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Annotated captions of Murray Gell-Mann on beauty and truth in physics in English

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Thank you for putting up these pictures of my colleagues over here.

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(Laughter) We'll be talking about them.

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Now, I'm going try an experiment. I don't do experiments, normally. I'm a theorist.

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But I'm going see what happens if I press this button.

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Sure enough. OK. I used to work in this field of elementary particles.

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What happens to matter if you chop it up very fine?

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What is it made of?

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And the laws of these particles are valid throughout the universe,

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and they're very much connected with the history of the universe.

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We know a lot about four forces. There must be a lot more,

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but those are at very, very small distances,

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and we haven't really interacted with them very much yet.

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The main thing I want to talk about is this:

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that we have this remarkable experience in this field of fundamental physics

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that beauty is a very successful criterion for choosing the right theory.

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And why on earth could that be so?

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Well, here's an example from my own experience.

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It's fairly dramatic, actually, to have this happen.

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Three or four of us, in 1957,

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put forward a partially complete theory of one of these forces, this weak force.

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And it was in disagreement with seven -- seven, count them, seven experiments.

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Experiments were all wrong.

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And we published before knowing that,

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because we figured it was so beautiful, it's gotta be right!

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The experiments had to be wrong, and they were.

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Now our friend over there, Albert Einstein,

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used to pay very little attention when people said,

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"You know, there's a man with an experiment that seems to disagree with special relativity.

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DC Miller. What about that?" And he would say, "Aw, that'll go away." (Laughter)

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Now, why does stuff like that work? That's the question.

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Now, yeah, what do we mean by beautiful? That's one thing.

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I'll try to make that clear -- partially clear.

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Why should it work, and is this something to do with human beings?

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I'll let you in on the answer to the last one that I offer,

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and that is, it has nothing to do with human beings.

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Somewhere in some other planet, orbiting some very distant star,

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maybe in a another galaxy,

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there could well be entities that are at least as intelligent as we are,

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and are interested in science. It's not impossible; I think there probably are lots.

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Very likely, none is close enough to interact with us.

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But they could be out there, very easily.

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And suppose they have, you know, very different sensory apparatus, and so on.

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They have seven tentacles, and they have 14 little funny-looking compound eyes,

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and a brain shaped like a pretzel.

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Would they really have different laws?

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There are lots of people who believe that, and I think it is utter baloney.

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I think there are laws out there,

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and we of course don't understand them at any given time very well

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-- but we try. And we try to get closer and closer.

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And someday, we may actually figure out the fundamental unified theory

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of the particles and forces, what I call the "fundamental law."

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We may not even be terribly far from it.

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But even if we don't run across it in our lifetimes,

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we can still think there is one out there,

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and we're just trying to get closer and closer to it.

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I think that's the main point to be made.

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We express these things mathematically.

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And when the mathematics is very simple --

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when in terms of some mathematical notation,

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you can write the theory in a very brief space, without a lot of complication --

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that's essentially what we mean by beauty or elegance.

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Here's what I was saying about the laws. They're really there.

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Newton certainly believed that.

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And he said, here, "It is the business of natural philosophy to find out those laws."

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The basic law, let's say -- here's an assumption.

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The assumption is that the basic law really takes the form

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of a unified theory of all the particles.

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Now, some people call that a theory of everything.

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That's wrong because the theory is quantum mechanical.

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And I won't go into a lot of stuff about quantum mechanics and what it's like, and so on.

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You've heard a lot of wrong things about it anyway. (Laughter)

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There are even movies about it with a lot of wrong stuff.

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But the main thing here is that it predicts probabilities.

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Now, sometimes those probabilities are near certainties.

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And in a lot of familiar cases, they of course are.

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But other times they're not, and you have only probabilities for different outcomes.

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So what that means is that the history of the universe is not determined just by the fundamental law.

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It's the fundamental law and this incredibly long series of accidents,

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or chance outcomes, that are there in addition.

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And the fundamental theory doesn't include those chance outcomes; they are in addition.

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So it's not a theory of everything. And in fact, a huge amount of the information

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in the universe around us comes from those accidents,

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and not just from the fundamental laws.

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Now, it's often said that getting closer and closer

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to the fundamental laws by examining phenomena at low energies, and then higher energies,

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and then higher energies, or short distances, and then shorter distances,

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and then still shorter distances, and so on, is like peeling the skin of an onion.

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And we keep doing that,

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and build more powerful machines, accelerators for particles.

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We look deeper and deeper into the structure of particles,

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and in that way we get probably closer and closer to this fundamental law.

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Now, what happens is that as we do that, as we peel these skins of the onion,

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and we get closer and closer to the underlying law,

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we see that each skin has something in common with the previous one,

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and with the next one. We write them out mathematically,

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and we see they use very similar mathematics.

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They require very similar mathematics.

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That is absolutely remarkable, and that is a central feature

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of what I'm trying to say today.

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Newton called it -- that's Newton, by the way -- that one.

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This one is Albert Einstein. Hi, Al! And anyway,

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he said, "nature conformable to herself" -- personifying nature as a female.

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And so what happens is that the new phenomena,

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the new skins, the inner skins of the slightly smaller skins of the onion

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that we get to, resemble the slightly larger ones.

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And the kind of mathematics that we had for the previous skin

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is almost the same as what we need for the next skin.

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And that's why the equations look so simple.

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Because they use mathematics we already have.

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A trivial example is this: Newton found the law of gravity,

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which goes like one over the square of the distance between the things gravitated.

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Coulomb, in France, found the same law for electric charges.

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Here's an example of this similarity.

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You look at gravity, you see a certain law.

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Then you look at electricity. Sure enough. The same rule.

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It's a very simple example.

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There are lots of more sophisticated examples.

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Symmetry is very important in this discussion.

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You know what it means. A circle, for example,

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is symmetric under rotations about the center of the circle.

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You rotate around the center of the circle, the circle remains unchanged.

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You take a sphere, in three dimensions, you rotate around the center of the sphere,

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and all those rotations leave the sphere alone.

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They are symmetries of the sphere.

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So we say, in general, that there's a symmetry

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under certain operations if those operations leave the phenomenon,

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or its description, unchanged.

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Maxwell's equations are of course symmetrical

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under rotations of all of space.

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Doesn't matter if we turn the whole of space around by some angle,

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it doesn't leave the -- doesn't change the phenomenon of electricity or magnetism.

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There's a new notation in the 19th century that expressed this,

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and if you use that notation, the equations get a lot simpler.

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Then Einstein, with his special theory of relativity,

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looked at a whole set of symmetries of Maxwell's equations,

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which are called special relativity.

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And those symmetries, then, make the equations even shorter, and even prettier, therefore.

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Let's look. You don't have to know what these things mean, doesn't make any difference.

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But you can just look at the form. (Laughter) You can look at the form.

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You see above, at the top, a long list

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of equations with three components for the three directions of space: x, y and z.

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Then, using vector analysis, you use rotational symmetry, and you get this next set.

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Then you use the symmetry of special relativity and you get an even simpler set

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down here, showing that symmetry exhibits better and better.

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The more and more symmetry you have, the better you exhibit the simplicity and elegance of the theory.

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The last two, the first equation says that electric charges and currents

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give rise to all the electric and magnetic fields.

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The next -- second -- equation says that there is no magnetism other than that.

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The only magnetism comes from electric charges and currents.

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Someday we may find some slight hole in that argument.

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But for the moment, that's the case.

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Now, here is a very exciting development that many people have not heard of.

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They should have heard of it, but it's a little tricky to explain in technical detail,

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so I won't do it. I'll just mention it. (Laughter)

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But Chen Ning Yang, called by us "Frank" Yang -- (Laughter)

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-- and Bob Mills put forward, 50 years ago,

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this generalization of Maxwell's equations, with a new symmetry.

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A whole new symmetry.

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Mathematics very similar, but there was a whole new symmetry.

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They hoped that this would contribute somehow to particle physics

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-- didn't. It didn't, by itself, contribute to particle physics.

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But then some of us generalized it further. And then it did!

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And it gave a very beautiful description of the strong force and of the weak force.

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So here we say, again, what we said before:

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that each skin of the onion shows a similarity to the adjoining skins.

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So the mathematics for the adjoining skins is very similar to what we need for the new one.

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And therefore it looks beautiful

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because we already know how to write it in a lovely, concise way.

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So here are the themes. We believe there is a unified theory underlying all the regularities.

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Steps toward unification exhibit the simplicity.

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Symmetry exhibits the simplicity.

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And then there is self-similarity across the scales -- in other words,

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from one skin of the onion to another one.

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Proximate self-similarity. And that accounts for this phenomenon.

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That will account for why beauty is a successful criterion for selecting the right theory.

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Here's what Newton himself said:

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"Nature is very consonant and conformable to her self."

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One thing he was thinking of is something that most of us take for granted today,

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but in his day it wasn't taken for granted.

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There's the story, which is not absolutely certain to be right, but a lot of people told it.

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Four sources told it. That when they had the plague in Cambridge,

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and he went down to his mother's farm -- because the university was closed --

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he saw an apple fall from a tree, or on his head or something.

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And he realized suddenly that the force that drew the apple down to the earth

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could be the same as the force regulating the motions of the planets and the moon.

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That was a big unification for those days, although today we take it for granted.

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It's the same theory of gravity.

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So he said that this principle of nature, consonance:

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"This principle of nature being very remote from the conceptions of philosophers,

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I forbore to describe it in that book,

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lest I should be accounted an extravagant freak ... "

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That's what we all have to watch out for, (Laughter) especially at this meeting.

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" ... and so prejudice my readers against all those things which were the main design of the book."

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Now, who today would claim that as a mere conceit of the human mind?

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That the force that causes the apple to fall to the ground

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is the same force that causes the planets and the moon to move around,

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and so on? Everybody knows that. It's a property of gravitation.

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It's not something in the human mind. The human mind can, of course, appreciate it

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and enjoy it, use it, but it's not -- it doesn't stem from the human mind.

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It stems from the character of gravity.

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And that's true of all the things we're talking about.

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They are properties of the fundamental law.

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The fundamental law is such that the different skins of the onion resemble one another,

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and therefore the math for one skin allows you to express beautifully and simply

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the phenomenon of the next skin.

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I say here that Newton did a lot of things that year:

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gravity, the laws of motion, the calculus, white light composed of all the colors of the rainbow.

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And he could have written quite an essay on "What I Did Over My Summer Vacation."

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(Laughter)

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So we don't have to assume these principles as separate metaphysical postulates.

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They follow from the fundamental theory.

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They are what we call emergent properties.

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You don't need -- you don't need something more to get something more.

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That's what emergence means.

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Life can emerge from physics and chemistry, plus a lot of accidents.

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The human mind can arise from neurobiology and a lot of accidents,

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the way the chemical bond arises from physics and certain accidents.

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It doesn't diminish the importance of these subjects

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to know that they follow from more fundamental things, plus accidents.

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That's a general rule, and it's critically important to realize that.

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You don't need something more in order to get something more.

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People keep asking that when they read my book, "The Quark and the Jaguar,"

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and they say, "Isn't there something more beyond what you have there?"

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Presumably, they mean something supernatural.

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Anyway, there isn't. (Laughter)

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You don't need something more to explain something more.

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Thank you very much. (Applause)