Watch Stephen Hawking Explain What He Thinks Came Before the Big Bang

It's one of the biggest brainteasers out there: If the Big Bang created everything we know about, what the heck was around before the big bang? No one knows for sure, but everyone has a favorite theory—everyone including renowned British theoretical physicist Stephen Hawking, of course.

He offered his theory to Neil de Grasse Tyson in a video clip published by Popular Science on Friday. "Nothing was around before the big, big bang," Hawking begins his answer.

03_02_stephen_hawking Stephen Hawking as seen in 2016. Niklas Halle'n/AFP/Getty Images

The Big Bang theory is the idea that the entire universe began as a pinprick that has been expanding ever since—essentially, that the only reason the universe feels so vast is because it's had 13.8 billion years to get that way. The idea itself has held up pretty well, although scientists still aren't quite sure what force is driving all that growth.

And of course, the theory itself doesn't do anything to explain where precisely that first dot of the universe came from in the first place, hence the brainteaser. And we do mean it when we say brainteaser—Hawking's explanation includes this excellent line: "Ordinary real time is replaced by imaginary time, which behaves like a fourth direction of space."

Read more: To Hear the First Stars in the Universe, Astronomers Had to Find to the Quietest Place on Earth

But don't let that scare you off; his main point is surprisingly easy to grasp: Hawking approaches the problem by offering a detailed analogy, comparing space-time to any other continuous, curved surface, like the surface of the Earth. "There is nothing south of the South Pole," Hawking says. The same principle holds with the universe: "There was nothing around before the Big Bang."

Watch the full response here:

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