0:00:07.187,0:00:11.372
There is something about physics

0:00:11.396,0:00:15.396
that has been really bothering me[br]since I was a little kid.

0:00:17.110,0:00:18.919
And it's related to a question

0:00:18.943,0:00:22.187
that scientists have been asking[br]for almost 100 years,

0:00:22.211,0:00:23.380
with no answer.

0:00:25.208,0:00:28.218
How do the smallest things in nature,

0:00:28.242,0:00:30.395
the particles of the quantum world,

0:00:30.419,0:00:33.450
match up with the largest[br]things in nature --

0:00:33.474,0:00:36.721
planets and stars and galaxies[br]held together by gravity?

0:00:37.350,0:00:40.123
As a kid, I would puzzle[br]over questions just like this.

0:00:40.147,0:00:43.039
I would fiddle around[br]with microscopes and electromagnets,

0:00:43.063,0:00:45.258
and I would read[br]about the forces of the small

0:00:45.282,0:00:46.616
and about quantum mechanics

0:00:46.640,0:00:50.204
and I would marvel at how well[br]that description matched up

0:00:50.228,0:00:51.398
to our observation.

0:00:52.320,0:00:53.903
Then I would look at the stars,

0:00:53.927,0:00:56.451
and I would read about how well[br]we understand gravity,

0:00:56.475,0:00:59.825
and I would think surely,[br]there must be some elegant way

0:00:59.849,0:01:02.494
that these two systems match up.

0:01:03.121,0:01:04.522
But there's not.

0:01:05.773,0:01:06.933
And the books would say,

0:01:06.957,0:01:10.140
yeah, we understand a lot[br]about these two realms separately,

0:01:10.164,0:01:12.774
but when we try to link[br]them mathematically,

0:01:12.798,0:01:14.128
everything breaks.

0:01:14.974,0:01:16.284
And for 100 years,

0:01:16.308,0:01:21.336
none of our ideas as to how to solve[br]this basically physics disaster,

0:01:21.360,0:01:23.174
has ever been supported by evidence.

0:01:24.471,0:01:26.125
And to little old me --

0:01:26.149,0:01:27.959
little, curious, skeptical James --

0:01:27.983,0:01:30.851
this was a supremely unsatisfying answer.

0:01:32.211,0:01:34.444
So, I'm still a skeptical little kid.

0:01:34.468,0:01:38.278
Flash-forward now[br]to December of 2015,

0:01:39.129,0:01:41.603
when I found myself smack in the middle

0:01:41.627,0:01:44.567
of the physics world[br]being flipped on its head.

0:01:46.099,0:01:49.419
It all started when we at CERN[br]saw something intriguing in our data:

0:01:49.443,0:01:51.717
a hint of a new particle,

0:01:51.741,0:01:55.957
an inkling of a possibly extraordinary[br]answer to this question.

0:01:57.877,0:02:00.004
So I'm still a skeptical[br]little kid, I think,

0:02:00.028,0:02:02.161
but I'm also now a particle hunter.

0:02:02.185,0:02:05.648
I am a physicist at CERN's[br]Large Hadron Collider,

0:02:05.672,0:02:09.143
the largest science[br]experiment ever mounted.

0:02:09.977,0:02:13.512
It's a 27-kilometer tunnel[br]on the border of France and Switzerland

0:02:13.536,0:02:15.386
buried 100 meters underground.

0:02:15.410,0:02:16.564
And in this tunnel,

0:02:16.588,0:02:20.541
we use superconducting magnets[br]colder than outer space

0:02:20.565,0:02:23.626
to accelerate protons[br]to almost the speed of light

0:02:23.650,0:02:27.527
and slam them into each other[br]millions of times per second,

0:02:27.551,0:02:30.377
collecting the debris of these collisions

0:02:30.401,0:02:34.372
to search for new, undiscovered[br]fundamental particles.

0:02:34.827,0:02:37.291
Its design and construction[br]took decades of work

0:02:37.315,0:02:40.347
by thousands of physicists[br]from around the globe,

0:02:40.371,0:02:42.912
and in the summer of 2015,

0:02:42.936,0:02:46.360
we had been working tirelessly[br]to switch on the LHC

0:02:46.384,0:02:50.851
at the highest energy that humans[br]have ever used in a collider experiment.

0:02:51.835,0:02:54.358
Now, higher energy is important

0:02:54.382,0:02:56.569
because for particles,[br]there is an equivalence

0:02:56.593,0:02:58.794
between energy and particle mass,

0:02:58.818,0:03:01.279
and mass is just a number[br]put there by nature.

0:03:02.168,0:03:03.486
To discover new particles,

0:03:03.510,0:03:05.632
we need to reach these bigger numbers.

0:03:05.656,0:03:08.910
And to do that, we have to build[br]a bigger, higher energy collider,

0:03:08.934,0:03:11.499
and the biggest, highest[br]energy collider in the world

0:03:11.523,0:03:12.989
is the Large Hadron Collider.

0:03:14.371,0:03:19.270
And then, we collide protons[br]quadrillions of times,

0:03:19.294,0:03:23.578
and we collect this data very slowly,[br]over months and months.

0:03:24.913,0:03:29.248
And then new particles might show up[br]in our data as bumps --

0:03:29.272,0:03:31.717
slight deviations from what you expect,

0:03:31.741,0:03:35.708
little clusters of data points[br]that make a smooth line not so smooth.

0:03:36.479,0:03:38.200
For example, this bump,

0:03:39.110,0:03:41.643
after months of data-taking in 2012,

0:03:41.667,0:03:43.796
led to the discovery[br]of the Higgs particle --

0:03:43.820,0:03:45.025
the Higgs boson --

0:03:45.049,0:03:48.414
and to a Nobel Prize[br]for the confirmation of its existence.

0:03:50.072,0:03:53.630
This jump up in energy in 2015

0:03:54.728,0:03:58.020
represented the best chance[br]that we as a species had ever had

0:03:58.044,0:03:59.521
of discovering new particles --

0:03:59.545,0:04:01.657
new answers to these[br]long-standing questions,

0:04:01.681,0:04:04.778
because it was almost[br]twice as much energy as we used

0:04:04.802,0:04:06.724
when we discovered the Higgs boson.

0:04:06.748,0:04:10.489
Many of my colleagues had been working[br]their entire careers for this moment,

0:04:10.513,0:04:12.589
and frankly, to little curious me,

0:04:12.613,0:04:15.523
this was the moment[br]I'd been waiting for my entire life.

0:04:15.547,0:04:17.278
So 2015 was go time.

0:04:18.754,0:04:20.964
So June 2015,

0:04:21.822,0:04:24.481
the LHC is switched back on.

0:04:25.140,0:04:28.017
My colleagues and I held our breath[br]and bit our fingernails,

0:04:28.041,0:04:30.552
and then finally we saw[br]the first proton collisions

0:04:30.576,0:04:32.532
at this highest energy ever.

0:04:32.556,0:04:34.632
Applause, champagne, celebration.

0:04:34.656,0:04:38.252
This was a milestone for science,

0:04:38.276,0:04:42.898
and we had no idea what we would find[br]in this brand-new data.

0:04:46.090,0:04:48.268
And then a few weeks later,[br]we found a bump.

0:04:50.292,0:04:51.968
It wasn't a very big bump,

0:04:53.052,0:04:55.564
but it was big enough to make[br]you raise your eyebrow.

0:04:55.588,0:04:57.839
But on a scale of one to 10[br]for eyebrow raises,

0:04:57.863,0:05:00.473
if 10 indicates that you've[br]discovered a new particle,

0:05:00.497,0:05:02.224
this eyebrow raise is about a four.

0:05:02.248,0:05:03.398
(Laughter)

0:05:04.532,0:05:09.743
I spent hours, days, weeks[br]in secret meetings,

0:05:09.767,0:05:12.127
arguing with my colleagues[br]over this little bump,

0:05:12.151,0:05:15.387
poking and prodding it with our most[br]ruthless experimental sticks

0:05:15.411,0:05:17.388
to see if it would withstand scrutiny.

0:05:18.088,0:05:21.549
But even after months[br]of working feverishly --

0:05:21.573,0:05:24.005
sleeping in our offices[br]and not going home,

0:05:24.029,0:05:26.106
candy bars for dinner,

0:05:26.130,0:05:27.700
coffee by the bucketful --

0:05:27.724,0:05:31.967
physicists are machines[br]for turning coffee into diagrams --

0:05:31.991,0:05:33.390
(Laughter)

0:05:33.414,0:05:35.950
This little bump would not go away.

0:05:36.804,0:05:38.942
So after a few months,

0:05:38.966,0:05:42.676
we presented our little bump to the world[br]with a very clear message:

0:05:43.557,0:05:46.268
this little bump is interesting[br]but it's not definitive,

0:05:46.292,0:05:49.621
so let's keep an eye on it[br]as we take more data.

0:05:49.972,0:05:52.263
So we were trying to be[br]extremely cool about it.

0:05:53.563,0:05:55.751
And the world ran with it anyway.

0:05:56.483,0:05:58.115
The news loved it.

0:05:58.835,0:06:01.390
People said it reminded[br]them of the little bump

0:06:01.414,0:06:04.837
that was shown on the way[br]toward the Higgs boson discovery.

0:06:04.861,0:06:07.989
Better than that,[br]my theorist colleagues --

0:06:08.648,0:06:10.965
I love my theorist colleagues --

0:06:10.989,0:06:14.601
my theorist colleagues wrote[br]500 papers about this little bump.

0:06:14.625,0:06:16.080
(Laughter)

0:06:16.674,0:06:20.640
The world of particle physics[br]had been flipped on its head.

0:06:21.845,0:06:26.087
But what was it about this particular bump

0:06:26.111,0:06:30.201
that caused thousands of physicists[br]to collectively lose their cool?

0:06:31.696,0:06:33.132
This little bump was unique.

0:06:34.298,0:06:35.667
This little bump indicated

0:06:35.691,0:06:38.713
that we were seeing an unexpectedly[br]large number of collisions

0:06:38.737,0:06:42.068
whose debris consisted[br]of only two photons,

0:06:42.092,0:06:43.336
two particles of light.

0:06:43.360,0:06:44.597
And that's rare.

0:06:45.169,0:06:47.789
Particle collisions are not[br]like automobile collisions.

0:06:47.813,0:06:49.332
They have different rules.

0:06:49.356,0:06:52.006
When two particles collide[br]at almost the speed of light,

0:06:52.030,0:06:53.451
the quantum world takes over.

0:06:53.475,0:06:54.735
And in the quantum world,

0:06:54.759,0:06:57.952
these two particles[br]can briefly create a new particle

0:06:57.976,0:07:00.756
that lives for a tiny fraction of a second

0:07:00.780,0:07:03.661
before splitting into other particles[br]that hit our detector.

0:07:03.685,0:07:07.090
Imagine a car collision[br]where the two cars vanish upon impact,

0:07:07.114,0:07:09.383
a bicycle appears in their place --

0:07:09.407,0:07:10.478
(Laughter)

0:07:10.502,0:07:12.963
And then that bicycle explodes[br]into two skateboards,

0:07:12.987,0:07:14.168
which hit our detector.

0:07:14.192,0:07:15.571
(Laughter)

0:07:15.595,0:07:17.548
Hopefully, not literally.

0:07:17.572,0:07:18.914
They're very expensive.

0:07:20.291,0:07:24.039
Events where only two photons[br]hit out detector are very rare.

0:07:24.063,0:07:27.785
And because of the special[br]quantum properties of photons,

0:07:27.809,0:07:31.597
there's a very small number[br]of possible new particles --

0:07:31.621,0:07:33.118
these mythical bicycles --

0:07:33.142,0:07:35.385
that can give birth to only two photons.

0:07:35.912,0:07:38.748
But one of these options is huge,

0:07:38.772,0:07:41.608
and it has to do with[br]that long-standing question

0:07:41.632,0:07:44.154
that bothered me as a tiny little kid,

0:07:44.178,0:07:45.538
about gravity.

0:07:48.046,0:07:50.718
Gravity may seem super strong to you,

0:07:50.742,0:07:54.842
but it's actually crazily weak[br]compared to the other forces of nature.

0:07:54.866,0:07:57.497
I can briefly beat gravity when I jump,

0:07:58.490,0:08:01.333
but I can't pick a proton out of my hand.

0:08:02.563,0:08:05.779
The strength of gravity compared[br]to the other forces of nature?

0:08:06.580,0:08:08.770
It's 10 to the minus 39.

0:08:08.794,0:08:11.331
That's a decimal with 39 zeros after it.

0:08:11.355,0:08:12.512
Worse than that,

0:08:12.536,0:08:15.563
all of the other known forces of nature[br]are perfectly described

0:08:15.587,0:08:17.624
by this thing we call the Standard Model,

0:08:17.648,0:08:21.083
which is our current best description[br]of nature at its smallest scales,

0:08:21.107,0:08:22.263
and quite frankly,

0:08:22.287,0:08:26.464
one of the most successful[br]achievements of humankind --

0:08:26.488,0:08:30.500
except for gravity, which is absent[br]from the Standard Model.

0:08:30.524,0:08:31.674
It's crazy.

0:08:32.145,0:08:35.246
It's almost as though most[br]of gravity has gone missing.

0:08:36.494,0:08:38.160
We feel a little bit of it,

0:08:38.184,0:08:39.861
but where's the rest of it?

0:08:39.885,0:08:41.167
No one knows.

0:08:42.102,0:08:46.506
But one theoretical explanation[br]proposes a wild solution.

0:08:48.220,0:08:49.559
You and I --

0:08:49.583,0:08:51.161
even you in the back --

0:08:51.185,0:08:53.330
we live in three dimensions of space.

0:08:53.354,0:08:55.911
I hope that's a[br]non-controversial statement.

0:08:55.935,0:08:57.764
(Laughter)

0:08:57.788,0:09:01.226
All of the known particles also live[br]in three dimensions of space.

0:09:01.250,0:09:03.440
In fact, a particle is just another name

0:09:03.464,0:09:06.473
for an excitation[br]in a three-dimensional field;

0:09:06.497,0:09:08.417
a localized wobbling in space.

0:09:09.388,0:09:12.917
More importantly, all the math[br]that we use to describe all this stuff

0:09:12.941,0:09:16.014
assumes that there are only[br]three dimensions of space.

0:09:16.038,0:09:19.419
But math is math, and we can play[br]around with our math however we want.

0:09:19.443,0:09:22.609
And people have been playing around[br]with extra dimensions of space

0:09:22.633,0:09:23.788
for a very long time,

0:09:23.812,0:09:26.397
but it's always been an abstract[br]mathematical concept.

0:09:26.421,0:09:29.593
I mean, just look around you --[br]you at the back, look around --

0:09:29.617,0:09:31.898
there's clearly only[br]three dimensions of space.

0:09:33.054,0:09:34.613
But what if that's not true?

0:09:36.209,0:09:42.464
What if the missing gravity is leaking[br]into an extra-spatial dimension

0:09:42.488,0:09:44.444
that's invisible to you and I?

0:09:45.455,0:09:48.549
What if gravity is just as strong[br]as the other forces

0:09:48.573,0:09:51.714
if you were to view it in this[br]extra-spatial dimension,

0:09:51.738,0:09:54.638
and what you and I experience[br]is a tiny slice of gravity

0:09:54.662,0:09:56.559
make it seem very weak?

0:09:58.258,0:09:59.433
If this were true,

0:09:59.457,0:10:02.205
we would have to expand[br]our Standard Model of particles

0:10:02.229,0:10:06.315
to include an extra particle,[br]a hyperdimensional particle of gravity,

0:10:06.339,0:10:09.334
a special graviton that lives[br]in extra-spatial dimensions.

0:10:09.358,0:10:10.823
I see the looks on your faces.

0:10:10.847,0:10:12.666
You should be asking me the question,

0:10:12.690,0:10:16.334
"How in the world are we going to test[br]this crazy, science fiction idea,

0:10:16.358,0:10:18.849
stuck as we are in three dimensions?"

0:10:18.873,0:10:20.155
The way we always do,

0:10:20.179,0:10:22.318
by slamming together two protons --

0:10:22.342,0:10:23.494
(Laughter)

0:10:23.518,0:10:26.082
Hard enough that[br]the collision reverberates

0:10:26.106,0:10:28.797
into any extra-spatial dimensions[br]that might be there,

0:10:28.821,0:10:31.420
momentarily creating[br]this hyperdimensional graviton

0:10:31.444,0:10:35.824
that then snaps back[br]into the three dimensions of the LHC

0:10:35.848,0:10:37.670
and spits off two photons,

0:10:38.378,0:10:39.716
two particles of light.

0:10:41.517,0:10:44.427
And this hypothetical,[br]extra-dimensional graviton

0:10:44.451,0:10:48.158
is one of the only possible,[br]hypothetical new particles

0:10:48.182,0:10:50.317
that has the special quantum properties

0:10:50.341,0:10:54.577
that could give birth to our little,[br]two-photon bump.

0:10:56.100,0:11:01.920
So, the possibility of explaining[br]the mysteries of gravity

0:11:01.944,0:11:05.442
and of discovering extra[br]dimensions of space --

0:11:05.466,0:11:07.058
perhaps now you get a sense

0:11:07.082,0:11:11.206
as to why thousands of physics geeks[br]collectively lost their cool

0:11:11.230,0:11:13.112
over our little, two-photon bump.

0:11:13.136,0:11:16.036
A discovery of this type[br]would rewrite the textbooks.

0:11:16.839,0:11:17.991
But remember,

0:11:18.015,0:11:19.739
the message from us experimentalists

0:11:19.763,0:11:22.002
that actually were doing[br]this work at the time,

0:11:22.026,0:11:23.180
was very clear:

0:11:23.204,0:11:24.378
we need more data.

0:11:24.402,0:11:25.921
With more data,

0:11:25.945,0:11:29.969
the little bump will either turn into[br]a nice, crisp Nobel Prize --

0:11:29.993,0:11:31.753
(Laughter)

0:11:31.777,0:11:34.741
Or the extra data will fill in[br]the space around the bump

0:11:34.765,0:11:36.631
and turn it into a nice, smooth line.

0:11:37.615,0:11:38.833
So we took more data,

0:11:38.857,0:11:41.434
and with five times the data,[br]several months later,

0:11:41.458,0:11:43.148
our little bump

0:11:43.172,0:11:45.520
turned into a smooth line.

0:11:49.317,0:11:52.801
The news reported on a "huge[br]disappointment," on "faded hopes,"

0:11:52.825,0:11:55.335
and on particle physicists "being sad."

0:11:55.359,0:11:57.170
Given the tone of the coverage,

0:11:57.194,0:12:00.682
you'd think that we had decided[br]to shut down the LHC and go home.

0:12:00.706,0:12:01.856
(Laughter)

0:12:02.728,0:12:04.331
But that's not what we did.

0:12:07.157,0:12:09.171
But why not?

0:12:10.575,0:12:13.420
I mean, if I didn't discover[br]a particle -- and I didn't --

0:12:14.309,0:12:17.338
if I didn't discover a particle,[br]why am I here talking to you?

0:12:17.362,0:12:19.799
Why didn't I just hang my head in shame

0:12:19.823,0:12:21.047
and go home?

0:12:25.269,0:12:28.620
Particle physicists are explorers.

0:12:29.521,0:12:32.473
And very much of what we do[br]is cartography.

0:12:33.568,0:12:36.420
Let me put it this way: forget[br]about the LHC for a second.

0:12:36.444,0:12:39.826
Imagine you are a space explorer[br]arriving at a distant planet,

0:12:39.850,0:12:41.175
searching for aliens.

0:12:41.199,0:12:42.721
What is your first task?

0:12:44.031,0:12:47.107
To immediately orbit the planet,[br]land, take a quick look around

0:12:47.131,0:12:49.017
for any big, obvious signs of life,

0:12:49.041,0:12:50.860
and report back to home base.

0:12:50.884,0:12:52.508
That's the stage we're at now.

0:12:53.369,0:12:54.856
We took a first look at the LHC

0:12:54.880,0:12:57.164
for any new, big,[br]obvious-to-spot particles,

0:12:57.188,0:12:59.138
and we can report that there are none.

0:12:59.731,0:13:02.404
We saw a weird-looking alien bump[br]on a distant mountain,

0:13:02.428,0:13:04.598
but once we got closer,[br]we saw it was a rock.

0:13:04.916,0:13:07.556
But then what do we do?[br]Do we just give up and fly away?

0:13:07.580,0:13:08.867
Absolutely not;

0:13:08.891,0:13:11.196
we would be terrible scientists if we did.

0:13:11.220,0:13:14.833
No, we spend the next couple[br]of decades exploring,

0:13:14.857,0:13:16.337
mapping out the territory,

0:13:16.361,0:13:18.726
sifting through the sand[br]with a fine instrument,

0:13:18.750,0:13:20.208
peeking under every stone,

0:13:20.232,0:13:21.786
drilling under the surface.

0:13:22.206,0:13:24.799
New particles can either[br]show up immediately

0:13:24.823,0:13:26.956
as big, obvious-to-spot bumps,

0:13:26.980,0:13:30.921
or they can only reveal themselves[br]after years of data taking.

0:13:32.203,0:13:36.613
Humanity has just begun its exploration[br]at the LHC at this big high energy,

0:13:36.637,0:13:38.428
and we have much searching to do.

0:13:38.452,0:13:44.277
But what if, even after 10 or 20 years,[br]we still find no new particles?

0:13:45.153,0:13:46.848
We build a bigger machine.

0:13:46.872,0:13:48.446
(Laughter)

0:13:48.470,0:13:50.160
We search at higher energies.

0:13:50.576,0:13:52.146
We search at higher energies.

0:13:53.046,0:13:56.099
Planning is already underway[br]for a 100-kilometer tunnel

0:13:56.712,0:13:59.688
that will collide particles[br]at 10 times the energy of the LHC.

0:13:59.712,0:14:02.049
We don't decide where[br]nature places new particles.

0:14:02.466,0:14:04.112
We only decide to keep exploring.

0:14:04.136,0:14:06.694
But what if, even after[br]a 100-kilometer tunnel

0:14:06.718,0:14:08.578
or a 500-kilometer tunnel

0:14:08.602,0:14:11.443
or a 10,000-kilometer[br]collider floating in space

0:14:11.467,0:14:13.045
between the Earth and the Moon,

0:14:13.069,0:14:16.131
we still find no new particles?

0:14:17.697,0:14:20.391
Then perhaps we're doing[br]particle physics wrong.

0:14:20.415,0:14:22.206
(Laughter)

0:14:22.230,0:14:24.187
Perhaps we need to rethink things.

0:14:25.227,0:14:28.489
Maybe we need more resources,[br]technology, expertise

0:14:28.513,0:14:30.021
than what we currently have.

0:14:30.710,0:14:34.051
We already use artificial intelligence[br]and machine learning techniques

0:14:34.075,0:14:35.228
in parts of the LHC,

0:14:35.252,0:14:37.658
but imagine designing[br]a particle physics experiment

0:14:37.682,0:14:39.351
using such sophisticated algorithms

0:14:39.375,0:14:42.543
that it could teach itself to discover[br]a hyperdimensional graviton.

0:14:42.567,0:14:43.724
But what if?

0:14:43.748,0:14:45.193
What if the ultimate question:

0:14:45.217,0:14:48.690
What if even artificial intelligence[br]can't help us answer our questions?

0:14:48.714,0:14:50.825
What if these open questions,[br]for centuries,

0:14:50.849,0:14:53.518
are destined to be unanswered[br]for the foreseeable future?

0:14:53.542,0:14:56.471
What if the stuff that's bothered me[br]since I was a little kid

0:14:56.495,0:14:59.018
is destined to be unanswered[br]in my lifetime?

0:15:00.495,0:15:01.651
Then that ...

0:15:02.382,0:15:04.476
will be even more fascinating.

0:15:06.244,0:15:09.469
We will be forced to think[br]in completely new ways.

0:15:10.461,0:15:12.519
We'll have to go back to our assumptions,

0:15:12.543,0:15:14.882
and determine if there was[br]a flaw somewhere.

0:15:15.501,0:15:18.896
And we'll need to encourage more people[br]to join us in studying science

0:15:18.920,0:15:21.982
since we need fresh eyes[br]on these century-old problems.

0:15:22.006,0:15:25.140
I don't have the answers,[br]and I'm still searching for them.

0:15:25.164,0:15:27.493
But someone -- maybe[br]she's in school right now,

0:15:27.517,0:15:29.201
maybe she's not even born yet --

0:15:29.883,0:15:33.016
could eventually guide us to see physics[br]in a completely new way,

0:15:33.040,0:15:37.308
and to point out that perhaps[br]we're just asking the wrong questions.

0:15:38.212,0:15:40.622
Which would not be the end of physics,

0:15:40.646,0:15:42.052
but a novel beginning.

0:15:43.304,0:15:44.454
Thank you.

0:15:44.478,0:15:47.019
(Applause)