EDIT: Let’s cool it with the downvotes, dudes. We’re not out to cut funding to your black hole detection chamber or revoke the degrees of chiropractors just because a couple of us don’t believe in it, okay? Chill out, participate with the prompt and continue with having a nice day. I’m sure almost everybody has something to add.
Cosmic Inflation is a good one to read up on if you never have. Because the slow acceleration we observe right now in the expansion is actually vastly inadequate to explain what we see now, so the big bang theory currently involves spacetime itself having to go through a few phase changes that are hard to wrap your head around.