Dancing in the Dark: The End of Physics? Page #3

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started telling me about

work that he'd been doing.

Drukier had hit upon a way of

detecting neutrinos, real particles

that share some characteristics

with the proposed WIMPs.

So what we realised is you could

use exactly that same

technique for WIMPs.

WIMPs have the same

kind of interactions,

they have the weak interactions,

the same ones that the neutrinos do.

I, at the time, was a post-doc

at Harvard and I convinced

Andre to come to Harvard for

a few months. And there, we also

worked with David Spergel, and the

three of us wrote down some of the

basic ideas for what you might do

if you wanted to detect the WIMPs.

WIMPs, the particles that could

be dark matter, are like ghosts.

They travel through ordinary matter.

But they are particles,

so every once in a while,

one of them

should collide with

the nucleus of an atom, in theory.

What's more, the theoretical

collision should release

a photon, a tiny flash of light -

dark matter detected.

Simple, in theory.

If you were to try to build one of

these experiments on a table top

or in a laboratory on the

surface of the Earth,

then your signal would be completely

swamped by cosmic rays.

These would just ruin your attempt

to do the experiment,

because the count rate from the

cosmic rays would be so high

that you'd never be

able to see the WIMPs.

So what you have to do

is go underground.

It is because of the ideas that

Katie had in the 1980s that

thousands of scientists have

been scurrying underground

in search of the dark ever since.

Juan Collar is one of them.

His search for dark matter has

taken him to Sudbury, a small

town in Canada, perched just above

the North American Great Lakes.

To look at it now,

you wouldn't think that this place

owes its existence to

one of the most catastrophic

events the world has ever witnessed.

Millions of years ago, a gigantic

comet crashed into what is

now Sudbury, creating, to date,

the second largest crater on Earth.

The comet brought with it

lots of useful metals that ended up

under what became

known as the Sudbury Basin.

When humans became clever enough,

they sunk holes into the crater

so they could get the metals out.

The area's nickel mines

are responsible for, amongst other

things, the town of Sudbury's main

tourist attraction, the Big Nickel.

What they're less well

known for is the part

they play in the search

for dark matter.

Juan and his colleagues

regularly make the two-kilometre

descent into the darkness in pursuit

of the universe's missing mass.

He's been making

the journey for some time.

How long have you been doing

experiments underground?

In my case, since 1986.

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