Dancing in the Dark: The End of Physics? Page #5

---

with all the certainty of youth -

"is not only of the WIMP variety,

but, furthermore, it is also cold."

It was 1984 and the University

of California in Santa Barbara

had organised a six-month workshop

on the structure of the universe.

I was there with my three very close

colleagues, and they were

George Efstathiou from England,

Simon White and Marc Davis.

We were very young, at the time,

we were only in our 20s,

and my first job was to try

and figure out,

together with my colleagues,

how galaxies formed. And to

our amazement we realised that

a particular kind of dark matter

known as cold dark matter, was

just... Would do the job just

beautifully.

Now that idea, at the time, was

really not accepted.

It was very unconventional. Because

the idea that dark matter existed

was not generally accepted and that

it should be an elementary particle,

and cold dark matter was just

outrageous, but that's how we were.

We were outrageous, too.

We were young, reckless.

I remember George Efstathiou used

to wear a leather jacket

and drive a bike,

very, very fast motorbike.

Simon and Marc were completely

reckless skiers.

I was the only reasonable

individual of the gang of four,

and then in the summer of 1984,

we had

a conference in Santa Barbara - by

the beach, sun shining,

beautiful day... I will never

forget.

I gave my first ever

talk on cold dark matter,

and at the end of it, I thought

it had gone rather well,

but at the end of it, a very, very

eminent astronomer came up

to me, whom I had met before

when I was a student in Cambridge,

and he says to me, "Carlos, I've got

something important to tell you."

He says, "I regard you as a very

promising young scientist but

"let me tell you something, if you

want to have a career in astronomy,

"the sooner you give up this cold

dark matter crap, the better."

And I remember how my world

crumbled. And I went up to Simon,

and I said, "Simon,

this is what I've just been told."

And Simon just looked at me

for what seemed a very long time,

and he said, "Just ignore him,

he's an old man."

He was 42.

HE CHUCKLES:

Since he was told to drop it,

Carlos has shown again

and again that his ideas about cold

dark matter really do seem to

hold water, at least mathematically.

And with the advent of computer

visualisations,

bare numbers have been transformed

into the intensely beautiful

infrastructure of our universe.

This is not a picture of the real

universe,

this is the output of our latest

simulation. So what

we do to simulate the universe

is that we create our own Big Bang

in a computer, and then, crucially,

we make an assumption about the

nature of the dark matter, and in

this particular case we have assumed

that the dark matter is cold dark

matter, and this is what comes out.

An artificial virtual universe,

but it is essentially

indistinguishable from the real one.

And it is this that validates

our key assumption that the universe

is made of cold dark matter.

Of course, the obvious drawback with

dark matter is that you can't

see it...

But in his universe,

Carlos can simply colour it in,

mainly purple in this case.

So this is the backbone

of the universe, this is

the large-scale structure of the

dark matter coming to us vividly.

You can almost touch it from this

realistic computer simulation.

This is cold dark matter.

When I look at these amazing

structures that come

out of the computers,

and the fact that

I have largely contributed to cold

dark matter becoming

the standard model of cosmology,

I'm just so glad I didn't listen

to my eminent colleague in the

1980s, who told me that the quicker

I gave

this up, the likelier it was that

I would have a successful career.

I'm just so glad

I didn't listen to him.

So cold dark matter it is, then.

Carlos and his young guns

were right.

Their ideas are now enshrined

in the standard model of cosmology.

And the standard model of cosmology

is a theory that's

accounted for everything very well.

It explains how Hubble's expanding

universe originated.

Our universe started...

13.8 billion years ago...

In an instant.

It tells us how the

universe got to be the size it is.

ALL:
This was a second

period in the birth of the universe.

It is called inflation.

It predicts precisely how much dark

matter there is in our universe.

ALL:
26% dark matter.

But it's a description of a problem,

rather than of a thing,

and this is where it gets

frustrating, because there

should be an answer from the

standard model of particle physics.

There are six quarks...

ALL:
Four types of gauge bosons.

Six leptons.

And the Higgs boson.

But there isn't, because,

so far, there isn't a particle

in the standard model of particle

physics that provides us with

dark matter for the standard model

of cosmology, cold or otherwise.

At CERN,

they're hoping to put that right.

John Ellis thinks they might have

found some likely dark matter

particle candidates down the back

of a mathematical sofa, twice as

many particles as the standard model

currently provides, to be precise.

This idea goes under the name of...

Supersymmetry.

So the particles of the standard

model include the electron,

and then there's

a couple of other heavier particles

very much like it -

called mu and tau.

Other particles include neutrinos

and quarks, up, down, charm,

strange, top and bottom quarks.

Photons, gluons and W and Z

are force-carrying particles.

Now, as I've written it, these

particles wouldn't have any mass,

but there is the missing link,

the infamous Higgs boson,

which gives masses to these

particles and completes the standard

model.

Now, what supersymmetry says is

that in addition to these particles,

everyone has a partner or mirror

particle, if you like,

which we denote by twiddle,

so there's a selectron, there's a

smuon,

there's a stau, there's a photino,

there's a gluino, sneutrinos...

Supersymmetry,

or SUSY if you're in the know,

is, according to its devotees,

a rather beautiful notion that

not only explains an awful

lot of problems in physics

and cosmology, but also provides us

with a dark matter particle,

perhaps, if it's real,

as opposed to just a nice idea.

And so far, it's been as elusive as,

well, as dark matter itself.

We were kind of hopeful that with

the first run of the LHC,

we might see some supersymmetric

particles, but we didn't.

And the fact of the matter is that

we can't calculate from first

principles

how heavy these

supersymmetric particles

might be, and so what the LHC has

told us so far is that they have

to be somewhat heavier than maybe

we'd hoped. But when we increase

the energy of the LHC, we'll be able

to look further, produce heavier

supersymmetric particles, if they

exist, so let's see what happens.

Also waiting to see what happens

and interpret the 40 million

pictures per second that the

ATLAS detector will produce, will be

Rate this script:0.0 / 0 votes