[RADIOLAB INTRO]

SOREN WHEELER: You could be like, "We just had a show about bliss and, you know, it's been the holiday times. I've been thinking about that snowflake."

JAD ABUMRAD: It's true, actually. You know, it's been snowing. I was in St. Louis just a couple days ago, and it was snowing these big, fat fluffy flakes, and I couldn't help but think some of those flakes must be perfectly-shaped crystalline structures.

ROBERT KRULWICH: You have a thing for ...

JAD: Right out of Plato's cave, except it wouldn't snow in a cave.

ROBERT: I don't know. I don't understand this yearning for the perfect when you got real, pretty great snowflakes falling right on your nose. Like, why would you ...

JAD: Hold on. Hold on. Let's just start it up. I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: This is Radiolab.

ROBERT: The podcast.

JAD: And today we're gonna continue the conversation we were just having—been having all week—about well, perfection. You know, like, striving for things which seem perfect versus living in the real world..

ROBERT: Right.

JAD: And recently ...

ROBERT: I got into a bit of a kerfuffle with a guy who—who yearns like you do for an ideal. His name is Jim Holt.

JIM HOLT: Okay.

ROBERT: And he wrote this really good book called, Why Does the World Exist? And just to get us started, in that book he quotes a poem.

JIM HOLT: Yeah.

ROBERT: Remember the line?

JIM HOLT: Yeah. "Kick at the rock, Sam Johnson, break your bones. But cloudy cloudy is the stuff of stones."

ROBERT: Cloudy cloudy is the stuff of stones.

JIM HOLT: Yeah.

ROBERT: Meaning what?

JIM HOLT: It's something—well, Samuel Johnson, who lived in the 18th century, was a contemporary of Bishop Berkeley. And Bishop Berkeley was an idealist. He believed that the world was essentially pure appearance. It was like a thought, not like a solid reality. It was a thought in the mind of God.

ROBERT: Like the rock really had no substance.

JIM HOLT: And Samuel Johnson, when he heard this, he thought it was ridiculous, and he went and kicked a stone and said, "I refute Berkeley thus."

ROBERT: [laughs]

JIM HOLT: Anyway, that's the story.

JAD: Wait, one guy thought it was a thought, the other guy thought the rock was a—what are they arguing about exactly?

ROBERT: Well, they're arguing about reality.

JIM HOLT: Just what is this world? What is its, you know, essential nature?

ROBERT: When you hold a rock in your hand, like, what's it made of?

JAD: What's it made of?

ROBERT: Yeah.

JAD: Minerals?

ROBERT: No. What I'm really asking is: what is the most essential nature of the rock? So if you look deep, deep, deep down into the rock, do you find something concrete? Do you find a little bit of thing?

JAD: Yeah?

ROBERT: Or do you find something more ethereal, something you can't touch? Something you can't pin down? Something like, oh, a thought. This is Jim's notion.

JIM HOLT: And this sounds like a—it sounds like I've been eating lotus leaves, it's a pipe dream. But this is what science has increasingly led us to.

JAD: That rocks are thoughts?

ROBERT: Well, to follow Jim's logic, he goes all the way back to the Greeks, to the first real attempt to get to what's really at the bottom of a rock.

JIM HOLT: You know, even in ancient times, the atomist Democritus and Leucippus thought that if you keep cutting up the stuff of reality that we see around us: tables and chairs and rocks and so forth, eventually you cut them up into such itty-bitty pieces that you can't cut any further and then you've got atoms. So there you've got—you've clearly got a fundamental stuff, the atom.

ROBERT: Yeah, that sounds very pleasing.

JIM HOLT: Right. But even going back to Newton, there were reasons to suspect that there was something a little funny about reality. It wasn't quite as substantial as we believed. You know, Newton, of course, came up with a theory of gravity. And the theory of gravity says if you've got the Sun and a planet, the sun exerts a gravitational force on the planet.

ROBERT: Right.

JIM HOLT: And Newton's contemporaries wanted to know ...

ROBERT: Well, how does it do that?

JIM HOLT: What is the mechanism by which gravity is mediated? How does the Sun, as it were, reach out to the Earth, and force it to move around in this orbit?

ROBERT: So if I were an atomist, if I were looking for stuff, then I'd need some kind of thing that carried gravity.

JIM HOLT: Yeah, yeah. But the problem is that it looks like there's nothing between the Earth and Sun except a void.

ROBERT: All that Newton had to fill that void was a mathematical equation that told him how the Sun and the Earth interact. And the thing is it worked. You could plug in the numbers and you could know how one was influencing the other, but Newton had no idea at all why the equation worked. He couldn't point to any, like, a little particle thing like a graviton and say, "There's your reason." It almost seemed like gravity was created from the equation itself, and this disturbed a lot of people, because at that time everybody thought ...

JIM HOLT: That nature has to be made out of hard, durable stuff.

ROBERT: You know, gears and sprockets.

JIM HOLT: Pushing and pulling. That's the essence of reality. And then in the 20th century, of course, it had gotten much much worse. You know, the atom, which was thought to be very, very tiny and you couldn't cut it any further, it was the limit to this, you know, splitting process.

ROBERT: Right.

JIM HOLT: And as we know all too well from the 20th century, you can split an atom. Yeah, and it has pretty interesting consequences. But we also discover the atom is almost entirely empty space. If you took a baseball and put it in the middle of Madison Square Garden, that would be like the nucleus, and the first level of electrons are as far away as the exterior of the Garden.

ROBERT: So you can think of this baseball, this nucleus, as a tiny tot all alone.

JIM HOLT: So it's basically—the atom is a big empty space.

ROBERT: Well, it doesn't feel that way. Like, watch this. I'm going to do this. [claps hands]. Right? [claps hands] If my hands are all atoms, and as you say, atoms are mostly empty space, then why don't my hands just go right through each other like two clouds? But you'll notice ... [claps hands]

JIM HOLT: Yeah, yeah. Why don't I fall through the floor here because the floor is mostly empty space, and I'm mostly empty space? That too, if you look at it in the micro-level, this apparent solidity is the product of a purely mathematical relation.

ROBERT: Well, that can't—isn't it more like my electrons don't like similar electrons? So the electrons on my hands just hate the electrons on the other hand?

JIM HOLT: No, it basically comes down to a pair of mathematical relations: the Pauli exclusion principle and the Heisenberg uncertainty principle. I mean, all of this gets very abstract ...

ROBERT: I understand it perfectly, of course, but I don't want to bore you with the details of his argument.

JAD: [laughs] You have no idea what he's saying, do you?

ROBERT: [laughs] Well, I'll say this: according to Jim, it's not that the electrons in my left hand are repelling the electrons in my right hand. It has to do with a law of nature that says two particles, identical particles, cannot be in the same place at the same time. So when you hear that sound, [claps hands] you can hear it as the sound of a law saying, "No! Not allowed! Not in nature!"

JIM HOLT: Exactly. And here's a slightly different way of putting that.

ROBERT: But wait, isn't this law that we are announcing, isn't this law about particles? Like, we're talking about atoms and electrons. Those are things. So we're still talking about things.

JIM HOLT: If you study quantum field theory, which is what all physics graduate students begin with in graduate school, you discover that even particles are unreal.

ROBERT: [laughs] Oh God!

JIM HOLT: They're just temporary properties of what are called "fields." And fields are just distributions of mathematical quantities through space-time. So they're not—they don't seem to be grounded in anything.

ROBERT: According to Jim, a field is kind of like a stream of numbers.

JIM HOLT: Pure information.

ROBERT: Numbers that tell you where a particle like an electron might be. So maybe the electron's over here. Oh, no, no. Maybe it's over there. Or maybe it's with this group. Or maybe it's with that group. The problem is, you can't ever see the thing itself, you can only see the effect it has on other things. So you can't observe it.

JIM HOLT: And if something is in principle unobservable, you may as well say it doesn't exist.

JAD: Wait a second. No. No, no.

ROBERT: What?

JAD: I mean, I'm on his side, but you could say that it's just not observable down there at the micro-scale. Up here, it's pretty observable. I mean, [bangs table] this table exists. [bangs mixer] This mixer. I mean, something is happening to give the world substance.

ROBERT: Well, according to Jim, what we think happens—and this is admittedly is a gross oversimplification. But in these fields, you're gonna get these little fluctuations, these little ...

JIM HOLT: Events.

ROBERT: Sudden hiccups of energy. Little bursts. And that's where stuffiness flickers into existence. But it's a very flickering existence. Stuff isn't permanent.

JIM HOLT: So what is a rock? I mean, a rock looks like a good, solid, persisting object, but it's really—our perception of it is energy transitions, changes in the distribution of energy from one state to another. When that happens, the energy is irradiated. It goes through my retina. It goes through my pupil, rather, and strikes my retina, and I perceive the rock.

ROBERT: So going back to that poem we started with, I don't know if Jim would call a rock, like Bishop Berkeley did, "A thought in the mind of God," but he might say that deep down what a rock is is an expression of rules or math, it's just here like a shadow of an idea.

JIM HOLT: Yeah. Yeah. I've heard one physicist say that the cosmos is ultimately a concept.

ROBERT: Are you increasingly convinced that the reason you can clap, the reason you don't fall through the floor, the reason that gravity works is all because of certain ideas that govern? Ideas rule the world?

JIM HOLT: Yeah. Yeah. Maybe, you know, a hundred years from now when string theory is finally worked out, we might have a very different conception of it. But it looks as though it's going to be mathematics and structure all the way down.

ROBERT: You're okay with this?

JIM HOLT: Well, I'm a sort of mathematical romantic. I love the idea that the essence of reality is not stuff, you know, stuff is kind of ugly. I mean, you want to get rid of stuff, there's too much stuff in your apartment.

ROBERT: I like stuff!

JIM HOLT: It's clutter. It's gross, viscous, absurd.

ROBERT: I don't know what to do if I don't have stuff.

JIM HOLT: Well, you know, this is the temperamental difference between us. I like the idea that reality consists—it's a flux of pure information with no further substance.

ROBERT: I don't know why this makes you so happy. I mean, here: I would love if I'm clapping or if I'm hitting someone in the face, I would love to think the billiard ball of me is hitting the billiard ball of them, and that explains what's going on. Now you've offered ...

JIM HOLT: But we're living in almost a spiritual realm. You want to live in this—in this gross material realm, where there's a lot of stuff.

ROBERT: Yeah, but your spiritual realm, it's literally empty. It feels so intuitively wrong.

JIM HOLT: But if you go back to the old 19th-century view, that we're made up of these little hard particle atoms that are all bumping around, is it any more plausible that you and I are just a bunch of dumb, hard particles in a certain configuration? And if that's true, you know, how are certain configurations of these particles tantamount to the horrible feeling of pain?

ROBERT: You could say pain, oh, that's ...

JIM HOLT: ... just a lot of elementary particles in a certain configuration.

ROBERT: But we all know that explanation isn't enough. So when you look down to the bottom of everything ...

JIM HOLT: Whether it's a mathematical object, or whether it's little billiard balls knocking around, it's still miraculous and probable that it should produce subjective experience, that it should produce, you know, pleasure and pain.

ROBERT: And that mystery, how you go from the most basic things, or actually, the most basic nothings to everything we see around us ...

JIM HOLT: I find that to be exhilarating. To worry about, you know, the metaphysics of physics, and the nature of reality, even though it doesn't lead you to any sort of comfortable intellectual closure, it makes for—it's a good way of idling away an otherwise boring afternoon, as we've just proved.

ROBERT: [laughs]

ROBERT: It also explains why when I head butted him with my—with my very strong forehead, he seemed to think of it as a fascinating thought.

JAD: [laughs]

ROBERT: Special thanks to Jim Holt, who actually we're both too shy to ever head butt each other. But anyway, he has a book, it's called Why Does the World Exist?: An Existential Detective Story.

JAD: Okay, well I guess that's it for this podcast. Happy new year, everybody. I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: Thanks for listening. And existing.

ROBERT: Temporarily.

[LISTENER: This is Norma from Tampa. I'm a Radiolab listener, and reading the credits has been my 2012 goal. Radiolab is supported in part by the National Science Foundation and the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org. Radiolab is produced by WNYC and distributed by NPR. Thanks, Radiolab!]

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