04:43
TED2014

Allan Adams: The discovery that could rewrite physics

Filmed:

On March 17, 2014, a group of physicists announced a thrilling discovery: the “smoking gun” data for the idea of an inflationary universe, a clue to the Big Bang. For non-physicists, what does it mean? TED asked Allan Adams to briefly explain the results, in this improvised talk illustrated by Randall Munroe of xkcd.

- Theoretical physicist
Allan Adams is a theoretical physicist working at the intersection of fluid dynamics, quantum field theory and string theory. Full bio

If you look deep into the night sky,
00:12
you see stars,
00:16
and if you look further, you see more stars,
00:18
and further, galaxies, and
further, more galaxies.
00:20
But if you keep looking further and further,
00:22
eventually you see nothing for a long while,
00:26
and then finally you see a
faint, fading afterglow,
00:29
and it's the afterglow of the Big Bang.
00:34
Now, the Big Bang was an era in the early universe
00:37
when everything we see in the night sky
00:40
was condensed into an incredibly small,
00:42
incredibly hot, incredibly roiling mass,
00:44
and from it sprung everything we see.
00:48
Now, we've mapped that afterglow
00:51
with great precision,
00:54
and when I say we, I mean people who aren't me.
00:56
We've mapped the afterglow
00:58
with spectacular precision,
01:00
and one of the shocks about it
01:01
is that it's almost completely uniform.
01:02
Fourteen billion light years that way
01:05
and 14 billion light years that way,
01:07
it's the same temperature.
01:09
Now it's been 14 billion years
01:11
since that Big Bang,
01:14
and so it's got faint and cold.
01:16
It's now 2.7 degrees.
01:18
But it's not exactly 2.7 degrees.
01:21
It's only 2.7 degrees to about
01:23
10 parts in a million.
01:25
Over here, it's a little hotter,
01:27
and over there, it's a little cooler,
01:28
and that's incredibly important
to everyone in this room,
01:30
because where it was a little hotter,
01:33
there was a little more stuff,
01:35
and where there was a little more stuff,
01:36
we have galaxies and clusters of galaxies
01:38
and superclusters
01:40
and all the structure you see in the cosmos.
01:41
And those small, little, inhomogeneities,
01:44
20 parts in a million,
01:47
those were formed by quantum mechanical wiggles
01:49
in that early universe that were stretched
01:52
across the size of the entire cosmos.
01:54
That is spectacular,
01:56
and that's not what they found on Monday;
01:58
what they found on Monday is cooler.
01:59
So here's what they found on Monday:
02:02
Imagine you take a bell,
02:04
and you whack the bell with a hammer.
02:07
What happens? It rings.
02:09
But if you wait, that ringing fades
02:11
and fades and fades
02:13
until you don't notice it anymore.
02:14
Now, that early universe was incredibly dense,
02:16
like a metal, way denser,
02:19
and if you hit it, it would ring,
02:21
but the thing ringing would be
02:23
the structure of space-time itself,
02:25
and the hammer would be quantum mechanics.
02:27
What they found on Monday
02:30
was evidence of the ringing
02:32
of the space-time of the early universe,
02:35
what we call gravitational waves
02:37
from the fundamental era,
02:39
and here's how they found it.
02:40
Those waves have long since faded.
02:42
If you go for a walk,
02:45
you don't wiggle.
02:46
Those gravitational waves in the structure of space
02:48
are totally invisible for all practical purposes.
02:50
But early on, when the universe was making
02:53
that last afterglow,
02:56
the gravitational waves
02:58
put little twists in the structure
03:00
of the light that we see.
03:03
So by looking at the night sky deeper and deeper --
03:04
in fact, these guys spent
three years on the South Pole
03:07
looking straight up through the coldest, clearest,
03:10
cleanest air they possibly could find
03:13
looking deep into the night sky and studying
03:15
that glow and looking for the faint twists
03:17
which are the symbol, the signal,
03:21
of gravitational waves,
03:23
the ringing of the early universe.
03:25
And on Monday, they announced
03:27
that they had found it.
03:29
And the thing that's so spectacular about that to me
03:31
is not just the ringing, though that is awesome.
03:33
The thing that's totally amazing,
03:36
the reason I'm on this stage, is because
03:37
what that tells us is something
deep about the early universe.
03:39
It tells us that we
03:43
and everything we see around us
03:44
are basically one large bubble --
03:46
and this is the idea of inflation—
03:49
one large bubble surrounded by something else.
03:51
This isn't conclusive evidence for inflation,
03:55
but anything that isn't inflation that explains this
03:57
will look the same.
03:59
This is a theory, an idea,
04:00
that has been around for a while,
04:02
and we never thought we we'd really see it.
04:03
For good reasons, we thought we'd never see
04:05
killer evidence, and this is killer evidence.
04:07
But the really crazy idea
04:09
is that our bubble is just one bubble
04:11
in a much larger, roiling pot of universal stuff.
04:14
We're never going to see the stuff outside,
04:18
but by going to the South Pole
and spending three years
04:20
looking at the detailed structure of the night sky,
04:23
we can figure out
04:25
that we're probably in a universe
that looks kind of like that.
04:27
And that amazes me.
04:30
Thanks a lot.
04:33
(Applause)
04:34

▲Back to top

About the Speaker:

Allan Adams - Theoretical physicist
Allan Adams is a theoretical physicist working at the intersection of fluid dynamics, quantum field theory and string theory.

Why you should listen

Allan Adams is a theoretical physicist working at the intersection of fluid dynamics, quantum field theory and string theory. His research in theoretical physics focuses on string theory both as a model of quantum gravity and as a strong-coupling description of non-gravitational systems.

Like water, string theory enjoys many distinct phases in which the low-energy phenomena take qualitatively different forms. In its most familiar phases, string theory reduces to a perturbative theory of quantum gravity. These phases are useful for studying, for example, the resolution of singularities in classical gravity, or the set of possibilities for the geometry and fields of spacetime. Along these lines, Adams is particularly interested in microscopic quantization of flux vacua, and in the search for constraints on low-energy physics derived from consistency of the stringy UV completion.

In other phases, when the gravitational interactions become strong and a smooth spacetime geometry ceases to be a good approximation, a more convenient description of string theory may be given in terms of a weakly-coupled non-gravitational quantum field theory. Remarkably, these two descriptions—with and without gravity—appear to be completely equivalent, with one remaining weakly-coupled when its dual is strongly interacting. This equivalence, known as gauge-gravity duality, allows us to study strongly-coupled string and quantum field theories by studying perturbative features of their weakly-coupled duals. Gauge-gravity duals have already led to interesting predictions for the quark-gluon plasma studied at RHIC. A major focus of Adams's present research is to use such dualities to find weakly-coupled descriptions of strongly-interacting condensed matter systems which can be realized in the lab.
More profile about the speaker
Allan Adams | Speaker | TED.com