Is our universe the only universe?
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0:00 - 0:02A few months ago
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0:02 - 0:04the Nobel Prize in physics
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0:04 - 0:06was awarded to two teams of astronomers
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0:06 - 0:09for a discovery that has been hailed
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0:09 - 0:11as one of the most important
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0:11 - 0:13astronomical observations ever.
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0:13 - 0:15And today, after briefly describing what they found,
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0:15 - 0:18I'm going to tell you about a highly controversial framework
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0:18 - 0:21for explaining their discovery,
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0:21 - 0:23namely the possibility
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0:23 - 0:25that way beyond the Earth,
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0:25 - 0:28the Milky Way and other distant galaxies,
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0:28 - 0:30we may find that our universe
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0:30 - 0:32is not the only universe,
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0:32 - 0:34but is instead
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0:34 - 0:36part of a vast complex of universes
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0:36 - 0:38that we call the multiverse.
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0:38 - 0:41Now the idea of a multiverse is a strange one.
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0:41 - 0:43I mean, most of us were raised to believe
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0:43 - 0:46that the word "universe" means everything.
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0:46 - 0:49And I say most of us with forethought,
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0:49 - 0:52as my four-year-old daughter has heard me speak of these ideas since she was born.
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0:52 - 0:54And last year I was holding her
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0:54 - 0:56and I said, "Sophia,
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0:56 - 0:59I love you more than anything in the universe."
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0:59 - 1:01And she turned to me and said, "Daddy,
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1:01 - 1:03universe or multiverse?"
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1:03 - 1:06(Laughter)
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1:06 - 1:09But barring such an anomalous upbringing,
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1:09 - 1:11it is strange to imagine
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1:11 - 1:13other realms separate from ours,
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1:13 - 1:15most with fundamentally different features,
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1:15 - 1:18that would rightly be called universes of their own.
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1:18 - 1:20And yet,
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1:20 - 1:22speculative though the idea surely is,
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1:22 - 1:24I aim to convince you
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1:24 - 1:26that there's reason for taking it seriously,
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1:26 - 1:28as it just might be right.
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1:28 - 1:31I'm going to tell the story of the multiverse in three parts.
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1:31 - 1:33In part one,
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1:33 - 1:35I'm going to describe those Nobel Prize-winning results
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1:35 - 1:37and to highlight a profound mystery
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1:37 - 1:39which those results revealed.
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1:39 - 1:41In part two,
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1:41 - 1:43I'll offer a solution to that mystery.
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1:43 - 1:45It's based on an approach called string theory,
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1:45 - 1:47and that's where the idea of the multiverse
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1:47 - 1:49will come into the story.
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1:49 - 1:51Finally, in part three,
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1:51 - 1:53I'm going to describe a cosmological theory
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1:53 - 1:55called inflation,
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1:55 - 1:58which will pull all the pieces of the story together.
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1:58 - 2:02Okay, part one starts back in 1929
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2:02 - 2:04when the great astronomer Edwin Hubble
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2:04 - 2:07realized that the distant galaxies
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2:07 - 2:09were all rushing away from us,
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2:09 - 2:11establishing that space itself is stretching,
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2:11 - 2:13it's expanding.
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2:13 - 2:16Now this was revolutionary.
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2:16 - 2:19The prevailing wisdom was that on the largest of scales
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2:19 - 2:21the universe was static.
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2:21 - 2:23But even so,
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2:23 - 2:26there was one thing that everyone was certain of:
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2:26 - 2:29The expansion must be slowing down.
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2:29 - 2:32That, much as the gravitational pull of the Earth
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2:32 - 2:35slows the ascent of an apple tossed upward,
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2:35 - 2:37the gravitational pull
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2:37 - 2:39of each galaxy on every other
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2:39 - 2:41must be slowing
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2:41 - 2:43the expansion of space.
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2:43 - 2:46Now let's fast-forward to the 1990s
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2:46 - 2:48when those two teams of astronomers
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2:48 - 2:50I mentioned at the outset
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2:50 - 2:52were inspired by this reasoning
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2:52 - 2:54to measure the rate
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2:54 - 2:56at which the expansion has been slowing.
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2:56 - 2:58And they did this
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2:58 - 3:00by painstaking observations
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3:00 - 3:02of numerous distant galaxies,
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3:02 - 3:04allowing them to chart
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3:04 - 3:07how the expansion rate has changed over time.
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3:07 - 3:10Here's the surprise:
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3:10 - 3:13They found that the expansion is not slowing down.
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3:13 - 3:15Instead they found that it's speeding up,
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3:15 - 3:17going faster and faster.
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3:17 - 3:19That's like tossing an apple upward
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3:19 - 3:21and it goes up faster and faster.
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3:21 - 3:23Now if you saw an apple do that,
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3:23 - 3:25you'd want to know why.
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3:25 - 3:27What's pushing on it?
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3:27 - 3:29Similarly, the astronomers' results
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3:29 - 3:32are surely well-deserving of the Nobel Prize,
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3:32 - 3:36but they raised an analogous question.
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3:36 - 3:38What force is driving all galaxies
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3:38 - 3:41to rush away from every other
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3:41 - 3:44at an ever-quickening speed?
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3:44 - 3:46Well the most promising answer
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3:46 - 3:49comes from an old idea of Einstein's.
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3:49 - 3:51You see, we are all used to gravity
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3:51 - 3:54being a force that does one thing,
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3:54 - 3:56pulls objects together.
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3:56 - 3:58But in Einstein's theory of gravity,
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3:58 - 4:00his general theory of relativity,
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4:00 - 4:03gravity can also push things apart.
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4:03 - 4:06How? Well according to Einstein's math,
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4:06 - 4:08if space is uniformly filled
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4:08 - 4:10with an invisible energy,
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4:10 - 4:13sort of like a uniform, invisible mist,
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4:13 - 4:16then the gravity generated by that mist
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4:16 - 4:18would be repulsive,
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4:18 - 4:20repulsive gravity,
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4:20 - 4:23which is just what we need to explain the observations.
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4:23 - 4:25Because the repulsive gravity
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4:25 - 4:27of an invisible energy in space --
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4:27 - 4:29we now call it dark energy,
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4:29 - 4:32but I've made it smokey white here so you can see it --
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4:32 - 4:34its repulsive gravity
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4:34 - 4:36would cause each galaxy to push against every other,
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4:36 - 4:38driving expansion to speed up,
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4:38 - 4:40not slow down.
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4:40 - 4:42And this explanation
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4:42 - 4:44represents great progress.
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4:44 - 4:47But I promised you a mystery
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4:47 - 4:49here in part one.
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4:49 - 4:51Here it is.
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4:51 - 4:53When the astronomers worked out
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4:53 - 4:56how much of this dark energy
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4:56 - 4:58must be infusing space
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4:58 - 5:00to account for the cosmic speed up,
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5:00 - 5:02look at what they found.
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5:09 - 5:11This number is small.
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5:11 - 5:13Expressed in the relevant unit,
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5:13 - 5:15it is spectacularly small.
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5:15 - 5:18And the mystery is to explain this peculiar number.
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5:18 - 5:20We want this number
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5:20 - 5:22to emerge from the laws of physics,
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5:22 - 5:25but so far no one has found a way to do that.
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5:25 - 5:28Now you might wonder,
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5:28 - 5:30should you care?
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5:30 - 5:32Maybe explaining this number
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5:32 - 5:34is just a technical issue,
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5:34 - 5:37a technical detail of interest to experts,
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5:37 - 5:39but of no relevance to anybody else.
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5:39 - 5:42Well it surely is a technical detail,
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5:42 - 5:44but some details really matter.
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5:44 - 5:46Some details provide
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5:46 - 5:48windows into uncharted realms of reality,
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5:48 - 5:51and this peculiar number may be doing just that,
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5:51 - 5:54as the only approach that's so far made headway to explain it
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5:54 - 5:57invokes the possibility of other universes --
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5:57 - 6:00an idea that naturally emerges from string theory,
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6:00 - 6:03which takes me to part two: string theory.
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6:03 - 6:07So hold the mystery of the dark energy
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6:07 - 6:09in the back of your mind
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6:09 - 6:11as I now go on to tell you
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6:11 - 6:14three key things about string theory.
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6:14 - 6:16First off, what is it?
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6:16 - 6:19Well it's an approach to realize Einstein's dream
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6:19 - 6:22of a unified theory of physics,
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6:22 - 6:24a single overarching framework
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6:24 - 6:26that would be able to describe
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6:26 - 6:28all the forces at work in the universe.
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6:28 - 6:30And the central idea of string theory
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6:30 - 6:32is quite straightforward.
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6:32 - 6:34It says that if you examine
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6:34 - 6:36any piece of matter ever more finely,
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6:36 - 6:38at first you'll find molecules
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6:38 - 6:41and then you'll find atoms and subatomic particles.
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6:41 - 6:43But the theory says that if you could probe smaller,
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6:43 - 6:46much smaller than we can with existing technology,
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6:46 - 6:49you'd find something else inside these particles --
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6:49 - 6:52a little tiny vibrating filament of energy,
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6:52 - 6:55a little tiny vibrating string.
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6:55 - 6:57And just like the strings on a violin,
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6:57 - 6:59they can vibrate in different patterns
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6:59 - 7:01producing different musical notes.
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7:01 - 7:03These little fundamental strings,
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7:03 - 7:05when they vibrate in different patterns,
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7:05 - 7:07they produce different kinds of particles --
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7:07 - 7:09so electrons, quarks, neutrinos, photons,
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7:09 - 7:11all other particles
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7:11 - 7:13would be united into a single framework,
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7:13 - 7:16as they would all arise from vibrating strings.
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7:16 - 7:19It's a compelling picture,
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7:19 - 7:21a kind of cosmic symphony,
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7:21 - 7:23where all the richness
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7:23 - 7:25that we see in the world around us
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7:25 - 7:27emerges from the music
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7:27 - 7:30that these little, tiny strings can play.
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7:30 - 7:32But there's a cost
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7:32 - 7:34to this elegant unification,
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7:34 - 7:36because years of research
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7:36 - 7:39have shown that the math of string theory doesn't quite work.
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7:39 - 7:41It has internal inconsistencies,
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7:41 - 7:43unless we allow
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7:43 - 7:46for something wholly unfamiliar --
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7:46 - 7:49extra dimensions of space.
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7:49 - 7:52That is, we all know about the usual three dimensions of space.
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7:52 - 7:54And you can think about those
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7:54 - 7:57as height, width and depth.
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7:57 - 8:00But string theory says that, on fantastically small scales,
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8:00 - 8:02there are additional dimensions
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8:02 - 8:04crumpled to a tiny size so small
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8:04 - 8:06that we have not detected them.
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8:06 - 8:08But even though the dimensions are hidden,
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8:08 - 8:11they would have an impact on things that we can observe
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8:11 - 8:14because the shape of the extra dimensions
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8:14 - 8:17constrains how the strings can vibrate.
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8:17 - 8:19And in string theory,
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8:19 - 8:22vibration determines everything.
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8:22 - 8:24So particle masses, the strengths of forces,
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8:24 - 8:27and most importantly, the amount of dark energy
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8:27 - 8:29would be determined
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8:29 - 8:31by the shape of the extra dimensions.
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8:31 - 8:34So if we knew the shape of the extra dimensions,
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8:34 - 8:37we should be able to calculate these features,
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8:37 - 8:40calculate the amount of dark energy.
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8:40 - 8:42The challenge
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8:42 - 8:44is we don't know
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8:44 - 8:47the shape of the extra dimensions.
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8:47 - 8:49All we have
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8:49 - 8:51is a list of candidate shapes
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8:51 - 8:54allowed by the math.
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8:54 - 8:56Now when these ideas were first developed,
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8:56 - 8:58there were only about five different candidate shapes,
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8:58 - 9:00so you can imagine
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9:00 - 9:02analyzing them one-by-one
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9:02 - 9:04to determine if any yield
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9:04 - 9:06the physical features we observe.
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9:06 - 9:08But over time the list grew
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9:08 - 9:10as researchers found other candidate shapes.
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9:10 - 9:13From five, the number grew into the hundreds and then the thousands --
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9:13 - 9:16A large, but still manageable, collection to analyze,
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9:16 - 9:18since after all,
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9:18 - 9:21graduate students need something to do.
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9:21 - 9:23But then the list continued to grow
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9:23 - 9:26into the millions and the billions, until today.
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9:26 - 9:28The list of candidate shapes
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9:28 - 9:33has soared to about 10 to the 500.
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9:33 - 9:36So, what to do?
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9:36 - 9:39Well some researchers lost heart,
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9:39 - 9:42concluding that was so many candidate shapes for the extra dimensions,
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9:42 - 9:45each giving rise to different physical features,
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9:45 - 9:47string theory would never make
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9:47 - 9:49definitive, testable predictions.
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9:49 - 9:53But others turned this issue on its head,
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9:53 - 9:55taking us to the possibility of a multiverse.
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9:55 - 9:57Here's the idea.
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9:57 - 10:00Maybe each of these shapes is on an equal footing with every other.
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10:00 - 10:02Each is as real as every other,
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10:02 - 10:04in the sense
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10:04 - 10:06that there are many universes,
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10:06 - 10:09each with a different shape, for the extra dimensions.
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10:09 - 10:11And this radical proposal
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10:11 - 10:14has a profound impact on this mystery:
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10:14 - 10:17the amount of dark energy revealed by the Nobel Prize-winning results.
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10:17 - 10:19Because you see,
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10:19 - 10:22if there are other universes,
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10:22 - 10:24and if those universes
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10:24 - 10:28each have, say, a different shape for the extra dimensions,
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10:28 - 10:30then the physical features of each universe will be different,
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10:30 - 10:32and in particular,
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10:32 - 10:34the amount of dark energy in each universe
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10:34 - 10:36will be different.
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10:36 - 10:38Which means that the mystery
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10:38 - 10:40of explaining the amount of dark energy we've now measured
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10:40 - 10:43would take on a wholly different character.
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10:43 - 10:45In this context,
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10:45 - 10:48the laws of physics can't explain one number for the dark energy
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10:48 - 10:51because there isn't just one number,
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10:51 - 10:53there are many numbers.
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10:53 - 10:55Which means
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10:55 - 10:58we have been asking the wrong question.
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10:58 - 11:00It's that the right question to ask is,
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11:00 - 11:03why do we humans find ourselves in a universe
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11:03 - 11:06with a particular amount of dark energy we've measured
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11:06 - 11:09instead of any of the other possibilities
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11:09 - 11:11that are out there?
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11:11 - 11:14And that's a question on which we can make headway.
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11:14 - 11:16Because those universes
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11:16 - 11:18that have much more dark energy than ours,
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11:18 - 11:21whenever matter tries to clump into galaxies,
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11:21 - 11:24the repulsive push of the dark energy is so strong
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11:24 - 11:26that it blows the clump apart
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11:26 - 11:28and galaxies don't form.
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11:28 - 11:31And in those universes that have much less dark energy,
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11:31 - 11:33well they collapse back on themselves so quickly
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11:33 - 11:36that, again, galaxies don't form.
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11:36 - 11:39And without galaxies, there are no stars, no planets
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11:39 - 11:41and no chance
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11:41 - 11:43for our form of life
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11:43 - 11:45to exist in those other universes.
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11:45 - 11:47So we find ourselves in a universe
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11:47 - 11:50with the particular amount of dark energy we've measured
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11:50 - 11:53simply because our universe has conditions
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11:53 - 11:57hospitable to our form of life.
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11:57 - 11:59And that would be that.
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11:59 - 12:01Mystery solved,
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12:01 - 12:03multiverse found.
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12:03 - 12:08Now some find this explanation unsatisfying.
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12:08 - 12:10We're used to physics
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12:10 - 12:13giving us definitive explanations for the features we observe.
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12:13 - 12:15But the point is,
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12:15 - 12:18if the feature you're observing
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12:18 - 12:20can and does take on
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12:20 - 12:22a wide variety of different values
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12:22 - 12:25across the wider landscape of reality,
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12:25 - 12:27then thinking one explanation
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12:27 - 12:29for a particular value
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12:29 - 12:32is simply misguided.
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12:32 - 12:34An early example
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12:34 - 12:37comes from the great astronomer Johannes Kepler
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12:37 - 12:39who was obsessed with understanding
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12:39 - 12:41a different number --
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12:41 - 12:45why the Sun is 93 million miles away from the Earth.
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12:45 - 12:48And he worked for decades trying to explain this number,
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12:48 - 12:51but he never succeeded, and we know why.
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12:51 - 12:53Kepler was asking
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12:53 - 12:55the wrong question.
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12:55 - 12:58We now know that there are many planets
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12:58 - 13:01at a wide variety of different distances from their host stars.
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13:01 - 13:04So hoping that the laws of physics
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13:04 - 13:07will explain one particular number, 93 million miles,
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13:07 - 13:10well that is simply wrongheaded.
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13:10 - 13:12Instead the right question to ask is,
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13:12 - 13:15why do we humans find ourselves on a planet
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13:15 - 13:17at this particular distance,
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13:17 - 13:20instead of any of the other possibilities?
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13:20 - 13:23And again, that's a question we can answer.
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13:23 - 13:26Those planets which are much closer to a star like the Sun
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13:26 - 13:28would be so hot
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13:28 - 13:30that our form of life wouldn't exist.
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13:30 - 13:33And those planets that are much farther away from the star,
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13:33 - 13:35well they're so cold
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13:35 - 13:37that, again, our form of life would not take hold.
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13:37 - 13:39So we find ourselves
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13:39 - 13:41on a planet at this particular distance
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13:41 - 13:43simply because it yields conditions
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13:43 - 13:46vital to our form of life.
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13:46 - 13:49And when it comes to planets and their distances,
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13:49 - 13:53this clearly is the right kind of reasoning.
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13:53 - 13:55The point is,
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13:55 - 13:58when it comes to universes and the dark energy that they contain,
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13:58 - 14:02it may also be the right kind of reasoning.
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14:02 - 14:05One key difference, of course,
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14:05 - 14:07is we know that there are other planets out there,
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14:07 - 14:10but so far I've only speculated on the possibility
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14:10 - 14:12that there might be other universes.
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14:12 - 14:14So to pull it all together,
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14:14 - 14:16we need a mechanism
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14:16 - 14:19that can actually generate other universes.
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14:19 - 14:22And that takes me to my final part, part three.
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14:22 - 14:25Because such a mechanism has been found
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14:25 - 14:28by cosmologists trying to understand the Big Bang.
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14:28 - 14:30You see, when we speak of the Big Bang,
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14:30 - 14:32we often have an image
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14:32 - 14:34of a kind of cosmic explosion
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14:34 - 14:36that created our universe
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14:36 - 14:39and set space rushing outward.
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14:39 - 14:41But there's a little secret.
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14:41 - 14:44The Big Bang leaves out something pretty important,
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14:44 - 14:46the Bang.
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14:46 - 14:49It tells us how the universe evolved after the Bang,
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14:49 - 14:51but gives us no insight
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14:51 - 14:55into what would have powered the Bang itself.
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14:55 - 14:57And this gap was finally filled
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14:57 - 14:59by an enhanced version of the Big Bang theory.
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14:59 - 15:02It's called inflationary cosmology,
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15:02 - 15:06which identified a particular kind of fuel
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15:06 - 15:08that would naturally generate
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15:08 - 15:10an outward rush of space.
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15:10 - 15:13The fuel is based on something called a quantum field,
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15:13 - 15:16but the only detail that matters for us
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15:16 - 15:19is that this fuel proves to be so efficient
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15:19 - 15:21that it's virtually impossible
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15:21 - 15:23to use it all up,
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15:23 - 15:25which means in the inflationary theory,
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15:25 - 15:28the Big Bang giving rise to our universe
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15:28 - 15:31is likely not a one-time event.
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15:31 - 15:34Instead the fuel not only generated our Big Bang,
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15:34 - 15:40but it would also generate countless other Big Bangs,
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15:40 - 15:43each giving rise to its own separate universe
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15:43 - 15:45with our universe becoming but one bubble
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15:45 - 15:48in a grand cosmic bubble bath of universes.
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15:48 - 15:50And now, when we meld this with string theory,
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15:50 - 15:52here's the picture we're led to.
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15:52 - 15:54Each of these universes has extra dimensions.
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15:54 - 15:57The extra dimensions take on a wide variety of different shapes.
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15:57 - 16:00The different shapes yield different physical features.
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16:00 - 16:03And we find ourselves in one universe instead of another
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16:03 - 16:06simply because it's only in our universe
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16:06 - 16:09that the physical features, like the amount of dark energy,
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16:09 - 16:13are right for our form of life to take hold.
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16:13 - 16:16And this is the compelling but highly controversial picture
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16:16 - 16:18of the wider cosmos
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16:18 - 16:20that cutting-edge observation and theory
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16:20 - 16:24have now led us to seriously consider.
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16:24 - 16:28One big remaining question, of course, is,
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16:28 - 16:31could we ever confirm
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16:31 - 16:34the existence of other universes?
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16:34 - 16:36Well let me describe
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16:36 - 16:39one way that might one day happen.
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16:39 - 16:41The inflationary theory
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16:41 - 16:43already has strong observational support.
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16:43 - 16:45Because the theory predicts
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16:45 - 16:47that the Big Bang would have been so intense
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16:47 - 16:50that as space rapidly expanded,
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16:50 - 16:52tiny quantum jitters from the micro world
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16:52 - 16:55would have been stretched out to the macro world,
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16:55 - 16:58yielding a distinctive fingerprint,
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16:58 - 17:00a pattern of slightly hotter spots and slightly colder spots,
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17:00 - 17:02across space,
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17:02 - 17:05which powerful telescopes have now observed.
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17:05 - 17:08Going further, if there are other universes,
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17:08 - 17:10the theory predicts that every so often
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17:10 - 17:12those universes can collide.
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17:12 - 17:14And if our universe got hit by another,
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17:14 - 17:16that collision
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17:16 - 17:18would generate an additional subtle pattern
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17:18 - 17:20of temperature variations across space
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17:20 - 17:22that we might one day
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17:22 - 17:24be able to detect.
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17:24 - 17:27And so exotic as this picture is,
-
17:27 - 17:29it may one day be grounded
-
17:29 - 17:31in observations,
-
17:31 - 17:34establishing the existence of other universes.
-
17:34 - 17:36I'll conclude
-
17:36 - 17:39with a striking implication
-
17:39 - 17:41of all these ideas
-
17:41 - 17:43for the very far future.
-
17:43 - 17:45You see, we learned
-
17:45 - 17:47that our universe is not static,
-
17:47 - 17:49that space is expanding,
-
17:49 - 17:51that that expansion is speeding up
-
17:51 - 17:53and that there might be other universes
-
17:53 - 17:55all by carefully examining
-
17:55 - 17:57faint pinpoints of starlight
-
17:57 - 18:00coming to us from distant galaxies.
-
18:00 - 18:03But because the expansion is speeding up,
-
18:03 - 18:05in the very far future,
-
18:05 - 18:08those galaxies will rush away so far and so fast
-
18:08 - 18:11that we won't be able to see them --
-
18:11 - 18:13not because of technological limitations,
-
18:13 - 18:15but because of the laws of physics.
-
18:15 - 18:17The light those galaxies emit,
-
18:17 - 18:20even traveling at the fastest speed, the speed of light,
-
18:20 - 18:22will not be able to overcome
-
18:22 - 18:25the ever-widening gulf between us.
-
18:25 - 18:27So astronomers in the far future
-
18:27 - 18:29looking out into deep space
-
18:29 - 18:32will see nothing but an endless stretch
-
18:32 - 18:36of static, inky, black stillness.
-
18:36 - 18:38And they will conclude
-
18:38 - 18:40that the universe is static and unchanging
-
18:40 - 18:43and populated by a single central oasis of matter
-
18:43 - 18:45that they inhabit --
-
18:45 - 18:47a picture of the cosmos
-
18:47 - 18:50that we definitively know to be wrong.
-
18:50 - 18:53Now maybe those future astronomers will have records
-
18:53 - 18:55handed down from an earlier era,
-
18:55 - 18:57like ours,
-
18:57 - 18:59attesting to an expanding cosmos
-
18:59 - 19:01teeming with galaxies.
-
19:01 - 19:03But would those future astronomers
-
19:03 - 19:06believe such ancient knowledge?
-
19:06 - 19:08Or would they believe
-
19:08 - 19:11in the black, static empty universe
-
19:11 - 19:15that their own state-of-the-art observations reveal?
-
19:15 - 19:17I suspect the latter.
-
19:17 - 19:19Which means that we are living
-
19:19 - 19:22through a remarkably privileged era
-
19:22 - 19:24when certain deep truths about the cosmos
-
19:24 - 19:26are still within reach
-
19:26 - 19:28of the human spirit of exploration.
-
19:28 - 19:33It appears that it may not always be that way.
-
19:33 - 19:35Because today's astronomers,
-
19:35 - 19:38by turning powerful telescopes to the sky,
-
19:38 - 19:41have captured a handful of starkly informative photons --
-
19:41 - 19:44a kind of cosmic telegram
-
19:44 - 19:46billions of years in transit.
-
19:46 - 19:50and the message echoing across the ages is clear.
-
19:50 - 19:53Sometimes nature guards her secrets
-
19:53 - 19:55with the unbreakable grip
-
19:55 - 19:57of physical law.
-
19:57 - 20:01Sometimes the true nature of reality beckons
-
20:01 - 20:04from just beyond the horizon.
-
20:04 - 20:06Thank you very much.
-
20:06 - 20:10(Applause)
-
20:10 - 20:12Chris Anderson: Brian, thank you.
-
20:12 - 20:14The range of ideas you've just spoken about
-
20:14 - 20:17are dizzying, exhilarating, incredible.
-
20:17 - 20:19How do you think
-
20:19 - 20:21of where cosmology is now,
-
20:21 - 20:23in a sort of historical side?
-
20:23 - 20:26Are we in the middle of something unusual historically in your opinion?
-
20:26 - 20:28BG: Well it's hard to say.
-
20:28 - 20:31When we learn that astronomers of the far future
-
20:31 - 20:34may not have enough information to figure things out,
-
20:34 - 20:37the natural question is, maybe we're already in that position
-
20:37 - 20:40and certain deep, critical features of the universe
-
20:40 - 20:43already have escaped our ability to understand
-
20:43 - 20:45because of how cosmology evolves.
-
20:45 - 20:47So from that perspective,
-
20:47 - 20:49maybe we will always be asking questions
-
20:49 - 20:51and never be able to fully answer them.
-
20:51 - 20:53On the other hand, we now can understand
-
20:53 - 20:55how old the universe is.
-
20:55 - 20:57We can understand
-
20:57 - 21:00how to understand the data from the microwave background radiation
-
21:00 - 21:03that was set down 13.72 billion years ago --
-
21:03 - 21:05and yet, we can do calculations today to predict how it will look
-
21:05 - 21:07and it matches.
-
21:07 - 21:09Holy cow! That's just amazing.
-
21:09 - 21:12So on the one hand, it's just incredible where we've gotten,
-
21:12 - 21:16but who knows what sort of blocks we may find in the future.
-
21:16 - 21:19CA: You're going to be around for the next few days.
-
21:19 - 21:21Maybe some of these conversations can continue.
-
21:21 - 21:23Thank you. Thank you, Brian. (BG: My pleasure.)
-
21:23 - 21:26(Applause)
- Title:
- Is our universe the only universe?
- Speaker:
- Brian Greene
- Description:
-
At the heart of modern cosmology is a mystery: Why does our universe appear so exquisitely tuned to create the conditions necessary for life? In this tour de force tour of some of science's biggest new discoveries, Brian Greene shows how the mind-boggling idea of a multiverse may hold the answer to the riddle.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 21:47
Jenny Zurawell edited English subtitles for Is our universe the only universe? | ||
Jenny Zurawell edited English subtitles for Is our universe the only universe? | ||
Ilana foss edited English subtitles for Is our universe the only universe? | ||
Ilana foss edited English subtitles for Is our universe the only universe? | ||
Jenny Zurawell edited English subtitles for Is our universe the only universe? | ||
Flávia Pires edited English subtitles for Is our universe the only universe? | ||
Jenny Zurawell approved English subtitles for Is our universe the only universe? | ||
Jenny Zurawell accepted English subtitles for Is our universe the only universe? |