Activity for celtschk‭

Type	On...	Excerpt	Status	Date
Answer	—	A: What Time is it IN SPACE? The main problem is to establish a common time standard to base your local clocks off. Then it doesn't matter if your local time system differs from that (for example, you will want to base your planetary time scales on the rotation of that planet), since you can convert between whatever your local t... (more)	—	over 9 years ago
Question	—	Power plants "” literally It is well known that some organisms can produce electricity. Therefore I think it would not be too much of a stretch to assume that also some plants might have evolved that ability (after all, it could be a great deterrent to predatory herbivores). How could such a plant be used for energy producti... (more)	—	over 9 years ago
Answer	—	A: How to avoid 'Geary-Syndrome' at relativistic speeds (in space)? Fight in a gas cloud. While cosmic gas clouds are still incredibly thin, at relativistic speeds they will anyway cause considerable friction to your space fighter, so I'd expect more or less the same sorts of maneuvers as in air to be possible. It also means that going faster will cost more energy, ... (more)	—	almost 10 years ago
Answer	—	A: hypothetical criteria for non-paradox FTL Time travel due to FTL follows directly from the relativity of simultaneity: In different frames, the temporal order of events is different. This is true for all events which are spacelike to each other, which just means that you need FTL to get from one event to the other. So if you want to solve it... (more)	—	almost 10 years ago
Answer	—	A: If we put humans on planets with atmospheres different from Earth's atmosphere, but still containing oxygen, would humans be able to breathe? There are three separate issues here: Too much oxygen, and the human body (as well as any other organic material) will be highly flammable. You don't really want to live there. Too high or too low oxygen partial pressure, and the metabolism won't work correctly. The other gases, or lack of them, ma... (more)	—	almost 10 years ago
Answer	—	A: What would be the effect of introducing genetically modified chimpanzees into human society? I think there would be mainly three types of reactions: Those groups who think that apes should be given human rights would use that as additional arguments; also if you can speak with the apes, more people will be convinced that those apes, while not exactly human, would certainly deserve a human-... (more)	—	almost 10 years ago
Question	—	Expanding your empire's space from the inside "” can it be useful? Imagine your scientists have found a way to increase the space of your empire, literally: They are able to create an artificial inflaton field which locally creates a "space bubble" connected with usual space by a wormhole. In other words, from outside it takes just the space of, say, a star, but it'... (more)	—	almost 10 years ago
Answer	—	A: What would a binary black hole look like from the surface of a planet orbiting that system How could it be possible? Obviously the black holes cannot be the source of light for the planet, so we need four bodies: The two black holes, a star and a planet. Moreover, the star should be in (at least approximately) constant distance to the star if it is supposed to support life. Now, how coul... (more)	—	almost 10 years ago
Answer	—	A: What if the speed of light were 100 times higher? If you say you want to make the speed of light 100 times as high, you have to say what you want to keep constant. I'll assume you want to keep constant the sizes of things (because if light is 100 times as fast, but all things are 100 times as large, the apparent speed is again the same), and also ke... (more)	—	almost 10 years ago
Question	—	Energy source for a generation ship A generation ship was sent out a long time ago, to colonize a far away planet. However the ship failed to reach its goal due to navigational issues (which also means they didn't have any clue where in the galaxy they actually were, and how to return to earth). They continued the journey in the hope t... (more)	—	almost 10 years ago
Answer	—	A: Traffic in Space (a traffic controller for low earth orbit) Note: I'm assuming all relevant space travel is close to earth (that is, there's no need to coordinate e.g. travel to Mars, as soon as it leaves the near-earth range). One point about space is that it is international. It is simply not possible to keep a spacecraft above a single country. Therefore ... (more)	—	almost 10 years ago
Answer	—	A: If our atmosphere was much thinner (half as thin as we have now) how would animals and humans evolve? Well, the first effect would of course be for anything that flies, like birds or bats. Half the air density means flying gets much harder. So I'd expect flying animals to be smaller in general, but with larger wings. If it is only the nitrogen that is less dense, this would probably be the main effe... (more)	—	almost 10 years ago
Answer	—	A: Communication with a big insect The first question is: What would be the first reaction of the ants on seeing the humans? Run away. Well, that's completely natural behaviour, and there's nothing you can tell from that; also, they are now gone, and so any communication attempt is moot anyway. However if they are intelligent, they'... (more)	—	almost 10 years ago
Question	—	How long until a small black hole makes the sun fail? Imagine aliens dropped a small black hole (say, 1% of the moon's mass, so you wouldn't notice the difference in gravitation) into the sun (from the far side of the sun, so nobody on earth can see it). That small black hole would then, of course, start eating the sun, so that it eventually fails. Now... (more)	—	almost 10 years ago
Answer	—	A: If there was a majority of land on earth (66 percent land), how would it affect the animals and plant? One effect I could imagine is that life would have entered land earlier in evolution, since there's less space in the upper ocean levels (the ones which are most life-friendly, because below there's no sunlight). Probably also the deep sea would be a bit more populated, but not much because there's s... (more)	—	almost 10 years ago
Answer	—	A: Can we identify black holes in our path flying between the stars? Another idea: Black holes shadow the cosmic microwave background. This might be used to detect them. Given that with high speeds, the microwave background in movement direction (that's the direction that's relevant if you want to avoid them) will be at higher frequencies due to the Doppler effect, I ... (more)	—	almost 10 years ago
Answer	—	A: What could cause infertility between humans living in gravity and humans in space? How could that cause speciation? It could be that our reproductive system doesn't work too well in zero gravity. That would impose a strong selection pressure to adapt the reproductive system to zero gravity, which then in turn might it incompatible with those living in a gravitational field. The inability of cross-breeding would o... (more)	—	almost 10 years ago
Question	—	Could a planet made completely of water exist? In the Star Trek: Voyager episode "Thirty Days", there was a planet made completely out of water, which is the inspiration for this question. However, that planet was held together by an artificial containment field. I'd like to know if a water planet would be possible that would be held together ju... (more)	—	almost 10 years ago
Answer	—	A: Is it possible to have a logically consistent world where F=mv instead of F=ma? tl;dr: Such a world would be quite different from ours. Basically, all modern formulations of classical mechanics fail on it, and you also could not base that world on an underlying quantum theory. I assume that you want the laws of physics as similar to ours as possible with this restraint. Esp... (more)	—	almost 10 years ago
Answer	—	A: Motivations for interstellar colonizations Let's listen to the head of the colonization movement, who happens to give a speech about this topic right now: Ladies and Gentlemen, thank you for giving me the opportunity to tell you about the importance of colonization. As you all know, there was short contact to an alien species, but we... (more)	—	almost 10 years ago
Answer	—	A: How can a spaceship unknowingly interfere with tides on a planet? All the answers so far dealt with the ship creating gravity itself. But there's another possibility: The ship might have some sort of gravity shields (to allow to pass close nearby heavy objects like neutron stars or black holes during travel without the ship being damaged), and they might have forgo... (more)	—	almost 10 years ago
Question	—	What would ammonia snowflakes look like? What I've found out is that Ammonia has (in the relevant temperature/pressure regime) cubic crystal structure. But what would that mean for ammonia snowflakes? Would they have fourfold symmetry? But then, you can also find threefold symmetries in a cube (just look at it from the corner), and cutting ... (more)	—	about 10 years ago
Answer	—	A: Can I keep our universe, but without the speed limit (of light)? First, the good news: You still can have quantum stuff. All the quantum weirdness already exists in non-relativistic quantum mechanics. Without the speed limit, full relativity is, of course, out of question. Therefore let's look at the alternatives: Preferred frame of reference Assumptions: Matte... (more)	—	about 10 years ago
Question	—	If a space ship crashes on a planet, is it realistic that things from that space ship could be rescued afterwards? The situation I'm considering is as follows: A space ship (a transport ship operated by two people) crashes onto a planet on which a swing-by was planned. The crew could escape using an escape capsule and land on the planet, while the space ship crashed on it. The escape capsule lands not too far fr... (more)	—	about 10 years ago
Question	—	Could higher land-based life exist on a planet with a pressure of about 1 MPa? This is somewhat of a follow-up question to my ammonia-based world question. I've found out that the melting point of ammonia is at 25°C at a pressure of about 1 MPa (about 10 times the atmospheric pressure on earth). I think that should be definitely warm enough for life. However, could higher land... (more)	—	about 10 years ago
Answer	—	A: What would happen if a virus could not be cured or contained? First, the deadliness of a virus can vary widely from mostly harmless (Herpes) to very deadly (Ebola). However, note that even for Ebola, there are people who survive without treatment. Indeed, Ebola cannot be cured; all the treatment does is to try to keep the patient alive for long enough that the ... (more)	—	about 10 years ago
Answer	—	A: If our universe was a simulation, what could a bug look like? One quite nasty type of bug (which can especially be hard to find, and can give quite inconsistent results) is out-of-range indices, in a language which doesn't range-check indices (likely to be used in simulations because range-checks cost valuable computing time, and do nothing useful if your code ... (more)	—	about 10 years ago
Answer	—	A: What could cause an avian species to become intelligent? Let me add another point of view. Most answers assume that the large brain evolved in order to gain intelligence. However, I've once read another hypothesis (unfortunately I don't remember where): The human brain originally grew big because humans were in an environment where the brain would often ge... (more)	—	about 10 years ago
Answer	—	A: What would be the effects of the common house cat rapidly acquiring flight ability? Well, one obvious effect of cats acquiring flight ability would be that they would be much more effective in catching birds (it of course depends on how well/fast the cats can fly). Probably the number of birds would be considerably reduced. I can imagine that this would give cats a much worse image,... (more)	—	about 10 years ago
Question	—	What would an ammonia-based world look like? Apart from the obvious difference that liquid ammonia needs a much colder temperature than liquid water (but ammonia-based life forms wouldn't feel that as particularly cold), what would be the most obvious visible differences of an ammonia-based world compared to a water-based one, as seen by a life... (more)	—	about 10 years ago
Answer	—	A: Can we breathe the moon's crust? At least the Artemis project thinks it is possible. The process they describe is $$\rm FeTiO3 + H2 \to Fe + TiO2 + H2O$$ and then split the water to hydrogen and oxygen (note that after splitting the same amount of hydrogen is resumed as is put in at the beginning, so apart from replacing losses, yo... (more)	—	about 10 years ago
Answer	—	A: Would living underground during an impact winter be ideal? Their main problem would probably be to find food. Plants don't grow underground/without sunlight. Of course, if they have sufficient supply of canned food to survive until the surface is habitable again, that would solve the problem. However without fresh food, there may still be deficiency disease... (more)	—	about 10 years ago
Answer	—	A: Why aren't animals photosynthetic? One possibility that has not yet been mentioned (actually inspired from githubphagocyte's comment on how the evolution of plants began in the first place): It could be that the animal doesn't do photosynthesis itself, but lives in symbiosis with a plant living on its surface. Probably not a macroscop... (more)	—	about 10 years ago
Answer	—	A: What effect could drop the freezing temperature of water globally to −40 Celsius? As others noted, there's no real physical effect that does this. However let's look at how a fictional effect might work. Water can be supercooled to quite low temperatures, that means, there does exist a liquid state of water; indeed that liquid state still exists at -40°C. That supercooled state ... (more)	—	about 10 years ago
Question	—	What minimal radius is needed for rotation to simulate gravitation without adverse effects on humans? A quite common idea to provide "gravitation" in space stations is to make them rotate, so the centrifugal force gives an effective gravitation. A possible design is a ring-shaped space station. Now of course it is easy to calculate how fast a space station has to rotate, as function of the radius, i... (more)	—	about 10 years ago
Answer	—	A: Are dragons cold or warm blooded? I think an interesting option could also be that dragons can switch between cold-blooded and warm-blooded metabolism. For example, they could be warm-blooded when young (providing them the needed energy to fly), but then convert to cold-blooded (or in-between) when they get old (so they can grow with... (more)	—	about 10 years ago
Answer	—	A: Hollow planet with another planet inside it Apart from the problems of formation and the problems of mechanical stability already mentioned by others, there's also the problem that gravitation cannot preserve that situation. If the sphere were perfectly symmetric, then the sphere would neither feel a net gravitation from the planet, nor the o... (more)	—	about 10 years ago
Answer	—	A: Is a man-eating plant realistic? A plant chasing humans would be unrealistic, but I think a plant generating a trap for human-sized animals could be possible in principle, given the right circumstances (maybe it evolved from one eating smaller animals, but those got extinct, and the trap size grew to capture ever larger animals). T... (more)	—	about 10 years ago
Answer	—	A: What environment would make leaves light blue? Plants would be blue if their photosynthesis were based on phycocyanin instead of chlorophyll. Since there are organisms on earth that use this, it's not entirely implausible that it could be used also by higher plants in an alternate world. So what environmental effects could cause phycocyanin inst... (more)	—	about 10 years ago
Answer	—	A: What geographic characteristics for a world would be needed/be most beneficial for airships to be a common mode of transportation? One disadvantage of airplanes is that they need a runway to start/land. So one thing that would discourage airplanes is a geography where you simply have no space for runways (hills/mountains everywhere). Also, airplanes depend on the availability of cheap fuel, so if you don't have that, they cannot... (more)	—	about 10 years ago
Answer	—	A: Is it possible for a species to have more than two sexes? It is not only possible, apparently it actually exists on earth. The abstract of the linked article reads: Two recently discovered cases of genetic caste determination in social insects might provide the first example of a major evolutionary transition from two to more than two sexes. I argue her... (more)	—	about 10 years ago
Answer	—	A: Feasibility of anti-matter as a fuel The main problem with antimatter would be containment. You cannot simply put it into a normal container, because the normal container would be made of matter, and the antimatter would annihilate with it. So you need to find a way to keep the antimatter safely away from any matter in your ship. At the... (more)	—	about 10 years ago
Answer	—	A: What determines the length of a day on a planet? I assume you mean the solar day (determined e.g. as the average time between two sunrises). Although you didn't say it, I also assume that you want a planet in the habitable zone (otherwise you've got much more freedom in your choices). tl;dr You want a planet orbiting a small star, ideally a red d... (more)	—	about 10 years ago
Answer	—	A: In space, do "shipping lanes" make sense? According to this answer to another question an Alcubierre drive would need to have a channel setup far in advance. So with such a technology, you'd need to have a network on established lanes just to be able to go faster than light. Outside the lanes you would not be able to go FTL at all, which for... (more)	—	about 10 years ago
Answer	—	A: How extensive could a habitable twilight zone be on a tidally locked planet? If the planet is tidally locked, the main determining property of the planet will be the heat transport from the warm to the cold side. There are two main heat transport mechanisms: Air currents (wind) and ocean currents. To simplify the writing, I'll define principal directions as follows (this is ... (more)	—	about 10 years ago
Answer	—	A: What would a planet spinning fast enough to allow geostationary orbit near the surface look like? I'm taking "near ground" as meaning "the height over ground is negligible compared to the radius of the planet". That is, we can as good approximation we can assume that the radius of the geostationary orbit is the same as the radius of the equator. tl;dr Such a planet would likely be a dead, airle... (more)	—	about 10 years ago
Answer	—	A: How could dragons be explained without magic? Growing from a very small size to an extremely large size is no problem, as dinosaurs show (and remember, ultimately even the largest dinosaur started as a single cell; the size of the egg is basically about how much initial nutrients are stored for the organism until it is ready to get out of the eg... (more)	—	about 10 years ago
Answer	—	A: How could a Dyson Sphere be destroyed through natural causes? What about the sphere being hit by a cosmic string? Some excerpts from the Wikipedia page: Cosmic strings, if they exist, would be extremely thin with diameters of the same order of magnitude as that of a proton, i.e. 1 fm, or smaller. [...] Even though cosmic strings are thought to be ex... (more)	—	about 10 years ago
Answer	—	A: How would having multiple moons affect tides? It would mean a more complicated modulation of the tides. On earth, we have a superposition of two cycles: An exactly 12 hour cycle of the sun, and a cycle deviating from that by the moon. The moon tides are dominant because the sun, although much more massive, is much farther away. Yet the effects a... (more)	—	about 10 years ago
Answer	—	A: What effects would a change in the nature of human sexuality have on society and infrastructure The most obvious result would be that there would be no concept of a family. Now the concept of a family influences a lot of things; for one, the concept of inheriting goods might not develop; without that, also the concept of property would be less strong. A lack of sexual/compassionate bindings wou... (more)	—	about 10 years ago

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