Stephen Hawking is considered one of the theoretical physicists in history. But, how much does he know? Can he explain what existed before time?

In a recent conversation with astrophysicist Neil deGrasse Tyson (via Popular Science), the famed physicist offered his take on what there was before the moment that time started: The Big Bang. He said there was nothing.

“Nothing was around before the big, big bang,” Hawking said. “According to Einstein’s General Theory of Relativity, space and time together form a space-time continuum or manifold which is not flat but curved by the matter and energy in it.”

He also says that before the Big Bang, time didn’t exist either.

Watch the video up top to hear his explanation.