[vinnie-io]

the universe just expands, then contracts due to gravity into a single black hole, explodes (big bang), and we start again

[MikeFez]

There's no evidence that this is the case, especially with the knowledge that the rate of expansion is increasing over time: https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_...

[Pietertje]

And this has been going on for ages and we simply are universe X in time.

Alternative hypothesis the OP seems to refer to is the one of Lee Smolin in which a black hole from a previous universe creates a new universe. Smolin wrote a book about his theory, The Life of the Cosmos. I haven't read it nor do I know / understand his theory fully, so interested to learn others viewpoint on this theory.

[zoroaster]

Yes, that was my case (2). Spatiotemporal marble bounded by big bang and expansion edge. But it's not very satisfying - what is outside? Why?

It does align w/ the "eternal recurrence" concept.