The Big Bang theory is nothing for a Catholic to get hung up on. You just need to keep a steady eye on this single truth (taken from Fr. Stanley Jaki, the "Pope's physicist"): "The intelligent Christian will . . . keep in mind [this]: The total inability of the scientific method to demonstrate creation out of nothing." Ponder that statement. The TOTAL inability. Something out of NOTHING. Keep a steady and sure eye on that concept, and you'll be fine when talking with any atheist. They can whip out formulas that take up a 5-acre chalk board: they can't begin to demonstrate creation out of nothing. It's a leap that the scientific method, by definition, can't account for. Science deals with the material, the observable, the empirical. The idea of nothingness leading to somethingness transcends all scientific tools. It's a philosophical or theological exercise, not a scientific one. The Big Bang theory does contradict the creation account in Genesis, but Catholics don't care. Catholics have never (never) taken the creation story as literal truth. I believe you can find statements in Thomas Aquinas' works, for instance, about the importance, but not literal truth, of the creation account in Genesis. Aquinas lived from 1225 to 1274. Hope this helps.