The universe didn't explode out of nothing, stupid. Anyone with half a working
brain can reason that the concept of "nothing" is a big
fat lie. Scientific evidence points to the theory that the universe we live in is constantly expanding and contracting. In other words, the universe has quite possibly always existed. If you want to be deep and spiritual about it, you could say that the universe (and other universes, or just all of creation) is God Himself.
Maybe. How would I know? Nobody knows.
ANYWAY, according to the Big
Bang theory, in the "beginning" the universe, ALL of the universe, was a hyper-
super-ultra-mega dense
ball of stuff. It was SO freakin' dense, it burst and expanded. The universe will continue to expand until it can't anymore, at which point it will begin to contract upon itself, becoming more and more dense, until the whole process must repeat itself again. Forever and ever.