The Big Bang Theory is the most popular alternative to religious beliefs in creation. The theory is that the universe was created 13.7 Billion years ago in a massive expansion of spacetime that was all like "KA-BOOM, BOOOOOOOOM... PRAHHHHHHH."
Although the theory is still just a theory, it is supported by lots of scientific evidence using fancy words and numbers. Naturally, Christian fundies ignore all the fancy words and numbers and continue to live in belief of God, the Bible and the Theory of Creationism, which is nice for them. That mythology is a bit silly though because the Christian mythology makes no more sense than Greek mythology Egyptian mythology and other mythology from the Bronze Age, the Iron Age or the Roman Empire.
Most atheists believe the Big Bang was a scientific process and since science exists that all makes sense. A few atheists
believe pretend that their god (the FSM) or their other god, (the IPU} created it from nothing but since both are imaginary this seems impossible.
- Big Bang More science