Greetings, PF community. I have a very simple question regarding the Big Crunch theory. As far as I know, the Big Bang was not an explosion in space, but expasion of space itself. But how about a possible Big Crunch? Does this theory deal with the contraction of space itself, or is it just galaxies attracting eachother due to gravitational forces? I may have a misconception, but I believe the Big Crunch could only possibly happen on a closed universe, and has to do with the overall density of the universe. But the point I'm still missing, is that I'm not sure if this theory implies a decrease in the expasion of the universe until a critical point in which space would begin to contract, or would it simply be an scenario where galaxies begin to attrack eachother and we end up with a very dense concentration of mass in an almost-empty universe. Perhaps I'm missing some fundamental concepts here, sorry if this is too basic. Thanks!