Back to the Big Bang.
There are, in fact, different theories about it. I, myself, believe in the one where the particles and whatnot rubbed together, causing intense friction, and then making a rather large explosion. As far as I have read, I still find it kind of creepy on how it was explained and fairly bizarre. Yet, it does add up and it does make sense.
Still though, I don't think we will ever know what made the big bang entirely, and I don't really think we should go that far. Some things are better left untold or finished.
There are so many mysteries about the universe and how it was born that I think that no matter how hard you study, each little discovery can be broken down into smaller parts and those parts separate into sections. Those sections form smaller parts, and soon enough, it'll seem endless to the things you can find.