Big bang is not certain. Yes the cosmological background radiation is evenly distributed, and yes Hubble law makes accurate predictions, but these aren't proofs. I watched a documentary recently on this subject and most theoretical physicists surveyed did not believe in the big bang.
I recently attended a lecture given by an astronomy professor/cosmologist who concurred that yes, the big bang is on its way out as the accepted truth. Like a swirling drain, we're getting closer, and there are aspects of the theory that are (likely) true, but it is far from bullet-proof and will likely go the way of the dozens of other origin theories that were disproven before it.
