How to pronounce "twists"

If you look deep into the night sky,

you see stars,

and if you look further, you see more stars,

and further, galaxies, and further, more galaxies.

But if you keep looking further and further,

eventually you see nothing for a long while,

and then finally you see a faint, fading afterglow,

and it's the afterglow of the Big Bang.

Now, the Big Bang was an era in the early universe

when everything we see in the night sky

was condensed into an incredibly small,

incredibly hot, incredibly roiling mass,

and from it sprung everything we see.

Now, we've mapped that afterglow

with great precision,

and when I say we, I mean people who aren't me.

We've mapped the afterglow

with spectacular precision,

and one of the shocks about it

is that it's almost completely uniform.

Fourteen billion light years that way

and 14 billion light years that way,

it's the same temperature.

Now it's been 14 billion years

since that Big Bang,

and so it's got faint and cold.

It's now 2.7 degrees.

But it's not exactly 2.7 degrees.

It's only 2.7 degrees to about

10 parts in a million.

Over here, it's a little hotter,

and over there, it's a little cooler,

and that's incredibly important to everyone in this room,

because where it was a little hotter,

there was a little more stuff,

and where there was a little more stuff,

we have galaxies and clusters of galaxies

and superclusters

and all the structure you see in the cosmos.

And those small, little, inhomogeneities,

20 parts in a million,

those were formed by quantum mechanical wiggles

in that early universe that were stretched

across the size of the entire cosmos.

That is spectacular,

and that's not what they found on Monday;

what they found on Monday is cooler.

So here's what they found on Monday:

Imagine you take a bell,

and you whack the bell with a hammer.

What happens? It rings.

But if you wait, that ringing fades

and fades and fades

until you don't notice it anymore.

Now, that early universe was incredibly dense,

like a metal, way denser,

and if you hit it, it would ring,

but the thing ringing would be

the structure of space-time itself,

and the hammer would be quantum mechanics.

What they found on Monday

was evidence of the ringing

of the space-time of the early universe,

what we call gravitational waves

from the fundamental era,

and here's how they found it.

Those waves have long since faded.

If you go for a walk,

you don't wiggle.

Those gravitational waves in the structure of space

are totally invisible for all practical purposes.

But early on, when the universe was making

that last afterglow,

the gravitational waves

put little twists in the structure

of the light that we see.

So by looking at the night sky deeper and deeper --

in fact, these guys spent three years on the South Pole

looking straight up through the coldest, clearest,

cleanest air they possibly could find

looking deep into the night sky and studying

that glow and looking for the faint twists

which are the symbol, the signal,

of gravitational waves,

the ringing of the early universe.

And on Monday, they announced

that they had found it.

And the thing that's so spectacular about that to me

is not just the ringing, though that is awesome.

The thing that's totally amazing,

the reason I'm on this stage, is because

what that tells us is something deep about the early universe.

It tells us that we

and everything we see around us

are basically one large bubble --

and this is the idea of inflation—

one large bubble surrounded by something else.

This isn't conclusive evidence for inflation,

but anything that isn't inflation that explains this

will look the same.

This is a theory, an idea,

that has been around for a while,

and we never thought we we'd really see it.

For good reasons, we thought we'd never see

killer evidence, and this is killer evidence.

But the really crazy idea

is that our bubble is just one bubble

in a much larger, roiling pot of universal stuff.

We're never going to see the stuff outside,

but by going to the South Pole and spending three years

looking at the detailed structure of the night sky,

we can figure out

that we're probably in a universe that looks kind of like that.

And that amazes me.

Thanks a lot.

(Applause)