I'm not sure that you will find a scientific answer to this question:
it also seems rather unlikely that the big bang happened of its own accord. Just one day the universe said, "Hey, Im bored. Why not have a Big Bang?"
Scientific theory can't deal with events that predate the birth of the universe as we see it nor can it answer the question "why?". I'm pretty sure that falls into the realm of religion.
Anyway, enjoy your stay with EVC, this is a great place to get excellent information about most religious and/or scientific questions.