Science tells us that the world is millions of years old. And each and every thing on the surface of the earth has a beginning somewhere. Hawking generally tells us that there is something before the world. That the something that is there even before the nothing is....gravity.
Gravity and God have had a very serious relationship. For some, gravity is like God's magic hammer that beats things into submission if they get out of line. For others, it is God's secret identity. For Catholics, a better understanding is that gravity orders things, much like the virtue of wisdom. It's the shepherd's staff so to speak.
For us Catholics, we need to realize that science and scripture aren't opposed to one another. They function differently and have different purposes. Science, as Hawking tells us, is based on observation. Scripture and, better, religion deal with what those observations mean.
God, in Hawking's book, was not necessary to the creation of the world. Jesus didn't even say much about how the world was created. Not much at all really. He told us more about what life meant and how life should be spent.
The Bible doesn't belabor the point on how the world was created. It only tells us that God was invested in it. Our faith tells us that he continues to be invested in us. To confuse the nature of science with religion would...and is...a grave mistake.