I think one thing we should keep in mind when trying to explain the big bang, or anything like that, is our understanding of "Nothing" or "empty space", is something that we have created. Its a word, with a meaning that the human brain created as an aid to an otherwise unexplainable instance. When people say they dont believe in the BIG BANG THEORY because of there understanding that supposedly "Nothing" created everything, I think it is a very arrogant idea, when we might not know what nothing really is. The fact that their is always something. I think the best way to understand is using the number 0. It is an occurring nothing, Though it makes up the largest things that we can comprehend.
10000000000000000000000000000000000000000000000000000000000000000000.
I think the number I just wrote above is a good metaphor for the argument of where the universe came from, or the Big bang, or what ever you want to call it. Alot of nothings can create a lot of somethings.