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SUBTITLED BY ANDROMEDA
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Now, on NOVA,
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take a thrill ride into a world|stranger than science fiction,
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where you play the game,
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by breaking some rules,
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where a new view of the universe,
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pushes you beyond the limits|of your wildest imagination.
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This is the world of string theory,
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a way of describing every force and|all matter from an atom to earth,
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to the end of the galaxies
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�from the birth of|time to its final tick�
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in a single theory,
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a theory of everything.
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Our guide to this brave|new world is Brian Greene,
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the bestselling author and physicist.
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And no matter how|many times I come here,
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I never seem to get used to it.
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Can he help us solve the|greatest puzzle of modern physics
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�that our understanding of the|universe is based on two sets of laws,
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that don't agree?
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Resolving that contradiction eluded even|Einstein, who made it his final quest.
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After decades, we may finally be|on the verge of a breakthrough.
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The solution is strings,
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tiny bits of energy vibrating|like the strings on a cello,
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a cosmic symphony at|the heart of all reality.
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But it comes at a price:
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parallel universes and 11 dimensions,
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most of which you've never seen.
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We really may live in a universe with|more dimensions than meet the eye.
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People who have said that there|were extra dimensions of space
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have been labeled crackpots,or|people who are bananas.
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A mirage of science and mathematics|or the ultimate theory of everything?
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If string theory fails to|provide a testable prediction,
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then nobody should believe it.
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Is that a theory of physics,
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or a philosophy?
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One thing that is certain is that|string theory is already showing us
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that the universe may be a lot stranger
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than any of us ever imagined.
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Coming up tonight...
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it all started with an apple.
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The triumph of Newton's|equations come from the quest
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to understand the planets and the stars.
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And we've come a long way since.
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Einstein gave the world a new picture
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for what the force of|gravity actually is.
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Where he left off, string|theorists now dare to go.
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But how close are they to|fulfilling Einstein's dream?
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Watch The Elegant Universe right now.
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50 years ago,
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this house was the scene
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of one of the greatest mysteries
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of modern science-
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a mystery so profound
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that today
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thousands of scientists
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on the cutting edge of physics
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are still trying to solve it.
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Albert Einstein spent
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his last two decades
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in this modest home
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in Princeton, New Jersey.
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And in his second floor study,
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Einstein relentlessly
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sought a single theory
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so powerful it would describe
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all the workings
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of the universe.
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Even as he neared
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the end of his life,
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Einstein kept a notepad
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close at hand,
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furiously trying to come up
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with the equations
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for what would come to be known
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as the "theory of everything. "
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Convinced he was on the verge
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of the most important discovery
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in the history of science,
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Einstein ran out of time,
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his dream unfulfilled.
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Now, almost
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a half-century later,
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Einstein's goal of unification-
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combining all the laws
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of the universe
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in one all-encompassing theory-
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has become the holy grail
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of modern physics,
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and we think we may at last
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achieve Einstein's dream
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with a new and radical set
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of ideas called string theory.
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But if this revolutionary theory
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is right,
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we're in for quite a shock.
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String theory says we may be
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living in a universe
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where reality
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meets science fiction...
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a universe of 11 dimensions
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with parallel universes
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right next door.
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An elegant universe,
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composed entirely
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of the music of strings.
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But for all its ambition,
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the basic idea of string theory
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is surprisingly simple.
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It says that everything
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in the universe,
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from the tiniest particle
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to the most distant star,
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is made from one kind
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of ingredient:
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unimaginably small,
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vibrating strands of energy
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called strings.
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Just as the strings of a cello
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can give rise
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to a rich variety
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of musical notes...
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the tiny strings
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in string theory vibrate
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in a multitude
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of different ways,
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making up all the constituents
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of nature.
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In other words, the universe
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is like a grand cosmic symphony,
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resonating with all
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the various notes
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these tiny, vibrating strands
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of energy can play.
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String theory is still
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in its infancy,
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but it's already revealing
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a radically new picture
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of the universe,
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one that is both strange
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and beautiful.
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But what makes us think
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we can understand
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all the complexity
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of the universe,
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let alone reduce it to
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a single theory of everything?
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We have R mu nu minus
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a half g mu nu R-
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you remember how this goes-
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equals eight pi g T mu nu.
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Comes from varying
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the Einstein-Hilbert Action,
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and we get the field equations
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and this term.
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You remember
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what this is called.
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No, that's the scalar curvature.
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This is the Ricci Tensor.
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Have you been
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studying this at all?
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No matter how hard you try,
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you can't teach physics
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to a dog.
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Their brains just aren't wired
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to grasp it.
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But what about us?
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How do we know that we're wired
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to comprehend the deepest laws
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of the universe?
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Well, physicists today
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are confident that we are,
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and we're picking up
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where Einstein left off
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in his quest for unification.
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Unification would be
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the formulation of a law
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that describes perhaps
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everything in the known universe
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from one single idea,
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one master equation.
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And we think that there might
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be this master equation
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because throughout the course
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of the last 200 years or so,
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our understanding
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of the universe
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has given us a variety
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of explanations
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that are all pointing
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towards one spot.
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They seem to all be converging
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on one nugget of an idea
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that we're still trying to find.
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Unification is where it's at.
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Unification is what we're trying
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to accomplish.
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The whole aim
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of fundamental physics
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is to see more and more
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of the world's phenomena
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in terms of fewer and fewer and
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simpler and simpler principles.
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We feel, as physicists,
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that if we can explain
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a wide number of phenomena
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in a very simple manner,
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that that's somehow progress.
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There is almost
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an emotional aspect
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to the way in which
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the great theories in physics
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sort of encompass a wide variety
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of apparently different
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physical phenomena.
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So this idea that
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we should be aiming
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to unify our understanding
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is inherent, essentially,
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to the whole way in which
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this kind of science progresses.
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And long before Einstein,
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the quest for unification began
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with the most famous accident
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in the history of science.
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As the story goes, one day in 1665,
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a young man was sitting under|a tree, when all of a sudden,
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he saw an apple fall from above.
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And with the fall of that apple,
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Isaac Newton revolutionized|our picture of the universe.
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In an audacious proposal for his time,
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Newton proclaimed that the force|pulling apples to the ground...
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and the force keeping the|moon in orbit around the earth
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were actually one and the same.
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In one fell swoop,
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Newton unified the heavens and the earth
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in a single theory he called gravity.
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The unification of the|celestial with the terrestrial-
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that the same laws that govern|the planets in their motions
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govern the tides and the|falling of fruit here on Earth.
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It was a fantastic unification|of our picture of nature.
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Gravity was the first force
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to be understood scientifically,
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though three morewould|eventually follow.
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And although Newton|discovered his law of gravity
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more than 300 years ago,
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his equations describing this force
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make such accurate predictions
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that we still make use of them today.
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In fact, scientists needed
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nothing more than Newton's equations
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to plot the course of a rocket|that landed men on the moon.
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Eleven, this is Houston.
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Yet, there was a problem.
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While his laws described|the strength of gravity
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with great accuracy,
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Newton was harboring|an embarrassing secret:
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He had no idea how|gravity actually works.
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For nearly 250 years,
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scientists were content|to look the other way
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00:13:06,630 --> 00:13:08,800
when confronted with this mystery.
262
00:13:08,830 --> 00:13:12,830
But in the early 1900s,
263
00:13:13,500 --> 00:13:17,200
an unknown clerk working|in the Swiss patent office
264
00:13:17,230 --> 00:13:18,660
would change all that.
265
00:13:18,700 --> 00:13:22,160
While reviewing patent applications,
266
00:13:22,200 --> 00:13:26,200
Albert Einstein was also|pondering the behavior of light.
267
00:13:26,680 --> 00:13:30,680
And little did Einstein know|that his musings on light
268
00:13:31,100 --> 00:13:35,100
would lead him to solve Newton's|mystery of what gravity is.
269
00:13:35,230 --> 00:13:39,230
At the age of 26, Einstein|made a startling discovery-
270
00:13:41,900 --> 00:13:45,900
that the velocity of light is|a kind of cosmic speed limit,
271
00:13:48,230 --> 00:13:51,900
a speed that nothing in|the universe can exceed.
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00:13:52,000 --> 00:13:55,900
But no sooner had the young|Einstein published this idea
273
00:13:56,000 --> 00:14:00,000
than he found himself squaring|off with the father of gravity.
274
00:14:01,700 --> 00:14:05,700
The trouble was
275
00:14:07,100 --> 00:14:11,000
the idea that nothing can go|faster than the speed of light
276
00:14:11,030 --> 00:14:14,860
flew in the face of|Newton's picture of gravity.
277
00:14:14,900 --> 00:14:18,900
To understand this conflict, we|have to run a few experiments.
278
00:14:22,030 --> 00:14:26,030
And to begin with, let's|create a cosmic catastrophe.
279
00:14:27,300 --> 00:14:31,300
Imagine that all of a sudden|and without any warning,
280
00:14:32,600 --> 00:14:35,700
the sun vaporizes and|completely disappears.
281
00:14:35,730 --> 00:14:39,730
Now let's replaythat catastrophe
282
00:14:41,400 --> 00:14:43,500
and see what effect it|would have on the planets
283
00:14:43,530 --> 00:14:45,260
according to Newton.
284
00:14:45,300 --> 00:14:49,300
Newton's theory predicts that|with the destruction of the sun,
285
00:14:49,830 --> 00:14:53,830
the planets would immediately|fly out of their orbits,
286
00:14:55,730 --> 00:14:58,260
careening off into space.
287
00:14:58,300 --> 00:15:02,300
In other words, Newton thought|that gravity was a force
288
00:15:07,000 --> 00:15:10,000
that acts instantaneously|across any distance,
289
00:15:10,100 --> 00:15:12,900
and so we would|immediately feel the effect
290
00:15:12,930 --> 00:15:14,260
of the sun's destruction.
291
00:15:14,300 --> 00:15:18,300
But Einstein saw a big|problem with Newton's theory-
292
00:15:18,400 --> 00:15:22,400
a problem that arose|from his work with light.
293
00:15:22,900 --> 00:15:26,900
Einstein knew light doesn't|travel instantaneously.
294
00:15:27,880 --> 00:15:31,880
In fact, it takes eight|minutes for the sun's rays
295
00:15:32,900 --> 00:15:36,560
to travel the 93 million|miles to the earth.
296
00:15:36,600 --> 00:15:40,600
And since he had shown that|nothing, not even gravity,
297
00:15:41,230 --> 00:15:43,260
can travel faster than light,
298
00:15:43,300 --> 00:15:47,300
how could the earth|be released from orbit
299
00:15:48,200 --> 00:15:52,200
before the darkness resulting|from the sun's disappearance
300
00:15:52,430 --> 00:15:55,700
reached our eyes?
301
00:15:55,800 --> 00:15:59,800
To the young upstart from|the Swiss patent office,
302
00:16:04,800 --> 00:16:08,360
anything outrunning|light was impossible,
303
00:16:08,400 --> 00:16:12,400
and that meant the 250-year-old|Newtonian picture of gravity
304
00:16:13,830 --> 00:16:15,300
was wrong.
305
00:16:15,400 --> 00:16:19,400
If Newton is wrong, then|why do the planets stay up?
306
00:16:20,080 --> 00:16:24,080
Because remember, the|triumph of Newton's equations
307
00:16:24,800 --> 00:16:28,300
come from the quest to understand
308
00:16:28,400 --> 00:16:31,150
the planets and the stars,|and particularly the problem
309
00:16:31,180 --> 00:16:33,900
of why do the planets have|the orbits that they do.
310
00:16:33,930 --> 00:16:36,960
And with Newton's equations,
311
00:16:37,000 --> 00:16:39,400
you can calculate the way|that the planets will move.
312
00:16:39,430 --> 00:16:43,430
Einstein's got to resolve this dilemma.
313
00:16:43,750 --> 00:16:47,750
In his late 20s, Einstein had to come up
314
00:16:48,100 --> 00:16:49,860
with a new picture of the universe
315
00:16:49,900 --> 00:16:53,800
in which gravity does not|exceed the cosmic speed limit.
316
00:16:53,830 --> 00:16:56,960
Still working his day|job in the patent office,
317
00:16:57,000 --> 00:17:01,000
Einstein embarked on a solitary|quest to solve this mystery.
318
00:17:01,530 --> 00:17:05,530
After nearly ten years|of wracking his brain,
319
00:17:07,050 --> 00:17:11,050
he found the answer in a|new kind of unification.
320
00:17:16,100 --> 00:17:20,100
Einstein came to think of|the three dimensions of space
321
00:17:20,600 --> 00:17:22,160
and the single dimension of time
322
00:17:22,200 --> 00:17:26,200
as bound together in a|single fabric of space-time.
323
00:17:33,000 --> 00:17:35,560
It was his hope that by understanding
324
00:17:35,600 --> 00:17:39,600
the geometry of this|four-dimensional fabric of space-time
325
00:17:40,180 --> 00:17:44,180
that he could simply talk about|things moving along surfaces
326
00:17:44,900 --> 00:17:47,100
in this space-time fabric.
327
00:17:49,400 --> 00:17:50,700
Like the surface of a trampoline,
328
00:17:50,800 --> 00:17:54,200
this unified fabric|is warped and stretched
329
00:17:54,300 --> 00:17:57,300
by heavy objects like planets and stars.
330
00:17:57,400 --> 00:18:01,400
And it's this warping,|or curving, of space-time
331
00:18:03,130 --> 00:18:06,610
that creates what we feel as gravity.
332
00:18:06,650 --> 00:18:10,100
A planet like the earth is kept in orbit
333
00:18:10,130 --> 00:18:11,800
not because the sun reaches out
334
00:18:11,900 --> 00:18:15,550
and instantaneously grabs hold|of it as in Newton's theory,
335
00:18:15,580 --> 00:18:19,200
but simply because it follows|curves in the spatial fabric
336
00:18:19,300 --> 00:18:21,160
caused by the sun's presence.
337
00:18:21,200 --> 00:18:23,800
So, with this new|understanding of gravity,
338
00:18:23,830 --> 00:18:26,300
let's rerun the cosmic catastrophe.
339
00:18:26,400 --> 00:18:29,300
Let's see what happens|now if the sun disappears.
340
00:18:29,330 --> 00:18:33,330
The gravitational|disturbance that results
341
00:18:34,600 --> 00:18:38,500
will form a wave that travels|across the spatial fabric
342
00:18:38,530 --> 00:18:42,210
in much the same way that|a pebble dropped into a pond
343
00:18:42,250 --> 00:18:45,900
makes ripples that travel|across the surface of the water.
344
00:18:46,000 --> 00:18:49,900
So we wouldn't feel a change|in our orbit around the sun
345
00:18:49,930 --> 00:18:53,460
until this wave reached the earth.
346
00:18:53,500 --> 00:18:57,500
What's more, Einstein calculated|that these ripples of gravity
347
00:18:59,930 --> 00:19:03,700
travel at exactly the speed of light.
348
00:19:03,730 --> 00:19:07,700
And so, with this new approach,
349
00:19:07,800 --> 00:19:10,500
Einstein resolved the|conflict with Newton
350
00:19:10,530 --> 00:19:12,760
over how fast gravity travels.
351
00:19:12,800 --> 00:19:16,700
And more than that, Einstein|gave the world a new picture
352
00:19:16,730 --> 00:19:19,060
for what the force of|gravity actually is:
353
00:19:19,100 --> 00:19:23,100
it's warps and curves in|the fabric of space and time.
354
00:19:24,300 --> 00:19:28,300
Einstein called this new picture|of gravity "general relativity,"
355
00:19:30,130 --> 00:19:32,500
and within a few short years,
356
00:19:32,600 --> 00:19:36,000
Albert Einstein became a household name.
357
00:19:36,030 --> 00:19:39,400
Einstein was like a|rock star in his day.
358
00:19:39,430 --> 00:19:41,760
He was one of the most widely known
359
00:19:41,800 --> 00:19:44,060
and recognizable figures alive.
360
00:19:44,100 --> 00:19:47,400
He and perhaps Charlie|Chaplin were the reigning kings
361
00:19:47,430 --> 00:19:48,500
of the popular media.
362
00:19:48,600 --> 00:19:51,200
People followed his work.
363
00:19:51,300 --> 00:19:55,300
And they were anticipating,|because of this wonderful thing
364
00:19:55,730 --> 00:19:57,500
he had done with general relativity-
365
00:19:57,600 --> 00:20:01,600
this recasting the laws of|gravity out of his head-
366
00:20:03,330 --> 00:20:05,860
there was the thought|he could do it again
367
00:20:05,900 --> 00:20:08,000
and they... you know,|people want to be in on that.
368
00:20:08,100 --> 00:20:11,100
Despite all that he had achieved,
369
00:20:11,130 --> 00:20:13,700
Einstein wasn't satisfied.
370
00:20:13,800 --> 00:20:17,300
He immediately set his sights|on an even grander goal:
371
00:20:17,330 --> 00:20:19,760
the unification of his|new picture of gravity
372
00:20:19,800 --> 00:20:23,600
with the only other force known|at the time, electromagnetism.
373
00:20:23,700 --> 00:20:27,700
Now, electromagnetism is a force|that had itself been unified
374
00:20:29,230 --> 00:20:31,160
only a few decades earlier.
375
00:20:31,200 --> 00:20:35,200
In the mid-1800s,|electricity and magnetism
376
00:20:36,830 --> 00:20:39,860
were sparking scientists' interest.
377
00:20:39,900 --> 00:20:43,900
These two forces seemed to|share a curious relationship
378
00:20:44,480 --> 00:20:48,480
that inventors like Samuel|Morse were taking advantage of
379
00:20:49,030 --> 00:20:51,900
in newfangled devices|such as the telegraph.
380
00:20:52,000 --> 00:20:56,000
An electrical pulse, sent|through a telegraph wire
381
00:20:58,030 --> 00:21:00,200
to a magnet thousands of miles away,
382
00:21:00,300 --> 00:21:04,300
produced the familiar dots|and dashes of Morse code
383
00:21:04,600 --> 00:21:08,000
that allowed messages to be|transmitted across the continent
384
00:21:08,030 --> 00:21:10,260
in a fraction of a second.
385
00:21:10,300 --> 00:21:14,100
Although the telegraph was a sensation,
386
00:21:14,130 --> 00:21:16,810
the fundamental science driving it
387
00:21:16,850 --> 00:21:19,460
remained something of a mystery.
388
00:21:19,500 --> 00:21:23,500
But to a Scottish scientist|named James Clerk Maxwell,
389
00:21:27,700 --> 00:21:31,700
the relationship between|electricity and magnetism
390
00:21:32,700 --> 00:21:36,700
was so obvious in nature|that it demanded unification.
391
00:21:39,500 --> 00:21:43,500
If you've ever been on top of a|mountain during a thunderstorm,
392
00:21:45,530 --> 00:21:49,500
you'll get the idea of how|electricity and magnetism
393
00:21:49,530 --> 00:21:51,300
are closely related.
394
00:21:51,400 --> 00:21:54,750
When a stream of electrically|charged particles flows,
395
00:21:54,780 --> 00:21:58,100
like in a bolt of lightning,|it creates a magnetic field,
396
00:21:58,130 --> 00:22:00,700
and you can see evidence|of this on a compass.
397
00:22:00,730 --> 00:22:04,730
Obsessed with this relationship,
398
00:22:11,800 --> 00:22:15,200
the Scot was determined|to explain the connection
399
00:22:15,230 --> 00:22:17,810
between electricity and magnetism
400
00:22:17,850 --> 00:22:20,870
in the language of mathematics.
401
00:22:20,910 --> 00:22:23,900
Casting new light on the subject,
402
00:22:24,000 --> 00:22:25,960
Maxwell devised a set
403
00:22:26,000 --> 00:22:29,100
of four elegant|mathematical equations...
404
00:22:29,200 --> 00:22:33,200
that unified electricity and magnetism
405
00:22:35,480 --> 00:22:39,480
in a single force|called electromagnetism.
406
00:22:41,730 --> 00:22:45,730
And like Isaac Newton before him,
407
00:22:45,900 --> 00:22:49,600
Maxwell's unification|took science a step closer
408
00:22:49,630 --> 00:22:52,200
to cracking the code of the universe.
409
00:22:52,300 --> 00:22:55,600
That was really the remarkable thing
410
00:22:55,700 --> 00:22:56,700
that these different phenomena
411
00:22:56,800 --> 00:22:59,160
were really connected in this way.
412
00:22:59,200 --> 00:23:03,200
And it's another example|of diverse phenomena
413
00:23:03,600 --> 00:23:07,100
coming from a single|underlying building block
414
00:23:07,200 --> 00:23:08,260
or a single underlying principle.
415
00:23:08,300 --> 00:23:12,100
Imagine that everything|that you can think of
416
00:23:12,130 --> 00:23:15,900
which has to do with|electricity and magnetism
417
00:23:16,000 --> 00:23:20,000
can all be written in|four very simple equations.
418
00:23:21,130 --> 00:23:23,800
Isn't that incredible?
419
00:23:23,900 --> 00:23:25,800
Isn't that amazing?
420
00:23:25,830 --> 00:23:27,700
I call that elegant.
421
00:23:27,800 --> 00:23:30,560
Einstein thought that this
422
00:23:30,600 --> 00:23:33,600
was one of the triumphant|moments of all of physics
423
00:23:33,630 --> 00:23:36,600
and admired Maxwell hugely|for what he had done.
424
00:23:36,630 --> 00:23:39,560
About 50 years
425
00:23:39,600 --> 00:23:42,800
after Maxwell unified|electricity and magnetism,
426
00:23:42,830 --> 00:23:45,960
Einstein was confident|that if he could unify
427
00:23:46,000 --> 00:23:49,400
his new theory of gravity with|Maxwell's electromagnetism,
428
00:23:49,500 --> 00:23:52,500
he'd be able to formulate|a master equation
429
00:23:52,600 --> 00:23:56,100
that could describe|everything, the entire universe.
430
00:23:56,130 --> 00:24:00,130
Einstein clearly believes|that the universe has
431
00:24:02,030 --> 00:24:05,600
an overall grand and beautiful pattern
432
00:24:05,630 --> 00:24:06,660
to the way that it works.
433
00:24:06,700 --> 00:24:08,760
And so to answer the question,
434
00:24:08,800 --> 00:24:10,700
why was he looking for the unification?
435
00:24:10,730 --> 00:24:12,160
I think the answer is simply
436
00:24:12,200 --> 00:24:15,400
that Einstein is one of those physicists
437
00:24:15,430 --> 00:24:18,600
who really wants to|know the mind of God,
438
00:24:18,630 --> 00:24:21,600
which means the entire picture.
439
00:24:25,400 --> 00:24:29,400
Today this is the|goal of string theory-
440
00:24:29,830 --> 00:24:33,830
to unify our understanding of everything
441
00:24:34,300 --> 00:24:37,150
from the birth of the universe
442
00:24:37,180 --> 00:24:40,000
to the majestic swirl of galaxies
443
00:24:40,100 --> 00:24:44,100
in just one set of principles-|one master equation.
444
00:24:45,930 --> 00:24:49,930
Newton had unified the|heavens and the earth
445
00:24:51,930 --> 00:24:53,760
in the theory of gravity.
446
00:24:53,800 --> 00:24:57,800
Maxwell had unified|electricity and magnetism.
447
00:24:59,000 --> 00:25:02,450
Einstein reasoned all that remained
448
00:25:02,480 --> 00:25:05,390
to build a theory of everything-
449
00:25:05,420 --> 00:25:08,300
a single theory that could encompass
450
00:25:08,330 --> 00:25:09,760
all the laws of the universe-
451
00:25:09,800 --> 00:25:13,800
was to merge his new picture of|gravity with electromagnetism.
452
00:25:14,400 --> 00:25:16,760
He certainly had motivation.
453
00:25:16,800 --> 00:25:19,400
Probably one of them|might have been aesthetics,
454
00:25:19,430 --> 00:25:21,260
or this quest to simplify.
455
00:25:21,300 --> 00:25:23,900
Another one might have|been just the physical fact
456
00:25:23,930 --> 00:25:25,900
that it seems like the speed of gravity
457
00:25:25,930 --> 00:25:27,300
is equal to the speed of light.
458
00:25:27,400 --> 00:25:30,860
So if they both go at the same speed,
459
00:25:30,900 --> 00:25:34,000
then maybe that's an indication|of some underlying symmetry.
460
00:25:34,100 --> 00:25:38,060
But as Einstein began trying
461
00:25:38,100 --> 00:25:40,300
to unite gravity and electromagnetism,
462
00:25:40,400 --> 00:25:43,160
he would find that the|difference in strength
463
00:25:43,200 --> 00:25:47,000
between these two forces would|outweigh their similarities.
464
00:25:47,100 --> 00:25:49,560
Let me show you what I mean.
465
00:25:49,600 --> 00:25:53,600
We tend to think that|gravity is a powerful force.
466
00:25:54,300 --> 00:25:57,200
After all, it's the force
467
00:25:57,300 --> 00:26:00,200
that right now is|anchoring me to this ledge.
468
00:26:00,230 --> 00:26:04,230
But compared to electromagnetism,
469
00:26:05,800 --> 00:26:07,260
it's actually terribly feeble.
470
00:26:07,300 --> 00:26:10,260
In fact, there's a simple|little test to show this.
471
00:26:10,300 --> 00:26:14,000
Imagine that I was to leap|from this rather tall building.
472
00:26:14,100 --> 00:26:17,000
Actually, let's not just imagine it.
473
00:26:17,030 --> 00:26:17,960
Let's do it.
474
00:26:18,000 --> 00:26:19,000
You'll see what I mean.
475
00:26:19,100 --> 00:26:23,100
Now, of course, I really|should have been flattened.
476
00:26:42,000 --> 00:26:43,260
But the important question is:
477
00:26:43,300 --> 00:26:45,800
what kept me from crashing|through the sidewalk
478
00:26:45,900 --> 00:26:48,200
and hurtling right down|to the center of the earth?
479
00:26:48,300 --> 00:26:52,300
Well, strange as it sounds,the|answer is electromagnetism.
480
00:26:56,200 --> 00:27:00,200
Everything we can see from|you and me to the sidewalk
481
00:27:01,030 --> 00:27:04,500
is made of tiny bits|of matter called atoms.
482
00:27:04,530 --> 00:27:07,660
And the outer shell of every atom
483
00:27:07,700 --> 00:27:10,500
contains a negative electrical charge.
484
00:27:10,600 --> 00:27:14,600
So when my atoms collide|with the atoms in the cement,
485
00:27:15,000 --> 00:27:19,000
these electrical charges repel|each other with such strength
486
00:27:19,300 --> 00:27:21,800
that just a little piece of sidewalk
487
00:27:21,830 --> 00:27:24,300
can resist the entire Earth's gravity
488
00:27:24,330 --> 00:27:26,060
and stop me from falling.
489
00:27:26,100 --> 00:27:29,200
In fact, the electromagnetic force
490
00:27:29,300 --> 00:27:33,300
is billions and billions of|times stronger than gravity.
491
00:27:34,300 --> 00:27:35,960
That seems a little strange
492
00:27:36,000 --> 00:27:37,800
because gravity keeps|our feet to the ground,
493
00:27:37,900 --> 00:27:39,200
it keeps the earth going around the sun.
494
00:27:39,300 --> 00:27:42,500
But in actual fact,|it manages to do that
495
00:27:42,530 --> 00:27:43,660
only because it acts
496
00:27:43,700 --> 00:27:46,600
on huge, enormous|conglomerates of matter-
497
00:27:46,700 --> 00:27:48,760
you know, you, me, the earth, the sun.
498
00:27:48,800 --> 00:27:51,660
But really at the level|of individual atoms,
499
00:27:51,700 --> 00:27:54,900
gravity is a really|incredibly feeble, tiny force.
500
00:27:54,930 --> 00:27:58,930
It would be an uphill|battle for Einstein
501
00:28:02,000 --> 00:28:05,900
to unify these two forces of|wildly different strengths.
502
00:28:05,930 --> 00:28:09,930
And to make matters|worse, barely had he begun
503
00:28:10,500 --> 00:28:13,800
before sweeping changes|in the world of physics
504
00:28:13,830 --> 00:28:15,460
would leave him behind.
505
00:28:15,500 --> 00:28:19,050
Einstein had achieved so much
506
00:28:19,080 --> 00:28:22,560
in the years up to about 1920
507
00:28:22,600 --> 00:28:26,500
that he naturally expected|that he could go on
508
00:28:26,530 --> 00:28:29,260
by playing the same theoretical games
509
00:28:29,300 --> 00:28:32,000
and go on achieving great things.
510
00:28:32,030 --> 00:28:33,360
And he couldn't.
511
00:28:33,400 --> 00:28:37,400
Nature revealed itself in other|ways in the 1920s and 1930s,
512
00:28:42,030 --> 00:28:44,510
and the particular tricks and tools
513
00:28:44,550 --> 00:28:47,000
that Einstein had at his disposal
514
00:28:47,100 --> 00:28:49,200
that had been so fabulously successful
515
00:28:49,230 --> 00:28:52,560
just weren't applicable anymore.
516
00:28:52,600 --> 00:28:56,600
You see, in the 1920s,a|group of young scientists
517
00:29:02,230 --> 00:29:04,360
stole the spotlight from Einstein
518
00:29:04,400 --> 00:29:07,200
when they came upwith|an outlandish new way
519
00:29:07,230 --> 00:29:08,500
of thinking about physics.
520
00:29:08,600 --> 00:29:12,600
Their vision of the|universewas so strange
521
00:29:15,030 --> 00:29:17,760
it makes science fiction look tame,
522
00:29:17,800 --> 00:29:21,800
and it turned Einstein's quest|for unification on its head.
523
00:29:22,100 --> 00:29:24,560
Unification, unification.
524
00:29:24,600 --> 00:29:28,600
Led by Danish physicist Niels Bohr,
525
00:29:28,630 --> 00:29:32,600
these scientists were uncovering
526
00:29:32,700 --> 00:29:35,600
an entirely new realm of the universe.
527
00:29:35,630 --> 00:29:39,100
Atoms- long thought to be
528
00:29:39,200 --> 00:29:41,360
the smallest constituentsof nature-
529
00:29:41,400 --> 00:29:45,400
were found to consist of|even smaller particles,
530
00:29:45,430 --> 00:29:49,400
the now familiar nucleus|of protons and neutrons
531
00:29:49,500 --> 00:29:51,560
orbited by electrons.
532
00:29:51,600 --> 00:29:54,700
And the theoriesof Einstein and Maxwell
533
00:29:54,800 --> 00:29:57,060
were useless at explaining
534
00:29:57,100 --> 00:29:59,750
the bizarre way these|tiny bits of matter
535
00:29:59,780 --> 00:30:02,400
interact with each|other inside the atom.
536
00:30:02,430 --> 00:30:05,900
There was a tremendous mystery
537
00:30:06,000 --> 00:30:08,160
about how to account for all this-
538
00:30:08,200 --> 00:30:11,800
how to account for what|was happening to the nucleus
539
00:30:11,830 --> 00:30:15,400
as the atom began to be|pried apart in different ways.
540
00:30:15,500 --> 00:30:19,500
And the old theories|were totally inadequate
541
00:30:20,100 --> 00:30:21,560
to the task of explaining them.
542
00:30:21,600 --> 00:30:24,360
Gravity was irrelevant-it|was far too weak-
543
00:30:24,400 --> 00:30:28,400
and electricity and|magnetism was not sufficient.
544
00:30:29,830 --> 00:30:33,830
Without a theory to explain|this strange new world,
545
00:30:35,200 --> 00:30:39,200
these scientists were lost in|an unfamiliar atomic territory
546
00:30:41,130 --> 00:30:45,130
looking forany recognizable landmarks.
547
00:30:54,050 --> 00:30:58,050
Then in the late|1920s, all that changed.
548
00:31:07,000 --> 00:31:08,360
During those years,
549
00:31:08,400 --> 00:31:12,100
physicists developed a new|theory called quantum mechanics,
550
00:31:12,200 --> 00:31:14,160
and it was able to describe
551
00:31:14,200 --> 00:31:16,900
the microscopic realm|with great success.
552
00:31:16,930 --> 00:31:18,700
But here's the thing:
553
00:31:18,800 --> 00:31:22,100
quantum mechanics was|so radical a theory
554
00:31:22,200 --> 00:31:23,900
that it completely shattered
555
00:31:24,000 --> 00:31:26,000
all previous ways of|looking at the universe.
556
00:31:26,030 --> 00:31:29,460
Einstein's theories demand
557
00:31:29,500 --> 00:31:32,600
that the universe is|orderly and predictable.
558
00:31:32,630 --> 00:31:36,630
But Niels Bohr disagreed.
559
00:31:37,200 --> 00:31:39,600
He and his colleagues proclaimed
560
00:31:39,700 --> 00:31:41,800
that at the scale of|atoms and particles,
561
00:31:41,830 --> 00:31:44,860
the world is a game of chance.
562
00:31:44,900 --> 00:31:48,900
At the atomic or quantum|level,uncertainty rules.
563
00:31:49,880 --> 00:31:53,880
The best you can do according|to quantum mechanics
564
00:31:54,900 --> 00:31:58,100
is predict the chance, or probability,
565
00:31:58,130 --> 00:32:01,660
of one outcome or another.
566
00:32:01,700 --> 00:32:05,200
And this strange idea...
567
00:32:05,300 --> 00:32:06,160
Thanks.
568
00:32:06,200 --> 00:32:10,200
opened the door to an unsettling|new picture of reality.
569
00:32:10,700 --> 00:32:14,700
It was so unsettling
570
00:32:19,600 --> 00:32:22,700
that if the bizarre|features of quantum mechanics
571
00:32:22,800 --> 00:32:24,950
were noticeablein our everyday world,
572
00:32:24,980 --> 00:32:27,690
like they are here in the Quantum Caf�,
573
00:32:27,720 --> 00:32:30,400
you might think you'd lost your mind.
574
00:32:30,430 --> 00:32:32,360
The laws in the quantum world
575
00:32:32,400 --> 00:32:35,800
are very different from the|laws that we are used to.
576
00:32:35,900 --> 00:32:39,560
Our daily experiences|are totally different
577
00:32:39,600 --> 00:32:42,200
from anything that you would|see in the quantum world.
578
00:32:42,300 --> 00:32:44,000
The quantum world is crazy.
579
00:32:44,100 --> 00:32:45,700
It's probably the best way to put it.
580
00:32:45,730 --> 00:32:46,800
It's a crazy world.
581
00:32:47,000 --> 00:32:49,460
For nearly 80 years,
582
00:32:49,500 --> 00:32:51,500
quantum mechanics has|successfully claimed
583
00:32:51,600 --> 00:32:54,000
that the strange and bizarre are typical
584
00:32:54,100 --> 00:32:56,200
of how our universeactually behaves
585
00:32:56,300 --> 00:32:57,560
on extremely small scales.
586
00:32:57,600 --> 00:33:01,600
At the scale of everyday|life,we don't directly experience
587
00:33:03,900 --> 00:33:05,700
the weirdness of quantum mechanics.
588
00:33:05,730 --> 00:33:09,100
But here in the Quantum Caf�,
589
00:33:09,200 --> 00:33:11,650
big, everyday things sometimes behave
590
00:33:11,680 --> 00:33:14,240
as if they were microscopically tiny.
591
00:33:14,270 --> 00:33:16,800
And no matter how many times I come here,
592
00:33:16,830 --> 00:33:19,260
I never seem to get used to it.
593
00:33:19,300 --> 00:33:21,700
I'll have an orange juice, please.
594
00:33:21,730 --> 00:33:23,700
I'll try.
595
00:33:23,800 --> 00:33:25,660
"I'll try," she says.
596
00:33:25,700 --> 00:33:29,700
You see, they're not used to people
597
00:33:31,300 --> 00:33:34,100
placing definite orders|here in the Quantum Caf�
598
00:33:34,130 --> 00:33:36,600
because here,everything|is ruled by chance.
599
00:33:36,630 --> 00:33:38,460
While I'd like an orange juice,
600
00:33:38,500 --> 00:33:40,500
there's only a particular probability
601
00:33:40,600 --> 00:33:41,900
that I'll actually get one.
602
00:33:42,000 --> 00:33:46,000
And there's no reason to be disappointed
603
00:33:47,230 --> 00:33:50,660
with one particular outcome or another
604
00:33:50,700 --> 00:33:54,100
because quantum mechanics suggests
605
00:33:54,200 --> 00:33:55,560
that each of the possibilities-
606
00:33:55,600 --> 00:33:58,800
like getting a yellow|juice or a red juice-
607
00:33:58,830 --> 00:34:00,260
may actually happen.
608
00:34:00,300 --> 00:34:02,260
They just happen to happen
609
00:34:02,300 --> 00:34:04,360
in universes that are parallel to ours-
610
00:34:04,400 --> 00:34:07,200
universes that seem as|real to their inhabitants
611
00:34:07,230 --> 00:34:09,660
as our universe seems to us.
612
00:34:09,700 --> 00:34:13,160
If there are a thousand possibilities
613
00:34:13,200 --> 00:34:15,500
and quantum mechanics|cannot with certainty say
614
00:34:15,530 --> 00:34:17,510
which of the thousand it will be,
615
00:34:17,550 --> 00:34:19,500
then all thousand will happen.
616
00:34:19,530 --> 00:34:22,100
Yeah, you can laugh at it
617
00:34:22,200 --> 00:34:23,760
and say,"Well, that has to be wrong. "
618
00:34:23,800 --> 00:34:27,400
But there are so many|other things in physics
619
00:34:27,600 --> 00:34:29,300
which at the time that|people came up with
620
00:34:29,330 --> 00:34:30,600
had to be wrong, but it wasn't.
621
00:34:30,800 --> 00:34:33,250
You have to be a|little careful, I think,
622
00:34:33,280 --> 00:34:35,700
before you say this is clearly wrong.
623
00:34:35,800 --> 00:34:39,800
And even in our own universe,
624
00:34:41,600 --> 00:34:44,160
quantum mechanics says there's a chance
625
00:34:44,200 --> 00:34:48,200
that things we'd ordinarily|think of as impossible
626
00:34:48,230 --> 00:34:50,460
can actually happen.
627
00:34:50,500 --> 00:34:54,250
For example, there's|a chance that particles
628
00:34:54,280 --> 00:34:57,790
can pass right through walls or barriers
629
00:34:57,820 --> 00:35:01,300
that seem impenetrable to you or me.
630
00:35:01,400 --> 00:35:03,060
There's even a chance
631
00:35:03,100 --> 00:35:06,000
that I could pass through|something solid, like a wall.
632
00:35:06,100 --> 00:35:09,000
Now, quantum calculations do show
633
00:35:09,100 --> 00:35:11,900
that the probability for this|to happen in the everyday world
634
00:35:12,000 --> 00:35:14,360
is so small that I'd need to continue
635
00:35:14,400 --> 00:35:16,900
walking into the wall|for nearly an eternity
636
00:35:16,930 --> 00:35:19,400
before having a reasonable|chance of succeeding.
637
00:35:19,500 --> 00:35:23,500
But here, these kind of|things happen all the time.
638
00:35:26,830 --> 00:35:28,260
You have to learn
639
00:35:28,300 --> 00:35:31,700
to abandon those assumptions that|you have about the world
640
00:35:31,800 --> 00:35:34,000
in order to understand|quantum mechanics.
641
00:35:34,100 --> 00:35:38,100
In my gut, in my belly,do|I feel like I have
642
00:35:38,400 --> 00:35:41,400
a deep, intuitive understanding|of quantum mechanics?
643
00:35:41,430 --> 00:35:41,990
No.
644
00:35:42,000 --> 00:35:46,000
And neither did Einstein.
645
00:35:46,100 --> 00:35:50,100
He never lost faith that|the universe behaves
646
00:35:51,200 --> 00:35:53,560
in a certainand predictable way.
647
00:35:53,600 --> 00:35:57,600
The idea that all we can|do is calculate the odds
648
00:35:58,300 --> 00:36:01,650
that things will turn|outone way or another
649
00:36:01,680 --> 00:36:04,960
was something Einstein deeply resisted.
650
00:36:05,000 --> 00:36:09,000
Quantum mechanics says that|you can't know for certain
651
00:36:09,130 --> 00:36:11,160
the outcome of any experiment.
652
00:36:11,200 --> 00:36:14,100
You can only assign|a certain probability
653
00:36:14,130 --> 00:36:16,410
to the outcome of any experiment.
654
00:36:16,450 --> 00:36:19,020
And this Einstein disliked intensely.
655
00:36:19,060 --> 00:36:21,600
He used to say,"God|does not throw dice. "
656
00:36:21,630 --> 00:36:25,630
Yet experiment after experiment
657
00:36:27,300 --> 00:36:29,960
showed Einstein was wrong
658
00:36:30,000 --> 00:36:33,150
and that quantum mechanics|really does describe
659
00:36:33,180 --> 00:36:36,300
how the world works at|the subatomic level.
660
00:36:36,330 --> 00:36:38,960
So quantum mechanics is not a luxury-
661
00:36:39,000 --> 00:36:41,600
something that you can do without.
662
00:36:41,630 --> 00:36:44,160
I mean, why is water the way it is?
663
00:36:44,200 --> 00:36:46,400
Why does light go|straight through water?
664
00:36:46,430 --> 00:36:47,360
Why is it transparent?
665
00:36:47,400 --> 00:36:48,600
Why are other things not transparent?
666
00:36:48,630 --> 00:36:50,360
How do molecules form?
667
00:36:50,400 --> 00:36:53,100
Why are they reacting|the way they react?
668
00:36:53,200 --> 00:36:56,800
The moment that you want|to understand anything
669
00:36:56,900 --> 00:37:00,900
at an atomic level-as|nonintuitive as it is-
670
00:37:01,800 --> 00:37:05,500
at that moment you can only make|progress with quantum mechanics.
671
00:37:05,530 --> 00:37:08,600
Quantum mechanics is|fantastically accurate.
672
00:37:08,700 --> 00:37:12,700
There has never been a|prediction of quantum mechanics
673
00:37:13,430 --> 00:37:17,430
that has contradicted|an observation- never.
674
00:37:17,730 --> 00:37:21,730
By the 1930s,
675
00:37:22,700 --> 00:37:26,400
Einstein's quest for|unification was floundering
676
00:37:26,430 --> 00:37:29,700
while quantum mechanics was unlocking
677
00:37:29,800 --> 00:37:31,500
the secrets of the atom.
678
00:37:31,600 --> 00:37:35,600
Scientists found that|gravity and electromagnetism
679
00:37:36,300 --> 00:37:39,700
are not the only forces|ruling the universe.
680
00:37:39,730 --> 00:37:42,810
Probing the structure of the atom,
681
00:37:42,850 --> 00:37:45,860
they discovered two more forces.
682
00:37:45,900 --> 00:37:49,900
One, dubbed the strong nuclear force,
683
00:37:51,030 --> 00:37:53,060
acts like a super-glue,
684
00:37:53,100 --> 00:37:56,100
holding the nucleus|of every atom together,
685
00:37:56,130 --> 00:37:58,560
binding protons to neutrons.
686
00:37:58,600 --> 00:38:02,600
And the other, called|the weak nuclear force,
687
00:38:03,800 --> 00:38:06,800
allows neutrons to turn into protons,
688
00:38:06,830 --> 00:38:09,800
giving off radiation in the process.
689
00:38:09,830 --> 00:38:12,000
At the quantum level,
690
00:38:12,100 --> 00:38:15,400
the force we're|most familiar with- gravity-
691
00:38:15,430 --> 00:38:18,700
was completely overshadowed by|electromagnetism
692
00:38:18,730 --> 00:38:21,260
and these two new forces.
693
00:38:21,300 --> 00:38:25,300
Now, the strong and weak|forces may seem obscure,
694
00:38:26,100 --> 00:38:27,660
but in one sense at least,
695
00:38:27,700 --> 00:38:31,250
we're all very much|aware of their power.
696
00:38:31,280 --> 00:38:34,800
At 5:29 on the morning of July 16, 1945,
697
00:38:34,900 --> 00:38:37,360
that power was revealed by an act
698
00:38:37,400 --> 00:38:39,200
that would change the course of history.
699
00:38:39,300 --> 00:38:42,600
In the middle of the|desert in New Mexico,
700
00:38:42,700 --> 00:38:44,860
at the top of a steel tower
701
00:38:44,900 --> 00:38:48,900
about a hundred feet above|the top of this monument,
702
00:38:48,930 --> 00:38:51,610
the first atomic bomb was detonated.
703
00:38:51,650 --> 00:38:54,300
It was only about five feet across,
704
00:38:54,400 --> 00:38:57,160
but that bomb packed a punch
705
00:38:57,200 --> 00:39:01,200
equivalent to about 20,000 tons of TNT.
706
00:39:01,630 --> 00:39:05,630
With that powerful explosion,
707
00:39:10,300 --> 00:39:14,300
scientists unleashed the|strong nuclear force-
708
00:39:14,430 --> 00:39:17,260
the force that keeps|neutrons and protons
709
00:39:17,300 --> 00:39:20,800
tightly glued together|inside the nucleus of an atom.
710
00:39:20,830 --> 00:39:23,010
By breaking the bonds of that glue
711
00:39:23,050 --> 00:39:25,200
and splitting the atom apart...
712
00:39:25,300 --> 00:39:29,150
vast, truly unbelievable amounts
713
00:39:29,180 --> 00:39:33,000
of destructive energy were released.
714
00:39:33,100 --> 00:39:37,100
We can still detect|remnants of that explosion
715
00:39:41,700 --> 00:39:44,800
through the other nuclear force-|the weak nuclear force-
716
00:39:44,830 --> 00:39:47,600
because it's responsible|for radioactivity.
717
00:39:47,630 --> 00:39:50,600
And today, more than 50 years later,
718
00:39:50,700 --> 00:39:52,800
the radiation levels|around here are still
719
00:39:52,900 --> 00:39:55,900
about ten times higher than normal.
720
00:39:56,000 --> 00:40:00,000
So although in comparison to|electromagnetism and gravity
721
00:40:01,730 --> 00:40:04,860
the nuclear forces act|over very small scales,
722
00:40:04,900 --> 00:40:08,800
their impact on everyday|life is every bit as profound.
723
00:40:08,900 --> 00:40:12,900
But what about gravity-Einstein's|general relativity?
724
00:40:17,030 --> 00:40:20,500
Where does that fit|in at the quantum level?
725
00:40:20,600 --> 00:40:24,460
Quantum mechanics tells us
726
00:40:24,500 --> 00:40:28,000
how all of nature's forces|work in the microscopic realm
727
00:40:28,030 --> 00:40:30,060
except for the force of gravity.
728
00:40:30,100 --> 00:40:33,900
Absolutely no one could|figure out how gravity operates
729
00:40:34,000 --> 00:40:37,900
when you get down to the size|of atoms and subatomic particles.
730
00:40:37,930 --> 00:40:40,360
That is, no one could figure out
731
00:40:40,400 --> 00:40:43,800
how to put general relativity and quantum mechanics
732
00:40:43,830 --> 00:40:46,060
together into one package.
733
00:40:46,100 --> 00:40:50,100
For decades, every attempt to|describe the force of gravity
734
00:40:54,930 --> 00:40:57,200
in the same languageas|the other forces-
735
00:40:57,230 --> 00:40:59,100
the language of quantum mechanics-
736
00:40:59,200 --> 00:41:01,560
has met with disaster.
737
00:41:01,600 --> 00:41:04,400
You try to put those two|pieces of mathematics together,
738
00:41:04,430 --> 00:41:07,760
they do not coexist peacefully.
739
00:41:07,800 --> 00:41:11,100
You get answers that the probabilities
740
00:41:11,200 --> 00:41:13,100
of the event you're|looking atare infinite.
741
00:41:13,200 --> 00:41:14,360
Nonsense.
742
00:41:14,400 --> 00:41:16,500
It's not profound, it's just nonsense.
743
00:41:16,600 --> 00:41:17,400
It's very ironic,
744
00:41:17,500 --> 00:41:19,400
because it was the first|force to actually be understood
745
00:41:19,430 --> 00:41:22,510
in some decent,quantitative way,
746
00:41:22,550 --> 00:41:25,560
but it still remains split off
747
00:41:25,600 --> 00:41:28,100
and very different from the other ones.
748
00:41:28,200 --> 00:41:31,350
The laws of nature are supposed|to apply everywhere.
749
00:41:31,380 --> 00:41:34,500
So if Einstein's laws are|supposed to apply everywhere
750
00:41:34,600 --> 00:41:36,500
and the laws of quantum mechanics
751
00:41:36,600 --> 00:41:37,760
are supposed to apply everywhere,
752
00:41:37,800 --> 00:41:40,900
well, you can't have|two separate everywheres.
753
00:41:40,930 --> 00:41:44,930
In 1933, after fleeing Nazi Germany,
754
00:41:50,700 --> 00:41:53,400
Einstein settled in|Princeton, New Jersey.
755
00:41:53,500 --> 00:41:55,960
Working in solitude,
756
00:41:56,000 --> 00:41:58,560
he stubbornly continued the quest
757
00:41:58,600 --> 00:42:01,500
he had begun more than a decade earlier
758
00:42:01,530 --> 00:42:05,260
to unite gravity and electromagnetism.
759
00:42:05,300 --> 00:42:08,960
Every few years,headlines appeared
760
00:42:09,000 --> 00:42:11,900
proclaiming Einstein was|on the verge of success.
761
00:42:12,000 --> 00:42:16,000
But most of his colleagues|believed his quest was misguided
762
00:42:16,130 --> 00:42:19,400
and that his best days|were already behind him.
763
00:42:19,500 --> 00:42:21,960
Einstein in his later years
764
00:42:22,000 --> 00:42:26,000
got rather detached from the|work of physics in general
765
00:42:26,300 --> 00:42:28,400
and stopped reading people's papers.
766
00:42:28,430 --> 00:42:30,160
I don't even think he knew
767
00:42:30,200 --> 00:42:32,300
there was such a thing|as the weak nuclear force.
768
00:42:32,330 --> 00:42:34,100
He didn't pay attention to those things.
769
00:42:34,130 --> 00:42:36,460
He kept working on the same problem
770
00:42:36,500 --> 00:42:38,700
that he had started|working on as a younger man.
771
00:42:38,800 --> 00:42:42,800
When the community of|theoretical physicists
772
00:42:43,630 --> 00:42:44,760
begin to probe the atom,
773
00:42:44,800 --> 00:42:48,800
Einstein very definitely|gets left out of the picture.
774
00:42:49,400 --> 00:42:53,400
He in some sense chooses not|to look at the physics
775
00:42:54,700 --> 00:42:55,760
coming from these experiments.
776
00:42:55,800 --> 00:42:59,800
Uh, that means that the|laws of quantum mechanics
777
00:43:00,330 --> 00:43:04,330
play no role in his sort|of further investigations.
778
00:43:04,830 --> 00:43:07,460
He's thought to be
779
00:43:07,500 --> 00:43:10,560
this doddering, sympathetic, old figure
780
00:43:10,600 --> 00:43:14,600
who led an earlier revolution|but somehow fell out of it.
781
00:43:16,030 --> 00:43:20,030
It is as if a general who|was a master of horse cavalry,
782
00:43:21,430 --> 00:43:23,760
who has achieved great|things as a commander
783
00:43:23,800 --> 00:43:26,100
at the beginning of the First World War,
784
00:43:26,200 --> 00:43:30,200
would try to bring|mounted cavalry into play
785
00:43:31,100 --> 00:43:34,800
against the barbed wire,|trenches and machine guns
786
00:43:34,900 --> 00:43:36,760
of the other side.
787
00:43:36,800 --> 00:43:40,800
Albert Einstein died on April 18, 1955.
788
00:43:43,800 --> 00:43:47,800
And for many years it|seemed that Einstein's dream
789
00:43:48,130 --> 00:43:51,000
of unifying the forces in a single theory
790
00:43:51,030 --> 00:43:52,800
died with him.
791
00:43:52,900 --> 00:43:56,200
So the quest for unification
792
00:43:56,230 --> 00:43:59,460
becomes a backwater of physics.
793
00:43:59,500 --> 00:44:03,300
By the time of Einstein's|death in the '50s,
794
00:44:03,330 --> 00:44:07,330
almost no serious physicists
795
00:44:09,600 --> 00:44:12,100
are engaged in this|quest for unification.
796
00:44:12,130 --> 00:44:16,130
In the years since,
797
00:44:20,300 --> 00:44:23,560
physics split into two separate camps:
798
00:44:23,600 --> 00:44:27,600
one that uses general relativity to|study big and heavy objects,
799
00:44:28,030 --> 00:44:31,500
things like stars, galaxies|and the universe as a whole...
800
00:44:31,530 --> 00:44:35,100
And another that uses quantum mechanics
801
00:44:35,130 --> 00:44:37,000
to study the tiniest of objects
802
00:44:37,030 --> 00:44:38,860
like atoms and particles.
803
00:44:38,900 --> 00:44:42,360
This has kind of been|like having two families
804
00:44:42,400 --> 00:44:45,200
that just cannot get along|and never talk to each other...
805
00:44:45,300 --> 00:44:48,150
living under the same roof.
806
00:44:48,180 --> 00:44:50,640
There just seemed to be no way
807
00:44:50,670 --> 00:44:53,100
to combine quantum mechanics...
808
00:44:53,130 --> 00:44:54,960
and general relativity
809
00:44:55,000 --> 00:44:57,300
in a single theory that could describe
810
00:44:57,400 --> 00:44:59,200
the universe on all scales.
811
00:44:59,230 --> 00:45:03,230
Now, in spite of this,
812
00:45:06,200 --> 00:45:09,800
we've made tremendous progress|in understanding the universe.
813
00:45:09,830 --> 00:45:12,960
But there's a catch.
814
00:45:13,000 --> 00:45:16,450
There are strange realms of the cosmos
815
00:45:16,480 --> 00:45:19,690
that will never be fully understood
816
00:45:19,720 --> 00:45:22,760
until we find a unified theory.
817
00:45:22,790 --> 00:45:26,440
And nowhere is this more evident...
818
00:45:26,480 --> 00:45:30,060
than in the depths of a black hole.
819
00:45:30,100 --> 00:45:34,100
A German astronomer|named Karl Schwarzschild
820
00:45:35,500 --> 00:45:39,500
first proposed what we now|call "black holes" in 1916...
821
00:45:40,430 --> 00:45:44,430
while stationed on the|front lines in World War I.
822
00:45:47,100 --> 00:45:51,100
He solved the equations of|Einstein's general relativity
823
00:45:53,730 --> 00:45:57,000
in a new and puzzling way.
824
00:45:57,100 --> 00:46:01,100
Between calculations of|artillery trajectories,
825
00:46:01,500 --> 00:46:05,500
Schwarzschild figured out that|an enormous amount of mass,
826
00:46:06,600 --> 00:46:10,600
like that of a very dense|star concentrated in a small area,
827
00:46:11,630 --> 00:46:15,400
would warp the fabricof|space-time so severely...
828
00:46:15,430 --> 00:46:19,430
that nothing, not even light,
829
00:46:20,200 --> 00:46:24,200
could escape its gravitational pull.
830
00:46:24,280 --> 00:46:28,280
For decades, physicists were skeptical
831
00:46:28,330 --> 00:46:30,360
that Schwarzschild's calculations
832
00:46:30,400 --> 00:46:32,400
were anything more than theory.
833
00:46:32,500 --> 00:46:36,500
But today, satellite telescopes|probing deep into space
834
00:46:38,580 --> 00:46:42,580
are discovering regions with|enormous gravitational pull
835
00:46:44,700 --> 00:46:48,700
that most scientists|believe are black holes.
836
00:46:49,530 --> 00:46:53,530
Schwarzschild's theory now|seems to be reality.
837
00:46:54,330 --> 00:46:57,500
So here's the question.
838
00:46:57,600 --> 00:47:00,060
If you're trying to figure out
839
00:47:00,100 --> 00:47:03,650
what happens in the|depths of a black hole,
840
00:47:03,680 --> 00:47:07,200
where an entire staris|crushed to a tiny speck,
841
00:47:07,230 --> 00:47:10,060
do you use general relativity-
842
00:47:10,100 --> 00:47:12,100
because the staris incredibly heavy-
843
00:47:12,200 --> 00:47:16,200
or quantum mechanics,because|it's incredibly tiny?
844
00:47:16,930 --> 00:47:20,160
Well, that's the problem.
845
00:47:20,200 --> 00:47:24,200
Since the center of a black|hole is both tiny and heavy,
846
00:47:24,580 --> 00:47:28,580
you can't avoid using both|theories at the same time.
847
00:47:28,930 --> 00:47:32,500
And when we try to put the|two theories together
848
00:47:32,530 --> 00:47:33,700
in the realm of black holes...
849
00:47:33,800 --> 00:47:35,900
they conflict, it breaks down.
850
00:47:35,930 --> 00:47:38,160
They give nonsensical predictions,
851
00:47:38,200 --> 00:47:40,400
and the universe is not nonsensical.
852
00:47:40,430 --> 00:47:41,300
It's got to make sense.
853
00:47:41,400 --> 00:47:44,400
Quantum mechanics works|really well for small things,
854
00:47:44,430 --> 00:47:46,800
and general relativity works really well
855
00:47:46,900 --> 00:47:47,700
for stars and galaxies.
856
00:47:47,700 --> 00:47:50,600
But the atoms- the small|things- and the galaxies,
857
00:47:50,630 --> 00:47:52,200
they're part of the same universe,
858
00:47:52,300 --> 00:47:55,000
so there has to be some description
859
00:47:55,030 --> 00:47:55,960
that applies to everything.
860
00:47:56,000 --> 00:47:59,200
So we can't have one description|for atoms and one for stars.
861
00:47:59,230 --> 00:48:03,230
Now, with string theory,we|think we may have found a way
862
00:48:04,250 --> 00:48:08,250
to unite our theory of the|large and our theory of the small
863
00:48:09,310 --> 00:48:13,310
and make sense of the universe at|all scales and all places.
864
00:48:14,330 --> 00:48:18,330
Instead of a multitude of tiny particles,
865
00:48:19,400 --> 00:48:23,400
string theory proclaims|that everything in the universe-
866
00:48:23,930 --> 00:48:25,960
all forces and all matter-
867
00:48:26,000 --> 00:48:29,000
is made of one single ingredient:
868
00:48:29,100 --> 00:48:33,100
tiny vibrating strands of|energy known as strings.
869
00:48:34,230 --> 00:48:37,200
A string can wiggle|in many different ways,
870
00:48:37,230 --> 00:48:39,060
whereas, of course, a point can't.
871
00:48:39,100 --> 00:48:41,900
And the different ways in|which the string wiggles
872
00:48:42,000 --> 00:48:45,200
represent the different|kinds of elementary particles.
873
00:48:45,230 --> 00:48:47,100
It's like a violin string
874
00:48:47,200 --> 00:48:51,200
and it can vibrate just like|violin strings can vibrate.
875
00:48:51,230 --> 00:48:55,200
Each note, if you like,|describes a different particle.
876
00:48:55,230 --> 00:48:58,700
So it has incredible unification power.
877
00:48:58,730 --> 00:49:00,000
It unifies our understanding
878
00:49:00,100 --> 00:49:01,760
of all these different|kinds of particles.
879
00:49:01,800 --> 00:49:05,400
So, unity of the different|forces and particles
880
00:49:05,430 --> 00:49:06,960
is achieved because they all come
881
00:49:07,000 --> 00:49:08,500
from different kinds of vibrations
882
00:49:08,600 --> 00:49:09,760
of the same basic string.
883
00:49:09,800 --> 00:49:13,800
It's a simple idea with|far-reaching consequences.
884
00:49:14,530 --> 00:49:18,530
What string theory does|is it holds out the promise
885
00:49:19,230 --> 00:49:22,300
that, look, we can really|understand questions
886
00:49:22,330 --> 00:49:24,600
that you might not even have thought
887
00:49:24,630 --> 00:49:25,760
were scientific questions,
888
00:49:25,800 --> 00:49:28,700
questions about how the universe began,
889
00:49:28,730 --> 00:49:30,760
why the universe is the way it is
890
00:49:30,800 --> 00:49:32,800
at the most fundamental level.
891
00:49:32,900 --> 00:49:36,000
The idea that a scientific theory
892
00:49:36,100 --> 00:49:38,100
that we already have in our hands
893
00:49:38,130 --> 00:49:40,100
could answer the most basic questions
894
00:49:40,200 --> 00:49:41,760
is extremely seductive.
895
00:49:41,800 --> 00:49:45,800
But this seductive new|theory is also controversial.
896
00:49:48,100 --> 00:49:52,100
Strings- if they exist-are so small
897
00:49:53,300 --> 00:49:56,500
there's little hope of ever seeing one.
898
00:49:56,530 --> 00:49:59,000
String theory and string theorists
899
00:49:59,100 --> 00:49:59,900
do have a real problem.
900
00:50:00,000 --> 00:50:02,060
How do you actually test string theory?
901
00:50:02,100 --> 00:50:05,600
If you can't test it in the way|that we test normal theories,
902
00:50:05,630 --> 00:50:08,100
it's not science, it's philosophy,
903
00:50:08,130 --> 00:50:09,360
and that's a real problem.
904
00:50:09,400 --> 00:50:13,400
If string theory fails to|provide a testable prediction,
905
00:50:14,030 --> 00:50:16,800
then nobody should believe it.
906
00:50:16,830 --> 00:50:19,460
On the other hand,
907
00:50:19,500 --> 00:50:22,700
there's a kind of|elegance to these things,
908
00:50:22,800 --> 00:50:24,360
and given the history
909
00:50:24,400 --> 00:50:27,800
of how theoretical physics|has evolved thus far,
910
00:50:27,900 --> 00:50:31,900
it is totally conceivable that some,
911
00:50:32,600 --> 00:50:36,000
if not all, of these ideas will|turn out to be correct.
912
00:50:36,030 --> 00:50:38,500
I think a hundred years from now,
913
00:50:38,530 --> 00:50:40,400
this particular period,
914
00:50:40,500 --> 00:50:43,760
when most of the brightest|young theoretical physicists
915
00:50:43,800 --> 00:50:47,800
worked on string theory, will|be remembered as a heroic age,
916
00:50:48,530 --> 00:50:52,360
when theorists tried and succeeded
917
00:50:52,400 --> 00:50:56,150
to develop a unified theory|of all the phenomena of nature.
918
00:50:56,180 --> 00:50:59,900
On the other hand, it may be|remembered as a tragic failure.
919
00:51:00,000 --> 00:51:02,800
My guess is that it will|be something like the former
920
00:51:02,830 --> 00:51:03,900
rather than the latter.
921
00:51:04,000 --> 00:51:07,600
Uh... but ask me a hundred years|from now, then I can tell you.
922
00:51:07,630 --> 00:51:11,630
Our understanding of|the universe has come
923
00:51:18,900 --> 00:51:22,400
an enormously long way during|the last three centuries.
924
00:51:22,430 --> 00:51:26,430
Just consider this.
925
00:51:26,900 --> 00:51:30,160
Isaac Newton, who was perhaps
926
00:51:30,200 --> 00:51:32,500
the greatest scientist of all time,
927
00:51:32,600 --> 00:51:36,600
once said, "I have been like|a boy playing on the seashore,
928
00:51:37,000 --> 00:51:39,760
"diverting myself in,|now and then, finding
929
00:51:39,800 --> 00:51:42,860
"a smoother pebbleor a|prettier shell than usual,
930
00:51:42,900 --> 00:51:46,900
while the great ocean of truth|lay before me all undiscovered. "
931
00:51:48,400 --> 00:51:52,400
And yet, 250 years later,
932
00:51:54,200 --> 00:51:57,600
Albert Einstein, who was|Newton's true successor,
933
00:51:57,700 --> 00:52:01,600
was able to seriously|suggest that this vast ocean,
934
00:52:01,630 --> 00:52:04,700
all the laws of nature, might be reduced
935
00:52:04,800 --> 00:52:06,660
to a few fundamental ideas
936
00:52:06,700 --> 00:52:10,600
expressed by a handful|of mathematical symbols.
937
00:52:10,700 --> 00:52:14,700
And today, a half-century|after Einstein's death,
938
00:52:18,430 --> 00:52:20,760
we may at last be on the verge
939
00:52:20,800 --> 00:52:24,800
of fulfilling his dream of|unification with string theory.
940
00:52:35,530 --> 00:52:39,530
But where did this daring and|strange new theory come from?
941
00:52:45,300 --> 00:52:49,300
How does string theory achieve|the ultimate unification
942
00:52:50,900 --> 00:52:53,700
of the laws of the large|and the laws of the small?
943
00:52:52,730 --> 00:52:56,460
And how will we know|if it's right or wrong?
944
00:52:55,500 --> 00:52:59,200
No experiment can ever|check up what's going on
945
00:52:59,230 --> 00:53:01,600
at the distances that are being studied.
946
00:53:01,630 --> 00:53:03,800
The theory is permanently safe.
947
00:53:03,900 --> 00:53:07,800
Is that a theory of|physics or a philosophy?
948
00:53:07,830 --> 00:53:09,410
It isn't written in the stars
949
00:53:09,450 --> 00:53:11,000
that we're going to succeed,
950
00:53:11,100 --> 00:53:13,600
but in the end, we hope we will have
951
00:53:13,630 --> 00:53:16,100
a single theory that governs everything.
952
00:53:17,400 --> 00:53:21,400
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