Activity for celtschk
| Type | On... | Excerpt | Status | Date |
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A: How large could a planet be yet still approach 1 Earth gravity and support life as we know it? For a spherically symmetric planet, surface gravitation is determined by just two quantities: The average density, $\rho$, and the radius, $R$. In particular, due to spherical symmetry you can consider the whole planet's mass to be concentrated in the center, and then you get for the gravitational ac... (more) |
— | over 8 years ago |
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A: Could a person see with glowing eyes? One way to give a glow without causing vision problems would be if that glow is monochromatic (just one frequency), and at the same time that person happens to be blind for exactly that frequency, without affecting vision of any other frequency. That way his seeing would only be minimally affected be... (more) |
— | over 8 years ago |
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Can there be planets with extremely strong magnetic fields? Would it be possible for a planet with surface conditions suitable for humans landing on it to have a very strong magnetic field, with field strengths on the planet's surface similar to the surface field strength of a typical kitchen magnet? (more) |
— | almost 9 years ago |
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A: How to make a rogue planet liveable? The main problem would be energy. Without a star as energy source, you will have to produce all the energy yourself. You'll need a lot of energy, so probably fusion is the right source (note that in the end, stars are also nothing but huge fusion reactors). I'll assume by then humanity has managed co... (more) |
— | almost 9 years ago |
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A: Properties of air cloud in space You need enough air that its own gravity holds it together. However that means in the center you'll have much more than atmospheric pressure; indeed I don't think your air will be gaseous in the center. In other words, what you have built is not an air cloud, but an air planet (except that it might n... (more) |
— | almost 9 years ago |
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A: Repulsive Universe I guess atoms would still form (hydrogen, some helium, traces of lithium). However there won't be galaxies or stars, as it's exactly the attractive nature of the gravitation that creates that type of structure. And it's exactly because attractive gravitation does not lead to an equilibrium that we ge... (more) |
— | almost 9 years ago |
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A: What common chemical/physical reactions would, in an atmosphere composed of ~20% Oxygen and ~80% Argon, behave differently than on Earth? I think plants would get into trouble. Plants need nitrogen compounds, which many of them get from bacteria that take the nitrogen from the air. Without nitrogen in the air, those bacteria cannot create nitrogen compounds, and thus those plants are in trouble. Note that the nitrogen compounds in dun... (more) |
— | almost 9 years ago |
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A: In what form can data survive the longest time? The most durable information storage is having it carved in stone or in clay that then got burned. Our oldest writings are of that form, and they are thousands of years old. The main problem of this data storage is to explain why the information is stored that way. But maybe it was done intentionally... (more) |
— | almost 9 years ago |
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A: How could an underwater civilization develop electricity? How would the civilization discover electricity? That one is easy: There are animals in the sea that use electricity, like the electric eel. The underwater civilization would certainly be curious about how that works. How could the civilization use electricity (without electrocuting themselves)? T... (more) |
— | almost 9 years ago |
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A: Could faster-than-light supernova remnants form a star system? When reading "faster than light" one normally thinks of it as faster than the limit speed of relativity, which is the same as the speed of light in relativity, as the photon is massless and therefore goes with that limit speed. But in your case, you literally are interested in the matter arriving ea... (more) |
— | about 9 years ago |
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A: Could a force with these properties exist in a parallel universe? tl;dr: No, it is not possible to have the force proportional to the product of the square roots of the charges. In an alternate universe there is a force known as the emotion force although the force has nothing to do with emotions. Anything that interacts through the emotion force has an emotion... (more) |
— | about 9 years ago |
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A: What would organisms be like in four physical dimensions? Well, the first obvious difference would be that the square-cube law would basically be replaced by a cube-tesseract law. Since 4/3 is closer to 1 than 3/2, this means that there could be greater variations in size. Another difference is that more of the (hyper-)volume is close to the (hyper-)surface... (more) |
— | about 9 years ago |
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A: Creating natural two tone hair growth The hair could contain a combination of chemical substances that changes colour after a given time. If the time needed for that process is long enough to allow the hair to significantly grow, but smaller than the life time of the hair (say, about half as long), then you get two-tone hair. See Wikipe... (more) |
— | about 9 years ago |
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A: How to Convince Humans to Allow a Machine Take-Over Machines are not in a hurry, impatience is one of those inferior human traits the machines want to eliminate. Therefore it is not necessary to have humans give up their life; it's sufficient to just prevent new humans to come into existence, and in about a hundred years the problem will have resolved... (more) |
— | about 9 years ago |
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How far would I have to be from a nuclear detonation in space in order to survive it? Assume someone detonates a Hiroshima-sized nuclear bomb in space. Since in space there's no air, the bomb will behave differently than on Earth. In particular, there will not be an air pressure wave, and certainly no "mushroom" cloud "” the energy will be sent in all directions equally, as kinetic en... (more) |
— | about 9 years ago |
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The AI that fails to be evil A recurring theme is how an artificial intelligence that was built with completely reasonable and positive goals instead does great harm to the world. However I'm now thinking about the reverse: A supervillain builds an AI specifically for making people's life miserable. Its task is very simple: Max... (more) |
— | about 9 years ago |
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A: How Do We Keep The Moon From Eating The World? Let's do a bit of math. According to Wikipedia, the mass of the moon is $7.3\cdot10^{22}\,\rm kg$ and its average orbital speed is $1.0\,\rm km/s$. That means its kinetic energy is $3.7\cdot 10^{28}\,\rm J$. According to the virial theorem the potential energy is $-2$ times the kinetic energy. To ge... (more) |
— | about 9 years ago |
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A: Is it possible for a planet to be devoid of polar ice caps? It is definitely possible. Like for example the earth at the time of the dinosaurs. Quote (from relatively far down on the page): As the world entered the Cretaceous Period, Antarctica was very much situated at or near the South Pole. But at least during a major part of this period, there were no... (more) |
— | about 9 years ago |
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A: Jumping vs. FTL speeds: economic differences I'm making the following simplifying assumptions: No time travel, time dilation or other temporal effects through use of those technologies (basically, the travelling works as if there were an universal absolute time). I ignore the cost of setting up/building drives or infrastructure, as there's no... (more) |
— | about 9 years ago |
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A: Does intelligence necessarily lead to an abstract language? Human language evolved for the interaction between humans. That may sound like a trivial fact, but it isn't: If there had not been social interaction between humans, humans would not have evolved language. Therefore the question basically reduces to: Does a species need to be social in order to deve... (more) |
— | about 9 years ago |
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A: How would a human livestock facility run by aliens operate? (Ab)Use Religion to control the people A properly maintained religion can get people to do almost everything, and can guide their behaviour. People have killed others in the name of their religion. People have willingly gone to their dead in the name of their religion. In short, a carefully crafted ... (more) |
— | about 9 years ago |
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Realistic spaceships: How to design a transport spaceship? OK, here's the problem: I want to have a spaceship that is built for transporting large machines (in particular, heavy mining equipment). It does not and is not designed to leave space; transport down to a planet (if necessary) is done by other, specialized ships. It is operated by two people, and it... (more) |
— | about 9 years ago |
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A: bringing darkness to live Well, as scientists have found out, the universe is full of dark matter; indeed there's more than five times as much dark matter than ordinary matter. Now dark matter is called such because we cannot see it, but only see its gravitational effects. It is thought that it consists of particles that don'... (more) |
— | about 9 years ago |
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A: How do I create a societal collapse with ruins, while the tech can make Ridiculously Human Military Androids? Your advanced civilization stored all knowledge in electronic systems. Moreover, all work was done by robots or androids. Therefore humans didn't have much practical knowledge (it wasn't needed because the androids did everything for you). Moreover, people didn't have knowledge such as how to make gu... (more) |
— | about 9 years ago |
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A: Where is the inside of the Tardis? Is it a world in itself? Is it part of a different world? I would say it's a bit of independent space that's "glued" to ordinary space at the entry door. That also explains how time travelling works: That independent space is "unglued" from space, and then "glued" again to space at another time. The rest of the police box is just a bit of camouflage in ord... (more) |
— | about 9 years ago |
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A: Orbiting one star in a binary system: what are the effects of the second star on the planet? OK, so we have two sun-like stars (I'll just write "suns" from now on) at $100\,\rm AU$ distance, and a (probably earth-like) planet at $1\,\rm AU$ distance from one of the suns. I'll call the sun the planet orbits the "near sun" and the other one the "far sun". I'll assume circular orbits throughout... (more) |
— | about 9 years ago |
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A: You have some cheat codes for real life, but they're expensive to use. Can they still be used? Whoever has this machines and the resources to operate it, basically has absolute power. It is the ultimate weapon (just delete your enemies). It will allow you to go to space easily. It will allow you to mass produce any item (which of course will rise a few interesting questions: If you perfectly c... (more) |
— | about 9 years ago |
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A: Ways to make contact with aliens on a much larger size scale? Well, some mosquitos when flying make a noise that is clearly audible by a human (as everyone who had one in the room at night knows from painful experience). So I assume that ship has the same ability to make such noise; possibly also when not actually flying. So the solution could be to sit down cl... (more) |
— | about 9 years ago |
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A: How to preserve the remaining trolls? Many animals also prefer to chase their food, but are not allowed to at zoos. And a troll that has to decide between starving and scavenging almost certainly would prefer the latter. Therefore a solution could be to feed the dead to the trolls instead of burial. Given that cultures developed that fe... (more) |
— | about 9 years ago |
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How to make a flying human We are in a future where genetics has advanced to a point where arbitrary modifications can be done to living beings. Now a geneticist wants to make a flying human. That is, he wants to modify a human so that his arms turn into wings (but still with hands at the end, so doing all things humans usuall... (more) |
— | over 9 years ago |
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A: What would the periodic table of a 4-Dimensional universe look like? In four dimensions, you don't have a rotation axis (fixed straight line) but a rotation plane (fixed plane). However, not every 4D rotation has a rotation plane; there are rotations which have no fixed points (except for the origin). Indeed, rotations in 4 dimensions have six parameters instead of th... (more) |
— | over 9 years ago |
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A: Taming wormholes Yes, the ends of a wormhole basically behave like a normal celestial body (assuming there's no additional physics not yet known to us that affects their movement). They would move with the expanding universe, and they might even orbit a star. However I have no idea what the apparent mass of a wormhol... (more) |
— | over 9 years ago |
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A: Future galactic economy Raw materials may be available everywhere, but maybe the best FTL drives are built in the Aldebaran system, the best conventional thrusters are built around Barnard's Star, the asteroid mining equipment industries still concentrate in our solar system, and the best computers are built at Betelgeuse. ... (more) |
— | over 9 years ago |
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A: Compatible biochemistry, or not? Well, I'm not a biologist or biochemist, but I think your scenario could be made to work (although still very unlikely) as follows: Our genetic code is based on four nucleotides which make up two pairs of complementary bases. Now there's no reason to assume that the genetic code of the aliens is the... (more) |
— | over 9 years ago |
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A: How would humans treat dogs that are more intelligent than humans and can speak? While there would certainly variations, I think for the dominant treatment there would be only three possibilities: Enslavement. If we can keep control over the dogs despite their intelligence, then the dogs will effectively be enslaved. Note that this is true even if those dogs are loved: We love ... (more) |
— | over 9 years ago |
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A: What would the biosphere look like with a constant twilight/midnight sun? Since in your world, there are no natural time cycles, life will not have an external synchronization. Therefore the main changes in your world will be to changing weather (unless your world doesn't have that either). Instead of day-active and night-active animals, you might have dry-active and rain-... (more) |
— | over 9 years ago |
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A: How might one create a room in which time flows faster? Here's one method that doesn't rely on either gravitational time dilation or simulation: If you look at the basic equations of quantum mechanics, you notice that if you scale all masses by a common factor, you'll get essentially the same physics, just at different length and time scales. In particul... (more) |
— | over 9 years ago |
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Animals for weightlessness OK, so humanity is going to space, and they are going to take farm animals into space, not only humans on earth value meat, but humans in space do, too. However, they don't want to waste precious resources such as artificial gravity for the farming, so instead of adapting the space ship, they decide ... (more) |
— | over 9 years ago |
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A: A one time source of high energy in a post apocalyptic world with limited energy There are many one-time energy sources around: They are called bombs. So maybe there's a leftover nuclear bomb around. People would naturally not normally want to trigger it. However, if it is the only way to open that alien construct, and can be done at a safe distance (say, the alien construct is ... (more) |
— | over 9 years ago |
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A pill to make you think faster: Side effects? OK, so scientists have found a great new substance: That substance makes you think ten times as fast! The advantages are obvious. However, as every medicine, this pill will have side effects. There are obvious side effects like that a faster-thinking brain will likely also have a much higher energy ... (more) |
— | over 9 years ago |
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A: What is the best way to exploit the energy from a red dwarf and send it to other systems? Here's an unconventional idea (which however assumes you are able to build large space constructs): Put a gigantic parabolic mirror around Barnard's star which concentrates the energy in a focal point near earth (or wherever else you need the energy), where you put a receiving station (which may simp... (more) |
— | over 9 years ago |
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How large could a planetary diamond be? Back in the days when men were real men, women were real women, and small, furry creatures from Alpha Centauri were real small furry creatures from Alpha Centaury, an obscenely rich woman decided she wanted to have the biggest diamond of all. Realizing that this would mean a diamond of planetary siz... (more) |
— | over 9 years ago |
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Radiation shielding for a space ship Space is full of radiation. When doing long stays in space, no matter whether it's a generation ship on its journey to a new colony, a research ship exploring new worlds, a freighter delivering goods, or simply a space station outside the protective magnetic field of earth or another planet, the peop... (more) |
— | over 9 years ago |
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A: Flu Rage virus used as interstellar weapon? I think all the virus would need to do to have that effect is to dramatically ramp up the levels of adrenaline and testosterone. I think it is perfectly possible that a custom-designed virus could cause that. Indeed, it could simply contain extra genes for those hormones, to be expressed by any infec... (more) |
— | over 9 years ago |
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Sharks with frickin' lasers! Yes, this is about Dr. Evil's dream: Sharks with frickin' lasers. Except that the lasers would not be artificially attached, but be part of the animal itself (bio-lasing instead of simply bioluminescence). In short: Would it be possible for an animal (shark or otherwise) to grow a laser at its head ... (more) |
— | over 9 years ago |
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On a generation ship, how to handle the dead? One thing that necessarily happens on a generation ship is that people die of old age. Now that poses a tension: On one hand, you need to handle the dead with dignity. On the other hand, you probably cannot afford losing the materials the dead are composed of. So in short: How would a generation shi... (more) |
— | over 9 years ago |
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A: Explaining uphill rivers scientifically? To add to the other answers, there's also the possibility of the water appearing to run uphill due to a an optical illusion. I'm not aware of any river where this is the case, but since it happens with roads I see no reason why it couldn't also happen with rivers. (more) |
— | over 9 years ago |
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A: Acceleration insulation: I can build the Moon cannon, now what? First, an "acceleration shield" in the true sense of the word is impossible. However, one could imagine something close to it: The reason why acceleration affects you is that it actually doesn't affect you: When the car accelerates, you don't accelerate with the car, and therefore the car presses ag... (more) |
— | over 9 years ago |
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Humans as pollinators Plants can have very different pollinators: The wind, insects, and even birds. However, is there a conceivable scenario where a plant could naturally have evolved to depend on humans as pollinators, where the humans (at least in the early stages of development) wouldn't know that they are pollinating... (more) |
— | over 9 years ago |
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A: Chemoautotrophic Flora! I think such plants would have no use for leaves. Leaves are basically solar energy collectors, and since your plants do not do photosynthesis, they have no use for them. I'd expect all the energy production to happen inside the roots. So the roots would be the most important parts of the plant; I co... (more) |
— | over 9 years ago |
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