The Most Unknown

Watch your head.

Nice.

This is beautiful.

We've gotten lucky here.

We've seen them before,

but they bloom only in certain conditions,

when the water level is very low.

So to have stumbled upon a bloom

of this exciting magnitude

is really... it's lucky.

So, I'm really excited.

It's kind of surprisingly hard to catch.

It's like you almost don't feel it.

These strange, squiggly slimes

form on the walls.

And these are really...

They're probably the most beautiful slime I've ever seen.

We don't understand how they form.

It's still a mystery,

but we know they're made by life.

This question of how much of the universe is understood

is very much a moving target.

Because as we are able to stand in a new place,

because we've learned something new,

we then see other wonders

that were not even visible to us before.

Wait, wait, wait...

Let us in.

That's forbidden.

Do I get points for pedestrians?

How can this be the right way?

- - Yeah, yeah.

He's late for lunch.

That's why he's impatient. He's late for lunch.

We are headed for physics lab

to talk to a physicist

in the physicist habitat,

which is always interesting to see, you know,

an organism in its natural habitat.

So, I'm a microbiologist

and I'm hoping that the physicist

will be able to communicate

what he does and why,

in terms that I can understand.

I'd like to keep an open mind about this.

You need to fill in some forms.

- So the disclaimer... - I love forms. I love forms.

Okay, and then we can eat some lunch in the cafeteria.

Oh my God, look at him! He's awesome.

The hair.

Galileo, Newton...

D'Angelo.

Okay, dark matter is something,

we do not know what it is.

We believe the dark matter is there,

but we have never detected it.

It's good, this cafeteria?

It's better than the average cafeterias, I would say.

Buongiorno. Ciao.

So I'm sorry, but you won't like this lunch much.

- What is dark matter? - Okay. We don't know.

That's great. That's why it's called dark.

Exactly.

Do you know we have dark matter

in microbiology too?

That's still the word.

What do you use it for?

Well, we...

We have some evidence that there are something like

35 trillion microbial species.

Mm-hmm.

And we've met about...

a million?

Mm-hmm.

So the rest is dark matter.

- Okay. - Yeah, we stole it.

I admit it.

Yeah. I think it makes sense,

because we...

What we call dark matter is

some kind of new particle

which we haven't discovered yet.

So, the hypothesis is

that dark matter is out there

because it's consistent with all of our observations.

- Exactly. - And so,

it might not be out there.

But we think it is,

- because of what we... - I think we detect it.

- We cannot say we are sure. - Uh-huh.

All observations point in that direction.

- This is very mysterious. - This is very mysterious, yes.

Dark matter is one of the big unknowns

in particle physics.

Of all matter that should be out there,

about 85% of this is invisible.

These particles are moving through us,

through our bodies while we're talking

and most of them just go without any interaction.

So how are you going to find it?

How are you going to detect it?

So...

why are we here?

Why are we here?

We are here, under about

1,800 meters of rock.

We are deep underground because all the experiments here,

whether they look for dark matter or for neutrino

or for any other kind of rare event,

they need to be shielded from the cosmic radiation.

There are protons or ions

that heat the atmosphere.

They create a shower of particles

that hit us above ground.

And the mountain is a filter for this.

So if you go here, you have the so-called cosmic silence.

- Cosmic silence? - Cosmic silence.

We're here in the cosmic silence under the mountain.

I love that.

So, you can't hear the cosmic rays here.

I would love to see the new detector.

Okay.

- It's not ready yet. - Okay.

So this is your new experiment?

Yes. This is a prototype still.

It will prove the old detector concept.

Okay, so this dark matter that we think exists,

but we're not that sure...

The crystal that you're going to put inside here

is going to help you?

It's going to be the best possible detector

-that you know how to build? - Yes.

There's crystals inside there.

How do you see what the crystal is seeing?

How does the crystal talk to you on the outside?

It emits light, and then you have

two photo multipliers on each side.

Then you read the photo multipliers...

- They go out? - ...that go out to here.

It's very simple.

Yeah. See, the lights?

My friend, the dark matter physicist.

What's simpler than that?

I keep having to, like, loosen my helmet,

'cause my head is getting bigger by the minute.

I...I'm...

I have to say that I was starting from

pretty much zero on dark matter.

So, this is what I understand about how it works.

We are rotating within a sea of dark matter particles.

There is a, uh...

container?

So we build a,

a detector, which is a...

which, whose core is a...

Special, very carefully grown crystal.

A sodium iodide crystal.

When the crystal gets hit

by this dark matter particle...

You see a tiny flash of light.

That light is going to be detected by these devices

that are sticking into the edge of the container.

And those devices then translate the light

into an electronic pulse that goes to a computer

that says, "Hey, dark matter particle.

I'm here."

So, if you just had to...

I know this is not what we do but,

if you just had to guess,

where are the...

where is the dark matter?

- Can you guess? - No.

- You would not... - Science is not about guessing.

I know, I know. It's not about guessing.

But I mean, sometimes I dream about a result that I might get.

I can tell you this. So here, you also see the models.

The models

foresee dark matter in this area here.

Extra dimensions models foresee

dark matter in this area here.

- These other guys, it's going to be here, so... - So we have no idea.

Some other guys would place it here, so we have no idea.

In my field, I would say 10 years ago,

if you asked me

where would we be now today,

I would've had a very hard time answering.

Because we're really... We're not just...

We're not just... We're not just...

We're not just filling in the details.

We're looking into some dark abyss

where we just can't see very far in.

And depending on where the flashlight shines first,

we might go a different direction completely.

So, it's very hard when you're

right on the edge of this big unknown.

It's very hard to say where

the science is going to go next.

Is that where

dark matter physics is now, or is it...

Is there something analogous?