Jim Holt

You're listening to Radiolab from WNYC.

Yeah.

Remember the line?

Yeah, kick at the rock, Sam Johnson, break your bones, but cloudy, cloudy is the stuff of stones.

Cloudy, cloudy is the stuff of stones.

Yeah.

It's something, well, Samuel Johnson, who lived in the 18th century,

It was a contemporary of Bishop Barclay, and Bishop Barclay 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.

like the rock really had no substance.

And Samuel Johnson, when he heard this, he thought it was ridiculous, and he went and kicked a stone and said, I refute Barclay thus.

Anyway, that's the story.

Well, they're arguing about reality.

Just what is this world?

What is its essential nature?

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

What's it made of?

And this sounds like I've been eating lotus leaves.

I mean, it's a pipe dream.

But this is what science has increasingly led us to.

You know, even in ancient times, the atomists, 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 clearly got a fundamental stuff.

Yeah, that sounds very pleasing.

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.

Newton, of course, came up with the 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.

And Newton's contemporaries wanted to know, well, how does it do that?

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?

Yeah, yeah.

But the problem is it looks like there's nothing between the Earth and the Sun except a void.

Because at that time, everybody thought that nature has to be made out of hard, durable stuff.

You know, gears, sprockets, pushing and pulling.

That's the essence of reality.

Then in the 20th century, of course, it got 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.

And as we know all too well from the 20th century, you can split an atom.

Yeah, it has pretty interesting consequences.

But we also discover the atom is almost entirely empty space.

Huh.

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.

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.

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.

And here's a...

It's a slightly different way of putting that.

Well, 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.

They're just temporary properties of what are called fields.

And fields are just distributions of mathematical quantities through space-time.

It's all, they're not, they don't seem to be grounded in anything.

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

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, goes through my pupil rather, and strikes my retina, and I perceive the rock.

Yeah.

Yeah.

I've heard one physicist say that the cosmos is ultimately a concept.

Yeah, yeah.

Maybe at 100 years from now, when string theory is finally worked out, we might have a very different conception of it.

But what it looks is that it's going to be mathematics and structure all the way down.

You're OK with this.

Well, I'm a sort of mathematical romantic.

I love the idea that the essence of reality is not stuff.

Stuff is kind of ugly.

I mean, you want to get rid of stuff.

There's too much stuff in your apartment.

It's gross, viscous, absurd.

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

Well, this is a temperamental difference between us.

I like the idea that reality consists, it's a flux of pure information with no further substance.

Now, you've offered- But we're living in an almost in a spiritual realm.

You want to live in this gross material realm.

And where there's a lot of stuff.

It feels so intuitively wrong.

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?

You could say pain, oh, that's just a lot of elementary particles in a certain configuration.

But we all know that explanation isn't enough.

So when you look down to the bottom of everything... Whether it's a mathematical object or whether it's little billiard balls knocking around, it's still...

miraculous and improbable that it should produce subjective experience, that it should produce pleasure and pain.

I find that to be exhilarating, to worry about the metaphysics of physics and the nature of reality, even though it doesn't lead you to any sort of comfortable intellectual closure.

It's a good way of idling away an otherwise boring afternoon, as we've just proved.