Robert Krulwich

Okay, so this is about what you do for a living.

You know that I have this neighbor and friend, Brian Greene.

Yes, I do know that.

And the thing about Brian is he is a theoretical physicist.

Now, theoretical physicists say that it's theoretically possible to know everything there is to know in the universe.

So one day they'll be able to explain not only how you could send a rocket to the moon, but the laws that govern space and energy and time.

and gravity, everything, the whole universe, one day they think might be totally understandable using logic and mathematical equations.

Yes.

That's the big, big goal.

This is like playing poker.

You're helping me.

I don't know what you're going to do.

All right.

We'll take it to the next step.

Okay.

All right, so... Well, you know we argue.

That's the fun thing we do.

Sure.

But unlike him, my position has always been that it's going to be very hard to answer all the puzzles in the universe.

And frankly, it's not a bad thing if some mysteries remain mysterious.

That's my view.

But because Brian's so smart, when I tell him, how do you know this, whatever, he always wins the arguments.

But...

A few months ago, this is the thing that got this whole thing started.

I was reading Harper's Magazine, and I found an article written by another physicist and a novelist, Alan Lightman.

And I thought, oh boy, this is going to drive Brian bats.

Because Alan says, there is a group of physicists, and Brian happens to be one of them, who've embraced a very exciting idea with an unfortunate effect.

If this idea turns out to be true, Alan writes, it will then be impossible for physicists to know everything.

Which I thought, ah, excellent.

What is the idea?

It has to do with more than one universe.

You know this, we've talked about it before, that there is a vogue now for the idea that instead of one universe encompassing everything, there might be more than one.

Now, in this view of things, there could be not just one universe or three or 19.

There could be 10,000.

There could be trillions.

There could be an infinite number.

And here's the crucial thing.

Each and every one of these universes can be different from its neighboring.

Some of them might have atoms, some of them might not have atoms.

You could have a universe with lots of stars, some with no stars, some could be made of Munster cheese.

I don't know.

The fundamental properties of each universe could be very different.

That's exactly right.

And that's the key to Alan Lightman's argument.

Well, then, going back to the beginning of our conversation, if a physicist's job is to explore everything, that is the universe, now the universe has just been demoted to a sub-universe, then...

When you get your diploma from a great university, the president of the university says, my friends, we are gathered here to meet the people who have earned the credentials to describe the sub-universe.

A little bit of what we could know.

It's like you've been demoted.

You thought that you were going to get to learn about everything, your words, and now it turns out that everything is sub.

Johannes Kepler was an astronomer and a kind of mapper of the solar system.

He was trying to figure out where the planets were and the nature of their orbits and stuff.

Mars, for example, is 141 million miles from the sun.

Jupiter...

483 million.

And when you start comparing the different distances of planets from the Sun, you realize that the fact that the Earth is 93 million miles away, it doesn't seem like a deep law of the universe anymore.

It just feels kind of arbitrary.

And then that forces you to change the question.

Not, why 93 million?

No, why are all these different planets at different distances from the Sun, and yet they all stick around the Sun?

They're all trapped in the neighborhood.

That question puts you on the road to a deeper thought.

The theory of gravity.

The point is, says Brian, if you're focused on one thing, you're going to think that one thing is the key to everything.

When your one turns to many, then you think, ah, well, the one thing really wasn't so special.

But...

The way Brian sees it.

And Brian says you can make the exact same kind of progress if you compare universes.

So instead of asking, why is our one universe the way it is?

Now you can ask, well, what do all of these universes so different one from the other still have in common?

There are an infinite number of them.

So if I told you that you could write anything down, and it might be a universe, black universes, white universes, green universes, soft universes, hard universes, muscular universes, teeny universes, huge universes, then the only one you know intimately is your own.

It seems to me that what do you know about those other universes, other than that they might be very different?

But Brian believes that one day we might be able to experimentally detect these other universes and somehow, you know, kind of pick up their distant vibrations, kind of like the way you hear your neighbor's music.

It's just...

And I say from my brain, I'm going to just assume certain things are always true.

There's always going to be gravity, say.

There's always going to be some particle or wave that creates matter.

There's always going to be, I don't know, what else?

Are there things that they're always going to be?

What are they that are always going to be?

Or why...

Was the world made in seven days?

Aren't we getting close to some sort of... You're believing in certain things to be always true the way religious people believe certain things are always true.

Not because you've seen it, it's just because you have a faith in it.

has to be there.

Oh, this is- Not belief, just logic.

This is just logic.

Aren't you worried, though, that there's another Brian Greene in universe number 3,790,208,645 who is sitting there talking to another radio reporter in another university and he's saying, well, we know all about the other universes because we're assuming...

that the math here is the same as the math there in that other place.

But as it turns out, their math and our math aren't the same, so they will not... You may just be wrong.

You somehow are feeling that the math is a clue

that everything follows your math.

If at some point the maths collide and then the universes collide, then that would be very unsettling to both of you, I would assume.

Well, I thought it would be fair to ask the author of the article, so I called Alan, who happened, as it turns out, to be in Phnom Penh, Cambodia.

And I sent him the interview with Brian.

He listened.

And I asked, well, what do you think about Brian's argument?

He said, well, I think it's going to be much harder than Brian thinks to actually sense or encounter or measure these other universes if they exist at all.

What does that mean?

And that we'll never, ever really understand everything?

Recently, I got into a bit of a kerfuffle with a guy who yearns like you do for an ideal.

His name is Jim Holt.

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.

Meaning what?

Yeah.

Minerals?

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?

Yeah.

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.

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.

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

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.

So you can think of this baseball, this nucleus, as a tiny dot all alone.

So it's basically, the atom is a big empty space.

Well, it doesn't feel that way.

Like, watch this.

I'm going to do this.

If my hands are all atoms, and as you say, atoms are mostly empty space, then why don't my hands just go right to each other like two clouds?

But you'll notice.

Isn't it more like my electrons don't like similar electrons, so the electrons in my hands just hate the electrons in the other hand?

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

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, you can hear it as the sound of a law saying, no, not allowed, not in nature.

Exactly.

But wait, isn't this law that we're 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.

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

Pure information.

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.

Well, according to Jim, what we think happens, and this admittedly is a gross oversimplification, but in these fields, you're going to get these little fluctuations, these little events, right?

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.

I don't know if Jim would call a rock like Bishop Barclay 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.

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.

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.

Yeah, but your spiritual realm, it's literally empty.

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

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

Special thanks to Jim Holt, who, actually, we were both too shy to ever headbutt each other until we came over to try it.

But anyway, he has a wonderful, the book is called Why Does the World Exist?

An Existential Detective Story.