We know the universe wasn't created by some god, how come we must agree without thought that the Big Bang was how everything began? Given the complexity of the universe I doubt we've already figured out its origins. And in all honesty, I think it's a red flag when I hear people give no speculation whether there was ever more than one Big Bang. How can we be sure one Big Bang took place? Give me a reason to think the Big Bang happened.
I also wonder, the universe is supposed to be expanding, but isn't it supposed to be infinite? How can an infinite universe expand?
Someone guide me through this.