3 ms·

I had a similar reaction to you. People seem to have very limited imaginations when thinking about the types of things that could exist. Or maybe the title is i

I had a similar reaction to you. People seem to have very limited imaginations when thinking about the types of things that could exist. Or maybe the title is incomplete. Maybe the paper is saying something more like, "Could life exist in a plane that otherwise has the same or very similar physics and chemistry as the universe?" In which case I could understand the skepticism about life's existence.

openasocket 7y ago
OP was referring to an orbit in the dynamical systems sense: https://en.wikipedia.org/wiki/Orbit_(dynamics) https://en.wikipedia.org/wiki/Orbit_(dynamics) which is far more general. It simply refers to a dynamical system where the trajectory of a particle repeats. If you have a system of particles in 2D space, governed by central forces between the particles, you won't have any particles that behave periodically in general, regardless of what those forces actually are. (There's actually some caveats to that statement. I believe the theorem OP's quoting assumes that the system has rotational symmetry, but giving up that symmetry may or may not actually give you stable orbits). Having some underlying periodicity is pretty important for more complex structures to emerge, otherwise it's just random chaotic motion.
- jeremysalwen 7y ago
  I mean, there are obviously a huge number of caveats associated with that, to the point that it's meaningless when we ate discussing "possible universes". There is no rule that a n^-2 force cannot exist in a 2d universe... which would obviously result in stable orbits. I mean come on, we have forces in our universe which are not n^-2. All this proves is that gravity couldn't work in the same way in a 2d universe..... so?? Heck, what about discrete universes? What about nonlocal universes?

3 ms·

I had a similar reaction to you. People seem to have very limited imaginations when thinking about the types of things that could exist. Or maybe the title is i

by ijpoijpoihpiuoh 7y ago

openasocket 7y ago
OP was referring to an orbit in the dynamical systems sense: https://en.wikipedia.org/wiki/Orbit_(dynamics) https://en.wikipedia.org/wiki/Orbit_(dynamics) which is far more general. It simply refers to a dynamical system where the trajectory of a particle repeats. If you have a system of particles in 2D space, governed by central forces between the particles, you won't have any particles that behave periodically in general, regardless of what those forces actually are. (There's actually some caveats to that statement. I believe the theorem OP's quoting assumes that the system has rotational symmetry, but giving up that symmetry may or may not actually give you stable orbits). Having some underlying periodicity is pretty important for more complex structures to emerge, otherwise it's just random chaotic motion.
- jeremysalwen 7y ago
  I mean, there are obviously a huge number of caveats associated with that, to the point that it's meaningless when we ate discussing "possible universes". There is no rule that a n^-2 force cannot exist in a 2d universe... which would obviously result in stable orbits. I mean come on, we have forces in our universe which are not n^-2. All this proves is that gravity couldn't work in the same way in a 2d universe..... so?? Heck, what about discrete universes? What about nonlocal universes?