Could the big bang be in an infinite repeating cycle?

UCL's Andrew Pontzen has a big answer for a big question...

Andrew - The idea of the big bang is that somehow, if you rewind the history of our universe, and we’re getting pretty good at doing this by piecing together all the evidence. If you rewind it
maybe 13.8 billion years into the past, then our universe was, essentially, infinitely dense or incredibly dense and the universe was born out of that primordial state.

我认为问题是什么是什么ts that up? How does something appear out of nothing that’s infinitely dense? What creates that? Of course, that’s a kind of question that’s been around forever. I think ever since humans first started asking any sort of philosophical question. The question of was there a single moment of creation or did somehow, the world that we know emerge from something else? The honest answer is we don’t know. We still don’t really know the answer to that question: what kicked off the big bang? We just don’t know.

We do have some ideas. There are things like this idea called “inflation,” which replaces the normal big bang picture with something slightly different where the universe expands in a really wierd way in it’s first tiny fraction of a second. And in that picture, it might well be quite natural that space and time have just existed forever. That there was not beginning to time and universes just kind of pop up within this bigger environment that we sometimes call the multiverse. So that, in a sense, there are theories that we’re trying to put to the test where time could have been around forever, and there could be this kind of idea of a repeating cycle.

Chris - That boggles your mind doesn't it? But you’re not going to give us an answer so we’ll have to say “the best I can do is say come back another time and we’ll do some experiments.”

Andrew - Yeah. It’s going right back to something that we discussed at the start of the programme. We can, actually, see light pretty much from the big bang itself. So we do live at a special time when we can actually tackle these questions scientifically, rather than just speculate about them. At the moment, what I just said is speculation but we do have ways that we’re trying to test it.