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If you look deep into the night sky,
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you see stars,
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and if you look further, you see more stars,
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and further, galaxies, and
further, more galaxies.
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But if you keep looking further and further,
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eventually you see nothing for a long while,
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and then finally you see a
faint, fading afterglow,
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and it's the afterglow of the Big Bang.
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Now, the Big Bang was an era in the early universe
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when everything we see in the night sky
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was condensed into an incredibly small,
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incredibly hot, incredibly roiling mass,
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and from it sprung everything we see.
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Now, we've mapped that afterglow
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with great precision,
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and when I say me, I mean people who aren't me.
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We've mapped the afterglow
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with spectacular precision,
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and one of the shocks about it
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is that it's almost completely uniform.
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14 billion light years that way
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and 14 billion light years that way,
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it's the same temperature.
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Now it's been 13 billion years
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since that Big Bang,
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and so it's got faint and cold.
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It's now 2.7 degrees.
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But it's not exactly 2.7 degrees.
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It's only 2.7 degrees to about
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10 parts in a million.
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Over here, it's a little hotter,
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and over there, it's a little cooler,
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and that's incredibly important
to everyone in this room,
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because where it was a little hotter,
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there was a little more stuff,
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and where there was a little more stuff,
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we have galaxies and clusters of galaxies
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and superclusters
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and all the structure you see in the cosmos.
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And those small, little, inhomogeneities,
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20 parts in a million,
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those were formed by quantum mechanical wiggles
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in that early universe that were stretched
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across the size of the entire cosmos.
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That is spectacular,
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And that's not what they found on Monday.
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What they found on Monday is cooler.
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So here's what they found on Monday.
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Imagine you take some hot, you take a bell,
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and you whack the bell with a hammer.
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What happens? It rings.
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But if you wait, that ringing fades
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and fades and fades
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until you don't notice it anymore.
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Now that early universe was incredibly dense,
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like a metal, way denser,
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and if you hit it, it would ring,
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but the thing ringing would be
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the structure of spacetime itself,
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and the hammer would be quantum mechanics.
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What they found on Monday
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was evidence of the ringing
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of the spacetime of the early universe,
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what we call gravitational waves
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from the fundamental era,
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and here's how they found it.
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Those waves have long since faded.
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If you go for a walk,
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you don't wiggle.
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Those gravitational waves in the structures of space
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are totally invisible for all practical purposes.
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But early on, when the universe was making
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that last afterglow,
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the gravitational waves
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put little twists in the structure
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of the light that we see.
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So by looking at the night sky deeper and deeper
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—in fact, these guys spent
three years on the South Pole
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looking straight up through the coldest, clearest,
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cleanest air they possibly could find
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looking deep into the night sky and studying
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that glow and looking for the faint twists
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which are the symbol, the signal,
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of gravitational waves,
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the ringing of the early universe.
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And on Monday, they announced
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that they had found it.
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And the thing that's so spectacular about that to me
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is not just the ringing, though that is awesome.
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The thing that's totally amazing,
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the reason I'm on this stage, is because
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what that tells us is something
deep about the early universe.
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It tells us that we
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and everything we see around us
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are basically one large bubble
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—and this is the idea of inflation—
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one large bubble surrounded by something else.
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This isn't conclusive evidence for inflation,
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but anything that isn't inflation that explains this
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will look the same.
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This is a theory, an idea,
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that has been around for a while,
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and we never thought we we'd really see it.
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For good reasons, we thought we'd never see
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killer evidence, and this is killer evidence.
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But the really crazy idea
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is that our bubble is just one bubble
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in a much larger, roiling pot of universal stuff.
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We're never going to see the stuff outside,
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but by going to the South Pole
and spending three years
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looking at the detailed structure of the night sky,
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we can figure out
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that we're probably in a universe
that looks kind of like that.
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And that amazes me.
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Thanks a lot.
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(Applause)