Dancing in the Dark: The End of Physics?

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In 1929, Edwin Hubble made

an alarming discovery.

He found that wherever

he pointed his telescope,

it revealed that everything

was getting further away.

The universe seemed to be expanding,

and if it was expanding -

they checked and it was -

and you think about it for any

length of time, which they did,

you have to conclude that it must be

expanding from some kind

of starting point.

Hubble had stumbled across what was

then a revolutionary idea,

but something that is now

scientific orthodoxy.

Our universe started 13.8 billion

years ago in an instant.

ALL:
This was the first period of

the birth of the universe.

It is known as the Big Bang.

Nowadays, our understanding

of the birth of the universe is

extremely detailed.

Then it underwent

a dramatic expansion.

ALL:
This was the second

period in the birth of the universe.

It is called inflation.

Thanks to science, we think

we know exactly how we got to now.

BOTH:
Atomic matter condensed

to form the stars

and planets that make our universe.

ALL:
This is the standard

model of cosmology.

And not content with painting

the biggest picture of all,

science has also created

a comprehensive list

of what the atoms we're

made from, are made from.

There are six quarks.

ALL:
Four types of gauge bosons.

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Six leptons.

And the Higgs boson.

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This is the standard

model of particle physics.

Together, these two paradigms

should explain everything.

And yet, just at the point where

things seem to be coming together,

some researchers are worried that

there's an increasingly

strong possibility that we might

have got the science wrong.

That our current theories

are looking shaky.

That we don't understand

our universe

or what we're made of,

or anything, really.

How does any theorist sleep at night

knowing that the standard

model of particle physics is off by

so many orders of magnitude?

We have no idea

what 95% of the universe is.

It hardly seems that we

understand everything.

This is about what the

universe is made of.

This is about our existence.

What is it that they say? They say

that cosmologists are always wrong

but never in doubt.

There are more theories than

there are theoreticians.

OK, I'm going to be honest here,

but we're in the strange situation

that it seems like every other year

there's a new unexplained signal.

Maybe we're just going to have to

scratch our heads

and start all over again.

Nestling beneath the huge

Andes Mountains that dominate

the whole of Chile lies its capital.

It was founded by the Conquistadors

in 1541, who gave it its name,

Santiago, St James, after the

patron saint of the motherland.

But in Spanish, Iago also means

Jacob, and it was Jacob who,

according to the Bible, dreamt

about climbing a ladder to heaven.

While the mountains may

hint at a metaphorical stairway

to paradise, they also provide

a practical route to enlightenment.

That's why British astrophysicist

Bob Nichol is here.

He's en route to some of the biggest

telescopes on the planet,

perched aloft on the roof

of the world, where he's continuing

the work of trying to understand

how the universe works.

So the amazing thing about cosmology

is that it only really started

in the 1920s, so when people started

looking through their telescopes,

they didn't know whether these fuzzy

things out there in the universe

were actually within our own galaxy

or actually separate galaxies from

our own. And then it was the great

astronomers like Hubble that came

along and measured the distances to

these faint nebulae that you

could see in your telescopes, and

suddenly discovered that they were

much further away than we expected

and therefore had to be outside

our galaxy and therefore discovered

a universe of other galaxies.

The discovery of a universe that was

far more complicated

than anyone could have imagined...

..and the idea that it all

started in an instant...

..suddenly provided a credible

creation story

that didn't rely on myths and magic.

The idea of the Big Bang

and the expanding universe was

a triumph for modern astronomy.

And everyone was happy with it,

until 1974, when astronomers

discovered a big problem.

So in the solar system,

we have a sun in the middle, which

provides all the gravity.

And then coming further out from

that, we have all the planets.

They're lined up

and rotate around the sun,

and the speed by which they

go round the sun decreases

as a function of the

distance away from the sun.

So by the time you

get to the outer planets,

they are moving a lot slower than

the ones in the centre.

So, for example, Neptune takes 165

Earth years to go round the sun.

So if I was to draw a graph of

that, it would look a bit like this.

So...

..you would expect the speed

of the planets in the centre to be

high, and as the gravity got weaker,

the speed would get smaller

and smaller and smaller

until you got out here.

Now, we have the same

set-up in our galaxy.

We have a large supermassive

black hole in the centre

and we have stars orbiting

around the centre of the galaxy.

So you'd expect that the stars

further away from the centre

of the galaxy would be moving slower

than the ones on the inside.

But that's not what we see.

What we see is the speed of the

stars is constant with distance,

so the stars out here

are travelling at the same

speed as the stars in the centre.

Wherever the speed of stars

in spiral galaxies were measured,

they produced the logic-defying

flat rotation curves.

The only way they made sense was

if there was more matter than

we thought, producing more gravity.

And since the extra stuff

couldn't be seen, it was given

the slightly sinister title

"dark matter".

Dark matter is a really

interesting problem.

It sounds exotic, but

it doesn't have to be.

Professor Katie Freese is

a theoretical physicist.

That is to say, the physics

she deals with is theoretical.

Katie herself is real.

There's a lot of dark things out

there in the universe.

Until I shine my light at these

bottles, I can't see them

and as soon as I take away

the light, they're dark.

That's what people thought. They

thought it might be gas,

it might be dust.

The dark matter could just be

ordinary stuff that you can't see.

These ordinary, but dark, dark

matter creatures are called MACHOs -

massive compact halo objects.

But the trouble was that even

the most generous

estimates for how much the MACHOs

might weigh fell pathetically

short of what would be needed to

explain the strange

goings-on in spiral galaxies

like ours.

Another explanation was required.

Well, there's an alternative idea

for what the dark matter could be.

What we think it is, is that it's

some new kind of fundamental

particle. Not neutrons, not protons,

not ordinary atomic stuff

but something entirely new.

And these particles are

everywhere in the universe.

They're flying around in our galaxy,

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