Even if we are to assume that our current understanding of physics is perfect and will not undergo any radical changes in the future (which is not a good assumption), then even so there are limits to our understanding of the universe and the nature of God.

All laws of physics break down at points in spacetime called singularities. The most common form of a singularity is a black hole. A black hole is a rip in spacetime, and it is extremely unlikely that we will ever know what truly happens in black holes since attempting to observe them generally destroys the observer.

The beginning of the universe is another singularity, although a bit differently. Space and time as we know it are currently thought to be properties that were created out of the Big Bang, and the laws of physics rely on the existence of said space and time. So what happened before the Big Bang? Since time is a property of the universe, that question is similar to asking what is north of the north pole, and cannot be correctly answered. All understanding of physics breaks down at the Big Bang, and anything before that cannot be definitively predicted.

The statements above are a major reason why many physicists, such as Einstein, Sagan, and Tyson refuse to be identified as atheists, despite the wishes of some atheist followers. To make a definitive statement about the nature of God would be to claim to have evidence that we will most likely never have access to.

As Sagan said, "An atheist is someone who is certain that God does not exist, someone who has compelling evidence against the existence of God. I know of no such compelling evidence. Because God can be relegated to remote times and places and to ultimate causes, we would have to know a great deal more about the universe than we do now to be sure that no such God exists. To be certain of the existence of God and to be certain of the nonexistence of God seem to me to be the confident extremes in a subject so riddled with doubt and uncertainty as to inspire very little confidence indeed."