Posts by celtschk
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 cons...
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, ...
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...
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 i...
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 ce...
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 ...
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 c...
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 thi...
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 ...
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 therefo...
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...
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 ...
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 s...
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 jus...
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 wav...
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...
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^{2...
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...
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 un...
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 l...
(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...
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 d...
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 cann...
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 bec...
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 the...
