[quote]The Universe was nothing, and then the big bang happened.[/quote] Uh..yeah..no. From my understanding: You cannot create or destroy matter. Therefore, all matter has always existed in some form. (This also means that the Universe is finite, as for the universe to be infinite, you'd always have to have new matter, as infinity is..infinite. And stuff.) Because the Universe has always existed, however, it's time would be infinite- from "negative infinity" (past) to "infinity" (future). This means that an unfathomable- and yes, Infinite- amount of things has happened and will happen. Now, we also have this thing called Gravity. Gravity affects all things, however with increased distance comes less power. So, we a finite universe (with matter that has always existed) that has always existed and will always exist. Given these quite literally unfathomable amounts of time, I think it is a logical jump to say that, Due to the gravitational forces that are slowly exerted over these immense amounts of time, all matter will eventually be pulled together. And, of course, as more matter comes together, the stronger the gravitational force becomes, compacting the matter until eventually it cannot sustain itself, and a "Big Bang" happens again. Cue expansion of the universe, and the start of the process of it slowly coming together again. Admittedly, there are a few things out of my understanding. Black holes, how they interact with this and the happenings if two were to collide. Space itself and what it is. Etc. Frankly, these things are above my pay grade. [spoiler]Which is 0, btw.[/spoiler]