[Bear_in_RoseBear]

But is space truly infinite, either?

Well now, that's a good question.

From our perspective, is there a actual difference between "really really big" and "infinite", anyway?

Probably not.

[Overtaxed]

So if the universe starts to collapse, does time run backwards? Could we do it all over again?

I seem to recall somesome saying the universe would NOT collapse.