3 ms·

Don't we more or less already know that the universe - at least the space itself, not the stuff in it - is indeed infinitely large?

by squigz 1mo ago

jahnu 1mo ago
It’s still an open question in cosmology. We’re still not sure even if it’s “flat”.
layer8 1mo ago
We don’t, and it’s likely that we will never know. Space may be non-Euclidian with a positive curvature, in which case it would correspond topologically to the “surface” of a four-dimensional sphere. One much larger than the observable universe (since the local curvature that we can measure is approximately flat), but nevertheless finite.
- squigz 1mo ago
  I really have no idea what this means but I guess my mental model of the universe is quite wrong haha
  - mbil 1mo ago
    Bringing it down a dimension: > The earth may be round, in which case we’re on the “surface” of a three-dimensional sphere. One much larger than what we’ve seen (since the ground around us is approximately flat), but nevertheless finite. Of course maybe the 4D sphere of the universe is itself hung in a vast field of other 4D universes, that field is the surface of a 5D sphere, etc.
  - layer8 1mo ago
    An ant on the surface of the Earth might believe that the Earth’s surface (“space”) is infinitely large. But because it can never look beyond the horizon, it can’t know. If it is intelligent, it has to assume that the surface might be curved and curve into a sphere, hence making it a finite surface. Actual space and the universe is sort-of an analogy one dimension higher up. “Sort of”, because (1) we don’t imagine a surrounding four-dimensional space for curved space in the sense in which Earth’s surface is embedded in three-dimensional space, and (2) the cosmological horizon has a different cause (namely the speed-of-light limit) than the horizon of a planet. Here is an alternative way to think about it: You can’t exclude the possibility that if you’d travel in a straight line in one direction through space, that you’d eventually end up where you started (i.e. like in the classic Asteroids game). Space might be connected like that, and then it would have a finite volume.

Don't we more or less already know that the universe - at least the space itself, not the stuff in it - is indeed infinitely large?

by squigz 1mo ago

Don't we more or less already know that the universe - at least the space itself, not the stuff in it - is indeed infinitely large?

jahnu 1mo ago

It’s still an open question in cosmology. We’re still not sure even if it’s “flat”.

layer8 1mo ago

We don’t, and it’s likely that we will never know. Space may be non-Euclidian with a positive curvature, in which case it would correspond topologically to the “surface” of a four-dimensional sphere. One much larger than the observable universe (since the local curvature that we can measure is approximately flat), but nevertheless finite.

squigz 1mo ago
I really have no idea what this means but I guess my mental model of the universe is quite wrong haha
- mbil 1mo ago
  Bringing it down a dimension: > The earth may be round, in which case we’re on the “surface” of a three-dimensional sphere. One much larger than what we’ve seen (since the ground around us is approximately flat), but nevertheless finite. Of course maybe the 4D sphere of the universe is itself hung in a vast field of other 4D universes, that field is the surface of a 5D sphere, etc.
- layer8 1mo ago
  An ant on the surface of the Earth might believe that the Earth’s surface (“space”) is infinitely large. But because it can never look beyond the horizon, it can’t know. If it is intelligent, it has to assume that the surface might be curved and curve into a sphere, hence making it a finite surface. Actual space and the universe is sort-of an analogy one dimension higher up. “Sort of”, because (1) we don’t imagine a surrounding four-dimensional space for curved space in the sense in which Earth’s surface is embedded in three-dimensional space, and (2) the cosmological horizon has a different cause (namely the speed-of-light limit) than the horizon of a planet. Here is an alternative way to think about it: You can’t exclude the possibility that if you’d travel in a straight line in one direction through space, that you’d eventually end up where you started (i.e. like in the classic Asteroids game). Space might be connected like that, and then it would have a finite volume.