Well, as most would say atheists our universe began with the Big Bang. Scientists are trying to find what there was before the Big Bang wich is extremely tricky. The Big Bang was caused by 2 colliding Branes, to find more information about that you can read about the M-theory because I'm not going to type out a ton of evidence when it most likely won't matter anyway.
One experiment "proving" the Big Bang would be the echoes of it wich can be heard through radio waves. This was discovered on accident by two scientists trying to discover something else wich I can't remember.
Also, there never was "nothing" as some people seem to think. There has always been energy. Wich in my opinion could lead to events like the Big Bang.
Sure, it's possible that God created the Big Bang. But the chances of that being true are extremely slim, the chances of it being the M-theory makes much more sense than saying that something that has been made up by us thousands of years ago and has nothing to back itself up.
If God was all-knowing he would know who would turn into an atheist, christian or whatever religion since they are his creations. If this world is a test then it's pure luck since people raised in a christian family will most likely be christian, atheist family atheist, etc.
Anyway I respect peoples beliefs. It makes me sad though that people believe I should go to hell because I've been raised in an atheist family. Even if I wanted to convert I wouldn't have a choice. Especially not now since I've done alot of research and a God wouldn't make sense to me the same as atheism doesn't make sense to you.
Most* atheist believe on that theory.
The big bang theory is nothing more than that, a theory.
Like any other religous believes, everything can't be proved, as well as to what "god" is the real god, or if there are multiple gods.
It seems to me that if there is a real god, and having prove, that would destroy every other religion and the believers.
Why wouldn't an all knowing god, or multiple gods( for other religions), let this happen?
As an atheist, i haven't even been think twice on the extraordinary chances earth has evolved, as well as the only place known to human life there is life, because we simply do not even know how the universe was evolved, therefore; how can we know if trillions miles away there is another planet with sustainable life?
Hence knowing there is a god? I loathe the fact that most of the world has a religious belief, and look down upon those who don't or disagree. In the end of any belief it ends up being nothing but self faith, like a self motivation.