How we explore unanswered questions in physics

There is something about phsyics

that has been really bothering me
since I was a little kid.

And it's related to a question

that scientists have been asking
for almost 100 years

with no answer.

How do the smallest things in nature --

the particles of the quantum world --

match up with the largest
things in nature --

planets and stars and galaxies
held together by gravity?

As a kid I would puzzle
over questions just like this.

I would fiddle around with
microscopes and electromagnets,

and I would read about
the forces of the small,

and about quantum mechanics,

and I would marvel

at how well that description
matched up to our observation.

And then I would look at the stars,

and I would read about how well
we understand gravity,

and I would think surely there
must be some elegant way

that these two systems match up,

but there's not.

And the books would say,

yeah, we understand a lot about
these two realms separetely,

but we try to link them mathematically,

everything breaks.

And for 100 years,

none of our ideas
as to how to solve this --

basically --

physics disaster,

has ever been supported by evidence.

And to little old me,

little, curious, skeptical James,

this was a supremely unsatisfying answer.

So I'm still a skeptical little kid --

well, flash-forward now
to December of 2015,

when I found myself smack in the middle

of the physics world
being flipped on its head.

It all started when we at CERN
saw something intriguing in our data;

a hint of a new particle,

an inkling of a possibly extraordinary
answer to this question.

So I'm still a skeptical
little kid, I think,

but I'm also now a particle hunter.

I am a physicist at CERN's Large
Hadron Collider,

the largest science
experiment ever mounted.

It's a 27-kilometer tunnel
on the border of France and Switzerland

buried 100 meters underground.

And in this tunnel,

we use superconducting magnets
colder than outer space

to accelerate protons
to almost the speed of light,

and slam them into each other
millions of times per second,

collecting the debris of these collisions

to search for new, undiscovered
fundamental particles.

Its design and construction
took decades of work

by thousands of physicists
from around the globe,

and in the summer of 2015,

we had been working tirelessly
to switch on the LHC

at the highest energy that humans
have ever used in a collider experiment.

Now, higher energy is important

because for particles
there is an equivalence

between energy and particle mass,

and mass is just number
put there by nature.

To discover new particles,

we need to reach these bigger numbers.

And to do that,

we have to build a bigger,
higher energy collider,

and the biggest, highest energy collider
in the world is the Large Hadron Collider.

And then we collide protons
quadrillions of times,

and we collect this data very slowly
over months and months.

And the new particles might show up
in our data as bumps --

slight deviations from what you expect.

Little clusters of data points
that make a smooth line not so smooth.

For example,

this bump,

after months of data taking in 2012,

led to the discovery
of the Higgs particle,

the Higgs boson,

and to a Nobel Prize
for the confirmation of its existence.

This jump up in energy in 2015

represented the best chance
that we as a species had ever had

at discovering new particles --

new answers to these
longstanding questions,

because it was almost twice
as much energy as we used

when we discovered the Higgs boson.

Many of my colleagues had been working
their entire careers for this moment,

and frankly,

to little curious me,

this was the moment I'd been
waiting for my entire life.

So 2015 was go time.

So June 2015,

the LHC is switched back on.

My colleagues and I held our breath
and bit our fingernails,

and then finally we saw the first
proton collisions

at this highest energy ever.

Applause, champagne, celebration.

This was a milestone for science,

and we had no idea what we would find
in this brand new data.

And then a few weeks
later we found a bump.

It wasn't a very big bump,

but it was big enough to make you
raise your eyebrow.

But on a scale of one to 10
for eyebrow raises,

if 10 indicates that you've
discovered a new particle,

this eyebrow raise was about a four.

(Laughter)

I spent hours, days, weeks
in secret meetings

arguing with my colleagues
over this little bump,

poking and prodding it with our
most ruthless experimental sticks

to see if it would withstand scrutiny.

But even after months
of working feverishly --

sleeping in our offices
and not going home,

candy bars for dinner,

coffee by the bucket full --

physicists are machines for turning
coffee into diagrams --

(Laughter)

This little bump would not go away.

So after a few months,

we presented our little bump to the world
with a very clear message:

this little bump is interesting
but it's not definitive,

so let's keep an eye on it
as we take more data.

And so we were trying to be
extremely cool about it.

And the world ran with it anyway.

The news loved it.

People said it reminded
them of the little bump

that was shown on the way
towards the Higgs boson discovery.

Better than that,

my theorist colleagues --

I love my theorist colleagues --

my theorist colleagues wrote 500 papers
about this little bump.

(Laughter)

The world of particle phsyics
has been flipped on its head.

But what was it about this particular bump

that cause thousands of physicists
to collectively lose their cool?

This little bump was unique.

This little bump indicated

that we were seeing an unexpectedly
large number of collisions

whose debris consisted
of only two photons --

two particles of light.

And that's rare.

Particle collisions are not
like automobile collisions.

They have different rules.

When two particles collide
at almost the speed of light,

the quantum world takes over.

And in the quantum world,

these two particles can briefly
create a new particle

that lives for a tiny fraction of a second

before splitting into other particles
that hit our detector.

Imagine a car collision where
the two cars vanish upon impact,

a bicycle appears in their place --

(Laughter)

And then that bicycle explodes
into two skateboards

which hit out detector.

(Laughter)

Hopefully not literally --

they're very expensive.

The events where only two photons
hit out detector are very rare.

And because of the special
quantum properties of photons,

we actually have --

there's a very small
number of new particles --

these mythical bicycles --

that can give birth to only two photons.

But one of these options is huge,

and it has to do with
that longstanding question

that bothered me as a tiny little kid

about gravity.