In a talk at the National Science Museum to mark the start of a new exhibition Prof Hawking also says the Large Hadron Collider may prove the existence of multiple universes.
Known as M-theory Hawking says multiple universes would occur naturally.
"These multiple universes can arise naturally from physical law. Each universe has many possible histories and many possible states at later times, that is, at times like the present, long after their creation.
Most of these states will be quite unlike the universe we observe, and quite unsuitable for the existence of any form of life. Only a very few would allow creatures like us to exist."
Ending his talk, he tells his audience: "So remember to look up at the stars and not down at your feet. Try to make sense of what you see and hold on to that child-like wonder about what makes the universe exist."