Look, it's pretty basic. I didn't believe in God either until my college philosophy teacher explained it to me, over the course of a semester. In fact, proving God exists can be boiled down to two sentances:
"We know that everything in this physical universe is TEMPORARY; the sun will eventually burn out, everything will eventually have an end"
"Because everything in our universe is temporary, there has to be at least ONE THING that is eternal, stretching infinately in both directions in time, into the past, and into the future, with NO beggining and NO end"
The news about Hawking's upcoming book challenges this argument, but unfortunately the article doesn't give details on why Hawking believes that the law of gravity proves that something can be created from nothing. If that can be proven (and I doubt it really can) then we can no longer prove that God exists with the above argument, and we are left with only faith.