Consider in the biggest picture we have of the universe, we bump into dark energy. Nobody has a clue about that. Everything is not just going away from everything else in an expanding universe, the expansion is speeding up.
Consider the smallest smallest picture we have of the universe, we bump into sub-atomic quantum physics. Nobody has a clue. Atoms in a wave form, unless somebody is watching, then suddenly they act as matter. Look up the double slit experiment (nice video with 'Dr. Quanum' on youtube)
Yeah, reality really is a trip.
The bigbang theory is just rewinding the clock on what we see, in the expanding universe. Not like that rules out God in any way, shape or form. If there was a big bang, then God did that.