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Activity for celtschk‭

Type On... Excerpt Status Date
Answer A: If this earth were cube shaped would it be possible during Magellanic era using a float ship to figure out that the earth is cube shaped?
While the other posts did already explain the issues with the cube-formed Earth, I just want to give a feeling of the dimensions we are speaking of. Imagine that the centre of the cube's faces are at Earth's radius, about 6300 kilometres above the cube's centre (that is, the cube is sized so that ...
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almost 2 years ago
Answer A: How would an interstellar spaceship's speedometer work if everything else is moving?
The first question is: What is instantaneous speed measured against (that is, what is the “ground” relative to which the speed is measured)? Remember that there is no such thing as absolute speed. The closest to an absolute speed would be the speed relatively to the cosmic microwave background. Th...
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over 2 years ago
Answer A: Natural ways to acquire gravity and heat for a colony on earth's moon
Gravity You seem to assume that the Moon's mass is mostly concentrated in its core. While I didn't find detailed data on the Moon's density distribution, this Wikipedia page tells that the density of the outer core is about $5\\,\rm g/cm^3$ (unfortunately that value is not referenced), while the a...
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almost 3 years ago
Question Could a habitable planet lit by the cosmic microwave background plausibly exist?
I've got this idea of a rogue planet that is moving that fast through the intergalactic void that the cosmic microwave radiation, thanks to the Doppler effect, actually provides enough heat that it is habitable (and of course, it should be actually inhabited). Thanks to the searchlight effect, I thin...
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almost 3 years ago
Answer A: How do you establish identity when people can change their appearance at will?
Since manipulation of the brain is prohibited and illegal modifications are assumed to be reliably caught, the obvious way to check someone's identity with biometry would be by checking their brain. One thing I could imagine is that there are recognisable patterns in the EEG that allow identificat...
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over 3 years ago
Question Is it realistic to see satellites moving across the sky centuries after humans stopped space activity?
After an age of highly developed technology, including many different satellites in various Earth orbits, humanity loses the technology needed to control those satellites. After many centuries, how realistic is it that you can still occasionally see a satellite moving across the sky (say, at least on...
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over 3 years ago
Answer A: How efficient can a Dyson sphere be?
I think a reasonable assumption is that you don't want to accumulate entropy from the Dyson sphere. That is, the entropy you get from the star must not be lower than the entropy you send to outer space (indeed, you'll have to send out more entropy because on one hand you have other sources of entropy...
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over 3 years ago
Answer A: Quantum Based AI getting around Isaac Asimov's "Three Laws of Robotics"
Quantum computers operate differently than classical computers, and most importantly, doing measurements in the middle of a quantum computation process will disturb the process, and possibly lead to unpredictable behaviour. So maybe the three-rule-enforcement unit monitors the quantum computer, by l...
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over 6 years ago
Answer A: Generation ships: Over coming agoraphobia when you land
Actually I don't think you'll have that problem, for a simple reason: It is very unlikely that the planet will be a perfect match before doing some serious terraforming. Therefore after landing, people will likely mostly stay in the space ship and in new buildings on the planet that "extend" the spac...
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over 6 years ago
Answer A: How does a species with three "sexes", where only two needed are at a time, determine the sex of its offspring?
Here's another option: There are three genes: The X gene, the Y gene, and the Z gene. And there are three sex chromosomes: The XY chromosome, the XZ chromosome and the YZ chromosome. Each sex chromosome has exactly the two genes found in its name. Just as with humans, each individual has two sex chr...
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over 6 years ago
Answer A: Making a lethal, hard to cure virus?
A possible way to have the virus spread quickly yet be deadly is to have a double effect. Shortly after infection, it basically acts like the common cold. The common cold spreads quite effectively every winter, but is neither feared much nor do people take too strict measures to avoid it. So if in th...
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almost 7 years ago
Answer A: What could cause the Earth to be so endangered that mankind needs to relocate to another system?
When the sun started to behave strangely, astronomers were confused: The accepted solar model didn't at all predict this behaviour. Indeed, based on the new data it could quickly be shown that their model of the sun was wrong due to some previously unknown factor (maybe the sun contained a considerab...
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about 7 years ago
Answer A: Stopping time, by speeding it up inside a bubble
Well, let's see how such a field would work. The Hamiltonian equations are $$\frac{\mathrm d xk}{\mathrm d t} = \frac{\partial H}{\partial pk} \quad \frac{\mathrm d pk}{\mathrm d t} = -\frac{\partial H}{\partial xk}$$ Now we want the field to affect the speed of things happening, so a natural assumpt...
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over 7 years ago
Answer A: When will uploaded minds be a reality?
Never. The problem is not being able to simulate a human brain; that one I consider possible, and probably even achievable on affordable hardware at some time in the future. The problem is taking an existing brain and reading out the full state. Since the properties of the person are not just in the...
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over 7 years ago
Answer A: Why do people in Cryogenic sleep not wear clothes?
The main function of clothing is to hinder the flow of heat. The last thing you want to do when putting people into cryogenic sleep is to hinder the flow of heat. Quite the opposite: You want to have perfect control of the temperature on the skin. So, you say, why not put on some special clothing th...
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over 7 years ago
Answer A: How could a vampire pathogen operate in hard science fiction?
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, o...
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over 7 years ago
Answer A: Ways to "kill" an AI?
Hostile takeover. The other AI has lots of useful routines that your AI doesn't want to simply erase or leave unused. Instead it takes over the other AI, that is, incorporates all its routines, so that while the routines, data, etc. are all there, the other AI as an independent being no longer is; i...
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over 7 years ago
Answer A: How could the air be stopped from falling off of a flat world?
The whole universe could be filled with air. That would also explain why the world isn't just in free-fall (and thus effectively gravitation-free): It is going at the limit speed where air resistance equals gravitational pull. Of course it would still not explain why the air doesn't fall as well. No...
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almost 8 years ago
Answer A: How would we see the world if we could see polarized light?
With many more than three colour receptors, our colour TVs, using just three colours for display, would not come even close to showing all the colours of the world. Moreover, LDCs inherently work with polarized light; as is, they would probably look very unnatural. However, in principle this could be...
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almost 8 years ago
Answer A: Why would a civilisation choose to inhabit a single enormous vessel instead of maintaining interstellar colonies?
The ship started out as a generational ship to colonize some far-away planet. However, when approaching that planet, nobody wanted to be a colonist. They lived on the ship, their parents lived on the ship, their grandparents lived on the ship. Indeed, some even doubted the historical record and claim...
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almost 8 years ago
Answer A: Is Cancer Biologically Universal?
Assuming the alien life form is multicellular, it should definitively know cancer. Cancer is basically a defect in the mechanism that controls the cell division. Cell division is absolutely essential for growth and reproduction. Also, the multicellular life will have evolved from single-cellular life...
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almost 8 years ago
Answer A: Speeding up time?
There's no way to achieve this in the known laws of physics. However given that near a mass the time "goes slower". I guess if you could create a negative mass, near it time should "go faster". So if you assume there's a way to create a large negative mass, then you could do that near that mass. O...
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almost 8 years ago
Answer A: Can a planet have 10x Earth mass, 4x Earth gravity and support intelligent life?
If $R$ is the planet's radius and $\rho$ is the planet's average density, then its surface gravity is $\propto \rho R$ and its mass is $\propto \rho R^3$. Let's measure in units where the Earth's radius and average density are both 1. Then for Dekuuna we have $\rho R=4$ and $\rho R^3=10$. Therefore ...
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almost 8 years ago
Answer A: Space Age to Bronze Age
The space age civilisation has heavily computerized systems. That is, all important aspects of the space ships, factories, and whatever else advanced technology they use is completely controlled by software. People don't know how to make things because they don't need to; "the system" provides them w...
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almost 8 years ago
Answer A: Dead bodies on a partially terraformed planet : Would they rot or dry?
tl;dr: The corpses would still decay, but probably much slower. From the Wikipedia article about decomposition: Decomposition begins at the moment of death, caused by two factors: autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes, and putrefaction, the brea...
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almost 8 years ago
Answer 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...
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almost 8 years ago
Answer 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...
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almost 8 years ago
Question 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?
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Question 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...
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over 8 years ago
Question 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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 ...
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over 8 years ago
Question 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...
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over 8 years ago
Answer 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'...
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over 8 years ago
Answer 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...
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over 8 years ago
Answer 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...
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over 8 years ago