This is a clip from a conversation with Leonard Susskind from Sep 2019. New full episodes every Mon & Thu and 1-2 new clips or a new non-podcast video on all other days. You can watch the full conversation here: https://www.youtube.com/watch?v=s78hvV3QLUE
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Leonard Susskind is a professor of theoretical physics at Stanford University, and founding director of the Stanford Institute for Theoretical Physics. He is widely regarded as one of the fathers of string theory and in general as one of the greatest physicists of our time both as a researcher and an educator.

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You worked and were friends with Richard Feynman.

How has he influenced you, changed you as a physicist and thinker?

What I saw, I think what I saw was somebody who could do physics in this deeply intuitive way, his style was almost to close his eyes and visualize the phenomena that he was thinking about and through visualization outflank the mathematical, the highly mathematical and very, very sophisticated technical arguments that people would use I think that was also natural to me, but I saw somebody who was actually successful at it who could do physics in a way that that I regarded as Simpler more direct more intuitive And while I don't think he changed my way of thinking, I do think he validated it.

He made me look at it and say, yeah, that's something you can do and get away with.

So do you find yourself, whether you're thinking about quantum mechanics or black holes or string theory, using intuition as a first step or step throughout using visualization?

I tend not to think about the equations, I tend not to think about the equations, I tend not to think about the symbols, I tend to try to visualize the phenomena themselves.

And then when I get an insight that I think is valid, I might try to convert it to mathematics, but I'm not a natural mathematician, or I'm good enough at it.

I'm good enough at it, but I'm not a great mathematician.

So for me, the way of thinking about physics is first intuitive, first visualization, scribble a few equations maybe, but then try to convert it to mathematics.

Experience is that other people are better at converting it to mathematics than I am.

And yet you've worked with very counterintuitive ideas.

So how do you visualize something counterintuitive?

Yeah, quantum mechanics is not intuitive.

Very little of modern physics is intuitive.

It means the ability to think about it with basic classical physics, the physics that we evolved with throwing stones, splashing water, whatever it happens to be.

Quantum physics, general relativity, quantum field theory are deeply unintuitive in that way.

But after time and getting familiar with these things, you develop new intuitions.

And it's to the point where me and many of my friends, I and many of my friends, can think more easily quantum mechanically than we can classically.

I mean, yes, our neural wiring in our brain is such that we understand rocks and stones and water and

Do you think it's possible to create a wiring of neuron-like state devices that more naturally understand quantum mechanics, understand wave function, understand these weird things?

I think many of us have evolved the ability to think quantum mechanically to some extent.

But that doesn't mean you can think like an electron.

Just visualizing four-dimensional space, or five-dimensional space, or six-dimensional space, I think we're fundamentally wired to visualize 3 dimensions.

I can't even visualize 2 dimensions or 1 dimension without thinking about it as embedded in 3 dimensions.

If I want to visualize a line, I think of the line as being a line in 3 dimensions.

Or I think of the line as being a line on a piece of paper with a piece of paper being in 3 dimensions, I never seem to be able to, in some abstract and pure way, visualize in my head the 1 dimension, the 2 dimension, the 4 dimension, the 5 dimensions, and I don't think that's ever going to happen.

The reason is, I think, neural wiring is just set up for that.

On the other hand, we do learn ways to think about 567 dimensions.

We learn ways, we learn mathematical ways, and we learn ways to visualize them, but they're different.

And so yeah, I think we do rewire ourselves, whether we can ever completely rewire ourselves to be completely comfortable with these concepts, I doubt.

So I'm sure there's somewhat, you could argue, creatures that live in a two-dimensional space.

And while it's romanticizing the notion of course, we're all living as far as we know in 3 dimensional space, but how do those creatures imagine 3D space?

Well, probably the way we imagine 4D, by using some mathematics and some equations and some tricks.


Speaker 0: You worked and were friends with Richard Feynman. How has he influenced you, changed you as a physicist and thinker?

Speaker 1: What I saw, I think what I saw was somebody who could do physics in this deeply intuitive way, his style was almost to close his eyes and visualize the phenomena that he was thinking about and through visualization outflank the mathematical, the highly mathematical and very, very sophisticated technical arguments that people would use I think that was also natural to me, but I saw somebody who was actually successful at it who could do physics in a way that that I regarded as Simpler more direct more intuitive And while I don't think he changed my way of thinking, I do think he validated it. He made me look at it and say, yeah, that's something you can do and get away with. Practically didn't get away with it.

Speaker 0: So do you find yourself, whether you're thinking about quantum mechanics or black holes or string theory, using intuition as a first step or step throughout using visualization?

Speaker 1: Yeah, very much so, very much so. I tend not to think about the equations, I tend not to think about the equations, I tend not to think about the symbols, I tend to try to visualize the phenomena themselves. And then when I get an insight that I think is valid, I might try to convert it to mathematics, but I'm not a natural mathematician, or I'm good enough at it. I'm good enough at it, but I'm not a great mathematician. So for me, the way of thinking about physics is first intuitive, first visualization, scribble a few equations maybe, but then try to convert it to mathematics.

Experience is that other people are better at converting it to mathematics than I am.

Speaker 0: And yet you've worked with very counterintuitive ideas. So how do you?

Speaker 1: No, that's true, that's true.

Speaker 0: So how do you visualize something counterintuitive? How do you dare?

Speaker 1: By rewiring your brain in new ways. Yeah, quantum mechanics is not intuitive. Very little of modern physics is intuitive. Intuitive, what does intuitive mean? It means the ability to think about it with basic classical physics, the physics that we evolved with throwing stones, splashing water, whatever it happens to be.

Quantum physics, general relativity, quantum field theory are deeply unintuitive in that way. But after time and getting familiar with these things, you develop new intuitions. I always said you rewire. And it's to the point where me and many of my friends, I and many of my friends, can think more easily quantum mechanically than we can classically. We've gotten so used to it.

Speaker 0: I mean, yes, our neural wiring in our brain is such that we understand rocks and stones and water and

Speaker 1: so on. We're sort of evolved for that. Evolved for it.

Speaker 0: Do you think it's possible to create a wiring of neuron-like state devices that more naturally understand quantum mechanics, understand wave function, understand these weird things?

Speaker 1: Well, I'm not sure. I think many of us have evolved the ability to think quantum mechanically to some extent. But that doesn't mean you can think like an electron. That doesn't mean another example. Forget for a minute quantum mechanics.

Just visualizing four-dimensional space, or five-dimensional space, or six-dimensional space, I think we're fundamentally wired to visualize 3 dimensions. I can't even visualize 2 dimensions or 1 dimension without thinking about it as embedded in 3 dimensions. If I want to visualize a line, I think of the line as being a line in 3 dimensions. Or I think of the line as being a line on a piece of paper with a piece of paper being in 3 dimensions, I never seem to be able to, in some abstract and pure way, visualize in my head the 1 dimension, the 2 dimension, the 4 dimension, the 5 dimensions, and I don't think that's ever going to happen. The reason is, I think, neural wiring is just set up for that.

On the other hand, we do learn ways to think about 567 dimensions. We learn ways, we learn mathematical ways, and we learn ways to visualize them, but they're different. And so yeah, I think we do rewire ourselves, whether we can ever completely rewire ourselves to be completely comfortable with these concepts, I doubt.

Speaker 0: So that it's completely natural.

Speaker 1: There's a tour it's completely natural.

Speaker 0: So I'm sure there's somewhat, you could argue, creatures that live in a two-dimensional space.

Speaker 1: Yeah, maybe there are.

Speaker 0: And while it's romanticizing the notion of course, we're all living as far as we know in 3 dimensional space, but how do those creatures imagine 3D space?

Speaker 1: Well, probably the way we imagine 4D, by using some mathematics and some equations and some tricks. You

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Leonard Susskind: Richard Feynman and Intuitive Visualization vs Rigorous Mathematics