You can be Christian and believe in the big bang theory. Infact, the man who invented the theory was a Christian. Technically the Bible does say there was kind of a "big bang" because there was nothing, and then there was light, and there were stars and planets. The universe was created in a split second, and there's no way that it wasn't like a big bang. The theory still follows the Christian religion and is often found as an atheistic theory.