Brian Greene sits down with Leonard Susskind for a conversation about the mysteries of the universe.

Added: 2026-06-03

[00:00:00]Mistake that we made was thinking that gravity and quantum mechanics were sufficiently separated that it needed a process to bring them together. In fact, they're almost the same thing. And gravity, as you said, is about big things, quantum mechanics is about small things.

[00:00:15]And it was the black hole that brought them together. The black hole was both big and heavy and also extremely quantum mechanical.

[00:00:24]>> I'm so pleased to be speaking with [music] Leonard Susskind. He is one of the co-founders of string theory. He's had profound impact on our understanding of black holes, on our understanding of quantum mechanics, on our understanding [music] of space and time and cosmology.

[00:00:40]So, we'll try to get to some of those topics here tonight. So, Lenny, thank you so much for joining us.

[00:00:46]>> And what intuition is, it's hard to say.

[00:00:48]It's a combination of experience, intuitive thinking. It's hard to say what it is.

[00:00:54]Um but yeah, that's where I am.

[00:00:56]>> And it does take a certain kind of confidence, right? Have you found yourself wrong in ways that were uncomfortable or were they generally >> generally just learning?

[00:01:06]>> wrong.

[00:01:06]>> Yeah.

[00:01:07]>> Laugh. Laugh.

[00:01:08]>> [laughter] >> When you think about mathematics, do you think of it as a human invention or do you kind of think of it as out there existing and we just sort of discover [music] things about it?

[00:01:19]>> I pretty much think the latter way. That that the mathematics is out there for me to use and um necessary for me to learn it.

[00:01:29]Everybody learns the same things, this universal mathematical truths.

[00:01:33]>> One of the implications would be like there's many Lenny Susskinds out there in this grander scheme of reality.

[00:01:43]Do you ever, late at night, think about those other versions of you that would emerge in this way of thinking about things?

[00:01:49]>> No, I usually fall asleep before I get to that.

[00:01:52]>> [laughter]