Creation of all - Question

Well, today I was bored in class so I was thinking about the creation of the universe, God and science, even though I am an Atheist.
The thing I wanna know, is how do people explain how God came to exist, or for the big bang theory, how there were atoms, or an atom in the first place. I don't understand how you can get something out of nothing like that. I have heard people say "God just is", meaning that he is consistent like time. But time is actually a fabricated term.
So anyway, my question is:
How do scientists and bible bashers explain the creation of their creating force ?