At the time of the Big Bang, all the matter in the universe was smooshed into an incredibly hot, infinitely dense speck of matter.

But what happened before that? It turns out, famed physicist Stephen Hawking has an answer, which he gave in an interview with his almost-as-famous fellow scientist, Neil deGrasse Tyson. Hawking discusses these ideas and others on the series finale of Tyson’s “StarTalk” TV show, which airs this Sunday (March 4) at 11 p.m. ET on the National Geographic Channel.

Hawking’s answer to the question “What was there before there was anything?” relies on a theory known as the “no-boundary proposal.”