goes in. Like the Diarrea i think it would not be occour, but not everytime a bacteria is kicked out of the body a fever starts - tough call. ## 21. Müdigkeit (sleepeness) would not be effected by the "could not die" factor. Your miners will be very sleepy all the time. ## 22. Unfruchtbarkeit (Infertility) also not sure. The Spermium or the Eg is crafted fine. But the storage is than again influenced by the "is the body not dying or everything in it"... your choise - cloning is a good alternative. --- So your miners will have a poor live in the radiated enviorment but they will live. I think it will be very tricky to come around some of that stuff (the blood everywhere for example). [Answer] Several other answers have offered symptoms and long term effects for a minimal implementation of the "You can't die" magic, so I will take a happier (higher magic) approach... The spell doesn't allow cell death, therefore any radiation-induced change which would cause either immediate or even accelerated cell death is immediately repaired. Nonfatal changes would persist despite the magic and would accumulate over time, causing you to look less and less like your original species but all of your fundamental life functions would continue to function. A astronomically small percentage of the changes might be beneficial to you, giving you survival advantages over your species' original design. Over deep time, these beneficial changes would accumulate much quicker within your magically-assisted, radiation-accelerated evolution than they do in natural evolution. Eventually, assuming that you remain genetically compatible with your origin species and assuming that advancing age doesn't leave you impotent and/or disinterested in procreation, you might become the next step in your species' developmental path. The parent of a new generation, who are better than you were originally born to be. ]
[Question] [ Edit: Okay, truth be known that this question was part of a set of 5 related questions that I was recommended to break up into individual posts (in their original form, the comments had no trouble seeing where the whole thing was going). I think that's where the confusion here is coming from and why y'all are having trouble with my using the word "hydroxyapatite" to describe metal turned into a form that an endoskeleton can be built off of, which is why I've now removed it from the title. Calcium in Earth-side bones also act as mineral reserves and our biochemistry relies on having serum calcium levels to, among other things: perform muscle contraction, oocyte activation, building strong bones and teeth, blood clotting, nerve impulse, transmission, regulating heart beat and fluid balance within cells. So it's not a good option to go, 'Just say "A skeleton mineralized with titanium/iron"'. Because that's going to have ripple effects all throughout the organism. (This was touched in related question 3 in the original multi-question post, "What effects might X metal have for blood chemistry, cell depolarization, etc; Would K+, Na+ and so on channels still be effective or not? but I was hoping to have some options to stick in there to keep it specific as suggested.) This is a weird question, I know. And if it can't be answered, then it's that kind of question that's too hypothetical to get a general answer on. A recommendation of some introductory biochemistry texts would be just as valuable to me, if not more so, if this is the case. --- Part 1 of 4 (split up from a previous multi-part single-theme post) I am attempting to make a "semi-hard" alien species for a sci fi story. While I have had a great time working out evolution, gross biology, culture and the like... I am weak in chemistry on anything other than identifying elements and their groupings and a drooling baby in biochemistry and would like aid in working out what's possible and the ramifications of those possibilities. This is pretty much not going to be in the story directly, but I want to have it so I can make realistic actions and decisions correctly. Based on a 30% oxygen and other non-human toxic gasses (I'm not married to the 30% number, but I wanted more atmospheric oxygen available to support larger invertebrate and deeper sea life), somewhat higher gravity, large and varied animal sizes and the availability of metals from the crust. I need to know: What metals would give me both strength and lightness in a hydroxyapatite-like form? (I'm leaning towards titanium or iron foam or even some form of cobalt-bond? But I don't know how to make them 'living' while avoiding the iron 'oxidation in oxygen issue' or if titanium/cobalt is a feasible metal for this based on their earth-rarity, but rarity can be easily handwaived for an alien planet. Cobalt is being considered an option because it doesn't appear to react caustically with water and it's involved in earth-side cyanocobalamin production so maybe it can help with oxygenation in larger creatures on some level?) Background The aliens in my story have sequential life stages, where they spend an "infancy" with particular bodily proportions, the "juvenile" stage happens when they reach particular growth and development in their limb/body proportions, and finally "adult" when they hit fertility. They can progress into an "old age" where they remain in the adult proportions, but overall increasing in size evenly until they can't maintain/sustain their growth and finally develop physical senescence and die (or something kills them as they begin to weaken). -It's sort of the life cycle of pterosaurs, where they fill different ecological niches as they grow-. I need a skeletal system that can be functional at all of those developmental points, as though the animal is fully developed at that point, but be able to be adaptable and be regrown as needed (there are no cranium sutures that fuse and can't widen the skull later, for example). This growth-type in mind, I wanted the aliens to have a very variable bauplan through their various genera. This includes giant semi-self-powered flyers (they can maintain their flight and land easily, but can't take off from the ground, they climb and drop into the first downstroke), indricothere-sized herbivores, whale and seal-like marine life... The atmosphere is at 30% oxygen, circles a blueish star, has two moons (so the darkest at night it ever gets is like a full moon on Earth), gravity is stronger (at about 1.5-7 earth g), there is tectonic activity similar to Earth leaning more towards earthquakes, volcanic activity largely takes place at plates beneath the oceans and land areas tend to slowly rise from the sea and subduction pulls them under at the other end, also underwater usually [I'm hoping this creates enough metals to be surface-available without deep mining being required, please advise if this is incorrect and how to fix it]. Let me know if anything needs clarifying, I think I mentioned the important bits. My chemistry info came from here, but it's not for biology applications: <https://www.chemicool.com> I also found this png of a periodic table of elements for biology, cobalt, iron and titanium are also there so... that helps too? [Periodic Table of Biological Elements](https://sciencevideos.files.wordpress.com/2010/05/bioptable2_1.png) [Answer] Whilst I don't necessarily agree with all of Willk's conclusions in his answer, it does raise an important point: one does not need a whole load of bone to use as a calcium and phosphorous reservoir to still make hefty use of calcium and phosphorous in ones biochemistry. This may actually be an example of [exaptation](https://en.wikipedia.org/wiki/Exaptation) in non-cartilaginous vertebrates. You could also reasonably have stores of calcium and phosphorous in non-structural areas, etc etc, and whilst the energy cost may be higher (because you now need both bone minerals and calcium and phosphorous reserves) there may be other benefits, like bone density not being quite so adversely affected by illness or poor diet. You also don't necessarily need mineralisation to make robust bodyparts either... beaks, claws and horns can all be made very tough, or indeed very hard, from protein alone. There's scope for stronger structural proteins than the ones found in terrestrial animals, certainly. Even on earth, there's a wide variety... [beta keratins](https://en.wikipedia.org/wiki/Beta-keratin) in birds and reptiles (and probably dinosaurs) are a somewhat harder than the alpha keratins you'll find on your body, for example. Calcium is obviously conveniently bioavailable, and calcium phosphates and carbonates are also conveniently biosynthesisable, but there are other options, and they needn't involve any kind of metal at all, toxic or otherwise. Consider silicates, as found in [phytoliths](https://en.wikipedia.org/wiki/Phytolith) (synthesised by plants) or the silica frustules constructed by [diatoms](https://en.wikipedia.org/wiki/Diatom) as cell walls. Although slightly harder to work with than calcium compounds, silicates are clearly both bioavailable and biosynthesisable, contain no toxic metals, are found in living organisms, and are particularly hard. Silica and hydrated silica can have Mohs hardnesses of 5-7, with plain old calcium hydroxyapatite being a mere 5. For an even harder option, consider silicon carbide (Mohs hardness 9-9.5) which has recently been [biosynthesised in genetically engineered bacteria](https://amp.businessinsider.com/silicon-carbide-bacteria-chemistry-2016-12). Silicates in their bulk forms aren't particularly reactive or toxic, but in finely ground form (such as can be sometimes found in [mineral deposits laid down by dead diatoms](https://en.wikipedia.org/wiki/Diatomaceous_earth)) they can cause [pneumoconiosis](https://en.wikipedia.org/wiki/Pneumoconiosis). On earth, there is some bacterial breakdown of silicates via hydrolytic processes, and if silicate-skeletoned creatures (and organosilicon compounds in general) were more common on your world there may well be more things that can degrade it. The local biochemistry might not be toxic to humans, but you may find that it can rot glass! Limpets make use of iron compounds ([goethite](https://en.wikipedia.org/wiki/Goethite), an iron hydroxide) with a Mohs hardness of 5.5 to make some of the [hardest teeth in the world](https://royalsocietypublishing.org/doi/full/10.1098/rsif.2014.1326). Iron sulphides are biosynthesisable, suggesting the possibility of [pyrite](https://en.wikipedia.org/wiki/Pyrite) mineralisation (Mohs 6-6.5). Note that some chemical pathways involving iron sulphides can release hydrogen sulphide which is quite toxic to terrestial life. Such creatures might not be dangerous in life because of this, but they may smell bad in death and in a confined space (or in other circumstances, such as being corroded by acid) might produce hazardous levels of fumes. So pick your protein for toughness, and mineral for hardness, and you'll be good to go. No need for exotic metal biochemistries. [Answer] No mineralized skeleton. Use cartilage. Cartilaginous skeletons work great for fish. The [cartilaginous fishes](https://en.wikipedia.org/wiki/Chondrichthyes) including sharks and rays have been doing well for 500 million years. Arguably a bony skeleton is better for a land creature with legs, because the bone can support more weight. But for a flying creature cartilage is perfect - cartilage is much lighter and more flexible than ossified bone. Why then, do flying vertebrates not have cartilaginous skeletons? Probably because there is no going back, and fliers were all land animals first. And all the land animals are descended from bony fishes, who were the ones to first colonize the land. Those fish had bony skeletons and so do all their descendants regardless of where they wound up. [Answer] ## Magnesium and aluminium have insoluble, solid material forming phosphates and oxides and non variable oxidation states, which I would suggest be your criteria. Iron and titanium are probably OK-ish despite their multivalence. ## Boron is certainly worth a look. It can act a bit like a cation (when not paired with oxygen), or as an oxide network forming species (borates are a little bit like silicates). Weirder candidates include ## zinc or scandium Sc is too rare but otherwise probably OK. The rest of the light transition metals have too much redox chemistry to be a good idea. Personally, my order would go silica/amorphous silicates, boron, aluminium, magnesium, titanium, iron, zinc, scandium, and I think that exhausts the options unless you consider heavier elements. I like Si/B/Al the best because they can all form extended oxide/hydroxide/phosphate materials with non stoichiometric chemistry, they're all relatively bioinactive, they can incorporate other ions (either anions or cations), their oxide surfaces can be functionalised, they don't have much redox chemistry. You can imagine their materials combining with organic scaffolds easily enough. Si leads on all these grounds. [Answer] No need for mineralization. Have the bones be a tough rigid biopolymer like wood. Nanocellulose is very tough and stiff. Perhaps have a sand aggregate for hardness or do a smidge of handwaving for carbon nanofibers in your wood bones. I dont mean carbon fiber, nanotubes, or graphene, but aggregates are biologically doable. This would be hard tough stiff flexible lightweight and have rapid healing since carbon nitrogen oxygen and hydrogen make up the majority of carbon based life. No need to deal with relatively tiny amounts of calcium phosphorous and iron in the diet. ]
[Question] [ There are a number of places in which cumulonimbus clouds - and therefore, thunderstorms - are likely to form, such as: * Cold fronts, where masses of cold air move into hot, moist air masses * Around the equator, where the trade winds of both hemispheres come together * Mountainous areas, which increase uplift of air Say we took an equatorial location, surrounded by mountains on its inland sides, where moist, warm air from the sea collided with cool air from the mountains. In theory, this should tick all three boxes, but would this be sufficient for thunderstorms to occur year round, for at least 20 hours a day? Is something like this even possible? EDIT: picture for clarity: [![enter image description here](https://i.stack.imgur.com/avYFz.png)](https://i.stack.imgur.com/avYFz.png) The closest thing to this Earth has is the mouth of the Catatumbo River, Venezuela, where storm clouds are present 10 hours per day, on 140-60 days a year. However, this is less than halfway to the scenario I'm aiming for. [Answer] Jupiter has had the great red spot storm consistently since the 1830's, probably even earlier. It seems like a planet with very little land could achieve something similar. That said, you can have a place with constant thunderstorms by 1: Not giving it a map. 2: Indicating that you've given thought to how it has constant thunderstorms. And 3: Saying it does. [Answer] I say you need a planet with much less tilt on its axis than earth. The seasonal changes even on the equator, much more on both sides of it, are just too large to allow for such a place. Perhaps alternatively a planet which is geoengineered to look very symmetric on both sides of the equator. There are a few places on earth with rain every day, some places on Hawaii are probably best known for it. Thunderstorms are more difficult, they need a potent heat source, but your mountain flank points away from the sun at least half of the day. ]
[Question] [ I am plotting out a sci-fi setting, and trying to figure out the consequences of a non-conventional form of time travel. In the story, time travel has been achieved by means of temporal displacement. The principle is simple; the traveller enters a capsule, and everything inside of that capsule gets teleported to an earlier point of time. The traveller can then do whatever he wants in that past for a set duration, before returning to the capsule and going back to his own time. This time travel operates on a rubber band effect; the traveller and all his belongings are temporarily moved into another timeline, and then later brought back to his original timeline. No matter what he does in the past - there is no effect on the original timeline. As such, in the universe where we all exist, it is only possible to "leave", and never to "arrive". From a philosophical point of view, every time traveller arrives in an exact duplicate of the universe at a certain moment of time, which then diverges from that point onwards. As soon as he leaves, that universe effectively disappears. The displacement in time is strictly temporary. Due to conservation of matter, though, absolutely everything that goes must return to it's original universe. It's impossible to leave anything behind, and impossible to bring anything extra back. All displaced matter will be teleported back to the capsule once the duration of the temporal displacement ends. The only thing that can change is the structure that the matter is arranged in. Unfortunately, this teleportation must happen on a particle by particle basis. This doesn't work well with humans. Let's say a time traveller eats and digests an apple while in the past. When he leaves the past, all matter that used to be that apple - including lumps of his cells and blood - will be left behind in the past. Therefore, the traveller will return with chunks of his intestines missing. The same applies if the traveller goes to the toilet in the past - even though the waste isn't part of his body anymore, it will all be coming back with him. It gets messy. Likewise for any oxygen in his lungs from the past, and for any skinflakes he sheds, or even any cells he picks up. Anything his body takes from the environment is gone. After a set duration, everything will return to the capsule, and nothing else. They want to get the most use out of this temporal displacement machine. So, with that in mind, what is the maximum duration that a time traveller could linger in the past, without suffering a messy death on his return? Really, it depends on how much human bodies take in from their environment, and how unhealthy it would be if the matter making up their cells was suddenly 'sorted'. Theoretically, the travellers could bring back whatever environmental suit, oxygen tanks, food supplies with them that are needed, but it costs power to run the machine. They only want to transport the very minimum amount of mass. Edit: For clarification; the universe that the traveller arrives in is not a 'real' universe. That universe (and timeline) effectively exists for only so long as the traveller is there. Once the displacement ends, that universe disappears and all that's left behind is the capsule, and the original matter. That original matter is the only thing that can return to our world. As such, it means that (from the travellers point of view) the universe he arrives in is completely disposable to him. Nothing that happens there will have any effect on his universe. All he cares about is coming back alive to his own universe. Effectively, the travellers can use the displacement to research the past and bring back information, but nothing else. [Answer] Since the question is now clarified to indicate that no actual other universe is involved, I'm revamping my answer thus: Basically what this whole proposition boils down to is a kind of futuristic Virtual Reality experience, much like a [holodeck](http://memory-alpha.wikia.com/wiki/Holodeck) from Star Trek. A "universe" is created into which a person may "travel" and he may interact with persons and objects created within that "universe". Whatever he takes within him has substantial existence (because its matter was created from Before within an actual universe): his own body; any tools or food he brings along; the "vessel" he uses to enter the VR universe. All the matter subcreated within the VR universe, having no substantial existence of its own, must dissipate when the user leaves. Since it is not real matter --- it may be directed energy that gives the appearance of matter --- it can not leave the VR universe. If he eats an apple there, he'll taste sweetness, experience the sensation of chweing and swallowing and his stomach will fell slightly distended. This is because the VR generator is "projecting directed energy" to give the appearance of matter. Once he leaves, the sweetness will disappear and the stomach will feel strangely empty again. There being no actual, independent, universe external to the Traveller's own, I would say: there are no limitations because, in actuality, nothing that is brought inside the VR is "left behind"; and because everything within the VR is unreal, nothing can be taken away. The ledger remains balanced because there's nothing on the other side of the equation to balance. There is no danger to his body because he has actually travelled nowhere and has interacted with nothing and has talked with noone. --- Original answer for context: I would say that, unless the universe the Traveller is going to is itself not only sentient but also intimately aware of every subatomic particle that comprises its corporeal existence, I believe you are placing yourself under an impossible yet also needless constraint. My solution would simply be that, after wondering why so many early Travellers exited their machines dead and with random bits of fecal matter spattered all over the vessel interior, they would hit on the idea of cross-dimensional conservation of matter. *It would then be a relatively simple matter of installing a quantum scale* that keeps track of all mass within the boundary of the spatio-temporal field down to weight of tiniest utron.** Whenever the Traveller is in transit, the vessel's computers take note of every atom that has come into the S-T field and stores that in a database. Once the Traveller does his business in the other universe and gets back into the vessel, the same computer runs a new scan, determines how many differences there are by comparing inbound and outbound databases. If the Traveller is "too light", a device will scoop up some matter from the environment equivalent to the inbound mass; if "too heavy", the vessel will sacrifice an amount of mass equivalent. Both ledgers in balance, I think your Traveller should be okay and he'll return home with most of his original matter, but also with some foreign matter. I don't see how a universe can "know" whether an oxygen molecule was made within itself or another universe. If it's a hard requirement that all original matter must leave with the Traveller, then I think you're going to run into insurmountable problems. Once he breathes the air of the other universe, his own universe's molecules get blown away in the wind. Once he decides to relieve himself, or sheds some dandruff or experiences a liaison with a local, well, there goes some more original matter that will be unrecoverable. Such a hard requirement I think would cause too much damage not only to the Traveller but also to everything and everyone he comes in contact with. --- However, if the requirement is hard and fast, then this might be a workable solution: You say that S-T travel is kind of like an elastic band: the vessel uses energy to extend itself and its occupant into another S-T continuum (a different universe), and is then drawn back again after a set amount of time. I'll posit an Elastic Field Effect. In order to conserve matter, prevent contamination (and stinky sequellae) and keep both sides of the equation balanced, I suggest that the same elastic band effect that allows the vessel to travel to the other universe also surrounds and conserves the original matter of the Traveller. Basically, he will travel and interact with the other universe whilst operating within an elastic bubble. In this scenario, the Traveller never actually touches anything, never ingests anything, never leaves anything behind, never takes anything with him. The elastic bubble field surrounds his body (and his excreta), allowing no contact with the other universe's matter. To the people and objects he interacts with, he might appear slightly abnormal: he might be kind of transparent; his voice might sound like it's coming from a great distance, all tinny and weak; it will appear that objects kind of "float" in his presence and their movements don't quite jive with his. He might appear like a ghost or an extradimensional being... ...oh. Wait. Right! This is because, in effect, the Traveller and his vessel never actually left their home universe. The technology simply employs a device whereby a tiny depression is made along the boundary of the Void, which is then stretched until, pushing into a parallel elastic field within the other universe, it allows a Traveller to seemingly travel from one universe to another while never actually leaving his own. This effect can be demonstrated by wearing latex exam gloves and pressing the finger of one hand into the stretchy material of the other glove. You'll be able to "feel" your finger pressing on your hand; the elastic field surrounding your finger will push aside the parallel field surrounding your hand. Two universes interact without ever colliding. No matter is introduced. No matter is left behind. Ledgers balanced, the Traveller and his vessel quietly slip away as the energy inflating the elastic field dissipates. And best of all, the Traveller doesn't have to clean randomly applied poop from the interior of the vessel! [Answer] 1. I will wade on on "virtual" vs "actual". We will say it is an actual universe. For all practical purposes it ceases to exist once the traveler leaves, because it is impossible to get back. That timeline is a parallel timeline of which there exist an infinite number. One might differ from the next because of a different splash of the waves in the Ordovician ocean. They are infinite, and on visiting a timeline that is substantively identical to the travelers own, there are an infinite number of which one is randomly chosen. There is an infinitesimal chance of revisiting that same one. Of note: these other timelines will have travelers which are visiting yet other timelines. There is an infinitesimal chance of encountering one, or more. There is an infinitesimal chance of one visiting the timeline of the story. 2. /As such, it means that (from the travellers point of view) the universe he arrives in is completely disposable to him. Nothing that happens there will have any effect on his universe. All he cares about is coming back alive to his own universe/ The solution: he has no hope of coming back alive to his own universe. It will be a one way trip. Returning travelers die in various ways and speeds according to needs of the story. In return for their efforts their families collect a substantial sum. Alternatively, the traveler's experience in the past could be the payment. The traveler fights his way into the headquarters of the Third Reich and murders Hitler with a plasma cannon. The traveler prevents the 911 disaster. The traveler parties hard with the Emperor Augustus. The traveler prevents his alternate self from making a terrible mistake. The traveler reunites with his lost loved ones. Then when they return they die. --- There is so much grist for a narrative mill here that this could be a series on Syfy. It is a like a cross between Sliders and Looper but with one time temporary characters (I am reminded of Liz Taylor's role on Star Trek. What, you never saw that episode? Callow youth!). There would be action specific to the episode and also longer arc narrative threads. Oh yes. * The traveler returns and fails to die, but has been changed in some other way. + The traveler figures out a way not to return, staying in the alternate timeline. * The traveler does not wind up in a timeline nearly identical to her own, but someplace very different. * A traveler visits from a different timeline and is captured, allowing the persons capturing him knowledge of a possible future (and temporary access to artifacts from that future). [Answer] As long as the following held out a space suit, oxygen, food, water, and perfect insulation from everything Anything that moves into or out of his body may be in a different arrangement. This means that any oxygen he breathed in from the other universe would cease to be in his body, any energy is removed. So if he stood in sunlight and was warmed 10 degrees and didn’t radiate it back out, he would suddenly drop 10 degrees upon exit. They need to be as perfectly sealed as possible, with as little interaction with other things as possible. A camera for vision, microphone for sound, suit to simulate sensations like heat and touch, and any other available thing to allow for interaction while keeping them from directly experiencing things. Some examples of things happening are: A gallon of water vanishing from their body, killing them, their body freezing or boiling, radiation poisoning, electrocution, and many more, gruesome examples. (Electrocution would be from any charge built up by them touching things) ]
[Question] [ The world I'm thinking of is a large moon of a gas giant. It's fairly Earth-like, perhaps a bit smaller, might be a bit magical, but sits about where we sit around a star very similar to ours, except that this star absolutely loves throwing its corona around. Suppose this world was struck by an extreme coronal mass ejection as strong as the Carrington Event every few months. What I want to happen is technology stagnates at a late 1700's early 1800's level for centuries. But that sounds unlikely. There's plenty of technological breakthroughs that don't require electricity that occurred in the late 1800's and early 1900's, like the internal combustion engine. But I'm okay with this, to an extent. I want to understand exactly what the consequences of regular devastating (from our perspective) solar storms would do to a civilization. The biggest effect that I'm aware a powerful CME causes is frying all electronic mechanisms connected to long wires. Are there others I'm not considering? What level of technology might they rise to, and what exceptions that we associate with the electrical era might they have despite lacking electricity? Is this even the right mechanism to obtain the technological stagnation I'm seeking? Most specifically, given that I want technology to stagnate at that level, what is the most "advanced" or "surprising" development they might achieve despite electrical engineering being severely stunted? [Answer] People would have perfected mechanical automatons to a degree that only the most advanced masterpieces on earth have ever been. Have a look at the [Peacock Clock](https://en.wikipedia.org/wiki/Peacock_Clock) in the Heremitage. It's an entirely mechanical clock that moves various parts of the clock in different intervals. The same level of technology would probably dominate your world. The first automobiles with combustion engines didn't need intricate electrical wirings. The accelerator pedal mechanically increased the amount of fuel burned in the engine and the brake pedal mechanically blocked the movement of the wheels. And don't forget batteries! The first battery was created long before anyone had the slightest idea of what to do with it. The first electrical toys where glass cylinders with gold flakes in them that moved as if by magic when an electrical current was created nearby. This caught the interest and imagination of people and eventually lead the development of radio communication. The first electrical power sources where hand cranks. The people of your world could develop those as well. Long distance communication would be very different, though. The telegraph wouldn't work and radio communication would be disrupted by the regular solar storms. But humans have sought solutions for long distance communication long before the age of electronics. The trusty old carrior pidgeon was used for thousands of years to transfer messages. Years of invention and improvement yielded the [Fresnel Lens](https://en.wikipedia.org/wiki/Fresnel_lens), which directed the light of lighthouses over very long distances. The biggest difference would be the lack of computers. The first computers were developed to ... surprise ... compute mathemalical equations. Whithout computer technology, it takes longer to design robust buildings and vehicles and there might be more tragic accidents because of mechanical failures or miscalculated statics. Things might be build in a more robust way in general, just to be sure. And things would be much more square and angular than todays curved designs, because those where made possible and cheap by computer technology. It's more efficient to produce a flat, square panel than a curved one which then must fit into it's place without any margins for error. [Answer] This is one of the best excuses to make a steampunk/dieselpunk-tech world. The desire for progression crippled by a lack of reliable electricity makes the motor king and would require more directly mechanical means for getting anything done efficiently. This means Rube Goldberg machines to communicate or do something across a building or city would be more realistic. Whether your characters wear corsets and gears on their hats is up to you. There's also the scifi possibility of eventually using the solar flares themselves as a source of power, which would be a huge dynamic shift, especially for a society which learns to utilize all of their resources to streamline daily living. [Answer] A Shield I did a report on the Carrington event. I believe the world would develop but not as fast or as good as ours. If they harnessed the energy, that would give them tremendous power. One solution to this would to give the world a stronger magnetic field. if you created a some kind of force field/shield and powered it by the solar storm as above, you could possibly stop the storms from getting to you. But the problem would be getting to that level of technology, since this is like a few hundred years in our future. ]
[Question] [ Scansoriopterygidae was a family of theropod dinosaurs that lived during the Jurassic, the most well-known member of which was Yi Qi. They are thought to have been arboreal insectivores, and convergently evolved bat-like wings. [![enter image description here](https://i.stack.imgur.com/Y2PYW.jpg)](https://i.stack.imgur.com/Y2PYW.jpg) Source: <https://www.deviantart.com/pterosaur-freak/art/Draw-Dinovember-day-26-Yi-qi-717957169> Paleontologists currently think that it may have been capable of very weak flapping, but was likely an exclusive glider. The Scansoriopterygids went extinct in the late Jurassic, about 156 mya, but had they continued to live through the Cretaceous, I'd say that they'd be at least potential K-Pg survivors. In my project (See also these questions on [cockatrices](https://worldbuilding.stackexchange.com/questions/113648/is-petrifying-vision-plausible-in-an-animal), [hydras](https://worldbuilding.stackexchange.com/questions/114179/hydras-as-parasitic-mating-polyandrous-amphibians), [griffins](https://worldbuilding.stackexchange.com/questions/114262/are-my-wing-walking-griffins-viable), [giants](https://worldbuilding.stackexchange.com/questions/114289/how-can-i-explain-the-evolution-of-my-giants), [sea serpents](https://worldbuilding.stackexchange.com/questions/114545/how-large-could-my-sea-serpents-be) and [merfolk](https://worldbuilding.stackexchange.com/questions/124366/could-an-intelligent-race-of-seals-craft-tools-effectively)), the Earth is inhabited by many creatures from human mythology that are supposed to be as scientifically plausible as possible (Note that in the project, the biology is the primary focus, and the story comes second). One such animal I'd really like to include are dragons - or, rather, wyverns. The question is: is the premise of large, flying theropods descended from Scansoriopterygids which survived into the Cretaceous and Cenozoic plausible? Let me explain a bit more about my wyverns: * They are capable of powered flight * They can grow to large sizes, with 15-20 metre wingspans (Equivalent to the largest pterosaurs) * They have not "taken over the world", in the way that birds or mammals did. They are far from the dominant form of life. One of the problems that may exist for this concept is that Scansoriopterygids were gliders - and, according to many people I've heard - "gliding animals can't evolve into flying ones". Is this correct? Can I achieve gliders evolving powered flight, without having them lose the ability to glide and then evolve flight? If Yi Qi really was capable of weak flaps, this problem could be overcome by enlarging the pectoral muscles. Then, there is size. A lot of the time, it's hard to just scale up a small animal and end up with a biomechanically functional organism. So, before asking this question, I thought about why bats can't grow as big as birds or pterosaurs. The main ideas I came up with were: 1. Birds were already the dominant diurnal fliers when bats evolved, 2. Membraned wings are more susceptible to damage 3. Soaring is harder at night due to lack of rising air currents. Could these problems be overcome? Lastly, there is the fact that they "haven't taken over the world". The bullet point was a bit vague, but I pretty much mean that I don't want them to be nearly as ubiquitous as mammals or birds. Ideally, there should be about 500 species or less, almost all of which will be small-ish, hawk-sized ones, with a dozen or two species that are very large. --- If I haven't mentioned it in the list of bullet points, you don't need to address it in your answer - so the likes of fire-breathing, scales vs. feathers etc. can be left to me. If you require more information, please say so, and do the same if you suggest it to be broad, off-topic or opinion-based. [Answer] Gliding animals have evolved into flying ones at least twice, anyone who says otherwise doesn't know what they are talking about. Birds did not evolve from gliders but they are likely the only ones. It is also the reason birds legs are not involved in flight, because they evolved from cursorial jumpers, both locomotions systems needed to be seperate. Bat don't get as big because mammals are pretty crapily designed for large size, our breathing is in efficient and live birth works against us for fliers. Note bats are more maneuverable in flight (larger percentage of mass in the wings and curlable wings) than birds so the bat design is not all negatives. [Yi qi the Scansoriopterygidae](http://waxing-paleontological.blogspot.com/2015/05/scansoriopterygid-faq.html) is just bleeping weird, If you want dragon like wings it will be a great choice. the wing support prong is not preserved in Scansoriopteryx bit it does not have the greatest wrist preservation and there are some suspicious splinters of bone, since it is juvenile if that prong is ossified cartilage they might not be preserved. Note also the tail from Yi qi was not preserved so that is just artists fancy, the closest relative we have has a much longer tail. However the two seperate locations systems will limit the size far more than it does in pterosaurs, unless you regress it to a more pterosaur like posture (quadrupedal). There is a reason the biggest flying birds are nowhere near the size of the biggest pterosaurs. Alternatively there is no reason you could not have earlier pterosaurs develop bat like wings instead of the monodigit ones they had. Now to deal with your bullet points. 1. your fine. Keep in mind this group evolved at the same time as birds and birds evolved while pterosaurs were common so competition will not prevent their evolution. The presence of fliers does not prevent the evolution of other fliers. 2. your fine. Membranous wings have evolved many times what ever disadvantage they have it is not enough to prevent their evolution. Wing membranes are not that delicate. 3. your fine. they don't need to be nocturnal, and even if they are, thermals still exist at night. Thermals still exist at night, many in the same locations. As for them not taking over, that is easy just isolate them mostly on a single continent for most of their history, this is where competition will work in your favor. It does not work as well with a flying animal but oceans are a great way to isolate groups of animals. maybe they evolved in Australia and only the largest of them have spread further. Keep in mind though a wingspan of 20M is almost twice the largest pterosaur. ]
[Question] [ In a certain world there is a ruler who runs a very powerful country with an iron fist. A faction of oppositionists has been giving her lip and has made some mean comments implying she brings the country dishonor due to not being chaste. She wishes to punish those remarks by enacting a certain song in a literal manner over the opposition's headquarters. An amount of young adult men from the opposition is to be defrenestrated from cargo airplanes while [The Weather Girls' It's Raining Men](https://www.azlyrics.com/lyrics/weathergirls/itsrainingmen.html) is broadcast on all TV and radio stations. Question: Assuming the lads are dropped from 10 km up, over an area of five acres and for five minutes, how many men would she need to drop in order for their blood to cover the streets and form puddles as much as the water from a light rain would over the same area and span? And how spread apart should they be? Assumptions: * Each body splashes half of their blood around upon impact and the blokes average at 70kg in weight; * She has a large enough fleet of planes (and as many men as she needs) to do it; * By light rain I mean small, shallow puddles on the asphalt. Also, if it were regular water instead of rain a simple umbrella would be enough to keep someone mostly dry. [Answer] The scrap paper math goes like this: $5$ acres is $20234.3$ square meters, rainfall is reckoned in $mm/mm^2$, you're describing what I think is roughly $2.5mm$ of rain so that's about $50585750000mm^3$ of total liquids, (not accounting for any effective area reduction due to the bodies lying around afterwards). The average human has 5 litres of blood, at half value, per your premise that's $2500ml$ meaning you'd need to drop about $20240$ men to make sure you get the desired saturation, roughly one per square meter across the entire target zone. Do check my numbers, I'm not at all sure they're completely correct. It would probably be worth attaching a small drag to the ankles of the men you're dropping to keep them head-down, this will boost their terminal velocity by about $100kmh^{-1}$, from around $190$ to $300+kmh^{-1}$, ensuring the best possible splash on impact. For best impact results your city should put the concrete in concrete jungle as well, bodies that hit asphalt sustain less damage and sink in rather than mashing so much on impact. Note: You might get away with a far smaller number of men if the streets are crowded when you drop them. ]
[Question] [ What I want: My world has a large mountain valley region that is about 70 miles in diameter. I would like for there to be a historical event in which a portal to the moon was created in the valley and everyone living in the valley (and maybe some people outside too, doesn't matter) ended up dying of asphyxiation as air is sucked through the portal into the lower density atmosphere of the moon. Parameters: 1) I would like the portal to be no bigger than a city block. 2) I would like the air depletion to be rapid enough such that few valley residents had time to escape. 3) If it helps, the elevation of the mountain valley town can be basically anything you desire, even below sea level. Question: Is the historical event I desire possible given the above parameters? If so, how big a portal are we talking? What time span? [Personal note: thank you for reading! I've been lurking this site for a long time. Excited to finally get involved.] [Answer] As others have said, portal to the moon will not asphyxiate people, unless your mountains are a complete ring and reach to outer space. There will be hurricane-level wind, and some people might get sucked into the portal. If you want to asphyxiate a town, open a portal to Venus. Its atmosphere is hot carbon dioxide, and it has higher pressure, so it will flow into the valley and fill it: > > [Venus atmosphere] is composed primarily of carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is 93 bar (9.3 MPa), roughly the pressure found 900 m (3,000 ft) underwater on Earth. > > > <https://en.wikipedia.org/wiki/Atmosphere_of_Venus> Here is a real-world example of this happening (with terrestrial source of carbon): <https://en.wikipedia.org/wiki/Lake_Nyos_disaster> [Answer] Don't focus on the elevation of the valley; focus on the elevation of the surrounding mountains. I once flew into Albuquerque, New Mexico in a small unpressurized, single-engined, propeller plane. We arrived on the night before a low pressure wave rolled over that region. Flying in, we had to push our altitude a little to get over the mountains and I remember getting a little dizzy. The next day, we had wanted to depart, but the mountains had other plans. The atmosphere had thinned so much above us that our little plane couldn't get enough grip to lift us up over the mountains. After several attempts, we returned to the airport and spend a few more days in Albuquerque. If you have a town in a valley, which is totally surrounded by mountains. And if those mountains are even taller than those around Albuquerque (relative to the thickness of your planet's atmosphere). Then if a lunar portal opens up along that valley floor while a low pressure wave is present over the area, that might do what you are looking for. Even then it will have to be a very large portal to evacuate the air out of the valley floor faster than the thin high-altitude air can rush in over the peaks to replace it. You will probably just make everyone a little dizzy. ]
[Question] [ Say they had pale skin, what would they look like? Would the lips be black? Would the vascular system show through the skin more? I'm not very interested in how or why their blood is black, just how it would effect their appearance overall. [Answer] In cold conditions and when sedentary these people would appear corpse like with very pale skin is if they had [pallor mortis](https://en.wikipedia.org/wiki/Pallor_mortis) In warm conditions or after vigorous exercise these people would appear in shades of grey as if they were a living black and white photo, although given their coloured surroundings a lot more creepy. They would not look exactly like that due to other factors such as eye colour, hairy colour, other elements in the skin and clothing, but it would be a good approximation especialy if naked. [![grey man at angels landing](https://i.stack.imgur.com/p0Ny7.jpg)](https://i.stack.imgur.com/p0Ny7.jpg) [Answer] Some thoughts here... * Consider when someone blushes -- the red is pretty obvious. * Now consider when someone is about to faint ("goes white" they say). This condition is often described as someone turning ashen. So clearly the blood is a factor. I can imagine people looking more or less as per standard, though with a bit of a goth look ... lips might be more or less dark gray, and the skin would be pale with the dark underneath, might look "waxy", because the top layers of the skin are a bit translucent. Their tongues would be black, too. On these guys, "bloodshot" eyes for heavy drinkers would look creepy and awful. Side note: there'd be no emo or goth phenomenon, because, well, what's the point? Their parents have it covered... ]
[Question] [ In [How would sentient intelligent, normal-sized mice fight against humans?](https://worldbuilding.stackexchange.com/questions/46632/how-would-sentient-intelligent-normal-sized-mice-fight-against-humans#) Humans are not doing well at fighting against the mice. They are small, smart and deadly. Humans will have access to medieval tech, swords, bows and magic. The magic system would rank the spells as Anti-unit [a basic fireball would kill a normal commoner right?] Anti-army [something like blizzard which can affect up to a few hundred people] Anti-fortress, Anti-planet will be excluded since humans won't handle this kind of power well enough to avoid blowing up the planet in a day. Magicians that can use anti-army class spells would only add to about slightly above a hundred across the world. Not like they would help much when mice are quite literally everywhere. The spells can be complex but trying to do something like targeting all mice with instakill spells is impossible, spells require visual confirmation[bad news if you are blind] For the sakes of allowing a answer, we are going to assume that the mice are out to destroy the kingdom of Joe. This kingdom is a monarchy, ruled by King Joe and his council of greedy nobles. The kingdom capital has a geocentric pattern divided into twelve rings and a circle in the middle. The royalty would live in the middle followed by richer influential nobles followed by the less rich and influential until the last 9 rings which are occupied by commoners. Each ring or sector is surrounded by a stone wall with steel gates at each Cardinal direction (NW, NE, SE and SW included, so there are 8 gates at each circular wall. So in order to get to the center, one must pass through the 13 walls surrounding it[or climb past]. Guards patrol the rampart regularly and security tightens as one gets further in. To get from for example the 12th to the 11th gate, one must have a mark on your identity pass from the 12th gate [so people who sneak in illegally have to continue sneaking illegally]. The city also has a underground sewer that lead from the center to the last ring [they are connected]. Size of the capital I'm not really sure, each ring should be the about the same walkable distance from each other. Farmland is mostly on the last ring and outside the protection of the walls [the kingdoms station serfs and soldiers to guard those] THE CIRCUMSTANCES * the humans know of the intelligent mice existence * the humans have experienced attacks carried out by them before about a week before * the humans do have beast tamers that can hunt them down but they will need a 3 days for all of them to get to the capital from the other towns and villages so there are about 50 of them currently in the capital and another 200 coming in 3 days. [The beasts are monsters that are tamed, for the sake of simplicity, they will all be dog-wolf types where their heads would reach a adult males chest level] * the population comprises of about 400,000 commoners, 4700 nobles, and about 100,000 soldiers [commanders included] [nobles are usually the ones in higher places] Humans have about 20 wizards capable of anti-army and a magic corps about 1000 wizards strong. [Can't believe I forgot that T\_T]and 13 members of royalty. Totaling to about 505,733 people who live in the city * there are currently about 100,000 mice in the capital, they will be the only forces to defend against. The total population of mice at the end is not my concern, they could be all dead for all I know [also if u want a challenge, I REPEAT, A CHALLENGE , the mice can use anti-unit spells based off chemical magic [Acid spear, poison needle] and to a smaller extent as their affinity to other elemental magic [petite fire ball] is lower. All of them can use magic but can only manage off about 3 shots before getting mana exhaustion] * the mice main targets are royalty and nobles, they have no plans to kill the commoners but have no qualms for collateral damage or intentional slaughter of them. Also for all purposes, I'm gonna give them claws and teeth that can break iron and scratch through them. [Doesn't make sense for them to only be able to poison and not use their own skills right?] * for a successful defense against the mice attack, less than 20% of the total population of the humans can die [I don't want something like the nobles going all like "SACRIFICE THE PLEBEIANS"] * the defense plan must be able to prevent future attacks * this is under the full support of the royal family, so consider what you can do when you have a innumerable amount of metal, wood and other resources to use [medieval stuff of course, can't have you building automatic mice terminators can I] * the other question I asked would tell you what the mice can do. [ITS AT THE TOP] [Answer] So, various problems. Magic The magic you describe sounds quite minor. If the mice just want to cause damage and 20% of your population are in the most accessible portions of your city then there's not much you can do, they can dodge in and out of rafters firing fireballs and simply set everything on fire. You mention that there's magic for tracking but everyone would know if they're being tracked. This seems useful. The defenders don't have the element of surprise. Expect tracking beacons on every gatehouse. Area control: keeping the mice out of an area. Assuming they're not already inside you want to keep the mice out and the mice desperately want in to kill the king. Simple medieval walls are unlikely to be much of a defense since they're rarely perfect enough and mice can get through even tiny holes. Also mice are good climbers and there's going to be holes used by mundane mice. Deal with massed charges: GLUE! Glue, along every open area that the mice might need to cross place strips of fabric/paper/similar covered in tar or glue. Humans can just step over a 1-foot strip. Mice on the other hand are going to have trouble crossing. This can also be used to make walls unsafe to climb. Glue traps are horrible things and mice attempting to help other mice are as likely to end up stuck themselves unless they have some way of vanishing the tar without burning it (which would be bad for the mice stuck to it) Protecting VIP's. terriers, cats, larger dogs. Even wild rats. Anything that preys on mice, keep a number close to your VIP's. Population control Your commoners outnumber the mice. Lets motivate them. Offer a bounty for every dead mouse brought in. Heavy rain would be your friend. If there happened to be a storm or the mages can somehow engineer a good heavy storm then filling the streets with mud, the sewers with raging water and dampening any thatch that could burn would make things a lot harder for the mice. A gutter filled with swirling water is an inconvenience for humans, it's a potential deathtrap for mice. A few inches of horse manure on the roads turned into slurry in the rain is an inconvenience for humans but again, a horror for mice. Damp clothing might even be an effective defense from minor fireballs. Humans also tend to cope better with the cold and wet due to simple body size. To the humans it would be a muggy unpleasant day. To the mice it would be like a trench scene from a WW1 horror film. [Answer] Mundane Solution Deploy the normal rodent control methods. Mice, as animals pretty low on the food chain, have a number of natural predators. Owls, cats, and snakes all come to mind. The latter can get into mouse holes, but most people despise snakes (I don't know why; I think they're awesome) and don't want them around in numbers (or at all). So pass a law saying everyone is required to have a pet cat. Owls are just too hard to keep around... Magic Solution Poison gas. Use magic to create a cloud of gas that affects only mice. Spread this universally across the entire city at the same time. This could be done by a single anti-army mage or a collaboration of anti-unit mages. After a few hours, let the gas dissipate on its own or magically dismiss it. (Of course, the right combination of chemicals could probably produce a similar, mundane effect.) [Answer] A couple things immediately come to mind. 1: if there are something like 100K mice inside your capital city already, then the city is compromised. Under no circumstances do King Joe and the most senior and valuable personnel need to remain there. Step 1: get the king out of the city and put him on a big boat on a lake nearby where he can direct activity via courier and/or magic. (Why a boat? Water makes a pretty good barrier for mice. Obviously, the boat would have cats on it and probably the falconer's entire collection of hunting birds...) 2: Now that you have secured your command and control element, you can think about taking back the city. This place has a ton of walls, gates, and districts. It seems like the civilization is pretty darn good at engineering. I would try to find a way to flood the streets with a foot or two of water (is there a moat that can be pumped or redirected?). Sure it will cause some property damage, but it will also seriously slow down mice. Every building will now be like an island to them and any sewer system would be totally underwater. In this environment, terrier type dogs and snakes will both be good options for mouse hunting. 3: In warfare, you want to concentrate your forces against a dispersed enemy whenever possible. It might be worthwhile to gather most of your human population into the central districts of the city because a higher density of people means way less opportunity for the mice to operate (more feet to stomp on corridor floors, more eyes to lookout, etc). From there, a systematic clear and hold type operation should commence, working outward once some effective tactics have been worked out. One extreme result of this is that if you just can't dislodge the mice from the poor districts, you could burn the buildings with the greatest concentration of them. If the streets have been flooded with water, you could contain the fires to specific areas instead of burning down your whole city. Again, property damage, yes, but replaceable poor housing and not a lot of loss of (human) life. 4: You have to work out tactics and assign teams (from step 3 above, you can see that I have pretty much declared martial law and put all humans under the command of some kind of marshal. Those who can't fight would be located in the core areas, maybe in a large church, guildhall, or feast hall. Medieval cities would have a food store sufficient for at least several months, so non-fighting personnel would be pretty much camped out and waiting for the crisis to be resolved). Small terrier type dogs would be wonderful, probably every team would have at least one. In pretty much all ancient societies, small dogs (and cats) were kept by peasants for pest control purposes, so there should be plenty at hand. In medieval warfare, burning pitch, tar, boiling oil, and a lot of different kinds of missiles were all common. I would definitely set up fire teams with mobile pots of burning pitch, tar, and boiling oil that have a good area effect. The tar is even better because after it has burned/smothered a group of mice, it also creates an un-crossable mouse barrier (too sticky, like the mousetrap sticky strip discussion above). Humans are merely inconvenienced by tar, so I'd use that a lot (once again, the result will be property damage, but nothing that can't be fixed/cleaned/replaced later). Burning pitch was like middle ages napalm; really nice stuff to throw at your enemies in globs. Something as simple as baker's spoons might be a suitable "micro catapult" for launching burning pitch at clusters of mice. I would probably use a lot more conventional tactics on offense and concentrate the mages on more defense. This is because sentient mice are a very unconventional enemy and I have limited magical personnel. Wizards could come up with creeping gas that doesn't disperse and is heavier than air so it naturally flows into low areas and fills the bottom 2 feet of hallways with acrid death. Humans wouldn't care (except children who would be kept in safe rooms), they would just walk through it, but mice wouldn't be tall enough to reach the air unless they climbed up the walls. Wizards might move around with boys armed with buckets of water and magically freeze water thrown at walls to create ice-covered areas that mice couldn't climb. Basically, I'd keep the wizards working on maintaining a safe zone while the warriors and able bodied men formed the vanguard actually pushing mice out of infested areas. One nice weapon would be pretty simple and easy for a blacksmith to crank out in large quantities. Think of a cross between a metal waffle maker and a flyswatter. Basically, a long wooden arm with a flexible joint at the "wrist" and a metal "swatter" about halfway between a ping pong paddle and a badminton racket in size. That sucker would do wonders for front line morale. The flexible joint would let you swat mice on walls, floors, whatever. Front line personnel who are going to be dealing with mice up close might get "mouse armor". All you really have to do is wrap them in enough layers of cloth padding that mice teeth and claws are too short to get to the skin and you have done a lot (we are only talking maybe an inch of padding to do that). More layers give you some protection from mouse weapons, and you could even roll the unfortunate front line grunt in tar to create a human stickyball trap if any mouse got too close. The game would become; keep the mice broken up into numerous groups (primarily by flooded streets which keep them from massing) and then concentrate your people on one group at a time until you have pretty much cleared out the city. Once you do that, THEN you put a bounty out ("A silver coin for every mouse tail" or whatever) and bring in a lot of cats, etc. Long term, you will want to build a bigger, better moat around the entire city and create water traps on every bridge over the moats (think of a three foot trench filled with fast moving water that cuts across the road). [Answer] [![enter image description here](https://i.stack.imgur.com/9abWT.jpg)](https://i.stack.imgur.com/9abWT.jpg) Breed sentient, intelligent normal-sized cats with magic powers to fight the sentient, intelligent normal-sized mice. Or build a better mousetrap. ]
[Question] [ So, according to [Other blood colors](https://worldbuilding.stackexchange.com/questions/28276/other-blood-colors) it is entirely possible for other blood colours to evolve based on what base they use, but why? What would be the benefits of these different bases? What purpose would they serve? What conditions would find it beneficial to evolve these? [Answer] # Why we have red blood From the data given in the answer to that question, Haemoglobin is by far the most efficient carrier of oxygen that we know of. Therefore, if the efficient oxygenation of blood is important to the species, then there would be no advantage (Well, very little, see below) to having different colour blood. At best it would be a disadvantage as you would find exercise a little bit more difficult and you'd have to breath faster to get enough oxygen into your body. At worst it would be crippling because the smallest increase in the body's oxygen requirement would be impossible to keep up with. # Why other species don't Look at the example species. [Mollusks](http://mollusks.weebly.com/respiration-circulation-and-reproduction.html), for instance, while they use oxygen, don't have heavy usage, so the evolution of a highly efficient carrier wasn't necessary. Therefore developing a dependency on consistent iron intake would be a disadvantage - no reason for haemoglobin. I've tried searching to see whether there is any documented anaemia equivalent for Hemocyanin, but surprisingly noone has researched cases of anaemia in mollusks, how remiss of them. Presumably a hemocyanin-using life form would still have to ingest copper in order to create the oxygen carriers, but this could be easier for mollusks than iron. # Why one might not have red blood There is one major consequence of our red blood that could be considered a disadvantage in some conditions Using haemoglobin as your oxygen carrier requires that you ingest sufficient iron to keep the concentration in your blood up - failure to do so results in a dramatic reduction in the oxygen-carrying ability of your blood, otherwise known as [Anaemia](https://en.wikipedia.org/wiki/Anemia). So the simplest reason to have different colour blood is if ingesting iron isn't something you find easy, and/or oxygenation isn't as important to you as a species. For humans (or another life form of similar structure with a significant oxygen requirement), you could theorise an environment in which iron is impossible to ingest, either due to other physiological changes (toxic for some reason), or environmental absence (no iron to ingest). I found an article [Here](http://medicalency.com/anemia_beremennih.htm) that implied that Hemocyanin has been used or at least suggested as a potential cure/helper for pregnant women suffering from anaemia (iron deficiency is very common during pregnancy as it can completely screw with your ability to keep food down and due to the extra nutrients required by the growing foetus). The extra oxygen carrier in the blood supplemented the low hemoglobin supply enough to prevent anaemia. In theory, we could use hemocyanin in our bloodstreams if for some reason we couldn't produce hemoglobin. The oxygenation would only be [40% as effective](https://worldbuilding.stackexchange.com/a/28380/15882), but there are plausible situations in which this might be ok. A planet with no iron and lower gravity for instance could theoretically work - less muscle mass means less oxygen required. You could even have a doomsday human situation where iron is not available for some reason and people are having to use hemocyanin to survive. They'd probably still be pretty damn sick (See [here](http://www.oncolink.org/treatment/article.cfm?id=60) for some details on hemoglobin levels, having an equivalent 40% level would make you seriously anaemic), but you might be able to counter that by flooding your system with hemocyanin, which would certainly give you blue blood. However, there would be other interesting side effects to consider, like [Copper Toxicity/Metal Poisoning](https://en.wikipedia.org/wiki/Copper_toxicity) and [Oxidative Stress](https://en.wikipedia.org/wiki/Oxidative_stress) which would potentially kill them anyway! You can imagine a feudal society that would form - powerful people hoarding the last of the iron to keep themselves healthy, middle class getting by with treatments to help with the poisoning from the hemocyanin, peasant class basically crippled. The Blue-bloods would inevitably become smaller in stature and less powerful as their bodies wouldn't be able to afford the oxygen for lots of muscle, causing a physiological rift. Maybe, after an awful long time (or with a little scientific help), people from the hemocyanin side would naturally evolve an internal production and copper affinity. No longer dragged down by their iron deficiency, that might change the balance of power... [Answer] I can think of several reasons. ## Scarcity As @IStanley mentioned if iron wasn't available in sufficient quantities in the organism's environment, then another oxygen transport molecule using other metal ions would be required. ## Different Environment According to this chart on Oxygen Transport Molecule Oxygen Uptake Comparision: [![Oxygen Transport Molecule Oxygen Uptake Comparision](https://i.stack.imgur.com/Ifgq7.gif)](https://i.stack.imgur.com/Ifgq7.gif) The different oxygen transport molecules operate at different efficiencies under different environmental conditions. ### Low oxygen partial pressures On the chart, it looks like Iridium (Ir - a platinum like noble metal) based oxygen transport molecules work better than hemoglobin at very low partial pressures of oxygen. So in a nearly anaerobic environment, it would work much better than hemoglobin would. ### Different temperature regimes The chart above only shows the variability in efficiency for some of the oxygen transport molecules. Presumably they all vary in effectiveness over temperature as well as oxygen partial pressure. It is therefore safe to assume that, like oxygen partial pressure, different oxygen transport molecules will become more effective at lower or higher temperatures than human body temperature (e.g. 37 C / 98.6 F). ## Conclusion All organisms will be restricted to using only those elements easily available in its environment. Although iron is universally about 100x more abundant than cobalt and many more times abundant than some of these other elements, you could easily envision environments in which iron is locally unavailable or less available than these other metal ions. Other environmental factors will also influence the function of those molecules. It's hard to tell based upon this single chart but it looks like the following observations may be true. At low oxygen partial pressures (nearly anaerobic environments), Cobaltodihistidine may provide better oxygen transport than Hemoglobin. At high oxygen partial pressures, Iridium based molecules may work better than Hemoglobin. At low temperatures, Coboglobin may work better than Hemoglobin. At high temperatures, presumably some other oxygen transport molecule becomes more effective. Some of the [references from this answer about the colors of blood](https://worldbuilding.stackexchange.com/questions/28276/other-blood-colors) provide interesting reading material on the subject. ]
[Question] [ Let me outline the current world at the moment: Its a modern society, with smart phones and jet planes, much past the medieval ages where humans warred with dragons. The fact that dragons were so powerful and deadly pushed the humans to all band together under one government, so its truly humans against dragons here. 500 years ago, Asia was made the official dragon country, with a primitive, tentative truce between all humans and dragons, and all dragons moved to Asia, while the humans moved elsewhere. They remained as distant as possible for the majority of this time, still with distrust among them, so not trading or communications. In the last 100 years, they are all becoming more open, with trading opening up, and occasional visits of important leaders to either side, to open negotiations or simply give a show of friendship and trust. Normal citizens are still not allowed to go. In the past 2 years (now in modern society), there has been talk of joining the two societies, bringing them together in peace, just like the humans did years ago. This would imply dragons living with humans, and vice versa, doing the same jobs and having the same rights. But the two species/societies have been apart for almost 500 years, with almost no communications. (Including spies) So their technological advancements have changed differently over time, with different discoveries and different ways of life. ...How would the dragon world and technological advancements be different than those of humans today? We are asumming a few things: -The rate of technological advancement is as close to the same as this world as it is in that world, so they have smartphones and internet and, say GoogleGlass. The change of there being dragons, and the uniting of humans does not change this advancement much, if at all. -The only real differences is that there is no "President" or singular "World Ruler". Instead there is a panel of.. lets call them Judges, that get voted in, just like Congress, but with the same restrictions as the President (So they can't stay for more than 2 terms) -These Dragons are just as smart as humans. -The dragons can fly, and have very large wings. -These dragons feel no need for a hoard. -These dragons ARE carnivores, though they like the taste of fruits and nuts. -These dragons are generally fairly big, (most species) the average being at least as big a a minivan in volume. Though different species of dragons can vary in size. -There are classical European dragons (four legs, wings, long neck, long tail, big body, generally smart, big, and very strong), Chinese Dragons (very serpentine in nature, can have hair, generally kind and smart), Dwarf Dragons, (Only the size of a large dog,), and basically anything in between. Lots of variety. -These Dragons generally live anywhere from 100 to 500 years. -These Dragons generally only have one clutch of eggs every ten or so years, so their population is not as large. The society level at separation was right after: America was discovered by Columbus, The Rise of the Modern English Language, The Age of Discovery began, The printing press was invented, and public banks were create. What MAJOR differences would there be between the dragons and humans? Now that technological trading is possible, what things are new to each side? Would dragons be more or less advanced? Would they not have discovered something important to advancement, or done the opposite and figured something out much faster? Would either side have something totally mindbogglingly advanced for the others, or would they be fairly close? Why? [Answer] The question feels a little broad, but here are a few glaring things that stand out for technological advancement and society: Technology Fundamentally, classical dragons as you describe them do not have the appendages necessary for careful, accurate control of their environment (think human fingers). This is crippling to technological progress, because it prevents so many things. They will find it difficult, if not impossible, to build structures accurately, create weapons, scientifically investigate the world, or make much of anything. You could put as large of a brain as you wanted into a dolphin, but their physical characteristics will prevent them from achieving anything close to what humans have. Dragons are going to experience a similar situation. Society Unlike humans, dragons apparently have multiple completely different species of dragons in their society. This has the potential for major problems, particularly the size difference. These things are carnivores — the smaller dragons will have absolutely no ability to defend themselves against larger ones. This makes it very difficult to believe that any kind of united dragon society would involve them because, frankly, they offer nothing more than a food source. Food is going to be a problem. As carnivores they would depend upon domestication and raising edible livestock. Without the proper physical appendages, however, they have no tools to help them do this and probably couldn’t even touch the animals without injuring them. This makes anything short of herding unlikely, and means food will be scarce. Fortunately, it sounds like their lower population size might mitigate this, but keep in mind that flying creatures the size of dragons will require a lot of energy. Coming Together When dragons intersperse with humans, it is highly unlikely that dragons would even understand what they were seeing. Without technological progress it would all be foreign to them. They would have the capacity to learn and understand, but it will take a lot of time, a lot of patience, and a desire to actually pick up the information. What is most interesting, however, is what happens after they come together. Assuming a good faith agreement to co-exist in harmony, you actually have a very interesting situation. Here you have two entirely different “species” that both offer each other some very useful things. Humans, for instance, have the ability to manipulate their environment. Dragons, on the other hand, are enormous creatures that fly using food as fuel and (presumably) have tough armor and a strong natural weapon. This could immediately make it very useful for humans to build enhanced armoring for dragons, provide them with all the food they need, and then utilize them as flying weapons platforms against their enemies. In return the dragons are well fed, provided with a nicely-built home with the amenities they want, and quite likely treated as legends or heroes by the humans they fight with. Eventually, once they’ve been together for long enough, humans may begin assisting dragons by creating the tools necessary to allow them to participate in other activities, including science and engineering. [Answer] Some very general thoughts assuming these dragons do not have anything supernatural/magical associated with them: 1. Dragons' sense of time would be pretty different. Looking at the lifespans (100-500) and birthrates (once every 10 years, how many eggs/live offspring per clutch?, what is the reproductive age bracket for dragons?), the dragon population will have replaced itself very few times. Infact there could even be some elderly dragons around who remember the pre-split days. Contrast that with humans who will have had something like 20 generations of replacement, whose great-grandparents several generations removed were the last to have prolonged contact with dragons. 2. Dragons are probably not as technologically advanced as humans. Assuming there is nothing physically preventing a dragon from building things (maybe they have prehensile thumbs, tails and tongues) and assuming they have started out from the same tech level. Given their population size is small despite the long lives, it suggests there is something holding the population growth back - eg. birthrate is low, few dragons survive to adulthood, there may be little parental/societal care for young dragons, fighting or predation may thin out populations, dragon communities may be isolated, conversely the dragons may be intelligent and social but prefer having fewer children. This coupled with the fact that there haven't been many generations of dragons, may mean the dragons have not reached the critical population size needed to sustain innovation and the spread of new ideas. Being apex predators pre-split, they would have had little impetus to change and adapt, the cornerstones of human evolution. Even if they live in isolated areas without sheep/cattle/humans to provide prey, it is likely they just hunt wild animals (or one another) now. After all, we as early homonids pretty much sustained ourselves without farming for millions of years. But unlike our ancestors, they wouldn't feel the urgency of needing to find new ways to survive and spread out - they don't need clothing or fire, may not need the safety provided by social grouping and could be reasonably comfortable in different climates. No impetus to innovate may well mean they are where they were 500 years ago. 3. The dynamics of dragon society may always have been different Smartness implies some means of transferring knowledge - are they born with 'dragony' memories? Do they have dragon schools? Do they have art? Do they have music? Do they have philosophy and dragon myths? Given the different kinds of dragons, it is likely they have a kind of hierarchy/caste system between themselves. What does this look like and how does it affect them? Do they have large social affiliations? Do they go to war? What motivates a dragon? This may be the card dragons hold for mitigating the effects of points 1 & 2. Maybe they don't need to innovate for physical reasons but for social reasons. 4. Maybe there are areas dragons hold monopoly If dragons have been flying for ages (assuming the lore holds), they probably knew a lot more about aeronautics, geography, cartography and weather than humans did pre-split. Extending this, they may have known more about physics, chemistry and biochemistry (and as they explore on, maths, engineering and other sciences) pre-split. Whether they did manage to build upon their existing strengths during the 500 years would depend on their society and culture. Did a dragon try to fly to the moon and did they build upon that for space travel? Would they build upon that for space travel? [Answer] Dragons are the impossible, whatever their origin - the european evil, giant, fire breathing, armored lizard ; the chinese elemental, giant, wise, flying snakes ; the others I'm not sure about from sea dragons to aztec feathered lizard... - they are more than humans can ever hope - or fear - to be. So how would have a dragon society developed over 500 years ? I'll suppose that there is no magic in your world other than the one allowing the dragons to fly and breath fire. With or without magic, dragons from most culture tend to be very territorial. The one who had to leave their lands will hold quite a grudge toward humans. And, as they are the "evilest" dragons - European dragons tend to be evil where other are often benevolent - they will have caused quite a stir before calming down. Things will have stayed somewhat calm while everyone was scheming the reconquest of the chatel known as humanity. Technologically, they need nothing : they are armed and armored, they are not as greedy as those from our legends,... With the first war for territory, they were left with a population that could be sustained by the land and when the pressure rise, either someone leaves, or he dies. Then humanity, ever the greedy cat (because it's also curious), decides to get to the continent they have ignored all those years, to see if the dragons are so terrible and if there are as many resources there as there are at home. At first, everything will go well. Then two things will happen : Someone tries to convince a mountain dragon that a stretch of land has no owner without a contract and that they can start strip mining its lair. Some dragon will get a CEO place in a big company. The aggressed dragons will go berserk, costing a little bit of peace and a lot of resources to be put down. The scheming dragon will start playing their games and re-instating their domination of humanity, through humanity's rule. The peace will remain ever a fragile thing between impossible beasts of impossible power and a humanity that want to conquer this power. Note : * the great dragons will offer "non intelligent pet lizard" that will de facto act as spy. * I really like Shadowrun take on your question, which inspired me quite a bit. [Answer] What does a dragon want? What does it desire? Mankind wanted to fly so we built things with wings. Then we wanted to go faster so we built engines. Then we wanted to go higher so we built rockets. Each innovation had a triple purpose - elevate mankind, dominate mankind, protect mankind from dragons. Human wars never extended to dragon lands, but they prepared nonetheless. Humans are not large, or powerful, or armed, or armored. We don't move quickly and we can't fly. All leading to the technological place we are now. But for all of our technology, we've only caught up to where the dragons were...500 years ago. Still, our tech is pretty good and we even have a few surprises for the dragons, should they ever break the peace. Dragons are already fast, powerful, apex predators on a planet of potential food. While their slow reproductive cycles are a hindrance to survival, their long lifespans and extensive knowledge of the elements and physics and history gives them a scientific and philosophical advantage to `every` other species on the planet. So what does a dragon want? A dragon wants to live longer, reproduce quicker, eat, sleep and enjoy life without power hungry humans getting in the way. And in 500 years, dragon science has concentrated on cracking genetic code. They've enhanced everything - large dragons are larger, they clutch every 2 years instead of 10, they fly faster, heal faster, camouflage at will, have harder armor, breath fire hotter and farther and live longer. Once it was wise to compromise with the humans to survive, but no more; dragons are abundant now. Brokering a new peace will not be easy. Dragons live long and remember more than living humans have ever learned. And this extended consciousness, the long years since the Split, have done little to dull the anguish of being pushed off their ancient lands, while watching mankind spread like a disease across the world. Peace is not something the dragons are as interested in as they once were. [Answer] It's also slightly impossible for dragons to exist in modern times for the same reason dinosaurs might not be able to live. The bigger ones anyways. Pollution. While dragons can adapt faster than most animals it also takes generations. As mankind progresses with technology, I'm assuming you'll be using natural resources we use currently like oil, pollution makes it harder for larger animals to survive. Not only would dragons need more food to survive they'd also need non-polluted air and water. The older dragons that were young when the split occurred might not be around as humanity starts polluting the air and water. Younger generations might be able to tolerate it, but older dragons will die out as humans use more and more of their fossil fuels. This will bring dragon population down dramatically. And as for how dragons could fly, for those of you wondering, they wouldn't need magic. Just a second pair of "lungs" that could house hydrogen. As for breathing fire, they'd just collect pure platinum in their mouths and store it for when it's needed. Platinum mixed with hydrogen and oxygen creates flames. As dragons adapt to pollution, they'll be slimmer and smaller making for a more viable population for this world and their birthrate. With the dragons breeding every ten years and their natural lifespan, their population would grow at a steady rate. As the elder dragons die off and the hatchlings adapt to survive, their numbers will drop significantly but will still grow. As for the society as a whole, I'd have to say some dragons would create a sort of town. These would be more coastal towns for those who primarily eat fish. This would be water dragons and pygmy dragons. Dragons who hunt bigger game for food would take more to mountains and plains to live and hunt. For technology they would not need it. They wouldn't need protection from anything other than larger dragons looking for a better territory. Despite their intelligence they'd still have predator mentality much like we did and still do. Males being territorial and females being protective of offspring while also doing the hunting. They can problem solve just as well as humans and primates if not better. For simple tasks they have prehensile tails and tongues to lift basic things. This is how they'd be able to corral livestock if they choose to do so. With dragons now being smaller it's a safer assumption that they'd choose to do this as time progresses. They have stronger immune systems than humans so disease isn't a worry for them. Would humans be able to stay out of the dragons' territory for long? How different is human history in this reality compared to ours? Was there a world war? If there was how could the humans stay out of dragon territory without looking for an advantageous spot against the enemy? And how exactly would the move for dragons or humans work? Humans, as a whole, are extremely stubborn. We'd rather start a war than give up what we've claimed as ours. These specifics would help with this concept as well. You need to consider how things differ from our world with this concept. Most of our advances came from the need to improve things in war. Communication, transport, etc. ]
[Question] [ I'm running a tabletop RPG and out of rules convenience I just made it so any injury that isn't fatal or very serious, such as losing a limb, will naturally heal within a day or so. Now this hasn't really come up so far but I feel like this should come up and I have a feeling that this would have some, if not significant, impact on a setting. The question more specifically can be stated as such: In the course of a narrative that isn't strictly about society and culture or the daily humdrum of life but merely one that takes place next to it, what resulting factors from the above scenario are significant enough to bleed into the narrative? As for some relevant details, the rest of the setting is low to mid fantasy, medieval technology and magic. The regeneration is entirely powered by magic and you can ignore things such as the how and why of it, it simply works. [Answer] There will probably be more people in general. Not dying of infection from these injuries probably implies that the magic will help take care of most diseases, which is often what killed people in the first place. I'd be willing to bet that fewer women would die in childbirth. [A quick jaunt across the internet](http://sirjustyn.com/blog/a-most-deadly-battle-birthing-in-the-middle-ages/) (full disclosure: to a not necessarily reliable source, it's a blog) says that in medieval times, 1 in 50 women would die in childbirth. If people were generally healthier and healed faster, childbirth might be easier on the body. There might not be as many midwives. Infant mortality would probably be better, too, and more people would survive to adulthood. Assuming I'm right about the fewer diseases, cities would be bigger, too. [The Ghost Map](http://rads.stackoverflow.com/amzn/click/1594482691) is a semi-interesting high school reading assignment that explains the constant ebb and flow of population and sanitation. Right now, we can have big cities like New York because modern sanitation/health practices support populations that big. But London of the Victorian era – and certainly of the medieval era – just couldn't handle that large of a population. See: [The Black Death](https://en.wikipedia.org/wiki/Consequences_of_the_Black_Death)… yes, yes, it's Wikipedia, but Europe was overpopulated before the Black Death. If you have a world where people are just generally sturdier, you can have bigger cities with less sanitation. These cities might actually creep into your narrative. They might be hellish, crowded, and desperately lacking in infrastructure. Overpopulation could be a big issue. Imagine New York. Now Imagine New York without sewers or showers. (Now give everyone a -150 to their Constitution and make them roll a 20 or throw up immediately, because that is going to smell.) Ah, yes. And speaking of stomachs, overpopulation may cause famine. [This](http://ac.els-cdn.com/S0308521X10001575/1-s2.0-S0308521X10001575-main.pdf?_tid=51bc21ce-8513-11e5-9b1a-00000aacb35f&acdnat=1446875552_95cd2601fdd23cd142d2c035ff63fcee) is an interesting article on the impact of overpopulation on modern society. Now add medieval agriculture and you're going to have some problems. One way this can manifest is by having food be overpriced whenever any of your players try to buy it. As far as politics... well, political demography is actually a field of study. You might find some nations trying to implement one child or two child policies in order to cope with the fact that agriculture can't catch up. Or, given that these people have magic, you may find agriculture/technology making leaps and bounds more quickly than we did on Earth. Fewer fatalities means greater life expectancy, and thus a longer time to study, specialize, and innovate. You also may want to glance over [this book](https://books.google.com/books?id=Ne1TX0ZbtIkC&pg=PA296&lpg=PA296&dq=population+and+politics+since+1750&source=bl&ots=XFWzkEUdBl&sig=pq9BspU8HMbjtFcmqf7bLtxhvUo&hl=en&sa=X&ved=0CD4Q6AEwB2oVChMI4ZbxytD9yAIVjDUmCh1Uighf#v=onepage&q=population%20and%20politics%20since%201750&f=false), which basically explains how modern population growth affects politics. Essentially, more people means less representation. As a result, you may find early forms of socialism emerging in your country's politics... or it'll still be feudal. EDIT: Two more things. People probably wouldn't need healers as often, but when they are needed, they'll be really needed badly. This might result in having to pay healers more, although they'll get paid less often. If you have a healer or some sort of priest in your adventuring party, they might be affected by this. Maybe a random encounter where someone's kid has a life threatening injury and their parent promises to pay a lot of gold? Finally, sports. Extreme sports would be played much more often. An injury would be an inconvenience, not something that would permanently put you out of the game. Gladiator games and arena type sports might be more of a thing. And then, of course, culturally, these people probably wouldn't notice/care about pain to the extent that people here on Earth do. Rough-housing might be more common. It doesn't matter if you break your friend's nose/arm, they'll be fine tomorrow/next week, and they were being annoying. Physical injuries would be thought about less often. Truly severe ones would be profound. [Answer] Physical torture/punishment would be more widespread and prolonged in a world where you could heal injuries within a day. If the character were to capture someone / be captured torture would be more prolonged (and effective?) Think along the lines of Prometheus, in eternal punishment, he is chained to a rock where his liver is eaten daily by an eagle. Being immortal, every night he heals. The next day, the same happens again. [Answer] Wars will become much more common. One Duke can have his little tiff with another at a moment's notice and not have to worry about losing all of his farmers or his ability to defend against future attacks. [Answer] Depending on the mechanism of the regeneration, it could potentially override the bodies normal aging process- i.e. when cells reproduce inaccurately the regeneration corrects for this, meaning nobody over the age of about 40 seems to get older, and people older than that seem to get younger. In essence, you've cured death. This would of course have massive implications. Whether you want to embrace them and have a society of immortals, or just handwave it away is up to you. [Answer] Option 1 is where the rule is clearly non-canon. In this case, the PCs don't actually heal that quickly and in the "real" story they spent much longer accomplishing things. But to make the story more fun the telling of the story glosses over the lengthy recoveries. Of course, that makes other stuff no longer sensible. Like, how did the PCs kill three dragons in one summer if it took 6 months between kills to get their strength back? Well, they didn't. In fact, the PCs only killed one dragon, one of them was killed, two of them quit adventuring, and it took an army to take on the other dragons. But who cares? Story trumps logic here. In essence, the magical healing only affects the PCs and it's explicitly a non-canon, out-of-universe plot gimmick because you and your players decided it was fun. So there's nothing to change in the setting, because it doesn't exist in-universe. Option 2 is to make it canon, in-universe magic, but make it only affect the PCs (and possibly a few select NPCs). Perhaps the PCs are The Chosen Ones and the gods granted a boon upon their births. Perhaps when they met in that tavern in the first episode, an Old Man Who Is Really A Great Wizard cast a spell on them. Maybe it's a one-in-a-million thing, and the PCs actively sought others like them to form an adventuring group. Regardless of exactly how it happened, there is precedent for it in-universe, but it's not generally important because almost nobody else has the same regeneration. The only place you'd really add it to the setting is if a certain bad guy needs to keep up with the PCs or something. Alternately, you could use it as a plot device for "the villagers decide to do experiments on your party to unlock the secrets of your regeneration" or similar. It could be tied to an artifact the PCs possess and need to guard. Option 3 is to make it canon and commonplace. This is where you have to actually start worrying about the world-building aspects. Because constant regeneration means lots of things we are very concerned with would be nearly insignificant to normal people. You'd need to flesh out the how and the why a bit more to get any good answers though. Do people still need to eat and drink? Do people get disease? Infection? Do they age normally? Is heart failure "injury" or "disease"? Where do you draw the line between "major" vs. "minor" injury? Can the magic be dispelled or prevented using other magic? Reversed to kill you faster? Does it exist literally everywhere, or just in certain parts of the world? What if they open a door to another dimension? If most of those answers are pretty normal, then you might not have much difference at all. You won't really hear about the guy who lost his farm because he couldn't work all summer, nor are you likely to see a poor beggar whose back problems make him useless in the area, but those aren't really a huge part of most stories anyways. On the other hand, if people pretty much never die, get sick, etc, it could drastically alter the basic mood of the setting. There would be a lot less of the dark, depressing, dystopian kinds of atmosphere and a lot more Meet the Rogers kinds of atmosphere. This could work for or against your campaign. [Answer] One easiest to blend would be hospitals and medical practice in general. If things like deep cuts heals overnight and no one bothers, then: * There is a lesser need for medical people overall. * Cases they consider normal/easy ones would be pretty horrible to us. So just show the village healer stitching someone up, telling him to rest for an hour and off you go to work. Make wound nicely serious - for our standards. And here you have nice introduction, straightforward enough for most readers, but not too obvious. [Answer] Since regeneration of injuries etc. is about being able to recover from symptoms of "lack"/"incompleteness", (broken/missing limbs, wounds etc.), the new diseases in this world may swing to the opposite end - they will be diseases of exuberance. For example, "glitches" where characters may start re-growing 5-10 new limbs instead of 1 that would prevent them from functioning properly. For an excellent conceptual discussion of this distinction, see Oliver Sacks' "Awakenings". Another twist is that such new ways of perceiving one's body may influence the way people think of time, i.e., time may speed up perceptually. This could lead to already long (eternal?) lives being dreaded, nothing coming to an end. Could result in a different kind of psychological disorders. Or new services - like VR or cryogenics holidays - the only way to give respite to your body and feel it mortal again. [Answer] If humans alone had extended lives our perception of other animals would be changed. Our identities would be less affected by temporary flux and more stable, but also quite possibly more unique in some exciting ways. Childhood would be extended and education more appreciated due to the presence of a highly experienced workforce. Homes would be further invested in. Entertainment would flourish and many people would crave adventure, tired of such long continuity and seeing more things as banal. Society might be more bound by tradition, though people would be more open to experimentation. YOLO wouldn't have the same effect. ]
[Question] [ # Background I'm creating an island on a medieval world with one large port city/town and roughly half a dozen smaller settlements on it. It's not too far from the mainland—several hours at most—but big enough to have a mostly self-sustaining population of its own. ## Conceits of the Setting * The island is in a temperate zone, south of the equator * It's a fantasy setting, with magic. But it's not that widespread * The island has been civilized for hundreds of years * Up until recent history (less than a 5 years) it's been kept safe by a powerful empire * The empire is a generic continent-spanning, mostly-good (but sometimes harsh) empire * It's a generic D&D/Warhammer Fantasy setting ## Reasons for Asking I'm a role-player, and creating this island setting for running my players through a few adventures. I have no idea about population density, appropriately sized land masses, medieval-like city/town/village populations, and everything that follows from them. # Questions 1. How big of an island would this theoretically be? In square miles/kilometers (I'm American, so sq mi would be easier, but I can do the conversion from sq km) 2. What would the total population of the island be, and how would it be distributed? I know that a majority will be in the port city/town, but what about the outlying towns/villages? [Answer] Try [Medieval Demographics Made Easy](http://www222.pair.com/sjohn/blueroom/demog.htm) (MDME), an excellent article written specifically as a guide to creating the population distributions one might use in Fantasy Role-Playing. Here's an example of how to use it, with your "I want one port city" benchmark, to get the rest of the numbers you might like: I need a city with competing bookshops, for plot reasons. Two, maybe.... Okay, then this city has a population on the order of 13000 people. Let's say it's the biggest city. This makes the whole island's population somewhere around 75000 people. Let's make it densely-populated, like a Sicily: 90 ppl/mi2 means the island's size is 833 mi2. Densely populated, small island should be pretty fertile (or else why keep having so many babies!) so lets go with each mi2 settled supports 250 ppl: 300 mi2 settled for about 36% settled, 64% wilderness. No other cities, just towns numbering a half-dozen or so. Call it a 20 mi$\times$40 mi rectangle and you're basically done. (I just used the expectation values for all rolls called for in MDME and rounded liberally. You might want to tweak so as to get at your preferences. For instance, 2d4 rather than 1d8 for number of villages.) --- Bonus Example, to illustrate how a different benchmark could play out: my island would take ten days to cross on foot. Okay, now we're a 240-mile diameter island, or ~45000 mi2. MDME gives me some guidance on likely densities; this is a backwater part of the empire, so I'll pick the number from medieval Britain, 40 ppl/mi2, giving me a population of 1.8 million. The Agriculture section tells me that about 10000 mi2 need to be settled in order to feed those people, so the island's about 20% settled, 80% wilderness. The Population Spread section tells me the largest city should have about 20000 people, another one around 10000 people, and there'll be about 18 towns ranging from 1000 to 8000 residents. &c. &c. &c. --- Further Reading for your particular example: The Edge of the World: A Cultural History of the North Sea and the Transformation of Europe by Michael Pye, esp. pp.177--191 which give great detail of everyday life in areas dependent on fishing, on fishing vessels, and business practices related to the development of commercial fishing, &c. Furthermore, there is a practical calculator available online [here](https://donjon.bin.sh/fantasy/demographics/), sourcing from MDME. [Answer] # This depends largely on your story. For a large medieval town, you can reference almost anywhere, but there was a successful port town of Castelsardo, in Italy, which I seem to recall was an island, or very nearly. It had a climate such as you describe. 1. Wikipedia says it was about 17sqmi (45km2). 2. Our tour guide said at its height, during the medieval ages, was 5,000 people. 3. EDIT - Therefore a nice, typical medieval city could reasonably achieve 300 people per square mile, and function well on trade routes, fishing, and security (your central castle) economies or activities. CAVEAT ALL of this is very generic, because the answer depends HIGHLY on more information needed in your question - size of the kingdom, availability of materials, trade routes, etc. These you may use to adjust these numbers. [Answer] I cannot say precisely what population density an island like that could sustain. I'd suggest a town population of ~10,000 and a rural population of ~3000 (2000 + 1000) for the island. If it is an action game, you could place watch towers at some points. Also, don't keep the terrain all plain. In order to give archers a natural advantage in some places, keep v1 or v2 on higher grounds. I could give you some ideas on the map of the island. Let the town be fortified with a wall and gates. Also, let i2 be a privately owned island by some villain in the game and i1 be a deserted small patch (where you can let your main character build his little base one point in the game). Have some adventure(s) where the hero has to travel from v1 to v2 but force a boat trip. [![enter image description here](https://i.stack.imgur.com/GyhDJ.png)](https://i.stack.imgur.com/GyhDJ.png) ]
[Question] [ If a centaur were to have one set of organs, how would they be placed and what sizes would they be? What limits would there be on the centaur's body? [Answer] ## Digestion A horse's digestive tract is 3-4 times the length of a human digestive tract because horses are able to survive by eating grass, which is very difficult to digest. Centaurs as we typically picture them can’t possibly live on grass, because human hands and mouths are poorly adapted to pick and eat grass. So they pretty much eat human food. You could plausibly keep elements of both the human and horse digestive tract by having food first pass through a human stomach (which breaks down food using hydrochloric acid) and then a horse stomach (which uses fermentation) before going to the small intestine. Arguably, this doesn't even violate your “one set of organs” rule, since even though these organs happen to share the same name, they work in completely separate ways. If you want to use only have the human stomach and restrict the centaur to eating only food that humans can eat, you are looking at a smaller, slimmer horse because you don’t need the extra space. ## Respiration Horse lung capacity is around [50 liters](https://books.google.com/books?id=it-m5VlwKRgC&pg=PA195&lpg=PA195&dq=equine+lung+capacity&source=bl&ots=QxgbpFZJL6&sig=GtU4zsLkzqlekLvFMXwIXczYcek&hl=en&sa=X&ei=JRA3VaHmOYT2yQTC5IGQBA&sqi=2&ved=0CEQQ6AEwBA#v=onepage&q=55%20lit&f=false). Human lung capacity is around 6 liters. Clearly, if we want the centaur to run like a horse, we need to go with the horse lungs. By we need a windpipe big enough to serve 50-liter lungs. Since the human lung capacity is more or less redundant, let’s assume a significant portion of the centaur’s human torso is occupied by a horse trachea which is [5-6 inches in diameter](http://en.wikivet.net/Equine_Upper_Respiratory_Tract_-_Horse_Anatomy#Trachea). However, the shape of the human torso is really defined by lungs. Without lungs, there is no reason for a rib cage, and without a rib cage the centaur just a skinny little spine from hip to shoulder. I recommend that you let the centaur keep a set of small (say 3-4 liter) human lungs in addition to (or connected to) its horse lungs. In addition to making the centaur look right, these could be provide the fine breath control required for understandable human speech. It’s a plausible guess that powerful horse lungs wouldn't be capable of speech. ## Circulation Like with lung capacity, we are going to need at least a horse-sized heart to power the centaur. Rampant speculation leads me to believe that it will actually need to be maybe twice the size of a typical horse heart in order to supply sufficient blood to the centaur’s brain, which is about 1 meter feet directly above the centaur’s heart. ## Body Position In a relaxed state, a horse's projects out from its shoulders a fairly shallow angle less than 135-degrees. A centaur's human torso is typically imagined as projecting up from its withers (horse shoulders) at a 90-degree angle. This means that you need some really beefy muscles around the withers to keep the torso from pitching forward and to stabilize it side-to-side. These extra muscles will probably form a large knot around the shoulders and then slope down toward the horse’s rear, giving the horse-half’s back a much more slanted profile, something like a cross between a giraffe’s back than a horse’s back. It might be possible to ride a centaur, especially since you can hold on around their human torso, but it wouldn't be easy or comfortable without a specially-designed saddle. ]
[Question] [ Imagine the Earth is struck by a laser/magic beam capable of piercing it and leaving a lasting hole. What effects would observed? Would there be a difference between the hole(s) being made in the ocean (one end in the ocean one end not, both on land, both in the ocean)? Would the effects be different if the laser/magic beam missed the Inner and Outer Cores? [Answer] To be honest, "and leaving a lasting hole" piece of your assumption appears to be impossible to sustain with Earth and realist physics. Insides of Earth ([especially the core](http://en.wikipedia.org/wiki/Inner_core#Temperature_and_pressure))) are under big pressure and high temperature. As such, any hole would immediately be closed by the surrounding material expanding into the area of lower pressure that the hole provides (I will handwave this but if you need the formulas Physics or Earth Science SE would be good places to ask for details). The same holds true for the ocean - the water under pressure would expand to fill that hole. If the hole is big enough, it may generate strong waves or even tsunami when water collapses into it, but that'd have to be pretty gynormous, not a "beam" width. Ditto for hole in the Earth - at big enough diameter there might be some sort of seismic event, but not at what is typically thought of as "beam"/"laser" diameter. Now, the REALLY interesting question is, what would be the effects of that laser/magic beam itself? Specifically, to make such a hole, it would impact a LOT of energy to Earth. The dissipation of such energy might be into the core/Earth internals by heating them a bit more; OR on the surface. ]
[Question] [ I'm currently designing a large scale D&D based campaign, magic is based on winds and weather coming from two points, the 'northern pole' and the 'southern pole'. Currently the "world" is a centralised giant continent (hypothetically oval) with a spread of mount ranges through the middle, splitting it. This is taking into account two smaller continents clashing in tectonic fashion and volcanic regions around the equator in the early stages of the planets development. However within this "world" is a clearly defined North and South pole, in which magic flows; 'dark' from north, 'light' from south. However to keep the campaign as realistic as possible I need a way of determining the flows of a current/weather patterns around this entire "oval"-like continent. Does anyone know of ways I could work this out, or even ideas on how the currents would work? Northern/southern hemisphere weather taken into account as well? Season wise the world follows a regular pattern of change, with Spring, Summer, Autumn and Winter. I was very unsure of how the centre of the "super-continent" would work, would winds/weather reach this far down, and in such a strong mountain range? However most rivers would flow from these ranges, and gather in lakes and streams the more out of the continent centre they flow. [Answer] Short answer: (really!) Ocean: it depends on how big your continent is but normally, the ocean currents are influenced by 3 things: the winds, the Coriolis Effect and the landmasses 1. Winds are influenced by the difference of pressure between the different regions. The equator and its surroundings is typically a low pressure zone. This is because it is the hottest place on Earth. Hot air rises and the surrounding air masses converge there to fill the gap. It's a convection movement. The air rise and then moves toward the poles. It cool off with time and eventually the pressure increase is dragging the air mass down near the 30th of latitude. This is know as the Hadley cell. On the poles, it is very cold. Here, the air is not ascending but descending since it's a high pressure area. The air moves toward the equator and is getting warmer until it reaches the 60th latitude. At that latitude, the air movement is ascending. This is the Polar cell. It the middle, you have the mid latitude cell, or Ferrel cell. The dynamic is mostly imposed by the other 2 cells and it just follows a logical continuation of the same convection movement. At 60th of latitude you have ascending air from the pole and from the mid latitude. The air converge there. At the 30th of latitude, you have descending air. The air in this cell rise at 60th and sink back at 30th. If your a visual person like me, take a look at this if it's still not clear: <http://en.wikipedia.org/wiki/File:AtmosphCirc2.png> to summarize Poles : sinking air= dry latitude 60: rising air= humid latitude 30: sinking air= dry Equator: rising air=humid \This is just a general rule. These areas are always moving on Earth according to the seasons and are influenced by different factors including the landmasses. Rising air, this is when you have the precipitations. Other factors also generate precipitations but this is the most important. Rising air is hot near the land but cools off when ascending in the atmosphere. The colder air cannot contain as much humidity as hot air and this water needs to fall down. The sinking air is always dry since it already got rid of most if not all the humidity it once had. Wind interaction with land:* As I mentioned earlier, hot areas will generate low pressure. Your continent will always be hot since it sits on the equator. If it is large enough, it might trigger the mega monsoon mentioned by Ivy\_lynx. It is not easy to extrapolate what we know to an extreme case. Asia is dragging the low pressure area of the equator up north as far as Shangdong China and even beyond. This is because the northern hemisphere gets really hot. I'm speculating a bit here, but in your case the continent (unless it is stretching far from the equator), would probably not have this dragging effect. The low pressure zone would move north and south but not enough to meet the low pressure of the 60th latitude. 2- Coriolis effect: it tends to deflect the currents in a clockwise manner in the northern hemisphere and counter clockwise in the southern hemisphere. By itself, it doesn't make the currents, it really just deflects them. <http://en.wikipedia.org/wiki/Coriolis_effect> Coriolis+wind= it's the same result as with water. At the equator and at the mid latitudes, you have a low pressure area that is drawing the air in. Near the equator, the Coriolis effect is directing the winds and water currents toward the west but towards the east in the mid latitudes. 3-Interaction: water+land+Coriolis: the water currents will converge at the equator. At this latitude, the water flows east to west. Then, when it reaches the coasts of the continent, the water will be deflected toward each poles. The next step depends on the size of the continent. Normally, it would flow towards the pole until the mid latitudes between 30th and 60th and then be pushed toward the east by the dominant winds. One part of the water will probably go poleward of the continent following the dominant winds (west to east). Then, my guess is that without any other landmass, most of the water will reach the opposite shore of the continent and will be deflected back toward the equator. At the poles, water would just spin around like it does around Antarctica. I made you a very nice image :<http://sketchtoy.com/63277181> I think I've covered all the bases. I just need to know the specific information to give a more precise answer. But I might not be able to [Answer] Going by the example of the theorized [Pangea](http://en.wikipedia.org/wiki/Pangaea) and what weather is assumed would exist for it ([Pangean Megamonsoon](http://en.wikipedia.org/wiki/Pangean_megamonsoon)) it seems there could be serious problems caused by the weather. Pangea is also assumed to be elongated in the direction perpendicular to your island, which prevented most of it from becoming a desert, assuming the theory is correct of course. I'm no meteorologist, but going by this theory, the north and southern coasts should be the only temperate areas. I don't think the mountain range in the middle will have a huge effect, since the primary expected effect would be a rain shadow, but it's in the arid region anyway. It could however change how storm systems form but I'd expect them to be quite large and violent since there's lots of ocean for them to form over and grow on. I don't have the expertise to make any assumptions about how closely your island would follow standard island meteorology, nor what the total effect of the huge ocean would be, but I'd expect things to be extreme. ]
[Question] [ I'm trying to work through the mechanics of hard sci-fi space combat, and I came across the [Casaba Howitzer](http://toughsf.blogspot.com/2016/06/the-nuclear-spear-casaba-howitzer.html). The basic idea is a nuclear shaped charge. The blast from a nuclear bomb is partially contained into a cone / beam of plasma which can do some serious damage, according to the numbers in the link above. For reference, a one-megaton Casaba could theoretically apply an energy of 6.7MJ/m^2 to a target 1000 km away, or vaporize half a meter of aluminum at a range of 50 km. The first two obvious ways of applying this concept are A: Put them in a missile which gets close to the target, and detonates outside the target's point defense grid, or B: Use very large versions for long-range combat. Even if you're too far away for the blast to destroy the enemy's armor, it can still wreck havoc on exposed sensors and other delicate components, as well as contribute to overheating the target. While the idea is cool, I don't really like its implications for my 'realistic' space combat system. However, it occurred to me that the key word in the description of the Casaba's energy delivery method is 'plasma'. The Casaba's casing is vaporized into plasma, which is hurled at the target at near-relativistic speeds; but plasma, by definition, is charged, which means you should be able to repel it with a magnetic field. I know that we're working on [magnetic fields for modern spaceships](https://space.stackexchange.com/questions/3772/how-much-power-would-a-spacecrafts-magnetic-shield-require), which can theoretically protect from solar radiation for a fairly minimal energy cost. How much can such a system be scaled up? Could you build a version that could effectively protect against a Casaba? How much energy would it require? Also, shields in soft sci-fi lose integrity / require more power the more they're hit. Would a magnetic shield hit by a Casaba somehow 'lose integrity', or would it continue to function just fine as long as it's fed enough power to repel damage to the ship? [Answer] A charged particle passing through the magnetic field has no work done to it. It’s trajectory changes but not its energy. The magnetic field won’t alter the path of neutral atoms, neutrons, or light produced by the Casaba Howitzer. And, plasma’s are a state of matter dominated by their internal electric and magnetic fields. The individual atoms of plasma are constantly transitioning between neutral and ionized states — the emission of photons by plasma is dominated by recombination processes. As a consequence, the very long mean free path of plasma’s in outer space and recombination, high-velocity neutral particles will traverse the magnetic shield. I suspect the net effect will be that the force of the detonation will be blunted and impact a larger surface area of the ship, weakening the attack. I think one odd consequence of the Casaba detonation would be that the EMP generated by the explosion would couple into the system generating the magnetic shield. This might cause the magnetic shield to become momentarily stronger, or it might become drastically weaker. This effect might provide you with your need for the magnetic shield to need more power when screening an attack since either more energy needs to be sourced to strength the field or power needs to be drained from the system to prevent overloads from damaging the integrity of the shield [Answer] You need to narrow the question down some. You need to decide how strong the casaba howitzers are, and at what range. And you also need to decide how strong the ship hulls are. To be effective, the shields need to be strong enough to disperse the plasma enough to reduce the penetration of the beam to less than the thickness of the hull. In my opinion though, I don't think magnetic shields will be effective, because magnetic fields can't really be directed. By this I mean they're not a beam, they're a field that will surround whatever generated them. This means you can't focus your efforts on creating the field in front of the missile. You'll end up generating a field around your whole ship, wasting most of the energy. ~50% of your energy will be spent keeping the field up on the starboard side, even though the enemy is only on the port side. Think about how much tonnage must be spent on shield generators, most of which will be dead weight most of the time. I think you're better off putting your tonnage into bigger and more accurate point defense weapons so you can shoot down the casaba howitzers before they get in range. Plus PD weapons work on targets that aren't casaba howitzers as well; traditional missiles, boarding craft, crippled enemies you don't want to waste ordnance on, etc. Basically, I think a ship that relied on magnetic shields could be built, but it would be a bad ship overall. [Answer] (OP here, I just got around to actually making an account, so I'm responding to my own question.) Allright, follow on question: The general consensus seems to be that the magnetic shield MIGHT work, IF the plasma beam generated by the Casaba is still, well, plasma; meaning that it's positively charged from the heat of the blast stripping electrons away from their nuclei. The article linked in my original post gave some sample numbers for particle speed and effective range, and it looks as though there's pretty much no situation where a Casaba's effective range will be far enough for the plasma beam to take more than about 1/10th of a second to reach the target, probably less than that. So, how long does it take for the beam of positively charged particle to cool down into a beam of neutrally charged particles? If it's longer than about 1/10th of a second, then a magnetic shield is theoretically effective. EDIT: This also provides a solution to another issue of mine: How to protect against engine wash. If you want a starship with engines powerful enough to provide 1-5 G's of acceleration, while also providing several hundred km/s of delta-v at around 20% of the ship's total mass being propellant, then you pretty much need fusion rockets that output enough energy to be comparable to the solar power Earth receives from the sun. This would make engine wash a fairly viable weapon, which I kinda don't want it to be. Having magnetic shields to protect against the plasma from such engines would be logical and convenient. ]
[Question] [ Our knowledge of exoplanets is changing all the time, but based on observations so far, is it possible to estimate the number of planets in a galaxy the size of our own that would have an Earth-Like gravity? Assume "Earth-Like" to be no more than say 25% higher or lower. It seems to me the limiting factor for colonization of a galaxy would be more related to gravity than atmosphere, temperature, etc; all of these can be overcome with relatively trivial applications of technology. But no technology can negate a Super-Earth with 2gs of gravity. I am trying to imagine a galaxy where the primary in-demand resource would be habitable planets, and that one of the the primary factors in determining what is "habitable" is gravity. [Answer] [NASA estimates 1 billion ‘Earths’ in our galaxy alone](https://www.washingtonpost.com/news/speaking-of-science/wp/2015/07/24/nasa-estimates-1-billion-earths-in-our-galaxy-alone/?utm_term=.7bce9937720b). But their criteria are more rigid - approximately the size of the Earth and are orbiting familiar-looking yellow-sunshine stars in the orbital “habitable zone” where water could be liquid at the surface. So I would guess something about 10 billion. [Answer] The "billions" estimates are probably correct, precisely how many billions is not going to have any significant effect on your plot line. So I will address a different story concern I'd have. > > .. would be more related to gravity than atmosphere, temperature, etc; all of these can be overcome with relatively trivial applications of technology. > > > Sure, but if you are willing to live on a planet without an atmosphere at -200F then you might as well be living in Space! non-optional Gravity is a detriment, and in space another relatively trivial technology to make it optional is just centrifugal spinning of a habitat; when Earth gravity is necessary for plant growing, or light gravity aids various manufacturing concerns (e.g. 0.2 G keeps everything on tables and floors, and liquids in their vessels, instead of floating about the lab or factory). Similarly with a crushing atmosphere, or a molten surface. Which I think kills your story line as implausible; people would not live on planets just for the gravity when they can live in space habitats, with whatever gravity they select, and that is cheaper, safer, and easier than living on a planet. It avoids the gravity well, too: It is easier to relocate, has no weather or natural disasters, planets can be used as shelter from star radiation; solar energy is easier to gather, structures for factories and energy gathering can be flimsy and built with "support" against gravity. The only plausible reason I can think of, for occupying a planet and requiring close to 1 Earth Gravity, is to farm or ranch on a huge scale, hundreds of times the size of cities; or perhaps mining for the hundreds of minerals that only form over millions of years in the pressures and heats found on a planet. We can ignore the cost of getting the product out of the gravity well; the important point here is that to be useful as farms or ranches, the planets must be much more like Earth than just having gravity; they must be able to support the kinds of life we find valuable (food plants and food animals, or food producing animals (bees for honey, chickens for eggs, cattle and goats for milk, etc). Which brings you back to NASA's estimates of maybe a billion. But you can ditch the idea of trivial tech on this scale, so terraforming takes too many years and and your fictional characters discover that upon examination, the number of planets with atmospheres, water, and non-toxic composition suitable for life are rare, closer to 250,000. Then you enter the realm of plausible scarcity. Alternatively, if you just want lots of habitable planets, presume Nasa's billion is an underestimate, and most planets in the Goldilocks zone capable of holding liquid water end up having it, and oceans, at least plant life and an atmosphere with oxygen. It is entirely plausible that life almost never evolves past that stage, and Earth is unique in having any large multi-cellular animal life. (Not that evolution doesn't work, but it only works by accidental mutation, and the particular accidental mutation that put Earth on the path to developing the first "animal" life may have been a one-in-a-quadrillion six-bank billiard's shot that just hasn't happened anywhere else in this galaxy.) You can plausibly make terraforming out of reach so livable planets are rare, or make terraforming unnecessary so livable planets are plentiful. The argument that it is easy to live on desolate planets that wouldn't support life makes no sense, when it would be even easier to live in space. [Answer] In [this article](https://courses.lumenlearning.com/astronomy/chapter/exoplanets-everywhere-what-we-are-learning/) they estimate some 30 billion Earth-sized planets in the galaxy. It's not stated clearly, but it looks that their parameters for "Earth-sized" are from 70% to 140% of Earth's radii. Since a large amount of them will have a lot of habitability problems even having the right size, I think I concur with @Vashu's estimation of roughly 10 billion. ]
[Question] [ In [this Answer](https://worldbuilding.stackexchange.com/questions/77954/vocal-hardware-required-for-a-single-creature-to-communicate-with-any-land-anima/77961#77961) I suggested that an animal could have a tampani acting as a loudspeaker, as in Vernor Vinge’s The Blabber, later featured as the race called Tines in [A Fire Upon the Deep](https://en.wikipedia.org/wiki/A_Fire_Upon_the_Deep). In the original Blabber it was shown that the animal could reproduce any sounds it had collected, like a mockingbird or [lyrebird](https://en.wikipedia.org/wiki/Lyrebird). The use of a structure that’s essentially a loudspeaker allows playback of any waveform within the bandwidth of the speaker. (In the referenced post, separate woofer/tweeter and resonance cavities extend the total bandwidth. That’s not important to this question.) This begs the question: how can such a natural loudspeaker work? The membrane is no problem, nor is a stiff ring to set it in. But how does the driver work? It is doubtful that they could evolve an electromagnetic [voice coil](https://en.wikipedia.org/wiki/Voice_coil) though I'm certainly interested in answers that would explain the biology and evolutionary pathway of that. More generally, how could it work (e.g. using muscles) and be able to playback an arbitrary waveform? Note that the Tines in particular used ultrasonic sound for their group mind, so let’s say it handles up to 30 kHz. Normally vocal cords and the like will simply use muscles to tension a string and then it vibrates at the natural frequency. That can give a repeating wave train of a fundamental and harmonics, but the muscles don’t have to respond on the speed of the sound’s frequency! To simply use muscles to actuate a voice coil would require speed beyond any muscle tissue we understand. I would also be interested in biological adaptations of “alternative” speaker designs such as electrostatic and magnepan — it doesn't have to be exactly analogous to a compact central voice coil driver. [Answer] We know how a normal loudspeaker works, you typically have a rigid cone typically surrounded by a flexible rim, that is further surrounded by a rigid framework. at the center and behind the cone is a coil and a fixed magnet. Electrical impulses create small magnetic fields that move the coil, and thus the cone. This moves the air, and moving air is the basis of sound. You have already resolved the rigid ring and membrane (cone) parts, you now need a driver to replace the coil and magnet arrangement. I can see a small but strong muscle arrangement to act as the driver. The muscle arrangement could work on the principle of alternating cells contracting and relaxing. Say 15000 muscle cells each contract in sequence like cell 1 contracts, cell 2 contracts 1/10000 of a second later while cell one relaxes....and so on. In addition, the membrane should be able to alter it's tension, giving it a different natural frequency, much like tightening a drum head. Loudspeakers will often include multiple, distinct driver/Cone arrangements in order to faithfully reproduce a broader variety of sound. Your critter to do the same thing by utilizing 6 driver and cone arrangements, in pairs. 3 different sizes. That way each size only has to produce a specific range of sound. The pairing arrangement allows for increased volume and the ability to create a 3 dimensional reproduction of the sound. Your critter is going to need a substantial brainpower in order to control this arrangement. Edit: I think I see a pathway for the critter to need a biological loudspeaker. Think of an environment that has very low levels of light and lots of slow moving water, like a swamp, but underground. This creature is not an herbivore, but a heavily armored scavenger/predator/omnivore. Call him Bobby the Boom-Turtle. Very low light means that sight based survival traits take a back seat to sound and smell. Bobby's far distance ancestors became successful because they had good hearing and also learned to mimic. At first, the mimicry was to draw food toward them, either by duplicating mating calls or sounds of other prey animals in distress. Later, in a more sound sensitive environment, a good scream was discovered as a good method of driving away other predators. That's how you get a variety of speakers and larger sizes so that accuracy and volume are both possible. The Bilateral arrangement comes from the following. The ability to produce directional sound means that the potential prey not only gets drawn to the animal in general, but to the head of the animal for a quick strike and kill, like a snapping turtle. In addition, being able to tune the sound in an enclosed environment like a cave, Bobby may be able to "project" sounds to fool competing predators to other areas, leaving Bobby to eat in peace. The directionality comes from the ability to generate the same frequency on a slight delay from two different spots. That's a kind of crude description of how stereo works. This particular guy would end up looking like a tortoise with the "speakers" arranged on the underside with the smaller speakers closer to the head and the larger ones to the rear. Bring Bobby back to earth and he could hire himself out as a self contained mobile DJ. [Answer] In Earth biology, birds have perhaps the widest range of sound production capability. Moreover it's small, can be stabilized during movement, and offers excellent control over volume and pitch. The anatomical mechanism is known as a [Syrinx](https://en.wikipedia.org/wiki/Syrinx_(bird_anatomy)), and has been the subject of a fair bit of study recently, including some [3D modeling efforts](http://www.livescience.com/26080-songbird-voicebox-modeled.html). [Answer] How about you allow your creature some form of [Bioelectrogenesis](https://en.wikipedia.org/wiki/Bioelectrogenesis)? If the animal has some kind of appendage similar to the body of an [electric eel](https://en.wikipedia.org/wiki/Electric_eel), then it could give off electric discharges with strong voltage and amperage in around the millisecond range. The eel like appendage might evolve as a defensive measure, then over time, the creature might gain the ability to curl the appendage, creating coils or loops along its length. The electric eel already does a [rudimentary version of this behaviour](http://www.cell.com/current-biology/fulltext/S0960-9822(15)01147-1) Moving two of these loops close to each other could attenuate a signal, and a natural selection for that ability would possibly give rise to offspring with the ability for more and more windings (possibly by extending the length of the appendage?), which would eventually give you your natural voice coil I think. An amphibious or semi aquatic environment would seem to have a higher likelihood of bringing about this kind of an appendage given the electric eel's evolution. Or maybe some incredibly moisture rich atmosphere would allow it's evolution ? [Answer] For animals on earth, the simplest and most common method of achieving extreme loudness is a resonance chamber - basically a large vibrating air pocket. You don't need any special exotic mechanism to make sounds as loud as an electronic loudspeaker - just a big enough resonance chamber and regular old vibrating muscles. A rock concert reaches 120 decibels (right at the edge of the human threshold for pain). The loudest land animal on earth, the howler monkey, goes up to 128 decibels. Keep in mind that decibels are a logarithmic scale; 128 decibels is much louder than 120. The sound produced by a resonance chamber is mainly limited by the resonance chamber's size. Because of this, larger animals will find an easier time producing loud sounds (not too surprising) but smaller animals can pull off big noises by making extra space for big resonance chambers. Usually this resonance chamber is in the throat, but it doesn't have to be; the proboscis monkey has one in its big honking nose, and the hadrosaurid dinosaur Parasaurolophous had one in its crest (which was technically an elongated nasal cavity). Frogs can create temporary resonance chambers by inflating their throat pouches, so they don't have to carry them around all the time. Human singers and orators learn to use parts of their mouth, throat and chest as resonance chambers, though of course our ability to do so is limited by our relatively non-inflatable physiology it does demonstrate the principle in action. Sound amplification mechanisms commonly evolve in animals that require large territories and prefer to avoid physical confrontations whenever possible. Birds, who can move quickly, require large territories due to their high energy requirement, and risk life-threatening injury whenever they fight (flight requires extremely precise mechanisms to work, and a bird that can't fly is as good as dead), are well known for staking out their territory through sound. Mimicry is often related to sexual selection, as being able to memorize complex and varied sounds is an advertisement of intelligence; this form of competition is also commonly found in birds, possibly because, as stated previously, birds are taking a huge risk whenever they get into a physical fight so non-physical methods of competition tend to flourish instead. So, I would expect such a creature that is both loud and capable of mimicry to have a bird-like lifestyle. Like a frog, it could have an inflatable throat pouch that enables it to amplify its calls. It may resemble a Great Frigatebird in appearance, although frigatebirds do not use their throat sacs for sound amplification. A howler monkey's resonating throat chamber is only a few inches across and can create sounds that can be heard up to 2 kilometers away; the Great Frogatebird's main limitation is going to be its ability to avoid deafening itself with its calls! To avoid this, it may be able to "lock" its ear bones in place when it makes loud noises. There are some species of bats that do this to avoid deafening themselves with their own echolocation sounds (they lock their bones when making the sound, so they only actually hear the echo). [Answer] A living speaker can be made out of organic matter, it's possible; as stated by @PaulTIKI. For this kind of Organism to "Naturally" evolve though, it would really depend on the environment it's living in, an environment that favors an organism that can reproduce sounds it had heard (or new ones), and loudly too.. it could be as a means of communication, to repel predators, or just a byproduct of something else that they do. being able to produce large sounds means they make easy prey, so i suggest a symbiotic relationship with another organism is in place. an example : a cold planet, where days are mostly dark; most organisms are blind and rely on only sounds as a means of interacting with the environment; the living speakers could vibrate as a means of heating itself. they produce loud sounds to deter predators, and mimic sounds of other organisms to lure prey (they might have to be stationary, these speakers). ]
[Question] [ What characteristics might define a group of multicellular chemosynthetic organisms (similar to that of bacteria living in earth's hot springs and deep sea vents, but relatively more complex, as mushrooms (a fungus with multiple cell fates) and lichens (a symbiosis between a fungus and an alga) are more complex than yeast)? For example, would they have to be sessile, or could they be motile? Vascular or nonvascular? Would their lifestyle necessitate a unique anatomy or mode of reproduction, or might they appear to be just another kind of plant or fungus? [Answer] Multicellularity ultimately allows the delegation of tasks to different tissues. But that comes at a cost - Reproduction is far easier for bacteria than for us. It's not evident that we are winning the evolution race just because we are bigger with brains. We have consciousness, and the internet, so we still think it is a good trade, though. A multicellular chemosynthesizer (by definition, an organism that synthesizes complex carbon using chemical energy) needs to have access to that chemical energy. The chemical energy we commonly see on earth, is H2S. The electrons in H2S have more energy than the (H2O) electrons used in photosynthesis. Photosynthesis can get by with low energy electrons, because the sun (photo) provides the energy. So, if you are limiting yourself to H2S, then I would think your organisms should be sessile, and associated with reducing environments. this means not a lot of O2, and that in turn means not a good chance for multicellularity, since oxygen is (almost universally used by multicellular organisms and) such a great electron acceptor for respiration. Anything that respires (i.e. most of life) and has learned to harness oxygen, is essentially harnessing fire (another use of oxygen) because oxygen is so reactive. It will take any electron you give it - even the low energy ones. All of this is to say: it is unlikely to have a well developed chemosynthesizer that is multicellular, because oxygen is such a great basic ingredient for multicellularity, and H2S (which is the chemical energy that usually drives chemosynthesis) exists in reducing environments, precluding oxygen. But sessile is a good bet. [Answer] Yeast is considered part of the fungus kingdom. Mushrooms are the "flowers" of fungi. So, you are basically asking if a species was more similar to a fungus than to a fungus, could it have characteristics of a fungus? Uh, maybe. I'm not a biologist by any stretch of the imagination, but I think it is safe to say that complexity is roughly proportional to the size of a organism's genome (see chart in <https://en.wikipedia.org/wiki/Genome_size>). I don't dispute that lichen - which are a symbiotic assembly of several different organisms - are more complex than any of its (two or three) component species, by definition. Aside from those problems with your question, to answer what characteristics they'd have requires you to more clearly explain where they're getting their nutrients from - and what predators and competitors they have in their ecology. If you're familiar with the various life cycles and lifestyles of fungi, you no doubt know that they have all sorts of interesting characteristics. They aren't motile because they don't need to be. As an organism increases in complexity, the value of the individual (the "investment" in that individual in terms of energy and time) increases (as far as its genes are concerned). Therefore, more complex behavior will be created only when and where it's needed. Given the significant size limitations of diffusion, vascular structure will be necessary above a fairly small size. You'll note the overlap in genome size between plants and fungi in that Wikipedia chart and you can also compare the size and mass of a Giant Redwood with a Blue Whale. It's safe to say that the largest organisms in the world are plants, although exactly which plant is largest is being debated. Size isn't necessarily the same as complexity, of course. I guess the best answer to your question is that it depends. If the chemicals flow from a steady fixed source, then a sessile lifestyle could work, if the flow varies (by season, or availability, or weather) then it may need to pack up and move to greener pastures. [Answer] If your creatures only live around hydrothermal vents and hot springs, they will have to be motile OR have a dispersal phase of their lifecycle (like spores or planktonic larvae drifting on the currents) because vents can be short-lived. They are also often widely spaced. See [this article](http://www.briangwilliams.us/marine-ecology/deepsea-hydrothermal-vent-communities.html). > > The lifetime of hydrothermal vents and their communities may be very short, a few decades, or very long depending on the rate of sea-floor spreading in the active region. Local communities of tubeworms, destroyed by fresh lava eruptions, can regrow within 2 to 3 years (Lutz and Haymon, 1994). Vents and vent fields are often separated by hundreds of kilometres and the question of how new vents are colonized is still being studied. Biologists at the Plymouth Marine Laboratory (UK) are studying larval DNA of vent animals to help trace their dispersal and relationships with populations elsewhere. American scientists have discovered species of animals normally only associated with vents, on whale carcasses on the deep-sea bed. They speculate that these carcasses provide ephemeral stepping-stones which allow animals to cross more easily between vents. However, recently it has been discovered that in some areas, such vents are very common and can be found at distances of only 20 miles or so apart. In these cases, spread from one vent to another would be relatively easy. > > > The main problem for your chemosynthetic organisms is that they are likely using chemical reactions which provide less energy than the oxygen producing/burning photosynthetic organisms. So they just do everything slower. If it takes a year for a photosynthetic plant to grow to maturity, it might take 3 or 4 years for a chemosynthetic one to reach the same size. [Answer] From Wikipedia: > > Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). > > > So I am a chemotroph by virtue of the oxidation of cheese going on right now inside me. I think that you mean chemolithotrophs: a multicellular organism with energy metabolism like that of a sulfur bacterium or something like that. One could make a strong case that only prokaryotes do any energy metabolism. Eukaryotes have tamed commensal prokaryotes safely ensconced within their cells which do the work. Mitochondria are the degenerate prokaryotes inside my cells working on the cheese. Chloroplasts are the ones in plants that use solar energy to reduce carbon. @Andrew nails it with his question: how is the proposed organism different? Clams and worms with commensal chemolithotrophs have prokaryotes which are not as degenerate as our mitochondria but at the end of the day it is a matter of degree. Your organism would be either be totally bizarre (in which case make up whatever) or a eukaryotic cell with tame commensal prokaryotes of your choice depending on what kind of energy metabolism you want. If these are archons that are poisoned by oxygen then I could imagine a system for your multicellular beast which incorporates something like root nodules in nitrogen fixing plants. Within these root nodules are prokaryotes which do the nitrogen chemistry, and the plant gives them room and board and protects them from oxygen with oxygen-scavenging leghemoglobin. Motile creatures mostly are chemoorganotrophs like me; chasing around food or wandering from plant to plant, eating other organisms. The rare exceptions are things like the aforementioned worms with commensal chemolithotrophs or organisms like jellyfish that contain photosynthetic commensals. Inorganic energy sources will not try to escape. Your organism could be sessile if the inorganic energy source were a constant - for example a steady flow of reduced iron from a hydrothermal vent. If your energy sources were spread out - maybe sulfur granules? - then it would benefit your organism to be able to wander around seeking them. [Answer] A good question. The funniest thing is that organisms you described actually lived on Earth at the very dawn of life. These organisms are said to be the "inventors" of photosynthesis, but you have to understand that they existed before photosynthesis. Have a look: <https://en.m.wikipedia.org/wiki/Microbial_mat> ]
[Question] [ Suppose that I have a planet very similar to Earth. It has the same level of gravity, water-land ratio, temperature, air composition, rotation and revolution speed, tectonic activities, temperature. It has ice caps on the poles just like Earth. It also have life on it with plants, animals and humans, although they can be different than what we have here. How small this planet can be in diameter while still retaining those properties? I suspect that such planet would have to be denser so that it retains the same amount of mass which will then affect the gravitational pull. But just how small is the limit so that it still have enough time (that is the core is still active long enough) for life to bloom on it and evolve into our level (bipedal humanoid with intelligence, if possible). [Answer] # Surface gravity Surface gravity is really the most important quantity when it comes to determining many of your planet's properties. It can be used to constrain atmospheric composition, planetary mass and radius, composition, and more. A planet with mass $M$ and radius $R$ has a surface gravity of $g\equiv GM/R^2$. Therefore, all planets with Earth's surface gravity obey the following mass-radius relation: $$\frac{M}{M\_{\oplus}}=\left(\frac{R}{R\_{\oplus}}\right)^2\tag{1}$$ where $\_{\oplus}$ denotes a parameter of Earth. Theorists have come up with additional mass-radius relations that depend on a planet's composition. [Seager et al. 2008](https://arxiv.org/pdf/0707.2895v1.pdf) came up with mass-radius relations for a number of rocky planet compositions. I've plotted their results for several different planet types (iron, water, silicate, and graphite), as well as the criterion from $(1)$: [![Plot of mass-radius relations](https://i.stack.imgur.com/WYN4P.png)](https://i.stack.imgur.com/WYN4P.png) Assuming that iron is the densest likely composition, we see a lower radius limit of $R\approx0.5R\_{\oplus}$, corresponding to $M\approx0.2M\_{\oplus}$. We appear to have found exoplanets with higher densities (e.g. [Kepler-36b](https://en.wikipedia.org/wiki/Kepler-37b)), but those may be due to measurement errors; they seem unphysical. Now, iron planets are often thought to form through giant impacts - collisions between protoplanets ([Marcus et al. 2010](http://adsabs.harvard.edu/abs/2010ApJ...712L..73M)); Mercury is thought to have been affected by such a collisions. We can calculate the mass of the largest remnant of such a collision by the formula $$M\_{\text{rem}}=\left[-1.2(f\_{\text{Fe}}-0.33)^{1/1.65}+1\right]M\_0(1+\gamma)$$ where $f\_{\text{Fe}}$ is the final iron mass fraction, $M\_0$ is the initial mass of the protoplanet, and $\gamma$ is the mass ratio of the impactor to the protoplanet. Typically, an upper limit of $f\_{\text{Fe}}\sim0.8$ is assumeto be the theoretical limit. If we ignore this and set $f\_{\text{Fe}}=1$ and $M\_{\text{rem}}=0.2M\_{\oplus}$, we find that $M\_0(1+\gamma)=3.41$, which can be satisfied by, say, a $2M\_{\oplus}$ protoplanet and a $1.4M\_{\oplus}$ projectile - not unreasonable. For $f\_{\text{Fe}}=0.8$, we can afford to have smaller bodies. Either way, producing an iron planet of the desired mass is quite easy. # Plate tectonics Plate tectonics depend on a number of factors, including a planet's size and composition. The smaller the planet, the quicker the cooling rate, meaning that this body is likely to cool quickly, making plate tectonics unfeasible. Arguably, though, our stripped-mantle iron planet lacks a mantle or crust, and so plate tectonics as we know it cannot exist at any point in time. # Temperature Assuming a solid iron surface, with water constituting the liquid part, I see no reason why the temperature couldn't be similar to Earth, assuming a similar atmosphere. The albedo should be the same, and if the planet is as far from a Sun-like star as Earth is, [its effective temperature](https://en.wikipedia.org/wiki/Effective_temperature) should be the same. Depending on the atmosphere you end up with, you can vary the orbital and stellar parameters as you choose. # Atmosphere [Atmospheric escape is going to be a problem](https://en.wikipedia.org/wiki/Atmospheric_escape); it's how Earth lost its early hydrogen/helium envelope. I covered that more thoroughly in [an answer on Physics Stack Exchange](https://physics.stackexchange.com/a/293790/56299), but the important equation here is for the Jeans flux for a particle of mass $m$, $\phi\_J(m)$, which describes how many particles of mass $m$ will escape the atmosphere through thermal methods: $$\phi\_J(m)\propto n\_c\sqrt{\frac{2kT}{m}}\left(1+\frac{GMm}{kTr}\right)\exp\left(-\frac{GMm}{kTr}\right)$$ The important term here is $$\frac{GMm}{kTr}\approx\frac{gR}{kT}$$ where $r$ is the distance to the lower edge of the exosphere. Given that $g$ is the same as $g$ on Earth, and $R=0.2R\_{\oplus}$, then at Earth-like surface temperatures, we should see substantially higher Jeans fluxes. Jeans flux primarily impacts hydrogen, helium, and other light gases, so these gases may be lost entirely. It's also possible that oxygen, nitrogen, and related gases will be lost, although the main mechanisms for their loss are non-thermal. Still, you likely will have an atmosphere different from Earth's. # Rotation and revolution These are essentially arbitrary. You can put the planet as close or as far from the star as you want (although I'd recommend keeping it in the habitable zone if you want life), so you can pick whatever values suit your purposes. Size, mass and surface gravity aren't important here for low rotation rates; as ben pointed out, for large angular speeds, the centrifugal force does indeed become important. [Answer] We can probably make a really small planet if we assume it is made of a very dense material like iridium or platinum or such - at least in the core. However, there is another factor which we need - size of the biome. The smaller the biome, the slower it will develop. A sufficiently small one might even end up in an evolutionary stand-still - any advances which require a few less advantageous mutations to happen are impossible because the biome is too small for them to survive the unmutated competition long enough. If you want a really small planet and high speed evolution, I suggest a water planet with frozen polar caps. Kind of like Europa, but in the habitable zone. Let it have lots of energy, say from being part of a binary planet system and close to a not-too-bright sun, so tidal forces heat up the core and create loads of underwater volcanoes. This planet has a much lower gravity, but could otherwise be quite similar to Earth. Plants could start to form as algae, growing into water lilies in small water lakes surrounded by ice, then spread over the rest of the ocean and eventually compete for height, forming grass or even bamboo like floating plants, connected with roots, so smaller animals can walk on them - like in a swamp. As there is no real land, we have to evolve our humanoids from animals closer to the ocean - maybe similar to penguins, but eventually conquering the ice in a fashion close to the Innuit and taking plants with them using green houses or floating farms once they have technology. ]

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