Now, what space ultimately is - I should confess, I think most physicists believe - we don't yet know.

I don't know what I believe in. I try not to think about it. I don't want to think about it.

In the context of general relativity, space almost is a substance. It can bend and twist and stretch, and probably the best way to think about space is to just kind of imagine a big piece of rubber that you can pull and twist and bend.

It’s hard to build models of inflation that don't lead to a multiverse. It’s not impossible, so I think there’s still certainly research that needs to be done. But most models of inflation do lead to a multiverse, and evidence for inflation will be pushing us in the direction of taking [the idea of a] multiverse seriously.

Our best theory of describing space at a fundamental level is probably string theory.

I believe that there are no mistakes in the universe, so I think it all happens as it should!