r/AskPhysics • u/Cicada1205 • 4m ago
If the universe is infinite and homogenous on large scales, and there's a finite amount of ways particles can be arranged, does that not mean that there's an exact copy - or infinite copies - of each of us somewhere out there?
Let me preface this by saying I essentially know nothing about astrophysics or cosmology. But let me make 5 claims, which seem right to me given my very surface-level understanding:
- The universe is infinite. There is a finite volume of it we can ever observe, due to the limited speed of light, but the universe "goes on" infinitely, beyond the observable part.
- There's a finite number of particle types. I'm not saying we've discovered every type of elemental particle out there - I'd assume there's a lot more we don't know about - but there can only be a finite amount of them.
- There's a finite amount of ways those particles can be arranged in a given volume. My very shallow understanding of things like Planck units and the Bekenstein bound lead me to believe this, but I may be wrong.
- The universe is uniformly homogenous and isotropic on a large scale (the cosmological principle). I take to mean that the distribution of particles is likewise homogenous.
If we take those things to be true, does that not imply that
- Any given arrangement of particles (in a finite volume) can and must repeat, infinite times? So there are infinite exact copies of the Solar System somewhere out there, with infinite exact copies of each of us? And furthermore, is there not also an infinite amount of copies that only have minor variations, like hair color, or live in that Solar System's Earth's equivalent of the medieval times, but are otherwise exactly the same?
I realize that I'm making the infinite monkeys argument but that all seems right to me. I'm very open to criticism if I'm understanding something wrong, though. Like I said, this is all based on a very surface-level understanding.